Dissertations / Theses on the topic 'Ethylene Systems'
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Mastroianni, Sergio. "New catalytic systems for the polymerisation of ethylene." Thesis, Imperial College London, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343906.
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Iemsam-Arng, J. "Poly(ethylene) glycol based delivery systems for nucleic acid therapies." Thesis, University College London (University of London), 2013. http://discovery.ucl.ac.uk/1381001/.
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Our work is aimed at developing a synthetic biocompatible gene and siRNA delivery system for the treatment of primary and metastatic tumours. To facilitate delivery of nucleic acid based drugs into the cell, one strategy is to formulate the naked gene with an amine based non-viral gene delivery system via the counterion interaction. The delivery systems including 4arm-PEG-amine, 4arm-PEG-N-2-ethylamine, 8arm-PEG-amine and 8arm-PEG-N-2-ethylamine were synthesised, characterised and complexed with a reporter gene (β-gal plasmid DNA) in phosphate buffer pH 6.0. The resulting complexes were sized and their zeta potential measured (Malvern Zetasizer 3000HS, Malvern Instruments, UK). The complexes were also imaged using transmission electron microscopy and characterised for DNA binding and DNA protection using gel electrophoresis and the ethidium bromide displacement assay. The in vitro transfection efficiency and cell cytotoxicity of the complexes were determined in the A431 and HeLa cells. Additionally, in vivo therapeutic studies in female nude tumour bearing mice were carried out. A promising DNA-polymer complex of 4arm-PEG-N-2-ethylamine produced a complex of 200-300 nm in diameter (polydispersity < 0.6). Complexes had a zeta potential of +19.8 mV (n=3) and were spherical, fibrillar and toroidal in shape. The new gene delivery complex protected DNA from degradation in serum up to 2 hours and was as efficient as poly(ethylenimine) (PEI) in transfecting the A431 cell line, but it was more than 3 orders of magnitude less cytotoxic than PEI. In vivo a gene medicine, comprising the polymer and the tumour necrosis factor alpha gene, was tumouricidal. When complexed with siRNA, the siRNA polymer complex demonstrated a trend of gene silencing activity. A new synthetic gene delivery polymer of 4arm-PEG-N-2-ethylamine has been synthesised. This polymer is biocompatible to cells and is an efficient in vitro and in vivo gene transfer agent.
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Cheung, Adolf S. F. "Phase behavior of two binary systems containing ethylene at supercritical conditions." Thesis, University of Ottawa (Canada), 1989. http://hdl.handle.net/10393/5719.
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Beigzadeh, Daryoosh. "Long-chain branching in ethylene polymerization using combined metallocene catalyst systems." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0020/NQ52024.pdf.
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Anantharaman, Bharthwaj. "Reaction mechanisms for catalytic partial oxidation systems : application to ethylene epoxidation." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/32328.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2005.Includes bibliographical references.
With the rapid advances in kinetic modeling, building elementary surface mechanisms have become vital to understand the complex chemistry for catalytic partial oxidation systems. Given that there is selected experimental knowledge on surface species and a large number of unknown thermochemical, rate parameters, the challenge is to integrate the knowledge to identify all the important species and accurately estimate the parameters to build a detailed surface mechanism. This thesis presents computational methodology for quickly calculating thermodynamically consistent temperature/coverage-dependent heats of formation, heat capacities and entropies, correction approach for improving accuracy in heats of formation predicted by composite G3- based quantum chemistry methods, and detailed surface mechanism for explaining selectivity in ethylene epoxidation. Basis of the computational methodology is the Unity Bond Index- Quadratic Exponential Potential (UBI-QEP) approach, which applies quadratic exponential potential to model interaction energies between atoms and additive pairwise energies to compute total energy of an adsorbed molecule. By minimizing the total energy subject to bond order constraint, formulas for chemisorption enthalpies have been derived for surface species bound to on-top, hollow and bridge coordination sites with symmetric, asymmetric and chelating coordination structures on transition metal catalysts. The UBI-QEP theory for diatomics has been extended for polyatomic adsorbates with empirical modifications to the theory.
(cont.) Formulas for activation energies have been derived for generic reaction types, including simple adsorption, dissociation-recombination, and disproportionation reactions. Basis of the correction approach is the Bond Additivity Correction (BAC) procedures, which apply atomic, molecular and bond- wise modifications to enthalpies of molecules predicted by G3B3 and G3MP2B3 composite quantum chemistry methods available in Gaussian® suite of programs. The new procedures have improved the accuracy of thermochemical properties for open and closed shell molecules containing various chemical moieties, multireference configurations, isomers and degrees of saturation involving elements from first 3 rows of the periodic table. The detailed mechanism explains the selectivity to ethylene oxide based on the parallel branching reactions of surface oxametallacycle to epoxide and acetaldehyde. Using Decomposition Tree Approach, surface reactions and species have been generated to develop a comprehensive mechanism for epoxidation. As a result of these developments in the thesis, chemisorption enthalpies can now be estimated within 3 kcal/mol of experimental values for transition metal catalysts and enthalpies predicted by G3B3 and G3MP2B3 Gaussian methods can be corrected within 0.5 kcal/mol. Examples of heterogeneous reaction systems involving silver-catalyzed ethylene epoxidation demonstrate the effectiveness of the methodologies developed in this work.
by Bharthwaj Anantharaman.
Ph.D.
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Polverari, Marco. "Dynamic and evanescent wave light scattering of poly(ethylene oxide) - latex systems." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=28515.
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The principal aims of the thesis were to carry out a systematic analytical study to determine the solution properties of narrow-distribution and broad-distribution linear poly(ethylene oxide) (PEO) polymer samples in aqueous and organic solution and to study the adsorption properties of these polymer samples onto glass interfaces and spherical latex particles. The deposition characteristics of various types of bare and PEO coated latex particles onto collector surfaces were also studied.These studies allowed to ascertain the presence of PEO clusters in aqueous solution. The cluster size was found to be time dependent and to vary between 0.45 $ mu$m and 0.90 $ mu$m. The clusters were found to be in a thermodynamic equilibrium with the free polymer in solution and were found to reform spontaneously after a 30 minute period following filtration.
Adsorption studies indicated that the adsorption of PEO onto latex particles is kinetically controlled and that increased surface roughness and polarity of the latex particles decreases PEO adsorption. PEO clusters in solution were found to increase the value of the effective diffusion constant, D$ rm sb{eff}$ and thus decrease the calculated hydrodynamic layer thickness.
Evanescent wave light scattering was used in conjunction with a hydrodynamic impinging jet method for the study of depositing and non-depositing colloidal systems near interfaces. For non-depositing systems a comparison of the measured particle concentration profiles to the theoretically expected particle concentration profiles, calculated from DLVO theory, was made. The agreement was found to be very good.
The deposition of bare and PEO-coated latex particles onto glass interfaces was also investigated. From the data it was found that bare and smooth latex particles adsorb much more strongly onto collector surfaces than "hairy" latex particles which have long copolymer chains, such as itachonic acid, grafted onto their surfaces. The results indicated that the thicker the adsorbed polymer layer, the stronger the steric force preventing deposition of the polymer coated colloidal particles onto the collector surface. When the combined ellipsometric layer thickness of the particles and the collector surface exceeded a critical value, found to be about 15 nm, no particle deposition onto the collector surface was possible.
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Nacerodien, Mogamat Thaabit. "Investigation of polymer grade blending in Ziegler-Natta Catalysed ethylene polymerisation systems." Master's thesis, University of Cape Town, 2014. http://hdl.handle.net/11427/9122.
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Includes bibliographical references.Polyethylene is one of the most widely used polymers to date and it is an important commodity in a variety of fields. Most existing polyethylene plants operate on technology involving heterogeneous Ziegler-Natta catalysts. Plants often change operating conditions to produce different polymer grades; this allows them to cater to a larger polymer market. A side-effect of this practice is the unwanted formation of off-spec polymer during the grade transition periods. Numerous studies have been conducted to address the issue of off-spec polymer formation. These studies involve applying optimal control theory to minimise the grade transition time or to minimise the amount of off-spec polymer generated during the transient period. This field of study is known as grade transition optimisation. The current study aims to provide an alternative approach to addressing the problem of offspec accumulation. It is proposed that stored off-spec polymer is blended with virgin polymer to provide a saleable and desirable product. The approach might be different, but the same techniques used in grade transition optimisation are applied. Polyethylene produced using Ziegler-Natta catalysts have relatively linear chains, thus a chain length distribution coefficient is sufficient to characterise the polymer product. The number average chain length and polydispersity index are adequate representatives of this distribution for reporting the properties of a polyethylene grade. For the purpose of applying optimal control theory, a polyethylene production process model was developed to calculate these average properties using a kinetic scheme based on fundamental principles. This process model is able to predict the polymer properties under both steady-state and unsteady-state behaviour. A key feature of the model is its ability to solve the system with low computational expense due to the use of the segregation approach to link particle properties to the overall bulk phase. This is especially useful since optimisation algorithms used in optimal control theory are iterative by nature. The Differential Evolution Algorithm (DEA) was used to minimise the objective functions that were developed for the optimisation schemes due to its ability to evaluate objective functions in parallel. A model of the blending aspect of the process was developed where it was derived that the polymer moments are additive on a mass basis. Pure grades were blended in a laboratory in various mass ratios and analysed using GPC to determine their molecular weight distribution curves. It was found that the model-predicted curves and the experimentally-determined curves were an excellent match, thus validating the model. In the current study, three procedures for blending off-spec material under standard industry conditions are proposed. The first method involves the introduction of off-spec polymer on a continuous basis to the virgin polymer stream during steady-state operation.
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Radcliffe, James Edward. "Discovery and development of novel P,N ligands for selective ethylene oligomerisation systems." Thesis, Durham University, 2015. http://etheses.dur.ac.uk/11301/.
