Γ-ray Dosage Research Articles

Thermal, Optical, and Color Modification in Makrofol VLG 7-1 Nuclear Track Detector Due to Gamma Irradiation

Makrofol VLG 7-1 is a sort of Makrofol (bisphenol-A polycarbonate) nuclear track detector. We believe that the current study is the first one that deals with the effect of γ-ray irradiation on Makrofol VLG 7-1. Samples of Makrofol films were treated with various γ-ray dosages (20–140 kGy). The resultant outcome of the γ-ray irradiation on the thermal and optical characteristics of the Makrofol samples were explored applying thermogravimetric analysis (TGA) and ultraviolet spectroscopy (UVs). The degradation temperature, activation energy of thermal decomposition, optical band gap, refractive index, Urbach energy, and optical dielectric parameters were characterized and interpreted based on the γ-ray dosage. The optical bandgap dropped from 4.26 to 4.14 eV for a γ-ray dosage of 140 kGy, accompanied with a rise in both Urbach energy and thermostability of the samples. We attribute this to the dominance of crosslinking. Additionally, the color differences between the pristine and the irradiated samples were characterized. The pristine Makrofol was uncolored. It exhibited noteworthy color changes during the γ-ray treatment, as the color intensity reached a value greater than 5. This is an acceptable match in commercial reproduction on printing presses.

Quantifiable Polymeric Fluorescent Ratiometric γ-ray Chemosensor.

Detection of γ-rays is of vital significance in various areas such as high-energy physics, nuclear medicine, national security, and space exploration. However, many current spectrometry methods are based on ionization effects, which are limited to electron counting and related techniques such as ionization-induced luminescence. Herein, we report an alternative, quantifiable γ-ray chemosensor based on a secondary effect from this ionizing radiation, that is, it was discovered that poly(methyl methacrylate) (PMMA) and polyvinyl chloride (PVC) are more sensitive to a γ-ray-induced acid generation process by surveying a series of commercially available polymers. Accordingly, a pH-sensitive fluorescent quinoline derivative is designed and embedded in PMMA or PVC films, which exhibits dramatic emission shift from blue (λem = 460-480 nm) to red (λem = 570-620 nm) upon exposure to γ-irradiation. A linear response of ratiometric fluorescence intensity (Ired/Iblue) to γ-ray dosage in a wide range (80-4060 Gy) was established, which can be used as a practical visual dosimeter complementary to current techniques.

Probing the Influence of γ-Sterilization on the Oxidation, Crystallization, Sliding Wear Resistance, and Cytocompatibility of Chemically Modified Graphene-Oxide-Reinforced HDPE/UHMWPE Nanocomposites and Wear Debris.

Osteolysis and aseptic loosening due to wear at the articulating interfaces of prosthetic joints are considered to be the key concerns for implant failure in load-bearing orthopedic applications. In an effort to reduce the wear and processing difficulties of ultrahigh-molecular-weight polyethylene (UHMWPE), our research group recently developed high-density polyethylene (HDPE)/UHMWPE nanocomposites with chemically modified graphene oxide (mGO). Considering the importance of sterilization, this work explores the influence of γ-ray dosage of 25 kGy on the clinically relevant performance-limiting properties of these newly developed hybrid nanocomposites in vitro. Importantly, this work also probes into the cytotoxic effects of the wear debris of different compositions and sizes on MC3T3 murine osteoblasts and human mesenchymal stem cells (hMSCs). In particular, γ-ray-sterilized 1 wt % mGO-reinforced HDPE/UHMWPE nanocomposites exhibit an improvement in the oxidation index (16%), free energy of immersion (-12.1 mN/m), surface polarity (5.0%), and hardness (42%). Consequently, such enhancements result in better tribological properties, especially coefficient of friction (+13%) and wear resistance, when compared with UHMWPE. A spectrum of analyses using transmission electron microscopy (TEM) and in vitro cytocompatibility assessment demonstrate that phagocytosable (0.5-4.5 μm) sterilized 1 mGO wear particles, when present in culture media at 5 mg/mL concentration, induce neither significant reduction in MC3T3 murine osteoblast and hMSC growth nor cell morphology phenotype, during 24, 48, and 72 h of incubation. Taken together, this study suggests that γ-ray-sterilized HDPE/UHMWPE/mGO nanocomposites can be utilized as promising articulating surfaces for total joint replacements.

