Nuclei at closed shells tend to be spherical and are well-described by the shell model, while those between closed shells are deformed and better described by collective models. The nuclei which are in transitional regions between spherical and deformed may be studied to gain insight into the nature of this transition. The stable isotopes of zirconium and xenon span such transitional regions and are the subject of this dissertation. Gamma-ray spectroscopy following inelastic neutron scattering has been performed on the stable isotopes of Zr as well as 132,134Xe at the University of Kentucky Accelerator Laboratory. Level lifetimes have been measured using the Doppler-shift attenuation method, which allow the determination of transition probabilities that are of utmost importance in elucidating the structure of these nuclei. The lifetime measurements were the focus of the study of the Zr isotopes. Previously measured level lifetimes in 94Zr by our group were called into question by recent electron scattering experiments. This motivated a re-measurement of these lifetimes and led to a study of the role of the chemical properties of the scattering samples employed in the measurements. Various Zr-containing compounds were characterized with powder X-ray diffraction and scanning electron microscopy and were employed as scattering samples. These studies revealed the impact of using amorphous materials and those composed of small particles as scattering samples on the resulting lifetimes, and has important implications for future lifetime measurements employing the Doppler-shift attenuation method. For the xenon experiments, highly enriched (>99.9%) 132Xe and 134Xe gases were converted to solid 132XeF2 and 134XeF2, and were used as scattering samples. The xenon isotopes have not been particularly well-studied as elemental targets are gases under ambient conditions, which introduces difficulties into the measurements. Much new information was obtained for these nuclei, including the placement of many new transitions and levels, and measurement of many new level lifetimes, allowing the determination of reduced transition probabilities. This additional information provided important insight into the structure of these two transitional nuclei.

While neutrino oscillations indicate that neutrino flavors mix and that neutrinos have mass, they do not supply information on the absolute mass scale of the three flavors of neutrinos. Currently, the only viable way to determine this mass scale is through the observation of the theoretically predicted process of neutrinoless double-beta decay (0νββ). This yet-to-be-observed decay process is speculated to occur in a handful of nuclei and has predicted half-lives greater than 10²⁵ years. Observation of 0νββ is the goal of several large-scale, multinational efforts and consists of detecting a sharp peak in the summed β energies at the Q-value of the reaction. An exceptional candidate for the observation of 0νββ is ⁷⁶Ge, which offers an excellent combination of capabilities and sensitivities, and two such collaborations, MAJORANA and GERDA, propose tonne-scale experiments that have already begun initial phases using a fraction of the material. The absolute scale of the neutrino masses hinges on a matrix element, which depends on the ground-state wave functions for both the parent (⁷⁶Ge) and daughter (⁷⁶Se) nuclei in the 0νββ decay and can only be calculated from nuclear structure models. Efforts to provide information on the applicability of these models have been undertaken at the University of Kentucky Accelerator Laboratory using gamma-ray spectroscopy following inelastic scattering reactions with monoenergetic, accelerator-produced fast neutrons. Information on new energy levels and transitions, spin and parity assignments, lifetimes, multipole mixing ratios, and transition probabilities have been determined for ⁷⁶Se, the daughter of ⁷⁶Ge 0νββ, up to 3.0 MeV. Additionally, inaccuracies in the accepted level schemes have been addressed. Observation of 0νββ requires precise knowledge of potential contributors to background within the region of interest, i.e., approximately 2039 keV for ⁷⁶Ge. In addition to backgrounds resulting from surrounding materials in the experimental setup, ⁷⁶Ge has a previously observed 3952-keV level with a de-exciting 2040-keV γ ray. This γ ray constitutes a potential background for 0νββ searches, if this level is excited. The cross sections for this level and, subsequently, for the 2040-keV γ ray has been determined in the range from 4 to 5 MeV.

