Superparamagnetic iron oxide nanoparticles (SPIONs), due to their controllable sizes, relatively long in vivo half-life and limited agglomeration are ideal for biomedical applications such as magnetic labeling, hyperthermia cancer treatment, targeted drug delivery and for magnetic resonance imaging (MRI) as contrast enhancement agents. However, very limited studies exist on detecting and characterizing these SPIONs in vitro in physiologically relevant conditions. It would be of interest to localize and characterize individual SPIONs at the nanoscale in physiologically relevant conditions. MFM offers great potential for this purpose. We evaluate the applicability of Magnetic Force Microscopy (MFM) in air as well as in liquid to characterize bare and SiO2 coated SPIONs on mica .The magnetic properties of bare and SiO2 coated SPIONs are compared on the nanoscale using MFM. MFM phase- shift dependence on scan height is investigated using SPION samples that have been coated in hydrophobic polymers, polystyrene (PS) and poly (methyl methacrylate) (PMMA). The polymers are used to spin-coat SPION samples and mimic cell lipid bilayers. Nanoscale MFM images of SPIONs in a liquid environment, covered with these hydrophobic polymers are also presented for the first time. The use of 3-merceptopropyltrimethoxysilane (3-MPTS) to covalently attach SiO2 SPIONs to gold substrates for the potential purpose of MFM imaging in liquid is also briefly addressed. These results will allow us to understand the feasibility of detecting magnetic nanoparticles within cell membranes without any labeling or modifications and present MFM as a potential magnetic analogue for fluorescence microscopy. These results could be applied to cell studies and will lead to a better understanding of how SPIONs interact with cell membranes and have a valuable impact for biomedical applications of all types of magnetic nanoparticles.

Superparamagnetic iron oxide nanoparticles (SPIONs), due to their controllable sizes, relatively long in vivo half-life and limited agglomeration are ideal for biomedical applications such as magnetic labeling, hyperthermia cancer treatment, targeted drug delivery and for magnetic resonance imaging (MRI) as contrast enhancement agents. However, very limited studies exist on detecting and characterizing these SPIONs in vitro in physiologically relevant conditions. It would be of interest to localize and characterize individual SPIONs at the nanoscale in physiologically relevant conditions. MFM offers great potential for this purpose. We evaluate the applicability of Magnetic Force Microscopy (MFM) in air as well as in liquid to characterize bare and SiO2 coated SPIONs on mica .The magnetic properties of bare and SiO2 coated SPIONs are compared on the nanoscale using MFM. MFM phase- shift dependence on scan height is investigated using SPION samples that have been coated in hydrophobic polymers, polystyrene (PS) and poly (methyl methacrylate) (PMMA). The polymers are used to spin-coat SPION samples and mimic cell lipid bilayers. Nanoscale MFM images of SPIONs in a liquid environment, covered with these hydrophobic polymers are also presented for the first time. The use of 3-merceptopropyltrimethoxysilane (3-MPTS) to covalently attach SiO2 SPIONs to gold substrates for the potential purpose of MFM imaging in liquid is also briefly addressed. These results will allow us to understand the feasibility of detecting magnetic nanoparticles within cell membranes without any labeling or modifications and present MFM as a potential magnetic analogue for fluorescence microscopy. These results could be applied to cell studies and will lead to a better understanding of how SPIONs interact with cell membranes and have a valuable impact for biomedical applications of all types of magnetic nanoparticles.

