159 research outputs found
Toxicity of the readily leachable fraction of urban PM2.5 to human lung epithelial cells: Role of soluble metals
No full textFine airborne particulate matter (PM2.5) has been repeatedly associated with adverse health effects in humans. The PM2.5 soluble fraction, and soluble metals in particular, are thought to cause lung damage. Literature data, however, are not consistent and the role of leachable metals is still under debate. In this study, Winter and Summer urban PM2.5 aqueous extracts, obtained by using a bio-compatible solution and different contact times at 37 °C, were used to investigate cytotoxic effects of PM2.5 in cultured lung epithelial cells (A549) and the role played by the leachable metals Cu, Fe, Zn, Ni, Pb and Cd. Cell viability and migration, as well as intracellular glutathione, extracellular cysteine, cysteinylglycine and homocysteine concentrations, were evaluated in cells challenged with both PM2.5 extracts before and after ultrafiltration and artificial metal ion solutions mimicking the metal composition of the genuine extracts. The thiol oxidative potential was also evaluated by an abiotic test. Results demonstrate that PM2.5 bioactive components were released within minutes of PM2.5 interaction with the leaching solution. Among these are i) low MW (<3 kDa) solutes inducing oxidative stress and ii) high MW and/or water-insoluble compounds largely contributing to thiol oxidation and to increased homocysteine levels in the cell medium. Cu and/or Ni ions likely contributed to the effects of Summer PM2.5 extracts. Nonetheless, the strong bio-reactivity of Winter PM2.5 extracts could not be explained by the presence of the studied metals. A possible role for PM2.5 water-extractable organic components is discussed. © 2017 Elsevier Lt
Challenges for semilocal density functionals with asymptotically nonvanishing potentials
No full textThe Becke-Johnson model potential [A. D. Becke and E. R. Johnson, J. Chem. Phys. 124, 221101 ( 2006)] and the potential of the AK13 functional [R. Armiento and S. Kummel, Phys. Rev. Lett. 111, 036402 ( 2013)] have been shown to mimic features of the exact Kohn-Sham exchange potential, such as step structures that are associated with shell closings and particle-number changes. A key element in the construction of these functionals is that the potential has a limiting value far outside a finite system that is a system-dependent constant rather than zero. We discuss a set of anomalous features in these functionals that are closely connected to the nonvanishing asymptotic potential. The findings constitute a formidable challenge for the future development of semilocal functionals based on the concept of a nonvanishing asymptotic constant.Funding Agencies|German-Israeli Foundation for Scientific Research and Development; University of Bayreuth Graduate School; Swedish Research Council (V.R.) [2016-04810]; Swedish e-Science Research Centre (SeRC)</p
Implementing and testing the AM05 spin density functional
No full textWe show that the spin density generalization of the AM05 density functional [R. Armiento and A. E. Mattsson, Phys. Rev. B 72, 085108 (2005)] predicts the correct ground spin state for iron, a system known to be heavily dependent on proper spin treatment. Using the fundamental assumptions in the subsystem functional scheme, we resolve an ambiguity in how to treat the separate spin densities in AM05 but also show that the other less preferred treatments give no significantly different numerical outcome of the iron body-centered-cubic and face-centered-cubic test cases. Details and formulas are given to aid in the implementation of functionals in general, and the spin-resolved AM05 exchange-correlation potentials in particular, into different types of computer codes
Content, mineral allocation and leaching behavior of heavy metals in urban PM2.5
No full textTo clarify the relationship between airborne particulate exposure and negative impacts on human health, focusing on the heavy metal content alone might not be sufficient. To address this issue, in the present work, mineral allocation and leaching behavior of heavy metals in the PM2.5 were investigated. This work, therefore, provides a novel perspective in the field of urban airborne particle investigation that is not currently found in the literature. Four sampling campaigns were performed in the urban area of Rome (Central Italy) during the winter and summer seasons (February and July 2013 and 2014, respectively). The measured concentrations of the regulated elements of As, Cd, Ni and Pb were consistent with those reported by the local Environmental Agency (ARPA Lazio), but non-regulated heavy metals, including Fe, Cu, Cr and Zn, were also found in PM2.5 and analyzed