<p>Ni-base superalloys are among the highest temperature capable alloys and are used pervasively throughout the transportation, energy, and nuclear industries. However, their microstructures have been largely limited to containing the γ´ (cubic) and γ´´ (tetragonal) phases to enable high strength at elevated temperatures, and this fixation has restricted alloy development opportunities. In the past three decades, a new set of alloys, strengthened by the γ´´´ (orthorhombic) phase, was developed by Haynes International. The alloys exhibit comparable strength to existing Ni-based superalloys and show a 25% decrease in the thermal expansion coefficient, designed for tighter clearances (thus improving engine efficiency) and help to reduce thermally induced fatigue from engine cycling. </p> <p>The newest iteration of such alloys, HAYNES^® 244^®, has a nominal composition of Ni-22.5Mo-8Cr-6W (wt.%), and each alloying element is used to help precipitate the γ´´´-Ni₂(Cr, Mo, W) phase. The deformation mechanisms of this material are currently unknown. Previous studies investigating the predecessor alloy, HAYNES^® 242^® alloy, showed deformation twinning to be the dominant deformation mechanism during mechanical testing, but the physical phenomena responsible for this mode of deformation were not clearly elucidated. As a result, the primary motivation of this project is to understand the deformation behavior of the 244 alloy from the atomistic level and upwards. </p> <p>This work details efforts to elucidate these deformation mechanisms using an integrated computational and experimental approach. First-principles calculations were performed to determine the entire generalized stacking fault energy (GSFE) surface and slip pathways of the γ´´´ phase for dislocation slip. The various planar defects that could form from dislocation slip were predicted to provide significant barriers for dislocation motion due to their very high planar defect energies (~1000 mJ/m²), likely precluding shearing of the precipitates. We incorporated these results into phase field dislocation dynamics (PFDD) to simulate dislocation-precipitate interactions of finite size. These results showed that the planar defect energies of the γ´´´ phase largely govern the deformation behavior and critical resolved shear stress for precipitate shearing, regardless of precipitate shape, size, or orientation. Extensive mechanical testing conducted from room temperature up to 760 ºC over strain rates ranging from 10^-9 s^-1 to 10^-4 s^-1 combined with transmission electron microscopy validated the predicted deformation structures of creep and tensile samples. Shearing of individual precipitates by intrinsic and extrinsic stacking faults, as well as extensive deforming twinning, was observed. The integrated GSFE and PFDD simulations showed that the precipitates would resist dislocation shearing and favor twinning as the preferred deformation mechanism at all temperatures and strain rates investigated. These results provide pathways for microstructural and composition modification to further increase the strength of γ´´´ strengthened alloys in the future.</p> <p><br></p>

Bifilms is the oxide layer created between two surfaces in the melt of light metals that form an oxide layer. These become planar inclusions in the final casting and are problematic for the mechanical properties such as cracks and crack initiations. Bifilms are too thin to be viewed properly in two dimension cross-section method as they will only appear as thin lines. Because of this, it is relevant to test if it is possible to use electrolytic extraction (EE) as a alternative method to investigate bifilms. Both the deeply etched surface and the inclusions on a filter from the extraction are looked at in the scanning electron microscope (SEM) to get an understanding of the size and shape of the inclusions. With this, a greater understanding of these types of defects can be achieved. After both the filtered inclusions and the surface are examined in SEM with images and Energy-dispersive X-ray spectroscopy (EDS), the images are measured in the software ImageJ. The measurements and analysis show that it is probably bifilms and that they can be relatively large, and not so circular. However, the measurements with the filter have shown high levels of oxygen and carbon. Some levels of chlorine, nitrogen and iron have also been found. But if the surface is compared to the metal surface, it can be concluded that it is likely that bifilms have been found. There are sufficient levels of aluminum and oxygen present. Images in SEM also show the appearance of film-like inclusions. If the method of electrolytic extraction is to be improved to investigate bifilms,optimizations such as filters of other compositions are recommended. / Bifilms är det oxidskikt som skapas mellan två ytor i smältan hos lätta metaller som bildar ett oxidskikt. Dessa blir sedan plana inneslutningar i den slutliga gjutningen och är problematiskt för de mekaniska egenskaperna i form av sprickor och sprickinitieringar. Bifilms är för tunna för att de ska kunna ses korrekt i en tvärsnittsmetod, eftersom de bara kommer att visas som tunna linjer. På grund av detta är det relevant att testa om det är möjligt att använda elektrolytisk extraktion (EE) som en alternativ metod. Både den djupt etsade ytan och inneslutningarna på ett filter från extraktionen tittas på i svepelektronmikroskop för att få en förståelse för inneslutningarnas storlek och form. I och med det kan en högre förståelse uppnås för dessa typer av defekter. Efter att både de filtrerade inneslutningarna och ytan granskats i SEM med bilder och Energy-dispersive X-ray spectroscopy (EDS), mäts bilderna i en mjukvara, ImageJ. De mätningarna och analyserna visar att det antagligen hittats bifilms och att de kan vara förhållandevis stora, samt inte så cirkulära. Däremot har mätningarna med filtret visat höga halter av syre och kol. Även vissa halter av klor, kväve och järn har hittats. Men om ytan jämförs med metallytan så kan en slutsats dras om att det är troligt att bifilms har hittats. Där finns tillräckliga halter av aluminium och syre. Även bilder i SEM påvisar filmliknande inneslutningar till sitt utseende. Om metoden med elektrolytisk extraktion ska förbättras för att undersöka bifilms behövs optimeringar, som till exempel filterav en annan sammansättning.

