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1
Hunt, Andrew. "Airborne magnetic particles." Thesis, University of Liverpool, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333692.
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Giles, Rory. "Novel magnetic particles for bioassays." Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066313/document.
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Les particules superparamagnétiques constituent un outil puissant pour de nombreuses applications biomédicales, ce potentiel est souvent restreint à cause de leur stabilité limitée dans les milieux biologiques ou du piégeage orientationnel sous champ magnétique. Dans cette thèse, ces problèmes ont été résolus en créant une nouvelle génération de particules à interfaces liquides fonctionnalisées. Ces particules sont formulées en utilisant des émulsions de ferrofluides qui incorporent des phospholipides fonctionnalisés, notamment biotinylés pour permettre la capture de streptavidine. La taille est contrôlée grâce à la microfluidique, permettant la production d'émulsions uniformes. L'utilisation de streptavidine fluorescente révèle que la capture est influencée par les propriétés du cosurfactant et du ligand ainsi que par le nombre de ligands disponibles. La mobilité des ligands est démontrée par l'adhésion observée entre les gouttelettes liées par de la streptavidine et le mouvement des billes couvertes de streptavidine capturées à l'interface. Enfin, le potentiel de ces particules est exploré en créant un dosage pour le diagnostic. La présence d'analytes en solution est indiquée par l’agglutination. Dans ce travail l'agglutination est provoquée par la complexation entre des émulsions biotinylés et la streptavidine (ou des billes couvertes de streptavidine). L’utilisation de gouttelettes de taille calibrée permet de compter avec précision des agrégats spécifiques par cytométrie de flux, la limite de détection étant dans la gamme femtomolaire. Cela surpasse la gamme picomolaire atteint généralement par des billes solidesColloidal superparamagnetic particles are a powerful tool in biotechnology, yet their applications are often hindered by limited stability in biological media or by orientation trapping under applied magnetic fields. In this thesis, these problems are addressed by developing novel magnetic particles bearing ligands at a liquid interface. Magnetic particle analogues are formulated using ferrofluidic emulsions, which incorporate functionalised phospholipids. Droplet size is controlled using microfluidic membrane emulsification to produce highly uniform populations. Ligands are modelled using biotinylated lipids, permitting the capture of streptavidin at the droplet interface. Fluorescently labelled proteins reveal that capture efficiency is influenced by the cosurfactant interfacial activity and the polymer spacer length of the ligand. Overall, capture saturation is found to be related to the number of ligands available at the interface. Ligand mobility is demonstrated by the formation of adhesion plaques between streptavidin cross-linked droplets and the motion of streptavidin coated beads caught at the interface. Finally, an application is explored by creating a new immunoassay. Polyvalent proteins or beads crosslink ligand functionalised droplets forming aggregates. Using size calibrated droplets specific aggregates can be accurately counted using flow cytometry and the limit of detection is found to be in the femtomolar range, this surpasses the picomolar range typically achieved using solid beads
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Suh, Su Kyung Ph D. Massachusetts Institute of Technology. "Controlled synthesis of magnetic particles." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/70458.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, February 2012.Cataloged from PDF version of thesis.
Includes bibliographical references.
Magnetic particles have been used for many applications demanding a broad range of particles morphologies and chemistries. Superparamagnetism is advantageous over ferromagnetism because it enables us to control and recover magnetic nanoparticles during and after chemical processing. Superparamagnetic particles have an oriented magnetic moment under a magnetic field but lose this behavior in the absence of a field. Ferromagnetic materials can be superparamagnetic when they consist of a single size domain, which is on the order of 10s of nanometers. However, since the magnetic force is proportional to the volume of the particle, one needs to apply higher gradient of magnetic field to recover smaller particles. Therefore, large particles are preferred for easy manipulation using external forces. For this reason, the synthesis of large, superparamagnetic particles is very important and is desirable for future applications. The purpose of this work is (1) to examine the three synthesis methods of superparamagnetic units, (2) to understand the behavior of particles created using these methods as well as the synthesis mechanisms, and (3) to investigate the potential applications of these particles. Large paramagnetic particles can be made by assembling superparamagnetic nanoparticles. We developed a method for the process-dependent clustering of monodisperse magnetic nanoparticles using a solvent evaporation method from solid-in-oilin- water (S/O/W) type emulsions. When polymers that are incompatible with the nanoparticle coatings were included in the emulsion formulation, monolayer- and multilayer-coated polymer beads and partially coated Janus beads were prepared. The precise number of nanoparticle layers depended on the polymer/magnetic nanoparticle ratio in the oil droplet phase parent emulsion. The magnetic nanoparticle superstructures responded to the application of a modest magnetic field by forming regular chains with alignment of nonuniform structures (e.g., toroids and Janus beads) in accordance with theoretical predictions and with observations in other systems. In addition, we synthesized non-spherical magnetic microparticles with multiple functionalities, shapes and chemistries. Particle synthesis is performed in two steps; polymeric microparticles homogenously functionalized with carboxyl groups were generated AA % using stop-flow lithography, and then in situ co-precipitation was used to grow magnetic nanoparticle at these carboxyl sites. With successive growth of magnetic nanoparticles, we obtained polymeric particles with saturations magnetization up to 42 emu per gram of microparticle, which is significantly greater than what can be obtained commercially. We also investigated the physical properties of magnetic nanoparticles grown in polymeric microparticles, and provide an explanation of the properties. Lastly, we used experimentation and modeling to investigate the synthesis of opaque microparticles made via stop-flow lithography. Opaque magnetic beads incorporated into hydrogel microparticles during synthesis changed the height and the degree of cross-linking of the polymer matrices formed. The effect of the concentration of the opaque material on the particle height was determined experimentally, and agreed well with model predictions based on the photopolymerization process over a wide range of UV absorbance. We also created particles with two independent anisotropies, magnetic and geometric, by applying magnetic fields during particle synthesis. Our work provides a platform for rational design of lithographic patterned opaque particles and also a new class of structured magnetic microparticles. Overall, this work demonstrates three strategies for creating magnetic substrates containing superparamagnetic nanoparticles and characterization of their resulting properties.
by Su Kyung Suh.
Ph.D.
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Goodluck, Olufemi W. (Olufemi Waheed). "Magnetic separation of strongly magnetic particles using alternating field." Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=65920.
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Dilanson, Nadea. "Halfsphere Derivatisation of Magnetic Micro Particles." Thesis, Mälardalen University, Mälardalen University, Department of Biology and Chemical Engineering, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-1415.
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Abstract
This exam project is an effort to derivatize one side of magnetic beads with one kind of molecule , and another one on the opposite side. First the surface of the sphere is loaded with a suitable linker with, e.g. amino or hydroxyl groups. In the second step, these groups are derivatized with a photosensitive protecting group such as Nitroveratryloxycarbonyl. In the third step, the particles are placed on a surface and then irradiated with UltraViolet light (320 nm) from above, which will cleave off the Nitroveratryloxycarbonyl on the upper half, while leaving in place the ones at the lower half. The linker groups of the upper half can now be derivatized by other reagents of choice. The remaining Nitroveratryloxycarbonyl groups can be removed by suspending the particles in a solvent and then exposing them to UltraViolet light. Finally the linker groups on this half of the particles can be derivatized by a second reagent.
Magnetic particles were marked with FITC, two different kinds of magnetic particles were selected, sikastar-NH2 function and sikastar-COOH function. Five different solvents were used to wash the magnetic particles and remove the bounded FITC, solvents are Acetone, 1-butanol, DMSO, 4-propanol, and Urea. Magnetic particles sikastar-NH2 and sikastar-COOH were washed with Tween 20 and SDS to remove non-specific binding of FITC. Sikastar particles were treated with IgG*FITC in constant presence of the following solvents: PBS*10, Pluronic-F127, Tween 20. Pegylation of sikastar particles got done to reduce non-specific binding. Derivatisation of Nitroveratryloxycarbonyl got done and specific bindning of IgG*FITC to micromer particles got done by protein thiolation.
When a different concentration of FITC was tested to control specific and non-specific binding to sikastar functions, we observed that we had a specific binding to sikastar-NH2 in the lowest concentration. In choice of magnetic particles we had specific binding with sikastar-NH2. Using a different solvents Acetone, 1-butanol, 4-propanol, and Urea to remove bounded FITC, sikastar-NH2 showed stronger fluoresence than sikastar-COOH after washing because of specific binding and it was difficult to remove FITC with Acetone, 1-butanol, 4-propanol,and Urea, on the other hand DMSO could remove bounded FITC from sikastar particles. When we washed magnetic particles sikastar-NH2 and sikastar-COOH with Tween 20 and SDS to remove non-specific binding of FITC, we could see that magnetic particles showed fluoresence in both functions due to non-specific binding. When sikastar particles got treated with IgG*FITC in constant presence of solvents PBS*10, Pluronic-F127, and Tween 20, we had a specific binding between sikastar particles and IgG*FITC in a presence of pluronic-F127. Pegylation of sikastar particles with a different kind of a PEG was possibl to reduce non-specific bindning. The derivatisation of Nitroveratryloxycarbonyl could be done in a N2 environment, and Nitroveratryloxycarbonyl-sikastar-NH2 could be radiated with UltraViolet light to remove Nitroveratryloxycarbonyl. Also thiolation method could be used to perform specific binding of IgG*FITC to micromer particles.
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Dean, Barbara. "Spin dynamics of fine magnetic particles." Thesis, University of Central Lancashire, 1991. http://clok.uclan.ac.uk/19258/.
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A computer model of fine magnetic particles has been developed based on the Landau-Lifshitz equation. It is a dynamic model which allows the detailed behaviour of the magnetic moments during magnetisation changes to be investigated. The model was initially used to study gyroremanent magnetisation (GRM) which is observed in magnetic rocks. Stephenson proposed that GRM was caused by the gyroscopic precession of the moments. In collaboration with Stephenson a model was developed to show the complex motion of the moments in an alternating field and it was found that positive and negative cycles of the field produced an asymmetry in the motion. This asymmetry leads to one of the easy magnetisation directions being favoured so that when the field is cycled to zero a remanence is produced, the observed GRM. The model was then extended to include thermal agitation through the addition of a random field term in the simulation. It was found that in the absence of thermal agitation two particles always moved coherently but when thermal agitation was included other modes appeared. This work showed the importance of ncluding thermal agitation in any micromagnetic model. The model was then used to simulate ferromagnetic resonance on a single particle and the results precisely matched the results predicted by analytical theory. The effect of particle anisotropy and alignment on the response was then investigated and the computed results agreed with experimental measurements. The model was further extended to include dipolar interactions firstly in a chain of spheres and then on an array of particles. Results agreed very well with experimental measurements on tapes with different packing densities and have helped to indicate the local fields acting in an assembly of fine magnetic particles.
