Nanoscale trace metal imprinting of biocalcification of planktic foraminifers by Toba's super-eruption.

Bioactive metal releases in ocean surface water, such as those by ash falls during volcanic super-eruptions, might have a potentially toxic impact on biocalcifier planktic microorganisms. Nano-XRF imaging with the cutting-edge synchrotron hard X-ray nano-analysis ID16B beamline (ESRF) revealed for the first time a specific Zn- and Mn-rich banding pattern in the test walls of Globorotalia menardii planktic foraminifers extracted from the Young Toba Tuff layer, and thus contemporaneous with Toba's super-eruption, 74,000 years ago. The intra-test correlation of Zn and Mn patterns at the nanoscale with the layered calcareous microarchitecture, indicates that the incorporation of these metals is syngenetic to the wall growth. The preferential Mn and Zn sequestration within the incipient stages of chamber formation suggests a selective incorporation mechanism providing a resilience strategy to metal pollution in the test building of planktic foraminifers.

Perspectives on heterococcolith geochemical proxies based on high-resolution X-ray fluorescence mapping.

Heterococcoliths are micron-scale calcite platelets produced by coccolithophores. They have been the most abundant and continuous fossil record over the last 215 million years (Myr), offering great potential for geochemical studies, although the heterococcolith fossil record remains underutilised in this domain. We have mapped heterococcoliths' composition using X-ray fluorescence (XRF) with a 100-nm resolution beam to decipher element distributions in heterococcoliths and to investigate the potential development of geochemical proxies for palaeoceanography. The study presents two Middle Jurassic Watznaueria britannica heterococcoliths from Cabo Mondego, Portugal. XRF analysis was performed with a 17 keV incident energy beam at the European Synchrotron Radiation Facility ID22NI beamline to study elements from Sr down to S. Ca, Sr and Mn are distributed following the heterococcolith crystalline arrangement. Cl, Br and S display an homogeneous distribution, whereas K, Fe, Cu, Zn and Rb are concentrated at the edges and in the central area of the heterococcoliths. Distributions of K, Fe, Ti, Fe, Cu, Zn, Rb and to a lesser extent V and Cr are highly influenced by clay contamination and peripheral diagenetic overgrowth. Mn is related to diagenetic Mn-rich CaCO3 overgrowth on top of or between heterococcoliths shields. Cl and Br are likely to be present in heterococcoliths inside interstitial nano-domains. We assume that the cytoplasm [Cl(-) ] and [Br(-) ] are mediated and constant during heterococcolithogenesis. Assuming a linear correlation between cytoplasm [Cl(-) ] and sea water [Cl(-) ], heterococcolith Cl may have potential as a salinity proxy. As S is incorporated into heterococcoliths by sulphated polysaccharides, our study suggests a role for such polysaccharides in heterococcolithogenesis for at least 170 Myr. The low Sr/Ca in the W. britannica specimens studied here may either highlight an unusual cellular physiology of Mesozoic coccolithophores or result from low growth rates in oligotrophic environments.

Hard X-ray nanoprobe investigations of the subtissue metal distributions within Daphnia magna.

The unique potential of nanoscale elemental imaging of major/minor and trace-level elemental distributions within thin biological tissue sections of the ecotoxicological model organism Daphnia magna is demonstrated by synchrotron radiation nano-X-ray fluorescence (nano-XRF). The applied highly specialized sample preparation method, coupled with the high spatial resolution (∼180 nm) and high X-ray photon flux (6 × 10(11) photons/s) available at the European Synchrotron Radiation Facility (ESRF) ID22NI beamline proved to be critical for the high-quality visualization of (trace-)metal distributions on the submicron level within the target structures of interest. These include the branchial sacs on the thoracic appendages (epipodites) of D. magna, which are osmoregulatory regions where ion exchange occurs. For the main element of interest (Zn), detection limits of 0.7 ppm (3 ag) was reached in fast-scanning mode using an acquisition time of 0.3 s/pixel. As demonstrated, synchrotron radiation nano-XRF revealed the elemental distributions of Ca, Fe, and Zn within this osmoregulatory region on the submicron scale, aiding the exploration of possible detoxification mechanisms of Zn within D. magna at the subtissue level.

