Activated Carbon (AC) is an amorphous carbon-based material characterized with a large surface area (~ 1,000 m2/g) and consists primarily of graphitic (sp2 hybrid) layers. Its amphoteric chemical property results because of the chemical treatment of the surface of AC with oxidizing agents, reducing agents, and grafting agents. β-cyclodextrin (β-CD) is a very interesting carbohydrate oligomer that provides very strong binding ability for small organic guest molecules in its inner cavity (6.0 ~ 6.5 Å) by van der Waals interactions and hydrogen bond formation between the guest molecules and the host. <p>Surface modification of AC with β-CD was synthesized by chemical methods: oxidation with HNO3, reduction with LiAlH4, and grafting β-CD onto the surface of AC via organic linkers such as glutaraldehyde and 1,4-phenylene diisocyanate. This surface grafted AC with β-CD, then, was evaluated for its surface area and sorption performance by using a solution dye sorption method using dye adsorbates. <p>Surface functional groups produced from oxidation (carboxylic acid, lactone, quinine, phenol, and nitro groups), reduction (alcohol and amine groups), and grafting (imine, hemiacetal, and urethane bonds) methods including microscopy of untreated, surface modified, and grafted ACs were characterized by various surface characterization methods: Diffuse Reflectance Infra-red Fourier Transform Spectroscopy (DRIFTS), Scanning Electron Microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), Thermogravimetric analysis (TGA), Differential thermogravimetry (DTG), Matrix Assisted Laser Desorption Ionization Time of Flight mass spectrometry (MALDI TOF MS), and Electron spin resonance (ESR) spectroscopy. A chemical method, the Boehm method, was used for identifying surface bound acidic and basic functional groups. Nitrogen porosimetry was used to analyze the surface area and pore structure characteristics of AC, surface modified ACs, and grafted ACs. <p>p-nitrophenol (PNP) and methylene blue (MB) were used as adsorbates for the dye sorption method. PNP and MB were used to measure the sorption performance of grafted ACs at equilibrium using UV-vis spectrophotometry in aqueous solution. Sorption capacity (Qe), surface area (m2/g), and binding affinity characteristics [KF (L/g), KL (g/mol), and KBET (L/g)] were determined at equilibrium conditions using fundamental sorption models such as Langmuir, Freundlich, and BET isotherms. The sorption performance of grafted ACs and granular AC were different according to the difference in surface area and pore structure characteristics of each material.

Crevice corrosion generally occurs on the crevice surface while the exterior or bold surfaces are not damaged. However, for copper and its alloys, the opposite is true; the bold surface is corroded while the crevice remains relatively corrosion-free. This unique type of corrosion is referred to as reverse crevice corrosion (RCC). In this research, commercially pure copper was chosen as the target metal to investigate RCC. Based on electrochemical measurements and surface analysis, reverse crevice corrosion was found to occur at room temperature. At elevated temperature only uniform corrosion was observed while under a deoxygenated environment, as expected, no corrosion was observed.<p> A multiple crevice assembly and a working electrode were designed especially for this research. Exposure test experiments were first performed at room temperature and 50 ºC. Several types of electrochemical tests were conducted including open circuit potential measurement, potentiodynamic measurement and electrochemical impendence spectroscopy (EIS). Atomic Force Microscopy (AFM) and Raman Spectroscopy were used to analyze the surfaces of the copper coupon.<p>The results of the exposure tests showed that RCC occurred at room temperature, but not at elevated temperature. Only uniform corrosion was observed at elevated temperature and no corrosion was occurred under a deoxygenated environment. It was found, based on the open circuit potential measurement, that the RCC process can be divided into three steps, a uniform corrosion phase, a corrosion slow-down step and a reverse crevice corrosion step. The first two steps can be combined into one phase, incubation phase. This hypothesis is supported with the results from Raman spectra and AFM. The EIS measurements revealed that the diffusion process from bulk solution to copper coupon surface is the rate controlling step for incubation phase and this diffusion process combined with the reduction of Cu (I) oxide in the crevice are the rate-controlling step corresponding to the last step.

Graduation date: 1991

No description available.

