Hexaferrites have a broad scope for application based on their physical properties. To study the influence of replacing cerium and gadolinium ions in hexaferrites, it is very important to understand their structural, electrical, and magnetic properties of hexaferrites. In this regard, the W-type strontium hexaferrite doped with Ce3 + and Gd3+ ions was prepared using a proteic sol-gel process under a pressure of 3000 psi and sintered at 1200º C for 2 h at a heating rate of 1 and 2º C/min. A pure W-type strontium hexaferrite was identified using X-ray diffraction (XRD); the XRD patterns exhibited increasing lattice parameters and unit cell volume as a function of doping. Scanning electron microscopy analysis indicated growth on plates with hexagonal divisions. The inserted Gd3+ and Ce3+ ions caused imbalance in the lattice. Therefore, some of the Fe3+ ions present in the octahedral site were converted to Fe2+ ions. Thus, the Curie temperature was reduced to 474º C, increasing the coercivity and reducing the superexchange interactions between Fe-O. The high saturation magnetization and low coercivity in the samples indicate that the hexaferrites are potential candidates for applications involving microwave absorption. In addition, impedance spectroscopy measurements indicated the presence of a replacement threshold with rare earth ions, which results in an increased resistivity; this is predominantly mediated by oxygen vacancies in the Ce3+-doped hexaferrite. / As hexaferritas apresentam um vasto campo de aplicações a depender de suas propriedades físicas. Estudar a influência da substituição dos íons de cério e gadolínio é de suma importância para entender como funciona o mecanismo de obtenção das propriedades estruturais, elétricas e magnéticas nas hexaferritas. Dessa forma, a hexaferrita de estrôncio tipo W foi dopada com íons de Ce3+ e Gd3+ foi obtida via processo sol-gel proteico à 3000 psi e sinterizada a 1200º C/2h com taxa de aquecimento de 1 e 2 /C/min. A fase pura da hexaferrita de estrôncio tipo W foi identificada por difração de raios X com aumento dos parâmetros de rede e volume da cela unitária em função da dopagem. As análises de microscopia eletrônica de varredura indicam o crescimento em placas com clivagens hexagonais. . Os íons de Gd3+ e Ce3+ quando inseridos provocou um desbalanceamento de cargas, levando a transformação de certa quantidade de íons Fe3+, presente no sítio octaédrico, para Fe2+. Tal fato leva a redução da temperatura de Curie para 474º C, aumento da coercividade e redução das interações de super troca entre Fe-O. A alta magnetização de saturação e baixa coercividade apresentadas pelas amostras, indicam que as hexaferritas são considerados candidatos em potencial para fins de absorção de micro-ondas. Além disso, as medidas de espectroscopia de impedância indicam que existe um limiar de substituição com os íons terra rara para que haja aumento da resistividade e a condução ocorra predominantemente mediada por vacâncias de oxigênio na hexaferrita dopada com íon de Ce3+. Palavras

This diploma thesis focuses on the preparation of the liposomes, containing lipids with gadolinium, which are used for a contrast magnetic resonance imaging. The liposomes were prepared by the lipid film hydration followed by an extrusion and also by a new nanofluid mixing method on the NanoAssemblr Benchtop. The preparation technology has been optimized for parameters such as the composition of lipids, the flow rate ratio and total flow rate. The method of modification of the liposomes surface by gadolinium complexes has been developed. This method is using a conjugation reaction between the lipids containing cyanuric acid and Gd-DOTA. Prepared Gd-liposomes, which contain gadolinium, were complexly defined by the characterization techniques of DLS and NTA. The morphology of liposomes was observed by TEM and cryo-TEM. Methods for the determination of phospholipid content (Stewart test) and residual water in the lyophylisates of liposomes (Karl-Fischer titration) were used. Gadolinium in liposomal preparations was determined by ICP-OES. Using MR, the concept of gadolinium liposomes was verified and designed for MRI imaging of thrombi. The concept describing the mechanism of liposomes formation based on the experimentally proven existence of a phospholipid bilayer fragment has been developed. This concept is based on the experimentally proven existence of a phospholipid bilayer fragment.

