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Dissertationen zum Thema „Metal-based systems“
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Paul, Satadal. „Theoretical investigation of magnetic behaviour in metal-based systems“. Thesis, University of North Bengal, 2013. http://hdl.handle.net/123456789/956.
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Ma, Wei. „Low temperature metal-based micro fabrication and packaging technology /“. View abstract or full-text, 2005. http://library.ust.hk/cgi/db/thesis.pl?MECH%202005%20MA.
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Ebenhoch, Carola [Verfasser]. „Memristive Systems Based on Metal Oxide Nanowires / Carola Ebenhoch“. Konstanz : KOPS Universität Konstanz, 2021. http://d-nb.info/1237222109/34.
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Zuki, Hafiza Mohamed. „Optical multi-metal ion sensing systems based on immobilised fluorescent reagents“. Thesis, University of Manchester, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.506630.
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Zhang, Guangrui. „Systems-based modelling and optimisation of fracture toughness of metal alloys“. Thesis, University of Sheffield, 2013. http://etheses.whiterose.ac.uk/4691/.
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The modelling, prediction and prevention of material failures is the key issue during material design and processing. Finite Element Methods (FEM) combined with physically-based models are a popular approach to modelling fracture characteristics. However, in industrial practice, the interlinked process with high dimensions and complexities could be too complicated to be expressed purely on the principles of physics. Mathematical models via data-driven modelling approaches, were developed to remedy the aforementioned disadvantages of physically-based models. Therefore, this project focuses on developing a hybrid model to assess the toughness of metal alloys, and to improve the current material design techniques through the model-based optimal design. Firstly, a data-driven model of the crack propagation of compact tension test is constructed; an error compensation strategy is also developed and tested. In order to improve the current material design technique through the model-based optimal design, a multi-objective particle swarm optimisation algorithm is proposed and tested using different benchmark functions. A data-driven model based finite element model structure is then proposed. Finally, the optimisation algorithm is applied together with the finite element analysis to the optimal design of material. The results show that the constructed model for compact tension test and the error compensation strategy performed well. The proposed multi-objective particle swarm optimisation algorithm outperforms the compared two particle swarm optimisation algorithms; it is also applied successfully to the optimal design of the small punch test.
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Travan, Andrea. „Nanocomposite systems based on metal nanoparticles and polysaccharides for biomedical applications“. Doctoral thesis, Università degli studi di Trieste, 2010. http://hdl.handle.net/10077/3629.
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2008/2009Questo lavoro riguarda lo sviluppo di materiali nanocompositi per applicazioni biomediche e si configura all’ interno del progetto europeo “Newbone” (EU-FP6); in particolare, lo scopo principale della tesi era realizzare un rivestimento biocompatibile e dotato di proprietà antibatteriche per protesi ortopediche. Sono stati preparati sistemi nanocompositi basati su un polisaccaride derivato dal chitosano (Chitlac) che permette di ottenere soluzioni colloidali di nanoparticelle (argento e oro) con proprietà antibatteriche. Parallelamente, è stato studiato un particolare meccanismo chimico di riduzione degli ioni argento ad opera dei residui di lattitolo del Chitlac; le proprietà ottiche delle nanoparticelle ottenute attraverso questo meccanismo sono state valutate attraverso spettroscopia Raman, evidenziando la possibilità di avere un incremento del segnale grazie al verificarsi dell’ effetto SERS. Essendo state riscontrate migliori proprietà biologiche del sistema a base di argento (Chitlac-nAg) rispetto a quello a base di oro in termini di efficacia antimicrobica e biocompatibilità, Chitlac-nAg è stato scelto per i successivi studi di realizzazione del rivestimento per la protesi. Test sul meccanismo antimicrobico della soluzione ChitlacnAg hanno dimostrato l’interazione tra le nanoparticelle e la membrana batterica. Allo stesso tempo, poiché la mancanza di barriere fisiche può favorire la diffusione delle nanoparticelle all’ interno delle cellule eucariote con rischio di effetti citotossici causati dalla loro internalizzazione, si è voluto realizzare delle strutture tridimensionali a base di Chitlac in grado di intrappolare le nanoparticelle. A questo scopo, sono state sfruttate le proprietà di gelificazione del polisaccaride alginato in modo da ottenere un sistema semi-solido in miscela con Chitlac-nAg; il materiale ottenuto possiede marcate proprietà antibatteriche senza però risultare tossico per le cellule eucariote, come dimostrato da test in vitro e in vivo. Questo risultato è particolarmente importante in relazione allo stato dell’ arte sull’ argomento. Poiché la parte portante della protesi è costituita da un polimero metacrilico, al fine di rivestire questo materiale di substrato è stata messa a punto una tecnica basata sull’ attivazione della superficie e successiva deposizione del rivestimento a base di Chitlac. Questa tecnica permette di ottenere un rivestimento nanocomposito costituito da nanoparticelle di argento incorporate nella matrice di Chitlac. Grazie a questo strato bioattivo la superficie della protesi acquisisce un’ efficace attività antibatterica che si manifesta quando i batteri entrano in diretto contatto con il materiale. Inoltre, test in vitro hanno dimostrato che le cellule eucariote aderiscono e proliferano sul rivestimento nanocomposito, suggerendo quindi una buona integrazione del materiale nei tessuti attorno all’ impianto. La combinazione di tali proprietà ha determinato la scelta di questo rivestimento per il test in vivo su “minipig” a conclusione del progetto europeo: questo test è al momento in via di svolgimento e da esso ci si può attendere una conferma degli incoraggianti risultati ottenuti dagli studi in vitro.
The present work is focused on the development of nanocomposite systems for biomedical applications and has been carried out in the framework of the European Project called “Newbone” (EU-FP6); in particular, the main goal of the thesis was to realize biocompatible coatings for orthopedic prosthesis endowed with antimicrobial properties. Nanocomposite systems based on a chitosan-derived polysaccharide (Chitlac) that stabilizes metal nanoparticles (silver and gold) have been prepared in colloidal solutions which possess broad spectrum antibacterial properties. As a complementary work, it was studied and defined a particular chemical mechanism of silver ions reduction carried out by the lactose moieties of Chitlac; the optical properties of the metallic nanoparticles obtained through this mechanism were tested by means of Raman spectroscopy, thus detecting considerable enhancements of the signal due to the SERS effect (Surface Enhanced Raman Scattering). Given the better biological properties of silver-based systems (Chitlac-nAg) with respect to gold in terms of antimicrobial efficacy and biocompatibility, only the former metal was chosen in the following steps towards the preparation of the nanocomposite coating for the prosthesis. Studies on the biocidal mechanism of the Chitlac-nAg solution ascribed the activity to the interaction metal-bacteria membrane. On the other hand, since the lack of physical barriers to nanoparticle diffusion into eukaryotic cells determines the risk of a massive uptake with cytotoxic outcomes, we focused our attention toward the preparation of Chitlac-based threedimensional structures entrapping silver nanoparticles. To this end, the gel forming properties of the polysaccharide alginate were exploited allowing the production of a semi-solid system in a mixture with Chitlac-nAg: this material displays potent antibacterial properties without showing cytotoxic effects towards eukaryotic cells, as verified by in vitro and in vivo tests. Such result was particularly important in relation to the state of the art in this research field. Since the core material of the prosthesis is made of methacrylic thermosets, in order to coat this substrate material we have devised a technique based on surface activation followed by deposition of the Chitlac-based layer. Such technique allows obtaining a nanocomposite coating where silver nanoparticles are entrapped within the Chitlac matrix. This bioactive layer endows the thermoset surface with considerable antimicrobial properties, as bacteria are rapidly killed upon direct contact with the material. At the same time, in vitro tests proved that eukaryotic cells adhere and proliferate on the nanocomposite coating, which indicates the possibility to have good integration of the material in the tissues surrounding the implant. The combination of these properties determined the choice of our coating for the final in vivo test in a minipig model as a conclusion of the European project; this test is in progress at the moment and it will hopefully confirm the encouraging studies in vitro.
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Naik, A. J. T. „Hetero-junction and nanomaterial systems for metal oxide semiconductor based gas sensing“. Thesis, University College London (University of London), 2015. http://discovery.ucl.ac.uk/1463687/.
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Investigations into a number of hetero-junction and nanoceramic materials systems for metal oxide semiconductor (MOS) gas sensing for potential environmental and bio-sensing applications are presented. The hetero-junction study encompasses investigations into various composite n-n hetero-contact systems such as WO3-ZnO and SnO2-ZnO and a p-n hetero-contact system, specifically CTO (Chromium Titanium Oxide) - ZnO. The facile fabrication of various arrays of hetero-junction MOS gas sensor devices has been demonstrated. A simple change in the compositional contribution of an individual metal oxide within a composite, exhibits the ability to tune the composite’s responsivity and selectivity. The hetero-junction systems were characterized by various techniques including Scanning Electron Microscopy (SEM), Raman spectroscopy, X-Ray Diffraction (XRD) and X-Ray Photoelectron Spectroscopy (XPS) and the influence of the physical and chemical properties of these materials towards the associated gas sensing properties, deduced. Further, the influence of fundamental properties of junctions such as contact potential and packing structure, towards the sensing properties, are also discussed. The nanomaterials study encompasses investigation into ZnO semiconducting oxides fabricated by various emerging fabrication technologies including Continuous Hydrothermal Flow Synthesis (CHFS) and other relatively high temperature routes. The chemical and physical properties of the nanoceramics have been investigated by various techniques including Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM) and Brunauer Emmett Teller (BET) surface area measurements. The investigation demonstrates emerging techniques for the production of nanomaterials, which can be successfully used in MOS gas sensing for the desired applications. Further, the study shows that the behaviour of the nanomaterials is complex and material surface area is not the only deterministic factor of enhanced responsivities, but microstructural factors such as morphology and particle size, as well as heat-treatment conditions are all influential over the overall sensing properties. This thesis presents an overview of emerging material systems for MOS gas sensing applications.
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Sidiropoulos, Themistoklis. „Enhanced light-matter interactions in laser systems incorporating metal-based optical confinement“. Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/30831.
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The aim of plasmonics is to exploit the strong coupling between photons and collective electron oscillations in metals, so-called surface plasmon polaritons, which enable a strong confinement of the electromagnetic field to metal-dielectric interfaces. The interaction of confined optical states with electronic transitions within matter accelerates these otherwise slow light-matter interactions. This work's purpose is to investigate accelerated light-matter interactions within plasmonic lasers, which arise due to optical confinement, and how these influence laser dynamics. In particular, this work focuses on the fabrication, demonstration and characterisation of plasmonic lasers. The devices investigated in this work consist of semiconductor nanowires made from zinc oxide (ZnO) placed in the proximity of a silver substrate. In this geometry the metal allows for strong optical confinement, whereas the semiconductor delivers the necessary gain to achieve lasing. Operating at room temperature, the emission from ZnO lies near the surface plasmon frequency, where confinement and loss become maximal, leading to accelerated spontaneous recombination, gain switching and gain recovery compared with conventional - photonic - ZnO nanowire lasers. To assess the lasing dynamics, in this work a novel double-pump spectroscopy technique is used, which exploits the non-linearity of the laser process to allow the investigation of accelerated light-matter interactions. This novel technique is necessary, as the speed of plasmonic devices is too fast for electrical detection, and the emission of single devices is too weak for non-linear spectroscopic techniques. Comparing photonic and plasmonic devices reveals contrasting dynamics between both, highlighting the benefits of plasmonic confinement, but also exposing an important limitation. Plasmonic devices could potentially be faster, but are ultimately limited by internal relaxation processes of the chosen gain medium. The findings of this work will improve the understanding of plasmonic lasers and their limitations, but also lead to improved knowledge of internal semiconductor processes.
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Sorarù, Antonio. „Molecular and nanodimensional metal based systems for the therapy against neurodegenerative diseases“. Doctoral thesis, Università degli studi di Padova, 2015. http://hdl.handle.net/11577/3424628.
