0000000000589480
AUTHOR
M. Spanò
showing 12 related works from this author
Presence of a soft excess between 0.6 keV and 0.9 keV in the energy spectrum of Cir X-1
2004
Abstract We report on the results of a new BeppoSAX (0.12–200 keV) observation of the peculiar X–ray binary source Circinus X–1 (Cir X–1) near the apastron. We produced a color-color diagram and selected seven different zones. We fitted the spectra obtained from each zone using a model consisting of a blackbody component, at a temperature of ∼0.5 keV, and a Comptonized component, with a seed-photon temperature of ∼1 keV, electron temperature of ∼2.7 keV and optical depth of ∼11. A soft excess between 0.6 keV and 0.9 keV is present in four out of the seven extracted spectra. To fit the soft excess we tried several continuum emission models, and we find good results only adding a further blac…
Inverted and mirror repeats in model nucleotide sequences.
2007
We analytically and numerically study the probabilistic properties of inverted and mirror repeats in model sequences of nucleic acids. We consider both perfect and non-perfect repeats, i.e. repeats with mismatches and gaps. The considered sequence models are independent identically distributed (i.i.d.) sequences, Markov processes and long range sequences. We show that the number of repeats in correlated sequences is significantly larger than in i.i.d. sequences and that this discrepancy increases exponentially with the repeat length for long range sequences.
Statistical properties of thermodynamically predicted RNA secondary structures in viral genomes
2008
By performing a comprehensive study on 1832 segments of 1212 complete genomes of viruses, we show that in viral genomes the hairpin structures of thermodynamically predicted RNA secondary structures are more abundant than expected under a simple random null hypothesis. The detected hairpin structures of RNA secondary structures are present both in coding and in noncoding regions for the four groups of viruses categorized as dsDNA, dsRNA, ssDNA and ssRNA. For all groups hairpin structures of RNA secondary structures are detected more frequently than expected for a random null hypothesis in noncoding rather than in coding regions. However, potential RNA secondary structures are also present i…
Moving across the static magnetic field of a 1.5 T MRI scanner: Analysing compliance with Directive 2013/35/EU
2018
Abstract Does the exposure of magnetic resonance imaging personnel to static magnetic fields fully comply with Directive 2013/35/EU? Despite the obligation to satisfy this question, a general answer cannot be provided, nor are final satisfying good practices methods for exposure assessment currently available. In order to contribute to fix this problem, three different 1.5 T scanners are analysed and – by a new theoretical insight – a positive answer is provided.
Sensitivity of alanine dosimeters with gadolinium exposed to 6 MV photons at clinical doses.
2011
In this study we analyzed the ESR signal of alanine dosimeters with gadolinium exposed to 6 MV linear accelerator photons. We observed that the addition of gadolinium brings about an improvement in the sensitivity to photons because of its high atomic number. The experimental data indicated that the addition of gadolinium increases the sensitivity of the alanine to 6 MV photons. This enhancement was better observed at high gadolinium concentrations for which the tissue equivalence is heavily reduced. However, information about the irradiation setup and of the radiation beam features allows one to correct for this difference. Monte Carlo simulations were carried out to obtain information on …
Inverted Repeats in Viral Genomes
2004
We investigate 738 complete genomes of viruses to detect the presence of short inverted repeats. The number of inverted repeats found is compared with the prediction obtained for a Bernoullian and for a Markovian control model. We find as a statistical regularity that the number of observed inverted repeats is often greater than the one expected in terms of a Bernoullian or Markovian model in several of the viruses and in almost all those with a genome longer than 30,000 bp.
