Comprehensive Characterization of Measurement Data Gathered by the Pressure Tube to Calandria Tube Gap Probe

Multi-frequency eddy current measurements are employed in estimating pressure tube (PT) to calandria tube (CT) gap in CANDU fuel channels, a critical inspection activity required to ensure fitness for service of fuel channels. In this thesis, a comprehensive characterization of eddy current gap data is laid out, in order to extract further information on fuel channel condition, and to identify generalized applications for multi-frequency eddy current data. A surface profiling technique, generalizable to multiple probe and conductive material configurations has been developed. This technique has allowed for identification of various pressure tube artefacts, has been independently validated (using ultrasonic measurements), and has been deployed and commissioned at Ontario Power Generation. Dodd and Deeds solutions to the electromagnetic boundary value problem associated with the PT to CT gap probe configuration were experimentally validated for amplitude response to changes in gap. Using the validated Dodd and Deeds solutions, principal components analysis (PCA) has been employed to identify independence and redundancies in multi-frequency eddy current data. This has allowed for an enhanced visualization of factors affecting gap measurement. Results of the PCA of simulation data are consistent with the skin depth equation, and are validated against PCA of physical experiments. Finally, compressed data acquisition has been realized, allowing faster data acquisition for multi-frequency eddy current systems with hardware limitations, and is generalizable to other applications where real time acquisition of large data sets is prohibitive.

Surface-Enhanced Raman Spectroscopy as a Probe of the Surface Chemistry of Nanostructured Materials

Surface-enhanced Raman spectroscopy (SERS) is now widely used as a rapid and inexpensive tool for chemical/biochemical analysis. The method can give enormous increases in the intensities of the Raman signals of low-concentration molecular targets if they are adsorbed on suitable enhancing substrates, which are typically composed of nanostructured Ag or Au. However, the features of SERS that allow it to be used as a chemical sensor also mean that it can be used as a powerful probe of the surface chemistry of any nanostructured material that can provide SERS enhancement. This is important because it is the surface chemistry that controls how these materials interact with their local environment and, in real applications, this interaction can be more important than more commonly measured properties such as morphology or plasmonic absorption. Here, the opportunity that this approach to SERS provides is illustrated with examples where the surface chemistry is both characterized and controlled in order to create functional nanomaterials.

The application of a novel, cell permeable activity-based probe for the detection of cysteine cathepsins.

Cysteine cathepsins, such as cathepsin S (CTSS), are implicated in the pathology of a wide range of diseases and are of potential utility as diagnostic and prognostic biomarkers. In previous work, we demonstrated the potency and efficiency of a biotinylated diazomethylketone (DMK)-based activity-based probe (ABP), biotin-PEG-LVG-DMK, for disclosure of recombinant CTSS and CTSS in cell lysates. However, the limited cell permeability of both the biotin and spacer groups restricted detection of CTSS to cell lysates. The synthesis and characterisation of a cell permeable ABP to report on intracellular CTSS activity is reported. The ABP, Z-PraVG-DMK, a modified peptidyl diazomethylketone, was based on the N-terminus of human cystatin motif (Leu-Val-Gly). The leucine residue was substituted for the alkyne-bearing proparcylglycine to facilitate conjugation of an azide-tagged reporter group using click chemistry, following irreversible inhibition of CTSS. When incubated with viable Human Embryonic Kidney 293 cells, Z-PraVG-DMK permitted disclosure of CTSS activity following cell lysis and rhodamine azide conjugation, by employing standard click chemistry protocols. Furthermore, the fluorescent tag facilitated direct detection of CTSS using in-gel fluorescent scanning, obviating the necessity for downstream biotin-streptavidin conjugation and detection procedures.

