Cone-Beam Composite-Circling Scan and Exact Image Reconstruction for a Quasi-Short Object

Here we propose a cone-beam composite-circling mode to solve the quasi-short object problem, which is to reconstruct a short portion of a long object from longitudinally truncated cone-beam data involving the short object. In contrast to the saddle curve cone-beam scanning, the proposed scanning mode requires that the X-ray focal spot undergoes a circular motion in a plane facing the short object, while the X-ray source is rotated in the gantry main plane. Because of the symmetry of the proposed mechanical rotations and the compatibility with the physiological conditions, this new mode has significant advantages over the saddle curve from perspectives of both engineering implementation and clinical applications. As a feasibility study, a backprojection filtration (BPF) algorithm is developed to reconstruct images from data collected along a composite-circling trajectory. The initial simulation results demonstrate the correctness of the proposed exact reconstruction method and the merits of the proposed mode

Diagnosis and application of laser wakefield accelerators

This thesis is concerned with experimental diagnostic methods of the laser-plasma interaction in laser wakefield accelerators, and how high energy photon beams from such accelerators may be exploited in a potential application. Raman scattered light from the 20 TW Astra laser pulse was found to have shorter wavelength than expected given the interferometrically-measured plasma density, due to the relativistic motion of plasma electrons. Simulations indicated that the scattering helps to shape the pulse, removing laser energy not trapped in the wake. The signature of Raman scatter from the 200 TW Astra-Gemini pulse was instead the generation of extended plasma filaments, the direction of which indicated weaker relativistic effects. Altering the focal spot position or quality generated more filaments and reduced electron beam charge, linking Raman scattering, pulse focussing, and accelerator performance. When a low intensity (10¹⁰ W/cm²) probe pulse crossed a high intensity (10¹⁹ W/cm²) drive pulse of equal frequency, the probe was observed to be amplified in intensity by up to 10⁵ over a distance of tens of microns. No frequency shift of the probe was observed, and the effect required the polarisations of the pulses to be parallel. In simulations the pulses created a ponderomotive grating, trapping electrons which were able to scatter the drive into the probe in the superradiant regime of Raman amplification. Laser wakefield-driven x-ray beams were used to perform a microtomographic scan of a human femoral trabecular bone sample. Under optimal conditions x-ray beams containing 1.3 ± 0.5 × 10⁹ photons were produced on 97% of laser shots, with critical energy 33 ± 12 keV and source size of 2-3 μm. Image resolution was 36 ± 7 μm and after 180 image acquisitions the 3D resolution of the tomogram was up to 50 μm. The average photon flux between 10 and 100 keV was 5.9 ± 2.4 × 10⁵ ph/s/mrad² which is comparable to microfocus sources capable of few-micron source sizes.Open Acces

Constraining new physics with fiducial measurements at the LHC

As Run 2 of the LHC completes, a vast set of particle collision data has been recorded by the experimental collaborations on the ring. This has enabled the collaborations to perform many measurements of fiducial particle collision properties, which have been found to be in good agreement with predictions from the Standard Model of particle physics. This collected data has also been used to perform many searches for a variety hypothesised extensions to the Standard Model, which have thus far not observed any significant sign of new physics. In this thesis contributions to the precision measurement program within the ATLAS collaboration at the LHC are presented. These contributions are primarily made to the measurement of detector corrected observables sensitive to large imbalances of momentum observed in the transverse plane. Additionally the opportunity of using such precision fiducial measurements to understand the nature of physics beyond the Standard Model is explored. This is found to give rise to interesting, competitive and complementary information to that derived from the dedicated searches. This work has led to the release of a publicly available program that can be used to automatically confront a hypothesised physics model with precision LHC measurement data. This program is called CONTUR and applications of this to a variety of hypothesised physics models are presented

Investigation of Membrane Receptors’ Oligomers Using Fluorescence Resonance Energy Transfer and Multiphoton Microscopy in Living Cells