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Tarrant, Lee. "A study of high gradient magnetic separation of strongly magnetic particles." Thesis, University of Salford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.265394.
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Tejwani, Saurabh. "Thermodynamic and transport properties of non-magnetic particles in magnetic fluids." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/54584.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2009.Cataloged from PDF version of thesis.
Includes bibliographical references.
Magnetic composites, obtained on associating magnetic fluid with non-magnetic particles, offer interesting opportunities in separations, assemblies and other applications, where the microstructure of the composite can be altered reversibly by an external field without altering the composition. The goal of our work in this area is to develop computational and simulation tools to assist in the in-depth understanding of the thermodynamic and transport properties of such non-magnetic nanoparticles immersed in magnetic fluids under varying magnetic field conditions. Also, in this work we have studied the relaxation and magnetization characteristics of magnetic nanoparticle clusters in presence of low external magnetic fields. Theoretical analysis of such a complex system is difficult using conventional theories, and hence we have used Monte Carlo Simulations to explore these effects. We simulated the interactions between non-magnetic particles (1000 nm) and magnetic nanoparticles (10 nm and 20 nm diameter) dispersed in organic phase. We observed that the presence of the non-magnetic particle in the system induces magnetic non-homogeneity. The magnetic nanoparticles present in the equatorial place of the non-magnetic particle with reference to the applied magnetic field have a higher magnetization as compared to the particles in the polar region. This effect was much more dominant for 20 nm particles than 10nm particles, because the magnetic inter-particle interactions are much stronger for the larger particles. We have also studied the effect of radial distance from the nonmagnetic particle on the magnetization and radial distribution function characteristics of the magnetic nanoparticles.
(cont.) We have evaluated the magnetophoretic forces the non-magnetic particles experience when subjected to magnetic field gradient. We have identified such forces arising from the inter-particle interactions between the magnetic nanoparticles. These forces were found to be significant for larger magnetic particles, smaller non-magnetic particles and lower magnetic fields. Diffusion coefficients were evaluated for non-magnetic nanoparticles in magnetic fluids using Brownian Dynamics Simulation. The chain-like structures formed by magnetic nanoparticles introduce anisotropy in the system with the diffusion coefficients higher along the direction of applied external magnetic field and lower in the perpendicular direction. It was observed that the anisotropy increases with higher magnetic particle concentration and larger non-magnetic particles. Anisotropy is negligible for small sized magnetic particles for which the inter-particle interaction is smaller, increases with increasing magnetic particle size and becomes constant thereafter. Results were compared with theoretical predictions. Néel Relaxation was studied for magnetic nanoparticle clusters. Chain-like, spherical and planar clusters were evaluated for the relaxation times. For chain-like structures the relaxation times increase significantly on increasing the chain length and particle size. For spherical clusters the relaxation times were fairly similar to that of individual magnetic nanoparticles. Hence, such a fast relaxation makes them ideal candidates for HGMS separations, since they will be released quickly from the magnetic wires during the elution step.
(cont.) Also, we studied the magnetization characteristics of rectangular and hexagonal packing arrangements of magnetic clusters in presence of remnant fields. The hexagonal arrangement revealed a novel oscillatory behavior. A theoretical model was developed to predict the magnetic particle size beyond which the oscillations are observed.
by Saurabh Tejwani.
Ph.D.
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Wells, S. "Preparation and properties of ultrafine magnetic particles." Thesis, Bangor University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.237506.
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Li, Keran. "Surfactant-free synthesis of magnetic latex particles." Thesis, Lyon 1, 2015. http://www.theses.fr/2015LYO10211/document.
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Ce travail de thèse décrit l'élaboration de latex hybrides oxyde de fer (OF)/polymère par polymérisation en émulsion sans tensioactif. Des nanoparticules d'OF cationiques ont été tout d'abord synthétisées par co-précipitation de sels de fer dans l'eau. Des latex hybrides magnétiques ont été ensuite obtenus par deux voies de polymérisation. La première consiste en la synthèse de particules de latex de morphologie 'carapace' par polymérisation en émulsion Pickering du styrène et du méthacrylate de méthyle (MMA). Un comonomère auxiliaire (acide (méth)acrylique ou acide 2-acrylamido-2-méthyl-1-propane sulfonique) a été utilisé pour favoriser l'adsorption des OF à la surface des particules de polymère produites. Les analyses par MET indiquent la présence d'OF à la surface des particules de polymère (structure carapace). L'analyse thermogravimétrique a permis de quantifier l'efficacité d'incorporation des OF, i.e. la fraction d'OF initialement introduits effectivement adsorbés à la surface des particules. L'efficacité d'incorporation augmente avec la quantité de comonomère auxiliaire, le pH et la concentration en OF et dépend de la nature du monomère hydrophobe. Dans la deuxième voie, les OF ont été encapsulés par polymérisation radicalaire contrôlée par transfert de chaîne réversible par addition-fragmentation (RAFT) en émulsion aqueuse. La stratégie utilisée repose sur l'utilisation de macroagents RAFT amphiphiles comportant des groupements acide carboxylique connus pour interagir avec la surface des OF. L'interaction entre les macroRAFTs et les OF a été étudiée à travers le tracé de l'isotherme d'adsorption. Des analyses SAXS et DLS indiquent la formation de clusters d'oxyde de fer. Ces derniers ont été ensuite engagés dans la polymérisation en émulsion du styrène ou d'un mélange de MMA et d'ABu (ratio massique : 90/10) pour former une écorce de polymère à leur surface. Les particules carapace et les OF encapsulés affichent un comportement superparamagnétiqueThis work describes the elaboration of polymer/iron oxide (IO) hybrid latexes through surfactant-free emulsion polymerization. Cationic iron oxide nanoparticles stabilized by nitrate counterions were first synthesized by the co-precipitation of iron salts in water. Magnetic hybrid latexes were next obtained by two polymerization routes carried out in the presence of IO. The first route consists in the synthesis of polymer latexes armored with IO via Pickering emulsion polymerization of methyl methacrylate (MMA) or styrene (St). An auxiliary comonomer (namely methacrylic acid, acrylic acid or 2-acrylamido-2-methy-1- propane sulfonic acid) was used to promote IO particle adhesion to the surface of the generated polymer particles. TEM showed the presence of IO at the surface of the polymer particles and the successful formation of IO-armored polymer particles. TGA was used to quantify the IO incorporation efficiency, which corresponds to the fraction of IO effectively located at the particle surface. The incorporation efficiency increased with increasing the amount of auxiliary comonomer, suspension pH and IO content or with increasing monomer hydrophobicity. In the second route, IO encapsulation was investigated via reversible addition-fragmentation chain transfer (RAFT)-mediated emulsion polymerization. The developed strategy relies on the use of water-soluble amphipathic macromolecular RAFT agents containing carboxylic acid groups, designed to interact with IO surface. The interaction between the macroRAFT agents and IO was investigated by the study of the adsorption isotherms. Both DLS and SAXS measurements indicated the formation of dense IO clusters. These clusters were then engaged in the emulsion polymerization of St or of MMA and nbutyl acrylate (90/10 wt/wt) to form a polymer shell at their surface. Both IO-armored latex particles and polymer-encapsulated clusters display a superparamagnetic behavior
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Miguel, López María del Carmen. "Dynamic Properties of Magnetic Colloidal Particles and Holes." Doctoral thesis, Universitat de Barcelona, 1985. http://hdl.handle.net/10803/667638.
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Our main goal is to study certain aspects of the dynamics of fluids with magnetic particles in suspension, based on their promising practical applications as new materials as welI as on its fundamental scientific interest.
In the introduction we brief the reader on the most essential properties of the system. We have characterized the monodomain magnetic particles and the time scales inherent to magnetic fluids. Having introduced the rotational diffusion equation as the most convenient tool to take into account the different mechanism inftuencing the dynamics of the particles, we have also proposed a fruitful approach for solving it in any general situation. We have also highlighted the macroscopic properties of the magnetic fluid treated now as a continuous medium and showed up the different phenomena associated with the lack of stability in the system.
In Chapter I we concentrate on two limit cases whose analysis is easier but very illustrative. The first part of the chapter is devoted to the study of a suspension of rigid dipoles, in which the magnetic moments are rigidly attached to the body of the particles themselves. In these conditions, if we apply an external magnetic field both the magnetic moment and the particle move together so that the magnetic torque acting upon it becomes zero. Thermal fluctuations tends to disrupt this order, and it turns out that, for instance, that the effective viscosity of the suspension depends on the dimensionless parameter comparing magnetic and thermal energies. In the second part we consider magnetic materials with finite anisotropy energy at high magnetic fields. For such monodomain particles the magnetic moments rapidly orient along the direction of the external field, and then as a second step the mechanical rotation of the particles takes place. In this case, the effective viscosity of the suspension is a function of the magnetic anisotropy constant of the material, of the volume of the particles as well as the thermal energy. Our results are compared to experimental measurements.
The second chapter is concerned with the determination of the viscosity and of some magnetic and optical properties of magnetic fluids in the whole range of possible experimental situations. The magnetic moments and the particles inside the liquid reorient separately but their dynamics are coupled thus giving rise to a more intricate relaxation process. We have compared part of our results with available experimental data for different ferrofluids showing quite a good agreement.
In Chapter III we joint to our discussion of magnetic fluids the presence of nonmagnetic particles of micrometer size and study their motion through the ferrofluid. The ferrofluid is considered now as a continuous medium with new transport coefficients already determined in the previous sections. Under the action of a rotating external magnetic field, we study the rotational motion of the nonmagnetic particles and compare our expressions to sorne measurements carried out in these composite systems. In this chapter we are also con cerned with the characterization of the hydrodynamic interactions among these particles in a carrier ferrofluid.
