Source: Dissertation Abstracts International, Volume: 38-05, Section: B, page: 2209. / Thesis (Ph.D.)--The Florida State University, 1977.

A micro heavy water concentration unit using the G.S. process was constructed to study possible process improvements. The deuterium isotope exchange was performed successfully in this unit. It was found that the use of monoethanolamine (MEA) in conjunction with the G.S. process had little or no effect on the recovery fraction of heavy water from the feed. However, the experiments indicated that the gas rate could be increased to attain a higher production rate, or equivalently, for the same production rate the size of the towers could be slightly reduced. The improvement was found only marginally attractive particularly because one more stage could be needed to recover the MEA which was introduced in the feed water.

This work describes the construction of an inductively-coupled plasma tandem quadrupole mass spectrometer where a quadrupole ion storage trap acts as a second sector and collision cell to achieve neutralization or collisional dissociation of interfering species before mass analysis. Because most elements exist as singly-charged ions in an inductively-coupled plasma (ICP) plume, the ICP can be used as an ionization source for mass analysis (ICP/MS). By reducing the sample to elemental ions before mass analysis, ICP/MS spectra tend to be simple compared with those obtained by ICP-optical emission spectrometry (ICP-OES) where elements may have hundreds to thousands of emission lines and spectral overlaps can be severe. This is especially troublesome in the analysis of rare earth elements which have the largest numbers of active emission lines when excited in an ICP. In addition, detection limits by ICP/MS are often up to 3 orders of magnitude lower than by ICP-OES. ICP/MS analysis is not immune from isobaric and isotopic interferences or matrix effects. For most analyses, an acid digestion precedes aspiration as an aqueous solution into an argon plasma gas. This can lead to large amounts of Ar+ etc., which may interfere to varying degrees with analytes of interest. Oxides, argides and hydrides of matrix ions or other analytes may also form and interfere. These same processes can also split peak areas between the atomic form of an analyte and the molecular. In isotope ratio studies where precise measurements on more than one isotope per analyte are needed, these effects may be compounded. Isobaric interferences normally require high resolution mass analysis to resolve if they cannot be separated prior to sample introduction. However, the interface between a high vacuum, high resolution sector or ion cyclotron resonance mass spectrometer and an atmospheric pressure plasma is non-trivial and such instruments are expensive. The focus of this work is new approach which uses a collision cell where weakly-bound molecular species can be dissociated and ions with relatively high electron affinities, such as Ar+, can be neutralized through charge exchange reactions.

The long wave aerobic photochemistry of two frequently used lignin model compounds ie. I (3,4-dimethoxy-alpha-(4-methyl-2-methoxyphenoxy)-beta-hydroxypropriophenone) and II (4-hydroxy-3-methoxyphenol)-2-(2-methoxyphenoxy)propan-1,3-diol) were studied in the presence of three UV absorbers 2,4-dihydroxybenzophenone (DHB), an aminated DHB (MDHB), a benzotriazole derivative (Tinuvin P) and an antioxidant; the additives being incorporated into thin films of I and II were applied on filter paper. Several products were identified and quantified using a combination of GC-MS and GC-FID techniques. The photodegradation mechanisms of I and II were found to be consistent with the phenacyl and ketyl pathways from which products were generated via oxidation, heterocoupling, H-abstraction and homocoupling reactions. In the presence of the inhibitors, some of these reaction pathways were minimized and others eliminated. In decreasing order, the Tinuvin P/Tempo pair were the most effective in protecting the models against photodegradation followed by MDHB and DHB. A synergistic photostabilization effect was also observed between Tinuvin P and the antioxidant, but was not retained during irradiation, probably due to the low regeneration rate of Tempo on the matrix. / The photostabilization effectiveness of MDHB can be related to the cooperative action of its UV absorbing, hydrogen donating and oxygen scavenging functionalities. However, the separation of product 12 from MDHB was not possible by GC and the photo-chemical fate of MDHB remains undetermined. No synergism was found between MDHB and Tempo. DHB displayed good UV absorbing characteristics but no other photostabilization properties were found to cooperate with it.