Investigating quaternary structure (oligomerization) of macromolecules (such as proteins and nucleic acids) in living systems (in vivo) has been a great challenge in biophysics, due to molecular diffusion, fluctuations in several biochemical parameters such as pH, quenching of fluorescence by oxygen (when fluorescence methods are used), etc. We studied oligomerization of membrane receptors in living cells by means of Fluorescence (Förster) Resonance Energy Transfer (FRET) using fluorescent markers and two photon excitation fluorescence micro-spectroscopy. Using suitable FRET models, we determined the stoichiometry and quaternary structure of various macromolecular complexes. The proteins of interest for this work are : (1) sigma-1 receptor and (2) rhodopsin, are described as below. (1) Sigma-1 receptors are molecular chaperone proteins, which also regulate ion channels. S1R seems to be involved in substance abuse, as well as several diseases such as Alzheimer’s. We studied S1R in the presence and absence of its ligands haloperidol (an antagonist) and pentazocine +/- (an agonist), and found that at low concentration they reside as a mixture of monomers and dimers and that they may form higher order oligomers at higher concentrations. (2) Rhodopsin is a prototypical G protein coupled receptor (GPCR) and is directly involved in vision. GPCRs form a large family of receptors that participate in cell signaling by responding to external stimuli such as drugs, thus being a major drug target (more than 40% drugs target GPCRs). Their oligomerization has been largely controversial. Understanding this may help to understand the functional role of GPCRs oligomerization, and may lead to the discovery of more drugs targeting GPCR oligomers. It may also contribute toward finding a cure for Retinitis Pigmentosa, which is caused by a mutation (G188R) in rhodopsin, a disease which causes blindness and has no cure so far. Comparing healthy rhodopsin’s oligomeric structure with that of the mutant may give clues to find the cure

Remote sensing data handbook

A digest of information on remote sensor data systems is given. It includes characteristics of spaceborne sensors and the supportive systems immediately associated therewith. It also includes end-to-end systems information that will assist the user in appraising total data system impact produced by a sensor. The objective is to provide a tool for anticipating the complexity of systems and potential data system problems as new user needs are generated. Materials in this handbook span sensor systems from the present to those planned for use in the 1990's. Sensor systems on all planned missions are presented in digest form, condensed from data as available at the time of compilation. Projections are made of anticipated systems

Colour coded

This 300 word publication to be published by the Society of Dyers and Colourists (SDC) is a collection of the best papers from a 4-year European project that has considered colour from the perspective of both the arts and sciences.The notion of art and science and the crossovers between the two resulted in application and funding for cross disciplinary research to host a series of training events between 2006 and 2010 Marie Curie Conferences & Training Courses (SCF) Call Identifier: FP6-Mobility-4, Euros 532,363.80 CREATE – Colour Research for European Advanced Technology Employment. The research crossovers between the fields of art, science and technology was also a subject that was initiated through Bristol’s Festival if Ideas events in May 2009. The author coordinated and chaired an event during which the C.P Snow lecture “On Two Cultures’ (1959) was re-presented by Actor Simon Cook and then a lecture made by Raymond Tallis on the notion of the Polymath. The CREATE project has a worldwide impact for researchers, academics and scientists. Between January and October 2009, the site has received 221, 414 visits. The most popular route into the site is via the welcome page. The main groups of visitors originate in the UK (including Northern Ireland), Italy, France, Finland, Norway, Hungary, USA, Finland and Spain. A basic percentage breakdown of the traffic over ten months indicates: USA -15%; UK - 16%; Italy - 13%; France -12%; Hungary - 10%; Spain - 6%; Finland - 9%; Norway - 5%. The remaining approximate 14% of visitors are from other countries including Belgium, The Netherlands and Germany (approx 3%). A discussion group has been initiated by the author as part of the CREATE project to facilitate an ongoing dialogue between artists and scientists. http://createcolour.ning.com/group/artandscience www.create.uwe.ac.uk.Related papers to this research: A report on the CREATE Italian event: Colour in cultural heritage.C. Parraman, A. Rizzi, ‘Developing the CREATE network in Europe’, in Colour in Art, Design and Nature, Edinburgh, 24 October 2008.C. Parraman, “Mixing and describing colour”. CREATE (Training event 1), France, 2008

NASA Tech Briefs, October 1996

Topics covered include: Sensors; Electronic Components and Circuits; Electronic Systems; Physical Sciences; Materials; Computer Programs; Mechanics; Machinery/Automation; Manufacturing/Fabrication; Mathematics and Information Sciences; Life Sciences; Books and Reports

Object Recognition

Vision-based object recognition tasks are very familiar in our everyday activities, such as driving our car in the correct lane. We do these tasks effortlessly in real-time. In the last decades, with the advancement of computer technology, researchers and application developers are trying to mimic the human's capability of visually recognising. Such capability will allow machine to free human from boring or dangerous jobs