Call number: LD2668 .T4 1957 M68 / Master of Science

Thesis. 1975. M.S.--Massachusetts Institute of Technology. Alfred P. Sloan School of Management. / Bibliography: leaves 58-64. / by Walter G. Lehmann. / M.S.

Microscope imaging is a fundamental experimental technique in a number of diverse research fields, especially biomedical research. It begins with basic arithmetic operations that intend to reproduce the information contained in the experimental sample. With the rapid advancement in CCD cameras and microscopes (e.g. STORM, GSD), image processing algorithms that extract information more accurate and faster are highly desirable. The overarching goal of this dissertation is to further improve image analysis algorithms. As most of microscope imaging applications start with fluorescence quantification, first we develop a quantification method for fluorescence of adsorbed proteins on microtubules. Based on the quantified result, the adsorption of streptavidin and neutravidin to biotinylated microtubules is found to exhibit negative cooperativity due to electrostatic interactions and steric hindrance. This behavior is modeled by a newly developed kinetic analogue of the Fowler-Guggenheim adsorption model. The complex adsorption kinetics of streptavidin to biotinylated structures suggests that the nanoscale architecture of binding sites can result in complex binding kinetics and hence needs to be considered when these intermolecular bonds are employed in self-assembly and nanobiotechnology. In the second part, a powerful lock-in algorithm is introduced for image analysis. A classic signal processing algorithm, the lock-in amplifier, was extended to two dimensions (2D) to extract the signal in patterned images. The algorithm was evaluated using simulated image data and experimental microscopy images to extract the fluorescence signal of fluorescently labeled proteins adsorbed on surfaces patterned with chemical vapor deposition (CVD). The algorithm was capable of retrieving the signal with a signal-to-noise ratio (SNR) as low as -20 dB. The methodology holds promise not only for the measurement of adsorption events on patterned surfaces but in all situations where a signal has to be extracted from a noisy background in two or more dimensions. The third part develops an automated software pipeline for image analysis, Fluorescencent Single Molecule Image Analysis (FSMIA). The software is customized especially for single molecule imaging. While processing the microscopy image stacks, it extracts physical parameters (e.g. location, fluorescence intensity) for each molecular object. Furthermore, it connects molecules in different frames into trajectories, facilitating common analysis tasks such as diffusion analysis and residence time analysis, etc. Finally, in the last part, a new algorithm is developed for the localization of imaged objects based on the search of the best-correlated center. This approach yields tracking accuracies that are comparable to those of Gaussian fittings in typical signal-to-noise ratios, but with one order-of-magnitude faster execution. The algorithm is well suited for super-resolution localization microscopy methods since they rely on accurate and fast localization algorithms. The algorithm can be adapted to localize objects that do not exhibit radial symmetry or have to be localized in higher dimensional spaces. Throughout this dissertation, the accuracy, precision and implementation of new image processing algorithms are highlighted. The findings not only further the theory behind digital image processing, but also further enrich the toolbox for microscopy image analysis.