A magnetic force microscope (MFM) is a special type of scanning force microscope which measures the stray field above a ferromagnetic sample with the help of a ferromagnetic cantilever. The aim of this project was to design and build a MFM head and interface it with a commercial scanning probe electronics controller with the help of an appropriate force sensor. The MFM head and the force sensor were to be designed to work at low temperatures (down to 4 K) and in high vacuum. During this work, a magnetic force microscope (MFM) head was designed. Its design is symmetrical and modular. Two dimensional views were prepared to ensure proper geometry and alignment for the various modules. Based on these views, individual parts in the various modules were manufactured and combined for the final assembly of the head. This MFM head has many essential and advanced features which were incorporated during the design process. Our MFM head has an outside diameter of 5 cm and thus has a low thermal mass. The head operates inside a 100 cm long vacuum can which is kept in a cold bath inside a superinsulated dewar. Other features of this MFM head include thermal compensation of the important parts, flexibility to use commercial MFM cantilevers and a large scan range compared to the previous designs. Some of the anticipated system specifications are: 1) room temperature scanning range of 175?? 175 ??m, 2) low temperature scanning range between 35-50 ??m, 3) smallest detectable magnetic force in the range of one pN and 4) smallest detectable magnetic force gradient in the range of 10-3 to 10 -5 N/m. This MFM head was interfaced to a commercial scanning probe electronics apparatus by designing a fiber-optic interferometer as the sensor for the detection of the cantilever deflection. The fiber-optic sensor also has features of its own such as stability, compactness and low susceptibility to noise because of all-fiber construction. With this MFM head, we hope to image many magnetic samples which were previously impossible to image at Texas A&M.

A magnetic force microscope (MFM) is a special type of scanning force microscope which measures the stray field above a ferromagnetic sample with the help of a ferromagnetic cantilever. The aim of this project was to design and build a MFM head and interface it with a commercial scanning probe electronics controller with the help of an appropriate force sensor. The MFM head and the force sensor were to be designed to work at low temperatures (down to 4 K) and in high vacuum. During this work, a magnetic force microscope (MFM) head was designed. Its design is symmetrical and modular. Two dimensional views were prepared to ensure proper geometry and alignment for the various modules. Based on these views, individual parts in the various modules were manufactured and combined for the final assembly of the head. This MFM head has many essential and advanced features which were incorporated during the design process. Our MFM head has an outside diameter of 5 cm and thus has a low thermal mass. The head operates inside a 100 cm long vacuum can which is kept in a cold bath inside a superinsulated dewar. Other features of this MFM head include thermal compensation of the important parts, flexibility to use commercial MFM cantilevers and a large scan range compared to the previous designs. Some of the anticipated system specifications are: 1) room temperature scanning range of 175?? 175 ??m, 2) low temperature scanning range between 35-50 ??m, 3) smallest detectable magnetic force in the range of one pN and 4) smallest detectable magnetic force gradient in the range of 10-3 to 10 -5 N/m. This MFM head was interfaced to a commercial scanning probe electronics apparatus by designing a fiber-optic interferometer as the sensor for the detection of the cantilever deflection. The fiber-optic sensor also has features of its own such as stability, compactness and low susceptibility to noise because of all-fiber construction. With this MFM head, we hope to image many magnetic samples which were previously impossible to image at Texas A&M.

The spintronic materials graphene and FeRh are of great scientific and technological interest due to their unique properties. Graphene's remarkable electronic transport and low spin interaction suggest it could be a near-perfect spin-transport material, while the equiatomic alloy FeRh undergoes a first-order antiferromagnetic (AF) to ferromagnetic (FM) phase transition when heated through a critical temperature ~370 K. Combining these materials could lead to a single multifunctional spin injection, transport and detection device in which a range of stimuli - heat, magnetic field, strain etc. - could be used to manipulate the device state. However, realisation of such a multifunctional device is extremely challenging. This thesis describes the progress made in developing a novel method of spin injection into graphene, and details a study of the metamagnetic phase transition in FeRh nanowires suitable for use as spin injection and detection electrodes. The measured values of spin lifetime and spin diffusion length in graphene are an order of magnitude lower than those predicted theoretically. In this project, a novel 1D contact geometry was investigated to determine whether the dwelling of spins underneath tunnel barrier contacts was the cause of the discrepancy. Although these devices exhibited very high charge carrier mobility - indicating successful device fabrication, defect-free graphene flakes and low levels of contamination - no spin signals were observed. Through a thorough investigation of this unexpected result it was determined that the quality of the graphene/- ferromagnetic interface was limiting the polarisation of injected spin current. The use of FeRh as a novel spin injection and detection material was investigated through magnetic force microscopy imaging of the AF and FM phases during heating and cooling sweeps. The results from FeRh full-films showed a strong dependence on surface morphology, as certain surface types were observed to favour the FM phase. These behaviours were confirmed in patterned nanowire devices, which indicated that the dependence on surface topology dominated over spatial confinement effects. In order to perform these studies a magneto-transport measurement system capable of performing measurements over a wide temperature range 2 K - 500 K in a rotatable magnetic field of up to 750 mT was developed. The noise base of the completed system was measured at just 10% above the theoretical minimum level.

