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[en] The ZED-2 (Zero Energy Deuterium) reactor is an experimental low-power critical facility located at the Atomic Energy of Canada Limited Chalk River Laboratories in Ontario, Canada. The facility is used to perform physics experiments in support of the CANDU and Advanced CANDU Reactor (ACR) programs. The reactor core is a large cylindrical vessel in which reactor fuel rods are positioned vertically. A heavy water moderator is pumped into the vessel to make the reactor critical. The ZED-2 design is very versatile: it can accommodate mixed fuel types in a variable number of fuel rods each with or without CANDU-type or ACR-type channels; channel coolants can be light or heavy water, or air, and can vary from channel to channel; lattices can be square or hexagonal with continuously variable lattice pitch; and some CANDU-type channels can be heated. Many of the experiments performed involve uniform cores containing the same type of fuel and channel in each fuelled location. However, at times a smaller number of fuel rods and channels are placed in the centre of a larger region of reference fuel to form a critical core assembly. These are called substitution experiments. The purpose of this paper is to describe why substitution experiments are performed, detail how they have historically been conducted and analyzed to extract the desired data from the test fuel, and finally how they are performed and analyzed today using specialized software.
[en] With the start of the Large Hadron Collider (LHC) at CERN it is now possible to study physics at the TeV-scale for the first time. At this unprecedented energy range it is expected that the Standard Model of particle physics will reach its limits and new phenomena can appear. One of the main goals of the ATLAS experiment is the search for physics beyond the Standard Model. This includes observing supersymmetric particles, which are predicted to have masses of several hundred GeV up to a few TeV. The subject of this thesis is the search for supersymmetric particles in final states with jets and missing transverse energy and the evaluation of the ATLAS discovery potential for supersymmetric particles in the Minimal Supersymmetric Standard Model (MSSM) parameter space for these channels. Different centre-of-mass energies of √(s)=14 TeV, 10 TeV and 7 TeV are assumed. For many R-parity conserving SUSY models, the decay of supersymmetric particles leads to detector signatures characterized by missing transverse energy and multi-jets, sometimes accompanied by leptons. In this thesis, SUSY searches with ≥2-6 jets and 0-2 leptons (electrons, muons) are studied, with a focus on 0-lepton channels, that are expected to be sensitive in large areas of the SUSY parameter space. The search strategies for supersymmetric particles are applied on a sets of differently constrained SUSY models and on several hundred SUSY signals, generated within the pMSSM subspace of the MSSM. The goal of this work is to explore the reach of the performed SUSY searches for completely different decay signatures. It will be shown that the ATLAS SUSY searches cover a large parameter space of SUSY models. The first p-p collisions at a centre-of-mass energy of √(s)=7 TeV in March 2010 allow a comparison of the measured data with the Monte Carlo predictions, in order to see how well the detector response is understood in the context of SUSY specific variables used in the 0-lepton analyzes. All measurements are found to be in agreement with the Standard Model expectations within the associated systematic uncertainties. The results indicate that the ATLAS SUSY searches cover a large parameter space and it is possible to discover or exclude some SUSY models already with a few pb-1 of integrated luminosity.
[en] Nanotechnology and its applications have captured a worldwide market. Nanomaterials that have been developed using this technology can be incorporated into the devices so that renewable energy can be converted or generated more efficiently. Nanomaterials have the potential to change the way we generate, deliver and use energy. Hydrogen cells are used in auto industry as a viable power source. Compressed hydrogen tanks are used to supply Hydrogen, and Oxygen is used from the air directly. There is no pollution caused by hydrogen fuel cell autos since the only emission is water. Organic dyes (dye sensitizers), which are sensitive to light, can absorb a broader range of the sun's spectrum. A dye-sensitized solar cell has three primary parts. On top is a transparent anode made of fluoride-doped tin dioxide (SnO/sub 2/: F) deposited on the back typically of a glass plate. On the back of this conductive plate is a thin layer of titanium dioxide (TiO/sub 2/), which forms into a highly nanoporous structure with an extremely large surface-area. After soaking the film in the dye solution, a thin layer of the dye is left covalently bonded to the surface of the TiO/sub 2/ . Computational material science and nanoscience can play many critical roles in renewable energy research. These include: finding the right materials for hydrogen storage; finding the most reliable and efficient catalyst for water dissociation in hydrogen production; finding a cheap, environmentally benign, and stable material for efficient solar cell applications; and understanding the photo-electron process in a nanosystem, and hence helping design efficient nanostructure solar cells. (author)
