Radiation-Induced Polymerization of Polymethacrylic Gel for Dosimetry

The aim of the present work is to investigate the effect of radiation on methacrylic acid (MAA) crosslinked with N, N’-methylene-bisacrylamide (BIS) for the purpose of developing a polymer gel dosimeter, namely, polymethacrylic gel (PMAAG). PMAAG of different concentrations of MAA and BIS were irradiated with the absorbed doses ranging from 0 Gy to 19 Gy. Using Raman spectrophotometer, five peak intensities were identified and represents the assigned bonding for C=C (2238 cm-1) of MAA, C=C (1634 cm-1) of BIS, C-C (2110 cm-1) of PMAA, C=O (1795 cm-1) of PMAA, CH2 (2905 cm-1) of PMAA, which have strong modes of vibration in the band positions. The Raman peak intensity y as a function of absorbed dose D was found to have a monoexponential expression in the form; −+=−010DDeAyy. The dose sensitivity D0 and half dose D1/2 were obtained and found to increase with the concentrations of MAA monomer and BIS crosslinker. The dose correlation factor of BIS, kBIS is always higher than kMAA of MAA (kBIS > kMAA) for all C-C, C=C, C=O and CH2 stretching modes, indicating BIS is a very significant parameter in the polymerization process. Additionally, a Nuclear magnetic resonance (NMR) spectrometer was used in order to measure the relaxation time of polymethacrylic (PMAA) gel dosimeters. The relaxation rate (ΔR2) dose sensitivity value (12.5 + 0.1 Gy) of MAA monomer by Lepage, et al 2001 is comparable with PMAAG experimental value gained which are 12.6 + 0.1 Gy. A comparison between and indirect measurements of polymer formed along with consumptions of monomer and crosslinker are also obtained from this experimental work. Finally, a UV-Vis spectrophotometer was used to records PMAAG degree of absorption in order to determine the accuracy of PMAAG. The PMAAG has a mean value of absorption of 0.614 at 375 nm. The dose derived from PMAAG is comparable to Fricke dosimeter and ionization chamber readings between 4.7 ± 0.1% and 11.6 ± 0.1%. The dose errors of less than 10 ± 0.1% are considered acceptable in radiation processing, an improvement of accuracy less than 5.0 ± 0.1% is acceptable in radiotherapy

Temperature stability and physical properties of Bi2O3-B2O3-ZnO-RHA glass system

Rice husk ash (RHA) is a product from the burning of the rice husk and it become a significant material for glass preparation due to high amount of amorphous silica that can be produced. From the recent studies, the highest amount of silica is observed at 550°C at 6 hours which is 99.36% by XRF detection. Nevertheless, the amount of silica decreasing proportionally if the temperature profile is higher than 550°C and the time taken is more than 6 hours. Quaternary glasses are prepared using melt-quenching method using the highest amount of silica from RHA combined with Bismuth Oxide (Bi2O3), Boron Oxide (B2O3), and Zinc Oxide (ZnO). The ratio of quaternary glass that used are 30%SiO2: 20%B2O3: xZnO : (50-x)%Bi2O3 (% mole) ; where x= 10,20,30,40. The physical properties and glass transition temperature (Tg) profiles are determined using standard measurement instrument. Moreover, the density measured will enhance the verification of Oxygen Packing Density for prepared quaternary glasses

From rice husk to transparent radiation protection material / Iskandar Shahrim Mustafa... [et al.]

