Dissertations / Theses on the topic 'Substrates'
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Babcock, Gwen. "Maize β-glucosidase substrate specificity and natural substrates." Thesis, Virginia Tech, 1993. http://hdl.handle.net/10919/45360.
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Babcock, Gwen. "Maize [beta]-glucosidase substrate specificity and natural substrates /." This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-10312009-020235/.
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Elwin, M. P. "Semiconductor gas sensor substrates." Thesis, Swansea University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.636796.
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The detection and monitoring of toxic and explosive gases is often performed using semiconductor gas sensors. The substrate forms an important part of these sensors and current designs were investigated and tested. Various new designs were developed and thick and thin-film technologies employed to fabricate substrates and complete sensors. Substrateless sensors were also analysed and alterations performed to fashion new devices. A number of ceramic materials were tested for their suitability as semiconductor gas sensor substrates. The adhesion of thin-films and thermal conductivity were found to be the most crucial properties, in addition to those typical of ceramics, such as high temperature stability. Alumina is routinely used in semiconductor gas sensors and many other substrates and its performance was compared with less commonly used materials such as beryllia and aluminium nitride. These materials have a much greater thermal conductivity than alumina, and this was shown to improve sensitivity. A semi-empirical formula was derived to enable the prediction of sensitivity loss of a semiconductor gas sensor fabricated on a substrate with high temperature gradients, compared with one where gradients are minimal. The heaters used to raise the temperature of the substrate are typically made from platinum films. The longevity of thin platinum films depends on the film thickness and substrate surface, but for a given film thickness on a given substrate, additional adhesion layers of various metals were also shown to change the films stability and hence lifetime. Various substrate geometries were investigated to optimise temperature distribution and sensitivity. Predominantly subtle effects were observed, but a significant increase of sensitivity was found with an increased surface area. Electrical circuitry used to control and monitor sensors was summarised and a new substrate developed which could be used in conjunction with switching circuitry, the main advantage being that the fabrication of the substrate was more economical than standard substrate configurations.
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Jagdeo, Julienne. "Identification of novel picornavirus proteinase substrates using terminal amine isotopic labeling of substrates." Thesis, University of British Columbia, 2017. http://hdl.handle.net/2429/61277.
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Viruses have exploited strategies of proteolysis for the purposes of processing viral proteins and manipulating cellular processes to direct synthesis of new virions and subvert host antiviral responses. Many viruses encode proteases within their genome, of which many have been well studied among the family of positive-sense single-stranded RNA picornaviruses. A subset of host proteins have already been identified as targets of picornaviral proteinases; however, the full repertoire of targets is not known. In this thesis, a novel proteomics-based approach termed terminal amine isotopic labeling of substrates (TAILS) was used to conduct a global analysis of protease-generated N-terminal peptides by mass spectrometry and identify novel substrates of the 3C (3Cpro) and 2A (2Apro) proteinases from poliovirus and coxsackievirus type B3 (CVB3). TAILS was performed on HeLa cell extracts subjected to purified poliovirus 3Cpro or CVB3 2Apro, and on mouse HL-1 cardiomyocyte extracts subjected to purified CVB3 3Cpro. A list of high confidence candidate substrates for all three proteinases was generated, which included a peptide corresponding to the known poliovirus 3Cpro substrate polypyrimide tract binding protein at a known cleavage site, thus validating this approach. Furthermore, three identical peptides in both the poliovirus and CVB3 3Cpro list of high confidence substrates were identified, suggesting that cleavage of these substrates may contribute to general strategy of picornaviral infection. A total of seven high confidence substrates were validated as novel targets of 3Cpro in vitro and during virus infection. Moreover, mutations in the TAILS-identified cleavage sites for these candidates blocked cleavage in vitro and during infection. Depletion of these proteins by siRNAs modulated virus infection, suggesting that cleavage of these substrates either promotes or inhibits virus infection. In summary, an in vitro TAILS assay can be utilized to identify novel substrates of viral proteinases that are cleave during infection. Moreover, TAILS can identify common substrates of viral proteinases between different viral species, revealing general strategies of infection utilized by related viruses. Finally, the identification of novel host substrates provides new insights the viral-host interactions mediated by viral proteinases that are required for successful infection.Medicine, Faculty of
Biochemistry and Molecular Biology, Department of
Graduate
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Sidibeh, Cherno Omar. "Production and cleavage specificity determination of serine proteases mMCP-4, mMCP-5, rMCP-2 and two platypus serine proteases of the chymase locus." Thesis, Uppsala universitet, Institutionen för biologisk grundutbildning, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-197088.
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Serine proteases are a family of enzymes with a wide array of functions across both eukaryotes and prokaryotes. Here we have attempted to produce the serine proteases rat mast cell protease 2 and mouse mast cell protease 5 in a culture of HEK 293 cells; and mouse mast cell protease 4, platypus granzyme B-like protease and platypus hypothetical protease in a baculovirus expression system. Following production we wanted to analyse these serine proteases using a phage display assay and a battery of chromogenic substrates.
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Bock, Henry. "Fluids confined by nanopatterned substrates." [S.l.] : [s.n.], 2001. http://edocs.tu-berlin.de/diss/2001/bock_henry.pdf.
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Richmond, Mark Andrew. "Neural substrates of conditioned behaviour." Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301735.
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Erb, Suzanne Dorothe. "Studies of photochemically responsive substrates." Thesis, University of Oxford, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314847.
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Wang, Weijen 1980. "Directive antenna using metamaterial substrates." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/17995.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2004.Includes bibliographical references (p. 83-86).
Using a commercially available software(CST Microwave Studio®), two kinds of simulations have been carried out on different metamaterials in the microwave regime. One is transmission and reflection of a unit cell in a waveguide, and the other is parallel plate slab farfield radiation. The S-parameters are obtained from the wave-guide simulation and are used to retrieve the effective permittivity and permeability with which we can estimate the farfield radiation using analytic method. Thus, by comparing the farfield radiation from two different methods, analytic and slab simulation, we find that the analytic method is able to indicate many major features of the slab simulation's farfield results, implying that within a certain frequency range, we can treat the metamaterial as being homogeneous. After comparing the radiation performance of different metamaterial as antenna substrates, a structure is chosen to be optimized in such a way that it improves in radiation power, beamwidth, and bandwidth.
by Weijen Wang.
M.Eng.
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Judge, Benjamin Michael. "Thermoplastic bonding of microfluidic substrates." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/78165.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 103-108).
The assembly of microfluidic components for lab on a chip (LOC) applications that are manufactured from commodity thermoplastics is challenging. A survey of plastic welding techniques validates that contour transmission laser welding is the most viable and commercially demonstrated option for flexibility and sensitive microfluidic tolerances. However, understanding laser energy transmission and absorption phenomenon further complicates analyzing microfluidic thermoplastic welding, since the instantaneous material properties vary with both temperature and pressure. Thermoplastic welding has steep thermal gradients due to high thermal resistances, resulting in asymmetric heat affected zones (HAZ). Welding fixture sensitivities may be engineered to tune the weld energy required and a desired HAZ bias to reduce microfluidic channel deformation. Energy imparted by resistively heating thin implants can be easily measured and observed. Resistive heating of implants was demonstrated as a low energy, parallel, and feasible microfluidic welding assembly process. Lessons from implant heating can be applied to more complicated but analogous processes.
by Benjamin Michael Judge.
M.Eng.
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Speed, Jonathon. "Tailoring plasmonic substrates for SERS." Thesis, University of Southampton, 2011. https://eprints.soton.ac.uk/191315/.
