85 research outputs found
Prognostic role of minimal residual disease before and after hematopoietic stem cell transplantation in childhood acute lymphoblastic leukemia
More than 80% of children with acute lymphoblastic leukemia (ALL) can be cured through intensive and risk-oriented chemotherapy protocols. Allogeneic hematopoietic stem cell transplantation (HSCT) is considered bene\ufb01cial for approximately 10% of the patients who are at veryhigh risk at frontline therapy and for the majority of patients after relapse. Consequently, it is critically important to identify prognostic factors in this group of patients in order to tailor risk-adapted therapy. In this retrospective study, we aimed to assess the prognostic role of minimal residual disease (MRD) before HSCT and at di\ufb00erent time points after transplantation in children with ALL
Simulations of ELT-GMCAO performance for deep field observations
The Global-Multi Conjugated Adaptive Optics (GMCAO) approach offers an
alternative way to correct an adequate scientific Field of View (FoV) using
only natural guide stars (NGSs) to extremely large ground-based telescopes.
Thus, even in the absence of laser guide stars, a GMCAO-equipped ELT-like
telescope can achieve optimal performance in terms of Strehl Ratio (SR),
retrieving impressive results in studying star-poor fields, as in the cases of
the deep field observations. The benefits and usability of GMCAO have been
demonstrated by studying 6000 mock high redshift galaxies in the Chandra Deep
Field South region. However, a systematic study simulating observations in
several portions of the sky is mandatory to have a robust statistic of the
GMCAO performance. Technical, tomographic and astrophysical parameters,
discussed here, are given as inputs to GIUSTO, an IDL-based code that estimates
the SR over the considered field, and the results are analyzed with statistical
considerations. The best performance is obtained using stars that are
relatively close to the Scientific FoV; therefore, the SR correlates with the
mean off-axis position of NGSs, as expected, while their magnitude plays a
secondary role. This study concludes that the SRs correlate linearly with the
galactic latitude, as also expected. Because of the lack of natural guide stars
needed for low-order aberration sensing, the GMCAO confirms as a promising
technique to observe regions that can not be studied without the use of laser
beacons. It represents a robust alternative way or a risk mitigation strategy
for laser approaches on the ELTs.Comment: 18 pages, 10 figures, accepted for publication on PAS
Multiple Spatial Frequencies Pyramid WaveFront Sensing
A modification of the pyramid wavefront sensor is described. In this conceptually new class of devices, the perturbations are split at the level of the focal plane depending upon their spatial frequencies, and then measured separately. The aim of this approach is to increase the accuracy in the determination of some range of spatial frequency perturbations, or a certain classes of modes, disentangling them from the noise associated to the Poissonian fluctuations of the light coming from the perturbations outside of the range of interest or from the background in the pupil planes; the latter case specifically when the pyramid wavefront sensor is used with a large modulation. While the limits and the effectiveness of this approach should be further investigated, a number of variations on the concept are shown, including a generalization of the spatial filtering in the point-diffraction wavefront sensor. The simplest application, a generalization to the pyramid of the well-known spatially filtering in wavefront sensing, is showing promise as a significant limiting magnitude advance. Applications are further speculated in the area of extreme adaptive optics and when serving spectroscopic instrumentation where “light in the bucket” rather than Strehl performance is required
Ingot Laser Guide Stars Wavefront Sensing
We revisit one class of z-invariant WaveFront sensor where the LGS is fired
aside of the telescope aperture. In this way there is a spatial dependence on
the focal plane with respect to the height where the resonant scattering
occurs. We revise the basic parameters involving the geometry and we propose
various merit functions to define how much improvement can be attained by a
z-invariant approach. We show that refractive approaches are not viable and we
discuss several solutions involving reflective ones in what has been nicknamed
"ingot wavefront sensor" discussing the degrees of freedom required to keep
tracking and the basic recipe for the optical design.Comment: 6 pages, 4 figures, AO4ELT5 Conference Proceeding, 201
A Holographic Diffuser Generalised Optical Differentiation Wavefront Sensor
The wavefront sensors used today at the biggest World's telescopes have
either a high dynamic range or a high sensitivity, and they are subject to a
linear trade off between these two parameters. A new class of wavefront
sensors, the Generalised Optical Differentiation Wavefront Sensors, has been
devised, in a way not to undergo this linear trade off and to decouple the
dynamic range from the sensitivity. This new class of WFSs is based on the
light filtering in the focal plane from a dedicated amplitude filter, which is
a hybrid between a linear filter, whose physical dimension is related to the
dynamic range, and a step in the amplitude, whose size is related to the
sensitivity. We propose here a possible technical implementation of this kind
of WFS, making use of a simple holographic diffuser to diffract part of the
light in a ring shape around the pin of a pyramid wavefront sensor. In this
way, the undiffracted light reaches the pin of the pyramid, contributing to the
high sensitivity regime of the WFS, while the diffused light is giving a sort
of static modulation of the pyramid, allowing to have some signal even in high
turbulence conditions. The holographic diffuser zeroth order efficiency is
strictly related to the sensitivity of the WFS, while the diffusing angle of
the diffracted light gives the amount of modulation and thus the dynamic range.
