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[en] Purpose: To characterize the dosimetric effects of field aperture margin design in Stereotactic Body Radiation Therapy (SBRT). Methods: Three artificial spherical PTVs, with diameter of 10mm, 20mm and 30mm, were created on CT images of a human body thoracic phantom. Seven non-coplanar isocentric fields were used for treatment planning. For each PTV, treatment plans with margins 0mm, 1mm, 2mm and 3mm were planned. Dosimetric comparison among plans was done considering the following parameters: prescribed isodose line for target coverage, maximum dose, mean dose as well as dose spillages of V80, V50, and V20. Results: Corresponding to aperture margins of 0mm, 1mm,2m and 3mm used in the treatment planning, the percentage of isodose line chosen for dose prescription increases from 65% to 93% for 10mm PTV, 70% to 92% for 20mm PTV, and 75% to 92% for 30mm PTV. The maximum dose decrease accordingly from 155.7% to 109.5% for 10mm PTV, 145% to 111.6% for 20mm PTV, 137% to 112.2% for 30mm PTV. The mean dose decrease from 138.% to 104.4% for 10mm PTV, 122.8% to 106.1% for 20mm PTV, 121.3% to 106% for 30mm PTV. Dose spillages (mm3) increase (V80−2.6 to 4.02, V50−4.55 to 9.3, V20–87.86 to 101.71) for 10 mm PTV, (V80−6.78 to 9.89, V50–13.46 to 20.4, V20-119.16 to 219.1) for 20 mm PTV, (V80–22.01 to 28.59, V50–41.56 to 52.66, V20-532.71 to 551.84) for 30 mm PTV. Conclusion: In SBRT treatment planning, tight field aperture margin requires prescribing dose to lower isodose line that leading to higher dose inhomogeneity and higher mean dose to PTV. Loose margin allows prescribing dose to higher isodose line, therefore improves the dose homogeneity. However, it increases dose spillages. Clinician could try different margins according to the PTV size and location of surrounding critical organs to optimize the dose delivered to the patient
[en] The thesis is centered around an adaptive method for calculating vorticity dominated flows in two dimensions. The authors uses the vortex method after a general transformation is applied to the flow region because the vortex elements describe the local flow more accurately if the transformation is suitably chosen. A good example of this is boundary layer flow, where vortex sheets serve to represent the vorticity as long as the Prandtl equation holds, but the method is inaccurate in the region where transition from Prandtl to fall Navier-Stokes equations occurs. Physical intuition tells us that the transition should be a natural process and therefore should be smooth, depending fully on the local flow and geometry. It is shown that this can be realized with a good spatial transformation which takes account of the above factors. In the special case of finite-area vortex regions and within 1st-order accuracy, the Biot-Savart law is explicit and equivalent to the elliptic vortex method with the axes ratio and orientation evolving according to the continuous transformation. The transformation is obtained from the real flow by averaging, truncation and satisfying the same boundary condition as the real flow. Some experiments for typical flows are carried out in detail. He also modeled a two-dimensional, dilute fluid-particle system with low Reynolds number flow around cylindrical particles and high Reyonlds number with respect to the bulk flow. Full particle methods are used to solve both the fluid and particle phase flows. The vortex method is used for the nearly incompressible fluid phase. The compressible particle phase is taken care of by using Voronoi diagrams suitably. On the microscopic scale the Stokes-Oseen formula is used to represent the forces on particles
[en] Quantitative convergent beam electronic diffraction (QCBED) method is a powerful tool for the investigation of the atomic and electronic structure of crystals. In this work, a global optimization algorithm has been adopted and a new fitting manner has been suggested in our recently developed QCBED program. A study of the charge density distribution in intermetallics is demonstrated as an example. Using the QCBED method, an investigation of lattice distortion in oxides is attempted
[en] This paper aims at investigating the reasons for the complex and long lead time from global suppliers that causes inventory shortages. It focuses on supply chain risk management in global sourcing. This study has revealed all the specific risks of a global sourcing project and has provided some solutions for risk management: three-step risk management, safety stock, data sharing and driving supplier performance. Design/methodology/approach: A qualitative study is conducted to propose concrete recommendations on three topics: risk management, safety stock and information sharing. A semi-structured survey-guided interview was used to collect related data, and the answers were assessed using syntactic, lexical, thematical and NVivo software analysis. Findings: This study has revealed all the specific risks of a global sourcing project and has provided some solutions for risk management: three-step risk management, safety stock, data sharing and driving supplier performance. Originality/value: Through research work, we have noticed that the world of the Supply Chain is constantly evolving and that it is becoming more and more complex. Through these interviews, we have noticed that the role of purchasing is changing differently in each sector.
