1,721,046 research outputs found
Improvement of an unstructured grid Finite Volume scheme for flood simulation
No full textIn this work a numerical model, designed to study the propagation of inundation waves over floodplains due to breach formations in river banks, is presented. The two-dimensional model is developed performing a space-time integration of the Shallow Water Equations with source terms due to bed slope and friction slope. The spatial domain is discretized using unstructured triangular grids, based on a Delaunay algorithm for 2D mesh generation. The numerical scheme is a Finite Volume Godunov-type method, based on classical approximate solutions of the Riemann problem. The second order space-time accuracy is achieved by the MUSCL and a SSPRK techniques, respectively. The model introduces successful recent novelties: a) in treating bed slope source terms (a Divergence Form for the Bed slope source term, Valiani and Begnudelli, 2006); b) in facing the wetting and drying sequence of partially submerged cells (Volume/Free surface Relationships, Begnudelli and Sanders, 2006). Such a numerical model is tested over significant test cases suggested in literature, and then applied to an hypothetical inundation of a floodplain area near Ferrara (Italy), due to a possible breach in the Po river bank. The numerical model is stable, accurate and - due to its flexibility - easily applicable to real world events. Consequently, it appears to be a proper tool for environmental planning and disaster prevention design
Helicrysum italicum (roth) G. Don, a promising species for the phytostabilization of polluted mine sites: A case study in the Montevecchio mine (Sardinia, Italy)
Full text linkMine exploitations worldwide have generated a great amount of tailings, which still contain large quantities of Potentially Harmful Elements (PHEs) able to contaminate soil, water, air, wildlife, and the food chain. Phytoremediation is an option to immobilize and/or extract PHEs from polluted mining areas. This study aims at assessing the phytoremediation properties of Helicrysum italicum (roth) G. Don, and in particular the capacity to absorb, transfer and accumulate some PHEs, such as Cd, Cu, Ni, Pb and Zn, in the plant tissues. A restricted literature review (7 papers) is also proposed in order to outline the H. italicum's behaviour and verify its possible use in phytoremediation strategy of polluted mine soils. A number of 22 contaminated sites from Montevecchio mine area (Sardinia, Italy) were sampled and the results compared with 6 uncontaminated sites. In each site both rhizospheric soil materials and H. italicum plants were sampled. Total composition and bioavailable fractions were analysed on soil samples. Helicrysum italicum roots, stems and leaves were separately analysed to extract PHEs; root/soil and leaf/root ratios were calculated to elucidate plant behaviour. Results show that Cd and Zn are the most bioavailable PHEs in contaminated sites compared to uncontaminated ones (300 and 500 folds, respectively), while Cd, Cu, Pb and Zn exceed the thresholds of the Italian environmental legislation when aqua regia extraction is executed. Helicrysum italicum plants growing on contaminated soils accumulate significantly more Cd, Ni, Pb and Zn than plants growing on uncontaminated soils, while no significant differences are found for Cu. For all considered PHEs the root/soil ratios are >1 in both contaminated/uncontaminated sites meaning that H. italicum can be defined as a tolerant species for remediation of metal-polluted soils. The leaf/root ratios weakly >1 of Zn, Pb and Cu and <1 of Ni and Cd indicate H. italicum not suitable for phytoextraction. Our results are aligned with the available literature indicating H. italicum a tolerant species, especially for Cd, Pb and Zn. The low leaf/root ratios, along with its being a spontaneous and perennial species able to propagate seeds directly on contaminated soils, recommended the use of H. italicum as pioneering strategy for the phytostabilization
Assessing the impact of artificial summer drainage on the benthic macroinvertebrates in a freshwater wetland in northeast Italy
Full text linkValle Mandriole is one of the two last remaining freshwater wetlands in the coastal area of Ravenna (NE Italy). In 2011, a management technique that involves the complete drainage of the southern portion of Valle Mandriole during summer has been undertaken. In the present study, the effects of this artificial drying on the benthic macroinvertebrate fauna were assessed using a beyond before-after-control-impact (beyond BACI) sampling design. Macroinvertebrates dwelling on macrophytes and in bare sediments were sampled in the impact location and in four control locations, two times before and two times after the drying period. Simultaneously, water samples were collected to monitor chemical properties potentially affecting the studied organisms. Biological and chemical data were analysed by multivariate statistical methods. The statistical analysis did not detect any significant effect of the management action on the benthic macroinvertebrates or on the water chemical and physical properties. This contrasts with some previous results, suggesting that the effects of a management strategy based on draining completely dry and then reflooding a wetland area are site specific. However, it is necessary to consider that the present study does have some limitations, in particular, the differences between impact and control locations and the timing of the sampling. The highest biodiversity was observed in one small and isolated control location; this highlights how maintaining, protecting, restoring and even creating small ponds may play an important role in biodiversity conservation
External physical examination of stillborns.
