The Experts below are selected from a list of 84897 Experts worldwide ranked by ideXlab platform
Jurgen Debus - One of the best experts on this subject based on the ideXlab platform.
-
dosimetric verificatIon in water of a monte carlo treatment planning tool for proton helium carbon and Oxygen Ion beams at the heidelberg Ion beam therapy center
Physics in Medicine and Biology, 2017Co-Authors: S Brons, Thomas Haberer, T Tessonnier, T T Bohlen, F Ceruti, A Ferrari, P Sala, Jurgen DebusAbstract:The introductIon of 'new' Ion species in particle therapy needs to be supported by a thorough assessment of their dosimetric properties and by treatment planning comparisons with clinically used proton and carbon Ion beams. In additIon to the latter two Ions, helium and Oxygen Ion beams are foreseen at the Heidelberg Ion Beam Therapy Center (HIT) as potential assets for improving clinical outcomes in the near future. We present in this study a dosimetric validatIon of a FLUKA-based Monte Carlo treatment planning tool (MCTP) for protons, helium, carbon and Oxygen Ions for spread-out Bragg peaks in water. The comparisons between the Ions show the dosimetric advantages of helium and heavier Ion beams in terms of their distal and lateral fall-offs with respect to protons, reducing the lateral size of the regIon receiving 50% of the planned dose up to 12 mm. However, carbon and Oxygen Ions showed significant doses beyond the target due to the higher fragmentatIon tail compared to lighter Ions (p and He), up to 25%. The Monte Carlo predictIons were found to be in excellent geometrical agreement with the measurements, with deviatIons below 1 mm for all parameters investigated such as target and lateral size as well as distal fall-offs. Measured and simulated absolute dose values agreed within about 2.5% on the overall dose distributIons. The MCTP tool, which supports the usage of multiple state-of-the-art relative biological effectiveness models, will provide a solid engine for treatment planning comparisons at HIT.
-
the relative biological effectiveness for carbon and Oxygen Ion beams using the raster scanning technique in hepatocellular carcinoma cell lines
PLOS ONE, 2014Co-Authors: Daniel Habermehl, Stefan Rieken, Jurgen Debus, K Ilicic, Sarah Dehne, Lena Orschiedt, S Brons, Thomas Haberer, Klausjosef Weber, Stephanie E CombsAbstract:Background Aim of this study was to evaluate the relative biological effectiveness (RBE) of carbon (12C) and Oxygen Ion (16O)-irradiatIon applied in the raster-scanning technique at the Heidelberg Ion beam Therapy center (HIT) based on clonogenic survival in hepatocellular carcinoma cell lines compared to photon irradiatIon. Methods Four human HCC lines Hep3B, PLC, HepG2 and HUH7 were irradiated with photons, 12C and 16O using a customized experimental setting at HIT for in-vitro trials. Cells were irradiated with increasing physical photon single doses of 0, 2, 4 and 6 Gy and heavy Ionsingle doses of 0, 0.125, 0.5, 1, 2, 3 Gy (12C and 16O). SOBP-penetratIon depth and extensIon was 35 mm +/−4 mm and 36 mm +/−5 mm for carbon Ions and Oxygen Ions respectively. Mean energy level and mean linear energy transfer (LET) were 130 MeV/u and 112 keV/um for 12C, and 154 MeV/u and 146 keV/um for 16O. Clonogenic survival was computated and realtive biological effectiveness (RBE) values were defined. Results For all cell lines and both particle modalities α- and β-values were determined. As expected, α-values were significantly higher for 12C and 16O than for photons, reflecting a steeper decline of the initial slope of the survival curves for high-LET beams. RBE-values were in the range of 2.1–3.3 and 1.9–3.1 for 12C and 16O, respectively. ConclusIon Both irradiatIon with 12C and 16O using the rasterscanning technique leads to an enhanced RBE in HCC cell lines. No relevant differences between achieved RBE-values for 12C and 16O were found. Results of this work will further influence biological-adapted treatment planning for HCC patients that will undergo particle therapy with 12C or 16O.
Sudipta Seal - One of the best experts on this subject based on the ideXlab platform.