Chapter IV is intended as a brief introduction to the multiple problems which arise when one handle the aggregation phenomena which may take place in these systerns. We study the kinetics of the forrnation of the aggregates by rneans of the Smoluchowski theory of coagulation in colloids. But we account for hydrodynarnic interactions which are not usually considered when studying such process and that gives rise to sorne corrections for high concentrations of particles. In addition, the rheology of the chains that are usually observed in systerns with dipolar interactions is given for a rather simplified situation in order to elucidate the effects of the dipolar magnetic interactions.
Finally, we sum up our main conclusions and indicate some of the perspectives stimulated by the contents of this monograph and in which we plan to pursue work in the near future.A lo largo de esta monografía nos hemos ocupado del estudio de sistemas fluidos, tanto con monodominios magnéticos como con dos tipos distintos de partículas, magnéticas y no magnéticas, en dispersión en un líquido newtoniano en situaciones fuera del equilibrio. El comportamiento de estos sistemas se ve influenciado en gran medida por la presencia de un campo magnético externo, lo que da lugar a nuevos fenómenos que han sido el fundamento de muchas aplicaciones prácticas. Sin embargo, esta influencia depende de los diferentes procesos de relajación que tienen lugar dentro las partículas, con respecto a sus ejes cristalinos, así como fuera de ellas, con respecto al fluido portador. Hemos descrito cuáles son estos procesos y obtenido la dependencia con respecto de los parámetros que describen las partículas y el fluido, de algunos coeficientes que caracterizan las propiedades reológicas, magnéticas y ópticas de la suspensión coloidal.
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Wooding, A. "The preparation and dispersion of magnetic ferrite particles." Thesis, Durham University, 1987. http://etheses.dur.ac.uk/6618/.
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Magnetic fluids containing magnetite (Fe(_3)O(_4)) have been prepared using colloidal size particles, obtained by alkaline treatment of mixed iron(II)/iron(III) chloride solutions. The particles have been dispersed in a variety of carrier liquids employing a wide range of surfactant materials. In non-aqueous carrier liquids, a single layer of surfactant is chemically adsorbed at the particle surface to effect steric stabilization. In aqueous media, a primary layer of chemisorbed surfactant interpenetrates a secondary layer which is physically adsorbed. This arrangement places hydrophilic charged groups at the surfactant/water interface, thereby maintaining a favourable interaction between the two phases. A wide variety of surfactants, including a range of straight-chain fatty acids, have been evaluated for use in aqueous magnetic fluids. Fluids incorporating up to 32 wt. % magnetite have been prepared. Stability towards dilution, changes in pH and quantity of dispersing agent have all been studied. Charge-stabilized magnetic fluids, in both acidic and alkaline aqueous media, have been investigated. Control of Fe(_3)O(_4) particle size, between 60Ǻ and 80Ǻ diameter, has-been achieved by altering the conditions under which precipitation occurs, namely temperature, reagent concentrations, viscosity and solvent composition. In addition, water was found to be capable of dispersing larger particles than organic carrier liquids. Particles as small as 30Ǻ diameter have been prepared by in situ magnetite precipitation with naturally occurring polymeric surfactants, such as proteins and polysaccharides. Functional groups along the polymer backbone are thought to coordinate to Fe(^2+) ions, thus maximising the number of particle nucleation sites. Small particles with narrow size distributions result. In this way, magnetic fluids have been prepared, stabilized with low toxicity naturally occurring materials for possible medical applications. Magnetite particles, too large for use in magnetic fluids, have been made by condensing iron(II) hydroxide with a variety of hydrated iron(III) oxide species. Particle size was dependent upon the size and solubility of the iron(III) precursor. Non-colloidal magnetite particles were also obtained by the aerial oxidation of iron(II) hydroxide suspensions at temperatures > 60 C.
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Lopes, Felipe Nathan de Oliveira. "Neoclassical transport of particles in magnetic confined plasmas." reponame:Repositório Institucional da UnB, 2017. http://repositorio.unb.br/handle/10482/24179.
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Dissertação (mestrado)—Universidade de Brasília, Instituto de Física, Programa de Pós-Graduação em Física, 2017.Submitted by Raquel Almeida (raquel.df13@gmail.com) on 2017-06-14T21:00:42Z No. of bitstreams: 1 2017_FelipeNathandeOliveiraLopes.pdf: 2581164 bytes, checksum: b145a85dc2b652f6416a58481ed46516 (MD5)
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Plasmas confinados em diferentes topologias magnéticas são uma tarefa importante na busca pela Energia de Fusão. Hoje em dia, as formas mais estudadas de Fusão Termonuclear Controlada focam em Confinamento Inercial, Stellarators e Tokamaks. No presente trabalho, estudaremos os diferentes mecanismos de transporte presentes nos plasmas toroidalmente confinados. Vamos rever a teoria a partir dos conceitos básicos de transporte de plasma, até as peculiaridades presentes em plasmas toroidalmente confinados, conhecido como tokamak. Na fronteira do modelo de transporte mais realista, a questão do transporte anômalo será tratada com a teoria do transporte turbulento, no âmbito da teoria girocinética. O uso de ferramentas computacionais auxiliará na análise do impacto das microinstabilidades no fluxo de partículas e calor, e auxiliará na validação dessa abordagem, feita com uma análise da literatura
Plasmas confined in several magnetics topologies are an important task in the quest for Fusion Energy. Nowadays, the most studied forms of Controlled Thermonuclear Fusion focus on Inertial Confinement, Stellarators and Tokamaks. In the present work, we are going to study the different transport mechanisms present in toroidally confined plasmas. We are going to review the theory from the basic concepts of plasma transport, until the peculiarities present in toroidally confi- ned plasmas, known as tokamak. In the border of the realistic transport model, the issue of the anomalous transport will be treated with the turbulent transport theory, in the framework of the gyrokinetic theory. The use of computational tools will help us to assist the analysis of microinstabilities impact on flux levels, and to give support in the validation of this approach, done with a thorough analysis the literatures.
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Jung, Ching-Shan. "Dispersions of magnetic particles in non-aqueous media." Diss., The University of Arizona, 1996. http://hdl.handle.net/10150/187323.
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The dispersion quality of magnetic inks made from iron based metal particles and cobalt modified iron oxide particles has been investigated using a magnetic probing technique known as DIMAG (Dispersion by MAGnetic measurement). Di(2-ethyl hexyl) phosphoric acid is used as a model dispersant while a vinyl acetatevinyl chloride copolymer that combined the functionality of a dispersant and a binder is used as a wetting binder. A comparison of the DCON values measured at different binder levels to the tape characteristics shows that dispersions with large negative DCON signals result in good quality tapes. To study the degradation of magnetic particles, the interaction of water vapor with iron based metal particles was measured under different temperature and humidity conditions using a flow microcalorimetric (FMC) technique. Water uptake by iron based metal particles increased linearly with relative humidity ranging from 30% to 70% RH in the temperature range 30°C to 70°C. Mossbauer measurements showed that the ratio of core iron to oxide iron decreased during aging. Particles coated with hydrophobic PVC exhibited much less water uptake than particles coated with a less hydrophobic polymer, poly(vinyl alcohol). A computational investigation using the method of molecular dynamics was also undertaken to characterize the state of magnetic particle dispersions. The simulations revealed that the microstructure of the spherical particulate dispersions consists of chain-like clusters resulting from magnetic dipole alignment. Acicular particles formed clusters such as dimers, chains and rings. The effect of fluid viscosity on the dispersion quality and the response of the magnetic dispersions to an external DC magnetic field are also reported.
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Carpino, Francesca. "Quadrupole Magnetic Field-Flow Fractionation: A Novel Technique For The Characterization Of Magnetic Particles." Cleveland, Ohio : Cleveland State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=csu1207595560.
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Thesis (Ph.D.)--Cleveland State University, 2008.Abstract. Title from PDF t.p. (viewed on May 8, 2008). Includes bibliographical references (p. 121-126). Available online via the OhioLINK ETD Center. Also available in print.
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Brandão, Barros Delfina Celeste. "Simultaneous detection of foodborne bacteria based on magnetic particles." Doctoral thesis, Universitat Autònoma de Barcelona, 2016. http://hdl.handle.net/10803/385720.
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En la actualidad, está ampliamente aceptado en Europa que la investigación y la innovación son factores clave para reforzar la capacidad industrial y las perspectivas de negocios.
La tecnología es necesaria para abordar los problemas del mundo, pero también lo es la investigación, que permite la aparición de tecnologías innovadoras. Por lo tanto, invertir en investigación e innovación es esencial para el desarrollo de soluciones para los desafíos sociales, como por ejemplo la seguridad alimentaria. En este contexto, surge el término KETS (Key Enabling Technologies), que permite unificar diferentes campos de la ciencia, tales como la nanotecnología, los materiales avanzados y la biotecnología, entre otros. Esto indica una clara convergencia de la tecnología en el desarrollo de nuevas soluciones. Por ejemplo, con el fin de ofrecer soluciones en seguridad alimentaria, la investigación en química analítica no está solamente basada en el desarrollo de estrategias para obtener información cualitativa y cuantitativa sobre la composición y naturaleza de las sustancias, sino que ésta ha convergido en un campo de investigación más aplicado y multidisciplinar, formando alianzas entre diferentes áreas de conocimiento a través de la ciencia. Esta nueva concepción abre la posibilidad de crear nuevos principios analíticos, procedimientos de detección automatizados o in-situ, así como sondas de detección específica o nuevos dispositivos sensores.
La presente Tesis doctoral es el resultado de dicho carácter multidisciplinar de la química analítica, y con el objetivo de proporcionar soluciones a problemas relacionados con la seguridad alimentaria, se ha desarrollado un nuevo dispositivo sensor en base a conocimientos de química analítica pero también de biotecnología, microbiología y materiales avanzados.
Por ello, el primer apartado de este trabajo pretende ser una introducción general sobre la inocuidad de los alimentos y su importancia a nivel mundial, haciendo especial énfasis en los patógenos alimentarios emergentes responsables de los principales brotes y la contribución de la tecnología de los biosensores como factor conductor para el desarrollo de nuevas metodologías para la detección de bacterias transmitidas por los alimentos mediante técnicas de multiplexado.
Además, se discutirá también la integración de nuevos materiales con dimensiones nano/micrométricas en biosensores electroquímicos, destacando algunas de las ventajas de las partículas magnéticas: i) su capacidad para preconcentrar las bacterias presentes en muestras complejas mediante una reacción inmunológica ii) us uso como plataforma para el bioreceptor en los dispositivos de biosensores iii) o como soporte para la inmovilización magnética en la superficie de un electrodo de trabajo por atracción magnética.
