Dissertations / Theses: 'Isolating mechanism'

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Bellamy, Stephen, and steve bellamy@flinders edu au. "RESOURCE PARTITIONING BETWEEN TWO SYMPATRIC AUSTRALIAN SKINKS, EGERNIA MULTISCUTATA AND EGERNIA WHITII STEPHEN BELLAMY Thesis submitted in total fulfilment of the requirements of the degree of Doctor of Philosophy AUGUST 2006 SCHOOL OF BIOLOGICAL SCIENCES FLINDERS UNIVERSITY, ADELAIDE, SOUTH AUSTRALIA ________________________________________." Flinders University. Biological Sciences, 2007. http://catalogue.flinders.edu.au./local/adt/public/adt-SFU20070124.145924.

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When species compete for resources, in a stable homogeneous environment, there are two possible outcomes. The first is that one species will out-compete the other and exclude it from the environment. This is known as the competitive exclusion principle. The second is that both species will manage to coexist. Coexistence can only occur if the species niches are differentiated such that interspecific competition is minimised, or eliminated. This outcome is known as resource partitioning. Two closely related Australian skink species of the Egernia genus, Egernia multiscutata and Egernia whitii, are abundant and sympatric on Wedge Island in South Australias Spencer Gulf. The species are morphologically very similar and appear to have very similar life histories and habitat requirements. Ostensibly, they would compete for limiting resources in this environment. This thesis is the first investigation into resource partitioning in this previously unstudied model organism. I report the results of multi-faceted investigations into the coexistence of the skinks, E. multiscutata and E. whitii on Wedge Island and the evidence for, and mechanisms of, any facultative resource partitioning between them. Study methods involved a transect survey of most of Wedge Island to determine the species distributions and any evidence for resource partitioning; a morphological comparison to investigate any potential competitive advantages of either species; a habitat choice experiment to establish retreat-site preferences in the absence of interspecific interference; and, a series of staged dyadic encounter experiments to investigate interspecific competitive interactions. Resource partitioning was evidenced by differential distributions of the species among substrates containing the elements required for permanent refuge shelters. This partitioning was not mediated by avoidance of particular substrates but by the presence of the opponent species, combined with attraction to suitable substrates. Asymmetries in some morphological characters were found to confer a potential competitive advantage to E. multiscutata in agonistic encounters with E. whitii. Both species were found to have the same refuge site preferences when interference competition was experimentally removed. This result was not concordant with observed resource partitioning in the field and suggests that the habitat choices of both species are modified by the presence of the opponent species. Analyses of staged dyadic encounter experiments showed that E. multiscutata was more likely to gain greater access to a contested habitat resource and more likely to exclude E. whitii from the resource than vice-versa. Nevertheless, the outcome of competitive interactions was not completely deterministic and there was some tolerance of co-habitation. E. multiscutatas competitive advantage was attributable largely to its greater mass and head dimensions relative to snout to vent length. However, differential behavioural responses to the threat of larger opponent size also played an important part in resource partitioning between the species.

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Ahmed, Yasir. "Positive assortative fertilization as a result of allopatry between Drosophila americana and D. novamexicana." Diss., University of Iowa, 2008. http://ir.uiowa.edu/etd/42.

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De, Rito James Nicholas. "Assessment of reproductive isolation between Yellowstone cutthroat trout and rainbow trout in the Yellowstone River, Montana." Connect to this title online, 2004. http://etd.lib.montana.edu/etd/view/item.php?id=19.

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Snyder, Robert Lee Cocroft Reginald B. "Diversification in plant feeding insects patterns of host-plant specialization and mating signal evolution inferred from species-level phylogeny and population genetics /." Diss., Columbia, Mo. : University of Missouri-Columbia, 2009. http://hdl.handle.net/10355/6770.

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The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Title from PDF of title page (University of Missouri--Columbia, viewed on March 29, 2010). Thesis advisor: Dr. Reginald B. Cocroft. Vita. Includes bibliographical references.

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Moran, Peter. "A behavioural and genomic approach to studying the evolution of reproductive isolation : a contact zone between closely related field crickets in the genus Teleogryllus." Thesis, University of St Andrews, 2017. http://hdl.handle.net/10023/10260.

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What processes contribute to the evolution of reproductive isolation and the coexistence of interfertile species in the same habitat? This thesis investigates the relative roles of species interactions and intraspecific processes in contributing to reproductive isolation. I combine behavioural and genomic approaches to test hypotheses about what mechanisms maintain the general species boundary between two closely related field cricket species: Teleogryllus oceanicus and T. commodus. These species are a classic study system for sexual communication and readily hybridize in the laboratory, however little is known about species interactions in sympatric populations. I examine patterns of geographic variation in two key sexual traits: calling song and cuticular hydrocarbons (CHCs), and the geographic distribution of genetic variation across a broad sample of allopatric and sympatric populations. I test whether X chromosomes play a pronounced role in population divergence and reproductive isolation. Using close range mating trials and hybridization experiments I identify numerous pre-mating and post-mating barriers between the species. The results indicate that the species are currently reproductively isolated and the pattern of population differentiation does not strongly support contemporary species interactions contributing to phenotypic diversity. Numerous barriers exist between the species, in particular hybrid females are sterile in both cross directions, while hybrid males are relatively fertile. This provides a rare exception to Haldane's rule which is central to many genetic theories of speciation. Established theory predicts that X chromosomes should play a pronounced role in the evolution of both pre- and postzygotic barriers. Contrary to this, I found no evidence that X chromosomes contribute to hybrid female sterility. Moreover, X-linked loci exhibited an unexpected pattern of reduced population differentiation within species, but increased species divergence compared to autosomal loci, which may indicate selective sweeps or sex-biased processes. Taken together, the results suggest that the causes and consequences of X chromosome evolution, in particular among XO taxa, may contradict some of the established theories.

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Sardari, Lodriche Soroush. "Natural antifungals, screening, isolation, synthesis, and mechanism of action." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0006/NQ29103.pdf.

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Köhler, Sonja. "Mechanisms for partial reproductive isolation in a Bombina hybrid zone in Romania." Connect to this title online, 2003. http://edoc.ub.uni-muenchen.de/archive/00001521/.

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Crowley, J. N. "A study of reaction mechanism by matrix isolation / FTIR spectroscopy." Thesis, University of East Anglia, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.378892.

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Roberts, Malcolm. "Studies with tissue cultures of tripterygium wilfordii. Isolation of metabolites and biotransformation studies." Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/30824.

