215 research outputs found
FLEXOB - Entwicklungstool fĂŒr dynamische, modellbasierte CAD-Systeme
Objektorientierte Modellierungstechniken werden gegenwĂ€rtig vor allem Entwicklern von CAD-Systemen angeboten. Sie erzeugen ĂŒber die Schritte OO-Modellanalyse und OO-Softwaredesign OO-Programme, die mit ihrer Compilation das durch den Softwareingenieur gefundene Modell festschreiben. Generell, aber insbesondere im Bauwerksdesign, ist dieses Vorgehen unbefriedigend, da hier eine Normung von Modellen nicht gelingt, der EntwurfsprozeĂ vergleichsweise lang ist und eine Kooperation von Ingenieurgewerken mit verschiedenen ModelldomĂ€nen die Regel sind. DarĂŒber hinaus weisen die Modelle in frĂŒhen Phasen ein hohes MaĂ an UnschĂ€rfe und Abstraktion auf. CAD-Tools, die diese Phasen unterstĂŒtzen, benötigen deshalb: statt eines genormten Produktmodells ein einheitliches, kognitiv begrĂŒndetes Modellstrukturierungsparadigma, fĂŒr das mit der Objektorientierung eine mögliche AusprĂ€gung gegeben ist, ein explizites, verfĂŒgbares DomĂ€nenmodell zur fortwĂ€hrenden Interpretation von Bauwerksmodellen, deskriptive Elemente, die die Interpretation von Objekten und Attributen erleichtern, ein Konzept zur Behandlung von UnschĂ€rfe und Abstraktion. Hieraus ergeben sich fĂŒr die Entwicklung von CAD-Systemen folgende Forderungen : Explizite VerfĂŒgbarkeit von Klassenobjekten und deren Erzeugung und VerĂ€nderung zur Laufzeit, Vererbung auf Klassen- und Instanzniveau, Erweiterte Attributkonzepte (Facetten), UnterstĂŒtzung der Aggregation als einer wesentlichen Modellstrukturierungsrelation, VerfĂŒgbarkeit von OO-Schnittstellen zum Aufbau von CAD-Systemen aus Tools einerseits, sowie zur Trennung von Modellverwaltung und ModellreprĂ€sentation andererseits. Als ein herausragendes Merkmal des Objektorientierten Paradigmas wird die AnwendungsnĂ€he genannt, da Erscheinungen der behandelten DomĂ€ne sich analog in Modellen und Programmen wiederfinden (sollen). Unter der Grundannahme, daĂ dieses Paradigma auch durch den Anwender zur Erstellung seiner Modellwelten verwendet wird, will FLEXOB eine homogene Umgebung schaffen, die die Modellwelt des Softwareingenieurs zu Analysezwecken dem Anwender zur VerfĂŒgung stellt und die die Erweiterung dieser Modellwelt auf deskriptivem Niveau ermöglicht. Das Tool FLEXOB und einige wesentliche Implementationsdetails werden im Beitrag vorgestellt. Es handelt sich bei diesem Tools um eine C++ Klassenbibliothek, die entweder als Objektmodul oder als Windows-DLL verwendet werden kann. Aspekte des Nutzungsregimes solch flexibler Modellverwaltungen werden im Beitrag ebenfalls angespochen
Electron Probe X-Ray Microanalysis of Epithelial Cells: Aspects of Cryofixation
Content and distribution of diffusible ions in epithelial cells were studied by scanning transmission electron microscopy and energy dispersive electron probe X-ray microanalysis of freeze-dried cryosections from trout kidney, rat liver and Malpighian tubules of Drosophila larvae. Cryofixation of small excised kidney and liver samples by rapid immersion into liquid propane resulted in intracellular K/Na-ratios \u3c 1. In contrast, K/Na-ratios \u3e 7 were obtained after in situ cryofixation by means of a cryopunching device which allows tissue pieces to be frozen during excision from the intact organ. Isolated hepatocytes cryofixed in a small droplet of culture medium had a K/Na-ratio of 3.7. After culturing the hepatocytes, the K/Na-ratio increased to 24. Effects of extracellular media of different composition on the intracellular element content were studied. Malpighian tubules of Drosophila larvae were cryofixed by rapid immersion into liquid propane, and the distribution of K across the cells forming the tubules from the basal to the apical cell membrane was measured. An increasing K gradient was found from the intermediate to the apical cytoplasm. The intracellular K distribution was dependent on ions and transport inhibitors present in the fluid surrounding the Malpighian tubules within the larvae. Content and distribution of ions in epithelial cells sensitively depend on the physiological state immediately before cryofixation. Thus, electron probe X-ray microanalysis of cells and cell functions requires careful selection and control of the cell system to be studied
Subunits α, ÎČ and Îł of the epithelial Na+ channel (ENaC) are functionally related to the hypertonicity-induced cation channel (HICC) in rat hepatocytes
Specific small interfering RNA (siRNA) constructs were used to test for the functional relation of subunits α, ÎČ, and Îł of the epithelial Na+ channel (ENaC) to the hypertonicity-induced cation channel (HICC) in confluent rat hepatocytes. In current-clamp recordings, hypertonic stress (300âââ400 mosM) increased membrane conductance from 75.4â±â9.4 to 91.1â±â11.2 pS (pâ<â0.001). The effect was completely blocked by 100 ΌM amiloride and reduced to 46, 30, and 45% of the control value by anti-α-, anti-ÎČ-, and anti-Îł-rENaC siRNA, respectively. Scanning acoustic microscopy revealed an initial shrinkage of cells from 6.98â±â0.45 to 6.03â±â0.43 pl within 2 min. This passive response was then followed by a regulatory volume increase (RVI) by 0.42â±â0.05 pl (pâ<â0.001). With anti-α-, anti-ÎČ-, and anti-Îł-rENaC siRNA, the volume response was reduced to 31, 31, and 36% of the reference level, respectively. It is concluded that all three subunits of the ENaC are functionally related to RVI and HICC activation in rat hepatocytes
Hypertonicity-induced cation channels rescue cells from staurosporine-elicited apoptosis
Cell shrinkage is one of the earliest events during apoptosis. Cell shrinkage also occurs upon hypertonic stress, and previous work has shown that hypertonicity-induced cation channels (HICCs) underlie a highly efficient mechanism of recovery from cell shrinkage, called the regulatory volume increase (RVI), in many cell types. Here, the effects of HICC activation on staurosporine-induced apoptotic volume decrease (AVD) and apoptosis were studied in HeLa cells by means of electronic cell sizing and whole-cell patch-clamp recording. It was found that hypertonic stress reduces staurosporine-induced AVD and cell death (associated with caspase-3/7 activation and DNA fragmentation), and that this effect was actually due to activation of the HICC. On the other hand, staurosporine was found to significantly reduce osmotic HICC activation. It is concluded that AVD and RVI reflect two fundamentally distinct functional modes in terms of the activity and role of the HICC, in a shrunken cell. Our results also demonstrate, for the first time, the ability of the HICC to rescue cells from the process of programmed cell death
Extended quantum conditional entropy and quantum uncertainty inequalities
Quantum states can be subjected to classical measurements, whose
incompatibility, or uncertainty, can be quantified by a comparison of certain
entropies. There is a long history of such entropy inequalities between
position and momentum. Recently these inequalities have been generalized to the
tensor product of several Hilbert spaces and we show here how their derivations
can be shortened to a few lines and how they can be generalized. All the
recently derived uncertainty relations utilize the strong subadditivity (SSA)
theorem; our contribution relies on directly utilizing the proof technique of
the original derivation of SSA.Comment: 4 page
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