A safety evaluation test on human for latex films made from Radiation Prevulcanized Natural Rubber Latex (RVNRL) with sulfur-containing antioxidant was studied. Sulfur test has confirmed that there was sulfur compound presence in RVNRL derived from antioxidant used in this study. Two types of safety evaluation test were being adopted which are Patch Test and Modified Draize-95 test and this test proved that there is no clinical evidence on the presence of sulfur compound in RVNRL that may induce Type IV allergy in the unsensitized general user population. Both clinical test shows that the highest score value produced by test subjects is 1 and not exceed the allowable limit.
The research on radiation induced mutation has been conducted as one of the promising method of plant breeding in Malaysia since 1980s. Nuclear Malaysia is leading research institute inMalaysia conducting plant mutationbreeding research. Gamma Greenhousefacility located in Nuclear Malaysiais one of the irradiation facilitiesto serve as a chronic irradiation facility for inducing mutation in various organisms including plants, fungi and microbes.Chronic irradiation refers to the exposure of materials at a lower dose rate over a long period of time. Previous studies have shown that this type of irradiation can minimize radiation damages to living materials and produces a wider mutation spectrum, therefore is very useful for trait improvements in irradiated organisms. Experiments on induce mutation using Gamma Greenhouse facility for crop improvement program have been conducted since its first operation in 2009. Various plant species including ornamental and herbal plants, food crops and industrial crops have been irradiated to improve their traits such as higher yield and biomass, pest and disease tolerance, higher bioactive compounds, longer bloom time and many others. Most of these crop improvement programs were done through collaborations with other agencies in Malaysia such as universities, research institutes and government departments. A number of publications on crop improvement using Gamma Greenhouse have been published inlocal and international journals as well as seminar presentations at national and international levels. The outputs from induced mutation via chronic radiation using Gamma Greenhouse could be of great interest for plant breeders dealing with improvement and development of new cultivars. This paper discusses the activities and achievement in plant breeding and improvement using Gamma Greenhouse Facility in Malaysia.
Samples of fine (PM2.5) and coarse (PM10-2.5) fraction of airborne particulate were collected on weekly basis during the period from May 2012 to July 2014 at Bangi, Selangor. The samples were collected using a Gent Stacked Filter Sampler in two fractions of < 2.5 µm and 2.5 - 10 µm sizes. This research paper aims at establishing the concentration level of PM2.5, PM10-2.5 and PM10 at Bangi area and investigates their possible sources and contribution to the ambient aerosol of the area. The samples were analyzed for their elemental composition and black carbon content by Particle Induced X-ray Emission (PIXE) and Smoke Stain Reflectometer, respectively. The average for PM2.5, PM10-2.5 and PM10 ranged from1.8 µg/m3 to 78.0 µg/m3, 9.6 µg/m3 to 76.8 µg/m3 and 12 µg/m3 to 134 µg/m3, respectively. Positive Matrix Factorization (PMF) technique was also applied to fine and coarse data set in order to identify the possible sources of particulate matter (PM) and their contribution to the ambient particulate matter concentrations in the area. The best solution was found to be five factors for both elemental compositions of fine and coarse PM, respectively. The PMF results show that motor vehicles and secondary sulphate contribute about 40.3% and 33.0% of the fine mass respectively followed by soil, sea salt and smoke/biomass burning with the average contribution of 10.5%, 10.3% and 6.4%, respectively. In case of coarse particles the PMF results show that a large fraction of about more than 50% of the coarse mass comes from motor vehicle. Soil dust including road dust and soil construction contribute about 32.5% of the coarse mass whilst the smoke/biomass burning factor contributes about 6.7% of the coarse mass.
For addressing the issue of adulteration and counterfeiting of the sources of origin for the edible bird’s nests (EBNs), a preliminary study of elemental characterization for their geochemical markers was performed. This study aims to characterize the elemental profiles as geochemical markers and evaluate the relationships between these markers which could be used for the verification of the geographical origin of EBN in Malaysia. EBN samples from house and cave nests that represent a range of geographical and environmental characteristics were analysed using Neutron Activation Analysis (NAA) technique. The method was validated by analysing the Standard Reference Material SRM-1515 (Apple Leaves) and SRM-1573a (Tomato Leaves) of NIST. A total of 18 elements were determined. The results showed a statistical analysis of one way ANOVA has proven that there have a significant different elemental profiles in both EBN, clearly V, As, Ba, Sc, Sm and Th were not detectable in the house EBNs. Therefore, initial finding could be concluded that those elements can be identified as the key elements for geochemical marker to differentiate the type of EBN. Furthermore the differnces probably due to natural presence of those elements as well as regional or location and seasonal variation factors affecting the dietry habits of the swiftlets.