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In a program aimed at the identification of compounds responsible for the immunosuppressive and antifertility activities of the perennial twining vine, Tripterygium wilfordii. 5 new and 13 known compounds were isolated from the TRP-4a tissue culture cell line developed from Tripterygium wilfordii. The structures of the new compounds were determined by a combination of spectral analysis, chemical correlation and single crystal X-ray diffraction analysis. 22β-Hydroxy-3-oxoolean-12-en-29-oic acid (137), 22α-hydroxy-3-oxoolean- 12- en-29-oic acid (138) and 3β, 22β-dihydroxyolean-12-en-29-oic acid (139) are new triterpenes possessing an oleanene-type skeleton and were chemically correlated with 3β, 22α-dihydroxyolean-12-en-29-oic acid (51), the structure of which was confirmed by single crystal X-ray diffraction analysis. Oleanolic acid (127), β-sitosterol (128) and polpunonic acid (55), were isolated previously from the TRP-4a cell line in earlier studies in this laboratory. α-Amyrin (145), β-amyrin (146), 3β, 29-dihydroxyolean-12-ene (151) and 3β, llα-dihydroxyolean-12-ene (152) are known triterpenes possessing an oleanene-type skeleton and are isolated for the first time from the TRP-4a cell line. Tingenone (148) and 22β-hydroxytingenone (150) are quinone methide triterpenes, also isolated for the first time from the TRP-4a cell line. Similarly, the novel diterpene, 12-methoxyabieta-8, 11, 13- trien-3α-ol (147) and the novel triterpene, methyl-22β-hydroxy-3, 21-dioxo-D:A-friedo-29-noroleanan-24-oate (149), a member of the friedelane family, are isolated for the first time. A biosynthetic pathway, based on the isolation of 149 and its structural similarity to polpunonic acid (55) and 22β-hydroxytingen6ne (150), is postulated for the quinone methides. The cytotoxic diterpenes, tripdiolide (1) and triptolide (2) and the hydroxy acid, 160, isolated as the methyl ester, 124, have been previously reported from this laboratory. Tripdiolide (1) and triptolide (2) have been shown to possess strong antifertility and immunosuppressive activities. In another aspect of our program, biotransformation studies of the synthetic precursors, 19 (4➙3)abeo-abieta-2, 8, 11, 13-tetraen-19-ol (171) and 19-hydroxy-18(4➙3)abeo-abieta-3, 8, 11, 13-tetraen-18-oic acid lactone (91), and the radioactive congeners, 182 and 209, were carried out using the TRP-4a cell line. It was hoped that the data obtained might shed some light on the "late stage" biosynthetic pathway of the diterpene triepoxides, tripdiolide (1) and triptolide (2). Synthesis of 171 was achieved in 5 steps from dehydroabietic acid (80). The radioactive congener, 182, was synthesised using ¹⁴C-paraformaldehyde with 0.4% incorporation of the radiolabel. Biotransformation of 171 using the TRP-4a cell line yielded 19(4➙3)abeo-abieta-2, 8, 11, 13-tetraen-19-al (185) and 19(4➙3)abeo-abieta-2, 8, 11, 13-tetraen-19-oic acid (186) for spectral identification. Biotransformation of 182 yielded the aldehyde, 183 (33.2%) and the acid, 184 (51.9%), the radioactive congeners of 185 and 186 respectively. Synthesis of 91 was achieved in 4 steps from dehydroabietic acid (80). The radioactive congener, 209, was synthesised using ¹⁴C-methyl iodide via ¹⁴C-dimethylsulphonium methylide, with 0.6% incorporation of the radiolabel. Biotransformation of 91 using TRP-4a tissue cultures yielded 19-hydroxy-7-oxo-18(4➙3)abeo-abieta-3, 8, 11, 13-tetraen-18-oic acid lactone (214), 2β, 19-dihydroxy-7-oxo-18(4➙3)abeo-abieta-3, 8, 11, 13-tetraen-18-oic acid lactone (215), 7β, 19-dihydroxy-18(4➙3)abeo-abieta-3, 8, 11, 13-tetraen-18-oic acid lactone (216) and 2β 19-dihydroxy-18(4➙3)abeo-abieta-3, 8, 11, 13-tetraen-18-oic acid lactone (96), for spectral identification. Biotransformation of 209 yielded the ketone, 210 (56.7%), the hydroxy ketone, 211 (5.9%), the benzylic alcohol, 212 (9.6%) and the C2 alcohol, 213 (6.8%), the radioactive congeners of 214,215,216 and 96 respectively. A biosynthetic pathway to the diterpene triepoxides is postulated based on the oxygenated biotransformation products. [formulas omitted]
Science, Faculty of
Chemistry, Department of
Graduate

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Wells, Elizabeth. "Biocatalytic imine reduction : isolation, application, structure and mechanism of imine reductases." Thesis, University of York, 2017. http://etheses.whiterose.ac.uk/18597/.

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Chiral amines are industrially useful chemicals found in the pharmaceutical, chemical and agrochemical industries. While many excellent methods have been developed for their synthesis using abiotic catalysis, these are often reliant on precious metals the global supply of which is becoming increasingly scarce. Additionally, those catalysts often require harsh, non-environmentally friendly reaction conditions such as high temperatures and pressures. Biocatalytic imine reduction, which involves the asymmetric reduction of imines to form chiral amines using imine reductases (IREDs), offers an efficient and sustainable synthesis of chiral amines which overcomes many of the limitations encountered in abiotic catalysis. Two NADPH-dependent IREDs were expressed and purified; SkR-IRED from Streptomyces kanamyceticus and SS-IRED from Streptomyces sp. GF3546, which catalyse the reduction of the model imine 2-methylpyrroline to (R)¬- and (S)- amine products respectively. The SkR¬-IRED monomer consists of an N-terminal Rossman fold motif and a C-terminal helical domain. SkR-IRED exists as a homodimer of two monomers which are linked by an unusual reciprocal domain sharing arrangement. The structure of SkR-IRED was used as a basis to study mechanism using mutagenesis experiments whichsuggested that residue Asp187 may be important for catalysis. The structure of SS-IRED was solved to a resolution of 3.2 Å in its apo form and revealed that the enzyme shares the structural features of SkR-IRED. Mutagenesis experiments suggested that residue Tyr169 is necessary for catalysis. Last, a novel IRED from the moss Physcomitrella patens (Pp-IRED) was expressed and purified. Pp-IRED was active towards the amine N-methyl-1-quinolin-6-ylmethanamine in the oxidative direction, the first IRED active towards this substrate. The structure of Pp-IRED was solved in both its apo form and in complex with NADPH (2.5 Å resolution). The structure was distinct from other IREDs as it did not display the reciprocal domain sharing arrangement seen in SkR-IRED and SS-IRED.

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Howard, Carl. "Active isolation of machinery vibration from flexible structures." Title page, abstract and table of contents only, 1999. http://web4.library.adelaide.edu.au/theses/09PH/09phh8478.pdf.

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Thesis (Ph. D.)--University of Adelaide, Dept. of Mechanical Engineering, 1999?
Copy 2 does not have a CD-ROM. Includes bibliographical references (p. 317-330). Also available in an electronic version.

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Rouget, Peter. "Design of mechanisms for filtering and isolations of industrial protocols." Thesis, Montpellier, 2019. http://www.theses.fr/2019MONTS027/document.

