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Lu, Qi Charles. "Active tamper-detector hardware mechanism and FPGA implementation /." Diss., Online access via UMI:, 2006.
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George, Lynnane E. "Active vibration control of a flexible base manipulator." Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/17115.
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Lee, Kam-fat Jonathan. "Design and control of a robotic manipulator with an active pneumatic balancing system /." [Hong Kong] : University of Hong Kong, 1992. http://sunzi.lib.hku.hk/hkuto/record.jsp?B13194367.
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Rivera-Rivera, Izarys. "Mechanism of active substrate delivery by the AAA+ protease adaptor CIpS." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/101352.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Biology, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references.
AAA+ molecular machines power myriad cellular processes including protein degradation, microtubule severing, membrane fusion, and initiation of DNA replication. Protein quality control in all organisms involves deployment of ATP-dependent proteases, consisting of hexameric AAA+ rings that unfold and translocate specific substrates into an associated peptidase barrel. Adaptor proteins assist in recognition and degradation of certain substrates, but how enzyme-adaptor pairs ensure proper substrate selection is incompletely understood. In this thesis I focus on the delivery mechanism employed by the bacterial adaptor protein CIpS. The CIpS adaptor collaborates with the AAA+ CIpAP protease to recognize and degrade N-end rule substrates. CIpS binds the substrate's N-degron and assembles into a high-affinity CIpS-substrate-CIpA complex, but how the N-degron is transferred from CIpS to the axial pore of the AAA+ CIpA unfoldase to initiate degradation is not known. Here, we demonstrate that the unstructured N-terminal extension (NTE) of CIpS enters the CIpA processing pore in the active ternary complex and that CIpA engagement of the CIpS NTE is crucial for CIpS-mediated substrate delivery. In addition, I report evidence that CIpA engagement of the CIpS NTE drives structural rearrangements in CIpS important for N-end rule substrate delivery. Furthermore, our preliminary experiments suggest that CIpS is able to resist degradation by CIpAP due to a combination of a high local stability and a challenging translocation sequence at the junction of the NTE and folded core domain. I propose a model in which CIpA remodels CIpS by translocating the NTE, triggering delivery of the N-end rule substrate. Similar mechanisms may be employed by other AAA+ enzymes that collaborate with adaptor proteins to remodel/disassemble substrates without destroying them by degradation.
by Izarys Rivera-Rivera.
Ph. D.
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Schaedler, Theresia Anna. "Molecular mechanism of transport by the secondary-active multidrug transporter LmrP." Thesis, University of Cambridge, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609036.
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Gómez, Jon Freire. "Active gurney flap mechanism for a full scale helicopter rotor blade." Thesis, University of Bristol, 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.690378.
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Amongst the objectives of the EU's Green Rotorcraft programme is the development of a functional and airworthy Active Gurney Flap (AGF) for a full-scale helicopter rotor blade. Interest in the development of this 'smart adaptive rotor blade' technology lies in its potential to provide a number of aerodynamic benefits, which would in turn translate into a reduction in fuel consumption and noise levels. With a technical specification informed by helicopter manufacturer Agusta Westland as a starting point, the AGF concept developed emerged from the application of a design methodology consisting of an initial concept generation phase and a subsequent selection process based on a series of problem-specific qualitative and quantitative performance criteria. This methodology resulted in a novel AGF concept design where the use of flexural pivots was favoured over bearing-type joints. As a first step towards full validation of both the concept design and the theoretical aerodynamic benefits of the AGF, a baseline design of the mechanism was successfully tested both in a fatigue rig and in a 2D wind tunnel environment at flight-representative deployment schedules. This baseline design was then reengineered with a view to making it fit for flight test. However, analysis of the flight test baseline design under full in-flight loading and blade deformations revealed that the stresses arising in the flexures exceeded the allowable limits. In order to overcome this problem, two complementary alternatives were investigated. Initially, a generic 2D and 3D shape optimisation of leaf-type crossed flexure pivot springs was carried out considering the pivots as individual isolated elements. This route produced important novel results in the field of crossed flexure pivots and proved that there is great scope for stress reduction through shape optimisation. Furthermore, a parametric optimisation of the AGF mechanism as a whole was performed, where the effect of a range of topological parameters was investigated. This second approach resulted in very significant stress reductions" sufficient so as to conclude that the proposed AGF concept has potential to become an airworthy design, although further work is needed to achieve a sufficiently mature technology readiness level.
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李錦發 and Kam-fat Jonathan Lee. "Design and control of a robotic manipulator with an active pneumatic balancing system." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1992. http://hub.hku.hk/bib/B31210429.
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Unsal, Memet. "Semi-active vibration control of a parallel platform mechanism utilizing magnetorheological damping." [Gainesville, Fla.] : University of Florida, 2006. http://purl.fcla.edu/fcla/etd/UFE0013824.
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Moon, Suk-Min. "Active damping control of a compliant base manipulator." Ohio : Ohio University, 1999. http://www.ohiolink.edu/etd/view.cgi?ohiou1175797025.
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Witter, Jeffrey Bruce. "Convection of magma in volcanic conduits as a degassing mechanism at active volcanoes /." Thesis, Connect to this title online; UW restricted, 2003. http://hdl.handle.net/1773/6721.
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Rao, Reshma R. "Understanding the active sites and reaction mechanism of water oxidation on metal oxides." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/122141.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2019Cataloged from PDF version of thesis.
Includes bibliographical references (pages 184-196).
Solar energy irradiating the Earth's surface exceeds human energy consumption by four orders of magnitude and the key to alleviating the global energy crisis lies in efficiently harnessing it. An ideal means of storing surplus energy from solar is to convert it to hydrogen using proton exchange membrane water electrolyzers, which are amenable to integration with solar devices due to their high performance under fluctuating power input. Water oxidation to molecular oxygen is the most energy intensive part of the water splitting process, limiting the overall efficiency of water splitting devices. Rutile Ruthenium Dioxide (RuO₂) is a gold standard catalyst for water oxidation in acidic solutions. It can also undergo fast surface redox reactions in the electrochemically stable potential window of water, making it an ideal material for electrochemical capacitors that can charge and discharge in a much shorter time scale than batteries.
Understanding the interaction of RuO₂ with water can provide critical insights into the physical origin of its fascinating electrochemical properties and the active site(s) for water oxidation. Herein, we use ambient pressure X-ray photoelectron spectroscopy, in situ surface diffraction, surface enhanced infrared spectroscopy, electrochemical mass spectrometry and ab initio density functional theory calculations on well-defined RuO₂ surfaces to understand the mechanism and kinetics of the water oxidation reaction. We elucidate how different surface terminations can alter the binding energetics of oxygenated intermediates by changing the local environment of surface ruthenium and oxygen atoms.
Going beyond the conventional approach of changing the surface chemistry to tune the energetics of active sites, we also consider how changing the nature of the electrolyte (pH, cations in the supporting electrolyte) can modify the interfacial dynamics and increase electrocatalytic activity. Finally, we consider the use of Li-rich layered ruthenium oxides as a means to access bulk ruthenium redox for electrocatalytic reactions. Thus, through the use of surface-sensitive in operando techniques, this thesis identifies the active sites and reaction mechanism for oxygen electrocatalysis and demonstrates how catalyst surface structure and interfacial water structure can be altered to improve kinetics for next-generation water oxidation catalysts.
by Reshma R. Rao.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Mechanical Engineering
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Cherbonnel, Angéline. "Study of the mechanism of action of metallic active oxygen barriers applied in polymers for food and drinks preservation." Thesis, Strasbourg, 2018. http://www.theses.fr/2018STRAF017.
