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Assessment of the tissue distribution of transplanted human endothelial progenitor cells by radioactive labeling
Background— Transplantation of endothelial progenitor cells (EPCs) improves vascularization and left ventricular function after experimental myocardial ischemia. However, tissue distribution of transplanted EPCs has not yet been monitored in living animals. Therefore, we tested whether radioactive labeling allows us to detect injected EPCs
Cutting simulation with consideration of the material hardening in the Shear Zone of AISI1045
By the use of high energy synchrotron X-ray diffraction it was possible to determine the stress state in the chip formation zone during orthogonal cutting of AISI1045. The analysis of the diffractograms showed a hardening of the material during the movement through the shear zone. For this reason nano indentation experiments on prepared chips have been carried out. With these experiments, the material hardening has been confirmed. The nano indentation experiments were reproduced by FEM simulations and it was possible to determine flow curves of the hardened material above the shear zone based on existing flow curves of AISI1045. Thus, cutting simulations have been carried out, which considered the material hardening in the shear zone. The simulation results were then compared with the results of the in-situ strain measurements
J004457+4123 (Sharov 21): not a remarkable nova in M31 but a background quasar with a spectacular UV flare
We announce the discovery of a quasar behind the disk of M31, which was
previously classified as a remarkable nova in our neighbour galaxy. The paper
is primarily aimed at the outburst of J004457+4123 (Sharov 21), with the first
part focussed on the optical spectroscopy and the improvement in the
photometric database. Both the optical spectrum and the broad band spectral
energy distribution of Sharov 21 are shown to be very similar to that of
normal, radio-quiet type 1 quasars. We present photometric data covering more
than a century and resulting in a long-term light curve that is densely sampled
over the past five decades. The variability of the quasar is characterized by a
ground state with typical fluctuation amplitudes of ~0.2 mag around B~20.5,
superimposed by a singular flare of ~2 yr duration (observer frame) with the
maximum at 1992.81 where the UV flux has increased by a factor of ~20. The
total energy in the flare is at least three orders of magnitudes higher than
the radiated energy of the most luminous supernovae, provided that it comes
from an intrinsic process and the energy is radiated isotropically. The profile
of the flare light curve appears to be in agreement with the standard
predictions for a stellar tidal disruption event where a ~10 M_sun giant star
was shredded in the tidal field of a ~2...5 10^8 M_sun black hole. The short
fallback time derived from the light curve requires an ultra-close encounter
where the pericentre of the stellar orbit is deep within the tidal disruption
radius. Gravitational microlensing provides an alternative explanation, though
the probability of such a high amplification event is very low.Comment: Accepted for publication in Astronomy and Astrophysics, 14 pages, 11
figure
Die Auswirkungen von Stickstoffmangel auf die Genomevolution in Escherichia coli
Bakterien nehmen Nährstoffe aus ihrer Umgebung auf und nutzen diese für die de novo Synthese von Aminosäuren, Nukleotiden und anderen Biomolekülen. Stickstoff, ein wesentlicher Bestandteil von Biomolekülen, ist oft ein limitierender Faktor für das Wachstum in Ökosystemen. Die vorliegende Studie zeigt, dass Proteine, die in die Stickstoff-Stressantwort von Escherichia coli involviert sind,eine reduzierte Anzahl an stickstoffreichen Aminosäuren aufweisen. Zudem führte andauernder Stickstoffmangel in kontinuierlichen E. coli Kulturen zu weiteren Reduktionen des Stickstoffbedarfs von Proteinen durch Änderungen der Genexpression. Die Adaption an den persistenten Stickstoffmangel erhöhte außerdem die Fitness der Bakterien unter diesen Nährstoffbedingungen. Die vorliegenden Daten sind von grosser Bedeutung für die Quantfizierung der Stärke des durch Stickstoffmangel ausgelösten Selektionsdruckes auf die molekulare Evolution von E. coli
A phenomenological model for the X-ray spectrum of Nova V2491 Cygni
The X-ray flux of Nova V2491 Cyg reached a maximum some forty days after
optical maximum. The X-ray spectrum at that time, obtained with the RGS of
