6 research outputs found
On The Doppler Velocity of Emission Line Profiles Formed in the "Coronal Contraflow" that is the Chromosphere-Corona Mass Cycle
This analysis begins to explore the complex chromosphere-corona mass cycle
using a blend of imaging and spectroscopic diagnostics. Single Gaussian fits to
hot emission line profiles (formed above 1MK) at the base of coronal loop
structures indicate material blue-shifts of 5-10km/s while cool emission line
profiles (formed below 1MK) yield red-shifts of a similar magnitude -
indicating, to zeroth order, that a temperature-dependent bifurcating flow
exists on coronal structures. Image sequences of the same region reveal weakly
emitting upward propagating disturbances in both hot and cool emission with
apparent speeds of 50-150km/s. Spectroscopic observations indicate that these
propagating disturbances produce a weak emission component in the blue wing at
commensurate speed, but that they contribute only a few percent to the
(ensemble) emission line profile in a single spatio-temporal resolution
element. Subsequent analysis of imaging data shows material "draining" slowly
(~10km/s) out of the corona, but only in the cooler passbands. We interpret the
draining as the return-flow of coronal material at the end of the complex
chromosphere-corona mass cycle. Further, we suggest that the efficient
radiative cooling of the draining material produces a significant contribution
to the red wing of cool emission lines that is ultimately responsible for their
systematic red-shift as derived from a single Gaussian fit when compared to
those formed in hotter (conductively dominated) domains. The presence of
counter-streaming flows complicates the line profiles, their interpretation,
and asymmetry diagnoses, but allows a different physical picture of the lower
corona to develop.Comment: 7 pages, 5 color figures. Accepted to Appear Ap
Two components of the coronal emission revealed by EUV spectroscopic observations
Recent spectroscopic observations have revealed the ubiquitous presence of
blueward asymmetries of emission lines formed in the solar corona and
transition region. These asymmetries are most prominent in loop footpoint
regions, where a clear correlation of the asymmetry with the Doppler shift and
line width determined from the single Gaussian fit is found. Such asymmetries
suggest at least two emission components: a primary component accounting for
the background emission and a secondary component associated with high-speed
upflows. The latter has been proposed to play a vital role in the coronal
heating process and there is no agreement on its properties. Here we slightly
modify the initially developed technique of Red-Blue (RB) asymmetry analysis
and apply it to both artificial spectra and spectra observed by the EUV Imaging
Spectrometer onboard Hinode, and demonstrate that the secondary component
usually contributes a few percent of the total emission, has a velocity ranging
from 50 to 150 km s-1 and a Gaussian width comparable to that of the primary
one in loop footpoint regions. The results of the RB asymmetry analysis are
then used to guide a double Gaussian fit and we find that the obtained
properties of the secondary component are generally consistent with those
obtained from the RB asymmetry analysis. Through a comparison of the location,
relative intensity, and velocity distribution of the blueward secondary
component with the properties of the upward propagating disturbances revealed
in simultaneous images from the Atmospheric Imaging Assembly onboard the Solar
Dynamics Observatory, we find a clear association of the secondary component
with the propagating disturbances.Comment: 19 figures, accepted by Ap
hsa-miR29b, a critical downstream target of non-canonical Wnt signaling, plays an anti-proliferative role in non-small cell lung cancer cells via targeting MDM2 expression
Summary
In non-small cell lung cancer cell lines, activation of β-catenin independent signaling, via Wnt7a/Frizzled9 signaling, leads to reversal of cellular transformation, reduced anchorage-independent growth and induction of epithelial differentiation. miRNA expression profiling on a human lung adenocarcinoma cell line (A549) identified hsa-miR29b as an important downstream target of Wnt7a/Frizzled9 signaling. We show herein that hsa-miR29b expression is lost in non-small cell lung cancer (NSCLC) cell lines and stimulation of β-catenin independent signaling, via Wnt7a expression, in NSCLC cell lines results in increased expression of hsa-miR29b. Surprisingly, we also identify specific regulation of hsa-miR29b by Wnt7a but not by Wnt3, a ligand for β-catenin-dependent signaling. Interestingly, knockdown of hsa-miR29b was enough to abrogate the tumor suppressive effects of Wnt7a/Frizzled9 signaling in NSCLC cells, suggesting that hsa-miR29b is an important mediator of β-catenin independent signaling. Finally, we show for the first time that hsa-miR29b plays an important role as a tumor suppressor in lung cancer by targeting murine double mutant 2 (MDM2), revealing novel nodes for Wnt7a/Frizzled9-mediated regulation of NSCLC cell proliferation