L’Imagerie par Résonance Magnétique est une technique d’imagerie possédant une des plus hautes résolutions d’images, utilisée pour le diagnostic clinique et en recherche. Cependant cette technique souffre d’une faible sensibilité intrinsèque due au faible contraste naturel entre les différents tissus. Pour pallier à cette limitation, des agents de contraste, principalement des complexes de Gd(III), sont actuellement utilisés et continus d’être développés. Ce projet de thèse s’inscrit dans la volonté de concevoir de nouveaux agents de contrastes plus efficaces et plus stables en utilisant la β- et l’α-cyclodextrines (CD) comme plateforme capables d’intégrer trois ou quatre fonctions pyridine-carboxylates ou pyridine-phosphonates, connues pour leur pouvoir chélatant du Gd(III). La première partie des travaux concerne les aménagements fonctionnels des CDs afin de pouvoir les fonctionnaliser régiosélectivement avec des bras chélatants du Gd(III) de types pyridino-carboxylate et pyridino-phosphonate. La deuxième partie traite de la caractérisation physico-chimique des nouveaux systèmes complexes Gd-ligands synthétisés (Gd-Lα et Gd-Lβ). Les principales propriétés caractérisant les agents de contraste ont été mesurées. Ainsi, de très bonne relaxivités ont été obtenue (25 mM-1s-1 < r1 < 40 mM-1s-1). Cependant, les stabilités des complexes se sont avérées faibles (4,24 < log KGdL < 5,58). En perspectives, il est nécessaire d’obtenir un juste équilibre entre une forte relaxivité et une stabilité élevée pour assurer la non-libération du Gd(III) toxique. / Magnetic Resonance Imaging is one of the most important and non-invasive tools for clinical diagnostics and biomedical researches. Nevertheless, this modality suffers from intrinsic low sensitivity. To overcome this limitation, contrast agents, mostly based on polyaminocarboxylate complexes of gadolinium are used. The aim of this project was to design new Gd(III)-based contrast agents using β- and α-cyclodextrins (CD), known to generate high relaxivity, functionalized with pyridine-carboxylate and pyridine-phosphonate ligands, known for their good affinity with the lanthanide cations. Here we first investigated the regio-functionalization of the β-CD on the primary face to access to scaffold called Lβ with four pyridine-carboxylate ligands. To develop an efficient and reproducible synthesis, HPLC analysis was implemented. Then, using these conditions, carboxylate- and phosphonate-ester, precursors to access α-CD ligands Lα and Lα’, were synthesized. The carboxylate-ester deprotection step successfully afforded the ligand noted Lα contrary to the deprotection of phosphonate ester which still have to be explored. Characterizations of these complicated Gd-ligands systems (Gd-Lα et Gd-Lβ) were reported. Their stability and relaxivity were measured and very good relaxivities were obtained (25 mM-1s-1 < r1 < 40 mM-1s-1). These new structures open the way to an improvement in term of stability.

