Pressboard, a high-density cellulose-based product, is used both as load bearing structures and dielectric insulation in oil-filled power transformers. During transformer operation, mechanical forces and vibrations are applied on the material. In particular, this investigation focuses on pressboard sheets placed between the turns of transformer windings, called the spacers, which during short circuit are subjected to high compressive forces of impulse nature. As a result of these forces, remaining deformations are created in the components. One step to reduce the negative consequences that come from the deformations is to understand how the fiber structure of the material changes by these forces, thus finding the week link. Understanding these changes could lead to future modification of the material to better withstand short circuits. To see the fiber structure and its changes in the material, pressboard has been investigated with a micro-CT at the Division of Applied Mechanics at Uppsala University. The scanned images have been reconstructed and analyzed in NRecon, CTAnalyser, and Matlab to investigate the density distribution changes and to identify the densification patterns. The study shows that pressboard initially has an inhomogeneous density distribution through the thickness and after mechanical indentations, the densification tends to begin in the more porous parts of the material. The project also included a prediction of the densification pattern, performed by finite element analysis (FEA) using a simplified material model. The results show that a material model with varying Young’s modulus through the thickness, based on a stiffness and porosity relationship, can produce similar densification patterns as in the experiments.

Abstract Subarachnoid haemorrhage (SAH) is a life-threatened disease with poor outcome. It is usually caused by an intracranial aneurysm (IA) rupture and rapid diagnosis and treatment are of great importance. Computed tomography (CT) is a reliable method to detect the blood in the subarachnoid (SA) spaces. Digital subtraction angiography (DSA) offers dynamic and morphological information of a ruptured IA. The treatment options for excluding an aneurysm from the main circulation are neurosurgical clipping and endovascular procedures. The purpose of the present study was to evaluate the risk factors of acute hydrocephalus (HC) and the reliability to localize the ruptured aneurysm based on non-contrast CT. The aim was also to compare the effect of neurosurgical and endovascular treatment on the development of chronic HC, and evaluate the incidence and the risk factors of early rebleeding (<  30 days) after coiling. The data of 180 operated patients with a ruptured IA were checked. Two neuroradiologists separately located the IAs based on non-contrast CT. The analyses of blood amount and distribution was a reliable method for estimating the location of ruptured middle cerebral artery (MCA) aneurysms and anterior communicate artery (ACoA) aneurysms. Intracerebral haemorrhage (ICH) was a predictor for detecting the precise site. The results confirmed that intraventricular haemorrhage (IVH) was the most consistent single risk factor for the development of acute HC. Haemorrhage in the basal region and the large total blood amount in the SA spaces were strong predictors. The effect of early treatment modality for ruptured IAs on the development of chronic HC with 102 clipped and 107 coiled patients was compared. The treatment method used was not significantly associated with the occurrence of chronic HC or the need for shunt operation. The incidence and risk factors of early rebleeding after coiling were investigated in 194 consecutive acutely (within 3 days) coiled patients with ruptured IAs. The incidence of early rehaemorrhage was 3.6%. The presence of ICH at admission and poor clinical condition were significant predictors for rebleeding. An early rehaemorrhage appeared as an enlargement of the ICH in all of these patients. In conclusion, the non-contrast CT is a reliable method to detect the location of ruptured IA in patients with MCA and ACoA aneurysms. The risk factor for the development of acute HC is IVH. Other predictors are the total SA blood amount and blood in the basal regions. The treatment method used for acutely ruptured IA has no significant effect on the occurrence of chronic HC. The incidence of early rebleeding after coiling is low. The risk factors of rebleeding are the presence of ICH and poor clinical condition. Rehaemorrhage appears often as an enlargement of the ICH.