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Cell culture is a fundamental procedure in many laboratories and precedes much research performed under the microscope. Despite the significance of this procedural stage, the monitoring of cells throughout growth is impossible due to the absence of equipment and methodological approaches. This thesis presents a low-cost, power-effective and versatile microscope with small enough dimensions to operate inside an incubator. Besides image acquisition, the microscope comprises other functions such as a data pipeline, implemented to save the images on the user’s computer via a server whilst also offering storage of the images on an integrated micro SD-card. Furthermore, a machine learning algorithm with a human-in-the-loop approach has been trained to segment the acquired images for cell proliferation and cell apoptosis tracking, and yielded promising results with an accuracy of 94%. For comparison, conventional segmentation techniques using operations such as the watershed function were deployed.The microscope described is versatile in operation as it offers the user to utilise one or more functions, depending on the purpose of the imaging. / Cellodling är en grundläggande process i många laboratiorium och föregår forskning som utförs under mikroskop. Trots inkubationens betydelse har övervakning av celler i detta skede inte varit möjlig på grund utav avsaknaden av relevant utrustning och metodologiska tillvägagångsätt. I denna examensuppsatts på avancerad nivå presenteras ett lågkostnads-, energieffektivt och versatilt mikroskop av centimeterstora dimensioner anpassat för användning i en inkubator. Förutom bildtagningsmekanismer erbjuder mikroskopet olika funktioner som till exempel ett integrerat dataflöde som möjliggör sparande av bilder på användarens dator via en server samtidigt som den erbjuder sparande av bilder på ett integrerat minneskort.Utöver detta har en human-in-the-loop maskininlärningsalgoritm för segmentation av celler implementerats i syfte att övervaka cellernas celldelning och celldöd. Denna algoritm påvisade goda resultat med en nogrannhet på 94%. I jämförelsesyfte har även en traditionell watershed-baserad cellsegmenteringsteknik utvecklats.Mikroskopet kan kallas versatilt då det tillåter användaren att anpassa dataflödet och välja vilka funktioner denne vill nyttja, allt utefter bildtagningens ändamål.