Effect of γ-irradiation on the physical and mechanical properties of kefiran biopolymer film

In this study, the effect of different γ-ray dosages (3, 6, and 9kGy) on the functional properties of kefiran biopolymer was investigated. The obtained results showed that increasing γ-ray dosage brought about an increase in the tensile strength of film specimens up to three-times. However, elongation at break, and tensile energy to break of γ-irradiated kefiran films decreased in the wake of increasing γ-ray dosage. γ-Irradiation could improve surface hydrophobicity, sensitivity of kefiran film specimens to water, and water vapor permeability, but yellowness of films increased, simultaneously. XRD spectrum confirmed increased crystallinity of γ-irradiated films. Melting point of films was constant but glass transition temperature decreased drastically at high γ-ray dosage (9kGy). ATR-FTIR analysis confirmed that γ-ray engendered no changes in chemical functional groups. According to the result, a mechanism was proposed to percept the effects of γ-irradiation on kefiran biopolymer and its role on the functional properties of kefiran film. Hence, the functional properties of kefiran films were depend on the ratio of cross-linkages between polymer chains and produced mono and disaccharide by γ-irradiation.

Simple small molecule carbon source strategy for synthesis of functional hydrothermal carbon: preparation of highly efficient uranium selective solid phase extractant

In this paper, simple small molecules, glyoxal and acrylonitrile, are chosen as starting materials to prepare an amidoxime-functionalized hydrothermal carbon-based solid phase extractant (HTC-AO) via a one-step hydrothermal process following a simple oximation. The resulting HTC-AO exhibits the anticipated properties, i.e., low porosity (0.01 cm3 g−1) and intraparticle diffusion coefficient (kint = 0.042 mmol g−1 min−0.5), high content of amidoxime groups (1.66 mmol g−1) and minimal undesired functional groups (typically carboxylic group: 0.07 mmol g−1; phenolic group: 0.38 mmol g−1; lactonic group: 0.01 mmol g−1). Moreover, the results of irradiation experiments under γ-ray dosages between 1 and 100 kGy indicate that HTC-AO has good radiation stability. The sorption behavior of U(VI) onto HTC-AO is investigated in detail using batch sorption experiments. A saturation U(VI) sorption capacity over that of all the uranium sorbents reported previously is found to be 1021.6 mg g−1 at pH 4.5 in single uranium solution, and a so far unreported highest uranium selectivity of 81.6% with a sorption capacity of 268.9 mg g−1 is observed at pH 2.5 in multi-ion solution. The significant outcomes in this work confirms that the “simple small molecule carbon source” strategy is practical and efficient, and may have the potential for the preparation of other types of functional materials such as highly specific catalysts, drug targeting carriers and others.

Radio sensitivity studies of morpho-physiological characteristics in some Iranian rice varieties (Oryza sativa L.) in M1 generation.

Gamma (γ) ionizing ray is a physical mutagen, producing variation in crop improvement and employing such as a complementary tool in breeding process. The γ-ray dosages are a critical issue, so it should be optimized. In this research, various doses of gamma radiation including 150, 250, 350 and 450 Gy applied on three rice varieties (Tarom-hashemi, Sange-tarom and Nemat), and their effects were evaluated on 50% lethal dose (LD50), rate and percent of germination, radicle and plumule length at in vitro, including cluster analysis of dosage quantities at genotypes, range of variation (R), variation coefficient of treatment regarding to control dosage (CVt/CVnt). Euclidean similarity coefficient including UPGMA (Unweighted Pair Group Method with Arithmetic Mean) algorithm was used for cluster analysis. The results indicated that 250 and 350 Gy γ-rays have much more better effects to create variation rather than other doses and also clearly showed that γ-ray made novel variation in panicle sterility percentage, plant height, 1000 grain weight and fertile tillers on the studied varieties. Meanwhile the dendrogram of clustering classified into 3 groups on the base of gamma effects and control doses were placed in different groups. The LD50 values related to seed germination computed 350, 310 and 170 at Sange-tarom, Tarom-hashemi and Nemat respectively. Key words: Gamma ray, rice, mutation, morpho-physiological characteristics.

Characteristics of self-powered detectors for measuring γ-ray dosage

Charge densities induced by gamma rays in self-powered detectors have been measured. Experimental results are given and some characteristics of self-powered detectors are discussed.

