Bibliographies thématiques / MONTE-CARLO TRACK STRUCTURE

Littérature scientifique sur le sujet « MONTE-CARLO TRACK STRUCTURE »

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Publié le 11 mars 2023

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Articles de revues sur le sujet "MONTE-CARLO TRACK STRUCTURE"

Toburen, Larry H. « Challenges in Monte Carlo track structure modelling ». International Journal of Radiation Biology 88, n^o 1-2 (19 mai 2011) : 2–9. http://dx.doi.org/10.3109/09553002.2011.574781.

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Douglass, Michael, Scott Penfold et Eva Bezak. « Preliminary Investigation of Microdosimetric Track Structure Physics Models in Geant4-DNA and RITRACKS ». Computational and Mathematical Methods in Medicine 2015 (2015) : 1–8. http://dx.doi.org/10.1155/2015/968429.

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The major differences between the physics models in Geant4-DNA and RITRACKS Monte Carlo packages are investigated. Proton and electron ionisation interactions and electron excitation interactions in water are investigated in the current work. While these packages use similar semiempirical physics models for inelastic cross-sections, the implementation of these models is demonstrated to be significantly different. This is demonstrated in a simple Monte Carlo simulation designed to identify differences in interaction cross-sections.

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Endo, S., E. Yoshida, H. Nikjoo, S. Uehara, M. Hoshi, M. Ishikawa et K. Shizuma. « A Monte Carlo track structure code for low energy protons ». Nuclear Instruments and Methods in Physics Research Section B : Beam Interactions with Materials and Atoms 194, n^o 2 (août 2002) : 123–31. http://dx.doi.org/10.1016/s0168-583x(02)00497-4.

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Pater, Piotr, Jan Seuntjens, Issam El Naqa et Mario A. Bernal. « On the consistency of Monte Carlo track structure DNA damage simulations ». Medical Physics 41, n^o 12 (18 novembre 2014) : 121708. http://dx.doi.org/10.1118/1.4901555.

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Díaz-Díaz, Jorge A., Eugenio Torres-García, Rigoberto Oros-Pantoja, Liliana Aranda Lara et Patricia Vieyra-Reyes. « New track-structure Monte Carlo code for 4D ionizing photon transport ». Radiation Effects and Defects in Solids 173, n^o 7-8 (28 juin 2018) : 567–77. http://dx.doi.org/10.1080/10420150.2018.1484744.

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Pasciak, A. S., et J. R. Ford. « High-speed evaluation of track-structure Monte Carlo electron transport simulations ». Physics in Medicine and Biology 53, n^o 19 (9 septembre 2008) : 5539–53. http://dx.doi.org/10.1088/0031-9155/53/19/018.

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Emfietzoglou, D., A. Akkerman et J. Barak. « New Monte Carlo calculations of charged particle track-structure in silicon ». IEEE Transactions on Nuclear Science 51, n^o 5 (octobre 2004) : 2872–79. http://dx.doi.org/10.1109/tns.2004.835061.

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Nikjoo, H., P. O'Neill, M. Terrissol et D. T. Goodhead. « Quantitative modelling of DNA damage using Monte Carlo track structure method ». Radiation and Environmental Biophysics 38, n^o 1 (12 mai 1999) : 31–38. http://dx.doi.org/10.1007/s004110050135.

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Sattinger, D., et Y. S. Horowitz. « Track structure calculations in LiF:Mg,Ti : A Monte Carlo study of the ‘track escape’ parameter ». Radiation Measurements 43, n^o 2-6 (février 2008) : 185–89. http://dx.doi.org/10.1016/j.radmeas.2007.12.024.

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Uehara, Shuzo, et Hooshang Nikjoo. « Monte Carlo Track Structure Code for Low-Energy Alpha-Particles in Water ». Journal of Physical Chemistry B 106, n^o 42 (octobre 2002) : 11051–63. http://dx.doi.org/10.1021/jp014004h.

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Thèses sur le sujet "MONTE-CARLO TRACK STRUCTURE"

Coghill, Matthew Taylor. « Radiobiological modeling using track structure analysis ». Thesis, Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/44731.

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The purpose of this thesis is to present data pertinent to and propose conclusions regarding the coordination of radiobiologic effectiveness (RBE) and linear energy transfer (LET). RBE is a quantity relating the effectiveness of different radiations in causing cell death. LET is a measure of the rate of energy transferred to material by an ionizing particle. This relationship of these values varies for different particles. The reason for this is still inconclusive. The petitioner has made use of a toolkit for Geant4, known as Geant4-DNA, to perform track-structure analysis on a chromosome model. Geant4 is an object-oriented program for the "simulation of the passage of particles through matter" developed by CERN that makes use of Monte Carlo methods and is expanded by Geant4-DNA to handle low-energy electron physics as well as physic-chemical effects. The chromosome model, in this case, has been developed by the petitioner as a nucleus with a basic, uniform distribution of chromatin. Radiation damage to DNA, in the form of aberrations, lesions and strand breaks, can be coordinated to energy deposited or number of ionizations occurring in the target (in this case DNA or chromatin fiber). Certain threshold values have been established as indicate of different types of DNA damage. The ultimate goal of this work is to score these clusters of events against the threshold values to determine the severity of DNA damage. The final comparison of the results for different particles will provide for a better understanding of the RBE-LET relationships by improving the understanding of the underlying nanodosimetric qualities.