In this paper, we report the dosimetry methodology used in the IAEA/WHO Thermoluminescent Dosimeter (TLD) Postal Dose Quality Audit Service and the results of 22 Malaysian radiotherapy centres participated in the audit from 2011 to 2015. Each participating centre was provided with a few sets of TLD capsule (two unit of TLD capsules to be irradiated and a control TLD in one set) as requested by the centres. The participating centres were asked to irradiate each TLD capsule at 2 Gy absorbed a dose to water under reference conditions i.e the TLD capsule is positioned at 10 cm depths in water, at central axis with 10 cm x 10 cm field size at 100 cm Source-Surface Distance or 100 cm Source-Axis Distance. In this period, a total of 70 photon beams consist of 43 beams and 27 beams produced by 6 MV and 10 MV photon beams, respectively have been audited. The results demonstrated that all participating centres comply with the acceptance limits of ± 5% as recommended by the International Commission on Radiation Units and Measurements (ICRU) Report 24, except eight photon beams from six centres. However, these centres presented better compliance results after being followed up with a second round of TLD irradiation.
The indoor and outdoor radon concentrations in Cameron Highlands (Peninsular Malaysia) and Ranau (East Malaysia) were measured. The measurements were carried out using passive method based on CR-39 solid state nuclear track detector (SSNTD) (for indoor measurements in Cameron Highlands) and active method using continuous radon/thoron progeny monitor (for indoor and outdoor measurements in Ranau and outdoor measurements in Cameron Highlands). The mean indoor radon concentrations in Cameron Highlands and Ranau were 50 Bqm-3 and 1.5 Bqm-3, respectively. The mean indoor radon concentration in Cameron Highlands was slightly higher compare to the world average. The maximum value recorded was 97 Bqm-3 which is almost similar to WHO reference level. The mean outdoor radon concentrations in Cameron Highlands and Ranau were 7.4 Bqm-3and 1.7 Bqm-3, respectively. The outdoor concentrations were low and comparable to world outdoor average.
The mass attenuation coefficients of solid water phantoms, Perspex® phantoms and Rhizophora spp. particleboards were determined by using Compton scattering technique measured using Ludlum configuration. The gamma energy of 137Cs sealed source were measured at 30°, 45°, 60° and 75° angles providing scattered gamma energies between 337.72 and 564.09 keV. The mass attenuation coefficients of solid water and fabricated Rhizophora spp. particleboards were the nearest to XCOM values of water with average percentage of discrepancies of 6.8% and 5.9%, respectively. The results indicated similar attenuation properties of solid water and fabricated Rhizophora spp. particleboards and the suitability of the Ludlum configuration to determine the mass attenuation coefficient of materials using Compton scatter technique.
Radiobiological model such as linear quadratic (LQ) is widely used in radiotherapy to predict the biophysical response of the tumour cell to the radiation. In clinical radiotherapy, LQ model is widely employed to plan treatment delivery and fractionation. Nevertheless, LQ model might not provide accurate prediction for high dose rate treatment. This study investigates the radiation cell survival responses using LQ model and alternative Multi-Target (MT) model. The experimental works were conducted in-vitro using HeLa cells that were irradiated using photon and electron beams of different energy. Cells irradiation were performed in full scatter condition and exposed to radiation doses ranges from 1 to 10 Gy. Clonogenic assay is used as an endpoint to obtain the cell survival curves which later be fitted with LQ and MT model. The results demonstrate that MT model produce the fitting curves that are closed to the experimental data compare to LQ model especially at high doses. Parameter analysis from both models indicates more biological damage inflicted by high energy electron beam. Correlation between the experimental cell survival data and radiobiological model analysis suggesting that alternative radiobiological model such as MT model could be applied in analysing cells’ radiation survival and damage in clinical radiotherapy.
