Determination of the packing fraction in photonic glass using synchrotron radiation nanotomography

Photonic glass is a material class that can be used as photonic broadband reflectors, for example in the infrared regime as thermal barrier coating films. Photonic properties such as the reflectivity depend on the ordering and material packing fraction over the complete film thickness of up to 100 μm. Nanotomography allows acquiring these key parameters throughout the sample volume at the required resolution in a non-destructive way. By performing a nanotomography measurement at the PETRA III beamline P05 on a photonic glass film, the packing fraction throughout the complete sample thickness was analyzed. The results showed a packing fraction significantly smaller than the expected random close packing giving important information for improving the fabrication and processing methods of photonic glass material in the future

Dataset of ptychographic X-ray computed tomography of inverse opal photonic crystals produced by atomic layer deposition

This data article describes the detailed parameters for synthesizing mullite inverse opal photonic crystals via Atomic Layer Deposition (ALD), as well as the detailed image analysis routine used to interpret the data obtained by the measurement of such photonic crystals, before and after the heat treatment, via Ptychographic X-ray Computed Tomography (PXCT). The data presented in this article are related to the research article by Furlan and co-authors entitled "Photonic materials for high-temperature applications: Synthesis and characterization by X-ray ptychographic tomography" (Furlan et al., 2018). The data include detailed information about the ALD super-cycle process to generate the ternary oxides inside a photonic crystal template, the raw data from supporting characterization techniques, as well as the full dataset obtained from PXCT. All the data herein described is publicly available in a Mendeley Data archive "Dataset of synthesis and characterization by PXCT of ALD-based mullite inverse opal photonic crystals" located at https://data.mendeley.com/datasets/zn49dsk7x6/1 for any academic, educational, or research purposes

Structural diversity of native Major Ampullate, Minor Ampullate, Cylindriform, and Flagelliform silk proteins in solution

The foundations of silk spinning, the structure, storage, and activation of silk proteins, remain highly debated. By combining solution small-angle neutron and X-ray scattering (SANS and SAXS) alongside circular dichroism (CD), we reveal a shape anisotropy of the four principal native spider silk feedstocks from Nephila edulis. We show that these proteins behave in solution like elongated semiflexible polymers with locally rigid sections. We demonstrated that minor ampullate and cylindriform proteins adopt a monomeric conformation, while major ampullate and flagelliform proteins have a preference for dimerization. From an evolutionary perspective, we propose that such dimerization arose to help the processing of disordered silk proteins. Collectively, our results provide insights into the molecular-scale processing of silk, uncovering a degree of evolutionary convergence in protein structures and chemistry that supports the macroscale micellar/pseudo liquid crystalline spinning mechanisms proposed by the community

Pushing the temporal resolution in absorption and Zernike phase contrast nanotomography: Enabling fast in situ experiments

Hard X-ray nanotomography enables 3D investigations of a wide range of samples with high resolution (<100 nm) with both synchrotron-based and laboratory-based setups. However, the advantage of synchrotron-based setups is the high flux, enabling time resolution, which cannot be achieved at laboratory sources. Here, the nanotomography setup at the imaging beamline P05 at PETRA III is presented, which offers high time resolution not only in absorption but for the first time also in Zernike phase contrast. Two test samples are used to evaluate the image quality in both contrast modalities based on the quantitative analysis of contrast-to-noise ratio (CNR) and spatial resolution. High-quality scans can be recorded in 15 min and fast scans down to 3 min are also possible without significant loss of image quality. At scan times well below 3 min, the CNR values decrease significantly and classical image-filtering techniques reach their limitation. A machine-learning approach shows promising results, enabling acquisition of a full tomography in only 6 s. Overall, the transmission X-ray microscopy instrument offers high temporal resolution in absorption and Zernike phase contrast, enabling in situ experiments at the beamline

Flexible plenoptic X-ray microscopy

X-ray computed tomography (CT) is an invaluable technique for generating three-dimensional (3D) images of inert or living specimens. X-ray CT is used in many scientific, industrial, and societal fields. Compared to conventional 2D X-ray imaging, CT requires longer acquisition times because up to several thousand projections are required for reconstructing a single high-resolution 3D volume. Plenoptic imaging—an emerging technology in visible light field photography—highlights the potential of capturing quasi-3D information with a single exposure. Here, we show the first demonstration of a flexible plenoptic microscope operating with hard X-rays; it is used to computationally reconstruct images at different depths along the optical axis. The experimental results are consistent with the expected axial refocusing, precision, and spatial resolution. Thus, this proof-of-concept experiment opens the horizons to quasi-3D X-ray imaging, without sample rotation, with spatial resolution of a few hundred nanometres