High pressure, high magnetic field and low temperature techniques are required to investigate magnetic transitions and quantum critical behaviour in different ferromagnetic materials to elucidate how novel forms of superconductivity and other new states are brought about. In this project, several instruments for magneto-transport and neutron scattering measurements have been designed and built. They include inserts for a dilution refrigerator and pressure cells for resistivity, magnetic susceptibility and inelastic neutron scattering measurements. The technical drawings of the low temperature inserts and pressure cells were produced with Solid Edge computer-aided software and the performance and safety assessments were evaluated with the ANSYS finite element analysis package. The pressure cells developed include diamond anvil cells, piston cylinder cells and some auxiliary equipment. Pressure effects on the physical properties such as the electrical resistivity and magnetic ordering of some ferromagnetic materials were studied with the equipment developed. A two-axis rotating stage was developed and deployed with a dilution refrigerator combined within a superconducting magnet to measure various physical properties as a function of the orientation of the sample with respect to applied field at sub-Kelvin temperature. The rotating stage is made of Beryllium Copper (BeCu) alloy. In order to avoid the entanglement of the wires, custom-designed “flexi cables” - copper tracks printed on a Kapton foil with a yield of nearly 100% - to work with the rotating stage were manufactured. The performance of the rotating stage has been demonstrated by a quantum oscillation in the electrical resistivity study of a high field ferromagnetic superconductor URhGe. A miniature diamond anvil cell based on the turnbuckle principle has been designed. The cell, made of BeCu alloy, is 7mm in length and 7mm in diameter. It has been shown to reach a maximum pressure of 10 GPa with diamond anvils with 800 μm culets. The small dimensions of the cell allow it to fit into the existing sample environment such as Physical Properties Measurement System (PPMS) and Magnetic Properties Measurement System (MPMS) from Quantum Design, USA, and onto the customized two-axis rotating stage built for the dilution fridge. It also thermalizes rapidly allowing rapid cooling and heating during the experiments. The cell can be used to make both resistivity and magnetic susceptibility measurements. To ensure the hydrostaticity of the pressure around the sample in the turnbuckle cell, a gearbox was designed for cryogenic loading of liquid argon and room temperature gas loading of either helium or argon at a loading pressure of up to 0.3 GPa. Pressure effects on the Curie temperature of a PrNi ferromagnet were studied in a diamond anvil cell. Four-probe resistance measurements under pressures up to 9 GPa were carried out in a PPMS. The possibility of tuning the physical properties of the material by altering the pressures has been demonstrated. By analysing the results of the electrical resistivity measurements under pressures, it was concluded that the Curie temperature of PrNi increases with pressure at the rate of 0.85 K per GPa. The quantity ∆(δρ/δτ)which reflects some part of the entropy change also increases with pressure. The expected quantum critical point has not been observed in this material up to 9 GPa. A large volume high-pressure piston-cell for inelastic neutron scattering measurements has been designed and can reach a pressure of up to 1.8 GPa with a sample volume in excess of 400 mm3. The dimension of the part of the cell exposed to the neutron beam has been optimized to minimize the attenuation of the neutron beam. The novel design of the piston seal also eliminates the use of a sample container, which makes it possible to accommodate larger samples and reduces the absorption. The pressure in the cell is measured by a manganin pressure gauge placed next to the sample. The performance of the cell was illustrated by an inelastic neutron scattering study of UGe2.