in detail. As a novelty, heavy metals were associated with the host-identified mineral phases, primarily oxides and alloys, and to a lesser extent, other minerals, such as sulfates, carbonates and silicates. Leaching tests of the collected samples were conducted in a buffered solution mimicking the bodily physiological environment. Despite the highest concentration of heavy metals found during the winter sampling period, all of the elements showed a leaching trend leading to major mobility during the summer period. To explain this result, an interesting comparative analysis between the leaching test behavior and innovative mineral allocation was conducted. Both the heavy metal content and mineral allocation in PM2.5 might contribute to the bioavailability of toxic elements in the pulmonary environment. Hence, for regulatory purposes, the non-linear dependency of heavy metal bioavailability on the total metal content should be taken into account. © 2017 Elsevier Lt
Screening for high-performance piezoelectrics using high-throughput density functional theory
No full textWe present a large-scale density functional theory (DFT) investigation of the ABO3 chemical space in the perovskite crystal structure, with the aim of identifying those that are relevant for forming piezoelectric materials. Screening criteria on the DFT results are used to select 49 compositions, which can be seen as the fundamental building blocks from which to create alloys with potentially good piezoelectric performance. This screening finds all the alloy end points used in three well-known high-performance piezoelectrics. The energy differences between different structural distortions, deformation, coupling between the displacement of the A and B sites, spontaneous polarization, Born effective charges, and stability is analyzed in each composition. We discuss the features that cause the high piezoelectric performance of the well-known piezoelectric lead zirconate titanate (PZT), and investigate to what extent these features occur in other compositions. We demonstrate how our results can be useful in the design of isovalent alloys with high piezoelectric performance
TRATTAMENTO ROBOTIZZATO DELL’ARTO SUPERIORE NEI PAZIENTI CON EMIPARESI SPASTICA IN FASE CRONICA TRATTATI CON TOSSINA BOTULINICA TIPO A: CONFRONTO TRA END-EFFECTOR E ESOSCHELETRO
No full textL’utilizzo di dispositivi robotici per l’arto superiore in riabilitazione è supportato da numerose evidenze che mostrano come essi
possano migliorare la funzione e la forza dell’arto superiore e l’attività di vita quotidiana. Tuttavia ci sono poche evidenze sulla scelta del dispositivo più appropriato da utilizzare. Inoltre pochi studi hanno indagato l’efficacia del trattamento robotico per l’arto superiore associato all’impiego di tossina botulinica. L’obiettivo di questo studio osservazionale è quello di identificare le differenze tra end effector e esoscheletro nel migliorare la funzione dell’arto superiore nei pazienti affetti da emiparesi spastica sottoposti ad infiltrazione di tossina botulinica di tipo A in fase cronica
Subsystem functionals and the missing ingredient of confinement physics in density functionals
No full textThe subsystem functional scheme is a promising approach recently proposed for constructing exchange-correlation density functionals. In this scheme, the physics in each part of real materials is described by mapping to a characteristic model system. The “confinement physics,” an essential physical ingredient that has been left out in present functionals, is studied by employing the harmonic-oscillator (HO) gas model. By performing the potential→density and the density→exchange energy per particle mappings based on two model systems characterizing the physics in the interior (uniform electron-gas model) and surface regions (Airy gas model) of materials for the HO gases, we show that the confinement physics emerges when only the lowest subband of the HO gas is occupied by electrons. We examine the approximations of the exchange energy by several state-of-the-art functionals for the HO gas, and none of them produces adequate accuracy in the confinement dominated cases. A generic functional that incorporates the description of the confinement physics is needed.Laboratory Directed Research and Development Progra
Unusually high concentrations of beryllium background values in volcanic rocks of Lazio: geochemistry and mineralogy
No full textBeryllium is widely distributed in soils at low levels (crustal abundance 2-6 mg/kg), but it can also occur naturally in higher concentrations in a variety of materials exploited for many industrial applications. Unfortunately, beryllium is also one of the most toxic natural elements and is known to be a human carcinogen.
