Gamma Exposure Research Articles

Enhancing biomass, hydrocarbon and biodiesel properties of green microalga Botryococcus braunii KMITL through gamma and UV radiation exposure.

This study investigated the effects of gamma (137Cs, 0-250Gy) and UV (UV-C, 0-12h) radiation on growth and biodiesel properties of Botryococcus braunii KMITL. For gamma radiation, maximum biomass (1.37 ± 0.02g L-1) was achieved with 50Gy, while a dose of 200Gy resulted in the highest hydrocarbon content (51.84 ± 0.20%) and yield (0.66 ± 0.01g L-1). For UV radiation, a 9h exposure produced the highest biomass (2.45 ± 0.05g L-1), hydrocarbon content (55.01 ± 1.22%), and yield (1.35 ± 0.04g L-1). Algae exposed to gamma radiation within the range of 0-150Gy exhibited C16:0 as the dominant fatty acid methyl ester (FAME), similar to those exposed to UV radiation, while algae exposed to 200-250Gy displayed C18:1n9t as the dominant FAME. High levels of gamma and UV radiation were observed to lengthen fatty acid chains and increase unsaturated fatty acids. The cetane values of biodiesel from algae exposed to gamma and UV radiation ranged from 64.55 ± 0.14-66.47 ± 0.20 and 59.43 ± 0.04-65.27 ± 0.22, respectively, all meeting standard criteria. Both gamma and UV radiation also improved the saponification value and cold flow properties of the biodiesel. These findings suggest that controlled levels of gamma and UV radiation effectively enhance hydrocarbon yields with significant implications for biofuel production.

8096 Optimization of Radiation Safety Release Instructions After Iodine-131 Treatment for Differentiated Thyroid Cancers

Abstract Disclosure: A.H. Smith: None. T. Greist: None. Introduction: Iodine-131 (I-131) is a common therapy for treatment of differentiated thyroid cancers (DTC); however its radioactivity poses a risk to public health. There is wide inter-facility variation in release instructions to minimize incident exposure to other individuals. Isolation measures to reduce gamma exposure may pose harm to an individual's mental or physical health, especially in new parents or patients who require caregivers. Most studies estimating incident exposure utilize cumulative dosimetry to estimate duration of safety release instructions, but this relies on expert assumptions of the clearance of I-131, which is altered in patients who have had their thyroid removed. Measuring real-time longitudinal gamma exposure would optimize recommendations to balance the radiation safety risks with the risks associated with isolation. Objective: Quantify real-time longitudinal incident gamma radiation exposure to others from patients with DTC status post thyroidectomy treated with I-131. Methods: Patients were asked to measure exposure rates at a distance of one meter three times a day for fourteen days, using a portable ion chamber at their homes. Exposure rates over time were used to form an exponential decay model and to estimate the time after which cumulative exposure is below a reasonably low threshold. Results: 32 patients were included in the study. The average effective half-life was 15.8 hours. Exposure readings over time were best fit with an exponential decay model using one decay rate, rather than a model that uses separate extrathyroidal and thyroidal decay rates. Among patients administered less than 114 mCi, cumulative gamma exposure is less than 100 mR after 24 hours of isolation. Between 114 and 163 mCi, cumulative gamma exposure is less than 100 mR after 48 hours of isolation. Conclusion: Cumulative gamma radiation exposure at one meter was found to be low enough to consider re-evaluating isolation protocols and safety release instructions for long-term distancing in patients status post thyroidectomy treated with I-131. Presentation: 6/1/2024

Fabrication, photovoltaic analysis, and electrical characterization of Au/ZnTPyP/p-Si/Ag heterojunction under gamma radiation effect for solar cell applications