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SERS is a useful spectroscopic technique that was discovered 30 years ago, and has recently seen a renaissance in research. Sphere segment void (SSV) substrates have been developed as reproducible, stable SERS substrates by electrodeposition of a metal through a colloidal template. The effect of adsorbing an organic monolayer on the surface of an SSV substrate was studied, which results in a slight shift in the plasmonic absorption. This was compared with the reduction of a diazonium salt on the surface, which results in a significant increase in plasmonic absorption, attributed to a physical sharpening of the metal structure, and in turn better defined plasmon modes. The Au surface was also modified with an ultra thin layer of Pt, and a comparison was made between oxidation-reduction cycled roughened (ORC) and SSV substrates with and without Pt. The SSV substrates were found to be more reproducible, and (after modification with a thin-layer of Pt), gave spectra more representative of bulk Pt substrates than ORC. Lastly the surface was functionalised with metallic nanoparticles (NPs), and a large increase in spectral intensity was observed. This was attributed to a strongly localised electric field between the NP and the substrate, which resulted in an additional enhancement of between 102-103 depending on the method of assembly used. Functionalisation of the NPs introduced the possibility of drug detection or studies in drug delivery using such a system.
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Rock, Martin. "Modified substrates for tetrapyrrole biosynthesis." Thesis, University of Cambridge, 1990. https://www.repository.cam.ac.uk/handle/1810/272742.
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Wang, Ying. "SURFACE MODIFICATION OF SILICATE SUBSTRATES." University of Akron / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=akron1164641616.
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Alrrshedan, Marrwa. "Photoluminescence from Bulk GaN Substrates." VCU Scholars Compass, 2012. http://scholarscompass.vcu.edu/etd/2802.
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Photoluminescence (PL) has been studied from different types of bulk GaN samples grown by hydride vapor phase epitaxy technique at Kyma Technologies. Point defects in bulk and at the surface affect the electrical and optical properties of GaN and could be analyzed by PL. The surface of the samples was polished with different techniques: one is chemical mechanical polish (CMP) and another is mechanical polish (MP). PL data from MP and CMP surfaces show that PL intensity from the CMP-treated surface is much higher than that from the MP-treated surface. This can be explained by defects formed during the process of MP polish. However, after the MP-treated surface is etched with RIE method, the optical quality of the MP-treated surface improves. In particular, as the depth of etching increases from 50 nm to 700 nm, the PL intensity increases by a factor of 1000. PL from the CMP surfaces of undoped bulk GaN samples contains a broad red luminescence (RL) band and a broad green luminescence (GL) band. However, PL from the CMP surfaces of Fe-doped GaN samples contained a blue luminescence band (labeled as BL2 in literature) and the yellow luminescence (YL) band. PL from MP-treated surfaces (both undoped and Fe-doped) was very weak and it contained relatively narrow red and green bands. These bands, labeled RL2 and GL2, respectively, are quenched at relatively low temperatures, in contrast to the RL and GL bands which are almost independent of temperature in the range from 15 to 300 K.
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Morgan, Laura. "Interfacial phenomena on sculpted substrates." Thesis, Imperial College London, 2008. http://hdl.handle.net/10044/1/11273.
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Karakossian, Movses H. "Molecular substrates of cerebellar plasticity." Diss., Restricted to subscribing institutions, 2007. http://proquest.umi.com/pqdweb?did=1428839071&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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CARRASCO, M. RENOM. "ASYMMETRIC HYDROGENATION OFINDUSTRIALLY RELEVANT SUBSTRATES." Doctoral thesis, Università degli Studi di Milano, 2016. http://hdl.handle.net/2434/361390.
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This thesis is divided in two parts:
In Part A (Chapters I to III), the studies on the asymmetric hydrogenation of substituted pyridines are described. These heteroaromatic compounds have proven very challenging to hydrogenate enantioselectively, however, the resulting chiral piperidines are of high industrial interest. In Chapter I, the state of the art and the mechanistic studies carried out on related N-heteroaromatic substrates are extensively discussed. In Chapter II, a new method for the asymmetric hydrogenation of 2-substitued pyridines is reported, together with complementary mechanistic studies that shed light on the origin of the enantioselectivity. In Chapter III, a method for the highly enantioselective hydrogenation of 3-substituted pyridines is disclosed. Furthermore, a deep mechanistic study reveals how this high level of stereocontrol can be achieved on substrates where no good results had been reported until now.
Part B (Chapter IV to VI) is centered on the problems associated with the high prices of noble metals. Two different solutions have been envisioned in the scientific community to overcome this problem. The first one relies on the replacement of the more commonly used expensive metals for cheap and abundant 1st row transition metals, such as Fe, Co, Ni or Cu. The second approach consists in recycling or reusing the noble metals for more than one reaction. In this regard, tandem catalysis is a commonly applied methodology, where the same metal is used to catalyze at least two different reactions in one pot. In our case, we focused on developing an asymmetric version of the tandem olefin metathesis–hydrogenation. Chapter IV contains an introduction on the topic. In Chapter V and VI, the conversion of different Ru-olefin metathesis catalysts to efficient asymmetric hydrogenation and asymmetric transfer hydrogenation catalysts is described, respectively. These transformations have been subsequently applied to the tandem metathesis-asymmetric hydrogenation and to the metathesis-asymmetric transfer hydrogenation.
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Dillard, Pierre. "Impact de la présentation des ligands sur la biophysique de l’adhésion des lymphocytes T." Thesis, Aix-Marseille, 2014. http://www.theses.fr/2014AIXM4085/document.
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Les lymphocytes T jouent un rôle central dans la réponse immunitaire adaptative. par l'intermédiaire d'un récepteur distinctif - le RCT (Récepteur des Cellules T), qui est responsable de la reconnaissance spécifique de peptides étrangers dans le corps. Les interactions moléculaires entre le RCT et son ligand, présenté par des cellules spécialisées (CPA cellules présentatrices d'antigène) sont suivies par un processus d'adhésion et d'étalement cellulaire caractérisé par d'importantes réorganisations à l'échelle supramoléculaire et cellulaire. Le rôle des propriétés physiques des cellules à ces échelles est encore mal compris. Dans cette thèse, nous nous sommes intéressés aux événements suivant cette reconnaissance en mimant la CPA par des substrats artificiels contrôlés exploitant plusieurs techniques de microscopie avancé. Nous avons réalisé une étude systématique de la dynamique d'étalement ainsi que de la morphologie (en terme d'aire d'adhésion et d'organisation de l'actine) des lymphocytes T humains de la lignée Jurkat sur des substrats présentant des anti-CD3 (un ligand spécifique du RCT) mobiles ou non. L'étalement des LT est fortement réduit sur les ligands mobiles par rapport aux ligands fixes. De plus le blocage de la myosine-II ou l'inclusion d'ICAM (le ligand des intégrines LFA-1) sur les substrats permettent de compenser ces différences. Nous proposons un modèle, inspiré de ceux sur la migration ou la croissance du cône neuronal , qui lie la dynamique du front d'étalement des lymphocytes T à la friction générée au niveau de la surface en tirant ou en fixant les ligandsT- cells play a central role in cell mediated adaptive immune response. They are a class of lymphocytes that carry distinctive receptors - the TCRs (T cell receptor), which are responsible for specific recognition of foreign peptides in the body. Molecular interactions between the TCR complex and its ligand is followed by cell adhesion and spreading accompanied by dramatic changes at molecular and cellular scale. In this thesis we focus on the events that immediately follow recognition. I report a systematic study of the spreading dynamics and morphology (in terms of adhesion area and actin organization) of T lymphocytes on substrates with mobile or immobilized anti-CD3 (a ligand targeting the TCR complex). The spreading behaviour is seen to be dramatically different on the two types of substrates. Interestingly, on blocking myosin-II or by inclusion of ICAM (ligand of LFA1 integrins) on the substrate, these differences tend to disappear. We propose a model, partially inspired by earlier models of neuronal growth cones and filopodia, that links the dynamics of the leading edge of the spreading T cell to the friction generated at the surface by dragging or pinning of the ligands. I also report studies on T cells interacting with substrates decorated with nano-scale islands of anti-CD3 in a sea of repulsive PEG or a supported lipid bilayer. Dramatic differences in adhesion, organization of actin, and receptor distribution are observed on different geometries. I report advances in multi channel RICM towards the reconstruction of not only the topography of the proximal membrane of the T cell with high level of confidence but also the distal surface of lamellipodia
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Sundermann, Lena. "Identification and characterization of new Greatwall kinase substrates." Thesis, Montpellier, 2018. http://www.theses.fr/2018MONTT016.