Los métodos de detección para seguridad alimentaria actuales han permitido un avance significativo en relación al desarrollo de métodos rápidos y sensibles, en los que la implementación de bioensayos con capacidad de multiplexado es una de las tendencias emergentes. Sin embargo, se han descrito pocas estrategias basadas en biosensores electroquímicos para la detección simultánea de bacterias en alimentos. Por esta razón, en el presente trabajo se propone desarrollar un biosensor electroquímico que detecte simultáneamente Salmonella enterica, Listeria monocytogenes y Escherichia coli, basado en el uso de partículas magnéticas.
Las estrategias presentadas en esta Tesis doctoral se basan por un lado en un reconocimiento electroquímico inmunológico, que proporciona la detección de las células bacterianas, y por otro un reconocimiento genético, que permite la detección del ADN bacteriano. Estas dos estrategias se combinan con un paso de separación inmunomagnética que da lugar a la captura y preconcentración de las bacterias a partir de muestras de alimentos. Así, se ha realizado un estudio de las partículas magnéticas de diferentes tamaños (micro y nanométrica), para después efectuarse la separación inmunomagnética de S. enterica, L. monocytogenes y E. coli. Además, se han comparado posteriormente las dos estrategias para la detección de Salmonella, usándose como modelo muestras leche.
Finalmente, se describe una estrategia de PCR multiplexada combinada con un magneto-genosensor electroquímico usando partículas magnéticas de sílice para la detección simultánea de S. enterica, L. monocytogenes y E. coli.Nowadays, it is widely recognised in Europe that research and innovation are key factors to reinforce the industrial capacities and business perspectives. We need technology to address world´s problems, but we also need research to develop innovative technologies. Therefore, investing in research and innovation is essential to develop solutions for societal challenges, as for instance Food Safety. In this context, it comes out the term KETs (Key Enabling Technologies) to unify different fields across science, such as Nanotechnologies, Advanced materials, Biotechnology, among others. This indicates a clear convergence of technologies to address new solutions. For instance, analytical chemistry research is not only based anymore on the development of strategies to obtain qualitative and quantitative information about the composition and nature of substances. In order to provide solutions in food safety, analytical chemistry research has been converging into a more applied and multidisciplinary research field, forming alliances between different fields across science. This opens the possibility for the creation of new analytical principles, automated or in-situ detection procedures, as well as specific detection probes or new sensing devices. This Dissertation is a result of the multidisciplinary character of analytical chemistry. The aim of providing solutions to problems related to food safety bonds different science fields as analytical chemistry, biotechnology and advanced materials for the development of a new sensing device. Therefore, it is intended to give a general introduction about food safety and its importance worldwide, with special focus on the emerging foodborne pathogens responsible for the main outbreaks and the contribution of biosensors technology as the driver factor for the development of new methodologies for foodborne bacteria detection with multiplexing capabilities. Furthermore, the integration of new materials with nano/micrometer dimensions on electrochemical biosensors will be also discussed, highlighting some advantages of the use of magnetic particles: i) preconcentration of the bacteria from complex samples through an immunological reaction, ii) as a platform for the biorecognition element in the biosensing devices iii) as a support for the magnetic immobilisation on the surface of a working electrode under magneto-actuation. The current state of art for detection methods for food safety shows a significant progress relative to the development rapid and sensitive methods, in which the implementation of bioassays with multiplexing capabilities is one of the emergent trends. However, few approaches based on electrochemical biosensors for the simultaneous detection of foodborne bacteria have been reported. For this reason, it is proposed to develop an electrochemical biosensor for the simultaneous detection of Salmonella enterica, Listeria monocytogenes and Escherichia coli, based on the use of magnetic particles. The strategies presented in this Dissertation are based on electrochemical magneto-immuno and genosensing, in which electrochemical magneto-immunosensing provides the detection of whole bacterial cells, whereas the electrochemical magneto-genosensing provides the detection of the bacterial DNA. These two strategies are combined with an immunomagnetic separation step to capture and preconcentrate bacteria from food samples. Hence, a study of different magnetic particles with micro and nanometer sizes will be achieved for the immunomagnetic separation of S. enterica, L. monocytogenes and E. coli. Afterwards, electrochemical magneto-immuno and genosensing will be compared for the detection of Salmonella in milk, as a model. Finally, triple-tagging multiplex PCR combined with an electrochemical magneto-genosensor using silica magnetic particles as a platform will be reported for the simultaneous detection of S. enterica, L. monocytogenes and E. coli.
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Holmes, Barry M. "Cobalt nano-particles for application in magnetic data storage." Thesis, Coventry University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.395324.
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Dowd, Victor. "Chromatographic media based on magnetic particles in protein separations." Thesis, University of Kent, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293310.
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Jung, Ching-Shan 1964. "Interaction of magnetic particles with recording media formulation components." Thesis, The University of Arizona, 1991. http://hdl.handle.net/10150/278067.
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The interaction of commercially available, iron based magnetic particles with certain particulate media formulation components was investigated using the technique of flow microcalorimetry. The heat of wetting of these particles by solvents was found to be a function of the solvent dipole moment, particle coercivity and surface area. Di(2-ethyl hexyl) phosphoric acid, a model dispersant, appeared to interact chemically with an iron particle of high coercivity. Solvent basicity influenced the heat and extent of interaction of the dispersant. Characterization of the interaction of a vinyl acetate-vinyl chloride copolymer that combined the functionality of a dispersant and a binder was also carried using the techniques of calorimetry and X-ray photoelectron spectroscopy.
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Lee, Seungwoo. "Development of magnetic composite photocatalytic particles for environmental applications." [Gainesville, Fla.] : University of Florida, 2004. http://purl.fcla.edu/fcla/etd/UFE0008266.
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Wang, Desheng. "CDSE Quantum Dots and Luminescent/Magnetic Particles for Biological Applications." ScholarWorks@UNO, 2005. http://scholarworks.uno.edu/td/142.
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CdSe semiconductor nanocrystals (quantum dots--QDs) with diameters ranging between 1.5 and 8 nm exhibit strong, tunable luminescence [1-5]. They have been widely investigated for their size-dependent optoelectronic properties [6], and for their potential use in optical devices [7], biological labels [8] and sensors [9]. Luminescent quantum dots (QDs) show higher photostability and narrower emission peaks compared to organic fluorophores [8]. The objective of my project was to apply QDs magnetic/luminescent nanoparticle as biological labels in cells. Luminescent CdSe QDs emit bright visible light with high quantum yield and sharp emission peak. The CdSe QDs were capped with a ZnS layer. This increased their emission efficiency and photostability due to the larger band gap of ZnS. The QDs were transferred from organic solvent (e.g. chloroform, hexane) to water by exchanging the capping group (Trioctylphosphine Oxide—TOPO) with mercaptoacetic acid. To develop a separation and detection tool for cells, we combined γ-Fe2O3 magnetic particles with CdSe/ZnS QDs in core-shell composite. The composite nanoparticles showed strong fluorescence emission and high water solubility. Different antibodies were attached to the particles through EDAC coupling. The antibody-coated particles were used to successfully separate and detect breast cancer cells in blood cells.
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Li, Dan Chemical Sciences & Engineering Faculty of Engineering UNSW. "Designing functional magnetic nanoparticles with flame spray pyrolysis for bio-applications." Publisher:University of New South Wales. Chemical Sciences & Engineering, 2009. http://handle.unsw.edu.au/1959.4/43346.
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Magnetic nanoparticles (MNPs) hold great promise in the fields of biology and medicine. The synthesis of functional MNPs with precisely controlled crystallographic, physicochemical, and magnetic properties on a large scale still remains the challenge today. This thesis reports the exploration of liquid-fed flame spray pyrolysis (FSP) in the synthesis of functional MNPs, their surface modifications, and potential bio-applications. Superparamagnetic and ferromagnetic maghemite (γ-Fe2O3) nanoparticles, and silica-coated maghemite (SiO2/γ-Fe2O3) nanocomposites were synthesised using FSP. The size of γ-Fe2O3 was controllable from 6 to 53 nm, with morphology evolving from a disordered near-spherical shape to fully ordered 2-D hexagonal/octagonal platelet. The saturation magnetisation (Ms) increased from 21 to 74 emu/g with increasing particle size, up to 13 nm when Ms approached the bulk γ-Fe2O3 characteristics. In the case of SiO2/γ-Fe2O3, three distinct morphologies, namely the single segregated γ-Fe2O3 core- SiO2 shell, transitional mixed morphologies, and multi γ-Fe2O3 cores embedded in submicron SiO2 shell, were obtained. The core size, composite size, and morphology of γ- Fe2O3 were tunable by varying %SiO2 loading and the use of a quartz tube enclosure during flame synthesis. The magnetic behaviour correlated well with the crystal microstructure. Following the core particle design, protein adsorption-desorption behaviour on FSP-madeMNPs was studied. Bovine serum albumin (BSA) adsorption was found to follow the Langmuir isotherm, with high binding capacities (150−348 mg BSA/g particle) and fast association constants. Electrostatically governed BSA orientations were proposed for different particle-buffer systems. The adsorbed BSA was effectively recovered by pH-shift using K2HPO4. Subsequently, terminal amine, aldehyde, carboxylic, epoxy, mercapto and maleimide functionality were anchored onto the FSP-made γ-Fe2O3 particles. These versatile functional groups led to conjugation of active trypsin. The immobilised trypsin exhibited superior durability with >60% residual activity after one week, and excellent reusability for >5 cycles. The trypsin-conjugated MNPs are promising carriers in proteomics, demonstrating good substrate specificity with equivalent or better sequence coverage compared to free trypsin in insulin and BSA digestion. In another application, a refined silanisation procedure simultaneously reduced γ-Fe2O3 to Fe3O4, and generated thiol enriched surface for matrix metalloproteinase-2 (MMP-2) conjugation. The highly active MMP-2-conjugated MNPs could potentially enhance the interstitial transport of macromolecule/nanoparticles in drug delivery.
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Pieler, Michael Martin [Verfasser]. "Investigation of influenza virus particle aggregation and purification with magnetic sulfated cellulose particles / Michael Martin Pieler." Magdeburg : Universitätsbibliothek, 2017. http://d-nb.info/1136955127/34.
