94 research outputs found
Comparison of aerodynamic coefficients obtained from theoretical calculations wind tunnel tests and flight tests data reduction for the alpha jet aircraft
The methods by which aerodynamic coefficients are determined and discussed. These include: calculations, wind tunnel experiments and experiments in flight for various prototypes of the Alpha Jet. A comparison of obtained results shows good correlation between expectations and in-flight test results
Search for short-period acoustic waves with high resolution 2D-spectra
The data for this contributionw ere takeninAugust 2000 with the “G¨ottingen” two-dimensional spectrometer in the VTT on Tenerife. Our spectrometer is based on two scanning
Fabry-Perot Interferometers (FPIs). The non-magnetic Fe I 5434˚A line was observed in the quiet Sun at disk center. Time sequences of 41 min duration and with 25 s cadence were taken. Strictly simultaneously with the narrow-band FPI images (32m˚A FWHM), broad-band images were recorded. The latter were reconstructed with speckle methods. With the known “true” broad-band object we are able to restore the narrow-band images as well. Our aim is to find
propagating acoustic waves at short periods and small scales. The results obtained so far are presented and the prospects are discussed
Dynamics of the solar chromosphere. V. High-frequency modulation in ultraviolet image sequences from TRACE
We search for signatures of high-frequency oscillations in the upper solar
photosphere and low chromosphere in the context of acoustic heating of outer
stellar atmospheres. We use ultraviolet image sequences of a quiet center-disk
area from the Transition Region and Coronal Explorer (TRACE) mission which were
taken with strict cadence regularity. The latter permits more reliable
high-frequency diagnosis than in earlier work. Spatial Fourier power maps,
spatially averaged coherence and phase-difference spectra, and spatio-temporal
k-f decompositions all contain high-frequency features that at first sight seem
of considerable intrinsic interest but actually are more likely to represent
artifacts of different nature. Spatially averaged phase difference measurement
provides the most sensitive diagnostic and indicates the presence of acoustic
modulation up to f=20 mHz (periods down to 50 seconds) in internetwork areas.Comment: 9 pages, 8 figure
Doppler shift oscillations in solar spicules
Consecutive height series of Ha spectra in solar limb spicules taken on the
53 cm coronagraph of Abastumani Astrophysical Observatory at the heights of
3800-8700 km above the photosphere have been analyzed. The aim is to observe
oscillatory phenomena in spicules and consequently to trace wave propagations
through the chromosphere. The Discrete Fourier Transform analysis of Ha Doppler
shift time series constructed from the observed spectra at each height is used.
Doppler velocities of solar limb spicules show oscillations with periods of
20-55 and 75-110 s. There is also the clear evidence of 3-min oscillations at
the observed heights. The oscillations can be caused by wave propagations in
thin magnetic flux tubes anchored in the photosphere. We suggest the
granulation as a possible source for the wave excitation. Observed waves can be
used as a tool for spicule seismology; the magnetic field strength in spicules
at the height of about 6000 km above the photosphere is estimated as 12-15 G.Comment: 7 pages, 8 figures, accepted in A&
The Position of High Frequency Waves with Respect to the Granulation Pattern
High frequency velocity oscillations were observed in the spectral lines Fe I
543.45nm and 543.29nm, using 2D spectroscopy with a Fabry- Perot and speckle
reconstruction, at the VTT in Tenerife. We investigate the radial component of
waves with frequencies in the range 8 - 22mHz in the internetwork, network and
a pore. We find that the occurrence of waves do not show any preference on
location and are equally distributed over down-flows and up-flows, regardless
of the activity of the observed area in the line of Fe I 543.45nm. The waves
observed in the lower formed line of Fe I 543.29nm seem to appear
preferentially over down-flows.Comment: Article has 12 pages and 7 images. It is accepted in Solar Physics
Journa
Inter-Network magnetic fields observed during the minimum of the solar cycle
We analyze a time series of high angular resolution magnetograms of quiet Sun
Inter-Network (IN) magnetic fields. These magnetograms have a spatial
resolution better than 0.5 arcsec, a noise of some 20 G, and they have been
obtained at the disk center during the minimum of the solar cycle. The IN
regions show a typical unsigned flux density of the order of 15 G. Signals
occur, preferentially, in the intergranular lanes, and the strongest signals
trace a network with a scale similar to the mesogranulation. All these features
are consistent with the IN magnetograms by Dominguez Cernena et al., obtained
during the maximum of the solar cycle. Consequently, the unsigned magnetic flux
of the structures that give rise to the IN polarization signals does not seem
to undergo large variations during the solar cycle.Comment: Accepted for publication in A&A. 7 Pages . 6 Figure
The RhoA GEF Syx Is a Target of Rnd3 and Regulated via a Raf1-Like Ubiquitin-Related Domain
Background: Rnd3 (RhoE) protein belongs to the unique branch of Rho family GTPases that has low intrinsic GTPase activity and consequently remains constitutively active [1,2]. The current consensus is that Rnd1 and Rnd3 function as important antagonists of RhoA signaling primarily by activating the ubiquitous p190 RhoGAP [3], but not by inhibiting the ROCK family kinases. Methodology/Principal Findings: Rnd3 is abundant in mouse embryonic stem (mES) cells and in an unbiased two-step affinity purification screen we identified a new Rnd3 target, termed synectin-binding RhoA exchange factor (Syx), by mass spectrometry. The Syx interaction with Rnd3 does not occur through the Syx DH domain but utilizes a region similar to the classic Raf1 Ras-binding domain (RBD), and most closely related to those in RGS12 and RGS14. We show that Syx behaves as a genuine effector of Rnd3 (and perhaps Rnd1), with binding characteristics similar to p190-RhoGAP. Morpholinooligonucleotide knockdown of Syx in zebrafish at the one cell stage resulted in embryos with shortened anterior-posterior body axis: this phenotype was effectively rescued by introducing mouse Syx1b mRNA. A Rnd3-binding defective mutant of Syx1b mutated in the RBD (E164A/R165D) was more potent in rescuing the embryonic defects than wild-type Syx1b, showing that Rnd3 negatively regulates Syx activity in vivo. Conclusions/Significance: This study uncovers a well defined Rnd3 effector Syx which is widely expressed and directl
Dilemma an der Grenze zwischen Belarus und Polen: Völkerrechtliche Tagesthemen 20
Ein Autokrat auf der einen und ein wankender Rechtsstaat auf der anderen Seite: An der polnisch-belarussischen EU-Außengrenze treffen menschenverachtende Praktiken auf den scheinbaren Widerwillen der EU-Mitgliedsstaaten, eine schnellstmögliche Abhilfe zu schaffen. Dieses gesellschaftliche und menschliche Dilemma erscheint auch bei rechtlicher Betrachtung einer einfachen Handhabung nur schwer zugänglich: Was geschieht, wenn es geflüchteten Menschen gelingt, das Territorium eines EU-Staates zu betreten? Ab wann übt ein Staat eigentlich Hoheitsgewalt aus, so dass er sich am Recht der EMRK messen lassen muss? Was bedeutet „Push-Back“ in diesem Zusammenhang? Kann Polen seine Grenze vollständig abriegeln? Welche Maßnahmen kann die EU treffen, um dem Dilemma ein Ende zu setzen? Im Rahmen der Völkerrechtlichen Tagesthemen wird sich der Referent Joschka Peters-Wunnenberg, LL.M. (Amsterdam) diesen und weiteren spannenden Fragen widmen
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