The objectives of the present project were to set up, optimise and characterise a digitalholographic microscopy (DHM) laboratory set-up designed for the study of eyetissue and to implement and optimise digital data processing and noise reductionroutines. This work is part of a collaborative project aiming to provide quantitativemethods for the in vitro and in vivo characterisation of human corneal transparency.The laboratory set-up is based on a commercial laboratory microscope with zoomfunction (a “macroscope”). In continuation of previous work, we completed and optimised,and extended a software for holographic signal processing and numericalpropagation of the wavefront.To characterise the set-up and quantify its performances for standard operationand in its DHM configuration, we compare the magnification and resolution to theoreticalvalues for a given set of parameters. We determined the magnification factorand the rotation angle between the object and camera planes. With a laser wavelengthof 532 nm, a x1 objective and a zoom setting of x2.9 (which corresponds to aplane sample wavefront), we measured a magnification of 1.68. With the same parameters,we measure a holographic resolution of about 11 m. The wavefront phasecould be determined with a precision of a fraction of the wavelength.We subsequently performed analysis of the relative contribution of coherent noiseand implemented and evaluated several noise reduction routines. While the impactof coherent noise remained visible in the amplitude image, interferometric precisionwas obtained for the phase of the wavefront and the set-up was considered qualifiedfor its intended use for corneal characterisation.A first test measurement was performed on primate cornea.Subsequent work will address the further quantitative characterisation of the setupfor the full set of parameters (objectives, zoom positions, wavelengths), test measurementson samples with known transmission and light scattering properties (e.g.solutions of PMMA beads) and the comparison of the results with the predictions ofa theoretical model, and measurements on animal and human tissue.

Infrared antennas are employed in sensing applications requiring specific spectral, polarization, and directional properties. Because of their inherently small dimensions, there is significant interaction, both thermal and electromagnetic, between the antenna, the antenna-coupled sensor, and the low-frequency readout structures necessary for signal extraction at the baseband modulation frequency. Validation of design models against measurements requires separation of these effects so that the response of the antenna-coupled sensor alone can be measured in a calibrated manner. Such validations will allow confident extension of design techniques to more complex infrared-antenna configurations. Two general techniques are explored to accomplish this goal. The extraneous signal contributions can be measured separately with calibration structures closely co-located near the devices to be characterized. This approach is demonstrated in two specific embodiments, for removal of cross-polarization effects arising from lead lines in an antenna-coupled infrared dipole, and for removal of distributed thermal effects in an infrared phased-array antenna. The second calibration technique uses scanning near-field microscopy to experimentally determine the spatial dependence of the electric-field distributions on the signal-extraction structures, and to include these measured fields in the computational electromagnetic model of the overall device. This approach is demonstrated for infrared dipole antennas which are connected to coplanar strip lines. Specific situations with open-circuit and short-circuit impedances at the termination of the lines are investigated.

Cell motility under physiological and pathological conditions including malignant progression of cancer and subsequent metastasis are founded on environmental confinements. During the last two decades, three-dimensional cell migration has been studied mostly by utilizing biomimetic extracellular matrix models. In the majority of these studies, the in vitro collagen scaffolds are usually assumed to be homogenous, as they consist commonly of one specific type of collagen, such as collagen type I, isolated from one species. These collagen matrices should resemble in vivo extracellular matrix scaffolds physiologically, however, mechanical phenotype and functional reliability have been addressed poorly due to certain limitations based on the assumption of homogeneity. How local variations of extracellular matrix structure impact matrix mechanics and cell migration is largely unknown. Here, we hypothesize that local inhomogeneities alter cell movement due to alterations in matrix mechanics, as they frequently occur in in vivo tissue scaffolds and were even changed in diseased tissues. To analyze the effect of structural inhomogeneities on cell migration, we used a mixture of rat tail and bovine dermal collagen type I as well as pure rat and pure bovine collagens at four different concentrations to assess three-dimensional scaffold inhomogeneities. Collagen type I from rat self-assembled to elongated fibrils, whereas bovine collagen tended to build node-shaped inhomogeneous scaffolds. We have shown that the elastic modulus determined with atomic force microscopy in combination with pore size analysis using confocal laser scanning microscopy revealed distinct inhomogeneities within collagen matrices. We hypothesized that elastic modulus and pore size govern cancer cell invasion in three-dimensional collagen matrices. In fact, invasiveness of three breast cancer cell types is altered due to matrix-type and concentration indicating that these two factors are crucial for cellular invasiveness. Our findings revealed that local matrix scaffold inhomogeneity is another crucial parameter to explain differences in cell migration, which not solely depended on pore size and stiffness of the collagen matrices. With these three distinct biophysical parameters, characterizing structure and mechanics of the studied collagen matrices, we were able to explain differences in the invasion behavior of the studied cancer cell lines in dependence of the used collagen model.

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