Effects of γ-Irradiation on the Surface and Catalytic Properties of Co3O4/MgO Systems Aged for One Year

The effects of γ-rays (20–160 Mrad) on the surface and catalytic properties of two Co3O4/MgO systems were investigated. The formulae of the investigated solids were 0.05Co3O4/MgO and 0.2Co3O4/MgO, respectively, both prepared by the impregnation method and calcined at 500°C. The irradiated samples were left for one year in sealed tubes before any measurements were undertaken. γ-Irradiation of the investigated solids resulted in a progressive decrease in the particle size of the Co3O4 and MgO phases. This treatment also led to a measurable increase in the specific surface area of the treated solids to an extent proportional to the γ-ray dosage. Treatment of the Co3O4/MgO system with different doses of γ-rays brought about a significant increase in the catalytic activity expressed both as the reaction rate constant and as the reaction rate constant per unit surface area. However, the curve relating to the catalytic activity and dosage of γ-rays showed maxima located at 40 and 80 Mrad for samples having the formula 0.05Co3O4/MgO and 0.2Co3O4/MgO, respectively. Furthermore, samples exposed to 160 Mrad showed a larger catalytic activity than the unirradiated samples. The results demonstrate the role of γ-rays in inhibiting the deterioration of the catalytic activity of the investigated systems as a function of aging time. The irradiation process did not modify the activation energy of the catalyzed reaction but altered the concentration of active centres on the surfaces of the solids without changing their energetic nature.

Crosslinking of Poly(L-lactide) by γ-Irradiation

The radiation crosslinking of poly(L-lactide) (PLLA) was investigated using triallyl isocyanurate (TAIC) as a crosslinking agent. The gel fraction of crosslinked PLLA increased with TAIC concentration and γ-ray dose. Crosslinking of PLLA started at low TAIC contents and low γ-ray dosage. Differential scanning calorimetry and dynamic mechanical thermal analysis revealed that PLLA was completely crosslinked at high weight ratios and high γ-ray doses.

The microstructures of solvent-welded joints of irradiated poly(methyl methacrylate)

The microstructures of solvent-welded joints of irradiated poly(methyl methacrylate) (PMMA) have been investigated. The morphologies of tensile, tear, and cleavage surfaces were examined and the effects of the solubility parameter, welding temperature, and γ-ray dosage on the mechanical strength were studied. Three solvents - methanol, ethanol, and N,N-dimethyl formamide (DMF) - were used with welding temperatures at 40, 50, and 60°C. The γ-ray dosages were 100, 200, and 300 kGy. The features of the tensile fracture surfaces exhibit either long and narrow hackles on the interface of PMMA with low dosage, or lamellae in the adherent near the interface with high dosage for methanol and ethanol. For DMF, the morphologies of the tensile fracture surfaces at low and high dosages consist of many elliptical paraboloids and feathers, respectively. The morphology of the tear fracture surface of PMMA shows equiaxed hackles for methanol and ethanol and polygons for DMF. The cleavage surface appears to be chevron curves. The cleavage surface shows discontinuity of the chevron curves at the welded interface for non-irradiated specimens and continuity on irradiated specimens. The slope of the chevron curve at the interface is continuous for ethanol and DMF but is discontinuous for methanol. A solvent-affected zone was observed and its size had no correlation with the mechanical strength of the joined PMMA.

Kinetics of diacetylene polymerization: an FT-Raman study

Changes in the FT-Raman spectrum of 1,4-bis(3-quinolyl)buta-1,3-diyne (DQ) as a function of γ-ray dosage is used to monitor the degree of monomer to polymer conversion in a solid-state to polymerization reaction. The relative intensities of the characteristic C≡C peaks in the nonresonant FT- Raman spectra provide a nondestructive quantitative means to measure the conversion from monomer to polymer

A sensitive chemical procedure for monitoring the radiolytic oxidation of proteins at γ-ray dosages down to 1 Krad

Abstract The radiolytic degradation of proteins in oxygenated solution is initiated by the attack of OH radicals at a multiplicity of main-chain and side-chain loci to give a wide variety of oxidized protein sites. A major fraction of these oxidation reactions lead to the introduction of reactive carbonyl groups into the protein co-valent structure. With γ-rays the total carbonyl yield correspond to G(>CO)t ≃ 1 for a number of different proteins. Outlined here is a sensitive chemical-spectrophotometric procedure for quantitatively monitoring G(>CO)t over a dose range of interest in radiation biology (1 to 50 Krad). Data obtained with pepsin, α-chymotryps in and β-lactoglobulin are discussed.

