1,721,074 research outputs found
The resolution of whole Earth seismic tomographic models
No full textWe evaluate the resolution of whole Earth structure achieved by compressional wave traveltime data from the International Seismological Centre (ISC); the measure of resolution we employ, provided by the direct calculation of the model resolution matrix, is more rigorous than the traditional (and computationally cheaper) one obtained through synthetic/checkerboard tests. Our work completes the introductive study of Boschi (2003), where only mantle models derived with a very simple regularization scheme were considered. Here, we expand Boschi's database with measurements of compressional waves reflected by, or refracted through, the Earth's core mantle boundary (CMB) and core. In analogy with the work of Soldati et al. (2003), we treat CMB topography and heterogeneous outer core structure as free parameters of our inversions; analysing model resolution matrices, we attempt to explain the known discrepancy between deep Earth structure mapped by seismic waves reflected and refracted by the core
Global seismic tomography and modern parallel computers
No full textA fast technological progress is providing seismic tomographers with computers of rapidly increasing speed and RAM, that are not always properly taken advantage of. Large computers with both shared-memory and distributed-memory architectures have made it possible to approach the tomographic inverse problem more accurately. For example, resolution can be quantified from the resolution matrix rather than checkerboard tests; the covariance matrix can be calculated to evaluate the propagation of errors front data to model parameters; the L-curve method can be applied to determine a range of acceptable regularization schemes. We show how these exercises can be implemented efficiently on different hardware architectures
Lung sonography for the cardiologist
No full textIn the recent years lung sonography has overcome his pioneer phase with the contribution of significant data from authors of different disciplines. Today there is therefore a strong evidence that this diagnostic method could have an important impact for the diagnosis of cardiothoracic symptoms, mainly dyspnea, in emergency or in ambulatory medicine. Since the cardiologist already uses ultrasound for the study of the heart, he or she could consider the integrated cardiopulmonary sonography extremely attractive in this specific context. In this review the authors describe the anatomical, biophysical and clinical basis of lung ultrasonography in a cardiological setting. © 2007 AIM Publishing Srl
Le attività produttive e la vulnerabilità territoriale nelle zone di pianura: il caso della provincia di Modena
No full textDopo avere descritto le caratteristiche fisiche del territorio dell'alta pianura modenese, in particolare gli aspetti idrogeologici, la presente nota individua le cause dei fenomeni di inquinamento a carico delle acque di falda, le modalità di diffusione degli inquinanti nel sottosuolo ed i criteri di valutazione della vulnerabilità territoriale. I rischi più elevati di contaminazione delle risorse idriche sotterranee derivano attualmente dall'inadeguato smantellamento dei liquami suini
Outer core density heterogeneity and the discrepancy between PKP and PcP travel time observations
No full text[1] We derive 3-D tomographic maps of the Earth's mantle, CMB and outer core, from seismic P, PcP, PKPbc, PKPdf travel time data, based on the bulletins of the International Seismological Centre (1964-1995), after source relocation by Antolik et al. [2001] and phase re-identification by Engdahl et al. [1998]. Maps of the CMB derived independently from core-reflected (PcP) or core-refracted (PKP) phases are not well correlated. We attempt to explain this discrepancy, and study the radial coherence of whole-Earth tomographic images, to identify possible trade-offs between CMB undulations and velocity anomalies in the mantle or outer core. Imaged velocity anomalies in the lowermost mantle are anticorrelated with the topography of the CMB; likewise, imaged lateral heterogeneities in the outer core are correlated with the topography of the CMB. This, together with the study of Piersanti et al. [2001], suggests that the core anomalies might not be entirely fictitious
Acute heart failure: New diagnostic perspectives for the emergency physician
No full textThe topic of heart failure (HF) in the emergency department is today relevant, since there are new serum markers and imaging techniques that may help in the diagnosis of this disease. Natriuretic peptides have now entered the flowchart for etiologic diagnosis in patients with acute dyspnea, when technical facilities are available. Recently, chest ultrasonography has been shown to be useful for the noninvasive assessment of extravascular lung water. Starting from this practical standpoint, we propose that simple chest ultrasonogrpahic signs can provide a totally noninvasive characterization of pulmonary congestion in patients with HF
Environmental problems induced by cattle farming in the Po Valley (Northern Italy)
No full textThe environmental impact resulting from the presence of widespread farming activities in the Po valley is discussed. In particular, for what concerns animal breeding, the data collected show that the pollutants' load is mainly derived from cattle farms which are, therefore, one of the main sources of potential pollution of the groundwater
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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