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This thesis documents the design, discovery, and development of a range of P,N-type ligands and their application in selective ethylene oligomerisation processes. Two classes of ligand have been investigated, PNE (Ph2P(CH2)2NC4H8E, E = NMe, O, CH2) ligands, and iminophosphine ligands (R(PR’2)C=NAr). The coordination chemistry of both these series of compounds has been investigated with various chromium species, and the behaviour of these molecules in ethylene oligomerisation systems probed. Chapter 2 explores the application of PNE ligands to ethylene oligomerisation. The coordination chemistry of the PNE ligands with a selection of group VI starting materials has been investigated. It has been shown that both the PNO and PNC ligands form bidentate complexes upon reaction with CrCl3(THF)3 (e.g. CrCl3(THF)(PNO), 2.1), while attempts to synthesise the PNN analogue proved unsuccessful. The coordination of PNE ligands with Cr(0) and Mo(0) has been studied, with the ligands exhibiting both mono- (e.g. Cr(CO)5(PNN) (2.4) and bi-dentate coordination (e.g. Mo(CO)4(PNN) (2.7)), dependant on the combination of metal and ligand used. Conversion of monodentate Cr(CO)5(κ1-PNN) (2.4) to bidentate Cr(CO)4(κ2-PNN) (2.10) is achieved on reaction with trimethylamine N-oxide. The application of PNE ligands to ethylene oligomerisation systems has been carried out. All of the catalytic systems tested gave primarily polymer products, with no selective ethylene oligomerisation occurring. Chapter 3 describes the development of a modular synthetic route to novel iminophosphine compounds via reaction of imidoyl chlorides with trimethylsilyl phosphines. Using this synthetic process, a library of iminophosphines has been synthesised (3.1-3.26) with varying steric and electronic characteristics. The donor properties of the iminophosphines have been analysed by measurement of ǀ1JSe-Pǀ couplings of the derivative phosphine selenides, with all the compounds demonstrating good phosphine donor properties. Finally, the E/Z isomerisation behaviour of the PCN compounds has been studied, revealing that P-aryl substituted iminophosphines exist as a mixture of the E and Z isomers in equilibrium in solution. Chapter 4 details investigations into the coordination chemistry of iminophosphine ligands with chromium. A selection of ligands have been reacted with CrCl3(THF)3, forming a range of bidentate CrIII(κ2-PCN) complexes (e.g. CrCl3(THF)(Ph(PPh2)C=NPh), 4.1). The coordination of iminophosphine ligands with Cr(0) has shown that the ligands react with Cr(CO)6 to yield both mono- and bi-dentate products (e.g. Cr(CO)4(Ph(PiPr2)C=N(2,6-iPr2C6H3)) (4.7) and Cr(CO)5(Ph(PiPr2)C=N(2,6-iPr2C6H3)) (4.8), respectively). The denticity of these Cr(CO)(6-n)(κn-PCN) complexes can be controlled through the removal and addition of CO in the atmosphere. Chapter 5 recounts the use of the novel iminophosphines as ligands in selective ethylene oligomerisation systems. A wide range of catalytic conditions were tested, including varying the chromium source, solvent, reaction temperature and pressure, the use of polymer reducing additives, and the dosing of O2 into the reaction. It has been shown that a catalytic process using Cr(2-EH)3, 1 equivalent of iminophosphine 3.9, 49 bar C2H4, in methylcyclohexane at 60 °C, with 0.66 ppm O2 and 100 equivalents of ZnEt2 yields a highly active and selective ethylene tri-/tetramerisation process.
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Alzamly, Ahmed. "The Role of Aluminate in the Activation of Catalytic Systems for Ethylene Oligomerization." Thèse, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/31024.
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The reaction mechanisms followed by ethylene polymerization and selective oligomerization (tri- and tetramerization) are conceptually very different, being a non-redox chain growth and a redox metallacycle ring expansion pathway respectively. With chromium being the metal of choice, metal oxidation states and the variation of ancillary ligand able to support specific metal oxidation states responsible for selective trimerization, tetramerization or nonselective oligomerization/polymerization were varied. In this research project we have explored a broad range of novel pyridine containing modified PN ligand scaffolds with the aim of probing the role of the pyridine donor substituent in stabilizing lower oxidation states and ultimately affecting the selectivity of the ethylene in the catalytic cycle. In this study, pyridine PNP pincer ligands in conjunction with chromium salts and alkylaluminium activators have been explored. Their catalytic activities toward ethylene oligomerization were rationalized through the isolation of different chromium-aluminate intermediates in different oxidation states during the catalytic reaction. Moreover, we explored other pyridine modification of NNP type ligand. Its anionic ligand shows a rare example of a Cr(II) hydride cluster which shows a high activity as a nonselective ethylene oligomerization catalyst. Finally, a cyclic PNPN type ligand was explored. The ligand enabled the isolation of a mix-valent Cr(I)/Cr(II) species which was found to be inactive toward ethylene oligomerization due to its geometric constraint.
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Hagan, Susan Anne. "Poly(lactic acid)-poly(ethylene glycol) copolymers for use as drug delivery systems." Thesis, University of Nottingham, 1998. http://eprints.nottingham.ac.uk/30646/.
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Block copolymers of polylactide and poly( ethylene glycol) (PLA-PEG) were investigated as biodegradable drug delivery systems. They are defined by the differing molecular weight ratios of polylactide to poly( ethylene glycol). Copolymers containing more hydrophilic PEG than hydrophobic PLA per molecule self-dispersed in water giving spherical nonionic micelles. Purification by gel permeation chromatography gave two peaks. The first peak only formed micelles (the second was PLA-depleted). Analysis by dynamic light scattering (DLS) and transmission electron microscopy (TEM) gave diameters of IS.6nm and 18.9nm for 1.5:2 and 2:5 PLA-PEG micelles respectively. PLA-PEG copolymers with more PLA than PEG per molecule (4:2 and 6:2 PLA-PEG) formed "solid particles" by the solvent-precipitation method. GPC purification again gave two peaks, but smaller second peaks. DLS analysis gave diameters of 15.1 nm and 20.8nm for 4:2 and 6:2 PLA-PEG particles respectively (confirmed by TEM and atomic force microscopy (AFM)). Static secondary ion mass spectrometry and X-ray photoelectron spectroscopy showed PEG at the surface of 4:2 and 6:2 PLA-PEG in water and acetone. Stability testing to salt suggested sterically stability. Rheological measurements determined PEG chain layer thicknesses, with the thickest chain for 2:5 PLA-PEG (where PEG chain length is 5000gmol-1 compared with 2000gmol-1). Testosterone and sudan black B (SBB), were used as "model" drugs with different hydrophobicities. Ultracentrifugation sedimentation velocity studies confirmed drug incorporation. Aromatic SBB loaded readily (≥59.0%w/w) compared with steroidal testosterone <2%w/w). Loading of testosterone esters of varying hydrophobicity into PLA-PEG particles showed little difference compared to between testosterone and SBB, suggesting that aromaticity is more significant. In vitro release studies (4:2 PLA-PEG particles/SBB) showed a small burst release, then linear release to twenty eight days. In vivo studies in the rat, using a radioactive marker, demonstrated extended blood circulation times for PLA-PEG micelles during the three-hour study, with increased blood levels and lower liver uptake for 1.5:2 over 2:5 PLA-PEG micelles. PLA-PEG particles were directed to the liver.
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Grigorian, V. "An investigation into the characterisation of the laser-induced incandescence method for the measurement of soot in practical systems." Thesis, Cranfield University, 2002. http://dspace.lib.cranfield.ac.uk/handle/1826/10755.
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The thesis describes the characterisation and application of the laser induced
incandescence
technique for making soot measurements in practical devices. Laser
induced incandescence is the phenomenon whereby particulates such a soot absorb
laser radiation and are heated to a
temperature much higher than the bath gas. The
broadband incandescence
signal from the hot particles can be detected and the signal is
proportional to volume fraction.
The
technique was used to study soot in partially premixed counterflow ethylene air
flames, iso-octane explosion flames, and to image soot in a D. I. Diesel engine. Mie
scattering, OH-LIF and absorption were used a complementary diagnostics.
Appropriate ratios of LII and Mie images allowed the relative particle size and number
density to be imaged. The counter flow burner measurements were used to study the
effects of strain on soot formation while the bomb work demonstrated soot production in
hydro-dynamically unstable cellular flames. The Diesel engine measurements are a
demonstration of optical diagnostics in a real device.
In order to characterise the LII signal behaviour two types of carbon aerosol generators
were built. The
liquid dispersion device produces almost spherical sub-micron carbon
black
particles. The device was used to characterise the soot field response, laser
fluence
response, signal decay and spectrum of the LII signal.
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Stanley, Nicholas. "Organic, metallic and mixed catalytic systems for the synthesis of poly(ethylene terephthalate-co-isosorbide terephthalate)." Thesis, Lille 1, 2017. http://www.theses.fr/2017LIL10053.