High amount of silica (SiO2) content, 99.36% was successfully prepared from Rice Husk Ash (RHA) through the burning of rice husk. Eventually, quaternary glasses were fabricated using melt quenching technique based on chemical compound composition xBi2O3 - (1-x)ZnO - 0.2B2O3 - 0.3(SiO2)RHA. The final thickness of glass samples prepared was within ~3.41mm. As the mole percentages of Bi2O3 increased, the glass density and molar volume was also increased from 4.45 gcm-1 to 6.60 gcm-1. The increment is due to larger atomic number of Bi3+ compared to the Si2+, B3+ and Zn in the glass samples. However, the oxygen packing density decreased as mole percentages of Bi2O3 were increased from 240.44 g-atom/l to 161.24 g-atom/l. The decreasing in oxygen packing density was due to the high non-bridging oxygen in the glass samples. The radiation attenuation parameterization was measured using 241Am as source of gamma ray interactions at energy 59.54 keV. The mass attenuation coefficient increased from 0.53cm2g-1 to 5.12cm2g-1 relatively towards the increment of Bi2O3 mole percentages. The phenomenon is due to the escalating in photoelectric absorption effect and declining in the Compton scattering caused by high atomic number of Bi3+ in the glass samples. Using Lorentz-Lorentz formulation, the refractive index obtained for glass samples prepared was within favourable range from 1.97 to 1.73

Acoustic evaluation of HEMA polymer gel dosimeter phantoms

A new method for the evaluation of radiotherapy 3D polymer gel dosimeters has been developed using ultrasound to assess the significant structural changes that occur following irradiation of the dosimeters. Polymer gel dosimeters were being fabricated using a monomer named 2-Hydroxyl-Ethyl-Meta-Acrylate (HEMA) with the presence of gelatine as a gelling agent. The readymade gel which is the concentration for HEMA fixed at 2, 4 and 5% would then undergo an ultrasonic evaluation to test for the propagation of sound speed through it. In the observation of relationship between the ultrasound propagation speeds as the doses increase (focusing at the cross region from overlapped beams) and concentration of monomer, the propagation speed for all the three polymer gel dosimeter phantoms still varies between 1460 to 1570 m/s which is still in the range of speed of sound for human tissue [3]. The ultrasonic absorption attenuation coefficient dose sensitivity for polymer gel dosimeters for 2, 4 and 5% of monomer are in the range of 0.02 to 0.6 dB which is equivalent to human tissue. As a comparison, it can be seen that gel phantoms with high concentration of monomer (5%) is more sensitive to the radiation compared to the lower (2% and 4%) concentrations. Regarding the absolute results of mechanical and acoustic properties; the copolymer-in-oil phantom is equivalent with soft tissue

Synthesis and optical characterization of zinc borotellurite glass doped with lanthanum nanoparticles

A glass series with chemical composition of {[(TeO2)0.7(B2O3)0.3]0.7(ZnO)0.3}1-x (La NPs)x where x = 0.01, 0.02, 0.03, 0.04 and 0.05 molar fraction was synthesized through conventional melt-quenching method. The fabricated glasses were characterized by using UV-Vis and FTIR technique in the range of 220 to 800 nm and 280 to 2000 cm-1 respectively. Various absorption bands that were recorded in FTIR spectra indicates the presence of TeO4, BO3 and BO4 unit. In this research, indirect energy band gap showed an increasing trend while refractive index values decreases as amount of La NPs increases due to the decrement of high polarizability nonbridging oxygen number in the glass system. Other optical parameter that also take part in governing the value of refractive index such as electronic polarizability was also determined

Indoor Radon Concentration Measurement in Selected Factories in Northern and Central Iraq

In this work, the outdoor radon concentration level and lung cancer risks have been measured in selected locations in northern and central Iraq during the summer season 2012 by using time integrated passive radon dosimeters containing LR-115 Type II plastic track detectors. These measurements were carried out in the factories for an exposure time of 60 day. The radon concentration in these factories ranges from (36.36 – 125.10) Bq.m-3 with an average of (59.93Bq.m-3), which within the acceptable radon levels (50-150) Bq.m-3 recommended by the International Commission on Radiological Protection (ICRP). The average absorption effective dose equivalent for a person living in factories for which the investigation were done was found to be (1.425mSv.y-1). It is observed that the average lung cancer per year per 106 person was found to be 25.654. Keyword: LR-115 Type II nuclear track detectors; Radon concentration; AEDE; PAEC