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Les plastiques sont devenus les matériaux les plus utilisés pour la préservation de denrées alimentaires. Malgré leurs nombreux avantages (transparence, prix, modularité, propriété barrière aux gaz), leur imperméabilité à l’oxygène doit être sans cesse améliorée afin d’éviter aux denrées de subir diverses réactions d’oxydation et ainsi prolonger leurs durées de conservation. Pour cela, une solution envisageable consiste à combiner à des polymères, des catalyseurs métalliques pour piéger l’oxygène. Cette possibilité a été étudiée dans cette thèse. Après un premier chapitre introductif, le deuxième décrit les propriétés physico-chimiques des différents catalyseurs métalliques sélectionnés (stabilité, constantes de protonation, constante de complexation envers le cobalt(II) et le manganèse (II), capacité d’oxygénation, électrochimie). Le troisième chapitre est consacré à leur utilisation en tant qu’oxydant métallique de substrats organiques. Enfin le quatrième et dernier chapitre présente une étude à l’état solide de l’oxydation de polymères en présence de catalyseurs métalliques. Une large part de ce dernier chapitre a été consacrée à la caractérisation des produits d’oxydationPlastics are becoming the most used material for food and drinks preservation. Despite their numerous advantages (transparency, price, modularity, gas barrier property), their oxygen barrier properties have to be improved to avoid hazardous oxidation reactions to foods and drinks and so to increase their shelf-life. One alternative to solve this problem is to combine polymers and metal catalysts to scavenge oxygen. This possible strategy was investigated during this Ph.D. project. After a first introductive chapter, the second depicts the physico-chemical properties of selected metal catalysts (stability, protonation constants, complexation constants towards cobalt(II) and manganese(II), oxygenation capacity, electrochemistry). The third chapter is devoted to their use as powerful oxidant of organic substrate. Finally, the last chapter is dedicated to a solid-state study of polymer oxidation in the presence of metal catalysts. A large part of this last chapter has been devoted to the thorough elucidation of the nature/structure of the oxidized product(s)
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Dang, Anh X. H. "Theoretical and experimental development of an active acceleration compensation platform manipulator for transport of delicate objects." Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/17277.
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Ehrhardt, Katharina. "Redox-active 3-benzyl-menadiones as new antimalarial agents : studies on structure-activity relationships, antiparasitic potency and mechanism of action." Thesis, Strasbourg, 2014. http://www.theses.fr/2014STRAF020.
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Le paludisme reste une des maladies infectieuses les plus importantes au monde. Récemment, le laboratoire de Dr E. Davioud-Charvet a conçu des 3-Benzyl-Ménadiones substituées (benzylMD) comme agents antipaludiques prometteurs. Les études sur le mode d'action ont mis en évidenceque ces molecules déstabilisent l'équilibre redox des érythrocytes infectés en agissant comme agent catalytique redox (redox-Cycler), une stratégie prometteur pour le développement de nouveaux agents antipaludiques. Le travail de thèse présenté a caractérisé l'activité in vitro et le mécanisme d'action de tête de série, la 3-[4-(trifluorométhyl)-Benzyl]-Ménadione 1c, ce qui représente une partie principale du développement des benzylMDs. Une deuxième partie explorait les relations structure-Activité de benzylMD dérivés. Dans l'ensemble, les résultats démontrent l'activité in vitro très prometteuse de la benzylMD 1 cet soutiennent l'amélioration de benzylMDs comme nouveaux candidats-Médicaments antipaludiquesMalaria is still one of the most important infectious diseases worldwide. Previously, the laboratory of Dr. E. Davioud-Charvet presented the chemical design of very promising antimalarial agents, 3-[substituted-Benzyl]-Menadiones (benzylMD). Studies on the mode of action evidenced that these agents disturb the redox balance of the parasitized erythrocyte by acting as redox-Cyclers - a promising strategy for the development of new antimalarial agents. The presented PhD work characterized the in vitro potency and the mechanism of action of the lead agent, the 3-[4-(trifluoromethyl)benzyl]-Menadione 1 c, which represents an essential part of the lead optimization stage of the benzylMD drug development process. A second part of this work focused on the structure-Activity relationships benzylMD derivatives. Overall, the presented findings demonstrate the promising in vitro potency of lead benzylMD 1c and highly support the further development of benzylMDs as antimalarial drug candidates
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Balasubramanian, Krithika. "ATP hydrolysis in Rho: Identifying active site residues and their roles." Diss., Temple University Libraries, 2010. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/80319.
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BiochemistryPh.D.
Escherichia coli transcription termination factor Rho is a hexameric RNA/DNA helicase that terminates transcription using energy derived from the hydrolysis of ATP. The ATP binding sites of Rho are located at the interfaces of adjoining subunit Cterminal domains and have the Walker A and B motifs, characteristic of many ATPases (Skordalakes & Berger, 2003; Richardson 2002). Available Rho crystal structures capture the protein with its active site in an open configuration that must close to permit ATP hydrolysis. Because of this, the identities of active site residues predicted to mediate ATP hydrolysis are uncertain. To determine which amino acids activate water, stabilize transition state, sense the γ- phosphoryl group, and coordinate the magnesium ion of MgATP, we have carried out site-specific mutagenesis on candidate residues which are conserved across bacterial species, and characterized the relevant properties of the mutant proteins. The residues chosen were E211 as the water activator, R212 as the γ sensor, R366 as the arginine finger, and D265 as the residue that coordinates Mg2+. Each mutant protein was investigated for its ability to oligomerize as hexamers, assayed for ATPase activity, ATP and RNA binding, and pre-steady-state kinetics. The results show that the mutant proteins form hexamers similarly as to wild type Rho. The RhoE211 mutants display at least a 200-fold lower activity as ATPases, bind both ATP and RNA with similar affinities as the wild type protein, and display no burst in pre-steady-state kinetics. RhoR212A protein has 20-fold lower activity as an ATPase compared to wild type Rho, binds ATP with at least a 50-fold weaker affinity, and RNA with a 2-fold higher KD compared to wild type Rho. RhoR366A functions as an ATPase with 50-fold lower activity, binds RNA with similar affinity as wild type Rho and binds ATP with a 5- fold weaker affinity. RhoD265N displays 150-fold lower ATPase activity compared to the wild type enzyme, binds ATP with a 10-fold weaker affinity, and binds RNA with similar affinity as wild type Rho. Pre-steady-state kinetics studies indicate that the mutant proteins investigated show no burst kinetics, indicating a failure or a significantly slower rate of the hydrolysis (chemistry) step. It is possible that the rate-limiting step is the chemistry step in these mutant proteins, contrary to the wild type protein where the chemistry step is much faster (300/s). Together, the results obtained are consistent with the proposed roles for these residues: E211 is involved in activating a water molecule, R212 functions as the γ sensor, R366 functions as the arginine finger and D265 is involved in coordination of the Mg2+ ion. This study has elucidated the mechanism of ATP hydrolysis, by determining some of the key residues involved in the hydrolysis reaction. This study is only a part of the characterization of the active site residues. There might be other residues involved in one or all of the functions proposed. Utilizing the findings from this study, other experiments and models can be implemented to understand how Rho hydrolyzes ATP and utilizes the energy to move along the RNA molecule and functions as a helicase.