Electrochemical capacitors, now often termed supercapacitors, are high power electrochemical energy storage devices that complement or replace high power batteries in applications ranging from wind turbines to hybrid engines to uninterruptable power supplies to electronic devices. My dissertation explores the applications of relatively uncommon techniques for both supercapacitor material syntheses and gaining better mechanistic understanding of factors impacting electrochemical performance of supercapacitors. From fundamental ion electroadsorption studies made possible by using small angle neutron scattering (SANS), to the systematic investigations of coating thickness and microstructure in metal oxide / carbon nanocomposite electrodes realized through the novel use of the atomic layer deposition (ALD) technique, new avenues of material characterization and fabrication have been studied. In this dissertation I first present the motivation to expand the knowledge of supercapacitor science and technology, and follow with an in-depth literature review of the state of the art. The literature review covers different types of supercapacitors, the materials used in the construction of commercial and exploratory devices, an exploration of the numerous factors which affect supercapacitor performance, and an overview of relevant materials synthesis and characterization techniques The technical objectives for the work performed in this dissertation are then presented, followed by the contributions that I made in this field in my two primary research thrusts: advances to the understanding of ion electroadsorption theory in both aqueous and organic electrolytes through the development of a SANS-based methodology, and advances to metal-oxide carbon nanocomposites as electrodes through the use of ALD. The understanding of ion electro-adsorption on the surface of microporous (pores < 2 nm) solids is largely hindered by the lack of experimental techniques capable of identifying the sites of ion adsorption and the concentration of ions at the nanoscale. In the first research thrust of my dissertation, I harness the high penetrating power and sensitivity of neutron scattering to isotope substitution to directly observe changes in the ion concentration as a function of the applied potential and the pore size. I have conducted initial studies in selected aqueous and organic electrolytes and outlined the guidelines for conducting such experiments for the broad range of electrode-ions-solvent combinations. I unambiguously demonstrate that depending on the solvent properties and the solvent-pore wall interactions, either enhanced or reduced ion electro-adsorption may take place in sub-nanometer pores. More importantly, for the first time I demonstrate the route to identify the critical pore size below which either enhanced or reduced electrosorption of ions takes place. My studies experimentally demonstrate that poor electrolyte wetting in the smallest pores may indeed limit device performance. The proposed methodology opens new avenues for systematic in-situ studies of complex structure-property relationships governing adsorption of ions under applied potential, critical for rational optimization of device performance. In addition to enhancing our understanding of ion sorption, there is a critical need to develop novel supercapacitor electrode materials with improved high-energy and high-power characteristics. The formation of carbon-transition metal oxide nanocomposites may offer unique benefits for such applications. Broadly available transition metal oxides, such as vanadium oxide, offer high ion storage capabilities due to the broad range of their oxidation states, but suffer from high resistivities. Carbon nanomaterials, such as carbon nanotubes (CNT), in contrast are not capable to store high ion content, but offer high and readily accessible surface area and high electrical conductivity. In the second research thrust of my thesis, by exploiting the ability of atomic layer deposition (ALD) to produce uniform coatings of metal oxides on CNT electrodes, I demonstrated an effective way to produce high power supercapacitor electrodes with ultra-high energy capability. The electrodes I developed showed stable performance with excellent capacitance retention at high current densities and sweep rates. Electrochemical performance of the oxide layers were found to strongly depend on the coating thickness. Decreasing the vanadium oxide coating thickness to ~10 nm resulted in some of the highest values of capacitance reported to date (~1550 F·g⁻¹VOx at 1 A·g⁻¹ current density). Similar methodology was utilized for the deposition of thin vanadium oxide coatings on other substrates, such as aluminum (Al) nanowires. In this case the VOₓ coated Al nanowire electrodes with 30-50% of the pore volume available for electrolyte access show volumetric capacitance of 1390-1950 F cc⁻¹, which exceeds the volumetric capacitance of porous carbons and many carbon-metal oxide composites by more than an order of magnitude. These results indicated the importance of electrode uniformity and precise control over conformity and thickness for the optimization of supercapacitor electrodes.

