A radiação espalhada em radiodiagnóstico, como em mamografia, é usualmente considerada um problema, uma vez que degrada o contraste da imagem. No entanto, pesquisas recentes mostram que a distribuição angular de fótons espalhados (perfil de espalhamento) pode fornecer informações sobre as estruturas que compõem um tecido biológico, permitindo, a partir da análise desta, identificar a presença de anormalidades no tecido. Neste estudo, foram utilizadas as técnicas de espalhamento de raios X em médio (WAXS) e baixo (SAXS) ângulo para determinar o perfil de espalhamento de tecidos mamários previamente classificados como: tecidos normais (adiposo e fibroglandular), neoplasias benignas e malignas, usando um tubo de raios X e radiação síncrotron. Através das informações de cada perfil foi possível identificar algumas estruturas moleculares e supramoleculares presentes nos tecidos estudados. Além disso, foi construído um modelo de classificação baseado na análise de discriminante dos perfis de espalhamento, o qual permitiu classificar corretamente todas as amostras analisadas neste estudo, quando combinadas as informações das regiões de médio e baixo ângulo. Portanto, os resultados obtidos neste trabalho sugerem a possibilidade do desenvolvimento de novas técnicas radiológicas que permitiriam ampliar a capacidade de diagnóstico do câncer mamário. / Scattering radiation in diagnostic radiology, such as mammography, is usually considered a problem, since it degrades the image contrast. However, recent investigations show that the angular distribution of scattered photons (scattering profile) can provide information about the structures that compose a biological tissue, allowing, from the analysis of the scattering profile, identify the presence of abnormalities in the tissue. In this study, we have used the wide angle x-ray scattering (WAXS) and small angle x-ray scattering (SAXS) techniques to determine the scattering profiles of human breast tissues previously classified as: normal tissue (adipose and fibroglandular), benign or malignant neoplasia, using a x-ray tube and synchrotron radiation. Through the information provide by each profile was possible to identify some molecular and supramolecular structures present in these tissues. In addition, we built a classification model based on discriminant analysis of scattering profiles, which enabled the correct classification of all samples analyzed in this study, when combined information from WAXS and SAXS regions. Therefore, the results obtained in this work suggest the possibility of developing new radiological techniques would expand the capability of breast cancer diagnosis.

A radiação espalhada em radiodiagnóstico, como em mamografia, é usualmente considerada um problema, uma vez que degrada o contraste da imagem. No entanto, pesquisas recentes mostram que a distribuição angular de fótons espalhados (perfil de espalhamento) pode fornecer informações sobre as estruturas que compõem um tecido biológico, permitindo, a partir da análise desta, identificar a presença de anormalidades no tecido. A proposta deste trabalho foi desenvolver medidas do perfil de espalhamento a médio (WAXS) e baixo ângulo (SAXS) de tecidos mamários previamente classificados, como tecidos normais, alterações benignas ou malignas, usando um tubo de raios X e radiação Síncrotron e, posteriormente, identificar as estruturas moleculares e supramoleculares presentes nos tecidos estudados e verificar estatisticamente se as informações contidas conjuntamente nos perfis de espalhamento a médio e baixo ângulo permitem diferenciar tecidos normais de alterados. Este tipo de estudo é potencialmente importante na área da Saúde por estar associado ao desenvolvimento de novas técnicas radiológicas que permitiriam ampliar a capacidade de diagnóstico do câncer mamário. / Scattering radiation in diagnostic radiology, such as mammography, is usually considered a problem, since it degrades the image contrast. However, recent research shows that the angular distribution of scattered photons (scattering profile) can provide information on the structures that compose a biological tissue, allowing, from the analysis of this, identify the presence of abnormalities in the tissue. The purpose of this study was to develop measurements of scattering profile at wide angle x-ray scattering (WAXS) and small angle x-ray scattering (SAXS) from breast tissue previously classified as normal tissue, benign or malignant disease, using a x-ray tube and synchrotron radiation and, subsequently, identify molecular and supra-molecular structures present in these tissues studied and verify statistically, if the information contained in both scattering profiles at wide and small angle allow differentiate normal tissues of changed. This type of study is potentially important in the health area, since to be associated with the development of new radiological techniques that would allow to expand the ability of breast cancer diagnosis.