The objective of this study is to discover the non-linear effect of market sentiment to characteristic factor returns. We run ¡¥Quantile Regression¡¦ to help us extract useful information and design an effective strategy. Based on the quantitative investment method, using the platform of Multi-Factor Model (MFM), we attempt to construct a portfolio and enhance portfolio performance. If the market-sentiment variable increases performance, we could conclude that some characteristic factors in a high sentiment period will perform better or worse in the next period. What is the market or investor sentiment? It is still a problem in the finance field. There is no co-definition or consensus so far. We do our best to collect the indirect data, such as transaction data, price and volume data, and some indicators in other studies, VIX, put/call ratio and so on. Then, we test the proxy variables independently, and obtain some interesting results. The market turnover, the ratio of margin lending on funds/ margin lending on securities, and the growth rate of consumer confidence index have significant effects on some of the characteristic factors. This holds that some market sentiment variables could influence stocks with certain characteristics, and the factor timing approach could improve portfolio performance under examination by information ratio.

The thesis is focused on the physics of magnetic nanoparticles (NPs), starting from the solution of magnetic structure, internal alignment within the single particle and role of interactions and particle structure in magnetic response of systems of the NPs. Moreover, the macroscopic arrangement of the NPs and its effect on the properties of system containing the NPs are discussed. The work brings several new results and concepts, such as the solution of magnetic structure of the ε-Fe2O3 phase, methods of proper detection and description of magnetic metal catalyst in carbon nanotubes and role of the NP arrangement and their effect on graphene placed on the top of substrates decorated with the NPs. 1