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La Division mitotique est une phase essentielle du cycle cellulaire qui assure la répartition correcte du contenu génétique. La mitose implique une réorganisation cellulaire profonde qui est principalement induite par une phosphorylation massive de protéines. Cette phosphorylation a lieu grâce à un équilibre fin entre kinases et phosphatases. À l'entrée mitotique, la phosphorylation protéique est induite par l'activation de la kinase cycline B/CDK1 et par l'inhibition de la phosphatase PP2A-B55. Résultats de notre et d'autres laboratoires ont récemment découvert une nouvelle voie essentielle pour moduler la phosphatase PP2A-B55 pendant la transition G2-M. Cette voie inclut la kinase Greatwall (GW) et ses substrats Arpp19 et ENSA. À l'entrée mitotique GW est activé et phosphoryle Arpp19 et ENSA les convertissant en inhibiteurs puissants de PP2A-B55. Étonnamment, aucun autre substrat de GW n'a été identifié jusqu'ici. Cependant, plusieurs éléments suggèrent fortement de nouveaux rôles de GW indépendamment de Arpp19 et de ENSA. L'objectif principal de ce travail était l'identification de nouveaux substrats de GW. À cette fin, j'ai utilisé plusieurs approches, y compris: (1) fractionnement biochimique des lysats de cellules ou des extraits d'oeufs de Xenopus combiné suivi d’une phosphorylation in vitro avec une kinase GW recombinante, (2) SILAC/phosphoproteomique des lysats de cellules exprimant différents niveau de GW, (3) Co-Immunoprecipitation, (4) BioID, et (5) une approche dirigée candidat. Les résultats de la phosphorylation in vitro ont révélé la présence de deux bandes de phosphorylation intéressantes qui sont actuellement analysées. Les deux approches SILAC/phosphoprotéinique et interactome ont révélé l'enrichissement des protéines impliquées dans la régulation post-transcriptionnelle de l'expression génique et des processus liés à l'ARN, une fonction physiologique déjà décrite pour cette voie chez la levure. Enfin, nous avons directement étudié la phosphorylation présumée par GW de trois candidats connus pour être impliqués dans le contrôle du cycle cellulaire. Bien que phosphorylées in vitro par GW, nous n’avons pu identifier le site de phosphorylation que dans l'une de ces trois protéines. Cette protéine, qui correspond à un inhibiteur de phosphatase, semble contrôler la sortie mitotique par la modulation de la déphosphorylation protéique. Un mutant non phosphorylable de cet inhibiteur induit une sortie mitotique perturbée avec une déphosphorylation ralentie des substrats mitotiques et une altération de la dégradation de la cycline B. J’ai pu attribuer ce défaut à une association perturbée de l'inhibiteur avec la phosphatase et, par conséquent, à un timing aberrant de l'inhibition de la phosphatase. Enfin, j'ai identifié le site de phosphorylation par GW comme le facteur clé contrôlant cette association. En résumé, j'ai identifié dans cette étude un nouveau substrat de GW contrôlant l'activité de la phosphatase essentielle pour une division mitotique correcteMitotic division is an essential phase of the cell cycle that ensures the correct repartition of the genetic content. Mitosis involves profound cellular reorganization that is mostly induced by massive protein phosphorylation. This phosphorylation is achieved thanks to the fine-tuning of the balance between kinases and phosphatases. At mitotic entry, protein phosphorylation is induced by the activation of the master kinase Cdk1-cyclin B and the inhibition of the phosphatase PP2A B55. Previous results from our and other laboratories recently discovered a new pathway essential to modulate PP2A-B55 during G2-M transition. This pathway includes the kinase Greatwall (GW) and its substrates Arpp19 and Ensa. At mitotic entry GW is activated and promotes the phosphorylation of Arpp19/Ensa converting them into potent inhibitors of PP2A B55. Surprisingly, no other substrates of GW have been identified so far. However, several pieces of data strongly suggest new roles of GW independently of Arpp19 and Ensa. The main aim of this work was the identification of new substrates of GW. To this end, I used several approaches including: (1) Biochemical fractionation of cell lysates or Xenopus egg extracts combined with in vitro phosphorylation with recombinant GW kinase, (2) SILAC/phosphoproteomics from cell lysates expressing different GW amounts, (3) Co-Immunoprecipitation, (4) BioID and (5) a candidate directed approach. Results from in vitro phosphorylation revealed the presence of two interesting phosphorylated bands that are currently being analysed. Both SILAC/phosphoproteomic and interactome approaches yielded the enrichment of proteins involved post-transcriptional regulation of gene expression and RNA related processes, a physiological function already described for this pathway in yeast. Finally, we directly investigated the putative phosphorylation by GW of three candidates known to be involved in the control of cell cycle. Although phosphorylated in vitro by GW, we could only identify the phosphorylation site in one of these three proteins. This protein, corresponding to a phosphatase inhibitor, appears to control mitotic exit through the modulation of mitotic protein dephosphorylation. A non-phosporylable mutant of this inhibitor promotes a perturbed mitotic exit with delayed dephosphorylation of mitotic substrates and impaired cyclin B degradation. I could attribute this defect to a perturbed association of the inhibitor with the phosphatase and consequently to an aberrant timing of phosphatase inhibition. Finally, I identified the GW phosphorylation site as a key factor controlling this association. In summary, I identified in this study a new substrate of GW controlling phosphatase activity essential for correct mitotic division
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Schubert, Martin, Hendrik Berg, Sabine Friedrich, and Karlheinz Bock. "Evaluation of dispensed carbon nanotube ink on flexible substrates for biocompatible application." Institute of Electrical and Electronics Engineers (IEEE), 2016. https://tud.qucosa.de/id/qucosa%3A33144.
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For biomedical electronics the compatibility to the biological environment should be well-considered. Therefore this paper evaluates dispensed carbon nanotubes (CNT's) on polyimide (PI) foil for conductive tracks and electrodes for flexible, biomedical applications. A CNT based ink is investigated regarding biocompatibility, flexibility, conductivity and suitability for electrode materials with contact to artificial body fluids. The testing methods comprise bending tests with resistance monitoring, adhesion tests and the utilization of dynamic fluidic and electrical load on dispensed structures. The CNT ink showed good bending properties up to 2653 cycles with an average sheet resistance of 32.5 Ohm/sq. A demonstration of biocompatibility using the adherent cell line HFFF2 resulted negatively. No delamination or dissolving effects occurred during exposure to 0.9 % sodium chloride solution.
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Nogueira, Jênifer Silva. "Germinação ex vitro e in vitro de gabirobeira." Universidade Federal de Goiás, 2012. http://repositorio.bc.ufg.br/tede/handle/tede/7497.