This work focuses on characterising the chiral and topological nature of magnetic skyrmions in noncentrosymmetric helimagnets. In these materials, the skyrmion lattice phase appears as a long-range-ordered, close-packed lattice of nearly millimetre-level correlation length, while the size of a single skyrmion is 3-100 nm. This is a very challenging range of lengthscales (spanning 5 orders of magnitude from tens of nm to mm) for magnetic characterisation techniques. As a result, only three methods have been proven to be applicable for characterising certain aspects of the magnetic information: neutron diffraction, electron microscopy, and magnetic force microscopy. Nevertheless, none of them reveals the complete information about this fascinating magnetically ordered state. On the largest scale, the skyrmions form a three-dimensional lattice. The lateral structure and the depth profile are of importance for understanding the system. On the mesoscopic scale, the rigid skyrmion lattice can break up into domains, with the domain size about tens to hundreds of micrometers. The information of the domain shape, distribution, and the domain boundary is of great importance for a magnetic system. On the smallest scale, a single skyrmion has an extremely fine structure that is described by the topological winding number, helicity angle, and polarity. These pieces of information reveal the underlying physics of the system, and are currently the focus of spintronics applications. However, so far, there is no experimental technique that allows one to quantitatively study these fine structures. It has to be emphasised that the word 'quantitative' here means that no speculations have to be made and no theoretical modelling is required to assist the data interpretation -- what has been measured must be straightforward, and give a unique and unambiguous answer. Motivated by these questions, we developed soft x-ray scattering techniques that allow us to acquire much deeper microscopic information of the magnetic skyrmions -- reaching far beyond what has been possible so far. We will show that by using only one technique, all the information about the magnetic structure (spanning 5 orders of magnitude in length) can be accurately measured. The thesis is structured as follows: The key development is the Dichroism Extinction Rule, which is summarised in Chapter 6, and quintessentially summarises the thesis. In Chapter 1, the well-established theory for skyrmions is introduced, reconstructing the picture from single skyrmions to the skyrmion crystal. A few comments about the current characterisation techniques will be given. In Chapter 2, we will start with the largest lengthscale, the long-range-ordered skyrmion lattice phase. This is an intensely studied phase, mostly using neutron diffraction, and we will show that this piece of information can be equivalently (or actually even better) obtained using resonant x-ray diffraction. The theoretical foundation of this technique is also given. In Chapter 3, we will demonstrate imaging technique with which we were able to effectively map the skyrmion domains. The measurements also suggest a way to control the formation of skyrmion domains, which might be the key for enabling skyrmion-based device applications. Chapters 4 and 5 present the highlights of this work, in which we will show that using the dichroism extinction rule, the topological winding number and the skyrmion helicity angle can be unambiguously determined. In this sense, this technique is capable of accurately measuring the internal structure of single skyrmions.