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Liamsuwan, Thiansin. « Development of Monte Carlo track structure simulations for protons and carbon ions in water ». Doctoral thesis, Stockholms universitet, Fysikum, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-81461.

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The goal of radiation therapy is to eradicate tumour cells while minimising radiation dose to healthy tissues. Ions including protons and carbon ions have gained increasing interest for cancer treatment. Advantages of ion beam therapy are conformal dose distribution, and for ions heavier than protons increased biological effectiveness in cell killing, compared to conventional radiation therapy using photons. Despite these advantages, fundamental problems in ion beam therapy include accuracy of dose determination at the cellular level, and characterisation of the radiation quality at the microscopic scale. Due to the high density of interactions along ion tracks, inhomogeneity of dose and track parameters at the cellular level is one of the major concerns for ion beam therapy. The aim of the thesis is to develop computational tools for dosimetry of ion tracks at the molecular level. Event-by-event Monte Carlo track structure (MCTS) simulations were developed for full-slowing-down tracks of protons and carbon ions in water representing cellular environment. In Paper I, the extension of the MCTS code KURBUC_proton was carried out to energies up to 300 MeV, covering the entire proton energy range used in radiation therapy. Physical properties and microdosimetry of proton tracks were investigated and benchmarked with the experimental data. Papers II-V describe the development of the MCTS code for full-slowing-down tracks of carbon ions. In Papers II-IV, the classical trajectory Monte Carlo (CTMC) model was developed for the calculation of interaction cross sections for low and intermediate energy carbon projectiles of all charge states (C0 to C6+) in water. In Paper V, the calculated cross sections were implemented in a new MCTS code KURBUC_carbon simulating carbon ions of energies 1-104 keV/u in water. This development allows the investigation of track parameters in the Bragg peak region of carbon ion beams. Publication of the thesis and the published papers make contribution to the physics of ion interactions in matter, and provide a new and complete database of electronic interaction cross sections for low and intermediate energy carbon projectiles of all charge states in water. The MCTS codes for protons and carbon ions provide new tools for biophysical study, including microdosimetry, of ion tracks at cellular and subcellular levels, in particular in the Bragg peak region of these ions.

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Submitted. Paper 5: Submitted.

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Lee, Brian. « A Monte Carlo investigation of radiation damage to chromatin fibers and production of DNA double strand breaks using Geant4-DNA code ». Thesis, Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/53106.

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In the presented research we propose to improve on historically accepted radiobiological models via Monte Carlo simulation of radiation tracks passing through a cell nucleus modeled with up-to-date subnuclear structures. This is performed by generating a radiation track database using the Monte Carlo code, Geant4-DNA, that simulates radiation interactions at the nanometer scale of DNA. These tracks are called upon from the database and intersected with a cell nucleus model that incorporates DNA-containing structures. This allows for a Monte Carlo simulation of how DNA double strand breaks are produced by radiation. The results can be used to correlate to many experimentally observed biological endpoints, e.g. chromosome aberrations as well as cell death.

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Pasciak, Alexander Samuel. « The development of a high speed solution for the evaluation of track structure Monte Carlo electron transport problems using field programmable gate arrays ». [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-2558.

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Dos, Santos Morgane. « Modélisation de la topologie des dépôts d’énergie créés par un rayonnement ionisant à l’échelle nanométrique dans les noyaux cellulaires et relation avec les événements précoces radio-induits ». Thesis, Bordeaux 1, 2013. http://www.theses.fr/2013BOR14865/document.

