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Marine microbes on the map: Defining spatial scales of functional microbial biogeography in the ocean
No full textMarine microorganisms have markedly great functional and phylogenetic diversity and sustain major elemental cycles, including those of carbon and nitrogen. However, a major challenge in microbial observation is that the spatial scales of microbial biodiversity patterns and microbial activity differentially change within their physical oceanographic environment, which requires sampling across multiple scales.
In this thesis, I applied a combination of metabarcoding (16S and 18S rRNA gene sequencing) and stable isotope C and N2 fixation measurements of surface ocean samples (0 - 40m) against the backdrop of chemical (dissolved inorganic nutrients, particulate organic matter) and physical (temperature, salinity, and surface currents) environmental variables in the Atlantic, Indian and the Arctic Ocean. I demonstrate how functional activity can be decoupled from phylogenetic diversity. I show that beta diversity patterns generally reflect ocean provinces and can also be used to refine oceanographic boundaries. In a pan-Arctic study, I show how microbial communities disperse and form regional and within-fjord signals, with different co-occurrence patterns between fjords with and without marine-terminating glaciers. The presented calculations of a productivity-specific length scale can help identify sample patchiness and scale sample diversity in relation to marine ecosystem structure. In order to harmonize research in meta-analyses and across global scales, we provided perspectives on best practices in method documentation. In conclusion, my work helps to better understand pelagic microbial ecosystems, taking into account the patchiness and ecosystem boundaries and their impact on productivity and food web interactions that are typically overlooked in marine microbial ecology. The presented approaches will support mapping microbiomes to relevant oceanographic scales and have potential implications for researching, observing, and monitoring marine ecosystem structures
Synthesis, NMR spectroscopic investigations and absolute quantification of dietary triacylglycerols
No full textFats and oils are important biological compounds. These are composed of fatty acids, phospholipids, cholesterol, sterols and triacylglycerols. Triacylglycerols (TAGs) are energy reservoirs for living organisms. TAGs are important components of lipid bilayer in the cells and cellular vesicles i.e., lipid droplets (LD). The most common fatty acids present in the plasma membrane are palmitic, stearic, linoleic, and linolenic acids. Proteins are attached to lipids in the plasma membrane and diffuse with a specific diffusion coefficient. The diffusion of the molecules across the membrane is described in terms of diffusion coefficients. The protein-lipid interactions play important role in the cell signaling and trafficking. The cell signaling and trafficking property of membrane lipids and proteins are important in the transport of drugs across the membrane. The fluidity of the membrane depends upon viscosity, chain length and degree of unsaturation of the unsaturated fatty acid chains.
Several symmetrical and unsymmetrical TAGs have been synthesized in purity as a synthetic standard for the analytical studies. The synthesis of symmetrical triacylglycerols (TAGs) is done using previously reported Hassner esterification method. Following this method tripalmitin [PPP], tristearin [SSS], triolein [OOO], trilinolein [LLL], trioctanein [OcOcOc] and trilaurein [LaLaLa] have been synthesized in purity. The basic scheme of the reaction is the same as reported. However, the change in the reaction time, temperature and catalyst showed different yield of the product. The detailed scheme of reaction and experimental procedures have been explained. The unsymmetrical TAGs have been synthesized in two-step reaction following a reported method. Firstly, four 1-monoacylglycerols have been synthesized enantiomerically. These include 1-palmitoyl glycerol, 1-stereoyl glycerol, 1-oleoyl glycerol and 1-linoleoyl glycerol. In the second step, asymmetrical TAGs are synthesized
Control of power grids under stochastic fluctuations in production, consumption, and trade
No full textThe threats posed by climate change require fundamental changes in the nature of the operation of power grids. The increase in fluctuating sources of renewable energy requires flexible and fast-acting control, data processing, and market adjustments. In turn, these lead to complex nonlinear interactions and non-trivial collective fluctuations, which require sophisticated methods of analysis. This dissertation reports on work using a variety of methods from statistical physics to extend the applicability of methods that are already commonly used in control engineering, machine learning, and economic analysis. First, we use the Belief Propagation algorithm (BP), an efficient local algorithm for Bayesian inference, optimization and network analysis, which improves upon Curie-Weiss mean-field theory by taking local correlations into account. We apply the algorithm to statistically analyze conditions under which an accurate estimate of power flows can be obtained from noisy and incomplete measurement sets, and show that it can be used for effective dimensional reduction of power grids. We derive a novel implementation of BP for supply networks, which strongly enhances its convergence and accuracy, explicitly demonstrate its applicability to power grid state estimation and natural gas pipeline network analysis, and discuss further applications to supply networks. Secondly, we map traders' abuse of reserve energy to a minority game and study it using agent-based modeling and the cavity method. The cavity method improves upon Curie-Weiss mean-field theory by including backreactions between traders and market prices, and is formally an approximation on the same level as BP. We show that for this application the cavity method has a natural interpretation in terms of self-consistent linear response. We derive policy recommendations by showing the effectiveness of penalties on large contributors to the abuse of reserve energy, and by demonstrating that external noise is [...
