High Gamma Radiation Research Articles

Thermoluminescence behavior of gamma irradiated Y2O3:Sm3+ nanophosphor

Thermoluminescence (TL) properties of 60Co gamma irradiated Sm3+ doped Y2O3 nanophosphors were investigated for possible application for high dose gamma radiation dosimetry. Sm3+ doped Y2O3 nanophosphors were synthesized by the solution combustion method. The crystalline phase was analyzed with X-ray diffraction and an average crystallite size was found to be ~20–33 nm. TL glow curves of gamma irradiated Sm3+ doped Y2O3 nanophosphors were recorded. The TL glow curves showed a prominent glow peak at ~400 K, a smaller intensity peak at 510 K and a very weak intensity glow peak at ~640 K. These glow peaks were ascribed to host defects and Sm3+ characteristic emission. The effect of Sm3+ concentration on the TL was explored and the optimum Sm3+ concentration was found to be 0.1 mol%. The number of overlapping TL glow peaks were identified from the broad TL glow curve by the thermal cleaning method. The kinetic parameters were obtained by the glow curve deconvolutions method using the general order kinetics expression. The variation of the TL intensity with dose, the effect of heating rates, repeatability and the fading effects of gamma irradiated Sm3+ doped Y2O3 nanophosphors were also studied. TL emission showed a strong green (545 nm) emission at ~400 K and a characteristic Sm3+ emission was observed at a high dopant concentration. The results obtained were favorable for the application of high dose gamma radiation dosimetry.

Black sand deposits; their spatial distribution and hazards along the northern coast of Sinai Peninsula, Egypt

Airborne Gamma Ray Spectrometric (AGRS) surveys and image processing techniques are utilized to define the occurrence of black sand deposits along Sinai's northern coastal plain. High contents of radioactive minerals are detected in these deposits; zones of high concentrations of uranium 238U, thorium 232Th, and potassium 40K could be outlined. Remote sensing and GIS techniques are integrated to study the pattern of coastline changes and its relationship to the distribution of black sand deposits during the period between 2000 and 2020. The results reveal high 232Th anomalies along El-Arish Beach due to its high monazite content; containing 7.92% ThO2. In addition, high uranium anomalies on the eastern sides of El-Bardawil Lake result from the abundance of zircon in the sediments surrounding the lake, which contain 5.29% U3O8. Areas of high radiation levels, which exceed the allowed limits for human exposure, are outlined by calculating adsorbed and annual effective dose rates. Unfortunately, many of these areas are open and easily accessible to the public, presenting a direct threat to the health of local inhabitants. These anomalous areas ought to be excluded from the ongoing national housing and land reclamation projects, where long-term exposure to high gamma radiation increases the cancer risk factor in humans.

Aging study on Resistive Plate Chambers of the CMS Muon Detector for HL-LHC

In the High Luminosity Large Hadron Collider (HL-LHC) program, during the next years, the instantaneous luminosity will increase up to 5 × 1034 cm−2 s−1 which means a factor five higher than the nominal LHC luminosity. In that period, the present CMS Resistive Plate Chambers (RPC) system will be subjected to background rates higher than those for which the detectors have been designed, which could affect the detector properties and induce aging effects. To study whether the present RPC system can sustain the hard background conditions during the HL-LHC running period, a dedicated longevity test is ongoing at the CERN Gamma Irradiation Facility, where a few spare RPCs are exposed to high gamma radiation for a long term period to mimic the HL-LHC operational conditions. During the longevity test, the main detector parameters are continuously monitored as a function of the integrated charge. Preliminary results of the study, after having collected a sufficient amount of the expected integrated charge at HL-LHC, will be presented.

