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Search Results: 1 - 10 of 15318 matches for " Marco Durante "
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Scanned carbon beam irradiation of moving films: comparison of measured and calculated response
Christoph Bert, Daniel Richter, Marco Durante, Eike Rietzel
Radiation Oncology , 2012, DOI: 10.1186/1748-717x-7-55
Abstract: All calculations were performed with GSI's treatment planning system TRiP. Interplay patterns between scanned particle beams and moving film detectors are very sensitive to slight deviations of the assumed motion parameters and therefore ideally suited to validate 4D calculations. In total, 14 film motion parameter combinations with lateral motion amplitudes of 8, 15, and 20 mm and 4 combinations for lateral motion including range changes were used. Experimental and calculated film responses were compared by relative difference, mean deviation in two regions-of-interest, as well as line profiles.Irradiations of stationary films resulted in a mean relative difference of -1.52% ± 2.06% of measured and calculated responses. In comparison to this reference result, measurements with translational film motion resulted in a mean difference of -0.92% ± 1.30%. In case of irradiations incorporating range changes with a stack of 5 films as detector the deviations increased to -6.4 ± 2.6% (-10.3 ± 9.0% if film in distal fall-off is included) in comparison to -3.6% ± 2.5% (-13.5% ± 19.9% including the distal film) for the stationary irradiation. Furthermore, the comparison of line profiles of 4D calculations and experimental data showed only slight deviations at the borders of the irradiated area. The comparisons of pure lateral motion were used to determine the number of motion states that are required for 4D calculations depending on the motion amplitude. 6 motion states per 10 mm motion amplitude are sufficient to calculate the film response in the presence of motion.By comparison to experimental data, the 4D extension of GSI's treatment planning system TRiP has been successfully validated for film response calculations in the presence of target motion within the accuracy limitation given by film-based dosimetry.Radiotherapy of tumors influenced by organ motion benefits from dedicated treatment planning. Our treatment planning system for scanned particle beams (Treatment plan
Nanolesions induced by heavy ions in human tissues: Experimental and theoretical studies
Marcus Bleicher,Lucas Burigo,Marco Durante,Maren Herrlitz
Beilstein Journal of Nanotechnology , 2012, DOI: 10.3762/bjnano.3.64
Abstract: The biological effects of energetic heavy ions are attracting increasing interest for their applications in cancer therapy and protection against space radiation. The cascade of events leading to cell death or late effects starts from stochastic energy deposition on the nanometer scale and the corresponding lesions in biological molecules, primarily DNA. We have developed experimental techniques to visualize DNA nanolesions induced by heavy ions. Nanolesions appear in cells as “streaks” which can be visualized by using different DNA repair markers. We have studied the kinetics of repair of these “streaks” also with respect to the chromatin conformation. Initial steps in the modeling of the energy deposition patterns at the micrometer and nanometer scale were made with MCHIT and TRAX models, respectively.
A Model of Photon Cell Killing Based on the Spatio-Temporal Clustering of DNA Damage in Higher Order Chromatin Structures
Lisa Herr, Thomas Friedrich, Marco Durante, Michael Scholz
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0083923
Abstract: We present a new approach to model dose rate effects on cell killing after photon radiation based on the spatio-temporal clustering of DNA double strand breaks (DSBs) within higher order chromatin structures of approximately 1–2 Mbp size, so called giant loops. The main concept of this approach consists of a distinction of two classes of lesions, isolated and clustered DSBs, characterized by the number of double strand breaks induced in a giant loop. We assume a low lethality and fast component of repair for isolated DSBs and a high lethality and slow component of repair for clustered DSBs. With appropriate rates, the temporal transition between the different lesion classes is expressed in terms of five differential equations. These allow formulating the dynamics involved in the competition of damage induction and repair for arbitrary dose rates and fractionation schemes. Final cell survival probabilities are computable with a cell line specific set of three parameters: The lethality for isolated DSBs, the lethality for clustered DSBs and the half-life time of isolated DSBs. By comparison with larger sets of published experimental data it is demonstrated that the model describes the cell line dependent response to treatments using either continuous irradiation at a constant dose rate or to split dose irradiation well. Furthermore, an analytic investigation of the formulation concerning single fraction treatments with constant dose rates in the limiting cases of extremely high or low dose rates is presented. The approach is consistent with the Linear-Quadratic model extended by the Lea-Catcheside factor up to the second moment in dose. Finally, it is shown that the model correctly predicts empirical findings about the dose rate dependence of incidence probabilities for deterministic radiation effects like pneumonitis and the bone marrow syndrome. These findings further support the general concepts on which the approach is based.