Various experiments on Yb₂Ti₂O₇ have shown evidence of strange magnetic behaviour at low temperatures. Specific heat measurements on powder samples of Yb₂Ti₂O₇ show evidence of a sharp peak, indicating the occurence of a first order phase transition. Meanwhile, neutron scattering, Mössbauer absorption, and μSR measurements find no evidence of long range order below the temperature of this phase transition, leaving the nature of the low temperature phase a mystery. Quantifying the magnetic interactions in this material should allow us to better understand the low temperature behaviour of this material. In this study, we fit a symmetry allowed nearest-neighbour bilinear exchange model to quasi-elastic neutron scattering data collected well above the temperature of the experimentally observed phase transition. This neutron scattering data shows evidence of rods of scattering intensity along the ⟨111⟩ crystallographic directions. Neutron scattering probes the correlations between magnetic moments in a material, so fitting an interaction model to the neutron scattering is equivalent to fitting the interactions to the magnetic correlations. These correlations are driven by the interactions between the magnetic moments, so the neutron scattering should give us direct access to the form of these interactions. Using this method we successfully identify an anisotropic nearest-neighbour bilinear exchange model that reproduces the experimentally observed quasi-elastic neutron scattering. With this model we then proceed to compute real space correlation functions, finding that the rods of neutron scattering arise from the presence of strong correlations along nearest-neighbour chains. We also compute the bulk susceptibility and local susceptibility, obtaining very good fits to experiment with no variation of the model determined from the neutron scattering. The success of these calculations provides a further independent confirmation of the success of our interaction model in describing the magnetic interactions in Yb₂Ti₂O₇. Finally, we present a brief summary of ongoing work based on our anisotropic exchange model, including mean field calculations to determine the low temperature ground state of this model and classical Monte Carlo simulations to study the phase transition present in this model. We also discuss potential further studies of this and other models.

La poursuite de nouveaux angles de recherche est depuis toujours l'un des facteurs clés du progrès scientifique. Au travers de ce travail, nous amenons de nouveaux éléments permettant d'ouvrir une discussion sur la dynamique moléculaire et la structure des biomolécules, étudiées par diffusion neutronique sous haute pression. Le projet d'étude s'axe sur différents sujets ayant pour dénominateur commun la haute pression en biologie, fil conducteur de ces recherches. L'intérêt de la haute pression en biologie n'est pas a priori évident ; pourtant, un grand nombre de points stimulent ce champ d'investigation. Une partie conséquente de la biosphère subit un environnement sous haute pression : les organismes barophiles des grands fonds marins subissent des conditions de stress uniques, qui soulèvent des questions sur l'adaptation biologique. D'autre part, la haute pression trouve un intérêt concret dans l'agro-alimentaire pour la conservation alimentaire ou, nouvellement, la fabrication de vaccins. Cependant, ces recherches se situent en aval des travaux qui nous intéressent dans cet ouvrage. La thèse présentée donne une vision plus théorique, ou phénoménologique, de processus tels que des états métastables protéiques, leur dénaturation, ou encore l'étude de la transition dynamique, aux travers d'expériences adaptées au besoin du sujet entrepris. Un tel travail ne permet pas de couvrir toutes les informations nécessaires pour aborder une vision globale du sujet. L'ouvrage se concentre donc sur l'étude par diffusion neutronique des effets de la pression en biophysique pour élaborer de nouvelles possibilités de recherches, qui seront discutées ici. / Seeking new research options have always been the heart of scientific progress. Through this work, new elements are brought to start a discussion about molecular dynamics and biomolecule structure studied through high pressure experiments with neutron scattering. The project explores different subjects all gathered around the high pressure guideline. High pressure interest in biology might seem quite opaque: however, a large amount of points justifies this investigation field. A large part of the biosphere undergoes high pressure stress due to the fact of its presence in the deep sea, raising question about biological adaptation to high pressure environment, for example. High pressure in the last decades has raised interest on other purposes like food conservation or vaccine fabrication. These research fields are on the final stage of the steps studied in this work, that starts its origin through more theoretical and phenomenological events. The manuscript covers different areas such as dynamical transition or metastable state and denaturation of proteins through experiments designed to the need of the research. Such a field requires a gigantic amount of investigation while restraining the possibilities of generalization. Thus, the work is focused on neutron scattering as a probe for high pressure studies in biophysics in order to elaborate new research clues in the field dealt with.

