Diesel particulate matter (DPM) is the solid portion of diesel exhaust, which occurs primarily in the submicron range. It is complex in nature, occuring in clusters and agglomerated chains, and with variable composition depending on engine operating conditions, fuel type, equipment maintenance, etc. DPM is an occupational health hazard that has been associated with lung cancer risks and other respiratory issues. Underground miners have some of the highest exposures to DPM, due to work in confined spaces with diesel powered equipment. Large-opening mines present particular concerns because sufficient ventilation is very challenging. In such environments, reliable DPM sampling and monitoring is critical to protecting miner health. Though complex, DPM is made up primarily of elemental (EC) and organic carbon (OC), which can be summed to obtain total carbon (TC). The Mine Safety and Health Administration (MSHA) currently limits personal DPM exposures in metal/non-metal mines to 160 µg/m3 TC on an 8-hour time weighted average. To demonstrate compliance, exposures are monitored by collecting filter samples, which are sent to an outside lab and analyzed using the NIOSH 5040 Standard Method. To support real-time results, and thus more timely decision making, the Airtec handheld DPM monitor was developed. It measures EC, which is generally well correlated with TC, using a laser absorption technique as DPM accumulates on a filter sample. Though intended as a personal monitor, the Airtec has application as an engineering tool. A field study is reported here which demonstrated the usefulness of the Airtec in tracking temporal and spatial trends in DPM. An approach to sensitizing the monitor to allow "spot checking" was also demonstrated. Since DPM in mine environments generally occurs with other airborne particulates, namely dust generated during the mining process, DPM sampling must be done with consideration for analytical interferences. A common approach to dealing with mineral dust interferences is to use size selectors in the sampling train to separate DPM from dust; these devices are generally effective because DPM and dust largely occur in different size ranges. An impactor-type device (DPMI) is currently the industry standard for DPM sampling, but it is designed as a consumable device. Particularly for continuous monitoring applications, the sharp cut cyclone (SCC) has been suggested as a favorable alternative. In another field study reported here, the effect of aging (i.e., loading as an artifact of sampling) on the DPMI and SCC was investigated. Results suggest the effective cut size of the DPMI will be reduced much more rapidly than that of the SCC with aging — though even in a relatively high dust, high DPM environment, the DPMI performs adequately. In a third field study, the possibility of attachment between DPM and respirable dust particles was investigated. Such a phenomenon may have implications for both reliable sampling and health outcomes. Data collected by transmission electron microscope (TEM) on samples collected in the study mine showed that DPM-dust attachment does indeed occur. Moreover, the study results suggest that respirable particulate sampling — as opposed to submicron sampling, which is currently used — may be favorable for ensuring that oversized DPM is not excluded from samples. This strategy may require additional sample preparation to minimize dust interferences, but methods have been previously developed and were demonstrated here. / Master of Science

The image analysis techniques presented in the présent thesis have been developed as part of a European projeet dedicated to the development of an automatic membrane protein crystallization pipeline. A large number of samples is simultaneously produced and assessed by transmission electron microscope (TEM) screening. Automating this fast step implicates an on-fine analysis of acquired images to assure the microscope control by selecting the regions to be observed at high magnification and identify the components for specimen characterization.The observation of the sample at medium magnification provides the information that is essential to characterize the success of the 2D crystallization. The resulting objects, and especially the artificial membranes, are identifiable at this scale. These latter present only a few characteristic signatures, appearing in an extremely noisy context with gray-level fluctuations. Moreover they are practically transparent to electrons yielding low contrast. This thesis presents an ensemble of image processing techniques to analyze medium magnification images (5-15 nm/pixel). The original contribution of this work lies in: i) a statistical evaluation of contours by measuring the correlation between gray-levels of neighbouring pixels to the contour and a gradient signal for over-segmentation reduction, ii) the recognition of foreground entities of the image and iii) an initial study for their classification. This chain has been already tested on-line on a prototype and is currently evaluated.

