Full Geant4 and FLUKA Simulations of an e-LINAC for its Use in Particle Detectors Performance Tests

In this work we present the results of full Geant4 and FLUKA simulations and comparison with dosimetry data of an electron LINAC of St. Maria Hospital located in Terni, Italy. The facility is being used primarily for radiotherapy and the goal of present study is the detailed investigation of electron beam parameters to evaluate the possibility to use the e-LINAC (during time slots when it is not used for radiotherapy) to test the performance of detector systems in particular those designed to operate in space. The critical beam parameters are electron energy, profile and flux available at the surface of device to be tested. The present work aims to extract these parameters from dosimetry calibration data available at the e-LINAC. The electron energy ranges is from 4 MeV to 20 MeV. The dose measurements have been performed by using an Advanced Markus Chamber which has a small sensitive volume.Comment: 10 pages, 10 figures, 2 table

On the use of highly pixellated CMOS imagers to measure therapeutic beam profile

The characterization of high-intensity charged-particle and photon beams at medical accelerators is often a time-consuming task. In this work, we discuss the possibility to use highly segmented CMOS imagers as a way to measure the fluxes with high spatial precision and in a short time. Quite recently CMOS imagers, designed to collect visible light, have been used to detect ionizing radiation, either charged particles (electron, proton) or photons. These devices, due to the very low single pixel noise, have a very high detection efficiency, once the interaction between radiation and silicon has taken place, and act primarily as counting detectors. We will show how it is possible to extract a precise beam shape using as a test case a therapeutic electron beam delivered by an Elekta e-LINAC at the S. Maria Hospital in Terni (Italy), and as sensors commercial off-the-shelf (COTS) CMOS imagers

Effetti di un'associazione antocianosidi-vincamina sulla funzione visiva

Il presente studio descrive gli effetti a breve termine di una associazione di farmaci, vincamina- antocianosidi, sulla funzione visiva. Detta funzione è stata studiata analizzando il visus, la frequenza critica di fusione, l'ERG e la curva adattometrica, prima e dopo l'assunzione del farmaco

Quantum Chemical and Kinetics Study of the Thermal Gas Phase Decomposition of 2‑Chloropropene

A detailed theoretical study of the kinetics of the thermal decomposition of 2-chloropropene over the 600–1400 K temperature range has been done. The reaction takes place through the elimination of HCl with the concomitant formation of propyne or allene products. Relevant molecular properties of the reactant and transition states were calculated for each reaction channel at 14 levels of theory. From information provided by the BMK, MPWB1K, BB1K, M05-2X, and M06-2X functionals, specific for chemical kinetics studies, high-pressure limit rate coefficients of (5.8 ± 1.0) × 10¹⁴ exp­[−(67.8 ± 0.4 kcal mol^–1)/<i>RT</i>] s^–1 and (1.1 ± 0.2) × 10¹⁴ exp­[−(66.8 ± 0.5 kcal mol^–1)/<i>RT</i>] s^–1 were obtained for the propyne and allene channels, respectively. The pressure effect over the reaction was analyzed through the calculation of the low-pressure limit rate coefficients and falloff curves. An analysis of the branching ratio between the two channels as a function of pressure and temperature, based on these results and on computed specific rate coefficients, show that the propyne forming channel is predominant

Full Geant4 and FLUKA simulations of an e-LINAC for its use in particle detectors performance tests

In this work we present the results of full Geant4 and FLUKA simulations and comparison with dosimetry data of an electron LINAC of St. Maria Hospital located in Terni, Italy. The facility is being used primarily for radiotherapy and the goal of present study is the detailed investigation of electron beam parameters to evaluate the possibility to use e-LINAC (during time slots when it is not used for radiotherapy) to test the performance of detector systems in particular those designed to operate in space. The critical beam parameters are electron energy, profile and flux available at the surface of device to be tested. The present work aims to extract these parameters from dosimetry calibration data available at e-LINAC. The electron energy range is from 4 MeV to 20 MeV. The dose measurements have been performed by using an Advanced Markus Chamber which has a small sensitive volume

Atmospheric Chemistry, Sources, and Sinks of Carbon Suboxide, C₃O₂

Carbon suboxide, O=C=C=C=O, has been detected in ambient air samples and has the potential to be a noxious pollutant and oxidant precursor; however, its lifetime and fate in the atmosphere is largely unknown. In this work, we collect an extensive set of studies on the atmospheric chemistry of C3O2. Rate coefficients for the reactions of C3O2 with OH radicals&lt;br /&gt;and ozone were determined using relative rate techniques as k4 = (2.6 ± 0.5) ´ 10-12 cm3 molecule-1 s-1 at 295 K (independent 15 of pressure between ~25 and 1000 mbar) and k6 &lt; 1.5 ´ 10-21 cm3 molecule-1 s-1 at 295 K. A theoretical study on the mechanisms of these reactions indicates that the sole products are CO and CO2, as observed experimentally. The UV absorption spectrum and the interaction of C3O2 with water were also investigated, enabling photodissociation and hydrolysis rates to be assessed. The role of C3O2 in the atmosphere was examined using in-situ measurements, an analysis of the atmospheric sources and sinks, and simulation with the EMAC atmospheric chemistry - general circulation model. The results indicate sub-pptv levels&lt;br /&gt;20 at the Earth´s surface, up to about 10 pptv in regions with relatively strong sources, e.g. by biomass burning, and a mean lifetime of ~3.2 days. These predictions carry considerable uncertainty, as more measurement data are needed to determine ambient concentrations and constrain the source strengths.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada