The Cabrières Biota (France) provides insights into Ordovician polar ecosystems.

Early Palaeozoic sites with soft-tissue preservation are predominantly found in Cambrian rocks and tend to capture past tropical and temperate ecosystems. In this study, we describe the diversity and preservation of the Cabrières Biota, a newly discovered Early Ordovician Lagerstätte from Montagne Noire, southern France. The Cabrières Biota showcases a diverse polar assemblage of both biomineralized and soft-bodied organisms predominantly preserved in iron oxides. Echinoderms are extremely scarce, while sponges and algae are abundantly represented. Non-biomineralized arthropod fragments are also preserved, along with faunal elements reminiscent of Cambrian Burgess Shale-type ecosystems, such as armoured lobopodians. The taxonomic diversity observed in the Cabrières Biota mixes Early Ordovician Lagerstätten taxa with Cambrian forms. By potentially being the closest Lagerstätte to the South Pole, the Cabrières Biota probably served as a biotic refuge amid the high-water temperatures of the Early Ordovician, and shows comparable ecological structuring to modern polar communities.

Short- and Long-Term Effects of X-ray Synchrotron Radiation on Cotton Paper.

X-ray analytical techniques are increasingly being used to study manuscripts and works of art on paper, whether with laboratory equipment or synchrotron sources. However, it is difficult to anticipate the impact of X-ray photons on paper- and cellulose-based artifacts, particularly due to the large variety of their constituents and degradation levels, and the subsequent material multiscale heterogeneity. In this context, this work aims at developing an analytical approach to study the modifications in paper upon synchrotron radiation (SR) X-ray radiation using analytical techniques, which are fully complementary and highly sensitive, yet not frequently used together. At the molecular scale, cellulose chain scissions and hydroxyl free radicals were measured using chromatographic separation techniques (size-exclusion chromatography-multiangle laser light scattering-differential refractive index (SEC-MALS-DRI) and reversed-phase high-performance liquid chromatography-fluorescence detector-diode array detector (RP-HPLC-FLD-DAD)), while the optical properties of paper were characterized using spectroscopy (UV luminescence and diffuse reflectance). These techniques showed different sensitivities toward the detection of changes. The modifications in the cellulosic material were monitored in real time, within a few days, and up to 2 years following the irradiation to define a lowest observed adverse effect dose (LOAED). As paper is a hygroscopic material, the impact of the humidity in the environment was studied using this approach. Three levels of moisture content in the paper, achieved by conditioning the samples and irradiating them at different relative humidities (RHs), were studied (0, 50, 80% RH). It was shown that very low moisture content accelerated molecular and optical modifications.

Investigation of (micro-)meteoritic materials at the new hard X-ray imaging PUMA beamline for heritage sciences.

At the French synchrotron facility SOLEIL, a new X-ray imaging facility PUMA (Photons Utilisés pour les Matériaux Anciens) has been made available to scientific communities studying materials from cultural heritage. This new instrument aims to achieve 2D and 3D imaging with microscopic resolution, applying different analytical techniques including X-ray fluorescence spectroscopy (XRF), X-ray absorption spectroscopy (XAS), X-ray diffraction and phase-contrast imaging. In order to discover its capabilities a detailed analytical characterization of this beamline as an analytical and imaging tool is deemed necessary. In this work, (confocal) XRF and XAS analyses are demonstrated using the Seymchan pallasite meteorite and an Antarctic unmelted micrometeorite as case studies. The obtained spatial resolution (2 µm × 3 µm) and sensitivity (detection limits <10 p.p.m. for 1 s acquisition at 18 keV) show that PUMA is a competitive state-of-the-art beamline, providing several high-profile and high-in-demand analytical methods while maintaining applicability towards a wide range of heritage-oriented sciences.

Scanning X-ray nanodiffraction: from the experimental approach towards spatially resolved scattering simulations.

