1,721,056 research outputs found
Messa a punto di metodi in vitro per la valutazione dell’innocuità dei liquidi astringenti
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Carbazole-Terpyridine Donor-Acceptor Dyads with Rigid π-Conjugated Bridges
No full textA series of molecules in which 9H‐carbazole (electron donor, D) and 2,2′:6′,2′′‐terpyridine (electron acceptor, A) are connected through rigid π‐conjugated bridges (D‐π‐A systems) have been synthesized and their photophysical properties examined in detail, with the support of DFT calculations. The bridges are made of different sequences of ethynylene, phenylene, and anthracene groups. The synthetic strategies involve condensation of 2‐acetylpyridine with the aromatic aldehyde moiety on different functionalized π‐conjugated bridges and couplings with carbazole derivatives. The system incorporating anthracene in the bridge shows the typical absorption and emission fingerprints of this polycyclic hydrocarbon. The other systems have HOMOs and LUMOs centred, respectively, over the carbazole and the bridge and exhibit solvatochromic charge‐transfer (CT) luminescence with high photoluminescence yield up to 70 %, except when an ethynylene unit is directly attached to the carbazole ring, due to a trans‐bent non‐emissive π–σ* excited state
Prefácio
No full textLa prefazione al volume sottolinea l'importanza che il punto di vista logistico ha assunto negli ultimi anni per lo studio dei processi globali. Colloca il libro all'interno dello sviluppo degli studi critici sulla logistica e indica alcuni terreni di ricerca per il futuro
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
Evasion of Gaseous Elemental Mercury from Forest and Urban Soils Contaminated by Historical and Modern Ore Roasting Processes (Idrija, Slovenia)
Full text linkConsiderable amounts of gaseous elemental mercury (Hg-0) can be released into the atmosphere from Hg-enriched substrates, such as those from former mining areas, posing a potential environmental threat. In this work, Hg-0 fluxes at the soil-air interface under natural vegetation covers were measured in various locations within the Idrija Hg mining area (Slovenia) and its surroundings. Sites were selected in order to compare Hg-0 fluxes from both forest soils heavily impacted by historical ore roasting and urban soils characterised by a different degree of Hg enrichment due to the natural occurrence of Hg in rocks or recent mining and roasting processes. Replicate measurements at each site were conducted using a non-steady state flux chamber coupled with a real-time Hg-0 analyser (Lumex RA-915M). Moreover, topsoil samples (0-2 cm) were analysed for Hg total concentration and speciation. Cinnabar was the predominant Hg form in almost all the sites. Despite Hg-0 being undetectable in soils using thermo-desorption, substantial emissions were observed (70.7-701.8 ng m(-2) h(-1)). Urban soils in a naturally enriched area showed on average the highest Hg-0 fluxes, whereas relatively low emissions were found at the historical roasting site, which is currently forested, despite the significantly high total Hg content in soils (up to 219.0 and 10,400 mg kg(-1), respectively). Overall, our findings confirm that shading by trees or litter may effectively limit the amount of Hg-0 released into the atmosphere even from extremely enriched soils, thus acting as a natural mitigation
The Legacy of the Idrija Mine Twenty-Five Years after Closing: Is Mercury in the Water Column of the Gulf of Trieste Still an Environmental Issue?
