Throughout the late 20th and early 21st century, the global temperature has been on the rise, a process that has been accelerated in the Arctic. The Arctic surface temperatures have risen at a factor of 3 greater rate than the global average, leading to the term Arctic Amplification of climate change. In this study, the enhanced warming of the Arctic, and the enhancement at the Arctic surface in comparison to the warming of the atmosphere aloft, is investigated through a reconstruction of the past surface energy balance by a model driven by downwelling irradiance reconstructed using radiosonde profiles and the radiative transfer code SBDART. The downwelling irradiance is shown to be increasing over the time-period of 1994-2009, and the sources of this increase are diagnosed. The time-evolution of the surface flux terms are discussed, and the sensitivity of the surface temperature to changes in atmospheric temperature is investigated.

Humic-based organic compounds containing phenol or benzoic acid groups strongly compete with phosphates for specific binding sites on the surface of these colloidal particles. To study the interactions between phenol groups and the surface binding sites of unmodified or modified colloidal particles, chemical force spectrometry (CFS) was used as a tool to measure the adhesion force between an atomic force microscopy (AFM) tip terminated with a phenol self-assembled monolayer and colloidal particles under varying pH conditions. Two modification methods, co-precipitation and post-precipitation, were used to simulate the naturally-occurring phosphate and humic-acid adsorption process. The pH dependence of adhesion forces between phenol-terminated tip and colloidal particles could be explained by an interplay of electrostatic forces, the surface loading of the modifying phosphate or humic acid species and ionic hydrogen bonding. Polydimethylsiloxane (PDMS) is a widely-used polymer in microfluidic devices. PDMS surfaces are commonly modified to make it suitable for specific microfluidic devices. We studied the surface modification of PDMS using four perfluoroalkyl-triethoxysilane molecules of differing length of perfluorinated alkyl chain. The results show that the length of fluorinated alkyl chain has important effects on the density of surface modifying molecules, surface topography and surface zeta potential. The perfluorinated overlayer makes PDMS more efficient at supporting electroosmotic flow, which has potential applications in microfluidic devices. The kinetic study of RNase A, lysozyme C, α-lactalbumin and myoglobin at different concentrations adsorbed on the self-assembled monolayers of 1-octanethiol (OT-Au) and 1H, 1H, 2H, 2H-perfluorooctyl-1-thiol (FOT-Au) has been carried out. The results show a positive relationship between the lower protein concentration and the increased adsorption rate constant (ka) on both surfaces. At low concentrations, the protein adsorption on an OT-Au surface has greater ka than it on a FOT-Au surface. Comparing ka values for four proteins on OT-Au and FOT-Au surface demonstrates that hard proteins (lysozyme and RNase A) have larger ka than soft proteins (α-lactalbumin and myoglobin) on both surfaces. The discussion is based on the hydrophobicity of OT-Au and FOT-Au surfaces, as well as average superficial hydrophobicity, flexibility, size, stability, and surface induced conformation change of proteins. / Thesis (Ph.D, Chemistry) -- Queen's University, 2011-10-14 21:08:31.617

No description available.

In this work, the modification of conducting substrates with thin (nanometer thick) aryl films via reaction with aryldiazonium salts was investigated. Two methods were used: modification by electro-reduction of the aryldiazonium salts and modification by spontaneous reaction of aryldiazonium the salts with the surface at open circuit potential. The majority of the studies were undertaken using p-nitrobenenze diazonium salt, which gives electro-active nitrophenyl (NP) films at the surface that can be detected and characterized by cyclic voltammetry. Films prepared spontaneously on carbon and gold electrodes at open circuit potential were characterized by electrochemistry, atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and water contact angle measurements. At both carbon and gold, spontaneous modification proceeds via electron transfer from the surface to the diazonium salt.Furthermore, on both types of surface, spontaneously prepared NP films were found to be loosely packed multilayers of less than 5 nm in thickness. The spontaneous reaction was utilized for the patterning of carbon, gold, silicon and copper surfaces by microcontact printing (μCP) with diazonium salts. The presence of spontaneously formed films upon printing was confirmed by cyclic voltammetry and AFM. The films were demonstrated to be useful for the tethering of further molecules to the surface. Patterns prepared by μCP were imaged using scanning electron microscopy (SEM) and condensation figures. The preparation of two-component systems, with different chemical functionalities attached to different, well-defined, regions of the surface, was demonstrated. The optimization of the long term activity of glucose oxidase hydrogels by covalent attachment of the hydrogels to modified carbon electrodes was investigated. Covalent attachment was demonstrated, but the resulting electrode-hydrogel surfaces did not show long-term activities superior to those for physisorbed hydrogels. It is suggested that the limiting factor for long-term hydrogel activity is not adhesion of the hydrogel to the surface, but degradation of enzymatic activity by H2O2.