Temple University--Theses
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Ravi, Ajaay. "Run-Time Active Leakage Control Mechanism based on a Light Threshold Voltage Hopping Technique (LITHE)." University of Cincinnati / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1302550444.
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Li, Ting. "Study on the immunomodulatory property and mechanism of active compounds derived from chinese medicinal herbs." HKBU Institutional Repository, 2010. https://repository.hkbu.edu.hk/etd_ra/1400.
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Grunkemeyer, Timothy John. "Exploring the Mechanism of Paraoxonase-1: Comparative and Combinatorial Probing ofthe Six-bladed β-propeller Hydrolase Active Sites." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1544445404861907.
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Kim, Hyun Jung. "Oxidation mechanism of riboflavin destruction and antioxidant mechanism of tocotrienols." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1184681773.
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Quaye, Osbourne. "On the Preorganization of the Active Site of Choline Oxidase for Hydride Transfer and Tunneling Mechanism." Digital Archive @ GSU, 2009. http://digitalarchive.gsu.edu/chemistry_diss/46.
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Choline oxidase catalyzes the two-step oxidation of choline to glycine betaine, one of limited osmoprotectants, with the formation of betaine aldehyde as an enzyme bound intermediate. Glycine betaine accumulates in the cytoplasm of plants and bacteria as a defensive mechanism to withstand hyperosmolarity and elevated temperatures. This makes the genetic engineering of relevant plants which lack the property of salt accumulation of economic interest, and the biosynthetic pathway of the osmolyte a potential drug target in microbial infections. The reaction of alcohol oxidation occurs via a hydride ion tunneling transfer from the substrate donor to a flavin acceptor within a highly preorganized active site environment in which choline and FAD are in a rigidly close proximity. In this dissertation, factors contributing to the enzyme-substrate preorganization which is required for the hydride ion tunneling reaction mechanism in choline oxidase have been investigated. Crystallographic studies of wild-type choline oxidase revealed a covalent linkage between C8M atom of the FAD isoalloxazine ring and the N(3) atom of the side chain of a histidine at position 99, and a solvent excluded cavity in the substrate binding domain containing glutamic acid at position 312 as the only negatively charged amino acid residue in the active site of the enzyme. The role of the histidine residue and the contribution of the 8á-N(3)-histidyl covalent linkage of the flavin cofactor to the reaction of alcohol oxidation was investigated in a variant form of choline oxidase in which the histidine residue was replaced with an asparagine. The role of the glutamate residue and the importance of the spatial location of the negative charge at position 312 was investigated in variant forms of choline oxidase in which the negatively charged residue was replaced with glutamine and aspartate. Mechanistic data obtained for the variant enzymes and their comparison to previous data obtained for wild-type choline oxidase are consistent with the residues at positions 99 and 312 being important for relative positioning of the hydride ion donor and acceptor. The residues are important for the enzyme-substrate preorganization that is required for the hydride tunneling reaction in choline oxidase.
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Zghibeh, Chaza. "The active site and mechanism of the class II fructose-1,6-bisphosphate aldolase of Escherichia coli." Thesis, University of Leeds, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.397438.
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Pillay, Ravi. "Value of contracting as an active purchasing mechanism of healthcare services : a South African case study." Master's thesis, University of Cape Town, 2015. http://hdl.handle.net/11427/15681.
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Strategic purchasing is a way of ensuring that the healthcare interventions that are provided, improves the health systems responsiveness. Contracting for health services, as a component of strategic purchasing, has been promoted as an important mechanism to improve the efficiency of resource use, quality in health care service provision and increase accountability, all of which contribute towards improving health system performance. Over the past two decades, many countries have adopted contracting as a mechanism to positively impact the performance of the health system. However, despite the increasing interest and experimentation with contracting as a way to improve health systems, the results remain controversial. Within South Africa's private healthcare market, medical schemes represent the largest source of private healthcare funding. Given the rate of increase of medical inflation within the South African private healthcare market, there is an absolute need for medical schemes to become more strategic in their purchasing decisions. This dissertation aims to address the gaps identified in the contracting literature by providing empirical evidence from an evaluation of a contractual agreement between a healthcare financing agency, medical scheme, and a managed care organisation in the private health sector in South Africa for the provision of a back rehabilitation programme to reduce the cost of back surgeries. The dissertation also attempts to formulate key learnings that will inform future policies regarding contracting for healthcare services within the private and public health sector in South Africa.
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Gupta, Amit Jean Verfasser], and Franz-Ulrich [Akademischer Betreuer] [Hartl. "A single molecule study of the GroEL active cage mechanism / Amit Jean Gupta. Betreuer: Franz-Ulrich Hartl." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2015. http://d-nb.info/1080122311/34.
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Ma, Xin Bo. "Characteristic analysis, regulating mechanism modeling and advanced control on hydraulic adjustable dampers for automotive semi-active suspensions." Thesis, University of Macau, 2018. http://umaclib3.umac.mo/record=b3951593.
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LENTINI, LUIGI. "Design, Test and Identification of an Active Aerostatic Thrust Bearing with a Compliant Mechanism and Piezo Actuator." Doctoral thesis, Politecnico di Torino, 2017. http://hdl.handle.net/11583/2670377.
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Aerostatic thrust bearings are currently used in applications where high accuracy is required, e.g., in machine tools, measuring instruments, manufacturing and medical equipment. Their appeal is due to the absence of contact between their moving and stationary parts, which ensures relative motions characterised by low friction, low wear and limited heat generation.
However, in some operating conditions, these systems may present low specific stiffness and be subject to instability. This thesis presents the design, modelling and testing of an actively compensated aerostatic thrust bearing. A support compensation strategy has been adopted as an active compensation method. The support compensation method consists in integrating conventional passive bearings with piezoelectric actuators which make it possible to compensate for variations in the bearing position. This compensation is obtained by exploiting changes in the stroke of the actuators and makes it possible to enhance both the static and the dynamic bearing performance. This integration has been possible thanks to the presence of a compliant mechanism which gives a directional guide to and opportunely pre-loads the actuator. Preliminary experimental tests have consisted in a "classical" static characterisation of the bearing where the load, air consumption and stiffness of the bearing have been obtained. Moreover, concerning the design of bearings, their dynamic performance is becoming a crucial aspect, due to the continual demand for higher performance from today’s applications. For this reason, a dynamic linear time-invariant model of the system has been proposed. Here, the linear approximation is made by presuming that around each operating condition the system motion may be considered as an equilibrium state, and the bearing is modelled as a SDOF system because of the physical constraints imposed. The model validation has been performed with the aid of step force and tracking tests. Step force tests have been firstly carried out to dynamically characterise the bearing in its passive configuration (without the automatic control) by utilising and comparing the Logarithmic Decrement and the Half Power Bandwidth methods. Secondly, step force tests have also been used to assess the capacity of compensation of the active bearing (with the automatic control). On the other hand, tracking tests have been performed to verify the positional accuracy of the bearing and assess its bandwidth. Results demonstrate both the effectiveness of the prototype and the sound of the adopted mathematical model.
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Uzdavinys, Povilas. "Establishing the molecular mechanism of sodium/proton exchangers." Doctoral thesis, Stockholms universitet, Institutionen för biokemi och biofysik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-147333.