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Reactive oxygen species (ROS) are harmful species produced during metabolic processes, such as photosynthesis and respiration, of living organism. In both case, the substrate (oxygen/water) undergoes several multi electronic reaction, during which some electrons can “escape” from the catalytic cycle and produce ROS, such as superoxide radical anion, hydrogen peroxide, hydroxyl radical and other derivatives. These species are really dangerous, since they are able to oxidize almost all cellular components. Indeed they can damage lipids, proteins, DNA, affecting cellular functions till cell death. Under oxidative stress condition, accumulation of damage due to ROS has been supposed to play a role in several pathologies, and in particular in age-related ones, such as Alzheimer’s disease (AD). This disease is characterized by an accumulation of neurotoxic senile plaques, mainly made of short peptide monomers, that tend to aggregate into fibrils, called amyloid β peptide (Aβ). Although the mechanism involved in the production of these peptides is still unknown, some hypothesis suggest that ROS are produced within the fibrils and are responsible for further Aβ production.
Nature has developed different catalytic strategies to limit ROS production, and the most important is the enzymatic pathway: superoxide dismutases (SOD) and catalase (CAT) enzymes are able to dismutate, respectively, superoxide and hydrogen peroxide. Nevertheless, in case of unpaired ROS production it is of huge interest to find new artificial systems that are able to help natural enzymes in their task. In this thesis, four different classes of synthetic enzymes (synzymes) that mimic natural anti ROS systems have been investigated:
I. Isostructural mononuclear manganese complexes, with general formula [Mn(L)X2], characterized by a pentadentate ligand L, containing different heteroatoms (N, O or S) have been used for the dismutation of hydrogen peroxide and superoxide anion. Their activity, also depending on heteroatoms, and stability were studied, first in organic solvents to have a comparison with literature similar compounds, then in aqueous solution, where only few compounds were known to work. The sulfur-containing complex [Mn(L)(OTf)2] was found to exhibit high dual SOD/CAT-like activity with excellent stability, when used in the presence of a base.
II. Isostructural dinuclear manganese complexes, with general formula [Mn2L2X], were widely studied as artificial catalases. A comparison with other dimanganese complexes, in terms of Michealis-Menten parameter, KM and kcat, was performed. Superoxide dismutase activity was also evaluated, demonstrating the unique dual SOD/CAT behavior of [Mn2L2X] with respect to other dinuclear complexes. Finally, the ligands were modified with mitochondriotropic functionalities. In particular, two fluorescent rhodamine derivatives and a triphenylphosphonium salt, were taken into account.
III. Some multimetallic manganese oxoclusters, containing 6-13 manganese atoms, were synthetized during a Short Term Scientific Mission in Dublin, in the group of Prof. Wolfgang Schmitt. The catalase-like activity of these compounds was tested for the first time. Their H2O2 dismutation capability was thus demonstrated and their stability in aqueous environment was checked. Preliminary test as SOD mimics were also performed.
IV. In the end, a completely inorganic compound, a polyoxometalate (POM) substituted with four ruthenium atoms, with formula [Ru4O4(OH)2(H2O)4(γ-SiW10O36)2]10-, able to dismutate hydrogen peroxide was studied. Its activity in different biological buffers and media was initially optimized. Its capability of interaction with Aβ peptides, coupled with its catalase activity, were exploited to control these two major events involved in Alzheimer’s disease. Preliminary test on neuronal cells were then performed (with Dr.ssa de Bartolo (ITM-CNR, Rende, CS)), confirming the interesting properties of the compound in vitro and finding a very low toxicity. Finally, encapsulation of POM was achieved in order to enables delivery and targeting in cells, using polymeric multilayer biocompatible microcapsules in which POM is deposited. The presence of POM and its catalytic activity were confirmed and analyzed.Le reazioni biochimiche che coinvolgono il trasferimento di elettroni dall’ossigeno per dare acqua, durante la respirazione cellulare, e dall’acqua per dare ossigeno, durante la fotosintesi, possono portare alla formazione di specie reattive dell’ossigeno (ROS, reactive oxygen species), dovute alla “perdita” di elettroni dal ciclo catalitico. Tra queste specie troviamo inizialmente il superossido O2-•, l’acqua ossigenata e il radicale ossidrile. Queste possono reagire con altre molecole per dare origine ad altre specie reattive, per esempio dell’azoto, ma soprattutto possono danneggiare peptidi, lipidi e DNA e causare ingenti danni alle funzioni cellulari fino a portare alla morte della cellula stessa. In condizioni di stress ossidativo, l’accumulo di queste specie sembra giocare un importante ruolo nelle malattie degenerative, come ad esempio il morbo di Alzheimer (AD). In questo caso, la malattia è caratterizzata dalla presenza di aggregati proteici in forma di placche, che hanno un effetto neurotossico. Questi accumuli proteici sono costituiti principalmente da peptidi di 40-42 amminoacidi chiamati β-amiloidi (Aβ), che tendono ad aggregare, in forma di fibrille. Le cause della formazione e accumulo di questi peptidi non sono ancora del tutto chiare, ma si hanno evidenze sul coinvolgimento delle ROS nella fase di formazione dei peptidi, e sull’aumento della loro produzione, dopo la formazione delle fibre, a causa di reazioni mediate dai metalli intrappolate nelle fibre stesse. La natura ha sviluppato dei sistemi per proteggersi da queste specie reattive, tra questi citiamo gli enzimi superossido dismutasi (SOD) e catalasi (CAT), capaci rispettivamente di eliminare superossido e acqua ossigenata, che tuttavia in certe situazioni di elevato stress ossidativo possono risultare insufficienti per prevenire i danni. È quindi di estremo interesse lo studio di composti artificiali capaci di aiutare gli enzimi naturali nel loro compito di eliminare le ROS dall’ambiente biologico. Considerando ciò, in questa tesi sono state considerate le seguenti quattro classi di composti, utilizzati come enzimi sintetici (synzymes), per imitare le funzioni dei sistemi anti ROS naturali: I. Complessi mononucleari ed isostrutturali di manganese, di formula generale [Mn(L)X2], caratterizzati da un legante pentadentato, L, contenente differenti eteroatomi (N, O, o S), sono stati studiati nella dismutazione dell’acqua ossigenata e del radicale anione superossido. L’attività è stata inizialmente analizzata in solvente organico (acetonitrile) per aver dei termini di paragone con altri composti di letteratura. In seguito l’attività è stata studiata anche in acqua, dove solo pochi composti di letteratura sono risultati attivi. Se utilizzati in presenza di base, i complessi [Mn(L)(OTf)2] contenenti zolfo mostrano una duplice attività SOD/CAT ed un’elevata stabilità. II. Complessi dinucleari ed isostrutturali di manganese, di formula generale [Mn2L2X], sono stati studiati inizialmente per l’eliminazione dell’acqua ossigenata. Un confronto con simili composti di letteratura è stato effettuato tramite il calcolo dei parametri, derivati dall’ equazione di cinetica enzimatica di Michalis-Menten, KM e kcat. E’ stata anche analizzata la capacità di smaltire il superossido, dimostrando le caratteristiche uniche di [Mn2L2X] nella duplice attività CAT/SOD, in ambiente acquoso, rispetto ad altri complessi dinucleari. Infine, modificando i leganti, si è cercato di introdurre nuove funzionalità adatte alla veicolazione del composto in cellula. In particolare, sono stati utilizzati residui organici noti per la loro affinità verso i mitocondri, come i derivati della rodamina e i sali di trifenilfosfonio. III. Sono stati studiati oxoclusters multimetallici di manganese, contenti 6-13 atomi di metallo, sintetizzati durante un Short Term Scientific Mission (STSM, COST action CM1203) a Dublino, presso il laboratorio del Prof. Wolfgang Schmitt, analizzandone per la prima volta l’attività di dismutazione dell’ acqua ossigenata e del superossido, oltre che la stabilità in soluzioni acquose. IV. Un composto completamente inorganico, un poliossometallato (POM) contenete quattro atomi di rutenio, di formula [Ru4O4(OH)2(H2O)4(γ-SiW10O36)2]10-, è considerato per la sua solubilità in ambiente acquoso e la capacità di dismutare efficacemente l’acqua ossigenata. L’attività è stata analizzata in diversi tamponi e mezzi comunemente usati per analisi di sistemi biologici. In soluzione, il complesso è capace di ridurre la produzione di ROS e anche di interagire con peptidi amiloidei, evitandone l’aggregazione in fibrille, dimostrandosi quindi promettente nel contrastare due importanti eventi che si verificano durante la malattia di Alzheimer. In collaborazione con la Dr.ssa de Bartolo (ITM-CNR, Rende, CS) sono state quindi effettuate prove preliminari in cellule neuronali, per verificare sia la tossicità del composto (che risulta essere nulla anche a 100µM di concentrazione) che l’effettiva attività anti-ROS e anti-amiloidogenica in vitro. Infine si è studiato l’inserimento del POM all’interno della shell di microcapsule polimeriche multistrato, con la prospettiva di controllarne la veicolazione in cellula.
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Koo, Yiu, und 顧耀. „Synthesis of metal-containing thiophene-based conjugated polymers for photovoltaic applications“. Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hub.hku.hk/bib/B41897262.
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Koo, Yiu. „Synthesis of metal-containing thiophene-based conjugated polymers for photovoltaic applications“. Click to view the E-thesis via HKUTO, 2009. http://sunzi.lib.hku.hk/hkuto/record/B41897262.
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PIETROBON, LUCA. „Synthesis and reactivity of new transition metal-based catalytic systems in carbonylation reactions“. Doctoral thesis, Università degli Studi di Trieste, 2022. http://hdl.handle.net/11368/3010971.
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Abstract
The aim of this PhD thesis was to explore the activity of new catalytic systems in some carbonylation reactions of organic substrates, like aromatic amines, olefins and/or iodoarenes which are transformed in isocyanates, ureas, esters, amides and polymers, interesting for the chemical industry.
In Chapter 1 the study of the synthesis of isocyanates and amides of industrial interest is reported. A catalytic system based on [PdCl2(dppf)]/FeCl3/O2 was studied for the synthesis of phenylisocyanate and N,N diphenylurea (DPU), by oxidative carbonylation of aniline. Also presented is a study of synthesis of cyclohexanoneoxime obtained by reduction of nitrobenzene in the presence of NH2OH.HCl with heterogeneous Pd catalysts, which by Beckmann rearrangement can lead to the formation of Caprolactam. A reactivity study of trifluoroacetate hydroxylamine (NH2OH.CF3COOH) for the synthesis of oximes and amides of industrial interest is also presented.
In Chapter 2, a study on the carbonylation of olefins with Pd-based heterogeneous pre-catalysts is presented. Through the study of methoxycarbonylation of cyclohexene these catalysts were compared to the activity of the homogeneous catalyst of [Pd(TsO)2(PPh3)2]. From a study of the reaction mechanism, the possibility of having a mixed homogeneous/heterogeneous catalysis is proposed.
In addition, a study of a new heterogeneous magnetic support obtained by decomposition of Fe(CO)5 is presented, which was suitably coated with a polyketone layer. Such a support was employed for the synthesis of a Pd-based heterogeneous catalyst (Pd/MIM) and successfully employed in methoxycarbonylation reaction of cyclohexene, methoxycarbonylation of iodobenzene and for nitrobenzene reduction reaction.
In conclusion, the hydration of olefins catalyzed by CF3COOH, which is commonly employed as an acidic promoter in palladium-catalyzed carbonylation reactions, was investigated to delineate possible eddy reactions for olefin carbonylation reactions for industrially employed two-phase systems.
In Chapter 3, a study was performed on the carbonylation of iodobenzenes. A new catalytic system based on [PdCl2(Xantphos)] was studied for alkoxycarbonylation reactions. In particular, the effects of some additives on the productivity of the reaction have been studied, defining as the best catalytic system the one formed by [PdCl2(Xantphos)] and the pair Ferrocene/ferrocenium.