XMM-Newton, shows deep, blue-shifted absorption by ions of a wide range of
ionization. We show that the deep absorption lines of the X-ray spectrum at
maximum, and nine days later, are well described by the following
phenomenological model with emission from a central blackbody and from a
collisionally ionized plasma (CIE). The blackbody spectrum (BB) is absorbed by
three main highly-ionized expanding shells; the CIE and BB are absorbed by cold
circumstellar and interstellar matter that includes dust. The outflow density
does not decrease monotonically with distance. The abundances of the shells
indicate that they were ejected from an O-Ne white dwarf. We show that the
variations on time scales of hours in the X-ray spectrum are caused by a
combination of variation in the central source and in the column density of the
ionized shells. Our phenomenological model gives the best description so far of
the supersoft X-ray spectrum of nova V2491 Cyg, but underpredicts, by a large
factor, the optical and ultraviolet flux. The X-ray part of the spectrum must
originate from a very different layer in the expanding envelope, presumably
much closer to the white dwarf than the layers responsible for the
optical/ultraviolet spectrum. This is confirmed by absence of any correlation
between the X-ray and UV/optical observed fluxes.Comment: 11 pages, 6 figure
A remarkable recurrent nova in M 31: The predicted 2014 outburst in X-rays with Swift
The M 31 nova M31N 2008-12a was recently found to be a recurrent nova (RN)
with a recurrence time of about 1 year. This is by far the fastest recurrence
time scale of any known RNe. Our optical monitoring programme detected the
predicted 2014 outburst of M31N 2008-12a in early October. We immediately
initiated an X-ray/UV monitoring campaign with Swift to study the
multiwavelength evolution of the outburst. We monitored M31N 2008-12a with
daily Swift observations for 20 days after discovery, covering the entire
supersoft X-ray source (SSS) phase. We detected SSS emission around day six
after outburst. The SSS state lasted for approximately two weeks until about
day 19. M31N 2008-12a was a bright X-ray source with a high blackbody
temperature. The X-ray properties of this outburst were very similar to the
2013 eruption. Combined X-ray spectra show a fast rise and decline of the
effective blackbody temperature. The short-term X-ray light curve showed
strong, aperiodic variability which decreased significantly after about day 14.
Overall, the X-ray properties of M31N 2008-12a are consistent with the average
population properties of M 31 novae. The optical and X-ray light curves can be
scaled uniformly to show similar time scales as those of the Galactic RNe U Sco
or RS Oph. The SSS evolution time scales and effective temperatures are
consistent with a high-mass WD. We predict the next outburst of M31N 2008-12a
to occur in autumn 2015.Comment: 13 pages, 7 figures, 3 tables; accepted for publication in A&
Discovery of a new photometric sub-class of faint and fast classical novae
We present photometric and spectroscopic follow-up of a sample of
extragalactic novae discovered by the Palomar 60-inch telescope during a search
for "Fast Transients In Nearest Galaxies" (P60-FasTING). Designed as a fast
cadence (1-day) and deep (g < 21 mag) survey, P60-FasTING was particularly
sensitive to short-lived and faint optical transients. The P60-FasTING nova
sample includes 10 novae in M31, 6 in M81, 3 in M82, 1 in NGC2403 and 1 in
NGC891. This significantly expands the known sample of extragalactic novae
beyond the Local Group, including the first discoveries in a starburst
environment. Surprisingly, our photometry shows that this sample is quite
inconsistent with the canonical Maximum Magnitude Rate of Decline (MMRD)
relation for classical novae. Furthermore, the spectra of the P60-FasTING
sample are indistinguishable from classical novae. We suggest that we have
uncovered a sub-class of faint and fast classical novae in a new phase space in
luminosity-timescale of optical transients. Thus, novae span two orders of
magnitude in both luminosity and time. Perhaps, the MMRD, which is
characterized only by the white dwarf mass, was an over-simplification. Nova
physics appears to be characterized by quite a rich four-dimensional parameter
space in white dwarf mass, temperature, composition and accretion rate.Comment: Submitted to ApJ, 12 pages. High resolution version at
http://www.astro.caltech.edu/~mansi/msFasting.pd
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