340 research outputs found
The Geant4-DNA project
The Geant4-DNA project proposes to develop an open-source simulation software
based and fully included in the general-purpose Geant4 Monte Carlo simulation
toolkit. The main objective of this software is to simulate biological damages
induced by ionising radiation at the cellular and sub-cellular scale. This
project was originally initiated by the European Space Agency for the
prediction of deleterious effects of radiation that may affect astronauts
during future long duration space exploration missions. In this paper, the
Geant4-DNA collaboration presents an overview of the whole ongoing project,
including its most recent developments already available in the last Geant4
public release (9.3 BETA), as well as an illustration example simulating the
direct irradiation of a chromatin fibre. Expected extensions involving several
research domains, such as particle physics, chemistry and cellular and
molecular biology, within a fully interdiciplinary activity of the Geant4
collaboration are also discussed.Comment: presented by S. Incerti at the ASIA SIMULATION CONFERENCE 2009,
October 7-9, 2009, Ritsumeikan University, Shiga, Japa
Geant4 physics processes for microdosimetry simulation: design foundation and implementation of the first set of models
New physical processes specific for microdosimetry simulation are under development in the Geant4 Low Energy Electromagnetic package. The first set of models implemented for this purpose cover the interactions of electrons, protons and light ions in liquid water; they address a physics domain relevant to the simulation of radiation effects in biological systems, where water represents an important component. The design developed for effectively handling particle interactions down to a low energy scale and the physics models implemented in the first public release of the software are described
Effect of orthopedic and functional orthodontic treatment in children with obstructive sleep apnea: A systematic review and meta-analysis
Orthodontic treatment is suggested in growing individuals to correct transverse maxillary deficiency and mandibular retrusion. Since, as a secondary effect, these orthodontic procedures may improve pediatric obstructive sleep apnea (OSA), this systematic review assessed their effects on apnea-hypopnea index (AHI) and oxygen saturation (SaO2). Twenty-five (25) manuscripts were included for qualitative synthesis, 19 were selected for quantitative synthesis. Five interventions were analyzed: rapid maxillary expansion (RME, 15 studies), mandibular advancement (MAA, five studies), myofunctional therapy (MT, four studies), and RME combined with MAA (one study). RME produced a significant AHI reduction and minimum SaO2 increase immediately after active treatment, at six and 12 months from baseline. A significant AHI reduction was also observed six and 12 months after the beginning of MAA treatment. MT showed positive effects, with different protocols. In this systematic review and meta-analysis of data from mainly uncontrolled studies, interceptive orthodontic treatments showed overall favorable effects on respiratory outcomes in pediatric OSA. However, due to the low to very low level of the body evidence, this treatment cannot be suggested as elective for OSA treatment. An orthodontic indication is needed to support this therapy and a careful monitoring is required to ensure positive improvement in OSA parameters
Models of biological effects of radiation in the Geant4 toolkit
A project, named Geant4-DNA, is in progress to extend the Geant4 simulation toolkit to model the effects of radiation with biological systems at cellular and DNA level. The first component implemented in the first development cycle of the project describes the fractional survival of a population of cells irradiated with photons or charged particles. The software system developed provides the user the option to choose among a small set of alternative models for the calculation of mammalian cell survival after irradiation. The flexible design adopted makes the system open to further extension to implement other cell survival models available in literature. The preliminary design of a prototype of the cell survival models implemented and preliminary results in some selected cell lines are described
Transience analysis of bursty traffic with erbium doped fiber amplifiers
Copyright © [2009] IEEE. Reprinted from ICTON 2009. ISBN 978-1-4244-4826-5.
This material is posted here with permission of the IEEE. Internal or personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution must be obtained from the IEEE by writing to [email protected].