In addition, a preliminary study of the amino-carbonylation reaction of iodobenzene is presented, the selectivity of the reaction is explored, and the possible competition of the base required for the catalytic cycle and the amine employed as a nucleophile.
In Chapter 4, the possibility of employing green surrogates for carbonylation reactions was investigated. A study was carried out on the generation of CO from formic acid, through the Morgan reaction, using heterogeneous acid catalysts. The best setup of the reactor has been studied to optimize the yield of carbon monoxide and avoid the mechanical degradation of acid resins used as catalysts.
A new multi-chamber reactor has also been designed to perform simultaneously several Palladium-catalyzed carbonylation reactions, employing CO generated by formic acid.
Finally, the first example of polymer obtained by catalytic carbonylation of ethylene (PK), employing CO generated by formic acid and acetic anhydride system, is presented. The HCOOH/CH3COO2 mixture plays both the role of solvent and carbon monoxide generator.
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Polad, Serkan. „Quantum Mechanical Treatment Of Fullerene-based Systems Doped With Various Metal And Non-metal Elements As Prospective Spin-qubits“. Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612173/index.pdf.
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In this thesis, We have calculated the optimized geometries, electronic structures and spin distributions of metal and non-metal elements Li, Na, N and P doped C60 fullerene dimers and trimers with different spin multiplicities using hybrid density functional theory (DFT) at the B3LYP/6-31G level of theory. Natural population analysis and Mulliken population analysis show that non-metal elements (N, P) inside the C60 fullerene dimers and trimers are well isolated and preserve their electronic structures while charge transfer processes occur between metal elements(Li, Na) and C60 structures. Energy calculations showed that both doped and undoped linear C60 structures are energetically lower than triangular C60 structures. Calculated spin density distributions make non-metal doped C60 structures advantageous over metal doped C60 cages as spin cluster qubits.
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Rose, Linsey. „Ribosomal RNA-based and bioluminescence-based techniques for the monitoring of heavy metal bioavailability in ecological systems“. Thesis, University of Aberdeen, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.311198.
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The aim of this research was the development of a novel microbial biosensor system based on the cellular rRNA contents of bacteria. This would be used for the assessment of cadmium toxicity and bioavailability to bacteria, and compared with the more widely used lux-based microbial biosensors. Experimentation was carried out to develop an efficient and reproducible protocol for the extraction and quantification of bacterial rRNA. This enabled the determination of cellular rRNA contents during growth of Pseudomonas fluorescens. The bacteria were then grown in cadmium supplemented medium to determine if any change in growth rate imposed by the presence of the metal was reflected by a change in cellular rRNA levels. It was found that in bacteria exposed to cadmium, an increase in rRNA content in comparison to control cells was observed. If this change in rRNA content and could be shown to be dose responsive, with respect to cadmium concentration, this could prove useful for the assessment of bacterial metabolic activity in response to heavy metals. In situ hybridization cellular rRNA and quantification using confocal microscopy were also carried out within these experimental systems. The toxicity of cadmium on bacterial metabolic activity was then assessed by the use of Escherichia coli and P. fluorescens lux-marked biosensors. EC50 values for cadmium were determined for each of the bacterial species. In order to determine how the bioavailability of a metal effects its toxicity, an experiment was carried out in which the toxicity of cadmium to lux-marked E. coli and P. fluorescens was assessed in the presence of environmentally relevant concentrations of sulphate. The speciation of cadmium within each experimental system was predicted using computer program, GEOCHEM. It was shown that increasing concentrations of sulphate effectively reduced the toxicity of cadmium to the bacteria and that this was due to a reduction in the concentration of free cadmium ions within the experimental systems. It was found that using the techniques employed within this project, cellular rRNA content was of little use for the further development of a bioassay system for the assessment of bacterial metabolic activity in response to cadmium. Lux-marked microbial biosensors did, however, appear to give a reliable assessment of bacterial metabolic activity in response to the heavy metal, and also allowed the toxicity of cadmium in the presence of other inorganic ions to be determined.
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Goswami, Tamal. „Theoretical investigation on aromaticity, magnetic exchange coupling and magnetic anisotropy in metal based systems“. Thesis, University of North Bengal, 2015. http://ir.nbu.ac.in/handle/123456789/1851.
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Abdin, Zainul. „Components models for solar hydrogen hybrid energy systems based on metal hydride energy storage“. Thesis, Griffith University, 2017. http://hdl.handle.net/10072/370890.
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Modelling and simulation are essential tools for concept evaluation and for predicting
the performance of a hybrid energy system, since prototyping and testing each candidate
design for such a complex system would almost always be prohibitively cumbersome,
expensive and time consuming. To meet the modelling and simulation objectives, the various
components of the system (sources, storage, loads, and converters) need to be characterised
and modelled in a tractable way. The tuning of the models to reflect the actual system
components is a key milestone in this process and requires reliable and comprehensive
experimental data. Furthermore, environmental conditions such as ambient temperature may
have a significant impact on the performance, which has to be taken into account.
The complexity of hybrid energy systems and their dependence on embedded control
software increases the difficulty in predicting interactions among the various components and
subsystems. A modelling environment that can model not only the components but also
control algorithms (such as Matlab/Simulink, Homer etc.) is therefore advantageous.
Effective diagnosis of faults in an installed system also presents a challenge, because of the
interactions between the components and the control system. Modelling may play an
important role in diagnosis of the operating components. For example, running an electrolyser
model and comparing actual electrolyser operating variables with those obtained from the
model may help to diagnose a fault in the real electrolyser.
This thesis focuses on modelling the principal components of hybrid solar energy
systems that include energy storage in the form of hydrogen: a large photovoltaic array
subject to manufacturer’s variability and temperature inhomogeneity; two types of
electrolyser as commonly found in hydrogen energy systems; a metal-hydride hydrogen
storage tank; a fuel cell. Attention is given here to building physics-based component models with minimum empiricism and to critically analysing the state of the art in modelling such
components. The models have been realised in Simulink, so that they are mutually compatible
and can be linked into a whole of system model. All the models were validated against
experimental data and performed at least as well as models found in the literature. The thesis
is based on six papers, four already published and two submitted.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Natural Sciences
Science, Environment, Engineering and Technology
Full Text
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Qian, Limin. „Soft X-Ray Spectroscopic Study of Fullerene Based Transition-Metal Compounds and Related Systems“. Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2001. http://publications.uu.se/theses/91-554-5104-7/.
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Tünnermann, Maike [Verfasser]. „Photocatalytic water reduction systems based on iridium and non-noble metal complexes / Maike Tünnermann“. Paderborn : Universitätsbibliothek, 2018. http://d-nb.info/1170228267/34.
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19
Farabi, Shiva. „Luminescent assemblies based on surface active transition metal complexes and supramolecular host-guest systems“. Thesis, University of Birmingham, 2012. http://etheses.bham.ac.uk//id/eprint/3833/.
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Miniaturisation of devices and components is becoming increasingly important in the field of molecular devices. The design of multicomponent supramolecular systems that undergo photoinduced energy or electron transfer processes has been well recognised in view of its potential for development of nanosized molecular devices for solar energy conversion and components in photonic devices. Consequently research has expanded to the properties of monolayers formed from rather simple organic molecules to biological systems and metal complexes. In the present approach, surface active Ru(II) and Os(II) complexes have been designed. Their attachment to surfaces and their photophysical properties in solution, as powders and as self-assembled monolayers have been investigated. The complexes present relatively high quantum yields and long lifetimes in solution, as powders and in monolayers. The complexes have been developed further to carry \(\beta\)-cyclodextrin recognition sites in their structure. This new group of molecules opens a window into guest-host chemistry on surfaces, with the view to examining photophysical properties of supramolecular functional surface-active systems. The surface active Ru(II) and Os(II) complexes bearing \(\beta\)-cyclodextrin exhibit formation of emissive monolayers. Later Ir(III) and Ru(II) metalloguests with a specific design to bind to \(\beta\)-cyclodextrin cavity have been synthesised and the photo-induced communication between metals were investigated both in solution and on gold surface. Finally, we propose a new and efficient method of sensitising Nd(III) NIR emission by non-covalent attachment of a BODIPY dye attached to \(\beta\)-cyclodextrin (BODIPY-CD). The BODIPY-CD has been proved to be a good sensitizer for neodymium complexes. This is the first time that NIR lanthanides have been sensitised through non-covalent host-guest approach using cyclodextrin. The inclusion of the hydrophobic biphenyl and phenyl tails in the cyclodextrin has been proved by the NMR studies.
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Dyasi, Nontsikelelo. „Model systems for the investigation of metal-support interactions in cobalt based Fischer-Tropsch“. Master's thesis, Faculty of Engineering and the Built Environment, 2021. http://hdl.handle.net/11427/33639.
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The catalyst used plays a pivotal role in the optimization of the Fischer Tropsch (FT) synthesis. Cobalt (Co)-based catalysts have been widely used in low temperature Fischer Tropsch synthesis for the production of longer chain olefins [1]. The interaction between the support and the active metal, Co, has been observed to affect the activity and selectivity of the FT synthesis [2]. In order to investigate metal support interactions independent of other support effects, the inverse method was used in the synthesis of model catalysts [3]. The inverse method mimics the interface bond between the support and the active metal, resulting in CoO-Si bond formation. By exposing Co nanoparticles (NPs) to a dilute solution of an alkoxide, tetraethyl orthosilicate (TEOS) or triphnyl ethoxy silane (TPEOS), Co-O-Si bond (ligand) is expected to form until it reaches equilibrium state. The concentration of the dilute alkoxide solution can be varied to observe its effect on the surface coverage of the Co NPs with the alkoxide. XRD analysis of the modified cobalt nanoparticles showed that there was no evidence of the formation of a crystalline silica phase as those characteristic diffraction lines were absent. The TPR profiles showed a shift to higher reduction temperatures with increasing silica loading suggesting that the surface modification results in retardation of reduction of the cobalt nanoparticles. CO-TPD studies of the model catalyst indicated that the total number of active sites available for CO adsorption and bond cleavage decreases upon surface modification, but it leads to a more facile CO bond cleavage as evidenced by decrease in energy of dissociation. The activity of these materials in the Fischer Tropsch synthesis decreased with increasing silicon content for the oxidized cobalt nanoparticles. This was attributed to the decline in the total number of active site available for CO bond cleavage with increasing silicon content. The methane selectivity passes a minimum with increasing silicon content. This may be related to the carbon coverage on the surface of the nanoparticles affecting the chain growth. It is recommended that Fischer Tropsch synthesis studies be conducted on the modified as-synthesized cobalt nanoparticles to compare the performance of the two catalysts.
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Kumagai, Takashi. „Visualization of Hydrogen-Bond Dynamics with Water-Based Systems Assembled on a Metal Surface“. 京都大学 (Kyoto University), 2011. http://hdl.handle.net/2433/142394.
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22
Regazzo, Paolo. „Active vibration control systems based on magneto-rheological fluids for sheet metal forming processes“. Doctoral thesis, Università degli studi di Padova, 2011. http://hdl.handle.net/11577/3421659.
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Forming operations are among the most frequently used processes in sheet metal working. Dynamic phenomena occurring represent critical aspects for geometrical accuracy of products and service life of machines parts in high-tech forming machine sector. Stiff presses allow high repeatability and dimensional accuracies but, at the same time, determine rapid and excessive deterioration of tools by stresses and wear. On the other hand, softer ones improve the efficiency and the service life of tools, but with higher energy dissipation and bigger scatter in product dimensions that make processes unreliable with respect to precision.
The right trade-off is often the main prerequisite for the technical and economic success of the whole process and must therefore be found, especially with complex non-symmetric geometry and if vibrations take place during the process.