In this thesis, the spectral behavior of the fundamental and sum-frequency waves, generated from the surface of a thin metal film in the Kretschmann configuration, is theoretically studied with coherent ultrashort pulses. As a first exploration of considering spectral response in nonlinear plasmonics, it is shown that the spectra of reflected sum-frequency waves exhibit pronounced shifts for the incident fundamental waves close to the plasmon coupling angle, whereas meanwhile those of reflected fundamental waves display energy holes. We also demonstrate that the scale of discovered plasmon-enhanced spectral changes is strongly influenced by the magnitude of the incidentce angle and the source pulse duration, and at a certain angle a spectral switch is observed. The appearance of large sum-frequency wave shifts can serve as an unambiguous plasmon signatur in nonlinear surface spectroscopy. Also, the discovered spectral switch can trigger extremely surface-sensitive nonlinear plasmonic sensors.

No description available.

Cell surface properties are crucial to the mechanisms by which groups of cells organize themselves during embryogenesis, cancer metastases and tissue engineering. Measured surface tension values provide a quantitative basis for predicting a range of cell behaviors including sorting of embryonic cells, self-organization of pancreatic islet cells and invasive potential of tumor cells. Tissue surface tensions are a measurement of the tension that acts along the interface between a cell aggregate and its surrounding media and it is typically measured by compressing an aggregate of cells. In this study a novel apparatus is used to measure the surface tensions of aggregated embryonic chick cells from heart, liver, neural retina and mesencephalon tissues. These surface tension values are consistent with the known engulfment behavior of the cells involved and are in close agreement with measurements made previously by other means. It has been suggested that surface tensions and cell rearrangement patterns are a direct result of adhesion forces between cells arising from cadherins. However, cadherin binding alone is insufficient to account for observed engulfment phenomena and recent experimental evidence suggests that actin dynamics are involved. A cell surface property referred to as interfacial tension or cortical tension takes into account both adhesion forces and forces derived from actin microfilaments and could shed new light on the mechanisms involved in cell interactions. Computer simulations indicate that the interfacial tension between cells can be measured through a modified compression test experiment. In this cell aggregate compression study, cell shapes as well as the aggregate profile are measured in addition to the compression force in attempts to measure cell interfacial tensions.

Since the advent of the industrial era atmospheric concentrations of greenhouse gases have been on the rise leading to increasing global mean temperatures. Through increasing temperatures and changes to distributions of precipitation, climate change will intensify the hydrologic cycle which will directly impact surface water sources while the impacts to groundwater are reflected through changes in recharge to the water table. The IPCC (2001) reports that limited investigations have been conducted regarding the impacts of climate change to groundwater resources. The complexity of evaluating the hydrologic impacts of climate change requires the use of a numerical model. This thesis investigates the state of the science of conjunctive surface-subsurface water modeling with the aim of determining a suitable approach for conducting long-term transient simulations at the watershed scale. As a result of this investigation, a coupled modeling approach is adopted using HELP3 to simulate surface and vadose zone processes and HydroSphere to simulate saturated flow of groundwater. This approach is applied to the Alder Creek Watershed, which is a subwatershed of the Grand River Watershed and located near Kitchener-Waterloo, Ontario. The Alder Creek Watershed is a suitable case study for the evaluation of climate change scenarios as it has been well characterized from previous studies and it is relatively small in size. Two contrasting scenarios of climate change (i.e., drier and wetter futures) are evaluated relative to a reference scenario that is based on the historical climatic record of the region. The simulation results show a strong impact upon the timing of hydrologic processes, shifting the spring snow melt to earlier in the year leading to an overall decrease in runoff and increase in infiltration for both drier and wetter future climate scenarios. Both climate change scenarios showed a marked increase to overall evapotranspiration which is most pronounced in the summer months. The impacts to groundwater are more subdued relative to surface water. This is attributed to the climate forcing perturbations being attenuated by the shift of the spring snow melt and the transient storage effects of the vadose zone, which can be significant given the hummocky terrain of the region. The simulation results show a small overall rise of groundwater elevations resulting from the simulated increase in infiltration for both climate change scenarios.

