294 research outputs found
Cytogenetic bio-dosimetry techniques in the detection of dicentric chromosomes induced by ionizing radiation: A review
Ionizing radiation is ubiquitous in the environment. Its source can be natural, such as radioactive materials present in soil and cosmic rays, or artificial, such as the fuel for nuclear power plants. Overexposure to ionizing radiation may damage living tissue and could cause severe health problems (i.e., mutations, radiation sickness, cancer, and death). Cytogenetic bio-dosimetry has the great advantage to take into account the inter-individual variation, and it is informative even when physical dosimetry is not applicable; moreover, it is the definitive method to assess exposure to ionizing radiation recommended by the World Health Organization (WHO). Such a procedure involves counting the frequency of dicentric chromosomes (DCs), which are the most studied chromosomal aberrations used as absorbed radiation biomarkers, during the metaphase of cells. A set of algorithms, tested on different programming languages to automatically identify DCs, is analyzed by the authors together with an Automated Dicentric Chromosome Identifying software (ADCI) mostly based on OpenCV programming libraries. The purpose of this work is to review the main results regarding the correlation between ionizing radiation and dicentric chromosomes in cytogenetic bio-dosimetry
The VLT-VIRMOS Mask Manufacturing Unit
The VIRMOS Consortium has the task to design and manufacture two
spectrographs for ESO VLT, VIMOS (Visible Multi-Object Spectrograph) and NIRMOS
(Near Infrared Multi-Object Spectrograph). This paper describes how the Mask
Manufacturing Unit (MMU), which cuts the slit masks to be used with both
instruments, meets the scientific requirements and manages the storage and the
insertion of the masks into the instrument. The components and the software of
the two main parts of the MMU, the Mask Manufacturing Machine and the Mask
Handling System, are illustrated together with the mask material and with the
slit properties. Slit positioning is accurate within 15 micron, equivalent to
0.03 arcsec on the sky, while the slit edge roughness has an rms on the order
of 0.03 pixels on scales of a slit 5 arcsec long and of 0.01 pixels on the
pixel scale (0.205 arcsec). The MMU has been successfully installed during
July/August 2000 at the Paranal Observatory and is now operational for
spectroscopic mask cutting, compliant with the requested specifications.Comment: Accepted for publication in PASP April 2001 PASP Latex preprint
style, 31 pages including 9 figures (5 jpg2eps compressed
First light of the VLT planet finder SPHERE. II. The physical properties and the architecture of the young systems PZ Tel and HD 1160 revisited
[Abridged] Context. The young systems PZ Tel and HD 1160, hosting known
low-mass companions, were observed during the commissioning of the new planet
finder SPHERE with several imaging and spectroscopic modes. Aims. We aim to
refine the physical properties and architecture of both systems. Methods. We
use SPHERE commissioning data and REM observations, as well as literature and
unpublished data from VLT/SINFONI, VLT/NaCo, Gemini/NICI, and Keck/NIRC2.
Results. We derive new photometry and confirm the nearly daily photometric
variability of PZ Tel A. Using literature data spanning 38 yr, we show that the
star also exhibits a long-term variability trend. The 0.63-3.8 mic SED of PZ
Tel B allows us to revise its properties: spectral type M7+/-1, Teff=2700+/-100
K, log(g)<4.5 dex, log(L/L_Sun)=-2.51+/-0.10 dex, and mass 38-72 MJ. The 1-3.8
mic SED of HD 1160 B suggests a massive brown dwarf or a low-mass star with
spectral type M5.5-7.0, Teff=3000+/-100 K, [M/H]=-0.5-0.0 dex,
log(L/L_Sun)=-2.81+/-0.10 dex, and mass 39-168 MJ. We confirm the deceleration
and high eccentricity (e>0.66) of PZ Tel B. For e<0.9, the inclination,
longitude of the ascending node, and time of periastron passage are well
constrained. The system is seen close to an edge-on geometry. We reject other
brown dwarf candidates outside 0.25" for both systems, and massive giant
planets (>4 MJ) outside 0.5" for the PZ Tel system. We also show that K1-K2
color can be used with YJH low-resolution spectra to identify young L-type
companions, provided high photometric accuracy (<0.05 mag) is achieved.
Conclusions. SPHERE opens new horizons in the study of young brown dwarfs and
giant exoplanets thanks to high-contrast imaging capabilities at optical and
near-infrared wavelengths, as well as high signal-to-noise spectroscopy in the
near-infrared from low (R~30-50) to medium resolutions (R~350).Comment: 25 pages, 23 figures, accepted for publication in A&A on Oct. 13th,
2015; version including language editing. Typo on co-author name on astroph
page corrected, manuscript unchange
Iatrogenic damage to the mandibular nerves as assessed by the masseter inhibitory reflex
Iatrogenic injury of the inferior alveolar or lingual nerves frequently leads to legal actions for damage and compensation for personal suffering. The masseter inhibitory reflex (MIR) is the most used neurophysiological tool for the functional assessment of the trigeminal mandibular division. Aiming at measuring the MIR sensitivity and specificity, we recorded this reflex after mental and tongue stimulations in a controlled, blinded study in 160 consecutive patients with sensory disturbances following dental procedures. The MIR latency was longer on the affected than the contralateral side (P < 0.0001). The overall specificity and sensitivity were 99 and 51%. Our findings indicate that MIR testing, showing an almost absolute specificity, reliably demonstrates nerve damage beyond doubt, whereas the relatively low sensitivity makes the finding of a normal MIR by no means sufficient to exclude nerve damage. Probably, the dysfunction of a small number of nerve fibres, insufficient to produce a MIR abnormality, may still engender important sensory disturbances. We propose that MIR testing, when used for legal purposes, be considered reliable in one direction only, i.e. abnormality does prove nerve damage, normality does not disprove it
Expected performance of the ASTRI-SST-2M telescope prototype
ASTRI (Astrofisica con Specchi a Tecnologia Replicante Italiana) is an
Italian flagship project pursued by INAF (Istituto Nazionale di Astrofisica)
strictly linked to the development of the Cherenkov Telescope Array, CTA.