Abstract Technical improvements in computed tomography (CT) scanners have provided new possibilities to exploit the resources of this imaging modality in the evaluation of patients with multiple injuries or patients being treated in an intensive care unit (ICU). The purpose of this study was to assess the significance of multi-detector computed tomography (MDCT) in diagnostics and treatment decisions concerning multiple trauma and critically ill patients. Findings of MDCT using a dedicated trauma protocol in 133 patients exposed to high-energy blunt trauma were retrospectively evaluated. Diagnostic information about the injuries that would enable planning of treatment was sought. The imaging protocol consisted of axial scanning of the head and helical scanning of the facial bones, cervical spine, thorax, abdomen, and pelvis. Ninety-nine of the patients (74%) had at least one finding consistent with trauma. Nineteen false negative findings and two false positive findings were made. The overall sensitivity of MDCT was 94%, specificity 100%, and accuracy 97%. The reliability of a structured 5-min evaluation of MDCT images from the scanner’s console was prospectively evaluated in 40 high-energy trauma patients. The dedicated trauma protocol covering the thorax, abdomen, and pelvis was used in MDCT scanning. The findings were compared with the final radiological diagnosis of the MDCT data made on a picture archiving and communicating system (PACS) workstation, the operative findings, and the clinical follow-up. The evaluation from the scanner’s console enabled diagnosis of all potentially life-threatening injuries, the sensitivity for all injuries being 60% and specificity 98%. The effects of MDCT on the treatment of patients in a 12-bed medical-surgical ICU were observed prospectively. Sixty-four patients with an ICU stay longer than 48 h had had inconclusive findings with other modalities of radiological imaging. They underwent altogether 82 MDCT examinations. Fifty examinations (61%) resulted in a change in treatment, and 20 (24%) of them otherwise contributed to or supported clinical decision-making. Twelve examinations (15%) failed to provide any additional information relevant to the patient’s treatment. MDCT examination was helpful in general ICU patients, with inconclusive findings with other imaging modalities. CT images of 127 mixed medical-surgical ICU patients were retrospectively reviewed for the previously determined findings. Forty-three of these patients underwent open cholecystectomy, revealing eight cases with a normal gallbladder (GB), 26 with an edematous GB, and nine with necrotic acute acalculous cholecystitis (AAC). Abnormal CT findings were present in 96% of all the ICU patients. Higher bile density in the GB body and subserosal edema were associated with an edematous GB. The most specific findings predicting necrotic AAC were gas in the GB wall or lumen, lack of GB wall enhancement, and edema around the GB. The frequent prevalence of nonspecific abnormal imaging findings in the GB of ICU patients limits the diagnostic value of CT scanning.

The aim of this thesis is to synthesize new kind of macrocyclic ligands for complexation of Zr4+ . Zirconium(IV) complexes have potential as contrast agents in immuno-PET. Three macrocyclic ligands L1, L2 and L3 with dif- ferent pendant arms (HOPO, maltol, hydroxamate) were designed. Despite numerous attempts syntheses of L1 and L2 were unsuccessful. Ligand L3 was synthesized and the protonation constants were determined by poten- tiometric titration. Complexes [Zr4+ (L3)] were studied too. Catechol ligand L4 was prepared and complexes with cations Zn2+ , Ga3+ and Zr4+ were investigated. 1

Electrical impedance tomography of soft tissue: Forward and inverse modelling The diploma thesis builds the neccesary apparatus to formulate and solve the inverse problem of Eletrical Impedance Tomography (EIT), including strategies to remedy the ill-conditioning of the problem. The problem itself lies in determining the structure of a body of interest by driving a set of electrical currents through electrodes connected to its surface. The aim of the thesis is to investigate possible utility of this method in medical applications, namely scanning for malignancies in the female breast, by studying the interaction of tissue with the electromagnetic field and by preparing a set of correspoding numerical experiments. An approximate characterization of the method's sensitivity with respect to noise is derived based on the most basic set of such numerical experiments, which were prepared by a complete software solution called prs4D developed by the author and his advisor, while some aspects of its implementation are included in the thesis.

