A simple optimized amplitude pupil mask for attempting to direct imaging of Proxima b with SPHERE/ZIMPOL at VLT

Proxima b is a terrestrial exoplanet orbiting in the habitable zone of our closest star Proxima Centauri. The separation between the planet and the star is about 40 mas and this is with current instruments only reachable with direct imaging, using a visual extreme AO system like SPHERE/ZIMPOL. Unfortunately, the planet falls under the first airy ring at 2$\lambda$/D in the I band, which degrades achievable contrast. We present the design, optical simulations and testing of an amplitude pupil mask for ZIMPOL that reshapes the PSF, increasing the contrast at $r = 2\lambda$/D about an order of magnitude. The simple mask can be inserted directly into the current setup of SPHERE.Comment: 11 pages, 8 figures, Poster presented at SPIE Astronomical Telescopes and Instrumentation 201

CEO Turnover and Director Reputation

This paper analyzes the reputational effects of forced CEO turnovers on outside directors. Directors interlocked to a forced CEO turnover experience large and persistent increases in withheld votes at subsequent re-elections relative to non-turnover-interlocked directors. Reputational losses are larger for turnovers with a higher potential for disrupting a firm's management, for directors favorably inclined to the CEO, and for directors with a committee-based responsibility for monitoring the CEO. Our results imply that the average forced CEO turnover signals a governance failure at the board level, and that shareholders rely on salient actions to update their beliefs about directors' hidden qualities

Bewertung des Potentials optimierter „Midpassage-Gap“-Spaltgeometrien zur Kühlung der ersten Turbinenleitreihe: Infrarotthermographie unter hohen Sichtwinkeln

Gasturbinen und Flugtriebwerke haben im Energie- und Mobilitätssektor eine große Bedeutung, welche in Zukunft noch weiter zunehmen wird. Um bei dieser Zunahme die Klimaziele einhalten zu können, sind eine weitere Steigerung des Wirkungsgrades sowie eine Senkung der Emissionen unumgänglich. Eine Steigerung des Wirkungsgrades lässt sich unter anderem durch die Erhöhung der Turbineneintrittstemperatur erreichen. Durch fortschrittliche Verbrennungskonzepte können die Stickoxidemissionen reduziert werden. Beide Maßnahmen führen jedoch zu einer deutlichen Zunahme der thermischen Belastung im seitenwandnahen Bereich der Turbine. Dies erfordert eine Intensivierung der Kühlung um ein Versagen der Bauteile auszuschließen. Um die Kühlwirkung ohne den zusätzlichen Einsatz von Kühlluft effizient zu steigern, rückt eine gezielte Nutzung der aus fertigungsbedingten Spalten ausgeblasenen Sperrluft zu Kühlzwecken mehr und mehr in den Fokus der Forschung. Im Rahmen dieser Arbeit wurde der fertigungsbedingte Spalt zwischen zwei Schaufelsegmenten, welcher auch als Midpassage-Gap bezeichnet wird, experimentell unter maschinenähnlichen Bedingungen thermisch untersucht. Um das Kühlpotential im kompletten seitenwandnahen Bereich untersuchen zu können, wurde im Rahmen der Arbeit die Weiterentwicklung eines Kalibrierverfahrens für Infrarotaufnahmen erforderlich. Damit sind nun verwertbare Messungen auch bei sehr großen Sichtwinkeln von bis zu 75° möglich. Die Ergebnisse der Arbeit zeigen, dass die aus besagtem Spalt ausgeblasene Sperrluft das Potential hat, neben dem saugseitigen Bereich der Seitenwand auch den seitenwandnahen Bereich der Schaufelsaugseite zu kühlen. Eine Variation der Spaltgeometrie hebt das Potential aber auch die Grenzen der Kühlwirkung der aus dem Midpassage-Gap ausgeblasenen Sperrluft hervor und gibt einen Einblick in die komplexe Interaktion zwischen Heißgas und Sperrluft. Die Daten stellen eine wertvolle Basis für die Auslegung und Optimierung des Kühlkonzepts zukünftiger Maschinen dar

Digital DC-Reconstruction of AC-Coupled Electrophysiological Signals with a Single Inverting Filter

