ARCHAEOMETRY, Issue 2 2005
S. FRISIA
Solar variability and volcanic activity strongly interact with climate and the environment. Synchrotron radiation X-ray microfluorescence (micro-XRF) to an annually laminated Alpine stalagmite confirmed that annual laminae result from hydrological variability and changes in the duration of soil microbial degradation. The latter is modulated by solar variability. At the centennial timescale, growth rate and solar activity appear to be correlated with temperature change, with low temperatures at solar minima. By combining micro-XRF and absorption spectroscopy techniques (XANES), we also found that speleothems are a new archive of aerosol sulphate related to volcanic activity. Peaks in S-concentration from c. 5.2 to 5.0 ka bp in an Alpine stalagmite suggest that multiple volcanic sulphate aerosol emissions enhanced Mid-Holocene summer cooling, thus favouring the preservation of the Alpine Iceman mummy in a persistent ice casket. [source]

An X-ray Spectromicroscopy Study of Albumin Adsorption to Crosslinked Polyethylene Oxide Films,

ADVANCED ENGINEERING MATERIALS, Issue 5 2010
Bonnie O. Leung
Abstract Synchrotron-based X-ray photoemission electron microscopy (X-PEEM) is used to characterize the near surface composition of polyethylene oxide (PEO) combined with 1.5, 5, and 10,wt.-% pentaerythritol triacrylate (PETA) crosslinker. It is found that as the concentration of PETA increases, it becomes the dominant component in the top 10,nm of the film surface. The same surfaces are also exposed to human serum albumin (HSA) and the distributions of the protein relative to PEO and PETA measured with X-PEEM. A positive correlation is found between levels of PETA and HSA at the surface. Above PETA concentrations of 5,wt.-%, HSA adsorption is significant, which suggests high levels of PETA (often used to immobilize PEO by crosslinking) can significantly reduce the non-fouling properties of PEO. [source]

Synchrotron-Based Micro-CT and Refraction-Enhanced Micro-CT for Non-Destructive Materials Characterisation,

ADVANCED ENGINEERING MATERIALS, Issue 6 2009
Bernd R. Müller
Abstract X-ray computed tomography is an important tool for non-destructively evaluating the 3-D microstructure of modern materials. To resolve material structures in the micrometer range and below, high brilliance synchrotron radiation has to be used. The Federal Institute for Materials Research and Testing (BAM) has built up an imaging setup for micro-tomography and -radiography (BAMline) at the Berliner storage ring for synchrotron radiation (BESSY). In computed tomography, the contrast at interfaces within heterogeneous materials can be strongly amplified by effects related to X-ray refraction. Such effects are especially useful for materials of low absorption or mixed phases showing similar X-ray absorption properties that produce low contrast. The technique is based on ultra-small-angle scattering by microstructural elements causing phase-related effects, such as refraction and total reflection. The extraordinary contrast of inner surfaces is far beyond absorption effects. Crack orientation and fibre/matrix debonding in plastics, polymers, ceramics and metal-matrix-composites after cyclic loading and hydro-thermal aging can be visualized. In most cases, the investigated inner surface and interface structures correlate to mechanical properties. The technique is an alternative to other attempts on raising the spatial resolution of CT machines. [source]

Design of A Soft X-ray Source with Periodic Microstructure Using Resonance Transition Radiation for Tabletop Synchrotron

IEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 3 2008
Koji Sugano Member
Abstract A soft X-ray source with a periodic aluminum multilayer structure with vacuum layers in between for tabletop synchrotrons with low-energy electrons was designed, and the dependence of radiation performance on structural parameters was clarified using a theoretical calculation of the resonance transition radiation. A photon density of 1 keV pr incident electron was calculated by optimizing the thickness of the aluminum and vacuum layers. Furthermore, the designed structure was fabricated by a microfabrication technique. The effects of dimensional error on the photon density are discussed on the basis of the calculated results and the prototype structure of a 6-MeV synchrotron. It is clarified that dimensional errors of 1.5% in Al layers and of plus or minus a few dozen nanometers in the vacuum layers are negligible in obtaining a photon density of more than 90% of the maximum value. © 2008 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source]