ATM Alters the Otherwise Robust Chromatin Mobility at Sites of DNA Double-Strand Breaks (DSBs) in Human Cells
Annabelle Becker, Marco Durante, Gisela Taucher-Scholz, Burkhard Jakob
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0092640
Abstract: Ionizing radiation induces DNA double strand breaks (DSBs) which can lead to the formation of chromosome rearrangements through error prone repair. In mammalian cells the positional stability of chromatin contributes to the maintenance of genome integrity. DSBs exhibit only a small, submicron scale diffusive mobility, but a slight increase in the mobility of chromatin domains by the induction of DSBs might influence repair fidelity and the formation of translocations. The radiation-induced local DNA decondensation in the vicinity of DSBs is one factor potentially enhancing the mobility of DSB-containing chromatin domains. Therefore in this study we focus on the influence of different chromatin modifying proteins, known to be activated by the DNA damage response, on the mobility of DSBs. IRIF (ionizing radiation induced foci) in U2OS cells stably expressing 53BP1-GFP were used as a surrogate marker of DSBs. Low angle charged particle irradiation, known to trigger a pronounced DNA decondensation, was used for the defined induction of linear tracks of IRIF. Our results show that movement of IRIF is independent of the investigated chromatin modifying proteins like ACF1 or PARP1 and PARG. Also depletion of proteins that tether DNA strands like MRE11 and cohesin did not alter IRIF dynamics significantly. Inhibition of ATM, a key component of DNA damage response signaling, resulted in a pronounced confinement of DSB mobility, which might be attributed to a diminished radiation induced decondensation. This confinement following ATM inhibition was confirmed using X-rays, proving that this effect is not restricted to densely ionizing radiation. In conclusion, repair sites of DSBs exhibit a limited mobility on a small spatial scale that is mainly unaffected by depletion of single remodeling or DNA tethering proteins. However, it relies on functional ATM kinase which is considered to influence the chromatin structure after irradiation.
Dosimetric precision of an ion beam tracking system
Christoph Bert, Alexander Gemmel, Nami Saito, Naved Chaudhri, Dieter Schardt, Marco Durante, Gerhard Kraft, Eike Rietzel
Radiation Oncology , 2010, DOI: 10.1186/1748-717x-5-61
Abstract: A beam tracking system has been developed and integrated in the scanned carbon ion beam therapy unit at GSI. The system adapts pencil beam positions and beam energy according to target motion.Motion compensation performance of the beam tracking system was assessed by measurements with radiographic films, a range telescope, a 3D array of 24 ionization chambers, and cell samples for biological dosimetry. Measurements were performed for stationary detectors and moving detectors using the beam tracking system.All detector systems showed comparable data for a moving setup when using beam tracking and the corresponding stationary setup. Within the target volume the mean relative differences of ionization chamber measurements were 0.3% (1.5% standard deviation, 3.7% maximum). Film responses demonstrated preserved lateral dose gradients. Measurements with the range telescope showed agreement of Bragg peak depth under motion induced range variations. Cell survival experiments showed a mean relative difference of -5% (-3%) between measurements and calculations within the target volume for beam tracking (stationary) measurements.The beam tracking system has been successfully integrated. Full functionality has been validated dosimetrically in experiments with several detector types including biological cell systems.At GSI Helmholtzzentrum für Schwerionenforschung (GSI) more than 430 patients with tumors mainly in the head and neck area were treated with a rasterscanned carbon beam [1,2]. For treatment of respiration-influenced tumors motion mitigation techniques will be required because the interference of target motion and scanned beam delivery potentially leads to mis-dosage, typically referred to as interplay [3,4]. Beam gating [5], rescanning [3], and beam tracking [6,7] have been proposed to adequately irradiate moving targets with scanned particle beams.Tracking has been suggested in different technical ways and for different treatment modalities. For photon radiotherapy
The Online Construction of Personal Identity Through Trust and Privacy
Massimo Durante
Information , 2011, DOI: 10.3390/info2040594
Abstract: Constructing a personal identity is an activity much more complex than elaborating a series of online profiles, which are only digital hints of the Self. The construction of our personal identity is a context-mediated activity. Our hypothesis is that young people are enabled, as digital natives and social network users, to co-construct the “context of communication” in which their narrative identities will be interpreted and understood. In particular, the aim of this paper is to show that such “context of communication”, which can be seen as the hermeneutical counterpart of the “networked publics” elaborated by Danah Boyd, emerges out of the tension between trust and privacy. In other terms, it is, on the one hand, the outcome of a web of trustful relations and, on the other, the framework in which the informational norms regulating teens’ expectations of privacy protection are set and evaluated. However, these expectations can be frustrated, since the information produced in such contexts can be disembedded and re-contextualized across time. The general and widespread use of information technology is, in fact, challenging our traditional way of thinking about the world and our identities in terms of stable and durable structures; they are reconstituted, instead, into novel forms.
