650 research outputs found
Simulating the tail of the interference in a Poisson network model
No full textInterference among simultaneous transmissions represents the main limitation factor for the capacity and connectivity of dense wireless networks. In this paper we provide efficient simulation laws for the tail of the interference in a simple wireless ad hoc network model. Particularly, we consider node locations distributed according to a Poisson point process and various classes of light-tailed fading distribution
Conductive tracks in graphene oxide foils induced by micro beams of MeV helium ions
No full textConductive tracks based on reduced graphene oxide (rGO) were induced by MeV energy helium ion microbeams in graphene oxide (GO) sheets. The computerized X-Y step motors movement of the GO foil in front of the fixed ion microbeam in a high vacuum produces a reduction of the functionalized oxygen groups, generating a graphene-like track with high electrical conductivity. The conductive track generated on the insulating matrix has a depth dependent on the range of ions used, maintains the electrical properties even under bending stress, and can electrically connect devices made of the same carbon-based material or different materials. Scanning electron microscopy, characteristic X-ray emission, electron conductivity measurements, Raman spectroscopy, surface wetting and roughness, X-ray diffraction, and optical spectroscopy are employed to investigate the ion beam modifications induced in the GO structure
Nuclear reactions for protontherapy intensification
No full textThis paper presents some experimental results about the 7Li, 11B and 19F (p, α) nuclear reactions developed using proton beams at energy below 3 MeV in order to be applied to protontherapy. The energy released by proton beams during radiotherapy acts mainly at the end of the proton path in the biological medium, where it increases at high density inside the tumor. At this depth, it is possible to inject in the tumor compounds containing Li, B and F to generate energetic alpha particles from nuclear reactions. At the proton Bragg peak position it is possible to produce 1–8 MeV alpha particles, which enhance the energy density deposited in the tumor increasing the probability to damage the cells. Thanks to the higher relative biological efficiency of the alpha particles with respect to protons, it is expected that the alpha synergic particles defeat the tumor at lower doses
Ion, electron and laser beams for Cultural Heritage investigations by Czech-Italian collaboration
No full textAn overview of physical investigations of cultural heritage samples using ion and laser beams performed in the frame of the international collaboration between the University of Messina (Italy) and the Nuclear Physics Institute-ASCR (Czech Republic) is presented. Solid samples are analysed in high vacuum using particle induced X-ray emission, Rutherford backscattering spectrometry, elastic recoil detection analysis, prompt γ activation analysis, nuclear reaction analysis, laser ablation, mass spectrometry, scanning electron microscopy, and many more. The elemental composition of the sample, the trace elements, the depth profiles, the morphology and the comparison between samples and references are reported. Both electron and ion microbeams are employed to have details of the spatial distribution maps of elements of interest
Gafchromic HD-V2 investigations using MeV ion beams in vacuum
No full textGafchromic HD-V2 films are employed to study the response to light ions useful in radiotherapy, such as protons, helium and carbon beams. The effects induced by the ions at an energy within about 300 keV and 16 MeV were investigated in terms of optical absorbance measurements in the irradiated active region of the film. The employed ion doses range between 0.4 Gy and 12 kGy. The results show that the net optical density increases almost exponentially with the absorbed dose and that it becomes saturated after prolonged dose higher than 1 kGy. The optical density produced in the film was measured by light transmission measurements at 700 nm wavelength, at which is observed the highest gafchromic sensitivity. Calibration curves of optical density versus exposure dose and type of ion are given. The dependence on the ion stopping power was presented and discussed
Enhancement of the polydimethylsiloxane (PDMS) luminescence to develop a proton scintillator
No full textThe polydimethylsiloxane (PDMS) luminescence, induced by MeV proton beams, has been investigated in the pure and doped polymer. Gold nanoparticles (AuNPs) and graphene oxide microparticles (GOμPs) have been employed at low concentration (0.1 wt%) to modify the PDMS properties. Measurements have demonstrated that AuNPs enhance the PDMS luminescence, while GOμPs quench the polymer luminescence. The first ones, embedded into PDMS, produce a visible luminescence whose intensity is proportional to the absorbed proton dose. A linearity between the luminescence intensity and the proton absorbed dose is observed up to about 2.5 kGy, while at higher doses a luminescence saturation region shows up. The polymer can be employed to monitor in vacuum the proton beam spot size and shape and as a plastic scintillator dosimeter with peculiar elastic properties and high biocompatibility, as it will be presented and discussed
Physical study of proton therapy at CANAM laboratory on medulloblastoma cell lines DAOY
No full text2.0 MeV proton beam accelerated at Tandetron is extracted in air through a thin film and allowed to scatter to irradiate the cell culture attached to the polymeric base of a biological flask. The irradiated cells were human medulloblastoma cell line Daoy treated with and without 5 nm sized spherical gold nanoparticles. Proton doses from 0.5 to 1.5 Gy have been employed to irradiate the cultures and to investigate the role of the radiotherapy performed with and without the use of the gold nanoparticles. Results indicated that cell survival is significantly reduced to about 50% when the nanoparticles at a concentration of about 6 × 1013 particles/ml are employed
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