413 research outputs found
Invasive intrauterine Therapie
Zusammenfassung: Einige fetale Fehlbildungen fĂŒhren bereits intrauterin zu OrganschĂ€den, die postpartal schwere bleibende Behinderungen zur Folge haben oder nicht mit dem Leben vereinbar sind. Fetale Eingriffe verlangen eine sichere prĂ€natale Diagnosestellung, Ausschluss assoziierter Fehlbildungen, ReversibilitĂ€t der schĂ€dlichen Krankheitseffekte und deutliche Verbesserung der Prognose durch den fetalen Eingriff an dafĂŒr spezialisierten multidisziplinĂ€ren Therapiezentren. In der invasiven fetalen Therapie wird sowohl offen, wie bei der fetalen Myelomeningozelen(MMC)-Operation, als auch fetoskopisch operiert. Zu nennen sind z.B. die reversible fetoskopische Balloneinlage in die Trachea zur Stimulation des Lungenwachstums bei der kongenitalen Zwerchfellhernie des Feten mit schwerer Lungenhypoplasie oder die Laserkoagulation plazentarer GefĂ€Ăverbindungen zum Stopp eines unausgeglichenen Blutflusses beim fetofetalen Transfusionssyndrom (FFTS). Hauptkomplikation der fetalen Chirurgie ist der vorzeitige Blasensprun
Exchange Interactions and High-Energy Spin States in Mn_12-acetate
We perform inelastic neutron scattering measurements on the molecular
nanomagnet Mn_12-acetate to measure the excitation spectrum up to 45meV (500K).
We isolate magnetic excitations in two groups at 5-6.5meV (60-75K) and
8-10.5meV (95-120K), with higher levels appearing only at 27meV (310K) and
31meV (360K). From a detailed characterization of the transition peaks we show
that all of the low-energy modes appear to be separate S = 9 excitations above
the S = 10 ground state, with the peak at 27meV (310K) corresponding to the
first S = 11 excitation. We consider a general model for the four exchange
interaction parameters of the molecule. The static susceptibility is computed
by high-temperature series expansion and the energy spectrum, matrix elements
and ground-state spin configuration by exact diagonalization. The theoretical
results are matched with experimental observation by inclusion of cluster
anisotropy parameters, revealing strong constraints on possible parameter sets.
We conclude that only a model with dominant exchange couplings J_1 ~ J_2 ~
5.5meV (65K) and small couplings J_3 ~ J_4 ~ 0.6meV (7K) is consistent with the
experimental data.Comment: 17 pages, 12 figure
Age and environment affect constitutive immune function in Red Knots (Calidris canutus)
We studied subspecies, age and environmental effects on constitutive immune function (natural antibody and complement titres, haptoglobin activity and leukocyte concentrations) in Red Knots (Calidris canutus). We compared C. c. islandica and C. c. canutus in the Wadden Sea and found no difference in immune function between subspecies. However, C. c. canutus on their wintering grounds in Banc dâArguin had higher natural antibody and lower complement levels than C. c. canutus or C. c. islandica in the Wadden Sea. This suggests that immune function is determined more by the surrounding environment than by subspecies. We also compared age classes in the Wadden Sea and found that first year birds had significantly lower natural antibody levels than adults, but that second year birds no longer differed from adults. Finally, we examined the interaction of age and environment in Banc dâArguin. We found that first year birds (but not adults) in a low quality habitat had higher leukocyte concentrations than first year birds or adults in a high quality habitat. Differences in available resources and defence needs between environments, and differences among individuals differentially distributed between sites, are likely important contributors to the variation in immune function we report. Future studies, which examine these factors on wild birds, will be important for our understanding of how animals function in their natural environment.