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Les rayonnements ionisants sont connus pour induire des dommages critiques au sein de la matière biologique et spécialement au sein de l’ADN. Parmi ces dommages, les cassures doubles brins de l’ADN (DSB) sont considérées comme les principales responsables des effets létaux des rayonnements. Comprendre et prédire comment ces cassures sont créées et réparées dans les noyaux cellulaires demeure un défi dans la recherche en radiobiologie. Ce travail s’inscrit dans ce contexte, dans la modélisation des cassures double brin de l’ADN (DSB) à partir des dépôts d’énergie créés par l’irradiation au niveau intracellulaire. Le détail topologique au niveau nanométrique des dépôts d’énergie nécessaire à ce travail est obtenu par modélisation Monte Carlo à l’aide du code Geant4 et, en particulier son extension Geant4-DNA pour des processus à très faible énergie. Les dommages étudiés étant ceux localisés dans l’ADN, le premier objectif de ce travail a été de réaliser une géométrie détaillée de celui-ci afin de l’implémenter dans les calculs Monte Carlo. Deux types de noyaux cellulaires, représentant un fibroblaste et un endothélium, ont été décrits afin d’évaluer l’influence de la densité d’ADN dans les résultats sur la topologie des dépôts pouvant donner lieux à des cassures de la molécule. Cette géométrie nous permet d’effectuer une première sélection des dépôts d’énergie pouvant contribuer aux cassures car situées sur la chaîne sucre-phosphate. Ces dépôts sont ensuite analysés à l’aide d’un algorithme de clustérisation de manière à les regrouper sous forme d’agrégats afin d’étudier leur localisation et complexité. Néanmoins, dans cette étude, seule les interactions physiques entre les rayonnements ionisants et la cible sont modélisées, il n’est donc pas possible d’obtenir un nombre absolu de cassures de brins car cette modélisation n’inclue pas l’étape de création et de transport des radicaux libres pouvant donner lieu à des dommages indirects. Ainsi, le but de ce travail était d’évaluer la dépendance relative des dommages radio-induits directs avec la densité d’ADN, la qualité du rayonnement, la morphologie du noyau ou encore la condensation de la chromatine. Les différentes modélisations réalisées ont permis de quantifier l’influence de ces différents paramètres dans le nombre et la complexité des dommages directs induits dans l’ADN, pouvant ensuite contribuer aux effets tardifs sur le devenir cellulaire
Ionizing radiations are known to induce critical damages on biological matter and especially on DNA. Among these damages, DNA double strand breaks (DSB) are considered as key precursor of lethal effects of ionizing radiations. Understand and predict how DNA double and simple strand breaks are created by ionising radiation and repaired in cell nucleus is nowadays a major challenge in radiobiology research. This work presents the results on the simulation of the DNA double strand breaks produced from the energy deposited by the irradiation at the intracellular level. At the nanometric scale, the only method to accurately simulate the topological details of energy deposited on the biological matter is the use of Monte Carlo codes. In this work, we used the Geant4 Monte Carlo code and, in particular, the low energy electromagnetic package extensions, referred as Geant4-DNA processes.In order to evaluate DNA radio-induced damages, the first objective of this work consisted in implementing a detailed geometry of the DNA on the Monte Carlo simulations. Two types of cell nuclei, representing a fibroblast and an endothelium, were described in order to evaluate the influence of the DNA density on the topology of the energy deposits contributing to strand breaks. Indeed, the implemented geometry allows the selection of energy transfer points that can lead to strand breaks because they are located on the backbone. Then, these energy transfer points were analysed with a clustering algorithm in order to reveal groups of aggregates and to study their location and complexity.In this work, only the physical interactions of ionizing radiations are simulated. Thus, it is not possible to achieve an absolute number of strand breaks as the creation and transportation of radical species which could lead to indirect DNA damages is not included. Nevertheless, the aim of this work was to evaluate the relative dependence of direct DNA damages with the DNA density, radiation quality, cell nuclei morphology or also chromatin condensation. The results presented in this work have allowed the quantification of the influence of these different parameters in the number and complexity of directs DNA damages which can then contribute to the late effects on cell fate

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Bäckström, Gloria. « Protons, other Light Ions, and 60Co Photons : Study of Energy Deposit Clustering via Track Structure Simulations ». Doctoral thesis, Uppsala universitet, Avdelningen för sjukhusfysik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-206385.

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Radiotherapy aims to sterilize cancer cells through ionization induced damages to their DNA whilst trying to reduce dose burdens to healthy tissues. This can be achieved to a certain extent by optimizing the choice of radiation to treat the patient, i.e. the types of particles and their energy based on their specific interaction patterns. In particular, the formation of complex clusters of energy deposits (EDs) increases with the linear energy transferred for a given particle. These differences cause variation in the relative biological effectiveness (RBE). The complexity of ED clusters might be related to complex forms of DNA damage, which are more difficult to repair and therefore prone to inactivate the cells. Hence, mapping of the number and complexity of ED clusters for different radiation qualities could aid to infer a surrogate measure substituting physical dose and LET as main predictors for the RBE . In this work the spatial patterns of EDs at the nanometre scale were characterized for various energies of proton, helium, lithium and carbon ions. A track structure Monte Carlo code, LIonTrack, was developed to accurately simulate the light ion tracks in liquid water. The methods to emulate EDs at clinical dose levels in cell nucleus-sized targets for both 60Co photons and light ions were established, and applied to liquid water targets. All EDs enclosed in such targets were analyzed with a specifically developed cluster algorithm where clustering was defined by a single parameter, the maximum distance between nearest neighbour EDs. When comparing measured RBE for different radiation qualities, there are cases for which RBE do not increase with LET but instead increase with the frequencies of high order ED clusters. A test surrogate-measure based on ED cluster frequencies correlated to parameters of experimentally determined cell survival. The tools developed in this thesis can facilitate future exploration of semi-mechanistic modelling of the RBE.

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Villegas, Navarro Fernanda. « Micro/nanometric Scale Study of Energy Deposition and its Impact on the Biological Response for Ionizing Radiation : Brachytherapy radionuclides, proton and carbon ion beams ». Doctoral thesis, Uppsala universitet, Medicinsk strålningsvetenskap, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-279385.