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Avec l’essor de l'Industrie 4.0, de nombreuses infrastructures ont été contraintes d’ouvrir leurs réseaux à Internet, principalement pour répondre au besoin croissant de supervision et de contrôle à distance. Mais là où ces infrastructures étaient auparavant isolées, épargnées par les menaces extérieures, leur ouverture a provoqué l’émergence de nouveaux risques, en particulier à travers le réseau, potentiellement sérieux et qui ne sont pas couverts.Les solutions de cybersécurité, comme les pare-feux, les systèmes de détection d’intrusion ou les systèmes de protection contre les intrusions, sont couramment utilisés pour répondre aux préoccupations liées à la cybersécurité des infrastructures industrielles. Cependant, la tendance à se fier aux systèmes logiciels pour assurer la protection du réseau a mis en lumière les vulnérabilités de ces systèmes, en raison de leurs implémentations logicielles inhérentes. En outre, l’industrie est liée à ses propres spécificités (faible latence, support de protocoles réseaux spécifiques), qui sont rarement couvertes par les solutions informatiques communes.L’objectif principal de cette thèse est d’étudier l’utilisation de dispositifs FPGA appliqués à la cybersécurité pour les réseaux industriels, soit comme support pour des applications de sécurité logicielle, soit pour effectuer des opérations critiques d’analyse réseau. Ce travail présente d’abord le contexte industriel, avec les systèmes de contrôle, leurs architectures, leurs besoins, les règles de mise en œuvre, les protocoles spécifiques et donne également deux exemples de systèmes de contrôle comme on peut en trouver dans l’industrie. Il met ensuite en lumière les problèmes de sécurité, avec une description des menaces les plus courantes, des études de cas sur leurs applications et leurs impacts dans un système de contrôle, et des discussions sur les contre-mesures de pointe disponibles sur le marché. Suite à l'établissement d'une cible de sécurité, nous mettrons en évidence la vulnérabilité des éléments logiciels et des systèmes d’exploitation. Nous verrons aussi comment l’absence d’analyse de sécurité tenant compte de l’état des processus peut mener à certaines vulnérabilités.Pour pallier à ces problèmes, nous proposons, par une première contribution, de renforcer la sécurité des systèmes logiciels en tirant parti des mécanismes de protection existants du FPGA. Enfin, pour répondre à des menaces applicatives spécifiques, nous proposons la mise en œuvre d’une architecture de reconnaissance de motifs, sur FPGA, prenant en considération le cadre temporel et l'état du procédé industriel. Cette thèse a été réalisée en collaboration avec le Laboratoire d'Informatique, de Robotique et de Microélectronique de Montpellier (LIRMM) et la société SECLAB
With the rise of Industry 4.0, many infrastructures were forced to open their networks to the Internet, mainly to meet the growing need for supervision and remote control. But where these infrastructures were previously isolated, spared from external threats, their opening has caused the emergence of new threats, particularly network ones, which were not addressed and present serious risks.Network cybersecurity solutions, like Firewalls, Intrusion Detection Systems or Intrusion Protection Systems are commonly used to address the concern of industrial infrastructures cybersecurity. However the trend of relying on software-based systems to ensure network protection brought to light the vulnerabilities of these systems, due to their inherent software implementation. Furthermore, the industry is tied to its own specificities (low-latency, support of specific network protocols), which are rarely covered by common IT solutions.The main goal of this thesis is to study the use of FPGA-based devices applied to cybersecurity for industrial networks. Either as support for software-based security applications, or to perform critical network analysis operations. First it presents the industrial context, with control systems, their architectures, needs, implementation rules, specific protocols and also gives two examples of control systems as they can be found in the industry. Then it highlights the security problematic, with a description of the most common threats, cases study about their applications and impact in a control system, and discussions on the state of the art counter-measures available on the market. Through the establishment of a security target, it points the vulnerability of software elements and operating systems as well as the lack of process state aware security analysis.To address these issues, we propose, through a first contribution, to enforce the security of the software system by taking advantage of existing FPGA's protection mechanisms. Finally, to answer specific application threats, we introduce an implementation of a brute force matching architecture with time and operational-process awareness, on FPGA.This thesis was conducted in collaboration between the Montpellier computer science, robotic and microelectronic laboratory (LIRMM) and the SECLAB company

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Karadag, Gokdeniz. "Secure Communication Channel Mechanisms For Isolated Networks." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/12611436/index.pdf.

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Current network security solutions are consisted of a single host, with network interfaces of the host connected to protected and external networks at the same time. This design ensures security by restricting traffic flow to a single point, where it can be examined and acted on by a set of rules. However, this design also has a flaw and a single point of failure, that being the vulnerabilities in the security device itself. An adversary would have unhindered access to protected networks if a vulnerability in the security device itself leads to its compromise. To prevent this possibility, high-security networks are completely isolated from external networks, by prohibiting any network connection and constituting a so-called air gap in between. But, data transfer needs do arise between external networks and high-security networks, and in current technology this problem does not have a solution without human intervention. In this theses, we propose a set of mechanisms that allows near-realtime data transfers between high-security network and external networks, without requiring any human intervention. The design consists of two hosts connected via a shared storage, transferring only application layer data between networks. This prevents attacks targeting network stacks of the security device'
s OS, and confines a compromised security device to the network that it is already connected to. In case of a compromise the amount of possible unwanted traffic to and from the high-security network is vastly reduced.

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Hughes, Alexandra. "Mechanisms of volume regulation in murine choroid plexus epithelial cells." Thesis, University of Manchester, 2010. https://www.research.manchester.ac.uk/portal/en/theses/mechanisms-of-volume-regulation-in-murine-choroid-plexus-epithelial-cells(66cb068e-0e38-4773-83ca-a7867aaff66c).html.

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The choroid plexuses are largely responsible for cerebrospinal fluid (CSF) secretion and therefore play a fundamental role in brain homeostasis. The membrane proteins involved in CSF secretion are not fully known. Several electroneutral transporters have been identified by molecular methods in choroid plexus epithelial cells but there is a lack of functional data to support their expression making it impossible to elucidate their role in CSF secretion fully. The activity of many of these transporters can be observed in cell volume regulation. Thus, the main aim of the present study was to determine the ability of mammalian choroid plexus epithelial cells to regulate their volume in response to anisosmotic challenge and to investigate the transporters involved.Experiments were performed on cells isolated from the mouse fourth ventricle choroid plexus. Cells were isolated using a combination of manual perturbation, the enzyme dispase and a Ca2+ free incubation to disrupt tight junctions. Cell volume was measured using a video-imaging method. Cells used in this study were all of a similar morphology and had a mean volume of 0.71 pL.Cells exhibited a HCO3- dependent regulatory volume increase (RVI) in response to hypertonic challenge. Strong evidence is presented that the Na+/H+ exchanger (NHE1) and the Cl-/HCO3- exchanger (AE2) contribute to the RVI but the Na+K+2Cl- cotransporter (NKCC1) and the epithelial Na+ channel (ENaC) do not. Choroid plexus cells exhibit a HCO3- dependent regulatory volume decrease (RVD) in response to hypotonic challenge. The RVD was unaffected by DIOA (an inhibitor of KCC activity), the K+ channel inhibitors TEA+, Ba2+ or 4AP or the Cl- channel inhibitors DIDS or NPPB. However removal of extracellular Ca2+ completely abolished cell swelling in response to hypotonic challenge. This sensitivity of volume change to Ca2+ was specific to cell swelling as cell shrinkage in hypertonic artificial CSF was unaffected by removal of extracellular Ca2+.Thus functional evidence is presented to further elucidate the role of several proteins in the choroid plexus cell volume regulatory response to anisosmotic challenge.

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Koehler, Sonja. "Mechanisms for partial reproductive isolation in a Bombina hybrid zone in Romania." Diss., lmu, 2003. http://nbn-resolving.de/urn:nbn:de:bvb:19-15211.

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Izadnia, Sharareh [Verfasser], and Frank [Akademischer Betreuer] Stienkemeier. "Fluorescence lifetime reduction mechanisms of organic complexes studied by cluster isolation spectroscopy." Freiburg : Universität, 2018. http://d-nb.info/1162443359/34.

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Thayer, Douglas Gary. "Multi-sensor control for 6-axis active vibration isolation /." Thesis, Connect to this title online Connect to this title online; UW restricted, 1998. http://hdl.handle.net/1773/9976.

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Cilliers, Frans Pieter. "A biochemical study of tissue type plasminogen activator in bovine milk." Thesis, Stellenbosch : Stellenbosch University, 2007. http://hdl.handle.net/10019.1/19586.

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Thesis (MSc)--University of Stellenbosch, 2007.
ENGLISH ABSTRACT: This study describes: 1. The isolation and the purification of tissue type plasminogen activator and urokinase plasminogen activator in bovine milk. 2. The biochemical characterisation of tissue type plasminogen activator in bovine milk. 3. An investigation of the influence of the addition of purified tissue type plasminogen activator to ultra high temperature milk, Gouda cheese and yoghurt.
AFRIKAANSE OPSOMMING: Hierdie studie beskryf: 1. Die isolering en suiwering van weefseltipe-plasminogeenaktiveerder en urokinase-plasminogeenaktiveerder in beesmelk. 2. Die biochemiese karakterisering van weefseltipe-plasmingeenaktiveerder in beesmelk. 3. `n Ondersoek na die invloed van die byvoeging van gesuiwerde weefseltipe-plasminogeenaktiveerder by ultra hoë temperatuur melk, Gouda kaas en joghurt.

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Bazm, Mohammad Mahdi. "Unified isolation architecture and mechanisms against side channel attacks for decentralized cloud infrastructures." Thesis, Nantes, 2019. http://www.theses.fr/2019NANT4042.