放射線前照射木材のクラフト蒸解 ＩＩ リグニンおよび炭水化物の挙動

Pre-irradiation of wood in alkaline aqueous ethanol increases kraft pulp yield by up to 1.2 %, as already reported. In order to clarify the mechanism of the pulp yield gain, the behaviors of lignin and carbohydrates during pre-irradiation and cooking were investigated.The results are summarized as follows : 1) γ-Irradiation of guaiacylethane in alkaline agueous ethanol produced 5- (1-hydroxyethyl) -guaicylethane, which is formed by radical coupling between α-hydroxyethyl radical from ethanol and guaiacylethane radical having an unpaired electron at C-5. 5, 5'-Dehydrodiguaiacylethane, which may be a predominant product produced by γ-irradiation in the absence of ethanol, was also detected.2) The yield of vanillin obtained by nitrobenzene oxidation of MWL decreased with an increase of γ-ray dosage. The presence of ethanol during γ-irradiation lessened the extent of this decrease and also the degradation of cellobiose.3) Gel filtration of the products obtained by γ-irradiation of MWL and cellobiose in the presence of 14C-ethanol showed the possible combination between ethanol and MWL or cellobiose.4) Molecular weight distributions of kraft lignin obtained from pre-irradiated beech chips were compared with those obtained from unirradiated chips. This result shows that γ-irradiation in the presence of ethanol decreases the ability of lignin to condense during kraft cooking.

Radiolysis, racemization, and the origin of optical activity

An investigation has been undertaken to determine whether ionizing radiation might engender racemization ( radioracemization) of optically active amino acids, along with their well-known radiolysis. We have exposed a number of solid and dissolved optically active amino acids to the ionizing radiation from a 3000-Ci 60Co γ-ray source for periods of time which would engender substantial, but not total radiolysis. γ-Ray doses which caused 55–68% radiolysis of solid amino acids typically engendered 2–5% racemization. Aqueous solutions of the sodium salts of amino acids which underwent 53–66% radiolysis typically showed 5–11% racemization. The corresponding hydrochloride salts in aqueous solution, however, underwent little or no racemization. In aqueous solution both percentage degradation and percentage racemization were approximately proportional to γ-ray dosage within the range employed (1–36 × 10 6 rads). Mechanisms for the radioracemization of amino acids in the solid state and as dissolved sodium salts are proposed, and the absence of racemization for dissolved hydrochloride salts is rationalized. Implications of these observations with regard to the origin of optical activity by the Vester-Ulbricht β-decay mechanism are discussed, as are their implications regarding the use of diagenetic racemization rates of ancient amino acid samples as criteria for geochronological and geothermometric calculations.

The thermal degradation of bulk polystyrene after small dose gamma irradiation

The results are reported of a study of the thermal degradation (TD) carried out on bulk polystyrene (BPS) intended for medicinal uses, which had been sterilized by irradiation with a γ-ray dosage of 2·5 Mrad. The methods used were pyrolytic gas chromatography and IR spectroscopy; these have shown the TD to be a two stage process with differing activation energies. The two stages run in parallel, i.e. decomposition to the monomer (depolymerization), and the formation of a larger molecular weight product (TD) compared with that of the monomer. Vacuum irradiation did not significantly affect the mechanism of TD of the BPS. Exposure to radiation in air gave rise to oxidative processes which had different effects on the depolymerization and TD. A mechanism has been suggested for these stages and for the change of activation energy of TD for the irradiated BPS when compared with that for the unexposed polymer.

Radiation effects on Arabidopsis thaliana—II killing and mutagenic efficiencies of heavy ionizing particles

Dry F 2 seeds obtained from F 1 hybrids between a hairless mutant and the wild strain of Arabidopsis were subjected to γ-rays from a Cs 137 source of the National Institute of Genetics, Misima and He 4 to C 12 and Ar 40 ions from the Hilac of the University of California. The range of heavy ionizing particles is very short and therefore the small Arabidopsis seeds seemed to be a suitable material. The average seed volume was calculated roughly from the weight and measurements of length and width of the seeds, to be 20·5 × 10 −3 mm 3. From this calculation it was concluded that Ar-ions must be stopped within the seeds but He-ions and C-ions certainly could penetrate and pass through seed tissue. Germination and survival rates in the control and in two γ-ray lots were very good. Survival rates decreased markedly with increasing dosage in the heavy-ion lots, especially those treated with He-ions. The frequency of plants with hairless sectors induced by somatic mutation per rad increased with increasing dosage in γ-ray, C-ion, and Ar-ion lots. Somatic mutation rates in the C-ion lots were very high; those of Ar-ion lots were very much lower. On the other hand, only one mutated plant was observed in one He-ion 2-krad lot, and the other four lots treated with He ions showed no mutation. An exponential relation was observed between mutation frequency and γ-ray dosage. In heavy-ion treatments, the frequency vs. dosage relation was fairly linear. RBE for somatic mutation at 0·5 per cent frequency was roughly estimated as 35 for C-ions. An estimate of the RBE for He-ions was difficult to obtain, but on the basis of the observation made at a dose level of 2 krad the RBE for somatic mutation with those ions may be around 10. From the results, the difference in dose vs. mutation rates between γ-rays and heavy ions, and the LET vs. RBE relation, were discussed.