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Research in radiotherapy for cancer treatment focuses on finding methods that can improve the compromise between tumour cell inactivation versus damage to the surrounding healthy tissue. As new radiation modalities such as proton therapy become accessible for everyday clinical practice, a better understanding of the variation in biological response of the tumour and healthy tissues would improve treatment planning to achieve optimal outcome. The development of radiobiological models capable of accurate predictions of biological effectiveness is needed. Existing radiation quality descriptors such as absorbed dose and LET are insufficient to explain variation in biological effectiveness for different treatment modalities. The stochastic nature of ionizing radiation creates discrete patterns of energy deposition (ED) sites which can now be analysed through sophisticated computer simulations (e.g. Monte Carlo track structure codes). This opens the possibility to develop a nanometre characterization of radiation quality based on the spatial cluster patterns of ED. The aim of this thesis is to investigate the track structure (ED spatial pattern) properties of several radiation qualities at a micro- and nanometric scale while exploring their influence in biological response through correlations with published experimental data. This work uses track structure data simulated for a set of 15 different radiation qualities: 4 commonly used brachytherapy sources, 6 different proton energies, 4 different carbon ion energies, and 60Co photons used as reference radiation for quantification of biological effectiveness. At a micrometre level, the behaviour of the microdosimetric spread in energy deposition for target sizes of the order of cell nuclei was analysed. The degree of the influence it had in the biological response was found to be negligible for photon sources but for protons and carbon ions the impact increased with decreasing particle energy suggesting it may be a confounding factor in biological response. Finally, this thesis outlines a framework for modelling the relative biological effectiveness based on the frequency distribution of cluster order as a surrogate for the nanometre classification for the physical properties of radiation quality. The results indicate that this frequency is a valuable descriptor of ionizing radiation. The positive correlation across the different types of ionizing radiation encourages further development of the framework by incorporating the behavior of the microdosimetric spread and expanding tests to other experimental datasets.

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Kanike, Vanaja. « “Acid-spike” effect in spurs/tracks of the low/high linear energy transfer radiolysis of water : potential implications for radiobiology and nuclear industry ». Mémoire, Université de Sherbrooke, 2016. http://hdl.handle.net/11143/9711.

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Résumé : Les ions hydronium (H3O + ) sont formés, à temps courts, dans les grappes ou le long des trajectoires de la radiolyse de l'eau par des rayonnements ionisants à faible transfert d’énergie linéaire (TEL) ou à TEL élevé. Cette formation in situ de H3O + rend la région des grappes/trajectoires du rayonnement temporairement plus acide que le milieu environnant. Bien que des preuves expérimentales de l’acidité d’une grappe aient déjà été signalées, il n'y a que des informations fragmentaires quant à son ampleur et sa dépendance en temps. Dans ce travail, nous déterminons les concentrations en H3O + et les valeurs de pH correspondantes en fonction du temps à partir des rendements de H3O + calculés à l’aide de simulations Monte Carlo de la chimie intervenant dans les trajectoires. Quatre ions incidents de différents TEL ont été sélectionnés et deux modèles de grappe/trajectoire ont été utilisés : 1) un modèle de grappe isolée "sphérique" (faible TEL) et 2) un modèle de trajectoire "cylindrique" (TEL élevé). Dans tous les cas étudiés, un effet de pH acide brusque transitoire, que nous appelons un effet de "pic acide", est observé immédiatement après l’irradiation. Cet effet ne semble pas avoir été exploré dans l'eau ou un milieu cellulaire soumis à un rayonnement ionisant, en particulier à haut TEL. À cet égard, ce travail soulève des questions sur les implications possibles de cet effet en radiobiologie, dont certaines sont évoquées brièvement. Nos calculs ont ensuite été étendus à l’étude de l'influence de la température, de 25 à 350 °C, sur la formation in situ d’ions H3O + et l’effet de pic acide qui intervient à temps courts lors de la radiolyse de l’eau à faible TEL. Les résultats montrent une augmentation marquée de la réponse de pic acide à hautes températures. Comme de nombreux processus intervenant dans le cœur d’un réacteur nucléaire refroidi à l'eau dépendent de façon critique du pH, la question ici est de savoir si ces fortes variations d’acidité, même si elles sont hautement localisées et transitoires, contribuent à la corrosion et l’endommagement des matériaux.
Abstract : Hydronium ions (H3O+) are formed within spurs or tracks of the low or high linear energy transfer (LET) radiolysis of pure, deaerated water at early times. The in situ radiolytic formation of H3O+ renders the spur and track regions temporarily more acid than the surrounding medium. Although experimental evidence for an acidic spur has already been reported, there is only fragmentary information on its magnitude and time dependence. In this work, spur or track H3O+ concentrations and the corresponding pH values are obtained from our calculated yields of H3O+ as a function of time, using Monte Carlo track chemistry simulations. We selected four impacting ions and we used two different spur and track models: 1) an isolated “spherical” spur model characteristic of low-LET radiation and 2) an axially homogeneous “cylindrical” track model for high-LET radiation. Very good agreement was found between our calculated time evolution of G(H3O+) in the radiolysis of pure, deaerated water by 300-MeV incident protons (which mimic 60Co gamma/fast electron irradiation) and the available experimental data at 25 °C. For all cases studied, an abrupt transient acid pH effect, which we call an “acid spike”, is observed during and shortly after the initial energy release. This acid-spike effect is virtually unexplored in water or in a cellular environment subject to the action of ionizing radiation, especially high-LET radiation. In this regard, this work raises a number of questions about the potential implications of this effect for radiobiology, some of which are briefly evoked. Our calculations were then extended to examine the effect of temperature from 25 to 350 °C on the yield of H3O+ ions that are formed in spurs of the low-LET radiolysis of water. The results showed an increasingly acidic spike response at higher temperatures. As many in-core processes in a water-cooled nuclear reactor critically depend on pH, the question here is whether these variations in acidity, even highly localized and transitory, contribute to material corrosion and damage.