The main objective of the current study is to investigate the impact of gamma rays on the characteristics and behavior of a fabricated heterojunction device based on tetra pyridyl-porphine zinc (ZnTPyP). The importance of this study includes determining critical parameters such as conversion efficiency (η). A cobalt-60 gamma source has been employed to investigate the effects of gamma exposure dosages ranging from 0 to 5 kGy on the morphological and optical features of the studied material. An atomic force microscope (AFM) was used to examine the morphological characteristics of the ZnTPyP film that formed on the glass substrate. The thin film’s optical characteristics were investigated on quartz for both as-deposited and irradiated films at various gamma doses (1 kGy and 3 kGy). Additionally, ZnTPyP is evaporated on p-type silicon substrates to create ZnTPyP/p-Si heterojunction. The current–voltage (I–V) curves at various doses of gamma radiation at 0, 1, 3, and 5 kGy for Au/ ZnTPyP /p-Si/Ag heterojunction device are experimentally measured. The predominant conduction processes are the thermionic emission and single-trap space-charge-limited current (SCLC). Furthermore, the values of the barrier height φB\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\left( {\\varphi_{B} } \\right)$$\\end{document} are estimated using two different methods, including I–V method and Norde’s equations at different doses, and their values are comparable. Under illumination at 0 kGy, we found the values of short-circuit current (Isc), open-circuit voltage (Voc), and photoconversion efficiency (η) to be 0.92 mA, 0.41 V, and 4.28%, respectively. On the hand, some important optical parameters are determined for both as-deposited and irradiated ZnTPyP films, such as skin depth (δ), and found that δ values reduce with increasing gamma doses, reflecting the efficiency and performance of photovoltaic cells. Finally, the study indicated the alteration in the studied optical parameters and slightly enhanced the Au/ZnTPyP/p-Si/Ag heterojunction efficiency when subjected to gamma radiation.

Identification of gamma irradiated polycarbonate-polybutylene terephthalate stiff polymer blend products using HS-GC/MS, FTIR and UV/Vis spectroscopy

In this study, the fragmentation products of Makro-blend stiff polymer due to gamma exposure were identified using Head space (HS), Gas Chromatography, and Mass Spectrometry (HS-GC/MS) techniques and Fourier Transform Infra-Red (FTIR) spectroscopy. As well the electronic transitions due to gamma exposure were examined using UV/Vis spectroscopy. For the un-irradiated and 10 kGy irradiated samples, one product was detected by (HS-GC/MS) method with a clear peak of Dimethoxyethane (MW = 90), which has a peak area percentage of 98.58% and 97.13%, respectively. With increasing gamma doses the number of identified components was increased. At 1200 kGy, ten components were detected: Biethylene (MW = 54), Dimethoxyethane (MW = 90), 1,1-Dimethoxy-2-propanone (MW = 118), 1,1-Dimethoxy-2-propanol (MW = 120), 1,1-Dimethoxycyclopentane (MW = 130), 1,1-Dimethoxyheptane (MW = 160), 1,1-Dimethoxyoctane (MW = 174), Dimethyl terephthalate (MW = 194), 4-(Diethoxymethyl) benzaldehyde (MW = 208), and Terephthalate dihexyl (MW = 334), which have peaks area percentages of 4.22, 2.98, 25.84, 2.2, 10.65, 38.86, 1.57, 5.91, 1.22, and 6.48, respectively. The recorded mass spectrum of each component confirms the molecular ion peak. The FTIR measurements demonstrate the decrease in the detected band intensities following gamma radiation. Accordingly, a chain scission occurs, which causes the carbonate bond to scission, resulting in the creation of a hydroxyl group and the (–H) abstraction from the backbone of the irradiation blend samples. The absorbance edge of the gamma-exposed samples shifted towards a higher wavelength. This pattern shows that the band gap energy is declining. The use of FTIR and HS-GC/MS in mass spectrometry analysis will be useful tools for examining radiation-induced polymeric fragments and advancing our understanding of the process underlying the creation of these fragments in polymers.

Uranium Mine Proposed Experimental Design for Natural Background Gross Gamma Exposure Rates, Post Remediation Final Status Survey Sampling Density, and Radiological Water Quality Modeling for a Worst-case Catastrophic Failure, Coles Hill, Virginia.