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Depuis les travaux de Ristenpart [Ristenpart et al., 2009], les attaques par canaux auxiliaires se sont imposées comme un enjeu sécurité important pour les environnements virtualises, avec une amélioration rapide des techniques d’attaque, et de nombreux travaux de recherche pour les détecter et s’en prémunir. Ces attaques exploitent le partage de ressources matérielles comme les différents niveaux de cache processeur entre des locataires multiples en utilisant la couche de virtualisation. Il devient alors possible d’en contourner les mécanismes de sécurité entre différentes instances virtualisées, par exemple pour obtenir des informations sensibles comme des clés cryptographiques. L’analyse des défis d’isolation et des formes d’attaques par canaux auxiliaires basées sur le cache dans les infrastructures virtualisées met en évidence différentes approches pour les détecter ou les contrer, entre machines virtuelles ou conteneurs Linux. Ces approches se distinguent selon la couche logicielle ou seront appliquées les contre-mesures, applicative, système ou matérielle. La détection reste principalement effectuée au niveau de la couche système ou de virtualisation, ce niveau permettant simplement d’analyser le comportement des instances virtualisées. De nouvelles formes distribuées d’attaques ont aussi pu être mises en évidence. Pour la détection, nous explorons une approche combinant des compteurs de performance matériels (HPCs) et la technologie Intel CMT (Cache Monitoring Technology), s’appuyant également sur la détection d’anomalies pour identifier les machines virtuelles ou les conteneurs malveillants. Les résultats obtenus montrent un taux élevé de détection d’attaques. Pour la réaction, nous proposons une approche de Moving Target Defense (MTD) pour interrompre une attaque entre deux conteneurs Linux, ce qui permet de rendre la configuration du système plus dynamique et plus difficilement attaquable, a différents niveaux du système et du cloud. Cette approche ne nécessite pas d’apporter de modification dans l’OS invite ou dans l’hyperviseur, avec de plus un surcoût très faible en performance. Nous explorons enfin l’utilisation de techniques d’exécution matérielle a base d’enclaves comme Intel SGX (Software Guard Extensions) pour assurer une exécution repartie de confiance de conteneurs Linux sur des couches logicielles qui ne le sont pas nécessairement. Ceci s’est traduit par la proposition d’un modèle d’exécution repartie sur infrastructure Fog pour conteneurs Linux. Il s’agit d’un premier pas vers une infrastructure repartie sécurisée Fog illustrant le potentiel de telles technologies
Since their discovery by Ristenpart [Ristenpart et al., 2009], the security concern of sidechannelattacks is raising in virtualized environments such as cloud computing infrastructuresbecause of rapid improvements in the attack techniques. Therefore, the mitigationand the detection of such attacks have been getting more attention in these environments,and consequently have been the subject of intense research works.These attacks exploit for instance sharing of hardware resources such as the processorin virtualized environments. Moreover, the resources are often shared between differentusers at very low-level through the virtualization layer. As a result, such sharing allowsbypassing security mechanisms implemented at virtualization layer through such a leakysharing. Cache levels of the processor are the resources which are shared between instances,and play as an information disclosure channel. Side-channel attacks thus use this leakychannel to obtain sensitive information such as cryptographic keys.Different research works are already exist on the detection/mitigation of these attackin information systems. Mitigation techniques of cache-based side-channel attacks aremainly divided into three classes according to different layer of application in cloud infrastructures(i.e., application, system, and hardware). The detection is essentially done atOS/hypervisor layer because of possibility of analyzing virtualized instances behavior atboth layers.In this thesis, we first provide a survey on the isolation challenge and on the cachebasedside-channel attacks in cloud computing infrastructures. We then present differentapproaches to detect/mitigate cross-VM/cross-containers cache-based side-channel attacks.Regarding the detection of cache-based side-channel attacks, we achieve that by leveragingHardware performance Counters (HPCs) and Intel Cache Monitoring Technology (CMT)with anomaly detection approaches to identify a malicious virtual machine or a Linux container.Our experimental results show a high detection rate.We then leverage an approach based on Moving Target Defense (MTD) theory to interrupta cache-based side-channel attack between two Linux containers. MTD allows us tomake the configuration of system more dynamic and consequently more harder to attackby an adversary, by using shuffling at different level of system and cloud. Our approachdoes not need to carrying modification neither into the guest OS or the hypervisor. Experimentalresults show that our approach imposes very low performance overhead.We also discuss the challenge of isolated execution on remote hosts, different scenariosto secure execution of Linux containers on remote hosts and different trusted executiontechnologies for cloud computing environments. Finally, we propose a secure model fordistributed computing through using Linux containers secured by Intel SGX, to performtrusted execution on untrusted Fog computing infrastructures

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Chen, Feilong. "Agent oriented fault detection, isolation and recovery and aspect-oriented plug-and-play tracking mechanism." Thesis, Texas A&M University, 2003. http://hdl.handle.net/1969/571.

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Greenwald, Katherine R. "Habitat fragmentation, functional landscape connectivity, and metapopulation processes in amphibians." Columbus, Ohio : Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1243366608.

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22

Hinzey, Adam H. "Social Influences on Breast Cancer Pathophysiology and Allodynia Following Nerve Injury: Mechanisms and Mediators." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1462842633.

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23

Rumbold, Karl 1973. "Isolation and properties of a feruloyl esterase from Aureobasidium pullulans and its mechanism in lignocellulose degradation." Thesis, Stellenbosch : Stellenbosch University, 2003. http://hdl.handle.net/10019.1/53480.