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L’objectif de cette thèse, en partenariat avec la société Roquette Frères et l’Institut Français des Matériaux Agrosourcés (IFMAS), est de développer des systèmes catalytiques permettant de catalyser de manière efficace la polyestérification d’alcools secondaires. Il s’agit de faciliter l'incorporation de monomères biosourcés tel que l'isosorbide dans des polyesters de type poly(éthylène téréphtalate) (PET). L’emploi de ce monomère biosourcé permet d’accéder à de nouvelles propriétés et de réduire la consommation de dérivés d’origine pétro-sourcés comme peut l’être le CHDM (cyclohexane diméthanol) ou le CBDO (tétraméthyl-cyclobutanediol) par exemple. Le Chapitre 1 propose une étude bibliographique sur les catalyseurs les plus performants actuellement utilisés pour la synthèse de PET. L’organocatalyse, qui a jusqu’ici été très peu étudiée dans ce type de réaction, est appliquée à la synthèse de poly(éthylène-téréphtalate-co-isosorbide téréphtalate) dans le Chapitre 2. Dans le Chapitre 3, des catalyseurs métalliques performants en synthèse de PET sont appliqués à la réaction, ainsi que des combinaisons bimétalliques. Dans le Chapitre 4, ces catalyseurs métalliques sont utilisés en combinaison avec les organocatalyseurs les plus performants, dans le but d’optimiser les propriétés et de réduire la quantité de métal utiliséeThe objective of this thesis, in partnership with the company Roquette Frères and the French Institute of Agro-Sourced Materials (IFMAS), is to develop catalytic systems which can efficiently catalyse the polyesterification of secondary alcohols. The particular aim is to simplify the incorporation of bio-sourced monomers such as isosorbide in to polyesters like poly(ethylene terephthalate) (PET). The use of this bio-sourced monomer allows access to new properties whilst also reducing the consummation of petro-sourced derivatives, much like in the case of cyclohexane dimethanol (CHDM) or cyclobutane diol (CBDO). Chapter 1 proposes a bibliographic study on the best performing catalysts currently used for the synthesis of PET. Organocatalysts, who have been rarely studied until now for this reaction, are applied to the synthesis of poly(ethylene terephthalate-co-isosorbide terephthalate) in Chapter 2. In Chapter 3, metallic catalysts known for their use in PET synthesis are applied to the reaction separately and in bimetallic combinations. In Chapter 4, these metallic catalysts are used in combinations with the best performing organocatalysts with the aim of optimising the properties whilst also reducing the metal quantities used
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Rodriguez, Joel. "Investigation of transient plasma ignition for a Pulse Detonation Engine." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2005. http://library.nps.navy.mil/uhtbin/hyperion/05Mar%5FRodriguez.pdf.
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Chapman, Brian G. "Study of drag reduction by zwitterionic and non-Ionic surfactants in low temperature ethylene glycol/ water recirculation systems /." Connect to this title online, 2005. http://hdl.handle.net/1811/313.
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Thesis (Honors)--Ohio State University, 2005.Title from first page of PDF file. Document formattted into pages: contains vi, 78 p.; also includes graphics. Includes bibliographical references (p. 62-63). Available online via Ohio State University's Knowledge Bank.
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Miles, William Clayton. "The Design of Stable, Well-Defined Polymer-Magnetite Nanoparticle Systems for Biomedical Applications." Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/28725.
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The composition and stability of polymer-magnetite complexes is essential for their use as a treatment for retinal detachment, for drug targeting and delivery, and for use as a MRI contrast agent. This work outlines a general methodology to design well-defined, stable polymer-magnetite complexes. Colloidal modeling was developed and validated to describe polymer brush extension from the magnetite core. This allowed for the observation of deviations from expected behavior as well as the precise control of polymer-particle complex size. Application of the modified Derjaguin-Verwey-Landau-Overbeek (DLVO) theory allowed the determination of the polymer loading and molecular weight necessary to sterically stabilize primary magnetite particles.
Anchoring of polyethers to the magnetite nanoparticle surface was examined using three different types of anchor groups: carboxylic acid, ammonium, and zwitterionic phosphonate. As assessed by dynamic light scattering (DLS), the zwitterionic phosphonate group provided far more robust anchoring than either the carboxylic acid or ammonium anchor groups, which was attributed to an extremely strong interaction between the phosphonate anchor and the magnetite surface. Coverage of the magnetite surface by the anchor group was found to be a critical design variable for the stability of the zwitterionic phosphonate groups, and the use of a tri-zwitterionic phosphonate anchor provided stability in phosphate buffered saline (PBS) for a large range of polymer loadings.
Incorporation of an amphiphlic poly(propylene oxide)-b-poly(ethyelene oxide) (PPO-b-PEO) diblock copolymer attached to the magnetite surface was examined through colloidal modeling and DLS. The relaxivity of the complexes was related to aggregation behavior observed through DLS. This indicated the presence of a hydrophobic interaction between the PPO layers of neighboring complexes. When this interaction was large enough, the complexes exhibited an increased relaxivity and cellular uptake.
Thus, we have developed a methodology that allows for design of polymer-magnetite complexes with controlled sizes (within 8% of predicted values). Application of this methodology incorporated with modified DLVO theory aids in the design of colloidally stable complexes with minimum polymer loading. Finally, determination of an anchor group stable in the presence of phosphate salts at all magnetite loadings allows for the design of materials with minimum polymer loadings in biological systems.Ph. D.
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Lucas, Bruce. "Fundamental Modeling of Solid-State Polymerization Process Systems for Polyesters and Polyamides." Diss., Virginia Tech, 2005. http://hdl.handle.net/10919/29378.
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The dissertation describes and assembles the building blocks for sound and accurate models for solid-state polymerization process systems of condensation polymers, particularly poly(ethylene terephthalate) and nylon-6. The work centers on an approach for modeling commercial-scale, as opposed to laboratory-scale, systems. The focus is not solely on coupled polymerization and diffusion, but extends to crystallization, physical properties, and phase equilibrium, which all enhance the robustness of the complete model.
There are three applications demonstrating the utility of the model for a variety of real, industrial plant operations. One of the validated simulation models is for commercial production of three different grades of solid-state PET. There are also validated simulation models for the industrial leaching and solid-state polymerization of nylon-6 covering a range of operating conditions. The results of these studies justify our mixing-cell modeling approach as well as the inclusion of all relevant fundamental concepts.
The first several chapters discuss in detail the engineering fundamentals that we must consider for modeling these polymerization process systems. These include physical properties, phase equilibrium, crystallization, diffusion, polymerization, and additional modeling considerations. The last two chapters cover the modeling applications.Ph. D.
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Junges, Fernando. "Novel catalyst systems based on Ni(II), Ti(IV), and Cr(III) complexes for oligo-and polymerization of ethylene." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2005. http://hdl.handle.net/10183/6358.
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Le complexe de Brookhart Ni(α-diimine)Cl2 (1) (α-diimine = 1,4-bis(2,6- diisopropylphenyl)-acenaphthenediimine) a été caractérisé après impregnation sur silice (S1) et a silices modifié avec MAO (4,0, 8,0 et 23,0 wt.% Al/SiO2 appelé S2, S3 et S4, respectivement). Le traitement de ces composés greffé avec MAO produit des catalyseurs actifs pour la polymérisation de l'éthylène. Un haute activité catalytique a été obtenue en utilisant le système supporté 1/S3 (196 kg de PE/mol[Ni].h.atm; toluene, Al/Ni = 1000, 30ºC, 60 min et pression atmosphérique d'éthylène). Les effets des conditions de la polymérisation ont été testés avec le catalyseur greffé S2 et la meilleure activité catalytique a été obtenue avec le solvant hexane, MAO comme cocatalyseur, la proportion molaire Al/Ni de 1000 et à la température de 30°C (285 kg de PE/mol[Ni].h.atm). Quand la réaction a été conduite selon la méthodologie in situ, l'activité a pratiquement doublé et les polymères ont montré des propriétés semblables. Les polymères produits par les catalyseurs supportés ont montré l'absence de température de fusion, resultats senblables à seux obtenus avec les systèms homogène par analyse DSC. En revanche, le polymères obtenus avec les système greffé presentent selon les courbes GPC une (MwD) polydispersité qui varie de 1,7 à 7,0. Un mélange de polyéthylène lineaire et ramifié (BPE/LPE) préparé utilisant les complexes Ni(α-diimine)Cl2 (1) (α-diimine = 1,4-bis(2,6-diisopropylphenyl)- acenaphthenediimine) et {TpMs*}TiCl3 (2) (TpMs* = hydridobis(3-mesitylpyrazol-1-yl)(5- mesitylpyrazol-1-yl)) greffés in situ sur silice modifiée avec MAO (4,0 wt. -% Al/SiO2, S2). Les réactions de polymérisation ont été exécutées dans le toluène à deux températures différentes (0 et 30°C), variant la fraction molaires du nickel (xNi), et utilisan MAO comme cocatalyseur externe. A toutes les températures, les activités montrent une tendence de variation linéaire avec xNi et indiquent l´absence d´effet synerque entre les espéces de nickel et du titane. Des activités les plus elèvees ont été trouvées à 0°C. Les températures de fusion pour les mélanges de polyéthylène produits à 0 °C diminuent alors que xNi augmente l'indiquant une bonne compatibilité entre les phases du polyéthylène obtenues avec les deux catalyseurs. La température de fusion des mélanges de polyéthylène dépendre de l'ordre selon lequel les catalyseurs ont été greffés sur la silice modifiée avec MAO. L'immobilisation initiale de 1 sur le support (2/1/S2) produit des polymères avec une temperature de fusion (Tm) inférieure à celle des polymère obtenus lorsque le titane a etè greffé inicialment 1/2/S2. L´observation des polyèthylènes obtenus avec les deux systèms (2/1/S2 et 1/2/S2) par microscopie electronique à balayage (SEM) a montré la formation de polymére sphérique montrant que la morphologie sphérique du support à été reproduite. Sont décrits la synthèse, la caractérisation et les propriètès catalytique pour l'oligomerization de l'éthylène de quatre composés organometalliques du CrIII possèdante les ligands (([bis[2-(3,5-dimethyl-1-pyrazolyl)ethyl]amine]chromiun(III)chloride (3a), [bis[2- (3,5-dimethyl-l-pyrazolyl)ethyl] benzylamine]chromiun(III)chloride (3b), [bis[2-(3,5- dimethyl-l-pyrazolyl)ethyl]ether] chromiun(III)chloride (3c), [bis[2-(3-phenyl-lpyrazolyl) ethyl]ether]chromiun(III)chloride (3d)). Concernent l'oligomerization, exception faite du composè 3a, tous les complexe du chrome se sont montré actif après activation avec MAO et les FR obtenues ont une effet differencie à celles atteintes avec CrCl3(thf)3. La coordination d´un ligand tridentatè sur le centre metallique ne provoque pas de changements considérables sur la formation des C4 et C6, mais la montantè de C8 est diminuèe et celles des C10 et +C12 ont ètè augmentèes. Les polymères produits par le catalyseur 3a à 3 et 20 atm d'éthylène possèdent, selon les analyses par DSC la températures de fusion de 133,8 et 136ºC respectivement. Ceci indique que dans les deux cas la production de polyèthylène de haut densité. Effectivement le masse molar moyenne, obtenus par GPC, est de 46647 g/mol avec Mw/Mn = 2,4 (3 atm). Le système 3c/MAO a montré des valeurs de FR, activité et sélectivité à α-olefins differents selon la pression d´éthylène utilisèe. Se qui montré une grand sensibilitè à la concentration d´éthylène solubilisè.The complex of Brookhart Ni(α-diimine)Cl2 (1) (α-diimine = 1,4-bis(2,6- diisopropylphenyl)-acenaphthenediimine) has been characterized after impregnation on silica (S1) and MAO-modified silicas (4.0, 8.0 and 23.0 wts.