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  • 1
    Online Resource
    Online Resource
    Evidence of VLP volcanic tremor in the band [0.2–0.5] Hz at Stromboli volcano, Italy
    American Geophysical Union (AGU) ; 2005
    In:  Geophysical Research Letters Vol. 32, No. 17 ( 2005-09)
    Details
    In: Geophysical Research Letters, American Geophysical Union (AGU), Vol. 32, No. 17 ( 2005-09)
    Abstract: We analyze time series of Strombolian volcanic tremor recorded with a network of broadband seismic stations. We evidence the occurrence of a significant component of volcanic tremor in the range [0.2–0.5] Hz by using linear and nonlinear methods. The polarization and ZLCC analysis show that the wave field is characterized by high apparent velocity (∼2 km/s). It comes mainly from the crater area with a clear amplitude decay towards the sea level. The previous properties are loosed when the tremor level is higher suggesting that in this case the wave field is more affected by oceanic noise. The waveform extracted by Independent Component Analysis (ICA) shows a behaviour like nonlinear “beats” as in the case of high frequency waveforms. We conclude that this component displays a behaviour like the wave field at higher frequencies in spite of its low frequency, and it is produced by the vibrations of the volcanic conduit.
    Type of Medium: Online Resource
    ISSN: 0094-8276 , 1944-8007
    URL: Article
    DOI: 10.1029/2005GL023466
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2005
    detail.hit.zdb_id: 2021599-X
    detail.hit.zdb_id: 7403-2
    SSG: 16,13
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  • 2
    Online Resource
    Online Resource
    STROMBOLIAN-LIKE VOLCANO ACTIVITY: A COMMON MACROSCOPIC BEHAVIOUR
    World Scientific Pub Co Pte Ltd ; 2009
    In:  International Journal of Modern Physics B Vol. 23, No. 28n29 ( 2009-11-20), p. 5543-5552
    Details
    In: International Journal of Modern Physics B, World Scientific Pub Co Pte Ltd, Vol. 23, No. 28n29 ( 2009-11-20), p. 5543-5552
    Abstract: We report the results of the analysis of the occurrence times of the strombolian-like explosions at Stromboli (Italy) and Erebus volcano (Antarctica). The distribution of the inter-times between successive explosion-quakes is exponential for both volcanoes, the only difference being the occurrence rate. It suggests that the signature of the standard Strombolian activity can be identified in a Poissonian process that rules the mechanism of generation of the explosions. Finally, we adopt coalescence Chandrasekar-Landau mean-field model for the formation of the exploding gas bubbles. The model provides a size distribution that is in a good agreement with the observed bubble dimensions.
    Type of Medium: Online Resource
    ISSN: 0217-9792 , 1793-6578
    URL: Article
    DOI: 10.1142/S0217979209063845
    RVK:
    UA 4381.B
    Language: English
    Publisher: World Scientific Pub Co Pte Ltd
    Publication Date: 2009
    detail.hit.zdb_id: 2086681-1
    detail.hit.zdb_id: 246716-1
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  • 3
    Online Resource
    Online Resource
    Model for high‐frequency Strombolian tremor inferred by wavefield decomposition and reconstruction of asymptotic dynamics
    American Geophysical Union (AGU) ; 2008
    In:  Journal of Geophysical Research: Solid Earth Vol. 113, No. B2 ( 2008-02)
    Details
    In: Journal of Geophysical Research: Solid Earth, American Geophysical Union (AGU), Vol. 113, No. B2 ( 2008-02)
    Abstract: We study the volcanic tremor time series recorded by a broadband three‐component seismic network installed at Stromboli volcano during 1997. By using decomposition methods in both frequency and time domains, we prove that Strombolian tremor can be described as a linear combination of nonlinear signals in time domain. These “components” are similar to those obtained for explosion quakes, with the only difference being the amplitude enhancement. We characterize each of these nonlinear signals both in terms of their wavefield properties as well as dynamic systems. Moreover, we take into account the complex processes of magma flow and turbulent degassing, looking at time and amplitude modulation of tremor on a suitable scale. The distribution of tremor amplitudes is Gaussian while the intertimes between the maxima in a suitable scale are described by a Poisson clustered process. Starting from these analyses, a first approximate model for volcanic tremor field can be deduced. The recorded signals, i.e., the elastic vibrations at a point, can be described by a nonlinear equation which gives limit cycles (different observed “nonlinear modes”). This equation is governed by a time‐dependent threshold which represents the variability of bubble flux. We take into account some inelasticity in the medium perturbing the elastic potential with a Gaussian function on a suitable scale. It acts as a radiance function modulating the frequency of the limit cycle. This proposed model is able to reproduce waveform, Fourier spectrum, and phase space dimension of one of the extracted nonlinear wave packets.