We present a new theoretical model and reconstruction results for a new class of fast x-ray CT machine -- the Real Time Tomography (RTT) system, which uses switched sources and an offset detector array. We begin by reviewing elementary properties of the Radon and X-ray transforms, and limited angle tomography. Through the introduction of a new continuum model, that of sources covering the surface of a cylinder in R³, we show that the problem of three-dimensional reconstruction from RTT data reduces to inversion of the three-dimensional Radon transform with limited angle data. Using the Paley-Wiener theorem, we then prove the existence of a unique solution and give comments on stability and singularity detection. We show, first in the two-dimensional case, that the conjugate gradient least squares algorithm is suitable for CT reconstruction. By exploiting symmetries in the system, we then derive a method of applying CGLS to the three-dimensional inversion problem using stored matrix coefficients. The new concept of source firing order is introduced and formalised, and some novel visualisations are used to show how this affects aspects of the geometry of the system. We then perform a detailed numerical analysis using the condition number and SVD of the forward projection matrix $A$, to show that the choice of firing order affects the conditioning of the problem. Finally, we give reconstruction results from both simulated phantoms and real experimental data that support the numerical analysis.

Abstract This thesis presents an effective optical method for measuring liquid sorption into paper. From the two tested methods, based on a streak-camera and optical coherence tomography (OCT), the last-mentioned proved very promising for investigating dynamical paper-liquid interactions as spatially and temporally dependent processes. The streak-camera measurements were performed to explore the relationship between paper properties and light migration in dry and refractive index matched paper in general. Based on streak-camera measurements, a novel procedure for determining the average refractive index of cellulose fibre tissue was also presented here. In addition, the streak camera method lent itself to paper porosity determination. Results of the performed OCT measurements proved that liquids cannot penetrate into paper before filling the pores and pits of the paper surface. As a liquid penetrated into paper, the border between the wetted and dry area could be investigated in the depth direction. The liquid penetration velocity seemed to be slower at the beginning and end of the process. Liquid absorption into paper fibres could be investigated concurrently. For the first time, the location and moment of structural changes in paper could be determined during wetting, and the effect of three different coexistent subprocesses related to paper wetting could be detected. OCT only fell short of detecting the effect of liquid migration along fibres. Despite the limitations of the utilized method (resolution, probing depth and depth scanning rate), the obtained OCT measurement results are very promising for the development of an effective paper wetting measurement device for industrial applications. Even if this thesis focused on paper wetting, it is reasonable to assert that the presented ideas and obtained results have more general value in terms of explaining liquid penetration into porous structures and offer an alternative method of evaluating that process.

Abstract To realize faster and more precise treatment of patients, CT technology has an urgent demand to make the CT detector arrays larger, and to cover a larger section of the body during one scan of X-ray imaging. A novel detector micro-module is developed in this thesis to meet this demand. In the novel detector micro-module, photocurrent signals are read out from the bottom side of the photodiode array chip. By avoiding the use of the top surface of the chip for routeing, as is the case in conventional CT modules, rectangular detector building blocks containing a certain number of detector elements can be produced. By tiling such building blocks in both x- and y-directions in a plane, detector arrays with any number of detector elements (in multiples of the number in a single building block) can be built. This cannot be achievable by the conventional method. The novel detector micro-module developed in this thesis consists of an array of 16×16 active elements, and the size of the array is 21×21mm2. The array of detector elements is soldered to a multilayer LTCC (low temperature co-fired ceramics) substrate via a BGA (ball grid array) with each element soldered onto one solder sphere, from which photocurrent signals are read out. In this thesis, the working principle and the evolution of CT detector modules are reviewed and the necessity of developing the novel detector modules is justified. The concept and the structure of the novel detector micro-module are presented. The thermo-mechanical stress modeling and simulation of the structure is performed. The design and the process technology of the photodiode array for the novel detector micro-modules are discussed. The electronic characteristics of the novel detector micro-modules and the related front-end electronics are theoretically analyzed. The LTCC multi-layer substrate is developed. The assembly process of the novel detector micro-module is developed. The basic detector characteristics and light response measurement results of the novel micro-module are presented and discussed. By improving the photodiode silicon process technology, a dark current density as low as 33pA/cm2 is achieved. Excellent mechanical accuracy is achieved with the LTCC substrate. The dimensional tolerance is +/-10μm and the flatness value is less than 50μm over a distance of a 30.5mm distance. A 64-slice detector module is produced successfully by tiling several novel micro-modules. The novel detector micro-modules are superior to conventional CT modules on many respects while being tileable. Their light sensitivity curve is smoother. They exhibit extremely low signal cross-talk; They have nearly zero wiring capacitance compared to up to 20pF in commercial CT detector modules. They also have almost zero wiring resistance compared to tens of ohm or more than one hundred ohms in the present products. This result will have a significant impact on CT technology and the CT industry because the detector will be no longer the limiting factor in CT system performance.