Multi-Conjugate Adaptive Optics images of the Trapezium Cluster
Multi-Conjugate Adaptive Optics (MCAO) combines the advantages of standard
adaptive optics, which provides high contrast and high spatial resolution, and
of wide field ~1' imaging. Up to recently, MCAO for astronomy was limited to
laboratory experiments. In this paper, we present the first scientific results
obtained with the first MCAO instrument put on the sky. We present a new study
of the Trapezium cluster using deep MCAO images with a field of view of 1'x1'
obtained at the VLT. We have used deep J, H and Ks images recently obtained
with the prototype MCAO facility MAD at the VLT in order to search for new
members and new multiple systems in the Trapezium cluster. On bright targets
(Ks~9mag), these images allow us to reach DeltaKs~6mag as close as 0.4" We
report the detection of 128 sources, including 10 new faint objects in the
magnitude range between 16.1<Ks<17.9mag. In addition to all previously known
multiple systems with separations greater than 0.1", we confirm the
multiplicity of TCC-055. We also report the detection in J, H and Ks of a very
red extended embedded protostellar object, HC419, previously detected in the
thermal infrared only. The analysis of the first MCAO images obtained on the
sky demonstrates not only the technical feasibility of MCAO but also its great
potential and versatility in terms of scientific outputs.Comment: High resolution version available on
http://arrakeen.free.fr/pub/madorion.pdf Accepted 25 Sep. 2007 for
publication in A&A, 14 pages, 11 figure
Discovery of optically faint obscured quasars with Virtual Observatory tools
We use Virtual Observatory (VO) tools to identify optically faint, obscured
(i.e., type 2) active galactic nuclei (AGN) in the two Great Observatories
Origins Deep Survey (GOODS) fields. By employing publicly available X-ray and
optical data and catalogues we discover 68 type 2 AGN candidates. The X-ray
powers of these sources are estimated by using a previously known correlation
between X-ray luminosity and X-ray-to-optical flux ratio. Thirty-one of our
candidates have high estimated powers (Lx > 10^44 erg/s) and therefore qualify
as optically obscured quasars, the so-called ``QSO 2''. Based on the derived
X-ray powers, our candidates are likely to be at relatively high redshifts, z ~
3, with the QSO 2 at z ~ 4. By going ~ 3 magnitudes fainter than previously
known type 2 AGN in the two GOODS fields we are sampling a region of redshift -
power space which was previously unreachable with classical methods. Our method
brings to 40 the number of QSO 2 in the GOODS fields, an improvement of a
factor ~ 4 when compared to the only 9 such sources previously known. We derive
a QSO 2 surface density down to 10^-15 erg/cm^2/s in the 0.5 - 8 keV band of >~
330/deg^2, ~ 30% of which is made up of previously known sources. This is
larger than current estimates and some predictions and suggests that the
surface density of QSO 2 at faint flux limits has been underestimated. This
work demonstrates that VO tools are mature enough to produce cutting-edge
science results by exploiting astronomical data beyond ``classical''
identification limits (R <~ 25) with interoperable tools for statistical
identification of sources using multiwavelength information.Comment: 16 pages, 6 figures, accepted for publication in Astronomy &
Astrophysics. PDF file with higher resolution figures available at
http://www.eso.org/~ppadovan/AVO-paper.pd
RATAN-600 7.6-cm Deep Sky Strip Surveys at the Declination of the SS433 Source During the 1980-1999 Period. Data Reduction and the Catalog of Radio Sources in the Right-Ascension Interval 7h < R.A. < 17h
We use two independent methods to reduce the data of the surveys made with
RATAN-600 radio telescope at 7.6 cm in 1988-1999 at the declination of the
SS433 source. We also reprocess the data of the "Cold" survey (1980-1981). The
resulting RCR (RATAN COLD REFINED) catalog contains the right ascensions and
fluxes of objects identified with those of the NVSS catalog in the
right-ascension interval 7h < R.A. < 17h. We obtain the spectra of the radio
sources and determine their spectral indices at 3.94 and 0.5 GHz. The spectra
are based on the data from all known catalogs available from the CATS, Vizier,
and NED databases, and the flux estimates inferred from the maps of the VLSS
and GB6 surveys. For 245 of the 550 objects of the RCR catalog the fluxes are
known at two frequencies only: 3.94 GHz (RCR) and 1.4 GHz (NVSS). These are
mostly sources with fluxes smaller than 30 mJy. About 65% of these sources have
flat or inverse spectra (alpha > -0.5). We analyze the reliability of the
results obtained for the entire list of objects and construct the histograms of
the spectral indices and fluxes of the sources. Our main conclusion is that all
10-15 mJy objects found in the considered right-ascension interval were already
included in the decimeter-wave catalogs.Comment: 26 pages, 18 figure
A mid-infrared study of very low mass stars and brown dwarfs in Upper Scorpius
We report the results of mid-IR observations with VISIR at the VLT of 10
ultracool dwarfs members of the nearby Upper Scorpius OB association in four
filters ranging between 8.59 (PAH1) to 12.8 m (Ne II), and one brown dwarf
with Spitzer between 3.6 and 24 m. Seven of our targets are detected in at
least one of the bands, and we derive upper limits on the fluxes of the
remaining 4. These results combined with previous studies from the literature
lead to an improved disk frequency of 5012%. This frequency is
significantly higher than that of accretors (16.3%6.2%). Only one object
showing mid-IR excess also has H emission at a level indicating that it
must be accreting. Four of the detected targets are multiple system candidates.
