Laue centennial-100 years of X-rays diffraction Preface

ISSN:1433-7266ISSN:2194-4946ISSN:0044-2968ISSN:2196-710

Anatomical Variation of Human Bone Bioapatite Crystallography

This systematic investigation of bioapatite, the mineral component of human bone, aims to characterize its crystallographic state, including lattice parameters and average crystallite size, and correlate these values with respect to anatomical position (bone function), physicality, and bone chemical composition. In sample sets of buried bone from three different human adult skeletons, anatomical variation of crystallographic parameters and correlation to chemical composition were indeed observed. In general, the observed bioapatite a unit-cell edge-length among all analyzed human bones in this study was larger by 0.1-0.2% compared to that of stoichiometric hydroxylapatite (HAp), and substantially larger than that of fluorapatite (FAp). Across all analyzed samples, the a (=b) lattice parameter (unit cell edge-length) varies more than does the c lattice parameter. Average crystallite size (average coherent diffracting domain size) in the c-direction was equal to approximately 25 nm, ranging among the analyzed 18 bone samples from about 20-32 nm, and varying more than crystallite size in the a,b-direction (similar to 8-10 nm). Neither lattice parameters nor average bioapatite crystallite sizes appeared to be correlated with bone mechanical function. The relative chemical composition of the bone material, however, was shown to correlate with the a (=b) lattice parameter. To our knowledge, this research provides, for the first time, the systematic study of the crystallographic parameters of human bone bioapatite in the context of anatomical position, physical constitution, and bone chemical composition using X-ray powder diffraction (XRPD) and Fourier transform infrared spectroscopy (FTIR)

Dielectric Characterization of a Nonlinear Optical Material

Batisite was reported to be a nonlinear optical material showing second harmonic generation. Using dielectric spectroscopy and polarization measurements, we provide a thorough investigation of the dielectric and charge-transport properties of this material. Batisite shows the typical characteristics of a linear lossy dielectric. No evidence for ferro- or antiferroelectric polarization is found. As the second-harmonic generation observed in batisite points to a non-centrosymmetric structure, this material is piezoelectric, but most likely not ferroelectric. In addition, we found evidence for hopping charge transport of localized charge carriers and a relaxational process at low temperatures

Microstructure and Crystallographic Characteristics of Stenolaemate Bryozoans (Phylum Bryozoa and Class Stenolaemata)

The bryozoan class Stenolaemata is currently represented by the order Cyclostomata. They produce skeletons made exclusively of calcite crystals assembled into different microstructures. Despite extensive previous research, no appropriate crystallographic techniques have been applied to decipher their crystallographic organization. We present an in-depth crystallographic study of the microstructures of three extant species (Fasciculipora ramosa, Hornera robusta, and Cinctipora elegans) using scanning electron microscopy and associated techniques (energy dispersive spectroscopy and electron backscatter diffraction), together with atomic force microscopy and micro-computed tomography. We differentiate two microstructures: foliated and tabular calcite, and establish consistent models of their crystallography. Foliated calcite of Fasciculipora ramosa and Cinctipora elegans consists of co-oriented laths arranged with their c-axes parallel to their elongation axis and to their main surfaces, and one a*-axis perpendicular to the latter (sheet texture). Tabular calcite of Hornera robusta consists of polygonal tablets with the c-axis as fiber axis (axial texture), perpendicular to the tablet surface. The foliated calcite of bryozoans is homeomorph to that of bivalves but has a significantly different crystallography. The tabular calcite of bryozoans lacks the spiral morphology of the tablet-shaped calcite of craniiform brachiopods, and has a different orientation of the c-axis with respect to the constituent tablets.Proyectos CGL2017-85118-P y PID2020116660GB-I00 (Ministerio de Ciencia e Innovación)Proyecto B-RNM-265UGR18 (Junta de Andalucía)Grupo de Investigación RNM363 (Consejería de Economía, Innovación, Ciencia y Empleo, Junta de Andalucía)Open Access financiado por la Universidad de Granada y por el Consorcio de Bibliotecas Universitarias de Andalucía (CBUA

Crystal Imperfections of Industrial Vanadium Phosphorous Oxide Catalysts

This study presents information about crystal imperfections in the main phase of industrial vanadium phosphorous oxide catalysts that are used to catalyze the oxidation of n-butane to maleic anhydride, being an important intermediate in the chemical industry. The mechanism of this reaction is still debated, and the catalytically active and selective surface centers have not yet been identified. The results presented are based on X-ray diffraction data obtained by both laboratory-scale and synchrotron powder diffraction experiments, as well as laboratory-scale single-crystal diffraction experiments. It has been proven that pronounced Bragg reflection broadening effects found in laboratory-scale powder diffraction patterns of industrial VPO catalysts are real and not due to an insufficient 2-θ resolution of the apparatus. In the framework of this work, a powder diffraction full profile fitting strategy was developed using the TOPAS software, which was applied to analyze the X-ray diffraction data of four differently activated industrial catalyst samples, originating from one batch after they had been catalytically tested. It was found that the reflection broadening is mainly caused by an anisotropic crystal size, which results in platelet-shaped crystallites of vanadyl pyrophosphate. A further contribution to the reflex broadening, especially for (111), was found to be a result of stacking faults perpendicular to the a direction in the crystal structure of vanadyl pyrophosphate. These results were used to elaborate on possible correlations between structural proxies and catalytic performance. A direct correlation between the extension of coherently scattering domains in the z direction and the catalyst�s selectivity could be proven, whereas the activity turned out to be dependent on the crystallite shape. Regarding the phase contents, it could be shown that sample catalysts containing a higher amount of β-VO(PO3)2 showed increased catalytic activity