% Al/SiO2 called S2, S3 and S4, respectively). The treatment of these heterogeneous systems with MAO produces some active catalysts for the polymerization of the ethylene. A high catalytic activity has been gotten while using the system supported 1/S3 (196 kg of PE/mol[Ni].h.atm; toluene, Al/Ni = 1000, 30ºC, 60 min and atmospheric pressure of ethylene). The effects of polymerization conditions have been tested with the catalyst supported in S2 and the best catalytic activity has been gotten with solvent hexane, MAO as cocatalyst, molar ratio Al/Ni of 1000 and to the temperature of 30°C (285 kg of PE/mol[Ni].h.atm). When the reaction has been driven according to the in situ methodology, the activity practically doubled and polymers showed some similar properties. Polymers products by the supported catalysts showed the absence of melting fusion, results similar to those gotten with the homogeneous systems by DSC analysis. But then, polymers gotten with the transplanted system present according to the GPC’s curves the polydispersity (MwD) varies between 1.7 and 7.0. A polyethylene blend (BPE/LPE) was prepared using the complex Ni(α-diimine)Cl2 (1) (α-diimine = 1,4-bis(2,6-diisopropylphenyl)-acenaphthenediimine) and {TpMs*}TiCl3 (2) (TpMs* = hydridobis(3-mesitylpyrazol-1-yl)(5-mesitylpyrazol-1-yl)) supported in situ on MAO-modified silica (4.0 wts. -% Al/SiO2, S2). Reactions of polymerization of ethylene have been executed in the toluene in two different temperatures (0 and 30°C), varying the molars fraction of nickel (xNi), and using MAO as external cocatalyst. To all temperatures, the activities show a linear variation tendency with xNi and indicate the absence of the effect synergic between the species of nickel and the titanium. The maximum of activity have been found at 0°C. The melting temperature for the blends of polyethylene produced at 0 °C decrease whereas xNi increases indicating a good compatibility between phases of the polyethylene gotten with the two catalysts. The melting temperature for the blends of polyethylene showed be depend on the order according to which catalysts have been supported on the MAO-modified silica. The initial immobilization of 1 on the support (2/1/S2) product of polymers with a melting temperature (Tm) lower to the one of the polymer gotten when the titanium has been supported inicially (1/2/S2). The observation of polyethylenes gotten with the two systems (2/1/S2 and 1/2/S2) by scanning electron microscopy (SEM) showed the spherical polymer formation showing that the spherical morphology of the support to been reproduced. Are described the synthesis, the characterization and the catalytic properties for the oligomerization of the ethylene of four organometallics compounds of CrIII with ligands ([bis[2-(3,5-dimethyl-1-pyrazolyl)ethyl]amine] chromium (III) chloride (3a), [bis[2-(3,5- dimethyl-l-pyrazolyl)ethyl]benzylamine] chromium (III) chloride (3b), [bis[2-(3,5-dimethyl-lpyrazolyl) ethyl]ether] chromiun(III)chloride (3c), [bis[2-(3-phenyl-lpyrazolyl) ethyl]ether]chromiun(III)chloride (3d)). In relation of the oligomerization, at exception made of the compounds 3a, all complex of the chromium showed be active after activation with MAO and the TOF gotten have one effect differentiated to those formed with CrCl3(thf)3. The coordination of a tridentate ligand on the metallic center doesn't provoke any considerable changes on the formation of the C4 and C6, but the amount of C8 are decrease and the C10 and C12+ have increased. The Polymers produced by the catalyst 3a to 3 and 20 bar of ethylene have, according to analyses by DSC, the temperatures of fusion of 133,8 and 136ºC respectively. It indicates that in the two cases the production of high density polyethylene. The molar mass, gotten by GPC, is 46647 g/mols with MwD = 2,4 (3 bar). The system 3c/MAO showed values of TOF, activity and selectivity to different α-olefins according to the pressure of ethylene uses. Himself that shown a big sensibility to the concentration of ethylene solubilized.
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Travelet, Christophe. "Supramolecular systems based on α-cyclodextrins and poly(ethylene oxide) : structure and properties of pseudo-polyrotaxanes, polyrotaxanes and sliding gels." Strasbourg, 2009. http://www.theses.fr/2009STRA6033.
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Nous avons étudié le processus de complexation entre les α-cyclodextrines (α-CD) et le poly(oxyéthylène) (PEO) dans l'eau, conduisant ainsi à la formation de complexes d'inclusion appelés pseudo-polyrotaxanes (PPR). A 30°C, nous avons établi que, dans une première étape, les α-CD complexent les chaînes de PEO, formant des molécules de PPR. A plus grande échelle, une agrégation rapide des molécules de PPR a lieu et des nano-cylindres à base d'α-CD complexées se forment. A plus grande échelle encore, les nano-cylindres à base d'α-CD s'associent de manière gaussienne, engendrant la formation de domaines précités. Ensuite, dans une seconde étape, le système subit une auto-réorganisation caractérisée par une augmentation de la compacité des domaines précités, et il se forme un gel physique. Nous avons ensuite investigué les polyrotaxanes (PR), c'est-à-dire les PPR à base d'α-CD et de PEO bouchonnés stériquement aux extrémités, en solution concentrée dans le diméthylsulfoxyde (DMSO) et avons établi qu'ils ont la particularité de former des gels physiques au cours du temps à température ambiante. L'origine moléculaire de l'auto-organisation est la cristallisation des segments de PEO nus et l'agrégation régulière des α-CD complexées provenant de liaisons hydrogène par l'intermédiaire de leurs groupements hydroxyles. Ensuite, nous avons étudié les gels chimiques obtenus par réticulation des PR par l'intermédiaire de leurs α-CD. La réaction de réticulation chimique avec la divinylsulfone (DVS) n'a pas lieu dans des conditions douces si bien que des domaines hautement réticulés cohabitent avec d'autres qui sont moins réticulésWe studied the threading process between α-cyclodextrins (α-CDs) and poly(ethylene oxide) (PEO° in water, thus leading to the formation of inclusion complexes called pseudo-polyrotaxanes (PPRs). At 30°C, we established that, in a first step, α-CDs thread onto PEO chains, forming PPR molecules. At a higher length-scale, rapid aggregation of the PPR molecules occurs and threaded α-CD-based nano-cylinders form. A higher length-scale, α-CD_based nano-cylinders associate in a Gaussian way engendering the formation of precited domains. Then, in a second step, the system undergoes its reorganization characterized by a compacity increase of the precipitated domains and forms a physical gel. Then, we studied chemical gels obtained by cross-linking PRs via their α-CDs. The chemical cross-linking reaction with divinym sulfone (DVS) does not occur in soft conditions so that highly cross-linked domains cohabit with less cross-linked ones
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Huang, Chien-Chang. "The application of tetrakis(dimethylamino)ethylene chemiluminescence in characterization of the surface properties of metal oxides and reversed microemulsion systems." Diss., Manhattan, Kan. : Kansas State University, 2009. http://hdl.handle.net/2097/1609.
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Nguyen, Ngoc Linh. "Toward Realistic DFT Description of Complex Systems: Ethylene Epoxidation on Ag-Cu Alloys and RPA Correlation in van der Waals Molecules." Doctoral thesis, SISSA, 2012. http://hdl.handle.net/20.500.11767/4699.
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In this thesis we have studied two different aspects of Density Functional Theory
(DFT): (i) the application of DFT with the generalized gradient approximation
(GGA) functional for exchange-correlation energy in modeling an heterogeneous
catalysis problem, and (ii) the development of a new self-consistent field (scf) strategy
to solve the Kohn-Sham (KS) equations that allows to improve the accuracy of
DFT method with exact exchange (EXX) and RPA correlation energy functionals
in the description of weak chemical interactions.
Ethylene epoxidation, one of the largest-scale catalytic processes in the chemical
industry, were studied in Chapter 2 of this thesis. The formation of the desired
product ethylene oxide (EO) in this reaction is promoted by a Ag-Cu alloy catalyst.
In this study, the oxidation of ethylene is considered to occur on the Ag-Cu structures
formed by thin copper-oxide layers on an Ag slab. These structures have been
determined by theoretical and experimental works to be the favorable structures
on the surfaces of Ag-Cu alloys in the high pressure and temperature conditions
relevant to experiment. According to the calculations for reaction pathways, we
found that the structures of Ag-Cu alloys are selective towards the formation of
the EO final product, rather than the undesired product acetaldehyde (Ac) which
is readily converted to carbon dioxide. The selectivity of Ag-Cu alloys is found
to be higher than pure Ag, in agreement with experimental results. To do this,
we carried out a study of the stability of the surface structures in thermodynamic
equilibrium conditions ( at T = 600 K and pO2 = 1 atm), and we have shown
that the higher selectivities relate to the formation of copper-oxide layers on the Ag
slab. Moreover, our theoretical results show that the high selectivity of a copperoxide
layer is maintained even when the thickness of the oxide is increased to two
layers. In particular, we have found that a very high selectivity could be obtained
by structure containing 1.25 ML of Cu and 0.25 ML of sub-surface oxygen. Another
important result is the finding of a selectivity indicator that allows to determine the
selectivity of the pure metals and alloy catalysts even with the thin oxide structures
in ethylene epoxidation reaction. In further works, this indicator could be applied
to predict the selectivity of other Ag-based alloys such as Ag-Pd, Ag-Pt, etc. These
alloys were found experimentally to be selective catalysts towards the formation of
EO.