Since the interaction of different elements determines the dynamic efficiency of forming machines, controls systems for the compensation of elastic deformations result fundamental for the component accuracy and the required tolerances.
Conventional actuators devices present strong limitations in both performances and reliability, with restricted possibilities of closed-loop controls. The best solution is represented by new technologies, able to enhance the control of phenomena process.
Magneto-rheological (MR) fluids represent one of the most versatile and promising solutions for the development of high efficiency damping systems, capable to grant high versatility of configuration and effective closed-loop control capabilities.
The main objective of this work is to study magneto-rheological fluids technology, used up-to-now especially in anti-seismic and automotive fields, in order to extend to the industrial material forming processes.
Due to the complexity of the physics fields involved, the majority of models are based on analytical descriptions that, though easy and fast to implement, present strong limitations for the accurate design of the functional devices. A new approach is introduced, focused on a multi-physics coupled numerical model of the vibration dampers, based on calibrations by physical-simulation.
Different damper prototypes are realized for the laboratory tests, in order to experimentally analyse fluid and device behaviours.
On these bases, the application of these innovative damping systems and the evaluation of their performances are extended in the industrial context. The experimental tests, conducted on an hydraulic press using both commercially available hydraulic dampers and MR dampers, are analysed with particular focus on the excited frequencies, the vibrations and the powers to quantify the impact of dynamic phenomena on the quality of final parts. The developed prototypes are able to elevated damping performances without complex adjustment calibration when setting up a new process, making flexible its design.Le operazioni di formatura sono tra i processi più diffusi nell’ambito della lavorazione della lamiera metallica. La presenza di fenomeni dinamici è critica per l’accuratezza geometrica dei manufatti e per la vita di servizio delle attrezzature, in particolare per le aziende ad elevata tecnologia nel settore della produzione di macchine utensili. Ottime ripetibilità ed accuratezze dimensionali sono ottenute grazie a presse ad elevata rigidezza strutturale a discapito, tuttavia, della vita degli utensili, esposti a rapidi ed eccessivi fenomeni di usura. Dall’altro lato, l’uso di architetture poco rigide permette di aumentare la durata degli utensili, ma con limiti di efficienza energetica e degli standard di precisione dimensionale. Pertanto il corretto bilanciamento dei differenti fattori rappresenta il prerequisito fondamentale per il successo tecnologico ed economico dell’intero processo. In particolare, nella produzione di geometrie complesse e non simmetriche, oppure quando fenomeni vibratori si manifestano durante il processo di lavorazione. Poiché l’efficienza dinamica di una macchina per formatura è il risultato dell’interazione di diversi fattori, risulta fondamentale un sistema di controllo avanzato per la compensazione delle deformazioni elastiche, soprattutto in relazione alle specifiche richieste dei prodotti. Gli attuatori tradizionali presentano grossi limiti sia nelle prestazioni sia in affidabilità, con poche possibilità di realizzare una catena chiusa nel controllo. La migliore soluzione è rappresentata dall’introduzione di nuove tecnologie, capaci di aumentare il controllo dei processi. I fluidi Magneto–Reologici (MR) rappresentano una delle più versatili e promettenti soluzioni per lo sviluppo di sistemi di smorzamento ad elevata efficienza, capaci di ottima versatilità e controllo continuo dei fenomeni dinamici. Il principale obbiettivo di questo lavoro consiste nello studio della innovativa tecnologia basata sui fluidi magneto–reologici, prevalentemente diffusa nell’ambito automotive e nei sistemi civili antisismici, in modo da estenderla anche ai processi di formatura dei materiali metallici. In seguito alla complessità dei molteplici campi fisici interagenti, la maggior parte dei modelli si basano su descrizioni analitiche che, sebbene relativamente semplici e veloci da implementare, presentano grossi limiti per un’accurata progettazione di dispositivi. Pertanto viene introdotto un nuovo approccio, basato su una modellazione multi-fisica accoppiata dei sistemi di smorzamento e una calibrazione mediante simulazione agli elementi finiti. Sono stati realizzati più prototipi di smorzatori magneto-reologici, in modo da analizzare le prestazioni sia dei fluidi che dei dispositivi stessi, attraverso test di laboratorio. Successivamente, l’applicazione di questi innovativi sistemi di smorzamento è estesa al contesto industriale e valutata mediante prove su una pressa idraulica per tranciatura. Attraverso test sperimentali che comprendono anche il confronto con dispositivi commerciali idraulici, le prestazioni degli smorzatori magneto-reologici vengono analizzate con particolare riferimento allo studio delle frequenze eccitate, alla tipologia di vibrazione e alle potenze in gioco, in modo da quantificare l’impatto dei fenomeni dinamici intervenenti sulla qualità dei prodotti finiti. I prototipi sviluppati sono in grado di elevare le performance di smorzamento senza complessi aggiustaggi durante il settaggio delle nuove sequenze di processo, rendendo flessibile la progettazione del processo stesso.
23
Ellern, Ilya. „Metal organic frameworks based microcantilever gas sensors for detection of volatile organic compounds“. Thesis, Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/49127.
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Metal Organic Frameworks (MOFs) are a new class of nanoporous materials with
high surface area, thermal/chemical stability and a taylorable pore size. These properties
make MOFs ideal for storage and gas separation applications. Piezoresistive
microcantilever sensors are microfabricated devices that are highly sensitive to surface
strain due to doped single crystal silicon regions. Changes in resistance generated by
surface strain can be measured with a high degree of accuracy using a Wheatstone bridge
and basic instrumentation. This thesis will discuss the use of piezoresistive
microcantilever sensors as a transduction mechanism for detection of volatile organic
compounds (VOC's) using MOF coatings. It will be shown that by coating a
microcantilever with MOFs it is possible to detect low levels of different VOC's
(hundreds of parts per million). Excellent sensitivity and a simple transduction
mechanism make these devices low power and highly compact. Such devices would be
capable of detecting a plethora of different analytes at low concentrations. Devices were
engineered for maximum response and microfabricated in the cleanroom with high yield.
A custom setup for testing the devices was designed and machined. A number of MOFs
were selected and tested, their response was recorded and analyzed. Twelve different
analytes including eleven VOC's and water were used to characterize the MOFs.
Microcantilever sensors were shown to be durable, reliable and stable in long term testing
despite being subjected to many different analytes. MOF coatings proved flexible,
durable, stable and reversible. This work will show a promising new technology for a
next generation gas sensor.
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Mileyeva-Biebesheimer, Olga. „An Investigation into Metal Oxide Nanoparticle Toxicity to Bacteria in Environmental Systems Using Fluorescence Based Assays“. University of Toledo / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1302125170.
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Pokhrel, Lok R. „Evaluation of Colloidal Stability and Ecotoxicity of Metal-based Nanoparticles in the Aquatic and Terrestrial Systems“. Digital Commons @ East Tennessee State University, 2013. https://dc.etsu.edu/etd/1132.
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Intrinsic to the many nano-enabled products are atomic-size multifunctional engineered nanomaterials, which upon release contaminate the environments, raising considerable health and safety concerns. This Ph.D. dissertation is designed to investigate (i) whether metals or oxide nanoparticles are more toxic than ions, and if MetPLATETM bioassay is applicable as a rapid nanotoxicity screening tool; (ii) how variable water chemistry (dissolved organic carbon (DOC), pH, and hardness) and organic compounds (cysteine, humic acid, and trolox) modulate colloidal stability, ion release, and aquatic toxicity of silver nanoparticles (AgNP); and (iii) the developmental responses of crop plants exposed to Ag- or ZnO- (zinc oxide) nanoparticles.
Results suggest that the MetPLATEcan be considered a high-throughput screening tool for rapid nanotoxicity evaluation. Detectable changes in the colloidal diameter, surface charge, and plasmonic resonance revealed modulating effects of variable water chemistry and organic ligands on the particle stability, dissolution, and toxicity of AgNPs against Escherichia coli or Daphnia magna. Silver dissolution increased as a function of DOC concentrations but decreased with increasing hardness, pH, cysteine, or trolox levels. Notably, the dissociated Ag+ was inadequate to explain AgNP toxicity, and that the combined effect of AgNPs and dissolved Ag+ under each ligand treatment was lower than of AgNO3. Significant attenuation by trolox signifies an oxidative stress-mediated AgNP toxicity; its inability to attenuate AgNO3 toxicity, however, negates oxidative stress as Ag+ toxicity mechanism, and that cysteine could effectively quench free Ag+ to alleviate AgNO3 toxicity in D. magna. Surprisingly, DOC-AgNPs complex that apparently formed at higher DOC levels might have led daphnids filter-feed on aggregates, potentially elevating internal dose, and thus higher mortality. Maize root anatomy showed differential alterations upon exposure to AgNPs, ZnONPs, or their ions.
Overall, various metal-based nanoparticles revealed lower toxicity than their ions against multiple organisms. This study showed that particle size, surface properties, and ion release kinetics of AgNPs modify following release into aquatic environment, suggesting potential implications to ecosystem health and functions, and that caution be applied when extending one species toxicity results to another because obvious differences in organism biology—supporting species sensitivity paradigm—can significantly alter nanoparticle or ionic toxicity.
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Reissner, Alexander. „Metal Hydrides as Enabling Technology for the use of Hydrogen-Based Energy Storage Systems on Telecommunication Satellites“. Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-229226.
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Next generation telecommunication satellites will demand an increasing amount of power in the range of 30 kW or more within the next 10 years. Battery technology that can sustain 30 kW for an eclipse length of up to 72 minutes will represent a major impact on the total mass of the satellite, even with new Li-ion battery technologies. Regenerative fuel cell systems (RFCS) were identified years ago as a possible alternative to rechargeable batteries. Nevertheless, one major drawback was identified by several independent system studies, namely the need to dissipate large amounts of heat from the fuel cell (FC) during eclipse. This in turn requires massive thermal hardware (mainly large radiators) that can contribute up to 50% of the system mass. In order to overcome this issue, the use of metal hydrides (MH) as combined hydrogen and heat storage system was suggested as a starting point of the research presented in this thesis. During eclipse the FC must dissipate waste heat, and at the same time the MH tank must absorb heat in order to desorb hydrogen. Rather than dissipating the waste heat from the FC directly through a radiator, it can be stored solely, or partly, in the MH tank, to be dissipated during Equinox, with a 20 times slower rate, requiring a radiator with significantly less volume and mass. This thesis aims to present the potential of using such MH storage tanks to alternately store hydrogen and waste heat from the FC on-board a spacecraft, investigated by theoretical and experimental means. The model application for the MH tank technology considered in this thesis is a 39 kW telecommunication satellite. Nevertheless, the derived results are to be considered a generic outcome and can be translated or scaled to many other applicationsEs kann davon ausgegangen werden, dass der Trend hin zu Telekommunikationssatelliten mit immer höherer Leistung in den nächsten 10 Jahren zu Satelliten-Plattformen mit 30kW und mehr führen wird. Batterien, welche eine Leistung von 30kW für Eklipse-Längen von 72 Minuten zur Verfügung stellen müssen, werden daher einen immer größeren Einfluss auf die Gesamtmasse des Satelliten haben. Regenerative Brennstoffzellensysteme wurden daher schon vor Jahren als mögliche Alternative zu wieder aufladbaren Batterien untersucht. Mehrere unabhängige Studien sind zu dem Schluss gekommen, dass die größte Problematik in der Einführung von Brennstoffzellensystemen auf Satelliten darin besteht, die relativ großen Mengen an Abwärme effizient abzustrahlen. Die Radiatoren, die hierfür benötigt werden können 50% der Masse des Gesamtsystems ausmachen. Um dieses Problem zu überwinden wurde als Startpunkt der vorliegenden Arbeit die Nutzung von Metallhydriden als kombinierter Wasserstoff- und Wärmespeicher vorgeschlagen. Während sich der Satellit im Erdschatten befindet produziert die Brennstoffzelle Abwärme, während zur gleichen Zeit der Metallhydrid-Tank Wärme benötigt um Wasserstoff freizusetzen. Die Abwärme der Brennstoffzelle muss daher nicht direkt über Radiatoren abgestrahlt werden, sondern wird von Metallhydrid-Tank absorbiert um dann während dem restlichen Erdumlauf 20 mal langsamer mit einem deutlich kleinerem und leichteren Radiator abgegeben werden zu können. Diese Arbeit hat zum Ziel, das durch analytische und experimentelle Methoden untersuchte Potential der Anwendung einer solchen Technologie auf Satelliten zu präsentieren. Die Modellapplikation für diese Arbeit ist ein 39kW Telekommunikationssatellit. Die Ergebnisse lassen sich allerdings auch auf andere Anwendungen skalieren und übertragen
27
Kim, Jeong Ah. „The role of legislation in driving good occupational health and safety management systems: A comparison of prescriptive based legislation“. Queensland University of Technology, 2004. http://eprints.qut.edu.au/15966/.
