<p> Fission-product bromine was isolated from a uranium target by the hot-atom reaction of the fission recoils with methane to form organic bromides. The organically-bound bromine was shown to be formed preferentially by primary (independently-formed) bromine with little contribution from secondary bromine. </p> <p> The delayed-neutron activity of the short-lived bromine isotopes was analyzed to obtain the relative yields of delayed neutrons from Br8?, Br88 and Br89 produced as primary fission products. The relative delayed-neutron yields are summarized below. (see abstract in text) </p> / Thesis / Doctor of Philosophy (PhD)

As the foremost production of electricity in the United State comes from coal-fired plants, there is much more to learn on the topic of mercury which is a common component in coal. The speciation of mercury in the flue gas determines the best control technology for a given system. Because of the difficulty in measuring mercury at different stages of the process, it is practical to use mercury reaction kinetics to theoretically determine mercury speciation based upon coal composition, plant equipment and operating conditions. Elemental mercury cannot be captured in wet scrubbers; however, its oxidized forms can. Chlorine is a reasonable oxidizing agent and is naturally found in bituminous coal, but bromine is an even better oxidizing agent because of its larger size, it has stronger London dispersion force interactions with mercury. Bromine additive technologies have recently been implemented in several companies to enhance mercury oxidation. Because capture technologies are highly dependent upon the form of mercury that is present, investigations into their speciation are extremely important. Though there have been numerous efforts to study mercury compounds as relevant to atmospheric studies, there is little data currently available for mercury compounds found in combustion flue gases. It would be particularly beneficial to obtain kinetic rate constants at various high temperature and pressure conditions typical for a combustion system. Prevalent species of mercury containing bromine in coal combustion flue gases were studied using density functional theory (DFT) and a broad range of ab initio methods. Reaction enthalpies, equilibrium bond distances, and vibrational frequencies were all predicted using DFT as well as coupled cluster (CC) methods. All electronic calculations were carried out using the Gaussian03 or MOLPRO software programs. Kinetic predictions of three first-stage and three second-stage oxidation reactions involving the formation of oxidized mercury via bromine containing compounds are presented. Understanding the speciation of mercury in the flue gases of coal combustion is paramount in developing efficient technologies to ensure its capture.

We derive tropospheric column BrO during the ARCTAS and ARCPAC field campaigns in spring 2008 using retrievals of total column BrO from the satellite UV nadir sensors OMI and GOME-2 using a radiative transfer model and stratospheric column BrO from a photochemical simulation. We conduct a comprehensive comparison of satellite-derived tropospheric BrO column to aircraft in-situ observations of BrO and related species. The aircraft profiles reveal that tropospheric BrO, when present during April 2008, was distributed over a broad range of altitudes rather than being confined to the planetary boundary layer (PBL). Perturbations to the total column resulting from tropospheric BrO are the same magnitude as perturbations due to longitudinal variations in the stratospheric component, so proper accounting of the stratospheric signal is essential for accurate determination of satellite-derived tropospheric BrO. We find reasonably good agreement between satellite-derived tropospheric BrO and columns found using aircraft in-situ BrO profiles, particularly when satellite radiances were obtained over bright surfaces (albedo >0.7), for solar zenith angle <80 degree and clear sky conditions. The rapid activation of BrO due to surface processes (the bromine explosion) is apparent in both the OMI and GOME-2 based tropospheric columns. The wide orbital swath of OMI allows examination of the evolution of tropospheric BrO on about hourly time intervals near the pole. Low surface pressure, strong wind, and high PBL height are associated with an observed BrO activation event, supporting the notion of bromine activation by high winds over snow. We also provide monthly climatological maps of free tropospheric BrO volume mixing ratio (VMR) derived using the so-called cloud slicing technique. In this approach, the derived slope of the total column BrO versus cloud pressure is proportional to free tropospheric BrO VMR. Estimated BrO VMR shows a minimum in the tropics and greater values at higher latitudes in both hemispheres. High tropospheric BrO VMR at high latitudes in spring could be influenced by near-surface bromine activation.

Thesis (Ph.D.)--McMaster University, 2004. / Advisor: G. J. Schrobilgen. Includes bibliographical references (leaves 333-352). Also available online.

