The morphology and mesostructure of the prismatic layer of a growing mollusc shell is observed by means of high-resolution synchrotron-based tomography and shown to be fully predicted by classical theories of normal grain growth.
The National Synchrotron Light Source II detects its first photons, beginning a new phase of the facility's operations. Scientific experiments at NSLS-II are expected to begin before the end of the year.
The authors showed that eruption styles can be broadly identified by relative variations in groundmass or bulk crystallinity determined by X-ray diffraction. Analysis of Mars Curiosity rover CheMin X-ray diffraction results from Gale crater indicate that the crystallinity of Martian sediment (52–54%) is similar to pyroclastic rocks from Gusev crater, Mars, and consistent with widespread distribution of basaltic strombolian or plinian volcanic ejecta.
Ferrihydrite was exposed to Tc(VII)(aq) containing cement leachates (pH 10.5–13.1), and crystallization of magnetite was induced via addition of Fe(II)aq. A combination of X-ray diffraction (XRD), chemical extraction, and X-ray absorption spectroscopy (XAS) techniques provided direct evidence that Tc(VII) was reduced and incorporated into the magnetite structure.
Calcite, the most stable modification of calcium carbonate, is a major mineral in nature. It is, therefore, highly relevant in a broad range of fields such as biomineralization, sea water desalination and oil production. Knowledge of the surface structure and reactivity of the most stable cleavage plane, calcite (10.4), is pivotal for understanding the role of calcite in these diverse areas.
Ath Godelitsas's insight:
In this work, amplitude modulation atomic force microscopy is used for three-dimensional (3D) mapping of the surface structure and the hydration layers above the surface.
The aim of this study was to investigate the main principles of morphological changes in human otoconia in dissolution experiments by exposure to hydrochloric acid, EDTA, demineralized water and completely purified water respectively. For comparison reasons artificial (biomimetic) otoconia (calcite gelatin nanocomposits) and natural calcite were used. Morphological changes were detected in time steps by the use of environmental scanning electron microscopy (ESEM).
Fractionation between 235U and 238U is a result of nuclear-field effects with enrichment of 238U in the reduced insoluble species (mostly UO2) and 235U in oxidised mobile species as uranyl ion, UO22+, and its complexes. Therefore, isotopic fractionation effects should be reflected in 238U/235U ratios in uranium ore minerals formed either by reduction of uranium to UO2 or chemical precipitation in the form of U6+ minerals.
Crystalline silver nanoparticles can be deformed at room temperature and without generating dislocations through the diffusion of surface atoms, as high-resolution transmission electron microscopy and atomistic simulations show.
Thew authors report viscosities of carbonate melts up to 6.2 GPa using a newly developed technique of ultrafast synchrotron X-ray imaging. These carbonate melts display ultralow viscosities, much lower than previously thought, in the range of 0.006–0.010 Pa s, which are ~2 to 3 orders of magnitude lower than those of basaltic melts in the upper mantle.
Utilizing grazing incidence small-angle X-ray scattering (GISAXS), the authors studied heterogeneous iron(III) (hydr)oxide nucleation and growth on quartz substrates for systems containing arsenate and phosphate anions.
Well-formed prehnite crystals from Loanhead Quarry (Ayshire, Scotland), characterized by Powder-XRD, EPMA and TGA, have thoroughly been investigated using 1H-NMR, FT-IR, 29Si-MAS NMR, EPR and TPD. Especial emphasis was given to the correlation of the hydrogen content of the mineral determined by a 1H-NMR probe developed at the Institute of Inorganic Chemistry of the Russian Academy of Sciences (Novosibirsk) (Gabuda et al., 1989) with relevant data obtained using the 1H(15N,ag)12C nuclear reaction at the 7 MV van de Graaff accelerator of the Nuclear Physics Institute of the University of Frankfurt.
Through comparison of recent extended X-ray absorption fine structure (EXAFS) measurements to state-of-the-art density functional theory (DFT) simulations, the authors were able to obtain a unique view into the molecular structure of medium-to-high concentrated electrolytes.
SEM image of a human otoconial individual. The green bar indicates the cross-sectional FIB cut that runs parallel to the largest diameter of the branches. (b) TEM micrograph of the FIB cut with merging branches in the centre surrounded by the belly area.
Ath Godelitsas's insight:
Otoconia as calcite–protein composites display a cylindrical body with terminal rhombohedral faces intersecting at the pointed ends. As evidenced by TEM on focused ion beam cuts, both the artificial composites and human otoconia show a particular distribution of areas with different volume densities leading to a dumbbell-shape of the more dense parts consisting of rhombohedral branches (with end faces) and a less ordered, less dense area (the belly region).
X-ray photoemission electron microscopy (XPEEM) enables natural remanent magnetisation to be imaged with ∼30 nm∼30 nm resolution across a field of view of 5–20 μm. The method is applied to structural features typical of the Widmanstätten microstructure (kamacite – tetrataenite rim – cloudy zone – plessite) in the Tazewell IIICD iron meteorite.
The measurements were conducted by micro-X-ray diffraction and X-ray absorption spectroscopy (both XANES and EXAFS) on hydrogeneous and diagenetic regions of the nodule. The hydrogenetic-diagenetic interface was imaged by X-ray microfluorescence, after which regions of interest were chosen to represent mineralogical and chemical transformations that occurred at the early stage of suboxic diagenesis. In the hydrogenetic nodule (oxic environment), Mn is speciated as Fe-vernadite, a nanocomposite material composed of intergrown feroxyhite (δ-FeOOH) and monodispersed phyllomanganate layers having no interlayer Mn (vernadite). In the diagenetic nodule (suboxic environment), Mn is speciated dominantly as Mg-rich 10 Å vernadite, which consists of a random intergrowth of vernadite and its transformation product todorokite.
This new technique combines the use of laser-induced plasma spectroscopy for the determination of potassium, with noble gas mass spectrometry for the determination of argon, both extracted simultaneously by laser ablation.
The oxidation rates obtained through this study are up to two orders of magnitude slower than reported in previous pyrite oxidation studies using ground rather than synthesized pyrite at similar pH values.