In spite of the great success of DFT when employing the well-known approximations
such as LDA or GGA exchange-correlation functionals, the standard DFT
approaches exhibit several serious shortcomings, and one of them is the poor or even
wrong evaluation of long-range dispersion interactions (i.e., van der Waals interactions). Calculations with the EXX/RPA-correlation energy within the adiabatic
connection uctuation-dissipation theorem (ACFDT) formalism have shown as a
promising approach that can give the correct description not only of weak bonds
but also of systems with covalent bonds. In Chapter 3, we developed the complete
scf procedure that enables the optimization of KS systems whose total energy is
computed with the EXX/RPA-correlation energy functionals. The implementation
has been applied to the study of some simple molecules. In future work, EXX/RPA
calculations could be applied to heterogeneous catalysis systems, where the role of
van der Waals interactions is still largely unknown. Moreover, improvement of the
accuracy of EXX/RPA calculations is also needed. According to ACFDT, one can
go beyond the RPA formalism by taking into account higher-level approximations of
the exchange-correlation kernel in the Dyson equation such as the time-dependent
EXX kernel.
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Prasetyo, Eko [Verfasser], and Elias [Akademischer Betreuer] Klemm. "Development of heterogenized catalyst systems for the synthesis of acrylic acid derivatives from carbon dioxide and ethylene / Eko Prasetyo. Betreuer: Elias Klemm." Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2015. http://d-nb.info/1074139712/34.
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Zahouani, Sarah. "Development of new types of mechanocatalytic systems." Thesis, Strasbourg, 2017. http://www.theses.fr/2017STRAE037/document.
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Le fascinant processus par lequel les signaux mécaniques sont transformés en réactions biochimiques dans la nature est appelé mécano-transduction. Le but de ma thèse a été de mimer la Nature en élaborant de nouveaux systèmes enzymatiques mécano-transductifs, i.e des matériaux capables de moduler une catalyse enzymatique lorsqu’ils sont sollicités mécaniquement. Nous avons d’abord étudié l’effet de l’étirement sur les chaînes constitutives de films multicouches de polyélectrolytes, matrices souvent utilisées pour le développement de biomatériaux intelligents. Dans le cadre d’une nouvelle stratégie axée sur la modulation mécanique de la conformation, nous avons ensuite élaboré des matrices étirables à base de poly(éthylène glycol)s. Nous avons en particulier développé de tout nouveaux revêtements covalents appelés nanogels qui se sont avérés être déposables sur le silicone étirable et fonctionnalisables avec différentes biomacromolécules, ouvrant ainsi de nouvelles routes biomimétiquesThe fascinating process by which mechanical signals are transformed into biochemical reactions in Nature is called mechanotransduction. The goal of my PhD was to mimic Nature by elaborating new types of mechanocatalytic materials, i.e materials able to modulate a catalytic activity when mechanically stimulated. We first aimed at understanding the impact of stretching on the structural properties of polyelectrolyte multilayers films, polymeric matrices often used for the design of smart biomaterials. Within the framework of a new strategy essentially relying on mechanically induced conformational changes, we then developed stretchable polymeric matrices based on poly(ethylene glycol)s. We more particularly designed new types of covalent coatings, called nanogels. We showed that these architectures were buildable on stretchable silicone and that they could be functionalized with different types of biomacromolecules; thus opening new biomimetic routes
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Kanjickal, Deenu George. "Perivascular Drug Delivery Systems for the Inhibition of Intimal Hyperplasia." University of Akron / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=akron1133715441.
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Simmons, Stephanie. "Influence of processing on the structure and properties of semi-crystalline polymer systems : 1) biodegradable starch/poly(ethylene-vinyl alcohol) blends and 2) polyolefinic thermoplastics." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/11379.
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Wheeler, Nicholas Robert. "Lifetime and Degradation Science of Polymeric Encapsulant in Photovoltaic Systems: Investigating the Role of Ethylene Vinyl Acetate in Photovoltaic Module Performance Loss with Semi-gSEM Analytics." Case Western Reserve University School of Graduate Studies / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=case1473440287427776.
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Bavarian, Neda. "Investigation of ethylene/propylene and ethylene/propylene/diene polymerization by Cp*TiMe3/B(C6F5)3 catalyst system." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0016/MQ52971.pdf.
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Mahajan, Vishal Khomdeo. "Study of chalcopyrite oxidation in hydrogen peroxide-ethylene glycol system." abstract and full text PDF (free order & download UNR users only), 2005. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1433392.
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Ilett, Stephen Mark. "A physico-chemical study of the poly(ethylene oxide) water system." Thesis, University of Nottingham, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334498.
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Ploetz, Christopher Daniel. "Micelles of polybutadiene-b-poly(ethylene oxide) in a binary solvent system." College Park, Md. : University of Maryland, 2008. http://hdl.handle.net/1903/8310.
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Thesis (M.S.) -- University of Maryland, College Park, 2008.Thesis research directed by: Dept. of Chemical and Biomolecular Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Cantu, Karina Arcaute. "Stereolithography of poly (ethylene glycol) hydrogels with application in tissue engineering as peripheral nerve regeneration scaffolds." To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2008. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.
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Atilgan, Nurdan. "Design, Synthesis And Electropolymerization Of A New Chemiluminescent Terthienyl System." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/3/12609858/index.pdf.
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ABSTRACT
DESIGN, SYNTHESIS AND ELECTROPOLYMERIZATION OF A NEW
CHEMILUMINESCENT TERTHIENYL SYSTEM
Atilgan, Nurdan
M.Sc. Department of Chemistry
Supervisor: Prof. Dr. Ahmet M. Önal Co-Supervisor: Assist. Prof. Dr. Atilla Cihaner September 2008, 57 pages A novel monomer, possessing chemiluminescence properties, 5,7-di-ethylenedioxythiophen-2-yl-2,3-dihydro-thieno[3,4-d]pyridazine-1,4-dione (ETE-Lum) was synthesized. Chemiluminescence properties of ETE-Lum were investigated in alkaline water solution in the presence of H2O2 and this reaction was catalyzed by Fe+3 ion and blood. This study submits a new opportunity to investigate forensic and analytical application instead of 5-amino-2,3-dihydro-1,4-phthalazine-dione (luminol). Response of other metalic cations was also investigated under the same reaction conditions. Electrochemical properties of ETE-Lum were studied in 0.1 M acetonitrile/tetrabutylammonium perchlorate solvent system containing BF3-Et2O and also in neat BF3-Et2O solution. In addition, the corresponding polymer film of ETE-Lum (PETE-Lum) was synthesized successfully via repetitive cycling by cyclic voltammetry and its electrochemical properties were investigated in a monomer-free electrolyte solution. Spectroelectrochemical behavior of the polymer film on indium tin oxide working electrode was also investigated by recording the electronic absorption spectra, in-situ, in monomer-free electrolyte solution at different potentials. Furthermore, spectroelectrochemical studies revealed that PETE-Lum had an electronic band gap of 1.66 eV. The results of electrochemical and electroluminesence measurements indicated that chemiluminecent unit of monomer was protected during polymerization. In addition, PETE-Lum film was found to be electrochemiluminescence active, maintaining its activitiy over 1000 cycles.
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CHAPMAN, DONALD RIVERS. "DETERMINING EMPLOYEE EXPOSURE TO ETHYLENE GLYCOL WHILE PERFORMING MAINTENANCE ON AN AIRCRAFT DEICING FLUID COLLECTION SYSTEM." University of Cincinnati / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1187020385.
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Scheele, Iris. "Hochauflösende Infrarot-Spektroskopie an schwach gebundenen Van-der-Waals-Systemen." [S.l.] : [s.n.], 2001. http://deposit.ddb.de/cgi-bin/dokserv?idn=963558668.
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Hyllestad, Ketil. "Scaling of Calcium Carbonate on a Heated Surface in a Flow Through System with Mono Ethylene Glycol." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for kjemisk prosessteknologi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-22335.
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Efficiency of industrial heat exchangers can be reduced due to precipitation of a solid mineral layer called scale. Reversibly soluble salts such as calcium carbonate are less soluble at elevated temperatures and therefore precipitate more easily in these units. The effect is also seen in oil wells, pipelines and desalination plants among others.The aim of this work was to determine growth rates and polymorphic composition of the formed scale at a range of inlet supersaturations, heated medium temperatures and solvent compositions. Experimental setup was prepared to study the effect of these parameters in a continuous flow system. An internally heated U-tube was placed in a reactor with constant stirring and supersaturation. Inlet/outlet temperature of the tube was continuously logged along with pH and bulk temperature.A reduced heat transfer from the tube to the bulk solution was observed with an increased thickness of the scaled layer. The overall growth rate of aragonite decreased by 3.8% from 5.36±0.18?10-6 kg/m2?s to 5.16±0.12?10-6 kg/m2?s when the experimental duration was changed from 90 to 180 minutes in a water solvent. An inlet supersaturation of 6.0 and a tube temperature of 90°C were used in these experiments. The decrease in crystal growth was caused by a reduced skin-temperature with reduced heat transfer. The growth rate was reduced to 2.6±0.3?10-6 kg/m2?s when the inlet supersaturation was reduced to 4.5 at comparable conditions and a time magnitude of 180 minutes. XRD- and SEM-analyses indicated a change from almost exclusively aragonite to a mixed polymorphic composition when the tube temperature was changed from 90°C to 50°C. Experimental results proved that there is a prolonged initiation period for scale growth in monoethylene glycol solutions compared to a pure de-ionized water solvent. To study the growth of scale in a MEG solution, the experimental procedure was changed to include a pre-scale period where a uniform layer of aragonite was formed. Subsequent growth could then continue with variable solvent composition on the outside of this layer.Heat transfer from the heated medium into the bulk solution was observed to decrease with a higher presence of MEG in the solvent, which elevated the skin-temperature. Thickness of the scaled layer was found to have a more profound effect on crystal growth in a combined water/MEG solvent than in a water solution. The results showed that there was a notable decrease in mass deposit with an elevated solvent concentration of MEG. Mass deposits per area after the pre-scale period were 0.90 mg/cm2 (50wt% MEG), 0.53 mg/cm2 (70wt% MEG) and 0.36 mg/cm2 (90wt% MEG) at an inlet supersaturation of 6.0 and a tube temperature of 90°C. This experimental setup allowed for a separate control of the kinetic and thermodynamic contributions to scale growth. The reduced deposition at comparable levels of supersaturation was caused by reduced growth kinetics due to the increased viscosity in a solvent with MEG.
