50 research outputs found
Simultaneous monitoring of the photometric and polarimetric activity of the young star PV Cep in the optical/near-infrared bands
We present the results of a simultaneous monitoring, lasting more than 2
years, of the optical and near-infrared photometric and polarimetric activity
of the variable protostar PV Cep. During the monitoring period, an outburst has
occurred in all the photometric bands, whose declining phase (J
3 mag) lasted about 120 days. A time lag of 30 days between
optical and infrared light curves has been measured and interpreted in the
framework of an accretion event. This latter is directly recognizable in the
significant variations of the near-infrared colors, that appear bluer in the
outburst phase, when the star dominates the emission, and redder in declining
phase, when the disk emission prevails. All the observational data have been
combined to derive a coherent picture of the complex morphology of the whole PV
Cep system, that, in addition to the star and the accretion disk, is composed
also by a variable biconical nebula. In particular, the mutual interaction
between all these components is the cause of the high value of the polarization
( 20%) and of its fluctuations. The observational data concur to
indicate that PV Cep is not a genuine EXor star, but rather a more complex
object; moreover the case of PV Cep leads to argue about the classification of
other recently discovered young sources in outburst, that have been considered,
maybe over-simplifying, as EXor.Comment: Accepted for publication on Ap
Resolving and probing the circumstellar disk of the Herbig Ae star MWC 480 at 1.4 mm: Evolved dust?
We present high resolution 0.45" x 0.32" observations from the BIMA array
toward the Herbig Ae system MWC 480 in the lambda = 1.4 mm dust continuum. We
resolve a circumstellar disk of radius ~170 AU and constrain the disk
parameters by comparing the observations to flat disk models. These results
show that the typical fit parameters of the disk, such as the mass, Md ~
0.04-0.18 Mo, and the surface density power law index, p=0.5 or 1, are
comparable to those of the lower mass T Tauri stars. The dust in the MWC 480
disk can be modeled as processed dust material (beta ~ 0.8), similar to the
Herbig Ae star CQ Tau disk; the fitted disk parameters are also consistent with
less-evolved dust (beta ~ 1.2). The possibility of grain growth in the MWC 480
circumstellar disk is supported by the acceptable fits with beta ~ 0.8. The
surface density power-law profiles of p=0.5 and p=1 can be easily fit to the
MWC 480 disk; however, a surface density power-law profile similiar to the
minimum mass solar nebula model p=1.5 is ruled out at an 80% confidence level.Comment: ApJ Accepted. 17 page
The Cyprinodon variegatus genome reveals gene expression changes underlying differences in skull morphology among closely related species
Genes in durophage intersection set at 15 dpf. This is a comma separated table of the genes in the 15 dpf durophage intersection set. Given are edgeR results for each pairwise comparison. Columns indicating whether a gene is included in the intersection set at a threshold of 1.5 or 2 fold are provided. (CSV 13Â kb
Searching for a link between the magnetic nature and other observed properties of Herbig Ae/Be stars and stars with debris disks
Among the 21 Herbig Ae/Be stars studied, new detections of a magnetic field
were achieved in six stars. For three Herbig Ae/Be stars, we confirm previous
magnetic field detections. The largest longitudinal magnetic field, =
-454+-42G, was detected in the Herbig Ae/Be star HD101412 using hydrogen lines.
No field detection at a significance level of 3sigma was achieved in stars with
debris disks. Our study does not indicate any correlation of the strength of
the longitudinal magnetic field with disk orientation, disk geometry, or the
presence of a companion. We also do not see any simple dependence on the
mass-accretion rate. However, it is likely that the range of observed field
values qualitatively supports the expectations from magnetospheric accretion
models giving support for dipole-like field geometries. Both the magnetic field
strength and the X-ray emission show hints for a decline with age in the range
of ~2-14Myrs probed by our sample supporting a dynamo mechanism that decays
with age. However, our study of rotation does not show any obvious trend of the
strength of the longitudinal magnetic field with rotation period. Furthermore,
the stars seem to obey the universal power-law relation between magnetic flux
and X-ray luminosity established for the Sun and main-sequence active dwarf
stars.Comment: 21 pages, 16 figures, 7 tables, accepted for publication in A&
A dual-frequency sub-arcsecond study of proto-planetary disks at mm wavelengths: First evidence for radial variations of the dust properties
(Abridged)
We attempt to characterize the radial distribution of dust in disks around a
sample of young stars from an observational point of view, and, when possible,
in a model-independent way, by using parametric laws.