Completely randomized experimental design statistical modeling techniques were employed to analyze exposure rate measurements for evaluating hypothetical natural background post uranium mill operations at Coles Hill, Virginia uranium milling processes. The proposed Coles Hill Uranium Mine is situated upstream of the Banister River. This River is nearly homogenous throughout the reach length used in analysis and feeds into the mouth of Kerr Reservoir, Lake Gaston, which serves as the main drinking water source for cities in the Hampton Roads area including Norfolk, Virginia Beach, and Chesapeake. A critical scan value (=DCGLscan) was developed to flag anomalies of surface contamination during simulated post remediation final status surveys. The natural background was critical for meeting the Multi-Agency Radiation Survey and Site Investigation Manual guidance for post remediation final status surveys. The overarching null hypothesis suggested that the selected mean natural background is equal to the survey unit's mean natural background. Using SAS Procedures Shapiro-Wilk Test, ANOVA, and CR, it was decided the exposure rate data was normal, had no extreme outliers, and no collinearity between the number of samples (=treatment) and the areas (=block). Using the q-hyper (hypergeometric) distribution, the soil sampling density was decided for a final status survey unit. The most likely worst-case catastrophic failure analysis, 500-year event, such as the1969 Hurricane Camille of 69 centimeters of rain in Nelson County, Virginia was included in the model. The model showed impact was minimal at most to the Banister River's drinking water and likely less than the Virginia's Drinking Water Standards for gross alpha, 226Ra and 228Ra, and total uranium.

Effect of gamma irradiation on properties of the synthesized PANI-Cu nanoparticles assimilated into PS polymer for electromagnetic interference shielding application

Conductive polymer nanocomposites for electromagnetic interference (EMI) shielding are important materials that can be combat the increasingly dangerous radiation pollution arising from electronic equipment and our surrounding environment. In this work, we have synthesized polyaniline-copper nanoparticles (PANI-Cu NPs) by the copper salt based oxidative polymerization method at room temperature and then added with different concentration (0, 1, 3 and 5 wt%) in polystyrene polymer forming PS/ PANI-Cu nanocomposites films by means of the traditional solution casting technique. The formed PANI-Cu NPs were investigated by UV/Vis spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM) and SEM/EDX elemental mapping techniques. On the other hand, the prepared PS/PANI-Cu nanocomposites films were evaluated by UV and SEM, the mechanical properties of the nanocomposites films were evaluated and showed an improvement by added PANI-Cu NPs up to 3 wt% and 50 kGy gamma exposure dose. The PS/PANI-Cu nanocomposites films were examined as electromagnetic interference shielding material. Electromagnetic shielding effectiveness of the produced nanocomposites were tested in the X-band of the radio frequency range namely from 8 to 12 GHz using the vector network analyzer (VNA) and a proper wave guide. All samples were studied before and after 50 kGy gamma-ray irradiation under the same condition of pressure and temperature. The results showed that the nanocomposites have improved shielding properties.

Determination of gamma radiation shielding efficiency by radiation-resistant composite ZrO2–Al2O3 – TiO2–WO3 – Nb2O5 ceramics

This work examines the prospects of using composite ZrO2–Al2O3 – TiO2–WO3 – Nb2O5 ceramics as shielding and radiation-resistant materials as structural materials in conditions of heightened radiation background, including gamma radiation and exposure to heavy ions. The key objective of the study is to determine the impact of the variation in composite ceramic composition on resistance to radiation damage caused by exposure to heavy ions comparable to nuclear fuel fission fragments, and to establish the effect of the radiation damage accumulation on the shielding characteristics of these ceramics, the maintenance of which determines the stability of the operation of nuclear materials by eliminating the ionization factor caused by the interaction of gamma quanta. During the studies, it was found that alterations in the phase composition of composite ceramics associated with the formation of ZrTiO4, AlWO3 and Nb2W3O14 phases in the structure lead not only to strengthening of the ceramics, but also to a rise in resistance to radiation damage, and associated changes in the damaged layer degradation, having an adverse impact on the shielding characteristics.

Assessment of radionuclides in the soil of Bonny Local Government Area Of Rivers State, Nigeria and evaluation of radiological risk

Twenty Samples each of soil from Bonny LGA, Rivers State, Nigeria were analyzed using NaI(IT) gamma detector to estimate radiation hazard due to the anthropogenic sources. The activity concentration of 232Th was found to be in the range 18.78 – 397.13 BqKg-1, 40K in the range 43.72 – 390.62 BqKg-1 and 226Ra in the range 10.77 – 57.84 BqKg-1 all in soil. These results were used to calculate the radiological hazard parameters including the Annual Gonadal Equivalent Dose. The calculated gamma exposure rates ranged between 10.00 – 270.79 nGyh-1 while the average value of the Excess Lifetime Cancer Risk (ELCR) was found to be 0.38 x 10-3 for soil which is higher than the world average of 0.29 x 10-3.