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Freitas, ValdinÃia Soares. "Polyamines and ethylene metabolisms and antioxidative defense system induction in two maize genotypes contrasting in salinity tolerance." Universidade Federal do CearÃ, 2015. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=15060.
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CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel SuperiorPolyamines and ethylene have been cited as important regulators of plant growth and development, and may be involved in plant defense against several abiotic stresses, such as salinity. To withstand with salt harmful effects, plants respond through a coordinated set of physiological and molecular responses to improve their performance under salinity. In order to test the hypothesis that salt tolerance degree in maize genotypes is related to changes in polyamine metabolism associated with ethylene production, two experiments were performed. In the first one, BR5033 (salt-tolerant) and BR5011 (salt-sensitive) maize genotypes were subjected to 80 mM NaCl stress to identify the pattern of ethylene production in leaves and roots. Two peaks of ethylene production at 5.5 h (phase I) and 12.5 h (phase II) after onset the salinity treatment were registered in salt-sensitive leaves; whereas only the first peak of ethylene synthesis was detected in salt-tolerant leaves. Surprisingly, the biphasic ethylene production in roots was much less pronounced than in leaves. In the second experiment, we sought to investigate whether the phases I and II of ethylene production alter the polyamine metabolism in the leaves of maize genotypes. In salt-tolerant genotype, the phase I of ethylene synthesis was associated with signaling events, as evidenced by increased H2O2 levels, which were generated by putrescine (Put) catabolism. An early signaling (at 5.5 h) in the salt-tolerant genotype seemed to be effective to suppress the second peak of ethylene production, known as âstress ethyleneâ. Yet, in the salt-sensitive genotype, the decreased H2O2 concentration during the phase I was associated with a marked increase in ethylene production, which was resulted from upregulation of acid 1-aminocyclopropane-1-carboxylic acid oxidase (ACO) activity and ZmACO5 gene expression. At the phase I, the total polyamine content was increased by salinity in the salt-tolerant, whereas it was decreased in the salt-sensitive one. In the salt-tolerant genotype, the increased total polyamine was sustained by high spermine (Spm) and spermidine (Spd) contents, while the decay in the salt-sensitive genotype was due to the reductions of Put and Spd forms. Otherwise, in the phase II, no significant changes in the total polyamines in salt-tolerant genotype (it was likely due to conversion of Put to Spm/Spd), and decreases in salt-sensitive genotype were registered. Under stress conditions, the salinity-induced improvement of Spd and Spm (free and soluble conjugated forms) in salt-tolerant genotype was bigger than in salt-sensitive one, thus suggesting a key role of polyamines in the maize salt stress acclimation processes. Finally, we investigated if the lack of ethylene production during phase II in salt-tolerant genotype was correlated to improved antioxidant capacity. Salt stress dramatically increased the superoxide levels, the electrolyte leakage and lipid peroxidation, it being more pronounced in both leaves and roots of salt-sensitive genotype. On the other hand, under salinity, salt-tolerant genotype displayed a better performance of enzymatic and non-enzymatic antioxidant system, evidenced by a higher ascorbate and glutathione content and upregulation of superoxide dismutase, ascorbate peroxidase and guaiacol peroxidase activity. In conclusion, our results suggest that the ethylene is intimately involved in salt stress acclimation through activation of intricate signaling pathways mediated by H2O2 that is originated from polyamine catabolism. An efficient signal network raises the polyamine content and antioxidant capacity and is responsible, at least in part, for greater tolerance to salinity of BR5033 maize genotype.
Poliaminas e etileno sÃo reguladores do crescimento e desenvolvimento vegetal, que tambÃm estÃo envolvidos nas respostas de defesa das plantas contra estresses abiÃticos, dentre eles a salinidade. Para lidar com o estresse salino, as plantas realizam ajustes fisiolÃgicos, bioquÃmicos e moleculares, que podem resultar em sua aclimataÃÃo diante dessa condiÃÃo adversa, tornando o indivÃduo mais tolerante ao estresse, em comparaÃÃo Ãqueles que nÃo se encontram aclimatados. Essa pesquisa foi desenvolvida para testar à hipÃtese de que o grau de tolerÃncia à salinidade entre genÃtipos de milho envolve alteraÃÃes no metabolismo das poliaminas associadas à produÃÃo de etileno. Para isso, foram realizados dois experimentos. No primeiro, plantas de milho dos genÃtipos BR5011 (sensÃvel) e BR5033 (tolerante) foram submetidas ao estresse salino (NaCl a 80 mM) para identificar o padrÃo de produÃÃo de etileno em folhas e raÃzes. Nas folhas do genÃtipo sensÃvel, a salinidade intensificou a produÃÃo de etileno apÃs 5,5 h (fase I) e 12,5 h (fase II) apÃs o inÃcio do estresse, enquanto no tolerante isso aconteceu somente com 5,5 h. Nas raÃzes, embora tenha sido observada a produÃÃo bifÃsica de etileno no genÃtipo sensÃvel, esse processo foi muito menos intenso que nas folhas. O segundo experimento teve como objetivo principal investigar se a produÃÃo de etileno pela salinidade nas fases I e II resultava em alteraÃÃes no metabolismo das poliaminas nas folhas dos genÃtipos de milho. No genÃtipo tolerante, a fase I de produÃÃo de etileno foi associada à eventos de sinalizaÃÃo, dado o aumento dos teores de H2O2, mediado pelo catabolismo da putrescina (Put). Essa sinalizaÃÃo pareceu ser eficiente para suprimir a produÃÃo do etileno em condiÃÃes de estresse (fase II ou âetileno do estresseâ) nesse genÃtipo. Jà no sensÃvel, a diminuiÃÃo dos teores de H2O2 na fase I foi acompanhada por um aumento acentuado na produÃÃo do etileno, decorrente de acrÃscimos na atividade da enzima oxidase do Ãcido 1-carboxÃlico-1-aminociclopropano (ACO) e na expressÃo de transcritos do gene ZmACO5 (principal membro expresso). Em geral, a salinidade aumentou os teores de poliaminas totais no genÃtipo tolerante, enquanto reduziu no sensÃvel. Na fase I, na condiÃÃo salina quando comparada com o controle, os teores de poliaminas totais foram aumentados no genÃtipo tolerante enquanto no sensÃvel esses teores foram reduzidos. No genÃtipo tolerante, o aumento nos teores de poliaminas totais foi sustentado principalmente pelo aumento nos teores de espermina (Spm) e espermidina (Spd), enquanto a diminuiÃÃo observada no genÃtipo sensÃvel foi devida, sobretudo, Ãs reduÃÃes nas formas de Put e Spd. Jà na fase II, no genÃtipo tolerante nÃo houve alteraÃÃes nos teores totais de poliaminas (provavelmente, devido a utilizaÃÃo de Put para a sÃntese de Spm e Spd), enquanto no sensÃvel esses teores foram reduzidos. Sob condiÃÃes de salinidade, o aumento nas formas livre e conjugada solÃvel de Spm e Spd foi mais pronunciado no genÃtipo tolerante do que no sensÃvel, sugerindo assim importante papel para essas duas poliaminas nos processos de aclimataÃÃo ao estresse salino em plantas de milho. Por fim, foi investigado se a ausÃncia de produÃÃo do etileno na fase II, causado pela salinidade no genÃtipo tolerante, foi relacionada com uma melhor capacidade antioxidante. O estresse salino aumentou drasticamente os teores do radical superÃxido, o vazamento de eletrÃlitos e a peroxidaÃÃo lipÃdica, sendo isso mais pronunciado nas folhas e raÃzes do genÃtipo sensÃvel. De modo geral, o genÃtipo tolerante teve melhor desempenho do sistema antioxidante enzimÃtico e nÃo enzimÃtico, sob condiÃÃes de estresse salino, evidenciado pelos maiores incrementos nos teores de ascorbato e glutationa e na atividade das enzimas dismutase do superÃxido, peroxidase do ascorbato e peroxidase do guaiacol. Em conclusÃo, os resultados aqui apresentados sugerem que o etileno està intimamente envolvido na aclimataÃÃo ao estresse salino, por meio da ativaÃÃo de vias de sinalizaÃÃo mediadas pelo H2O2 produzido a partir do catabolismo de poliaminas. AlÃm disso, sugere-se que essa sinalizaÃÃo induz o aumento nos teores de poliaminas e melhor capacidade antioxidante no genÃtipo BR5033, sendo isto, pelo menos em parte, responsÃvel por sua maior tolerÃncia ao estresse salino, quando comparado ao BR5011.
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Thorpe, Sandra Denise. "Preparation and characterization of sodium poly(aL-glutamate)/poly(pyrrole)/poly(ethylene oxide) polymeric blends for a responsive peptide drug delivery system." DigitalCommons@Robert W. Woodruff Library, Atlanta University Center, 2004. http://digitalcommons.auctr.edu/dissertations/1703.
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Blends of sodium poly(a,L-glutamate) (MW 49K), poly(pyrrole) and poly(ethylene oxide) (MW lOOK) were prepared by a solution-blending process. A series of blend compositions were studied and characterized to determine optimal parameters and conditions necessary for the encapsulation and stability of the peptide portion of this ternary system. The retaining of the conformational structure of the peptide is important for its activity in a delivery system. Results derived from Infrared Spectroscopy (lR) indicated that the helical conformation of the peptide was maintained. The solid-state morphological properties of the ternary blends were studied by Differential Scanning Calorimetry (DSC) and Scanning Electron Microscopy (SEM). Results suggest the formation of a solid-state system with miscible properties that are due to noncovalent interactions, such as, ion-dipole and hydrophobic interactions. Preliminary cell culture studies utilizing ovarian cancer cells indicate that these cells will proliferate and adhere to the surface of these polymer blends.
