Search

Transition metal diboride thin films are promising functional materials for their outstanding mechanical properties and thermal stability. By combining experiment and simulations, we discuss angular distribution of the sputtered species, their scattering in the gas phase, re-sputtering and potential evaporation from the grown films for the complex evolution of film compositions, as well as energetic preference for vacancy formation and competing phases as factors for governing the phase constitution. By co-sputtering from two compound targets, we developed phase-pure crystalline (Ta,Al)B2 solid solution thin films and correlate the stoichiometry changes with the evolution of their microstructure, hardness, and elastic modulus.

Climate change and evolution are topics at the forefront of political discussions, debates, and the public sphere. Regardless of evidence on both topics, the public as a whole still believes they are under debate. It is imperative that the public have access to correct and easy-to-digest information on these topics to make informed environmental and ecological decisions. To date, scientifically accurate digital platforms aimed at informing the public on these topics are overly complex and jargon-ridden. Time Scavengers (www.timescavengers.blog) was created to address these issues and is maintained by a group of academics, graduate students, avocational scientists, and educators. The site includes many informational pages about geology, climate change, and evolution, all written for the public with useful descriptions and figures. To make the process of science more transparent, the site includes blogs to provide insight into data collection and interpretation, field work, and public outreach. The site also includes additional pages with links to relevant content and activities appropriate for K-12 classrooms. The overarching goals of the site are to bridge the gap between scientists and the public through engaging, informational pages and personal experiences and to increase science literacy through easy-to-digest content.

Abstract The present study demonstrates the importance of converting signal intensity maps of organic tissues collected by laser-induced breakdown spectroscopy (LIBS) to elemental concentration maps and also proposes a methodology based on machine learning for its execution. The proposed methodology employs matrix-matched external calibration supported by a pixel-by-pixel automatic matrix (tissue type) recognition performed by linear discriminant analysis of the spatially resolved LIBS hyperspectral data set. On a swine (porcine) brain sample, we successfully performed this matrix recognition with an accuracy of 98% for the grey and white matter and we converted a LIBS intensity map of a tissue sample to a correct concentration map for the elements Na, K and Mg. Found concentrations in the grey and white matter agreed the element concentrations published in the literature and our reference measurements. Our results revealed that the actual concentration distribution in tissues can be quite different from what is suggested by the LIBS signal intensity map, therefore this conversion is always suggested to be performed if an accurate concentration distribution is to be assessed.

In present study, an in-vitro physiologically based extraction test has been applied for extraction of bio-accessible trace metal fractions in airborne particulate matter (APM) samples collected from different urban sites in Austria and Pakistan using the leaching agents H2O, sodium chloride, ammonium acetate, ammonium citrate, synthetic gastric juice and artificial lung fluids. Obtained extracts were then measured using an ETV-ICP-OES procedure which allowed highly sensitive measurement of dissolved analytes even in the presence of leaching agents. Derived results indicated that the investigated leaching agents extract different amounts of trace metals. In general, leaching agents with organic nature yielded comparatively greater extractable and thus bio-accessible trace metal fractions to that of simple solvents like H2O or aqueous NaCl solution. With water, only 26.3±4.0% of Cd was found to be bio-accessible whereas 88.4±24.8 of Cd was obtained as bio-accessible fraction with the use of synthetic gastric juice. The concentrations of bio-accessible metal fractions varied from 0.4 ng m−3 (Cd) to 714 ng m−3 (Zn) and 0.3 ng m−3 (Cd) to 190 ng m−3 (Zn) for PM10 samples collected from Karachi (Pakistan) and Graz (Austria) respectively.

The determination of mineral dust and elemental carbon in snow samples is of great interest, since both compounds are known to be light-absorbing snow impurities. Different analytical methods have to be used to quantify both compounds. The occurrence of mineral dust, which contains hematite, leads to a bias in the quantification of elemental carbon and organic carbon via thermal–optical analysis. Here we present an approach which utilizes this interference to determine the concentration of iron via thermal–optical analysis using a Lab OC / EC Aerosol Analyzer (Sunset Laboratory Inc.) and the EUSAAR2 protocol. For this, the temperature dependency of the transmittance signal determined during the calibration phase, i.e., when all carbonaceous compounds are already removed, is evaluated. Converting the transmittance signal into an attenuation, a linear relationship between this attenuation and the iron loading is obtained for loadings ranging from 10 to 100 µg Fe cm−2. Furthermore, evaluation of the transmittance signal during the calibration phase allows to identify samples which need to be re-evaluated, since the analysis of elemental carbon and organic carbon is biased by constituents of mineral dust. The method, which was initially designed for snow samples, can also be used to evaluate particulate matter samples collected within the same high alpine environment. When applying the method to a new set of samples it is crucial to check whether the composition of iron compounds and the sample matrix remain comparable. If other sources than mineral dust determine the iron concentration in particulate matter, these samples cannot be evaluated with thermal–optical analysis. This is shown exemplarily with data from particulate matter samples collected in a railway tunnel.

The demand for high-resolution imaging, and high sample throughputs in LA-ICP-MS experiments has led to developing rapid-response ablation cells with low dispersion. These cells can achieve short transient signals called single pulse responses (SPRs), whose width is in the single-digit millisecond range at 1% of the maximum. However, coupled with ICP-Q-MS, recording those short signals poses a problem due to the sequential measurement of selected m/z ratios. If more than one m/z ratio is targeted, the time resolution of quadrupole detection systems is insufficient for accurately determining short SPRs. This work focuses on utilizing rapid response ablation cells for the analysis of multiple elements with quadrupole-based detection systems in the SPR mode. To achieve this, an ArF-excimer laser equipped with a rapid-response ablation chamber is coupled to an ICP-MS with a short settling time of 0.2 ms and below. The two naturally occurring Ag-isotopes were analyzed in the NIST SRM 612 to optimize the dwell times for ideal data acquisition. The data shows that the ratio of the dwell time and the settling time, plays a crucial role. With the optimized parameters, the natural ratio of 107Ag and 109Ag within a 10 ms FW0.01M transient signal could be determined. This concept of LA-ICP-MS was then applied for depth profiling analysis of Al-doped SiC, a wide bandgap semiconductor. This procedure acquired depth profiles on 30 different sample locations in approximately 2 minutes with an exceptional depth resolution of 55 nm. [ABSTRACT FROM AUTHOR]

Great strides have been made in understanding the phylogeny of the five extant echinoderm classes, however, many Palaeozoic groups have yet to be examined in a rigorous, quantitative framework. The aberrant morphologies of Paracrinoidea, an unusual group of Palaeozoic echinoderms, have hindered their inclusion in large‐scale phylogenetic and morphologic studies. This study uses a combined approach of phylogenetic analysis and morphological disparity to elucidate species relationships within the clade. Findings from this study suggest that Paracrinoidea is a monophyletic group and that respiratory structures, oral plate arrangement, and ambulacral morphologies are important for defining subclades within Paracrinoidea. Examination of paracrinoids in a quantitative framework, facilitates their inclusion in larger projects examining Palaeozoic echinoderm evolution, ecology and biogeography. [ABSTRACT FROM AUTHOR]