Experimental studies on the “Phantom Yaw Effect” at maneuvering slender bodies

Asymmetric vortices can occur unexpectedly on slender bodies at high angles of attack. These vortices separating from the nose or/and shoulder region induce a side force and also a corresponding yawing moment often referred to as "phantom yaw". In the last decades, there have been many experimental and also numerical studies on this phenomenon. The aim was to understand this effect and to find the in fluencing parameters. There have also been investigations on using the asymmetric vortices for control purposes in addition to the fins. Despite this, another target of research has been the suppression of the vortex inducing side forces and yawing moments in order to increase the stability of e.g. a missile in a maneuver. Most of the wind tunnel tests have been done without model motion at several but fixed angles of attack. Since slender bodies as missiles achieve these high angles of attack via very rapid pitching maneuvers, the model motion is supposed to have some impact on the test results. One reason for the lack of dynamic test data at high Reynolds numbers are high inertial and aerodynamical forces acting on the test model and it's support. They result in contradicting design issues. On the one hand, the support needs to be stiff to withstand all forces and moments and on the other hand, the aerodynamic behaviour of the model shall not be changed by the support. Nonetheless, a maneuver simulator has been built at the DLR Goettingen. By means of this device, wind tunnel tests in a transonic wind tunnel at high Mach and Reynolds numbers, pitching rates of up to omega = 700°/s and pitching maneuvers from alpha = 0 ... 45° have been done. We compared the "phantom yaw"' emergence at a clean configuration with the ones at a configuration housing a pair of symmetric longitudinal slot nozzles which were fed by natural ventilation. The results showed a yawing moment for the clean configuration at angles of attack higher than alpha = 38°. They also showed that the jet flow through the slot nozzles successfully suppressed the yawing moment by causing a fixed separation. Differences between static and dynamic tests could be seen as well

Materielle Dimensionen von Geschlecht an der Ganztagsschule. Eine ethnographische Einzelfallstudie

Die Geschlechtersozialisation von Schüler:innen wird hinsichtlich ihrer materiellen Dimensionen fokussiert und in ein Verhältnis zur Schulkultur der aufgesuchten Ganztagsschule gesetzt. Es zeigen sich soziomaterielle Verschränkungen von Körpern, Räumen und Dingen in gendered performances als sozialisatorische Praxis von Geschlecht. Geschlechterpraktiken in Klasse 5 und 9 verweisen als klassenverbandsspezifische Aufführungen auf die Verfestigung von Geschlecht und die graduelle Relevanz von Materialität. Die ethnographische Forschungsausrichtung schärft den soziomateriellen Blick auf Schule und Geschlecht sowie die Perspektive der Schüler:innen. (DIPF/Orig.

Preprosubtilisin Carlsberg processing and secretion is blocked after deletion of amino acids 97-101 in the mature part of the enzyme

During an investigation into the substrate specificity and processing of subtilisin Carlsberg from Bacillus licheniformis, two major independent findings were made: (i) as has been shown previously, a stretch of five amino acids (residues 97-101 of the mature enzyme) that loops out into the binding cleft is involved in substrate binding by subtilisin Carlsberg. In order to see whether this loop element also determines substrate specificity, the coding region for these five amino acids was deleted from the cloned gene for subtilisin Carlsberg by site-directed mutagenesis. Unexpectedly the resulting mutant preproenzyme (P42c, Mr=42 kDa) was not processed to the mature form (Mr = 30 kDa) and was not released into the medium by a proteasedeficient B. subtilis host strain; rather, it accumulated in the cell membrane. This result demonstrates that the integrity of this loop element, which is very distant from the processing cleavage sites in the preproenzyme, is required for secretion of subtilisin Carlsberg. (ii) In culture supernatants from B. subtilis harbouring the cloned wild-type subtilisin Carlsberg gene the transient appearance (at 0-3 h after onset of stationary phase) of a processing intermediate (P38c, Mr = 38 kDa) oftbis protease could be demonstrated. P38c very probably represents a genuine proform of subtilisin Carlsberg

Cascaded exciton emission of an individual strain-induced quantum dot

Single strain-induced quantum dots are isolated for optical experiments by selective removal of the inducing InP islands from the sample surface. Unpolarized emission of single, bi- and triexciton transitions are identified by power-dependent photoluminescence spectroscopy. Employing time-resolved experiments performed at different excitation powers we find a pronounced shift of the rise and decay times of these different transitions as expected from cascaded emission. Good agreement is found for a rate equation model for a three step cascade

Direct observation of dynamic surface acoustic wave controlled carrier injection into single quantum posts using phase-resolved optical spectroscopy

A versatile stroboscopic technique based on active phase-locking of a surface acoustic wave to picosecond laser pulses is used to monitor dynamic acoustoelectric effects. Time-integrated multi-channel detection is applied to probe the modulation of the emission of a quantum well for different frequencies of the surface acoustic wave. For quantum posts we resolve dynamically controlled generation of neutral and charged excitons and preferential injection of holes into localized states within the nanostructure.Comment: 10 pages, 4 figure

Zur praktischen Relevanz des Institutionsbegriffs

'Auf dem Hintergrund der allgemeinen Schwierigkeiten sozialwissenschaftlicher Theorie, ihren (vielschichtigen, widersprüchlichen, dynamischen) Gegenstand zu erfassen, wird versucht, eine allgemeine Konzeption des Institutionsbegriffs zu umreißen. Dabei werden Institutionen als stabile Relationen in einem dynamischen Kontext gesehen, wobei die Hervorhebung als Institution auch von der Bezugsperspektive abhängig ist. In der Folge werden Phasen des Institutionalisierungsprozesses, das Funktionsniveau von Institutionen, ihr produktiver und reproduktiver Prozess, Formen und Typen ihres Operierens und themenspezifische Aspekte ihrer Praxis diskutiert.' (Autorenreferat)'After a short look at the principal difficulties of social sciences focussing a contradictory, changing and moving target, the article tries to develop a general concept of institutions. Institutions are defined as stable relations in a dynamic context. What is emphasized as institution depends to a certain degree on the frame of reference. Following this, certain aspects of institutions are analyzed: the process of institutionalization, the level of functioning, productive and reproductive functions, forms and types of operating and the effect of topics on institutions.' (author's abstract

Combined electrical transport and capacitance spectroscopy of a MoS2−LiNbO3{\mathrm{MoS_2-LiNbO_3}} field effect transistor

We have measured both the current-voltage ($I_\mathrm{SD}$-$V_\mathrm{GS}$) and capacitance-voltage ($C$-$V_\mathrm{GS}$) characteristics of a $\mathrm{MoS_2-LiNbO_3}$ field effect transistor. From the measured capacitance we calculate the electron surface density and show that its gate voltage dependence follows the theoretical prediction resulting from the two-dimensional free electron model. This model allows us to fit the measured $I_\mathrm{SD}$-$V_\mathrm{GS}$ characteristics over the \emph{entire range} of $V_\mathrm{GS}$. Combining this experimental result with the measured current-voltage characteristics, we determine the field effect mobility as a function of gate voltage. We show that for our device this improved combined approach yields significantly smaller values (more than a factor of 4) of the electron mobility than the conventional analysis of the current-voltage characteristics only.Comment: to appear in Applied Physics Letter