1,721,114 research outputs found
Nano-imaging of environmental dust in human lung tissue by soft and hard X-ray fluorescence microscopy
Full text linkIt is well recognized that a large number of pulmonary diseases are induced by the effects of inhaled particulates. Anthracosis is defined as an asymptomatic, mild form of pneumoconiosis caused by the accumulation of “black carbon” in the lungs due to repeated exposure to air pollution or inhalation of smoke or coal dust particles. Since the human population is progressively exposed to an increasing number and doses of anthropogenic micro and nano particles/compounds, there is a pressing urgency to explore toxicological impact arising from these exposures and the molecular mechanisms driving the body defense or possible related diseases. The toxicity mechanisms are clearly related to chemical composition and physical and surface properties of materials. A combination of synchrotron radiation-based (SR-based) nano X-ray fluorescence (XRF) imaging and soft X-ray microscopy was used to chemically characterize environmental particulates (anthracosis) in lung tissues from urban subjects with the aim of better understanding the complex nature of related lungs' deposits. High-resolution XRF analyses performed at ESRF and Elettra synchrotrons allowed discriminating single particles in the heterogeneous aggregates found in the lung tissue. The small particles have variable composition resulting from the different combinations of Ti with O, K and Si, Al and Si, or Zn and Fe with O. Interestingly, simultaneous absorption and phase contrast images showed the particulate morphology and allowed to predict the presence of very dense nanoparticles or high concentration of heavy elements
Recent achievements in reproductive medicine applications at the TwinMic soft spectromicroscopy beamline of Elettra
No full textWe present here two reproductive medicine studies at the TwinMic soft spectromicroscopy beamline of Elettra Synchrotron (Trieste, Italy), which can open new opportunities for more direct clinical applications. In particular we demonstrate the TwinMic imaging capabilities for monitoring ovarian tissue preservation and follicles quality and to investigate of chemical changes in sperm undergoing oxidative stress conditions and iron toxicity
Electrodeposition of Co/CoO nanoparticles onto graphene for ORR electrocatalysis: a study based on micro-X-ray absorption spectroscopy and X-ray fluorescence mapping
No full textElectrodeposition of graphene-supported Co for ORR electrocatalysts from an acetonitrile solution has been studied by a multi-technique approach, combining a suite of spectroscopic methods with electrochemical measurements, allowing a molecular-level understanding of potentiostatic and pulsed-potential plating processes from the organic solvent onto a freestanding graphene film. The formation of the graphene film by the light-scribe approach has been monitored by Raman spectroscopy; the electrodeposition process has been clarified by cyclic voltammetry and the compositional and chemical-state distribution of Co have been investigated ex situ by soft X-ray absorption spectroscopy and fluorescence mapping, showing that both spatial distribution and valence state are homogeneous and independent of the local current density. The deposit consists in micrometric aggregates of Co/CoO nanoparticles with diameter ca. 30 nm (pulsed) and 200 nm (potentiostatic deposition). Potentiostatic deposition allows to obtain better ORR electrocatalytic perfomance in terms of nnumber of transferred electrons, onset/ half-wave potential and current density
Automatic Differentiation for Inverse Problems in X-ray Imaging and Microscopy
Full text linkComputational techniques allow breaking the limits of traditional imaging methods, such as time restrictions, resolution, and optics flaws. While simple computational methods can be enough for highly controlled microscope setups or just for previews, an increased level of complexity is instead required for advanced setups, acquisition modalities or where uncertainty is high; the need for complex computational methods clashes with rapid design and execution. In all these cases, Automatic Differentiation, one of the subtopics of Artificial Intelligence, may offer a functional solution, but only if a GPU implementation is available. In this paper, we show how a framework built to solve just one optimisation problem can be employed for many different X-ray imaging inverse problems
XRFitProc: A novel web-based x-ray fluorescence fitting system