    Type of Medium: Online Resource
    ISSN: 0148-0227
    URL: Article
    DOI: 10.1029/2006JB004838
    Language: English
    Publisher: American Geophysical Union (AGU)
    Publication Date: 2008
    detail.hit.zdb_id: 161666-3
    SSG: 16,13
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  • 4
    Online Resource
    Online Resource
    Statistical analysis of Stromboli VLP tremor in the band [0.1–0.5] Hz: some consequences for vibrating structures
    Copernicus GmbH ; 2006
    In:  Nonlinear Processes in Geophysics Vol. 13, No. 4 ( 2006-08-10), p. 393-400
    Details
    In: Nonlinear Processes in Geophysics, Copernicus GmbH, Vol. 13, No. 4 ( 2006-08-10), p. 393-400
    Abstract: Abstract. We analyze time series of Strombolian volcanic tremor, focusing our attention on the frequency band [0.1–0.5] Hz (very long period (VLP) tremor). Although this frequency band is largely affected by noise, we evidence two significant components by using Independent Component Analysis with the frequencies, respectively, of ~0.2 and ~0.4 Hz. We show that these components display wavefield features similar to those of the high frequency Strombolian signals (〉0.5 Hz). In fact, they are radially polarised and located within the crater area. This characterization is lost when an enhancement of energy appears. In this case, the presence of microseismic noise becomes relevant. Investigating the entire large data set available, we determine how microseismic noise influences the signals. We ascribe the microseismic noise source to Scirocco wind. Moreover, our analysis allows one to evidence that the Strombolian conduit vibrates like the asymmetric cavity associated with musical instruments generating self-sustained tones.
    Type of Medium: Online Resource
    ISSN: 1607-7946
    URL: Article
    DOI: 10.5194/npg-13-393-2006
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2006
    detail.hit.zdb_id: 2078085-0
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  • 5
    Online Resource
    Online Resource
    Self-sustained oscillations at Volcán de Colima (México) inferred by Independent Component Analysis
    Springer Science and Business Media LLC ; 2012
    In:  Bulletin of Volcanology Vol. 74, No. 1 ( 2012-1), p. 279-292
    Details
    In: Bulletin of Volcanology, Springer Science and Business Media LLC, Vol. 74, No. 1 ( 2012-1), p. 279-292
    Type of Medium: Online Resource
    ISSN: 0258-8900 , 1432-0819
    URL: Article
    DOI: 10.1007/s00445-011-0520-x
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2012
    detail.hit.zdb_id: 635594-8
    detail.hit.zdb_id: 1458483-9
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  • 6
    Online Resource
    Online Resource
    Decomposition of high-frequency seismic wavefield of the Strombolian-like explosions at Erebus volcano by independent component analysis
    Oxford University Press (OUP) ; 2009
    In:  Geophysical Journal International Vol. 177, No. 3 ( 2009-06), p. 1399-1406
    Details
    In: Geophysical Journal International, Oxford University Press (OUP), Vol. 177, No. 3 ( 2009-06), p. 1399-1406
