Graphite and graphite composite materials are of great importance in various applications; however, they have been widely used in nuclear applications. Primarily in nuclear applications such, as a moderator where its primary aim is to stop the fast neutrons to thermal neutron. The composite graphite (HTR-10) has potential applications as a moderator and other applications including in aerospace field. Structurally the composite shows stable hexagonal form of graphite and no traces of the unstable Rhombohedral patterns. Thermal conductivity indicates the same trends observed and known for nuclear graded graphite. The composite was made as a mixture of 64 wt% of natural graphite, 16 wt% of synthetic graphite binded together by 20 wt% of phenolic resin. The resinated graphite powder was uni-axially pressed by 19.5 MPa to form a disc shaped specimen. The disc was then cut and annealed to 1800 °C. The composite was further cut into two directions (parallel and perpendicular) to the pressing direction. For characterization the samples were cut into 2.5 x 2.5 x 10 mm3. There were exposed to proton irradiation for 3 and 4.5 hrs respectively and characterized both structurally and thermally. Through the study what we have observed was that as the composite is exposed to proton irradiation there is an improvement structurally. Thus, the D peak in the Raman spectroscopy has decreased substantially with the irradiated samples. XRD has indicated that there is no un-stable Rhombohedral phase pattern in both the pristine and the irradiated samples. However this was further confirmed with that thermal conductivity is also increasing with irradiation exposure. This is anomalous to irradiated graphite in which defects are supposedly induced. Looking into the electrical resistivity we have noted that pristine samples have higher resistivity as compared to the irradiated samples. Seebeck coefficient indicates that there is some form of structural perfection and the samples have a phonon drag dip at the known graphite temperature of 35 K. This has shown us there are no impurities induced by irradiation of the samples. / Dissertation (MSc)--University of Pretoria, 2013. / gm2014 / Physics / Unrestricted

Thesis (Ph.D.)--Boston University / The large electromagnetic field enhancement provided by nanostructured noble metal surfaces forms the foundation for a series of enabling optical analytical techniques, such as surface enhanced Raman spectroscopy (SERS), surface enhanced IR absorption spectroscopy (SEIRA), surface enhanced fluorescent microscopy (SEF), to name only a few. Critical sensing applications have, however, other substrate requirements than mere peak signal enhancement. The substrate needs to be reliable, provide reproducible signal enhancements, and be amenable to a combination with microfluidic chips or other integrated sensor platforms. These needs motivate the development of engineerable SERS substrate "chips" with defined near- and far-field responses. In this dissertation, two types of rationally designed SERS substrates - nanoparticle cluster arrays (NCAs) and SERS stamp - will be introduced and characterized. NCAs were fabricated through a newly developed template guided self-assembly fabrication approach, in which chemically synthesized nanoparticles are integrated into predefined patterns using a hybrid top-down/bottom-up approach. Since this method relies on chemically defined building blocks, it can overcome the resolution limit of conventional lithographical methods and facilitates higher structural complexity. NCAs sustain near-field interactions within individual clusters as well as between entire neighboring clusters and create a multi-scale cascaded E-field enhancement throughout the entire array. SERS stamps were generated using an oblique angle metal deposition on a lithographically defined piston. When mounted on a nanopositioning stage, the SERS stamps were enabled to contact biological surfaces with pristine nanostructured metal surfaces for a label-free spectroscopic characterization. The developed engineered substrates were applied and tested in critical sensing applications, including the ultratrace detection of explosive vapors, the rapid discrimination of bacterial pathogens, and the label-free monitoring of the enzymatic degradation of pericellular matrices of cancer cells.

