Anisotropy of the eddy viscosities and their pressure dependence in the near wall region of three-dimensional turbulent boundary layers

  &nbsp

Hemodynamic and inotropic effects of endothelin-1 in vivo

Endothelin-1 (ET-1) is known to have strong vasoactive properties. Contradictory results have been reported with regard to its inotropic effects. This study examined the dose-dependent (500, 1000, 2500, 5000 and 10,000 ng ET-1/kg vs. NaCl controls) hemodynamic and inotropic effects of ET-1 in 53 open-chest rats during and after a 7-min infusion. Besides measurements in the intact circulation the myocardial function was examined by isovolumic registrations independent of peripheral vascular effects. A transient ET-1 induced (500, 1000, 2500, 5000 ng ET-1/kg) decrease of the left ventricular systolic pressure (LVSP) and the mean aortic pressure (AoPmean) was followed by a dose-related rise of these pressures (LVSP: -1%, -1%, +8%, +16% vs. preinfusion values; AoPmean: -11%, +9%, +39%, +52%). Heart rate (HR) was not influenced by ET-1. Due to the dose-dependent decrease of the stroke volume (SV) the cardiac output (CO) was reduced (CO: -8%, -23%, -40%, -50%). After an initial vasodilatation ET-1 elevates the total peripheral resistance (TPR: -1%, +49%, +139%, +215%) dose-dependently. 10,000 ng ET-1/kg was a lethal dose resulting in cardiac failure within minutes (low output). Since the maximum of the isovolumic LVSP (peak LVSP) and the corresponding dP/dtmax (peak dP/dtmax) were unchanged under ET-1, the isovolumic measurements do not indicate a positive inotropic effect of ET-1 in vivo in contrast to published results of in vitro experiments. It may be possible that a direct positive inotropic effect of ET-1 observed in in vitro studies is counterbalanced in vivo by an indirect negative inotropic effect due to the coronary-constrictive effect of ET-1

Energiegefilterte Rückstreuelektronen-Abbildung und -Spektroskopie im Rasterelektronenmikroskop

Das Ziel dieser Arbeit war die Entwicklung eines neuen Abbildungs- und Analyseverfahrens für den Einsatz im Rasterelektronenmikroskop. Es basiert auf der Bandpaßenergiefilterung der Rückstreuelektronen mit Hilfe eines energiedispersiven toroidalen Sektorfeld-Spektrometers. Dieses ermöglichte neben der Aufnahme von Rückstreuelektronenspektren, die Abbildung mit Hilfe von Rückstreuelektronen, die bezüglich ihrer Energie bandpaßgefiltert sind. Dadurch wurde eine tiefenselektive Abbildung eines Objektes im SEM möglich, die zerstörungsfrei ist und eine laterale Auflösung in der Größenordnung von konventionellen BSE-Abbildungen liefert. Die theoretische Grundlage ist die elastische Streuung und der kontinuierliche Energieverlust der Rückstreuelektronen auf ihrem Weg durch das Objekt. Durch die Untersuchung der Winkel-, Energie- und Austrittstiefenverteilungen der Rückstreuelektronen mit Hilfe von Monte-Carlo Simulationen konnte gezeigt werden, daß durch das Setzen entsprechender Energiefenster in das Spektrum der BSE selektiv einzelne Tiefen von Mehrfachschichtobjekten abgebildet werden können

Probing the centre of the large circumstellar disc in M17

We investigated the nature of the hitherto unresolved elliptical infrared emission in the centre of the ~20000 AU disc silhouette in M 17. We combined high-resolution JHKsL'M' band imaging carried out with NAOS/CONICA at the VLT with [Fe II] narrow band imaging using SOFI at the NTT. The analysis is supported by Spitzer/GLIMPSE archival data and by already published SINFONI/VLT Integral Field Spectroscopy data. For the first time, we resolve the elongated central infrared emission into a point-source and a jet-like feature that extends to the northeast in the opposite direction of the recently discovered collimated H2 jet. They are both orientated almost perpendicular to the disc plane. In addition, our images reveal a curved southwestern emission nebula whose morphology resembles that of the previously detected northeastern one. Both nebulae are located at a distance of 1500 AU from the disc centre. We describe the infrared point-source in terms of a protostar that is embedded in circumstellar material producing a visual extinction of 60 <= Av <= 82. The observed Ks band magnitude is equivalent to a stellar mass range of 2.8 Msun <= Mstar <= 8 Msun adopting conversions for a main-sequence star. Altogether, we suggest that the large M 17 accretion disc is forming an intermediate to high-mass protostar. Part of the accreted material is expelled through a symmetric bipolar jet/outflow.Comment: 6 pages, 3 figures, accepted by MNRAS (16 May 2008

Real-time Monitoring of High-speed Spindle Operations Using Infrared Data Transmission

AbstractHigh-performance cutting is carried out with high cutting and feed speeds. Particularly, the use of heavy cutting tools (e.g. in planing machines), it is important to monitor the clamping and balance condition of the mounted tool, as well as the process forces. Therefore, a real-time monitoring system for high-speed operations based on the IrDA protocol was developed. It could be shown that infrared data transmission systems allow shorter reaction times compared to conventional wireless LAN applications. The presented monitoring system provides a reaction time of 7.14 ms at a bandwidth of 42.5 kHz and a data rate of 4.1 MBit/s

Mirroring E-service for Brick and Mortar Retail: An Assessment and Survey

The digital transformation increasingly impacts the competitive retail market structure in favor of e-commerce and digital business models, while many Brick and Mortar (BaM) retailers are struggling to meet customers’ expectations. Supported by the customer adaption of e-commerce and digital technologies, this paper applies the lens of channel complementary theory to BaM. We examine, which e-service touchpoints from e-commerce can be transferred to the physical servicescape of BaM retail to complement customer journeys. Drawing from the dominant design theory, we first assess leading e-commerce solutions to identify dominant e-service touchpoints, which are then mirrored for their application in BaM retail. Second, we surveyed 250 shoppers to elicit the likeliness of use regarding these touchpoints. Our results provide a foundation for both academia and retail to advance the knowledge of relevant e-service touchpoints in BaM