Phosphorus L2,3 -edge XANES: overview of reference compounds

JOURNAL OF SYNCHROTRON RADIATION, Issue 2 2009
Jens Kruse
Synchrotron-based X-ray absorption near-edge structure (XANES) spectroscopy is becoming an increasingly used tool for the element speciation in complex samples. For phosphorus (P) almost all XANES measurements have been carried out at the K -edge. The small number of distinctive features at the P K -edge makes in some cases the identification of different P forms difficult or impossible. As indicated by a few previous studies, the P L2,3 -edge spectra were richer in spectral features than those of the P K -edge. However, experimentally consistent spectra of a wide range of reference compounds have not been published so far. In this study a library of spectral features is presented for a number of mineral P, organic P and P-bearing minerals for fingerprinting identification. Furthermore, the effect of radiation damage is shown for three compounds and measures are proposed to reduce it. The spectra library provided lays a basis for the identification of individual P forms in samples of unknown composition for a variety of scientific areas. [source]

X-ray emission spectroscopy with a laser-heated diamond anvil cell: a new experimental probe of the spin state of iron in the Earth's interior

JOURNAL OF SYNCHROTRON RADIATION, Issue 5 2005
Jung-Fu Lin
Synchrotron-based X-ray emission spectroscopy (XES) is well suited to probing the local electronic structure of 3d transition metals such as Fe and Mn in their host phases. The laser-heated diamond anvil cell technique is uniquely capable of generating ultra-high static pressures and temperatures in excess of 100,GPa and 3000,K. Here X-ray emission spectroscopy and X-ray diffraction have been interfaced with the laser-heated diamond cell for studying the electronic spin states of iron in magnesiowüstite-(Mg0.75,Fe0.25)O and its crystal structure under lower-mantle conditions. X-ray emission spectra of the ferrous iron in a single crystal of magnesiowüstite-(Mg0.75,Fe0.25)O indicate that a high-spin to low-spin transition of ferrous iron occurs at 54 to 67,GPa and 300,K and the ferrous iron remains in the high-spin state up to 47,GPa and 1300,K. This pilot study points to the unique capability of the synchrotron-based XES and X-ray diffraction techniques for addressing the issue of electronic spin transition or crossover in 3d transition metals and compounds under extreme high- P,T conditions. [source]

The Structure of Yttrialite and Its Identification Using Laboratory and Synchrotron-Based Powder X-Ray Diffraction

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2009
William J. Heward
A highly crystalline sample of the impurity stabilized phase y -Y2Si2O7, generally known as yttrialite, has been formed from the melt of a glass with a nominal composition of 62(SiO2),10(Al2O3),28(Y2O3) mol%. Powder X-ray diffraction patterns were collected using in-house instrumentation and the 11-BM diffractometer at the Advanced Photon Source, Argonne National Laboratory, Argonne, IL. Rietveld refinements were carried out on the patterns using two structural models. On patterns collected using in-house instrumentation the correct structure assignment was difficult to determine; however, the extremely high-quality data afforded by the 11-BM instrument showed conclusively that the sample was found to crystallize in the monoclinic system (SG=P21/m) with lattice parameters a=5.03032(6), b=8.06892(6), c=7.33620(6) Å, and ,=108.673(1). Furthermore, simulations have shown that it is likely that this structure model can be used to describe natural yttrialite or yttrialite that is formed at low temperatures, though the possibility that such materials are paracrystalline is also discussed. [source]

Deformation Behavior of PET, PBT and PBT-Based Thermoplastic Elastomers as Revealed by SAXS from Synchrotron

MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 7 2003
Norbert Stribeck
Abstract The present paper discloses the changes in the nanostructure as revealed by small-angle X-ray scattering (SAXS) of synchrotron radiation of anisotropic semi-crystalline samples of polyester and poly(ether ester) type differing in their chemical composition, while subjected to controlled progressive elongation. From the group of polyesters poly(ethylene terephthalate) (PET), and poly(butylene terephthalate) (PBT) were selected. Two PBT-based commercial poly(ether ester)s were also studied differing in the molecular weight of their soft segments (poly(tetramethylene glycol), PTMG) being 1000 and 2000, respectively. A blend of PBT and EM550 (40/60 by wt.) was also characterized. All materials underwent the same sample preparation process resulting in highly oriented "bristles" of 1 mm diameter. It was found that ,b, the elongation at break, strongly depends on the flexibility of the glycol residues of the materials studied , ranging from ,b,=,8% for PET that contains ethylene glycol residues, through ,b,=,18% for PBT including the more flexible tetramethylene glycol (TMG) up to ,b,=,510% for the PEE containing the longest PTMG moieties. During straining the relationship between the external elongation , and the changes in the long spacing L was determined. After relaxation from each deformation step the relationship between the tensile set ,r and the long period L was also followed and discussed. Such analysis led to a model describing the nanostructure evolution during the deformation-relaxation cycle that finally was verified and refined utilizing the multidimensional chord distribution function computed from the anisotropic SAXS patterns. 2D SAXS patterns (pseudo color) of bristles of PET (PBT), respectively, cold drawn, ,,=,3.5 (,,=,2.3) and annealed with fixed ends for 6 h at 240,°C (180,°C), recorded at room temperature at a forced tensile deformation , or tensile set (residual elongation) ,r in percent. [source]

X-ray excited optical luminescence from crystalline silicon

PHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 9 2009
Paul Gundel
Abstract Synchrotron based X-ray excited optical luminescence (XEOL) has been measured with many direct bandgap semiconductors. We present XEOL measurements on crystalline silicon (Si), obtained despite of its indirect bandgap and the consequently low luminescence efficiency. Spectra of monocrystalline and multicrystalline (mc) Si at room temperature are compared to theoretical spectra. A possible application in the synchrotron-based research on mc-Si is exemplified by combining XEOL, X-ray fluorescence (XRF) spectroscopy, photoluminescence (PL) spectroscopy, and microscope images of grain boundaries. This approach can be utilized to investigate the recombination activity of metal precipitates, to analyze areas of different lifetimes on mc-Si samples and to correlate additional material parameters to XRF measurements. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Innentitelbild: Label-Free Chemical Imaging of Catalytic Solids by Coherent Anti-Stokes Raman Scattering and Synchrotron-Based Infrared Microscopy (Angew. Chem.

ANGEWANDTE CHEMIE, Issue 47 2009
47/2009)
Die katalytische Umsetzung von Thiophenderivaten an Zeolithkristallen wurde mit einer Kombination aus multipler kohärenter Anti-Stokes-Raman-Streuung (CARS) und Synchrotron-basierter IR-Mikroskopie untersucht. In der Zuschrift auf S.,9152,ff. zeigen B.,M. Weckhuysen et,al., dass räumlich hoch aufgelöste chemische Informationen über Reaktanten und Produkte auch ohne Markierung zugänglich sind. Die Schwingungsbanden der CARS- und IR-Spektren belegen Wechselwirkungen zwischen Thiophen und Zeolithgerüst mit anschließender Ringöffnung. [source]

Label-Free Chemical Imaging of Catalytic Solids by Coherent Anti-Stokes Raman Scattering and Synchrotron-Based Infrared Microscopy,

ANGEWANDTE CHEMIE, Issue 47 2009
Marianne
Innenaufnahme: Die Kombination aus den beiden im Titel genannten Verfahren während der katalytischen Umsetzung von Thiophenderivaten an Zeolithkristallen ergibt räumlich und zeitlich aufgelöste chemische Informationen auch ohne Markierungen (siehe Bild). Das reagierende Thiophen befindet sich hauptsächlich im Kristallinneren, während das Produkt in den geraden Poren des Zeoliths gefunden wird. [source]

A New Fluorite Type Compound Pb5Bi17X5O43: Synchrotron and Neutron Structure Determination (X: P) and Conduction Properties (X: P, V and As).