The Significance of Cathepsin V and its N-terminally Truncated Form in Thyroid Physiology and Carcinogenesis
No full textAs cell biologists and specialized in proteases, our group has made significant contributions to the understanding of the role of cathepsins, in the maintenance of thyroid function. In this study, we examined the significance of cathepsin V in thyroid physiology and carcinogenesis. Immunofluorescence analysis of non-cancerous and cancerous human thyroid tissue showed the localization of cathepsin V at the apical plasma membrane domain of thyrocytes and within the follicle lumen of normal thyroid tissue, whereas cathepsin V was found within nuclei in cells of follicular and papillary thyroid carcinoma tissue. These results prompted us to explore which molecular form of cathepsin V can be secreted and/or sorted to the nuclear compartment of thyrocytes. To this end, we created two cell lines stably expressing full-length (hCV-eGFP) and N-terminally truncated cathepsin V (h56NCV-eGFP), both tagged with eGFP at their C-termini, which are referred to as Nthyori-CV and Nthyori-NCV, respectively. We found that hCV-eGFP chimeric protein follows the canonical transport pathway of cathepsins from the rough endoplasmic reticulum (ER) lumen through the Golgi apparatus to endo-lysosomes. In addition, our results revealed that Nthyori-CV cells secrete the proform of the hCV-eGFP chimeric protein in a TSH-regulated pattern into the extracellular space. On the other hand, h56NCV-eGFP chimeric protein which lacks the ER lumen-targeting signal peptide and part of the propeptide escaped the secretory pathway, which explains its unusual presence in the cytosol and accumulation in the nuclei of Nthyori-NCV cells. In particular, it was more abundant in the nuclei during S phase, suggesting that nuclear cathepsin V might be involved in the regulation of cell cycle progression of thyrocytes. Thus, we investigated the effect of h56NCV-eGFP expression on the proliferation rate of thyrocytes. We found that Nthyori-NCV cells are more proliferative than both Nthyori-CV and wild-type controls
Synthesis, Structure and Catalysis of Noble Metal-Containing Polyoxo- and Thiometalates
No full textPolyoxometalates (POMs) are discrete, anionic metal-oxo clusters with a rich variety in structure and composition associated with a wide range of physicochemical properties and applications in areas as diverse as catalysis, magnetism, materials science, molecular electronics, biology, and medicine. This thesis is constructed upon the synthesis, characterization and applications of three different classes of compounds that include the palladium(II)- and lead(II)-containing heteropolytungstates, and platinum(II)-containing thiometalate. Majority of the materials are noble metal-based systems, which were proven to be highly efficient catalyst precursors for various types of organic transformations such as the Suzuki-Miyaura cross-coupling reactions of aryl halides, selective hydrogenation of 1-octyne to 1-octene, and hydrogenation of o-xylene to cis- and trans-1,2-dimethylcyclohexane
Network tariffs and access allocation in electricity distribution networks with distributed generation and flexible consumers
No full textThis thesis analyses pricing and market design to allocate network access and recover network cost in electricity distribution networks with distributed generation and flexible consumers. The challenge of coordinating new, flexible, and increasingly active network users is the overarching motivation for the analyses in the four different papers. First, an introduction gives an overview of the background, main contents and conclusions. This is followed by the four academic papers, each picking up a separate, topical aspect of coordinating new network users in distribution grids.
The first paper contributes to the ongoing debate on integrating self-supply into the tariff structure of distribution grids and provides options to prevent a potentially inefficient, self-reinforcing dynamic. By analysing the evolution of self-supply shares in distribution grids depending on network charges, several options are revealed that adjust common charging parameters in order to maintain or restore financial stability. Paper 2 analyses the theoretical efficiency limits of the two-part tariff which is common in practice and trades-off economic efficiency with other requirements for the design of network charges. A formal comparison to the efficient benchmark of peak-load pricing reveals specific circumstances under which a two-part tariff simply cannot deliver fully efficient incentives. Paper 3 applies this to the practical challenge of steering investments into new technology for network users efficiently with network tariffs, thus broadening the perspective of the thesis from just self-supply and mere financial stability to efficient integration of active network users. The analysis shows how common uniform pricing distorts not only operation of existing assets, but also investments into new ones and thereby may lead to developing the distribution system inefficiently. The last paper focuses on access rights allocated by market mechanisms as an alternative or complement to regulated, listed access prices. Thus, it presents an account of different dimensions of access and the design of products and market rules for market-based allocation of access to electricity distribution grids. The paper finds that while differentiated access rights can theoretically be allocated efficiently by regulated, listed prices as well as in a market-based setting, pricing requires information on demand which network users ideally reveal in a market setting. A discussion of options for product and market design for access auctions carves out the potential benefits, as well as remaining challenges with market-based allocation
The Influence of the Bauhaus in Australia: Experimentation and Collaboration in the Work of Dahl Collings, Geoffrey Collings, Alistair Morrison, and Richard Haughton James
No full textIn tracing the complex circulation of Bauhaus principles and approaches to design in Australia throughout the 1940s and 1950s, this dissertation establishes the various exchanges between the Australian artists Dahl and Geoffrey Collings and Alistair Morrison, the British artist Richard Haughton James, and Walter Gropius, László Moholy-Nagy, and György Kepes in London during the period from 1935 to 1937.