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Well-defined ultrathin films of palladium, with coverages ranging from submonolayer, &#920;Pd = 0.5 monolayer (ML), to multilayer, &#920;P d = 8 ML, were electrochemically deposited on Pt(111) using potentiostatic and potentiodynamic methods. In both methods, between the coverage regimes studied, the growth of the Pd films follows the Stranski-Krastanov mechanism. The interfacial electrochemical properties associated with the film-to-bulk transition were characterized by conventional voltammetric techniques in combination with low-energy electron diffraction (LEED) and Auger electron spectroscopy (AES). The voltammetric peaks associated with H-atom adsorption and desorption on terrace sites indicate that the Pd electrodeposit starts to exhibit bulk-like properties at a coverage of 3 ML. Voltammetric cycling, in sulfuric acid solution, between the hydrogen evolution and the double-layer regions, was found to exert minimal influence on the annealing (smoothening) of the electrodeposited Pd films. However, cycling within the same potential region in the presence of bromide anions (at which Br- adsorption/Br desorption takes place) smoothens the initially rough Pd films essentially as well as high-temperature annealing. The influence of chemisorbed bromine on the anodic dissolution of Pd was also studied; this was for comparison with previous work on the anodic dissolution of Pd, in inert electrolyte, catalyzed by chemisorbed iodine. The present studies indicated that a small but measurable amount of bromine was desorbed along with dissolution of the Pd step atoms; bromine at the Pd terrace behaved identically to iodine in that the coverage of iodine is maintained regardless of the amount or origin of the of anodically stripped Pd. Atomically smooth, well-defined ultrathin Pd films were prepared by a constant potential deposition (CPD) method followed by multiple potential cycles, in dilute Brsolution, within the double-layer region and reductive removal of Brads, by simple emersion at a potential just before the hydrogen evolution reaction potential (EHER). A previously adapted method for the same purpose involved the chemisorption of iodine onto ultrathin PdCPD films, from dilute I- solution, followed by reductive desorption of Iads in iodide-free solution at pH 10 and at a potential just before EHER.

Thesis (M. Sc)--York University, 2000. Graduate Programme in Physics and Astronomy. / Typescript. Includes bibliographical references (leaves 128-135). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://wwwlib.umi.com/cr/yorku/fullcit?pMQ59206.

This dissertation investigates the impact of bromine on tropospheric ozone, OH, and mercury in the preindustrial and present-day atmosphere through use of modeling and observations from satellite. We developed bromine simulation capabilities coupled to oxidant-aerosol chemistry in the GEOS-Chem chemical transport model (CTM). Standard gas-phase mechanisms for bromine chemistry were unable to reproduce recent estimates of tropospheric BrO from satellite. Agreement was improved significantly after imposing HBr+HOBr heterogeneous chemistry in the model. Under present-day conditions, we find that bromine decreases ozone by 6.5%, < 1 – 8 ppb, and global mean OH by 4%. Most ozone loss is due to HOBr production and photolysis, with additional contributions from \(NO_x\) and ozone loss through \(BrNO_3\) hydrolysis. Simulations of the pre-industrial atmosphere are important as baselines for ozone air quality and radiative forcing calculations. However, standard models for the pre-industrial overestimate ozone observations taken a century ago at Montsouris and cannot reproduce the observed aseasonality. We find that bromine chemistry significantly improves this agreement. However, bromine chemistry has negligible impact on the ozone radiative forcing, as concentrations of BrO remain similar. Despite the small change in BrO concentrations, lower ozone in the preindustrial leads to a 40% greater Br mixing ratios. We estimate that this change may have increased the lifetime of atmospheric Hg(0) against oxidation to Hg(II) by 70% since the pre-industrial, making atmospheric mercury a more global pollutant. Additionally, we develop a retrieval algorithm for stratospheric profiles of BrO number density from SCIAMACHY limb near-UV observations. Zonal means of our BrO profile retrievals throughout April 2008 show common features expected from stratospheric photochemistry and dynamics. We apply simulated \([BrO]/[Br_y]\) ratios to the BrO profile retrievals and estimate a stratospheric loading of \(23.5 \pm 6 ppt Br_y\). This supports the 23 ppt stratospheric \(Br_y\) assumed in the satellite-derived climatology of tropospheric BrO that we used to evaluate our GEOS-Chem simulation. Our results imply \(7 \pm 6 ppt\) Br from short-lived bromocarbons, at the higher end of the 3 – 8 ppt range suggested by observations. / Engineering and Applied Sciences