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Dissertation (PhD)--University of Stellenbosch, 2003.
ENGLISH ABSTRACT: The production, purification and functional characterisation of feruloyl esterase from Aureobasidium pullulans were set as the primary objectives of this study. A further objective was to investigate a possible co-operative effect with other selected lignocellulolytic enzymes on substrates relevant to industry. In a comprehensive review, feruloyl esterases from various micro-organisms were compared both functionally and with regard to their primary structure, where applicable. Feruloyl esterases show intriguing differences in substrate specificity and sequence structure. Enzymes that are closely related regarding their amino acid sequence exhibit different substrate specificities. Sequence similarities can be found with a range of other enzyme families, including serine esterases, acetyl xylan esterases, lipases, tannases, glycosyl hydrolases and xylanases. More data on the three dimensional structure of feruloyl esterases as well as an examination of all available feruloyl esterases with the same substrates is necessary before structure-function relationships can be established and before the feruloyl esterases can be organized into discrete families based on ancestral origins. The highest production levels of feruloyl esterase by A. pullulans are achieved when grown on birchwood xylan. Expression was not repressed when glucose or xylose was present in the medium. However, free ferulic acid supplemented to the medium affected fungal growth and therefore did not increase feruloyl esterase activity. It is also suggested that the synthesis of feruloyl esterase is independently regulated from xylanase synthesis. Feruloyl esterase from A. pullulans acts on a- and l3-naphthyl acetate, as well as naphthol AS-D chloroacetate as substrates. Feruloyl esterase from A. pullulans was purified to homogeneity using ultrafiltration with high molecular weight cut-off, anion exchange, hydrophobic interaction and ultimately gel filtration chromatography. With a molecular weight of 210 kDa, the enzyme is the largest of the feruloyl esterases reported to date. Kinetic data was produced using both synthetic and natural substrates. A. pullulans feruloyl esterase shows properties similar to other fungal feruloyl esterases, especially from Aspergillus niger cinnamic acid esterase and Penicillium funiculosum feruloyl esterase B. The N-terminal sequence of A. pullulans feruloyl esterase was identified, but no similarities to known enzyme families were found. Peptide mass mapping did not reveal structural information. In an effort to evaluate the significance of feruloyl esterase from A. pullulans in the degradation of lignocellulose, dissolving pulp and sugar cane bagasse were selectively treated using feruloyl esterase and hemicellulolytic enzymes. The enzymatic degradation reaction was monitored using microdialysis sampling, anion exchange chromatography, online desalting and mass spectrometry. It has been shown, that feruloyl esterase activity together with xylanase activity releases monosaccharides from both substrates. Sugars of higher degree of polymerisation were not released, giving evidence for the recalcitrance of the material. The fibre architecture of the substrates was apparently not accessible to the enzymes and therefore complete hydrolysis was hindered.
AFRIKAANSE OPSOMMING: Die produksie, suiwering en funksionele karakterisering van feruloïel esterase afkomstig van Aureobasidium pullulans was die primêre doelwitte van hierdie studie. 'n Verdere doelwit was om vas te stelof daar 'n kooperatiewe effek met ander geselekteerde lignosellulitiese ensieme op substrate wat industrierelevant is, bestaan. Die feruloïel esterase van verskillende mikro-organismes is vanuit die oogpunt van funksie en primêre struktuur omvattend met mekaar vergelyk, waar toepaslik. Interessante verskille tussen die substraat spesifisiteit en volgordestruktuur van feruloïel esterase kan waargeneem word. Ensieme wat nou aanmekaar verwant is wat hul aminosuurvolgorde betref, het duidelik verskillende substraatspesifiteite. Volgordeverwantskap kan in 'n reeks van ander ensiemfamilies, insluitende serienesterase, asetielxilaanesterase, lipases, tannases, glikosielhidrolases en xilanases vasgestel word. Meer inligting oor die driedimensionele struktuur van feruloïel esterase asook 'n analise van al die beskikbare feruloïel esterase met dieselfde substrate is nodig voordat struktuur-funksie verwantskappe vasgestel kan word en voordat die feruloïel esterases in eie families op die grond van huloorsprong georganiseer kan word. Die hoogste produksie vlakke deur feruloïel esterase van A. pullulans word bekom deur dit op berkhoutxilaan te groei. Ekspressie was nie onderdruk wanneer glukose of xilose in die medium aanwesig was nie. Wanneer vrye feruliensuur by die medium bygevoeg is, is die fungale groei beïnloed en het die feruloïel esterase aktiwiteit nie vermeerder nie. Dit word ook voorgestel dat die sintese van feruloïel esterase onafhanklik deur xilanase sintese gereguleer word. Feruloïel esterase van A. pullulans reageer op a- en f3- naftolasetaat, asook naftol AS-D chloroasetaat as substrate. Feruloïel esterase van A. pullulans is tot homogeniteit deur ultrafiltrering met .n hoë molekulêre gewiggrens, anioonuitruiling, hidrofobiese interaksie en eindelik gelfiltrasie-chromatografie gesuiwer. Met 'n molekulêre gewig van 210 kDa, is die ensiem die grootste van die feruloïel esterases tot dusver beskryf. Kinetiese data is met behulp van sintetiese en natuurlike substrate geproduseer. A. pullulans feruloïel esterase het eienskappe wat vergelykbaar is aan die van ander fungal feruloïel esterases, veral die wat afkomstig is van Aspergillus niger sinnamiensuur esterase en Penicillium funiculosum feruloïel esterase B. Die N-terminale volgorde van A. pullulans feruloïel esterase is identifiseer maar geen ooreenkoms aan bekende ensiemfamilies kon vasgestel word nie. Peptiedmassakaartering kon ook geen strukturele inligting gee nie. Oplosbare pulp en suikerrietbagasse is geselekteerd met behulp van feruloïel esterase en lignosellulitiese ensieme behandel om die belang van feruloïel esterase van A. pullulans in die afbraak van lignosellulose vas te stel. Die hidroliese-reaksie is deur mikrodialise monsterneming, anioonuitruilingschromatografie, oplyn ontsouting en massaspektrometrie gemonitor. Wanneer die aktiwiteit van feruloïel esterase met die van xilanase gekombineer is, is monosakkariede deur albei substrate afgeskei. Suikers met 'n hoër graad van polimerisering is nie afgeskei nie, wat 'n bewys van die materiaal se weerstandbiedendheid is. Dit het geblyk asof die vesel-argitektuur van die verbruikte substraat nie toeganklik was vir ensieme nie en dus is algehele hidroliese verhinder.

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Muranjan, Madhavi. "Isolation, identification and mechanism of action of a trypanocidal serum protein from African Buffalo : xanthine oxidase /." The Ohio State University, 1996. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487932351057923.

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25

Or, Cho-tsun, and 柯楚浚. "Isolation and identification of anti-inflammatory constituent from Ligusticum chuanxiong and its underlying mechanisms." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hub.hku.hk/bib/B43784318.

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Or, Cho-tsun. "Isolation and identification of anti-inflammatory constituent from Ligusticum chuanxiong and its underlying mechanisms." Click to view the E-thesis via HKUTO, 2009. http://sunzi.lib.hku.hk/hkuto/record/B43784318.

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27

FAKHOURI, Muhannad Yacoub. "Application of Sliding Isolation Bearings with Upward Lifting Mechanism for Seismic Performance Enhancement of Multi-Story Structures." 京都大学 (Kyoto University), 2012. http://hdl.handle.net/2433/157552.

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28

Gao, Hong Wei. "Isolation and purification of compounds from Salvia miltiorrhiza Bunge (Danshen) and pharmacological activity evaluation and mechanism exploration." Thesis, University of Macau, 2017. http://umaclib3.umac.mo/record=b3690832.

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29

Watson, Peter Duncan. "Isolation and characterisation of adaptation mechanisms within the pheromone signal transduction pathway of Schizosaccharomyces pombe." Thesis, University of Warwick, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.396871.

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30

Zuo, Tianming. "Synthesis, Isolation, and Characterization of Tb-based Large Cage TNT-EMFs and Dimetallic Endohedral Metalloazafullerenes." Diss., Virginia Tech, 2008. http://hdl.handle.net/10919/25993.

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A family of novel large cage Tb-based TNT-EMFs Tb3N@C2n (40 â ¤ n â ¤ 44), and a family of novel dimetallic endohedral metalloazafullerenes with the molecular formula of M2@C79N (M=Y, Tb, and La), were for the first time systematically synthesized, isolated, and structurally characterized. The protocol developed in this thesis provides an effective and systematic method for the synthesis, purification, and characterization of TNT-EMFs and other novel EMFs. Structural information about this family of Tb-based TNT-EMFs strongly supports the TNT formation mechanism of TNT-EMFs. It also demonstrates for the first time that EMFs do not necessarily choose an IPR-obeying cage even if the IPR cages are available. At room temperature and in a non-polar organic solvent, the fluorescence of the hydrogenated product of Tb3N@C80 was for the first time successfully obtained based on the proposed idea: de-shielding the screen effect of the fullerene cage on the metal ions or clusters inside the fullerene cage. The structural characterization of Tb2@C79N using single crystal X-ray diffraction crystallography demonstrated that the fullerene cage of M2@C79N is an Ih eighty-atom cage. The presence of the N atom in the molecule was further confirmed by mass spectra of the 15N labeled samples. ESR data demonstrated that there is a single-electron bond between the two Y atoms in Y2@C79N molecules. Theoretical calculations showed for the first time that the single-electron bond is low-lying at the HOMO -2 orbital and thereby resulting in a large HOMO-LUMO gap. It is, in fact, this large HOMO-LUMO gap and the low-lying single-electron orbital (hidden at HOMO-2) that are jointly responsible for the stability of M2@C79N. The single-electron bonds are the longest metal-metal bond reported so far. The chromatographic retention behavior of TNT-EMFs was also systematically studied on 5PBB and 5PYE columns. Both experimental and theoretical data demonstrated that the 5PBB column is sensitive to a fullerene's predicted cage size but indifferent to its cage symmetry, while the 5PYE column is more sensitive to the density and distribution of Ï electrons in a fullerene cage. Therefore, the 5PYE column is more suitable for separating structural isomers. The combination of the 5PBB column in the first stage and the 5PYE column in the second provides a highly effective way for isolating specific isomers.
Ph. D.