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Countries seek to control exposure to hazardous substances and environments by the enactment of legislation. In the past thirty years, two major different approaches to occupational health and safety legislation have been devleoped by countries around the world. The performance-based legislative approach has been linked with the emergence of occupational health and safety management systems but no research has previously been done to determine whether or not the legislative approach taken by government influences the introduction or form of occupational health and safety management systems used by organisations. Similarly, although the reasons why Australia and other countries have moved to performance-based legislation have been explained in terms of social, political and economic factors that influenced the change, little research has been done on the effectiveness of this approach compared with the prescriptive approach of countries such as Korea. -I- The overall aim of this research is to develop a conprehensive understanding of the management of expusre to heavy metals in selected industries in Korea and Australia. The specific objectives of the study are to determine: The effectiveness of heavy metal exposure management in the fluorescent lamp manufacturing industry in Korea, and an Oral Health Service, and lead-risk workplaces in Queensland, Australia; The management of the legislative arrangements for health surveillance in Korea and Queensland, Australia; The characteristics of the occupational health and safety management systems that are in use in the heavy metal industries in Korea in Australia; and The effectiveness of prescriptive and performance based legislative systems in protecting the health and safety of workers in heavy metal based industries. Secondary analysis of biological monitoring data from 6 fluorescent lamp manufacturing companies (8 workplaces) in Korea was used to examine the extent of mercury exposure and the effectiveness of the health surveillance system in that country. A survey of dental workers in an oral health service in Queensland provided data on the extent of mercury exposure to the workforce and workers' attitudes to the management of occupational risks. The efficiency of the lead health surveillance in Queensland was examined by way of a questionnaire survey of lead designated doctors in the state. A survey of registered lead-risk companies and the oral health servies in Queensland, and 5 of the fluorescent lamp manufacturing companies in Korea provided data on the occupational health and safety management systems in place in these organisations. The health surveillance system for mercury exposed workers in Korea was found to have reduced the incidence of workers with biological levels of mercury above the Baseline Level from 14% in 1994 to 7% in 1999. Bilogical testing of dental workers in Queensland discovered no workers with biological levels of mercury approaching the Baseline Level and air monitoring failed to locate any areas where workers were likely to be exposed to levels approaching the Workplace Exposure Standard. The staff of the Oral Health Service were generally aware of the occupational health and safety management systems in place but only 43% felt that mercury management in the workplace effectively prevented exposure. The lead surveillance system in Queensland was found to be inadequately managed with approximately 37% of registered doctors no longer practicing in the field and their being no way for the government to collect reliable data on the extent of lead exposure in workplaces. The occupational health and safety management systems in the companies surveyed in Queensland and Korea were found to be influenced by the legislative arrangements in place in each of the locations. The Korean systems were more geared to meeting the regulatory requirements whereas the Queensland systems were geared more towards a risk management approach. However substantial differences were also noted depending on the size of the organisation in each case. Legislative arrangements in Korea and Queensland were found to provide reasonable protection from heavy metal exposure to workers however improvements in both systems are needed. The legislation was also found to influence the occupational health and safety management systems in place with performance-based legislation producing systems having a wide risk management focus while a narrower regulatory based focus was noted in Korea where more prescriptive legislation is in force. A confounding factor in the nature of the occupational health and safety management system in place is the size of the organisation and particular attention needs to be paid to this when legislative approaches are considered.
28
Kim, Jeong-Ah. „The role of legislation in driving good occupational health and safety management systems: A comparison of prescriptive based legislation“. Thesis, Queensland University of Technology, 2004. https://eprints.qut.edu.au/15966/1/Jeong-ah_Kim_Thesis.pdf.
Der volle Inhalt der QuelleAnnotation:
Countries seek to control exposure to hazardous substances and environments by the enactment of legislation. In the past thirty years, two major different approaches to occupational health and safety legislation have been devleoped by countries around the world. The performance-based legislative approach has been linked with the emergence of occupational health and safety management systems but no research has previously been done to determine whether or not
the legislative approach taken by government influences the introduction or form of occupational health and safety management
systems used by organisations. Similarly, although the reasons why Australia and other countries have moved to performance-based
legislation have been explained in terms of social, political and economic factors that influenced the change, little research has been
done on the effectiveness of this approach compared with the prescriptive approach of countries such as Korea.
-I-
The overall aim of this research is to develop a conprehensive
understanding of the management of expusre to heavy metals in selected industries in Korea and Australia.
The specific objectives of the study are to determine:
The effectiveness of heavy metal exposure management in the fluorescent lamp manufacturing industry in Korea, and an Oral Health Service, and lead-risk workplaces in Queensland, Australia; The management of the legislative arrangements for health surveillance in Korea and Queensland, Australia;
The characteristics of the occupational health and safety management systems that are in use in the heavy metal industries in Korea in Australia; and The effectiveness of prescriptive and performance based legislative systems in protecting the health and safety of workers in heavy metal based industries.
Secondary analysis of biological monitoring data from 6 fluorescent lamp manufacturing companies (8 workplaces) in Korea was used to examine the extent of mercury exposure and the effectiveness of the health surveillance system in that country. A survey of dental workers in an oral health service in Queensland provided data on the extent of mercury exposure to the workforce and workers' attitudes to the management of occupational risks. The efficiency of the lead health surveillance in Queensland was examined by way of a questionnaire survey of lead designated doctors in the state. A survey of registered lead-risk companies and the oral health servies in Queensland, and 5 of the fluorescent lamp manufacturing companies in Korea provided data on the occupational health and safety management systems in place in these organisations.
The health surveillance system for mercury exposed workers in Korea was found to have reduced the incidence of workers with biological
levels of mercury above the Baseline Level from 14% in 1994 to 7% in 1999. Bilogical testing of dental workers in Queensland discovered no
workers with biological levels of mercury approaching the Baseline Level and air monitoring failed to locate any areas where workers were likely to be exposed to levels approaching the Workplace Exposure Standard. The staff of the Oral Health Service were generally aware of the occupational health and safety management systems in place but only 43% felt that mercury management in the workplace effectively prevented exposure.
The lead surveillance system in Queensland was found to be inadequately managed with approximately 37% of registered doctors
no longer practicing in the field and their being no way for the government to collect reliable data on the extent of lead exposure in workplaces. The occupational health and safety management systems in the companies surveyed in Queensland and Korea were found to be influenced by the legislative arrangements in place in each of the locations. The Korean systems were more geared to meeting the regulatory requirements whereas the Queensland systems were geared more towards a risk management approach. However
substantial differences were also noted depending on the size of the organisation in each case.
Legislative arrangements in Korea and Queensland were found to provide reasonable protection from heavy metal exposure to workers however improvements in both systems are needed. The legislation was also found to influence the occupational health and safety management systems in place with performance-based legislation producing systems having a wide risk management focus while a narrower regulatory based focus was noted in Korea where more
prescriptive legislation is in force. A confounding factor in the nature of
the occupational health and safety management system in place is the size of the organisation and particular attention needs to be paid to this
when legislative approaches are considered.
29
Sommer, Samantha. „Hybrid Metal-Ligand Hydrogen-Bonded (MLHB) Architectures Based on the Quinolone Subunit: Understanding and Expanding the Accessible Space of Supramolecular Systems“. Thesis, University of Oregon, 2015. http://hdl.handle.net/1794/19298.
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Despite the prevalence of supramolecular architectures derived from metal-ligand or hydrogen-bonding interactions, few studies have focused on the simultaneous use of these two strategies to form discrete metal-ligand hydrogen-bonded (MLHB) assemblies.
The design, synthesis, and characterization of 2-quinolone based hybrid subunits, 7-DPQ and 5-PYQ, that contain phosphine and pyridyl metal binding sites, respectively, is reported. Both subunits give two-fold symmetric hydrogen-bonded tectons that assemble with metal precursors to give hybrid MLHB structures. Treatment of [Cp*RhCl2]2 with the 7-DPQ subunit yields hybrid MLHB assemblies with closed topology. 1H diffusion ordered spectroscopy experiments established the stability of the structures in solution, and the measured hydrodynamic radii match those determined crystallographically, suggesting that the closed topology is maintained in solution and the solid state.
In order to further explore possible MLHB architectures and test the selectivity boundaries of our quinolone-based subunits we report the selective assembly of 5-PYQ with mono- and bis-platinated anthracene precursors. Addition of 5-PYQ to [1-trans-Pt(PEt3)2NO3]-8-chloroanthracene yielded a hybrid MLHB structure with preorganization for a hybrid MLHB polymer. Despite the systems preorganization for the hybrid polymeric structure the assembly of 5-PYQ with 1,8-bis(trans-Pt(PEt3)2NO3)anthracene selects only for one discrete closed self-assembled macrocycle. The strong π-π stacking interactions of the 5-PYQ subunits erode the hydrogen-bonding fidelity to favor ambidentate coordination modes of 5-PYQ and give the non-hybrid macrocycle.
In the course of investigating the intricacies of hybrid MLHB supramolecular structures we observed that, in addition to metal-ligand and hydrogen-bond interactions, the π-π stacking interactions of the 7-DPQ and 5-PYQ subunits played a critical role in determining the final assemblies. In fact, the prominent π-π interactions were typically found to be more favorable than the quinolone interligand hydrogen-bonding interactions.
These results contribute to the overall knowledge of the design principles, synthesis, characterization, and fundamental assembly trends when exploiting both hydrogen-bonding and metal-ligand interactions to form stable supramolecular architectures. These studies have provided the foundation for expanding the accessible space of supramolecular chemistry to include rationally designed hybrid MLHB systems to give structures that more closely mimic the complex supramolecular systems observed in Nature.
This dissertation includes both previously published/unpublished and co-authored material.10000-01-01
30
Rae, Bruce R. „Micro-systems for time-resolved fluorescence analysis using CMOS single-photon avalanche diodes and micro-LEDs“. Thesis, University of Edinburgh, 2009. http://hdl.handle.net/1842/4219.