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Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq
The genus Campomanesia spp. has great economic potential unexploed. How its seeds not tolerate desiccation its propagations has been made by seeds extraction, when they are in germinate at appropriate physiological conditions. Several problems such as dormancy, recalcitrance, seasonality, difficulty of propagation has difficult he rational exploration of various species. Environmental conditions appropriate for the germination process may be provided in laboratories by in vitro multiplication. In this work techniques were applied to study some factors that affect ex vitro and in vitro germination of gabirobeira seeds and anther and ovaries culture through micropropagation. The results indicated that ex vitro germination the test substrates (Sand, Bioplant®, Tri-mix®, Bioplant®+Sand (1:1 v/v), Tri-mix®+Sand) for all substrates were superior to Tri-mix® substrate for germination percentage and for emergency speed of index. For the in vitro germination was found that all the culture medium tested in the absence of sucrose had a satisfactory germination rate. Evaluating the effects of accelerated aging and GA3 in the in vitro germination conclude that premature aging interfered the gabirobeira seeds ability of germination and GA3 is unnecessary for the germination stage. In the anthers and ovaries of culture, no callus formation in any of the treatments. However, the PVP was effective as an antioxidant. Keywords: sucrose,
A gabirobeira pertence ao gênero Campomanesia spp. possui grande potencial econômico não explorado. Como suas sementes não toleram a dessecação, sua propagação tem sido realizada logo após a extração, quando estas estão em condições fisiológicas apropriadas para germinar. Vários problemas como dormência, recalcitrância, sazonalidade e dificuldades de propagação têm inviabilizado a exploração econômica racional de várias espécies. Condições ambientais apropriadas para o processo de germinação podem ser fornecidas em laboratórios por meio da multiplicação in vitro. Neste trabalho, foram aplicadas técnicas para estudar alguns fatores que interferem na germinação ex vitro e in vitro de sementes de gabiroba e na micropropagação através da cultura de anteras e ovários. Os resultados indicaram que ao testar os substratos (Areia, Bioplant®, Tri-mix®, Bioplant®+Areia (1:1 v/v), Trimix ®+Areia)todos os substratos foram superiores ao substrato Tri-mix® para a porcentagem de germinação e vigor. Para a germinação in vitro verificou-se que todos os meios de cultura testados (MS, MS meia força, WPM e WPM meia força) na ausência de sacarose tiveram uma taxa de germinação satisfatória. Avaliando os efeitos do envelhecimento acelerado e de GA3 na germinação in vitro, o envelhecimento acelerado interferiu na capacidade germinativa das sementes de gabiroba e verificou-se que a aplicação de GA3 exógeno é desnecessária para a etapa de germinação. Na cultura de anteras e ovários, não houve calogênese em nenhum dos tratamentos testados. No entanto, o PVP foi eficiente como antioxidante.
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Willes, Jorge Alex. "Tecnologias em telhados verdes extensivos: meios de cultura, caracterização hidrológica e sustentabilidade do sistema." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/11/11136/tde-03122014-171411/.
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Tanto no meio rural como urbano as novas tendências são de buscar uma melhoria de técnicas e de uso de materiais alternativos buscando-se uma maior sustentabilidade. A utilização de plantas nas paredes e telhados é um dos mais recentes campos da pesquisa ambiental e busca encontrar uma solução ecológica e sustentável para melhorar a qualidade de vida urbana e rural. Uma cobertura verde consiste de um substrato leve e de uma vegetação apropriada, plantada sobre uma base impermeável. Podem conter também camadas adicionais, tais como, um sistema de drenagem e irrigação e uma barreira anti-raízes. Os efeitos positivos da vegetação sobre o ambiente urbano já são bem conhecidos e neste caso da cobertura, diminuem as enxurradas, filtro biológico, redução da poluição do ar, amenizam o calor nas edificações durante o verão e o conservam durante o inverno. Há também benefícios para a fauna, com retorno de espécies que mantêm o equilíbrio biológico local. Essas coberturas podem ter muitas aplicações, como em indústrias, residências, escritórios e outras propriedades comerciais e rurais. Uma criteriosa seleção de plantas permite que a cobertura verde tenha sucesso em condições adversas. Por outro lado, são necessárias pesquisas no sentido de assegurar um meio de cultura que retenha água e ao mesmo tempo proporcione uma boa drenagem para que as raízes não apodreçam, permitindo uma maior gama de espécies de plantas na cobertura. Neste sentido, realizou-se um estudo dos substratos mais abundantes na região, buscando tecnologias apropriadas para a confecção dos telhados verdes e identificando as melhores técnicas de aplicação, de acordo com a necessidade de cada ambiente. Para a realização deste trabalho foram utilizados dez tipos de substratos que foram pré-selecionados de acordo com a disponibilidade no mercado, de mais fácil obtenção e de melhor custo beneficio ambiental. As análises estatísticas utilizam o delineamento experimental inteiramente ao acaso, em esquema fatorial com três repetições e utilizando o programa estatístico SAS para auxiliar na análise e confecção dos gráficos e discussões. Na avaliação do conjunto de características, a turfa marrom (TM) apresentou o menor valor de densidade seca, maior porosidade total, maiores valores de água facilmente disponível, água disponível e capacidade de retenção de água, e mesmo valor de espaço de aeração daquele sugerido como referência sendo um bom material para o uso em telhados verdes, formando compostos com outros materiais e buscando as melhores características e sustentabilidade do sistema. Dentre os substratos comerciais estudados, o substrato para espécies hortícolas (SH) apresentou os maiores valores de capacidade de retenção de água e água disponível para as plantas, possibilitando um maior intervalo entre irrigações ou chuvas, características importantes para o uso em telhados verdes. No entanto, tornam-se necessários mais estudos com a finalidade identificar mais materiais e substratos apropriados para o uso em telhados verdes, levando-se em conta as diferentes características de cada local, tipo de vegetação escolhida, capacidade de suporte da edificação, dentre outro fatores.Rural and urban new trends seek an improvement in techniques and use of alternative materials for greater sustainability. The use of plants on walls and roofs is one of the newest fields of environmental research, looking for a green and sustainable solution to improve the quality of urban and rural life. A green cover consists of a substrate and appropriate vegetation planted on an impermeable base. It can also contain additional layers, such as a system of drainage and irrigation with an anti-root barrier. The positive effects of roof vegetation on urban environment are well known, as reducing the runoff,acting as a biological filter, reducing air pollution, minimizing heat inside the buildings during summer and maximizing during the winter. There are also benefits to fauna, with the return of various species, maintaining the local biological balance. The coverage can be adapted to industries, homes, offices and other commercial and rural properties. Careful selection of plants allows the green roof to succeed in adverse conditions. In addition, research is necessary to ensure a culture medium that retains water that the same time provides good drainage to prevent root rot, allowing a wider range of plant species in the cover. In this sense, a study was conducted involving the most abundant substrates of our region, seeking appropriate technologies for the manufacture of green roofs and identifying the best application techniques, according to the needs of each environment. For this work ten types of preselected substrates were used according to market availability, easier to obtain and with a better environmental cost/benefit ratio. Statistics of the experimental design was completely randomized in a factorial format with three replications and using the SAS statistical software to assist in the analysis and construction of graphs and discussions. In evaluating the feature of the cover set, brown peat (TM) presented the lowest value of dry density, higher porosity, higher values of easily available water, available water capacity and water retention, and even the amount of aeration space, suggested TM as being a good reference material for use in green roofs. Among the studied commercial substrates, the substrate for horticultural species (SH) showed the highest values of water holding capacity and water available to plants, allowing a longer interval between irrigations or rainfall, an important characteristic for its use on green roofs. However, more studies are needed in order to identify the most suitable materials and for use in green roof substrates, taking into account the different characteristics of each site, vegetation type, bearing capacity of the building, among other factors.
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Engelman, Zoar Jacob. "Arrhythmic substrates in structural heart disease." Thesis, University of Auckland, 2011. http://hdl.handle.net/2292/9508.
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Mortality due to structural heart disease (SHD) remains high despite advances in clinical therapies. The aim of this thesis is to elucidate how structural remodeling in heart disease may lead to the development of potentially life threatening arrhythmias. This objective was advanced by the combined use of mathematical modelling and an experimental model of myocardial infarction (MI). The computer model was used to investigate possible electrical effects of tissue remodelling associated with SHD. Heterogeneous discontinuities resembling patchy fibrosis were incorporated into a 2D array of coupled myocytes with uniform electrical properties. It was shown that structural discontinuities alone can alter dynamic instability and provide a rate-dependant substrate for electrical reentry. This challenges the wide-spread notion that dynamic instability of this kind is due to changes in cellular electrical properties. Experimental studies were carried out in sheep with healed reperfusion MI. Intramural electrical activation in the infarct border zone (BZ) was recorded with a high density mapping array. Novel techniques were developed that enable the spread of activation in this region to be reconstructed in 3D at higher resolution than has previously been possible. Heart structure was also reconstructed in 3D using magnetic resonance imaging and serial histology. Intracardiac left ventricular mapping was carried out simultaneously. The BZ substrate was characterised by systematic intramural pacing. This confirmed that activation delay, consistent with tortuous electrical pathways, is the origin of apparently slow conduction in the BZ. Stimulus-site specific, low-level activation in the BZ was followed by uniform propagation around the infarct boundary at relatively normal conduction velocities. Electrical activity in the intramural BZ was recorded during induction and maintenance of ventricular tachycardia (VT). BZ activation delays were amplified during VT induction and in some cases contributed substantially to the cycle length during VT. For the first time, complex intramural activation patterns were tracked through the BZ during reentry. In general, local intramural and endocardial activation patterns were non-stationary during VT despite relatively monomorphic limb-lead electrocardiograms. This signifies a heterogeneous substrate capable of supporting multiple arrhythmic circuits.