[en] Using redox-active alkylamine adsorbates, the authors have studied monolayer growth and adsorbate-adsorbate exchange kinetics on YBa2Cu3O7-δ. Herein the authors show that the formation kinetics for monolayers of FcC-(O)NH(CH2)4NH2[Fc=(η5-C5H4)Fe(η5-C5H5)] do not follow typical Langmuir adsorption isotherm behavior. Specifically, a parabolic tailing in the isotherms has been attributed to the diffusion of adsorbates through the porous material. The displacement of surface-adsorbed FcC(O)NH(CH2)4NH2 by another redox-active alkylamine, Fc(CH2)6NH2, has been studied and determined to be a reversible and dynamic process. Concentration dependence studies suggest that the exchange takes place via an associative process involving surface Cu(II) sites. The lability of the surface-adsorbed alkylamine ligands and the proposed exchange mechanism are consistent with the solution coordination chemistry of Cu(II)
[en] Severe water shortage has long been acknowledged as one major limiting factor for global cotton production, and cultivation of cotton varieties with strong drought resistance is of important economic and social significances. In this study, the Xinjiang upland cotton variety Xinluzao 42 was transformed with the SiDhn2 gene by optimized agrobacterium transformation system. The integration of SiDhn2 gene into cotton genome was confirmed by PCR and Southern blot hybridization, and the drought resistance of transgenic and corresponding receptor cotton plants and their physiological indexes under drought stress were detailedly analyzed. Multiple physiological and biochemical indexes including soluble sugar content, free proline content, chlorophyll content, relative water content, net photosynthetic rate, transpiration rate, intercellular CO/sub 2/ concentration in transgenic cotton expressing SiDhn2 gene under drought stress were significantly higher than those of receptor cotton. More importantly, the transgenic cotton plants exhibited remarkably decreased boll abscission rate and highly increased seed yield, indicating the significant role of SiDhn2 gene in cotton drought resistance and its great application potential in agricultural production. (author)
[en] Flavor release from powders depends on the glass transition temperature (Tg) and water absorption. This study reports a simple method to estimate the apparent Tg by aroma sensing upon flavor release from spray-dried powders. Four different wall materials (maltodextrin (MD), MD blends with fructose at 20 and 40wt%, and yeast cells) were used to encapsulate flavors by spray- drying. The apparent Tg values of MD and MD with 20 and 40wt% fructose were determined as 130, 110, and 75 °C, respectively, similar to those calculated by the Gordon–Taylor equation. The slow flavor release from dried-yeast powder afforded the highest Tg. (Author)
[en] The particle packing of MP tape media is explored by means of a new measurement technique. Utilizing a narrow gap length record head, the tape is evaluated throughout its thickness with the use of an incremental DC erase measurement. A quantitative analysis of the medium noise spectra at different erase currents allows for the packing fluctuations at different depths into the tape to be proportioned. The technique provides a method for evaluating the interface between the magnetic recording layer and non-magnetic underlayer in dual-layer tape, and measurements indicate that interfacial roughness at the magnetic coating backside in some dual-layer media is a major source of medium noise
[en] A Gas Phase Field Ionization Ion Source has been built specifically for use with the University of Melbourne Proton Microprobe. The source is extremely bright making it suitable for use with high resolution probe forming systems. Beam current stability and emitter lifetime is greatly enhanced by the use of iridium field emitters, allowing for reproducible source performance. Current output as a function of source parameters has been measured indicating that nano amps of current are available in a beam up to 105 times brighter than that presently used in the Melbourne probe
[en] The influence of two different locations of sputter guns on the morphological and structural properties of Cu–In–Ga precursors and Cu(In,Ga)Se2 (CIGS) thin films was investigated. All the precursors contained cauliflower-like nodules, whereas smaller subnodules were observed on the background. All the precursors revealed apparent three-layered structures, and voids were observed at the CIGS/SLG interface of Sets 1 and 2 films rather than Set 3 film. EDS results indicated that all CIGS thin films were Cu-deficient. Based on the grazing incidence X-ray diffraction (GIXRD) patterns, as-selenized films showed peaks corresponding to the chalcopyrite-type CIGS structure. Depth-resolved Raman spectra showed the formation of a dominant CIGS phase inside the films for all the as-selenized samples investigated, and of an ordered vacancy compound (OVC) phase like Cu(In,Ga)3Se5 or Cu(In,Ga)2Se3.5 at the surface and/or CIGS/SLG interface region of Sets 2 and 3 films. No evidence was obtained on the presence of an OVC phase in Set 1 CIGS film, which may be speculated that long-time annealing is contributed to suppress the growth of OVC phases. The results of the present work suggest that the metallic precursors deposited with the upright-location sputter gun might be more appropriate to prepare CIGS thin films than those sputtered with the titled-location gun.