Increase In Gamma Dose Research Articles

Optical and electrical properties of gamma irradiated PADC detector

PADC (Polyallyldiglycol carbonate) detector subjected to gamma rays undergoes change in optical and electrical properties. The optical band-gap is determined using Tauc's plot. The band-gap is found to be unchanged up to the dose of 10 3 Gy , and then starts decreasing with increasing dose. The band-gap is lowered from 4.04 eV for the pristine material to 2.46 eV for the highest dose ( 10 6 Gy ). The dielectric constant of the detector is influenced due to the gamma exposure. At lower doses (up to 10 4 Gy ), the detector seems to be not polarised, so no change in dielectric constant is observed. But at the dose of 10 5 Gy , the value is increased slightly while at the highest dose ( 10 6 Gy ), the dielectric constant of the detector is found to be enhanced significantly. The results indicated a decrease in track registration sensitivity with increase in gamma dose.

Comparative study of symmetric and asymmetric somatic hybridization between common wheat andHaynaldia villosa

Symmetric and asymmetric protoplast fusion between long term cell suspension-derived protoplasts ofTriticum aestivum (cv. Jinan 177) and protoplasts ofHaynaldia villosa prepared from one-year-old embryogeneric calli was performed by PEG method. In asymmetric fusion, donor calli were treated with gamma ray at a dose of 40, 60, 80 Gy (1.3 Gy/min) respectively and then used to isolate protoplasts. Results of morphological, cytological, biochemical (isozyme) and 5S rDNA spacer sequence analysis revealed that we obtained somatic hybrid lines at high frequency from both symmetric and asymmetric fusion. Hybrid plants were recovered from symmetric and low dose gamma-fusion combinations. GISH (genomicin situ hybridization) analysis proved exactly the existence of both parental chromosomes and the common occurrence of several kinds of translocation between them in the hybrid clones regenerated from symmetric and asymmetric fusion. And the elimination of donor DNA in hybrid clones regenerated from asymmetric fusion combinations was found to increase with the increasing gamma doses. It is concluded that transference and recombination of nuclear DNA can be achieved effectively by symmetric and asymmetric fusion, hybrids with small fragment translocation which are valuable in plant breeding can be obtained directly by asymmetric fusion.

Effect of Gamma Irradiation on the Dielectric Properties of (CH3)2NH2Ga(SO4)2 · 6H2O Crystals in the Vicinity of the Ferroelectric Transition

The effect of gamma irradiation on the dielectric permittivity and loss tangent of (CH3)2NH2Ga(SO4)2 · 6H2O crystals was studied near the ferroelectric transition at different frequencies. Irradiation was found to sharply reduce e and tan δ at gamma doses below 5 × 107 R. At higher doses, e and tan δ level off. With increasing gamma dose, the ferroelectric transition shifts to lower temperatures, irrespective of frequency.

Chromosome elimination in asymmetric somatic hybrids: effect of gamma dose and time in culture

Mesophyll protoplasts of a kanamycin-resistant line of Nicotiana plumbaginifolia were gamma-irradiated and fused with mesophyll protoplasts of N. tabacum plants bearing the sulfur mutation. Hybrid calli were recovered by selection on media containing kanamycin. In one group of experiments, the degree of elimination of donor (N. plumbaginifolia) genetic material in the hybrid calli was assessed by dot-blot hybridization using a N. plumbaginifolia-specific repetitive-DNA sequence as a probe. The elimination of donor DNA was found to increase with increasing gamma dose for all doses tested (5-50 krad). Elimination of donor DNA was also found to continue in the calli for the first 12 months in culture. The degree of chromosome elimination was quite variable; for a 50-krad dose, some hybrids were recovered that retained less than 15% of the donor genome, whereas others retained nearly 50%. In a second set of experiments, the degree of donorchromosome elimination was assessed from the fraction of hybrid calli that exhibited complementation of the Su phenotype due to retention of a wild-type Su allele of the donor. When N. plumbaginifolia protoplasts were inactivated by treatment with iodoacetate, rather than gamma irradiation, all the hybrid calli were green. However, when the donor protoplasts were inactivated by irradiation, the fraction of hybrid calli that were able to complement the Su mutation decreased with increasing gamma dose; for a 50-krad dose only 40% of the hybrid calli were green. From these data, the degree of radiation-induced donor-chromosome elimination was calculated and was found to agree closely with that measured by dot-blot hybridization. We conclude that radiation-induced elimination of donor chromosomes increases with gamma dose and time in culture in N. tabacum (+)N. plumbaginifolia hybrids, but that donor-chromosome elimination is an inherently variable process.

Some temperature dependent properties of potassium dihydrogen phosphate

Single crystals of potassium dihydrogen phosphate (KDP) have been grown at room temperature from saturated aqueous solutions. The thermal behaviour has been studied by differential thermal analysis and confirmed by X-ray diffraction and infrared spectroscopy. When heated to 613 K, KDP loses its water content and a transition takes place from the tetragonal orthophase to the monoclinic meta-phase. The resistivity of KDP crystals has been found to decrease exponentially with temperature over the temperature range of 293 K to 383 K above which it attains a constant value independent of further temperature rises up to 478 K. A value of 0.588 eV has been estimated for the activation energy of rotation of the phosphate group which controls conduction over the temperature dependent region of the resistivity curve. Glow curves of gamma-ray irradiated single crystals subsume peaks similar to those detected for the polycrystalline powder. Energy depths varying from 0.20 eV to 0.46 eV have been calculated for the various trapping states created by gamma irradiation. Effects of increasing gamma dose have been studied and found to cause an increase in number and intensity of the glow peaks. Slight shifts in peak temperatures to lower values are also noted at high gamma doses and attributed to the combined effect of dose rate and interactions between trapping centres.

