533 research outputs found
An Inner Disk in the Large Gap of the Transition Disk SR 24S
We report new Atacama Large Millimeter/sub-millimeter Array (ALMA) Band 3
observations at 2.75 mm of the TD around SR 24S with an angular resolution of
0.11'' 0.09'' and a peak signal-to-noise ratio of . We
detect an inner disk and a mostly symmetric ring-like structure that peaks at
0.32'', that is 37 au at a distance of 114.4 pc. The full
width at half maximum of this ring is 28 au. We analyze the observed
structures by fitting the dust continuum visibilities using different models
for the intensity profile, and compare with previous ALMA observations of the
same disk at 0.45 mm and 1.30 mm. We qualitatively compare the results of these
fits with theoretical predictions of different scenarios for the formation of a
cavity or large gap. The comparison of the dust continuum structure between
different ALMA bands indicates that photoevaporation and dead zone can be
excluded as leading mechanisms for the cavity formation in SR 24S disk, leaving
the planet scenario (single or multiple planets) as the most plausible
mechanism. We compared the 2.75 mm emission with published (sub-)centimeter
data and find that the inner disk is likely tracing dust thermal emission. This
implies that any companion in the system should allow dust to move inwards
throughout the gap and replenish the inner disk. In the case of one single
planet, this puts strong constraints on the mass of the potential planet inside
the cavity and the disk viscosity of about 5 and
, respectively.Comment: Accepted to Ap
IMMUNOLOGICAL SIGNATURE IN NAÏVE AND SUNITINIB-TREATED SOFT TISSUE SARCOMA PATIENTS: ROLE OF MYELOID CELLS
Although designed to directly target cancer cells and tumor associated-vasculature, anti-angiogenic drugs (e.g. sunitinib), have been described to influence tumor-host interactions. Sunitinib is currently in use at our Institute for the treatment of progressive, advanced soft tissue sarcomas (STS) of different histology. However, the systemic and local immune responses and their modulation by anti-angiogenic therapies are unknown in these neoplasms, namely solitary fibrous tumors (SFTs), clear cell sarcoma (CCS) and alveolar soft part sarcoma (ASPS). This thesis aims to shed light on the immunological status of these STS patients and to address the question to which extent sunitinib induces immune modulation in these patients. Thus, my research focused on the characterization of both tumor-infiltrating and circulating immune cells of STS patients. Fine analysis of the immune contexture at the tumor site in na\uefve and in sunitinib-treated tumors revealed that myeloid cells, namely tumor-associated macrophages, represent a key component of the tumor microenvironment and that their reprogramming is part of the response to sunitinib treatment. Immune monitoring of circulating cells in these STS patients indicated that circulating myeloid suppressor cells were associated to disease progression and were the major player in mediating the immune-suppressive status in na\uefve and in sunitinib-treated SFT patients. Moreover, evidence have been provided that, in sunitinib-treated SFT patients, myeloid suppressor cells may be part of acquired resistance, thus supporting the notion that myeloid cells are the most relevant hurdle in the efficacy of anti-angiogenic treatments. Collectively the results of this thesis shed light on an unappreciated phenomenon of immune dysfunction in STS patients and indicate that in SFTs sunitinib transiently relieves systemic immunosuppression and reprograms the immune microenvironment. Moreover, for the first time, an antigen-specific T cell response has been evidenced in CCS, and, this tumor-specific response has occurred in association to sunitinib-induced immune modulation. Overall, this thesis poses the rationale for the development of immune-based clinical approaches aimed at achieving a more durable disease control in these cancer patients, for which effective medical therapies are still needed
An Inner Disk in the Large Gap of the Transition Disk SR 24S
We report new Atacama Large Millimeter/sub-millimeter Array (ALMA) Band 3
observations at 2.75 mm of the TD around SR 24S with an angular resolution of
0.11'' 0.09'' and a peak signal-to-noise ratio of . We
detect an inner disk and a mostly symmetric ring-like structure that peaks at
0.32'', that is 37 au at a distance of 114.4 pc. The full
width at half maximum of this ring is 28 au. We analyze the observed
structures by fitting the dust continuum visibilities using different models
for the intensity profile, and compare with previous ALMA observations of the
same disk at 0.45 mm and 1.30 mm. We qualitatively compare the results of these
fits with theoretical predictions of different scenarios for the formation of a
cavity or large gap. The comparison of the dust continuum structure between
different ALMA bands indicates that photoevaporation and dead zone can be
excluded as leading mechanisms for the cavity formation in SR 24S disk, leaving
the planet scenario (single or multiple planets) as the most plausible
mechanism. We compared the 2.75 mm emission with published (sub-)centimeter
data and find that the inner disk is likely tracing dust thermal emission. This
implies that any companion in the system should allow dust to move inwards
throughout the gap and replenish the inner disk. In the case of one single
planet, this puts strong constraints on the mass of the potential planet inside
the cavity and the disk viscosity of about 5 and
, respectively
Estimating the fossil disc mass during supermassive black hole mergers: The importance of torque implementation
In this paper, we revisit the issue of estimating the "fossil" disc mass in
the circumprimary disc, during the merger of a supermassive black hole binary.