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Sodium/proton exchangers are ubiquitous secondary active transporters that can be found in all kingdoms of life. These proteins facilitate the transport of protons in exchange for sodium ions to help regulate internal pH, sodium levels, and cell volume. Na+/H+ exchangers belong to the SLC9 family and are involved in many physiological processes including cell proliferation, cell migration and vesicle trafficking. Dysfunction of these proteins has been linked to physiological disorders, such as hypertension, heart failure, epilepsy and diabetes. The goal of my thesis is to establish the molecular basis of ion exchange in Na+/H+ exchangers. By establishing how they bind and catalyse the movement of ions across the membrane, we hope we can better understand their role in human physiology. In my thesis, I will first present an overview of Na+/H+ exchangers and their molecular mechanism of ion translocation as was currently understood by structural and functional studies when I started my PhD studies. I will outline our important contributions to this field, which were to (i) obtain the first atomic structures of the same Na+/H+ exchanger (NapA) in two major alternating conformations, (ii) show how a transmembrane embedded lysine residue is essential for carrying out electrogenic transport, and (iii) isolate and recorde the first kinetic data of a mammalian Na+/H+ exchanger (NHA2) in an isolated liposome reconstitution system.
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Kuriger, Rex J. "Kinematics, statics, and dexterity of planar active scaffolding structures." Ohio : Ohio University, 1997. http://www.ohiolink.edu/etd/view.cgi?ohiou1177095329.
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Ehrhardt, Katharina [Verfasser], and Michael [Akademischer Betreuer] Lanzer. "Redox-active 3-benzyl-menadiones as new antimalarial agents: Studies on structure-activity relationships, antiparasitic potency and mechanism of action / Katharina Ehrhardt ; Betreuer: Michael Lanzer." Heidelberg : Universitätsbibliothek Heidelberg, 2017. http://d-nb.info/1178007898/34.
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Voegele, Alexis. "Study of the translocation mechanism of the cyaa toxin from bordetella pertussis." Thesis, Université de Paris (2019-....), 2019. https://theses.md.univ-paris-diderot.fr/VOEGELE_Alexis_va.pdf.
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La toxine adénylcyclase (CyaA) est un des principaux facteurs de virulence produite par Bordetella pertussis, l’agent de la coqueluche. CyaA a l’unique capacité de transloquer son domaine catalytique directement à travers la membrane plasmique. Puis le domaine catalytique lie la calmoduline (CaM) pour produire de grandes quantités d’AMPc, conduisant à l’intoxication de la cellule. Bien que plusieurs modèles aient été proposés, le mécanisme moléculaire et les forces impliquées dans la translocation de CyaA restent peu connus. Un gradient de calcium, un potentiel de membrane et des acylations post-traductionnelles sont requis pour la translocation de CyaA. Pendant mon doctorat, je me suis principalement intéressé au processus de translocation. Il a été montré précédemment que la suppression de la région de translocation abolit le passage du domaine catalytique. Dans cette région, le peptide P454 (résidus 454 à 484 de CyaA) a été identifié et montre des propriétés membranaires, i.e interaction avec la membrane, repliement en hélice α au contact de la membrane et perméabilisation membranaire. Nous avons étudié le rôle de P454 dans le processus de translocation. Nous avons observé que des lipides fluides et chargés négativement favorisent l’insertion de P454 dans les membranes. Le peptide possède deux arginines qui sont impliquées dans ses activités membranaires. P454 possède aussi la capacité de transloquer à travers la membrane et de former un complexe avec la CaM. Nous avons identifié plusieurs résidus de P454 impliqués dans la liaison à la membrane et la CaM. Dans le contexte de la toxine entière, ces résidus sont essentiels pour la translocation du domaine catalytique et la production d’AMPc. On propose un modèle de translocation dans lequel le segment P454 de la région de translocation déstabilise la membrane, favorisant sa translocation. Dans le cytosol, le segment P454 est piégé par la CaM et le complexe pourrait agir comme une force tirant le domaine catalytique à travers la membrane. Nous avons aussi montré que la liaison à la CaM du peptide liant la CaM dans le domaine catalytique induit des effets allostériques qui stabilisent le site catalytique, permettant la catalyse rapide d’ATP en AMPc. La pertinence de ces résultats pour la translocation et l’activation de CyaA sont discutéesThe adenylate cyclase toxin (CyaA) is one of the major virulence factor produced by Bordetella pertussis, the causative agent of whopping cough. CyaA has the unique capacity to translocate its catalytic domain directly across the plasma membrane. Then, the catalytic domain binds to calmodulin (CaM) to produce high levels of cAMP, leading to cell intoxication. Although several models have been proposed, the molecular mechanism and the forces involved in the translocation of CyaA remain elusive. The calcium gradient, the membrane potential across the plasma membrane and post-translational acylation are required for an efficient CyaA translocation. During my PhD, I mainly investigated the translocation process. It has been previously shown that deletion of the translocation region abolishes the delivery of the catalytic domain into the cytosol of target cells. In this region, the peptide P454 (residues 454 to 484 of CyaA) was identified and exhibits membrane-active properties related to antimicrobial peptides, i.e membrane interaction, α-helical folding upon membrane insertion and membrane permeabilization. We have investigated the role of P454 on the translocation process. We observed that negatively charged and fluidic membrane favor P454 membrane insertion. The peptide contains two arginine residues that are critically involved in its membrane-active properties. We further identified that P454 exhibits the intrinsic propensity to translocate across lipid bilayers and forms a stable complex with CaM. We identified several residues from P454 involved in both membrane interaction and CaM binding. We showed in the context of the full-length CyaA toxin that these residues are essential for the efficient translocation of the catalytic domain into the cell and production of cAMP. We propose a translocation model in which the membrane-active P454 segment from the translocation region destabilizes the membrane, favoring its translocation. In the cytosol, the P454 segment is trapped by CaM and the formation of the complex may act as a driving force pulling the catalytic domain across the plasma membrane. We further showed that CaM binding to the main CaM-binding site in the catalytic domain induces local and long-range allosteric effects that stabilize the enzymatic site, allowing fast ATP catalysis to cAMP, leading to host subversion. The relevance of these results for the translocation and activation of CyaA are discussed
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Foerster, Stefanie Anette Erica. "EPR spectroscopic investigation of the active site of [NiFe]-hydrogenase a contribution to the elucidation of the reaction mechanism /." [S.l.] : [s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=968375529.
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Kinnunen, Hanne. "Active sites, agglomerates or increased cohesion? : investigations into the mechanism of how lactose fines improve dry powder inhaler performance." Thesis, University of Bath, 2012. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.564006.
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Dry powder inhalers (DPIs) are used for delivering drugs to the airways. In addition to the drug, the formulations often contain a coarse carrier, most commonly alpha lactose monohydrate. The presence of fine lactose particles in the formulation is known to improve the formulation performance. The active site, drug-fines agglomeration and increased cohesion theories have been suggested to explain improved DPI performance upon addition of fine excipient particles. This project aimed to investigate the validity of those theories. The viability of the active sites theory in explaining the improved DPI performance was investigated by studying the impact of loaded drug dose on the in vitro performance for formulation series prepared with coarse carriers with different surface characteristics. The formulations prepared with the rougher lactose carrier were seen to outperform the formulations prepared with the smoother carrier at all drug concentrations. These findings were concluded to be non-compatible with the active sites theory. The impact of addition of lactose fines with different size distributions on powder flow and fluidisation properties and in vitro performance was studied. Powder cohesion increased independent of size distribution of the fines, but did not necessarily correspond to improved performance. Therefore, the increased cohesion theory was concluded not to be the sole explanation for the improvement in DPI performance in the presence of lactose fines. Instead, the increase in performance could be preliminarily attributed to the formation of agglomerated systems. The formation and co-deposition of drug-fines agglomerates, and consequential improvement in the DPI performance was proved using morphologically directed Raman spectroscopy. The project also aimed to develop a universal model for predicting DPI performance based on the lactose properties for a wide range of carriers with different properties. No simple linear correlations between any the lactose properties and the final DPI performance were found. Therefore no single parameter can be used as a universal predictor for DPI performance. To establish more complex relationships, artificial neural networks were used for modelling the importance of different lactose properties in determining DPI performance. The proportion of fine lactose particles (<4.5 μm) was identified as the most important parameter. However, this parameter was capable of explaining only approximately half of the variation seen in the formulation performance. The current study showed that to obtain more accurate predictions for the purposes of quality-by-design approach, also other lactose properties need to be characterised.