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Rautenbach, Daniel. "The electrochemical hydroxylation of aromatic substrates." Thesis, Port Elizabeth Technikon, 2002. http://hdl.handle.net/10948/94.
Full textAbstract:
The electrochemical hydroxylation of aromatic substrates was investigated in some detail, with the view to develop a method, which could produce dihydroxybenzenes in acceptable yields. Of particular interest was the selectivity and yield of the 1,4-dihydroxybenzenes. Two distinctly different methods were investigated in order to achieve this goal, acyloxylation and direct electrochemical hydroxylation. Acyloxylation is the process where radical cations generated at the anode undergoes nucleophilic attack by acetate anions. The resulting aromatic acetates so produced can then be hydrolysed to the phenolic compounds. Two nucleophile systems were considered in the investigation, acetates (acetoxylation) and trifluoro-acetates (trifluoro-acetoxylation). These investigations were conducted under a variety of conditions using phenol and phenyl acetate as starting materials. From the results it was, however, concluded that the acetoxylation of these aromatic compounds occurs in unacceptable product and current yields. Trifluoro-acetoxylation on the other hand showed promise, but due to the nature and cost of the reagents it was deemed to be an impractical process. Direct electrochemical hydroxylation: in which the radical cations produced at the anode undergoes nucleophilic attack by water producing the corresponding dihydroxybenzenes. These dihydroxybenzenes are then further oxidised to the benzoquinones, which then undergo reduction at the cathode in order to produce the corresponding dihydroxybenzene. In this process phenol, 2-tert-butylphenol and 2,6-di-tert-butylphenol were investigated as substrates. The results indicated that the yield towards the 1,4-dihdroxybenzenes increased as the degree of substitution on the ring increased.
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Stamboulides, Christos. "Microscopic ice friction of polymeric substrates." Thesis, University of British Columbia, 2010. http://hdl.handle.net/2429/26716.
Full textAbstract:
Interest in snow and ice friction comes from the need to understand and control phenomena of practical importance such as glacier and avalanche movement, traction of automobile tires, snow and ice sports. The need to minimize friction on ice and snow in competitive winter sports is the main motivation behind the present work.
A novel tribometer was designed and utilized in conjunction with a conventional rheometer for measuring and understanding the mechanisms of ice friction over polymeric surfaces. Experiments were performed to measure friction between ultra-high molecular weight polyethylene, polytetrafluoroethylene and poly(methyl methacrylate), and ice as a function of sliding velocity, temperature, surface roughness and hydrophobicity. Various techniques were utilized to modify the properties and characteristics of the polymeric surfaces. Light microscopy and scanning electron microscopy as well as surface profilometry were utilized to perform surface analysis and characterize the surface. A goniometer set-up was used for the measurement of the water contact angle measurements and X-ray photoelectron spectroscopy for conducting the elemental analysis.
Overall it was found that the magnitude of the sliding velocity and temperature play important roles in ice friction. The more hydrophobic polymers exhibit a lower coefficient of friction. Liquid fluorinated additives as well as a plasma enhanced chemical vapour deposition in a fluorinated gas can improve the hydrophobicity of a polymer and decrease its coefficient of friction over ice. These two concepts can directly be applied in snow winter sports and more specifically in ski and snowboard bases production and preparation where greater speeds, shorter times and therefore less friction are in high demand.
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Rigby, Annette. "Synthesis of new aminopeptidase sensitive substrates." Thesis, Northumbria University, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.410375.
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Gray, Philip James. "Novel tandem reactions of allenic substrates." Thesis, University College London (University of London), 2008. http://discovery.ucl.ac.uk/1444232/.
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This thesis describes the development of novel tandem reactions of allenic substrates, designed for the synthesis of structurally complex heterocyclic and carbocyclic systems together with the development of methodology for stereocontrolled preparation of functionalised olefins. Consequently, the thesis is divided into three sections. The first of these introduces the allenic functionality highlighting the special properties associated with allenic compounds and the recent advances in allene chemistry with particular emphasis on the application of allenic substrates to heterocyclisation, carbocyclisation and carbometallation. The second section describes the results obtained during the course of this study and is divided into three sub-sections. The first of these summarises the development of novel aza-annulation methodology for the preparation of biologically relevant nitrogen containing molecular architectures using electron deficient allenes as substrates for regioselective vinylogous urethane and amide formation. The application of this methodology towards the synthesis of the cytotoxic alkaloid N-oxo-rhazinilam is also discussed. This is followed by a discussion of a tandem enamine formation cyclisation sequence using allenic substrates for the preparation of substituted cyclopentanones. The final section describes a preliminary study of a novel carbometallation reaction of allenic substrates for stereocontrolled preparation of fiinctionalised alkenes. Chapter three provides a summary of these three areas of research as well as highlighting potential avenues for further exploration. Chapter four details all of the relevant experimental procedures and compound characterisations.
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Njoku, Chinwe Christiana. "Heterogeneous mixtures for synthetic antenna substrates." Thesis, Loughborough University, 2013. https://dspace.lboro.ac.uk/2134/12074.
Full textAbstract:
Heterogeneous mixtures have the potential to be used as synthetic substrates for antenna applications giving the antenna designer new degrees of freedom to control the permittivity and/or permeability in three dimensions such as by a smooth variation of the density of the inclusions, the height of the substrate and the manufacture the whole antenna system in one process. Electromagnetic, fabrication, environmental, time and cost advantages are potential especially when combined with nano-fabrication techniques. Readily available and cheap materials such as Polyethylene and Copper can be used in creating these heterogeneous materials. These advantages have been further explained in this thesis. In this thesis, the research presented is on canonical, numerical and measurement analysis on heterogeneous mixtures that can be used as substrates for microwave applications. It is hypothesised that heterogeneous mixtures can be used to design bespoke artificial dielectric substrates for say, patch antennas. The canonical equations from published literature describing the effective permittivity, ε_eff and effective permeability, μ_eff of heterogeneous mixtures have been extensively examined and compared with each other. Several simulations of homogenous and heterogeneous media have been carried out and an extraction/inversion algorithm applied to find their ε_eff and μ_eff. Parametric studies have been presented to show how the different variables of the equations and the simulations affect the accuracy of the results. The extracted results from the inversion process showed very good agreement with the known values of the homogenous media. Numerically and canonically computed values of ε_eff and μ_eff of various heterogeneous media were shown to have good agreement. The fabrication techniques used in creating the samples used in this research were examined, along with the different measurement methods used in characterising their electromagnetic properties via simulations and measurements. The challenges faced with these measurement methods were explained including the possible sources of error. Patch antennas were used to investigate how the performance of an antenna may be affected by heterogeneous media with metallic inclusions. The performance of the patch antenna was not inhibited by the presence of the metallic inclusions in close proximity. The patch measurement was also used as a measurement technique in determining the ε_eff of the samples.
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Black, Kate. "Compliants substrates for materials on silicon." Thesis, University of Liverpool, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.495007.
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Black, Kate. "Compliant substrates for materials on silicon." Thesis, University of Liverpool, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.494119.