‘Probing with the prototype’: using a prototype e-participation platform as a digital cultural probe to investigate youth engagement with the environment

This study describes how we used a prototype e-participation plat-form as a digital cultural probe to investigate youth motivation and engagement strategies. This is a novel way of considering digital cultural probes which can contribute to the better creation of e-participation platforms. This probe has been conducted as part of the research project STEP which aims at creating an e-participation platform to engage young European Citizens in environmental decision making. Our probe technique has given an insight into the environ-mental issues concerning young people across Europe as well as possible strat-egies for encouraging participation. How the e-participation platform can be utilised to support youth engagement through opportunities for social interac-tion and leadership is discussed. This study leads to a better understanding of how young people can co-operate with each other to provide collective intelli-gence and how this knowledge could contribute to effective e-participation of young people.

The 100th anniversary of the four-point probe technique: the role of probe geometries in isotropic and anisotropic systems

The electrical conductivity of solid-state matter is a fundamental physical property and can be precisely derived from the resistance measured via the four-point probe technique excluding contributions from parasitic contact resistances. Over time, this method has become an interdisciplinary characterization tool in materials science, semiconductor industries, geology, physics, etc, and is employed for both fundamental and application-driven research. However, the correct derivation of the conductivity is a demanding task which faces several difficulties, e.g. the homogeneity of the sample or the isotropy of the phases. In addition, these sample-specific characteristics are intimately related to technical constraints such as the probe geometry and size of the sample. In particular, the latter is of importance for nanostructures which can now be probed technically on very small length scales. On the occasion of the 100th anniversary of the four-point probe technique, introduced by Frank Wenner, in this review we revisit and discuss various correction factors which are mandatory for an accurate derivation of the resistivity from the measured resistance. Among others, sample thickness, dimensionality, anisotropy, and the relative size and geometry of the sample with respect to the contact assembly are considered. We are also able to derive the correction factors for 2D anisotropic systems on circular finite areas with variable probe spacings. All these aspects are illustrated by state-of-the-art experiments carried out using a four-tip STM/SEM system. We are aware that this review article can only cover some of the most important topics. Regarding further aspects, e.g. technical realizations, the influence of inhomogeneities or different transport regimes, etc, we refer to other review articles in this field.

A probe for the instantaneous measurement of surface temperature.

"Technical documentary report no.RTD-TDR-63-4015, AF Flight Dynamics Laboratory, Research and Technology Division, Air Force Systems Command, Wright Patterson Air Force Base, Ohio."

Holography, probe branes and isoperimetric inequalities

In many instances of holographic correspondences between a d-dimensional boundary theory and a (. d+. 1)-dimensional bulk, a direct argument in the boundary theory implies that there must exist a simple and precise relation between the Euclidean on-shell action of a (. d-. 1)-brane probing the bulk geometry and the Euclidean gravitational bulk action. This relation is crucial for the consistency of holography, yet it is non-trivial from the bulk perspective. In particular, we show that it relies on a nice isoperimetric inequality that must be satisfied in a large class of Poincaré-Einstein spaces. Remarkably, this inequality follows from theorems by Lee and Wang.

On the interaction of bovine serum albumin with ionic surfactants: Temperature induced EPR changes of a maleimide nitroxide reflect local protein dynamics and probe solvent accessibility

The interaction of bovine serum albumin (BSA) with the ionic surfactants sodium dodecylsulfate (SDS, anionic), cetyltrimethylammonium chloride (CTAC, cationic) and N-hexadecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (HPS, zwitterionic) was studied by electron paramagnetic resonance (EPR) spectroscopy of spin label covalently bound to the single free thiol group of the protein. EPR spectra simulation allows to monitor the protein dynamics at the labeling site and to estimate the changes in standard Gibbs free energy, enthalpy and entropy for transferring the nitroxide side chain from the more motionally restricted to the less restricted component. Whereas SDS and CTAC showed similar increases in the dynamics of the protein backbone for all measured concentrations. HPS presented a smaller effect at concentrations above 1.5 mM. At 10 mM of surfactants and 0.15 mM BSA, the standard Gibbs free energy change was consistent with protein backbone conformations more expanded and exposed to the solvent as compared to the native protein, but with a less pronounced effect for HPS. In the presence of the surfactants, the enthalpy change, related to the energy required to dissociate the nitroxide side chain from the protein, was greater, suggesting a lower water activity. The nitroxide side chain also detected a higher viscosity environment in the vicinity of the paramagnetic probe induced by the addition of the surfactants. The results suggest that the surfactant-BSA interaction, at higher surfactant concentration, is affected by the affinities of the surfactant to its own micelles and micelle-like aggregates. Complementary DLS data suggests that the temperature induced changes monitored by the nitroxide probe reflects local changes in the vicinity of the single thiol group of Cys-34 BSA residue. (C) 2011 Elsevier B.V. All rights reserved.

