Increased strontium uptake in trabecular bone of ovariectomized calcium-deficient rats treated with strontium ranelate or strontium chloride

Based on clinical trials showing the efficacy to reduce vertebral and non-vertebral fractures, strontium ranelate (SrR) has been approved in several countries for the treatment of postmenopausal osteoporosis. Hence, it is of special clinical interest to elucidate how the Sr uptake is influenced by dietary Ca deficiency as well as by the formula of Sr administration, SrR versus strontium chloride (SrCl2). Three-month-old ovariectomized rats were treated for 90 days with doses of 25 mg kg-1 d-1 and 150 mg kg-1 d-1 of SrR or SrCl2 at low (0.1% Ca) or normal (1.19% Ca) Ca diet. Vertebral bone tissue was analysed by confocal synchrotron-radiation-induced micro X-ray fluorescence and by backscattered electron imaging. Principal component analysis and k-means clustering of the acquired elemental maps of Ca and Sr revealed that the newly formed bone exhibited the highest Sr fractions and that low Ca diet increased the Sr uptake by a factor of three to four. Furthermore, Sr uptake in bone of the SrCl2-treated animals was generally lower compared with SrR. The study clearly shows that inadequate nutritional calcium intake significantly increases uptake of Sr in serum as well as in trabecular bone matrix. This indicates that nutritional calcium intake as well as serum Ca levels are important regulators of any Sr treatment

A three-dimensional view of structural changes caused by deactivation of fluid catalytic cracking catalysts

Since its commercial introduction three-quarters of a century ago, fluid catalytic cracking has been one of the most important conversion processes in the petroleum industry. In this process, porous composites composed of zeolite and clay crack the heavy fractions in crude oil into transportation fuel and petrochemical feedstocks. Yet, over time the catalytic activity of these composite particles decreases. Here, we report on ptychographic tomography, diffraction, and fluorescence tomography, as well as electron microscopy measurements, which elucidate the structural changes that lead to catalyst deactivation. In combination, these measurements reveal zeolite amorphization and distinct structural changes on the particle exterior as the driving forces behind catalyst deactivation. Amorphization of zeolites, in particular, close to the particle exterior, results in a reduction of catalytic capacity. A concretion of the outermost particle layer into a dense amorphous silica–alumina shell further reduces the mass transport to the active sites within the composite

Grazing exit versus grazing incidence geometry for x-ray absorption near edge structure analysis of arsenic traces

In the presented study the grazing exit x-ray fluorescence was tested for its applicability to x-ray absorption near edge structure analysis of arsenic in droplet samples. The experimental results have been compared to the findings of former analyses of the same samples using a grazing incidence GI setup to compare the performance of both geometries. Furthermore, the investigations were accomplished to gain a better understanding of the so called self-absorption effect, which was observed and investigated in previous studies using a GI geometry. It was suggested that a normal incidence-grazing-exit geometry would not suffer from self-absorption effects in x-ray absorption fine structure XAFS analysis due to the minimized path length of the incident beam through the sample. The results proved this assumption and in turn confirmed the occurrence of the self-absorption effect for GI geometry. Due to its lower sensitivity it is difficult to apply the GE geometry to XAFS analysis of trace amounts few nanograms of samples but the technique is well suited for the analysis of small amounts of concentrated sample

Factors infuencing bacterial dynamics along a transect from supraglacial runoff to proglacial lakes of a high Arctic glacieri

Bacterial production in glacial runoff and aquatic habitats along a c. 500m transect from the ablation area of a Svalbard glacier (Midre Lov´enbreen, 791N, 121E) down to a series of proglacial lakes in its forefield were assessed. In addition, a series of in situ experiments were conducted to test how different nutrient sources (glacial flour and dissolved organic matter derived from goose faeces) and temperature affect bacterial abundance and production in these ecosystems. Bacterial abundance and production increased significantly along this transect and reached a maximum in the proglacial lakes. Bacterial diversity profiles as assessed by denaturing gradient gel electrophoresis indicated that communities in glacial runoff were different from those in proglacial lakes. Heterotrophic bacterial production was mainly controlled by temperature and phosphorus limitation. Addition of both glacial flour and dissolved organic matter derived from goose faeces stimulated bacterial production in those lakes. The results suggest that glacial runoff sustains an active bacterial community which is further stimulated in proglacial lakes by higher temperatures and nutrient inputs from bird faeces. Thus, as in maritime temperate and Antarctic settings, bacterial communities developing in the recently deglaciated terrain of Svalbard receive important inputs of nutrients via faunal transfers from adjacent ecosystems

