Magnetic fluid aggregates magnetic columns when a perpendicular magnetic field is applied. The arrangement of magnetic columns forms hexagonal structures in equilibrium state. We study the ordering classification of colummnar lattices with time elapsed. The perpendicular magnetic field can be categorized as AC and DC fields. To couduct experiments, AC filed changes frequency, and DC field changes the final intensity of magnetice field. We use the bond-orientation correlation function, FFT, and Delaunay triangulation plots of the images to analyze the data which is obtained from experiments. Through digital image processing techniques, we can also determine positions, displacements,and average speed of magnetic columns to undersand the two-dimensional ordering processes, while applying megnetic fields.

The investigation covers two possible areas of application of magnetic fluids, one involving the production of torque by means of rotating magnetic fields and the other the use Of magnetic fluids in the separation of non-magnetic ores on a density basis. The' emphasis-was upon the use of cheap, primitive ferrofluids Le'. non-collOidal suspension of relatively large particles. a Moskowitz and Rosensweig were the first to report electromechanical energy conversion with a rotating magnetic field. Their theory is not confirmed by their experimental results, howevert nor the fact that the fluid can rotate in the opposite direction to the field. This phenomenon has been investigated experimentally for a range of field intensities, wave velocities, particle sizes, volume loading and fluid viscosities. The torque per unit volume has been found to be related linearly to the volume loading but-nonlinearly to the frequency of the supply, field intensity and viscosity. For the primitive ferrofluids the results clearly indicate a combination of saliency and hysteresis torques. No satisfactory explanation for the reverse motion of the fluid has been produced and attempts to quantify the energy transfer have not been successful. Due to the inherently low permeability of the fluid, the torque per unit volume is much smaller than for conventional a. c. machines. Primitive magnetic fluids have also been shown to have potential in the separation of ores according to their densities. The novelty of this work is that the particles, which flocculate in the presence of stationary fields, are kept in suspension by agitation caused by a rotating wave. This agitation also serves to reduce the effective viscosity which at high volume loading can be high at zero field conditions. An effective specific gravity of about 12 has been obtained. The experimental results confirm the theory that the magnetic force in the linear condition is proportional to the magnetic energy - density gradient (in space) but with saturation the force is proportional to the field gradient and independent of body shape. A practical system seems to be feasible.

This thesis is devoted to the study of a deformable material interface between two immiscible moving media, both of them being magnetizable. The first part concerns the establishment of a complete set of dynamical equations allowing a complete description of the non equilibrium phenomena including a coupling between the internal angular momentum and the electromagnetic field. The effects of the relaxation processes are also discussed. We show that the deformation of the interface introduces a nonlinear term, proportional to the mean curvature, in the surface dynamical equations of mass momentum and angular momentum. That term intervenes also in the singular magnetic and electric fields inside the interface which lead to the influence of currents and charge densities at the interface. In a second part, we give the expression for the entropy production inside the interface as well as in the bulk phase. Using the general principles of non equilibrium thermodynamics, we compute the different thermodynamical fluxes.

In this work we studied the convective heat transfer in a magnetic fluid in both zero and applied magnetic fields. The natural convection is observed in a quasi-one dimensional magnetic fluid in a horizontal temperature gradient. The horizontal non-homogeneous magnetic fields were applied across the sample cell either parallel or anti-parallel to the temperature gradient. The temperature profile was measured by eight thermocouples and temperature sensitive paint. The flow velocity field and streamlines were obtained by optical flow method. Calculated Nusselt numbers, Rayleigh number, and Grashof number show that the convective flow is the main heat transfer mechanism in applied fields in our geometry. It was found that when the field gradient is parallel with temperature gradient, the fields enhance the convective heat transfer while the fields inhibit it in anti-parallel configuration by analyzing the temperature difference across the sample, flow patterns, and perturbation Q field in applied fields. Magnetic Rayleigh number and magnetic Grashof number show that the thermomagnetic convections dominate in high magnetic fields. It is shown that the physical nature of the field effect is corresponding to the magnetic body force which is perpendicular to the gravity in our experiments. When the direction of the magnetic body force is same with temperature gradient in parallel configuration, the body force increases the convective heat transfer; while it has opposite effect in anti-parallel configuration. Our study will not only shed light on the fundamental mechanisms for thermomagnetic convection but also help to develop the potential field-controlled heat transfer devices.

A ball bearing is widely used in the precision machine, and the ball is its major component. The sphericity and the surface roughness of the ball significantly influence the bearing per-formance and reliability. First, this study considers the gyro-scopic effect and modifies the theoretical model of magnetic fluid grinding to analyze the kinematics characteristics of ball grinding process. According to the apparent changes in the spin angle and the shaft angular speed, the theoretical analysis qualitatively predicts the onset of skidding between contacts. Moreover, the gyroscopic effect is helpful to the randomizing for the ball motion. Second, the grinding trajectory on ball is theoretically analyzed for the new self-developed grinding machine to ob-tain the high efficiency and high precision grinding of balls. Results show that the grinding trajectory is uniform when the spin angle stably changes from 0 to 2p periodically.