CHEMINFORM, Issue 3 2003
Pascal Roussel
Abstract For Abstract see ChemInform Abstract in Full Text. [source]

Intense heavy ion beams as a tool to induce high-energy-density states in matter

CONTRIBUTIONS TO PLASMA PHYSICS, Issue 5-6 2003
N.A. Tahir
Abstract Because of the volume character of energy deposition of energetic ions in matter, an intense heavy ion beam is a very suitable laboratory tool to create large samples of high-energy-density matter. This paper shows with the help of two-dimensional numerical simulations how such an intense heavy ion beam can be employed to achieve this goal. The beam parameters considered in this study are those of the beams that are delivered by the existing heavy ion synchrotron, SIS18 and that which will be available at the future facility SIS100, respectively at the Gesellschaft für Schwerionenforschung (GSI), Darmstadt. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Low temperature powder diffraction and DFT solid state computational study of hydrogen bonding in NH4VO3

CRYSTAL RESEARCH AND TECHNOLOGY, Issue 9 2009
. Smr
Abstract The crystal structure of NH4VO3 was refined by the geometry optimization done by total energy minimization in solid state using DFT/plane waves approach. The lattice parameters were derived by the Le Bail technique from the low temperature X-ray (40-293 K) and synchrotron (100-293 K) powder diffraction data. The structure is formed by the infinite chains of irregular VO4 tetrahedra running approximately parallel to the c -axis, which are interlinked by the ammonium ions placed between them. The ammonium ions link to the [VO4], chains through one linear, one bifurcated and two trifurcated N-H,O hydrogen bonds. Considering their stability there are six distinct N-H,O hydrogen bonds: two strong with the N-H,O bond angles close to the straight, two medium with the bond angles of 123° and 148° and two very bent (105° and 107°) and hence weak hydrogen bonds. There is a reasonable agreement between the energies of the stretching ,(NH) modes estimated using the optimised N,O contact distances and those obtained experimentally. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Application of Synchrotron Radiation Techniques for Model Validation of Advanced Structural Materials,

ADVANCED ENGINEERING MATERIALS, Issue 6 2009
Annick Froideval
Abstract Synchrotron radiation techniques represent powerful tools to characterize materials down to the nanometer level. This paper presents a survey of the state-of-the-art synchrotron-based techniques which are particularly well-suited for investigating materials properties. Complementary X-ray absorption techniques such as extended X-ray absorption fine structure (EXAFS), X-ray magnetic circular dichroism (XMCD), photoemission electron microscopy (PEEM) are used to address the individual local atomic structure and magnetic moments in Fe,Cr model systems. The formation of atomic clusters/precipitates in such systems is also investigated by means of scanning transmission X-ray microscopy (STXM). Such advanced analytical techniques can not only offer valuable structural and magnetic information on such systems, they can also serve for validating computational calculations performed at different time and length scales which can help improve materials lifetime predictions. [source]

Interface Reactions in Ultrathin Functional Dielectric Films,

ADVANCED ENGINEERING MATERIALS, Issue 4 2009
Dieter Schmeißer
The functional properties of shrunken materials should not be influenced by the reduction of the dimensions. Here, an important consideration is the control of interfacial reactions. We report on synchrotron-based spectroscopic analysis of interfaces of ultrathin functional materials (thickness <10 nm). Examples of high- k oxides, as well as of a ferroelectric polymer, are shown. We demonstrate that our spectroscopic findings are also reflected in the electric properties of thin-film devices. [source]