Optical properties of thin films monitored in real-time at high gamma radiation doses using long period fiber gratings

In this work, we report an all-optical-fiber-based method to monitor in real-time the changes in thin film optical properties when exposed to harsh environments such as high doses of gamma radiation. The method is based on a long period grating (LPG) inscribed in a radiation resistant optical fiber, which is coated with a thin film to be analyzed. Due to impact of the environment on the film properties, the transmission spectrum of the LPG changes. To validate this methodology, we deposited oxides of various metals, i.e. aluminum (Al2O3), titanium (TiO2), and tantalum (Ta2O5), as well as a polymeric film, namely polystyrene (PS), on the LPG surface and measured the resonant wavelength shift induced by high doses of gamma exposure (dose rate of 2.3 kGy/h, up to a total dose of 46 kGy). The changes could be observed in real-time up to maximum reached dose and during the recovery period. The results are significantly dependent on thin film material. Among the oxides, TiO2 thin film demonstrated the highest susceptibility to irradiation, whereas Al2O3 exhibited the least impact. Additionally, a good recovery potential for Ta2O5 thin film was observed, hinting at its promising application in dosimetry. Conversely, the PS film exhibited a permanent effect induced by irradiation. This is the first real-time experimental study of the impact of high dose gamma radiation on thin film optical properties using a universal optical-fiber-based device. The findings pave the way for assessing radiation hardness of thin film materials or utilizing such a method to optimize material treatment involving ionizing radiation.

Evidence for ionization damage in mid-wave infrared nBn detectors

The effects of 63 MeV proton and 60Co gamma irradiation on the operation of 4.3 μm cutoff nBn photodetectors are demonstrated separately, and both are shown to yield a total ionizing dose (TID) effect. The effect is shown here in an InAsSbBi nBn detector and has been observed in other bulk alloy nBn detectors, and is unusual as it is notably absent in superlattice nBn detectors. The non-antireflection coated detectors exhibit a pre-radiation quantum efficiency of 17% at 3.3 μm wavelength and a dark current density of 50 μA/cm2, or roughly 300× the Rule 07 expectation, at their ideal operating voltage of −0.4 V bias at 150 K. Step-wise proton irradiation and in situ measurement indicate that the dark current increases to about 400× Rule 07 at the highest proton dose level of 150 krad(Si) (9.10 × 1011 p+/cm2), while the quantum efficiency is degraded at a relatively faster rate than the majority of analogous detectors characterized by our lab. Both the photocurrent and dark current are also shown to exhibit a turn-on voltage magnitude reduction of 100 mV following either gamma or proton irradiation, a trend which is attributable to negative trapped charge at the barrier interface (TID effect). This theory is further supported by an observed capacitance density magnitude reduction with dose and affirmed with Silvaco TCAD simulations. Following both proton exposure and subsequent anneal and gamma exposure and subsequent anneal; dark current, photocurrent, and CV all approach their pre-radiation baseline values.

Assessment of outdoor gamma exposure levels at some borehole and well sites in Dutse, Nigeria

The lives on the earth are continuously exposed to ionizing radiation originating mainly from natural sources. Fortunately, the associated health hazard is not an acute problem globally. However, health complications are inevitable in areas assumed to have high background ionizing radiation levels. The present study aims to unveil the scenarios of outdoor gamma radiation levels at Dutse, the northwestern part of Nigeria. In this study, gamma exposure levels (GEL) across sixty-six (66) selected boreholes and local wells located in the said region have been measured using a well-calibrated hand dosimeter (Radiation Alert Inspector). Using the GEL values some significant radiation parameters were calculated to determine the possibility of radiological health risks to the local people. The measured gamma exposure level around the boreholes is seen to vary from 1.1 - 1.9 μrem/hr with a mean of 1.5 μrem/hr and around the wells it ranges between 1.1 – 1.8 μrem/hr with a mean of 1.5 μrem/hr. For boreholes, the estimated annual effective dose (AED) varies between 13.50 – 23.31 μSv/yr with a mean of 17.29 μSv/yr and for wells the same resulted 13.50 – 22.08 μSv/yr with a mean of 17.92 μSv/yr. All the obtained dose values are lower than the UNSCEAR proposed world average level of 70 μSv/yr. The estimated average ELCR values was found to be 0.061 × 10-3 and 0.064 × 10-3 for boreholes and wells respectively. All findings were below the UNSCEAR recommended world average level of (0.29 × 10-3). In summary, this work indicates a low risk of exposure to outdoor ionizing radiation among the inhabitants around the study locations.