Effect of high gamma irradiation doses on structure and morphology properties for Epoxy resins

Effects of gamma irradiation doses on epoxy resins thin, composed films was investigated. The structure properties of irradiated epoxy resin films with different thickness was measured using X-Ray Diffraction (XRD). Epoxy-resin thin films were exposed to gamma- rays with doses ranging from 0 to 120 kGy. The XRD parameters were calculated in 2 theta (2 θ) range between (4° to 90°). Via the X-ray diffraction analysis, it was found that all physical parameters such as; lattice aspacing (d), inter-chain separation (R), interlayer distance (D), average crystal size (LC), degree of crystallinity (χC), Number of crystallites per unit area (N), dislocation density (δ), micro-strain (ε), average lattice strain (LS), and distortion parameters (g) and total broadening (L) could be determined. The results indicate that all parameters were dependent on (FWHM) and equal to zero, except at 120KGy. The Structure of epoxy thin films was transformed from the amorphous to crystal phase by applying the small thickness thin films and high gamma irradiation doses. Moreover, adding the material hardened in epoxy thin film composites and exposed to gamma irradiation increased crystallinty. The surface morphology was investigated by means of a scanning electron microscope (SEM). Via SEM, the crystal phase morphology is improved and the microstructure is homogenous for different thickness thin films and high gamma irradiation doses. The epoxy resins thin films proved to be an excellent material in different applications requiring low, tensile strength, high elasticity, low wear resistance and moderate thermal resistance especially in manufacture insulators.

Structural and optical properties of sol-gel synthesized h-MoO3 nanorods treated by gamma radiation

High energy external gamma radiation has always an impact on semiconductor material by altering its physico-chemical properties. In this paper, the effect of gamma-radiation is observed on sol-gel synthesized metastable h-MoO3 nanorods with absorbed dose variation. The irradiated sample shows a remarkable change in their structural parameters such as average crystallite size decreased, strain, and dislocation density increased and so on are confirmed from the x-ray diffraction (XRD). Functional groups and the corresponding vibration and stretching are analyzed from the Fourier transform infrared spectroscopy (FTIR). The change in surface morphology is observed from the field emission scanning electron microscopy (FESEM) image and found no remarkable change. However, the optical band gap decreases with increasing absorbed dose and calculated 2.84 eV, 2.82 eV, 2.80 eV and 2.77 eV for 0 kGy, 40 kGy, 80 kGy, and 120 kGy, respectively by Kubelka-Munk (K-M) function from the diffuse reflectance data of UV–vis-NIR spectrophotometer.