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Wang, Jianren. "Nanostructured Redox-Active Mesoporous Silica Films Based on An Electron-Hopping Mechanism : Charge Transfer Behaviors And Energy Storage Potentials." Electronic Thesis or Diss., Université de Lorraine, 2020. http://www.theses.fr/2020LORR0216.
Full textAbstract:
Un nouveau type de matériaux de stockage d'énergie à base de silice fonctionnant avec un mécanisme de saut d'électrons a été préparé en combinant une méthode d'auto-assemblage électrochimique (EASA) et une réaction de clic d'azide-alcyne catalysée par le cuivre (CuAAC). Les centres actifs redox (molécules de ferrocène ou de cobaltocénium) répartis à la surface du film de silice peuvent directement commuter les électrons par le biais du processus de saut d'électrons. Les résultats démontrent que ce mécanisme de transfert de charge est capable de fournir un taux de transfert d'électrons rapide même sur le substrat de silice isolant, ce qui se traduit par une performance de taux supérieure par rapport aux matériaux faradiques traditionnels. La haute densité des molécules redox et la voie de diffusion des contre-ions lisses ont été identifiées comme jouant un rôle essentiel pour assurer le processus de saut d'électrons rapide. En outre, l'assemblage à grande échelle du système de saut d'électrons a été réalisé en générant le film de silice fonctionnalisé au ferrocène sur une électrode autoportante en mousse de graphène, présentant une densité de capacité 100 fois plus élevée que celle générée sur une électrode ITO, tout en maintenant la performance de taux élevé. Enfin, une tentative a été faite pour assembler la silice fonctionnalisée au ferrocène sur un dispositif planaire flexible, et les résultats préliminaires ont prouvé la faisabilité de l'idée que nous proposons. Globalement, dans cette thèse, l'étude systématique du potentiel du processus de saut d'électrons dans le domaine du stockage de l'énergie, qui pourrait ouvrir une nouvelle voie pour la construction de matériaux de stockage de l'énergieA new type of silica-based energy storage materials operating with electron-hopping mechanism has been prepared by combining electrochemically-induced self-assembly method (EASA) and a copper-catalyzed azide-alkyne click (CuAAC) reaction. The redox active centers (ferrocene or cobaltocenium molecules) distributed on the surface of the silica film can directly commute electrons via the electron-hopping process. The results demonstrate this charge transfer mechanism is able to deliver a fast electron transfer rate even on the insulating silica substrate, resulting in a superior rate performance in comparison to the traditional faradic materials. The high density of redox molecules and the smooth counter ions diffusion pathway have been identified playing a pivotal role to ensure the fast electron-hopping process. Besides, the large-scale assembly of the electron-hopping system has been achieved by further generating the ferrocene functionalized silica film on a free-standing graphene foam electrode, exhibiting a 100-times higher capacity density, in comparison to that generating on ITO electrode, while maintaining the high rate performance. Finally, an attempt has been tried to assemble the graphene-supported ferrocene-functionalized silica into a flexible planar device, and the preliminary results has proved the feasibility of our proposed idea. Overall, in this thesis, the systematical study for the potential of the electron-hopping process in the energy storage field, which may pave a new way for the construction of energy storage materials
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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.
Full text
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Fite, Alemu. "The antimicrobial interaction of acidified nitrite with other physiologically active compounds (PAC), the potential host defence mechanism of dietary nitrate." Thesis, University of Aberdeen, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369736.
Full textAbstract:
Transfer of nitrite at salivary concentrations enhance the antimicrobial activity of stomach acid against food borne pathogens and may be involved in the host defence of humans and animals. Studies from experimental animals, microbial tests, human ex vivo and in vivo investigations support the hypothesis that dietary nitrate is beneficial for health. The positive findings that acidified nitrite is antimicrobial at the acidic conditions of the stomach is viewed in conjunction with the potential production of nitrogen, intermediates such as NO, a molecule of significant importance in science. This led to propose that acidified nitrite can kill or inhibit enteric bacterial species that are associated with gastrointestinal diseases and could modify the antimicrobial effects of acidified nitrite by other physiologically active compounds. By a systematic exposure of selected enteric bacterial species to acidified nitrite and other PAC alone or in combinations, it was found that acidified nitrite, especially at low pH values was inhibitory to bacterial growth or killer of bacterial cells. Glutathione and vitamin C inhibited the antimicrobial effects of nitrite whilst thiocyanate and iodide enhanced it. Thiocyanate produced an effective antimicrobial activity that was comparable to nitrite but there was no synergistic antimicrobial interaction between acidified nitrite and thiocyanate. The addition of thiocyanate enhanced the antimicrobial effects of cow's milk in a pH-dependent activity. The overall results reported here suggested to conclude that dietary factors found in fruits and vegetables are not only beneficial in the supply of vitamins, antioxidants and enzymes but also antimicrobial agents that are worth investigation for therapeutic purposes.
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Hagras, Muhammad A. "Overexpression of active AKT3 induces differential binding of coregulator proteins to the estrogen receptor as a possible mechanism of Tamoxifen resistance." Scholarly Commons, 2008. https://scholarlycommons.pacific.edu/uop_etds/688.
Full textAbstract:
Tamoxifen is an effective anti-estrogen for treatment of women with hormonedependent breast cancer but acquired drug resistance limits its therapeutic benefit. We have previously reported that expression of active Akt3 in MCF-7 breast cancer cells results in estrogen-independent tumors that are actually stimulated to grow after tamoxifen treatment. We hypothesize that this tamoxifen resistance may be attributed to binding of different co-regulator proteins and/or different binding affinity of these proteins to the estrogen receptor in M CF-7 cells overexpressing active Akt3 as compared to parental MCF-7 cells. We have immuno-precipitated the estrogen receptor along with bound co-regulator proteins in both cells lines after tamoxifen, estradiol, or vehicle treatment. After 2-D gel electrophoresis separation of these immuno-precipitated proteins and comparing them using PDQuest 2-D analysis software, we identified protein spots that were statistically different under the treatment conditions between the two cell lines. The isolated protein spots were subjected to MALDI-TOF mass spectrometry. By searching protein databases through the MASCOT website for protein identification, we have identified estrogen receptor co-regulator proteins that may play a potential role in tamoxifen resistance. Current studies are focused on addressing the role of differential protein binding as a possible mechanism of tamoxifen resistance in Akt3 over-expressing breast cancer cells.
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Gasmi, Hanane. "Microparticules à libération controlée : impact du gonflement sur la cinétique de libération de substance active." Thesis, Lille 2, 2015. http://www.theses.fr/2015LIL2S057/document.
