Effect Of Pre-irradiation Research Articles

Beauty Today and Youth Tomorrow?

As demonstrated by the simultaneous proliferation of tanning salons and a tremendous growth in interest in new agents that may reverse photoaging or at least wrinkles that accompany tanning, many people want both.1In this month'sArchives of Dermatology, Bech-Thomsen and colleagues2present provocative data suggesting that in hairless mice, preirradiation with long-wave (A range) ultraviolet radiation (UV-A), similar to the wavelengths emitted by most tanning salon units, provides significant protection against the development of skin tumors in mice subsequently exposed to broad-band ultraviolet radiation (ie, the sun). These well-designed experiments suggest that, at least in the hairless mouse, a brief visit to a tanning parlor before exposure to the sun (ie, both sunburn-spectrum [B range] ultraviolet radiation [UV-B] and UV-A) might help reduce the risk of sun-induced nonmelanoma skin cancer. Somewhat surprisingly, the authors do not relate this apparent protective effect of preirradiation to increases in skin

Thin Film Adhesion to Ion Bombarded Surfaces

AbstractWe report on the use of 20 MeV C14+ ion beams for pre-irradiation of Si, SiO2 and Al2O3 surfaces with resulting alterations in the adhesion of subsequently deposited Au and Ag thin films. The effect does not follow the same pattern for Au and Ag films, nor is there a simple correlation to the previously observed adhesion effect induced by ion irradiation after film deposition. Possible mechanisms, both for pre-irradiation and post-irradiation effects, are discussed, as is the importance of chemical structures with respect to interfacial bond strength.

Thermal decomposition of γ-irradiated silver malonate

The effects of pre-irradiation with γ-rays on the isothermal decomposition kinetics of silver malonate have been studied quantitatively. Such pretreatment reduced the length of the induction period to the onset of reaction and increased the rate of subsequent salt breakdown, which has been shown to proceed by a nucleation-and-growth mechanism. Between 6.5 × 106 and 1.0 × 109 rad, the shapes of the isothermal, fractional-decomposition vs. time curves were unchanged as a result of irradiation and the increase in reaction rate was directly proportional to the γ-ray dose. It is concluded that pre-exposure to ionizing radiation increases the number of nuclei that are active in salt breakdown in direct proportion to the dose to which the sample had previously been exposed. The influence of radiation on the induction period is also discussed; the evidently greater reductions in length, for samples exposed to larger radiation doses, are attributed to radiation damage of the crystal, associated with the presence of radicals detected by an e.s.r. signal.

Reduction reactivity of CuO-Cr 2O 3 mixed oxides with hydrogen and the effect of gamma pre-irradiation

The physico-chemical properties and parameters of CuO-Cr 2O 3 mixed oxides as well as their reactivity toward reduction with hydrogen have been investigated by means of various methods (X-ray analysis, electron spectroscopy for chemical analysis (ESCA), DTA, IR spectroscopy and scanning electron microscopy). A series of mixed oxides of various compositions in the range 0–100% of each component were prepared by calcinating the mass of coprecipitated basic carbonates in air. The reduction kinetics were studied by isothermal thermogravimetry in the temperature range 180–470 ° C. The effect of the origin of the oxides on the reactivity of the oxide system during its hydrogen reduction was proved by comparing its properties with those of a previously studied series of analogous mixed oxides, which were prepared from different precursors. The pre-irradiation of the system by 60Co γ radiation results in a positive kinetic effect (an increase in the reduction rate) if the lowest dose applied is 2.57 × 10 6 Gy. The magnitude of the radiation effect is greatly dependent on the composition of the mixed oxides.