Using the Higgs to Probe Naturalness

The extreme sensitivity of the mass of the Higgs boson to quantum corrections from high mass states, makes it 'unnaturally' light in the standard model. This 'hierarchy problem' can be solved by symmetries, which predict new particles related, by the symmetry, to standard model fields. The Large Hadron Collider (LHC) can potentially discover these new particles, thereby finding the solution to the hierarchy problem. However, the dynamics of the Higgs boson is also sensitive to this new physics. We show that in many scenarios the Higgs can be a complementary and powerful probe of the hierarchy problem at the LHC and future colliders. If the top quark partners carry the color charge of the strong nuclear force, the production of Higgs pairs is affected. This effect is tightly correlated with single Higgs production, implying that only modest enhancements in di-Higgs production occur when the top partners are heavy. However, if the top partners are light, we show that di-Higgs production is a useful complementary probe to single Higgs production. We verify this result in the context of a simplified supersymmetric model. If the top partners do not carry color charge, their direct production is greatly reduced. Nevertheless, we show that such scenarios can be revealed through Higgs dynamics. We find that many color neutral frameworks leave observable traces in Higgs couplings, which, in some cases, may be the only way to probe these theories at the LHC. Some realizations of the color neutral framework also lead to exotic decays of the Higgs with displaced vertices. We show that these decays are so striking that the projected sensitivity for these searches, at hadron colliders, is comparable to that of searches for colored top partners. Taken together, these three case studies show the efficacy of the Higgs as a probe of naturalness.

Surface enrichment in gold/silver alloys: effects of temperature studied by atom probe tomography

Bimetallic alloys are increasingly used in heterogeneous catalysis. This interest is explained by the emergence of new features that are absent in the parent single metals. Synergistic effects between the two combined elements create a more efficient catalyst. One of the most challenging aspect of multicomponent materials in catalysis is the ability to fine-tune the catalytic properties of an alloy by controlling the nature and composition of the surface [1]. For example, the gold/silver alloy combines a high activity and a large selectivity for a broad range of oxidation reaction.It is well established that the surface composition of alloys may deviate from that of the bulk phase. Surface enrichment has also important consequences in some applications of heterogeneous catalysis. In some cases, the thermal and chemical treatments can lead to opposite trends regarding the nature of the metal prone to surface enrichment. Using atom probe tomography we aim to link the physicochemical conditions the composition of the very first atomic layers of bimetallic catalysts and eventually to fine-tune the catalytic features of the latter.

Scanning probe studies of thin films

The first part of this thesis deals with the phenomenon of thermoelectricity. It involves the improvement of the thermoelectric properties of silicon using innovative nanostructures. My contribution was to help fabricate these thermoelectric devices, and is the focus of this part of the thesis.

The second part and primary focus of this thesis is the analysis of thin films using scanning probe techniques. These surface techniques include atomic force microscopy, electric force microscopy, Kelvin probe force microscopy, and scanning tunneling microscopy. The thin films studied are graphene and molybdenum disulfide, two remarkable materials that display unique two-dimensional qualities. These materials are shown to be useful in studying the properties of adsorbates trapped between them and the substrate on which they rest. Moreover, these adsorbed species are seen to affect the structural and electronic properties of the thin films themselves. Scanning probe analyses are particularly useful in elucidating the properties of these materials, as surface effects play a significant role in determining their characteristics.