Cyclic influences on the heavy metal chronology in a Central Mediterranean area (Palermo Gulf, Italy)
2010
PurposeThe evaluation of long-term heavy metal concentrations in the Gulf of Palermo (Italy) has been carried out in order to investigate how changes of pollution levels in the last 50 years can be reflected in marine sediments. Measurements of Cr, Cu, Hg, Pb, and Zn concentrations were performed on dated fractions of a sediment core. Time series analysis has allowed to obtain information on the chronology of the heavy metal pollution of the area and to identify seasonal components and trends.Materials and methodsHeavy metal concentrations in the <63 μm fraction of core sections were obtained by Atomic Absorption Spectrophotometry, after wet sieving, drying, and digestion procedures. Dating…
34. Accomplishing the requirements within the new decree 159/2016: Comparative study of eddy currents induced in a human phantom moving near differen…
2018
Purpose In order to provide adequate risk-reducing procedures for MRI personnel (radiographers, anaesthetists, physicists, nurses, technicians, cleaners, etc.), different studies have been developed in the past years. Further to those, in the present work risk assessment concerned with currents induced by non-uniform static magnetic fields in MRI operators performing different tasks in proximity of the scanner has been investigated across a set of different 1.5 T MRI scanners. Methods The first step has been to empirically map the magnetic field around the different scanners and to select a proper adult human body as a heterogeneous volume conductor model. Then, upon observing the way tasks…
On the soft excess in the x-ray spectrum of circinus X-1: Revisitation of the distance to circinus X-1
2005
We report on a 300 ks BeppoSAX (0.12-200 keV) observation of Circinus X-1 (Cir X-1) at phases between 0.62 and 0.84 and on a 90 ks BeppoSAX observation of Cir X-1 at phases 0.11-0.16. Using the canonical model adopted until now to fit the energy spectrum of this source, large residuals appear below 1 keV. These are well fitted using an equivalent hydrogen column of 0.66¿1022 cm-2, adding absorption edges of O VII, O VIII, and Ne IX in the spectra extracted from the observation at phases 0.62-0.84 and adding absorption edges of O VII, O VIII, Mg XI, and Mg XII and absorption lines of O VIII and Mg XII in the spectra extracted from the observation at phases 0.11-0.16. During the observation a…
Misure preliminari su scanner MRI 7T di stabilità nel tempo di Dosimetri gel di tipo Fricke
2016
L’ottimizzazione delle procedure che utilizzano radiazioni ionizzanti in campo medico costituisce un elemento chiave per la sicurezza del paziente e l’esito dei trattamenti radioterapici. In particolare è fondamentale arrecare il minor danno possibile ai tessuti sani circostanti la neoplasia da trattare (Attix, 2004). La misurazione precisa della dose somministrata nei tessuti e la sua mappatura in tre dimensioni sono di fondamentale importanza in termini di riuscita e di pianificazione dei trattamenti radioterapici (Khan, 2009). In questo lavoro sono presentate le misure preliminari effettuate per testare la stabilità temporale di dosimetri gel di tipo Fricke tramite scanner pre-clinico 7T…
Accomplishing the requirements within the new decree 159/2016: Comparative study of eddy currents induced in a human phantom moving near different MR…
2019
Purpose. In order to provide adequate risk-reducing procedures for MRI personnel (radiographers, anaesthetists, physicists, nurses, technicians, cleaners, etc.), different studies have been developed in the past years. Further to those, in the present work risk assessment concerned with currents induced by non-uniform static magnetic fields in MRI operators performing different tasks in prox imity of the scanner has been investigated across a set of different 1.5 T MRI scanners. Methods. The first step has been to empirically map the magnetic field around the different scanners and to select a proper adult human body as a heterogeneous volume conductor model. Then, upon observing the way ta…
Moving inside a MRI room: A risk assessment analysis
2018
Moving across the stray magnetic field generated by a medical magnetic resonance imaging system may induce electric stimulation near or even beyond the threshold of physiological significance and adequate risk-reducing procedures for the involved personnel may be re quired. With this in mind, a set of different scanners has been analysed. Results suggest that a 1.5 T magnet may be expected in general to comply with the requirements of the currently in force European Electromagnetic Fields Directive for ensuring the health and safety of workers.