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Fluorescence based analysis is a fundamental research technique used in the life sciences. However, conventional fluorescence intensity measurements are prone to misinterpretation due to illumination and fluorophore concentration non-uniformities. Thus, there is a growing interest in time-resolved fluorescence detection, whereby the characteristic fluorescence decay time-constant (or lifetime) in response to an impulse excitation source is measured. The sensitivity of a sample’s lifetime properties to the micro-environment provides an extremely powerful analysis tool. However, current fluorescence lifetime analysis equipment tends to be bulky, delicate and expensive, thereby restricting its use to research laboratories. Progress in miniaturisation of biological and chemical analysis instrumentation is creating low-cost, robust and portable diagnostic tools capable of high-throughput, with reduced reagent quantities and analysis times. Such devices will enable point-of-care or in-the-field diagnostics. It was the ultimate aim of this project to produce an integrated fluorescence lifetime analysis system capable of sub-nano second precision with an instrument measuring less than 1cm3, something hitherto impossible with existing approaches. To accomplish this, advances in the development of AlInGaN micro-LEDs and high sensitivity CMOS detectors have been exploited. CMOS allows electronic circuitry to be integrated alongside the photodetectors and LED drivers to produce a highly integrated system capable of processing detector data directly without the need for additional external hardware. In this work, a 16x4 array of single-photon avalanche diodes (SPADs) integrated in a 0.35μm high-voltage CMOS technology has been implemented which incorporates two 9-bit, in-pixel time-gated counter circuits, with a resolution of 400ps and on-chip timing generation, in order to directly process fluorescence decay data. The SPAD detector can accurately capture fluorescence lifetime data for samples with concentrations down to 10nM, demonstrated using colloidal quantum dot and conventional fluorophores. The lifetimes captured using the on-chip time gated counters are shown to be equivalent to those processed using commercially available external time-correlated single-photon counting (TCSPC) hardware. A compact excitation source, capable of producing sub-nano second optical pulses, was designed using AlInGaN micro-LEDs bump-bonded to a CMOS driver backplane. A series of driver array designs are presented which are electrically contacted to an equivalent array of micro-LEDs emitting at a wavelength of 370nm. The final micro-LED driver design is capable of producing optical pulses of 300ps in width (full width half maximum, FWHM) and a maximum DC optical output power of 550μW, this is, to the best of our knowledge, the shortest reported optical pulse from a CMOS driven micro-LED device. By integrating an array of CMOS SPAD detectors and an array of CMOS driven AlInGaN micro-LEDs, a complete micro-system for time-resolved fluorescence analysis has been realised. Two different system configurations are evaluated and the ability of both topologies to accurately capture lifetime data is demonstrated. By making use of standard CMOS foundry technologies, this work opens up the possibility of a low-cost, portable chemical/bio-diagnostic device. These first-generation prototypes described herein demonstrate the first time-resolved fluorescence lifetime analysis using an integrated micro-system approach. A number of possible design improvements have been identified which could significantly enhance future device performance resulting in increased detector and micro-LED array density, improved time-gate resolution, shorter excitation pulse widths with increased optical output power and improved excitation light filtering. The integration of sample handling elements has also been proposed, allowing the sample of interest to be accurately manipulated within the micro-environment during investigation.
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Reissner, Alexander [Verfasser], Martin [Akademischer Betreuer] Tajmar und Andreas [Gutachter] Werner. „Metal Hydrides as Enabling Technology for the use of Hydrogen-Based Energy Storage Systems on Telecommunication Satellites / Alexander Reissner ; Gutachter: Andreas Werner ; Betreuer: Martin Tajmar“. Dresden : Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2017. http://d-nb.info/1140735268/34.
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Kijak, Anna M. „Analytical Preconcentration Systems Based on Nanostructured Materials“. Miami University / OhioLINK, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=miami1049915571.
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Robinson, Simon Jonathan. „Catalytic and selective transition metal mediated isomerisations of allylic alkoxides to enolates“. Thesis, University College London (University of London), 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286152.
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Bhowmik, Ayan. „Refractory metal laves phase alloys based on the Cr-Ta system“. Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.607770.
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González, Fernández Alfredo A. „Studies and integration of Silicon-based light emitting systems“. Doctoral thesis, Universitat de Barcelona, 2014. http://hdl.handle.net/10803/285863.
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This project presents the study of luminescent devices and materials based on silicon for its use in the fabrication of an optical system that integrates light emitter, waveguide, and light sensor in a single chip obtained by the use of standard CMOS techniques and materials. The atomic and structural characteristics of the materials are analysed and related to its luminescent response. Taking into account the results from the active material characterization, the design, fabrication, and characterization of electroluminescent devices based on such materials is presented. Finally, the design, fabrication and characterization of a complete CMOS compatible Integrated Optical System consisting of a transceiver, is discussed and analysed.
The active materials used for light emission were different Silicon Rich Silicon Dioxide(SRO) and SRO-Si3 N4 bi-layers, obtained by a variety of CMOS compatible techniques and fabrication parameters. Two contributing mechanisms to photoluminescence in SRO were identified in all cases, respectively linked to the presence of radiative defects, and to Quantum Confinement phenomena. It is proposed and tested a model to describe the latter, based on the effective mass approximation, and the relation between the amount of Si-Si links and the volume of nano-agglomerates present in the material. In bi-layer samples, an additional luminescence band was observed, found to be generated in the transition material between silicon nitride and dioxide, and related to energy states introduced by defects. Samples with SRO thickness ten times higher than that of nitride, presented a clear dominance of the photoluminescence related to the dioxide.
The centres responsible for electroluminescence in the electronicd evices were found to be fundamentally the same as those for photoluminescence despite the differences in measured spectra, and it was concluded that the influence of the architecture on the light output is of significant importance. It was shown that bi-layered devices delivered better results in terms of efficiency, light emission control, distribution and stability. The carrier transport mechanisms observed in the devices were dominated by material breakdown in single-layered devices, and Trap-assisted Tunnelling in the bi-layers.
The Optical System integrating the light emitter, a waveguide, and a light detector, was designed and fabricated based on the results from the fabrication and analysis of the stand alone light emitting devices. During the design stage, it was corroborated by computer simulations that the characteristics of thelight emittedby thedevices thatpresented thehighest e.ciency and reliability, were suitable for its transmission trough the proposed waveguide architecture. The detection capabilities of the designed light sensors were also theoretically corroborated to be appropriated for the detection of the emitted light type.
The proper functioning of the elements conforming the finally fabricated system was probed. Differences were found in the operation of the stand alone light emitting devices and those integrated, but the resulting luminescence was within the boundaries of the transmittable spectrum. The operation of the Integrated Optical System was tested and preliminarily studied, obtaining positive results in its stimulus-detection response, fulfilling the main objective of the work, and opening the door for further studies which can lead to the optimization of the design for particular applications.Este proyecto aborda el estudio de dispositivos y materiales luminiscentes basados en silicio para su uso en la fabricación de un sistema óptico que integre emisor de luz, guía de ondas, y sensor en un solo chip obtenido mediante el uso de técnicas y materiales estándar para la fabricación CMOS. Las características atómicas y estructurales de los materiales son analizados y relacionados con su respuesta luminiscente. Considerando los resultados de la caracterización del material activo, se presenta el diseño, fabricación, y caracterización de dispositivos electroluminiscentes basados en dichos materiales. Finalmente, se discute y analizan el diseño, fabricación, y caracterización de un transceptor como Sistema Óptico Integrado. Los materiales activos para la emisión de luz fueron distintos Dióxidos de Silicio enriquecidos con Silicio (SRO por sus siglas en inglés) y bi-capas SRO-Si3 N4, obtenidos mediante una variedad de técnicas compatibles con los procesos CMOS y distintos parámetros para los mismos. Se identificaron dos mecanismos que contribuyen a la fotoluminiscencia del SRO en todos los casos, relacionados con defectos radiativos y fenómenos de Confinamiento Cuántico, respectivamente. Se sugiere y pone a prueba un modelo para describir este último, basado en la aproximación de la masa efectiva y la relación entre la cantidad de enlaces Si-Si y el volumen de nano-aglomerados. En muestras bi-capa, se observó una banda adicional de luminiscencia, cuya generación fue identificada en el material de transición entre el nitruro de silicio y el óxido, y relacionada con estados de energía introducidos por defectos. Muestras con un espesor de SRO diez veces mayores a aquel del nitruro presentaron una clara dominación de la luminiscencia relacionada con el óxido. Se halló que los centros responsables por la electroluminiscencia en los dispositivos electrónicos son fundamentalmente los mismos que los responsables de la fotoluminiscencia a pesar de las diferencias en los espectros medidos, y se concluyó que la influencia de la arquitectura sobre el espectro de salida es de importancia significativa. Se mostró que dispositivos bi-capa entregan mejores resultados en términos de eficiencia, control sobre la luz emitida, distribución de la misma, y estabilidad en el funcionamiento. Se observó que los mecanismos de transporte de carga hallados en los dispositivos están dominados por ruptura del material en el caso de dispositivos de una sola capa, y Tuneleo Asistido por Trampas en el caso de dispositivos bi-capa. El Sistema Óptico que integra el emisor, una guía de ondas, y el detector de luz, fue diseñado y fabricado con base en los resultados de la fabricación y análisis de los dispositivos emisores de luz aislados. Durante la etapa de diseño, se corroboró mediante simulaciones por computadora que las características de la luz emitida por los dispositivos que presentaron la máxima eficiencia y fiabilidad fueran apropiadas para su transmisión a través de la guía de ondas propuesta. También se corroboró teóricamente que las capacidades de detección de los sensores diseñados fuera la adecuada para el tipo de luz emitida. Se exploró el apropiado funcionamiento de los elementos del sistema finalmente fabricado. Se encontraron diferencias en la operación de los dispositivos emisores de luz aislados y aquellos integrados, pero la luminiscencia resultante se halló dentro de los límites del espectro transmisible. La operación del Sistema Óptico Integrado fue probada y estudiada de manera preliminar, con la obtención de resultados positivos en su respuesta estímulo-detección, cumpliendo así con el objetivo principal del trabajo, y abriendo la puerta para estudios posteriores que pueden guiar a la optimización del diseño del sistema para aplicaciones particulares.
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Bektas, Murat. „Fundamentals Of A Metal Surface Imaging System Based On Laser-optic Principles“. Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/2/12610595/index.pdf.
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The confocal laser-scanning microscope (CLSM), known simply as a confocal microscope, is an important instrument which allows us to observe an object or a surface in three-dimensions with confocal microcopy technique. The basic difference of confocal microscopy is detecting the in- focused light, while the out of focus light is blocked out by the help of a pinhole. By this optical dissection ability of confocal microcopy, CLSM provides the images of investigated object or the surface with higher resolution and contrast as against conventional microscopic systems. Various types of Laser Scanning confocal microscopes have been developed and due to its high resolution and contrast they have become an invaluable tool for investigations in many areas like biology and medicine. In addition to its wide range of use, confocal microscope can be used for detecting of possible defects on metal surfaces.
In this thesis our goal was to develop the analytical and theoretical back ground necessary for the successful completion of a laser/optic system coupled to a fiber bundle waveguide based on confocal scanning principles to effectively image a non-uniform, metal surface with speed and precision in order to assess any surface damage. In addition to this analysis we demonstrate a working confocal microscopy set-up and investigate the factors which affect the image quality by the experiments conducted in METU (Middle East Technical University) Laser Laboratory
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Wang, Wanhe. „Development of luminescent iridium(III) complex-based probes for monitoring analytes in environmental and biological systems“. HKBU Institutional Repository, 2019. https://repository.hkbu.edu.hk/etd_oa/660.
