Current Issue : July - September Volume : 2013 Issue Number : 3 Articles : 4 Articles
This paper summarizes the scientific trends associated with the rapid development of the technique of high-energy X-ray\r\ndiffraction over the past decade pertaining to the field of liquids, glasses, and amorphous materials. The measurement of highquality\r\nX-ray structure factors out to large momentum transfers leads to high-resolution pair distribution functions which can\r\nbe directly compared to theory or combined with data from other experimental techniques. The advantages of combining highly\r\npenetrating radiation with low angle scattering are outlined together with the data analysis procedure and formalism. Also included\r\nare advances in high-energy synchrotron beamline instrumentation, sample environment equipment, and an overview of the role\r\nof simulation and modeling for interpreting data from disordered materials. Several examples of recent trends in glass and liquid\r\nresearch are described. Finally, directions for future research are considered within the context of past and current developments\r\nin the field....
A Monte Carlo simulation was used to study imaging and dosimetric characteristics of a novel design of megavoltage (MV) X-ray\r\ndetectors for radiotherapy applications. The new design uses Cerenkov effect to convert X-ray energy absorbed in optical fibres\r\ninto light for MV X-ray imaging. The proposed detector consists of a matrix of optical fibres aligned with the incident X rays\r\nand coupled to an active matrix flat-panel imager (AMFPI) for image readout. Properties, such as modulation transfer function,\r\ndetection quantum efficiency (DQE), and energy response of the detector, were investigated. It has been shown that the proposed\r\ndetector can have a zero-frequency DQE more than an order of magnitude higher than that of current electronic portal imaging\r\ndevice (EPID) systems and yet a spatial resolution comparable to that of video-based EPIDs. The proposed detector is also less\r\nsensitive to scattered X rays from patients than current EPIDs....
Small tip-type CNT emitters with the diameter of 0.8mm were fabricated for miniaturized X-ray tubes. The CNT emitters were\r\nprepared by dropping CNTs and silver nanoparticles on a flat surface of a W metal tip followed by annealing at 800?C for 2 h\r\nunder vacuum. The CNT emitters exhibit good field emission properties with the threshold electric field of 1.15 V/�µm and the\r\nfield enhancement factor of 12,050. CNTs were well attached to a flat W tip surface without coating on the side plane of the tip,\r\nand thus beam divergence could be minimized. Consequently, a miniaturized X-ray tube with the inner diameter of 5mm was\r\nsuccessfully demonstrated using the tip-type CNT emitter....
The self-assembly technique has been applied for the fabrication of thin films including macrocyclic molecules. Thesemultilayered\r\nstructures, grown by sequential deposition of oppositely charged molecules, were characterised with X-ray reflectometry. The data\r\nobtained indicate regular thickness of ion pair layers formed regardless of the number of depositions made as well as the number\r\nof ion groups occurring in the molecule. Savitzky-Golay algorithm was used for the calculation of the layer thickness. Formation\r\nof self-assembled multilayers (SAMs) occurs not only for polymeric structures but also for small ionic compound systems and\r\nresults from the electrostatic interaction of many strongly dissipated charges on the whole structure of the molecule....
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