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Petrolli, Lorenzo. « A CONVERGENT AND MULTISCALE ASSESSMENT OF DNA DAMAGE BY PARTICLE RADIATION ». Doctoral thesis, Università degli studi di Trento, 2022. https://hdl.handle.net/11572/338714.

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The mutation/deletion of the hereditary material in the cell nuclei is a chronic biochemical hazard; in fact, nuclear DNA faces tens of lesions from metabolic intermediates, hydrolytic reactions and external vectors a minute. The canonical lesions of DNA involve the DNA backbone as well as the nucleic bases and are mostly associated with reversible chemical modifications. However, the radiation field from beams of accelerated ions accounts for a dense streak of collisions and reactions with the DNA molecule, thereby achieving lethal clusters of elemental lesions. Double strand breaks (DSB), i.e., the cleft of the DNA backbone over both strands, are hazardous fractures of the chromatin fold associated with the radiation field, underlying cytotoxic outcomes and chromosomal aberrations. Eukaryotic cells, however, rejoin the fractured DNA moieties from DSB events via an apt enzymatic machinery, or the DDR. Prior to the deployment of enzymatic effectors, host enzyme sensors engage the DNA termini in reversible supramolecular assemblies, which requires that the fractured DNA moieties be fully exposed. The in silico assessments of the early layout of DNA lesions by radiations have defined DSBs as the closely associated modifications of the DNA backbone by means of “coarse” criteria, that is, within an arbitrary distance of the two clefts. However, the diverse DSB motifs, i.e. at a strand break distance of zero to several nucleotides, account for a different contact interface between the DNA termini, thus modulating the dynamics of the lesion sites. Moreover, it is reckoned that in the absence of excess external stimuli, far-distanced DSBs may not fracture the broken DNA moieties by thermal dissociation, within the characteristic timescales of the DDR activity. This thesis elaborate tackles the in silico assessment of the distribution of DSBs in a chromatin-like fold and the local mechanical strain enforced by blunt DSBs, by means of state-of-the-art Monte-Carlo track structure tools and classical molecular dynamics. We infer that i) a Poisson fit describes the spectrum of DSB motifs by the direct effect of accelerated hydrogen ions (H+) at a Bragg peak relevant energy range (500 keV - 5 MeV) and, notably, we observe a bias towards short-distanced, staggered DSBs; ii) the nucleosome fold, i.e. the elemental unit of the chromatin hierarchical framework, exerts an excess kinetic barrier on the disruption of DSBs, which is not observed in linear DNA, mediated by the contact interface between DNA and the core histone fold. In conclusion, we remark that in the absence of further data from in vitro and in vivo assessments, the (kinetic, thermodynamic) inferences about the thermal and mechanical resilience of broken DNA frameworks are as reliable as the force fields underneath; in fact, it is debated whether all-atom force fields and water models overestimate the force of the intermolecular contacts and over-stabilize the DNA double helix.

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Mustaree, Shayla. « The •OH scavenging effect of bromide ions on the yield of H[subscript 2]O[subscript 2] in the radiolysis of water by [superscript 60]Co γ-rays and tritium β-particles at room temperature : a Monte Carlo simulation study ». Mémoire, Université de Sherbrooke, 2016. http://hdl.handle.net/11143/8183.

