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

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

NNcon: improved protein contact map prediction using 2D-recursive neural networks

Protein contact map prediction is useful for protein folding rate prediction, model selection and 3D structure prediction. Here we describe NNcon, a fast and reliable contact map prediction server and software. NNcon was ranked among the most accurate residue contact predictors in the Eighth Critical Assessment of Techniques for Protein Structure Prediction (CASP8), 2008. Both NNcon server and software are available at http://casp.rnet.missouri.edu/nncon.html

NNcon: improved protein contact map prediction using 2D-recursive neural networks

Protein contact map prediction is useful for protein folding rate prediction, model selection and 3D structure prediction. Here we describe NNcon, a fast and reliable contact map prediction server and software. NNcon was ranked among the most accurate residue contact predictors in the Eighth Critical Assessment of Techniques for Protein Structure Prediction (CASP8), 2008. Both NNcon server and software are available at http://casp.rnet.missouri.edu/nncon.html

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 μm. 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

Accurate prediction of protein secondary structure and solvent accessibility by consensus combiners of sequence and structure information

Background : Structural properties of proteins such as secondary structure and solvent accessibility contribute to three-dimensional structure prediction, not only in the ab initio case but also when homology information to known structures is available. Structural properties are also routinely used in protein analysis even when homology is available, largely because homology modelling is lower throughput than, say, secondary structure prediction. Nonetheless, predictors of secondary structure and solvent accessibility are virtually always ab initio. Results: Here we develop high-throughput machine learning systems for the prediction of protein secondary structure and solvent accessibility that exploit homology to proteins of known structure, where available, in the form of simple structural frequency profiles extracted from sets of PDB templates. We compare these systems to their state-of-the-art ab initio counterparts, and with a number of baselines in which secondary structures and solvent accessibilities are extracted directly from the templates. We show that structural information from templates greatly improves secondary structure and solvent accessibility prediction quality, and that, on average, the systems significantly enrich the information contained in the templates. For sequence similarity exceeding 30%, secondary structure prediction quality is approximately 90%, close to its theoretical maximum, and 2-class solvent accessibility roughly 85%. Gains are robust with respect to template selection noise, and significant for marginal sequence similarity and for short alignments, supporting the claim that these improved predictions may prove beneficial beyond the case in which clear homology is available. Conclusion: The predictive system are publicly available at the address http://distill.ucd.ieScience Foundation IrelandIrish Research Council for Science, Engineering and TechnologyHealth Research BoardUCD President's Award 2004au, da, ke, ab, sp - kpw30/11/1

Heavy metals concentrations and speciation of Pb and Ni in airborne particulate matter over two residential sites in Greater Cairo - reflection from synchrotron radiation

Synchrotron radiation-based techniques [X-ray absorption near-edge structure (XANES) and X-ray fluorescence (XRF)] combined with inductively coupled plasma-mass spectrometry (ICP-MS) were used for the assessment of heavy metals concentrations as well as lead (Pb) and nickel (Ni) speciation in airborne particulate matter (PM10) over two residential sites in Greater Cairo. Nineteen 24 h high-volume samples collected at Giza (G) Square and Helwan (H) University (Egypt) were selected for this study. Mean concentrations of heavy metals in PM10 at both sites were found to have the same descending order of Pb > Cu > Ni > Cd > Co > As, of which concentrations of Pb, Cu, Ni and Cd in H samples were higher than those in G samples. For Pb, synchrotron-based XRF results were in good agreement with concentrations obtained by ICP-MS. The XANES spectra of PM10 at the Pb L 2-edge and Ni K-edge were compared with those of Pb and Ni in model standard compounds to provide information on the potential oxidation states as well as the chemical forms of those elements. The data show that Pb has similar chemical environments in both series G and H with the predominance of Pb2+oxidation state. Nickel was found as Ni(OH)2, NiO and Ni metal in the analyzed samples. However, the content of Ni in the background filter shows a very strong interference with that of the collected PM10. Carcinogenic and non-carcinogenic risks resulting from the inhalation of the studied heavy metals were assessed for children and adult residents and were found below the safe limits, at both sites

Thermal Decomposition Pathways of ZnxFe3- xO4Nanoparticles in Different Atmospheres

This article shows how initial composition and thermal treatment of nonstoichiometric zinc ferrite nanoparticles (nZFN) can be chosen to adjust the structure and cation distribution and enhance magnetism in the resulting nanoscale material. It also provides insight into new prospects regarding the production and design of nanoscale materials. Investigations were conducted before and after heating of nZFN in an inert atmosphere and a vacuum up to temperature of 1170 °C. Annealing leads to partial reduction of Fe ions, enhanced magnetism, and an increase in the size of the particles independent of the atmosphere. Use of the inert atmosphere delivers a solid solution of magnetite and zinc ferrite with a reduced Zn content in the structure as a result of sublimation of newly formed ZnO and reduction of Fe, and it favors crystallization. A preference for normal-spinel phase and enhancement of magnetic saturation from 20 Am2/kg up to 101 Am2/kg was observed. Vacuum annealing with high probability produces ZnO, Fe3O4, and Fe2O3 multiphase system with signs of amorphization, mainly on the surface. A large fraction of Fe ions is reduced and the volume ratio of Fe3O4 to Fe2O3 increases with heating time. The final solid product from a complete decomposition of ZFN is magnetite

Raising the COx Methanation Activity of a Ru/γ-Al2O3 Catalyst by Activated Modification of Metal–Support Interactions

Ru/Al2O3 is a highly stable, but less active catalyst for methanation reactions. Herein we report an effective approach to significantly improve its performance in the methanation of CO2/H2 mixtures. Highly active and stable Ru/γ-Al2O3 catalysts were prepared by high-temperature treatment in the reductive reaction gas. Operando/in situ spectroscopy and STEM imaging reveals that the strongly improved activity, by factors of 5 and 14 for CO and CO2 methanation, is accompanied by a flattening of the Ru nanoparticles and the formation of highly basic hydroxylated alumina sites. We propose a modification of the metal–support interactions (MSIs) as the origin of the increased activity, caused by modification of the Al2O3 surface in the reductive atmosphere and an increased thermal mobility of the Ru nanoparticles, allowing their transfer to modified surface sites