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Ogur, Erich Okoth. "Effect of Magnetic Field on the Alignment and Orientation of Magnetic Particles in Injection moulding." Thesis, University of Warwick, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.487981.
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This thesis presents a study on the effect of magnetic field on the distribution and orientation of magnetic particles in injection moulding. The experimental work, using various materials such as polyester resin, nickel particles, polypropylene (PP), polycarbonate (PC) and methods (single component injection and co-injection moulding), has led to a deeper understanding of the mechanism that governs magnetic particle orientation under an external magnet in the complex environment of polymer injection. A simulation model was developed to provide a theoretical basis for realistic magnetic mould tool design. As there was no previous data available, it was hoped to elucidate some gUidelines by simulation experiments. In addition, the relationship between the rheological property of the polymer mixtures and the relevant moulding parameters such as tool temperature, melt temperature and speed of injection moulding was investigated using a comprehensive design of experiments methodology. It was found that the ferromagnetic nickel flakes remained magnetic enough to overcome the strong drag forces imposed on them by the polymeric fluid matrix and were able to be orientated. The focus of the experimental work was carried out using both the single component injection and co-injection moulding processes. A link was established between the melt temperature gradient and magnet effect. In the co-injection moulding experiments, it became clear, that the core melt had a longer residence time due to the thermal barrier provided by the skin melt and this facilitated a much more visible magnetic effect compared with samples produced using the injection moulding process.
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Liébana, Girona Susana. "Affinity bioseparation and biosensing using magnetic particles for food safety." Doctoral thesis, Universitat Autònoma de Barcelona, 2013. http://hdl.handle.net/10803/129323.
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La presente Tesis describe el diseño y la evaluación de nuevas estrategias, tanto ópticas como electroquímicas, para la detección rápida de bacterias patógenas en seguridad alimentaria. En la misma, se evalúan diferentes plataformas electroquímicas, basadas principalmente en biocompósitos de grafito-epoxi así como en el acoplamiento de partículas magnéticas a compósitos de grafito-epoxi. Las partículas magnéticas utilizadas permitieron la inmovilización covalente del bioreceptor en su superficie, tales como partículas magnéticas modificadas con estreptavidina, anticuerpos o bacteriófagos, así como también la inmovilización electroestática del analito mediante las partículas magnéticas de sílice. De este modo, se estudiaron diversas interacciones de bioafinidad tales como biotina-avidina, anticuerpo-antígeno y bacteriófago-receptores de superficie bacterianos.
En primer lugar, se evaluó un método rápido de cribado para la tuberculosis bovina en leche y productos lácteos basado en un genosensor electroquímico de ADN específico para M. bovis. En este estudio se evaluaron dos plataformas: i) biocompósitos grafito-epoxi de avidina (Av-GEB), y ii) magneto-electrodos basados en compósitos grafito-epoxi (m-GEC) acoplados a partículas magnéticas. Se determinaron muestras de leche provenientes de granjas y se compararon con el test de tuberculina, así como en un ensayo inter-laboratorio de PCR.
A continuación se estudiaron diferentes estrategias bioanalíticas para la detección de bacterias patógenas utilizando Salmonella como modelo. La primera estrategia se basa en un doble bioreconocimiento de la bacteria, i.e. inmunológico y genético. Las bacterias fueron capturadas y pre-concentradas de muestras alimentarias mediante partículas magnéticas modificadas con el anticuerpo específico para Salmonella a través de la reacción inmunológica. Tras la separación inmunomagnética, las bacterias capturadas fueron lisadas y el ADN amplificado específicamente mediante PCR con cebadores doblemente marcados. Por último, el amplicon fue detectado mediante un magneto-genosensor electroquímico.
La segunda estrategia se basó, por primera vez, en el uso de bacteriófagos como elemento de bioreconocimiento en la separación magnética de bacterias patógenas. Así, se exploró el potencial de los fagos tomando como modelo el fago P22 específico para Salmonella, el cual se inmovilizó de forma orientada sobre las partículas magnéticas. A continuación las bacterias fueron capturadas y pre-concentradas mediante las partículas modificadas a través de la interacción fago-huésped. Para confirmar la identidad de las bacterias se procedió a la amplificación del ADN mediante PCR de doble marcación y detección mediante un magneto-genosensor electroquímico.
La tercera estrategia presentada para detección de Salmonella se basó en la detección de la célula entera mediante un doble reconocimiento inmunológico. Las bacterias fueron capturadas y pre-concentradas de muestras alimentarias mediante separación inmunomagnética. A continuación, la marcación enzimática se realizó mediante un segundo anticuerpo específico para Salmonella, llevándose a cabo de este modo la detección mediante un magneto-inmunosensor electroquímico. Aunque los límites de detección obtenidos fueron superiores, el tiempo de ensayo y la complejidad del procedimiento fueron reducidos considerablemente. Las características analíticas de esta estrategia fueron evaluadas no solo para detección electroquímica sino también óptica, desarrollando de este modo un magneto-inmunoensayo óptico como última estrategia presentada para detección de Salmonella.
Finalmente, la última estrategia desarrollada en la Tesis se basó en la detección de los tres patógenos más frecuentes en seguridad alimentaria (Salmonella, Listeria y E. coli) mediante un magneto-genosensor electroquímico. Tras la extracción del genoma bacteriano se realizó la amplificación de este mediante PCR utilizando cebadores con tres marcas diferentes. Los amplicones marcados fueron inmovilizados en partículas magnéticas de sílice y posteriormente detectados electroquímicamente.
Cabe destacar que biosensores basados en las estrategias presentadas en esta Tesis son herramientas ideales para ser utilizados en la detección rápida, económica y sensible del riesgo de contaminación de patógenos en una gran variedad de matrices.This dissertation reports the design and evaluation of novel strategies, based on both optical and electrochemical detection, for the rapid detection of pathogenic bacteria in food safety applications. Different electrochemical platforms, based on the coupling of magnetic particles with magneto graphite-epoxy composite as well as graphite-epoxy biocomposite, were explored. Magnetic particles which allow covalent or electrostatic immobilisation were used, e.g. silica, streptavidin, antibody and phage-modified magnetic particles. Thus, several bioaffinity interactions such as biotin-avidin, antibody-antigen and bacteriophage-bacterial surface receptors were evaluated. Firstly, a rapid method for screening-out of bovine tuberculosis in milk and dairy products based on electrochemical genosensing of DNA specific of M. bovis is presented. In this study, two different platforms for electrochemical genosensing were evaluated: i) an avidin-biocomposite (Av-GEB), and ii) streptavidin-modified magnetic particles coupled with a magneto-electrode based on graphite-epoxy composite (m-GEC). The comparison with the tuberculin skin test and an inter-laboratory PCR assay was performed with raw milk samples collected from local dairy farm tanks. Moreover, different biosensing strategies for pathogenic bacteria were evaluated by using Salmonella as a model. The first approach relies on a double biorecognition of the bacteria, i.e. immunological and genetic biorecognition. The bacteria were captured and pre-concentrated from food samples with magnetic particles by the immunological reaction with the specific antibody against Salmonella. After the immunomagnetic separation, the captured bacteria were lysed, and further amplification of the genetic material by Polymerase Chain Reaction with a double-tagging set of primers was performed to confirm the identity of the bacteria. The double-tagged amplicon was then detected by electrochemical magneto- genosensing. The second strategy is based, for the first time, on the use of bacteriophages, as biorecognition element for the magnetic separation of pathogenic bacteria. The phage capabilities were explored by using the phage P22 towards Salmonella as a model which was immobilised in an oriented way on magnetic particles. The bacteria were then captured and pre-concentrated by the phage-modified magnetic particles throughout the phage-host interaction. To confirm the identity of the bacteria, further double-tagging PCR amplification of the captured bacteria DNA and electrochemical magneto-genosensing of the amplicon were performed. The third strategy for Salmonella detection relies on the detection of the whole bacteria by a double immunological recognition. The bacteria were captured from food samples and pre-concentrated by immunomagnetic separation. Then, the enzymatic labelling of the bacteria was also performed using a specific antibody against Salmonella, performing thus the electrochemical magneto-immunosensing. Although higher LODs were obtained, the assay time and complexity of the procedure were reduced considerably. The analytical features of the magneto-immunosensing of Salmonella were evaluated not only for electrochemical but also for optical detection, developing thus an optical magneto-immunoassay as the last strategy presented for Salmonella detection in this dissertation. Finally, the last strategy developed is based on the electrochemical magneto-genosensing of the three most common pathogenic bacteria in food safety (Salmonella, Listeria and E. coli). This approach was performed by the release of the bacteria genome followed by PCR in order to obtain the tagged amplicons by using three different coding tags. The tagged amplicons were then immobilised on silica magnetic particles. To confirm the identity of the three bacteria, the tagged amplicons were detected by electrochemical magneto-genosensing using three different electrochemical reporters. It is important to highlight that biosensing devices based on these strategies are ideal tools for being used as an alarm to rapidly detect the risk of contamination by pathogens in an inexpensive and sensitive manner and in a wide variety of matrixes.
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Carinelli, Soledad. "Biomarkers detection of global infectious diseases based on magnetic particles." Doctoral thesis, Universitat Autònoma de Barcelona, 2019. http://hdl.handle.net/10803/667765.
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Las enfermedades infecciosas suponen una gran amenaza para la salud mundial debido a la rápida diseminación y adaptación de los patógenos. El papel principal del diagnóstico clínico es identificar de forma fehaciente una enfermedad en un paciente. Los dispositivos de diagnóstico rápido permiten detectar enfermedades y monitorearlas de forma confiable en cualquier centro sanitario. Entre estos dispositivos, los biosensores electroquímicos presentan una alta sensibilidad y especificidad así como una instrumentación sencilla, pudiendo expandirse fácilmente a plataformas de detección múltiple. Además, la integración de partículas magnéticas (MPs) en métodos de diagnóstico rápido incrementa la sensibilidad y especificidad debido su capacidad para aislar y preconcentrar una molécula diana cuando éstas son modificadas con elementos de bioreconocimiento específico. Así, las MPs modificadas pueden unirse específicamente a biomarcadores y concentrarlos de muestras complejas bajo la actuación magnética, eliminando posibles interferencias. En esta tesis se presenta el desarrollo de estrategias de diagnóstico basados en tecnologías emergentes, asequibles y que requieren un entrenamiento mínimo de los usuarios finales, tales como los biosensores electroquímicos con accionamiento magnético.