2D and 3D chemical imaging of Li-ion battery electrodes at nanoscale resolution

A new chemical imaging technique, 3D XANES microscopy, combines the high resolution and large field of view (FOV) of full-field transmission X-ray microscopy (TXM) with the chemical speciation capabilities of X-ray absorption near edge structure (XANES) to visualize the sample’s chemistry in 2D and 3D. This technique is a powerful method to examine the relationship between morphology and chemical speciation in complex materials with hierarchical structure such as battery electrodes. 3D XANES TXM offers chemical speciation at the nanoscale in thick samples (up to 30 µm) with minimal preparation requirements. Further, because it is not a scanning technique, its high throughput allows the analysis of large areas in minutes to a few hours. Using the TXM on beam line 6-2 at the Stanford Synchrotron Radiation Lightsource (SSRL), which is capable of imaging from 4.5 to 14 keV with down to 30 nm resolution and up to 30 micron FOV, the 3D XANES microscopic technique has been used to construct chemical maps of various composite systems in 2D and 3D. Concepts of technique and data processing which involves the evaluation of up to 1 Million XANES spectra for a single 2D map will be discussed and results from XANES microscopy of Li-ion battery electrodes and other materials will be presented

Nanostructure and phase imaging of ancient ceramics using full field hard x-ray microscopy

What started as a philosophical concept more than 2400 years ago by introducing átomos, the indivisible, still puzzles scientists because state and order of atoms determine the properties of all materials. It remains a mystery whether the potters in ancient Greece were aware of this concept when they created their famous black and red vessels. But it is obvious that they possessed the knowledge to change macroscopic properties of the material by controlling processes which happen at the nano-scale. In this presentation I will present the application of full field hard x-ray transmission microscopy (TXM) to the analysis of Roman ceramics (Terra Sigilatta). The x-ray microscope on BL 6-2 at the Stanford Synchrotron Radiation Lightsource is capable of imaging in the energy range from 5-14 keV, with up to 30 nm resolution [1]. Recent advances in data collection and evaluation [2] paved the way for single pixel x-ray absorption near edge structure (XANES) spectroscopy, combining the high resolution and large field of view of full-field transmission X-ray microscopy with the chemical information derived from X-ray absorption spectroscopy in order to trace chemical phase transformations in 2D and even 3D [3]. Aim of this study is to gain knowledge about the firing protocols used for production of the ceramics. This is crucial for a better understanding of the manufacturing process of Terra Sigillata and the development of the iron oxide-rich clay material based ceramic technology in the Mediterranean: from the remarkable proto-geometric vases to classical Attica black-gloss figurines and finally to the high-gloss terra sigilatta - all obtained through control of vitrification and redox chemistry. Results from the TXM study and complementary analyses using micro-X-ray fluorescence [4] and time of flight secondary ion mass spectroscopy (TOF-SIMS) support the hypothesis of a three step firing process showing that the potters were able to control/change the nano-porosity of the material in the first two steps, consequently providing control over oxygen diffusion, and therefore the color of the material, in the third step

Iron overload of human colon adenocarcinoma cells studied by synchrotron-based X-ray techniques

Fast- and slow-proliferating human adenocarcinoma colorectal cells, HT-29 and HCA-7, respectively, overloaded with transferrin (Tf), Fe(III) citrate, Fe(III) chloride and Fe(II) sulfate were studied by synchrotron radiation total-reflection X-ray spectrometry (TXRF), TXRF-X-ray absorption near edge structure (TXRF-XANES), and micro-X-ray fluorescence imaging to obtain information on the intracellular storage of overloaded iron (Fe). The determined TfR1 mRNA expression for the investigated cells correlated with their proliferation rate. In all cases, the Fe XANES of cells overloaded with inorganic Fe was found to be similar to that of deliquescent Fe(III) sulfate characterized by a distorted octahedral geometry. A fitting model using a linear combination of the XANES of Tf and deliquescent Fe(III) sulfate allowed to explain the near edge structure recorded for HT-29 cells indicating that cellular overload with inorganic Fe results in a non-ferritin-like fast Fe storage. Hierarchical cluster analysis of XANES spectra recorded for Fe overloaded HT-29 and HCA-7 cells was able to distinguish between Fe treatments performed with different Fe species with a 95 % hit rate, indicating clear differences in the Fe storage system. Micro-X-ray fluorescence imaging of Fe overloaded HT-29 cells revealed that Fe is primarily located in the cytosol of the cells. By characterizing the cellular Fe uptake, Fe/S content ratios were calculated based on the X-ray fluorescence signals of the analytes. These Fe/S ratios were dramatically lower for HCA-7 treated with organic Fe(III) treatments suggesting dissimilarities from the Tf-like Fe uptake