This thesis described the modification of glassy carbon (GC) electrodes with aminophenyl (AP) films via in situ reduction of aminobenzene diazonium ions. The characterisation of the AP modified GC was conducted electrochemically by oxidation of the AP functionalities in acidic aqueous conditions. Ferricyanide and ruthenium hexamine redox probes were also used to investigate the blocking properties of the AP films. Before electrochemical oxidation of the AP functionalities, AP films were shown to have a nett positive charge at pH 7. After electrochemical oxidation in protic conditions, the film was either neutral or negatively charged. The preparation of diazonium cation terminated surface, which is termed 'sticky surface', by reaction of the AP modified electrodes with NaNO₂ in acidic condition, was investigated and the sticky surface was electrochemically characterised. More than one species was formed in the reaction of the AP film with NaNO₂. The reactions of sticky surface with aniline, citrate- and thiol-capped gold nanoparticles (Au-nps) were also studied. Spontaneous reaction of sticky surface with thiol-capped Au-nps had been achieved, and suggested that the reaction leads to the formation of Au–C bonds, via the loss of nitrogen. However, for the reaction of the sticky surface with citrate-capped Au-nps, it was unclear whether covalent bonding had been achieved. The reason for this was due to the possibility of an electrostatic interaction between the negatively charged citrate-capped Au-nps and the positively charged sticky surface. The stability of the sticky surface in acidic aqueous conditions was studied electrochemically and by reaction with thiol-capped Au-nps. It was found that the diazonium cations on the sticky surface are not stable over one hour in aqueous acidic conditions, or even in low temperature. The electro-catalytic activity of the thiol-capped Au-nps attached to the GC electrode via sticky surface towards the oxidation of ascorbic acid was briefly examined, and the surface was found to catalyse the oxidation reaction.

Theoretical and experimental results show that the performance of a load-bearing surface in hydrodynamic lubrication may be enhanced by engineering a definable surface texture onto the surface. These surface textures are in the form of protrusions (positive asperities) or cavities (negative asperities) of known size and geometry. The benefits of such surface textures include lower friction torque, higher load capacity and lower operating temperatures. This Thesis details a fabrication process to manufacture such surface textures/asperities on flat surfaces. The asperities are fabricated using a UV photolithography process followed by electroplating. A complete surface characterization is done to evaluate the effectiveness of the manufacturing process. From the characterization results, some errors in asperity geometry are identified and statistically quantified. These errors are found to be normally distributed and the random surface roughness is 1 to 3 orders of magnitude less than the deterministic feature size. The accuracy of the manufacturing process for fabricating the asperities was found to lie within 6.5 % of the desired value over all the errors studied. Finally, a sensitivity analysis is done to theoretically evaluate the effect of some of these errors in the hydrodynamic lubrication regime.

No description available.

In this thesis, I analyze the weight functions used in moving least squares (MLS) methods to construct implicit surfaces that interpolate or approximate polygon soup. I found that one previous method that presented an analytic solution to the integrated moving least squares method has issues with degeneracies because they changed the weight functions to decrease too slowly. Inspired by their method, I derived a bound for the choice of weight function for implicit moving least squares (IMLS) methods to avoid these degeneracies in two-dimensions and in three-dimensions. Based on this bound, I give a theoretical proof of the correctness of the moving least squares interpolation and approximation scheme with weight function used in Shen et al. when used on closed polyhedrons. Further, previous IMLS implicit surface reconstruction algorithms that ll holes and gaps create surfaces with obvious bulges due to an intrinsic property of MLS. I propose a generalized IMLS method using a Gaussian distribution function to re-weight each polygon, making nearer polygons dominate and reducing the bulges on holes and gaps.

As the developments in nanoscale fabrication and characterization technology, the investigation and applications of light in metal nanostructures have been becoming one of the most focused research areas. Metal materials allow to couple the incident light energy into electromagnetic waves propagating on the metal surface under certain configurations, which is called surface plasmon (SP). This feature tremendously expanded the application possibility of metals in optical regime, such as extraordinary transmission (EOT), near-field optics and surface enhanced spectroscopies. In this talk, various metal structures will be demonstrated which could control SP’s propagation, resonance andlocal field enhancement. A number of SP applications are benefited – the plasmonic bragg reflector (PBR), the frequency sensitive plasmonic microcavity, the subwavelength metallic taper, the long range surface plasmon (LRSP) waveguide and surface enhanced Raman spectroscopy (SERS). Especially for SERS, long-term effort was devoted into it to achieve the single molecule detection limit. / Graduate

This university Bachelor's Thesis was performed to explore the influence of surface roughness on the thermography measurement. Thermography is a non-destructive testing method which can be used to detect cracks. However, it is hard to define how the surface roughness influences the emissivity and the result of a thermography measurement, as well as how the angle of the excitation source influences the result. Therefore, this work aims to define how the heating angle and surface roughness influence the thermography measurement, define the relationship between surface roughness and emissivity for the same crack, and define the influence of the angles which composed of the heating source, the direction of crack and the direction of surface roughness on thermography measurement. In this report, the theories of radiation and Signal-to-noise ratio (SNR) were explained, clearly. Also, two kinds of experiments were set up. One is focus on how the heating angle influence the thermography measurement, the other is focus on how the angle of the heating source, in relation to the crack direction and the direction of surface roughness, influence the SNR value. The conclusions of these experiments are that the heating of a crack increases as the angle decreases (from wide side to narrow side) and the angle ofincreases (from horizontal to vertical). Moreover, the SNR value decreases as the surface roughness increases. For the same surface roughness, the SNR value increases with increased crack angle (0°, 45° or 90°) and with decreased sample position angle (horizontal, 45°or vertical). What is more, the higher surface roughness, the larger the influence of the crack angle and the sample position angle. Finally, when the surface is polish, the crack angle and the sample position angle does not have any influence.