The effect of geometry on the fluorescence radiation field

In X-ray fluorescence spectroscopy, a photon beam is focused on the sample to induce the production of characteristic radiation carrying useful information on the composition of the target. Even if the interpretation of the measurement is simple, the quantification of the total emitted intensity is not straightforward because the primary photons are produced deep in the target and the radiation reaching the detector can be sensibly modified by the interactions which the photons undergo before leaving the specimen. In this work we show that the geometry of the system plays an important role in determining the properties of the radiation field.     

Kinetics of the copolymerization of N-phenylmaleimide with styrene in a gamma-radiation field

Conclusions The radiation copolymerization of N-phenylmaleimide with styrene in acetone at room temperature proceeds with the formation of a complex of the growing polymer radical with the monomer in an intermediate step as indicated by anomalously high specific heats of copolymerization and the reaction order of one-half relative to the monomer.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1677–1679, July, 1988.     

The effect of gamma-radiation on yeast cell wall glucans

The solubility and the degree of degradation of water-insoluble particulate glucan isolated from Saccharomyces cerevisiae were studied after -irradiation. The different radiolytic stability of /1–3/-, /1–6/- and -glucan linkages of the complex polysaccharide can be used to achieve its fragmentation and provide a new insight to its macromolecular structure.     

Study of gamma-radiation effects on crotamine and crotoxin

Summary Crotoxin is a 23 kDa neurotoxin from Crotalus durissus terrificus and is composed of a 9 kDa acidic subunit (crotapotin) and a 14 kDa basic subunit (phospholipase A₂). Crotamine is 4882 Da, basic polypeptide with myotoxic activity. These toxins, when submitted to gamma-rays, in aqueous solution, present structural modifications, preserving their immunogenic properties. In the present work, we investigated some structural modifications on both crotoxin and crotamine after gamma-radiation using various doses, in the presence or not of “scavenger” substances. Our results indicate that irradiation leads to progressive changes in the structure of the toxin, which could explain the lower toxicity observed.     

The effect of gamma-radiation on polymer composites based on thermoplastic matrices

The effect of ⁶⁰Co γ-radiation on polymer composite materials (PCMs) based on reinforcing glass cloth, polyethylene (PE), polyamide (PA) and polypropylene (PP) matrices has been studied. It has been found that PCMs based on more durable PP and PA matrices have a substantially lower radiation resistance as compared to their PE-matrix analogs. More stable carbon-reinforced plastics based on the PE matrix also have a lower radiation resistance as compared to fiberglass plastics. High-strength PE fiber, PE film, and PE-matrix composites behave in fundamentally different manners under the action of radiation.     

The effect of post-irradiation annealing on the crosslinking of high-density polyethylene induced by gamma-radiation

Samples of two high-density polyethylenes having different crystallinity levels were gamma irradiated under vacuum at doses ranging from 20 to 300 kGy. Subsequently, the vials containing the irradiated samples were exposed to different post-irradiation treatments. Parts of the specimens were annealed while still under vacuum. The annealing time was 4 h and the annealing temperatures 110 °C or 150 °C. Others were exposed directly to air opening the vials without any thermal treatment. It was verified that in all cases the dosage to produce an incipient gel increases with the crystallinity of the initial sample. The amount of gel produced after exposing specimens of the same polymer to a given dose increases with the annealing temperature. The largest increment in the amount of gel produced at the completion of the post-irradiation treatment was found on the samples with the highest initial crystallinity level.Evidence of oxidation was found in all irradiated samples. The extent of oxidation depends on the initial crystallinity of the sample, the irradiation dose and the type of post-irradiation treatment. The heat of fusion measured in the annealed samples decreases with the gel content while the fusion temperature was slightly affected. Ductile or brittle behaviors were observed after testing specimens under tensile stress. The yield stress increases proportionally to the crystallinity level that, in turn, depends on the total dosage applied to the samples. The extensibility of ductile samples is determined by the amount of gel produced regardless of the degree of initial crystallinity and the type of annealing process applied to each sample.     

A dielectric study of the glass transition region in segmented polyether-urethane copolymers

Ten polyether-urethane thermoplastic elastomers of varying chemical structure have been characterized by dielectric spectroscopy and scanning calorimetry. In the temperature range corresponding to the glass-rubber transition of the predominantly polyether phase, modification of the primary dielectric transition and the occurrence of a second transition at somewhat higher temperature have been observed. Through comparison with calorimetric data, these events have been related to supercooling of crystallizable polyether segments. Supercooling suppresses dielectric loss processes in some regimes and enhances losses in others. By systematic variation of chemical structure these phenomena have been classified.     

On the effect of a radiation field in modifying the intermolecular interaction between two chiral molecules

The change in the mutual energy of interaction between a pair of chiral molecules coupled via the exchange of a single virtual photon and in the presence of an electromagnetic field is calculated using nonrelativistic quantum electrodynamics. The particular viewpoint adopted is one that has an intuitive physical appeal and resembles a classical treatment. It involves the coupling of electric and magnetic dipole moments induced at each center by the incident radiation field to the resonant dipole-dipole interaction tensor. The energy shift is evaluated for fixed as well as random orientations of the molecular pair with respect to the direction of propagation of the field. A complete polarization analysis is carried out for the former situation by examining the effect of incident radiation that is linearly or circularly polarized and traveling in a direction that is parallel or perpendicular to the intermolecular distance vector. After tumble averaging, all polarization dependence of the energy shift vanishes. In both cases the interaction energy is directly proportional to the irradiance of the applied field, and is discriminatory, changing sign when one optically active species is replaced by its enantiomer. The asymptotic behavior of the energy shift at the limits of large and small separations is also studied.     

