404 research outputs found
In-situ/operando characterization of FeOx-based chemiresistive sensor of acetone vapours by X-ray absorption spectroscopy
Potentially toxic elements speciation in bottom ashes from a municipal solid waste incinerator: A combined SEM-EDS, µ-XRF and µ-XANES study
Bottom Ashes from Municipal Solid Waste Incinerators and Waste to Energy plants represent an interesting source of secondary raw materials for many applications, like urban mining and inclusion in concrete, and road pavement. However, Bottom Ashes may contain potentially toxic elements, whose actual toxicity depends essentially on their oxidation state and mineralogical environment. For this reason, a representative sample of bottom ashes from Parma Waste to Energy plant has been selected to investigate the chemical speciation of Cr, Ni, Pb, Co, Zn and Cu by means of complementary techniques: Scanning Electron Microscopy with Energy Dispersive X-Ray Spectroscopy (SEM-EDS), micro X-Ray Fluorescence (µ-XRF) mapping and X-Ray Absorption Near Edge Structure (XANES) measurements by synchrotron radiation. This multi-technique approach allowed to obtain a general image of the mineralogical and chemical environment in which these elements are found. SEM-EDS analyses show the presence of Zn and Pb both in minerals and in glass matrix. Cr has been detected in the form of oxide and in spinel structure (chromite) whereas Co and Cu are found as alloy or metal inclusions. µ-XRF mapping reveals that Cu, Ni and Cr are generally associated to Na, K and Si suggesting their presence in glass matrix. XANES investigations exhibit that Cu has a variable oxidation state that suggesting its presence in the form of oxide, hydroxide, acetate and metal. Zn is mainly found as +II and in a number of different phases (including Zn-carbonates, in agreement with SEM-EDS data). Cr has been found only as +III, with XANES features resembling those of chromite, whereas as +VI was never identified. Ni and Co were found either as metal form and oxides. Pb spectra show a good match with oxides
A target repurposing approach identifies N-myristoyltransferase as a new candidate drug target in filarial nematodes
Myristoylation is a lipid modification involving the addition of a 14-carbon unsaturated fatty acid, myristic acid, to the N-terminal glycine of a subset of proteins, a modification that promotes their binding to cell membranes for varied biological functions. The process is catalyzed by myristoyl-CoA:protein N-myristoyltransferase (NMT), an enzyme which has been validated as a drug target in human cancers, and for infectious diseases caused by fungi, viruses and protozoan parasites. We purified Caenorhabditis elegans and Brugia malayi NMTs as active recombinant proteins and carried out kinetic analyses with their essential fatty acid donor, myristoyl-CoA and peptide substrates. Biochemical and structural analyses both revealed that the nematode enzymes are canonical NMTs, sharing a high degree of conservation with protozoan NMT enzymes. Inhibitory compounds that target NMT in protozoan species inhibited the nematode NMTs with IC50 values of 2.5-10 nM, and were active against B. malayi microfilariae and adult worms at 12.5 µM and 50 µM respectively, and C. elegans (25 µM) in culture. RNA interference and gene deletion in C. elegans further showed that NMT is essential for nematode viability. The effects observed are likely due to disruption of the function of several downstream target proteins. Potential substrates of NMT in B. malayi are predicted using bioinformatic analysis. Our genetic and chemical studies highlight the importance of myristoylation in the synthesis of functional proteins in nematodes and have shown for the first time that NMT is required for viability in parasitic nematodes. These results suggest that targeting NMT could be a valid approach for the development of chemotherapeutic agents against nematode diseases including filariasis
Comprehensive Analysis of Two H13-Type Starting Materials Used for Laser Cladding and Aerosol Particles Formed in This Process
Laser cladding with H13 steel powders was performed and the related material transformations were studied for the particles emitted during this process. Fractions of various sizes of the aerosol particles formed during the laser cladding were collected on a cascade impactor, while the electromobility and the aerodynamic size of the particles were measured using a scanning mobility particle spectrometer and an aerodynamic particle sizer, respectively. The aerosol particles deposited onto the impactor plates were analyzed using scanning electron microscopy–energy-dispersive X-ray spectroscopy, as well as total-reflection X-ray fluorescence and X-ray absorption near-edge structure spectroscopy. Both the concentration and mean oxidation state of the major components were correlated with the aerosol particle size. The ultrafine aerosol particles (with a diameter less than about 100 nm) were predominantly oxidized and formed as the result of an evaporation–oxidation–condensation process sequence. The larger particles (>200 nm in geometric diameter) were primarily the residues of the original metal powder and exhibited a composition change as compared to the as-received metal powder. Correlations between the changes in the concentration ratio of the components were detected and explained