Gold nanoparticles (AuNPs) have been extensively investigated as dose enhancement agent to increase the lethal dose to the tumours while minimizing dose to the normal tissue. Their intriguing properties and characteristics such as small size and shape provide favorable option in increasing radiotherapy therapeutic efficiency. In this study, the effects of AuNPs size on the dose enhancement effects irradiated under megavoltage photon beams were investigated. The study was conducted in-vitro on HeLa cells using AuNPs of 5 nm and 15 nm sizes. The cells samples were incubated with AuNPs and irradiated with photon beam of energy 6 MV and 10 MV at 100 cm SSD and 10 cm x 10 cm field size. Clonogenic assay were performed to observe the dose enhancement effects on cell survival. Dose enhancement factor (DEF) were extrapolated and evaluated from the cell survival curves. The results show that both sizes of AuNPs produce dose enhancement with the larger size AuNPs of 15 nm produce more dose enhancement compare to 5 nm AuNPs for 6 MV photon beam. Dose enhancements were observed for 10 MV photon beams but DEF for both sizes AuNPs shows no differences. In conclusion, larger size AuNPs produce higher dose enhancement compare to small size of AuNPs which conclude that nanoparticles size is important factor that need to be taken into account for AuNPs to be applied in radiotherapy.
Therapeutic application of metallic nanoparticles such as gold nanoparticles have been extensively investigated and intriguing finding have been reported. Superparamagnetic iron oxide nanoparticles (SPION) could also potentially have therapeutic properties that can be exploited to enhance radiotherapy outcome. In this study, investigations on the dose enhancement effects inflicted by SPIONs under irradiation with megavoltage photon beam radiotherapy were conducted. T24 human bladder cancer cell lines were pretreated with 1 mMol/L of SPION and irradiated with 6 MV and 10 MV photon beam at different doses.The non-treated cells irradiation was used as a control. Clonogenic assay was performed to determine the cell survival. Linear quadratic (LQ) model are used as fitting curve and does enhancement factors (DEF) were extrapolated from the curves. The cytotoxicity indicated cell growth normally after 72 hours and no long term cytotoxicity effects of SPIONs towards the cells were observed. The dose enhancement effects were observed for both 6 MV and 10 MV photon beam with DEF obtained 1.71 and 2.50, respectively. This reduction of cell colonies growth could be resulted from the interaction that induced free radical and reactive oxygen species (ROS) by megavoltage photon beams. The SPIONs were therefore act as multifunction nanoparticle both in diagnostic agent and radiotherapy as radiation dose enhancer, thus clearly qualified as future theranostic agents.
The purpose of the study was to determine the effect of out-of-field photon beams radiotherapy to the cancer cell survival. In this study, HeLa and T24 cancer cells were irradiated with 6 MV and 10 MV photon beams in two different conditions, one with intercellular communication with the in-field cell and one without the communication. Cells survival was determined by clonogenic assay. In the presence of intercellular communication, the cell death was increased which indicate the presence of radiation induced bystander effects (RIBE). The effects were also dependent on the cell types and photon energy where the HeLa cells exhibit less survival compares to T24 cells and the effects were prominent at higher photon energy. This study demonstrates that the out-of-field cells in conjunction with RIBE plays important roles in the cells response towards megavoltage photon beam radiation therapy.
The thermoluminescence kinetic parameters of Ge-doped flat fibre have been investigated comprehensively using the computerized glow curve deconvolution analysis. The Ge-doped flat fibre was irradiated to 6 MV and 10 MV photon beam with dose ranging from 100 cGy to 300 cGy. Analysis was done using WinGCF software on the dependence of the glow curve intensity on dose delivered and the determination of the trap parameters. Ge-doped flat fibre was found to be linear over the entire dose range explored for both 6 MV and 10 MV irradiations with r2 value of 0.9955 and 0.9933 respectively. The glow curve consists of five individual glow peaks. The peak height increases with increasing irradiation dose. The first peak (P1) is a dominant individual peak for low temperature peak (LTP) with the maximum temperature ranging from 167.4°C to 179.0°C for both beams studied. Meanwhile, peak (P4) is a dominant individual glow curve for high temperature peak (HTP) with maximum temperature for 6 MV and 10 MV and is observed between 264.5°C to 279.4°C. Peak 1 has the lowest activation energy which is less than 0.72 eV while peak 2 shows the highest activation energy (1.3 eV < Ea < 2.1 eV) which indicates the deepest electrons trap. The results showed that the peak integral will increases as the dose increases. The Ge-doped flat fibre demonstrated the second-order kinetic peak behavior by exhibiting the symmetric shape of the glow curve with high temperature half of the curve slightly broader than the low temperature half, which suggests the possibility of electron retrapping.