A magnetic fluid system could potentially replace mechanically moving parts in a satellite as a means of increasing system reliability and mission lifetime, but rather than a standard ferrofluid with magnetic particles, liquid oxygen (LOX) may be a more adequate working fluid. As a pure paramagnetic cryogen, LOX is already heavily used in space, but still requires basic research before being integrated into system development. The objectives of the research conducted were to verify LOX as a magnetic working fluid through experiment and establish a theoretical model to describe its behavior. This dissertation presents the theoretical, experimental, and numerical results of a slug of LOX being pulsed by a 1.1 T solenoid in a quartz tube with an inner diameter of 1.9 mm. The slug oscillated about the solenoid at 6-8 Hz, producing a pressure change of up to 1.2 kPa. System efficiency based on the Mason number was also studied for various geometric setups, and, using a one-dimensional, finite-differenced model in Matlab 2008a, the numerical analyses confirmed the theoretical model. The research provides groundwork for future applied studies with complex designs.

The subject is to study two-dimension phase transition. The nano-magnetic particles dispersed in magnetic fluid can aggregate to form magnetic columns under external perpendicular magnetic field. At some appropriate condition, these magnetic columns are able to form two-dimension lattices. It is a novel mesoscopic system for studying two-dimensional melting transition. By controlling external magnetic field, we explore phenomena of phase transition and defect dynamics. This article can be divided to three parts. In the first part, we study the phase transition with two-dimension lattice forming with magnetic fluid, then we classify the crystal, hexatic and liquid phases in the melting process with translational correlation function and bond-orientational correlation function. In the second part, we analyze the defect dynamics within the lattice with Burgers Vector. In the third part of this article, the external DC magnetic field is replaced with the AC magnetic field, we find that the two-dimension lattices are also formed in low frequency region. The relationship between the two-dimension lattice forming and the AC frequency are studied.

Recent advancements in microfabrication technology have led to the development of micro-total analytical systems (μ-TAS), more popularly known as lab-on-a-chip (LOC) devices. These devices have a relatively small size and are capable of performing sample and reagent handling steps together with analytical measurements. Rapid mixing is essential in such microfluidic systems for various applications e.g., biochemical analysis, sequencing or synthesis of nucleic acids, and for reproducible biological processes that involve cell activation, enzyme reactions, and protein folding. In this work a numerical model is developed using a lattice Boltzmann method (LBM) to study microscale mixing. The study involves two mixing methods, namely, electroosmotic mixing and magnetic assisted mixing. A single component LBM model is developed to study electroosmotic flow in a square cavity. Mixing is studied by introducing two types of tracer particles in the steady electroosmotic flow and characterized by various mixing parameters. The results show that rapid mixing can be achieved by using a steady electric field and a homogeneous zeta potential. A multicomponent LBM method is also developed to study magnetic assisted mixing in a channel configuration. The ferrofluid flow is influenced by two magnets placed across a microchannel. The interacting field induced by these magnets promotes cross-stream motion of the ferrofluid, which induces its mixing with the other nonmagnetic fluid. Two fluids, one magnetic and another non-magnetic fluid, are introduced in a channel, when two magnets are placed across it at a distance apart. In the presence of the magnetic field, the magnetic fluid tries to follow a zig-zag motion generating two rolls of vortices thereby enhancing mixing. A parametric study characterizes the effects of diffusivity, magnetic field strength, and relative magnet positions on a mixing parameter. Mixing is enhanced when the magnetic field strength and diffusivity are increased. However, contrary to the observed trend, placing the magnets very close to each other axially results in local ferrofluid agglomeration rather than promoting mixing. / Ph. D.

Master of Science / Food Science Institute / Jayendra Amamcharla / Greek yogurt is one of the largest-growing sectors in the dairy industry accounting for over 25% of yogurt sales in the United States. Greek yogurt is produced by removing a portion of water and water soluble components from yogurt. Consequently, a large quantity of Greek yogurt whey (GYW) is being produced as a co-product. GYW is compositionally different from cheese whey, and thus poses economic and environmental challenges to the dairy industry. The objective of the present study was to evaluate two physical treatments as alternative methods for separating valuable GYW components: magnetic fluid treatment (MFT) and the addition of sepiolite, a clay mineral. A MFT chamber was designed using four pairs of neodymium magnets arranged to produce a magnetic field strength of 0.6 Tesla. Three batches of GYW each from two manufacturers were procured. A 2×3 factorial design was used with MFT or without MFT and the addition of zero, two, or four grams of sepiolite per 100g of GYW. The pH of GYW was adjusted to 7.2 using 5N NaOH solution, and the GYW was pumped at a rate of 7.5 L/min through the MFT system with or without MFT chamber attached. The sample was split into three sub-samples, heated to 80°C, and sepiolite was added as per the experimental design. The samples were centrifuged at 1,000g for five minutes. The top aqueous layer was separated and analyzed for total solids, ash, lactose, protein, calcium, phosphates, and sodium content along with color. MFT did not influence the analyzed whey components (P > 0.05) except for lactose. However, addition of sepiolite influenced protein content and a* and b* color values for the top aqueous layers (P < 0.05). Both levels of sepiolite addition resulted in about a 50% decrease in protein compared to original GYW. Adding two grams of Sepiolite per 100g of GYW from manufacturer 1 resulted in b* decreasing from 25.99 to 8.16 compared to treated GYW with no sepiolite. Sepiolite was found to have possible applications in the removal of proteins and color pigments in GYW.

