6,090 research outputs found
A multi-flow model for microquasars
We present a new picture for the central regions of Black Hole X-ray
Binaries. In our view, these central regions have a multi-flow configuration
which consists in (1) an outer standard accretion disc down to a transition
radius r_J, (2) an inner magnetized accretion disc below r_J driving (3) a non
relativistic self-collimated electron-proton jet surrounding, when adequate
conditions for pair creation are met, (4) a ultra relativistic
electron-positron beam. This accretion-ejection paradigm provides a simple
explanation to the canonical spectral states, from radio to X/gamma-rays, by
varying the transition radius r_J and disc accretion rate independently. Large
values of r_J and low accretion rate correspond to Quiescent and Hard states.
These states are characterized by the presence of a steady electron-proton MHD
jet emitted by the disc below r_J. The hard X-ray component is expect to form
at the jet basis. When r_J becomes smaller than the marginally stable orbit
r_i, the whole disc resembles a standard accretion disc with no jet,
characteristic of the Soft state. Intermediate states correspond to situations
where r_J ~ r_i. At large accretion rate, an unsteady pair cascade process is
triggered within the jet axis, giving birth to flares and ejection of
relativistic pair blobs. This would correspond to the luminous intermediate
state, with its associated superluminal motions.Comment: 12 pages, 3 figures. Proceedings of ``High Energies in the
Highlands'', Fort-William, 27 June-1 July 200
UN NUOVO ALGORITMO PER LA DETERMINAZIONE DELL\u2019AMPIEZZA DELLA TENSIONE TANGENZIALE NEI CRITERI DI FATICA BASATI SUL PIANO CRITICO
I criteri di fatica multiassiale ad alto numero di cicli basati sull\u2019approccio di piano critico richiedono la determinazione dell\u2019ampiezza delle tensioni tangenziali di fatica \uf074a agenti sui diversi piani passanti per il punto del materiale analizzato. Tipicamente la determinazione di \uf074a viene effettuata considerando il Minimo Cerchio Circoscritto alla curva descritta dalla punta del vettore \uf074 agente nel piano nel periodo di sollecitazione. In genere tale determinazione richiede un certo sforzo computazionale. In questo lavoro viene descritta una procedura numerica per la determinazione Minimo Cerchio Circoscritto ad una curva nota per punti caratterizzato da velocit\ue0 di esecuzione superiore a quelle esistenti
Effect of insulin glargine on cardiovascular risk analysed by mean HRV
Type 2 diabetes mellitus is an insidious disease that is increasingly present in geriatric population [1]. The greatest difficulty is represented by glycaemic control in geriatric patients often not very compliant with diet therapy and drug therapy. A new insulin glargine 300 units/ml formulation seems im- prove patient compliance due to the lower volume of insulin to be injected and improved glycaemic control over 24 hours. The HRV signal, derived from digital electrocardiographic recording, is the simplest and most imme- diate analysis that consists in calculating some temporal parameters [2]. HRV is a simple statistics derived from beat-beat intervals of sinus origin expressed as units of time in milliseconds. Data in the literature indicate that a decrease in HRV, measured with time domain analysis, denotes a worse prognosis and/or an increased risk of mortality in patients with heart disease, especially in the elderly ones
FROM 2D TO 3D SUPERVISED SEGMENTATION AND CLASSIFICATION FOR CULTURAL HERITAGE APPLICATIONS
The digital management of architectural heritage information is still a complex problem, as a heritage object requires an integrated representation of various types of information in order to develop appropriate restoration or conservation strategies. Currently, there is extensive research focused on automatic procedures of segmentation and classification of 3D point clouds or meshes, which can accelerate the study of a monument and integrate it with heterogeneous information and attributes, useful to characterize and describe the surveyed object. The aim of this study is to propose an optimal, repeatable and reliable procedure to manage various types of 3D surveying data and associate them with heterogeneous information and attributes to characterize and describe the surveyed object. In particular, this paper presents an approach for classifying 3D heritage models, starting from the segmentation of their textures based on supervised machine learning methods. Experimental results run on three different case studies demonstrate that the proposed approach is effective and with many further potentials
The XMM/BeppoSAX observation of Mkn 841
Mkn 841 has been observed simultaneously by XMM and BeppoSAX in January 2001.
Due to operational contingency, the 30ks XMM observation was split into two
parts, separated by about 15 hours. We first report the presence of a narrow
iron line which appears to be rapidly variable between the two pointings,
requiring a non-standard interpretation. We then focus on the analysis of the
broad band (0.3-200 keV) continuum using the XMM/EPIC, RGS and SAX/PDS data.
The Mkn 841 spectrum is well fitted by a comptonization model in a geometry
more photon-fed than a simple slab geometry above a passive disk. It presents a
relatively large reflection (R>2) which does not agree with an apparently weak
iron line. It also show the presence of a strong soft excess wellfitted by a
comptonized spectrum in a cool plasma, suggesting the presence of a
multi-temperature corona.Comment: 4 pages, 5 figures. Proc. of the meeting: "The Restless High-Energy
Universe" (Amsterdam, The Netherlands), E.P.J. van den Heuvel, J.J.M. in 't
Zand, and R.A.M.J. Wijers Ed
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