Doctor Scientiae - DSc / Semiconductor nanocrystals or quantum dots (QDs) are fluorescent nanometer-sized particles which have physical dimensions that are smaller than the excitonic Bohr radius, large surface area-to-volume ratios, broad absorption spectra and very large molar extinction coefficients. Biomedical applications of QDs are mainly based on II-VI QDs containing cadmium, such as CdSe/ZnS. These cadmium-based systems are associated with high toxicity due to cadmium. As a result, potential replacements of cadmium-based QDs in biological applications are needed. In this study, InP/ZnSe QDs were synthesized for the first time using a one-pot hot injection method. Furthermore, a growth-doping method was used for silver, cobalt and iron incorporation into the InP core. Water compatibility was achieved through ligand exchange with 3- mercaptopropionic acid. In vitro cytotoxicity and imaging/internalization of the as-prepared MP A-InP/ZnSe and MP A-capped CdTe/ZnS QDs were evaluated. InP/ZnSe QDs were successfully synthesized with ZnSe shell causing a 1.4 times reduction in trap-related emission.

A biological pathway is a series of reactions and molecular interactions. Pathway information provides a blueprint for biomedical researchers to devise new treatment and diagnostic solutions for human diseases. Pathway data are publicly available in many databases. Most of the databases however have only partial coverage of human biological pathways, especially for signal transduction and gene regulatory pathways. Comprehensive knowledge and a combined view for all types for biological pathways may lead to insights into the molecular physiology of cells and drug discovery. In this project, we collected human signaling pathway data from different database sources. The pathway data comes from the Biocarta, Protein Lounge, Resnet and NCI-Nature Curated databases. We analyzed the structures of collected data, and developed a comprehensive data model to manage integrated information of molecules, complexes, regulation relationships of molecules, and reactions involved in signaling and regulatory pathways. The integrated database, the Human Pathway database (HPD), is a data warehouse of a comprehensive collection of biological reactions, regulators, and metabolites, serving as a potential platform for future pathway analysis studies. We developed the database to manage integrated biomolecular information related to pathways. In HPD, which uses Oracle 10g, there are a total of 1,895 pathways, 10,631 molecular entities (proteins, complexes and compounds) and 4,370 reactions that were consolidated and integrated into a single relational database platform using Oracle 10g. We also developed a prototypical GUI for the navigation and querying of biological pathways. Such a system, when completed, and used in conjunction with future pathway data visualization and analysis tools, could provide a framework for systems biology studies. We developed HPD with comprehensive annotation data. For example, the kinase - disease association information and perturbation effect of several environmental factors are unique in HPD. The potential for merging similar pathways—“pathway mergability” —was created based on gene/protein identifiers and to provide with non-redundant pathway information. To test the technology we have done two case studies. The first case study addressed the Alzheimer’s disease by coupling pathway network analysis with gene expression data. The second case study addressed the cellular responses by coupling the pathway network analysis with protein expression data. These case studies demonstrate how an integrated pathway database can be used to generate new insights into the discovery of biomarkers, and extend our understanding of cellular physiology.

During the past few decades, examinations of social, biological, and communication networks have taken on increased attention. While numerous models of these networks have arisen, some have lacked visual representations. This is particularly true in ecology, where scientists have often been restricted to at most three dimensions when creating graphical representations of pattern and process. I will introduce an application of dot product representation graphs that allows scientists to view the high dimensional connections in ecological networks. Using actual data, example graphs will be developed and analyzed using key measures of graph theory.

Dielectric properties play an influential role in the development of medical devices. Understanding the behavior of these properties and how they respond to external stimuli, such as heat, over an extended frequency has yet to be researched. The focus of this study is to examine the impact of temperature on dielectric properties from 500 MHz to 10 GHz in order to better match the antenna properties of medical applications to the dielectric properties of biological tissue in question; more specifically, microwave ablation, microwave hyperthermia, and thermal modeling of brown adipose tissue’s metabolic processes. The dielectric properties of biological tissue samples from porcine lung, liver, heart, skin, fat, and muscle as well as brown adipose tissue and white adipose tissue from rat have been tested. These results have then been used to develop medical applications involving microwave antennas.

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