Studies on a series of polymethine cyanine dyes and analogs (1-24) show that certain near-infrared cyanines are capable of damaging DNA in the absence of light and external reducing agents. Experimental results imply that in this DNA thermal cleavage, the cyanine reduces Cu(II) to Cu(I) which reacts with O2 to generate the reactive oxygen species (ROS) O2∙- and ∙OH. The formation of these ROS is also thought to be responsible for the irreversible bleaching of the dyes in aqueous solutions. A correlation between structural features and DNA thermal cleavage activity as well as dye bleaching is suggested. Long polymethine chains appear to confer instability to cyanines in aqueous solutions and further contribute to undesired thermal DNA cleavage. These drawbacks can be overcome by introducing an electron-withdrawing group to the polymethine bridge of the cyanine dye.

Chlorhexidine mouth rinses remove dental plaque from teeth, preventing dental caries, dental decay, and more serious systemic infections. Tooth discoloration due to extrinsic staining is the most prominent side effect of regular chlorhexidine use. Decreasing the concentration of chlorhexidine reduces staining area and severity. Staining can also be prevented and treated by tooth bleaching, a common cosmetic dental procedure that diminishes extrinsic staining by oxidizing chromagens adsorbed onto the tooth surface. In the proposed trial, common bleaching agents will be investigated for their efficacies in preventing chlorhexidine staining. Results of the trial could further the development of a chlorhexidine mouth rinse that is suitable for long term use.

The stability of hydrogen peroxide (H2O2) is a critical factor for the brightening of mechanical pulps. Inorganic ions, including Fe, Mn and Cu catalytically decompose H2O2. These troublesome metals promote the rapid transformation of H2O2 to nonselective hydroxyl radicals that degrade the cellulose fibres and decrease yields. / The interaction of aqueous metal•complexes with magnesium metal (Mg°) or bimetallic mixtures of magnesium with either palladium (Pd°/Mg°) or silver (Ag°/Mg°) were optimized to remove metals (Mn, Cu and Fe) from solution with concomitant release of the complexing reagent. The analyte metals were removed by both cementation on the surfaces of the excess Mg° and by precipitation as hydroxides. Overall, the reactions were rapid (3 or 10 min) and very efficient. The accelerators (Ag or Pd) were deposited on the surfaces of the Mg°. In a separate study, the excess of Mg° could be reused to mediate more metals removal without apparent loss of reactivity. Among the other iminodiacetate analogs (CDTA, MEDTA, EGTA, HEDTA, DPTA and MTBE), the EGTA and HEDTA proved to be possible substitutes for both efficient metal removal of Mn, Cu and Fe from solution and efficient release of chelating reagent. The measurement of particle size, performed by laser granulometry, demonstrated that smaller particles of precipitate were generated from metal-EDTA complexes by reaction with NaOH than by reaction with Pd°/Mg° bimetallic mixture. If the suspensions of particles were analyzed in the absence of ultrasound, the particles became aggregated into large flocs (up to 150 mum3 ). The reactivity of the bimetallic mixtures was exploited to remove Cu, Mn, Fe, Zn and Al that had been initially chelated with EDTA or DTPA from a thermomechanical pulp (TMP). After 15 min, the metals had been removed efficiently with the bimetallic mixtures. The EDTA released from the TMP filtrate could be recycled efficiently for a total of three cycles. On the other hand, the DTPA was not released as efficiently. Measurements of turbidity and chemical oxygen demand (COD) indicated no appreciable difference between the pulp samples with either chelating reagent. Residual H2O2 and ISO brightness measurements indicated no apparent differences among pulps that had been treated wi

Many low molecular weight chlorinated organic compounds produced by the pulp and paper industry during kraft bleaching of the wood pulp are toxic. Mass balance studies suggest that mineralization of chlorinated organics is occurring in pulp and paper mill wastewater treatment systems. To understand the nature of dechlorination activity, molecular tools such as oligonucleotide primers and corresponding DNA probes were developed to monitor the presence of microorganisms possessing key genes (dehalogenases) responsible for the degradation of chloroaliphatic organics in kraft pulp mill effluent treatment systems. Oligonucleotide primers designed from the coding sequence of known dehalogenases and a methane monooxygenase gene, which is known to catalyze dehalogenation reactions, were used for polymerase chain reaction (PCR) analysis, using genomic DNA extracted from dehalogenating bacterial isolates and total community DNA extracted from water and sediments of lagoon treatment systems. PCR amplification with dhlB oligonucleotide primers, designed from the haloacid dehalogenase of Xanthobacter autotrophicus, revealed the presence of dehalogenase genes in both aerated lagoons and stabilization basins. Similar results were obtained with mmoX primers designed from the methane monooxygenase gene of Methylococcus capsulatus. DNA sequence analysis of several PCR fragments showed significant similarity to known dehalogenase genes. The molecular tools developed in this study revealed the presence of different types of microorganisms with dechlorination potential in the microbial community of pulp mill effluents.