As the binary orbital decay speeds up due to the emission of gravitational
waves, the gas in the circumprimary disc might be forced to accrete rapidly and
could in principle provide a significant electromagnetic counterpart to the
gravitational wave emission. Since the luminosity of such flare is proportional
to the gaseous mass in the circumprimary disc, estimating such mass accurately
is important. Previous investigations of this issue have produced contradictory
results, with some authors estimating super-Eddington flares and large disc
mass, while others suggesting that the "fossil" disc mass is very low, even
less than a Jupiter mass. Here, we perform simple 1D calculations to show that
such very low estimates of the disc mass are an artifact of the specific
implementation of the tidal torque in 1D models. In particular, for moderate
mass ratios of the binary, the usual formula for the torque used in 1D models
significantly overestimates the width of the gap induced by the secondary and
this artificially leads to a very small leftover circumprimary disc. Using a
modified torque, calibrated to reproduce the correct gap width as estimated by
3D models, leads to fossil disc masses of the order of one solar mass. The
rapid accretion of the whole circumprimary disc would produce peak luminosities
of the order of 1-20 times the Eddington luminosity. Even if a significant
fraction of the gas escapes accretion by flowing out the secondary orbit during
the merger (an effect not included in our calculations), we would still predict
close to Eddington luminosities that might be easily detected
A super-resolution analysis of the DSHARP survey: Substructure is common in the inner 30 au
The DSHARP survey evidenced the ubiquity of substructure in the mm dust
distribution of large, bright protoplanetary discs. Intriguingly, these
datasets have yet higher resolution information that is not recovered in a
CLEAN image. We first show that the intrinsic performance of the CLEAN
algorithm is resolution-limited. Then analyzing all 20 DSHARP sources using the
1D, super-resolution code Frankenstein (frank), we accurately fit the 1D
visibilities to a mean factor of 4.3 longer baseline than the Fourier transform
of the CLEAN images and a factor of 3.0 longer baseline than the transform of
the CLEAN component models. This yields a higher resolution brightness profile
for each source, identifying new substructure interior to 30 au in multiple
discs; resolving known gaps to be deeper, wider, and more structured; and known
rings to be narrower and brighter. Across the survey, high contrast gaps are an
average 14% wider and 44% deeper in the frank profiles relative to CLEAN, and
high contrast rings are an average 26% narrower. Categorizing the frank
brightness profiles into trends, we find that the relative scarcity of features
interior to 30 au in the survey's CLEAN images is an artifact of resolving
power, rather than an intrinsic rarity of inner disc (or compact disc)
substructure. Finally the rings in the frank profiles are narrower than the
previously inferred deconvolved widths, indicating smaller alpha / St ratios in
the local gas disc
Trends in high energy particle accelerators
Particle accelerators of higher and higher energy and intensity are required, as the investigation of subatomic matter needs to be pursued with higher and higher resolving power. To keep pace with this need while keeping physical dimensions and the cost of accelerator installations affordable, ever new ideas and technologies must be devised. After a brief general introduction and a summary of accelerator physics basics, we review the main lines of development of state of the art installations recently built, in construction or on the drafting board. New physics and technology challenges they pose and main topics still open to further research and development are also outlined
High-resolution observations of molecular emission lines toward the CI Tau proto-planetary disc: Planet-carved gaps or shadowing?
Recent observations have revealed that most proto-planetary discs show a
pattern of bright rings and dark gaps. However, most of the high-resolution
observations have focused only on the continuum emission. In this Paper we
present high-resolution ALMA band 7 (0.89mm) observations of the disc around
the star CI Tau in the CO & CO -2 and CS -6 emission
lines. Our recent work demonstrated that the disc around CI Tau contains three
gaps and rings in continuum emission, and we look for their counterparts in the
gas emission. While we find no counterpart of the third gap and ring in
CO, the disc has a gap in emission at the location of the second
continuum ring (rather than gap). We demonstrate that this is mostly an
artefact of the continuum subtraction, although a residual gap still remains
after accounting for this effect. Through radiative transfer modelling we
propose this is due to the inner disc shadowing the outer parts of the disc and
making them colder. This raises a note of caution in mapping high-resolution
gas emission lines observations to the gas surface density - while possible,
this needs to be done carefully. In contrast to CO, CS emission shows
instead a ring morphology, most likely due to chemical effects. Finally, we
note that CO is heavily absorbed by the foreground preventing any
morphological study using this line
The time evolution of dusty protoplanetary disc radii: Observed and physical radii differ
Proto-planetary disc surveys conducted with ALMA are measuring disc radii in
multiple star forming regions. The disc radius is a fundamental quantity to
diagnose whether discs undergo viscous spreading, discriminating between
viscosity or angular momentum removal by winds as drivers of disc evolution.
Observationally, however, the sub-mm continuum emission is dominated by the
dust, which also drifts inwards, complicating the picture. In this paper we
investigate, using theoretical models of dust grain growth and radial drift,
how the radii of dusty viscous proto-planetary discs evolve with time. Despite
the existence of a sharp outer edge in the dust distribution, we find that the
radius enclosing most of the dust increases with time, closely
following the evolution of the gas radius. This behaviour arises because,
although dust initially grows and drifts rapidly onto the star, the residual
dust retained on Myr timescales is relatively well coupled to the gas.
Observing the expansion of the dust disc requires using definitions based on
high fractions of the disc (e.g. 95 per cent) and very long
integrations with ALMA, because the dust grains in the outer part of the disc
are small and have a low sub-mm opacity. We show that existing surveys lack the
sensitivity to detect viscous spreading. The disc radii they measure do not
trace the mass radius or the sharp outer edge in the dust distribution, but the
outer limit of where the grains have significant sub-mm opacity. We predict
that these observed radii should shrink with time
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