Structural analysis of silk proteins using x–ray and neutron scattering

The silk fibres spun by insects and spiders have intrigued scientists for many years. Their mechanical performance is remarkable when one considers that the fibres are spun under ambient conditions from aqueous protein solutions without requiring many of the harsh processing conditions used in the production of man-made fibres. Yet, despite this interest, very little is known about the initial structure of the precursor proteins prior to spinning. One reason for this lies in the difficulty of handling the native proteins without accidental aggregation. Therefore in this thesis a novel sample preparation protocol for native silk is developed and small angle scattering (SAS) techniques are combined with circular dichroism (CD) and atomic force microscopy (AFM) to examine the structure and morphology of the proteins with different mechanical properties and thus biological function in nature. This work highlights the importance of studying native, functional proteins, at close to in vivo conditions, since clear differences in the structure and interaction of native and reconstituted silks can be attributed to the additional processing which reconstituted silks have undergone in order to be solubilised. Indeed native silk proteins are found to be more inherently non-interacting at quite high protein concentrations than reconstituted silk. Upon dilution, inter-chain interactions can be observed by SAS and CD as the protein is driven from its equilibrium conformation. This interaction and the shear-induced assembly of these proteins are also followed by AFM. Interestingly, native silk proteins from spider and silkworms retain a semiflexible conformation in solution. Indeed by comparing the silks from the major and minor ampullate, flagelliform and cylindriform glands of Nephila edulis with the cocoon silk of Bombyx mori silkworms, important insights are gained into how their flexibility suggests similarities in the local environment of the protein chains thereby dictating the hierarchical structure of silk fibres

Structural analysis of silk proteins using x–ray and neutron scattering

The silk fibres spun by insects and spiders have intrigued scientists for many years. Their mechanical performance is remarkable when one considers that the fibres are spun under ambient conditions from aqueous protein solutions without requiring many of the harsh processing conditions used in the production of man-made fibres. Yet, despite this interest, very little is known about the initial structure of the precursor proteins prior to spinning. One reason for this lies in the difficulty of handling the native proteins without accidental aggregation. Therefore in this thesis a novel sample preparation protocol for native silk is developed and small angle scattering (SAS) techniques are combined with circular dichroism (CD) and atomic force microscopy (AFM) to examine the structure and morphology of the proteins with different mechanical properties and thus biological function in nature. This work highlights the importance of studying native, functional proteins, at close to in vivo conditions, since clear differences in the structure and interaction of native and reconstituted silks can be attributed to the additional processing which reconstituted silks have undergone in order to be solubilised. Indeed native silk proteins are found to be more inherently non-interacting at quite high protein concentrations than reconstituted silk. Upon dilution, inter-chain interactions can be observed by SAS and CD as the protein is driven from its equilibrium conformation. This interaction and the shear-induced assembly of these proteins are also followed by AFM. Interestingly, native silk proteins from spider and silkworms retain a semiflexible conformation in solution. Indeed by comparing the silks from the major and minor ampullate, flagelliform and cylindriform glands of Nephila edulis with the cocoon silk of Bombyx mori silkworms, important insights are gained into how their flexibility suggests similarities in the local environment of the protein chains thereby dictating the hierarchical structure of silk fibres.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Modified x-ray polymer refractive cross lens with adiabatic contraction and its realization

A refractive x-ray lens with reduced focal length, due to continuous reduction in the designed aperture over the length of the lens, is presented. The lens elements have refractive parabolic sidewalls like geometrical prisms, with a varying cross section over the length of the lens, in accordance with the x-ray propagation law. The focusing effect occurs directly in the lens due to the fact that the initial x-ray beam is directed toward the focal point, and due to the phase retardation caused by the refractive properties of the sidewall surfaces. An array of such adiabatic lens elements with different optical parameters, arranged in a number of rows, represented by polymer microstructures, has been produced using x-ray lithography. Preliminary testing of the lenses has resulted in a focal spot of 67 nm at a photon energy of 18.6 keV

On stars and spikes: Resolving the skeletal morphology of planktonic Acantharia using synchrotron X-ray nanotomography and deep learning image segmentation

Acantharia (Acantharea) are wide-spread marine protozoa, presenting one of the rare examples of strontium sulfate mineralization in the biosphere. Their endoskeletons consist of 20 spicules arranged according to a unique geometric pattern named Müller's principle. Given the diverse mineral architecture of the Acantharia class, we set out to examine the complex three-dimensional skeletal morphology at the nanometer scale using synchrotron X-ray nanotomography, followed by image segmentation based on deep learning methods. The present study focuses on how the spicules emanate from the robust central junction in the orders Symphyacanthida and Arthracanthida, the geometry of lateral spicule wings as well as pockets of interspicular space, which may be involved in cell compartmentalization. Through these morphometric studies, we observed subtle deviations from the previously described spatial arrangement of the spicules. According to our data, spicule shapes are adjusted in opposite spicules as to accommodate the overall spicule arrangement. In all types examined, previously unknown interspicular interstices were found in areas where radial spicules meet, which could have implications for the crystal growth mechanism and overall endoskeletal integrity. A deeper understanding of the spiculogenesis in Acantharia can provide biomimetic routes towards complex inorganic shapes