The effect of high-intensity gamma radiation on PETG and ASA polymer-based fused deposition modelled 3D printed parts

There is growing interest in the application of 3D printing for demanding environments subject to gamma radiation in areas such as the nuclear industry and space exploration. In this work, the effect of gamma radiation on fused deposition modelled 3D printed parts composed of polyethylene terephthalate glycol (PETG) and acrylic styrene acrylonitrile (ASA) polymers was studied. Dose levels of up to 2.25 MGy were applied to the printed components, doses equivalent to over 1 year operating near spent nuclear fuel cells. Infrared spectroscopy showed the evidence of cross-linking by the formation of peaks corresponding to –OH and C–H bonds. Tensile and hardness testing was used to assess changes in mechanical properties and showed a reduction in ultimate tensile stress and maximum strain in parts made from both polymers, but with PETG retaining greater strength and ductility than ASA, especially at intermediate gamma exposure. Young’s modulus and hardness showed either modest increases or a fairly flat response with exposure. Mechanical properties were heavily dependent on the build structure, with horizontal build samples pulled parallel to the filament direction being several times stronger than vertical build samples pulled normal to the layers. Non-irradiated samples pulled parallel to the filament direction were indicative of ductile failure, with rough surfaces, distinct infill and wall regions and evidence of thinning occurring after fracture, but irradiated fracture surfaces were flatter, smoother and without local thinning, suggesting gamma radiation-induced embrittlement in the material. For samples pulled perpendicular to the filament direction, all fractures occurred between layers, creating flat fracture surfaces with no evidence of necking and indicative of brittle failure regardless of whether the samples were irradiated.

Gamma Irradiation Promotes the Growth Rate of Thai Pigmented Rice As Well As Inducing the Accumulation of Bioactive Compounds and Carbohydrate Hydrolyzing Enzymes Inhibitors (α-Glucosidase and α-Amylase) under Salt Conditions.

Rice contains many bioactive compounds that perform various biological activities. Some of these compounds have been identified as α-glucosidase and α-amylase inhibitors, including guaiacol, vanillin, methyl vanillate, vanillic acid, syringic acid, and 2-pentyl furan. In this study, we assessed the growth rate, photosynthetic pigment content, phenolic content, and flavonoid content of gamma-irradiated Thai pigmented rice. Bioactive components of gamma-irradiated rice that had been subjected to salt treatment were also investigated. The findings showed that production of photosynthetic pigments, which are associated with plant growth, was induced by low gamma exposure. Phenolic and flavonoid content of rice was increased after gamma irradiation at 5 to 1,000 Gy. Both gamma irradiation and the salt conditions changed the quantity of vanillin, methyl vanillate, and vanillic acid in the rice. However, at a salt concentration of 40 mM, the salt stress had more of an effect than the gamma dosage. However, the high concentrations of methyl vanillate and vanillic acid detected in the rice under salt conditions were ameliorated by gamma irradiation. Guaiacol served as the substrate of guaiacol peroxidase for catalyzed reactive oxygen species, as evidenced by the observation that the guaiacol content of rice decreased between increased gamma dosages. A gamma dose of 40 to 1,000 Gy resulted in the production of syringic acid. Under salt stress, syringic acid buildup was also seen to be ameliorated by gamma irradiation. In comparison to salt conditions, particularly for 20 mM salt, gamma irradiation had less of an impact on the 2-pentyl furan in rice.

Effects of gamma irradiation on the properties of Ce2S3 thin films

Cerium sulphide (Ce2S3) thin films were prepared via successive ionic layer adsorption and reaction (SILAR) scheme. The optical, structural, and electrical investigations of both virgin and gamma-exposure samples were conducted, focussing on the gamma irradiation dose. The objective was to examine the impact of gamma irradiation on the characteristics of the Ce2S3 thin films. An X-ray diffraction (XRD) study of the samples established the orthorhombic phase of the Ce2S3 thin films and revealed that the crystallinity was improved with the gamma dose. The Field emission scanning electron microscope (FESEM) images of the virgin thin film detected a smooth surface with spherical grains with distinct grain boundaries. In contrast, after the gamma exposure, the thin film surface revealed a cluster of small particles. Energy dispersive X-ray (EDX) study inveterate the stoichiometry of the prepared Ce2S3 thin films. The gamma exposure dose caused a deviation in the bandgap, which was related to the quantum confinement effect. Photoluminescence (PL) spectra proved that the emission intensity of the Ce2S3 thin films decreased with increasing gamma dosage, and this phenomenon was attributed to the additional crystallites and a smaller number of structural defects. This simple approach to amend the characteristics of Ce2S3 thin films by gamma exposure could become an attractive option to explore this material for dosimetry and radiation sensing.