No full textX-ray fluorescence (XRF) spectroscopy is a widely used technique in microscopy, spanning from biology to cultural heritage applications. Its purpose is to characterize qualitatively and quantitatively, the presence of elemental species in a sample. This is accomplished through fitting the acquired data to a Gaussian model, identifying which XRF lines and associated elements are present. As a result, 2D images of cumulative count-rate maps associated with each element are produced. This procedure is not trivial to apply efficiently in a workflow, as it requires the user to be able to set a series of parameters (e.g., beam energy, background subtraction, etc.) on top of selecting XRF lines under investigation. Furthermore, users should easily and swiftly be able to change setup parameters and evaluate the effects on the results. In the present work, we introduce a web-based application that allows users to load the XRF data, setup a fit and inspect the results interactively within a simple graphical user interface (GUI) that enables easily going back and forth from setup to result inspection. In particular, it is possible to quickly view the count-rate maps and curve fitting simultaneously, on any single pixel spectra present in the images. The web-application can be accessed locally by a web-browser, but runs remotely on a cloud, freeing from the need of installing any software and will be made publicly available in the near future. At present, it has been designed to work on both conventional and sparse XRF data such as Compressive Sensing, in an embarrassingly parallel manner
Enlightening Gliotoxin Biological System in Agriculturally Relevant Trichoderma spp
No full textGliotoxin (GT) is a dual fungal secondary metabolite (SM). It displays pleiotropic activities and possesses medicinal properties and biocontrol abilities but, unfortunately, has toxic properties in humans. Various Trichoderma species are used as fungal biological control agents (BCAs), as a sustainable alternative for crop protection worldwide. Among them is Trichoderma virens, a GT-producing fungus. Since no information was available on the genetically coded prerequisites for the production of GT in other Trichoderma spp., genome analyses were carried out in 10 Trichoderma spp. genomes. Moreover, a real-time PCR assay setup ad hoc and high-performance liquid chromatography (HPLC) analyses were employed to understand the GT-producing biological systems in T. virens GV29-8 (TvGv29-8) and Trichoderma afroharzianum T6776 (TaT6776), two relevant biocontrol fungi. The structure of the GT biosynthesis genes (GT-BG) is polymorphic, with two distinct types associated with the ability to produce GT. GliH, a key protein for GT synthesis, is absent in most of the Trichoderma GT biosynthetic pathways, which may be the reason for their inability to produce GT. The GT-BG are expressed in TvGv29-8 as expected, while they are silent in TaT6776. Interestingly, in the GT-non-producing TaT6776, only gliA (putative GT transporter) and gtmA (putative GT S-methyltransferase) were induced by exogenous GT, underlining the ability of this strain to reduce the deleterious effect of the toxin. This ability is confirmed by growth assays and by the detection of the bis-thiomethylated form of GT catalyzed by GtmA in the culture medium supplemented with GT. To the best of our knowledge, this is the first general description of the GT biological system in different Trichoderma spp. as far as the GT-BG content and organization is concerned and a preliminary insight into their functionality
High-lateral resolution X-ray fluorescence microspectroscopy and dynamic mathematical modelling as tools for the study of electrodeposited electrocatalysts
No full textEnergy-dispersive X-ray fluorescence and diffraction portable system for cultural heritage applications
No full textA portable X-ray diffraction (XRD) and X-ray fluorescence (XRF) system, based on energy dispersive detection in reflection geometry, has been developed for the non-invasive study of cultural heritage materials. This analytical system is an open-work platform based on a low-power miniaturized X-ray tube (Ag anode), a single Si-drift detector, and a set of collimators that have been mounted on a compact and versatile manual or motorized stage, which allows independent and precise angular positioning of both source and detector and the study of complex geometry objects. The design of two instruments and experimental setups, and their advantages are discussed. The XRF and XRD analytical performance has been tested through the analysis of standard reference materials and some applications, including provenance study of obsidian and 'green stone' artifacts, identification of pigments in a model of fresco painting, and chemical element analysis of bones. The main advantages of portable energy dispersive X-ray diffraction systems compared with commonly used angle dispersive X-ray diffraction (ADXRD) instruments are shorter measurement times and compactness. Moreover, optimum XRF spectra can be collected because a polychromatic beam is used instead of a (quasi) monochromatic beam as in an angle dispersive X-ray diffraction-X-ray fluorescence portable system. Results demonstrate that it is possible to identify the main crystalline phases in a measurement time of 100s-600s and the system is sensible enough for answering common questions, as the ones presented, in the cultural heritage field
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
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