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Canaveze, Yve. "Diferenciação de laticíferos articulados em plantas de Tabernaemontana catharinensis (Apocynaceae)." Botucatu, 2016. http://hdl.handle.net/11449/138104.
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Orientador: Silvia Rodrigues MachadoResumo: Neste estudo buscamos avaliar diferentes aspectos da diferenciação de laticíferos. O crescimento intrusivo (capacidade de crescer penetrando a lamela média de células adjacentes) e a ação indutora dos laticíferos (capacidade de induzir uma célula vizinha a adquirir características de laticíferos) são mecanismos de crescimento interessantes que podem ocorrer nos laticíferos, mas que são mal compreendidos. O etileno e o ácido jasmônico são hormônios vegetais liberados durante a herbivoria e podem afetar a diferenciação de estruturas secretoras relacionadas à defesa, como laticíferos e ductos resiníferos. Utilizando métodos convencionais em microscopia eletrônica de transmissão, para caracterização da ultraestrutura celular, e imunocitoquímicos, para a detecção de componentes de parede celular, exploramos o desenvolvimento de laticíferos articulados anastomosados com crescimento intrusivo e a ação indutora dos laticíferos no embrião maduro e na planta de Tabernaemontana catharinensis A.DC. (Apocynaceae). Além disso, pulverizamos soluções de etileno 2%, ácido jasmônico 0,1% ou água deionizada em plantas (n = 33) de T. catharinensis cultivadas em condições controladas e avaliamos a influência destes reguladores vegetais sobre a diferenciação dos laticíferos nos tecidos primários e floema secundário. Ultraestruturalmente, verificamos que o processo de incorporação de células ao sistema laticífero é distinto no embrião e na planta. Entretanto, em ambos os casos, o protoplasto da cél... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: In this study, we evaluated different aspects of the laticifer differentiation. The intrusive growth (the capacity of grow penetrating the middle lamella that cements adjacent cells) and the inducing action of laticifers (the capacity of induced an adjacent cell to acquirer laticifer features) are exciting growth mechanisms that may occur in laticifers, but they are poorly understood. Ethylene and jasmonic acid are plant hormones released during the herbivory and may affect the differentiation of secretory structures related with plant defense, as laticifers and resin ducts. Using transmission electron microcopy conventional methods (for characterization of the cell ultrastructure), and immunocytochemistry (for detection of the cell wall compounds), we explored the development of the articulated anastomosing laticifers with intrusive growth and the induction action of laticifer in the mature embryo and plant of Tabernaemontana catharinensis A.DC. (Apocynaceae). Additionally, we sprayed solutions of the 2% ethephon, 0.1% jasmonic acid and deonized water in plants of T. catharinensis (n = 33) growing under controlled conditions and evaluated the influence of these plant regulators on laticifer differentiation in the primary tissues and secondary phloem. In the ultrastructure, we verified that the process of cell incorporation within the laticifer system is distinct in the embryo and plant. However, in both the cases the protoplast of the incorporated cells acquires similar feat... (Complete abstract click electronic access below)
Doutor
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Eysholdt-Derzsó, Emese [Verfasser], Margret [Akademischer Betreuer] Sauter, and Dietrich [Gutachter] Ober. "Ethylene Response Factor VII transcription factors control the reshaping of the root system architecture in response to hypoxia / Emese Eysholdt-Derzsó ; Gutachter: Dietrich Ober ; Betreuer: Margret Sauter." Kiel : Universitätsbibliothek Kiel, 2018. http://d-nb.info/1236287878/34.
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Mahagamasekera, Mahagamage Gesha Patalee. "Daylily (Hemerocallis) as a model system for the study of ethylene-insensitive flower senescence : tissue culture and aspects of the development of proteolytic enzyme activities, with special emphasis on leucine aminopeptidase." Thesis, University of Canterbury. Plant and Microbial Sciences, 2000. http://hdl.handle.net/10092/5669.
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A micropropagation technique has been developed using petal and ovary explants from floral buds of several daylily cultivars. The growth regulators NAA and BA or 2iP in ½ strength MS was used for the initiation of shoot primordia while rooting was carried out in growth regulator-free ½ strength MS. Many plantlets of cv. Stella D'oro were grown successfully in the glasshouse to supply flowers for the experiments on senescence in this study.
The role of proteolytic enzymes with special emphasis on leucine aminopeptidase (LAP), in senescence of ethylene-insensitive flowers was studied using daylily flowers. During bud development the LAP activity began to increase and reached a maximum 6 hr after the flower was fully open. Increase in endopeptidase activity began only after the flower was fully open and reached a maximum value 12 hr later. As the flower senesced, both enzymes decreased. In contrast, carboxypeptidase level remained constant throughout flower development. Therefore, LAP appears to be responsible, at least for the initiation of proteolysis during senescence of petals, while endopeptidase may be responsible for the massive proteolysis that occurred during later stages of senescence. Carboxypeptidase on the other hand does not seem to play a special role during senescence. There was no evidence for the presence of endogenous inhibitors or promoters against the 3 proteolytic enzymes studied here nor the occurrence of low-pH extractable forms of the 3 enzymes in daylily petals.
When experiments were carried out to determine the effect of numerous chemicals on vase life of daylily flowers, cycloheximide was the only chemical that delayed senescence of daylily flowers. Cycloheximide treatment also retained the high levels of LAP and lap mRNA associated with full bloom flowers. In contrast to flowers, several chemicals including ethrel, cycloheximide, BA, sucrose, fructose were effective in retaining the green colour of daylily leaf discs for a longer time than those kept in water while ABA accelerated yellowing of leaf discs. GA3 kept the green colour of the leaf discs a little longer than water controls. Silver thiosulfate, ascorbic acid, casein hydrolysate, glyphosate, kinetin and IAA caused yellowing of leaf discs around the same time as water controls. 8-hydroxyquinoline caused browning of leaf discs, so did the glucose in 8-hydroxyquinoline. Green leaf discs treated with cycloheximide and ethrel had lower levels of LAP than the yellow ones in water. Yellow leaf discs in ABA also had lower levels of the enzyme than the green ones in water. Yellow leaf discs in silver thiosulfate had similar levels of LAP to those kept in water. In contrast to flower senescence, yellowing of daylily leaf discs was not always accompanied by a reduction in LAP. Therefore, LAP appears to have different roles during senescence of leaves and flowers.
IEF gel analysis revealed that daylily extracts had 2 closely run LAP isozyme bands of pI 5. LAP in daylily is a thermolabile, metallo enzyme, whose activity was enhanced by Mn++. EDTA, PMSF, NEM and Zn++ inhibited enzyme activity while Mg++ and leupeptin had no effect. It also did not need SH-protecting agents for activity. The optimum pH for the enzyme activity was 8.
Dot blot hybridization of mRNA from daylily petals using lap cDNA probe from Arabidopsis thaliana showed that LAP in daylily petals is under developmental regulation. Petals from buds and full bloom flowers of daylily had equal amounts of lap mRNA while those from senesced flowers had very low amounts of lap mRNA.
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Myint, Myo. "Production d'antibiotiques par des techniques non conventionnelles de fermentation." Toulouse, INSA, 1989. http://www.theses.fr/1989ISAT0033.
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Les pristinamycines sont des antibiotiques issus du metabolisme secondaire de streptomyces pristinaespiralis. Dans un premier temps, l'environnement necessaire a la production en culture sur milieu synthetique, semi-synthetique ou complexe est caracterise. La production des pristinamycines est influencee par les facteurs physico-chimiques tels que le ph et l'oxygene dissous, notamment, qu'il faut reguler tout au cours de la fermentation, par la concentration en phosphate, parametre determinant, qui doit rester inferieure a une valeur seuil. D'autre part, la synthese des antibiotiques est inhibee si la concentration initiale en antibiotiques dans le milieu est superieure a egale a 10% du niveau de production. Dans un deuxieme temps, diverses strategies sont envisagees afin de prolonger la production des pristinamycines et d'augmenter les titres en antibiotique. Dans certaines conditions la production discontinue peut etre menee de maniere repetitive sur pied de cuve. 4 cycles de production sur milieu complexe insoluble et 7 cycles sur milieu synthetique sont rendus possibles. Par une autre approche de fermentation extractive utilisant les systemes biphasiques aqueux, une methode d'extraction des pristinamycines en cours de fermentation a ete mise au point. Le systeme dextrane/polyethyleneglycol/eau est etudie in vitro et optimise notamment par greffage d'acides gras sur le polyethyleneglycol afin d'augmenter le coefficient de partage des pristinamycines. In vivo, la production de pristinamycines en systemes biphasiques aqueux est amelioree d'un facteur 1,5 en milieu complexe semi-soluble et 2,8 en milieu synthetique par rapport aux fermentations discontinues classiques
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AIDO, LAETITIA. "Optimisation de la fabrication de l'indole-2 carboxylate d'ethyle : automatisation de la reaction de wislicenus et thoma et de la reaction d'hydrogenation de brehm, etude de differents systemes de commande : correlateur logique (...) microprocesseur." Paris 6, 1986. http://www.theses.fr/1986PA066370.
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Cette etude a ete faite pour demontrer l'efficacite des methodes d'optimisation et d'automatisation; elle a permis un gain de rendement de 36 points (de 41 a 77%) associe a une forte diminution de la duree globale de la reaction (76h a 2h30)
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Thomas, Joshua Brock. "Lightly crosslinked poly(ethylene glycol)-tethered, pH-responsive biomaterials." Thesis, 2006. http://hdl.handle.net/2152/2940.
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Chen, Tzu-Ying, and 陳姿穎. "Isothermal Vapor-Liquid Equilibrium for Binary Mixtures of Ethylene Glycol Purification Related Systems." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/p6wqwn.