Effect of ultraviolet irradiation on beef carcass yield

The results of testing the use of ultraviolet radiation (UVR) spectrum C (wavelength 253.7 nm) to reduce the contamination of chilled beef in half carcasses are presented. It is determined that the efficiency of UVR with a wavelength of 253.7 nm is directly proportional to the distance between meat half-carcasses in the cooling chamber: if the distance is longer than the efficiency of processing is higher. The efficiency of UVR processing of beef half-carcasses is proved by placing them in a chill chamber and storing them at 17 cm distance one from the other. This condition and the exposure of UVR for 45 min, gives a decrease in the number of mesophilic aerobic and facultative-anaerobic microorganisms on the carcasses surface to 95.15 ± 0.23%. An ecological regime to storage of chilled cattle in half carcasses (suspension) was developed using a UVR with a wavelength of 253.7 nm at 45 minutes exposure and 17 cm distance between the carcasses without breaking the technological process. The developed mode allows to double the shelf life of the raw meat in the chilled state. For efficient UVR processing of slaughtered animals (cattle) the half-carcasses are needed to be placed in a cooling and storage chamber (air temperature – 6.0 ± 2.0°C, relative humidity – 85.0 ± 0.5%) at 17 cm distance one from other. In this condition and 45 minutes exposure the number of mesophilic aerobic and facultative-anaerobic microorganisms on the surface of the experimental half-carcasses decreased from (4.45 ± 0.17) × 103 CFU/cm2 at the beginning of the experiment to (0.22 ± 0.01) × 103 CFU/cm2 after UVR treatment. Keywords: Muscle tissue; half-carcasses; ultraviolet irradiation; air-recirculator; temperature; exposure; microorganisms References Begum, M., Hocking, A. D., & Miskelly, D. (2009). Inactivation of food spoilage fungi by ultra violet (UVC) irradiation. Int. J Food Microbiol., 129, 74-77. Degala, H. L., Mahapatra, A. K., Demircib, A., & Kannana, G. (2018). Evaluation of non-thermal hurdle technology for ultraviolet-light to inactivate Escherichia coli K12 on goat meat surfaces. Food Control, 90, 113-12. doi: 10.1016/j.foodcont.2018.02.042 Diez, A. M., Santos, E. M., Jaime, I., & Rovira, J. (2009). Effectiveness of combined preservation methods to extend the shelf life of Morcilla de Burgos. Meat Science, 81, 171-177. doi: 10.1016/j.meatsci.2008.07.015 Gorbunova, N. A., & Tunieva, E. K. (2016). Risks and safety of using nanotechnologies of food products: a review. Theory and practice of meat processing, 1(3), 35-47. doi: 10.21323/2414-438X-2016-1-3-35-47 Hardin, M. D. (2014). Microbial contamination: Decontamination of Processed Meat. Encyclopedia of Meat Sciences. Kansas State University. Manhattan. RS. USA, 280-284. doi: 10.1016/b978-0-12-384731-7.00246-4 Isohanni, P. M., & Lyhs, U. (2009). Use of ultraviolet irradiation to reduce campylobacter jejuni on broiler meat. Poultry Sci., 88, 661-668. Keklik, N. M., Krishnamurthy, K., & Demirci, A. (2012). Microbial decontamination of food by ultraviolet (UV) and pulsed UV light. Microbial Decontamination in the Food Industry, 344-369. doi: 10.1533/9780857095756.2.344 Koutchma, T. N., Forney, L. J., & Moraru, C. I. (2009). UV processing effects on quality of foods, in Ultraviolet Light in Food Technology – Principles and Applications. Boca Raton. FL: CRC Press, 103-124. Lonergan, S. M., Topel, D. G., & Marple, D. N. (2019). The Science of Animal Growth and Meat Technology: Second Edition. Chapter, 15, 255-269. doi: 10.1016/B978-0-12-815277-5.00015 Miller, R. V., Jeffrey, W., Mitchell, J. D., & Elasri, M. (1999). Bacterial responses to ultraviolet light. ASM News, 65, 535-541. Palii, A. P., & Palii, A. P. (2019). Technical and technological innovations in dairy cattle. Monograph. Kharkiv: Mis'kdruk. ISBN 978-617-619-207-7 (In Ukrainian) Paliy, A. P., Rodionova, K. O., Braginec, M. V., Paliy, A. P., & Nalivayko, L. I. (2018). Sanitary-hygienic evaluation of meat processing enterprises productions and their sanation. Ukrainian Journal of Ecology, 8(2), 81-88. doi: 10.15421/2018_313 Rodionova, K. O., & Paliy, A. P. (2016). The effectiveness of application ultraviolet radiation for the sanitation of production premises of meat processing enterprises. Journal for Veterinary Medicine, Biotechnology and Biosafety, 2(4), 20-24. Rodionova K. А., & Paliy A. P. (2019). Analysis of contemporary meat and meat products’ processing methods. Journal for Veterinary Medicine, Biotechnology and Biosafety, 5(2), 32-40. Sommers, C., Sheena, S., Scullena, O. J., & Mackayb, W. (2017). Inactivation of Staphylococcus saprophyticus in chicken meat and purge using thermal processing, high pressure processing, gamma radiation, and ultraviolet light (254 nm). Food Control, 75, 78-82. doi: 10.1016/j.foodcont.2016.12.020 Stefanova, R., Vasilev, N. V., & Spassov, S. L. (2010). Irradiation of Food, Current Legislation Framework, and Detection of Irradiated Foods. Food Analytical Methods, 3(3), 225-252. doi: 10.1007/s12161-009-9118-8 Yeh, Y., de Moura, F. H., Van Den Broek, K., & de Mello, A. S. (2018). Effect of ultraviolet light, organic acids, and bacteriophage on Salmonella populations in ground beef. Meat Science, 139, 44-48. doi: 10.1016/j.meatsci.2018.01.007 Zhou, G. H., Xu, X. L., & Liu, Y. (2010). Preservation technologies for fresh meat - A review. Meat Science, 86(1), 119-28. doi: 10.1016/j.meatsci.2010.04.033

Targeting NRF2, Regulator of Antioxidant System, to Sensitize Glioblastoma Neurosphere Cells to Radiation-Induced Oxidative Stress.