Preirradiation of host (monkey) cells mitigates the effects of UV upon simian virus 40 DNA replication

We are examining the effects of preirradiation of host (monkey) cells upon the replication of UV-damaged SV40. Control cells and cells preirradiated with low fluences (5 or 10 J/m 2) of UV were infected with undamaged SV40, and the immediate effects of a subsequent irradiation were determined. UV inhibited total SV 40 DNA synthesis (incorporation of thymidine into viral DNA) in both preirradiated and control cells, but the extent of inhibition was less in the preirradiated cells. A test fluence of 60 J/m 2 to SW40 replicating in preirradiated cells reduced synthesis only as much as a test fluence of 25 J/m 2 in control cells. The fraction of recently replicated SV40 molecules that re-entered the replication pool and subsequently completed one round of replication in the first 2 h after UV was also decreased less in the prerradiated cells. Thus preirradiation of the host cell mitigates the immediate inhibitory effects of a subsequent UV exposure upon SV40 replication.

Suppressive effect of preirradiation with blue light on near ultraviolet light induced conidiation in Alternaria tomato

Conidiophore formation in Alternaria tomato (Cke.) Weber (ATCC 38852) was induced by irradiation with near ultraviolet light, and conidia formed in subsequent darkness. However, blue light applied before the inductive near ultraviolet radiation suppressed the induction. Preirradiation with blue light just before the inductive near ultraviolet radiation was most suppressive. An action spectrum for this suppression showed a peak around 447 nm, with a shoulder between 400 and 440 nm, a minor peak around 478 nm in the blue region, and another near 385 nm in the near ultraviolet region. This action spectrum is very similar to the ubiquitous blue light response (cryptochrome).

Dual ion beam study on deuterium permeation

The D permeation rate under bombardment of 50 keV D + was measured at 500°C for Type 316 stainless steel which was pre-irradiated by 320 keV He ++. In addition, the D permeation rate was also measured during simultaneous bombardment of 57.5 keV D + and 280 keV He ++ at 442°C. By pre-irradiation of 3 × 10 17 He ++ cm −2, the D permeation rate was reduced to about 1 4 of that without He ++ irradiation. It was also found that a reduction of D permeation rate to about 1 3 occurred by simultaneous He ++ irradiation of 1.3 × 10 14 ion/ cm 2 s −1 in addition to the pre-irradiation effect. The change of the diffusion constant by the He ++ irradiation was also evaluated with a computer code, which was developed to solve the diffusion equation by the Crank-Nicolson's method.

Radiation pretreatments of cellulose materials for the enhancement of enzymatic hydrolysis—II. Wood chips, paper, grain straw, hay, kapok

The effect of γ-ray pre-irradiation of cellulose materials such as wood chips, paper, grain straw, hay and kapok on glucose production on enzymatic hydrolysis by cellulase has been investigated. These materials have been irradiated in air, water and acetate buffer solution over the dose range 10 3–4 x 10 6 Gy. In the relatively low dose range, up to about 5 x 10 5 Gy, the glucose yields after enzymatic hydrolysis are practically insensitive to radiation. At higher dose levels, up to 1.7–2 x 10 6 Gy, the pre-irradiation becomes very effective on enzymatic cellulose conversion. It has been found that the radiation-induced degradation of cellulose into low molecular weight polysaccharides is dependent on the nature and chemical composition of the cellulose materials and on the radiation environmental conditions. Further increases of dose causes radiation-induced structural modifications in polysaccharides previously produced, which can lead to a decrease in glucose production by enzymatic hydrolysis.

Helium pre-irradiation effect on deuterium permeation in stainless steel

Helium pre-irradiation effect on deuterium permeation in stainless steel

Changes in developmental capacity of artemia cyst and chromosomal aberrations in lettuce seeds flown aboard Salyut-7 (Biobloc III experiment)

This paper gives the results of investigations performed on the first container (A) of the Biobloc III experiment, flown aboard the orbital station Salyut 7 for 40 days. The space flight resulted in a decreased developmental capacity of Artemia cysts, hit or not hit by the HZE particles. No effect was observed in cysts in bulk. A synergetic effect of microgravity and gamma pre irradiation is described. The germination of in-flight lettuce seeds was decreased. The space flight resulted also in a higher percentage of cells with chromosomal aberrations. Relations between biological response, TEL and location of HZE particles are discussed.