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31

Thaver, Veneesha. "Isolation and characterization of the cytotoxicity, intracellular bioactivity and mechanism of antimycobacterial action of Euclea natalensis-derived naphthoquinones." Thesis, University of Pretoria, 2010. http://hdl.handle.net/2263/31311.

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The major cause of HIV-related mortality in Sub-Saharan countries is pulmonary tuberculosis (TB), which is an escalating threat due to the emergence of multidrug resistant (MDR) and extremely multidrug resistant (XDR) TB. There is clearly an urgent requirement for the identification of novel, affordable anti-TB (as well as anti-HIV) drugs. This study was undertaken with the objective of isolating and characterizing the antimycobacterial potential of 3 naphthoquinones, i.e. neodiospyrin, diospyrin and 7- methyljuglone present in the roots of Euclea natalensis. The laboratory research included: i) isolation of diospyrin and neodiospyrin, from the roots of E. natalensis; ii) assessment of the cytotoxicity of these agents and synthetic 7-methyljuglone for eukaryotic cells (Vero and THP-1 cells); iii) determination of the intracellular bioactivities of the naphthoquinones against the H37Rv strain of Mycobacterium tuberculosis (MTB); and iv) mechanistic studies designed to investigate the effects of the test agents on cation (K+/ Ca2+) fluxes and energy metabolism (ATP levels) in MTB and M. smegmatis. With respect to the first objective, the naphthoquinones (diospyrin and neodiospyrin) were isolated from crude methanol extracts of crushed roots using chromatography and spectroscopic analysis. The yields of the compounds were 0.16 %, 0.32 %, and 0.12 % for neodiospyrin, diospyrin (isolated from plant) and synthetic 7-methyljuglone (synthesised in laboratory), respectively. The effects of the compounds (0.3-50μg/ml) on the viability of Vero and THP-1 cells were measured using the XTT assay (sodium 3’-[1-(phenyl amino-carbonyl)-3, 4 tetrazolium]-bis-[4-methoxy-6-nitro] benzene sulfonic acid hydrate) based on cellular metabolic activity. All 3 test compounds were found to possess cytotoxic activity at 1.5- 12.5g/ml) for both cell lines. Intracellular bioactivity of the test agents was measured using MTB-infected THP-1 cells as a surrogate for infected human macrophages. Following exposure of the MTBinfected cells to the test naphthoquinones, at a concentration range of 6.25-25g/ml, for 5 days, the cells were lysed and the viability of MTB in the lysates was then measured using the BACTEC radiometric system. All 3 test agents were found to be bioactive intracellularly, with complete inhibition of growth detected at 12.5, 25, and 6.25g/ml in the case of neodiospyrin, diospyrin, and synthetic 7-methyljuglone respectively. The effects of the 3 naphthoquinones on mycobacterial cation fluxes were measured according to the magnitude of uptake of 86Rb+ (a surrogate for K+) and 45Ca2+, while ATP was measured using a chemiluminescence procedure. None of the test agents was found to affect Ca2+ uptake by the bacteria. However, all 3 test agents were found to be potent inhibitors of uptake of K+ by MTB and M. smegmatis, with inhibition detected at submicrogram concentrations of these agents. All 3 test agents, especially synthetic 7- methyljuglone, were found to interfere with energy metabolism in MTB, manifested as decreases in mycobacterial ATP levels. Synthetic 7-methyljuglone which has the lowest MIC value for MTB (0.5μg/ml), and which was the most potent inhibitor of energy metabolism in MTB, shows promise as a potential anti-TB agent.These agents also are of potential value in drug modelling, possibly in the design of novel anti-TB agents which selectively target mycobacterial K+ transporters.
Thesis (PhD)--University of Pretoria, 2010.
Immunology
Unrestricted

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32

Sen, Keya. "The Relationship between Social Isolation and Wellbeing in Older Adults." Thesis, University of North Texas, 2020. https://digital.library.unt.edu/ark:/67531/metadc1707364/.

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This dissertation contributes to research on social isolation in older adults aged 65 years and above through three essays that expand our understanding of the social determinants of health and identify the social and interpersonal factors that contribute to elderly wellbeing. This dissertation examines the significant factors contributing to the problem of social isolation, and how the availability of interest-based, low-cost engagement resources in the community can alleviate social isolation and foster healthy aging. Essay 1 is a systematic literature review with implications for future research that explores how technological skills and training based on user intention and availability of resources can alleviate social isolation. Essay 2 is a qualitative study that evaluates the effectiveness of a unique community-based senior exercise program in fostering social integration and in reducing social isolation. Essay 3 is a quantitative study that examines the magnitude and direction of the correlated relationships among the determinants of social inclusion and the impact of social and interpersonal processes on senior wellbeing. These three essays provide insight into the social isolation phenomenon that negatively impacts senior wellbeing and recommends solutions derived from a data driven examination of the problem that is especially applicable to economically disadvantaged senior communities. Moreover, this research provides community partners and gatekeepers a foundation for future research on the social isolation phenomenon and strategies for developing digital confidence and mobility program strategies that foster social inclusion and reduce social isolation for older adults.

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Power, Gavin Jude. "Isolation, structural characterisation and mechanisms of action of novel insulin-releasing peptides from amphibian skin secretions." Thesis, University of Ulster, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.554281.

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Amphibian skin secretions are considered to be one of the richest resources of bioactive molecules in the animal kingdom for pharmaceutical prospecting. This thesis has investigated amphibian skin peptides of eight different species of anurans (frogs and toads) for insulin-releasing and anti-diabetic properties. The skins of Pseudis paradoxa, Hylarana guntheri, Hylomantis lemur and Leptodactylus laticeps, were tested for the presence of peptides with stimulatory effects on insulin-release from the clonal BRIN-BDll cell line. Upon purification of the skin secretions/extract, multiple insulin-releasing peptides were isolated and fully characterised by mass spectrometry along with N-terminal amino acid sequencing by Edman degradation. A number of synthetic peptides demonstrated potent in vitro biological activities, possessing the ability to stimulate insulin release up to a concentration of 3 flM without any association of cellular toxicity. For example, brevinin-2GUb isolated from the skin extract of H. guntheri stimulated insulin release 3.7 fold compared to 5.6 mmol/l glucose control (P

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34

Koch, T. "An application of matrix isolation and reflection-absorption infrared spectroscopy to reaction mechanisms in atmospheric cryochemistry." Thesis, University of East Anglia, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384825.

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35

Goyal, Naveen. "Numerical Simulaion of Pandemic Flu Dispersal in an Airborne Infection Isolaton Room to Examine the Health-Care Worker Exposure." University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1342729671.

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36

Le, Toan T. "A Single-Stage Passive Vibration Isolation System for Scanning Tunneling Microscopy." DigitalCommons@CalPoly, 2021. https://digitalcommons.calpoly.edu/theses/2272.

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Scanning Tunneling Microscopy (STM) uses quantum tunneling effect to study the surfaces of materials on an atomic scale. Since the probe of the microscope is on the order of nanometers away from the surface, the device is prone to noises due to vibrations from the surroundings. To minimize the random noises and floor vibrations, passive vibration isolation is a commonly used technique due to its low cost and simpler design compared to active vibration isolation, especially when the entire vibration isolation system (VIS) stays inside an Ultra High Vacuum (UHV) environment. This research aims to analyze and build a single-stage passive VIS for an STM. The VIS consists of a mass-spring system staying inside an aluminum hollow tube. The mass-spring system is comprised of a circular copper stage suspended by a combination of six extension springs, and the STM stays on top of the copper stage. Magnetic damping with neodymium magnets, which induces eddy currents in the copper conductor, is the primary damping method to reduce the vibrations transferred to the mass-spring system. FEMM and MATLAB® are used to model magnetic flux density and damping coefficients from eddy current effect, which will help determine the necessary damping ratios for the VIS. Viton, which demonstrates a high compatibility with vacuum environments, will also serve as a great damping material between joints and contacts for the housing tube. Viton will be modeled as a Mooney-Rivlin hyperelastic material whose material parameters are previous studied, and Abaqus will be used as a Finite Element Analysis software to study the Viton gaskets’ natural frequencies. The natural frequencies of the aluminum hollow tube will also be investigated through Abaqus.