Primary goal of the ASTRI program is the design and production of an end-to-end
prototype of a Small Size Telescope for the CTA sub-array devoted to the
highest gamma-ray energy region. The prototype, named ASTRI SST-2M, will be
tested on field in Italy during 2014. This telescope will be the first
Cherenkov telescope adopting the double reflection layout in a
Schwarzschild-Couder configuration with a tessellated primary mirror and a
monolithic secondary mirror. The collected light will be focused on a compact
and light-weight camera based on silicon photo-multipliers covering a 9.6 deg
full field of view. Detailed Monte Carlo simulations have been performed to
estimate the performance of the planned telescope. The results regarding its
energy threshold, sensitivity and angular resolution are shown and discussed.Comment: In Proceedings of the 33rd International Cosmic Ray Conference
(ICRC2013), Rio de Janeiro (Brazil). All CTA contributions at arXiv:1307.223
Modeling the drug release from hydrogel-based matrices
In this work the behavior of hydrogel-based matrices, the most widespread systems for oral controlled release of pharmaceuticals, has been mathematically described. In addition, the calculations of the model have been validated against a rich set of experimental data obtained working with tablets made of hydroxypropyl methylcellulose (a hydrogel) and theophylline (a model drug). The model takes into account water uptake, hydrogel swelling, drug release, and polymer erosion. The model was obtained as an improvement of a previous code, describing the diffusion in concentrated systems, and obtaining the erosion front (which is a moving boundary) from the polymer mass balance (in this way, the number of fitting parameters was also reduced by one). The proposed model was found able to describe all the observed phenomena, and then it can be considered a tool with predictive capabilities, useful in design and testing of new dosage systems based on hydrogels
SPHERE: the exoplanet imager for the Very Large Telescope
Observations of circumstellar environments to look for the direct signal of
exoplanets and the scattered light from disks has significant instrumental
implications. In the past 15 years, major developments in adaptive optics,
coronagraphy, optical manufacturing, wavefront sensing and data processing,
together with a consistent global system analysis have enabled a new generation
of high-contrast imagers and spectrographs on large ground-based telescopes
with much better performance. One of the most productive is the
Spectro-Polarimetic High contrast imager for Exoplanets REsearch (SPHERE)
designed and built for the ESO Very Large Telescope (VLT) in Chile. SPHERE
includes an extreme adaptive optics system, a highly stable common path
interface, several types of coronagraphs and three science instruments. Two of
them, the Integral Field Spectrograph (IFS) and the Infra-Red Dual-band Imager
and Spectrograph (IRDIS), are designed to efficiently cover the near-infrared
(NIR) range in a single observation for efficient young planet search. The
third one, ZIMPOL, is designed for visible (VIR) polarimetric observation to
look for the reflected light of exoplanets and the light scattered by debris
disks. This suite of three science instruments enables to study circumstellar
environments at unprecedented angular resolution both in the visible and the
near-infrared. In this work, we present the complete instrument and its on-sky
performance after 4 years of operations at the VLT.Comment: Final version accepted for publication in A&
Post conjunction detection of Pictoris b with VLT/SPHERE
With an orbital distance comparable to that of Saturn in the solar system,
\bpic b is the closest (semi-major axis \,9\,au) exoplanet that has
been imaged to orbit a star. Thus it offers unique opportunities for detailed
studies of its orbital, physical, and atmospheric properties, and of
disk-planet interactions. With the exception of the discovery observations in
2003 with NaCo at the Very Large Telescope (VLT), all following astrometric
measurements relative to \bpic have been obtained in the southwestern part of
the orbit, which severely limits the determination of the planet's orbital
parameters. We aimed at further constraining \bpic b orbital properties using
more data, and, in particular, data taken in the northeastern part of the
orbit.
We used SPHERE at the VLT to precisely monitor the orbital motion of beta
\bpic b since first light of the instrument in 2014. We were able to monitor
the planet until November 2016, when its angular separation became too small
(125 mas, i.e., 1.6\,au) and prevented further detection. We redetected \bpic b
on the northeast side of the disk at a separation of 139\,mas and a PA of
30 in September 2018. The planetary orbit is now well constrained.
With a semi-major axis (sma) of au (1 ), it
definitely excludes previously reported possible long orbital periods, and
excludes \bpic b as the origin of photometric variations that took place in
1981. We also refine the eccentricity and inclination of the planet. From an
instrumental point of view, these data demonstrate that it is possible to
detect, if they exist, young massive Jupiters that orbit at less than 2 au from
a star that is 20 pc away.Comment: accepted by A&
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