Biomedical applications of the ESRF synchrotron-based microspectroscopy platform.

Very little is known about the sub-cellular distribution of metal ions in cells. Some metals such as zinc, copper and iron are essential and play an important role in the cell metabolism. Dysfunctions in this delicate housekeeping may be at the origin of major diseases. There is also a prevalent use of metals in a wide range of diagnostic agents and drugs for the diagnosis or treatment of a variety of disorders. This is becoming more and more of a concern in the field of nanomedicine with the increasing development and use of nanoparticles, which are suspected of causing adverse effects on cells and organ tissues. Synchrotron-based X-ray and Fourier-transformed infrared microspectroscopies are developing into well-suited sub-micrometer analytical tools for addressing new problems when studying the role of metals in biology. As a complementary tool to optical and electron microscopes, developments and studies have demonstrated the unique capabilities of multi-keV microscopy: namely, an ultra-low detection limit, large penetration depth, chemical sensitivity and three-dimensional imaging capabilities. More recently, the capabilities have been extended towards sub-100nm lateral resolutions, thus enabling sub-cellular chemical imaging. Possibilities offered by these techniques in the biomedical field are described through examples of applications performed at the ESRF synchrotron-based microspectroscopy platform (ID21 and ID22 beamlines).

X-ray diffraction microtomography (XRD-CT), a novel tool for non-invasive mapping of phase development in cement materials.

A recently developed synchrotron-based imaging technique, X-ray diffraction microtomography (XRD-CT), has been applied here for the first time to a complex system, the hydrating Portland cement paste, in order to monitor the evolution of microstructure and phase formation with a 3D non-invasive imaging approach. The ettringite-XRD-peak-based image reconstructions, combined with transmission microtomography (X-microCT) images, allowed to assess the ubiquitous distribution of this phase, which appears early in the hydration process and showed its preferential concentration in the relatively less compact regions of the paste. The comparison of greyscale histograms for cement pastes after 9 and 58 h from hydration showed an increase of ettringite content with age, in agreement with the quantitative Rietveld analysis of the sum patterns. By renormalizing the greyscale histograms to the relative weight fraction, as obtained from Rietveld refinements, a new technique which allows estimation of phase contents with spatial resolution has been developed. The results achievable by combining XRD-CT, X-microCT and Rietveld appear very promising to provide experimental snapshots of the cement hydration process to be compared with results obtained from computer simulations.

High-resolution angular beam stability monitoring at a nanofocusing beamline.

Two semi-transparent imaging beam-position monitors developed at the ESRF have been installed at the micro-analysis beamline ID22 for monitoring the angular stability of the X-ray beam. This system allows low-frequency (10 Hz) angular beam stability measurements at a submicroradian range. It is demonstrated that the incoming macro-beam angular fluctuations are one of the major sources of focal spot instabilities downstream of the Kirkpatrick-Baez mirrors. It is also shown that scanning the energy by rotating the so-called fixed-exit monochromator induces some unexpected angular beam shifts that are, to a large extent, deterministic.

Two-dimensional hard x-ray beam compression by combined focusing and waveguide optics.

A two-dimensionally confining x-ray channel waveguide structure is combined with a high gain Kirkpatrick-Baez prefocusing mirror system yielding a hard x-ray beam with a cross section of 25 x 47 nm(2) (FWHM). Unlike the previously employed resonant beam coupling scheme, the incoming beam is coupled in from the front side of the waveguide and the waveguided beam is no longer accompanied by spurious reflected or transmitted beams. The field distribution in the waveguide channel has been calculated numerically. The calculated transmission and far-field intensity pattern are in good agreement with the experimental results.