As propriedades de espalhamento de raios X e atenuação de tecidos mamários normais (adiposo e fibroglandular), neoplásicos (benigno e maligno) e vários materiais tecido-equivalente (nylon, poliacetato, polimetilmetacrilato (PMMA), água, músculo-equivalente, osso-equivalente e adiposo-equivalente) foram determinados usando um sistema de raios X dispersivo em energia (SRXDE). O SRXDE consistiu de um tubo de raios X com anodo de tungstênio operando a 60kVp, um goniômetro e dois detectores: um detector de telureto de cádmio (CdTe), posicionado a 7 graus com relação ao feixe incidente usado para detectar a distribuição em energia dos fótons espalhados (numa faixa de momento transferido de 0,5nm-1 - 3,5nm-1) e um detector de silício (Silicon Drift Detector, SDD), posicionado a zero graus e usado para detectar a distribuição em energia do feixe transmitido (com amostra) ou do feixe incidente (sem amostra). A distribuição espectral foi processada para se obter o perfil de espalhamento e o coeficiente de atenuação linear de 100 amostras de tecidos mamários (59 normal, 30 maligno e 11 benigno). Este sistema foi, também, aplicado ao estudo de regiões de transição entre tecidos com diferentes composições. Os resultados encontrados neste trabalho mostram que os tecidos mamários podem ser caracterizados através de suas propriedades de atenuação e espalhamento. Perfis de espalhamento neoplásico apresentam formato do pico principal significativamente diferente na faixa de momento transferido de 0,8nm-1 - 2,0nm-1, aos tecidos normais. Especificamente, o tecido adiposo apresentou um perfil de espalhamento muito diferente (pico principal em 1,12nm-1 e LMA de 0,33nm-1) quando comparado com tecidos neoplásico maligno e benigno e normal fibroglandular (pico principal em torno de 1,54nm-1 e LMA em torno de 0,73nm-1). O coeficiente de atenuação linear observado para os tecidos maligno, benigno e fibroglandular são muito similares e mostraram diferenças menores que 8% para energias entre 10 e 35keV. Entretanto, o tecido adiposo apresentou diferenças significativas com relação aos outros tecidos em toda faixa de energia (diferenças de até 40% foram observadas). Os resultados obtidos da varredura espacial das amostras heterogêneas mostram que o sistema desenvolvido permite o estudo de regiões de transição entre tecidos com diferentes composições. Finalmente, nossos resultados foram comparados com dados experimentais previamente publicados na literatura, mostrando boa concordância dentro das incertezas estatísticas. / The X-ray scattering and attenuation properties for normal (adipose and glandular) and neoplastic (benign and malignant) breast tissues and several tissue-equivalent materials (nylon, polyacetate, polymethylmethacrylate (PMMA), water, muscle-equivalent, bone-equivalent and adipose-equivalent) were determined using an energy dispersive X-ray system (EDXS). The EDXS consisted of a tungsten anode X-ray tube operating at 60kVp, a goniometer, and two detectors: a Cadmium Telluride (CdTe) detector, positioned at 7 degrees with relation to the incident beam used for detecting the energy distribution of scattered photons (over the momentum transfer range of 0,5nm-1- 3,5nm-1) and a Silicon Drift Detector (SSD), positioned at zero degree used for detecting the energy distribution of the transmitted beam (with the sample) or the incident beam (without the sample). The spectra distributions were processed to obtaine the scattering profile and the linear attenuation coefficient of 100 samples of breast tissues (59 normal, 30 malignant and 11 benign). This system was also applied to the study of the transition regions between tissues with different composition. The results found in this work show that breast tissues may be characterized through their attenuation and scattering properties. Neoplastic scattering profiles presented format and the main peak position significantly different in the range of momentum transfer from 0,8nm-1- 2,0nm-1, to normal tissues. Specifically, adipose tissue presented a very different scattering profile (main peak at 1,12nm-1and FWHM of 0,33nm-1) when compared with malignant, benign and also normal glandular tissues (main peak around 1,54nm-1and FWHM about of 0,73nm-1). The linear attenuation coefficient observed for malignant, benign and normal glandular tissues were quite similar and showed differences smaller than 8% for energies between 10 and 35keV. However, adipose tissue presented significant differences from the others tissues type in all energy range (differences up to 40% were observed). The results of the spatial scan of heterogeneous samples show that the developed system allows the study of transition regions between tissues with different composition. Finally, our results were compared with previous experimental data showing a good agreement within the experimental uncertainties