<p>Aim and Objectives: To assess the effect of bleaching on the marginal integrity of Class V composite resin restorations. To determine the effect of a 6% hydrogen peroxide over the counter and a 38% hydrogen peroxide in-office vital bleaching treatment products on the microleakage of Class V composite restorations.</p>

Coral reefs are among the most diverse and productive ecosystems on earth, and are critical to the survival of tropical marine ecosystems and sustenance of local human populations. However, coral reefs are quite vulnerable to disturbances, both natural and anthropogenic. This thesis looks at how coral reef communities have responded to climactic disturbances, particularly the 1997-98 El Niño Southern Oscillation (ENSO) and subsequent coral bleaching and mortality that affected much of the Indian Ocean, including the coastal waters of Tanzania, where the study was conducted. In particular, it investigates the effects of coral bleaching, habitat degradation and reef spatial arrangement on reef fish assemblages. Habitat structural complexity and spatial arrangement of reefs had an effect on reef fish communities. Fish communities showed patterns in distribution among habitats and between patch and continuous reefs. Fishes preferred live to bleached/dead or eroded coral, but trophic groups reacted differently to patch and continuous reefs. There were slight changes in fish abundance and significant changes in fish diversity on experimental, bleached branching Acropora coral plots over a period of one year. While fish abundance on one site increased shortly after a bleaching event, 6 years later fish abundance had decreased significantly. Conversely, coral reef communities in northern Tanzania had changed little over an 8-year period, with minor changes associated with the 1997-98 ENSO and the presence or absence of fisheries management. The coral reefs in the region were found to show high variability in community structure and responses of associated fish and invertebrate communities. The findings of this thesis indicate the importance of habitat structure and spatial arrangement of reefs, the detrimental effects of coral bleaching, and the possibility that some reefs and some (generalist) reef fish taxa may exhibit resilience to climate change. / At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.

There is little published information on the distribution, abundance, seasonality and ecological roles of benthic algae on the Great Barrier Reef, although they are of fundamental importance in the ecology of coral reef communities. This study sought to provide information on algal community dynamics in two contrasting reef-flat zones: the live coral and algal turf-dominated outer flat, and the fleshy macroalgaldominated inner flat, at Heron Reef, Great Barrier Reef, Queensland, Australia.Algal community structure on dead coral limestone was studied on the inner and outer reef flat over a three-year period (from May 1986 to February 1989), and algal transplant and grazer exclusion experiments were carried out to determine the role of grazers in producing and maintaining community structure.Changes during ecological succession provide useful information about structuring processes in natural communities. Algal succession was studied using artificial substratum (concrete), because it provided a flat surface which offered logistical advantages over naturally contoured coral substratum, and because previous studies had found that artificial substrata adequately mimicked natural surfaces in marine successional studies. Succession on natural substratum was also studied for comparison, using coral clumps which had died after a bleaching episode in February 1987. The effects of season on algal succession, were investigated using four series of concrete settlement blocks, started in February, May, August and November 1986. The effect of habitat complexity on succession was examined by comparing succession on an exposed concrete surface with succession on a protected concrete surface provided with crevices. Each successional study lasted two years. Cover data for all algal species present on each sample were obtained using a sampling grid of sixty points, and these data were analysed using the non-parametric multivariate analysis program, PRIMER.A total of 105 algal taxa were identified in this study, with 101 of these recorded in the natural reef flat algal community over the three-year period. Fleshy macroalgae were the dominant group on the inner flat (56% cover), and filamentous turf algae iv were dominant on the outer flat (47% cover). The importance of water temperature and grazing intensity in producing the differences in distribution of these two groups of algae on the reef-flat were considered. Temperature was rejected as a factor, because there was virtually no temperature difference between the two sites over a two-year period. Grazing was found to be an important factor, based on a much higher rate of damage to algal transplants on the outer flat than on the inner flat; and on the development of higher algal biomass on caged than on uncaged concrete settlement blocks.Between 58 and 69 algal taxa were recorded in each of the four successional studies on exposed concrete, 78 taxa were recorded on protected concrete, and 85 taxa were recorded on bleached coral. Algal successional trajectories were similar on concrete and on bleached coral, but the rate varied substantially. Succession was fastest on bleached coral, slowest on exposed concrete, and intermediate on protected concrete. On all substrata, at both sites, early dominance by green and brown filamentous algae decreased over time, while the abundance of other forms increased. Dominance in terms of cover by early successional algae (in particular Ectocarpus) was prolonged on concrete in comparison to bleached coral, and this effect was stronger on exposed concrete than on protected concrete.It is hypothesised that inhibition of algal community development on concrete because of a relatively dense growth of early successional algae was due to one or both of two factors: 1. Reduced algal recruitment due to a lower level of substratum heterogeneity; and 2. Reduced grazing by the dominant herbivores in the system, parrotfish (Family Scaridae), because of the hardness of concrete.Succession was faster on the outer flat than on the inner flat. On bleached coral, succession to a community similar to the natural background algal community took between three and nine months on the outer flat, and between one and two years on the inner flat.There was no regular seasonal pattern of change in the reef flat algal community over a three-year period, but during early succession, algal community structure was v strongly influenced by season of initial exposure of the concrete settlement blocks. However, this variability did not persist, and by two years all seasonal series of blocks had similar communities. Six species of algae were fertile within 10 days of establishment, including the common early successional algae Ectocarpus, Enteromorpha and Polysiphonia, illustrating the potential of these species for rapid exploitation of available space.The results of this study provide much needed baseline data on algal community dynamics on the southern Great Barrier Reef, and on succession and community development following a bleaching episode. Given the rapid and dense colonisation of bare substratum by algae, and the very low rate of recruitment by corals, it seems that corals will be at a disadvantage in maintaining their abundance in this reef flat environment if coral bleaching becomes a regular event.

Diss. (sammanfattning). Uppsala : Sveriges lantbruksuniv., 2003. / Härtill 4 uppsatser.

Thesis (M.S.)--West Virginia University, 2005 / Title from document title page. Document formatted into pages; contains viii, 56 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 52-55).

Thesis (M.S.)--University of Michigan, 1991.