ID22: a multitechnique hard X-ray microprobe beamline at the European Synchrotron Radiation Facility.

The ID22 beamline is dedicated to hard X-ray microanalysis allowing the combination of fluorescence, spectroscopy, diffraction and tomography techniques in a wide energy range from 6 to 70 keV. The recent installation of an in-vacuum undulator, a new sample stage and the adaptation of various focusing optics has contributed to a great improvement in the capabilities of the beamline, which is now accessed by a wide user community issued from medical, earth and environmental science, archaeology and material science. Many applications requiring low detection limits for localization/speciation of trace elements together with structural analysis have been developed at the beamline on the (sub)micrometer scale. The possibility of combining simultaneously different analytical probes offers the opportunity of a thorough study of a given sample or scientific problem. This paper presents a review of the recent developments of the beamline and a detailed description of its capabilities through examples from different fields of applications.

Sagittal focusing of synchrotron radiation diffracted on the walls of a longitudinal hole drilled into a single-crystal monochromator.

A very simple method of sagittal focusing of X-ray synchrotron radiation is presented. A special ray-tracing program which utilizes the diffraction-refraction effect is developed. It is demonstrated both by ray-tracing simulations and by an experiment whereby a reasonably good sagittal concentration of 8 keV synchrotron radiation may be achieved by diffraction on the walls of a cylindrical hole drilled into an Si crystal. The holes were drilled parallel to the (111) planes and their diameter, 1 mm, was chosen so that the focusing distance fits the geometrical arrangement of beamline BM5 at the ESRF. Two such crystals have been used in a dispersive and non-dispersive arrangement. The better result was achieved using the dispersive arrangement. The intensity at the centre of the focus is increased by five times with respect to unfocused radiation. Excellent agreement exists between the ray-tracing simulations and experimental results.

Storage of X-ray photons in a crystal resonator

The temporal structure and high brilliance of the X-ray beams produced by third-generation synchrotrons open up new possibilities in time-dependent diffraction and spectroscopy, where timescales down to the sub-nanosecond regime can now be accessed. These beam properties are such that one can envisage the development of the X-ray equivalent of optical components, such as photon delay lines and resonators, that have proved indispensable in a wide range of experiments--for example, pump-probe and multiple-interaction experiments--and (through shaping the temporal structure and repetition rate of the beams) time-dependent measurements in crystallography, physics, biology and chemistry. Optical resonators, such as those used in lasers, are available at wavelengths from the visible to soft X-rays. Equivalent components for hard X-rays have been discussed for more than thirty years, but have yet to be realized. Here we report the storage of hard X-ray photons (energy 15.817 keV) in a crystal resonator formed by two plates of crystalline silicon. The photons are stored for as many as 14 back-and-forth cycles within the resonator, each cycle separated by one nanosecond.

Electromigration in Al thin films induced by surface acoustic waves: application to imaging.

The propagation of a high amplitude surface acoustic wave in an Al thin film induces a large-scale electromigration phenomenon resulting in a permanent etching of the acoustic field in the film. The etched patterns depend on the time of propagation and on the acoustic characteristics. Preliminary observations of a few grooved structures in Al films have been performed by different techniques. A first explanation of this phenomenon based on dynamical Grinfeld instabilities is proposed. By providing permanent pictures of acoustic fields emitted by transducers, this effect could be used to perform imaging of surface acoustic wave propagation.

High-frequency X-ray beam chopper based on diffraction by surface acoustic waves.

The diffraction of an X-ray beam on an ultrasonic wave propagating at the surface of a crystal gives rise to diffraction satellites whose temporal structure is correlated to that of the ultrasonic wave. By matching the temporal structure of the surface acoustic wave with the filling mode of the storage ring, it is possible to select or reject the incident X-ray pulses. A few examples of the performance of this MHz-range chopper for various filling modes are presented.