The scope of patents covering SARS-CoV-2 and diagnostics, vaccines and treatments related to the virus remains unclear, but the pandemic may have created a permanent demand for SARS-CoV-2-related ...products and spark long-term interest in relevant intellectual property rights.
One major challenge in the field of lithium-ion batteries is to understand the degradation mechanism of high-energy lithium- and manganese-rich layered cathode materials. Although they can deliver 30 ...% excess capacity compared with today's commercially- used cathodes, the so-called voltage decay has been restricting their practical application. In order to unravel the nature of this phenomenon, we have investigated systematically the structural and compositional dependence of manganese-rich lithium insertion compounds on the lithium content provided during synthesis. Structural, electronic and electrochemical characterizations of Li
Ni
Mn
O
with a wide range of lithium contents (0.00 ≤ x ≤ 1.52, 1.07 ≤ y < 2.4) and an analysis of the complexity in the synthesis pathways of monoclinic-layered LiLi
Ni
Mn
O
oxide provide insight into the underlying processes that cause voltage fading in these cathode materials, i.e. transformation of the lithium-rich layered phase to a lithium-poor spinel phase via an intermediate lithium-containing rock-salt phase with release of lithium/oxygen.
During X‐ray diffraction experiments on single crystals, the diffracted beam intensities may be affected by multiple‐beam X‐ray diffraction (MBD). This effect is particularly frequent at higher X‐ray ...energies and for larger unit cells. The appearance of this so‐called Renninger effect often impairs the interpretation of diffracted intensities. This applies in particular to energy spectra analysed in resonant experiments, since during scans of the incident photon energy these conditions are necessarily met for specific X‐ray energies. This effect can be addressed by carefully avoiding multiple‐beam reflection conditions at a given X‐ray energy and a given position in reciprocal space. However, areas which are (nearly) free of MBD are not always available. This article presents a universal concept of data acquisition and post‐processing for resonant X‐ray diffraction experiments. Our concept facilitates the reliable determination of kinematic (MBD‐free) resonant diffraction intensities even at relatively high energies which, in turn, enables the study of higher absorption edges. This way, the applicability of resonant diffraction, e.g. to reveal the local atomic and electronic structure or chemical environment, is extended for a vast majority of crystalline materials. The potential of this approach compared with conventional data reduction is demonstrated by the measurements of the Ta L3 edge of well studied lithium tantalate LiTaO3.
An approach to reliably extract the desired intensities and filter out multiple‐beam X‐ray diffraction, which often causes interference for high X‐ray energies and for large unit cells, is presented. Here, a universal concept of data acquisition and post‐processing for resonant X‐ray diffraction experiments is described, including the measurement of the energy‐dependent intensity at several azimuth angles and subsequently only considering the unaffected data points.
Physical properties of crystalline materials often manifest themselves as atomic displacements either away from symmetry positions or driven by external fields. Especially the origin of multiferroic ...or magnetoelectric effects may be hard to ascertain as the related displacements can reach the detection limit. Here we present a resonant X-ray crystal structure analysis technique that shows enhanced sensitivity to minute atomic displacements. It is applied to a recently found crystalline modification of strontium titanate that forms in single crystals under electric field due to oxygen vacancy migration. The phase has demonstrated unexpected properties, including piezoelectricity and pyroelectricity, which can only exist in non-centrosymmetric crystals. Apart from that, the atomic structure has remained elusive and could not be obtained by standard methods. Using resonant X-ray diffraction, we determine atomic displacements with sub-picometer precision and show that the modified structure of strontium titanate corresponds to that of well-known ferroelectrics such as lead titanate.
