Global ETD Search

41	Investigation of unique marine environments for microbial natural products Thornburg, Christopher C. 25 March 2013 (has links) Metagenomics has revealed that the marine microbial biosphere is immensely more diverse than originally considered, and is an almost untapped reservoir for the potential discovery of microbial natural products. Despite numerous advances in culturing, biosynthetic engineering and genomic-based screening efforts to uncover much of this diversity in relatively accessible environments, a high rediscovery rate has resulted in the investigation of unique, relatively unexplored ecosystems harboring phylogenetically diverse communities of marine organisms. The focus of this research was to establish a culture repository of microorganisms collected from the Red Sea and from deep-sea hydrothermal vents, and to assess their biosynthetic potential for the production of new chemical scaffolds. Cultivation of marine cyanobacteria from the Red Sea has led to the identification of five new cyclic depsipeptides, apratoxin H, grassypeptolides D and E, Ibu-epidemethoxylyngbyastin 3 and leptochelin, the latter possessing a unique chemical scaffold capable of binding metals. A collection of deep-sea hydrothermal vent sediment and microbial mat samples led to the isolation of 64 unique bacterial strains, with eight assigned as members of the order Actinomycetales. Importantly, these isolates, along with a collection of deep-vent invertebrates and microbes, have led to the development of methods for the collection, culturing and biological screening of organisms from this extreme environment for future natural products research. / Graduation date: 2013 Cyanobacteria Actinobacteria Red Sea Deep-Sea Hydrothermal Vents Anticancer Antimicrobial Marine natural products Hydrothermal vents -- Microbiology Marine microbiology -- Axial Seamount Cyanobacteria -- Red Sea Extreme environments -- Microbiology Antineoplastic agents Drug development
42	Anoxygenic photosynthetic communities and heavy element transformations in extreme environments: hydrothermal and hypersaline ecosystems Csotonyi, Julius Thomas 20 January 2011 (has links) The current research project investigated the anoxygenic phototrophic and metal(loid) transforming bacteria of hypersaline and deep ocean hydrothermal environments. The East German Creek brine springs, an unusual flowing hypersaline system, was enumerated using classical techniques. Subterranean sulfide supported purple sulfur and nonsulfur bacteria, but at the highly oxygenated surface, aerobic anoxygenic phototrophs (AAP) were numerically dominant (up to 16-36% of cultivable bacteria). Strains (EG8, EG13, EG17, EG19) with unusual phylogenetic affiliation and novel photosynthetic and metal(loid) reducing traits were described taxonomically. Chromocurvus halotolerans gen. nov., sp. nov. was proposed as a second example of a gammaproteobacterial AAP. It exhibited bent rod-shaped cells, unusual among AAP. Facultatively anaerobic Charonomicrobium ambiphototrophicum gen. nov., sp. nov. was capable of both aerobic and anaerobic anoxygenic photosynthesis, and incapable of photoautotrophy, distinguishing it from both AAP and purple nonsulfur bacteria. Roseovarius vanadiphilum sp. nov. surprisingly produced 4.5 times more biomass and 2 times more bacteriochlorophyll (BChl) at extremely high NaVO3 concentration (7.5 g/l) than in metal-free medium. A second novel metabolic mode, anaerobic respiration on the toxic metalloid tellurate, was described for a relative of non-phototrophic Shewanella frigidimarina (ER-Te-48), from deep ocean hydrothermal vent Paralvinella worms at Explorer Ridge in the Pacific Ocean. Other strains respired on SeO32- (ER-Se-17L), VO3- (ER-V-6), and VO43- (AV-V-25). These organisms provided the first examples of anaerobic respiration on Te, Se and V at hydrothermal vents. High level resistance of AAP to metal(loid)s prompted investigation of the influence of TeO32- on photosynthetic pigment production in species including Erythromicrobium ramosum (from a terrestrial hydrothermal system) and Erythrobacter litoralis (from a hypersaline supralittoral system). Tellurite enhanced photosynthetic pigment production up to 3.4 times, consistent with an antioxidant carotenoid-based defense mechanism. However, in E. litoralis BChl precursors such as Mg protoporphyrin or its monomethyl ester also accumulated, indicating biosynthetic pathway interruption. In hydrothermal and hypersaline ecosystems, largely devoid of eukaryotic phototrophs but often enriched in metal(loid)s, AAP and metal(loid) reducers are key modulators of nutrient and toxin availability. The presented results on their ecology, physiology and biochemistry have important implications for theoretical understanding of extreme environments and hold potential for biotechnological applications. extreme environments aerobic anoxygenic phototrophs microbial photosynthesis bacteriochlorophyll carotenoids microbial ecology hypersaline springs hydrothermal vents tellurium microbial metal reduction bioremediation microbial mats purple nonsulfur bacteria selenite metavanadate Roseovarius tellurite metalloids