Lifetime evaluation of left ventricular structure and function in male ApoE null mice after gamma and space-type radiation exposure.

The space radiation (IR) environment contains high charge and energy (HZE) nuclei emitted from galactic cosmic rays with the ability to overcome current shielding strategies, posing increased IR-induced cardiovascular disease risks for astronauts on prolonged space missions. Little is known about the effect of 5-ion simplified galactic cosmic ray simulation (simGCRsim) exposure on left ventricular (LV) function. Three-month-old, age-matched male Apolipoprotein E (ApoE) null mice were irradiated with 137Cs gamma (γ; 100, 200, and 400cGy) and simGCRsim (50, 100, 150cGy all at 500 MeV/nucleon (n)). LV function was assessed using transthoracic echocardiography at early/acute (14 and 28days) and late/degenerative (365, 440, and 660days) times post-irradiation. As early as 14 and 28-days post IR, LV systolic function was reduced in both IR groups across all doses. At 14days post-IR, 150cGy simGCRsim-IR mice had decreased diastolic wall strain (DWS), suggesting increased myocardial stiffness. This was also observed later in 100cGy γ-IR mice at 28days. At later stages, a significant decrease in LV systolic function was observed in the 400cGy γ-IR mice. Otherwise, there was no difference in the LV systolic function or structure at the remaining time points across the IR groups. We evaluated the expression of genes involved in hemodynamic stress, cardiac remodeling, inflammation, and calcium handling in LVs harvested 28days post-IR. At 28days post-IR, there is increased expression of Bnp and Ncx in both IR groups at the lowest doses, suggesting impaired function contributes to hemodynamic stress and altered calcium handling. The expression of Gals3 and β-Mhc were increased in simGCRsim and γ-IR mice respectively, suggesting there may be IR-specific cardiac remodeling. IR groups were modeled to calculate the Relative Biological Effectiveness (RBE) and Radiation Effects Ratio (RER). No lower threshold was determined using the observed dose-response curves. These findings do not exclude the possibility of the existence of a lower IR threshold or the presence of IR-induced cardiovascular disease (CVD) when combined with additional space travel stressors, e.g., microgravity.

Option gamma and stock returns

Stocks with high net gamma exposure systematically underperform stocks with low net gamma exposure. This effect is distinct from other well-known return predictors, and survives many robustness checks. We show that stocks with low net gamma exposure negatively predict future realized volatility, and argue that investors command a risk premium to hold low net gamma exposure stocks, which are riskier. Lastly, we show that the volatility predictability stems from a non-informational channel, and not from private information.

Evaluation of potential radiological hazards of unfired construction materials containing fly ash in Vietnam.

In this study, the specific activities of 226Ra, 232Th and 40K in the unfired construction materials (solid card bricks, 4-hole bricks, pavement bricks) containing fly ashand bottom ash from a coal-fired thermal power plant in Vietnam were measured using the low-level gamma-ray spectrometer with HPGe detector. Also, the 222Rn concentrations in these materials were analyzed using RAD7 radon monitor and then radon mass exhalation rate and emanation fraction of these materials were calculated. The potential radiological hazards for residents living in the model room made of these materials were evaluated. The average specific activity of 226Ra, 232Th and 40K were found as 67.7, 79.3 and 703.5Bqkg-1, respectively. The total annual effective dose (due to external gamma exposure and internal radon exposure for resident living in the CEN model room made of the unfired brick samples) was found as 0.9mSvy-1 which is lower than the worldwide average dose of 2.4mSvy-1. Calculations from ResRad-Build code showed that the doses due to radon exposure account for from 62.3% (at the first year) to 98.8% (at the next 30years) of the total gamma and radon dose. Under low air exchange to the outside environment, from the 6th year onwards, the total dose may exceed the average dose value from natural radiation exposure sources.