In most of the tribological experiments studying friction and wear behaviour, the contact interface is hidden. The present work attempts to overcome this hidden-interface problem by carrying out real-time tribological experiments inside Transmission Electron Microscope (TEM). This is achieved by developing an in situ TEM triboprobe which can carry out nanoscale indentation, sliding and reciprocating tests on an electron transparent sample inside TEM. A novel in situ TEM triboprobe is developed by characterising the individual components involved in the development. Coarse positioning of a sharp probe is achieved using inertial sliders. Fine motion of the probe is controlled using a 4-quadrant tube piezoceramic. This triboprobe is capable of carrying out high stiffness tribological experiments inside TEM. The interface is viewed at high resolutions in real time during the experiments using a movie rate CCD camera. In indentation experiments a sharp probe is brought into contact with the sample surface. During indentation of Aluminium alloy tribolayer, it has been observed that the cracks originate from subsurface and propagate to the surface causing delamination-like material removal. Indentation experiments on protruding silicon particle in Aluminium-Silicon (Al-Si) alloy shows that initial deformation is elastic. Once the load is increased, the particle starts indenting the soft aluminum matrix, and results in sinking of the particle into the aluminium matrix. Once the particle starts sinking, the increase in the displacement causes the generation of a crack and the propagation of this crack results in the fracture of the particle. The sliding experiments inside TEM allowed the direct visualization of asperity level interaction during sliding. The preliminary experimental results of nanoscale sliding experiments carried out using an AFM tip as the sample. The adhesive instability is observed as snap-in and snap-out events. The snap-out distance seems to depend on the local geometry of the contact. To simulate reciprocating wear, a sharp diamond probe is brought into contact with Al-Si alloy and reciprocated sinusoidally at 0.5Hz. At lower loads no wear is observed. However, when the normal load is increased, material starts getting removed in thin slivers, and most of the wear debris generated get swept away from the track. Some wear debris get entrapped in between the sliding surfaces; subsequently they join to form larger wear particles. The trapped particles generated during the test act like rollers and a significant increase in the stroke-length is observed accompanying the rolling action of the particle. The phenomena like agglomeration and dissociation of the wear particles has also been observed. Repeated deformation of the trapped particles leads to the formation of tiny liquid drop on some of the wear debris. The liquid consists of gallium which comes from the sample preparation technique. The interaction between the liquid droplets has been studied by carrying out liquid-bridge pulling experiments. Liquid gallium gets cooled with time during tensile pulling of the droplets. A nano-filament is formed between the droplets during pulling. After some time, the droplet gets solidified and coalescence of droplets does not take place. Further frictional heating was necessary to form the bridge again. The in situ TEM triboprobe, which allow the tribological processes to be observed dynamically under high resolutions, is a power full tool in detecting fundamental tribological interactions.

The aim of this thesis is to investigate the methodology of three dimensional chemical imaging of nanoparticles through the use of scanning transmission electron microscope (STEM) – energy dispersive X-ray (EDX) spectroscopy. In this thesis, an absorption correction factor is derived for spherical nanoparticles that can correct X-ray absorption effects. Quantification of EDX spectra of nanoparticles usually neglects X-ray absorption within the nanoparticle but may lead to erroneous results, thus an absorption correction is important for accurate compositional quantification. The absorption correction presented is verified through comparison with experimental data of Au X-ray peaks in spherical Au nanoparticles and is found to agree excellently. This absorption correction allows accurate compositional quantification of large ( > 100 nm) particles with STEM-EDX.Three dimensional chemical mapping is achievable through the use of EDX spectroscopy with electron tomography. Here, the methodology of STEM-EDX tomography is fully explored, with a focus on how to avoid artefacts introduced through detector shadowing and low counts per pixel. A varied-time acquisition scheme is proposed to correct for detector shadowing that is shown to provide a more constant intensity over a series of projections, allowing a higher fidelity reconstruction. The STEM-EDX tomography methodology presented is applied to the study of AgAu nanoparticles synthesized by the galvanic replacement reaction. The elemental distribution as a function of the composition of the as-synthesized nanoparticles is characterised and a reversal in the element segregated to the surface of the nanoparticles is found. The composition at which the reversal takes place is shown to correlate with a peak in the catalytic yield of a three component coupling reaction. It is hypothesized that a continuous Au surface results in the optimum catalytic conditions for the reaction studied, which guides the use of galvanically prepared AgAu nanoparticles as catalysts.