[en] A large part of the biomass is used for non-commercial purposes and mostly for cooking and heating, but the use is not sustainable, because it destroys soil-nutrients, causes indoor and outdoor pollution, adds to greenhouse gases, and results in health problems. Commercial use of biomass includes household fuelwood in industrialized countries and bio-char (charcoal) and firewood in urban and industrial areas in developing countries. The most efficient way of biomass utilization is through gasification, in which the gas produced by biomass gasification can either be used to generate power in an ordinary steam-cycle or be converted into motor fuel. In the latter case, there are two alternatives, namely, the synthesis of methanol and methanol-based motor fuels, or Fischer-Tropsch hydrocarbon synthesis. This paper deals with the technological overview of the state-of-the-art key biomass-conversion technologies that can play an important role in the future. The conversion routes for production of Heat, power and transportation fuel have been summarized in this paper, viz. combustion, gasification, pyrolysis, digestion, fermentation and extraction. (author)
[en] The goal of this study was to use liver explant correlation to assess the diagnostic accuracy of diffusion-weighted (DW)-MRI for hepatocellular carcinoma (HCC). Thirty-seven patients were retrospectively identified who had undergone liver transplantation and had preoperative, respiratory-triggered, single-shot echo-planar DW-MRI. Two independent blinded observers evaluated the DW-MRI images for HCC and comparison was made with the explanted specimens. By pathology, 29 HCCs (mean largest diameter 2.0 cm; range 0.7–4.0 cm) were identified in 20 patients. Sensitivity and specificity for reader 1 were 55 and 92%, and for reader 2 were 45 and 100%. There was ‘substantial’ inter-observer agreement (kappa = 0.64). DW-MR is not sensitive enough for HCC to be used as a stand-alone sequence, although its high specificity suggests that it is likely valuable as a component of a liver MRI protocol.
[en] In the present work we describe our results concerning the calculation of equation of state of symmetric zero temperature nuclear matter and the microscopic optical potential using the soft-core Argonne inter-nucleon potentials in first order Brueckner–Hartree–Fock (BHF) theory. The nuclear matter saturates at a density 0.228 nucleon/fm3 with 17.52 MeV binding energy per nucleon for Argonne av-14 and at 0.228 nucleon/fm3 with 17.01 MeV binding energy per nucleon for Argonne av-18. As a test case we present an analysis of 65 and 200 MeV protons scattering from 208Pb. The Argonne av-14 has been used for the first time to calculate nucleon optical potential in BHF and analyze the nucleon scattering data. We also compare our reaction matrix results with those using the old hard-core Hamada–Johnston and the soft-core Urbana uv-14 and Argonne av-18 inter-nucleon potentials. Our results indicate that the microscopic potential obtained using av-14 gives marginally better agreement with the experimental data than the other three Hamiltonians used in the present work. (author)
[en] The reaction 96Mo(d, p)97Mo has been studied at 12 MeV using the tandem Van de Graaff accelerator and a multi-channel magnetic spectrograph at the Atomic Weapon Research Establishment, Aldermaston, England. Angular distributions of protons are measured at 12 different angles from 5° to 87.5° at an interval of 7.5° and the reaction products are detected in nuclear emulsion plates. Thirty levels in the energy range from 0.000 to 2.458 MeV have been observed and absolute differential cross-sections for these levels have been measured. The data are analyzed in terms of the distorted-wave Born approximation (DWBA) theory of the direct reactions, and spins, parities and spectroscopic factors are deduced for various levels. Ambiguity in the spin assignments of d5/2 and d3/2 which is allowed in ln = 2(d, p) transition is removed by using the corresponding L-value of the 95 Mo(t, p)97Mo reaction at Et = 12 MeV. Determined value of the sum of spectroscopic factors for transfers of d5/2 neutrons suggests configuration mixing in the ground state of 96Mo. The properties of the levels in 97Mo are compared with previous experimental results and theoretical predictions. (author)
[en] In this work we study the process e++e-→J/Ψ+ηc at energy √S = 10.6 GeV observed recently at B-factories whose measurements were made by Babar and Belle groups. We calculate the cross-section for this process in the Bethe–Salpeter formalism under Covariant Instantaneous Ansatz. To simplify our calculation, the heavy quark approximation is employed in the quark and gluon propagators. In the exclusive process of e+e- annihilation into two heavy quarkonia, the cross-section calculated in this scenario is compatible with the experimental data of Babar and Belle. (author)
[en] Lowering the string scale in the TeV region provides a theoretical framework for solving the mass hierarchy problem and unifying all interactions. The apparent weakness of gravity can then be accounted by the existence of large internal dimensions, in the sub-millimeter region, and transverse to a braneworld where our universe must be confined. I review the main properties of this scenario and its experimental implications. (author)