Perspectives in science最新文献

Over 18 months long measurements of outdoor radon in three areas (a total of 69 locations) in England were conducted between years 2015 and 2017 using PADC based passive nuclear track detectors. Special measurement equipment and protocols to counteract unfavourable weather conditions have been designed, developed and optimised for the low level radon concentration.

The purpose of this study is to evaluate the patients’ radiation dose in three different modalities of CT scanners (64, 16 and 2 slices) and the biological effects during CT brain examinations.

A total of 60 patients were examined in three different hospitals in Morocco. The data were collected from CT Brain examinations at of 20 CT scans per hospital. For each examination, we have reported CT acquisition parameters including the number of series, use of contrast medium; tube kV, tube current and rotation time, slice thickness as well as the displayed CT dose index (CTDI_vol) and the Dose Length Product (DLP). Cancer and biological heredity risks were estimated using the International Commission on Radiological Protection (ICRP) conversion factors.

The average dose values for CT brain for 2 slices was 305 ± 112 mGy.cm. The mean dose value for 16 slices was 716 ± 179 mGy.cm, while the average dose for 64 slices was 1136 ± 708 mGy.cm. The patient cancer risks per procedure ranged between 4 and 13 per 10⁵ CT procedures. This risk is 4, 8 and 13 per 10⁵ CT procedures for 2 slices, 16 slices and 64 slices respectively. The patient heredity risks varied between 1 and 5 per million CT procedures. It is 1, 3 and 5 for 2 slices, 16 slices and 64 slices respectively.

Dual slice scanner delivered the least effective dose while 16 and 64 slice scanners delivered the highest effective dose. The dose values of this study were comparable to the international reference levels of CT examination. CT dose optimization protocol is not implemented in the Moroccan hospitals. These values could be used as our hospital's Dose Reference Levels (DRL) until a more detailed study survey can be conducted in Morocco for the establishment of the country's reference levels.

The natural radioactive nuclides especially ²¹⁰Po, are volatilized at the temperature (600–800 °C) of a burning cigarette and are taken into the human body. Therefore, analysis of natural radioactivity of ²¹⁰Po in cigarettes and the effective dose to smokers should be evaluated. The activity concentration of ²¹⁰Po in sixteen brands of Philippine cigarettes was measured by alpha spectrometry, and estimation of effective dose of ²¹⁰Po to smokers was performed. The activity concentration of ²¹⁰Po in cigarettes distributed in the Philippines ranged from 5.5 to 17.8 mBq/cigarette and the mean value of their activity concentrations was 12.0 mBq/cigarette. The mean value of annual effective doses of ²¹⁰Po to smokers obtained from these activity concentrations was 0.021 mSv/y, which was lower than the reference level (1–20 mSv/y) for existing situation in ICRP Publication 103.

Currently there is a growing interest in the development of optically stimulated luminescence (OSL) dosimeters that may be useful for assessing the neutron flux contribution on the doses in radiotherapy due to neutrons produced in the interaction of megavoltage photon beams. In this work, OSL responses of MgB₄O₇:Ce,Li with ¹¹B are presented for some photon beams, including 6 MV and 10 MV. For 10 MV, the behavior of the phosphor containing ¹⁰B was also evaluated. The material with ¹⁰B exhibited an OSL response slightly more intense than that with ¹¹B, indicating a possible application of this new material for dosimetry in photon radiotherapy.

A laser microdissection system was used for isolating fission track stars to improve the cutting efficiency in the FT-TIMS particle analytical technique. The background interference of track detectors to determine isotopic ratios was studied. Several swipe samples were successfully measured for particle analysis by FT-TIMS. The results show that the laser microdissection system could effectively improve the ability of FT-TIMS particle analytical technique.

The aim of this work is to study the calibration methodology of a new eye dosimeter, developed by Dosimetry Laboratory of the Nuclear Research Center of Algiers, using TLD-700 thermoluminescent detectors (LiF: Mg, Ti). Qualification and type test of this dosimeter have been performed in terms of operational quantity Hp(3) at Secondary Standard Dosimetry Laboratory (SSDL) using the cylindrical phantom according to ISO 12794, ORAMED 2012 and IEC 62387, 2012. Furthermore, two dosimeter holders have been tested for two positions (frontal and lateral) in order to determine the “best dosimeter position” which allows good estimation of dose received by lens.

A new measurement method for determination Solid State nuclear track by the change of the specific heat capacity is proposed. The feasibility of the method is discussed in both theory and practice, to determine the solid state nuclear tracks by specific heat capacity when annealing. In the research, the change of the specific heat capacity is related with nuclear track numbers after annealing and it could be measured and verified time after time. The theory and experiments are introduced with details. The potential applications of this method in the future are discussed, such as determination of the neutron flux at high lever reactors and geologic age of the geological samples.

Cigarette smoking is one of the pathways that might cause radiation exposure due to the presence of radioactive elements in tobacco leaves used in the manufacture of cigarettes. From the health point of view, the knowledge of radioactivity content of the various radionuclides in tobacco leaves and their derivative products is important to assess the radiological effects associated with tobacco smoking for smokers. In this work, naturally occurring radionuclides ²²⁶Ra, ²³²Th and ⁴⁰K and man-made ¹³⁷Cs were measured in tobacco using gamma-ray spectrometry. Results show that the average concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K vary from 4.30 ± 0.2 to 11.85 ± 0.7 (average 8.17), 1.35 ± 0.1 to 16.12 ± 0.9 (average 6.08), and 565.6 ± 15.5 to 1235.81 ± 35 (average 908.09) Bq kg⁻¹, respectively. ¹³⁷Cs activity concentrations were ranged from 0.15 ± 0.01 to 0.67 ± 0.9 (average 0.44) Bq kg⁻¹. The most important radiological parameters, including radium equivalent (Ra_eq), total annual effective dose (AED) and excess lifetime cancer risk (ELCR) were calculated. For smokers, the total AED resulting from activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K in tobacco samples ranged from 0.44 to 2.29 (average 1.39) mSv y⁻¹, while of ¹³⁷Cs varied from 0.01 to 0.04 (average 0.025) μSv y⁻¹ and so very little is contributing to the total dose due to inhalation to smokers. ELCR was higher than the world's average of 1.45 × 10⁻³ for tobacco and coal samples. The excess lifetime cancer risk ranged from 1.55 × 10⁻³ to 8.01 × 10⁻³ with an average value of 4.88 × 10⁻³ for all tobacco samples under investigation.

The sorption experiments with the five rock samples drilled in the deep-well in the exocontact zone of Nizhnekansky granitoid massif (EZNGM) in the range of depth 166–476 m were carried out. The distribution of radium was studied. The radiograms of radionuclide sorption were obtained by digital autoradiography. Heterogeneous sorption of radium was demonstrated by digital radiography and phases with higher sorption ability were revealed. The technique for the treatment of radiograms with the help of ImageJ program for obtaining quantitative parameters of radionuclides distribution in the granite-gneiss rock samples was developed. Relative sorption efficiency of different mineral phases of the rock samples of Eniseysky area (EZNGM) toward radium is presented in the paper.

Charged particle therapy exploits proton or ¹²C beams to treat deep-seated solid tumors. Due to the advantageous characteristics of charged particles energy deposition in matter, the maximum of the dose is released to the tumor at the end of the beam range, in the Bragg peak region. However, the beam nuclear interactions with the patient tissues induces fragmentation both of projectile and target nuclei and needs to be carefully taken into account. In proton treatments, target fragmentation produces low energy, short range fragments along all the beam range, which deposit a non negligible dose in the entry channel. In ¹²C treatments the main concern is represented by long range fragments due to beam fragmentation that release their dose in the healthy tissues beyond the tumor. The FOOT experiment (FragmentatiOn Of Target) of INFN is designed to study these processes, in order to improve the nuclear fragmentation description in next generation Treatment Planning Systems and the treatment plans quality. Target (¹⁶O and ¹²C nuclei) fragmentation induced by –proton beams at therapeutic energies will be studied via an inverse kinematic approach, where ¹⁶O and ¹²C therapeutic beams impinge on graphite and hydrocarbon targets to provide the nuclear fragmentation cross section on hydrogen. Projectile fragmentation of ¹⁶O and ¹²C beams will be explored as well. The FOOT detector includes a magnetic spectrometer for the fragments momentum measurement, a plastic scintillator for ΔE and time of flight measurements and a crystal calorimeter to measure the fragments kinetic energy. These measurements will be combined in order to make an accurate fragment charge and isotopic identification.