We report and analyse a diffuse, unusually high (up to 80 mg/kg, average approximately 18 mg/kg), natural occurrence of beryllium in pyroclastic layers related to the Pleistocene activity of the Vico volcano (northern Latium).
The naturally occurring beryllium content in most of the studied samples is extremely high and even greater than that found in sites contaminated by the accidental release of beryllium into the environment by industrial activities. Only 8 out of the 120 analysed samples gave values below the Italian limit for potentially unacceptable risk for industrial soil-use (10 mg/kg); in no case values below the limit for residential soil-use (2 mg/kg) were observed.
Additionally, experiments to define Be leachability have been carried out for selected samples, providing evidence of significant mobility in contrast with data presented in the literature that indicate beryllium as an element with low mobility in oxidising surface environmental conditions. This is a crucial point to consider, because a relatively high mobility under certain pH and redox conditions involve a significant risk factor.
The geochemical behaviour of the element explains the anomalous Be concentration values because its incompatibility in common rock-forming silicate minerals is concentrated via fractionation during magma crystallisation. An additional contribution may be related to the volcanic late-stage fluids permeating through the emplaced rocks.
Combined mineralogical (optical microscopy, SEM-EDAX, EMPA and X-ray diffraction) and geochemical analyses suggests that the higher beryllium concentration in pyroclastics and associated soils are related to the presence of finely dispersed Be-containing minerals, such as gadolinite (Cámara et al., 2008), or hellandite-group minerals (Oberti et al., 2001). However, the possible presence of Be in volcanic glasses is also presently under investigation.
Finally the occurrence of such natural high background concentrations of potentially harmful elements, as it is the case for beryllium studied here, highlights the need for systematic geochemical studies and mapping to produce multi-purpose reference databases for risk assessment and land management.
Cámara, F., Oberti, R., Ottolini, L., Della Ventura, G., Bellatreccia, F. (2008) American Mineralogist, 93, 996-1004.
Oberti, R., Ottolini, L., Camara, F., Della Ventura, G. (1999) American Mineralogist, 84, 913-921
Chemical contamination can promote turnover diversity of benthic prokaryotic assemblages: the case study of the Bagnoli-Coroglio bay (Southern Tyrrhenian Sea)
No full textChemical contamination of marine ecosystems represents a major concern for the detrimental consequences at different levels of biological organization. However, the impact of chronic contamination on the diversity and assemblage composition of benthic prokaryotes is still largely unknown, and this limits our understanding of the potential implications on ecosystem functioning. The Bagnoli-Coroglio bay (Gulf of Naples, Tyrrhenian Sea) is a typical example of coastal area heavily contaminated by metals and hydrocarbons, released for decades by industrial activities, which ceased at the beginning of nineties. In the present study we analyzed the abundance, diversity and assemblage composition of benthic prokaryotic assemblages at increasing distance from the historical source of contamination in relation to the heavy hydrocarbons (C > 12), polycyclic aromatic hydrocarbons (PAHs) and heavy metal concentrations in the sediments. Prokaryotic abundance in the sediments differed among sites, and was mostly driven by environmental factors rather than by contamination levels. Conversely, the richness of prokaryotic taxa was relatively high in all samples, was driven by contamination levels and decreased significantly with increasing contamination (15–38%). Moreover, our results indicate large variations in the composition of the benthic prokaryotic assemblages among sites, mostly explained by the different levels and types of chemical contaminants found in the sediments. Overall, our findings suggest that chemical contaminants, even after decades from the end of their release, can profoundly influence the richness and turnover diversity of the benthic prokaryotic assemblages, in turn promoting a high diversification of the benthic bacterial and archaeal assemblages by selecting those lineages more adapted to specific mixtures of different contaminants. Our results open new perspectives for understanding of the long-term effects of chemical contamination on the benthic prokaryotic assemblages and the ecological processes they mediate
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