Radiation pre-treatments of cellulose materials for the enhancement of enzymatic hydrolysis—I: Pure cotton

The effect of γ-ray pre-irradiation of cotton cellulose on glucose production on enzymatic hydrolysis by cellulase has been investigated. Pure cotton has been irradiated in air, in water and in acetate buffer solution over the dose range 10 3–10 6 Gy. Pre-irradiation in water or in acetate buffer solution is more effective than in air. The results show that the glucose yield is not always an increasing function of dose, and that for some dose levels, the glucose yields from the irradiated samples are lower than those from non-irradiated samples.

Switching in Poly(N-vinylcarbazole) Thin Films: Effect of γ-Ray Irradiation and Heat Treatment

The effects of preirradiation with γ-rays or preheat treatment on the switching characteristics of poly(N-vinylcarbazole) (PVCz) films were studied. The dark conductivity and threshold voltage increased when PVCz was irradiated. The magnitude of the effects of irradiation depend on the state of PVCz. PVCz irradiated with γ-rays in a film form showed a higher conductivity and threshold voltage than films cast after irradiation in powder form. Purification of irradiated PVCz by precipitation from a benzene solution reduced the effects of γ-irradiation. Preheat treatment increases crystallinity and conductivity but not the threshold voltage.

Effects of pre-irradiation and quenching on the low-temperature thermoluminescence of KCl:Sr

The effect of quenching from 650 degrees C to room temperature as well as that of heavy predoses at room temperature on the thermoluminescence induced by X-irradiation at temperatures between 80 and 300K in KCl:Sr (80 ppm) samples have been investigated. These heavy predoses strongly reduce the glow peaks in the 170-300K range which are clearly related to interstitial centres involving impurity-vacancy dipoles. This result gives additional evidence to support the idea that such dipoles are also involved in the thermoluminescent processes operative above room temperature. The study of quenched samples has revealed the existence of a dipole aggregation process which is induced by irradiation. It is suggested that the energy transfer mechanism is the recombination of the radiation-induced interstitials and vacancies close to the dipoles, either during irradiation or in the thermoluminescence run.

The effect of γ-radiation energy transfer in the radiocatalytic decomposition of 2-propanol

The effects of pre-irradiation with γ-rays of heat treatment in vacuum on the surface acidity and basicity of TiO 2, Fe 2O 3, V 2O 5 and Cr 2O 3 and on the radiocatalytic decomposition of 2-propanol have been studied. Since pre-irradiation and heat treatment have very different effects, the radiocatalytic effects cannot be accounted for by local, radiation-induced, temperature increase. The radiocatalytic effects are attributed to transfer of absorbed radiation energy from the catalysts. This conclusion is supported by comparing the yields of the gas- and of the liquid phase radiolysis with the radiocatalytic transformation of 2-propanol.

Effect of ionizing radiation on the kinetics of hydrogenation on the Ni-MgO mixed catalyst

The effect of gamma pre-irradiation of the mixed nickel-magnesium oxide catalyst on the kinetics of hydrogenation of maleic acid in the liquid phase has been studied. The changes of the hydrogenation rate are compared with the changes of the adsorbed amount of the acid and with the changes of the solution composition, activation energy, and absorbed dose of the ionizing radiation. From this comparison and from the interpretation of the experimental data it can be deduced that two types of centers can be distinguished on the surface of the catalyst under study, namely the sorption centres for the acid and hydrogen and the reaction centres.

Effect of sublethal preirradiation of recipients on growth of grafted syngeneic tumors in newborn mice

The great importance of immunologic factors has been demonstrated by studies of the mechanisms of pathogenesis of various tumors [2]. Immunologic insufficiency as a rule leads to stimulation of tumor growth ~n ~uo. However, a few years ago it was shown in the writer's laboratory that some tumors grow less well when transplanted into syngeneic newborn mice than into mature mice. Of 12 tumor strains studied, eight strains grew less well in newborn mice under certain conditions. These included both tumors arising spontaneously and subsequently transplanted a few times and also continuous strains [ii, 12].