The effect of gamma-radiation on soluble and insoluble collagens.

The effect of γ-radiation on soluble and insoluble collagens was studied by the modifications in the electron microscopical appearance, X-ray diffraction pattern, optical birefringence, thermal stability and the tensile properties of collagen fibres obtained from rat- and kangaroo-tail tendons. The γ-ray dosages used were 10 and 30 Mrad. At 10 Mrad collagen fibrils from rat-tail tendon did not show any change in the electron microscope while those from kangaroo-tail tendon showed partial disorder or disappearance of the cross-striations and exhibited twisting. At 30 Mrad, the latter fibrils appeared gelatinised while rat-tail-tendon fibrils retained the fibril form but without the cross-striations. These results are in conformity with the corresponding X-ray diffraction patterns and the data on the optical birefringence and thermal and mechanical stability of these fibrils, and point to the possibility that soluble collagen is more resistant to γ-radiation than insoluble collagen.

Gamma-Ray Protection in Radium Therapy

It is suggested that if the γ-ray dosage received by radium therapists during their radium work could be assessed (even if only roughly), more specific opinion might be formed as to what levels of exposure have proved to be safe. Calculations and measurements of local dosage and integral dose received by radium mould technicians and radium therapists are made in order to make such assessment. On the basis of these results the implications of the various proposed standards of protection are examined and set out in terms of actual working conditions. For this purpose protection is considered in the categories in which it seems the subject should be divided, viz., local exposure of the hands, local exposure of the gene material and integral dose throughout the whole body. In relation to medical work it is concluded (1) that many busy radium personnel may receive local exposure to the hands in excess of that now recommended in the U.S.A. as a safe amount (1 r per day), (2) that if circumstances dictate it sho...

Geometrical Method of Dosefinding for Radium Sources: with Special Reference to the Treatment of Carcinoma Cervix Uteri

The solution of the problem of the accurate determination of the dose distribution in volume produced by X or γ radiation in radiotherapy was made possible by the introduction of Mayneord's dosefinder. Mayneord (1943) has shown that the distribution due to most complicated arrangements of X-ray fields or radium sources can be analysed by the use of the dosefinder, but this method takes time and as Mayneord (1943) himself has said, “rapid methods of three-dimensional dose studies are urgently required”. In the case of external sources of radiation, standard dose distribution charts are of limited value even when modifications are often required for individual cases. For intra-cavitary or interstitial radium therapy, however, the actual positions attained by the radium sources are often very different from those prescribed in the planned technique. The volume dose distribution consequently differs from that intended, and the use of standard dosage charts may lead to large errors in estimating, for example, the dosage in the pelvis (Sandler, 1938, 1943) unless this is taken into account. The need for individual dosefindings becomes still more urgent when intra-cavitary radium is to be later supplemented by external X radiation as in the treatment of carcinoma cervix. The problem of the harmonious combination of both radiations resolves itself into that of devising an X-ray distribution which will compensate adequately for the gradual fall in γ-ray dosage towards the pelvic wall in what has been called the “radium paralethal zone” (Sandler, 1943).

A Dosage System for Linear Gamma-ray Sources

For tubular γ-ray applicators, a close approximation to a uniform dosage rate over a cylindrical surface of given length (l) and radius (h) may be obtained from an axially placed linear radioactive source of the same length, subdivided into three contiguous equal lengths, the outer sources having a higher linear density (ρ2) than that of the inner source (ρ1). The relation between ρ2 and the shape factor l/h has been determined on the basis of Sievert's expression for the γ-ray dosage rate near to an unscreened uniform linear source. Calculations of actual dosage rates are based on Sievert's formula for a linear source enclosed in an absorbing cylinder. The results, which have been confirmed experimentally, are presented in graphical form by two charts, which facilitate the planning of tubular applicators. One of these graphs gives the percentage content of the inner source, while the other gives the milligramme-hours required for a dose of 1000 r, for a comprehensive range of the shape factor.