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Abstract: Monte Carlo simulations were used here to compare the radiation chemistry of pure water and aqueous bromide solutions after irradiation with two different types of radiation, namely, tritium β-electrons (~7.8 keV) and [superscript 60]Co γ-rays/fast electron (~1 MeV) or high energy protons. Bromide ions (Br-) are known to be selective scavengers of hydroxyl radicals •OH precursors of hydrogen peroxide H[subscript 2]O[subscript 2]. These simulations thus allowed us to determine the yields (or G-values) of H[subscript 2]O[subscript 2] in the radiolysis of dilute aqueous bromide solutions by the two types of radiations studied, the first with low linear energy transfer (LET) (~0.3 keV/μm) and the second with high LET (~6 keV/μm) at 25 °C. This study was carried out under a wide range of Br- concentrations both in the presence and the absence of oxygen. Simulations clearly showed that irradiation by tritium β-electrons favored a clear increase in G(H[subscript 2]O[subscript 2]) compared to [superscript 60]Co γ-rays. We found that these changes could be related to differences in the initial spatial distributions of radiolytic species (i.e., the structure of the electron tracks, the low-energy β-electrons of tritium depositing their energy as cylindrical “short tracks” and the energetic Compton electrons produced by γ-radiolysis forming mainly spherical “spurs”). Moreover, simulations also showed that the presence of oxygen, a very good scavenger of hydrated electrons (e-[subscript aq]) and H• atoms on the 10[superscript-7] s time scale (i.e., before the end of spur expansion), protected H[subscript 2]O[subscript 2] from further reactions with these species in the homogeneous stage of radiolysis. This protection against e-[subscript aq] and H• atoms therefore led to an increase in the H[subscript 2]O[subscript 2] yields at long times, as seen experimentally. Finally, for both deaerated and aerated solutions, the H[subscript 2]O[subscript 2] yield in tritium β-radiolysis was found to be more easily suppressed than in the case of cobalt-60 γ-radiolysis, and interpreted by the quantitatively different chemistry between short tracks and spurs. These differences in the scavengeability of H[subscript 2]O[subscript 2] precursors in passing from low-LET [superscript 60]Co γ-ray to high-LET tritium β-electron irradiation were in good agreement with experimental data, thereby lending strong support to the picture of tritium-β radiolysis in terms of short tracks of high local LET.
Résumé: Les simulations Monte Carlo constituent une approche théorique efficace pour étudier la chimie sous rayonnement de l'eau et des solutions aqueuses. Dans ce travail, nous avons utilisé ces simulations pour comparer l’action de deux types de rayonnement, à savoir, le rayonnement γ de [indice supérieur 60]Co (électrons de Compton ~1 Me V) et les électrons β du tritium (~ 7,8 keV), sur la radiolyse de l’eau et des solutions aqueuses diluées de bromure. Les ions Br- sont connus comme d’excellents capteurs des radicaux hydroxyles •OH, précurseurs du peroxyde d’hydrogène H[indice inférieur 2]O[indice inférieur 2]. Les simulations Monte Carlo nous ont donc permis de déterminer les rendements (ou valeurs G) de H[indice inférieur 2]O[indice inférieur 2] à 25 °C pour les deux types de rayonnements étudiés, le premier à faible transfert d'énergie linéaire (TEL) (~0,3 keV/μm) et le second à haut TEL (~6 keV/μm). L’étude a été menée pour différentes concentrations d’ions Br-, à la fois en présence et en absence d'oxygène. Les simulations ont montré que l’irradiation par les électrons β du tritium favorisait nettement la formation de H[indice inférieur 2]O[indice inférieur 2] comparativement aux rayons γ du cobalt. Ces changements ont pu être reliés aux différences qui existent dans les distributions spatiales initiales des espèces radiolytiques (i.e., la structure des trajectoires d'électrons, les électrons β du tritium déposant leur énergie sous forme de «trajectoires courtes» de nature cylindrique, et les électrons Compton produits par la radiolyse γ formant principalement des «grappes» de géométrie plus ou moins sphérique). Les simulations ont montré également que la présence d'oxygène, capteur d’électrons hydratés et d’atomes H• sur l'échelle de temps de ~10[indice supérieur -7] s (i.e., avant la fin des grappes), protégeait H[indice inférieur 2]O[indice inférieur 2] d’éventuelles réactions subséquentes avec ces espèces. Une telle «protection» conduit ainsi à une augmentation de G(H[indice inférieur 2]O[indice inférieur 2]) à temps longs. Enfin, en milieu tant désaéré qu’aéré, les rendements en H[indice inférieur 2]O[indice inférieur 2] obtenus lors de la radiolyse par les électrons β du tritium ont été trouvés plus facilement supprimés que lors de la radiolyse γ. Ces différences dans l’efficacité de capture des précurseurs de H[indice inférieur 2]O[indice inférieur 2] ont été interprétées par les différences quantitatives dans la chimie intervenant dans les trajectoires courtes et les grappes. Un excellent accord a été obtenu avec les données expérimentales existantes.

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Chapitres de livres sur le sujet "MONTE-CARLO TRACK STRUCTURE"

Nikjoo, H., S. Uehara, I. K. Khvostunov et F. A. Cucinotta. « Track Structure in Molecular Radiation Biology ». Dans Advanced Monte Carlo for Radiation Physics, Particle Transport Simulation and Applications, 251–60. Berlin, Heidelberg : Springer Berlin Heidelberg, 2001. http://dx.doi.org/10.1007/978-3-642-18211-2_40.

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Turner, J. E., R. N. Hamm, R. H. Ritchie et W. E. Bolch. « Monte Carlo Track-Structure Calculations for Aqueous Solutions Containing Biomolecules ». Dans Computational Approaches in Molecular Radiation Biology, 155–66. Boston, MA : Springer US, 1994. http://dx.doi.org/10.1007/978-1-4757-9788-6_11.

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Emfietzoglou, D. « Inelastic Cross-Sections for Use in Monte Carlo Track Structure Codes ». Dans Advanced Monte Carlo for Radiation Physics, Particle Transport Simulation and Applications, 273–78. Berlin, Heidelberg : Springer Berlin Heidelberg, 2001. http://dx.doi.org/10.1007/978-3-642-18211-2_43.

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Hugtenburg, Richard P. « Track-Structure Monte Carlo Modelling in X-ray and Megavoltage Photon Radiotherapy ». Dans Radiation Damage in Biomolecular Systems, 301–11. Dordrecht : Springer Netherlands, 2011. http://dx.doi.org/10.1007/978-94-007-2564-5_18.

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Dingfelder, M., et W. Friedland. « Basic Data for Track Structure Simulations : Electron Interaction Cross-Sections in Liquid Water ». Dans Advanced Monte Carlo for Radiation Physics, Particle Transport Simulation and Applications, 267–72. Berlin, Heidelberg : Springer Berlin Heidelberg, 2001. http://dx.doi.org/10.1007/978-3-642-18211-2_42.