Full text linkMercury (Hg) contamination in the Gulf of Trieste (northern Adriatic Sea) due to mining activity in Idrija (Slovenia) still represents an issue of environmental concern. The Isonzo/Soča River’s freshwater inputs have been identified as the main source of Hg into the Gulf, especially following periods of medium-high discharge. This research aims to evaluate the occurrence and distribution of dissolved (DHg) and particulate (PHg) Hg along the water column in the northernmost sector of the Gulf, a shallow and sheltered embayment suitable for the accumulation of fine sediments. Sediment and water samples were collected under unperturbed and perturbed environmental conditions induced by natural and anthropogenic factors. Mercury in the sediments (0.77–6.39 μg g−1) and its relationship to grain size were found to be consistent with previous research focused on the entire Gulf, testifying to the common origin of the sediment. Results showed a notable variability of DHg
Environmental concerns and future perspectives related to the legacy of metal(loid) contamination in the vicinity of a dismissed Pb-Zn mining area (Raibl, NE Italy)
No full textThe occurrence of relevant amounts of potential toxic elements (PTEs) in the environment as a legacy of past extraction and metallurgical activities at decommissioned mining areas represents a worldwide concern, potentially posing a threat to ecosystems and human health. This aspect is strongly dependent on the mobility and bioavailability of PTEs once released in the environment (Favas et al., 2011). However, in addition to being sources of contamination, mine waste such as tailings ponds can potentially be a resource since they may still host notable amounts of various elements of economic interest such as those included in European Union’s list of Critical Raw Materials (CRMs) (Rosario-Beltré et al., 2023).
This study is focused on the assessment of metal(loid) distribution and environmental impact related to past extraction activities on the soils at the Pb-Zn Raibl mining district (NE Italy), which ended in 1991. Concentrations of several PTEs (As, Cd, Fe, Pb, Tl, Zn) and CRMs (As, Ge, Mn, Sb) were determined on sub-surface samples of various solid matrices (soils, waste rocks, tailings) collected throughout the mining district. A single-step extraction with 0.5 M HCl solution was used to evaluate the labile fraction of PTEs, potentially more mobile and bioavailable in the environment.
As expected, mine waste heaps, consisting of waste rocks and flotation tailings stored in tailings impoundments and scattered within the mining district, showed high concentrations of metal(loid)s (≤ 100 mg/kg for Sb, Cd and Ge; > 500 mg/kg for Tl and Mn; > 1,000 mg/kg for As; > 1 wt% for Zn; > 10 wt% for Fe and Zn). Notably low concentrations were found in samples collected upstream the former mine, which are considered representative of the natural background of the study area. Overall, the leachable metal(loid)s concentrations are well correlated with the total content, with the highest PTEs (i.e. Zn, Pb, Fe, Cd) values generally observed in unprocessed waste rock samples. The only exception is represented by Tl which showed the highest labile concentration in tailings (up to 255 mg/kg), confirming their potential impact on local water resources (Barago et al., 2023). However, the highest percentages of the metal(loid)s leachable fraction were generally found for soils with a greater organic matter (OM) content, due to the lower pH and the potential formation of soluble organometallic complexes during soil ageing. Considering that remediation of the en-tire area is not feasible due to the extension of the contamination, this potential in-creased in the mobility of PTEs as soil ages should be considered when evaluating appropriate management strategies aimed at limiting PTEs dispersion and impact on local ecosystems. These strategies may also include the reprocessing of mine wastes accumulated in tailings ponds, which could both reduce the risk to water resources and human health and to recover critical or strategic elements such as As or Ge. Fur-ther research is still ongoing with the aim of broadening knowledge on the residual content in CRMs and PTEs buried in tailings ponds and providing data to assess the feasibility of this approach.
REFERENCES
Barago, N., Pavoni, E., Floreani, F., Crosera, M., Adami, G., Lenaz, D., and Covelli, S., 2023. Hydrogeo-chemistry of thallium and other potentially toxic elements in neutral mine drainage at the decom-missioned Pb-Zn Raibl mine (Eastern Alps, Italy). Journal of Geochemical Exploration, 245, 107129.
Favas, P.J.C., Pratas, J., Gomes, M.E.P., and Cala, V., 2011. Selective chemical extraction of heavy metals in tailings and soils contaminated by mining activity: environmental implications. Journal of Geo-chemical Exploration, 111, 160-171.
Rosario-Beltré, A.J., Sánchez-España, J., Rodríguez-Gómez, V., Fernández-Naranjo, F.J., Bellido-Martín, E., Adánez-Sanjuán, P., and Arranz-González J.C., 2023. Critical raw materials recovery potential from Spanish mine wastes: a national-scale preliminary assessment. Journal of Cleaner Production, 407, 137163
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
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