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Transition metal complexes offer potential alternatives to fluorescent organic compounds in various sensing applications. They show several characteristic properties over organic dyes, such as strong luminescence emission, long emission lifetime and large Stoke shift. Among transition metal complexes, cyclometalated iridium(III) (Ir) complexes are most widely explored for sensing applications, due to their bright and tuneable phosphorescence emission. Up to now, Ir(III) complexes have been successfully applied to detect a range of analytes in environmental and biological systems, such as cations, anion, small molecules and proteins. In this thesis, we deeply explored the capability of Ir(III) complexes to the detection of a range of targets including metal ions, small molecules and biomarkers. Several strategies are used to improve the biocompatibility of Ir(III)-based probes while retaining their desirable characteristics. In chapter 2, we developed a novel Ir(III) complex for the detection of Al3+ with a detection limit of 1 μM. The long lifetime of the complex was harnessed to distinguish luminescence response to Al3+ from autofluorescence in biological samples by TRES experiment, while the probe was also successfully applied for imaging Al3+ in living cells. The results have been published as Chem. Commun., 2016, 52, 3611. In chapter 3, we reported a new reaction-based luminogenic probe for imaging both H2S and hypoxia in living zebrafish. This probe demonstrated their utility for the detection of H2S in solution, living cells and zebrafish model, while it was also capable of discriminating hypoxic from normoxic cells and zebrafish model. The results have been published as Sens. Actuator B-Chem., 2018, 255, 1953. In chapter 4, we conjugated a natural product oridonin to an Ir(III) scaffold for tracking intracellular NF-κB. This complex was successfully applied to track NF-κB translocation induced by TNF-α, without affecting the translocation process. The results have been published as Chem. Eur. J., 2017, 23, 4929. In chapter 5, an Ir(III) scaffold with galactose moiety was designed and synthesized for discriminating ovarian carcinoma cell lines from normal cell lines. This probe can selectively "light up" ovarian carcinoma cells with negligible luminescence in normal cells. The results have been published as Anal. Chem., 2017, 89, 11679. These works have further demonstrated the utility of Ir(III) complex in the monitoring environment and studying biomolecules in living systems. In particular, the conjugation of endogenous molecule galactose or a natural compound oridonin to Ir(III) scaffolds highlights an effective solution to develop biocompatible probes. However, it should be pointed out that there is a need for developing a general strategy to improve the biocompatibility of luminescent Ir(III) complex-based probes, while there is huge potential for incorporating luminescent Ir(III) complexes-based sensing platforms into portable devices, and exploring theranostic probes.
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Burwell, Edwin Dudley IV. „A MICROPLASMA-BASED SPUTTERING SYSTEM FOR DIRECT-WRITE, MICROSCALEFABRICATION OF THIN-FILM METAL STRUCTURES“. Case Western Reserve University School of Graduate Studies / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=case1449545772.
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Choi, Jaehyouk. „Fully-integrated DLL/PLL-based CMOS frequency synthesizers for wireless systems“. Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/42698.
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A frequency synthesizer plays a critical role in defining the performance of wireless systems in terms of measures such as operating frequency range, settling time, phase noise and spur performance, and area/power consumption. As the trend in mobile system design has changed from single-standard systems to multi-standard/multi-application systems, the role of frequency synthesizers has become even more important.
As the most popular architecture, a phase-locked loop (PLL)-based frequency synthesizer has been researched over the last several decades; however, many unsolved problems related to the PLL-based synthesizer are still waiting for answers. This dissertation addresses key challenges related to fully integrated PLL-based frequency synthesizers, including the problem of large area consumption of passive components, the inherent reference-spur problem, and the problem of trade-offs between integer-N PLLs and fractional-N PLLs.
In this dissertation, new techniques and architectures are presented and developed to address those challenges. First, a low-phase-noise ring oscillator and a capacitor multiplier with a high-multiplication factor efficiently minimize the silicon area of sub-components, and a compact programmable delay-locked loop (DLL)-based frequency multiplier is developed to replace the PLL-based frequency synthesizer. Second, the charge-distribution mechanism for suppressing reference spurs is theoretically analyzed, and an edge interpolation technique for implementing the mechanism is developed. Finally, the concept and the architecture of sub-integer-N PLL is proposed and implemented to remove trade-offs between conventional integer-N PLLs and fractional-N PLLs.
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Agarwal, Kuldeep. „Physics Based Hierarchical Decomposition of Processes for Design of Complex Engineered Systems“. The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1322152146.
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Albert-Soriano, María. „Towards sustainability in organic transformations catalysed by 1,3-bis(carboxymethyl)imidazole-based systems“. Doctoral thesis, Universidad de Alicante, 2020. http://hdl.handle.net/10045/115117.
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Esta tesis doctoral describe la síntesis y aplicación como catalizadores de varios sistemas basados en el zwitterion 1,3-bis(carboximetil)imidazol. En el Capítulo 1 se describe la síntesis del compuesto 1,3-bis( carboximetil)imidazol, así como de tres sales de imidazolio derivadas (cloruro, bromuro y yoduro) y cinco estructuras metal-orgánicas conteniendo este compuesto como ligando (cobre, calcio/cloro, calcio/bromo, bario/cloro y bario/bromo). En todas las metodologías seguidas se utilizan materiales de partida fácilmente disponibles, tienen una preparación sencilla y son eficientes y reproducibles. En el Capítulo 2 se describe la síntesis de amidas a partir de ácidos carboxílicos y formamidas mediante acoplamiento oxidativo, usando la estructura metal-orgánica conteniendo cobre. Se ha obtenido una gran variedad de amidas combinando distintos ácidos y formamidas. Además, esta metodología se ha aplicado a la síntesis de dos compuestos interesantes en escala preparativa. En el Capítulo 3 se describe la síntesis de quinolinas mediante la reacción de Friedlander usando todas las estructuras metal-orgánicas preparadas. Estos sistemas son complementarios, esto es, la formación de las quinolinas a partir de cada sustrato depende del sistema utilizado, pero esto permite tener accesos a una gran variedad de quinolinas, partiendo de 2- aminobenzaldehídos o 2-aminoaril cetonas. En el Capítulo 4 se describe la síntesis de quinolinas mediante la reacción de Friedliinder utilizando solo el cloruro de 1,3-bis(carboximetil)imidazolio. A partir de diferentes 2-aminobenzaldehídos y 2-aminoaril cetonas, se ha preparado una gran cantidad de quinolinas diferentes. Dos de ellas se han podido preparar en escala preparativa. En el Capítulo 5 se describe la síntesis de N-alilanilinas, 2-alilanilinas y 4-alilanilinas mediante sustitución de alcoholes alílicos con anilinas. La regioselectividad de la reacción depende de los diferentes contraiones de la sal de 1,3-bis(carboximetil)imidazolio usada: cloruro, bromuro o yoduro. Se han preparado dos alilanilinas en escala de multigrano, demostrando la efectividad de los catalizadores. Todos los sistemas catalíticos preparados en esta tesis se han usado durante varios ciclos, y todos los procesos se han llevado a cabo sin añadir disolventes.
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Ozsuer, Erhan. „Development Of A Web-based Manufacturing Application System For Rotational Parts“. Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/1059930/index.pdf.
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Developing process plans and part programs rapidly and correctly for CNC machine tools plays a vital role in manufacturing. This study is concerned with the development of a web-enabled virtual design and manufacturing application system for rotational parts. The object oriented methodology is used in the application development. Windows Distributed interNet Application (DNA) architecture which describes a framework of building software technologies in an integrated web and client-server model of computing, is employed in the system. The entire system was modeled with Unified Modeling Language (UML), which is an industry-standard visual modeling notation to express software development architectures. Feature-based design approach, being a practical way of linking the design with manufacturing, is implemented in the rotational part design.
Users have to be registered in order to use the system. With the supplied web site, users can easily register to system. After registration, the user obtains a password and a unique username. Upon the user authentication, the user session starts. A typical user session involves new or past project selection, material selection, part sketching, blank size definition and cutting parameters determination. After all the steps are completed, process plan and part-program, which are required to manufacture the part on Denford Mirac CNC Turning Machine are generated and displayed on the web site and then saved to the database. The application enables the users to see past projects and to generate new process plan and part programs for different cutting parameters. The process plan, part program and the 2D wire frame drawing of the corresponding part are demonstrated on the web site for the chosen projects.
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Sinha, Rajib. „Industrial Ecology Approaches to Improve Metal Management : Three Modeling Experiments“. Licentiate thesis, KTH, Industriell ekologi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-164872.
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A linear model of consumption − produce-use-dispose − has constantly increased the pressure on the environment in recent decades. There has been a great belief that technology will solve the problem, but in many cases it is only partly contributing to the solution. For a full solution, the root causes of problems need to be identified. The drivers-pressures-state-impact-response (DPSIR) framework allows the drivers of a specific problem to be identified by structuring the causal relations between humans and the environment. A state/ impact-based approach can help identify pressures and drivers, and make what can be considered an end-of-pipe response. Rather than that mainstream approach, this thesis adopts a pressure-based driver-oriented approach, which could be considered a proactive approach to environmental resource management. In physical resource management, material flow analysis (MFA) is one of the tools used for communication and decision support for policy response on resource productivity and pollution abatement. Here, element flow analysis (EFA), a disaggre- gation of MFA for better mass balance, was applied in pollution control and resource management. The pressure-based driver-oriented approach was used to model element flows and thus identify the drivers of problems in order to improve pollution control and resource management in complex systems. In one case study, a source-storage-transport model was developed and applied in five lakes in the Stockholm region to identify the drivers of copper pollution by monitoring the state of the environment through element flow modeling linking diffuse sources and fate in the lakes. In a second case study, a system dynamics modeling approach was applied in dynamic element flow modeling of the global mobile phone product system to investigate the drivers for closing the material flow loop through a sensitivity analysis. In a third case study, causal loop diagram modeling was used for proactive resource management to identify root causes of a problem in a complex system (product systems of physical consumer goods) by qualitatively analyzing unintended environmental consequences of an improvement action. In the case study on lakes in the Stockholm region, the source-transport-storage model proved capable of predicting copper sources through monitoring the sediment copper content in the heavily copper-polluted lakes. The results also indicated how the model could help guide policy makers in controlling copper pollution. The system dynamics study proposed an eco-cycle model of the global mobile phone product system by tuning the drivers, which could lessen the pressures on resources by decreasing the resource demands for production and increasing resource recovery at product end-of- life. The causal loop diagram study showed that a broader systems approach is required to understand and identify the drivers for proactive resource management in a complex system, where improvement actions can lead to unintended consequences.QC 20150420
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Ilina, Yulia. „Structural characterization of Ni-containing metalloenzymes from archaea by X-ray crystallography and transmission electron microscopy“. Doctoral thesis, Humboldt-Universität zu Berlin, 2019. http://dx.doi.org/10.18452/20596.
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In der vorliegenden Arbeit werden zwei Enzymsysteme – Ni-haltige Kohlenmonoxid-Dehydrogenase (CODH) und [NiFe]-haltige Hydrogenase – strukturell untersucht.
Im 1. Teil werden die Untersuchungen des ACDS-Komplexes aus A. fulgidus mittels Transmissionselektronenmikroskopie (Negativkontrastierung und der Kryo-Einbettung) geschildert. Die 3D-Rekonstruktion mit einer Auflösung von 29 Å wird de novo ermittelt und drei mögliche Positionen für die CODH-Untereinheit vorgeschlagen.
Im 2. Teil wird die Röntgenkristallstrukturanalyse der CODH-Untereinheit des ACDS Komplexes aus A. fulgidus geschildert. Das Protein besteht aus α- und ε-Untereinheiten, die zusammen eine α2ε2-Stöchiometrie bilden (Afα2ε). Während die Gesamtstruktur von Afα2ε2 jener von M. barkeri (Mbα2ε2) ähnelt, führt der Austausch der koordinierenden Cys zu Asp und Glu zu einer Deletion des verbrückenden FeS-Zentrums. Die Rolle der ε-Untereinheit wird durch kinetische Studien untersucht. Die CO-abhängige FAD-Reduktionsaktivität von Afα2ε2 folgt einer Michaelis-Menten Kinetik. Die Mbα2ε2 hat ein ähnliches Kinetikverhalten. Im Gegensatz dazu weist die CODH-II von C. hydrogenoformans, die keine ε-Untereinheit hat, eine lineare Abhängigkeit der CO-abhängigen FAD-Reduktionsaktivität von Flavin auf. Diese Beobachtungen sind im Einklang mit der Annahme, dass die ε-Untereinheit ein Gerüst für die Flavinbindung bereitstellt.