O principal interesse neste estudo foi a proposição de uma nova classe de material que permite a ação combinada da Terapia Fotodinâmica (TFD) e da Hipertermia (HPT), projetadas para trabalhar sinergicamente, que possa levar a uma considerável regressão de tumores neoplásicos após mínimas doses de dissipação de calor e/ou fotossensitização luminosa. Esta nova classe de material se baseia em um lipossoma de longo tempo de circulação associado ao fármaco fotossensibilizador (FS) zinco ftalocianina (ZnPC), na presença de fluido magnético (FM) constituído por nanopartículas de ferrita de cobalto (CoFe2O4) recobertas com ácido cítrico. As propriedades fotofísicas (em meio orgânico e em meio lipossomal) e os estudos fotobiológicos em células da linhagem B-16 foram desenvolvidos para avaliar as propriedades da ZnPC na ausência e na presença de FM. As propriedades fotofísicas da ZnPC em meio orgânico e lipossomal, na ausência e na presença de FM, foram realizadas empregando-se técnicas de espectroscopia no estado estacionário e resolvido no tempo. Foi possível determinar importantes parâmetros que elucidaram o potencial fotodinâmico da partícula mista ZnPC/FM com um apropriado sistema de liberação, confirmando sua viabilidade para aplicação em estudos in vitro e in vivo. A interação de fluidos magnéticos biocompatíveis (FMBs) com a macromolécula biológica, a soro albumina bovina (BSA), foi estudada por meio da determinação da constante de ligação (Kb) e do número de sítios de ligação (n),. Este formalismo aplicado para nanopartículas magnéticas usadas em aplicações biológicas foi realizado pela primeira vez neste rabalho. As toxicidades da ZnPC, do FM e da partícula mista ZnPC/FM, em meio homogêneo e lipossomal, na ausência e na presença de luz e/ou campo magnético, foram estudadas. Na última parte deste trabalho iniciou-se o desenvolvimento de um modelo tumoral subcutâneo na região dorso-lateral de camundongos C57BL6J. Este é considerado o primeiro passo para a transferência dos resultados fotobiológicos no desenvolvimento de um tratamento clínico proposto para a terapia de humanos. Os nossos resultados demonstraram que o complexo ZnPC/FM em meio lipossomal apresenta propriedades fotofísicas e fotobiológicas úteis, ativados pela luz e campo magnético, como uma geração de fármacos atuando sinergicamente pela TFD e pela HPT. / The main goal in this study was to introduce a new material class that allows the combined action of Photodunamic therapy (PDT) and Hyperthermia therapy (HPT), designed to work in a synergetic ways, leading to an expected enhancement of the tumor damage after minimum drug doses and based on heat dissipation and /or light photosensitization. This new material class is a ?stealth? liposome associated with the photosensitizer drug zinc phthalocyanine (ZnPC), in the presence of a magnetic fluid (MF) based on nanoparticles of cobalt-ferrite (CoFe2O4) surface-coated with citric acid. Photophysical properties (in organic and liposomal medium) and photobiological studies in B-16 tumor cell lines were developed to evaluate the properties of the ZnPC in the absence and in the presence of MF. The photophysical properties of the ZnPC in organic and liposomal medium, were realize using spectroscopy techniques in the steady state and by time resolved studies. It was possible to quantify important parameters that elucidated and confirm the photodynamic potential of the ZnPC/MF complex as an appropriate drug delivery system, confirming its viability for application in vitro and in vivo studies. The interaction of the biocompatible magnetic fluids (FMBs) with the biological macromolecule, serum albumin proteins (BSA),was investigated through the determination of the binding constant (Kb) as well as the binding stoichiometry of the complex (n). This is the first time that this formalism was applicable to magnetic nanoparticles used in biological application. The toxicities of the ZnPC, the MF and also for the combined particle (the ZnPC/MF complex), in homogeneous and liposomal medium, in the absence and in the light presence and/or magnetic field were studied, and all the parameters that will allow the used of this synergic compound have been defined. In the last part of this work it was also started the establishment of one animal model by development of subcutaneous tumoral skin cancer in the back-lateral area of C57BL6J mice. This are the first step in the transfer of the photobiological results to the development of a clinical trial proposal for human therapy Our results demonstrated that the ZnPC/MF complex in liposome medium showed useful photophysical and photobiological properties, acting by light activation and AC magnetic field as a new generation of synergic drugs for TFD and cellular HPT.