When interpolating a data mesh using triangular B&#233;zier patches, the requirement of C¹ or G¹ continuity imposes strict constraints on the control points of adjacent patches. However, fulfillment of these continuity constraints cannot guarantee that the resulting surfaces have good shape. This thesis presents an approach to constructing surfaces with approximate C¹/G¹ continuity, where a small amount of discontinuity is allowed between surface normals of adjacent patches. For all the schemes presented in this thesis, although the resulting surface has C¹/G¹ continuity at the data vertices, I only require approximate C¹/G¹ continuity along data triangle boundaries so as to lower the patch degree. For functional data, a cubic interpolating scheme with approximate C¹ continuity is presented. In this scheme, one cubic patch will be constructed for each data triangle and upper bounds are provided for the normal discontinuity across patch boundaries. For a triangular mesh of arbitrary topology, two interpolating parametric schemes are devised. For each data triangle, the first scheme performs a domain split and constructs three cubic micro-patches; the second scheme constructs one quintic patch for each data triangle. To reduce the normal discontinuity, neighboring patches across data triangle boundaries are adjusted to have identical normals at the middle point of the common boundary. The upper bounds for the normal discontinuity between two parametric patches are also derived for the resulting approximate G¹ surface. In most cases, the resulting surfaces with approximate continuity have the same level of visual smoothness and in some cases better shape quality.

The dissociative adsorption of three carboxylic acids (acetic acid, propanoic acid, and acrylic acid), allyl alcohol, and allyl aldehyde on Si(100)2×1 at room temperature has been investigated by X-ray photoelectron spectroscopy (XPS) and temperature programmed desorption (TPD), as well as density-functional theory (DFT) calculations. The C 1s features obtained by XPS measurement for acetic acid, propanoic acid, and acrylic acid show that formation of bidentate carboxylate at a low exposure is followed by that of unidentate carboxylate at a higher exposure, with approximately equal population for both adstructures. The signatures of C 1s features attributed to methyl (285.7 eV), ethyl (285.3 eV), ethenyl (285.0 eV), and bidentate carboxyl (286.8 eV) and unidentate carboxyl (289.8-289.3 eV) carbons were observed for the studied carboxylic acids. The results showed that the carboxyl group is more reactive than the alkyl or alkenyl group towards the Si(100)2×1 surface, with O−H dissociation preferred over [2+2] C=C cycloaddition and the other plausible reaction products. This was also supported by our DFT calculation which showed that the bidentate carboxylate adstructure is the most stable configuration among the calculated adstructures for the aforementioned carboxylic acids. The combined temperature-dependent XPS and TPD studies provided strong evidence for the formation of ketene, acetaldehyde and CO from acetic acid, CO and ethylene from propanoic acid, and CO, ethylene, acetylene, and propene from acrylic acid. Furthermore, the TPD results provided further evidence for the preferred structure of the adsorbate from each of the carboxylic acid on the surface. In addition to carboxyl group, reactivity of the hydroxyl and carbonyl functional groups relative to that of ethenyl group was studied by investigating the reaction of allyl alcohol and allyl aldehyde on Si(100)2×1 at room temperature. The C 1s XPS results supported O−H dissociation for allyl alcohol and [2+2] C=O cycloaddition for allyl aldehyde over the [2+2] C=C cycloaddition. The similarity between the observed C 1s features for allyl alcohol and allyl aldehyde helped to identify the structure of the adsorption products of these two molecules on the surface. The presence of the related C 1s feature of C=C for allyl alcohol and allyl aldehyde, and the absence of C 1s feature of C=O for allyl aldehyde provided strong evidence to support that [2+2] C=C cycloaddition does not occur in the presence of hydroxyl or carbonyl groups. Furthermore, by comparing the experimental results and the adsorption energies of the adstructures calculated by DFT, it was concluded that these molecules do not react with the Si dimers through both of their functional groups, while the reaction of only one of the two functional groups is preferred on the surface. Formation of ethylene, acetylene, and propene from allyl alcohol and allyl aldehyde, simultaneously to CO from allyl alcohol, was concluded from the corresponding TPD results, which also confirm the structure of the adsorbates on the surface. The present research shows that reactions involving oxygen-containing functional groups are favoured over the other plausible reactions including [2+2] C=C cycloaddition on the Si(100)2×1. The preference of the surface to react with one of the two functional groups calls for future studies for the selective functionalization of Si(100)2×1 with potential applications in molecular electronics.