    Type of Medium: Online Resource
    ISSN: 0956-540X , 1365-246X
    URL: Issue
    URL: Article
    DOI: 10.1111/gji.2009.177.issue-3
    DOI: 10.1111/j.1365-246X.2009.04157.x
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2009
    detail.hit.zdb_id: 2006420-2
    detail.hit.zdb_id: 1002799-3
    SSG: 16,13
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  • 7
    Online Resource
    Online Resource
    Modelling the macroscopic behavior of Strombolian explosions at Erebus volcano
    Elsevier BV ; 2009
    In:  Physics of the Earth and Planetary Interiors Vol. 176, No. 3-4 ( 2009-10), p. 174-186
    Details
    In: Physics of the Earth and Planetary Interiors, Elsevier BV, Vol. 176, No. 3-4 ( 2009-10), p. 174-186
    Type of Medium: Online Resource
    ISSN: 0031-9201
    URL: Article
    DOI: 10.1016/j.pepi.2009.05.003
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2009
    detail.hit.zdb_id: 3901-9
    SSG: 16,13
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  • 8
    Online Resource
    Online Resource
    Self-sustained vibrations in volcanic areas extracted by Independent Component Analysis: a review and new results
    Copernicus GmbH ; 2011
    In:  Nonlinear Processes in Geophysics Vol. 18, No. 6 ( 2011-12-08), p. 925-940
    Details
    In: Nonlinear Processes in Geophysics, Copernicus GmbH, Vol. 18, No. 6 ( 2011-12-08), p. 925-940
    Abstract: Abstract. We investigate the physical processes associated with volcanic tremor and explosions. A volcano is a complex system where a fluid source interacts with the solid edifice so generating seismic waves in a regime of low turbulence. Although the complex behavior escapes a simple universal description, the phases of activity generate stable (self-sustained) oscillations that can be described as a non-linear dynamical system of low dimensionality. So, the system requires to be investigated with non-linear methods able to individuate, decompose, and extract the main characteristics of the phenomenon. Independent Component Analysis (ICA), an entropy-based technique is a good candidate for this purpose. Here, we review the results of ICA applied to seismic signals acquired in some volcanic areas. We emphasize analogies and differences among the self-oscillations individuated in three cases: Stromboli (Italy), Erebus (Antarctica) and Volcán de Colima (Mexico). The waveforms of the extracted independent components are specific for each volcano, whereas the similarity can be ascribed to a very general common source mechanism involving the interaction between gas/magma flow and solid structures (the volcanic edifice). Indeed, chocking phenomena or inhomogeneities in the volcanic cavity can play the same role in generating self-oscillations as the languid and the reed do in musical instruments. The understanding of these background oscillations is relevant not only for explaining the volcanic source process and to make a forecast into the future, but sheds light on the physics of complex systems developing low turbulence.