Primero, se presentan dos tipos de pruebas diagnósticas para la cuantificación de linfocitos CD4 en sangre entera, usando MPs, para el seguimiento rápido de pacientes con HIV en entornos de bajos recursos. Se describen dos formatos, uno en formato tipo ELISA con detección óptica y otro usando electrodos de grafito-epoxi con biosensado electroquímico. En ambos casos la estrategia involucra a) el aislamiento de células CD4 usando MPs-antiCD3 y su marcación utilizando anticuerpos antiCD4 biotinilados; b) la marcación enzimática con estreptavidina-peroxidasa; y c) la detección basada en la actividad enzimática. Esta doble marcación (a través de los receptores CD3 yCD4) no sólo evita interferencias de otras células que expresan alguno de estos receptores, sino que aumenta la especificidad del ensayo.
Segundo, se describe un ensayo de liberación de interferon-basado en la detección electroquímica de dicho trascripto producido por linfocitos T previamente aislados de sangre. Este test utiliza MPs para el aislamiento y preconcentración de tres dianas diferentes (linfocitos T, mRNA y ADN doblemente marcado) en el mismo ensayo. Primero, los linfocitos T se aislan usando MPs-antiCD3. En segundo lugar, el mRNA de los linfocitos se preconcentra sobre MPs modificadas con polidT mediante unión a la cola de poli(A). Posteriormente se retrotranscribe el mRNA y se amplifica el cDNA mediante PCR múltiplex con marcación doble para la amplificación de IFN- y GAPDH. Finalmente, se inmovilizan los amplicones biotinilados en MPs-estreptavidina, y se realiza el genosensado electroquímico para la detección de IFN- a través del otro marcador del cebador. Esta estrategia se propone como alternativa a los ensayos de liberación de IFN- que se usan en la actualidad para la identificación de la Tuberculosis.
Por último, se presenta el diseño de un test de diagnóstico rápido, específico y altamente sensible basado en la amplificación isotérmica sobre MPs con detección electroquímica. Las técnicas de amplificación isotérmicas han surgido como una alternativa a la PCR para la identificación de microorganismos infecciosos, debido a la barrera que éstos últimos muestran para su implementación en entornos de bajos recursos. El último capítulo presenta la detección electroquímica de ADN usando sondas candado con amplificación isotérmica de círculo rodante y amplificación círculo a círculo. Esta estrategia ha demostrado ser una poderosa herramienta para la detección específica y sensible de ácidos nucleicos para su aplicación en el diagnóstico clínico.
Los biosensores desarrollados en esta tesis representan una gran promesa para la detección de forma más rápida, simple y económica comparado con los métodos tradicionales de diagnóstico de enfermedades infecciosas. Además, las estrategias desarrolladas en esta tesis demuestran un gran potencial para su aplicación en entornos de bajos recursos.Infectious diseases are becoming a major threat worldwide due to the fast dissemination and adaptation of pathogens favored by the unrestricted globalization. The primary role of diagnostics is to identify a disease. The rapid identification of a disease allows the patient to be placed on a specific antimicrobial therapy and avoid prolonged management on empiric, potentially inappropriate drug. Therefore, point-of-care (POC) devices that can reliably detect and/or monitor diseases would result in an improved care, and minimization of patient and societal cost of illness. Among them, electrochemical biosensors have the advantage of high sensitivity/specificity as well as simplicity of instrumentation, and can be easily expanded to multiplex detection platform. Furthermore, the integration of magnetic particles (MPs) in POC tests provides an even increased sensitivity and specificity due to the isolation and preconcentration of the target, whether MPs are modified with a specific recognition biomolecule. Modified-MPs can thus specifically bind the biomarkers and preconcentrate them from the complex specimen under magnetic actuation, preventing interferents before testing. Affordable emerging technologies requiring minimal training for final users, such as magnetic actuated electrochemical biosensors, are presented in this dissertation. Firstly, two simple diagnostic tests for CD4+ T lymphocytes quantification, directly in whole blood, and based on magnetic particles are presented. The assay is performed in an ELISA-like format for the optical detection or using graphite-epoxy electrodes for the electrochemical biosensing strategy. In both cases, the strategy has involved three main steps: a) immunomagnetic separation of CD4+ cells by antiCD3-MPs and labeling by using biotinylated antiCD4 antibody; b) enzymatic labeling; and c) detection based on the peroxidase activity. The dual labeling (CD3 and CD4 receptor) not only avoids interferences of other cells, but also increases the specificity of the assay. Thus, the development and evaluation of magnetic-actuated rapid HIV diagnostic platforms appropriate for their use in low resource settings for the following-up of patients under treatment is demonstrated. Secondly, an interferon- release assay based on electrochemical detection for interferon- transcript detection produced by isolated T lymphocytes is described. This approach also involves the integration of MPs for the isolation and preconcentration of three different targets (including whole T lymphocytes, mRNA transcripts and double-tagged DNA) in the same test. Accordingly, T lymphocytes are isolated from whole blood using antiCD3-MPs. Secondly, mRNA presenting poly(A) tail is preconcentrated on polydT-MPs from T lymphocyte. Afterward, mRNA is retrotranscripted and cDNA amplified by multiplex double-tagging PCR for the specific amplification of IFN- and GAPDH. Finally, one of the tags of the primers is used for the amplicons immobilization on streptavidin-MPs as support, while the electrochemical magneto-genosensing for transcript detection is performed using the other tag. This strategy results in an alternative for IFN- release assays, which can be used for identifying infectious states such as Tuberculosis. Finally, the design of a diagnostic test involving a rapid, specific and highly sensitive procedure based on isothermal amplification on MPs with electrochemical readout is presented. Isothermal amplification techniques are emerging as good candidates to replace PCR for the identification of infectious microorganism, since PCR-based method can be a critical barrier in low resource settings. An electrochemical DNA detection using padlock probes and the subsequent amplification with rolling circle and circle to circle amplification is presented in Chapter 6. This strategy has demonstrated to be a powerful combination for highly specific and sensitive nucleic acid detection that can be applied in clinical diagnosis. The electrochemical biosensors developed in this dissertation, offers considerable promise for obtaining information in a faster, simpler and cheaper manner compared to traditional methods for infectious disease diagnosis. Moreover, the strategies possess great potential in many applications, in low resource settings.
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Abul, Kashem Mottakin Mohammad [Verfasser]. "Magnetic Particles in Supported Polymer Nanostructures / Mottakin Mohammad Abul Kashem." Aachen : Shaker, 2013. http://d-nb.info/1051575680/34.
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Adams, Christopher Francis. "Assessment of magnetic particles for neural stem cell-based therapies." Thesis, Keele University, 2015. http://eprints.keele.ac.uk/2494/.
Full textAbstract:
Transplantation of genetically engineered neural stem cells (NSCs) into sites of central nervous system (CNS) disease/injury is a promising strategy to promote repair of damaged tissue. However, translating this strategy into the clinic requires several challenges to be overcome including facilitating ‘combinatorial therapy’ (achieving multiple therapeutic goals – essential in CNS injury/disease). Nanotechnologies are emerging as multifunctional platforms capable of meeting this requirement. For example, magnetic particles (MPs) and implantable hydrogels offer several biomedical advantages for transplant populations, including: safe genetic manipulation; non-invasive cell tracking, via MRI; and safe and efficient accumulation of cells at sites of injury. However, the use of these nanotechnologies remains to be explored in detail for NSC transplantation therapies. In this thesis, it is shown that MPs can mediate gene delivery to NSCs grown as neurospheres and monolayers with the most efficient transfection efficiencies achieved using oscillating magnetofection protocols (9.4% and 32.2% respectively). In both culture systems, developed protocols had no effect on key regenerative properties of NSCs such as cell viability, proliferation, stemness and differentiation. Further, ‘magnetofected’ monolayer NSCs were shown to have survived and differentiated in a cerebellum slice model acting as host tissue, indicating safety of the procedures. It was also shown that assessing procedural safety and extent of transfection of magnetofection protocols may be feasible by employing mass spectrometry and proteomics analysis. It was also found that tailored enhancement of particle magnetite content offers a means to efficiently label NSCs, up to a maximum of 95.8%. Labelling procedures had no effect on cell viability, proliferation, stemness or differentiation. In addition, labelled cells could survive and differentiate in a slice model of spinal cord injury indicating safety of the labelling procedures. Functional labelling was also demonstrated by magnetic capture of labelled cells in an in vitro flow system. Hydrogels offer major advantages for delivery of transplant populations into injury sites. Here it was shown that an intraconstruct genetic engineering approach was feasible for NSCs cultured with a clinically translatable, collagen hydrogel system. Magnetofection protocols safely increased MP mediated transfection of NSCs grown in ‘2-D’ and ‘3-D’ hydrogel cultures.
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Gélinas, Stéphanie. "Preparation of magnetic carriers through functionalization of nanosized maghemite particles." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0023/NQ50168.pdf.
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Zulqarnain, Kamran. "Scale-up of affinity separation based on magnetic support particles." Thesis, University College London (University of London), 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313426.
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Jaroensutasinee, K. "Chaotic motion of charged particles in non-uniform magnetic fields." Thesis, University of Warwick, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282433.
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Jenkins, Stuart Iain. "Applications of magnetic particles for oligodendrocyte precursor cell transplantation strategies." Thesis, Keele University, 2013. http://eprints.keele.ac.uk/3821/.