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This thesis describes the development of processes to fabricate compliant layers for the epitaxy of gallium nitride on silicon. A range of metalorganic chemical vapour deposition processes have been investigated. Three generic materials systems have been explored, namely: a perovskite-based rare earth aluminate; a rocksalt nitride system; and a hexagonal symmetry oxide based buffer layer. Single source precursors for the deposition of lanthanum- and praseodymium- aluminate have been demonstrated using LnAl(OPri)6(PriOH)]2 (Ln = La or Pr) for the first time. Annealing the films above 850°C crystallises them to form a rhombohedral perovskite phase. The growth of gallium nitride on these films has been investigated to establish their chemical stability. The GaN growth is textured and the interface between the oxide and GaN is abrupt indicating negligible interdiffusion. The promotion of better epitaxy via a SrO seed layer to inhibit adverse interfacial interactions is considered.
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Jupp, Raymond A. "Substrates and inhibitors of aspartic proteinases." Thesis, Cardiff University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.238215.
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Valler, M. J. "Substrates and inhibitors of aspartic proteinases." Thesis, Bucks New University, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376428.
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Ishaq, Salma. "New substrates for Pauson-Khand reaction." Thesis, University College London (University of London), 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.428148.
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Duncan, Tod. "Identifying substrates of CDK2:cyclin A." Thesis, University College London (University of London), 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.396250.
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Klier, Jurgen. "Liquid helium on weak binding substrates." Thesis, University of Exeter, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337745.
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Stubbington, Liam Thomas Edward. "Lipid bilayers on deformable elastic substrates." Thesis, Durham University, 2018. http://etheses.dur.ac.uk/12771/.
Full textAbstract:
In this thesis an experimental model for the interface between the cell membrane and the supporting cytoskeleton has been developed and analysed. The experimental platform is a novel approach to the design of supported membrane based devices and technologies. The system consists of a single component lipid bilayer coupled to an elastic substrate, the area of which can be reversibly increased and decreased. We uncover three independent mechanisms that the membrane may use to respond to changes in substrate area. If the elastic support is partially hydrophilic, the area of the planar portion of the membrane is strongly coupled to the substrate area. The membrane responds to increasing substrate area by absorbing lipid protrusions, and when the substrate area is decreased the excess membrane area is projected back out in the form of lipid tubes. This mechanical remodelling of the membrane occurs above the plane of the support and mimics the passive means of membrane area regulation recently uncovered in live cells. In contrast, when the surface support is completely hydrophilic, two further mechanisms of substrate stress relaxation are uncovered. When the pH of the solu- tion is greater than 7 the membrane is able to slide over the expanding and contract- ing substrate. This membrane sliding motion occurs in the plane of the support and is dynamic. The effectiveness at which membrane tension is relaxed is dependent on the rate at which the substrate area is changed. When the pH is reduced below pH 7, the membrane area becomes strongly coupled to that of the support and the membrane dramatically ruptures, opening large circular pores, in response to substrate deformation. The pores exhibit a dynamic area change, revealing a complex flow of membrane across the support to equilibrate stress. This novel supported membrane behaviour reveals the rich physics possessed by supported lipid systems, that may assist in the design of new supported lipid based technologies.
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Erdas, Yonca. "Novel chemical modification of cellulosic substrates." Thesis, University of Manchester, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.488431.
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Constrained by lack of availability of suitable land the consumption of cotton has leveled off while that of polyester has increased rapidly, the demand for clothes, which are made from cotton is increasing in the highly sophisticated countries. Cotton production is criticised as it is a polluting process and the land could be used for food production in the poor countries. Therefore much attention has been directed towards re-engineering of synthetic fibres aimed at mimicking cotton properties such as breathability, comfort, antistatic and dyeability. Even so world cotton production is still growing slowly; it is expected to increase to 20.1 m tonnes for 2003/04, according to the International Cotton Advisory Committee. It is likely that there will always be a demand for cotton, and more research will be directed to environmentally friendly cotton production, coloration and finishing. Coloration of cotton is carried out by using vat, sulphur, azoic, direct and reactive dyes. Reactive dyes are a very important group of dyestuffs for colouring cotton because of their desirable properties which include unrestricted shade range, ease of application, low cost and good fastness to light, washing and rubbing. When they are applied to cellulose by an exhaustion process, they require relatively high levels of electrolyte (salt) to increase the substantivity of the anionic dyestuff for cellulose and thereby achieve high visual colour yields. Discharge of highly saline effluent is becoming environmentally less acceptable, as increased salinity in rivers upsets the delicate balance of aquatic flora and fauna. Hence some recent developments in cotton dyeing with reactive dyes have focused on reduced salt usage. This thesis evaluates one of the options for low salt cotton reactive dyeing; chemical modification (pre-treatment) of cellulose with cationic agents. This has the effect of eliminating the inherent electrostatic repulsion between the anionic (negative) dye and the fibre, so that the use of electrolyte can either be reduced or eliminated. The (negative) surface charge of cotton was modified to a positive charge by using initially a commercial polymeric cationic fixing agent. The amount of cationic agent applied by an exhaustion technique to a cotton fabric, was quantitatively determined using Congo Red, the method being based on the titration of a known concentration of Congo Red with a solution of the treatment agent. The application of this procedure to determine the exhaustion properties of potential cationic pre-treatment agents for cotton was then studied. The pre-treated cotton was dyed to evaluate the effect of the treatment on both dye exhaustion and fixation under three different sets of dyeing conditions and a comparison was made with untreated cotton dyed conventionally. Lower colour yield, inferior wash and light fastness, shade change, ring dyeing and poor migration (levelness) were obtained on the pre-treated fabric. Therefore, pre-treatment of cotton with polymeric cationic agents was adjudged to be of no further interest. To avoid the technical problems associated with the use of polymeric pre-treatment agents, further modification of cotton was carried out with low molecular weight (monomeric) species. A systematic study of the introduction of different amino groups into cotton, via reaction with a commercially available reactive, water soluble dichlorotriazine agent followed by amination with different amines, was undertaken. Where possible, the characterization of the reaction products was made by using a variety of analytical methods. Once the resulting adducts had been characterised, the dyeing behaviour of reactive dyes on the derived substrate was evaluated. The present study also involved the synthesis and application of other pre-treatment agents, e.g. 2,4-bis(4-sulphophenylamino-)-6-chlorotriazine and dyes with a view to obtaining a better understanding of the causes of the shade changes arising from the use of cationic agents to cotton.
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Sun, Jingyu. "Carbon nanotube growth on perovskite substrates." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:2b77fe9b-7313-49b2-b490-70574b4af565.
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This thesis reports on the chemical vapour deposition (CVD) growth of carbon nanostructures (mainly carbon nanotubes (CNTs)) on perovskite oxide surfaces with the aid of various catalysts. Two types of perovskite oxide, single crystal SrTiO3 (001) and polycrystalline BaSrTiO3, have been used as catalyst supports (in metal-catalyst-involved CVD routes) or as catalysts (via metal-catalyst-free CVD routes) for the growth of carbon nanostructures. In metal-catalyst-involved cases, SrTiO3 (001) single crystal has been proven, for the first time, to serve as a substrate for the growth of CNTs. Fe and Ni catalysts can be tailored in a controllable manner on SrTiO3 (001) surfaces prior to the CNT synthesis, forming truncated pyramid shaped nanocrystals with uniform size distributions. The growth of vertically aligned CNT carpets was realised with the aid of Fe on SrTiO3 (001) surfaces, and it was further found that the CNTs grow via a base growth model. Furthermore, it is possible to grow helical carbon nanostructures on BaSrTiO3 substrates by introducing a Sn catalyst into the system. The synthesised helical carbon nanostructures follow a tip growth mode, where the structural and chemical aspects of catalyst particles gave rise to a wide range of carbon morphologies. CNTs were also grown on single crystal SrTiO3 (001) and polycrystalline BaSrTiO3 substrates via metal-catalyst-free routes. The surface-roughness-tailored growth of CNTs was surprisingly achieved on a series of engineered SrTiO3 (001) surfaces, where a correlation between the surface roughness/morphology of the substrates and the relevant catalytic activity was revealed. The growth of CNTs arises because the catalyst fabrication methods lead to the formation of SrTiO3 asperities with nanoscale curvatures, over which the CNTs are generated throughout a lift-off process. Facet-selective growth of CNTs was observed on polycrystalline BaSrTiO3 surfaces, where BaSrTiO3 (110) facets lead to the growth of CNTs on them, whereas the (001) facets result in no growth at all. This observation was further analysed in the content of the adsorption and diffusion of carbon species on distinct BaSrTiO3 facets, before reaching the conclusion that the formation of CNTs occurs through a metal-free, stack-up process driven by the assembly of the carbon fragments.