This project presents an attempt to construct a setup and implement a reliable technique for measuring the magnetocaloric effect (MCE) on various materials via a direct method for the acquisition of the data. The main objective of the latter is to produce a ∆Tadiabatic vs T graph over a reasonable temperature span (-100◦C up to 220◦C) by thermal monitoring of a magnetic material exposed to an oscillating magnetic field with a maximum strength of 1.2T. The setup consists of a vacuum-insulated glass tube containing the sample placed between two electromagnets of a vibrating-sample magnetometer (VSM) and increasingly heated by a resistance wire, while the temperature is recorded directly by a thermocouple. The first experiments are performed on Gadolinium (Gd) samples as a reference material in order to verify the overall reliability of the system. The obtained results on Gadolinium show that meaningful data can be acquired with this direct method, although the initially-extracted ∆Tadiabatic near room temperature stands at the accuracy limit (25%) generally accepted with this method. Unexpected interference signals from the thermocouple are encountered for high temperatures and are shown to be due to magnetic dependence from one of its constituents. Data from high temperatures can however be reliably corrected with respect to a baseline signal from a neutral nonmagnetic material. As such magnetocaloric properties of two Manganese-rich high entropy alloys are investigated with one exhibiting at most ∆Tadiabatic = 0.2◦C at its Curie temperature TC = 60◦C. Suggestions regarding the possibility of operating the setup at sub-zero temperatures are put forward and promising results from a new spot- welded thermocouple show a significantenhancement of the initial setup accuracy. / Detta projekt presenterar ett försök att konstruera en installation och implementera en pålitlig teknik för att mäta den magnetokolorisk effekten (MCE) på olika material via en direkt metod för insamling av data. Det sistnämnda syftet är att producera en ∆Tadiabatisk vs T över ett rimligt temperaturintervall (-100◦C up to 220◦C). Detta genom en termisk övervakning av ett magnetiskt material utsatt för ett oscillerande magnetfält med en maximal magnitud på 1.2 T. Utrustningen utgörs av ett vakuumisolerade glasrör som innehåller provet, vilket är placerat mellan två elektromagneter från en vibrating-sample magnetometer (VSM) och som stegvis värms upp av en resistanstråd, medan temperaturen registreras direkt av ett termoelement. De inledande experimenten utförs på prover av Gadolinium (Gd) som referensmaterial för att verifiera systemets totala tillförlitlighet. De erhållna resultaten från Gadolinium proverna visar att meningsfulla data kan produceras med denna direkta metod. Även om de extraherade ∆Tadiabatisk vid rumstemperatur befinner sig inom precisions gränsen (25%), vilken är allmänt accepterad med avseende på den direkta metoden. Oväntade missvisande signaler från termoelementet uppträder vid höga temperaturer och visar sig bero på magnetiskt beroende från instumentet. Data från höga temperaturer kan emellertid pålitligt korrigeras med en baslinjesignal från ett neutralt icke-magnetiskt material. Därmed undersöks de magnetokoloriska egenskaper hos två Mangan-rika hög entropi legeringar, där en uppvisar som högst ∆Tadiabatisk = 0.2◦C vid dess Curie-temperatur TC = 60◦C. Förslag beträffande möjligheten att använda installationen vid temperaturer under noll läggs fram. Lovande resultat från ett nytt punktsvetsat termoelement visar en betydande förbättringav den inledande installationens noggrannhet.

Proton MR spectroscopy is a tool that provides quantified brain bioprofiles. Two methods exist: single- and multi-voxel spectroscopy. No studies compare their clinical validity in vivo. Gadolinium based MR contrast agents are used to improve lesional conspicuity. Adverse events are reported. Brain deposition occurs following administration in people and murine models. In dogs, doses are anecdotal and deposition is not described. Eight normal dogs underwent MRI at 3 Tesla with two methods of spectroscopy and were administered varying doses of gadodiamide. No differences were seen between single- and multi-voxel spectroscopy when interrogating identical regions of interest. Brains were harvested and evaluated for gadolinium depots using inductively coupled plasma mass spectrometry. Gadolinium was found in the brains of all dogs with dose dependency. Further, adequate normal brain conspicuity was seen at a dose of 0.5 mmol/kg. Thus, clinical trials of gadolinium chelated contrast agents at this dose are recommended.

<p>This thesis contains two parts; Both of which are parts of the requirements for the Degree of Master of Engineering </p> </p> <p> Part A: Industrial Project</p> </p> <p> Part B: McMaster (On-Campus) Project </p> / <p> This document reports the results of a study of several parameters of a neutron radiographic system of the direct conversion type, and of their effects on certain image characteristics. These parameters are: thickness of the converter, backing material of the very thin converter layers, level of water in the beam tube, exposure time, and film type. The image characteristics are relative optical density, specific contrast, and unsharpness, the latter interpreted quantitatively through the edge-spread function. Theoretical treatments and empirical data are presented and compared. Emphasis is put on investigations of the perfonnance of thin (~2000 A) layers of gadolinium converter, and on the experimental analysis of the edge-spread function. </p> / Thesis / Master of Engineering (ME)