The industrial use of recycled aluminium is greatly limited by the degraded mechanical properties due to the increased impurities. Fe, one of the common impurity content in Al alloys, is difficult to eliminate once introduced into aluminium during primary production or recycling processes. Due to the low solid solubility of Fe in Al, the formation of Fe-rich intermetallic compounds (Fe-IMCs) is inevitable, which is one of the main causes for the deterioration of mechanical properties in various cast Al alloys. In order to obtain desirable mechanical properties of recycled Al alloys, modification and refinement of the Fe-IMCs are urgently required as the compact and refined morphologies of such intermetallics are generally non detrimental to Al alloy's performance. However, manipulating the solidification behaviour of the Fe-IMCs phases, including nucleation and growth, is very challenging because of the inherently more difficult heterogeneous nucleation of the Fe-IMCs compared with that of a pure metal or a solid solution; and the strong growth anisotropy. Limited understanding on mechanisms of nucleation and growth of the multicomponent Fe-IMCs is available in the literature. The aim of this study is to gain a deeper understanding on the heterogeneous nucleation and growth behaviour of Fe-IMCs in various Al alloys. The nucleation and growth of both primary and eutectic Fe-IMCs have been investigated during various solidification conditions including a number of different cooling rates and casting temperatures. Based on the experimental results of the solidification of several ternary and quaternary alloys, effect of Mg on the solidification behaviour of Fe-IMCs was investigated. Further the surface modified TiB2 particles were used to enhance the heterogeneous nucleation of Fe-IMCs in order to refine the Fe-IMCs particles. The dominant Fe-IMC in Al-5Mg-2Si-1.2Fe-0.7Mn alloy is identified, using transmission electron microscopy (TEM), as α-AlFeMnSi with a body centred cubic (BCC) lattice structure and lattice parameter of 1.256nm. In the current alloy system, the nucleation of primary α-AlFeMnSi occur at lower cooling rate (≤0.8K/s) when required nucleation undercooling is reached, as the slower cooling rate allows longer diffusion time for the solute to form a stable nucleation embryo. When casting with 20K superheat, the size of primary α-AlFeMnSi increases gradually from 24.5±3.1μm (870K/s) to 251.3±75.3μm (0.02K/s) and the size of α-AlFeMnSi eutectic increased gradually from 102.0μm (870K/s) to 623.3μm (0.02K/s). The Fe and Mn concentration in α-AlFeMnSi appears to reduce with the increased cooling rate due to the relatively insufficient solute supply when solute concentration is low (1.2wt.% Fe and 0.7wt.% Mn). Microstructure observation reveals that the {011} plane, especially on <111> orientation, is the preferred growth orientation of BCC primary α-AlFeMnSi, resulting in rhombic dodecahedral in 3D. The eutectic α-AlFeMnSi, prefers to initiate on the primary α-AlFeMnSi. In addition to the substantial nucleation undercooling, the research revealed that the nucleation of primary α-AlFeMnSi also rely on the local solute concentration and the solute diffusion. Compared with α-Al, the growth of α-AlFeMnSi is less sensitive to the cooling rate changes due to the complexities in multi-components interaction and different diffusion efficiency of different elements. The addition of Mg to Al-1.2Fe-0.7Mn and Al-2Si-1.2Fe-0.7Mn alloys was found to lead to a morphology change of Fe-IMCs. Al6(Fe,Mn), the predominant Fe-IMC in the Al-1.2Fe-0.7Mn-xMg alloy, changed from needle morphology to interconnected lamellar morphology when Mg composition increased from 0.004wt.% to 6.04wt%. A Mg-rich layer at about 5-20nm in thickness was commonly observed on the Fe-IMC/α-Al interface in the alloys with Mg content. The eutectic lamellar spacing for Al6(Fe,Mn) increases from 1.8±0.3μm to 4.5±0.8μm when Mg content increased from 0.004wt.% to 6.04wt.%. In the case of α-Al12(Fe,Mn)3Si, the predominant Fe-IMC in Al-2Si-1.2Fe-0.7Mn-yMg alloys, its lamellar spacing of the eutectic increased from 1.4±0.3μm to 3.25±0.8μm when Mg increased from 0.04wt.% to 5.41wt.%. Owing to the strong anisotropy of the Fe-IMC crystals, the segregation of solute Mg on preferred growth orientation is higher, causing greater growth restriction on this orientation. Consequently, the growth velocity on other orientations becomes relatively more significant. To optimise the morphology of Fe-IMCs in Al alloys, a novel Αl-Ti-B(Fe) grain refiner for Fe-IMCs has been developed to enhance the heterogeneous nucleation of Fe-IMCs. The addition of the novel grain refiner to an Al-5Mg-2Si-1.2Fe-0.7Mn alloy under controlled solidification condition results in a considerable refinement of the primary Fe-IMCs from 251.3±75.3μm to 110.9±45.5μm and from 127.3±36.2μm to 76.5±18.2μm at cooling rates of 0.02K/s and 0.15K/s, respectively. TEM investigations on the refiner reveal a Fe-rich adsorption monolayer in a zigzag fashion on the prismatic planes on the boride particles. This surface modification is beneficial for the heterogeneous nucleation of the Fe-IMCs. Further investigation of the Al alloy with this grain refiner addition revealed that there existed specific orientation relationships (ORs) between TiB2 and Fe-IMCs: (001)[020]Al13Fe4 // (11-20)[10-10]TiB2, and (001)[120]Al13Fe4 ∠6.05˚ (11-20)[10-11]TiB2; (0-11)[100]α-AlFeMnSi // (0001)[-2110]TiB2, and (0-11)[111]α-AlFeMnSi ∠4.5˚ (0001)[10-10]TiB2. The Fe adsorption on substrate particle, the observed ORs between TiB2 and Fe-IMCs, and the refinement of primary α-AlFeMnSi with the addition of modified TiB2 provide evidence of structure templating and composition templating required by heterogeneous nucleation of Fe-IMCs. This research has delivered contribution to the understanding and new approach for optimizing the morphology of Fe-IMCs in the Fe-containing Al alloys. Using the slow cooling rates (≤0.15K/s), the formation compact primary α-AlFeMnSi can be considerably encouraged. With a lower casting temperature, the size and volume fraction of large Chinese-script α-AlFeMnSi can be significantly reduced. With addition of reasonable Mg content the morphology of Fe-IMC can be modified. Particularly, with the addition of the Al-Ti-B(Fe) grain refiner in well-controlled condition, the primary α-AlFeMnSi can be significantly refined. Thus, by implementing these approaches, the optimized Fe-IMC morphology in the microstructure of Fe-containing Al alloy is able to offer promising mechanical performance.

