204 research outputs found
Effects of ionizing radiation in biomolecules, cells and tissue/organs: basic mechanisms and applications for cancer therapy, medical imaging and radiation protection
No full textAuger-electron angular distributions calculated without the two-step approximation: Calculation of angle-resolved resonant Auger spectra of C_2H_2
No full textAnalytic expressions for the direct, resonant, and interference contributions to the differential cross section of a resonant Auger process, produced by the inner-shell photoionization of a linear molecule either “fixed in space” or belonging to a gas of randomly oriented molecules, have been derived following Dill’s procedures [ Dill et al. Phys. Rev. Lett. 45 1393 (1980)], but going beyond the two-step approximation. Angle-resolved Auger spectra of the C2H2 molecule measured on top of the C 1s→π* resonance [ Kivimäki et al. J. Phys. B 30 4279 (1997)] have been calculated together with asymmetry parameters, analyzing also the different contributions to the electron angular distributions
Vertical transport through laterally periodically modulated heterostructures
No full textThe ballistic transport in a laterally periodically modulated heterojunction connecting two reservoirs is studied: this can model the presence of an ordered layer of self-organized quantum dots. The problem is solved in the envelope function formalism using a three-dimensional (3D) generalization of the transfer matrix approach that exploits the two-dimensional (2D) lattice periodicity. Illustrative numerical results are presented showing qualitatively different behaviors of the transmission coefficients due to the multichannel nature of the propagation, In particular, deep minima of the transmission occur due to destructive interference between different conducting channels, a situation that cannot be realized in the absence of the lateral modulation. (C) 2001 Elsevier Science Ltd. All rights reserved
On Molière and Fermi-Eyges scattering theories in hadrontherapy
No full textWe consider the evaluation of lateral spread distributions of charged particle beams at therapeutic energies, due to an absorber in the form of a homogeneous slab or of a stack. We show that the Molière theory has the same degree of flexibility as the Fermi-Eyges, but is much more accurate and does not present particular computing difficulties with the energy loss formula we have employed. It is also shown that the non-Gaussian shape of the projected one dimensional (1D) distributions is not a complication for passing from the projected to the spatial two-dimensional (2D) distribution, if one assumes circular symmetry. All the calculations are compared with the results of the FLUKA code. The nuclear interaction is not considered here, because it is outside of the scope of this work. © 2017 Institute of Physics and Engineering in Medicine
Anomalous doping dependence of fluctuation induced diamagnetism in Y1-xCaxBa2Cu3OY superconductors
No full textAnomalou Doping Dependence of the Fluctuation-Induced Diamagnetism in Superconductors of YBCO Family
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On the parametrization of lateral dose profiles in proton radiation therapy
No full textPurpose: The accurate evaluation of the lateral dose profile is an important issue in the field of proton radiation therapy. The beam spread, due to Multiple Coulomb Scattering (MCS), is described by the Molière's theory. To take into account also the contribution of nuclear interactions, modern Treatment Planning Systems (TPSs) generally approximate the dose profiles by a sum of Gaussian functions. In this paper we have compared different parametrizations for the lateral dose profile of protons in water for therapeutical energies: the goal is to improve the performances of the actual treatment planning. Methods: We have simulated typical dose profiles at the CNAO (Centro Nazionale di Adroterapia Oncologica) beamline with the FLUKA code and validated them with data taken at CNAO considering different energies and depths. We then performed best fits of the lateral dose profiles for different functions using ROOT and MINUIT. Results: The accuracy of the best fits was analyzed by evaluating the reduced χ2, the number of free parameters of the functions and the calculation time. The best results were obtained with the triple Gaussian and double Gaussian Lorentz-Cauchy functions which have 6 parameters, but good results were also obtained with the so called Gauss-Rutherford function which has only 4 parameters. Conclusions: The comparison of the studied functions with accurate and validated Monte Carlo calculations and with experimental data from CNAO lead us to propose an original parametrization, the Gauss-Rutherford function, to describe the lateral dose profiles of proton beams
CSR STRATEGIES AND VALUE CREATION IN THE AGRO-FOOD SECTOR: A COMPARATIVE PERSPECTIVE
No full textThe research aims to analyze and compare CSR strategies of four companies in the Italian Agro-food sector with the aim of investigating the level of integration of the CSR policies into the business strategy. The analysis aims to investigate 1) whether the leadership of the market, in terms of revenues, geographical and sectoral pervasiveness, is a factor that can lead to a greater focus on social and environmental issues and to a greater integration of CSR in business strategy and (2) the role of the CSR strategies in value creation in the Agro-food sector in the current economic recession. The findings underlines the best practices and the positioning of each company in terms of CSR integration into the business strategy
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