Quality of the radiation field image

The work defines and analyzes the resolution angle in image obtained by a directional detector. The effect of both the relative directivity diagram of the detector used and complexity of the scanned field are discussed.     

International cooperation in the field of radiation application

Bilateral and multilateral research cooperations have been implemented at TRCRE, JAERI, producing favorable results in the field of radiation application. Frameworks and some achievements are described and the significance of the international cooperation is discussed.     

The influence of gamma-radiation on the stability of benzyldibutylamine in benzene

The composition of degradation products of the radiolysis of benzyldibutylamine and benzene was identified by means of mass, NMR and infrared spectra, elementary analysis and gas liquid chromatography. The mass balance indicated that benzyldibutylamine was stable when irradiated by a medium-high dose of 143 kGy and its mass loss did not exceed 10% of the irradiated fraction.     

Effect of gamma-radiation in vinylpyrrolidone

The effects of gamma-irradiation in purified N-vinylpyrrolidone monomer have been studied. Dependence of crosslinking and water swelling ability upon the administered dose of ionizing radiation have been documented.     

Magnetic field effects on recombination radiation in tetracene crystal

Recombination radiation in tetracene crystal is shown to be modified by the application of a magnetic field. Relative variations of radiation intensity with field and orientation can be explained in terms of molecular singlet fission and triplet exciton-charge carrier interaction.     

Theoretical study of the effect of radiation on thymine

The possible effects of radiation exposure to DNA are studied by investigations for the thymine residue. Detailed analysis of the various addition and other products is undertaken theoretically, using the semiempirical AM1 procedure. The results agree with the experimental finding that the loss of hydrogen on radiation exposure occurs from the C₅-methyl group and hydroxyl radical addition occurs at C₆, yielding the ‘5-yl’ radical. This radical is nonplanar, the axial conformer being slightly preferred over the equatorial one. In contrast, the other possible radical, the ‘6-yl’ radical, is almost planar. These results are important in understanding the conformational changes in DNA as a consequence of radiation exposure.     

The microwave radiation effect on the polymerization of styrene

Styrene was cured by microwave radiation at two different powers: 300 and 500 W. The temperature profile of the sample during the microwave curing process was determined to select a suitable temperature for comparison with the conventional method of cure. The results indicate a similar comparable temperature of about 80°C irrespective of the microwave power used. The percentage conversion of the cure was followed by Fourier transform infrared (FTIR) spectroscopy. The thermal polymerization at 79(±1)°C displayed a gradual increase in the rate of reaction at the gel effect from about 30 to 50% conversion of the reaction. The microwave cure at 300 and 500 W displayed a large and sharp gel effect from about 20 to 69 and 64% conversion of the reaction, respectively. The limiting conversion decreased with increase in microwave power which was also observed in the polymerization of methyl methacrylate (MMA). Based on similarity in temperature and reaction conditions, the 500 W cure was found to show a reaction rate enhancement of 190% and the 300 W cure 120%. A comparison of microwave induced reactions with thermal methods, therefore, must also specify the microwave power used. © 1996 John Wiley & Sons, Inc.     

Magnetic field effect on the photoconductivity of poly-n-vinylcarbazole

Magnetic fields were found to increase the photocurrent in poly-N-vinylcarbazole (PVCz) films by up to 5–6% at 1 kG. This positive magnetic field effect was sensitive to both applied voltage and temperature, and was enhanced with dimethyl-terephthalate (DMTP) doping by a factor of two. Magnetic fields were also found to increase the prompt exciplex fluorescence of PVCz films doped with DMTP by up to 2% at 500 G. The observations made clear that a carrier generation process via an exciplex state has an important role in photo-carrier generation even in undoped PVCz films.     

Magnetic field effect on the fluorescence of glyoxal

Fluorescence from the ¹A_u state of glyoxal is quenched by a magnetic field and the pre-exponential factor of phosphorescence from the ³A_u state increases with increasing magnetic field. These findings are explained by the enhancement of intramolecular intersystem crossing by the magnetic field.     

Image of an infinite radiation field

Image of an infinite, monoenergetic radiation field, scanned by a directional detector is analyzed. The condition for ideally true image is discussed and the method for reconstruction of the directional flux densities of the radiation field, according to the data measured by a directional detector, are given.     

Effect of gamma-radiation on amorphous mixed zirconium-titanium phosphates

A precipitation method was used to prepare amorphous mixed zirconium-titanium phosphates with various titanium contents. In this way the acidic solutions of ZrOCl₂.8H₂O and TiCl₄ in various ratios were rapidly mixed with a phosphoric acid solution under continuous stirring. The resulting precipitate, characterized as [Zr_xTi_/1–x//HPO₄/₂.n H₂O] was contacted with water of ethanol, then washed to pH 3.0 and dried at room temperature. The samples were irradiated with -rays of a⁶⁰Co source giving a 6.6×10⁷ Gy total dose. The thermal, chemical and ion-exchange properties of irradiated samples were investigated.     

Useful transformation of a radiation field

The paper deals with the characteristics of the radiation field, namely the flux density and current density. Two transformations of the general radiation field are presented which could considerably simplify the calculations in several situations.