-
luminescence properties of europium doped cerium oxide nanoparticles role of vacancy and oxidatIon states
Langmuir, 2009Co-Authors: Amit Kumar, Suresh Chandra Babu, Ajay S Karakoti, Alfons Schulte, Sudipta SealAbstract:Enhancing the optical emissIon of cerium oxide nanoparticles is essential for potential biomedical applicatIons. In the present work, we report a simple chemical precipitatIon technique to synthesize europium-doped cerium oxide nanostructures to enhance the emissIon properties. Structural and optical properties showed an acute dependence on the concentratIon of Oxygen Ion vacancy and trivalent cerium, which, in turn, could be modified by dopant concentratIon and the annealing temperature. Results from X-ray photoelectron spectroscopy showed an increase in tetravalent cerium concentratIon to 85% on annealing at 900 degrees C. The concentratIon of Oxygen Ion vacancy increased from 1.7x10(20) cm(-3) to 4.1x10(20) cm(-3) with the increase in dopant concentratIon. Maximum emissIon at room temperature was obtained for 15 mol % Eu-doped ceria, which improved with annealing temperature. The role of Oxygen Ion vacancies and trivalent cerium in modifying the emissIon properties is discussed.
-
luminescence properties of europium doped cerium oxide nanoparticles role of vacancy and oxidatIon states
Langmuir, 2009Co-Authors: Amit Kumar, Suresh Chandra Babu, Ajay S Karakoti, Alfons Schulte, Sudipta SealAbstract:Enhancing the optical emissIon of cerium oxide nanoparticles is essential for potential biomedical applicatIons. In the present work, we report a simple chemical precipitatIon technique to synthesize europium-doped cerium oxide nanostructures to enhance the emissIon properties. Structural and optical properties showed an acute dependence on the concentratIon of Oxygen Ion vacancy and trivalent cerium, which, in turn, could be modified by dopant concentratIon and the annealing temperature. Results from X-ray photoelectron spectroscopy showed an increase in tetravalent cerium concentratIon to 85% on annealing at 900 °C. The concentratIon of Oxygen Ion vacancy increased from 1.7 × 1020 cm−3 to 4.1 × 1020 cm−3 with the increase in dopant concentratIon. Maximum emissIon at room temperature was obtained for 15 mol % Eu-doped ceria, which improved with annealing temperature. The role of Oxygen Ion vacancies and trivalent cerium in modifying the emissIon properties is discussed.
-
mechanisms of room temperature metastable tetragonal phase stabilisatIon in zirconia
International Materials Reviews, 2005Co-Authors: Satyajit Shukla, Sudipta SealAbstract:AbstractMechanisms of tetragonal phase stabilisatIon, at room temperature, in nanocrystalline ( 1 μm) are reviewed in detail. The merits, demerits and scope of each individual model are outlined. The analysis of the literature shows that, although the mechanism of tetragonal phase stabilisatIon in bulk ZrO2 is well understood, the room temperature tetragonal phase stabilisatIon mechanism in undoped, nanocrystalline ZrO2 is controversial. Various proposed models, based on surface energy (nanocrystallite size), strain energy, internal and external hydrostatic pressure, structural similarities, foreign surface oxides, anIonic impurities, water vapour and lattice defects (Oxygen Ion vacancies), are discussed in detail. It is proposed that generatIon of excess Oxygen Ion vacancies within the nanocrystalline ZrO2 is primarily responsible for the room temperature tetragonal phase stabilisatIon, below a critical size. Hence, the mechanism of ...
Stephen J. Skinner - One of the best experts on this subject based on the ideXlab platform.
-
mass transport in la0 8sr0 2 0 95crxfe1 xo3 δ scandia stabilized zirconia dual phase composite as a dense layer in Oxygen transport membranes
Journal of Physical Chemistry C, 2018Co-Authors: Zonghao Shen, J A Kilner, Stephen J. SkinnerAbstract:Electrical and Oxygen-Ion transport in the dual-phase composite systems (La0.8Sr0.2)0.95CrxFe1–xO3−δ (LSCrF) (x = 0.3, 0.5, 0.7)–10 mol % Sc2O3–1 mol % CeO2–89 mol % ZrO2 (10Sc1CeSZ) have been inve...