Full textAbstract:
Les études de libération de substance active à partir de système polymériques tels que des microparticules à base d’acide poly(lactique-co-glycolique) (PLGA) ont été largement explorées au cours de ces dernières décennies . L’objectif principal de ce travail consiste à mieux comprendre les mécanismes de transport de masse contrôlant la libération de substance active à partir des microparticules de PLGA. Un nouvel aperçu devait être acquis sur la base de suivi expérimental de la cinétique de gonflement de microparticules. Dans un premier temps, des microparticules à base de PLGA chargées de différents types de substances actives (acide, base et neutre), tels que kétoprofen, prilocaine base libre et dexamethasone ont été préparées par simple émulsion (huile dans eau) en utilisant une méthode d'extraction/évaporation du solvant. Les microparticules obtenues avaient des taux d’efficacité d’encapsulation qui sont variables selon la substance active utilisée. Une caractérisation des propriétés clés des microparticules obtenues a été réalisée en utilisant différentes techniques (microscopie optique, microscopie électronique). La chromatographie par permeation de gel a été utilisé pour déterminer le poids moléculaire du PLGA après exposition des microparticules au milieu de libération à différents temps afin d’évaluer la cinétique de dégradation du polymère. La diffraction des rayons X et la calorimétrie différentielle à balayage étaient utilisés pour étudier l’état physique du polymère, de la substance active pure ainsi que les microparticules chargées en substance active. Les études de libération ont montré deux types de profils de libération : un profil tri-phasique et un profil plus ou moins mono-phasique. Le profil tri-phasique observé est constitué de trois phases : une phase de libération initiale rapide suivie d’une libération constante qui est suivie ; à son tour ; par une seconde phase de libération rapide. En revanche, les différentes phases étaient difficilement distinguées pour le deuxième type de profil obtenu, du fait de la libération rapide de substance active ce qui permet de dire que les profils obtenus étaient plus ou moins mono-phasique. L’élucidation des mécanismes de libération de substance active était basée sur le suivi expérimental de la cinétique de gonflement des microparticules. Comme pour les cinétiques de libération obtenues à partir des microparticules à base de PLGA, différentes phases peuvent être distinguées pour les profils de gonflement. Les transitions d’une phase à une autre semblent s’accorder entre le profil de libération et celui du gonflement. Ainsi, le gonflement des microparticules pourrait contribuer au contrôle de la libération de la substance active à partir des microparticules à base de PLGAThe drug release studies from polymeric system such as Poly(lactic-co-glycolic) acid (PLGA)-based microparticles have been widely investigated during recent decades. The main objective of this work is to better understand the mass transport mechanisms controlling the drug release kinetics from PLGA microparticles. New insight was to be gained based on the experimental monitoring of the swelling kinetics of single microparticle. Initially, PLGA microparticles containing different type of drugs (acidic, basic and neutral), such as ketoprofen, prilocaine free base and dexamethasone were prepared using simple oil in water emulsion extraction/evaporation solvent technique. The characterization of the key properties of microparticles was performed using different techniques (optical microscopy, electron microscopy). The gel permeation chromatography was used to determine the molecular weight of PLGA following exposure of microparticles to the release medium at various times to assess the kinetic degradation of the polymer. The X-ray diffraction and differential scanning calorimetry were used to study the physical state of the polymer, drug and drug-loaded microparticles. Release studies have shown two types of release profiles: tri-phasic and more or less mono-phasic profile. The tri-phasic profile is composed of three phases: an initial rapid release phase followed by a constant release which is followed by a second phase of rapid release. In contrast, at the investigated higher initial drug loadings, different release phases could hardly be distinguished: The profiles were more or less mono-phasic. The elucidation of drug release mechanisms was based on the experimental results of the swelling kinetics of single microparticles. As for drug release, distinct phases can be distinguished for microparticles swelling. The transition from one phase to another seem to coincide for microparticle swelling and drug release. Thus also microparticle swelling might contribute to a significant extent to the control of drug release
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Adigun, Risikat Ajibola. "Insight into the Reactivity of Metastasis Inhibitor, Imidazolium trans-[tetrachloro (dimethyl sulfoxide)(imidazole)ruthenate(III)], with Biologically-active Thiols." PDXScholar, 2012. https://pdxscholar.library.pdx.edu/open_access_etds/378.
Full textAbstract:
Imidazolium trans-[tetrachloro (dimethyl sulfoxide)(imidazole)ruthenate(III)], NAMI-A, is an experimental metastasis inhibitor whose specific mechanism of activation and action remains to be elucidated. In the nucleophilic and reducing physiological environment; it is anticipated that the most relevant and available reductants upon introduction of NAMI-A as a therapeutic agent will be the biologically-relevant free thiols. The kinetics and mechanisms of interaction of NAMI-A with biologically-active thiols cysteamine, glutathione, cysteine and a popular chemoprotectant, 2-mercaptoethane sulfonate (MESNA) have been studied spectrophotometrically under physiologically-relevant conditions. The reactions are characterized by initial reduction of NAMI-A with simultaneous formation of dimeric thiol and subsequent ligand exchange with water to various degrees as evidenced by Electospray Ionization Mass Spectrometry. Stoichiometry of reactions shows that one molecule of NAMI-A reacted with one mole of thiol to form corresponding disulfide cystamine, dimeric MESNA, oxidized glutathione and cystine. Observed rate constants, ko, for the reaction of NAMI-A with cysteamine, MESNA, GSH and cysteine were deduced to be 6.85 + 0.3 x 10-1, 9.4 + 0.5 x 10-2 , 7.42 + 0.4 x 10-3 and 3.63 + 0.3 x 10-2 s-1 respectively. Activation parameters determined from Arrhenius plots are indicative of formation of associative intermediates prior to formation of products. A negative correlation was obtained from the Brønsted plot derived from observed rate constants and the pKa of the different thiols demonstrating significant contribution of thiolate species towards the rate. In conclusion, interactions of NAMI-A with biologically-active thiols are kinetically and thermodynamically favored and should play significant roles in in vivo metabolism of NAMI-A.
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Haidasz, Evan. "Synthesis, Kinetics, and Mechanism of Catalytically Active Aminic Radical-Trapping Antioxidants & Development of the Fluorometric and Spectrophotometric Tools Used in Their Analysis." Thesis, Université d'Ottawa / University of Ottawa, 2017. http://hdl.handle.net/10393/36077.
Full textAbstract:
Amine and nitroxide based radical-trapping antioxidants (RTAs) have long been known to display remarkable efficacy as inhibitors of hydrocarbon autoxidation. Their unique ability to catalytically trap the chain-carrying peroxyl radicals responsible for oxidative degradation of organic materials has led to their widespread use in petroleum-derived materials. While a great deal of research has been done to understand and expand upon this reactivity, little improvement in the chemistry behind diarylamine and nitroxide RTAs has emerged.
In recent years our group has established that heterocyclic analogues of phenolic and diarylaminic RTAs are more stable to one-electron oxidation than the equivalent phenyl derivatives. This has allowed substitution of these RTAs with strong electron donating groups without compromising their stability to oxidation, and has led to the development of some of the most effective RTAs ever reported – compounds which often have reactivities ca. 200-fold greater than the current industrial standards. Herein, we describe the development of novel fluorometric and spectrophotometric methods to measure the reactivities of these RTAs, which replace more traditional approaches that are often laborious and require highly specialised equipment. Co-autoxidations with the highly absorbent probes PBD-BODIPY and STY-BODIPY allow for rapid and convenient measurement of RTA activity under a wide variety of conditions by UV/Vis spectrophotometry. Similarly, the high temperature activity of these RTAs can be measured in heavy hydrocarbon autoxidations, where hydroperoxide formation is monitored through the use of a pro-fluorescent phosphine.