43	Anoxygenic photosynthetic communities and heavy element transformations in extreme environments: hydrothermal and hypersaline ecosystems Csotonyi, Julius Thomas 20 January 2011 (has links) The current research project investigated the anoxygenic phototrophic and metal(loid) transforming bacteria of hypersaline and deep ocean hydrothermal environments. The East German Creek brine springs, an unusual flowing hypersaline system, was enumerated using classical techniques. Subterranean sulfide supported purple sulfur and nonsulfur bacteria, but at the highly oxygenated surface, aerobic anoxygenic phototrophs (AAP) were numerically dominant (up to 16-36% of cultivable bacteria). Strains (EG8, EG13, EG17, EG19) with unusual phylogenetic affiliation and novel photosynthetic and metal(loid) reducing traits were described taxonomically. Chromocurvus halotolerans gen. nov., sp. nov. was proposed as a second example of a gammaproteobacterial AAP. It exhibited bent rod-shaped cells, unusual among AAP. Facultatively anaerobic Charonomicrobium ambiphototrophicum gen. nov., sp. nov. was capable of both aerobic and anaerobic anoxygenic photosynthesis, and incapable of photoautotrophy, distinguishing it from both AAP and purple nonsulfur bacteria. Roseovarius vanadiphilum sp. nov. surprisingly produced 4.5 times more biomass and 2 times more bacteriochlorophyll (BChl) at extremely high NaVO3 concentration (7.5 g/l) than in metal-free medium. A second novel metabolic mode, anaerobic respiration on the toxic metalloid tellurate, was described for a relative of non-phototrophic Shewanella frigidimarina (ER-Te-48), from deep ocean hydrothermal vent Paralvinella worms at Explorer Ridge in the Pacific Ocean. Other strains respired on SeO32- (ER-Se-17L), VO3- (ER-V-6), and VO43- (AV-V-25). These organisms provided the first examples of anaerobic respiration on Te, Se and V at hydrothermal vents. High level resistance of AAP to metal(loid)s prompted investigation of the influence of TeO32- on photosynthetic pigment production in species including Erythromicrobium ramosum (from a terrestrial hydrothermal system) and Erythrobacter litoralis (from a hypersaline supralittoral system). Tellurite enhanced photosynthetic pigment production up to 3.4 times, consistent with an antioxidant carotenoid-based defense mechanism. However, in E. litoralis BChl precursors such as Mg protoporphyrin or its monomethyl ester also accumulated, indicating biosynthetic pathway interruption. In hydrothermal and hypersaline ecosystems, largely devoid of eukaryotic phototrophs but often enriched in metal(loid)s, AAP and metal(loid) reducers are key modulators of nutrient and toxin availability. The presented results on their ecology, physiology and biochemistry have important implications for theoretical understanding of extreme environments and hold potential for biotechnological applications. extreme environments aerobic anoxygenic phototrophs microbial photosynthesis bacteriochlorophyll carotenoids microbial ecology hypersaline springs hydrothermal vents tellurium microbial metal reduction bioremediation microbial mats purple nonsulfur bacteria selenite metavanadate Roseovarius tellurite metalloids
44	Hardness assurance testing and radiation hardening by design techniques for silicon-germanium heterojunction bipolar transistors and digital logic circuits Sutton, Akil Khamisi 04 May 2009 (has links) Hydrocarbon exploration, global navigation satellite systems, computed tomography, and aircraft avionics are just a few examples of applications that require system operation at an ambient temperature, pressure, or radiation level outside the range covered by military specifications. The electronics employed in these applications are known as "extreme environment electronics." On account of the increased cost resulting from both process modifications and the use of exotic substrate materials, only a handful of semiconductor foundries have specialized in the production of extreme environment electronics. Protection of these electronic systems in an extreme environment may be attained by encapsulating sensitive circuits in a controlled environment, which provides isolation from the hostile ambient, often at a significant cost and performance penalty. In a significant departure from this traditional approach, system designers have begun to use commercial off-the-shelf technology platforms with built in mitigation techniques for extreme environment applications. Such an approach simultaneously leverages the state of the art in technology performance with significant savings in project cost. Silicon-germanium is one such commercial technology platform that demonstrates potential for deployment into extreme environment applications as a result of its excellent performance at cryogenic temperatures, remarkable tolerance to radiation-induced degradation, and monolithic integration with silicon-based manufacturing. In this dissertation the radiation response of silicon-germanium technology is investigated, and novel transistor-level layout-based techniques are implemented to improve the radiation tolerance of HBT digital logic. Bit error rate testing Displacement damage Heterojunction bipolar transistor Radiation effects Radiation hardening by design Silicon germanium Single event upset Ionization Heterojunctions Bipolar transistors Logic circuits Radiation hardening Hardness Germanium compounds Silicon compounds Extreme environments
