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Search Results: 1 - 10 of 6096 matches for " Stefano Scaringi "
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Vascular Invasion, Satellite Nodules and Absence of Tumor Capsule Strongly Correlate with Disease-Free Survival and Long-Term Outcome in Patients Resected for Hepatocellular Carcinoma  [PDF]
Benedetta Pesi, Luca Moraldi, Daniela Zambonin, Francesco Giudici, Tiziana Cavalli, Rami Addasi, Francesca Leo, Stefano Scaringi, Giacomo Batignani
Journal of Cancer Therapy (JCT) , 2014, DOI: 10.4236/jct.2014.514134
Abstract: Background: Hepatocellular carcinoma (HCC) is one of the most common cancer in the world. Liver resection (LR) is the most used therapy in well compensated liver cirrhosis and maybe used as a first-line treatment. Aim of the study is to evaluate survival rates in patients who underwent LR for HCC and to identify risk factors able to influence the prognosis. Material/Method: A retrospective study was carried out in 115 patients whounderwent LR for HCC. We evaluated overall and disease-free survival rates at 1, 3 and 5years (y) and a series of variables included: type of resection, clamping, blood loss, transfusions, tumor size, presence of capsule, satellite nodules and vascular invasion. Results: The 1-, 3-, 5-y survival rates were 90.2%, 67% and 52.7%, and disease-free survival rates
Broad-band variability in accreting compact objects
Simone Scaringi
Physics , 2014,
Abstract: Cataclysmic variable stars are in many ways similar to X-ray binaries. Both types of systems possess an accretion disk, which in most cases can reach the surface (or event horizon) of the central compact object. The main difference is that the embedded gravitational potential well in X-ray binaries is much deeper than those found in cataclysmic variables. As a result, X-ray binaries emit most of their radiation at X-ray wavelengths, as opposed to cataclysmic variables which emit mostly at optical/ultraviolet wavelengths. Both types of systems display aperiodic broad-band variability which can be associated to the accretion disk. Here, the properties of the observed X-ray variability in XRBs are compared to those observed at optical wavelengths in CVs. In most cases the variability properties of both types of systems are qualitatively similar once the relevant timescales associated with the inner accretion disk regions have been taken into account. The similarities include the observed power spectral density shapes, the rms-flux relation as well as Fourier-dependant time lags. Here a brief overview on these similarities is given, placing them in the context of the fluctuating accretion disk model which seeks to reproduce the observed variability.
A physical model for the flickering variability in cataclysmic variables
Simone Scaringi
Physics , 2013, DOI: 10.1093/mnras/stt2270
Abstract: Aperiodic broad-band variability (also known as flickering) is observed throughout all types of accreting compact objects. Many statistical properties of this variability can be naturally explained with the fluctuating accretion disk model, where variations in the mass-transfer rate through the disk are modulated on the local viscous timescale and propagate towards the central compact object. Here, a recently developed implementation of the model is applied for the first time to the time-averaged, high-frequency variability of a cataclysmic variable star (MV Lyrae) observed with the Kepler satellite. A qualitatively good fit to the data is achieved, suggesting the presence of geometrically thick inner flow with large viscosity parameter, extending from $\sim0.12R_{\odot}$ all the way to the white dwarf surface. A simple spectral model of the system suggests that the geometrically thick component would not contribute much to the observed optical flux originating from the geometrically thin outer disk. Instead, X-ray reprocessing from the geometrically thick disk onto the thin disk is proposed as a mechanism to explain the observed variability. Similar flows are also deduced in accreting neutron stars/black holes (X-ray binaries) and Active Galactic Nuclei. Additionally, eclipse mapping studies of cataclysmic variables also seem to suggest the presence of a geometrically extended flow towards the inner-edges of the accretion disk. The fluctuating accretion disk model applied here is encouraging in understanding the origin of flickering in cataclysmic variables, as well as in X-ray binaries and Active Galactic Nuclei, by providing a unifying scheme by which to explain the observed broad-band variability features observed throughout all compact accreting systems.