Geophysical methods are non-invasive and allow an effective way of understanding subsurface structures and their physical properties. One of the main challenges is the often non-uniqueness of the geophysical models and that several different models can explain a dataset to an agreeable fit. Moreover, noise and limitations in resolution, which are inherent to field data, are additional obstacles for obtaining a true physical property model of the subsurface. Facing all these challenges, geophysicists have dedicated their efforts for decades to recover models that represent, as close as possible, the true subsurface. Joint inversion and integration of multiple geophysical data are two main approaches that I studied to better resolve subsurface structures. I further used these approaches, together with new software and hardware implementations for data acquisition and inversion, for near-surface applications.  In this thesis, radio-magnetotelluric (RMT), boat-towed RMT, boat-towed controlled source MT (CSMT), electrical resistivity tomography (ERT), and first-arrival traveltime tomography are jointly used for quick clay investigations and fracture zone delineation under shallow water-bodies. The joint approach, as compared with any individual method, shows a better ability to both resolve the geological targets and to assist in understanding the subsurface geology that hosts these targets. For examples: by performing the joint inversion of lake-floor ERT and boat-towed RMT data, a fracture zone is better delineated with greater details compared with single inversion; by employing boat-towed CSMT measurements and jointly inverting with boat-towed RMT data, the subsurface structures, especially at greater depth, are better resolved than by inverting each dataset alone. During my PhD studies, two types of new implementations were employed. (1) Boat-towed data acquisition system was implemented to expand the RMT and CSMT method from land to shallow-water applications. This is significant since many large-scale underground infrastructures are likely to cross these water zones (for example multi-lane train or bypass tunnels, such as the Stockholm bypass). (2) The modification of a well-structured code EMILIA allows joint inversion of boat-towed RMT and lake-floor ERT datasets, and the modification of another well-structured code MARE2DEM can accurately model high frequency CSMT data and handle joint inversion of boat-towed RMT and boat-towed CSMT datasets. Thus, the code modification as another type of new implementation guarantees the success of near-surface applications using the boat-towed RMT and CSMT data acquisition systems. Studies conducted during my PhD work, included under the SEG-GWB (the Society of Exploration Geophysicists - Geoscientists Without Borders) program and the TRUST (TRansparent Underground STructure) umbrella project, are useful for near-surface applications including, for examples, engineering purposes such as planning of underground infrastructures, site characterization in connection with energy or waste storage, and geohazard investigations.

Les hautes pressions sont précieuses à plusieurs disciplines scientifiques. Ce sera le cas dans cette thèse avec le développement d'un nouvel appareil permettant des possibilités inédites de tomographie et de déformation sous haute pression et haute température. Il apporte la possibilité de nouvelles études scientifiques dans les différents champs disciplinaires que sont les sciences de la Terre, la chimie mécanique, la physique des matériaux et la physique des liquides. / High pressures are essential in several scientific field. This will be the case in this thesis with the development of a new device enabling new possibilities tomography and deformation under high pressure and high temperature. It brings the possibility of further scientific studies in the various disciplines that are Earth science, mechanical chemistry, physics of materials and liquids physics.