The key step in Korcek’s proposed diarylamine catalytic cycle has been studied and found to proceed through different mechanisms depending on the structure of the intermediate N,N-diarylalkoxyamine. While unactivated alkoxyamines widely react through N-O homolysis/disproportionation to regenerate the diarylamine RTA, activation of either the aryl or alkyl fragments allows regeneration through a more efficient, pericyclic retro-carbonyl-ene (RCE) reaction. Additionally, the mechanism behind the high temperature RTA activity of dialkylnitroxides – key intermediates in the activity of hindered amine light stabilizers (HALS) – has been evaluated and found to be dependent on in situ formation of carboxylic acids. Upon protonation by these acids, dialkylnitroxides become potent RTAs capable of trapping oxygen-centered radicals. The oxoammonium ions arising from this reaction then oxidize alkyl radicals competitively with O2 addition to regenerate the nitroxide.
Lastly, we have extended the strategy used for heterocyclic phenols and diarylamines to the development of highly reactive azaphenoxazine and azaphenothiazine RTAs. While synthesis of these compounds is complicated by the presence of a favorable smiles rearrangement, synthesis of the ‘correct’ isomers yields extremely potent RTAs, capable of trapping peroxyl radicals under diffusion control. Applying these compounds in both ambient and high temperature autoxidations reveals that they may be some of the most effective RTAs ever reported, outperforming even the most reactive of the heterocyclic diarylamines previously studied.
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Rosengard, Peninah S. 1970. "Relationship between measures related to the cochlear active mechanism and speech reception thresholds in backgrounds with and without spectral and/or temporal fluctuations." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/28598.
Full textAbstract:
Thesis (Ph. D.)--Harvard-MIT Division of Health Sciences and Technology, 2004.Includes bibliographical references (p. 191-203).
The importance of the cochlear active mechanism in the reception of speech in different types of noise was explored. The perceptual effects of loudness recruitment, a consequence of loss of the active mechanism, were assessed in simulated-loss listeners using a multiband expansion algorithm that models abnormal cochlear linearity. While this algorithm, which derives the expansion characteristic from absolute hearing thresholds, can accurately simulate the mean speech intelligibility results of hearing-impaired listeners, its ability to simulate the performance of individual listeners is limited. Given the relationship between loudness perception and the active mechanism, deriving the expansion characteristic from estimates of cochlear compression should provide a more accurate model of an individual listener's impairment. Towards this aim, the reliability of two psychoacoustic methods used to estimate the magnitude of compression (growth of masking and temporal masking) was assessed. Results suggest that growth of masking is a more reliable measure of compression in listeners with both normal and impaired hearing. The relationship between the compressive characteristics of the auditory system and speech perception in complex acoustic backgrounds was also evaluated. The operational status of the active mechanism was assessed behaviorally using three independently derived measures: (1) slope ratio of off- and on-frequency growth of masking functions, (2) equivalent rectangular bandwidth of auditory filters, and (3) masker-phase masking differences. These measures were correlated with speech reception thresholds (SRTs) in backgrounds with and without spectral and/or temporal-modulations. The relationship between slope ratios, filter bandwidths, and the maximum
(cont.) SRT difference (SRT in steady noise minus SRT in temporally modulated, spectral gap noise) was significant. These results indicate that the ability to take advantage of momentary fluctuations in the amplitude or frequency spectrum of background noise requires an intact active mechanism. The speech reception performance of two hearing-impaired listeners was modeled using a customized version of the expansion algorithm. The algorithm was customized to an individual's impairment based on psychoacoustic measures used to evaluate the integrity of the active mechanism. The maximum SRT difference in the simulated-loss listeners more closely matched the results of their hearing-impaired counterparts, compared to SRTs measured using the original algorithm. These results provide further evidence of the importance of the active mechanism to the perception of speech in modulated noise.
by Peninah S. Rosengard.
Ph.D.
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林季儀. "A study of Mechanism Active Air Absorber." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/17384603496446208354.
Full textAbstract:
碩士建國科技大學
機械工程系暨製造科技研究所
98
High-performance cushioning device is a dispensable element for high speed and low frequency vibration of automation equipment. The purpose of the study is to design an Absorber stop device with wide applicability and good cushioning properties. In this paper, we present an 8-linkage mechanism of indirect serial type and have it serially connected. We make use of the pneumatic cylinder, reducing valve, relief valve, throttle valve, quick exhaust valve and solenoid valve to act in concert with sensors, the basic pressure and electrical control element, to obtain a control circuit for the pressure Absorber device. This will be the design and production of an adjustable and active pressure Absorber device that is capable of reducing Absorber energy and with diversified performance curves.
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Chuang, Fang-sheng, and 莊芳昇. "The Active Defense Mechanism of Internet Worm." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/41636392178231267421.
Full textAbstract:
碩士樹德科技大學
資訊管理研究所
94
With the popularization and the complexity of the Internet that connects tens of millions of computers, the Internet worms are easy to increase faster, hide longer incubation period longer, and spread wider. The damages caused by the Internet worms were so substantial that they become the primary issue in the study of network safety. The Internet worms become more aggressive. They used to spread via Email or Windows Network and caused minor damages. But now, they can even attack the operating system loopholes and application software with DDoS. Facing the mutating network worms, the traditional passive protection techniques that deployed on the network border independently become obsolete because they cannot work with each other. The purpose of the study is to develop a cooperatively Internet worm’s detective and defense mechanism that based on the analysis of Netflow and Syslog. Whenever the Internet worms attack, the system can detect and then activate the defense mechanism that corporate with different defensive techniques to minimize the damages.
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Contini, C., Maria G. Katsikogianni, F. T. O'Neill, M. O'Sullivan, D. P. Dowling, and F. J. Monahan. "Mechanism of action of an antioxidant active packaging prepared with Citrus extract." 2014. http://hdl.handle.net/10454/11500.
Full textAbstract:
yesActive packaging consisting of polyethylene terephthalate (PET) trays coated with a Citrus extract, without and with plasma pre-treatment, can reduce lipid oxidation in cooked meat. The mechanism of action of the packaging was investigated by quantifying the extent of transfer of antioxidant components from the active packaging into cooked turkey meat. Kinetic studies revealed the affinity for water of phenolic compounds and carboxylic acids in the Citrus extract, suggesting their diffusion into the water phase of the meat facilitated their antioxidant effect. Analysis by high-performance liquid chromatography permitted the identification of carboxylic acids and flavanones as major components of the extract. Their quantification in meat after contact with the trays revealed a release of 100% of the total coated amount for citric acid, 30% for salicylic acid, 75% for naringin and 58% for neohesperidin, supporting the release of these components into cooked meat as a mechanism of action of the antioxidant active packaging.
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Chen, J. L., and 陳俊良. "Active Control System by High Pressure Servo-mechanism." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/01735517052111720431.
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Shian, Chen Jr, and 陳智賢. "ARMS:A Rule Conflict Resolution Mechanism For Active Database System." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/33612987786260829281.