45	Facilitating Information Retrieval in Social Media User Interfaces Costello, Anthony 01 January 2014 (has links) As the amount of computer mediated information (e.g., emails, documents, multi-media) we need to process grows, our need to rapidly sort, organize and store electronic information likewise increases. In order to store information effectively, we must find ways to sort through it and organize it in a manner that facilitates efficient retrieval. The instantaneous and emergent nature of communications across networks like Twitter makes them suitable for discussing events (e.g., natural disasters) that are amorphous and prone to rapid changes. It can be difficult for an individual human to filter through and organize the large amounts of information that can pass through these types of social networks when events are unfolding rapidly. A common feature of social networks is the images (e.g., human faces, inanimate objects) that are often used by those who send messages across these networks. Humans have a particularly strong ability to recognize and differentiate between human Faces. This effect may also extend to recalling information associated with each human Face. This study investigated the difference between human Face images, non-human Face images and alphanumeric labels as retrieval cues under different levels of Task Load. Participants were required to recall key pieces of event information as they emerged from a Twitter-style message feed during a simulated natural disaster. A counter-balanced within-subjects design was used for this experiment. Participants were exposed to low, medium and high Task Load while responding to five different types of recall cues: (1) Nickname, (2) Non-Face, (3) Non-Face & Nickname, (4) Face and (5) Face & Nickname. The task required participants to organize information regarding emergencies (e.g., car accidents) from a Twitter-style message feed. The messages reported various events such as fires occurring around a fictional city. Each message was associated with a different recall cue type, depending on the experimental condition. Following the task, participants were asked to recall the information associated with one of the cues they worked with during the task. Results indicate that under medium and high Task Load, both Non-Face and Face retrieval cues increased recall performance over Nickname alone with Non-Faces resulting in the highest mean recall scores. When comparing medium to high Task Load: Face & Nickname and Non-Face significantly outperformed the Face condition. The performance in Non-Face & Nickname was significantly better than Face & Nickname. No significant difference was found between Non-Faces and Non-Faces & Nickname. Subjective Task Load scores indicate that participants experienced lower mental workload when using Non-Face cues than using Nickname or Face cues. Generally, these results indicate that under medium and high Task Load levels, images outperformed alphanumeric nicknames, Non-Face images outperformed Face images, and combining alphanumeric nicknames with images may have offered a significant performance advantage only when the image is that of a Face. Both theoretical and practical design implications are provided from these findings. Human factors social media human faces information retrieval recall user interface crisis response extreme environments human computer interaction twitter information management human information processing memory encoding human face recognition Engineering Industrial Engineering
46	Systematic Analysis of the Small-Signal and Broadband Noise Performance of Highly Scaled Silicon-Based Field-Effect Transistors Venkataraman, Sunitha 17 May 2007 (has links) The objective of this work is to provide a comprehensive analysis of the small-signal and broadband noise performance of highly scaled silicon-based field-effect transistors (FETs), and develop high-frequency noise models for robust radio frequency (RF) circuit design. An analytical RF noise model is developed and implemented for scaled Si-CMOS devices, using a direct extraction procedure based on the linear two-port noise theory. This research also focuses on investigating the applicability of modern CMOS technologies for extreme environment electronics. A thorough analysis of the DC, small-signal AC, and broadband noise performance of 0.18 um and 130 nm Si-CMOS devices