Orientational Switching of Mesogens and Microdomains in Hydrogen-Bonded Side-Chain Liquid-Crystalline Block Copolymers Using AC Electric Fields ,

ADVANCED FUNCTIONAL MATERIALS, Issue 4 2004
C.-Y. Chao
Abstract In this report, we show that the microstructures of hydrogen-bonded side-chain liquid-crystalline block copolymers can be rapidly aligned in an alternating current (AC) electric field at temperatures below the order,disorder transition but above the glass transition. The structures and their orientation were measured in real time with synchrotron X-ray scattering. Incorporation of mesogenic groups with marked dipolar properties is a key element in this process. A mechanism related to the dissociation of hydrogen bonds is proposed to account for the fast orientation switching of the hydrogen-bonded blends. [source]

Design of A Soft X-ray Source with Periodic Microstructure Using Resonance Transition Radiation for Tabletop Synchrotron

On the precision and accuracy of structural analysis of light-induced metastable states

JOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 6 2007
Vincent Legrand
Bragg diffraction data were collected on single crystals of the spin-crossover complex [Fe(phen)2(NCS)2] in its low-spin and light-induced metastable high-spin states. Experimental variables included the temperature (32 and 15,K), the X-ray source (sealed tube and synchrotron), and the time interval between laser light excitation of the sample (, = 647,nm). From a comparison of the structural parameters refined, it is shown that photo-crystallographic measurements suffer significantly and systematically from bias if the probed sample contains residual ground-state species, resulting from an incomplete photo-conversion or a significant metastable- to ground-state relaxation. It follows that a 4% population of species in a different spin state affects the Fe,N bond lengths by more than three standard deviations, and the FeN6 polyhedron volume by as much as seven standard deviations, while the mean atomic position misfit exceeds 0.005,Å. [source]

Application of white-beam X-ray microdiffraction for the study of mineralogical phase identification in ancient Egyptian pigments

JOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 6 2007
P. A. Lynch
High-brightness synchrotron X-rays together with precision achromatic focusing optics on beamline 7.3.3 at the Advanced Light Source have been applied for Laue microdiffraction analysis of mineralogical phases in Egyptian pigments. Although this task is usually performed using monochromatic X-ray diffraction, the Laue technique was both faster and more reliable for the present sample. In this approach, white-beam diffraction patterns are collected as the sample is raster scanned across the incident beam (0.8,µm × 0.8,µm). The complex Laue diffraction patterns arising from illumination of multiple grains are indexed using the white-beam crystallographic software package XMAS, enabling a mineralogical map as a function of sample position. This methodology has been applied to determine the mineralogy of colour pigments taken from the ancient Egyptian coffin of Tjeseb, a priestess of the Apis bull dating from the Third Intermediate to Late period, 25th Dynasty to early 26th Dynasty (747 to 600 BC). For all pigments, a ground layer of calcite and quartz was identified. For the blue pigment, cuprorivaite (CuCaSi4O10) was found to be the primary colouring agent with a grain size ranging from ,10 to 50,µm. In the green and yellow samples, malachite [Cu2(OH)2CO3] and goethite [FeO(OH)] were identified, respectively. Grain sizes from these pigments were significantly smaller. It was possible to index some malachite grains up to ,20,µm in size, while the majority of goethite grains displayed a nanocrystalline particle size. The inability to obtain a complete mineralogical map for goethite highlights the fact that the incident probe size is considerably larger than the grain size. This limit will continue to improve as the present trend is toward focusing optics approaching the diffraction limit (,1000× smaller beam area). [source]

Fracture of poly(vinylidene fluoride): a combined synchrotron and laboratory in-situ X-ray scattering study

JOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 2007
Günther A. Maier
Semi-crystalline polymers show a complex fracture mechanism, which is controlled by the micro-mechanisms associated with formation and breakdown of a plastic deformation region. Such regions develop at notches, cracks or other stress-raising defects. In the present paper, we use time-resolved synchrotron X-ray scattering techniques during the deformation process in poly(vinylidene fluoride) to study the plastic zone formation and fracture processes at different strain rates. This gives new insight into the micro-mechanisms of cavitation, lamellae separation and fibril formation in this particular material. [source]

