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  • 1
    ISSN: 1432-1858
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Technology
    Notes: Abstract  The present study is focused on the development of a gas sensor for application in a high temperature environment. The sensor has been realised using thin films prepared on silicon substrates including a high temperature stable heating and wiring system. TiO2 acts as sensitive layer. Measurements have been carried out in synthetic gas mixtures as well as in gases in a given application. Neural networks and multivariate data analysis have been used for determining the gas concentrations. The capability to detect CO, NO x , and toluene is shown.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0827
    Keywords: Endochondral mineralization ; Cartilage ; Alkaline phosphatase ; In vitro ; Levamisole
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Isolated mesenchymal limb bud cells from day-12 mouse embryos grown at high density in organoid culture at the medium/air interphase differentiate into chondrocytes and form cartilage nodules. Upon addition of β-glycerophosphate (β-GP), cartilage undergoes endochondral mineralization. This β-GP-induced mineralization was investigated by measuring the calcium content in the cultures and the activity of alkaline phosphatase (AP) in the cell mass and the medium. Calcium incorporation depended on the amount of β-GP added. After continuous treatment, mineralization began on day 8 of the culture period and increased linearly until day 15. In long-term cultures, periodical treatment for 6 days caused an increase in mineralization the older the cultures were, but the slope of increase was proportionately less steep. Treatment at the latest period on days 19–24 resulted in a markedly reduced mineralization. After short-term treatment (48 hours), mineralization increased also the older the cultures were and proceeded during further cultivation in β-GP-free medium. This kinetic behavior indicates a dependency of mineralization on cartilage maturation in this in vitro system. AP activity increased enormously and nearly logarithmically in the cell mass in β-GP-free medium, whereas β-GP treatment inhibited this drastic increase. In the medium, considerable activities of AP were also measurable from day 10 onward. It increased in β-GP-free medium up to day 14, but was diminished after mineralization had been induced. Levamisole inhibited AP activity dose dependently when added directly to the enzyme-containing medium (100% inhibition at 10-3 M). Added to the cultures from day 7 to 14, it partially inhibited AP activity and mineralization at 5×10-5 M; mineralization was totally inhibited at 10-3 M, but AP activity was still present. This high concentration was cytotoxic, as revealed ultrastructurally and by GAG estimation. This in vitro system comprises cartilage development and maturation, β-GP-inducible endochondral mineralization, and final degenerative changes; it may be an appropriate model for investigations on endochondral mineralization.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1436-5057
    Keywords: 65L60 ; Numerical analysis ; nonlinear differential equations ; finite elements ; numerical simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Das Problem der Berechnung des elektrostatischen Potentials in eindimensionalen Mehrschichtstrukturen mit quantifizierter Elektronenladung wird unter Zuhilfenahme der Theorie monotoner Operatoren und von Störungstheorie untersucht. Eine Fehlerabschätzung wird gegeben für den Fall einer Diskretisierung mit Lagrange-finiten Elementen erster Ordnung. Eine praktische Implementierung dieser Methode bei Verwendung eines quasi-Newton Algorithmus sowie numerische Resultate werden gezeigt.
    Notes: Abstract The problem of computing the electrostatic potential in a one dimensional multilayer semiconductor device with quantized electrons density is analysed using results of monotone operator theory and perturbation calculus. An error estimate is proved for the discretization with Lagrange finite elements of degree one. A practical implementation of the method, using a quasi-Newton algorithm is presented together with some numerical results.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 174 (1994), S. 421-431 
    ISSN: 1432-1351
    Keywords: Phototransduction ; Photoreceptor ; Cytoplasmic calcium ; Microfluorometry ; Bee
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract We have measured Cai at rest and upon light stimulation in the photoreceptors of the honeybee drone microfluorometrically with the fluorescent Ca2+ indicator dyes fura-2, fluo-3 and Ca-green 5N. In darkness, Cai was ∼ 90 nM after 5 min of dark adaptation. A saturating light step caused Cai to rise in the bulk cytoplasm to ∼ 750 nM within 1 s. Our measurements with the low affinity dye Ca-green 5N showed that bright 1-s light flashes cause a rapid increase in Cai which was graded with stimulus intensity. Ca-green 5N fluorescence reached a peak in about 200 ms, and then decayed to a slightly lower sustained plateau. The fluorescence signal peaked, when the receptor potential was repolarizing from its peak to the plateau. This observation is in agreement with the proposal that the peak-to-plateau transition of the receptor potential is caused by the rise in Cai From our Fluo-3 measurements it appears that the latency of the Ca2+ increase is by 3–4 ms longer than the latency of the receptor potential elicited by bright 100-ms light flashes. This result provides no support for the proposal that Ca2+ mediates the opening of those membrane channels responsible for the upstroke of the receptor potential.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 186 (2000), S. 497-503 