No full textOur experience with an epidemiologic study of ge netic and mal formative causes of stillbirth was entirely in agreement with Dr. Schneiderman's editoriali concernin g the diagnostic power of external physical examination ( EPE) . The to pics and recommendations mentioned by Dr. Schneiderman are particularly pertinent to stillborn in fants (0 . 8 per ce n t of all newborns) , 25 to 30 per cent of whom are affected by genetic or malformative disorders
Potentially Toxic Elements (PTEs) Distribution in Drainage Canal Sediments of a Low-Lying Coastal Area
Full text linkThis study examines the accumulation, distribution, and mobility of Potentially Toxic Elements (PTEs) in the sediments of a low-lying coastal drainage network (Ravenna, Italy). The aim is to understand the geochemical processes occurring between drainage water and canal bed sediments and assess factors affecting and driving PTE distribution and enrichment in these environments. A geochemical database resulting from the analysis of 203 drainage sediment samples was analyzed using Principal Component Analysis and compared to undisturbed near-surface sediment samples from the same depth and depositional environment. The results reveal PTEs exceeding national regulation limits. Distance from the sea, electrical conductivity of drainage water, and fertilizer use were identified as the main driving factors. The primary mechanisms for PTE precipitation (As, Co, Mo) and subsequent enrichment in the sediments is attributed to the absorption on Fe- and Mn-oxyhydroxides (HFO and HMO), particularly in high salinity areas near the coast. While Cu, Zn, Pb, Cr, and V also have affinity for HFO and HMO, their adsorption efficiency decreases due to the competition with salt-derived cations during ongoing salinization processes. Anthropogenic sources, including agriculture, hunting activities, traffic dust, and railways, contribute to the local abundance of other elements (Cr, Ni, Cu, Zn, Pb, and Sn). This paper's significant progress lies in assessing the concurrent interactions of chemical and physical processes that drive PTE distribution and accumulation in reclaimed low-lying coastal plains. The findings are significant for assessing PTE accumulation risks and sediment toxicity in coastal areas affected by water salinization, drainage, and subsidence, providing valuable information to water management institutions globally.This study investigates the presence of harmful substances called Potentially Toxic Elements (PTEs) in the sediment of the drainage canals in Ravenna's coastal area (Northern Italy). Researchers want to understand how these substances accumulate and spread in the sediment and what factors influence their distribution. They collected sediment samples from the bottom of the drainage canals and compared them to natural sediment samples. The results show that the PTE levels exceed the national and international limits. The distance from the sea, the water salinity, and the fertilizers are found to be the main factors affecting the distribution of PTEs. The researchers also discover that some PTEs (Arsenic, Cobalt, and Molybdenum) are absorbed by certain minerals in the sediment, especially in areas with high salinity close to the coast. However, other harmful elements, like copper, zinc, lead, chromium, and vanadium are not as strongly absorbed due to competition with salt-related substances. The abundance of other elements like chromium, nickel, copper, zinc, lead, and tin come from human activities like agriculture, hunting, traffic, and railways. These findings are important for understanding the risks associated with these substances in the sediment, particularly in low-lying coastal areas that have been reclaimed for human use.First study on Potentially Toxic Elements (PTEs) enrichment in drainage canal sediments of reclaimed low-lying coastal area Key roles of (i) Fe- and Mn-oxyhydroxides in PTE enrichments and (ii) salt-derived cations in adsorption efficiency Distance from the sea, salinity of drainage water, and use of fertilizers are the main factors affecting the distribution and enrichment of PTE
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
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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