This thesis presents theoretical studies of several x-ray spectroscopies - x-ray absorption, x-ray photoelectron emission, radiative and non-radiative resonant Raman scattering spectroscopy. The main focus point is investigating the influence of nuclear dynamics on these spectra for a variety of small molecules - naphthalene, biphenyl, ethylene, the water dimer, HCl, CO. The theoretical tools used consist of the basic equations of the relevant x-ray spectroscopy. Wave packet methods are also used. The molecular parameters needed for our simulations are obtained through suitable quantum chemical calculations, based on either wave function or density functional methods. Our simulations are compared to experimental data, where available. Simulations of x-ray absorption and x-ray photoionization spectra for naphthalene and biphenyl show that the spectral shapes are heavily influenced by the joint effect of two factors -- chemical shifts and excitations of vibrational progression. Comparison between the two molecules and also comparison to a reference case -- benzene, provides useful insight into the molecular behavior under core excitation. In a further step, we consider the O1s x-ray photoelectron spectrum of the water dimer. A substantial broadening of the two bands originating from the donor and the acceptor oxygen is found. It is caused by excitations of soft intermolecular vibrational modes, associated with the hydrogen bond. Another strong influence of the nuclear dynamics is clearly seen in the resonant x-ray Raman scattering of HCl. Vibrational collapse is observed experimentally and confirmed theoretically for distinctive situations. This effect allows to eliminate completely the vibrational broadening, and hence, considerably increase the spectral resolution. We considered also the vibrational dynamics in resonant soft x-ray Raman scattering from ethylene. The importance of vibronic coupling and symmetry effects is discussed and emphasized. We obtained excellent agreement with the experimental data. We predict an interference effect in the resonant Auger scattering from fixed-in-space molecules. By exciting a molecule to a dissociative state and measuring the angular distribution of the Auger electrons in coincidence with the molecular ion, one can observe this effect. The interference pattern can be used after Fourier transformation for extracting structural data about the studied system. We have found that two-center interference leads to an enhancement of the recoil effect. Finally, it is shown that core excitation to doubly-excited dissociative Pi state is accompanied by Doppler splitting of the atomic peak in resonant Auger scattering from carbon monoxide. / QC 20100910

Poly(p-phenylenebenzobisimidazole), PBI, is a rigid-rod polymer with a fully conjugated backbone having superior mechanical properties, thermo-oxi- dative and solvent stabilities. The stabilities cause processing difficulties and in terms limit its applications in critical technologies, such as conducting polymers, nonlinear optics, and solid polyelectrolytes. In this study, a chemical derivative of PBI, poly[1,7-dihydrobenzo[1,2- d:4,5-d¡¦]diimidazo-2,6-diyl[2-(2-sulfo)-p-phenylene]], sPBI, was synthesized by polycondensation reaction of 1,2,4,5-tetraaminobenzene tetrahydrochloride with 2-sulfoterephthalic acid in poly(phosphoric acid). Isolated sPBI was measured in 30oC methanesulfonic acid for an intrinsic viscosity as high as 10.5 dL/g. sPBI polymer was then reacted with 1,3-propanesultone in dimethylsulfoxide containing sodium hydride for water-soluble rigid-rod polyelectrolyte, poly[1,7- dipropylsulfobenzo-[1,2-d:4,5-d¡¦]diimidazo-2,6-diyl-[2,(2-sulfo)-p-phenylene]], sPBI-PS(Na+). sPBI-PS(Na+) was further converted to sPBI-PS(Li+) with hydrochloride and followed with lithium hydroxide. Various analyses were applied to ascertain chemical structure, purities and thermal properties of synthesized monomers and polymers. sPBI-PS(Li+) aqueous solutions were doped individually with lithium salts of LiI, LiBF4, and LiCF3SO3 at concentrations up to 1.7¡Ñ10-5 wt./wt., which were cast into freestanding films of 10-25 £gm in thickness. Direct-current conductivity measured at room- temperature parallel to the film surface was as large as 9.74¡Ñ10-5 S/cm. The ionic nature of the conductivity was revealed by constant-voltage depletion measurements. X-ray scattering results suggested that the cast film was in-plane isotropic but out-of-the plane anisotropic with the rigid-rod backbone lying in the plane of the film.