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Baptista-Hon, Daniel Tomas. "Cellular substrates of iron overload cardiomyopathies." Thesis, University of Edinburgh, 2011. http://hdl.handle.net/1842/15878.
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Cardiomyopathies and arrhythmias are major causes of death in untreated hereditary haemochromatosis, acute iron poisoning and during secondary iron overload resulting from repeated blood transfusions in β-thalassaemia. Iron overload cardiomyopathies are associated with systolic and diastolic dysfunction, suggesting that Ca2+ homeostasis is impaired. However, the cellular mechanisms of these dysfunctions are unknown. The data presented in this thesis establishes for the first time iron effects on cardiomyocyte Ca2+ handling, as well as the potential cellular substrates responsible for this impairment during iron overload. Exposure of isolated rat ventricular cardiomyocytes to 200μM iron led to biphasic changes in systolic Ca2+ release. Phase 1: an initial reduction of systolic Ca2+ release followed by; Phase 2: increased Ca2+ release with arrhythmogenic spontaneous Ca2+ release, cell contracture and cell death. There is evidence that Fe2+ enters cardiomyocytes via L-type Ca2+ channels (LTCC) and reduces the Ca2+ trigger. The close apposition of LTCCs to cardiac ryanodine receptors (RyR2) suggests RyR2 may be a first target. Indeed RyR2 activity was drastically reduced on exposure to nanomolar [Fe2+] in single channel studies. Together with evidence that Fe2+ may reduce the Ca2+ trigger from LTCC, this is consistent with iron reducing sarcoplasmic reticulum (SR) Ca2+ release during Phase 1. In Phase 2, the presence of spontaneous Ca2+ release events is consistent with SR Ca2+ overload. Indeed, in single rat ventricular cardiomyocytes SR Ca2+ content was found to be increased by 27% during Phase 2. The cellular substrates responsible for this increased SR Ca2+ content were 2-fold: 1) through reduced extrusion via both the Na+ Ca2+ Exchanger (NCX) and Plasmalemmal Ca2+ ATPase (PMCA) and 2) through increased resequestration via the SR Ca2+ ATPase. Iron catalyses the production of reactive oxygen species (ROS) during the Fenton reaction. To investigate whether iron effects might be due to ROS, I used the cell permeant ROS scavenger Tempol. Tempol attenuated Phase 2 effects but Phase 1 effects were not affected. This is consistent with the hypothesis that Phase 1 effects were due to direct effects of Fe2+ affecting LTCC trigger and RyR2 function. The attenuation of Phase 2 effects suggests that ROS damage to key Ca2+ handling mechanisms, such as NCX and PMCA might account for a reduced Ca2+ extrusion and subsequent SR Ca2+ overload.
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Macro, Jason Brindley. "Substituted diazirines as polyfunctional photoactive substrates." Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.670217.
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Yoo, In Kyeong. "Electrical crosstalk in multilayer ceramic substrates." Diss., Virginia Tech, 1990. http://hdl.handle.net/10919/39951.
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Silantyeva, Elena A. "Functionalized Nanofiber Substrates for Nerve Regeneration." University of Akron / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=akron1555582661302756.
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Owsley, Jack Lee III. "CHARACTERIZATION OF DOPED GALLIUM NITRIDE SUBSTRATES." Wright State University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=wright1357763392.
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Minett, William T. "Cell adhesion on synthetic polymer substrates." Thesis, Aston University, 1986. http://publications.aston.ac.uk/14512/.
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Jalil, Rashid. "Novel substrates for graphene based electronics." Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/novel-substrates-for-graphene-based-electronics(76a5a002-f663-432a-9b5c-273999583b36).html.
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Delcassian, Derfogail. "Biomimetic substrates for immune cell activation." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/30729.
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This thesis describes the fabrication of biomimetic substrates, and their use as tools to probe cellular interactions of key immune cells. Nanoparticles of gold and zinc sulfide have been fabricated, and patterned into nanoarrays. Adaptive (T cell) and innate (NK cell) immune cell responses to nanoscale spacing of ligand-receptor pairs were measured, and the effect of presenting stimulatory ligands on substrates with varying mechanical properties has been tested for T cell responses. The advanced materials in this thesis act to create artificial immune synapses, and probe the effect of these stimuli on engagement and activation of human immune cells. Specifically, block co-polymers were used to form polymer micelles which encapsulate metal ions and form metal or metal compound nanoparticles. Micelles encapsulating metal ions or nanoparticles were formed and deposited onto substrates using Block Co-polymer Micellar Lithography (BCML) to form nanoparticle arrays with controlled inter-particle spacing. Well controlled gold nanoparticle arrays with spacing between 25-150nm have been produced. The technique has been further developed to include fabrication of zinc sulfide particles and nanoarrays. Zinc sulfide nanoparticles showed a unique internal structure with 5nm crystalline domains set in an amorphous matrix and an optical band gap of between 3.88-4.28eV. Nanoparticle arrays were then functionalised with biological ligands, notably antibodies that engage with the NK cell surface receptor CD16, or the T cell TCR/CD3 moiety. The cellular response to these materials was measured, and was sensitive to the nanoscale arrangement of stimulatory ligands; both cell types responded to ligands with 25nm, but not 104nm, inter-ligand spacing. In an alternative approach, spherical PEG hydrogel particles of diameter 5-50μm were formed with controlled rigidity between 3-2000kPa. T cell response as a function of substrate rigidity was tested, and cells showed maximal response to anti-CD3 functionalised substrates with rigidities of 3-5kPa.
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Williams, Steven Edwin. "Characterisation and representation of arrhythmia substrates." Thesis, King's College London (University of London), 2015. http://kclpure.kcl.ac.uk/portal/en/theses/characterisation-and-representation-of-arrhythmia-substrates(b591acfd-9ca4-45a0-a3b0-169128bac9d7).html.
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Cardiac arrhythmias arise from a variety of structural and electrical substrates and range in clinical presentation from asymptomatic to severely disabling or life threatening. Existing techniques for the characterisation of arrhythmia substrates include surface electrocardiography and intracardiac mapping together with ultrasound, computed tomography and magnetic resonance imaging. In this thesis I study a spectrum of arrhythmia characterisation techniques to improve the understanding of complex arrhythmia mechanisms. The role of surface electrocardiography and intra-cardiac contact mapping together with cardiac magnetic resonance imaging are studied in a variety of atrial and ventricular arrhythmias as well as in an animal model of atrial ablation. Arrhythmia characterisation techniques result in large quantities of data that are frequently considered in combination with other modalities and visualised within the 3- dimensional nature of cardiac structures. Since no techniques are currently available to display multiple parameters without loss of fidelity of either parameter, I developed a new system for data representation. Termed Dot Mapping, this system allows two or more datasets to be concurrently displayed by using separate visual entities (colour and dots) for each. The function, development and feasibility of the system are studied. In summary, this thesis explores and develops a number of techniques for assessing arrhythmia substrates, including surface electrocardiography, intra-cardiac mapping and cardiac magnetic resonance imaging. New (and existing) data thus created are displayed using a new data representation technique designed to optimise the co-display of multiple related modalities.
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Zwan, Rick van der. "Possible neural substrates for binocular rivalry." Thesis, The University of Sydney, 1994. https://hdl.handle.net/2123/28543.