Radiation techniques for acromegaly
Giuseppe Minniti, Claudia Scaringi, Riccardo Enrici
Radiation Oncology , 2011, DOI: 10.1186/1748-717x-6-167
Abstract: Acromegaly is a disorder caused by a pituitary GH-secreting adenoma and characterized by high circulating levels of GH and IGF-I. It is associated with increased morbidity and mortality rates, especially due to respiratory, cardiovascular disease, and malignant diseases [1]. Surgery, medical therapy, and radiotherapy (RT) are the available treatments employed with the aim of normalizing GH and IGF-I hypersecretion, controlling pituitary tumor mass effects, preventing recurrences, and improving morbidity. Transsphenoidal surgery is the procedure of choice for the initial management of acromegaly, leading to the remission of disease in 42-65% of patients [2], and achieving a rapid improvement of metabolic and cardiovascular abnormalities [3,4]. Medical therapy, mainly with long-acting somatostatin analogs, permits a normalization of GH/IGF-I hypersecretion in up to 70% of cases with an apparently low incidence of side effects [5]. RT is currently proposed to a subset of patients with persistent active disease after surgery and/or during medical therapy. In most of published studies conventional RT achieves tumor growth control in 85-95% of cases, dropping out GH/IGF-I levels to less than 5 ng/ml in up to 80% of patients 10-15 years after RT [6]. Despite its efficacy, there are concerns about the necessity and potential toxicity of RT and its use remains matter of debate.More recently, stereotactic radiation techniques have been employed in patients with acromegaly with the aim of treating less normal brain and of minimizing the long-term consequences of RT while improving its effectiveness [7]. Stereotactic radiotherapy can be given as a single treatment (stereotactic radiosurgery-SRS) using either cobalt-60 gamma radiation-emitting sources (Gamma-Knife) or linear accelerator (LINAC), or as fractionated stereotactic radiotherapy (FSRT). Although stereotactic techniques have the clear advantage to offer a more precise radiation delivery compared with conventional RT, t
Reversibility of time series: revealing the hidden messages in X-ray binaries and cataclysmic variables
S. Scaringi,T. J. Maccarone,M. Middleton
Physics , 2014, DOI: 10.1093/mnras/stu1824
Abstract: We explore the non-linear, high-frequency, aperiodic variability properties in the three cataclysmic variables MV Lyr, KIC 8751494 and V1504 Cyg observed with Kepler, as well as the X-ray binary Cyg X-1 observed with RXTE. This is done through the use of a high-order Fourier statistic called the bispectrum and its related biphase and bicoherence, as well as the time-skewness statistic. We show how all objects display qualitatively similar biphase trends. In particular all biphase amplitudes are found to be smaller than $\pi/2$, suggesting that the flux distributions for all sources are positively skewed on all observed timescales, consistent with the log-normal distributions expected from the fluctuating accretion disk model. We also find that for all objects the biphases are positive at frequencies where the corresponding power spectral densities display their high frequency break. This suggests that the noise-like flaring observed is rising more slowly than it is falling, and thus not time-reversible. This observation is also consistent with the fluctuating accretion disk model. Furthermore, we observe the same qualitative biphase trends in all four objects, where the biphases display a distinct decrease at frequencies below the high-frequency break in their respective power spectral densities. This behaviour can also be observed in the time-skewness of all four objects. As far as we are aware, there is no immediate explanation for the observed biphase decreases. The biphase decreases may thus suggest that the fluctuating accretion disk model begins to break down at frequencies below the high frequency break.
Kepler observations of the eclipsing cataclysmic variable KIS J192748.53+444724.5
S. Scaringi,P. J. Groot,M. Still
Physics , 2013, DOI: 10.1093/mnrasl/slt099
Abstract: We present results from long cadence Kepler observations covering 97.6 days of the newly discovered eclipsing cataclysmic variable KIS J192748.53+444724.5/KIC 8625249. We detect deep eclipses of the accretion disk by the donor star every 3.97 hours. Additionally, the Kepler observations also cover a full outburst for this cataclysmic variable, making KIS J192748.53+444724.5 the second known eclipsing cataclysmic variable system in the Kepler field of view. We show how in quiescence a significant component associated to the hot-spot is visible preceding the eclipse, and that this component is swamped by the brightness increase during the outburst, potentially associated with the accretion disk. Furthermore we present evidence for accretion disk radius changes during the outburst by analysing the out-of-eclipse light levels and eclipse depth through each orbital cycle. We show how these parameters are linearly correlated in quiescence, and discuss how their evolution during the outburst is suggesting disk radius changes and/or radial temperature gradient variations in the disk.