L'objectif de la thèse était d'étudier les propriétés structurales et dynamiques de deux systèmes biologiques, avec une approche centrée sur les techniques de diffusion de neutrons. Les premier système biologique porte sur le système de transport FHA/FhaC de la bactérie à Gramm négatif Bordetella pertussis. C'est un modèle pour le système de transport bactérien à deux partenaires (TPS), qui est largement utilisé par de nombreuses bactéries à Gramm negatif, essentiellement pour excréter des facteurs de virulence. Cette thèse comporte une analyse structurale sur le complexe chaperonneprotéine client Fha30/Par27 mais aussi une étude sur les propriétés mécaniques de Fha30, qui possède une structure particulière en hélice beta. Le deuxième système porte sur le complexe de réplication des virus de la famille des Rhabdoviridae. Outre son importance en termes de santé humaine, le complexe de réplication comporte des protéines aux propriétés qui, sur le plan structural, sont très intéréssantes, comme par exemple la phosphoprotéine qui comporte des parties structurées reliées par des parties dépourvues de structure. On trouvera dans cette thèse une étude des propriétés dynamiques des différents domaines de la phosphoprotéine, mais aussi une étude structurale sur le complexe que celle-ci forme avec la nucleoprotéine. / The main goal of this thesis is to study the dynamical and structural properties of two biological systems, with an aproach centered on neutron scaterring techniques. The first system consists of the transport system FhaB/FhaC from Gramm negative bacteria Bordetella pertussis. It is a model system for the so called Two Partner Secretion (TPS) system, wich is widespread among Gramm negative bacteria to export virulence factors to the medium. This thesis emphasizes on the complexe Fha30, a N-terminal fragment of FHA, forms with the periplasmic chaperonne Par27, and on the mechanical properties of FHA, which has an uncanny beta helix structure. The other system is the replication complex of the Rhabdoviridae virus family. Apart from it's importance in humant health issues, the replication complex is composed of proteins with interesting structural and dynamical properties, specially the phosphoprotein which is composed of structured parts linked by flexible linkers. This thesis emphasizes on the dynamical properties of different fragments of the phosphoprotein, but also on the structural aspects of the complex the latter forms with the nucleoprotein. . Le deuxième système porte sur le complexe de réplication des virus de la famille des Rhabdoviridae. Outre son importance en termes de santé humaine, le complexe de réplication comporte des protéines aux propriétés qui, sur le plan structural, sont très intéréssantes, comme par exemple la phosphoprotéine qui comporte des parties structurées reliées par des parties dépourvues de structure. On trouvera dans cette thèse une étude des propriétés dynamiques des différents domaines de la phosphoprotéine, mais aussi une étude structurale sur le complexe que celle-ci forme avec la nucleoprotéine.

In this work, microfluidic and millifluidic droplets are utilized to study and control complex fluid behavior with high composition resolution. Different techniques are used on two length scales to create unique approaches towards the same goal of merging droplet-based experiments with classical colloidal characterization experiments. First, a microfluidic dehydrating droplet device is characterized and a procedure established by concentrating a phase separating organic-inorganic system on chip and using geometric calculations to determine composition. The device is then expanded to a more complex, particle-polymer system to investigate suspension stability and interparticle behavior. A model system containing silica particles and PEO polymer is found to transition from a bridging flocculation mechanism to polymer-coated particle jamming based on the mass ratio of polymer to particle. Lastly, a phase separating particle-polymer system consisting of polystyrene particles and hydroxyethyl cellulose is concentrated on-chip. Interparticle interactions are controlled by varying particle size, polymer size, and polymer type and the effects on phase behavior are examined. Droplet experiments are scaled-up to millifluidic droplets and concentration gradients are used to produce high composition resolution in place of time, used in the dehydrating microfluidic experiments. A novel, millifluidic containment device is created to study aggregation and sedimentation in droplets containing carbon black and OLOA surfactant suspended in dodecane. A slow increase in stabilization behavior is observed as opposed to the previously observed sharp “on-off” effect. The droplet production technique is then improved to achieve more complex composition paths and the device is expanded for a small angle neutron scattering (SANS) application. SANS is performed on flowing droplets with varying concentration to map interparticle interactions and phase behavior of complex particulate systems. Feasibility of device is demonstrated and preliminary model systems of silica particles and polymer, salt, and surfactant are analyzed and characterized.