Peroxide pre-vulcanized natural rubber latex prepared by using gamma irradiation technique is an alternative over the conventionally prepared peroxide pre-vulcanized that used activator to promote the peroxide decomposition in natural rubber latex. Through this technique the problems aroused by some activators such as tends to darken the natural rubber latex film during the drying process can also be overcome. For this preliminary study, data obtained from crosslink density and mechanical measurements were used to evaluate the effectiveness of gamma irradiation in the vulcanization process. Increasing the quantity of tert-butyl hydroperoxide (t-BHPO) from 0.1 pphr to 0.3 pphr while the irradiation dose maintain at 12 kGy has successfully delivered peroxide vulcanized natural rubber latex films with average tensile strength, modulus @ 500% and modulus @ 700% around 15.33, 1.01 and 3.42 MPa, respectively. The effective pre-vulcanization irradiation dose with respect to maximum crosslinking density (85.8 %) was observed on film prepared at 0.1 pphr t-BHPO.
This study was performed to observe the variation in the distribution of 210Po,210Pb and 210Po/210Pb activity ratio throughtheir vertical profile of the sediment cores takenat surrounding Sungai Linggi estuary. Five sediment cores were takenin February 2011 and were cutto an intervalof 2 cm layer. Activity concentrations of 210Po and 210Pb were determined using alpha radiochemical analysis and gamma direct measurement, respectively. Generally, the measured activity of 210Po, 210Pb and 210Po/210Pbwere in the ranges of 22.73 –139.06 Bqkg-1dw., 37.88 –176.24 Bqkg-1dw.and 0.23 –1.34, respectively. The variation in the distribution profile for the radionuclides are believed to be influencedby human activities such as agriculture, fertilizer, vehicles, burned fuel fossil and forest, industrialand others via river input from land-base.Other factor is due to organic mattercontent played importantrole as the geochemical carrier to transportthose radionuclides at study area. It was provedthat hasa strong correlation between the radionuclide distribution and the sedimentcomposition of organic matter.Furthermore, in those rangesreflectedthat 210Pb activities were higher than210Po with an activity ratio average of 0.79. This is probably due to dramatic increase of excess 210Pb supplied from atmospheric deposition, in situ decay of 226Ra and as a result of diagenetic remolibilazationof 210Pbin deeper layesof the sediment column. Thus, thosefactors are majorcontributions on thevariation of 210Po and 210Pb in the sediment core at surrounding Sungai Linggi estuary.
Natural radioactivityin thesurface soil from thevicinity of Lynas Rare-earth plantin Kuantan, Pahanghad been studied with aim of evaluating environmental radioacitivityof thatarea. The radioactivities of the samples have been measured usinga low-background HPGe gamma detector. The concentration of 226Ra ranged found to be between 8.7 –76.9 Bq/kg (mean 33.7 Bq/kg); activity of 238U from 8.7 to 80.5 Bq/kg (mean 36.9 Bq/kg); as for 232Th, it ranged from 6.2 to 121.5 Bq/kg(mean 58.2 Bq/kg)and that of 40K,the values was from 19.1 to 778.9 Bq/kg (mean of 221.3 Bq/kg). Activity standard deviation for226Ra, 238U, 232Th and 40K were 14.2 Bq/kg, 14.7 Bq/kg, 26.1 Bq/kg and 185.6 Bq/kg, respectively. To evaluate the risk of radiation hazard to human, several parameters, i.e. the radium equivalent activity, External hazard index, Representative level index and dose rate in air from the terrestrial natural gamma radiation were calculatedwith the mean valuesfound to be136.7 Bq/kg, 0.4, 1.0, 65 nGy/h, respectively. The data were discussed and compared with those obtained from the previous studies given in the literatures. Thisstudy found that themean dose equivalent received by an individual at the vicinity area (outdoor) of Lynas plant was estimated to be 82.0 Sv/yr, whichis far below the annual dose limitof1,000 Sv/yrfor general public as stipulated in the national act.