The final part of this thesis is concerned with the study of Akt in live cells using protein capture agents previously developed by my colleagues. The activation and degradation of Akt is investigated using various biological assays, including Western blots, in vitro kinase assays, and cell viability assays. Finally, the usefulness of synthetic capture agents in perturbing protein pathways and as delivery agents is assessed and analyzed.

Through Wafer 3D Vertical Micro-Coaxial Probe for High Frequency Material Characterization and Millimeter Wave Packaging Systems

This work presents the development of an in-plane vertical micro-coaxial probe using bulk micromachining technique for high frequency material characterization. The coaxial probe was fabricated in a silicon substrate by standard photolithography and a deep reactive ion etching (DRIE) technique. The through-hole structure in the form of a coaxial probe was etched and metalized with a diluted silver paste. A co-planar waveguide configuration was integrated with the design to characterize the probe. The electrical and RF characteristics of the coaxial probe were determined by simulating the probe design in Ansoft’s High Frequency Structure Simulator (HFSS). The reflection coefficient and transducer gain performance of the probe was measured up to 65 GHz using a vector network analyzer (VNA). The probe demonstrated excellent results over a wide frequency band, indicating its ability to integrate with millimeter wave packaging systems as well as characterize unknown materials at high frequencies. The probe was then placed in contact with 3 materials where their unknown permittivities were determined. To accomplish this, the coaxial probe was placed in contact with the material under test and electromagnetic waves were directed to the surface using the VNA, where its reflection coefficient was then determined over a wide frequency band from dc-to -65GHz. Next, the permittivity of each material was deduced from its measured reflection coefficients using a cross ratio invariance coding technique. The permittivity results obtained when measuring the reflection coefficient data were compared to simulated permittivity results and agreed well. These results validate the use of the micro-coaxial probe to characterize the permittivity of unknown materials at high frequencies up to 65GHz.

A dioxaborine cyanine dye as a photoluminescence probe for sensing carbon nanotubes

The unique properties of carbon nanotubes have made them the material of choice for many current and future industrial applications. As a consequence of the increasing development of nanotechnology, carbon nanotubes show potential threat to health and environment. Therefore, development of efficient method for detection of carbon nanotubes is required. In this work, we have studied the interaction of indopentamethinedioxaborine dye (DOB-719) and single-walled carbon nanotubes (SWNTs) using absorption and photoluminescence (PL) spectroscopy. In the mixture of the dye and the SWNTs we have revealed new optical features in the spectral range of the intrinsic excitation of the dye due to resonance energy transfer from DOB-719 to SWNTs. Specifically, we have observed an emergence of new PL peaks at the excitation wavelength of 735 nm and a redshift of the intrinsic PL peaks of SWNT emission (up to 40 nm) in the near-infrared range. The possible mechanism of the interaction between DOB-719 and SWNTs has been proposed. Thus, it can be concluded that DOB-719 dye has promising applications for designing efficient and tailorable optical probes for the detection of SWNTs.

Study of heterostructures of Cu3BiS3–buffer layer measured by Kelvin probe force microscopy measurements (KPFM)

The interface formed between Cu3BiS3 thin films and the buffer layer is a potentially limiting factor to the performance of solar cells based on Al/Cu3BiS3/buffer heterojunctions. The buffer layers of ZnS and In2S3 were grown by coevaporation, and tested as an alternative to the traditional CdS deposited by chemical bath deposition. From the Kelvin probe force microscopy measurements, we found the values of the work function of ZnS, In2S3, and CdS, layers deposited into Cu3BiS3. Additionally, different electronic activity was found for different grain boundaries (GBs), from studies under illumination, we also found the net doping concentration and the density of charged GB states for Cu3BiS3 and Cu3BiS3/CdS.