A conventional x-ray fluorescence computed tomography (XFCT) technique requires monochromatic synchrotron x-rays to simultaneously determine the spatial distribution and concentration of various elements such as metals in a sample. However, the synchrotron-based XFCT technique appears to be unsuitable for in vivo imaging under a typical laboratory setting. In this study we demonstrated, for the first time to our knowledge, the possibility of performing XFCT imaging of a small animal-sized object containing gold nanoparticles (GNPs) at relatively low concentrations using polychromatic diagnostic energy range x-rays. Specifically, we created a phantom made of polymethyl methacrylate plastic containing two cylindrical columns filled with saline solution at 1 and 2 wt% GNPs, respectively, mimicking tumors/organs within a small animal. XFCT scanning of the phantom was then performed using microfocus 110 kVp x-ray beam and cadmium telluride (CdTe) x-ray detector under a pencil beam geometry after proper filtering of the x-ray beam and collimation of the detector. The reconstructed images clearly identified the locations of the two GNP-filled columns with different contrast levels directly proportional to gold concentration levels. On the other hand, the current pencil-beam implementation of XFCT is not yet practical for routine in vivo imaging tasks with GNPs, especially in terms of scanning time. Nevertheless, with the use of multiple detectors and a limited number of projections, it may still be used to image some objects smaller than the current phantom size. The current investigation suggests several modification strategies of the current XFCT setup, such as the adoption of the quasi-monochromatic cone/fan x-ray beam and XFCT-specific spatial filters or pinhole detector collimators, in order to establish the ultimate feasibility of a bench-top XFCT system for GNP-based preclinical molecular imaging applications.

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A study on the Mode II interlaminar fracture characteristics of non-woven carbon tissue (NWCT) interleaved composites was carried out using the endnotched-flexure (ENF) test. The NWCT interleaved composites were made by interleaving NWCT-prepreg between CFRP layers. CFRP specimen [024] as well as NWCT interleaved specimen [012/T/012] were prepared to compare the characteristics. The symbol ‘‘/T/’’ means that the NWCT layeris located at the 0/0 mid-plane of the interleaved specimen. Three kinds of interlaminar cracks, which have different positions in the NWCT layer, were introduced to the interleaved specimen. The ENF testing results were analyzed using the normal distribution. The mean GIIC of the interleaved specimen with an upper crack is about 26% higher than that of the CFRP specimen due to a blunt shape of crack tip by Teflon film in the NWCT layer. The mean GIIC of the interleaved specimens with a center crack and a lower crack is about 260 and 205% higherthan that of the CFRP specimen due to the short fiber bridging from in-plain random short carbon fibers in the NWCT layer, respectively. The fracture surfaces of the specimens and the fracture process on the specimen side-sections were observed with an optical microscope and a scanning electron microscope, and then they were analyzed for the failure mechanism. The size and spacing of hackles on the fracture surface are affected by both the length and fiber volume of short carbon fibers in the NWCT layer.

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