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Grosswendt, B. « The Track Structure of Photons, Electrons and α-Particles from the Point of View of the Formation of Ionization Clusters ». Dans Advanced Monte Carlo for Radiation Physics, Particle Transport Simulation and Applications, 237–50. Berlin, Heidelberg : Springer Berlin Heidelberg, 2001. http://dx.doi.org/10.1007/978-3-642-18211-2_39.

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Nikjoo, Hooshang, et Shuzo Uehara. « Comparison of Various Monte Carlo Track Structure Codes for Energetic Electrons in Gaseous and Liquid Water ». Dans Computational Approaches in Molecular Radiation Biology, 167–85. Boston, MA : Springer US, 1994. http://dx.doi.org/10.1007/978-1-4757-9788-6_12.

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Sifre, Sergi Pérez, et Roman Lenner. « Evaluating the influence of daily truck traffic flow on load effects using Monte Carlo simulations ». Dans Advances in Engineering Materials, Structures and Systems : Innovations, Mechanics and Applications, 2165–69. CRC Press, 2019. http://dx.doi.org/10.1201/9780429426506-373.

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Actes de conférences sur le sujet "MONTE-CARLO TRACK STRUCTURE"

Fang, Genshen, Weichiang Pang et Yaojun Ge. « Flutter Fragility Analysis of Long-Span Bridges Based on 3D Typhoon Model Using Geographically Weighted Regression ». Dans IABSE Congress, Nanjing 2022 : Bridges and Structures : Connection, Integration and Harmonisation. Zurich, Switzerland : International Association for Bridge and Structural Engineering (IABSE), 2022. http://dx.doi.org/10.2749/nanjing.2022.1775.

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<p>The long-span bridges in coastal region of China exposed to the challenge of typhoon-induced flutter instability with the continuous increase the span length and flexibility of bridges. A Monte- Carlo-technique-based framework to analyse the flutter fragility long-span bridges subjected to typhoon winds is developed. A 3D typhoon boundary layer wind field model and a geographically- weighted-regression (GWR) -based stochastic track model are proposed to generate a large quantity of synthetic tracks around the bridge site before achieving the typhoon wind hazard curves at the height of the bridge deck. The flutter critical wind speed of the bridge is derived accounting for the structural modal and damping randomness as well as experiment-induced errors of aeroelastic flutter derivatives. The typhoon-induced flutter failure probabilities of the bridge are then predicted and compared with code-suggested target reliability indices.</p>

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Fang, X., et J. Tang. « Granular Damping Analysis Using a Direct Simulation Monte Carlo Approach ». Dans ASME 2006 International Mechanical Engineering Congress and Exposition. ASMEDC, 2006. http://dx.doi.org/10.1115/imece2006-14448.

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Granular damping, which possesses promising features for vibration suppression in harsh environment, has been studied using empirical analysis and more recently using the discrete element method (DEM). The mechanism of granular damping is highly nonlinear, and, when numerical analyses are performed, usually a relatively long simulation time of structural vibration is needed to reflect the damping behavior especially at low frequency range. The present research explores the granular damping analysis by means of the Direct Simulation Monte Carlo (DSMC) approach. Unlike the DEM that tracks the motion of granules using the direct numerical integration of Newton's equations, the DSMC is a statistical approach derived from the Boltzmann equation to describe the velocity evolution of the granular system. Since the exact time and locations of contacts among granules are not calculated in the DSMC, a significant reduction in computational time/cost can be achieved. While the DSMC has been exercised in a variety of granular systems, its implementation to granular damping analysis poses unique challenges. In this research, we develop a new method that enables the coupled analysis of the stochastic granular motion and the structural vibration. The complicated energy transfer and dissipation due to the collisions between the granules and the host structure and among the granules is directly and accurately incorporated into the analysis, which is essential to damping evaluation. Also, the effects of granular packing ratio and the excluded volume of granules, which may not be included in conventional DSMC method, are explicitly taken into account in the proposed approach. A series of numerical analyses are performed to highlight the accuracy and efficiency of the new approach. Using this new algorithm, we can carry out parametric analysis on granular damping to obtain guidelines for system optimization.

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Crews, John H., Ralph C. Smith et Jennifer C. Hannen. « Development of Robust Control Algorithms for Shape Memory Alloy Bending Actuators ». Dans ASME 2012 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/smasis2012-7989.

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In this paper, we present a systematic approach to developing robust control algorithms for a single-tendon shape memory alloy (SMA) bending actuator. Parameter estimation and uncertainty quantification are accomplished using Bayesian techniques. Specifically, we utilize Markov Chain Monte Carlo (MCMC) methods to estimate parameter uncertainty. The Bayesian parameter estimation results are used to construct a sliding mode control (SMC) algorithm where the bounds on uncertainty are used to guarantee controller robustness. The sliding mode controller utilizes the homogenized energy model (HEM) for SMA. The inverse HEM compensates for hysteresis and converts a reference bending angle to a reference temperature. Temperature in the SMA actuator is estimated using an observer, and the sliding mode controller ensures that the observer temperature tracks the reference temperature. The SMC is augmented with proportional-integral (PI) control on the bending angle error.