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Binocular rivalry is the perceptual consequence of dichoptic input which is not
congruent between both visual inputs. There is some evidence, both theoretical and
empirical, that the perception of binocular rivalry is mediated by interactions between
binocular neurones, rather than by interactions between monocular neurones. This
evidence suggests also a model of perception which predicts binocular rivalry as a
consequence of normal interactions between binocular neurones in a retinotopic array.
This model accounts for rivalry without postulating any additional interconnections
beyond those already thought to exist between binocular neurones simply assumes an
orderly mapping of tuning characteristics across groups of cells, as is typically observed
in visual cortex. On the basis of this model, and findings already reported, it was
hypothesised that binocular rivalry reflects extrastriate rather than area V1 processing
(no process so far attributed to area V1 has yet been reported to be affected by
binocular rivalry). It was hypothesised also that area V2 was the most likely area in
which such processing first arises.
Area V2 has been associated with the perception of 'purely subjective contours'. It has
been shown that some cells in area V2 are tuned for such contours, which are
characterised by the absence of Fourier components at the orientation of the perceived
contour, while no cells in area V1 have been found to be similarly sensitive (von der
Heydt and Peterhans 1989). This characteristic of area V2 neurones enables purely
subjective contours to be used to test the two hypotheses described above. Real contour
tilt aftereffects, which are thought to arise in area V1, are not affected by rivalry during
their induction. If purely subjective contour tilt aftereffects (Paradiso, Shimojo and
Nakayama 1989) are subject to the same types of processing as their real contour
counterparts, as suggested by the rationale and model of von der Heydt and Peterhans
(1989), interactions between subjective contour tilt aftereffects and binocular rivalry
should indicate the role, if any, of area V2 in rivalry.
It was found that purely subjective contour tilt aftereffects (Experiment One) and tilt
illusions (Experiment Four) exhibit angular functions like those observed for real
contour tilt aftereffects and illusions. Just as for real contour effects, these functions can
be described in terms of direct effects (Experiment Two) and indirect effects
(Experiment Three), suggesting purely subjective contours are processed as if they were
real contours. Unlike real contour direct effects, purely subjective contour direct and
indirect effects are reduced in magnitude by periods of rivalry during their induction
(Experiment Five). In keeping with their suggested extrastriate locus (eg. Wenderoth,
van der Zwan and Williams 1993), the magnitude of a real contour indirect effect is
also reduced by periods of rivalry occurring during its induction (Experiment Six).
These results suggest that rivalry does arise first in area V2. If this is true then complete
interocular transfer of the purely subjective aftereffect, induced with or without rivalry,
should occur because area V2 is almost exclusively binocular. This proved not to be the
case, however, suggesting the ocular dominance observed in most binocular cells has to
be taken into account in any explanation of rivalry (Experiment Seven). This was tested
using real contours and found to be the case. These last results suggested also that
rivalrous interactions occur between groups of binocular neurones only in extrastriate
cortex (Experiment Eight). This hypothesis was tested by examining the effect of
binocular rivalry on the duration of the plaid motion aftereffect, which is thought to
arise no earlier than area MT, a visual cortical area which is also thought to be almost
exclusively binocular. It was found that rivalry did reduce the duration of plaid motion
aftereffects but not linear motion aftereffects, and that the impact of rivalry might be
linked to plaid sensitive cells in area MT, although this last conclusion is tenuous
(Experiments Nine and Ten). Finally, it was shown also that the magnitude of the
reduction in duration of the aftereffect was proportional to the predominance of the
plaid stimulus during rivalry, a finding which supports the mechanism of rivalry
suggested by the binocular model.
The results together suggest that binocular rivalry does arise through binocular
interactions, but that such interactions cannot be attributed to a single cortical area. All
groups of binocular neurones may be subject to the processes that ultimately give rise to
the perception of rivalry, a conclusion which does not invalidate the binocular model of
rivalry. This has some consequences for binocular vision, particularly stereopsis, which
might occur qualitatively during binocular rivalry.
49
Valentine, Wendy Leesa 1964. "Crosstalk minimization using multiple dielectric substrates." Thesis, The University of Arizona, 1993. http://hdl.handle.net/10150/278345.
Full textAbstract:
A method to predict appropriate dielectric constants and thicknesses for double dielectric substrate microstrip structures to minimize forward crosstalk is presented. Ratios of the elements in the capacitance matrix are compared to those in the inductance matrix to determine if forward crosstalk will be minimized. Curves showing C(rat) where C(rat) is the ratio of the C₁₁ element to the C₁₂ element, as a function of the relative permitivity, εᵣ and SPICE simulations are presented for particular geometries. The method accurately predicts combinations of dielectrics that will produce a structure exhibiting greatly reduced crosstalk.
50
Heinrich, Lydia Alexandra. "Biosourced Coating Systems for Metallic Substrates." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSE1004.
Full textAbstract:
Le remplacement de monomères d'origine pétrosourcée par des analogues biosourcés améliore la durabilité et diminue la dépendance aux ressources fossiles. De plus, de nouvelles caractéristiques et propriétés sont souvent découvertes. Les polyesters aliphatiques biosourcés ont déjà partiellement remplacé les produits traditionnels. Dans le contexte du projet Sorago, une résine entièrement biosourcée pour les revêtements de prélaquage des produits intérieurs a déjà été introduite sur le marché (Estetic® bio Air, Arcelor Mittal). Pour permettre l'utilisation du produit dans des applications extérieures, sa résistance à la lumière UV et à l'humidité sont à améliorer. Cela pose deux problèmes : Une disponibilité limitée de monomères pouvant introduire de la rigidité dans la résine et la relation entre la structure de la résine et sa dégradation. La vanilline a été choisie comme synthon pour la gamme des monomères rigides et biosourcées. La transformation de sa fonction aldehyde par réaction de Perkin et sa réactivité a été examinée. Dans une série des copolymerisations, l'influence des conditions de réaction sur la composition du produit final a été proposée. Une relation structure-propriétés concernant la température de la transition vitreuse et la viscoélasticité des plusieurs monomères biosourcées a été établie, et comparée avec celle des monomères petrosourcées. Une série des prototypes avec des propriétés très variées a été soumise à un test de vieillissement rapide. Leur dégradation a été suivie sur la base de leur rétention de brillance, par FTIR et par des tests de µ-dureté et d'épaisseur des films. La performance des prototypes biosourcés s'est révélée inférieure à celle d'une résine standard pétrosourcée mais aucune évidence qui suggère que cela est du à la présence des monomères biosourcées n'a été détectée. Cela suggère que la création d'une résine biosourcée et suffisamment durable pour l'extérieur sera possibleMoving away from petroleum and towards biobased materials not only leads to greater sustainability and lower dependence on diminishing fossil resources, but can also catalyse the discovery of new properties. Aliphatic polyesters based on renewable resources have already started to replace traditional products. Within the Sorago project, a fully biobased resin for interior coil coatings has recently been proposed on the market (Estetic® Bio Air, Arcelor Mittal). In order to extend the possible use of the biobased product to exterior applications, an improvement of its resistance to humidity and UV radiation is crucial. This presents two challenges: The limited availability of monomers which provide rigidity in the resin structure and the relationship between the resin composition and its weatherability. Vanillin was chosen as a possible extension to the range of rigid, biobased monomers for polyesterification reactions. The transformation of its aldehyde and its reactivity was studied in terms of catalytic activation and through a series of copolymerisations which revealed the influence of the reaction conditions on the composition of the product. A structure-property relationship concerning the coating glass transition temperature and visco-elastic behaviour of the coating was furthermore established for a series of renewable monomers and contrasted with petroleum based equivalents. Series of prototypes with a wide variety of properties were then subjected to accelerated weathering tests. Their degradation was followed directly by gloss retention and different mechanisms were revealed using FTIR, µ-hardness and film thickness measurements. While the performance of the biobased coating was subpar, no evidence linking its degradation to the presence of renewable monomers was found, suggesting that the creation of a sufficiently durable and renewable exterior coating will be possible