We used the IRAM PdBI interferometer to provide very high angular resolution
(down to 0.4" in some sources) observations of the continuum at 1.3 mm and 3 mm
around a sample of T Tauri stars in the Taurus-Auriga region. The sample
includes single and multiple systems, with a total of 23 individual disks. We
used track-sharing observing mode to minimize the biases. We fitted these data
with two kinds of models: a "truncated power law" model and a model presenting
an exponential decay at the disk edge ("viscous" model). ect evidence for tidal
truncation is found in the multiple systems. The temperature of the mm-emitting
dust is constrained in a few systems.
Unambiguous evidence for large grains is obtained by resolving out disks with
very low values of the dust emissivity index Beta. In most disks that are
sufficiently resolved at two different wavelengths, we find a radial dependence
of Beta, which appears to increase from low values (as low as 0) at the center
to about 1.7 -- 2 at the disk edge. The same behavior could apply to all
studied disks. It introduces further ambiguities in interpreting the brightness
profile, because the regions with apparent Beta = 0 can also be interpreted as
being optically thick when their brightness temperature is high enough. Despite
the added uncertainty on the dust absorption coefficient, the characteristic
size of the disk appears to increase with a higher estimated star age.
These results provide the first direct evidence of the radial dependence of
the grain size in proto-planetary disks.Comment: 27 pages plus 14 pages of figure
FHL2 interacts with CALM and is highly expressed in acute erythroid leukemia
The t(10;11)(p13;q14) translocation results in the fusion of the CALM (clathrin assembly lymphoid myeloid leukemia protein) and AF10 genes. This translocation is observed in acute myeloblastic leukemia (AML M6), acute lymphoblastic leukemia (ALL) and malignant lymphoma. Using a yeast two-hybrid screen, the four and a half LIM domain protein 2 (FHL2) was identified as a CALM interacting protein. Recently, high expression of FHL2 in breast, gastric, colon, lung as well as in prostate cancer was shown to be associated with an adverse prognosis. The interaction between CALM and FHL2 was confirmed by glutathione S-transferase-pulldown assay and co-immunoprecipitation experiments. The FHL2 interaction domain of CALM was mapped to amino acids 294–335 of CALM. The transcriptional activation capacity of FHL2 was reduced by CALM, but not by CALM/AF10, which suggests that regulation of FHL2 by CALM might be disturbed in CALM/AF10-positive leukemia. Extremely high expression of FHL2 was seen in acute erythroid leukemia (AML M6). FHL2 was also highly expressed in chronic myeloid leukemia and in AML with complex aberrant karyotype. These results suggest that FHL2 may play an important role in leukemogenesis, especially in the case of AML M6
Elaboration and characterization of mullite-zirconia composites from gibbsite, boehmite and zircon
cited By 9International audienc
Multiphase Composites Obtained by Sintering Reaction of Boehmite and Zircon Part I: Development and Microstructural Characterization (Retraction of vol 46, pg 291, 2014)
International audienc
Multiphase composites obtained by sintering reaction of boehmite and zircon part I: Development and microstructural characterization
cited By 0International audienceIn this work, different composites (zircon-mullite, zirconia-mullite-zirconia, mullite-zirconia and alumina-zirconia-mullite) were developed by reactive sintering of a powder mixture of boehmite (AlOOH)) and zircon (ZrSiO)4. These powder mixtures were mixed and ground by ball milling and then pressed in cylindrical form. Finally, the green specimens were sintered in air during 2 hours between 1400°C and 1600°C, with a heating and cooling rate of 5°C/min. The dilatometric curves show that there are several microstructural transformations in these mixtures. X-rays diffraction spectra showed formation of several composites depending on the initial conditions (% of boehmite and zircon and sintering temperature). The micrographic observations of the samples confirmed the presence of various phases. © 2014 Science of Sintering