Der 3. Teil ist der F420-reduzierenden Hydrogenase aus M. barkeri (MbFRH) gewidmet. Die Struktur von MbFRH wird mittels Röntgenkristallographie bestimmt und ergibt eine dodekamerische Anordnung von ca. 1.2 MDa. Zusammen mit der etablierten Elektronenübertragungskette, beobachtet in FRH aus M. marburgensis, wird in MbFRH auch ein [2Fe2S]-Cluster und eine Fe-Stelle detektiert. Schließlich führen die schwingungsspektroskopischen Analysen zusammen mit der Röntgenkristallographie zu dem Schluss, dass MbFRH in einem bisher strukturell nicht charakterisierten, katalytisch aktiven Nia-S Zustand isoliert wird.In this work, we structurally characterize two metal-based enzyme systems from archaea: Ni-containing CO dehydrogenase (CODH) and [NiFe] containing hydrogenase. In the first chapter we investigate, using transmission electron microscopy, the ACDS complex from A. fulgidus (AfACDS). The purified ACDS complex can be visualized as an intact globular protein particle by negative stain and vitrification techniques. The 3D reconstruction is determined de novo to 29 Å-resolution by single-particle analysis. We suggest three possible positions for the CODH subunit within ACDS by rigid-body fitting. In the second chapter we determine the X-ray crystal structure of the CODH subunit. The 220 kDa protein is composed of α- and ε-subunits that form a heterodimer with (α2ε2) stoichiometry (Afα2ε2). While the overall structure of Afα2ε2 resembles the previously reported structure of the α2ε2-subunit from M. barkeri (Mbα2ε2), the naturally-occurring exchange of the Cys to Asp and Glu results in a depletion of the bridging iron-sulfur cluster. The role of the ε-subunit is investigated by kinetics studies. CO-dependent FAD reduction activity of Afα2ε2 exhibits Michaelis-Menten type kinetics. The same kinetic type is demonstrated for the Mbα2ε2-subunit. In contrast, the ε-subunit lacking CODH-II from C. hydrogenoformans shows linear dependency between CO-dependent FAD reduction activity and flavin concentration. The data suggests that the ε-subunit provides a scaffold for the flavin binding. In the third chapter we study the F420-reducing hydrogenase from M. barkeri (MbFRH). Its structure is solved by X-ray crystallography, revealing a dodecameric arrangement of 1.2 MDa. Along with the established ET chain observed in FRH from M. marburgensis, one solvent-exposed [2Fe2S] cluster and an additional Fe metal site are detected. The combined approach of X-ray crystallography and vibrational spectroscopy reveals that MbFRH is isolated in the previously structurally uncharacterized Nia-S state.
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Secondo, Lynn E. „Toxicological Inhalation Effects of Metal-Based Nanoparticle Aerosols as Studied by a Portable In Vitro Exposure Cassette“. VCU Scholars Compass, 2018. https://scholarscompass.vcu.edu/etd/5705.
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The toxicology of aerosols in occupational settings is often performed through particle collection on a filter followed by reconstitution into cell culture media which can alter the biological effects. Current in vitro exposure systems require additional instruments to control temperature and humidity, making the system bulky and difficult to take to the field. The Portable In Vitro Exposure Cassette (PIVEC) was designed for personal monitoring, characterized using copper nanoparticles, tested with alveolar cells, and set-up for real-time monitoring. Three differently sized copper nanoparticles, 40-800 nm, were dispersed as a dry aerosol and measured gravimetrically and on a number concentration basis to determine the deposition efficiency of the PIVEC. A549 cells, a human alveolar adenocarcinoma epithelial line, were exposed to the aerosols and oxidative stress and cell viability were monitored post-exposure. The deposition efficiency ranged from 0.5% to 18% depending on method of analysis and size of particle. Oxidative stress increased within the first two hours post exposure, however there was no significant difference in cell viability at the four hour time point at deposited doses up to 1.63 mg/cm2.
Validation of the PIVEC was done in the laboratory using diesel exhaust. Metal oxide fuel additives are used to reduce emissions; however, additives have been shown to increase emitted nanoparticles. The PIVEC was used to determine the potential cytotoxicity and oxidative activity changes in A549 cells after exposure to either model particles or exhaust generated with or without a commercial, nano-cerium oxide based additive. Acellular experiments suggest a correlation between the deposition and the type of fuel used for the newly designed PIVEC. Cellular results suggest a decrease in cytotoxicity and no statistically significant effect on reactive oxygen species generation with the use of the nano-cerium oxide additive.
Rapid monitoring of oxidative stress was performed using an enzyme-based biosensor. The functionalized biosensor uses cytochrome c to measure reactive oxygen species through electrochemical detection during aerosol exposures. When compared to a traditional biological assay, the biosensor response was similar. The PIVEC is a unique device, designed to monitor aerosols using air-liquid interface in vitro techniques including a real-time monitor for oxidative stress.
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Karayilan, Dilek. „Removal Of Hydrogen Sulfide By Regenerable Metal Oxide Sorbents“. Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12605046/index.pdf.
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ABSTRACT
REMOVAL OF HYDROGEN SULFIDE
BY REGENERABLE METAL OXIDE SORBENTS
Karayilan, Dilek
M.S., Department of Chemical Engineering
Supervisor : Prof. Dr. Timur Dogu
Co-Supervisor: Prof. Dr. GülSen Dogu June 2004, 166 pages High-temperature desulfurization of coal-derived fuel gases is an essential process in advanced power generation technologies. It may be accomplished by using metal oxide sorbents. Among the sorbents investigated CuO sorbent has received considerable attention. However, CuO in uncombined form is readily reduced to copper by the H2 and CO contained in fuel gases which lowers the desulfurization efficiency. To improve the performance of CuO-based sorbents, they have been combined with other metal oxides, forming metal oxide sorbents. Sulfidation experiments were carried out at 627 oC using a gas mixture composed of 1 % H2S and 10 % H2 in helium. Sorbent regeneration was carried out in the same reactor on sulfided samples at 700 oC using 6 % O2 in N2. Total flow rate of gas mixture was kept at 100 ml/min in most of the experiments. In this study, Cu-Mn-O, Cu-Mn-V-O and Cu-V-O sorbents were developed by using complexation method. Performance of prepared sorbents were investigated in a fixed-bed quartz microreactor over six sulfidation/regeneration cycles. During six cycles, sulfur retention capacity of Cu-Mn-O decreased slightly from 0.152 to 0.128 (g S)/(g of Sorbent) while some decrease from 0.110 to 0.054 (g S)/(g of Sorbent) was observed with Cu-Mn-V-O. Cu-V-O showed a very good performance in the first sulfidation and excessive thermal sintering in the first regeneration prevented further testing. Sulfur retention capacity of Cu-V-O was calculated as 0.123 (g S)/(g of Sorbent) at the end of the first sulfidation. In addition, SO2 formation in sulfidation experiments was observed only with Cu-V-O sorbent.
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Huang, Yan-Yu. „CMOS-based amplitude and phase control circuits designed for multi-standard wireless communication systems“. Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/44908.
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Designing CMOS linear transmitter front-end, specially the power amplifiers (PAs), in multi-band wireless transceivers is a major challenge for the single-chip integration of a CMOS radio. In some of the linear PA systems, for example, polar- or predistortion-PA system, amplitude and phase control circuits are used to suppress the distortion produces by the PA core. The requirements of these controlling circuits are much different from their conventional role in a receiver or a phase array system. In this dissertation, the special design issues will be addressed, and the circuit topologies of the amplitude and phase controllers will be proposed.
In attempt to control the high-power input signal of a PA system, a highly linear variable attenuator with adaptive body biasing is first introduced. The voltage swing on the signal path is intentionally coupled to the body terminal of the triple-well NMOS devices to reduce their impedance variation. The fabricated variable attenuator shows a significant improvement on linearity as compared to previous CMOS works. The results of this research are then used to build a variable gain amplifier for linear PA systems that requires gain of its amplitude tuning circuits. Different from the conventional attenuator-based VGAs, the high linearity of the suggested attenuator allows it to be put after the gain stage in the presented VGA topology. This arrangement along with the current boosting technique gives the VGA a better noise performance while having a linear-in-dB tuning curve and better worst-case linearity.
The following part of the dissertation is about a compact, linear-in-degree tuned variable phase shifter as the phase controller in the PA system. This design uses a modified RC poly-phase filter to produce a set of an orthogonal phase vectors with smaller loss. A specially designed control circuit combines these vectors and generates an output signal with different phases, while having very small gain mismatches at different phase setting. The proposed amplitude and phase control circuits are then verified with a system level analysis. The results show that the proposed designs successfully reduce the non-linear effect of a wireless transmitter.
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Baydemir, Tuncay. „Investigations On The Properties And Drug Releases Of Biodegradable Polymer Coatings On Metal Substrates As Drug Carriers“. Phd thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/3/12611140/index.pdf.
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The use of various biodegradable polymers for the improvement of different controlled and long-lasting drug release systems is an active research area in recent years. The application of different metal prostheses, especially titanium based ones,
to the human body is also very common. A most important disadvantage of these prostheses is the risk of infection at the application areas that necessitates the removing of the prosthesis with a second surgical operation and reapplication of it after recovery. One of the best ways to solve this problem is to render metal prostheses infection free with controlled and sustainable drug (antibiotic) release systems.
The long term sustained release of relevant antibiotics from the various biodegradable polymer coated metal implants is studied in this thesis. Virtual fatigue analysis and drug loading capacities of titanium and stainless steel samples with different surface pattern and modifications were studied. Various biodegradable
polymer and drug combinations were examined and used for coating of metal prosthesis. The aim is to design polymer-drug coated metal implants that are capable of releasing a feasible amount of drug up to a period of at least 1 month. Various
coating techniques and surface modifications were also employed to improve the adhesional properties of the drug containing polymers. Their adhesion abilities on the metal substrates were tested by Lap-shear and T-peel tests. Polymer degradation
kinetics was followed by viscosity studies. Calibration lines for different drugs were obtained and drug releases on different systems were followed by using UV spectroscopy and microbial antibiotic sensitivity tests.
Among the techniques applied to prevent fast release of drugs initially, the coatings of Vancomycin absorbed β
-TCP (&
#946
-tricalcium phosphate) homogeneously distributed in poly(D,L-lactide-co-glycolide) solution in chloroform followed by an inert coating with poly(L-lactide) system proved to be feasible. By this technique, initial burst release was minimized and drug release from implants lasted nearly 2 months. Multiple coatings on polymer plus drug coating layer also gave promising results. In vivo studies on dorsal muscles of native rabbits with antibiotic loaded implants gave no negative effect on the surrounding tissues with high compatibility free of infection.
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Park, Yunseo. „Direct Conversion RF Front-End Implementation for Ultra-Wideband (UWB) and GSM/WCDMA Dual-Band Applications in Silicon-Based Technologies“. Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/7563.
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This dissertation focuses on wideband circuit design and implementation issues up to 10GHz based on the direct conversion architecture in the CMOS and SiGe BiCMOS technologies. The dissertation consists of two parts: One, implementation of a RF front-end receiver for an ultra-wideband system and, two, implementation of a local oscillation (LO) signal for a GSM/WCDMA multiband application. For emerging ultra-wideband (UWB) applications, the key active components in the RF front-end receiver were designed and implemented in 0.18um SiGe BiCMOS process. The design of LNA, which is the critical circuit block for both systems, was analyzed in terms of noise, linearity and group delay variation over an extemely wide bandwidth. Measurements are demonstrated for an energy-thrifty UWB receiver based on an MB-OFDM system covering the full FCC-allowed UWB frequency range.
For multiband applications such as a GSM/WCDMA dual-band application, the design of wideband VCO and various frequency generation blocks are investigated as alternatives for implementation of direct conversion architecture. In order to reduce DC-offset and LO pulling phenomena that degrade performance in a typical direct conversion scheme, an innovative fractional LO signal generator was implemented in a standard CMOS process. A simple analysis is provided for the loop dynamics and operating range of the design as well as for the measured results of the factional LO signal generator.
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Linder, Marc [Verfasser]. „Automotive cooling systems based on metal hydrides / by Marc Linder“. 2010. http://d-nb.info/1005593779/34.
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