The observed disk frequency for sub-stellar objects in the Upper Scorpius
association is similar to that of stars, consistent with a common formation
scenario. It is also similar to the disk fractions observed in younger
clusters, suggesting that the disk lifetimes might be longer for ultracool
dwarfs than for higher-mass stars.Comment: 10 pages, 4 figures, accepted for A&
Experimental tissue engineering of fetal skin
Purpose: In some human fetuses undergoing prenatal spina bifida repair, the skin defect is too large for primary closure. The aim of this study was to engineer an autologous fetal skin analogue suitable for in utero skin reconstruction during spina bifida repair. Methods: Keratinocytes (KC) and fibroblasts (FB) isolated from skin biopsies of 90-day-old sheep fetuses were cultured. Thereafter, plastically compressed collagen hydrogels and fibrin gels containing FB were prepared. KC were seeded onto these dermal constructs and allowed to proliferate using different culture media. Constructs were analyzed histologically and by immunohistochemistry and compared to normal ovine fetal skin. Results: Development of a stratified epidermis covering the entire surface of the collagen gel was observed. The number of KC layers and degree of organization was dependent on the cell culture media used. The collagen hydrogels exhibited a strong tendency to shrink after eight to ten days of culture in vitro. On fibrin gels, we did not observe the formation of a physiologically organized epidermis. Conclusion: Collagen-gel-based ovine fetal cell-derived skin analogues with near normal anatomy can be engineered in vitro and may be suitable for autologous fetal transplantation
Detection of Extended Red Emisson in the Diffuse Interstellar Medium
Extended Red Emission (ERE) has been detected in many dusty astrophysical
objects and this raises the question: Is ERE present only in discrete objects
or is it an observational feature of all dust, i.e. present in the diffuse
interstellar medium? In order to answer this question, we determined the blue
and red intensities of the radiation from the diffuse interstellar medium (ISM)
and examined the red intensity for the presence of an excess above that
expected for scattered light. The diffuse ISM blue and red intensities were
obtained by subtracting the integrated star and galaxy intensities from the
blue and red measurements made by the Imaging Photopolarimeter (IPP) aboard the
Pioneer 10 and 11 spacecraft. The color of the diffuse ISM was found to be
redder than the Pioneer intensities, contrary to that expected for scattered
light (Diffuse Galactic Light [DGL]). The red DGL was calculated using the blue
diffuse ISM intensities and the approximately invariant color of the DGL
calculated with the DGL model. Subtracting the calculated red DGL from the red
diffuse ISM intensities resulted in the detection of an excess red intensity.
This represents the likely detection of ERE in the diffuse ISM since H-alpha
emission cannot account for the strength of this excess and the only other
known emission process applicable to the diffuse ISM is ERE. Thus, ERE appears
to be a general characteristic of dust. From the correlation between N_HI and
ERE intensity the ERE photon conversion efficiency was estimated at 10 +/- 3%.Comment: 44 pages (41 figures included), to be published in the ApJ, new
version corrected for small error in fig. 2
Hot subdwarfs from the ESO Supernova Ia Progenitor Survey: II. Atmospheric parameters of subdwarf O stars
We address the origin and evolutionary status of hot subdwarf stars by
studying the optical spectral properties of 58 subdwarf O (sdO) stars.
Combining them with the results of our previously studied subdwarf B (sdB)
stars, we aim at investigating possible evolutionary links. We analyze
high-resolution ESO VLT UVES spectra from the ESO Supernova Ia Progenitor
Survey (SPY). Effective temperatures, gravities, and helium abundances are
determined simultaneously by fitting the profiles of H and He lines using
dedicated synthetic spectra in NLTE. Evidence for cool companions to 8 sdOs as
well as a binary consisting of two sdO stars is found. A correlation between He
abundances and the presence of carbon and/or nitrogen lines emerges: below
solar He abundance, no sdO shows C or N lines. In contrast, C and/or N lines
are present in ALL sdOs with super- solar He abundance. We thus use the solar
He abundance to divide our sample into He-deficient and He-enriched sdOs. While
He-deficient sdOs are scattered in a wide range of the Teff-log(g)-diagram,
most of the He-enriched sdOs cluster in a narrow region at Teff = 40,000 ...
50,000K and log(g)=5.5 ... 6.0. An evolu- tionary link between sdBs and sdOs
appears plausible only for the He-deficient sdOs indicating that they are the
likely successors to sdBs. The properties of He-enriched sdOs cannot be
explained with canonical single star evolutionary models. Alternative scenarios
(late hot flasher) as well as for binary evolution (white dwarf merger;
post-RGB evolution) are tested. While we regard the post-RGB scenario as
inappropriate, the white dwarf merger and the late hot flasher scenarios remain
viable to explain the origin of He-enriched sdOs.Comment: 14 pages, 10 figures, Astronomy & Astrophysics accepte
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