572 research outputs found
Applications of DMDs for astrophysical research
A long-standing problem of astrophysical research is how to simultaneously
obtain spectra of thousands of sources randomly positioned in the field of view
of a telescope. Digital Micromirror Devices, used as optical switches, provide
a most powerful solution allowing to design a new generation of instruments
with unprecedented capabilities. We illustrate the key factors
(opto-mechanical, cryo-thermal, cosmic radiation environment,...) that
constrain the design of DMD-based multi-object spectrographs, with particular
emphasis on the IR spectroscopic channel onboard the EUCLID mission, currently
considered by the European Space Agency for a 2017 launch date.Comment: 10 pages, Proc. SPIE 721
Dust and dark Gamma-Ray Bursts: mutual implications
In a cosmological context dust has been always poorly understood. That is
true also for the statistic of GRBs so that we started a program to understand
its role both in relation to GRBs and in function of z. This paper presents a
composite model in this direction. The model considers a rather generic
distribution of dust in a spiral galaxy and considers the effect of changing
some of the parameters characterizing the dust grains, size in particular. We
first simulated 500 GRBs distributed as the host galaxy mass distribution,
using as model the Milky Way. If we consider dust with the same properties as
that we observe in the Milky Way, we find that due to absorption we miss about
10% of the afterglows assuming we observe the event within about 1 hour or even
within 100s. In our second set of simulations we placed GRBs randomly inside
giants molecular clouds, considering different kinds of dust inside and outside
the host cloud and the effect of dust sublimation caused by the GRB inside the
clouds. In this case absorption is mainly due to the host cloud and the
physical properties of dust play a strong role. Computations from this model
agree with the hypothesis of host galaxies with extinction curve similar to
that of the Small Magellanic Cloud, whereas the host cloud could be also
characterized by dust with larger grains. To confirm our findings we need a set
of homogeneous infrared observations. The use of coming dedicated infrared
telescopes, like REM, will provide a wealth of cases of new afterglow
observations.Comment: 16 pages, 8 figures, accepted by A&
Search for low instability strip variables in the young open cluster NGC 2516
In this paper we revise and complete the photometric survey of the
instability strip of the southern open cluster NGC 2516 published by Antonello
and Mantegazza (1986). No variable stars with amplitudes larger than
were found. However by means of an accurate analysis based on a new statistical
method two groups of small amplitude variables have been disentangled: one with
periods (probably Scuti stars) and one with periods
. The position in the HR diagram and the apparent time-scale may
suggest that the stars of the second group belong to a recently discovered new
class of variables, named Dor variables. They certainly deserve
further study. We also present a comparison between the results of the
photometric survey and the available pointed ROSAT observations of this
cluster.Comment: 7 pages, 2 ps figures. Accepted for P.A.S.
A successful experimental model for intimal hyperplasia prevention using a resveratrol eluting balloon
Objective: Restenosis due to intimal hyperplasia is a major clinical problem that compromises the success of angioplasty
and endovascular surgery. Resveratrol (RSV) has demonstrated a beneficial effect on restenosis from angioplasty. Unfortunately,
the physicochemical characteristics of RSV reduce the practicality of its immediate clinical application. This
work proposes an experimental model aiming to setup an intravessel, elutable, RSV-containing compound.
Methods: A 140 mg/mL RSV sterile injectable solution with a suitable viscosity for intravascular administration by drugdelivery
catheter (RSV-c) was prepared. This solution was locally administered in the common iliac artery of adult male
New Zealand White rabbits using a dedicated device (Genie; Acrostak, Geneva, Switzerland) after the induction of intimal
hyperplasia by traumatic angioplasty. The RSV concentrations in the wall artery were determined, and the thickness of the
harvested iliac arteries was measured over a 1-month period.
Results: The Genie catheter was applied in rabbit vessels, and the local delivery resulted in an effective reduction in restenosis
after plain angioplasty. Notably, RSV-c forced into the artery wall by balloon expansion might accumulate in the interstitial
areas or within cells, avoiding the washout of solutions. Magnification micrographs showed intimal proliferation was
significantly inhibited when RSV-c was applied. Moreover, no adverse events were documented in in vitro or in vivo studies.
Conclusions: RSV can be advantageously administered in the arterial walls by a drug-delivery catheter to reduce the risk of
restenosis
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