-
on the oxide Ion conductivity of potassium doped strontium silicates
Energy and Environmental Science, 2014Co-Authors: Ryan D Bayliss, John A. Kilner, Stuart N Cook, Sarah Fearn, C Greaves, Stephen J. SkinnerAbstract:Recent reports of remarkably high Oxygen Ion conductivity in a new family of layered strontium silicates have questIoned the ratIonale for materials design in solid electrolytes. Here, we present a re-investigatIon of the crystal structure, microstructure, total conductivity and perform the first direct investigatIon of Oxygen Ion diffusivity of a nominal Sr0.8K0.2Si0.5Ge0.5O2.9 compositIon. The results show very low levels of oxide Ion conductivity, which do not correlate with total electrical conductivity. Furthermore, sub-micron elemental mapping reveals a previously unreported inhomogeneous chemical compositIon. The absence of evidence for secondary phases in the diffractIon data suggests that the additIonal phases are amorphous in nature.
-
anisotropic Oxygen Ion diffusIon in layered prbaco2o5 δ
Chemistry of Materials, 2012Co-Authors: Monica Burriel, Stephen J. Skinner, R J Chater, J Penamartinez, Sarah Fearn, A Berenov, J A KilnerAbstract:Oxygen diffusIon and surface exchange coefficients have been measured on polycrystalline samples of the double perovskite oxide PrBaCo2O5+δ by the isotope exchange depth profile method, using a time-of-flight SIMS instrument. The measured diffusIon coefficients show an activatIon energy of 1.02 eV, as compared to 0.89 eV for the surface exchange coefficients in the temperature range from 300 to 670 °C. Inhomogeneity was observed in the distributIon of the Oxygen-18 isotopic fractIon from grain to grain in the ceramic samples, which was attributed to anisotropy in the diffusIon and exchange of Oxygen. By the use of a novel combinatIon of electron back scattered diffractIon measurements, time-of-flight, and focused Ion beam SIMS, this anisotropy was confirmed by in-depth analysis of single grains of known orientatIon in a ceramic sample exchanged at 300 °C. DiffusIon was shown to be faster in a grain oriented with the surface normal close to 100 and 010 (ab-plane oriented) than a grain with a surface normal...
-
Oxygen Ion conductors
Materials Today, 2003Co-Authors: Stephen J. Skinner, John A. KilnerAbstract:Ionic conductors have always provided a fascinating interdisciplinary field of study ever since their discovery by Faraday at the Royal InstitutIon in London over 200 years ago. More recently, and particularly in the past decade, the pace of research has been rapid, driven by the requirements for new clean energy sources, sensors, and high energy density batteries. A very interesting subgroup of this class of materials are the oxides that display Oxygen Ion conductivity. As well as the intrinsic interest in these materials, there has been a continued drive for their development because of the promise of important technological devices such as the solid oxide fuel cell (SOFC), Oxygen separatIon membranes, and membranes for the conversIon of methane to syngas1. All of these devices offer the potential of enormous commercial and ecological benefits provided suitable high performance materials can be developed. In this article we will review the materials currently under development for applicatIon in such devices with particular reference to some of the newly discovered oxide Ion conductors.
T Tessonnier - One of the best experts on this subject based on the ideXlab platform.
-
dosimetric verificatIon in water of a monte carlo treatment planning tool for proton helium carbon and Oxygen Ion beams at the heidelberg Ion beam therapy center
Physics in Medicine and Biology, 2017Co-Authors: S Brons, Thomas Haberer, T Tessonnier, T T Bohlen, F Ceruti, A Ferrari, P Sala, Jurgen DebusAbstract:The introductIon of 'new' Ion species in particle therapy needs to be supported by a thorough assessment of their dosimetric properties and by treatment planning comparisons with clinically used proton and carbon Ion beams. In additIon to the latter two Ions, helium and Oxygen Ion beams are foreseen at the Heidelberg Ion Beam Therapy Center (HIT) as potential assets for improving clinical outcomes in the near future. We present in this study a dosimetric validatIon of a FLUKA-based Monte Carlo treatment planning tool (MCTP) for protons, helium, carbon and Oxygen Ions for spread-out Bragg peaks in water. The comparisons between the Ions show the dosimetric advantages of helium and heavier Ion beams in terms of their distal and lateral fall-offs with respect to protons, reducing the lateral size of the regIon receiving 50% of the planned dose up to 12 mm. However, carbon and Oxygen Ions showed significant doses beyond the target due to the higher fragmentatIon tail compared to lighter Ions (p and He), up to 25%. The Monte Carlo predictIons were found to be in excellent geometrical agreement with the measurements, with deviatIons below 1 mm for all parameters investigated such as target and lateral size as well as distal fall-offs. Measured and simulated absolute dose values agreed within about 2.5% on the overall dose distributIons. The MCTP tool, which supports the usage of multiple state-of-the-art relative biological effectiveness models, will provide a solid engine for treatment planning comparisons at HIT.