The presence of glioma stem cells (GSCs), which are enriched in neurospheres, may be connected to the radioresistance of glioblastoma (GBM) due to their enhanced antioxidant defense and elevated DNA repair capacity. The aim was to evaluate the responses to different radiation qualities and to reduce radioresistance of U87MG cells, a GBM cell line. U87MG cells were cultured in a 3D model and irradiated with low (24 mGy/h) and high (0.39 Gy/min) dose rates of low LET gamma and high LET carbon ions (1-2 Gy/min). Thereafter, expression of proteins related to oxidative stress response, extracellular 8-oxo-dG, and neurospheres were determined. LD50 for carbon ions was significantly lower compared to LD50 of high and low dose rate gamma radiation. A significantly higher level of 8-oxo-dG was detected in the media of cells exposed to a low dose rate as compared to a high dose rate of gamma or carbon ions. A downregulation of oxidative stress proteins was also observed (NRF2, hMTH1, and SOD1). The NRF2 gene was knocked down by CRISPR/Cas9 in neurosphere cells, resulting in less self-renewal, more differentiated cells, and less proliferation capacity after irradiation with low and high dose rate gamma rays. Overall, U87MG glioma neurospheres presented differential responses to distinct radiation qualities and NRF2 plays an important role in cellular sensitivity to radiation.

Influence of high gamma radiation on the optical and photoluminescence characteristics of ZnO thin films

In this study, the researchers attempt to investigate the effect of irradiation of gamma doses in the range 25–150 kGy on the optical properties of sputtered ZnO thin films. The samples have a hexagonal wurtzite structure. The optical properties of the samples, such as the absorbance, transmittance, and reflectance, have been studied as a function of γ- irradiation doses. Several optical parameters, such as refractive index, optical energy gap, Urbach energy, oscillatory energy, dispersion energy, oscillator strength, and dielectric constant have been found to be affected by changing the γ- irradiation doses. The refractive index dispersion curve of the γ-irradiated and non-irradiated ZnO thin films meet the criteria of the single-oscillator model. The room temperature photoluminescence spectra of the samples under excitation 400 and 437 nm showed green emission nearly at 2.597 and 2.559 eV, and yellow emission approximately at 2.15 eV. The green emission bands can be attributed to a transition from CB to VZn −2 and −1 respectively, while the yellow emission band can be attributed to a transition between a shallow donor and a deep level.

Calculated and experimental response of calcium silicate polycrystalline to high and very-high neutron doses

In the scope to the discovery of new detectors for high and very-high gamma and neutron radiation dose (mGy-MGy), synthetic polycrystals of CaSiO3 have been produced by the devitrification method in our laboratory. CaSiO3 polycrystals were irradiated with thermal, epithermal and a small fraction of fast neutrons. In the position of irradiation, the thermal neutron flux is about 83% of the total neutron flux and the thermal neutron fluences range from 5.82 × 1013 to 2.97 × 1016 n/cm2. This thermal neutron reacts with Ca, Si and O through (n,γ) process, all or part of the gamma emitted in this reaction is absorbed by the sample and is responsible for the induction of thermoluminescence (TL). The total energy emitted by the (n,γ) reaction was calculated analytically. Furthermore, Monte Carlo simulations using MCNP5 radiation transport code was carried out to calculate the deposited dose on CaSiO3 by the neutron interaction finding doses ranging from 42 Gy to 21 kGy. CaSiO3 TL glow curves, after radiation exposure from the reactor, display the main prominent TL peak around 234–259 °C and when exposed to gamma radiation (Co-60) it shows the main TL peak around same 234–272 °C.