Outcomes of the International Union of Crystallography Commission on Powder Diffraction Round Robin on Quantitative Phase Analysis: samples 1a to 1h

JOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 4 2001
Ian C. Madsen
The International Union of Crystallography (IUCr) Commission on Powder Diffraction (CPD) has sponsored a round robin on the determination of quantitative phase abundance from diffraction data. Specifically, the aims of the round robin were (i) to document the methods and strategies commonly employed in quantitative phase analysis (QPA), especially those involving powder diffraction, (ii) to assess levels of accuracy, precision and lower limits of detection, (iii) to identify specific problem areas and develop practical solutions, (iv) to formulate recommended procedures for QPA using diffraction data, and (v) to create a standard set of samples for future reference. Some of the analytical issues which have been addressed include (a) the type of analysis (integrated intensities or full-profile, Rietveld or full-profile, database of observed patterns) and (b) the type of instrument used, including geometry and radiation (X-ray, neutron or synchrotron). While the samples used in the round robin covered a wide range of analytical complexity, this paper reports the results for only the sample 1 mixtures. Sample 1 is a simple three-phase system prepared with eight different compositions covering a wide range of abundance for each phase. The component phases were chosen to minimize sample-related problems, such as the degree of crystallinity, preferred orientation and microabsorption. However, these were still issues that needed to be addressed by the analysts. The results returned indicate a great deal of variation in the ability of the participating laboratories to perform QPA of this simple three-component system. These differences result from such problems as (i) use of unsuitable reference intensity ratios, (ii) errors in whole-pattern refinement software operation and in interpretation of results, (iii) operator errors in the use of the Rietveld method, often arising from a lack of crystallographic understanding, and (iv) application of excessive microabsorption correction. Another major area for concern is the calculation of errors in phase abundance determination, with wide variations in reported values between participants. Few details of methodology used to derive these errors were supplied and many participants provided no measure of error at all. [source]

Repair of rabbit segmental defects with the thrombin peptide, TP508

JOURNAL OF ORTHOPAEDIC RESEARCH, Issue 5 2004
Michael R. Sheller
Abstract The synthetic peptide, TP508 (Chrysalin®), was delivered to rabbit segmental bone defects in biodegradable controlled-release PLGA microspheres to determine its potential efficacy for enhancing healing of non-critically and critically sized segmental defects. Non-critically sized radial defects were created in the forelimbs of New Zealand White rabbits, which were randomized into three treatment groups receiving 10, 50 and 100 ,g doses of TP508 in the right radius and control microspheres (without TP508) in the left radius. Torsional testing of the radii at six weeks showed a significant increase in ultimate torque, failure torque, ultimate energy, failure energy, and stiffness when treated with TP508 compared to controls (p < 0.01 for all measures). Thus, TP508 appeared to enhance or accelerate bone growth in these defects. In a second set of experiments, critically sized ulnar defects were created in the forelimbs of New Zealand White rabbits, which were randomized into two groups with each rabbit receiving microspheres with 100 or 200 ,g of TP508 into the right ulnar defect and control microspheres (without TP508) alone into the left ulnar defect. Bone healing was evaluated with plain radiographs, synchrotron-based microtomography, and mechanical testing. Radiographs of the rabbit limbs scored by three blinded, independent reviewers demonstrated a significantly higher degree of healing when treated with TP508 than their untreated control limbs (p < 0.05). Three-dimensional synchrotron tomography of a limited number of samples showed that the new bone in TP508-treated samples had a less porous surface appearance and open marrow spaces, suggesting progression of bone remodeling. Torsional testing of the ulnae at nine weeks showed a significant increase in maximum torque and failure energy when treated with TP508 compared to controls (p < 0.01 for both measures). These results suggest that TP508 in a controlled release delivery vehicle has the potential to enhance healing of segmental defects in both critically and non-critically sized defects. © 2004 Orthopaedic Research Society. Published by Elsevier Ltd. All rights reserved. [source]