Harry L Tuller - One of the best experts on this subject based on the ideXlab platform.
-
scalable Oxygen Ion transport kinetics in metal oxide films impact of thermally induced lattice compactIon in acceptor doped ceria films
Advanced Functional Materials, 2014Co-Authors: Jennifer L M Rupp, Emiliana Fabbri, Dario Marrocchelli, Jeong Woo Han, Di Chen, Enrico Traversa, Harry L TullerAbstract:In this paper, we focus on the effect of processing-dependent lattice strain on Oxygen Ion conductivity in ceria based solid electrolyte thin films. This is of importance for technological applicatIons, such as micro-SOFCs, microbatteries, and resistive RAM memories. The Oxygen Ion conductivity can be significantly modified by control of lattice strain, to an extent comparable to the effect of doping bulk ceria with catIons of different diameters. The interplay of dopant radii, lattice strain, microstrain, anIon-catIon near order and Oxygen Ion transport is analyzed experimentally and interpreted with computatIonal results. Key findings include that films annealed at 600 °C exhibit lattice parameters close to those of their bulk counterparts. With increasing anneal temperature, however, the films exhibited substantial compactIon with lattice parameters decreasing by as much as nearly 2% (viz, Δd600-1100°C: -1.7% (Sc+3) > -1.5% (Gd +3) > -1.2% (La+3)) for the annealing temperature range of 600-1100°C. Remarkably 2/3rd of the lattice parameter change obtained in bulk ceria upon changing the acceptor diameter from the smaller Sc to larger La, can be reproduced by post annealing a film with fixed dopant diameter. While the impact of lattice compactIon on defect associatIon/ordering cannot be entirely excluded, DFT computatIon revealed that the main effect appears to result in an increase in migratIon energy and consequent drop in Ionic conductivity. As a consequence, it is clear that annealing procedures should be held to a minimum to maintain the optimum level of Oxygen Ion conductivity for energy-related applicatIons. Results reveal also the importance to understand the role of electro-chemo-mechanical coupling that is active in thin film materials. Electro-chemo-mechanic coupling is investigated for Ionic conducting ceria-based materials. The impact of lattice strain on the near order characteristics and Ionic conductivity is experimentally studied for bulk pellets and thin films. Density functIonal theory computatIon reveals an increase in migratIon energy and consequent drop in Ionic conductivity, observed for lattice strains of up to 2% in doped ceria thin films. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
-
a novel titanate based Oxygen Ion conductor gd2ti2o7
Solid State Ionics, 1995Co-Authors: Steve Kramer, Harry L TullerAbstract:Abstract Electrical conductivity measurements are reported on the rare-earth pyrochlore compound Gd2Ti2O7 as a functIon of temperature, Oxygen partial pressure and aliovalent dopant concentratIon. Doping experiments were performed on both the Gd and Ti catIon sublattices with doping levels of 0.0 to 15.0 mol% catIon substitutIon. For Ca doped (Gd1 − x Cax)2Ti2O7, the Ionic conductivity, σi, was observed to increase over 2 orders of magnitude with increasing x reaching a maximum value of 5 × 10−2 S/cm at 1000 °C and x = 0.10. This value represents the highest Ionic conductivity reported to date for a titanate based material. Accompanying the increase in σi was a corresponding decrease in Ionic activatIon energy Ei which dropped from 0.94 to 0.63 eV in the compositIon range of x = 0.00 to x = 0.02. Similar increases in σi and decreases in Ei were evident for “B” site Al doping in Gd2(Ti1 − yAly)2Ti2O7 but valid only up to a doping level of y = 0.01. At higher dopant levels, σi dropped sharply when the solubility limit was exceeded, as confirmed by X-ray diffractIon lattice parameter measurements. The compositIon dependence of the Ionic conductivity for both “A” and “B” site acceptor dopants are discussed in terms of defect interactIons leading to favorable transport paths.