Neutron Radiographic Study of the Effect of Heat-Driven Water Transport on the Tensile Strength of Bentonite-Bonded Moulding Sand

Wet tensile testing is a common method to assess the stability of bentonite bonded moulding sands. For wet tensile testing, a specimen is first heated from above in order to simulate heat-driven moisture transport induced by the casting process. Then, tensile stress is applied until rupture. In this study, neutron radiography imaging was applied to moulding sands in-situ during heating and wet tensile testing in order to investigate the effects of water kinematics on the tensile strength. Neutron radiography allowed the localization of the rupture plane and the quantitative determination of the local water content with sub-mm resolution. Quantification of the temperature at the rupture plane and of the heat kinematics within the specimen was accomplished by temperature measurements both in-situ and ex-situ. In this way, experimental data correlating the wet tensile strength with the specific conditions of moulding sands at the rupture plane were obtained for the first time. Series of experiments with different initial sand moisture contents were conducted. The results show that the weakest location within a sand profile can be pinpointed at the interface between evaporation and condensation zone (i.e., at the 100 °C isotherm), where water vaporisation starts and the water bridges connecting the sand grains collapse. This weakest location has maximum strength, if the local water content at the rupture plane is between 5 and 9 wt.%. Less water leads to a strong decrease of wet tensile strength. More water requires an initial water content above 5 wt.%, which leads to a decrease of the tensile strength of the unheated sand

Biodegradation of textile waste by marine bacterial communities enhanced by light

Knowledge of biofilm formation on pollutants in the marine realm is expanding, but how communities respond to substrates during colonization remains poorly understood. Here, we assess community assembly and respiration in response to two different micropollutants, virgin high‐density polyethylene (HDPE) microbeads and textile fibres under different light settings. Raman characterization, high‐throughput DNA sequencing data, quantitative PCR, and respiration measurements reveal how a stimulation of aerobic respiration by micropollutants is translated into selection for significantly different communities colonizing the substrates. Despite the lack of evidence for biodegradation of HDPE, an increased abundance and respiration of bacterial taxa closely related to hydrocarbonoclastic Kordiimonas spp. and Alteromonas spp. in the presence of textile waste highlights their biodegradation potential. Incubations with textile fibres exhibited significantly higher respiration rates in the presence of light, which could be partially explained by photochemical dissolution of the textile waste into smaller bioavailable compounds. Our results suggest that the development and increased respiration of these unique microbial communities may potentially play a role in the bioremediation of the relatively long‐lived textile pollutants in marine habitats, and that the respiration of heterotrophic hydrocarbon‐degrading bacteria colonizing marine pollutants can be stimulated by light

A Study on Ikaite Growth in the Presence of Phosphate

Phosphate is a common component in natural growth solutions of ikaite. Although phosphate often occurs as a minor constituent, its presence may promote the formation of ikaite as it significantly inhibits the precipitation of calcite. The interactions of phosphate with ikaite and the role of a potential uptake of phosphate by ikaite, however, are poorly understood. In this study, the influence of phosphate on ikaite growth at 1 °C was investigated. Ikaite and calcite seeded growth experiments were conducted in cryo-mixed-flow reactors at saturation ratios 1.5 ≤ Ωikaite ≤ 2.9 (Ω = ionic activity product/solubility product). From these growth experiments, the rate constant k = 0.10 ± 0.03 µmol/m2/s and the reaction order n = 0.8 ± 0.3 were derived for ikaite. The reaction order implies a transport or adsorption controlled growth mechanism which supports a low energy pathway of ikaite growth via an attachment of hydrous CaCO30 complexes without any extensive dehydration of aqueous species as, for instance, required for calcite growth. A potential depletion of aqueous phosphate due to an uptake by ikaite growth was not detectable. Furthermore, growth retardation by phosphate, as known for calcite growth, was not evident. Thus, a significant incorporation of phosphate into growing ikaite could be precluded for the conditions applied in this study. The observed lack of incorporation of phosphate agrees with the previously suggested growth mechanism via the attachment of hydrous CaCO30 complexes which likely does not facilitate substantial substitution of carbonate by phosphate ions

Mosaic structure in the spines of Holopneustes porossisimus

Sea urchin spines of Holopneustes porossisimus are porous singlecrystals, with the pores being filled with a material rich in carbon,silicon, fluorine and sodium. The magnesian calcite constituting thespine is highly strained. Even though the spines appear to be singlecrystalline on a macroscopic scale, the calcitic material exhibits anextended defect network. We find dislocations as well as rotational andother, not yet identified boundaries. We also observe within spinecalcite a patterned distribution of sulphur. Both distributions, that ofthe defect network and that of sulphur resemble in their pattern to eachother and have a similar mesh size of 50 nm. We conclude from theseobservations that they arise from the growth process of the spine andaccount for the mosaicity within the spine single crystals