: An enhancement on the method of X-ray diffraction simulations for applications using nanofocused hard X-ray beams is presented. We combine finite element method, kinematical scattering calculations, and a spot profile of the X-ray beam to simulate the diffraction of definite parts of semiconductor nanostructures. The spot profile could be acquired experimentally by X-ray ptychography. Simulation results are discussed and compared with corresponding X-ray nanodiffraction experiments on single SiGe dots and dot molecules.

Full optical characterization of coherent x-ray nanobeams by ptychographic imaging.

Scanning coherent diffraction microscopy (ptychography) is an emerging hard x-ray microscopy technique that yields spatial resolutions well below the lateral size of the probing nanobeam. Besides a high resolution image of the object, the complex wave field of the probe can be reconstructed at the position of the object. By verifying the consistency of several independent wave field measurements along the optical axis, we address the question of how well the reconstruction represents the nanobeam. With a single ptychogram the wave field can be properly determined over a large range along the optical axis, also at positions inaccessible otherwise.

A large-volume gas cell for high-energy X-ray reflectivity investigations of interfaces under pressure.

A cell for the investigation of interfaces under pressure is presented. Given the pressure and temperature specifications of the cell, P ≤ 100 bar and 253 K ≤ T ≤ 323 K, respectively, high-energy X-rays are required to penetrate the thick Al(2)O(3) windows. The CH(4)(gas)/H(2)O(liquid) interface has been chosen to test the performance of the new device. The measured dynamic range of the high-energy X-ray reflectivity data exceeds 10(-8), thereby demonstrating the validity of the entire experimental set-up.

Molecular layering of fluorinated ionic liquids at a charged sapphire (0001) surface.

Room-temperature ionic liquids (RTILs) are promising candidates for a broad range of "green" applications, for which their interaction with solid surfaces plays a crucial role. In this high-energy x-ray reflectivity study, the temperature-dependent structures of three ionic liquids with the tris(pentafluoroethyl)trifluorophosphate anion in contact with a charged sapphire substrate were investigated with submolecular resolution. All three RTILs show strong interfacial layering, starting with a cation layer at the substrate and decaying exponentially into the bulk liquid. The observed decay length and layering period point to an interfacial ordering mechanism, akin to the charge inversion effect, which is suggested to originate from strong correlations between the unscreened ions. The observed layering is expected to be a generic feature of RTILs at charged interfaces.

Water and ice in contact with octadecyl-trichlorosilane functionalized surfaces: a high resolution x-ray reflectivity study.

We present a high energy x-ray reflectivity study of the density profiles of water and ice at hydrophobic and hydrophilic substrates. At the hydrophobic water/octadecyl-trichlorosilane (water-OTS) interface, we find clear evidence for a thin density depletion layer with an integrated density deficit corresponding to approximately 40% of a monolayer of water molecules. We discuss the experimental results in terms of a simple model of hydrophobic/hydrophilic solid-liquid interfaces. Our results also exclude the presence of nanobubbles. A detailed study of possible radiation damage induced by the intense x-ray beam at the dry OTS surface and at the ice-OTS, as well as at water-OTS interfaces, discloses that noticeable damage is only induced at the water-OTS interface, and thus points to the dominant role of highly mobile radicals formed in bulk water close to the interface.

High-resolution in situ x-ray study of the hydrophobic gap at the water-octadecyl-trichlorosilane interface.

The knowledge of the microscopic structure of water at interfaces is essential for the understanding of interfacial phenomena in numerous natural and technological environments. To study deeply buried liquid water-solid interfaces, high-energy x-ray reflectivity measurements have been performed. Silicon wafers, functionalized by a self-assembled monolayer of octadecyl-trichlorosilane, provide strongly hydrophobic substrates. We show interfacial density profiles with angstrom resolution near the solid-liquid interface of water in contact with an octadecyl-trichlorosilane layer. The experimental data provide clear evidence for the existence of a hydrophobic gap on the molecular scale with an integrated density deficit rhod = 1.1 A g cm(-3) at the solid-water interface. In addition, measurements on the influence of gases (Ar, Xe, Kr, N(2), O(2), CO, and CO(2)) and HCl, dissolved in the water, have been performed. No effect on the hydrophobic water gap was found.