By properly choosing these two parameters it is possible to build a WFS with
high sensitivity and high dynamic range in a static fashion. Introducing
dynamic parts in the setup allows to have a set of different diffuser that can
be alternated in front of the pyramid, if the change in the seeing conditions
requires it.Comment: 11 pages, 5 figure
Multiple spatial frequencies wavefront sensing
We describe the concept of splitting spatial frequency perturbations into
some kind of pupil planes wavefront sensors. Further to the existing approach
of dropping higher spatial frequency to suppress aliasing effects (the
so-called spatial filtered Shack-Hartmann), we point out that spatial
frequencies splitting and mixing of these in a proper manner, could be handled
in order to exhibit some practical or fundamental advantages. In this framework
we describe the idea behind such class of concepts and we derive the
relationship useful to determine if, by which extent, and under what kind of
merit function, these devices can overperform existing conventional sensors.Comment: 6 pages, 3 figures, in AO4ELT5 Proceeding
Prospects of Deep Field Surveys with Global-MCAO on an ELT
Several astronomical surveys aimed at the investigation of the extragalactic
components were carried out in order to map systematically the universe and its
constituents. An excellent level of detail is needed, and it is possible only
using space telescopes or with the application of adaptive optics (AO)
techniques for ground-based observatories. By simulating K-band observations of
6000 high-redshift galaxies in the Chandra Deep Field South region, we have
already shown how an extremely large telescope can carry out photometric
surveys successfully using the Global-MCAO, a natural guide stars based
technique that allows the development of extragalactic research, otherwise
impracticable without using laser guide stars. As the outcome of the analysis
represents an impact science case for the new instruments on upcoming
ground-based telescopes, here we show how the investigation of other observed
deep fields could profit from such a technique. Further to an overview of the
surveys suitable for the proposed approach, we show preliminary estimations
both on geometrical (FoV and height) and purely AO perspectives (richness and
homogeneity of guide stars in the area) for planned giant telescope.Comment: 8 pages, 6 figures, AO4ELT5 conferenc
Deep observations with an ELT in the Global Multi Conjugated Adaptive Optics perspective
Deep observations of the Universe, usually as a part of sky surveys, are one
of the symbols of the modern astronomy because they can allow big
collaborations, exploiting multiple facilities and shared knowledge. The new
generation of extremely large telescopes will play a key role because of their
angular resolution and their capability in collecting the light of faint
sources. Our simulations combine technical, tomographic and observational
information, and benefit of the Global-Multi Conjugate Adaptive Optics (GMCAO)
approach, a well demonstrated method that exploits only natural guide stars to
correct the scientific field of view from the atmospheric turbulence. By
simulating K-band observations of 6000 high redshift galaxies in the Chandra
Deep Field South area, we have shown how an ELT can carry out photometric
surveys successfully, recovering morphological and structural parameters. We
present here a wide statistics of the expected performance of a GMCAO-equipped
ELT in 22 well-known surveys in terms of SR
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