Neutron detection is important in several fields, especially detection of illicit nuclear material. Historically, 3He has been the basis for these technologies. Modern realities have necessitated the development of new technologies and the exploration of new materials to meet this need. One potential solution is known as capture-gating, which is a measurement approach that is good at differentiating between incident neutrons and gamma rays. The key issue is that materials used in current capture-gating devices can suffer from poor optical performance. This is due to the fact that the these detectors, whether composed of a heterogeneous or homogeneous mixture of materials, are made of dissimilar materials. In the homogeneous case, this frequently results in a cloudy material (e.g. lithium-gadolinium-borate crystals), while heterogeneous cases suffer from index mismatch (e.g. glass inside a plastic scintillator). The goal of this thesis is material development and processing toward an index-matched, gadolinium-based glass, heterogeneous capture-gated neutron detector. This involved identifying the refractive index range of known gadolinium glasses and the development of polystyrene (PS) and polyvinyl toluene (PVT) co-polymers with a range of refractive indices. Specifically 1:3, 1:1, and 3:1 PS:PVT ratios were manufactured and their refractive indices were compared to those of pure PS and PVT. Two methods for uniform glass dispersion were explored; the use of a rotisserie oven and the use of centrifugal planetary mixer. Ellipsometry, refractometry, and spectroscopic transmission were all performed to optically evaluate the manufactured polymers and polymer/glass composites. The ability to produce a PS/PVT copolymer with a refractive index in the range of known gadolinium glasses was demonstrated. In addition, the benefit of matching the refractive indices when producing a glass/polymer composite was explored and the effect of index mismatch was observed. The ability to predict the refractive index of a PS/PVT blend was demonstrated but can still be improved upon. While a novel index-matched gadolinium-based heterogeneous capture-gated neutron detector was not developed as part of this work, progress was made on all material aspects to further develop a detector meeting that description. More work still needs to be done in fine tuning the index match of the glass and polymer components, in determining the ideal method of glass dispersion, and in producing larger samples.

Tableau d’honneur de la Faculté des études supérieures et postdoctorales, 2012-2013. / L'objectif principal de ce projet de doctorat est de développer et de caractériser un agent de contraste pour la détection in vivo, en imagerie par résonance magnétique (IRM) pondérée en T₁; d'un groupe de cellules préalablement marquées in vitro. Le but de ce marquage est de visualiser et de suivre le développement de cellules après leur implantation dans un modèle préclinique et ce, en contraste "positif". Pour ce faire, la stratégie choisie pour cette thèse est de synthétiser des nanoparticules ultrafines (< 3 nm) d'oxyde de gadolinium recouvertes d'un ligand biocompatible. La première étape de ce projet consistait, après optimisation d'une synthèse de nanoparticules de Gd₂O₃ recouvertes de diéthylène glycol, à mener une expérience d'ingestion cellulaire avec des cellules de glioblastome multiforme de souris (GL-261). Le rehaussement du signal des cellules en IRM a été démontré après l'ingestion, tout comme la possibilité de les détecter après une implantation sur la membrane chorioallantoïque d'un oeuf de poulet fertilisé. Des études MET ont révélé que les particules s'accumulent et s'agrègent dans les endosomes cellulaires pendant l'ingestion. La seconde étape de la thèse a donc consisté à analyser in vitro, en milieu aqueux, l'impact de cette agrégation sur les propriétés relaxométriques des particules. Pour ce faire, des analyses MET, DLS et avec des relaxomètres à champs magnétiques variables ont été menées. Ces études ont démontré que l'agrégation influence les propriétés relaxométriques des suspensions de Gd₂O₃, surtout à champs magnétiques élevés (> 7 T, ou 300 MHz). Finalement, une synthèse alternative en une étape, recouvrant les nanoparticules de polyethylene glycol (PEG), a été développée afin de limiter l'agrégation. Les propriétés physicochimiques des particules de PEG-Gd₂O₃ (1,3 nm) ont été étudiées par MET, DLS, DRX, EDS, FTIR et ATG. Les relaxivités longitudinale et transverse mesurées à 1.41 T (60 MHz, 37°C, pH 5) ont été de 14,2 et 17,2 mM⁻¹s⁻¹. La performance de ce produit de contraste a été testée en injectant in vivo des cellules de glioblastome multiforme (F98) préalablement marquées. Les cellules implantées ont été visualisées en IRM et ont toutes développé des tumeurs cérébrales malignes en quelques jours. En conclusion, les nanoparticules développées auront permis de détecter efficacement des cellules implantées in vivo.

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