Στην παρούσα διατριβή παρουσιάζεται η σύνθεση regio-εκλεκτικών υποκατεστημένων παραγώγων φθαλαζινών, με διαδικασίες οι οποίες χαρακτηρίζονται από απλές σχετικά συνθετικές πορείες ενώ ταυτόχρονα συνοδεύονται και από υψηλές αποδόσεις. Οι φθαλαζίνες και τα παράγωγα αυτών παρουσιάζουν συνθετικό αλλά και ευρύτερο φαρμακολογικό ενδιαφέρον. Επιπρόσθετα η σύνθεση υποκατεστημένων φθαλαζινών αποκτά μια επιπλέον σημασία αφού μέσω κατάλληλων τροποποιήσεων μπορεί τα ανωτέρω μόρια να οδηγήσουν στην παραλαβή μη φυσικών αρωματικών αμινοξέων. Η μεθοδολογία η οποία αναπτύχθηκε ως προς τη σύνθεση των φθαλαζινών περιλαμβάνει: (α) πρωτόκολλο άμεσου/εμμέσου παραγωγοποίησης της ξανθόνης προς την 2-βρωμο-ξανθεν-9-όνη αλλά και την 2,7-διβρωμο-ξανθεν-9-όνη. (β) πυρηνόφιλη διάνοιξη, (γ) οξειδωτικό μετασχηματισμό ακυλο-υδραζονών της ξανθόνης Παράλληλος στόχος της παρούσης εργασίας αποτελεί και η ανάπτυξη ενός αποτελεσματικού πρωτοκόλλου για τη σύνθεση υποκατεστημένων (στη θέση 3) 1,2 βενζοϊσοξαζολίων καθώς και των Ν-οξειδίων αυτών. Η ανάπτυξη 1,2 βενζοϊσοξαζολίων υποκατεστημένα στον C-3 με φαρμακοφόρες ομάδες παρουσιάζει έντονο ερευνητικό ενδιαφέρον κυρίως λόγω των εφαρμογών τους στη φαρμακευτική. Εν κατακλείδι από την παρούσα εργασία αναδεικνύεται η δυνατότητα του μορίου της ξανθόνης να αποτελέσει μια ιδιαιτέρως χρήσιμη συνθόνη η οποία μέσω κατάλληλων τροποποιήσεων δυνατόν να οδηγήσει στην παραλάβη βιοδραστικών μορίων. Κατά αντιστοιχία με τη σύνθεση των φθαλαζινών η σύνθεση των βενζοϊσοξαζολίων και τωβ Ν-οδειδίων αυτών, ξεκινά με την ίδια εφαρμογή του πρωτοκόλλου άμεσου/έμμεσου παραγωγοποιήσεως της ξανθόνης, Ακολουθεί διάνοιξη αυτού και μετατροπή της σχηματιζόμενης καρβοξυλομάδας σε οξίμη. Η διασικασία ολοκληρώνεται με διεργασίες κυκλοαφυδάτωσης. Για την παραλαβή των Ν-οξειδίων αυτών ως αντιδραστήριο χρησιμοποιείται ο φαινυλο-ιωδο-διακετόξυ εστέρας. / There are numerous naturally occurring xanthones. The xanthone core is present in a large family of natural products with a broad spectrum of biological and pharmacological activities. In the present work is evaluated the usefulness of substituted xanthones as synthones towards synthesis of regio substituded phthalazines, 1,2 benzisoxazoles and N-oxides of them. The above molecus are of considerable pharmacological significance and also very useful in synthesis. The synthesis of phthalazines is achieved with simple synthetic roots followed by high yields. The procedure includes: • Protocol of direct/indirect derivatisation of xanthone mainly towards 2-bromo-xanthe-9-on and 2,7-dibromo-xanth-9-on. • Nucleophilic ring opening • Oxidative transformation of acyl-hydrazones of xanthone A parallel aim of this work is the development of an efficient protocol towards synthesis of substituted in potition 3 1,2 benzisoxazoles and the corresponding N-oxides. Following a similar strategy with the one used in the synthesis of phthalazines, xanthone is being derivatized and after the ring’s opening is transformed to the corresponding oxime. Cyclization of oxime is achieved with dehydration procedures. Finally the N-oxides of benzisoxazoles are obtained using PIDA as oxidative agent.