operating at cryogenic temperatures is presented. The room temperature RF noise model is extended to model the high-frequency noise performance of scaled MOSFETs at temperatures down to 77 K and 10 K. Significant performance enhancement at cryogenic temperatures is demonstrated, indicating the suitability of scaled CMOS technologies for low temperature electronics. The hot-carrier reliability of MOSFETs at cryogenic temperatures is investigated and the worst-case gate voltage stress condition is determined. The degradation due to hot-carrier-induced interface-state creation is identified as the dominant degradation mechanism at room temperature down to 77 K. The effect of high-energy proton radiation on the DC, AC, and RF noise performance of 130 nm CMOS devices is studied. The performance degradation is investigated up to an equivalent total dose of 1 Mrad, which represents the worst case condition for many earth-orbiting and planetary missions. The geometric scaling of MOSFETs has been augmented by the introduction of novel FET designs, such as the Si/SiGe MODFETs. A comprehensive characterization and modeling of the small-signal and high-frequency noise performance of highly scaled Si/SiGe n-MODFETs is presented. The effect of gate shot noise is incorporated in the broadband noise model. SiGe MODFETs offer the potential for high-speed and low-voltage operation at high frequencies and hence are attractive devices for future RF and mixed-signal applications. This work advances the state-of-the-art in the understanding and analysis of the RF performance of highly scaled Si-CMOS devices as well as emerging technologies, such as Si/SiGe MODFETs. The key contribution of this dissertation is to provide a robust framework for the systematic characterization, analysis and modeling of the small-signal and RF noise performance of scaled Si-MOSFETs and Si/SiGe MODFETs both for mainstream and extreme-environment applications. RF measurements Extreme environment electronics Proton radiation tolerance Silicon Scaled CMOS Modeling Sub-circuit model Hot-carrier degradation Cryogenic performance SiGe MODFET Short-channel FETs RF noise Field-effect transistors Radio frequency Extreme environments
47	Analysis of microbial diversity in an extreme environment: White Island, New Zealand Ibáñez-Peral, Raquel January 2009 (has links) "June, 2008". / Thesis (PhD)--Macquarie University, Division of Environmental & Life Sciences, Dept. of Chemistry & Biomolecular Sciences, 2009. / Bibliography: p. 227-259. / Literature review -- Materials and methods -- Sampling sites and sampling material -- Enrichment cultures and molecular analyses -- Optical and binding characterisation of the QDs -- Applications of the QDs -- Concluding remarks. / White island, the most active volcano in New Zealand, is a poorly studied environment that represents an ideal site for the investigation of acidophilic thermophiles. The microorganisms present on here are continually exposed to extreme environmental conditions as they are surrounded by steamy sulphurous fumaroles and acidic streams. The sediment temperature ranges from 38°C to 104°C whilst maintaining pH values below 3. A survey of the volcanic hydrothermal system of White Island was undertaken in order to gain insights onto the microbial diversity using culture-dependant techniques and molecular and phylogenetic analyses. A novel liquid medium based on "soil-extract" was designed which supported growth of bacterial and archaeal mixed cultures. Molecular analyses revealed that the dominant culturable bacterial species belong to the Bacteroidetes, Firmicutes and α-Proteobacteria groups. Several previously uncultured archaeal species were also present in the mixed cultures. The knowledge gained from these studies was intended to help in the development of a novel microbial detection technique suitable for community analysis. -- Conventional molecular techniques used to study microbial biodiversity in environmental samples are both time-consuming and expensive. A novel bead-based assay employing Quantum dots (QDs) was considered to have many advantages over standard molecular techniques. These include high detection speeds, sensitivity, specificity, flexibility and the capability for multiplexed analysis. QDs are inorganic semiconductor nanoparticles made up of crystals about the size of proteins. It has been claimed that the physical and chemical properties of the QDs have significant advantages compared to organic dyes, including brighter fluorescence and resistance to photo-bleaching. Their optical properties facilitate the simultaneous imaging of multiple colours due to their flexible excitation and narrow band emission. Functionalised QDs are able to bind to different biological targets such as DNA, allowing high-throughput analysis for rapid detection and quantification of genes and cells. -- The optical and physical characteristics of the QDs as well their interaction with biomolecules are shown to be suitable for the development