Through various case studies, visual analysis, and by drawing on the critique of unidirectional notions of agency and influence, I demonstrate how certain practices of collaboration and experimentation used at the Bauhaus were applied and advocated by the Collingses, Morrison, and James in Australia throughout their wide-ranging artistic practices, which included photography, film, design, and painting. Furthermore, I demonstrate how this group of designers promoted the Bauhaus and its associated collaborative and experimental principles in their lectures, writings, and exhibitions and through their involvement in professional art and design organizations. I argue that this group of designers all subsequently played crucial roles in introducing Australia to the Bauhaus and improving art and design standards in Sydney and Melbourne during the post-war period, enriching Australia’s art and culture for decades.
The Impact of Environmental Changes on the Microbial Community Dynamics and Abundance of Pathogenic Vibrio species in Coastal Ecosystems
No full textCoastal ecosystems are highly dynamic regions and extremely important to the livelihoods and health of the people living in coastal regions. Tourism, the aquaculture industry, and human health are all directly tied to the microbial community in these regions. Furthermore, many key aquaculture stocks, such as oysters, may serve as vectors for a variety of foodborne diseases in humans, both at the harvesting area and when imported far inland. Rising sea surface temperatures in the North Atlantic and North Sea have been heavily implicated in the spread and rising abundance of the human pathogenic Vibrio species: Vibrio cholerae, Vibrio parahaemolyticus, and Vibrio vulnificus in North America and Northern Europe. This study investigates how environmental changes may impact the growth and behavior of these key Vibrio species within the context of the surrounding microbial community.
The genetic accessibility of V. cholerae, V. parahaemolyticus, and V. vulnificus environmental strains was initially assessed, and this work resulted in the development of new genetic tools and a rapid fluorescent protein-labelling protocol which worked universally in all tested strains. In a small-scale microcosm investigation, red fluorescent protein-labelled Vibrio clones were co-incubated with a native microbial community under three discrete temperatures. These microcosm experiments indicated that increased temperatures alone do not confer greater competitive fitness to these Vibrio species. Finally, through environmental field sampling for pathogenic Vibrio, two discrete pathogenic Vibrio populations in the North Sea and the North Atlantic, where identified and further characterized, allowing for future speculation on the role these species may play in their respective regions
Chemoselective Organocatalyzed Aldol Reactions
No full textChemoselectivity is the selectivity observed when a chemical reagent reacts preferentially with a particular functional group in a molecule having two or more different functional groups. The concept is routinely applied during complex syntheses to avoid the use of protecting groups. Thus, broadening chemoselectivity should lead to increased tactical or yield or waste reduction advantages during natural product or drug syntheses. With this in mind, I have investigated the reaction of aldehydes with cyclohexanones containing a 4-substituted linear or branched 1,3-diketone unit (triketones). The question was, could amino acid catalysis chemoselectively provide either the aldol or Knoevenagel condensation product? The key to this question was understanding the different mechanisms of these reactions and then exploiting those differences by tailoring the reaction medium to favor one over the other. A comprehensive experimental section detailing the synthesis of the aldol catalysts, synthesis of the triketone substrates, and formation of Knoevenagel
and aldol products is additionally provided
An Insight into Derivatization of closo-Dodecaborate and Synthesis and Application of Indocyanine Green Dye
No full textThe content of this Ph.D. thesis is divided into two main topics.
The first chapter presents a novel synthesis of dodecahydro-closo-dodecaborate anion [B12H12]2- derivatives. Nowadays, boron-rich dodecahydro-closo-dodecaborate anion [B12H12]2- has gained wide interest and providing great opportunities in designing of various geometric and electronic structures with promising properties useful for modern host-guest chemistry and organoelement chemistry, in addition to its wide application in medicinal chemistry. Herein, we report our efforts on the development of a novel synthesis of cyclic oxonium derivatives of [B12H12]2-and effective approach to mono-halogenation [B12H11X]2- (X= I, Br, Cl) of dodecahydro-closo dodecaborate anion, the procedure yields therefore much purer material than any of the literature procedures, the yields are very high, and work-up is very straight-forward. Additionally, an attractive methodology for construction of B-N bond has been established. In general, derivatization of the dodecahydro-closo-dodecaborate dianion [B12H12]2- suffers from the lack of efficient methodology for introducing N-containing organic moieties to boron cage, thus, we have developed an approach based on the palladium-catalyzed cross-coupling amination of [B12H11I]2- . The new methodology provides broad scope of B12-N-containing organic moieties in good to excellent yield.
The second chapter highlights the synthesis and application of heptamethine cyanine green dyes. In details, synthesis of heptamethine indocyanine green dyes by addressing different positions in the chemical structure of the cyanine dye skeleton with the aim to generate green dye with optimal aqueous solubility and fewer tendencies to form aggregation. The staining ability of dye, toxicity, and stability in aqueous solution have been investigated. Two of the new substances stained the model for inner limiting membrane (ILM) in green and showed good stability in aqueous solution