Adjusting for Berkson error in exposure in ordinary and conditional logistic regression and in Poisson regression

BackgroundINTEROCC is a seven-country cohort study of occupational exposures and brain cancer risk, including occupational exposure to electromagnetic fields (EMF). In the absence of data on individual exposures, a Job Exposure Matrix (JEM) may be used to construct likely exposure scenarios in occupational settings. This tool was constructed using statistical summaries of exposure to EMF for various occupational categories for a comparable group of workers.MethodsIn this study, we use the Canadian data from INTEROCC to determine the best EMF exposure surrogate/estimate from three appropriately chosen surrogates from the JEM, along with a fourth surrogate based on Berkson error adjustments obtained via numerical approximation of the likelihood function. In this article, we examine the case in which exposures are gamma-distributed for each occupation in the JEM, as an alternative to the log-normal exposure distribution considered in a previous study conducted by our research team. We also study using those surrogates and the Berkson error adjustment in Poisson regression and conditional logistic regression.ResultsSimulations show that the introduced methods of Berkson error adjustment for non-stratified analyses provide accurate estimates of the risk of developing tumors in case of gamma exposure model. Alternatively, and under some technical assumptions, the arithmetic mean is the best surrogate when a gamma-distribution is used as an exposure model. Simulations also show that none of the present methods could provide an accurate estimate of the risk in case of stratified analyses.ConclusionWhile our previous study found the geometric mean to be the best exposure surrogate, the present study suggests that the best surrogate is dependent on the exposure model; the arithmetic means in case of gamma-exposure model and the geometric means in case of log-normal exposure model. However, we could present a better method of Berkson error adjustment for each of the two exposure models. Our results provide useful guidance on the application of JEMs for occupational exposure assessments, with adjustment for Berkson error.

Comparative study of lignin and sodium lignosulfonate extracted from irradiated and non-irradiated sawdust wastes

Recent technologies in the production of chemicals and bio-material products are focusing on lignocellulosic biomass resources since it is the world's most abundant economical material, recyclable, sustainable, low cost, as well as highly renewable natural resources. This biomass refers to agricultural wastes such as woody plants (soft and hardwood). Lignin is extracted from these agro-wastes using chemical methods and ionizing radiation. The outcome of employing gamma radiation as a pretreatment step prior chemical treatment on the duration for alkaline, acid, and production of sodium lignosulfonate (NaLS) was examined. The structure of the produced NaLS was verified utilizing Nuclear magnetic resonance (1H-NMR, 13C-NMR) and Liquid chromatography–mass spectrometry (LC–MS). A comparison between the physicochemical properties of sodium lignosulfonate extracted from both non-irradiated and irradiated sawdust waste was studied using FTIR, XRD, EDX and TGA. The degree of sulfonation of the produced NaLS was determined utilizing the potentiometric titration method. The findings demonstrated that gamma exposure pretreatment step reduces the time of alkaline, acid, and sulfonation processes as well as a higher yield percentage and degree of sulfonation.

An experimental approach to determine the gamma radiation interaction mean free path and exposure buildup factor for biomolecules

This experimental approach was designed to understand the gamma interaction parameters for the essential biomolecules, including starch soluble, cholesterol, myristic acid, glucose, oxalic acid, dextrose, salicylic acid, ethyl cellulose and sucrose. The empirical determination of gamma interaction parameters, such as interaction mean-free-path (MFP), buildup factor, and effective atomic number (Zeff) was performed by measuring mass attenuation coefficient (μ/ρ) at energies of 356 keV, 511 keV, 662 keV, 1173 keV, 1275 keV and 1332 keV. This was achieved using weak radioactive sources and a NaI(Tl) scintillation spectrometer with collimated and non-collimated transmission geometry. The experimentally determined values of gamma-ray interaction parameters were obtained non-destructively and precisely agreeing with the expected values from simulations and codes. In addition, the research findings also revealed a novel trend in gamma interaction mean free path as a function of energy and variable buildup factors for the selected biomolecules. These research findings provide valuable insight into the process of gamma radiation interaction. This approach may fulfil the increasing demand of medical, technical and academic research laboratories for a cost-effective and reliable empirical methodology to understand gamma radiation interaction with matter.