    ISSN: 1432-1351
    Keywords: Key words Honeybee ; Photoreceptors ; Spikes ; Ca2+ channels ; Neomycin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Photoreceptor cells of the honeybee drone fire, in the presence of the polycationic aminoglycoside neomycin, repetitive slow spike-like potentials superimposed on the receptor potential plateau phase. We have used conventional intracellular recordings and microfluorometric intracellular Ca2+ measurements to characterize these spike potentials. We have shown that the spike frequency increases in a light-intensity-dependent manner. The spikes are fired only when light stimuli depolarize the cell from a resting potential of −50 to −60 mV to at least −40 to −45 mV; they are tetrodotoxin insensitive and blocked by the Ca2+ channel blockers Ni2+, Cd2+, ω-agatoxin TK, verapamil and methoxyverapamil. Depolarization of the photoreceptors with high extracellular K+ in the presence of neomycin in darkness does not generate spikes. Small intracellular Ca2+ oscillations superimposed on the plateau phase of the light-induced increase in intracellular free Ca2+ concentration have a similar temporal pattern as the spike-like potentials. We conclude that the spike-like potentials require stimulation by light and are generated by voltage-dependent Ca2+ channels localized on the soma of the photoreceptors, distal to the basal lamina.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Histochemistry and cell biology 81 (1984), S. 353-361 
    ISSN: 1432-119X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The binding of six different FITC-labelled lectins to mesenchyme, blastemal cells and cartilage was investigated in limb buds of mouse embryos during their development from day 10 to day 13. Concanavalin A, wheat germ agglutinin and phaseolus vulgaris agglutinin labelled mesenchymal cells of earlier stages, day 10 or 11, distinctly more than those of later stages. Chondrogenic blastema, basement membrane and muscle were always strongly stained. The galactosamine-specific ricinus communis agglutinin (RCA) bound preferentially to the blastema, whereas the mesenchyme was only weakly labelled. The galactose-specific peanut agglutinin (PNA), however, stained solely the blastema. In the mesenchyme, no binding was detectable light microscopically with this lectin. In cartilage, RCA-and PNA-staining was found to a lesser extent. With the fucose-specific lectin Lotus A, no staining was detectable. Due to the apparent differences in the binding of PNA in mesenchyme and blastema, peroxidase-labelled PNA was used to study the binding behaviour electron microscopically. It is shown that peroxidase-PNA very strongly labelled the intercellular matrix and the plasma membrane of cells in the late blastemal stages, whereas in young blastema no reaction product was detectable. In, contrast to light microscopic findings, some label could be demonstrated also in the mesenchyme. The results show, a general reduction of lectin receptors in more developed mesenchyme of later stages and the occurrence of galactose and galactose derivatives during early chondrogenesis in the matrix and at the cell membrane. The significance of these changes for chondrogenesis, however, remains to be elucidated.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 31 (1975), S. 227-228 
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Zusammenfassung In einer Organkultur von Extremitätenknospen (Mäuse-Embryonen Tag 11) gelingt es bereits nach Gaben von 0,01 μg/ml Actinomycin-D in den ersten 24 h die Bildung der Knorpelanlagen von Scapula und Humerus zu unterdrücken, also Dysmelien oder Phokomelien in vitro zu erzeugen. Dieses Modell scheint zur in vitro-Testung von teratogenen Substanzen geeignet zu sein.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1432-0827
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Lasers in medical science 6 (1991), S. 363-366 
    ISSN: 1435-604X
    Keywords: Laser vascular welding ; Tissue fusion ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract The central problem in microsurgery is the reconstruction of small vessels. The long operating time, foreign body granuloma formation around the suture material as well as aneurysmal alterations of the vessel wall after conventional suture technique make the search for alternatives indispensable. Some of these disadvantages can be avoided as demonstrated by our animal experiments and histological examinations in laser-assisted anastomosing. The aim of this study is to show these aspects in connection with laser application and compare them with conventional suture techniques.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Monatshefte für Mathematik 110 (1990), S. 321-327 
    ISSN: 1436-5081
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract We explicitly compute the outer automorphism group Out π1 M of the fundamental group of the Hantzsche — Wendt manifoldM. It is an extension 1→(ℤ2)3→Outπ1 M→S 3⊕ℤ2→1, but not the semidirect product (ℤ2)3⋉(S 3⊕ℤ2) as claimed in [3] (see also [4]). As a consequence, we get a quick algebraic computation of the symmetry groups of the Borromean rings and the figure-8-knot.
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