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碩士國立臺灣科技大學
化學工程系
103
A static-type apparatus with a liquid-phase circulation loop was used to measure isothermal vapor-liquid equilibrium (VLE) data for the binary systems of solvent A + 1,2-butanediol and solvent A + ethylene glycol at 393.15 K, 423.15 K, and 453.15 K. And also measured the binary systems of solvent B + 1,2-butanediol at 353.15 K, 393.15 K, 433.15 K, and 473.15 K, and solvent B + ethylene glycol at 393.15 K, 433.15 K, and 473.15 K. The experimental results exhibit no azeotropic behavior and positive deviations from Raoult’s law for each binary system. The thermodynamic consistency of the new binary VLE data has been confirmed by the point, area, and infinite dilution tests. The Wilson-HOC, the NRTL-HOC, and the UNIQUAC-HOC models were used to correlate each binary system measured in this work. Each model yielded satisfactory results.
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Lin, Chia-Ying, and 林佳穎. "The study of thermal stability and fire retardant systems of ethylene-vinyl acetate copolymer/montmorillonite nanocomposites." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/18297844281976192973.
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碩士國立雲林科技大學
環境與安全衛生工程系碩士班
99
To achieve the purpose of safety equipment and development of fire retardant and wire cable materials has trended to low smoke and halogen-free flame retardant technology in the business. However, many polymer flame retardant materials required a very high proportion of the metal hydrate filler within the polymer matrix（60 wt%）to achieve a suitable level of flame retardant, which may lead to a lack of flexibility, poor mechanical properties and problems during compounding. In this study, the aluminum hydroxide added montmorillonite（MMT）as the halogen-free flame retardant of EVA, according to the different EVA/ATH/MMT（0, 1, 2, 3 wt%）weight percentage of the preparation of nanocomposite material formulation. And through the XRD test, tensile test, DSC analysis, TGA analysis, LOI test and FE-SEM analysis to explore the addition of organic modified clay（OMMT）and researched the layer-distance, thermal properties, mechanical properties and flame retardant properties. In addition, use XRD to make the characterization analysis, it is found that increasing the polymers into the MMT, layer-distance increased from 1.27 nm to 1.96 nm when used the octadecylamine modified the MMT. For the tensile test, it is found that the montmorillonite weight percentage 3 wt% has the best tensile strength. In addition, the halogen-free flame retardant grade of EVA are added the OMMT in 3 wt%, the composition of nanocomposites was 47 wt% of the ATH filler has the best elongation and fire retardant （LOI was 28）. Improvements in tensile and flame retardant properties were observed in nanocomposites.
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PIZZI, ELISA. "Synthesis, characterization and functionalization of PEDOT conducting systems on ethylene vinyl alcohol copolymer supports and derivatives." Doctoral thesis, 2014. http://hdl.handle.net/11573/647627.
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The research work described in this PhD thesis focuses on methods and strategies of employing a polymer substrate for poly(3,4-ethylenedioxythiophene) (PEDOT) synthesis. For the purpose an ethylene vinyl alcohol copolymer (EVAL) was chosen. It offers many potentialities. Serving as mechanical support and/or functionalizable phase, it was differently combined with PEDOT to give conducting composite polymer flms or it was modified to obtain electro-active materials. Aim of the work is to show how, starting from the same base, it is possible to introduce functionalities into supported conducting systems both through the substrate and through the conducting phase, and all the strategies that were adopted.
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PIZZI, ELISA. "Synthesis, characterization and functionalization of PEDOT conducting systems on ethylene vinyl alcohol copolymer supports and derivatives." Doctoral thesis, 2014. http://hdl.handle.net/11573/917285.
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The research work described in this PhD thesis focuses on methods and strategies of employing a polymer substrate for poly(3,4-ethylenedioxythiophene) (PEDOT) synthesis.
For the purpose an ethylene vinyl alcohol copolymer (EVAL) was chosen. It offers many potentialities. Serving as mechanical support and/or functionalizable phase, it was differently combined with PEDOT to give conducting composite polymer flms or it was modified to obtain electro-active materials.
Aim of the work is to show how, starting from the same base, it is possible to introduce functionalities into supported conducting systems both through the substrate and through the conducting phase, and all the strategies that were adopted.
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Kavimandan, Nikhil Jayant Peppas Nicholas A. "In vitro and in vivo behavior of insulin delivery systems based on poly(ethylene glycol)-grafted poly(methacrylic acid) hydrogels." 2005. http://repositories.lib.utexas.edu/bitstream/handle/2152/1588/kavimandann71672.pdf.
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Huynh, KN. "Extending the shelf life of fresh horticultural produce under industrial settings by modified atmosphere packaging systems." Thesis, 2021. https://eprints.utas.edu.au/39109/1/Huynh_whole_thesis.pdf.
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Fresh horticultural produce is subject to rapid postharvest quality deterioration and senescence due to natural plant physiological processes and microbial degradation. Extending the shelf life of fresh produce has become important to expand market reach, reduce food waste, improve consumer satisfaction and encourage repeat purchases. Postharvest technologies such as modified atmosphere packaging (MAP), sanitisation, ethylene scavenging have been suggested to improve quality retention and extend the shelf life of fruit and vegetables. However, there is a knowledge gap in defining and understanding the opportunity to combine and optimise the different technology options to deliver improved MAP-based shelf life outcomes in industrial settings. This thesis therefore investigated the potential of combination technologies for improving the shelf life of three high-value, perishable produce types: raspberries, blueberries, and broccoli. The modified atmosphere/modified humidity (MA/MH) packaging types studied in this work included microperforated bags with high water vapour transmission rates (WVTR) that were tailored for each study produce, and a mineral-clay impregnated bag with low WVTR. Complementary treatments were chosen to target the major issue limiting shelf life with each produce type such as sanitisation using SO\(_2\) or H\(_2\)O\(_2\) vapour-releasing technologies for raspberries and blueberries, and ethylene scavenging for broccoli. In addition, microperforated lidding film, that develops MAP in unvented punnets was also trialled for raspberries and blueberries. This approach was to help overcome the short shelf life issues with atmospheric conditions used in current vented clamshell systems.
In raspberries, MAP reduced mould growth, weight loss and anthocyanin accumulations that led to fruit darkening compared to the current vented clamshells. In the commercial trials over two harvests, a modified atmosphere of 14-15% O\(_2\) & 7-8% CO\(_2\), established in a microperforated bag containing 12 punnets x 125g berries, was found to extend the storability of raspberries to 20-21 days at 2ᵒC. This would add 14 days extra compared to the existing industrial average shelf life of 6 days. The additions of sanitisers to MAP did not provide more benefits to the shelf life of raspberries in this study. In sealed punnets with six 70-μm perforations (creating a percentage of vented area of 5 x 10-9) and containing 125g berries, a passive MAP formed and improved the storability of raspberries to 11 days at 2ᵒC, compared to the vented clamshells and packages with none to five 70-μm perforations. The aroma profiles of the raspberries stored in the MA was closer to that of the berries on day 0 with noticeably smaller peak areas for terpenes/terpenoids than the clamshell fruit.
In blueberries, MAP also reduced mould growth and weight loss during 10 weeks of the two commercial trials, as well as 8 weeks of the punnet-scale trial. An atmospheric condition of 16-18% O\(_2\) & 2-4% CO\(_2\), established in both mineral-clay impregnated and microperforated bags packing 12 punnets x 125 g berries, extended the shelf life of ‘Legacy’ blueberries to 6 weeks and ‘Powder Blue’ blueberries to 8 weeks at 2ᵒC. This is equal to 2-4 weeks extra storage compared to the current average shelf life of 4 weeks. At the dose used in this study, SO\(_2\) effectively controlled mould growth but led to softening and bleaching at various degrees of severity. In the sealed punnets of 125g blueberries, the best quality retention was found in packages with two 70-μm perforations (providing a percentage of vented area of 1.68 x 10\(^{-9}\)) plus an initially reduced O\(_2\) level of 17% or 14.5% O\(_2\). Similar to raspberries, blueberries packed in MA had significantly smaller peak areas of terpenes/terpenoids, compared to clamshell fruit.
Broccoli is highly perishable with rapid quality loss under abuse temperatures and exposure to ethylene. MAP systems with > 1% O\(_2\) and < 15% CO\(_2\) maintained the chlorophyll contents and GC-MS aroma profiles of broccoli closest to day 0, while minimising weight losses to < 2% under three simulated shipping conditions. The scenarios studied included high-value, long domestic routes (7 days) with either good temperature management (2ºC) or broken cool chain (13ºC) and refrigerated sea-freight for exportation (42 days at 2ºC). In contrast, top-icing adversely affected the visual quality and aroma profiles of broccoli, particularly at 13ºC. Because MA was also developed in the packages with ethylene scavengers, it was not possible to examine the sole effects of ethylene scavenging on broccoli quality in this trial.
This research has therefore demonstrated that MAP can extend the storability of raspberries, blueberries, and broccoli beyond current average values under commercial scales and settings. The extended shelf life would allow longer domestic routes and exportation with good end quality. The specific atmospheric conditions, benefits of bulk-pack MAP, the model of retail MAP and considerations for further research have been reported to inform the berry and broccoli industries and help justify establishing new MAP-based extended shelf life offerings. In addition, the design approach used in this Thesis allowed the testings of various MAP designs from one film and one gas mixture. This methodology can benefit future trials and optimisations of retail packaging for other products.
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Kavimandan, Nikhil Jayant. "In vitro and in vivo behavior of insulin delivery systems based on poly(ethylene glycol)-grafted poly(methacrylic acid) hydrogels." Thesis, 2005. http://hdl.handle.net/2152/1588.
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Khan, Isaac John. "The utility of L-tyrosine based polycarbonate copolymers containing poly(ethylene glycol) as a degradable carrier for the release of a hydrophobic peptide molecule." 2009. http://hdl.rutgers.edu/1782.2/rucore10001600001.ETD.000051844.
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