High level gamma radiation effects on platinum and silicon diode cryogenic temperature sensors

High energy physics research facilities require a vast cryogenic infrastructure to cool superconducting magnets, superconducting RF cavities, and other components to their necessary operational temperatures. The temperature sensors used to monitor this infrastructure are invariably exposed to leakage radiation in varying doses depending upon their location. Compared to many other cryogenic temperature sensors, platinum resistance thermometers (PRTs) and silicon diode thermometers (SiDTs) have the advantages of adhering to standard curves and requiring a single fixed current for operation. This work examines the gamma radiation-induced calibration offsets on two PRT models, the ceramic encapsulated PT-103 and the glass encapsulated PT-111, and a SiDT model DT-670-SD, all manufactured by Lake Shore Cryotronics. Subgroups of each model were subjected to a gamma radiation dose ranging from 10 kGy to 5 MGy with temperature calibrations performed pre- and post-irradiation over their respective operating ranges. The data were analyzed in terms of the temperature-equivalent change in the measured parameter. The PRTs behaved very well in radiation with the PT-103 and PT-111 subgroup average offsets for all tested irradiation levels being less than ±25 mK and ±35 mK respectively over the 20 K to 325 K temperature range. The SiDT model DT-670-SD behavior was more complicated with a clear change in response at 30 K. Below 30 K, the offsets consistently increased from slightly positive to roughly -5 K as the radiation dose increased. Above 30 K, the induced offset had nearly saturated at 10 kGy ranging from about 0 K at 30 K to +23 K at 300 K, and exhibiting that same behavior and offset for all higher radiation doses. Equivalent temperature offset data over the sensors’ operating temperature ranges are presented by sensor model and total gamma dose.

Particle size dependent TL response of CaF2:Dy phosphor for gamma dosimetry

CaF2:Dy phosphor was prepared by ball milling method over particle size ranging from 140 nm to 35 nm, and their thermoluminescence properties were studied by irradiation with 60Co gamma rays. The XRD revealed that the crystallite size was of ∼45 nm for pristine, 19.1 nm for 10 h and 9.99 nm for 50 h ball-milled phosphor samples and confirmed by FESEM. The UV–visible spectra indicate that the absorption and scattering of radiation increased with a decrease in the particle size along with the blue shift in the absorption peak. CaF2:Dy particles of different sizes were irradiated with gamma dose from 1 Gy to 20 kGy and respective thermoluminescence response was studied. It was observed that the ∼65 nm particle size phosphor showed a linear response with gamma dose range from 1 Gy to 12 kGy. These results reveal that the CaF2:Dy phosphor can be used for high gamma radiation measurement and food irradiation dosimetry.

Role of Diosmin in protection against the oxidative stress induced damage by gamma-radiation in Wistar albino rats

The benchmark of this study is to evaluate the radio protective efficiency of diosmin, a natural citrus flavone of hesperidin derivative on radiation-induced damage in wistar albino rats. Rats orally administered two diosmin doses (100 and 200 mg/kg body wt.) for a month (every other day) prior to exposure to high gamma radiation single dose (8Gy) or cumulative dose (10Gy). To evaluate the radio protective efficiency of diosmin various biochemical estimations, histopathological alterations as well as comet assay and caspase-3 activity for assessment of apoptosis were performed. Results indicated that radiation-induced decline in the levels of antioxidant parameters (SOD and GSH), increased lipid peroxidation, DNA damage and apoptosis were improved by pre-administration of diosmin. Diosmin dose (200 mg/kg body wt.) restored the antioxidant status to near normal and reduced lipid peroxidation, DNA and tissue damage. These results were confirmed by histopathological examinations, which showed that pre-administration of diosmin protected the liver and kidney of albino rats against gamma-irradiation induced damage. Hence, it has been illustrated that diosmin might be an effective radio protector against radiation-induced damage in rats. Moreover, diosmin alone pretreated group did not show any biochemical alterations or DNA damage indicating the protective nature of the drug.

Application of CdZnTe Quasi-Hemispherical Detectors in Strong Gamma-Radiation Fields

The results of a study of some ways to improve spectroscopy characteristics of the CdZnTe quasi-hemispherical detectors when working in high gamma radiation fluxes are presented. It was shown that the use of IR illumination with a wavelength of 1050 nm or 1200 nm or at slight warm-up of the detector to +30°C … +40°C can significantly improve spectroscopy performance of the CdZnTe detectors of size 3.5 mm × 3.5 mm × 1.75 mm when operating in a tested gamma-radiation field with a dose rate up to 590 mGy/h.

