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The external radiation hazard
Published in Alan Martin, Sam Harbison, Karen Beach, Peter Cole, An Introduction to Radiation Protection, 2018
Alan Martin, Sam Harbison, Karen Beach, Peter Cole
The fast neutron dosimeter is based on a poly-allyl diglycol carbonate (PADC, also called CR-39) plastic plate worn in a holder similar to a TLD badge. The fast neutrons interact with the material of the holder assembly and the CR-39 plastic and cause recoil protons to be ejected. These protons create ionization tracks as damage to the polymeric structure of the CR-39 plastic. Chemical etching and subsequent electrochemical etching of the damage tracks can then develop them into pits with a diameter in the range of 20 to 200 μm, thereby enabling an automated scanner to assess the number of such tracks per square centimetre, which is a measure of the neutron dose.
Radiation Detectors for Individual Monitoring
Published in K. N. Govinda Rajan, Radiation Safety in Radiation Oncology, 2017
The principle of monitoring is similar to the film dosimetry described earlier. The nuclear tracks are formed by the recoil nuclei in elastic neutron collisions with hydrogen, carbon, and oxygen atoms that form the components of the plastic. These tracks can be enlarged by suitable chemical or electrochemical etching processes or both combined, at elevated temperatures. Through proper calibration, the track density can be related to the neutron DE. The sensitivity of CR-39 dosimeter can be enhanced by keeping a hydrogenous material (e.g., polyethylene) in front of the dosimeter. The additional proton recoils generated in the proton radiator produce more tracks in the CR-39, increasing its sensitivity. This dosimeter can detect fast neutrons over a wide energy range (100 keV to 20 MeV), has a relatively flat energy response, and is insensitive to β or γ. The CR-39 dosimeters are commercially available and their individual sensitivities depend on the type of CR-39 material used, thickness of the radiator, conditions of the etching process, and so on, and must be used as per the etching recommendations of the manufacturer for correct results. One problem with the CR-39 dosimeter, however, is the high-background track density (due to natural background, material defects, etc.), which determines the lower dose limit for neutron monitoring. Since the BG track density increases with time, these dosimeters have a limited life.
Ophthalmic lenses
Published in Pablo Artal, Handbook of Visual Optics, 2017
Most current ophthalmic lenses are made with plastics due to several factors, mainly that they are safer, since they do not break like glass and they are also lighter. The only disadvantage is that they scratch more easily. The main plastics for ophthalmic uses, whose characteristics are in Table 10.2, are as follows: CR-39. This plastic is a polymerizable thermosetting resin, formed by allyl diglycol carbonate. The name comes from Columbia Resin No. 39, because it was the 39th formula of a thermosetting plastic developed by the Columbia Resins Project at the Pittsburgh Plate Glass Company in 1940. Their most important characteristic is a high degree of scratch resistance, but lower than that of glass.Trivex, which is a urethane-based prepolymer. PPG named the material Trivex because of its three main performance properties, that is, superior optics, ultra-lightweight, and extreme strength. This plastic has the same UV blocking properties and shatter resistance of polycarbonate. Its low refractive index of 1.532 may result in slightly thicker lenses. It can be easily tinted.Polycarbonate is a thermoplastic, lighter than other plastics. This material blocks UV rays and it is shatter resistant and it is better than CR-39, and it is used in sports glasses and glasses for children and teenagers. Because polycarbonate is soft and will scratch easily, scratch-resistant coating is typically applied after shaping and polishing the lens. Standard polycarbonate has a high Abbe value of 30, thus producing lenses with a high chromatic aberration.High-index plastics (thiourethanes) are high-index plastics, producing thin lenses, but not lighter, than most plastics due to the high density. As most with high-index plastics, lenses have a high level of chromatic aberration. Another advantage of high-index plastics is their strength and shatter resistance, although not as shatter resistant as polycarbonate.