Le présent travail est consacré à l'analyse du comportement mécanique des polymères semi-cristallins à deux échelles : celle de l'empilement lamellaire et celle des structures sphérolitiques. A l'échelle de l'empilement, des simulations en champs complet dans le domaine des petites déformations sont réalisées sous ABAQUS®. L'influence des paramètres sur la réponse macroscopique lors de sollicitations long-terme en relaxation et cyclage est analysée : le choix du comportement viscoélastique de la phase amorphe d'une part, et les effets de microstructure et d'hétérogénéités induites d'autre part. Les résultats obtenus avec une microstructure simplifiée permettent de mettre en évidence plusieurs effets de microstructure. A l'échelle sphérolitique, la technique de corrélation d'images numériques est mise au point in-situ sous MEB pour la mesure de champs cinématiques. Les champs de déformation obtenus en traction uniaxiale sur deux polymères semi-cristallins montrent l'existence d'une déformation hétérogène en lien avec la microstructure sphérolitique. Des méthodes déterministe et statistique de la littérature sont mises en œuvre à partir des mesures de champs pour identifier la taille d'un domaine sur lequel la déformation moyenne mesurée coïnciderait avec la déformation macroscopique. En l'absence de toute information sur la taille d'un Volume Elémentaire Représentatif (VER) dans les polymères semi-cristallins, une telle estimation constitue une avancée notable. Enfin, des perspectives sont données pour la modélisation en transition d'échelles du comportement mécanique de ces matériaux via une combinaison d'outils numériques et expérimentaux.

The always growing demands on the electronics design of modern electron microscopes cause increased requirements to the measurement tasks in the electronics development of these systems. In this thesis, we report the findings of designing noise measurements setup in Carl-Zeiss, Oberkochen. The aim of this thesis was to explore the design setup for noise measurement and to provide an interface which help us analyze these measurements using C# and agilent multimeter. This was achieved by the construction and evaluation of a prototype for a noise measurment application. For this purpose Design Science Research (DSR) was conducted, situated in the domain of noise measurement research. The results consist of a set of design principles expressing key aspects needed to address when designing noise measurement functionality. The artifacts derived from the development and evaluation process each one constitutes an example of how to design for noise measurement functionality of this kind.

Reproduction de : Mémoire d'ingénieur : informatique : Grenoble, CNAM : 1985. / Titre provenant de l'écran-titre. Bibliogr. p. 143-145.

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The Confocal Scanning Laser Holography (CSLH) microscope non-intrusively measures the three-dimensional (3D) temperature and composition of a solid, fluid, or plasma. A unique reconstruction algorithm uses phase-shift data from the recorded holograms and boundary conditions of the specimen to measure the 3D temperature. The CSLH microscope uniquely combines holography with a scanning confocal microscope to determine the phase-shift in a hologram and to reconstruct the 3D temperature. The confocal aspect of the microscope reduces optical aberrations in the hologram and increases sensitivity to a temperature at a scan position in the specimen. The optical design maintains a stationary focal point on the pinhole aperture within the confocal optics during scanning. The CSLH microscope uses a focused laser beam instead of a collimated beam to probe the specimen. The advantage of the focused probe beam over the collimated beam is that different phase-shift data is obtained for each scan position of the probe beam. Another advantage is preventing rotational scanning of the laser about the specimen or rotating the specimen, increasing the number of practical applications. This limits the scan angle to the cone angle of the probe beam only. Reconstruction of the 3D temperature given restricted scanning from a single viewing window places a burden on the reconstruction algorithm to produce low reconstruction error. Three-dimensional reconstruction using methods of tomography prove inaccurate due to the small cone angle. The result is ill-conditioned reconstruction matrices. A unique low reconstruction error algorithm given a single viewpoint window that specifies a particular scanning geometry and requires boundary conditions is derived for the microscope. This research involved the design, building, and evaluation of a specific CSLH microscope intended for fluid flow and heat transfer studies in micro-gravity space based experiments. The fluid specimen used to evaluate the microscope sets a benchmark for resolution, sensitivity, and performance. The reconstruction error is primarily due to measurement error, residual optical aberrations affecting holograms, and vibrations since the reconstruction algorithm error is negligible. Additional knowledge gained includes the understanding of sensitivity to optical alignment as well as methods to accurately determine the phase-shift in a varying fringe contrast hologram. A significant trade-off is that as the cone angle of the probe beam increases, the reconstruction error decreases but the optical aberrations increase. One of the more difficult challenges during scanning is to maintain a fixed focal point on the confocal apertures as the beam is tilted off the optical axis centerline. Further recommended advancements for the microscope are improving the optical lenses to provide pupil planes that are stationary during scanning and the miniaturization of the microscope using diffraction grating lenses instead of glass lenses for more practical applications. Determining the internal temperature of a flame by passing a focused laser beam through the flame is an example of a practical application. The CSLH microscope is uniquely capable of non-intrusively measuring the 3D temperature of a specimen given a single viewpoint window for scanning with applications in the physical and biological sciences.