Search results for "Radiation"
showing 10 items of 5298 documents
Exposure of -alanine and -ammonium tartrate ESR dosimeters to thermal neutrons: Experiments and Monte Carlo simulations
2008
Abstract Electron spin resonance solid state dosimetry with alanine and ammonium tartrate pellets is a valuable tool in both medical and industrial applications when dealing with photon and charged particle beams. Its use in neutron beams is limited by the low nuclear cross section values of atoms in the pellets. Addition of boron (10B) or gadolinium ( Gd 2 O 3 ) , known to have high neutron capture cross sections, has been proposed to improve neutron sensitivity. In this paper we present the results of an experimental study concerning neutron sensitivity vs. gadolinium concentration in dosimeter mixtures, with the aim of optimizing mixture composition and maximizing the electron spin resol…
Neutron and gamma-ray radiation fields characterisation in a 241Am–Be irradiator in view of its use as research testing tool
2020
Abstract A neutron irradiation facility based on four 241Am–Be sources, each one with an activity of 111 GBq, placed in Plexiglas pipes inside a tank filled with water used both as a moderator and a biological shielding, has been realized at the Engineering Department of Palermo University. In view of its use as a testing tool in various research activities, a characterisation of the irradiator has been carried out through the determination of neutron and gamma-ray flux profiles, the evaluation of the thermal to total neutron flux percentage ratio and of the epithermal neutron shaping factor. To this aim, results of a Monte Carlo (MCNP5 code) simulation based on a previously validated sourc…
Pulsed EPR analysis of tooth enamel samples exposed to UV and gamma-radiations
2011
Abstract The electron paramagnetic resonance (EPR) spectroscopy is widely applied for retrospective dosimetric purposes by means of quantitative detection of radicals in tooth enamel and bone samples. In this work we report a study by cw and pulsed EPR on two samples of human tooth enamel respectively irradiated by UV (254 nm) and γ-exposed. The continuous wave (cw) EPR spectra have shown the usual presence in both samples of two types of CO 2 − radicals, with axial and orthorombic g tensors. We have obtained the electron spin echo detected EPR (ED-EPR) spectra at 80 K of the two samples, and we have shown that they are suitable to mark the difference between the effects produced by the dif…
Self-broadening coefficients and improved line intensities for the ν7 band of ethylene near 10.5μm, and impact on ethylene retrievals from Jungfraujo…
2014
Relying on high-resolution Fourier transform infrared (FTIR) spectra, the present work involved extensive measurements of individual line intensities and self-broadening coefficients for the ν7 band of 12C2H4. The measured self-broadening coefficients exhibit a dependence on both J and Ka. Compared to the corresponding information available in the latest edition of the HITRAN spectroscopic database, the measured line intensities were found to be higher by about 10% for high J lines in the P branch and lower by about 5% for high J lines of the R branch, varying between these two limits roughly linearly with the line positions. The impact of the presently measured line intensities on retrieva…
Results of the measurements carried out in order to verify the validity of the poisson-exponential distribution in radioactive decay events
1978
Abstract Berkson, examining a series of 250,000 disintegration time intervals, found a significant departure of the distribution from the Poisson-exponential law. Therefore he proposed to repeat the experiment using a large number of intervals and to check the interval recordings by using more than one recording instrument simultaneously. Accepting these suggestions we developed two systems of data collecting provided with different controls. In several experiments we collected data for more than one million decay intervals. The results elaborated using the Pearson ξ 2 test reflect a Poisson process of the radioactive decay events.
Unified mapping of the dynamics of solitons in fiber-optic waveguides
2013
This thesis examines the dynamical behaviour of solitons which are affected, when entering a fiber-optic waveguide, by a slight distortion of profile as compared to the stationary profile in the guide. Our theoretical model combines the propagation equation of the electric field (Non-Linear Schrödinger Equation) and the system of equations of evolution of the physical parameters of the pulse (derived from the collective coordinates theory). We establish a general mapping which reveals an unsuspected diversity of dynamic behaviour around the stationary state of the pulse, in relation with the initial perturbation of the pulse's profile. This mapping establishes a classification of solitons i…
ESR response to 60Co-rays of ammonium tartrate pellets using as additive
2007
Abstract This work presents experimental results regarding a new ammonium tartrate blend for ESR dosimetry, with a higher sensitivity and a lower lowest detectable dose (LDD) to Co 60 γ -rays than the recently used pure ammonium tartrate. The blend composed by ammonium tartrate and gadolinium-oxide ( Gd 2 O 3 ) shows a greater sensitivity ( ∼ 2 times) and a smaller LDD than ammonium tartrate. The increased sensitivity was mainly attributed to the great atomic number ( Z = 64 ) of gadolinium, that increases the effective atomic number of the blend; the interaction probability with photons and consequently the radical yield is therefore enhanced. Moreover ammonium tartrate with Gd 2 O 3 has a…
Ben Ambridge y Elena V. M. Lieven: Child language acquisition: Contrasting theoretical approaches
2013
Traditional analytic approaches establish a strong connection between discourse markers (DMs) and a number of prosodic cues regularly associated to them (esp...
68Ge content quality control of 68Ge/68Ga-generator eluates and 68Ga radiopharmaceuticals – A protocol for determining the 68Ge content using thin-la…
2014
(68)Ge breakthrough from a (68)Ge/(68)Ga-generator appears to be one of the most critical parameters for the routine clinical application of this generator and (68)Ga-radiopharmaceuticals. We report a TLC-based (thin-layer chromatography) protocol which allows the (68)Ge breakthrough of a generator to be determined within 1 h post-initial elution. The protocol can also be adapted to allow the (68)Ge content of a (68)Ga-radiopharmaceutical preparation to be determined prior to in vivo application.
Seasonal variation of air kerma in the "Vulcano Porto" area (Aeolian Islands, Italy).
2001
Abstract Air kerma was measured in the “Vulcano Porto” area of the Vulcano Island, belonging to the Aeolian Islands, in the Mediterranean Sea. Measurements were carried out using thermoluminescence dosimeters. The relationship between observed dose values and source lithology has been assessed. Data show a seasonal variation due to weather conditions but also probably related to features of the soils, making the variation more evident.