Chromosome aberrations, micronucleus frequency, and catalase concentration in a population chronically exposed to high levels of radon
Published in International Journal of Radiation Biology, 2023
Dwi Ramadhani, Sofiati Purnami, Devita Tetriana, Irawan Sugoro, Viria Agesti Suvifan, Nastiti Rahadjeng, Septelia Inawati Wanandi, Heri Wibowo, Ikuo Kashiwakura, Tomisato Miura, Mukh Syaifudin
Details about the measurements of indoor radon concentration can be found in Nugraha et al. (2021). Briefly, four series of radon level measurements were conducted in 2018–2019. The measurements were performed using solid-state nuclear track detectors (SSNTDs), Raduet® (Radosys, Ltd, Hungary). Passive detectors (CR-39) were placed in the house of each participant. After three months of exposure, CR-39 was chemically etched for 24 h in 6 M NaOH at 60 °C. Radon concentrations were then calculated using the alpha track densities identified under an optical microscope. The annual effective dose for each subject was obtained from raw data and calculations available in Nugraha et al. (2021). In brief, the annual effective dose was defined as the total exposure of an individual to both external and internal sources. External exposure originates from environmental gamma radiation, whereas internal exposure comes from ingestion and inhalation. Lastly, the cumulative dose was calculated by multiplying the annual effective dose by the age of each individual.
Cytoproliferative effect of low dose alpha radiation in human lung cancer cells is associated with connexin 43, caveolin-1, and survivin pathway
Published in International Journal of Radiation Biology, 2021
Vasumathy Rajan, Badri Narain Pandey
The α-particle irradiation was carried out with alpha irradiator (BARC-BioAlpha) designed and developed at Bhabha Atomic Research Center, Mumbai with 241Am source for in vitro radiobiological experiments (Jyothish Babu et al. 2013; Karthik et al. 2019). Dosimetry was carried out by CR-39 track dosimetry as described earlier (Jyothish Babu et al. 2013; Karthik et al. 2019). The flux of the source and dose rate was found to be 2000/cm2/s and 1.36 cGy/min, respectively. For α-irradiation, cells (1.5 × 106) were cultured overnight at 37 °C in specially designed irradiation dish bottomed with 2.5 µm thick mylar membrane (Goodfellow, UK), which was pre-coated with fibronectin (Karthik et al. 2019). For fibronectin coating, the irradiation dish was layered with fibronectin solution [(Sigma, stock: 0.1 mg/ml), diluted in culture medium (1:10 in DMEM supplemented with FCS and antibiotics)], and incubated at 37 °C (5% CO2 in a humidified incubator for 1 h) followed by removal of fibronectin solution and washing the dish with PBS. For γ-irradiation, cultures in the same dishes were irradiated (1 Gy/min) with 60Co teletherapy unit (Bhabhatron II, Panacea Medical Technologies Pvt. Ltd., Bangalore, India). For sham irradiation, cells in the same dishes were handled under similar incubation conditions without irradiation.
Boron phenyl alanine targeted chitosan–PNIPAAm core–shell thermo-responsive nanoparticles: boosting drug delivery to glioblastoma in BNCT
Published in Drug Development and Industrial Pharmacy, 2021
Monireh Soleimanbeigi, Fatemeh Dousti, Farshid Hassanzadeh, Mina Mirian, Jaleh Varshosaz, Yaser Kasesaz, Mahboubeh Rostami
Two CR-39 detectors were covered with 30 µg of l-BPA, and 30 µg of BPA@BPA@CSSU-PNI2 lyophilized NPs. We irradiated the CR-39 detectors for 30 min, with thermal neutron flux of 5.6 × 108 (n cm−2 s−1) (Tehran Research Reactor) [61]. A sheet without sample was irradiated in the same condition as negative control. After the irradiation, the CR-39 sheets were chemically etched with a solution of NaOH (6.25 N) at 70 °C for 5 h. The background was obtained by processing the control sheet under same conditions. The sheets were observed using an optical microscope at a magnification of 5 [62].