Since the introduction of digital electrocardiographs, high-pass filters have been necessary for successful analog-to-digital conversion with a reasonable amplitude resolution. On the other hand, such high-pass filters may distort the diagnostically significant ST-segment of the ECG, which can result in a misleading diagnosis. We present an inverting filter that successfully undoes the effects of a 0.05 Hz single pole high-pass filter. The inverting filter has been tested on more than 1600 clinical ECGs with one-minute durations and produces a negligible mean RMS-error of 3.1*10(-8) LSB. Alternative, less strong inverting filters have also been tested, as have different applications of the filters with respect to rounding of the signals after filtering. A design scheme for the alternative inverting filters has been suggested, based on the maximum strength of the filter. With the use of the suggested filters, it is possible to recover the original DC-coupled ECGs from AC-coupled ECGs, at least when a 0.05 Hz first order digital single pole high-pass filter is used for the AC-coupling

[NEt3Me][O3], Synthesis, Crystal Growth and Crystal Structure Analysis

[NEt3Me][O3] was obtained for the first time by an ion exchange reaction in liquid ammonia. It was thoroughly characterized by X‐Ray diffraction [P21; a=598.51(4) pm, b=1032.03(7) pm, c=723.83(6) pm, β=92.677(3)°, R=0.0384, 15070 reflections] applying non‐spherical and spherical atomic form factors for the refinements. In contrast to previous reported ozonides, [NEt3Me][O3] is the first to adopt the tungsten carbide (WC) motif of cation/ anion arragemnent and shows an untypical hydrogen bond between the central oxygen atom of the ozonide and the cation. Additionally, IR spectroscopy as well as quantum‐chemical calculations were applied to further characterize the compound. The obtained ozonide showed high solubility in ammonia as well as acetonitrile and good properties as a synthon in ozonide chemistry

Growth hormone, but not insulin-like growth factor I, induces a serum protease activity for insulin-like growth factor binding protein-3 in hypophysectomized rats in vivo

AbstractInsulin-like growth factor binding proteins (IGFBPs) modulate IGF action. Proteolytic cleavage of IGFBPs yields lower molecular forms with reduced ability to bind IGFs, thereby increasing IGF bioavailability. In serum from normal adult rats, we found a proteolytic activity for IGFBP-3, presumably a cation-dependent serine protease. It is lacking in serum from hypophysectomized rats and restored by infusion of growth hormone (GH), but not IGF I. Thus, IGF I does not appear to mediate the GH effect on IGFBP-3 proteolysis. Rather, GH seems to modulate IGF action indirectly via alteration of IGFBP-3 structure

Conductivity and Redox Potentials of Ionic Liquid Trihalogen Monoanions [X3]−, [XY2]−, and [BrF4]− (X=Cl, Br, I and Y=Cl, Br)

The ionic liquid (IL) trihalogen monoanions [N2221][X3]− and [N2221][XY2]− ([N2221]+=triethylmethylammonium, X=Cl, Br, I, Y=Cl, Br) were investigated electrochemically via temperature dependent conductance and cyclic voltammetry (CV) measurements. The polyhalogen monoanions were measured both as neat salts and as double salts in 1‐butyl‐1‐methyl‐pyrrolidinium trifluoromethane‐sulfonate ([BMP][OTf], [X3]−/[XY2]− 0.5 M). Lighter IL trihalogen monoanions displayed higher conductivities than their heavier homologues, with [Cl3]− being 1.1 and 3.7 times greater than [Br3]− and [I3]−, respectively. The addition of [BMP][OTf] reduced the conductivity significantly. Within the group of polyhalogen monoanions, the oxidation potential develops in the series [Cl3]−>[BrCl2]−>[Br3]−>[IBr2]−>[ICl2]−>[I3]−. The redox potential of the interhalogen monoanions was found to be primarily determined by the central halogen, I in [ICl2]− and [IBr2]−, and Br in [BrCl2]−. Additionally, tetrafluorobromate(III) ([N2221]+[BrF4]−) was analyzed via CV in MeCN at 0 °C, yielding a single reversible redox process ([BrF2]−/[BrF4]−)