Radiolabeled compounds, cis-diammine-(1,1-cyclobutanedicarboxylato)-$\sp{\rm 193m}$Pt(II) (carboplatin) and dipyrrolidinedithiocarbamato-$\sp{212}$Pb(II) (Pb(PDC)$\sb2$) were synthesized in microscale quantities. High performance liquid chromatography (HPLC) techniques were employed as both a synthetic tool and mode of product analysis. The specific activities of the purified radiochemicals were in the gigabecquerel per mg range. This was adequate for radiobiological experiments and is several orders of magnitude higher than that required for tracer studies. The radionuclide $\sp{\rm 193m}$Pt with 4.3 day half-life emits numerous low energy Auger electrons by virtue of its 3-step isomeric decay essentially by internal conversion. The yields and energies of the electrons were calculated using Monte Carlo methods. This radionuclide was produced by the $\sp{192}$Pt(n,$\gamma)\sp{\rm 193m}$Pt reaction. Other avenues of production, $\sp{192}$Os($\alpha$,3n)$\sp{\rm 193m}$Pt, were also considered. The $\beta$ emitting $\sp{212}$Pb, which decays to $\alpha$ particle emitting daughters, was isolated from a $\sp{226}$Ra generator. The clonogenic survival of Chinese hamster V79 cells was investigated using both radiolabeled and nonradiolabeled forms of the compounds. The effects of the two types of ionizing radiation (Auger electrons and $\alpha$ particles), kinetics of cellular uptake and retention, and subcellular distribution of these compounds were studied. The dosimetry calculations were performed using the radiation spectra, biokinetics, and Medical Internal Radiation Dose (MIRD) formalism. The mean lethal values of dose (D$\sb{37}$) for the radiolabeled carboplatin and $\sp{212}$Pb(PDC)$\sb2$ were 0.453 grays and 0.85 grays, respectively. The values of relative biological effectiveness (RBE) were estimated to be about 8.8 for radiolabeled carboplatin and 4.6 (2.4 with recoil of the daughter nuclei included) for radiolabeled $\sp{212}$Pb(PDC)$\sb2.$ The results confirm the inadequacy of the current methods of dose calculation (MIRD) and International Commission on Radiation Units and Measurements (ICRU) and point to the potential usefulness of $\sp{\rm 193m}$Pt-carboplatin in chemo-Auger combination therapy of cancer.

No description available.

Solid graphitic carbonaceous matter (CM) is closely associated with the Oklo uranium ore deposits and several of the natural fission reactors in Gabon, West Africa. This material facilitated the containment of uranium and numerous fissiogenic isotopes in these natural reactors for a period of nearly 2 Ga. Hence it is the subject of detailed studies because it may be useful as an analogue for carbonaceous materials, e.g. technical bitumens, that are currently being considered for the encapsulation and storage of anthropogenic radioactive waste. Chemical and structural analyses of the uraniferous CM associated with the natural fission reactors indicate that it is a polymer-like solid composed mainly of polycyclic aromatic hydrocarbons (PAHs) that are randomly oriented (turbostratic) and vary in size from several to several tens of A. Short-chained aliphatic hydrocarbons and oxygen-bearing moieties are attached to the PAH sheets and frequently bridge adjacent sheets. The Oklo uraniferous CM exhibits very high free radical concentrations, which can exceed 1021 free radicals/g organic carbon. The organic free radicals are stable PAH moieties located at or very near the surfaces of these organic solids, mainly on the internal surfaces of pores. Despite their presence, these pores could not have served as effective conduits for the transport of radionuclides by aqueous solutions through and out of the CM matrix. This is because of the very small average size of the pores, together with the CM's non-wettability by aqueous solutions. The Oklo CM has endured oxidation-reduction reactions during uranium mineralization, exposure to ionizing radiation, and alteration associated with the radiolysis products of water during and after natural reactor operation, perhaps up until the present time. Still, the CM acted as an effective barrier to radionuclide migration out of the CM-rich natural fission reactors. Properties, including its aromatic composition, resistance to alteration by ionizing radiation, and its non-wettability to aqueous solutions, make the Oklo uraniferous CM an effective barrier to radionuclide migration. These properties should be incorporated into man-made carbonaceous materials currently being considered for use in the storage of radioactive waste.

This study focuses on understanding the photochemical reactions that occur between ultraviolet stabilizers and lignin during irradiation in order to further comprehend the photo-protection mechanisms of these stabilizers during brightness reversion. The stabilizers chosen for study included a variety of ultraviolet absorbers (UVAs), in addition to a hindered nitroxide free radical (4-hydroxy-TEMPO). Irradiated samples were analyzed using quantitative 31P NMR, in addition to a technique known as 'Derivatization Followed by Reductive Cleavage'. / Benzophenone-based UVAs have been shown to be actively involved in photochemical reactions with lignin during irradiation, while benzotriazole-based UVAs are comparatively photostable under identical irradiation techniques. All additive combinations were found to inhibit the formation of carboxylic acids and photochemical condensation reactions in lignin; however, the joint application of 2,4-DHB and 4-hydroxy-TEMPO demonstrated synergistic inhibition of these reactions. / All additive combinations were shown to impede the formation of catechol structures and to retard the cleavage of lignin beta-arylether groups during irradiation. The combined use of Tinuvin 1130 and 4-hydroxy-TEMPO provided the most efficient inhibition of these reactions. These results provide insight into the excellent photoyellowing inhibition provided by this additive combination when applied onto mechanical pulps.

No description available.

The nuclear hyperfine population distributions of the deuterium atom produced in the 266 nm photolysis of DI were measured with a technique that applies spatial filtering of the nascent recoiling photoproducts to yield a reduced Doppler profile. A novel method of resonance detection for Cl atom photoproducts is also presented along with time-of-flight measurements of chlorine atoms as photoproducts from the dissociation of Cl2, thiophosgene, and phosgene. The resonance detection method permits high-resolution frequency scanning of the hyperfine structure of the chlorine atom. The results of these measurements are also presented / acase@tulane.edu