Effect of Pre-Gamma Irradiation on CR-39

The effect of pre-gamma irradiation on track density, bulk etch rate and light absorbance in CR-39 was investigated. CR-39 detectors were irradiated with gamma doses over a range of 0 to 280 kGy (0 to 28 Mrad). The detectors were overlaid with 0.77 mm of polyethylene and exposed to a known fluence of 252Cf spontaneous fission neutrons. All detectors were then etched in 6.25N sodium hydroxide solution at 70 oC for 4 h and track densities were determined with an optical microscope. The bulk etch rates were determined by measuring the change in thickness before and after etching. The net track density decreased and the bulk etch rate increased non-linearly with increasing gamma doses. UV spectrophotometric measurements showed significant changes in light absorbance for gamma irradiated CR-39.

Gamma radiation induced changes in the glow curve of CaSo4: Dy tld phosphor

Abstract The changes in the glow curve shape of CaSO4: Dy phosphor induced by gamma radiation in dose region 0.1 Gy-2.6 × 105 Gy were studied. With increase in gamma dose, initially, the glow curve shows a rapid increase in its peak width followed by its decrease with subsequent increase in gamma dose. This variation in peak width has been found to be due to the rapid growth and shift (towards lower temperatures) of a shoulder located at about 340°C for low doses. The shift and growth of the shoulder has been explained by preferential filling, first, of deeper trap components followed by filling of shallower trap components. In addition, for doses above 2 Gy, a high temperature peak distribution, peaking around 420°C, is noted.

Effect of ionizing radiation on the kinetics of reduction of NiO-MgO mixed oxids with hydrogen

The low-temperature reduction of the mixed system nickel oxide-magnesium oxide with hydrogen was studied thermogravimetrically in the region 260-470 °C. The two oxides form in the whole composition region solid solutions, some physicochemical parameters of which vary nonmonotonically with the sample composition. The kinetics and degree of reduction of nickel oxide are appreciably affected by the presence of the unreduced magnesium oxide, in higher concentrations lowering the reaction rate. The kinetics of the reduction can be quantitatively described by the equation 1-(1-α)1/3 = kt, valid in dependence on the composition in differently wide ranges of the degree of reduction α. The reaction rate can be varied, particularly for samples with low contents of magnesium oxide, by heat treatment in inert atmosphere at 700 °C, and for all samples by irradiation by gamma rays or fast neutrons. The reduction rate grows with the increasing content of magnesium oxide up to a constant value. The positive effect increases with the increasing gamma dose and, according to the kind of radiation, in the order γ, n. The variation of the reactivity of irradiated or thermally treated mixed oxides is due predominantly to the shift of the equilibrium of the lattice defects, formation and stabilization of new centres, which affect the rate of nucleation of the forming metal phase.

The effects of high gamma doses on the response of plastic track detectors

Systematic studies have been made concerning the effects of high doses of gamma rays on the track-registration properties of various plastic Solid State Track Detectors (SSTDs). The detectors were first exposed to 252Cf fission fragments and then to gamma doses ranging between 30 and 160 megarad. The results show that both the length and the width of latent damage trails are affected when exposed to gamma doses of the order of a few megarads. Furthermore, it was found that the general etching velocity, V g, increases with increasing gamma dose. The above mentioned results suggest that: (a) gamma doses below the megarad region do not affect the track-registration characteristics of plastic SSTDs, and (b) the change in track parameters (in the megarad region) can be employed as an index of gamma dose. This new type of gamma dosimeter, due mostly to its extremely small size and flexibility, offers greater advantages over other detectors for in-core gamma dosimetry.

Chemical consequences of nuclear recoil following the radiative capture of neutrons by cobalt in metal acetylacetonates: Radiation annealing

It has already been reported that γ- and X-radiation causes annealing in pure trisacetylacetone Co(III) following radiative neutron capture. These measurements have now been extended to the cobalt complex dispersed in a matrix of the pure aluminium and rhodium acetylacetonates, which are isomorphous with the former. The results with such diluted samples of cobaltic acetylacetonate show a change both in the initial separable activity, as well as in the subsequent annealing compared to the results for the pure cobalt complex. The kinetics of thermal annealing in all these systems show that the γ-irradiated samples have faster annealing rates. The results on samples irradiated with γ-rays prior to radiative neutron capture in the pure cobalt complex indicate that the inorganic yield increases with increasing gamma dose. For these samples also, thermal annealing rates have been found to show a marked increase. A detailed study has shown the close similarity of radiation and thermal annealing. The paper also gives the results of a study with 58 m Co dispersed in trisacetylacetone Co(III) both as an interstitial impurity, as well as in the form of the complex.

NMR Study of γ Ray Induced Polymerisation of Ethyl Acrylate

Experimental results from proton magnetic resonance absorption studies of ethyl acrylate during polymerization are reported. A 100 c cobalt-60 source was used in irradiations up to 2 x 10/sup 5/ r/hr. Resonance patterns varied with increasing gamma doses due to viscosity changes with polymerization. (A.C.)