1,003 research outputs found
Using the transit of Venus to probe the upper planetary atmosphere
The atmosphere of a transiting planet shields the stellar radiation providing
us with a powerful method to estimate its size and density. In particular,
because of their high ionization energy, atoms with high atomic number (Z)
absorb short-wavelength radiation in the upper atmosphere, undetectable with
observations in visible light. One implication is that the planet should appear
larger during a primary transit observed in high energy bands than in the
optical band. The last Venus transit in 2012 offered a unique opportunity to
study this effect. The transit has been monitored by solar space observations
from Hinode and Solar Dynamics Observatory (SDO). We measure the radius of
Venus during the transit in three different bands with subpixel accuracy:
optical (4500A), UV (1600A, 1700A), Extreme UltraViolet (EUV, 171-335A) and
soft X-rays (about 10A). We find that, while the Venus optical radius is about
80 km larger than the solid body radius (the expected opacity mainly due to
clouds and haze), the radius increases further by more than 70 km in the EUV
and soft X-rays. These measurements mark the densest ion layers of Venus'
ionosphere, providing information about the column density of CO2 and CO. They
are useful for planning missions in situ to estimate the dynamical pressure
from the environment, and can be employed as a benchmark case for observations
with future missions, such as the ESA Athena, which will be sensitive enough to
detect transits of exoplanets in high-energy bands.Comment: 13 pages, 2 figures; published in Nature Communications; the full and
copy-edited version is open access at
http://www.nature.com/ncomms/2015/150623/ncomms8563/full/ncomms8563.htm
The molecular chaperone Hsp90 is a component of the cap-binding complex and interacts with the translational repressor Cup during Drosophila oogenesis
In metazoa, the spatio-temporal translation of diverse mRNAs is essential to guarantee proper oocyte maturation and early embryogenesis. The eukaryotic translation initiation factor 4E (eIF4E), which binds the 5′ cap structure of eukaryotic mRNAs, associates with either stimulatory or inhibitory factors to modulate protein synthesis. In order to identify novel factors that might act at the translational level during Drosophila oogenesis, we have undertaken a functional proteomic approach and isolated the product of the Hsp83 gene, the evolutionarily conserved chaperone Hsp90, as a specific component of the cap-binding complex. Here we report that Hsp90 interacts in vitro with the translational repressor Cup. In addition, we show that Hsp83 and cup interact genetically, since lowering Hsp90 activity enhances the oogenesis alterations linked to diverse cup mutant alleles. Hsp90 and Cup co-localize in the cytoplasm of the developing germ-line cells within the germarium, thus suggesting a common function from the earliest stages of oogenesis. Taken together, our data start elucidating the role of Hsp90 during Drosophila female germ-line development and strengthen the idea that Cup has multiple essential functions during egg chamber development
Wake Modeling with the Actuator Disc Concept
Abstract The wakes induced by the wind turbines are modeled with the finite-volume code WindSim, based on the solving of the Reynolds Averaged Navier-Stokes (RANS) equations of an Atmospheric Boundary Layer. The RANS equations of an uncompressible flow are solved with a multigrid coupled solver (MIGAL); turbulence is closed with the RNG k-ɛ model. The rotor of a wind turbine is modeled by an actuator disc providing a resistive force which is calculated from the thrust coefficient curve of wind turbine. The axial thrust can be distributed over the swept area in three different manners: by a uniform, parabolic or a polynomial distribution.A wake is therefore generated downstream of each turbine with wake deficit and induced turbulence.When using the actuator disc technique it is also interesting to observe how the wake-wake, wake-terrain interactions are predicted; moreover, also simulations with actuator discs and flows with thermal effects can be carried out.In this work we present first a series of simulations over a single turbine for a grid sensitivity study, in the second part a validation against production data from the offshore wind farm Horns Rev is presented
The decay of unstable k-strings in SU(N) gauge theories at zero and finite temperature
Sources in higher representations of SU(N) gauge theory at T=0 couple with
apparently stable strings with tensions depending on the specific
representation rather than on its N-ality. Similarly at the deconfining
temperature these sources carry their own representation-dependent critical
exponents. It is pointed out that in some instances one can evaluate exactly
these exponents by fully exploiting the correspondence between the 2+1
dimensional critical gauge theory and the 2d conformal field theory in the same
universality class. The emerging functional form of the Polyakov-line
correlators suggests a similar form for Wilson loops in higher representations
which helps in understanding the behaviour of unstable strings at T=0. A
generalised Wilson loop in which along part of its trajectory a source is
converted in a gauge invariant way into higher representations with same
N-ality could be used as a tool to estimate the decay scale of the unstable
strings.Comment: 18 pages, 4 figures v2: typos correcte
ASCA and BeppoSAX observations of the peculiar X-ray source 4U1700+24/HD154791
The X-ray source 4U1700+24/HD154791 is one of the few galactic sources whose
counterpart is an evolved M star. In X-rays the source shows extreme erratic
variability and a complex and variable spectrum. While this strongly suggests
accretion onto a compact object, no clear diagnosis of binarity was done up to
now. We report on ASCA and BeppoSAX X-ray broad band observations of this
source and on ground optical observations from the Loiano 1.5 m telescope.Comment: 5 pages, 4 figures, uses aipproc.sty, to appear in Proceedings of the
Fifth Compton Symposiu
Maxillary fungus ball: zinc-oxide endodontic materials as a risk factor
open7openNICOLAI, Piero; MENSI, Magda; Marsili, F.; Piccioni, M.; SALGARELLO, Stefano Alessandro; GILBERTI, Maria Enrica; Apostoli, P.Nicolai, Piero; Mensi, Magda; Marsili, F.; Piccioni, M.; Salgarello, Stefano Alessandro; Gilberti, Maria Enrica; Apostoli, P
A Genome-scale CRISPR Screen Identifies the ERBB and mTOR Signaling Networks as Key Determinants of Response to PI3K Inhibition in Pancreatic Cancer.
KRAS mutation is a key driver of pancreatic cancer and PI3K pathway activity is an additional requirement for Kras-induced tumorigenesis. Clinical trials of PI3K pathway inhibitors in pancreatic cancer have shown limited responses. Understanding the molecular basis for this lack of efficacy may direct future treatment strategies with emerging PI3K inhibitors. We sought new therapeutic approaches that synergize with PI3K inhibitors through pooled CRISPR modifier genetic screening and a drug combination screen. ERBB family receptor tyrosine kinase signaling and mTOR signaling were key modifiers of sensitivity to alpelisib and pictilisib. Inhibition of the ERBB family or mTOR was synergistic with PI3K inhibition in spheroid, stromal cocultures. Near-complete loss of ribosomal S6 phosphorylation was associated with synergy. Genetic alterations in the ERBB-PI3K signaling axis were associated with decreased survival of patients with pancreatic cancer. Suppression of the PI3K/mTOR axis is potentiated by dual PI3K and ERBB family or mTOR inhibition. Surprisingly, despite the presence of oncogenic KRAS, thought to bestow independence from receptor tyrosine kinase signaling, inhibition of the ERBB family blocks downstream pathway activation and synergizes with PI3K inhibitors. Further exploration of these therapeutic combinations is warranted for the treatment of pancreatic cancer
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