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Yun, Yuan. "Kinematics, dynamics and control analysis for micro positioning and active vibration isolation using parallel manipulators." Thesis, University of Macau, 2011. http://umaclib3.umac.mo/record=b2542954.

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38

Pinelo, Laura F. "An Investigation of the Thermal and Photochemical Reaction Mechanisms of Cycloalkenes and Ferrocenes with Ozone by Matrix Isolation Spectroscopic Analysis and Theoretical Calculations." University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1427981459.

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39

Eroz, Murat. "Advanced models for sliding seismic isolation and applications for typical multi-span highway bridges." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19709.

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Thesis (Ph.D)--Civil and Environmental Engineering, Georgia Institute of Technology, 2008.
Committee Chair: DesRoches, Reginald; Committee Member: Goodno, Barry; Committee Member: Jacobs, Laurence; Committee Member: Streator, Jeffrey; Committee Member: White, Donald.

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40

Goritzka, Veronika [Verfasser], and Holger [Akademischer Betreuer] Rohde. "Molekulargenetische Mechanismen der Carbapenemresistenz bei klinischen Isolaten von Pseudomonas aeruginosa / Veronika Goritzka. Betreuer: Holger Rohde." Hamburg : Staats- und Universitätsbibliothek Hamburg, 2016. http://d-nb.info/1103233327/34.

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Goritzka, Veronika Verfasser], and Holger [Akademischer Betreuer] [Rohde. "Molekulargenetische Mechanismen der Carbapenemresistenz bei klinischen Isolaten von Pseudomonas aeruginosa / Veronika Goritzka. Betreuer: Holger Rohde." Hamburg : Staats- und Universitätsbibliothek Hamburg, 2016. http://nbn-resolving.de/urn:nbn:de:gbv:18-78899.

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42

Mair, Magdalena [Verfasser], and Joachim [Akademischer Betreuer] Ruther. "Mechanisms and evolution of prezygotic reproductive isolation in the parasitoid wasp genus Nasonia / Magdalena Mair ; Betreuer: Joachim Ruther." Regensburg : Universitätsbibliothek Regensburg, 2020. http://d-nb.info/1203874820/34.

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43

Sarkar, Sujan K. "Reaction Mechanism and Detection of Elusive C, N, and O Centered Radicals and Intermediates in Solution and Solid State." University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1448037904.

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44

Abu, Hanieh Ahmed. "Active isolation and damping of vibrations via stewart platform." Doctoral thesis, Universite Libre de Bruxelles, 2003. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/211336.

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In this work, we investigate the active vibration isolation and damping of sensitive equipment. Several single-axis isolation techniques are analyzed and tested. A comparison between the sky-hook damper, integral force feedback, inertial velocity feedback and LagLead control techniques is conducted using several practical examples.

The study of single-axis systems has been developed and used to build a six-axis isolator. A six degrees of freedom active isolator based on Stewart platform has been designed manufactured and tested for the purpose of active vibration isolation of sensitive payloads in space applications. This six-axis hexapod is designed according to the cubic configuration; it consists of two triangular parallel plates connected to each other by six active legs orthogonal to each other; each leg consists of a voice coil actuator, a force sensor and two flexible joints. Two different control techniques have been tested to control this isolator :integral force feedback and Lag-Lead compensator, the two techniques are based on force feedback and are applied in a decentralized manner. A micro-gravity parabolic flight test has been clone to test the isolator in micro-gravity environment.

ln the context of this research, another hexapod has been produced ;a generic active damping and precision painting interface based on Stewart platform. This hexapod consists of two parallel plates connected to each other by six active legs configured according to the cubic architecture. Each leg consists of an amplified piezoelectric actuator, a force sensor and two flexible joints. This Stewart platform is addressed to space applications where it aims at controlling the vibrations of space structures while connecting them rigidly. The control technique used here is the decentralized integral force feedback.

Doctorat en sciences appliquées
info:eu-repo/semantics/nonPublished

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45

Alhafez, Nahla. "Genetic and behavioural mechanisms of reproductive isolation and speciation in recently-diverged sibling species of the malaria vector Anopheles gambiae s.l." Thesis, Keele University, 2016. http://eprints.keele.ac.uk/3211/.

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Anopheles gambiae s.l. species are reported as the most important vectors due to their ability to spread and exploit both temporary and man-made breeding sites. These factors combined with their capacity to transmit malaria, make them wide-open subject for researchers to find alternative different methods to control malaria disease. Historically, there were many attempts to limit or eradicate malaria disease by controlling the mosquitoes. The control methods varied between using insecticide-treated bed nets and indoor residual spraying, in addition to other methods that based on sterile insect technique (SIT) or genetic modification techniques. However, the success of any attempts to eliminate malaria depends on our understanding of the genetic diversity of the vectors in field. In this regard, two distinct sibling species Anopheles coluzzii and Anopheles gambiae s.s. were defined in An. gambiae complex based on single nucleotide polymorphisms intergenic spacer (IGS) near the centromere of the X chromosome. These species were found to mate assortatively even within mixed swarms. Moreover, genetic differences between them were limit to three regions that were 2L, 3L and X chromosome near the centromere regions. Several studies tried to explain the sympatric speciation process between the An. gambiae s.l. sibling species based on these islands of speciation and their role in assortative mating behaviour, but no full explanation was concluded so far. Therefore, two objectives were taken into consideration in this thesis. The first was genetic objective that aims to identify the islands of speciation that more likely responsible for assortative mating. The second was behavioural objective that aims to identify the mechanisms of assortative mating using recombinant and parental strains. These studies were important step for trying to explain the speciation process within An. gambiae s.l. species that in turn important for malaria control strategies.

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46

Jean, Pierrick. "Isolation vibratoire par contrôle semi-actif d'amortisseurs magnéto-rhéologiques pour l'interface lanceur/charge utile." Phd thesis, Conservatoire national des arts et metiers - CNAM, 2006. http://tel.archives-ouvertes.fr/tel-00352710.

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Le travail présenté dans cette thèse a pour objet l'isolation vibratoire entre 5 et 100 Hz d'une charge utile durant les 150 premières secondes de son lancement, par contrôle semi-actif d'amortisseurs magnéto-rhéologiques. L'isolateur envisagé est une interface souple dont les modes, compris entre 2 et 7 Hz, sont amortis par le dispositif à amortissement contrôlable. Dans un premier temps, afin de réaliser des simulations de contrôle semi-actif réalistes, un modèle de l'amortisseur magnéto-rhéologique utilisé est identifié à partir des mesures de l'effort et de la vitesse du piston. Puis on étudie l'isolateur semi-actif à 1 degré de liberté, à la fois par simulations et expérimentalement. On s'intéresse en particulier au contrôleur skyhook damper et à ses performances d'isolation haute fréquence et d'amortissement basse fréquence pour différents types d'excitations large bande, performances qui sont systématiquement comparées à celles de l'isolateur passif optimal. On présente ensuite une étude originale qui concerne un isolateur semi-actif à 6 degrés de liberté, basé sur la plateforme de Stewart, dont un démonstrateur expérimental a été développé et testé. On détaille en particulier les résultats du contrôle par Integral Force Feedback semi-actif pour les excitations lanceur reproduites expérimentalement. Enfin, l'étude est étendue à la configuration échelle 1 pour laquelle on envisage les performances de confort et de sécurité de l'isolateur. On considère en particulier un cas d'excitation transitoire latérale, la rafale de vent, pour laquelle on développe un contrôleur on-off à seuil de déclenchement, lequel semble également efficace pour l'isolation vibratoire. L'isolateur semi-actif ainsi obtenu semble présenter de meilleures performances qu'un isolateur passif stationnaire, tout en étant conforme aux contraintes propres à l'environnement lanceur.