Dielectric properties of oven dry Malaysian wood

Four species of selected local hard wood had been studied for dielectric properties. Measurements were made at frequency 10-2 Hz to 106 Hz from room temperature to 100°C. Dielectric behaviors show that the low frequency dispersion (LFD) proposed by Jonscher and the DC conductivity dominated the profile of the dielectric processes. Dielectric analysis was made by shifting the data of relative dielectric permittivity and the loss factor to become a master curve. From the shift of the loss peak at various fixed temperatures the activation energy was determined by plotting of Arrhenius plot of ln ε” against 1000/T. The dielectric properties of wood were found to be dependent on temperature and density of wood species. Impedance, Z, and modulus, M, plots were also used to reveal the model of the dielectric behaviour in wood

A simple rectangular microstrip technique for determination of moisture content in Hevea rubber latex

A simple rectangular microstrip sensor for determination of moisture content in Hevea Rubber Latex is presented in this paper. The microstrip patch sensor was designed to operate at microwave frequency range from 1 to 5 GHz on a RT/Duroid substrate with 6.15 ±0.015 permittivity and 1.27 mm thickness. The width and length of the rectangular patch antenna was 18 mm and 38 mm, respectively. The reflection coefficient of the sensor loaded with Hevea latex at various percentages of moisture content from approximately 36.1% to 88.6 %. Calibration equations have been established between moisture content and phase of reflection coefficient at several selected frequencies. These equations were used to predict the amount of moisture content on Hevea latex based on the measured reflection coefficient values. The actual values of moisture content were obtained using standard oven drying method. The lowest mean relative error between actual and predicted moisture contents was 0.04 at 1 GHz

6 MV photon beam induced optical properties of dyed polyvinyl alcohol/trichloroacetic acid blends

The objective of the work is to study the effect of photon on the optical properties of dyed polyvinyl alcohol-trichloroacetic acid (PVA-TCA) blends prepared through solvent casting technique at radiotherapy dose. The films were cut into 2 × 2 cm2 and kept away from direct sunlight at room temperature until irradiation process. The films were simultaneously irradiated with a 6 MV photon beam produced by linear accelerator Siemens MXE-2. The dose exposure given was set from 50 to 400 cGy. The optical properties were measured using the UV-visible spectrophotometer Shimadzu-1800, set at a wavelength range between 200 nm and 800 nm. The absorbance spectra were obtained with the existence of three absorbance band peaks at 273 nm, 444 nm and 582 nm. Initially, all absorbance increased with increasing dose applied. The results gained indicate that the optical energy band gap, Eg is equivalent to 5.20 eV while the absorption edge is 4.96 eV. These two parameters decreased with increasing dose. It is due to the increase of structural order between the conduction band and the valence band getting narrower. This also indicates that the film is undergoing a red shift. Hence, the value of Urbach energy, ΔE obtained is 0.089 eV, which increased with increasing dose since the lattice vibration depended on the applied dose. In conclusion, the PVA/TCA blends have a good optical characteristic in terms of dose response and optical transition

UV-Vis spectral evaluation of CR-39 detector exposed with diagnostic dosage

The effects of the X-ray irradiation and chemical etching on the physical and optical properties of CR-39 plastic detectors were investigated for different doses of X-ray. CR-39 detectors were etched in the solution of the 3 M of NaOH after irradiation for revelations of the track. The tracks formed on CR-39 either by irradiated X-ray or due to the effect of environment. The changes in the thickness after exposed have significant decrease in 60 kVp and started to increase in range of 70 kVp up to 100 kVp due to the formation of oxidation layer on surface by free radicals. The optical band gaps before etching and after etching were determined by using Ultraviolet-visible (UV-Vis) spectroscopy. The optical band gap is attributed to the indirect transition due to its amorphous nature which is significantly decline trend energy in increase of the energy fluence of radiation. The Urbach’s energy, is defined as the width of the tail localized states in the forbidden band gap which change increment trend as increase in dose delivered due to the distortion structure of the CR-39 in terms of the electron charges in valences electron hence attributes to the induced modification of angle bond between the neighboring atoms