Full textAbstract:
碩士靜宜大學
資訊管理學系
88
The purpose of this study is to research on conflict resolution for active rules in Active Database Management System (ADMS). ADMS is equipped with supervision system and under some special conditions, database system can respond actively by making use of relative operation. The basic core of active database is active rule. Active rule is a principle of “Event-Condition-Action”. When a data transaction actuates more than one rule, those rules will be collected as one conflict set. How to select the rules from the conflict set to be executed of the rule is called as conflict resolution. We proposed ARMS(Active Rule Management System): rule conflict resolution mechanism for active database system. In the conflict set, binary relationship between any two rules can be “tight conflict” or “loose conflict”. The rules that are tight conflict each other will be collected in a “tight conflict subset”. By such a way, the conflict set can be composed of one or several “tight conflict subsets”. And, these tight conflict subsets can be processed in parallel. In each tight conflict subset, the execution order for rules will be decided by default priority and user-defined priority. However, according to executive order to assess on “condition” rule, if the “condition” is true, then rule “action” shall be executed continuously to achieve every rule of each “tight conflict subset”. The presentation of this system is to make clear definition for the relation of rules in the conflict set, and an effective conflict resolution is carried out for active database management system to manage several “tight conflict subsets” in parallel.
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Yang, Shan-Chih, and 楊善智. "Improving TCP Performance by Utilizing Active Window Control Mechanism." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/27994975179737471193.
Full textAbstract:
碩士國立中正大學
電機工程研究所
89
Available bit rate (ABR) service is one kind of service that has been developed specifically to support data traffic over the ATM network. The source end system of an ABR connection transmits its data according to the rate informed by the ATM network to fairly utilize available bandwidth and minimize cell loss at the ATM layer. However, most data traffic today is connected to ATM networks via Ethernet. Simulation results show that as TCP traffic is carried over a path with concatenated Ethernet-ATM/ABR links, the packet queues are formed at the edge device interconnecting the Ethernet and the ATM network, instead of inside the ATM network. Furthermore, the edge device requires a buffer size equal to the sum of the receiver window sizes of all participating TCP connections. Two mechanisms are proposed to improve the TCP performance in such an environment - the BDP (bandwidth-delay product) -Aware mechanism and the active window control (AWC) mechanism. The AWC mechanism is the core of this thesis. It is proposed to reduce the buffer requirement and improve the TCP performance without changing the TCP protocol at the hosts. Through estimating the window size of the TCP source and modifying the window field in the TCP segment header skillfully, the edge device can control TCP sources actively. Simulation and experiment results show how the AWC improves the TCP performance.
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Yeh, Chi-Hsin, and 葉奇鑫. "A Defense Mechanism for the Active Spread of Botnet." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/40816429903714693138.
Full textAbstract:
碩士國立中央大學
資訊工程學系
101
Botnet is one of the most serious security threats. Because the zombie network is a combination of a variety of unique malware attack techniques, attackers not only can hidden themselves but also can control multiple bots to do many malicious behaviors. So more and more attackers turn their target on botnets, they continuously improve and enhance botnet malware. Depending on the invasive ways of botnet malware, we can divide invasive ways into two types: active and passive ways. For the latter, victims install and execute the botnet malware by themselves, because they have a bad habit of network usage. Even if their computers have been cleared the malware, they are likely to be a bot again in a short time. It explains the passive decoy botnet is difficult to prevent. We will focus on the defense mechanism of active intrusion, and we use dynamic extensible honeypot system to provide a special connection to the server and remove malwares to prevent the active spread of botnet.
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Shirey, Theresa A. Roberts Rodney G. "Active and passive interaction control for robotic manipulators." 2004. http://etd.lib.fsu.edu/theses/available/etd-04122004-171214.
Full textAbstract:
Thesis (Ph. D.)--Florida State University, 2004.Advisor: Dr. Rodney G. Roberts, Florida State University, College of Engineering, Dept. of Electrical and Computer Engineering. Title and description from dissertation home page (viewed June 15, 2004). Includes bibliographical references.
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Chen, I.-Chun, and 陳逸群. "The Robust of Various controllers for Active Vibration Suppression Mechanism." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/94806410558062831989.
Full textAbstract:
碩士國立臺灣大學
機械工程學研究所
96
In the field of precision manufacture, vibration is influential in mechanical productions and instrumental measurements. Consequently, how to attenuate vibrations from the process of production and measurement is one of the main concerns of the research. Conventional vibration attenuation mechanisms are passive mechanisms, which are excellent in reducing cost and providing high stability. However, passive mechanisms are limited in reduction performances when facing rapidly-changed disturbances. Thanks to IC technology, traditional passive mechanisms transform into the active one. Active mechanisms measure plants in the first place then generate thrusts or torques in accordance with its feedback data. With those thrusts and torques, they help plants to remain stable or to reduce disturbances in order to achieve better performances. This study discusses the impacts of different loadings on transient performances as well as steady performances of active mechanisms. In our system, we apply laser interferometer as a sensor and VCM as an actuator. As to system identification, we adapt HP35665A dynamic signal analyzer as our model. We use SMC, IMP as well as PID controller to compensate outer disturbances and stimulate the possible result by using Simulink (Matlab).
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Liu, Yi-Wen, and 劉逸文. "WebSocket Proxy for group channel and server active cache mechanism." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/30985658106783127155.
Full textAbstract:
碩士國立中央大學
資訊工程學系在職專班
102
With current bi-directional web technologies, the efficiency of WebSocket is superior to other bi-directional web communication technologies (for example: Ajax). In 2011, it was defined by IETF as the RFC 6455 standard, and WebSocket API has been incorporated by W3C as a standard for HTML5. This paper focuses on the discussion of the efficiency of WebSocket protocol. When WebSocket is used for interactive video services or WebTV, access to the same video from different users causes repeated transmission of the same data. Therefore, in this paper, WebSocket proxy is utilized as a mechanism to group channels and another server Active Cache mechanism is to resolve the issue of repeated data transmission. The group channel mechanism is driven by the request of end users. When users make request on the same channel, the connection to the same information on the server can be merged, and information can be transmitted to the users as a group to save network bandwidth. However, it is limited by the fact that only completely identical connection can be merged. Therefore, another server Active Cache mechanism is developed. It works by initiating caching based on response from the server. Although it can resolve the limitation on the channel grouping mechanism, it creates additional bandwidth load because of caching control. Therefore, there is a need to discuss the benefits of transmission via caching control. This paper also discusses the distribution architecture of both mechanisms in order to improve the efficiency of WebSocket protocol application and make WebSocket protocol more suitable for network environment with high bandwidth cost.
50
Lin, Cheng-Yen, and 林政彥. "Design and analysis of a microgripper with an active release mechanism." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/88468381437732666854.
Full textAbstract:
碩士國立中興大學
精密工程學系所
101
A new microgripper integrated with a bistable mechanism is presented to provide a way for motion control of microgripper, where gripping and release are achieved when the bistable mechanism moves forward and backward, respectively. The design parameters are displacement, bistability, and the actuated force. With current applied to the microgripper, the relationship between displacement and the reaction force of the compliant bistable mechanism are investigated. UV-LIGA process are used for the fabrication of the prototype, We use photolithography and electrodeposition to fabricate Ni microgripper on glass substrates. On the fabrication aspect, taking advantage of good adhesion and selectively etching properties between Ni, Cu and Ti, using Cu as the sacrificial layer to fabricate the Ni microgripper. In the experimental setup is using of the DC power supply and the permanent magnet to provide electromagnetic force driving the microgripper. With the embedded bistable mechanism, the microgripper actively releases the microobject and requires no power input during holding of microobjects to reduce energy consumption.