Experimental quantification of the Fe-valence state at amosite-asbestos boundaries using acSTEM dual-electron energy-loss spectroscopy
Determination of the oxidation state and coordination geometry of iron in Fe-bearing minerals expands our knowledge obtained by standard mineralogical characterization. It provides information that is crucial in assessing the potential of minerals to interact with their surrounding environment and to generate reactive oxygen species, which can disrupt the normal function of living organisms. Aberration-corrected scanning transmission electron microscopy dual-electron energy-loss spectroscopy (acSTEM Dual-EELS) has only rarely been applied in environmental and medical mineralogy, but it can yield data that are essential for the description of near-surface and surface mechanisms involved in many environmental and health-related processes. In this study, we have applied the energy loss near-edge structure (ELNES) and L2,3 white-line intensity-ratio methods using both the universal curve and progressively larger integrating windows to verify their effectiveness in satisfactorily describing the valence state of iron at amosite grain boundaries, and, at the same time, to estimate thickness in the same region of interest. The average valence state obtained from acSTEM Dual-EELS and from a simplified geometrical model were in good agreement, and within the range defined by the bulk and the measured surface-valence states. In the specific case presented here, the use of the universal curve was most suitable in defining the valence state of iron at amosite grain boundaries. The study of ELNES revealed an excellent correspondence with the valence state determined by the L2,3 white-line intensity-ratio method through the use of the universal curve, and it seems that the spectra carry some information regarding the coordination geometry of Fe. The combination of visual examination, reconstruction of the grain boundaries through a simple geometrical model, and Dual-EELS investigation is a powerful tool for characterizing the grain boundaries of hazardous minerals and foreseeing their potential activity in an organism, with the possibility to describe toxic mechanisms in a stepwise fashion
Characterization of unique aerosol pollution episodes in urban areas using TXRF and TXRF-XANES
Identifying sources of unique, short-time aerosol pollution episodes in urban areas is a difficult task since they could last only for a couple of hours. With the combination of size-fractioned sampling with May-type cascade impactor and total-reflection X-ray fluorescence (TXRF) in addition to X-ray absorption near-edge structure spectroscopy various sources could be identified in samples collected in Budapest (Hungary) and Cassino (Italy). Using short-time (1–4 h), size-fractionated (70 nm up to 10 μm into 7 stages) sampling method, TXRF is capable of detecting transition metals in the order of 0.1 ng/m3. The present study discusses pollution episodes with Cu and Br concentrations in the range of 1–40 ng/m3. The contribution of both exhaust and non-exhaust type traffic-related emission sources were found to be dominant in the Cu species. Wear products of brake system were identified in coarse particles in addition to resuspension of roadside dust. The ratio of organic/inorganic Br could be determined for a pollution episode with elevated Br concentration
Deposit shape control for local repair and welding by cold spray
Cold spray (CS) has proven to be a versatile deposition method with considerable capabilities in multiple fields including coating, additive manufacturing, and repair. Despite the significant progress in new applications of cold spray, there are still several challenges associated with controlling the shape of cold spray deposits that consequently affect their range of application and functionality. In this study, we discuss and demonstrate a new application of CS to connect adjoining edges along with repair local damages, focusing on deposit shape prediction. To do so, we start by proposing a numerical model that can predict the CS deposit geometry, by providing specific input parameters for a given set of particle and substrate properties, substrate geometry and nozzle position. Then we employ this numerical method to design the toolpath required for filling the artificial local damages and/or the welding grooves with controlled geometries. Through comparing the predictions with the shape of experimentally obtained depositions, we propose some corrections for the model. In both local repair and welding cases, the experimental results show a great resemblance to the predicted deposit profile and after applying the corrective measures, to the deposit height