A procura de novas escalas de simples utilização para mensurar a função motora é um objetivo comum aos centros de atendimento de doenças neuromusculares. A nova escala de avaliação MFM (Bèrard et al., 2005), validada no Brasil por Iwabe et al. (2008), foi aplicada em 33 pacientes com DMD, com idades entre seis e dezesseis anos, cadeirantes e deambulantes, que estavam em seguimento no ambulatório de doenças neuromusculares do HCFMUSP, recebendo corticoterapia. Os objetivos foram: verificar a aplicabilidade da escala e analisar a evolução da função motora dos pacientes com DMD em corticoterapia. Os pacientes foram avaliados em cinco visitas ao longo de um período de aproximadamente 18 meses (V0, V1, V2, V3, V4 e V5). A V0 correspondeu à avaliação inicial antes do início da corticoterapia, ocorrendo um intervalo de tempo de aproximadamente três meses até a V2. Entre V3, V4 e V5, o intervalo de tempo foi de quatro meses. A MFM avalia três dimensões: D1, relativa à posição ereta e transferências, com 13 itens; D2, relativa à motricidade proximal e axial, com 12 itens; D3 que refere-se à motricidade distal, com sete itens, e o escore total que engloba todas as três dimensões. A fim de analisar funções motoras especificas de acordo com a fase de evolução da doença, foram constituídos três grupos de pacientes: deambulantes, cadeirantes e pacientes que perderam a marcha ao longo do seguimento. Os resultados demonstraram que nos pacientes deambulantes ocorreu manutenção do quadro motor até 10 a 14 meses após início do tratamento na D1 e escore MFM total. Notou-se melhora da função motora de D2 nos primeiros seis meses, com conseqüente piora após 14 meses, e ganhos funcionais para D3 em todo o seguimento. Nos pacientes que perderam a marcha e cadeirantes ocorreram perdas funcionais nas últimas visitas, exceto para a motricidade distal (D3) que se manteve estável ao longo de todo o seguimento de 18 meses. Concluímos que a escala MFM demonstra-se eficaz para monitorar a evolução da doença, valorizando períodos de melhora, assim como de estabilidade funcional frente a tratamentos específicos, detectando alterações a curto prazo, e assim facilitando a adoção de intervenções adequadas ao momento da reavaliação do paciente. A D1 da escala MFM demonstra-se adequada no acompanhamento dos pacientes que mantêm a marcha, sendo útil para prever perdas futuras da função motora do paciente com DMD / The research for new simple evaluation scales has been a common aim among neuromuscular disease rehabilitation centers. We used the new MFM scale (Bèrard et al., 2005), which was validated in Brazil by Iwabe et al. (2008) to evaluate 33 patients with DMD aged 6-16 years, both ambulant and non-ambulant. All of them were receiving corticosteroid treatment in neuromuscular disorder center at HCFMUSP. Objectives: to verify the MFM scale applicability and to analyze the motor function evolution in DMD patients treated by corticosteroids. The patients were evaluated through five visits spread out over a period of about 18 months (V0, V1, V2, V3, V4 e V5). The V0 was related to evaluation before the beginning of corticosteroids treatment at intervals of about 3 months until V2. The interval time among V3, V4 and V5 was about 4 months. The MFM scale evaluates 3 dimensions: D1, relates to standing and transfers by 13 items; D2, related to axial and proximal motor capacity by 12 items; D3 related to distal motor capacity by 7 items and the total score which includes all of the three dimensions. In order to analyze the specific motor function according to the evaluation stage, the patients were divided into 3 groups: ambulatory, non-ambulatory and those who lost the ability to walk during the study. The results showed that there was stability in the ambulatory motor function patients about 10-14 months after the beginning of corticosteroids treatment in D1 and total score MFM. We saw improvements in D2 for the first six months followed by some loss after 14 months, and improvement for D3 during all the study. In those patients who lost the ability to walk and were non-ambulatory, there was functional loss in the last visits, except for distal motor capacity (D3), which kept stable during 18 months. We conclude that the MFM scale is an effective tool for detecting the disease progression showing some improvements periods as well as the stability moments due to specifics treatments. It is possible to detect changes in a short interval which helps the choices for the adequate management at the patients revaluation. The D1 subscore of MFM scale shows to be appropriate in monitoring ambulant patients, which is useful for predicting future loss of motor function of patients with DMD

Les alliages Heusler de type Ni-Mn-X (X=In, Ga, Sn et Sb) possèdent d'intéressantes propriétés mécaniques, magnétiques et thermiques qui découlent de la transition structurale martensite-austénite. Le couplage de ces propriétés entraîne de potentielles applications dans le domaine des actionneurs, des capteurs ou des refroidisseurs. La fabrication de ces matériaux en films, d'un grand intérêt pour les microsystèmes, reste difficile à maitriser et fait l'objet de ce travail de thèse. Une partie du travail effectué durant cette thèse porte donc sur l'élaboration d'un film de type Ni-Co-Mn-In en utilisant un procédé de co-pulvérisation. L'objectif de la thèse a porté sur l'obtention d'un film présentant une transition structurale et magnétique à température ambiante. Après une étude de la structure et de la microstructure des phases martensite et austénite, les propriétés magnétiques ont été investiguées. Le changement d'état magnétique obtenu pour certains films lors de la transition du premier ordre a entrainé des propriétés magnétocaloriques et d'actionnement intéressantes. Les meilleurs résultats sont obtenus pour un film de composition Ni45,2Co4,7Mn36,2In13,9. La réalisation de mesures de résistivité sous champ magnétique intense constitue un sujet novateur sur des films de ce type. Grâce à ces mesures, une étude de l'irréversibilité et du blocage de la transformation structurale induit par le champ magnétique (kinetic arrest) a été réalisée. La compréhension des phénomènes intervenant dans l'hystérésis thermique et le blocage sous champ magnétique est en effet importante pour les applications basées sur ces matériaux à fort couplage mécanique, magnétique et thermique. / Ni-Mn-X (X=In, Ga, Sn and Sb) Heusler type alloys present interesting mechanical, magnetical and thermal properties owing to the martensite-austenite structural transition. Combining these properties induce many potentials applications in the field of actuators, sensors and coolers. Processing these materials into films is of great interest for micro-devices but remains a challenge. It shall be the purpose of this thesis. Part of this thesis shall be dedicated to the development of a Ni-Co-Mn-In Heusler film using a co-sputtering process. The main achievement of the thesis is to have obtained a film exhibiting a structural and magnetic transformation at room temperature. After a study of the structure and microstructure of martensite and austenite phases, magnetic properties are investigated. The evolution of the magnetic state during the first order transformation observed in some films leads to interesting magnetocaloric and activating properties. Optimal results, both in terms of working temperature and functional properties, are obtained for a film with a composition of Ni45,2Co4,7Mn36,2In13,9. Resistivity measurements under high magnetic field are novel on such films. These new measurements have made it possible to study the irreversibility and phase transformation blocking induced by a magnetic field (kinetic arrest). Understanding the physical effect underlying the thermal irreversibility and the blocking by a magnetic field is indeed important for applications based on such materials with strongly coupled mechanical, magnetical and thermal properties.