By choosing to view this document, you agree to all provisions of the copyright laws protecting it.In this paper, we investigate experimentally the impact of optical amplifiers, namely Erbium Doped Fiber
Amplifiers (EDFA) on Optical Burst Switching (OBS) networks, operating at 2.5 Gb/s (typical bit rate for
current passive optical networks - PON). Bursts with 212 – 1 and 216 – 1 pseudo random binary sequence (PRBS)
were studied, with different idle times. The use of traffic with variable idle time was assessed
in order to evaluate the effect on the burst initial amplitude. We also analyzed the performance of the packet
based system by measuring the Q factor at the receiver and concluded that the performance is not affected by the
type of traffic (variable or fixed idle times)
EP-1347: Could “radical” RT be a reasonable choice in bone oligometastatic prostate cancer patients?
Simulation study of dose enhancement in a cell due to nearby carbon and oxygen in particle radiotherapy
The aim of this study is to investigate the dose-deposition enhancement by
alpha-particle irradiation in a cellular model using carbon and oxygen chemical
compositions.A simulation study was performed to study dose enhancement due to
carbon and oxygen for a human cell where Geant4 code used for the
alpha-particle irradiation to the cellular phantom. The characteristic of dose
enhancement in the nucleus and cytoplasm by the alpha-particle radiation was
investigated based on concentrations of the carbon and oxygen compositions and
was compared with those by gold and gadolinium.The results show that both the
carbon and oxygen-induced dose enhancement was found to be more effective than
those of gold and gadolinium. We found that the dose-enhancement effect was
more dominant in the nucleus than in the cytoplasm if carbon or oxygen is
uniformly distributed in a whole cell. In the condition that the added chemical
composition was inserted only into the cytoplasm, the effect of the dose
enhancement in nucleus becomes weak.We showed that high-stopping-power
materials offer a more effective dose-enhancement efficacy and suggest that the
carbon nanotubes and oxygenation are promising candidates for dose utilization
as dose enhancement tools in particle therapy.Comment: 19 pages, 6 figures, 4 tables. presented to 7th KOREA-JAPAN Joint
Meeting on Medical Physics (2014.09.25) accepted to Journal of the Korean
Physical Society (2015.03.10
Measurement of the Generalized Forward Spin Polarizabilities of the Neutron
The generalized forward spin polarizabilities and of
the neutron have been extracted for the first time in a range from 0.1 to
0.9 GeV. Since is sensitive to nucleon resonances and
is insensitive to the resonance, it is expected that the
pair of forward spin polarizabilities should provide benchmark tests of the
current understanding of the chiral dynamics of QCD. The new results on
show significant disagreement with Chiral Perturbation Theory
calculations, while the data for at low are in good agreement
with a next-to-lead order Relativistic Baryon Chiral Perturbation theory
calculation. The data show good agreement with the phenomenological MAID model.Comment: 5 pages, 2 figures, corrected typo in author name, published in PR
The brief international cognitive assessment for multiple sclerosis (BICAMS): Normative values with gender, age and education corrections in the Italian population
Background: BICAMS (Brief International Cognitive Assessment for Multiple Sclerosis) has been recently developed as brief, practical and universal assessment tool for cognitive impairment in MS subjects. It includes the Symbol Digit Modalities Test (SDMT), the California Verbal Learning Test-2 (CVLT2) and the Brief Visuospatial Memory Test-Revised (BVMT-R) . In this study we aimed at gathering regression based normative data for the BICAMS battery in the Italian population.Methods: Healthy subjects were consecutively recruited among patient friends and relatives. Corrections for demographics were calculated using multivariable linear regression models. Test-retest reliability was assessed using the Pearson correlation coefficient.Results: The BICAMS battery was administered to 273 healthy subjects (180 women, mean age 38.9 ± 13.0 years, mean education 14.9 ± 3.0 years). Test-retest reliability was good for all the tests.Conclusions: The study provided normative data of the BICAMS for the Italian population confirming good test-retest reliability which can facilitate the use of the battery in clinical practice, also for longitudinal patient assessments
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