A novel epitaxially grown LSO-based thin-film scintillator for micro-imaging using hard synchrotron radiation

JOURNAL OF SYNCHROTRON RADIATION, Issue 5 2010
Paul-Antoine Douissard
The efficiency of high-resolution pixel detectors for hard X-rays is nowadays one of the major criteria which drives the feasibility of imaging experiments and in general the performance of an experimental station for synchrotron-based microtomography and radiography. Here the luminescent screen used for the indirect detection is focused on in order to increase the detective quantum efficiency: a novel scintillator based on doped Lu2SiO5 (LSO), epitaxially grown as thin film via the liquid phase epitaxy technique. It is shown that, by using adapted growth and doping parameters as well as a dedicated substrate, the scintillation behaviour of a LSO-based thin crystal together with the high stopping power of the material allows for high-performance indirect X-ray detection. In detail, the conversion efficiency, the radioluminescence spectra, the optical absorption spectra under UV/visible-light and the afterglow are investigated. A set-up to study the effect of the thin-film scintillator's temperature on its conversion efficiency is described as well. It delivers knowledge which is important when working with higher photon flux densities and the corresponding high heat load on the material. Additionally, X-ray imaging systems based on different diffraction-limited visible-light optics and CCD cameras using among others LSO-based thin film are compared. Finally, the performance of the LSO thin film is illustrated by imaging a honey bee leg, demonstrating the value of efficient high-resolution computed tomography for life sciences. [source]

Improved tomographic reconstructions using adaptive time-dependent intensity normalization

JOURNAL OF SYNCHROTRON RADIATION, Issue 5 2010
Valeriy Titarenko
The first processing step in synchrotron-based micro-tomography is the normalization of the projection images against the background, also referred to as a white field. Owing to time-dependent variations in illumination and defects in detection sensitivity, the white field is different from the projection background. In this case standard normalization methods introduce ring and wave artefacts into the resulting three-dimensional reconstruction. In this paper the authors propose a new adaptive technique accounting for these variations and allowing one to obtain cleaner normalized data and to suppress ring and wave artefacts. The background is modelled by the product of two time-dependent terms representing the illumination and detection stages. These terms are written as unknown functions, one scaled and shifted along a fixed direction (describing the illumination term) and one translated by an unknown two-dimensional vector (describing the detection term). The proposed method is applied to two sets (a stem Salix variegata and a zebrafish Danio rerio) acquired at the parallel beam of the micro-tomography station 2-BM at the Advanced Photon Source showing significant reductions in both ring and wave artefacts. In principle the method could be used to correct for time-dependent phenomena that affect other tomographic imaging geometries such as cone beam laboratory X-ray computed tomography. [source]

Humic acid metal cation interaction studied by spectromicroscopy techniques in combination with quantum chemical calculations

JOURNAL OF SYNCHROTRON RADIATION, Issue 2 2010
M. Plaschke
Humic acids (HA) have a high binding capacity towards traces of toxic metal cations, thus affecting their transport in aquatic systems. Eu(III),HA aggregates are studied by synchrotron-based scanning transmission X-ray microscopy (STXM) at the carbon K -edge and laser scanning luminescence microscopy (LSLM) at the 5D0,7F1,2 fluorescence emission lines. Both methods provide the necessary spatial resolution in the sub-micrometre range to resolve characteristic aggregate morphologies: optically dense zones embedded in a matrix of less dense material in STXM images correspond to areas with increased Eu(III) luminescence yield in the LSLM micrographs. In the C 1s -NEXAFS of metal-loaded polyacrylic acid (PAA), used as a HA model compound, a distinct complexation effect is identified. This effect is similar to trends observed in the dense fraction of HA/metal cation aggregates. The strongest complexation effect is observed for the Zr(IV),HA/PAA system. This effect is confirmed by quantum chemical calculations performed at the ab initio level for model complexes with different metal centres and complex geometries. Without the high spatial resolution of STXM and LSLM and without the combination of molecular modelling with experimental results, the different zones indicating a `pseudo'-phase separation into strong complexing domains and weaker complexing domains of HA would never have been identified. This type of strategy can be used to study metal interaction with other organic material. [source]