Feasibility Evaluation of Integrating UsabilityEngineering Issues in a Design for Multi-XCollaborative Framework  [PDF]
Stefano Filippi
Intelligent Information Management (IIM) , 2011, DOI: 10.4236/iim.2011.31004
Abstract: Design for manufacturing, design for assembly, and, in general, design for X, are methods helping an effective generation of industrial products. In parallel with the development of these methods, the research about usability engineering has generated many important results, both from the design, and the evaluation and testing points of view. The research described in this paper aims at evaluating the feasibility of the integration of two new usability methods, the design for innovative usability - DFIU -, and the integrated method for usability evaluation and testing - IMUET -, in an existing design for X named design guidelines collaborative framework - DGLs-CF -. Indeed, the DGLs-CF is a design for multi-X method, given that it covers both the manufacturing and the verification phases of the industrial product lifecycle. All these methods are currently under development by the author’s research group. To evaluate this feasibility, the first task of the research aims at describing and classifying the components of the three methods. Next, these components are semantically related to each other. Finally, the last activity verifies the compatibility between the components of the two usability methods and the data structures of the DGLs-CF to check the feasibility from the implementation point of view. The result of this research will consist of precise indications both for the development of a design for multi-X collaborative framework covering homogeneously the design, manufacturing, verification, and use phases of the industrial product lifecycle, and to be used as a reference for researchers interested in considering the integration of usability issues in their design tools, methods, and processes.
A General Purpose Analysis Package  [PDF]
Stefano Federico
Atmospheric and Climate Sciences (ACS) , 2012, DOI: 10.4236/acs.2012.22022
Abstract: This paper presents a general-purpose analysis package able to solve two- and three- dimensional analysis problems. The system can use the following methods of solution: Successive Approximation (SA), Optimal Interpolation (OI), and 3D-Var. Analyses are given for the following parameters: zonal and meridional wind components, temperature, relative humidity, and geopotential height. The analysis package was applied to produce analyses at 6 h time interval for the period 1-11 August 2008. The period was selected for data availability and forty-one analyses were collected. The results show the validity of the different solutions, which can be chosen depending on the physical problem to solve and on the computational resources available. In particular, assuming the observations as the reference, all solutions show a decrease of the RMSE compared to the background. The decrease is consistent with the particular setting of the analysis system used in this paper. The comparison between different solutions shows that the SA converges to OI in few iterations, and that the SA solution with ten iteration is, in practice, equal to OI. Moreover, the 3D-Var method shows its potential to improve the analysis, once the horizontal and vertical length-scales and the background and observational errors are set optimally, because its solution may be sizeably different from two-dimensional methods.
Preliminary Results of a Data Assimilation System  [PDF]
Stefano Federico
Atmospheric and Climate Sciences (ACS) , 2013, DOI: 10.4236/acs.2013.31009
Abstract:

A data assimilation system combines all available information on the atmospheric state in a given time-window to produce an estimate of atmospheric conditions valid at a prescribed analysis time. Nowadays, increased computing power coupled with greater access to real-time asynoptic data is paving the way toward a new generation of high-resolution (i.e. on the order of 10 km) operational mesoscale analyses and forecasting systems. Moreover, better initial conditions are increasingly considered of the utmost importance for Numerical Weather Prediction (NWP) at the short range (0 - 12 h). This paper presents a general-purpose data assimilation system, which is coupled with the Regional Atmospheric Modelling System (RAMS) to give the analyses for: zonal and meridional wind components, temperature, relative humidity, and geopotential height. In order to show its potential, the data assimilation systems applied to produce analyses over Central Europe. For this application the background field is given by a short-range forecast (12 h) of the RAMS and analyses are produced by 2D-Var with 0.25? horizontal resolution. Results show the validity of the analyses because they are closer to the observations, consistently with the settings of the data assimilation system. To quantify the impact of improved initial conditions on the forecast, the analyses are then used as initial conditions of a short-range (6 h) forecast of the RAMS model. The results show that the RMSE is effectively reduced for the one- and two hours forecast, with some improvement for the three-hours forecast.

Continued Fractions and Dynamics  [PDF]
Stefano Isola
Applied Mathematics (AM) , 2014, DOI: 10.4236/am.2014.57101
Abstract:

Several links between continued fractions and classical and less classical constructions in dynamical systems theory are presented and discussed.


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