of a novel bead-based technique able to target the key microbial species and identify them by flow cytometric measurements (FCM). The broad absorption and narrow emission spectra of the QDs, as well as their fluorescence intensity and specify to target biomolecules, was compared to other organic fluorophores. The potential advantages and limitations of QDs as a fluorophores for biological applications are discussed. -- The data acquired during this study provides a broad overview of the microbial diversity and ecology of the volcanically-active hydrothermal systems of White Island and constitutes the baseline for the development of a novel bead-based technique based on QDs. / Mode of access: World Wide Web. / xvii, 259 p. ill. (some col.) Extreme environments -- Microbiology Quantum dots Microbiology -- Technique Microorganisms -- Detection Microbial diversity Nanoparticles White Island volcano thermophiles acidophiles Quantum dots nanoparticles flow cytometry fluorophore
48	Design and characterization of BiCMOS mixed-signal circuits and devices for extreme environment applications Cardoso, Adilson Silva 12 January 2015 (has links) State-of-the-art SiGe BiCMOS technologies leverage the maturity of deep-submicron silicon CMOS processing with bandgap-engineered SiGe HBTs in a single platform that is suitable for a wide variety of high performance and highly-integrated applications (e.g., system-on-chip (SOC), system-in-package (SiP)). Due to their bandgap-engineered base, SiGe HBTs are also naturally suited for cryogenic electronics and have the potential to replace the costly de facto technologies of choice (e.g., Gallium-Arsenide (GaAs) and Indium-Phosphide (InP)) in many cryogenic applications such as radio astronomy. This work investigates the response of mixed-signal circuits (both RF and analog circuits) when operating in extreme environments, in particular, at cryogenic temperatures and in radiation-rich environments. The ultimate goal of this work is to attempt to fill the existing gap in knowledge on the cryogenic and radiation response (both single event transients (SETs) and total ionization dose (TID)) of specific RF and analog circuit blocks (i.e., RF switches and voltage references). The design approach for different RF switch topologies and voltage references circuits are presented. Standalone Field Effect Transistors (FET) and SiGe HBTs test structures were also characterized and the results are provided to aid in the analysis and understanding of the underlying mechanisms that impact the circuits' response. Radiation mitigation strategies to counterbalance the damaging effects are investigated. A comprehensive study on the impact of cryogenic temperatures on the RF linearity of SiGe HBTs fabricated in a new 4th-generation, 90 nm SiGe BiCMOS technology is also presented. SiGe RF switches BiCMOS FET-based SOI PIN diode BiCMOS circuits Radiation hardening by design Transient response Transient radiation effects Extreme environments Mixed-signal circuits Silicon-germanium Single-pole single-throw(SPST) Single-pole four-throw(SP4T) Single-pole double-throw(SPDT) Voltage references Cryogenic temperatures Large-signal linearity Non-linearities Small-signal linearity Large-signal linearity Radiation Single event transient (SET) Total ionizing dose (TID) Radiation Precision voltage reference Bandgap reference (BGR) Bulk FET
49	Identifikation von Genen und Mikroorganismen, die an der dissimilatorischen Fe(III)-Reduktion beteiligt sind / Isolation of Genes and Microorganisms Involved in Dissimilatory Fe(III)-Reduction Özyurt, Baris 21 January 2009 (has links) No description available. 500 Naturwissenschaften allgemein Mathematics and Computer Science Metagenomik dissimilatorische Fe(III)-Reduktion Dissimilatory iron reduction DIR dissimilatory oxido-reduction of iron dissimilatory iron(III) reduction metal reduction ferricironreduction microbial iron respiration bacterial respiration microorganisms for energy production dissimilatory iron reducing bacteria dissimilatory metal reducing bacteria DMRB energy production electricity energy transduction microbial electricity electron donor electron acceptor electron transfer carbon source carbohydrate mannit mannitol biofilm mineral mineral formation microbial degradation ribosomal proteins cytochromes hypothetical proteins enzymes oxidation reduction ferric iron iron oxide Fe(II) Fe(III) soluble iron insoluble iron ferric reductase activity iron mineral formation mineralisation <i>E. coli</i> Escherichia coli environmental microorganisms life in extreme environments uncultivable bacteria soil microbial ecology anaerobic growth anaerobic incubation environmental sequences environmental DNA DNA extraction functional screening metagenomic metagenome meta-genome microbial ecology environmental genomics soil metagenome BACs sequencing bioinformatics microbial communities 16S rRNA phylogenetics 30 42.30 42.30 58.30 42.49 58.30 42.13 RA W

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