Ce travail de thèse porte sur l'étude des parois de domaines dans des nanofils magnétiques. Nous avons étendu le diagramme de phase des parois de domainesdéjà connu pour des géométries allant des nanobandes aux nanofils. Les différents types de parois et des transitions de phases sont présentés.Nous avons introduit de nouveaux estimateurs s'appuyant sur des grandeurs physiques connues, pour mieux caractériser les configurations magnétiques des parois et prédire leur type en fonction de la géométrie.Pour valider notre approche théorique, nous nous sommes ensuite intéressés à les observer par microscopie.Nous avons choisi le Dichroisme Circulaire Magnétique des rayons X associé à la Microscopie par Emission de PhotoElectrons (XMCD-PEEM). Ce type de microscopie permet d'atteindre une résolution spatiale suffisante pour observer les parois de domaine. Les configurations expérimentales (échantillons et dispositif expérimental) permettent d'avoir accès à la fois à l'aimantation de surface maisaussi à l'ombre du fil projetée sur le substrat. Cette ombre contient l'information sur l'aimantation dans le volume, moyennée le long du chemin desrayons X dans le matériau. Cette configuration donne lieu à des contrastes magnétiques complexes. Nous avons donc développé un modèle permettant de simuler le contraste XMCD à partir de configurations micromagnétiques à l'équilibre. La comparaison entre les contrastes expérimentaux et les contrastes simulés donne lieu à un très bon accord quantitatif.De plus, les paramètres expérimentaux ont été étudiés afin d'obtenir le meilleur contraste réflétant au mieux la configuration micromagnétique de l'échantillon.La suite de ce travail consistera, notamment, à étudier la propagation de la paroi point de Bloch dans les nanofils. / The work performed during my thesis was based on magnetic domain walls in magnetic nanowires. We extended the phase diagram of domain walls already known to a geometry ranging from nanostrips to nanowires. The various types of domain wall and transition phase types are presented. We introduced new estimators based on physical known features, in order to better characterize domain walls magnetic configurations of domain walls and then to predict the type of domain wall according to the geometry.To validate our theoretical approach, we were interested in imaging these domain walls. We chose the X-ray Magnetic Circular Dichroism along with the PhotoEmission Electron Microscopy (XMCD PEEM). This microscopy method enables to reach spatial resolution required to observed domain wall configuration. The experimental conditions (sample and set up) enable to have access both the surface magnetization and also the shadow of the wire projected on to the substrate. This enable caries information about volume magnetization, averaged along the path of the X-ray through the wire. This experimental configuration gives rise to complex contrasts. Thus, we developped a model that enables to simulate the XMCD contrast from steady state micromagnetic configurations. Comparison between experimental and simulated contrasts gives rise to a good quantitative agreement. Moreover, experimental parameters were studied in order to get the best magnetic contrast, reflecting the true magnetic configuration of the sample.For the future, the work consists in the study of the domain wall propagation in nanowires, particularly the propagation of the Bloch point wall.