Sous la rature, la littérature. L’expérience de la philologie italienne au service de la littérature comparée
Erica Durante
Trans : Revue de Littérature Générale et Comparée , 2006,
Abstract: Dans l’Italie de la fin des années quarante, Benedetto Croce et Gianfranco Contini ont débattu autour d’une critique des textes littéraires fondée sur l’étude des brouillons des écrivains. Celle qui s’annon ait comme une question de critique littéraire nationale est devenue une interrogation plus générale sur l’écriture, l’étude des uvres littéraires et a représenté un enrichissement précieux pour l’histoire de la littérature et de la critique littéraire européenne du XXe siècle. In the 1940s, in Italy, Benedetto Croce and Gianfranco Contini discussed a brand of literary criticism based on the study of the writers’ rough drafts. What appeared to be a question of national literary criticism, became a more general controversy about writing and literature, and ended up representing a precious enrichment for the history of literature and for European literary criticism of the 20th century. En Italia a final de los a os cuarenta, Benedetto croce y Gianfranco Contini debatieron sobre la crítica de textos literarios fundada en el estudio de los borradores de los autores. Lo que se antojaba como una cuestión de crítica literaria nacional pronto se convirtió en una preocupación más amplio sobre la escritura, el estudio de las obras literarias, cuyo efecto representó un enriquecimiento invaluable para la historia de la literatura y de la crítica literaria europea del siglo XX.
Présentation "Université invitée" : Naples capitale du comparatisme
Erica Durante
Trans : Revue de Littérature Générale et Comparée , 2006,
Abstract: Nous avons décidé d’inaugurer cette nouvelle rubrique avec l’Italie, un pays qui nous est particulièrement proche, en termes de culture et de tradition littéraire et intellectuelle. En septembre dernier, c’est à Venise que l’Association Internationale de Littérature Comparée, a célébré le cinquantième anniversaire de sa fondation ; “un retour symbolique” dans ce lieu ouvert au monde et aux échanges entre les langues et les hommes d’Orient et d’Occident.Tout comme Venise, certaines villes ital...
A representa o da oralidade nos textos publicitários
Denise Durante
Alfa : Revista de Linguística , 2004,
Abstract: Este estudo, baseado nos pressupostos teóricos da Análise da Conversa o, aborda o aproveitamento de recursos expressivos da oralidade em textos escritos de natureza publicitária veiculados na mídia impressa. O corpus é formado por anúncios publicados pela revista Veja.
La ense anza en el ambiente clínico: principios y métodos
Eduardo Durante
REDU : Revista de Docencia Universitaria , 2012,
Abstract: La ense anza en los ambientes clínicos es una estrategia fundamental en la ense anza de las profesiones de la Salud. Considerada como educación no formal en contraste con la educación formal de las aulas, la ense anza en los ambientes clínicos tiene su propia estructura y métodos de ense anza. Tomando en cuenta los principios del constructivismo, del desarrollo de la expertise y de la reflexión se ofrece un modelo de ense anza clínica. La creación de un clima de aprendizaje estimulante, la evaluación de los estudiantes en la práctica, principalmente a través de la observación directa de sus desempe os, la provisión de devoluciones significativas y el compromiso en la reflexión son los principales componentes de este modelo. El modelo de rol, la supervisión, el andamiaje, el estímulo de la verbalización de sus agujeros de conocimiento y la promoción de la reflexión son métodos de ense anza que el docente clínico debería utilizar de acuerdo a las características del estudiante y su contexto. Los ambientes tradicionales de la ense anza clínica son al lado de la cama del enfermo y la consulta ambulatoria. Ambos presentan desafíos al docente clínico, el que deberá ajustar sus habilidades a la particular realidad de cada uno de ellos. La ense anza clínica en la comunidad ofrece posibilidades únicas para el aprendizaje contextualizado de la futura práctica profesional. La simulación puede ofrecer un medio para volver más efectiva la ense anza clínica al proveer la oportunidad de práctica en tareas globales. ASTRACT Clinical Teaching: principles and methods. Clinical teaching is one of the main teaching strategies in Health Professions Education. Contrasting the formal education in the class, clinical teaching has its own methods and structure. Based on the constructivist principles of learning, expertise development and reflection- on- action, a model for clinical teaching is provided. The promotion of the stimulating learning climate, students’ assessment in practice, especially by using direct observation of their performances, giving feedback and promotion of reflection are the main component s of this model. Role modeling, coaching, scaffolding, articulation and exploration are teaching methods the clinical teacher should perform according to the student’s characteristics and their context. The traditional environments of the clinical education are at the side of the bed of the patient and the outpatient consultation. Both of them challenge the clinical teacher, who should adequate his/ her teaching skills to their particular characteristics. Clin
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