Characterization of germanium linear kinoform lenses at Diamond Light Source

JOURNAL OF SYNCHROTRON RADIATION, Issue 3 2009
L. Alianelli
The unprecedented brilliance achieved by third-generation synchrotron sources and the availability of improved optics have opened up new opportunities for the study of materials at the micrometre and nanometre scale. Focusing the synchrotron radiation to smaller and smaller beams is having a huge impact on a wide research area at synchrotrons. The key to the exploitation of the improved sources is the development of novel optics that deliver narrow beams without loss of brilliance and coherence. Several types of synchrotron focusing optics are successfully fabricated using advanced miniaturization techniques. Kinoform refractive lenses are being developed for hard X-ray beamlines, and the first test results at Diamond are discussed in this paper. [source]

Spatial resolution limits for synchrotron-based spectromicroscopy in the mid- and near-infrared

JOURNAL OF SYNCHROTRON RADIATION, Issue 4 2008
Erika Levenson
Spatial resolution tests were performed on beamline 1.4.4 at the Advanced Light Source in Berkeley, CA, USA, a third-generation synchrotron light source. This beamline couples the high-brightness synchrotron source to a Thermo-Electron Continuµm XL infrared microscope. Two types of resolution tests were performed in both the mid-IR and near-IR. The results are compared with a diffraction-limited spot size theory. At shorter near-IR wavelengths the experimental results begin to deviate from diffraction-limited so a combined diffraction-limit and electron-beam-source-size model is employed. This description shows how the physical electron beam size of the synchrotron source begins to dominate the focused spot size at higher energies. The transition from diffraction-limited to electron-beam-size-limited performance is a function of storage-ring parameters and the optical demagnification within the beamline and microscope optics. The discussion includes how different facilities, beamlines and microscopes will affect the achievable spatial resolution. As synchrotron light sources and other next-generation accelerators such as energy-recovery LINACs and free-electron lasers achieve smaller beam emittances, beta-functions and/or energy spreads, diffraction-limited performance can continue to higher-energy beams, perhaps ultimately into the extreme ultraviolet. [source]

A high-throughput determination of metal concentrations in whole intact Arabidopsis thaliana seeds using synchrotron-based X-ray fluorescence spectroscopy

JOURNAL OF SYNCHROTRON RADIATION, Issue 4 2006
Lester W. Young
The identification of genes involved in metal metabolism in plants requires the `screening' of thousands of genetic variants. While inductively coupled plasma mass-spectroscopy has been used to identify variants with an altered total metal concentration, a more convenient high-throughput technique capable of examining individual seeds (or other tissues) would be useful. Here, the high brightness of synchrotron radiation has been utilised to examine relative metal concentrations in seeds of the genetically well characterised plant Arabidopsis thaliana. The relative concentrations of Mn, Fe, Ni, Cu and Zn in individual seeds were determined using a 500,µm × 500,µm beam. Metal concentrations were normally distributed, except where metal-containing dust contaminated the samples. Neither seed orientation nor genetic background (from three `wild type' variants with different genetic lineages) had a significant affect on the Zn-normalised metal concentration. No advantages, such as the observation of tissue-specific metal accumulation, were obtained by using a 50,µm × 50,µm beam. A high-throughput proof-of-concept experiment was demonstrated that could be used to screen libraries of genetic variants for individuals with altered metal concentrations. Further work is required to standardise the technique before screening of libraries is possible. [source]