The internal structure of single carbon fibers determined by simultaneous small- and wide-angle scattering

Assessing lesion malignancy by scanning small-angle x-ray scattering of breast tissue with microcalcifications

Scanning small-angle x-ray scattering (SAXS) measurements were performed on 36 formalin-fixed breast tissue biopsies obtained from two patients. All samples contained microcalcifications of type II, i.e. formed by hydroxyapatite. We demonstrate the feasibility of classifying breast lesions by scanning SAXS of tissues containing microcalcifications with a resolution of 35 [Formula: see text]m [Formula: see text] 30 [Formula: see text]m. We report a characteristic Bragg peak found around q  =  1.725 nm^-1 that occurs primarily for malignant lesions. Such a clear SAXS fingerprint is potentially linked to structural changes of breast tissue and corresponds to dimensions of about 3.7 nm. This material property could be used as an early indicator of malignancy development, as it is readily assessed by SAXS. If this fingerprint is combined with other known SAXS features, which also indicate the level of malignancy, such as lipid spacing and collagen periodicity, it could complement traditional pathology-based analyses. To confirm the SAXS-based classification, a histopathological workup and a gold standard histopathological diagnosis were conducted to determine the malignancy level of the lesions. Our aim is to report this SAXS fingerprint, which is clearly related to malignant breast lesions. However, any further conclusion based on our dataset is limited by the low number of patients and samples. Running a broad study to increase the number of samples and patients is of great importance and relevance for the breast-imaging community.

Structural evolution during the graphitization of polyacrylonitrile-based carbon fiber as revealed by small-angle X-ray scattering

On the basis of a Debye–Bueche correlation length analysis, the small-angle X-ray scattering (SAXS) intensity components due to different scatterers within polyacrylonitrile-based carbon fiber were determined and analyzed separately. According to Guinier's law and other related methods, an intensity component indicating a relatively large scatterer was ascribed to the amorphous structure within the boundaries of fibrils. Results indicated that the amorphous regions decreased in dimension and finally transformed completely into voids as the heat treatment temperature rose to 2773 K. The general trend for microvoids was a systematic change from many small voids to a few large voids, while the local density fluctuation within the samples weakened and finally faded away. In conclusion, the graphitization process of carbon fibers as revealed by SAXS is a systematic evolution from a quasi-two-phase system (fibril, amorphous region and microvoid within the fibril) of high-strength carbon fiber to the true two-phase structure (crystallite and microvoid) of high-modulus graphite fiber.

Hard X-ray imaging of bacterial cells: nano-diffraction and ptychographic reconstruction

Ptychographic coherent X-ray diffractive imaging (PCDI) has been combined with nano-focus X-ray diffraction to study the structure and density distribution of unstained and unsliced bacterial cells, using a hard X-ray beam of 6.2keV photon energy, focused to about 90nm by a Fresnel zone plate lens. While PCDI provides images of the bacteria with quantitative contrast in real space with a resolution well below the beam size at the sample, spatially resolved small angle X-ray scattering using the same Fresnel zone plate (cellular nano-diffraction) provides structural information at highest resolution in reciprocal space up to 2nm(-1). We show how the real and reciprocal space approach can be used synergistically on the same sample and with the same setup. In addition, we present 3D hard X-ray imaging of unstained bacterial cells by a combination of ptychography and tomography.

Microcracks in Carbon/Carbon Composites: A Microtomography Investigation using Synchrotron Radiation

The mechanical properties of brittle matrix composites such as carbon/carbon (C/C) are closely related to the generation and propagation of microcracks. A better understanding of the role of microcracking requires a quantification of the three-dimensional morphology of the crack network. In this study we demonstrate that phase contrast microtomography using synchrotron radiation is a unique tool to get 3D information about cracks in C/C. This is shown for three different C/C specimens subjected to different final heat treatment temperatures (HTT). The results are discussed qualitatively with respect to the influence of HTT on the distribution of microcracks and their relevance for the mechanical properties of C/C.

Mapping fibre orientation in complex-shaped biological systems with micrometre resolution by scanning X-ray microdiffraction

A fully automated procedure to extract and to image local fibre orientation in biological tissues from scanning X-ray diffraction is presented. The preferred chitin fibre orientation in the flow sensing system of crickets is determined with high spatial resolution by applying synchrotron radiation based X-ray microbeam diffraction in conjunction with advanced sample sectioning using a UV micro-laser. The data analysis is based on an automated detection of azimuthal diffraction maxima after 2D convolution filtering (smoothing) of the 2D diffraction patterns. Under the assumption of crystallographic fibre symmetry around the morphological fibre axis, the evaluation method allows mapping the three-dimensional orientation of the fibre axes in space. The resulting two-dimensional maps of the local fibre orientations - together with the complex shape of the flow sensing system - may be useful for a better understanding of the mechanical optimization of such tissues.