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Oligodendrocyte precursor cells (OPCs) are a major transplant population to promote myelin repair and central nervous system (CNS) regeneration in conditions such as Multiple Sclerosis and spinal cord injury. Magnetic particles (MPs) can offer a multifunctional platform for cell therapies, facilitating labelling for cell tracking (e.g. by MRI and histopathology); biomolecule delivery (including nonviral gene delivery, enhanceable by novel ‘magnetofection’ strategies); and magnetic cell targeting of transplant populations. However, MP-based applications for neural tissue engineering have received limited attention to date. This thesis demonstrates that ~60% of OPCs (derived from a primary source) can be safely labelled using two well-characterised MP formulations, including a novel multimodal MP with transfection plus cell labelling capabilities. A rapid, technically simple, high-throughput ultrastructural imaging technique, OTOTO SEM, has been developed to study the surface interactions of MPs with precursor cells. Safe MP-mediated transfection of OPCs was demonstrated, including with multiple and therapeutic genes. Transfection efficiency was enhanced by static/oscillating ‘magnetofection’ techniques (~21%; competitive with nonviral alternatives). Organotypic cerebellar slice cultures were developed as a model of ‘host’ neural tissue, and ‘magnetofected’ OPCs exhibited normal migration, proliferation and differentiation profiles following transplantation onto such slices. Safe labelling (~45%) and transfection (enhanced by static/oscillating magnetofection strategies: ~6%) of oligodendrocytes was achieved utilising identical protocols to those developed for OPCs. A comparative intralineage analysis demonstrated that MP-uptake and amenability to transfection were significantly lower in oligodendrocytes compared to OPCs. Inter-cellular comparisons of MP-handling by the four major CNS glial subtypes (viz. OPCs, oligodendrocytes, astrocytes, microglia; derived from the same primary source) revealed major differences in the rate/extent of MP uptake, amenability to transfection, optimal magnetofection frequency, and MP-associated toxicity. Finally, a stoichiometrically-defined glial co-culture model was developed and utilised to test the hypothesis that microglia represent an ‘extracellular barrier’ to MP uptake by other glia.
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李浩然 and Ho-yin Lie. "A three dimensional approach for determining the surface magnetic field of strange stars." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2000. http://hub.hku.hk/bib/B31224805.
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Lie, Ho-yin. "A three dimensional approach for determining the surface magnetic field of strange stars." Hong Kong : University of Hong Kong, 2000. http://sunzi.lib.hku.hk/hkuto/record.jsp?B23234532.
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King, James Gagwane. "Magnetic properties of arrays of magnetite particles produced by the method of electron beam lithography (EBL)." Thesis, University of Edinburgh, 1996. http://hdl.handle.net/1842/15171.
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This study involves the production of arrays of parallelepiped magnetite particles in the size range 0.1 - 1 μm. This was achieved by utilising electron beam lithography techniques which are often employed in the design of semi-conductor devices. These particles are required in order to understand the mechanism of reversal of magnetisation for pseudo-single-domain (PSD) particles important to paleomagnetic studies. The samples used by previous researchers are magnetite powders. In such samples, despite attempts to disperse the particles onto non-magnetic matrix, there is no way of eliminating particle clumping, and magnetostatic interaction. Low temperature magnetic measurements obtained using samples of cubic arrays of magnetite particles shows that the effect of particle clumping is to increase the amount of saturation isothermal remanence (SIRM) lost at the Verwey transition. The dependence of SIRM lost at the Verwey transition on particle size in the PSD size range, is consistent with the vortex domain structure predicted for unconstrained 3-D micromagnetic studies. The results shows that 'true' magnetic memory is a stress related phenomenon. Magnetic properties of cubic arrays of magnetite particles measured at room temperature are not consistent with the mechanism of magnetic reversal of coherent rotation of atomic magnetic moments, but are generally in good agreement with that of vortex nucleation and propagation in general. The method of domain classification using the coercivity ratio often used in rock magnetism, is shown to be not useful in classifying PSD in the submicron size range. Magnetic properties of rectangular parallelepiped magnetite particles are more complex than expected from the simple demagnetisation shape anisotropy contribution.
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Braybrook, Julian Hugh. "Effects of paramagnetic and ferromagnetic particles on magnetic resonance (MR) imaging." Thesis, University of Cambridge, 1989. https://www.repository.cam.ac.uk/handle/1810/250949.
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Zhang, Bangwei. "Guiding nonmagnetic particles by external magnetic field in a microfluidic device." Thesis, Wichita State University, 2008. http://hdl.handle.net/10057/2100.
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This report presents the fabrication of a micro fluidic device using the UV lithography method in order to separate nonmagnetic fluoresbrite carboxy microspheres from the mixed ferrofluids in microchannels. The microfluidic device is fabricated using a SU8-50 negative photoresist that is exposed to the UV lights with a mask (Y shape) on the top of the photoresist. By applying the external magnet from a side of the microchannel, the fluoresbrite carboxy microspheres and ferrofluids are separated into different channels because of the magnetic force acted on the nonmagnetic spheres. During the fabrication, a number of different parameters, such as UV exposure times, UV power, photoresist thickness, etc. were conducted and optimized for our needs. In addition, in the magnetic field testing, different pumping speeds, and particle concentrations associated with the
different distances between the magnet and the microfluidic system were studied for an efficient separation.Wichita State University, College of Engineering, Dept. of Mechanical Engineering
Includes bibliographic references (leaves 64-67)
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Martin, Gino. "A theoretical study of ordering in systems containing fine magnetic particles." Thesis, Bangor University, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314484.
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Urban, Ilona. "Functionalised magnetic nano-particles for the selective removal of radioactive contaminants." Thesis, University of the West of England, Bristol, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.444508.
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Pedchenko, B. O., A. S. Yermolenko, Stanislav Ivanovych Denisov, Станіслав Іванович Денисов, and Станислав Иванович Денисов. "Langevin equations for suspended magnetic particles drifting under the Magnus force." Thesis, Sumy State University, 2017. http://essuir.sumdu.edu.ua/handle/123456789/63757.
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The Magnus effect, i.e., dependence of the trajectory of a body on its rotation, is widely used in sport, science and technical applications. Recently we have shown [1, 2] that due to the Magnus force the single-domain ferromagnetic particles, which are suspended in a viscous fluid and subjected to a harmonic driving force and a non-uniformly rotating magnetic field, can perform drift in a preferred direction. This result has been obtained within the deterministic approach when thermal fluctuations, leading to translational and rotational Brownian motion of particles, are ignored. Our estimations show [2] that it is possible for relatively large particles (> 102 nm). Therefore, to study the drift phenomenon for smaller particles, it is necessary to account for these fluctuations in basic equations.
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Prikockis, Michael Vito. "Physics and Applications of Interacting Magnetic Particles: Effect of Patterned Traps." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1452073910.
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Wu, Min. "Magnetic and structural properties of ball-milled Mn and CrMn particles." Morgantown, W. Va. : [West Virginia University Libraries], 1999. http://etd.wvu.edu/templates/showETD.cfm?recnum=628.
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Thesis (M.S.)--West Virginia University, 1999.Title from document title page. Document formatted into pages; contains viii, 46 p. : ill. Vita. Includes abstract. Includes bibliographical references (p. 43-45).
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Zhang, Bangwei Asmatulu Ramazan. "Guiding nonmagnetic particles by external magnetic field in a microfluidic device." A link to full text of this thesis in SOAR, 2008. http://hdl.handle.net/10057/2100.
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Spinella-Mamo, Vincent Paul. "Control of micro- and nano- particles with electric and magnetic fields." Connect to Electronic Thesis (CONTENTdm), 2008. http://worldcat.org/oclc/458547540/viewonline.
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Blanco-Mantecon, Mireia. "Interactions, particle size and surface effects in magnetic nanoparticle systems." Thesis, Bangor University, 2000. https://research.bangor.ac.uk/portal/en/theses/interactions-particle-size-and-surface-effects-in-magnetic-nanoparticle-systems(2f7d3ef7-ef4c-43b0-b3ad-9e5c68f629e5).html.
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This work has involved the study of the magnetic behaviour of small magnetic nanoparticle systems. Due to the reduced size of magnetic nanoparticles they present distinctive properties, such as size and surface effects, that have been analysed in this work, as well as the effect of interactions in such systems. The samples chosen for the study were magnetite particles in the form of a ferrofluid and Co nanoclusters in a nonmagnetic matrix of Cu. Both systems present very narrow particle size distributions, which facilitates the interpretation of the data. The samples have been subjected to basic characterisation, which includes the determination of the distribution of magnetic particle sizes using the magnetisation curves at room temperatures, TEM microscopy and X-ray diffraction, in the case of the ferrofluid samples. For the nanoclusters, a time of flight spectrometer has been used to obtain the number of atoms per cluster. Many of the measurements have been performed at low temperatures, where thermal effects are minimised. For such measurements the samples have been frozen in a zero applied field, so that they have a random distribution of magnetic moments prior to the measurement. The energy barrier distributions have been calculated via the temperature decay of remanence (TDR). From this study, an effective anisotropy constant has been calculated. For the study of the interactions, surface and size effects, magnetisation, susceptibility (ZFC), remanence and delta-M curves, as well as the time dependence of magnetisation have been studied. The attempt frequency of the different particle size systems has been calculated using different techniques. The basic magnetic behaviour can be explained on the basis of the Neel blocking model. It has been found that the systems with the smaller particles have significant surface effects, which are enhanced at lower temperatures. Interactions, which are weak due to the low concentration of magnetic material in the samples (<10%), have been found to be overall demagnetising and the evolution of the magnetic properties with dilution has been explained. As is the case for the surface effects, interaction effects are stronger at low temperatures due the reduction of thermal effects. The experimental results have been compared with calculations from a Montecarlo model for fine particles, which includes the effects of concentration, anisotropy, particle size and temperature.
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Rahman, Md Mahbubor. "Preparation of Temperature Responsive Magnetic Polymer Particles for Nucleic Acid (DNA/RNA) Separation." Thesis, Lyon 1, 2011. http://www.theses.fr/2011LYO10253.