This diploma thesis deals with the structural analysis of semiconductor nanowires by transmission electron microscopy. The construction of microscope is introduced together with its basic imaging modes and with the function of each construction element in these modes. In the experimental part the results of analysis of several germnaium nanowires are discussed, with emphasis on their crystallographic structure and orientation.

No description available.

Masters of Science / The infants of women who smoke during pregnancy have a lower birth mass than those born of women who abstain. Animal studies reveal that reduced growth due to maternal nicotine exposure during gestation is accompanied by lung hypoplasia. Biochemical analysis suggests that these lungs contain more cells which implies that lung damage occurs. In this study we examined the in vivo effects of maternal nicotine exposure (lmg/Kg/day), the equivalent of 32 cigarettes per day, on the following parameters of fetal and neonatal Wistar rat lung:(i) the content and distribution of glycogen in fetal and neonatal lung (ii) the status of connective tissue in neonatal lung (iii) the cell composition of the alveoli in neonatal lung. Fetal rat lungs of ages 17, 18, 19 and 20 days and neonatal lungs of 1, 7, 14 and 21 day old pups were used. Light microscope techniques and special stains were used to investigate glycogen, connective tissue, macrophage numbers and morphological status of the lungs. Fetal rat lungs of ages 17, 18, 19 and 20 days and neonatal lungs of 1, 7, 14 and 21 day old pups were used. Light microscope techniques and special stains were used to investigate glycogen, connective tissue, macrophage numbers and morphological status of the lungs. Transmission electron microscope (TEM) techniques were employed to investigate the characteristics and composition of the alveolus The results show clearly that maternal nicotine exposure elevates pulmonary alveolar macrophage numbers'(PAM's) and lung glycogen levels. The quantity of elastic fibres in 1 day old neonates was significantly reduced but no changes in the quantity of reticulin and collagen fibres was observed. As a result of this change in connective tissue status, emphysema-like lesions and alveolar collapse was evident in the lungs of nicotine-exposed pups. TEM investigations revealed that changes to the composition of alveoli occurred. These included increased numbers of type II pneumocytes with high numbers of lamellar bodies with degenerative changes. Thickening of the blood-air barrier was also observed. The effect of maternal nicotine exposure has been documented in this study. However, it has not been possible to pinpoint the mechanisms involved but explanations have been proposed. Further research is required to elucidate the mechanisms by which nicotine produces these effects. Information thus obtained could help prevent the harmful effects to the fetus and neonate caused by smoking during pregnancy.

No description available.

Electron Ptychography is a technique to retrieve the phase information of the medium through which the electron wave travels in a Transmission Electron Microscope (TEM). Phase calculation is carried out by acquiring an oversampled dataset of diffraction patterns from the sample and execution of a Fourier-based mathematical solution or algorithm using the collected dataset of intensity patterns. The phase of the electron wave contains valuable information about the structure of the material under study. In this contribution, we provide a scientific background necessary for understanding the phase calculation method, examine the capabilities and limitations of the Electron Ptychography in experimental setup and introduce two novel methods to increase the signal to noise ratio by using the same dose budget used in a classic Ptychography experiment. / Thesis / Master of Applied Science (MASc)

The topic of this master’s thesis is the design of a sample manipulator for TEM. Regarding which the segment of the sample manipulator used to move the sample in the direction of the x-axis (so-called x-stage) was designed. The introductory theoretical part is concerned with a brief description of transmission electron microscopy focused on the imaging methods used in TEM and the procedures of preparing and loading TEM samples. The theoretical part follows with the design of precise mechanisms, especially with respect to the inaccuracies of their operation and the technological aspect of the design. In the practical part, a detailed analysis of the design of the x-stage is presented. Kinematics and dynamics of the mechanism is analyzed in depth, following with the description of the overall design of the mechanism and some of its parts in detail.