Abstract
Homoepitaxial growth of SrTiO
3
thin films on 0.5 wt% niobium doped SrTiO
3
(100) substrates with high structural perfection was developed using liquid-delivery spin metal–organic vapor ...phase epitaxy (MOVPE). Exploiting the advantage of adjusting the partial pressures of the individual constituents independently, we tuned the Sr/Ti ratio of the gas phase for realizing, stoichiometric, as well as Sr deficient layers. Quantitative energy dispersive X-ray spectroscopy in a scanning transmission electron microscope confirm Sr deficiency of up to 20% in nominally off-stoichiometrically grown films. Our MOVPE process allows to grow such layers in phase pure state and without extended defect formation. Indications for oxygen deficiency could not be identified. Sr deficient layers exhibit an increased permittivity of
ɛ
r
= 202 and a larger vertical lattice parameter. Current–voltage characteristics (IVCs) of metal–oxide–semiconductor (Pt/SrTiO
3
/SrTiO
3
:Nb) structures reveal that Sr deficient SrTiO
3
films show an intrinsic resistive switching with on–off ratios of three orders of magnitude at RT and seven orders of magnitude at 10 K. There is strong evidence that a large deviation from stoichiometry pronounces the resistive switching behavior. IVCs conducted at 10 K indicate a defect-based mechanism instead of mass transport by ion diffusion. This is supported by in-situ STEM investigations that show filaments to form at significant higher voltages than those were resistive switching is observed in our samples.
We demonstrate the growth of large (Mg,Zr):SrGa12O19 (SGMZ) single crystals and use a combination of X-ray imaging techniques to analyze their structural and chemical homogeneity. Single-crystal ...cylinders with lengths and diameters up to about 2.5 cm are achieved. Our characterization of polished sections reveals a localized (0001) facet that is typically formed at the center of the growth interface. Such facets are seen as the key factor limiting the growth of large-area crystals with excellent structural quality due to local deviations in the segregation behavior of the dopants. We developed a lab-based X-ray diffraction imaging technique with high sensitivity that exposes subtle variations in lattice parameters and lattice tilts, which are attributed to changes in the chemical composition and the resulting elastic deformation. The relationship between unit-cell dimensions and composition is verified by micro X-ray fluorescence mapping. In this way, we find a Ga-rich center region with a reduced unit-cell volume that is surrounded by a ring of increased tilt and elastic strain. Furthermore, we observe a 6-fold in-plane anisotropy of dopant incorporation and tree-ring-shaped structures caused by macrosteps. With rocking curve widths below 23 arcsec in ∼90% of the crystal, SGMZ crystals are largely homogeneous and hence suitable for the preparation of high-quality substrates. For most applications, the substantially enhanced crystal size enabled by very high Mg and Zr codoping levels outweighs the issues related to concentration variations arising from their addition.
Cholangiocarcinoma (CCA) is a fatal bile duct cancer associated with infection by the liver fluke, Opisthorchis viverrini, in the lower Mekong region. Numerous public health interventions have ...focused on reducing exposure to O. viverrini, but incidence of CCA in the region remains high. While this may indicate the inefficacy of public health interventions due to complex social and cultural factors, it may further indicate other risk factors or interactions with the parasite are important in pathogenesis of CCA. This systematic review aims to provide a comprehensive analysis of described risk factors for CCA in addition to O. viverrini to guide future integrative interventions.
We searched five international and seven Thai research databases to identify studies relevant to risk factors for CCA in the lower Mekong region. Selected studies were assessed for risk of bias and quality in terms of study design, population, CCA diagnostic methods, and statistical methods. The final 18 included studies reported numerous risk factors which were grouped into behaviors, socioeconomics, diet, genetics, gender, immune response, other infections, and treatment for O. viverrini. Seventeen risk factors were reported by two or more studies and were assessed with random effects models during meta-analysis. This meta-analysis indicates that the combination of alcohol and smoking (OR = 11.1, 95% CI: 5.63-21.92, P < 0.0001) is most significantly associated with increased risk for CCA and is an even greater risk factor than O. viverrini exposure. This analysis also suggests that family history of cancer, consumption of raw cyprinoid fish, consumption of high nitrate foods, and praziquantel treatment are associated with significantly increased risk. These risk factors may have complex relationships with the host, parasite, or pathogenesis of CCA, and many of these risk factors were found to interact with each other in one or more studies.
Our findings suggest that a complex variety of risk factors in addition to O. viverrini infection should be addressed in future public health interventions to reduce CCA in affected regions. In particular, smoking and alcohol use, dietary patterns, and socioeconomic factors should be considered when developing intervention programs to reduce CCA.
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