Keratins are important structural components of hair and skin. There has been extensive study of keratins from the health and medical perspectives, although little work has been done to date to investigate their basic physicochemical properties in the form of biomaterials. The work presented in this thesis aimed to study surface and interfacial adsorption and solution aggregation of water soluble keratin polypeptides (made available by previous work within the research group). A range of physical techniques were employed including spectroscopic ellipsometry (SE), neutron reflection (NR), dual polarisation interferometry (DPI), quartz crystal microbalance with dissipation (QCM-D), dynamic light scattering (DLS) and small-angle neutron scattering (SANS).A major technical advantage of the neutron techniques is the use of hydrogen/deuterium substitution to enhance structural resolution. This approach was explored to study the interaction of keratins with both conventional surfactants and novel biosurfactants. The work presented comprises four results chapters. The first examines and compares four widely used interfacial techniques, SE, DPI, QCM-D and NR, by studying the adsorption of C12E6 at the silicon oxide/water interface. Whilst the data exhibits a large degree of consistency in the interfacially adsorbed amount, each technique helped reveal unique structural information with a high degree of complementarity. The second results chapter reports on findings regarding the properties of keratin polypeptides in surface adsorption and solution aggregation. It was found that the keratins adsorbed strongly on the surface of water, and formed rugby-shaped nanoaggregates in solution, the size and shape of which responded to salt concentration. The third results chapter reports on the interfacial behaviour of keratin/surfactants complexes in bulk solution, with cationic DTAB and anionic SDS as model conventional surfactants. It was found that both the electrostatic and hydrophobic forces contributed strongly to the surface adsorption processes. The final results chapter reports on interactions of a coated keratin film with novel biosurfactants including rhamnolipids (R1 and R2 with 1 and 2 sugar head(s), respectively) and Mel-C. The keratin films formed were found to be exceptionally stable and reproducible below pH 8, and these films could be widely used as model keratin substrates for screening their binding with surfactants and bioactive molecules. Both rhamnolipids and Mel-C exhibited strong adsorption onto the keratin substrate and interestingly, whilst R1 exhibited a completely reversible adsorption, R2 showed only a partially reversible adsorption. Mel-C showed some degree of irreversible adsorption similar to R2 and exhibited the strongest adsorption at around pH 4-5. These results show mild interactions with the keratin substrate, but indicate that the extent of adsorption and desorption could be manipulated by surfactant structure or solution conditions. The findings presented in this thesis are fundamental in aiding the development of the use of keratin polypeptides as biomaterials, in applications such as personal care. The work is also highly relevant to the understanding of the interactions between surfactants and keratin molecules at interfaces and in solution.

New and more efficient magnetic materials for energy applications are a big necessity for sustainable future. Whether the application is energy conversion or refrigeration, materials based on sustainable elements should be used, which discards all rare earth elements. For energy conversion, permanent magnets with high magnetisation and working temperature are needed whereas for refrigeration, the entropy difference between the non-magnetised and magnetised states should be large. For this reason, magnetic materials have been synthesised with high temperature methods and structurally and magnetically characterised with the aim of making a material with potential for large scale applications. To really determine the cause of the physical properties the connections between structure (crystalline and magnetic) and, mainly, the magnetic properties have been studied thoroughly. The materials that have been studied have all been iron based and exhibit properties with potential for the applications in mind. The first system, for permanent magnet applications, was Fe5SiB2. It was found to be unsuitable for a permanent magnet, however, an interesting magnetic behaviour was studied at low temperatures. The magnetic behaviour arose from a change in the magnetic structure which was solved by using neutron diffraction. Substitutions with phosphorus (Fe5Si1-xPxB2) and cobalt (Fe1-xCox)5PB2 were then performed to improve the permanent magnet potential. While the permanent magnetic potential was not improved with cobalt substitutions the magnetic transition temperature could be greatly controlled, a real benefit for magnetic refrigeration. For this purpose AlFe2B2 was also studied, and there it was found, conclusively, that the material undergoes a second order transition, making it unsuitable for magnetic cooling. However, the magnetic structure was solved with two different methods and was found to be ferromagnetic with all magnetic moments aligned along the crystallographic a-direction. Lastly, the origin of magnetic cooling was studied in Fe2P, and can be linked to the interactions between the magnetic and atomic vibrations.