Polychromatic CT Data Improvement with One-Parameter Power Correction

Standard approaches to tomography reconstruction of the projection data registered with polychromatic emission lead to the appearance of cupping artifacts and irrelevant lines between regions of strong absorption. The main reason for their appearance is the fact that part of the emission with low energy is being absorbed entirely by high absorbing objects. This fact is known as beam hardening (BH). The procedure of processing projection data collected in polychromatic mode is presented; it reduces artifacts relevant to BH and does not require additional calibration experiments. The procedure consists of two steps: the first is to linearize the projection data with one-parameter power correction, and the second is to reconstruct the images from linearized data. Automatic parameter adjustment is the main advantage of the procedure. The optimization problem is formulated. The system flowchart is presented. The reconstruction with different powers of correction is considered to evaluate the quality reconstruction

Monitored Tomographic Reconstruction—An Advanced Tool to Study the 3D Morphology of Nanomaterials

Detailed and accurate three-dimensional (3D) information about the morphology of hierarchically structured materials is derived from multi-scale X-ray computed tomography (XCT) and subsequent 3D data reconstruction. High-resolution X-ray microscopy and nano-XCT are suitable techniques to nondestructively study nanomaterials, including porous or skeleton materials. However, laboratory nano-XCT studies are very time-consuming. To reduce the time-to-data by more than an order of magnitude, we propose taking advantage of a monitored tomographic reconstruction. The benefit of this new protocol for 3D imaging is that the data acquisition for each projection is interspersed by image reconstruction. We demonstrate this new approach for nano-XCT data of a novel transition-metal-based materials system: MoNi4 electrocatalysts anchored on MoO2 cuboids aligned on Ni foam (MoNi4/MoO2@Ni). Quantitative data that describe the 3D morphology of this hierarchically structured system with an advanced electrocatalytically active nanomaterial are needed to tailor performance and durability of the electrocatalyst system. We present the framework for monitored tomographic reconstruction, construct three stopping rules for various reconstruction quality metrics and provide their experimental evaluation

Anion and Cation Order in Iodide-Bearing Mg/Zn–Al Layered Double Hydroxides

Uptake of iodine in hydrotalcite-like minerals is a potential retardation mechanism for dose-relevant ¹²⁹I in the near-field of a deep repository for radioactive waste. The location of iodide in (Zn/Mg)­Al layered double hydroxides (LDH) was investigated using a combination of advanced atomic-scale techniques. Wavelet transform analysis of Zn K-edge extended X-ray absorption fine structure (EXAFS) spectra and geometry optimization based on ab initio density functional calculations allowed the distribution of Al³⁺ in the cationic layer to be determined. Using Rietveld refinement of synchrotron X-ray powder diffraction data (XRD) and EXAFS at the I K-edge enabled the average location of iodide in the interlayer to be established. Additional short- and medium-range structural information was also obtained from the pair distribution function analysis of the XRD data in support of the findings obtained with the long- and short-range techniques. By combining the results, a local order of Al³⁺ in Zn₂Al–I and Zn₃Al–I LDHs was shown generating hexagonal and orthorhombic supercells, respectively. Furthermore, an uncorrelated distribution between I^– anions and Zn²⁺/Al³⁺ cations was demonstrated, resulting from a dynamic disorder of water and iodide position in the interlayer space

Micro-morphology of pineal gland calcification in age-related neurodegenerative diseases

The formation of concrements in human pineal gland (PG) is a physiological process and, according to many researchers, is associated with the involution of PG structures. The majority of scientific publications concern progressive calcification of pineal gland (PG), leaving out studies on the destruction of already formed calcified concrements. Our study fills the gap in knowledge about calcified zones destruction in PG in normal agind and neuropathological conditions, that hasn't been addressed until now

Revisiting the local structure in Ge-Sb-Te based chalcogenide superlattices

\u3cp\u3eThe technological success of phase-change materials in the field of data storage and functional systems stems from their distinctive electronic and structural peculiarities on the nanoscale. Recently, superlattice structures have been demonstrated to dramatically improve the optical and electrical performances of these chalcogenide based phase-change materials. In this perspective, unravelling the atomistic structure that originates the improvements in switching time and switching energy is paramount in order to design nanoscale structures with even enhanced functional properties. This study reveals a high- resolution atomistic insight of the [GeTe/Sb\u3csub\u3e2\u3c/sub\u3eTe\u3csub\u3e3\u3c/sub\u3e] interfacial structure by means of Extended X-Ray Absorption Fine Structure spectroscopy and Transmission Electron Microscopy. Based on our results we propose a consistent novel structure for this kind of chalcogenide superlattices.\u3c/p\u3