Gamma irradiation-induced phase transitions of boron nitride nanoparticles

Recently different methods are explored to synthesize suparhard orthorhombic boron nitride (o-BN) nanomaterials which have a wide range of industrial applications in the sensors, fiters, battery, biological applications and deep ultraviolet light emitting diodes. In this research work, a simple method is reported to synthesis of cubic boron nitride nanoparticles (c-BNNPs) via gamma irradiation induced phase transition of hexagonal boron nitride nanoparticles (h-BNNPs). X Ray Diffraction (XRD) and Raman Spectroscopy results confirmed the phase transition of h-BNNPs to o-BNNPs at the dose of 21 kGy. At the dose of 24 kGy, high resolution transmission electron microscopy (HRTEM) results showed that phase of hexagonal boron nitride nanoparticles (h-BNNPs) are transformed to B2O3 whereas at lower dose (18 kGy), coalescence of hexagonal boron nitride nanoparticles (h-BNNPs) is observed through high resolution transmission electron microscopy (HRTEM) results. X-rays diffractions (XRD) results showed that grain size of hexagonal boron nitride nanoparticles (h- BNNPs) is increased. Mechanism of phase transition and coalescence of hexagonal boron nitride nanoparticles (h-BNNPs) are explained via high energy and short wavelength gamma radiations act on B-N covalent bond isotopically.

Oxidation kinetics of boron carbide ceramic under high gamma irradiation dose in the high temperature

In the presented work, high purity boron carbide (purity of 99.9%, and bulk density 1.8 g/cm3 at 20 °C) compounds were gamma-irradiated at dose rate of D = 30 rd/sec using Co60 gamma source. The irradiation of the samples at different gamma doses (5·109; 1·1010; 1.5·1010 and 2·1010 Mrd) was carried out at room temperature and atmospheric pressure. The Differential Scanning Calorimetry (DSC) was used to study the solvothermal chemical reaction mechanisms of boron carbide from room temperature up to 900 K and the oxidation kinetics, rate of oxidation diffusion (plots of Jander), depth of oxidation and activation energy from 900 ≤ T ≤ 1250 K after gamma irradiation at different gamma absorption doses. The depth of the gamma irradiation dose on the surface determined the “critical limit” for the thin oxide layer for boron carbide. Also, depths of gamma irradiation dose is calculated activation energy by the Arrhenius plots. The activation energy was found to increase from 99.59 J mol−1 to 102.93 J mol−1 as the gamma irradiation dose increased from 5·109 to 2·1010 Mrad.

Measured radiation effects on InGaAsP/InP ring resonators for space applications.

Photonic ring resonators can be considered building blocks of new concept satellite payloads for implementing several functions, such as filtering and sensing. In particular, the use of a high Q-factor ring resonator as sensing element into a Resonant Micro Optic Gyroscope (RMOG), provides a remarkable improvement of the performance with respect to the competitive technologies. To qualify a ring resonator for Space applications, the radiation effects on it in the Space must be carefully evaluated. Here, we investigate the effects of gamma radiation on a high Q InGaAsP/InP ring resonator, for the first time, to our knowledge. The ring resonator under study has a footprint of about 530 mm2 and it is based on a InGaAsP/InP rib waveguide, with a width of 2 µm and a thickness of 0.3 µm, formed on a 0.7 µm thick slab layer on an InP substrate 625 µm thick. For a total dose of about 320 krad Co60 gamma irradiation, a mean variation of about 13% and 4% was measured for Q and extinction ratio (ER), respectively, with respect to the values before irradiation (Q = 1.36 × 106, ER = 6.24 dB). Furthermore, the resonance peak red-shifts with a linear behaviour was observed increasing the total dose of the absorbed radiation, with a maximum resonance detuning of about 810 pm. These non-significant effects of a quite high gamma radiation dose confirm the potential of high-Q InP-based ring resonators into Space systems or subsystems.