    Type of Medium: Online Resource
    ISSN: 1607-7946
    URL: Article
    DOI: 10.5194/npg-18-925-2011
    Language: English
    Publisher: Copernicus GmbH
    Publication Date: 2011
    detail.hit.zdb_id: 2078085-0
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  • 9
    Online Resource
    Online Resource
    P27 DOPPLER ULTRASOUND SELECTION AND FOLLOW–UP OF THE INTERNAL MAMMARY ARTERY AS CORONARY GRAFT
    Oxford University Press (OUP) ; 2023
    In:  European Heart Journal Supplements Vol. 25, No. Supplement_D ( 2023-05-18), p. D49-D49
    Details
    In: European Heart Journal Supplements, Oxford University Press (OUP), Vol. 25, No. Supplement_D ( 2023-05-18), p. D49-D49
    Abstract: The impact of coronary artery disease (CAD) on all–cause mortality and overall disabilities is well–established. Percutaneous and/or surgical coronary revascularization procedures dramatically reduced the occurrence of adverse cardiovascular events in patients suffering with atherosclerosis. Specifically, guidelines from the European Society of Cardiology on the management of myocardial revascularization promoted coronary artery by–pass graft (CABG) intervention in patients with specific alterations in coronary tree due to higher beneficial effects of this procedure as compared to percutaneous one. Left internal mammary artery (LIMA) is one of the best–performing vessels in CABG procedures due to its location and its own structural characteristics. Nevertheless, non–invasive assessment of its patency is challenging. Doppler Ultrasonography (DU) might perform as a reliable technique for non–invasive evaluation of the patency of LIMA. Data from literature revealed that DU may detect severe ( & gt;70%) stenosis of the LIMA graft. In this case, pulsed–wave Doppler might show peak diastolic velocity/peak systolic velocity & lt; 0.5 and diastolic fraction & lt; 50%). Stress test might also be adopted for the evaluation of patency of LIMA through DU. The aim of this narrative review is to evaluate the impact of DU on the evaluation of the patency of LIMA graft in patients who undergo follow–up after CABG intervention. The aim of this narrative review is to evaluate the impact of DU on the evaluation of the patency of LIMA graft in patients who undergo follow–up after CABG intervention.
    Type of Medium: Online Resource
    ISSN: 1520-765X , 1554-2815
    URL: Article
    DOI: 10.1093/eurheartjsupp/suad111.113
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2023
    detail.hit.zdb_id: 2141255-8
    detail.hit.zdb_id: 1463769-8
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  • 10
    Online Resource
    Online Resource
    P4547Serum biochemical determinants of peripheral congestion assessed by bioimpedance vector analysis in acute heart failure
    Oxford University Press (OUP) ; 2019
    In:  European Heart Journal Vol. 40, No. Supplement_1 ( 2019-10-01)
    Details
    In: European Heart Journal, Oxford University Press (OUP), Vol. 40, No. Supplement_1 ( 2019-10-01)
    Abstract: The pathophysiology of peripheral congestion is poorly investigated in patients with acute heart failure (AHF). Purpose This study evaluated the relative contribution of serum colloid osmotic pressure (COP), relative plasma volume status (PVS), biomarkers of renal function, electrolytes, haemoglobin, and brain natriuretic peptide (BNP) in peripheral fluid overload using bioimpedance vector analysis (BIVA). Methods We retrospectively analysed data from 485 patients with AHF. Hydration status was evaluated by semiquantitative and quantitative approach using BIVA (R/Xc graph) and Hydration Index (HI), respectively. COP was calculated from albumin and total protein concentration, while relative PVS was calculated from validated equations. Results Congestion assessed by BIVA was observed in 304 (63%) patients and classified as mild (30%), moderate (42%), and severe (28%). On univariate analysis, HI was inversely correlated with COP (P 〈 0.01), glomerular filtration rate (P 〈 0.01), and haemoglobin (P 〈 0.01), while positive correlations were found for relative PVS (P 〈 0.05), BNP (P 〈 0.01), and blood urea nitrogen (BUN; P 〈 0.01). On stepwise multivariate analysis, COP explained 12% of the total variability, while BUN, PVS, haemoglobin, and BNP added a further 6%, 4%, 2%, and 1%, respectively, to the final explanatory model. Conclusions COP was the major determinant of the presence and entity of peripheral congestion assessed by BIVA. BUN, PVS, haemoglobin, and BNP revealed reduced influence on congestion as compared with COP. Routine laboratory testing could be useful in peripheral fluid accumulation. Future studies should evaluate the relationship between COP and pharmacological target therapies for the fluid management of AHF patients. Acknowledgement/Funding None
    Type of Medium: Online Resource
    ISSN: 0195-668X , 1522-9645
    URL: Article
    DOI: 10.1093/eurheartj/ehz745.0938
    Language: English
    Publisher: Oxford University Press (OUP)
    Publication Date: 2019
    detail.hit.zdb_id: 2001908-7
    detail.hit.zdb_id: 603098-1
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