Polymer clay nanocomposites have been a popular area of materials research since they were first introduced in the 1990s. The inclusion of clays into many different host polymers has been shown to improve the properties of matrix polymers in a number of ways including increased mechanical strength, thermal stability and improved barrier properties while keeping the composite light weight and transparent. Although there is a great deal of published work on the preparation and property measurements of polymer clay nanocomposites, there is no model to design a nanocomposite with a given set of properties for a specific end-use. While it is important to know the structure property relationships of materials, the understanding of how nanocomposites reach their final forms and properties is equally important. A thorough understanding of processing effects on the final structure of polymer clay nanocomposites is still missing. With this perspective, this thesis addresses building structure-processing relationships of polymer clay nanocomposites by analyzing multiaxial deformation behavior using in-situ x-ray scattering techniques. This thesis can be divided into two distinct parts. The first part concerns the design of the in-situ multiaxial deformation device (IMDD) used to create the deformation conditions that polymers go through during processing such as blow molding and thermoforming. The device was designed to overcome several concerns with in situ measurement by maintaining constant sample to detector distance, minimizing the material between the incident beam and the detectors, as well as exposing the same point on the sample throughout deformation. A new design to create biaxial deformation, termed in-situ biaxial deformation device (IBDD), is also introduced in this part of the thesis.. In addition, a new heating unit, attached to IBDD, is designed for higher temperature studies, up to 150°C, to imitate industrial processing conditions more closely. The second part of the thesis addresses the effect of strain, strain rate, and temperature as well as the amount of clay on the polymer morphology evolution during multiaxial deformation.. Two different polymer/clay systems were studied: poly(ethylene)/clay and poly(propylene)/clay. It was observed that the morphological evolution of polyethylene and polypropylene is affected by the existence of clay platelets as well as the deformation temperature and the strain rate. Martensitic transformation of orthorhombic polyethylene crystals into monoclinic crystal form was observed under strain but is hindered in the presence of clay nanoplatelets. The morphology evolution of poly(propylene) crystal structure during multiaxial deformation was more subtle where the most stable α-crystalline form went through strain induced melting. This was more noticeable in the nanocomposites with clays up to 5 wt%. It was also noted that the thickness of the interlamellar amorphous region increased with increasing strain at room temperature due to the elongation of the amorphous chains. The increase in the amorphous layer thickness is slightly higher for the poly(ethylene)/clay nanocomposites compared to neat poly(ethylene) while the increase in the lamellar long spacing is slightly higher for the neat poly(propylene) compared to poly(propylene)/clay nanocomposites. The rate of change in the characteristic repeat distance in both poly(ethylene) and poly(propylene) systems is higher at faster strain rates, at room temperature, where it remained constant during higher temperature deformations. Time dependent recovery after deformation studies have shown that poly(ethylene)/clay system reverts back to its initial configuration. The recovery in the amorphous chains was however observed to take longer in the clay added poly(ethylene)s. Crystalline relaxation was observed to happen almost instantly in the poly(ethylene)/clay system. On the other hand, amorphous chains in the poly(propylene)/clay system did not revert back to the initial configuration in the period of time that the recovery observations were performed while the crystalline configuration recovered back almost fully in the given time.

The L10 FePt phase belongs to the most promising hard ferromagnetic materials for high density recording media. The main challenges for thin FePt films are: (i) to lower the process temperature for the transition from the soft magnetic A1 to the hard magnetic L10 phase, (ii) to realize c-axes preferential oriented layers independently from the substrate nature and (iii) to control layer morphology supporting the formation of FePt - L10 self-organized isolated nanoislands towards an increase of the signal-to-noise ratio. In this study, dc magnetron sputtered FePt thin films on amorphous substrates were inve-stigated. The work is focalized on the correlation between structural and magnetic properties with respect to the influence of deposition parameters like growth mode (co-sputtering vs. layer – by - layer) and the variation of the deposition gas (Ar, Xe) or pressure (0.3 - 3 Pa). In low-pressure Ar discharges, high energetic particle impacts support vacancies formation during layer growth lowering the phase transition temperature to (320 +/- 20)°C. By reducing the particle kinetic energy in Xe discharges, highly (001) preferential oriented L10 - FePt films were obtained on a-SiO2 after vacuum annealing. L10 - FePt nano-island formation was supported by the introduction of an Ag matrix, or by random ballistic aggregation and atomic self shadowing realized by FePt depositions at very high pressure (3 Pa). The high coercivity (1.5 T) of granular, magnetic isotropic FePt layers, deposited in Ar discharges, was measured with SQUID magnetometer hysteresis loops. For non-granular films with (001) preferential orientation the coercivity decreased (0.6 T) together with an enhancement of the out-of- plane anisotropy. Nanoislands show a coercive field close to the values obtained for granular layers but exhibit an in-plane easy axis due to shape anisotropy effects. An extensive study with different synchrotron X-ray scattering techniques, mainly performed at the ESRF, BM-20 (ROBL-Beamline), pointed out the importance of in-situ investigations to clearly understand the kinetic mechanism of the A1 to L10 transition and ordering and to control FePt nanoclusters evolution.