GAMMA IRRADIATION-INDUCED CHEMICAL DECOMPOSITION-RELATED BANDGAP ENGINEERING IN SnO2 NANOPARTICLES

Gamma irradiation-induced chemical decomposition and related phase transformation from SnO2 nanoparticles (NPs) to SnO have been studied using X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM) and UV–Vis spectroscopy. XRD studies show that the SnO2NPS are crystalline in nature with rutile structure. Crystallinity of the NPs increases with the increase of gamma irradiation doses, which is consistent with the results of TEM. At high gamma irradiation doses, SnO phase appears from SnO2 matrix, which pushes the SnO2 phase toward stoichiometry. The band gap energy has been found in the range of 3.84–3.76[Formula: see text]eV, larger than the band gap of bulk SnO2. The larger band gap is attributed due to small particle size, which is confirmed by TEM studies. Optical reflectance and band gap decrease with the increase of gamma irradiation doses due to creation of defects. This property of SnO2 NPs makes it suitable for use in optical devices.

Improved Offset Voltage Stability of 4H-SiC CMOS Operational Amplifier by Increasing Gamma Irradiation Resistance

We modified the active layout of an operational amplifier (op-amp) to exhibit high gamma irradiation resistance of over 100-kGy using our 4H-SiC complementary MOS technology, which can be applied for measuring instruments installed in nuclear power plants. The op-amp with the modified active layout features both a thin gate oxide and newly developed gate-electrode structure for suppressing the leakage current. From an experiment we conducted, the leakage current of the p-channel MOSFET with modified active layout remained unchanged from the initial value after irradiation, although that of it with the conventional layout we previously evaluated increased by about two orders of magnitude. The offset voltage of the improved op-amp was maintained below 2.8 mV up to 100-kGy irradiation. The improved op-amp also showed a healthy amplification characteristic without distortion.

EFFECT OF GAMMA IRRADIATION ON ANTIOXIDANT POTENTIAL AND BIOACTIVES OF A COSMECEUTICALLY SIGNIFICANT CHLORELLA EMERSONII KJ725233

Objective : Gamma radiation induces free radicals with a corresponding alteration in the cell’s antioxidant defense system. The present study thus aimed at determining the role of gamma irradiation in improving the cosmeceutical potential of CEK in terms of antioxidants.
 Methods : C.emersonii KJ725233 was subjected to low (100 Gy) and high (1000 Gy) gamma irradiation doses and its effect on the chlorophyll content was evaluated. The quantitative alterations in the antioxidant content of CEK were evaluated by phosphomolybdenum assay (TAC), ferric reducing antioxidant potential (FRAP), 2, 2 - Dipheny-1-picryl hydrazyl radical scavenging assay (DPPH), total phenolic (TPC) and total flavonoid content (TFC). Also, the corresponding qualitative alterations in the bioactives of CEK were determined by GC-HRMS analysis. 
 Results : A 179.57±2.55% increase in the total chlorophyll content alongwith a 71.76±2.96%, 32.08±2.16%, 11.67±0.89%, 42.85±8.0% and 31.37±3.18% increase was observed in the TAC, FRAP, DPPH radical scavenging, TPC and TFC was observed in CEK irradiated at 1000 Gy. GC-HRMS analysis revealed the induction of Vitamin E on irradiation at both the doses with a corresponding decrease in the phytol content whereas 100 Gy stimulated the induction of phytosterols.
 Conclusion : The potent intrinsic antioxidant activity of cosmeceutically significant CEK can be elevated with the induction of the most sought after antioxidant in cosmetology – Vitamin E on irradiation.

Chemical and radiation grafted chitosan for the mitigation of arsenic from contaminated water

The removal of As (V) from aqueous solution was investigated with the grafted polymeric adsorbent (chitosan-g-HEMA) synthesized by using high energy 60Co gamma radiation as well as by conventional chemical method. The swelling behavior of grafted polymer at different pH conditions and their kinetic studies were investigated. Fourier Transform Infrared Spectroscopy (FTIR) was used to characterize the grafted polymer and the morphological structure was analyzed by Scanning Electron Microscope (SEM). As (V) ions uptake capacity of the adsorbent was evaluated in the light of varying pH, contact time, temperature, adsorbent dose, and different arsenate ion concentration. The adsorption data was fitted well in the Langmuir model and various static parameters were calculated. The removal of toxic As (V) ions was carried out by batch method using grafted sorbents synthesized by both gamma radiation and chemical grafting methods and it was observed that the adsorbent synthesized by the use of gamma radiation shows higher adsorption capacity as compared to the chemically grafted polymer.