An EXAFS and XANES Study of V, Ni, and Fe Speciation in Cokes for Anodes Used in Aluminum Production

Lower-quality petroleum coke with higher levels of sulfur and metal impurities will have to be used for the manufacturing of anodes for aluminum production in the future. The sulfur and metallic impurities affect the anode properties in the aluminum production process, but the chemical identity of the metal species in the coke is not known. In this study, industrial petroleum cokes with high sulfur levels were analyzed by X-ray absorption near edge structure (XANES) and Extended X-ray absorption fine structure (EXAFS) in order to determine the identity of the V, Ni, and Fe impurities. The XANES spectra were compared with pure-phase standards. EXAFS was used to compare the impurity metal structures with known crystal structures. It was found that V is present mainly as hexagonal V3S4. Ni is present mainly as hexagonal NiS, and Fe is present as hexagonal FeS. This knowledge of the chemical states of the metal elements in coke, which are known to affect anode performance, is the first step in understanding the mechanism of the action of these elements on anode reactivity.acceptedVersio

Age Dependent Differences in Collagen Alignment of Glutaraldehyde Fixed Bovine Pericardium

Bovine pericardium is used for heart valve leaflet replacement where the strength and thinness are critical properties. Pericardium from neonatal animals (4–7 days old) is advantageously thinner and is considered as an alternative to that from adult animals. Here, the structures of adult and neonatal bovine pericardium tissues fixed with glutaraldehyde are characterized by synchrotron-based small angle X-ray scattering (SAXS) and compared with the mechanical properties of these materials. Significant differences are observed between adult and neonatal tissue. The glutaraldehyde fixed neonatal tissue has a higher modulus of elasticity (83.7 MPa) than adult pericardium (33.5 MPa) and a higher normalised ultimate tensile strength (32.9 MPa) than adult pericardium (19.1 MPa). Measured edge on to the tissue, the collagen in neonatal pericardium is significantly more aligned (orientation index (OI) 0.78) than that in adult pericardium (OI 0.62). There is no difference in the fibril diameter between neonatal and adult pericardium. It is shown that high alignment in the plane of the tissue provides the mechanism for the increased strength of the neonatal material. The superior strength of neonatal compared with adult tissue supports the use of neonatal bovine pericardium in heterografts

An EXAFS and XANES Study of V, Ni, and Fe Speciation in Cokes for Anodes Used in Aluminum Production

Lower-quality petroleum coke with higher levels of sulfur and metal impurities will have to be used for the manufacturing of anodes for aluminum production in the future. The sulfur and metallic impurities affect the anode properties in the aluminum production process, but the chemical identity of the metal species in the coke is not known. In this study, industrial petroleum cokes with high sulfur levels were analyzed by X-ray absorption near edge structure (XANES) and Extended X-ray absorption fine structure (EXAFS) in order to determine the identity of the V, Ni, and Fe impurities. The XANES spectra were compared with pure-phase standards. EXAFS was used to compare the impurity metal structures with known crystal structures. It was found that V is present mainly as hexagonal V3S4. Ni is present mainly as hexagonal NiS, and Fe is present as hexagonal FeS. This knowledge of the chemical states of the metal elements in coke, which are known to affect anode performance, is the first step in understanding the mechanism of the action of these elements on anode reactivity

An EXAFS and XANES Study of V, Ni, and Fe Speciation in Cokes for Anodes Used in Aluminum Production

Lower-quality petroleum coke with higher levels of sulfur and metal impurities will have to be used for the manufacturing of anodes for aluminum production in the future. The sulfur and metallic impurities affect the anode properties in the aluminum production process, but the chemical identity of the metal species in the coke is not known. In this study, industrial petroleum cokes with high sulfur levels were analyzed by X-ray absorption near edge structure (XANES) and Extended X-ray absorption fine structure (EXAFS) in order to determine the identity of the V, Ni, and Fe impurities. The XANES spectra were compared with pure-phase standards. EXAFS was used to compare the impurity metal structures with known crystal structures. It was found that V is present mainly as hexagonal V3S4. Ni is present mainly as hexagonal NiS, and Fe is present as hexagonal FeS. This knowledge of the chemical states of the metal elements in coke, which are known to affect anode performance, is the first step in understanding the mechanism of the action of these elements on anode reactivity

Collagen Fibril Intermolecular Spacing Changes with 2‑Propanol: A Mechanism for Tissue Stiffness

Materials composed primarily of collagen are important as surgical scaffolds and other medical devices and require flexibility. However, the factors that control the suppleness and flexibility of these materials are not well understood. Acellular dermal matrix materials in aqueous mixtures of 2-propanol were studied. Synchrotron-based small-angle X-ray scattering was used to characterize the collagen structure and structural arrangement. Stiffness was measured by bend tests. Bend modulus increased logarithmically with 2-propanol concentration from 0.5 kPa in water to 103 kPa in pure 2-propanol. The intermolecular spacing between tropocollagen molecules decreased from 15.3 to 11.4 Å with increasing 2-propanol concentration while fibril diameter decreased from 57.2 to 37.2 nm. D-spacing initially increased from 63.6 to 64.2 nm at 50% 2-propanol then decreased to 60.3 nm in pure 2-propanol. The decrease in intermolecular spacing and fibril diameter are due to removal of water and the collapse of the hydrogen bond structure between tropocollagen molecules causing closer packing of the molecules within a fibril. We speculate this tighter molecular packing may restrict the sliding of collagen within fibrils, and similar disruption of the extended hydration layer between fibrils may lead to restriction of sliding between fibrils. This mechanism for tissue stiffness may be more general

Supplemental Material, DS3_VET_10.1177_0300985818789483l - Tropical Keratopathy (Florida Spots) in Cats

<p>Supplemental Material, DS3_VET_10.1177_0300985818789483l for Tropical Keratopathy (Florida Spots) in Cats by Pompei Bolfa, Susyn J. Kelly, Hannah C. Wells, Katie H. Sizeland, Erin M. Scott, Nigel Kirby, Stephen Mudie, Anibal G. Armien, Richard G. Haverkamp, and Patrick J. Kelly in Veterinary Pathology</p

Supplemental Material, DS2_VET_10.1177_0300985818789483l - Tropical Keratopathy (Florida Spots) in Cats

<p>Supplemental Material, DS2_VET_10.1177_0300985818789483l for Tropical Keratopathy (Florida Spots) in Cats by Pompei Bolfa, Susyn J. Kelly, Hannah C. Wells, Katie H. Sizeland, Erin M. Scott, Nigel Kirby, Stephen Mudie, Anibal G. Armien, Richard G. Haverkamp, and Patrick J. Kelly in Veterinary Pathology</p