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Abstract: Hard dental tissues possess a complex hierarchical structure that is particularly evident in enamel, the most mineralised substance in the human body. Its complex and interlinked organisation at the Ångstrom (crystal lattice), nano-, micro-, and macro-scales is the result of evolutionary optimisation for mechanical and functional performance: hardness and stiffness, fracture toughness, thermal, and chemical resistance. Understanding the physical–chemical–structural relationships at each scale requires the application of appropriately sensitive and resolving probes. Synchrotron X-ray techniques offer the possibility to progress significantly beyond the capabilities of conventional laboratory instruments, i.e., X-ray diffractometers, and electron and atomic force microscopes. The last few decades have witnessed the accumulation of results obtained from X-ray scattering (diffraction), spectroscopy (including polarisation analysis), and imaging (including ptychography and tomography). The current article presents a multi-disciplinary review of nearly 40 years of discoveries and advancements, primarily pertaining to the study of enamel and its demineralisation (caries), but also linked to the investigations of other mineralised tissues such as dentine, bone, etc. The modelling approaches informed by these observations are also overviewed. The strategic aim of the present review was to identify and evaluate prospective avenues for analysing dental tissues and developing treatments and prophylaxis for improved dental health.

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Abstract: Tissue engineering (TE) holds promise for generating lab-grown patient specific organs which can provide: (1) effective treatment for conditions that require volumetric tissue transplantation and (2) new platforms for drug testing. Even though volumetric structural information is essential for confirming successful organ maturation, TE protocol designs are currently informed through destructive and 2D construct assessment tools (e.g. histology). X-ray phase-contrast computed-tomography (PC-CT) can generate non-destructive, high resolution, 3D density maps of organ architecture. In this work, PC-CT is used as new imaging tool for guiding two TE protocols currently at the in-vitro testing stage. The first (1) involves cell-repopulation of an oesophageal scaffold, with the aim of using the regenerated construct for treating long-gap oesophageal atresia, whilst for the second (2) a lung-derived scaffold is populated with islets for regenerating a pancreas, with the “repurposed” lung offering a platform for diabetes drug testing. By combing 3D images and quantitative information, we were able to perform comprehensive construct evaluation. Specifically, we assessed volumetrically: (1) the cell-distribution within the regenerated oesophagi and (2) islet integration with the vascular tree of the lung-derived scaffold. This new information was proven to be essential for establishing corresponding TE protocols and enabled their progression to more advanced scale-up models. We are confident that PC-CT will provide the novel insights necessary to further progress TE protocols, with the next step being in-vivo testing. Crucially, the non-destructive nature of PC-CT will allow in-vivo assessments of TE constructs following their implantation into animal hosts, to investigate their successful integration.

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Abstract: I13 is a 250 m long hard X-ray beamline for imaging and coherence experiments at the Diamond Light Source [1]. The beamline comprises two independent experimental branches: one for imaging in direct space using X-ray microscopy and one for imaging in reciprocal space using coherent imaging techniques. The mechanical stability is very important for implementation of increased capabilities at latest generation of long beamlines [2]. Therefore, the beam stability monitoring is essential part of the day-to-day operation of the beamlines as well as for analysis of mechanical instability sources for the Diamond II upgrade. In this paper we present the setup developed to measure mechanical stability of beamline based on optical autocollimator.

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Abstract: Solar energy powered interfacial evaporation is the most meaningful strategy for energy utilization, water desalination and mineral purification. It can achieve high efficiency, low-density energy and sustainable harvest and utilization. However, the microstructure and surface/interface design still lead to a balance between solar-thermal conversion, water conduction and thermal management, which also determines the efficiency of photothermal interfacial evaporation. Here, a free-standing, ultra-thin carbon film with a tunable nanopore diameter was prepared and used as a blackbody layer for solar photothermal evaporation. By the three-dimensional reconstruction methods, the effect of pore structure on interfacial evaporation is systematically studied. HPCF with an average pore size of about 300 nm exhibited outstanding photothermal evaporation performance, reaching up to 1.96 kg m−2 h−1 with excellent stability. Ultra-hydrophobic, optically enhanced absorption graphene array is constructed on the carbon film surface through femtosecond laser nano processing, further increasing the evaporation rate to 2.12 kg m−2 h−1 (1 sun) and 5.55 kg m−2 h−1 (3 suns).

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Abstract: In this work, a characterization and optimization of phase-sensitive X-ray imaging techniques with a focus on the field of laboratory astrophysics is given. Here, the advent of hard X-ray free electron lasers offers novel opportunities as single-pulse imaging with sub-picosecond temporal resolution becomes possible. The use of phase-sensitive techniques is often mandatory as micro- and nanoscopic samples show little or no attenuation contrast. In order to fully benefit from the short pulse lengths at X-ray free electron lasers, these methods should be reconcilable with single-exposure acquisition schemes. This task is complicated by zeroes in the respective transfer functions of the imaging systems. Therefore, direct inversions are typically not possible and sophisticated algorithms are required for the image reconstruction. Overall, this thesis mainly focuses upon the grating-based X-ray imaging technique, also known as Talbot interferometry. For comparison, propagation-based phase contrast imaging will also be considered. The investigations are divided into analytical considerations, numerical simulations, and experimental implementations of the respective imaging techniques. An analytical examination of the image formation within a Talbot interferometer is presented. This process can become complicated, especially for applications in X-ray microscopes. Here, transverse shifts of the interference pattern in general depend nonlinearly on the phase differences across the X-ray wave field. Existing reconstruction methods on the basis of deconvolutions then rely on idealized conditions, thus limiting the experimental applicability of the method. In addition, the achievable spatial resolution of Talbot interferometry in single-exposure applications is typically limited to the demagnified fringe period of the interference pattern. In order to resolve the limitations regarding the applicability, three novel reconstruction methods for Talbot interferometry are conceptualized and implemented: the design of a beam-splitting diffraction grating featuring only two diffraction orders, a two-stage deconvolution approach, and a statistical image reconstruction method based on an analytical forward model of the imaging process and a regularized maximum likelihood approach. The three schemes are validated on the basis of simulated data. They all prove advantageous when the premises for standard deconvolution-based reconstructions are not met. The statistical image reconstruction technique seems most promising as it achieves the best reconstruction quality at low photon numbers and also circumvents the abovementioned limitations regarding the spatial resolution. Building up on the simulative studies, two experimental realizations of Talbot interferometry at synchrotron light sources are presented. In the first experiment, the single-exposure phase imaging capabilities of Talbot interferometry in conjunction with the statistical image reconstruction method are investigated and characterized on the basis of simple test samples. The broadened experimental applicability is demonstrated through the retrieval of Fresnel diffraction images in an X-ray projection microscope. While a comparative implementation of propagation-based phase contrast imaging at the same instrument still yields a superior spatial resolution, the mitigation of limitations due to the fringe period is also verified experimentally. In the second experiment, single-exposure phase imaging with both the grating-based and the propagation-based approach is employed in order to monitor the moistening process of wood on the level of single wood cells...