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Abstract: In this work, novel bioinspired polyurethane (PU) scaffolds were fabricated via freeze casting for PU-based Pancreatic Ductal Adenocarcinoma (PDAC) model. In order to reproduce the tumour micro-environment that facilitates cellular kinetics, the PU scaffolds were surface modified with extracellular matrix (ECM) proteins including collagen and fibronectin (Col and FN). Synchrotron-based small- and wide-angle X-ray scattering (SAXS/WAXS) techniques were applied to probe structural evolution during in situ mechanical testing. Strains at macroscopic, nano-, and lattice scales were obtained to investigate the effects of ECM proteins and pancreatic cell activities to PU scaffolds. Significant mechanical strengthening across length scales of PU scaffolds was observed in specimens surface modified by FN. A model of stiffness modulation via enhanced interlamellar recruitment is proposed to explain the multi-scale strengthening mechanisms. Understanding multi-scale deformation mechanisms of a series of PU scaffolds opens an opportunity in developing a novel pancreatic cancer model for studying cancer evolution and predicting outcomes of drug/treatments.

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Abstract: We performed simulations and experimental tests of a new method for improving the spatial resolution of x-ray imaging detectors using tilted angle irradiation. In this method, the x-ray beam arrives at the detector surface at an angle of <90° so that the beam footprint is expanded and the spatial resolution is increased. The proposed method is applicable for imaging with x-rays in the energy range of E = 0.2-15 keV, which is widely used for x-ray microscopy. The tilted angle irradiation technique can be applied to different types of x-ray microscopy detectors, including indirect conversion detectors (which consist of a scintillator optically coupled to the imaging camera), direct conversion detectors (such as CCD- and CMOS-based soft x-ray cameras) and some other semiconductor detectors. The experimental study described here employed an indirect detector configuration where a thin scintillator was optically coupled to an imaging camera via microscope optics. The spatial resolution was improved by a factor of 2.5 by using a tilt angle of 12° for 13.5 keV x-rays. This study will be continued using different xray energies and detector configurations.

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Abstract: The electron-ion collider (EIC) will be built at the Brookhaven National Laboratory over the next ten years, with the purpose of giving insight into nucleon structure, origins of nucleon mass and spin, and quark and gluon confinement. This thesis pertains to the silicon vertex tracker for an EIC experiment; the detector closest to the interaction point. The purpose of a silicon vertex tracker is to locate the origin vertex position of charged particles and measure the particle momentum, and the EIC physics goals require detector resolutions beyond current state-of-the-art silicon vertex trackers. The aim of this thesis is to find a suitable silicon sensor technology for further developments by tests performed in a lab and at a testbeam, and to find a silicon vertex tracker geometry with performance matching the EIC physics requirements using simulations. The baseline sensor for the studies comes from the ALICE inner tracker upgrade, and is called the ALPIDE sensor. A new monolithic silicon sensor development designed to increase depletion is tested and compared to the performance of an ALPIDE-like sensor, and found to improve charge collection performance while keeping the sensor capacitance low. This aids tracking performance, and the new development is thus considered a possible path for development of an EIC-specific sensor. Simulations of different silicon vertex tracker geometries and parameters are performed using GEANT4, and a high-performing layout consisting of inner and outer silicon sensor layers surrounded by a gaseous detector and silicon disks is developed. It is also found that if a more compact tracker is desired, an all-silicon concept outperforms a combination of silicon and gaseous detectors. Further simulations of the best-performing layouts with current projections of possible silicon sensor material thickness and pixel size show that they meet the requirements of the EIC physics goals in terms of momentum resolution if a 3 T solenoidal magnetic field is used, and pointing resolution regardless of magnetic field strength. The silicon vertex tracker developed in this work is one of two baseline tracker concepts used in the ongoing development of an EIC reference detector. The performance of different detector concepts is also studied using realistic electron-proton collision events generated using PYTHIA and propagated through the detector simulation, with a focus on charmed meson reconstruction. It is found that a compact all-silicon tracker can perform as well as an all-silicon concept with a larger radius in these studies, but a large-radius combination of silicon and gaseous detectors is always better than all-silicon concepts in the studied open charm case.

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Abstract: Modules for the ATLAS Inner Tracker (ITk) strip tracker include a DC-DC converter circuit glued directly to the silicon sensor which converts the 11 V supplied to the module to the 1.5 V required for the operation of the readout chips. The DC-DC converter unit, consisting of a copper solenoid and custom ASIC, is located directly above the silicon strip sensor and therefore needs to be shielded to protect the sensor from EMI noise created during the operation of the circuit. Despite dedicated shielding, consisting of an aluminium shield box with continuous solder seams encompassing the surface components and a copper layer in the PCB beneath it, module channels connected to sensor strips located beneath the converter circuit were found to show a noise increase. While the DC-DC converter unit causing the underlying EMI noise operates at a frequency of 2 MHz, module characterisation measurements for ITk strip tracker modules are typically performed asynchronously to the DC-DC switching and are therefore averaged over the full range of time bins with respect to the converter frequency. In order to investigate the time dependence of the noise injection relative to the DC-DC switching frequency, a dedicated setup to understand the time-resolved performance change in modules was developed. By using a magnetic field probe to measure the field leaking through the shield box and triggering on its rising edge, data taking could be synchronised with the DC-DC switching. This paper illustrates the concept and setup of such time-resolved performance measurements using magnetic triggering and presents results for the observed effects on signal and noise for ATLAS ITk strip modules from both laboratory and beam tests.

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Abstract: Objective: The objective of the study was to specify the thickness of Zn and Pb accumulation within the tidemark (TM), a narrow structure between the non-calcified and the calcified articular cartilage. It is considered an active or resting calcification front. This banded structure of the cartilage-bone interface is known to undergo changes in osteoarthritis. Therefore, gaining knowledge about this structure is of interest. Methods: Femoral head samples were collected from patients suffering from various bone diseases, 6 samples have been investigated. Thin bone slices (3μm thick) were measured with high resolution synchrotron micro-X-ray fluorescence (SR micro-XRF) analysis using a beam with dimensions of 500 × 800 nm2. The tidemark region was found in all analyzed samples. The Savitzky-Golay filter was used to smooth the measured imaging data and Kaplan-Meier estimation to gain reliable tidemarks medians for Pb and Zn. To our knowledge this was the first time that these methods have been applied to gain information on histological structures obtained by elemental imaging. Results: The thickness of the Zn and Pb layer ranged from about 3 to 11 μm for Zn and 4 to 14.5 μm for Pb. Our Zn ratios (TM/matrix) were found to be 1.5-3-fold ratio between Zn tidemark values and in mineralized matrix and are similar in all samples. Conclusions: The determined thickness of the layer is much smaller than found in previous measurements with the beam having 20 × 14 μm2 size. The Zn ratios agree with our previous findings.