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Gokulakrishnan, Ponnuthurai, Jiankun Shao, Michael Klassen, David Davidson et Ronald Hanson. « The Effect of Nitrogen Impurities on Oxy-Fuel Combustion Under Supercritical-CO2 Conditions ». Dans ASME Turbo Expo 2022 : Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/gt2022-81576.

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Abstract The direct-fired supercritical-CO2 (sCO2) cycle has demonstrated the ability to produce clean energy by burning hydrocarbon feed stocks under oxy-fuel conditions. High-pressure operation of the direct-fired cycle allows for more economic extraction of CO2 for carbon capture and storage. However, the presence of nitrogen impurities in the oxidizer (i.e., N2) and in fuel feed stocks (e.g., NH3) can generate NOx in the exhaust. The presence of NOx in the recycled-CO2 stream can impact the combustion process as well as the structural integrity of the system. Also, even trace amounts of nitrogen oxides (considered acid gases) can be detrimental for CO2 capture, transportation and storage at supercritical conditions. Therefore, it is critical to understand and accurately model the effects of nitrogen impurities on NOx formation and the impact of NOx in the recycled CO2 on combustion kinetics under oxy-fuel sCO2 conditions. It is also important to understand the effects of pressure with a sCO2 medium as the direct-fired sCO2 cycle operates up to 300 atm pressure. In this work, experimental and modeling work were performed to study the effect of nitrogen species on emissions as well as effect of NOx on ignition of CH4 and syngas fuels at sCO2 conditions. A chemical reactor network simulation was used to investigate the effects of nitrogen impurities in fuel and oxidizer stream on emissions from a direct-fired combustor condition. Monte Carlo simulations were also carried out to study the impact of model input variables on the emission profile. High-pressure shock tube ignition delay time experiments were performed to investigate the effect of NOx on ignition at conditions relevant to direct-fired oxy-fuel sCO2 combustion. The ignition delay time measurements were made for syngas and CH4 fuels with and without NO addition using CO2 as bulk diluent at nominal pressures around 100 atm. Experimental data showed that the presence of NO promotes the ignition at the oxyfuel sCO2 combustion conditions. Reaction sensitivity analyses and model uncertainty analyses were conducted to identify important reactions and their rate uncertainty on the model predictions, respectively.

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Rapports d'organisations sur le sujet "MONTE-CARLO TRACK STRUCTURE"

Turner, J. E., R. N. Hamm, R. H. Ritchie et W. E. Bolch. Monte Carlo track-structure calculations for aqueous solutions containing biomolecules. Office of Scientific and Technical Information (OSTI), octobre 1993. http://dx.doi.org/10.2172/10192405.

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Wilson, W. E., Miller. J. H. et D. J. Lynch. Final Report : Monte Carlo Track-Structure Simulations for Low-LET Selected-Cell Radiation Studies. Office of Scientific and Technical Information (OSTI), juin 2005. http://dx.doi.org/10.2172/840862.

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Bichsel, H. Monte Carlo calculations of track structures. Office of Scientific and Technical Information (OSTI), décembre 1995. http://dx.doi.org/10.2172/244506.

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Amela, R., R. Badia, S. Böhm, R. Tosi, C. Soriano et R. Rossi. D4.2 Profiling report of the partner’s tools, complete with performance suggestions. Scipedia, 2021. http://dx.doi.org/10.23967/exaqute.2021.2.023.

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This deliverable focuses on the proling activities developed in the project with the partner's applications. To perform this proling activities, a couple of benchmarks were dened in collaboration with WP5. The rst benchmark is an embarrassingly parallel benchmark that performs a read and then multiple writes of the same object, with the objective of stressing the memory and storage systems and evaluate the overhead when these reads and writes are performed in parallel. A second benchmark is dened based on the Continuation Multi Level Monte Carlo (C-MLMC) algorithm. While this algorithm is normally executed using multiple levels, for the proling and performance analysis objectives, the execution of a single level was enough since the forthcoming levels have similar performance characteristics. Additionally, while the simulation tasks can be executed as parallel (multi-threaded tasks), in the benchmark, single threaded tasks were executed to increase the number of simulations to be scheduled and stress the scheduling engines. A set of experiments based on these two benchmarks have been executed in the MareNostrum 4 supercomputer and using PyCOMPSs as underlying programming model and dynamic scheduler of the tasks involved in the executions. While the rst benchmark was executed several times in a single iteration, the second benchmark was executed in an iterative manner, with cycles of 1) Execution and trace generation; 2) Performance analysis; 3) Improvements. This had enabled to perform several improvements in the benchmark and in the scheduler of PyCOMPSs. The initial iterations focused on the C-MLMC structure itself, performing re-factors of the code to remove ne grain and sequential tasks and merging them in larger granularity tasks. The next iterations focused on improving the PyCOMPSs scheduler, removing existent bottlenecks and increasing its performance by making the scheduler a multithreaded engine. While the results can still be improved, we are satised with the results since the granularity of the simulations run in this evaluation step are much ner than the one that will be used for the real scenarios. The deliverable nishes with some recommendations that should be followed along the project in order to obtain good performance in the execution of the project codes.

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