Lag-phase and rate of synthesis in phytochrome-mediated induction of phenylalanine ammonia-lyase in mustard (Sinapis alba L.) cotyledons

Mustard seedlings were irradiated with continuous far-red light either with or without far-red preirradiation for between 6 and 44 h. The preirradiation increases the rate of light-mediated phenylalanine ammonia-lyase (EC 4.3.1.5) accumulation in the cotyledons up to 5-fold but does not eliminate the apparent lag-phase of induction which lasts between 30 and 60 min, both with and without a preirradiation. No differential effect of inhibitors presumed to be acting close to gene transcription was observed for plants, whether given a preirradiation or not. These results do not support the notion that two different induction mechanisms are involved in the action of phytochrome on phenylalanine ammonia-lyase synthesis during primary and secondary irradiation. There was however a strong promotive effect of preirradiation on P fr-mediated enzyme accumulation which can be explained by an elevated level of the rate of enzyme synthesis left over from the previous light treatment and a transient increase in the capacity of the system to increase the rate of enzyme synthesis in response to active phytochrome.

Thermal decomposition of γ-irradiated zinc hydroxy azide

The effect of pre-irradiation by γ-rays (60Co) at varying dosages on subsequent thermal decomposition of differently treated samples of zinc hydroxy azide is reported here. The same kinetic forms as in the case of untreated sample, viz., the unimolecular decay law followed by the contracting cube, fit thea, t data. The rate constants increase only marginally. The effect of increasing dosage from 10 krad to 24 Mrad is very small. The effect of pre-irradiation on decomposition of the aged sample is slightly more pronounced than in the case of the fresh sample.

Effects of electron beam preirradiation on the γ radiolysis of polyethylene

AbstractThe γ radiolysis of polyethylene preirradiated with electron beams to 3 Mrad was carried out at 30–100°C in vacuo with a dose rate of 6.35 × 105 rad/hr. The hydrogen formation in the γ radiolysis was little affected by the preirradiation of electron beams, whereas the formation of trans‐vinylene unsaturation and gel was somewhat retarded. The rates of the formation of hydrogen and trans‐vinylene unsaturation were described by the zero‐order formation kinetics with respect to each concentration combined with the first‐order disappearance. The apparent rate constants and activation energies for the formation and disappearance of hydrogen and trans‐vinylene unsaturation were almost independent of the preirradiation. The gel fraction was analyzed by using the Charlesby–Pinner equation. The G values of crosslinking and main chain scission were increased by the preirradiation, whereas their activation energies remained unaltered. On the basis of these results the effects of preirradiation on the reactions induced by γ rays in polyethylene were discussed.

Preirradiation history of Djermaia (H) chondritic breccia

Djermaia is a unique case among gas-rich chondrites. Twelve light xenoliths studied so far in the two available stones show unequivocal evidences of large preirradiation effects, which stand out most clearly when both cosmic-ray track and spallogenic rare-gas data are considered and compared to data from chondrites with a simple radiation history. Each of the two stones studied displays a specific xenolith population with distinct morphological and preirradiation characteristics. The first population consists of rounded and more- or less-shocked xenoliths which show evidences of short solar-flare irradiation (<1 my) and a longer residence under heavier shielding (∼50 g/cm 2). The second population shows neither clear indication of surface erosion nor evidence of solar-flare effects, and its preirradiation occured in deep-seated locations (∼150 g/cm 2).The size distribution of xenoliths is also different for the two populations, indicative of more active reworking processes in the top ∼20 cm of the Djermaia regolith than at a depth of ∼50 cm. The amount of 21Ne sp accumulated during the preirradiation stage is substantial (25–60% of total 21Ne sp), corresponding to a formal preexposure time of ∼15 my for both stones, assuming static irradiation conditions. These results give an insight into the dynamics of the upper levels of the H-asteroid regolith, which appears to be in good agreement with the model of Housen, Wilkening, Chapman, and Greenberg ( Icarus, 1979 , 39, 317–351).