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47

De, Marneffe Bruno. "Active and passive vibration isolation and damping via shunted transducers." Doctoral thesis, Universite Libre de Bruxelles, 2007. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210613.

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Many different active control techniques can be used to control the vibrations of a mechanical structure: they however require at least a sensitive signal amplifier (for the sensor), a power amplifier (for the actuator) and an analog or digital filter (for the controller). The use of all these electronic devices may be impractical in many applications and has motivated the use of the so-called shunt circuits, in which an electrical circuit is directly connected to a transducer embedded in the structure. The transducer acts as an energy converter: it transforms mechanical (vibrational) energy into electrical energy, which is in turn dissipated in the shunt circuit. No separate sensor is required, and only one, generally simple electronic circuit is used. The stability of the shunted structure is guaranteed if the electric circuit is passive, i.e. if it is made of passive components such as resistors and inductors.

This thesis compares the performances of the electric shunt circuits with those of classical active control systems. It successively considers the use of piezoelectric transducers and that of electromagnetic (moving-coil) transducers.

In a first part, the different damping techniques are applied on a benchmark truss structure equipped with a piezoelectric stack transducer. A unified formulation is found and experimentally verified for an active control law, the Integral Force Feedback (IFF), and for various passive shunt circuits (resistive and resistive-inductive). The use of an active shunt, namely the negative capacitance, is also investigated in detail. Two different implementations are discussed: they are shown to have very different stability limits and performances.

In a second part, vibration isolation with electromagnetic (moving-coil) transducers is introduced. The effects of an inductive-resistive shunt circuit are studied in detail; an equivalent mechanical representation is found. The performances are compared with that of resonant shunts and with that of active isolation with IFF. Next, the construction of a six-axis isolator based on a Stewart Platform is presented: the key parameters and the main limitations of the system are highlighted.

Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished

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48

Mnguni, Sandiso. "Reproductive isolation mechanisms of two cryptic species of Eccritotarsus (Hemiptera: Miridae), biological control agents of water hyacinth, Eichhornia crassipes (Martius) Solms-Laubach (Pontederiaceae)." Thesis, Rhodes University, 2019. http://hdl.handle.net/10962/68133.

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Water hyacinth, Eichhornia crassipes (Martius) Solms-Laubach (Pontederiaceae), is one of the world’s worst alien invasive plants. It is indigenous to the Amazon basin in South America but has become a problematic alien invasive in other parts of the world. As such, several host-specific biological control agents have been sourced from the native distributions in South America and have been released to control this plant where it has become problematic. Two of these agents include the geographically and reproductively isolated cryptic species of Eccritotarsus (Hemiptera: Miridae). One of these species was collected in the upper reaches of the Amazon River in Peru, while the other was collected over 3500km away from that site, in Florianopolis, southern Brazil. These cryptic species were thought to be a single species until recently, when DNA barcoding indicated that they were likely to be two species, and the species status has now been confirmed by interbreeding experiments and detailed morphological studies. The Brazilian population remains Eccritotarsus catarinensis (Carvalho), while the Peruvian population is now known as Eccritotarsus eichhorniae (Henry). The aim of this project was to investigate the mating behaviour and other behavioural traits of the two species that have resulted in reproductive isolation, and which could have led to speciation. In addition, investigations involving analysis of chemical compound compositions of the two species aimed to determine the extent to which the compounds played a role in the development and maintenance of reproductive isolation. To achieve the aims, behavioural-observation experiments were conducted in the form of no-choice, bi-choice and multi-choice tests in 1:1, 2:1 and 3:1 sex ratio assessments, both within and between species. Chemical compound compositions of E. catarinensis and E. eichhorniae were also assessed using Nuclear Magnetic Resonance (NMR), Solid-phase micro-extraction (SPME) and Gas-Chromatography Mass-Spectrometry (GC-MS) techniques. In no-choice experiments, the highest number of single and multiple copula incidences, and average total copula duration was found within species while copulation between species was much rarer. In bi-choice experiments, E. eichhorniae females and E. catarinensis males only chose to mate with their respective conspecifics, and within species copulations continued to have higher average total copula duration. In multi-choice experiments, the highest number of single and multiple copula incidences and average total copula duration was also found within species. GC-MS analysis suggested that E. catarinensis females and E. eichhorniae males have unique chemical compounds missing in their conspecifics and same sex of the other species. Further analysis suggested that E. catarinensis females and E. eichhorniae males have similar chemical compound compositions, whereas as E. eichhorniae females and E. catarinensis males have similar chemical compound compositions. These results suggest that there are behavioural differences that led to the development and maintenance of prezygotic reproductive isolation mechanisms, and that this is probably driven by pheromones in chemical compound compositions. These two species were geographically isolated in the native range and the populations have diverged to the point that they are now reproductively incompatible and therefore, distinct species. The main driver of the speciation is most likely mate recognition and attraction, as only reproductively important traits such as pheromones, genitalia, the scent glands and antennae have changed, while other traits, including host range and morphology, have remained remarkably stable. This provides evidence that differences in sexual selection in isolated populations may be important drivers of speciation and reproductive isolation in cryptic species.

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49

Pinarbasi, Seval. "A New Formulation For The Analysis Of Bonded Elastic Layers." Phd thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12608310/index.pdf.

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Elastic layers bonded to reinforcing sheets are widely used in many engineering applications, e.g., as elastic foundations to machinery, as seismic isolators to structures, etc. Because of its practical importance, the behavior of bonded elastic layers under some basic deformation modes (e.g., compression, bending and shear modes) has attracted the attention of many researchers. However, the analytical works available in literature involve, with the object of obtaining design formulas, many simplifying assumptions. In this dissertation, a new formulation is developed for the analysis of bonded elastic layers, which removes most of the assumptions used in the earlier formulations. Since the displacement boundary conditions are included in the formulation itself, there is no need to start the formulation with some assumptions on stress and/or displacement distributions or with some limitations on geometrical and/or material properties. For this reason, the solutions derived from this formulation are valid not only for &ldquo
thin&rdquo
layers of strictly/nearly incompressible materials but also for &ldquo
thick&rdquo
layers and/or compressible materials. The advanced solutions obtained within the framework of the new formulation are used to study the behavior of bonded elastic layers under basic deformation modes. The effects of three key parameters, shape factor, Poisson&rsquo
s ratio and reinforcement flexibility, on effective layer moduli, displacement/stress distributions, and location/magnitude of maximum stresses are investigated. It is shown that the stress assumptions of the &ldquo
pressure&rdquo
method are inconsistent with the results obtained for thick layers and/or compressible materials and/or flexible reinforcements, and that the assumption &ldquo
plane sections remain plane&rdquo
is not valid, in general.

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50

Zimmer, Claudia [Verfasser], Lisa Maria [Akademischer Betreuer] Schulte, Lisa Maria [Gutachter] Schulte, and Bruno [Gutachter] Streit. "Mechanismen reproduktiver Isolation bei schwefelangepassten Formen des Atlantikkärpflings (Poecilia spec.) / Claudia Zimmer ; Gutachter: Lisa Maria Schulte, Bruno Streit ; Betreuer: Lisa Maria Schulte." Frankfurt am Main : Universitätsbibliothek Johann Christian Senckenberg, 2019. http://d-nb.info/120229815X/34.

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Dissertations / Theses on the topic 'Isolating mechanism'

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