Primary Mandibular Condyle Xanthoma: Case Report and Literature Review
Bone xanthoma is a rare benign primary bone lesion histologically characterized by sheets of foamy cells which are macrophages with a cytoplasm filled with droplets of fat. It is usually associated with endocrine or metabolic diseases, in the absence of which the lesion is called primary xanthoma. Because of the lack of pathognomonic radiologic and clinical features, they require a differential diagnosis with a broad spectrum of lesions with a varying degree of malignant potential. We describe a case of primary mandibular xanthoma of a 16-year-old girl without typical cutaneous manifestations and alterations in lipid values. The temporomandibular joint involvement at the mandibular condyle is peculiar in the case described here. We present even a qualitative systematic review of the literature on primary xanthoma of the jaws in others to draw up treatment guidelines
Characterization of the ultrafine and fine particles formed during laser cladding with the Inconel 718 metal powder by means of X-ray spectroscopic techniques
Additive manufacturing is a rapidly growing industrial technology. Still, there is a lack of knowledge regarding the fine particle emission and new particle formation during the processes and their consequences on the performance of the operation and the operator's health as well. Therefore, we studied the properties of the emitted particles during the 3D printing process using the Inconel 718 (Ni-based) superalloy. The number and the mass concentrations were measured with a Scanning Mobility Particle Counter and Sizer. Size-fractionated samples were collected by a cascade impactor, and the elemental composition of the particles was determined by total-reflection X-ray fluorescence analysis, Scanning Electron Microscopy, Energy Dispersive Spectroscopy, and microscopic X-ray fluorescence analysis in the different size fractions. The oxidation states of the metals (Cr, Mn, Fe, Ni) in the samples were determined with the X-ray absorption near-edge structure (XANES) method. Most of the particles were found in the ultrafine region with a size below 100 nm, and the mass size distribution had the maximum at 85 nm. In the original powder, Ni was dominating with appr. 52 wt%, and the proportion of Cr was around 20 wt%, and Mn was below 1 wt%. In the released particles, the Ni content decreased to appr. 26 wt%, the Cr content increased to appr. 47 wt% and Mn increased to around 10 wt% for particles with a size between 0.07 and 10 ÎĽm. According to the XANES results, Cr, Mn and Fe were found to be oxidized significantly, whereas Ni remained in the metallic form in the total emitted aerosol containing mostly ultrafine particles. The enrichment and oxidation of metals were correlated with each other
Environmental impacts and risk assessment in the re-use of Cr-bearing pyrolyzed tannery wastes: A case study in a residential area
Increasing concern has been raised on the environmental impacts of chromium -tanning wastes recycling. In particular, the pyrolytic conversion of leather industry sludges into Cr(VI)-free carbonized residues is believed to represent a viable route for a sustainable re -use of this type of wastes. The aim of this study was to determine the impact of recycled Cr-bearing pyrolyzed char (named KEU) as backfilling material for road construction in an urban area in Tuscany (Italy). Geochemical and chromium -isotope data, together with microstructural analyses (HR-TEM and XAS), indicate that the presence of KEU results in a significant enhancement of the natural Cr background. The results support the hypothesis that, in environmental conditions, the Cr (III) hosted in KEU is converted into Cr(VI), which is leached out by rainwater. Indeed, Cr(VI) is dispersed in surface water, reaching concentrations up to 18 mg/L and it also occurs in coatings on the surface gravel of unpaved roads. The 53 Cr/ 52 Cr ratio measured in KEU, reported in delta 53 Cr notation, was in the restricted range delta 53 Cr = - 0.031 +/- 0.057 %o ; on the contrary, the delta 53 Cr in water varied between + 1.581 +/- 0.038 %o and + 3.261 +/- 0.191 %o , indicating the reduction of Cr(VI) after the pristine oxidative mobilization. The risk -based soil screening levels (SSLs) for total Cr are well above the concentration measured in soil for all the exposure pathways. On the contrary, the SSL for Cr(VI)indicates that soil contamination poses health hazards for residents
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