Oxygen-induced Reactions Research Articles

Mechanism of heel build-up on adsorbents through oxygen induced reactions

Oxygen induced reactions during the desorption of volatile organic compounds (VOCs) from adsorbents (such as activated carbon) promote heel buildup and reduce the adsorbent’s lifetime. This study aims to improve the understanding of heel build-up mechanisms in the presence of oxygen in the desorption purge gas. Three activated carbons (ACs) and one zeolite adsorbent were exposed to an extreme condition of 1,2,4-trimethylbenzene (TMB) and high oxygen concentration at three temperatures (150, 200, and 250 °C). Thermogravimetric analysis and gas chromatography-mass spectrometry (GC–MS) were used to assess the thermal stability and chemical structure of the formed heel, respectively. Additionally, nitrogen adsorption was performed to evaluate the effect of heel formation on the adsorbent’s pore properties. Increasing the desorption temperature in the presence of oxygen was found to reduce the BET surface area and increase the oxygen-induced reactions on the adsorbents. Among the three tested temperatures, minimum heel formation was obtained at the intermediate temperature, 200 °C. Compared to zeolite, ACs were more susceptible to oxygen induced reactions at elevated temperatures due to their wide pore size distribution. Further analysis using GC–MS revealed that oxygen presence during the desorption process can form a broad range of organic species in terms of molecular weight, chemical structure, and functional group.

Verification of dose distribution in high-dose-rate brachytherapy using a nanoclay-based radio-fluorogenic gel dosimeter

Dose distributions have become more complex with the introduction of image-guided brachytherapy in high-dose-rate (HDR) brachytherapy treatments. Therefore, to correctly execute HDR, conducting a quality assurance programme for the remote after-loading system and verifying the dose distribution in the patient treatment plan are necessary. The characteristics of the dose distribution of HDR brachytherapy are that the dose is high near the source and rapidly drops when the distance from the source increases. Therefore, a measurement tool corresponding to the characteristic is required. In this study, using an Iridium-192 (Ir-192) source, we evaluated the basic characteristics of a nanoclay-based radio-fluorogenic gel (NC-RFG) dosimeter that is a fluorescent gel dosimeter using dihydrorhodamine 123 hydrochloride as a fluorescent probe. The two-dimensional dose distribution measurements were performed at multiple source positions to simulate a clinical plan. Fluorescence images of the irradiated NC-RFG were obtained at a high resolution (0.04 mm pixel–1) using a gel scanner with excitation at 465 nm. Good linearity was confirmed up to a dose range of 100 Gy without dose rate dependence. The dose distribution measurement at the five-point source position showed good agreement with the treatment planning system calculation. The pass ratio by gamma analysis was 92.1% with a 2%/1 mm criterion. The NC-RFG dosimeter demonstrates to have the potential of being a useful tool for quality assurance of the dose distribution delivered by HDR brachytherapy. Moreover, compared with conventional gel dosimeters such as polymer gel and Fricke gel dosimeters it solves the problems of diffusion, dose rate dependence and inhibition of oxygen-induced reactions. Furthermore, it facilitates dose data to be read in a short time after irradiation, which is useful for clinical use.

Eikonal model description of forward energy distribution in oxygen-induced reactions at 60 A GeV and 200 A GeV

The forward energy flow cross section is described in terms of the projectile-nucleon abrasion probability which is calculated in the impact parameter representation within the framework of the Glauber multiple scattering formalism. Realistic nuclear densities and the nucleon-nucleon inelastic cross section have been used in the calculation. The recent WA80 data are in reasonable agreement with the calculation. A simple relationship has been obtained between the abrased nucleons from the target and projectile and the zero degree energy.

Oxygen-induced reactions at 60A GeV and 200A GeV studied by calorimetry

Results based on calorimetric measurements are presented from reactions of 60A GeV and 200A GeV16O projectiles with C, Cu, Ag, and Au nuclei. Minimum-bias cross sections are discussed. Energy spectra measured at zero degrees and transverse-energy distributions for the pseudorapidity range 2.4≦η≤5.5 are shown. An analysis of the average transverse energy in terms of the number of participating nucleons and the number of binary nucleon-nucleon collisions is presented. Estimates of nuclear stopping and of attained energy densities are made.

Forward and transverse energy distributions in oxygen-induced reactions at 60 A GeV and 200 A GeV

Results are presented from reactions of 60 A GeV and 200 A GeV 16O projectiles with C, Cu, Ag, and Au nuclei. Energy spectra measured at zero degrees and transverse energy distributions in the pseudorapidity range from 2.4 to 5.5 are shown. The average transverse energy per participant is found to be nearly independent of target mass. Estimates of nuclear stopping and of attained energy densities are made.

Fusion, transfer, and elastic scattering at sub-barrier energies for 16,18O ions on 208Pb and 15N and 16O ions on 209Bi.

The fusion of the heavy asymmetric systems of $^{16}$O,${\mathrm{}}^{18}$O${+\mathrm{}}^{208}$Pb and $^{15}$N,${\mathrm{}}^{16}$O${+\mathrm{}}^{209}$Bi was studied at bombarding energies near and below the Coulomb barrier. The fusion-fission, transfer, and elastic angular distributions were measured for all four systems. The evaporation residue component of the fusion was measured for only the $^{16}$O${+\mathrm{}}^{208}$Pb\ensuremath{\rightarrow}${\mathrm{}}^{224}$Th reaction; in agreement with statistical model calculations, the cross section for the evaporation residues was found to be negligible compared to the fission, and hence can be ignored in all the systems. The shapes of the fission fragment angular distributions are then a direct measure of the entrance channel spins which lead to fusion. The experimental sub-barrier fusion cross sections are underpredicted by the one-dimensional barrier penetration model in all cases. However, if the zero point motion of the targets is included in the barrier penetration model, the energy dependence of both the total fusion and the fission angular distributions can be explained for the $^{15}$N${+\mathrm{}}^{209}$Bi system alone. To fit the low-energy fusion of the oxygen reactions requires considerably more zero point motion---this being inconsistent with the fact that this effect should be the same in all the reactions. Also, the cross sections measured for the transfer channels were found to exhibit the same trend as the fusion at the lower energies. This correlation suggests that some of the sub-barrier fusion in the oxygen-induced reactions may be due to transfer-related processes.

ChemInform Abstract: THE OXYGEN‐INDUCED REACTIONS OF ORGANOBORANES WITH 3,4‐EPOXY‐1‐BUTYNES, A NEW ROUTE TO FUNCTIONALIZED ALLENES

Chemischer InformationsdienstVolume 4, Issue 36 Preparative Organic Chemistry ChemInform Abstract: THE OXYGEN-INDUCED REACTIONS OF ORGANOBORANES WITH 3,4-EPOXY-1-BUTYNES, A NEW ROUTE TO FUNCTIONALIZED ALLENES A. SUZUKI, A. SUZUKISearch for more papers by this authorN. MIYAURA, N. MIYAURASearch for more papers by this authorM. ITOH, M. ITOHSearch for more papers by this authorH. C. BROWN, H. C. BROWNSearch for more papers by this authorP. JACOB, P. JACOBSearch for more papers by this author A. SUZUKI, A. SUZUKISearch for more papers by this authorN. MIYAURA, N. MIYAURASearch for more papers by this authorM. ITOH, M. ITOHSearch for more papers by this authorH. C. BROWN, H. C. BROWNSearch for more papers by this authorP. JACOB, P. JACOBSearch for more papers by this author First published: September 4, 1973 https://doi.org/10.1002/chin.197336199Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume4, Issue36September 4, 1973 RelatedInformation

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