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Le problème dans le diagnostique biomédical réside non seulement dans les outils de détections mais aussi dans la préparation des échantillons qui nécessitent impérativement un prés traitement. Ce prétraitement consiste à libérer le matériel nucléique (ADN/ ARN) dans le milieu et le capturer et le purifier par la suite avant les étapes d'amplification et de détection. Ainsi, l'utilisation de nanoparticules de latex magnétiques stimulables permettra non seulement d'augmenter la sensibilité de certains testes, mais aussi une possible utilisation dans des automates ou intégration dans des microsystèmes ou la rapidité de séparation magnétiques. Ainsi, l'objectif de cette étude est d'élaborer de particules de latex magnétiques stimulables pour le transport des acides nucléiques. Des émulsions magnétiques (huile magnétique/eau) sont encapsulées par polymérisation radicalaire en milieu dispersé. La polymérisation est réalisée en réacteur fermé en utilisant le persulfate de potassium comme amorceur (KPS), un mélange de monomères styrène 60%/DVB 40% ou DVB. L'optimisation de ces deux formulations permet l'obtention de particules parfaitement coeur-écorce. L'utilisation de ces particules magnétiques semences de polymérisation par précipitation a permet l'obtention de particules magnétiques cationiques et thermosensibles. L'utilisation d'un agent de réticulation est indispensable à l'obtention d'une écorce sensible à la température et l'utilisation d'un monomère aminé (AEMH) et un amorceur cationique (V50) sont indispensables pour l'obtention de particules de latex magnétiques cationiques (amine et amidine en surface). L'évaluation de ces particules lors de la capture des acides nucléiques a montré une influence marquée de la température d'analyse sur le pourcentage d'adsorption et de désorption. Ces valeurs sont plus élevées pour l'adsorption à 18°C et pour la désorption à 40°C. La synthèse de particules de latex magnétiques fonctionnalisées par l'acide phenyl boronique a été réalisée en utilisant le NIPAM, le MBA et l'APB. Les particules obtenues sont sensibles à la température et ai glucose. Des particules thermosensibles carboxyliques via l'acide acrymique (AA) ont été fonctionnalisée par greffage chimique en utilisant l'amino acide pheny boronique. Les deux types de particules montrent une sensibilité à la température et également au glucose. La fixation spécifique de l'ARN a été examiné et la tendance des résultats montre une immobilisation sensible au pH et la températureThe use of nucleic acid (DNA/RNA) as a diagnostic and therapeutic molecule has become promising in biomedical field. The particles having magnetic and temperature responsive property could be of great interest for better use in controlled switching nucleic acid separation, purification and concentrating. The aim of this work is to prepare functionalized temperature responsive magnetic polymer particles and to use them as efficient solid support for the extraction of nucleic acids (DNA/RNA) from any biological sample. Here, we report amine (NH2) and boronic acid [-B(OH)2] functionalized temperature responsive magnetic polymer particles synthesis, characterization and application in nucleic acid separation. Divinylbenzene (DVB) cross-linked magnetic polystyrene (PSt) particles were prepared first by seed emulsion polymerization of DVB and St in the presence of oil-in-water (o/w) magnetic emulsion. Thereafter, DVB cross-linked magnetic polystyrene particles were functionalized by the seed precipitation polymerization of N-isopropylacrylamide (NIPAm) with either of the functional monomer aminoethylmethacrylate hydrochloride (AEMH), vinylphenylboronic acid (VPBA) or acrylic acid (AA).Moreover, aminophenylboronic acid (APBA) were grafted onto carboxylic acid functionalized temperature responsive magnetic particles. All of the prepared magnetic particles were successfully characterized to obtain the morphology, surface functionality, chemical composition, colloidal properties in terms of size and zeta potential and magnetic property of the particles. Importantly, size shrinkage upon heating attests temperature responsiveness of magnetic polymer particle. Further investigation revealed that only amine or boronic acid group containing magnetic polymer particles are able to separate nucleic acid. Interestingly, RNA adsorption is strongly occurred than that of DNA onto boronic acid magnetic polymer particles due to the opportunity of boronate ester formation with cis-diol of RNA. The prepare temperature magnetic polymer particles would be a potential candidate to develop an automated microsystem device for nucleic acid separation
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Couture, Gilles. "Anomalous Magnetic Moment of the W Boson in Different Models." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/26982.
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We consider the anomalous magnetic moment of the W boson, ĸ, from an experimental and from a theoretical point of view. In the first chapter,we consider five experiments where this parameter could in principle be measured. Our results show that the W pair-production remains the best process to measure ĸ. Single W production is very sensitive to ĸ, but it is plagued by very small cross-sections. Photon-electron colliders can also be valuable for measuring ĸ through single W production. In the second chapter, we consider a composite model where ĸ is essentially free. We found that it is impossible to rule out such a model from a single measurement of ĸ. We give detailed production rates for these processes.
In the second half of the thesis, we set limits on the corrections to ĸ at the one loop level; first in the minimal SM and then in a two-Higgs-doublet model. The main results are that measured corrections of 0.1 would clearly indicate non-perturbative physics while the minimal SM can accommodate corrections up to 0.02. Possible extensions of the SM cannot increase this figure by much: unless one is willing to introduce several extra weakly interacting families, it remains that 75%, or more, of the corrections will arise from the minimal SM.Science, Faculty of
Physics and Astronomy, Department of
Graduate
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Ronhovde, Cicily J. "Biomedical applications of mesoporous silica particles." Diss., University of Iowa, 2017. https://ir.uiowa.edu/etd/5837.
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Mesoporous silica particles are of significant interest for biomedical applications due to their good general biocompatibility compared to other nanoparticle matrices such as quantum dots, high specific surface areas up to 1000 m2/g, and extreme synthetic tunability in terms of particle size, pore size and topology, core material, and surface functionalization. For one application, drug delivery, mesoporous silica nanoparticles (MSNs) of two pore structures, MCM-41 – parallel, hexagonally ordered pores approximately 3 nm in diameter – and wormhole (WO) – interconnected, disordered pores also approximately 3 nm in diameter – were synthesized with particle diameters under 100 nm. Additionally, a magnetic Fe3O4 nanoparticle core was incorporated into Fe3O4-core WO-MS-shell particles. The particles were loaded with doxorubicin, a chemotherapeutic, and the drug release into phosphate buffered saline (PBS, 10 mM, pH 7.4) at 37 °C was monitored by fluorescence spectroscopy. The data were fit to three models: Korsmeyer-Peppas, first order exponential release, and Weibull. The Korsmeyer-Peppas model provided useful information concerning the kinetics and mechanism of drug release from each MSN type. A small but statistically significant difference in the release kinetics was found due to the different pore topologies. A much larger kinetic effect was observed due to the inclusion of an iron oxide core. Applying a static magnetic field to the Fe3O4-core WO-MS shell particles did not have a significant impact on the doxorubicin release. This is the first time that the effects of pore topology and iron oxide core have been isolated from pore diameter and particle size for these materials.
In vitro cell studies were conducted to determine the cytotoxicity of the bare and doxorubicin-loaded materials against three cancerous cell lines – A549 human lung carcinoma cells, HEC50CO human endometrial cancer cells, and CT26 mouse colon cancer cells. The MCM-41 and WO MSNs generally displayed similar toxicities within each cell line, and the Fe3O4-core WO-MS shell particles were less toxic. Doxorubicin-loaded particles generally displayed greater toxicity than bare MSNs, but the A549 cells were very resistant to all concentrations of MSNs tested.
For another biomedical application, tissue phantom development, mesoporous silica particles with approximately 10 μm diameters and C18 surface functionalization were evaluated for their use as a substrate for optical tissue phantoms. Tissue phantoms are synthetic imitations of biological material, and C18-modified silica provides a substrate that is simple to load with optically active biological molecules. The molecules are then hydrophobically trapped to maintain a clear optical boundary between the biological loading within the particle and an aqueous suspension gel. Several preparation techniques were evaluated for the dispersal of hydrophobic particles in aqueous media, and qualitative analysis indicated that surfactant coating of the outer surface could fully disperse the hydrophobic particle while maintaining the clear optical boundary. A novel analysis was developed to provide a single numerical indicator of clustering for a quantitative assessment of particle dispersal in tissue phantoms.
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Beydoun, Donia Chemical Engineering & Industrial Chemistry UNSW. "Development of a novel magnetic photocatalyst : preparation, characterisation and implication for organic degradation in aqueous systems." Awarded by:University of New South Wales. Chemical Engineering and Industrial Chemistry, 2000. http://handle.unsw.edu.au/1959.4/20451.
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Magnetic photocatalysts were synthesised by coating a magnetic core with a layer of photoactive titanium dioxide. This magnetic photocatalyst is for use in slurry-type reactors in which the catalyst can be easily recovered by the application of an external magnetic field. The first attempt at producing this magnetic photocatalyst involved the direct deposition of titanium dioxide onto the surface of magnetic iron oxide particles. The photoactivity of these Fe3O4/TiO2 was lower than that of single-phase TiO2 and was found to decrease with an increase in the heat treatment. These observations were explained in terms of an unfavourable heterojunction between the titanium dioxide and the iron oxide core. Fe ion diffusion from the iron oxide core into the titanium dioxide matrix upon heat treatment, leading to a highly doped TiO2 lattice, was also contributing to the observed low activities of these samples. These Fe3O4/TiO2 particles were found to be unstable, with photodissolution of the iron oxide phase being encountered. This photodissolution was dependent on the heat treatment applied, the greater the extent of the heat treatment, the lower the incidence of photodissolution. This was explained in terms of the stability of the iron oxide phases present, as well as the lower photoactivity of the titanium dioxide matrix. In fact, the observed photodissolution was found to be induced-photodissolution. That is, the photogenerated electrons in the titanium dioxide phase were being injected into the lower lying conduction band of the iron oxide core, leading to its reduction and then dissolution. Thus, the approach of directly depositing TiO2 onto the surface of a magnetic iron oxide core proved ineffective in producing a stable magnetic photocatalyst. The introduction of an intermediate passive SiO2 layer between the titanium dioxide phase and the iron oxide phase inhibited the direct electrical contact and hence prevented the photodissolution of the iron oxide phase. Improvements in the photoactivity were seen to be due to the inhibition of both the electronic and chemical interactions between the iron oxide and titanium dioxide phases. Preliminary optimisation experiments revealed that a thin SiO2 layer is sufficient for inhibiting the photodissolution. The thickness of the TiO2 coating was found not to have a significant effect on the photocatalytic performance of the coated particles. Finally, heat treating for 20 minutes at 450??C was sufficient for converting the titanium dioxide into a photoactive phase, longer heating times had no beneficial effect on the photoactivity.
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Dudchenko, N. O., A. B. Brik, and V. P. Ponomar. "Preparation of Magnetic Fine Particles for Different Applications by Reducing of Non-Magnetic Hematite and Goethite with Biomass." Thesis, Sumy State University, 2015. http://essuir.sumdu.edu.ua/handle/123456789/42631.
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Phase transformations of natural and synthetic hematite and goethite by reducing with starch at temperature range up to 650°C were investigated. The saturation magnetization of all initial samples was ~1 A*m2/kg, while the saturation magnetization of the samples after phase transformations increases greatly (up to 70 A*m2/kg for synthetic goethite sample). It was shown by X-Ray diffraction method that all phases
transformed into magnetite. Rather high saturation magnetization of obtained magnetic particles makes them promising for different medical-biological applications (cells separation, DNA purification, targeted drug delivery, adsorbents of radioactive waste, etc.).