2'-5'-oligoadenylate synthetases (OAS) are interferon-stimulated proteins that act in the innate immune response to viral infection. Upon binding to viral double-stranded RNAs, OAS enzymes produce 2'-5'-linked oligoadenylates that stimulate RNase L and ultimately slow viral propagation. Studies have linked mutations in the OAS1 gene to increased susceptibility to West Nile virus (WNV) infection, highlighting the importance of the OAS1 enzyme. Here I report that the 5'-terminal region (5'-TR) of the WNV genome, comprising both the 5'-untranslated region (5'-UTR) and initial coding region, is capable of OAS1 activation in vitro. This region contains three RNA stem loops (SLI, SLII, and SLIII), whose relative contribution to OAS1 binding affinity and activation were investigated using electrophoretic mobility shift assays and enzyme kinetics experiments. Stem loop I (SLI) is dispensable for maximum OAS1 activation, as a construct containing only SLII and SLIII was capable of enzymatic activation. Mutations to the RNA binding site of OAS1 confirmed the specificity of the interaction. Solution conformations of both the 5'-TR RNA of WNV and OAS1 were then elucidated using small-angle x-ray scattering. I also report that the 3' terminal region (3'-TR) is able to mediate specific interaction with and activation of OAS1. Binding and kinetic experiments identified a specific stem loop within the 3'-TR that is sufficient for activation of the enzyme. The solution confirmation of the 3'-terminal region was determined by small angle X-ray scattering, and computational models suggest a conformationally restrained structure comprised of a helix and short stem loop. Structural investigation of the 3'-TR in complex with OAS1 is also presented. Finally, we show that genome cyclization by base pairing between the 5'- and 3'-TRs, a required step for replication, is not sufficient to protect WNV from OAS1 recognition. The purity, monodispersity and homogeneity of all samples subjected to SAXS analysis were evaluated using dynamic light scattering and/or analytical ultra-centrifuge. These data provide a framework for understanding recognition of the highly structured terminal regions of a flaviviral genome by an innate immune enzyme. / October 2015

Porous, high surface area activated carbon (AC) can be used to remove certain irritating and toxic gases from contaminated air streams. Impregnating AC with carefully selected chemicals can improve ACs adsorption capacity for certain gases and provide adsorption capacity for gases that un-impregnated AC cannot fi lter. Impregnated activated carbons (IACs) and ACs can be used as the active component in respirators. Comparative studies of di fferent commercially available AC samples and of IAC samples, prepared from a wide variety of di fferent chemicals, were performed. The gas adsorption capacity of the samples was tested using sulfur dioxide (SO2), ammonia (NH3), hydrogen cyanide (HCN) and cyclohexane (C6H12) challenge gases and compared to results obtained from a commercially available broad spectrum respirator carbon. The samples were characterized using wide angle x-ray di raction (XRD), small angle x-ray scattering (SAXS), nitrogen adsorption isotherms, thermal gravimetric analysis (TGA) and scanning electron microscopy (SEM). Highlights of this work include the discovery of a IAC sample prepared from zinc nitrate (Zn(NO3)2) and nitric acid (HNO3) that, after heating at 180 C under argon, had overall dry gas adsorption capacity that was greater than the commercially available sample. The importance of pore size on the C6H12 adsorption capacity of AC was demonstrated using SAXS and nitrogen adsorption data. A relationship between decreased humid C6H12 capacity and pre-adsorbed water was shown using SAXS, TGA and gravimetric studies.