Microstructure versus Size: Mechanical Properties of Electroplated Single Crystalline Cu Nanopillars

We report results of uniaxial compression experiments on single-crystalline Cu nanopillars with nonzero initial dislocation densities produced without focused ion beam (FIB). Remarkably, we find the same power-law size-driven strengthening as FIB-fabricated face-centered cubic micropillars. TEM analysis reveals that initial dislocation density in our FIB-less pillars and those produced by FIB are on the order of 10^(14)  m^(-2) suggesting that mechanical response of nanoscale crystals is a stronger function of initial microstructure than of size regardless of fabrication method

The Effect of Anti-Hypertensive Agents on Platelets, Prostacyclin and Thromboxane and Observations on Prostacyclin and Thromboxane in Normal and Hypertensive Pregnancy

Prostacyclin (PGI2) is a potent vasodilator and anti-platelet prostaglandin which is the major product of arachidonic acid metabolism in vascular tissue. It is thought to function as a local vasoprotective agent, protecting blood vessels from platelet deposition and subsequent damage. Thromboxane A2(TxA2) is the major product of arachidonic acid metabolism in platelets, and has actions directly opposed to those of prostacyclin as it is a potent vasodilator and platelet aggregating agent, which is synthesised and released when platelet aggregation occurs. It has been proposed that a balance exists between these two substances to maintain vascular integrity. Disturbance of this balance may be important in diseases associated with platelet consumption and vasoconstriction such as pregnancy induced hypertension (PIH) and prostacyclin deficiency and excess TXA2 production have both been implicated in the pathophysiology of this condition. Recently, adrenoceptor antagonists and calcium channel blocking agents have been used in the treatment of PIH. The aims of this thesis were firstly to study the effects of these drugs on platelet function and PGI2 and TxA2 production in vitro, and secondly, to study plasma levels of PGI2 and TXA2 metabolites in normal pregnancy and PIH, and assess the effect of treatment with an adrenoceptor antagonist (labetalol) on levels of these substances and platelet consumption in PIH. The effects of seven adrenoceptor antagonists on platelet aggregation and TxA2 production in platelet rich plasma were studied in vitro. Labetalol, pindolol and propranolol inhibited platelet aggregation and TxA2 generation in a dose dependent manner, probably by preventing release of arachidonic acid from membrane phospholipids. This effect was independent of any adrenoceptor blocking property, as several other adrenoceptor antagonists - atenolol, metoprolol, timolol and prazosin were without effect. This platelet inhibitory effect may be related to membrane stabilising activity or lipid solubility as these properties were common to all three effective agents. The effects of labetalol, pindolol and propranolol on vascular PGI2 production was studied using umbilical artery, however, these agents had little effect, causing only slight inhibition of PGI2 production at high drug concentrations. These 3 agents acted synergistically with PGI2 - either exogenous or derived from vessel wall - to inhibit platelet aggregation in platelet rich plasma. It has recently become possible to measure platelet aggregation in whole blood. This may be more physiological than traditional turbidometric techniques using platelet rich plasma as it leaves platelet in their natural milieu surrounded by red and white cells which can themselves influence platelet aggregation. The effects of labetalol, pindolol, propranolol and atenolol on platelet aggregation in whole blood was studied. Labetalol, pindolol and propranolol inhibited aggregation in a dose dependent manner and acted synergistically with exogenous PGI2 to inhibit platelet aggregation. They also inhibited PGI2 and TXA2 production from whole blood. Atenolol had no effect on either aggregation or TxA2 or PGI2 production. The calcium channel blocking agent nicardipine was similarly assessed and found to inhibit aggregation but it had no effect on TxA2 or PGI2 production. Labetalol and nicardipine were also found to act synergistically with low concentrations of aspirin to inhibit platelet aggregation in whole blood. Cross-sectional and longitudinal studies of plasma levels of PGI2 and TxA2 metabolites throughout normal pregnancy were performed. Prostacyclin metabolites were found to be increased in the first trimester compared to the non-pregnant state, while TxA2 metabolite levels were slightly reduced in the second and third trimesters. Cross-sectional and longitudinal studies of these substances in PIH were also performed and plasma PGI2 metabolites were found to be reduced, providing further evidence that PIH is associated with PGI2 deficiency. No change in TxA2 metabolites was noted in PIH. The effects of treatment with labetalol on plasma levels of PGI2 and TxA2 metabolites, and on platelet consumption were studied in PIH. Labetalol therapy did not affect levels of TXA2 metabolites but seemed to increase PGI2 metabolite levels if these were initially low, although no consistent effect on plasma PGI2 metabolite levels was noted if these were initially within the normal range. Following therapy with labetalol platelet consumption was significantly reduced especially in severe PIH. This reduction in platelet consumption suggests that the anti-platelet properties of labetalol studied in vitro may well exist in vivo, and such platelet protective therapy may be of value in the treatment of this disease. The anti-platelet properties of adrenoceptor antagonists, used either alone or in combination with prostacyclin or aspirin, which have been described in this thesis, require further clinical evaluation, but offer new therapeutic possibilities not only in PIH but also in other vascular disorders associated with platelet activation

Mechanical compatibility of sol–gel annealing with titanium for orthopaedic prostheses

Sol–gel processing is an attractive method for large-scale surface coating due to its facile and inexpensive preparation, even with the inclusion of precision nanotopographies. These are desirable traits for metal orthopaedic prostheses where ceramic coatings are known to be osteoinductive and the effects may be amplified through nanotexturing. However there are a few concerns associated with the application of sol–gel technology to orthopaedics. Primarily, the annealing stage required to transform the sol–gel into a ceramic may compromise the physical integrity of the underlying metal. Secondly, loose particles on medical implants can be carcinogenic and cause inflammation so the coating needs to be strongly bonded to the implant. These concerns are addressed in this paper. Titanium, the dominant material for orthopaedics at present, is examined before and after sol–gel processing for changes in hardness and flexural modulus. Wear resistance, bending and pull tests are also performed to evaluate the ceramic coating. The findings suggest that sol–gel coatings will be compatible with titanium implants for an optimum temperature of 500 °C

In situ characterization of vertically oriented carbon nanofibers for three-dimensional nano-electro-mechanical device applications

We have performed mechanical and electrical characterization of individual as-grown, vertically oriented carbon nanofibers (CNFs) using in situ techniques, where such high-aspect-ratio, nanoscale structures are of interest for three-dimensional (3D) electronics, in particular 3D nano-electro-mechanical-systems (NEMS). Nanoindentation and uniaxial compression tests conducted in an in situ nanomechanical instrument, SEMentor, suggest that the CNFs undergo severe bending prior to fracture, which always occurs close to the bottom rather than at the substrate–tube interface, suggesting that the CNFs are well adhered to the substrate. This is also consistent with bending tests on individual tubes which indicated that bending angles as large as ~70° could be accommodated elastically. In situ electrical transport measurements revealed that the CNFs grown on refractory metallic nitride buffer layers were conducting via the sidewalls, whereas those synthesized directly on Si were electrically unsuitable for low-voltage dc NEMS applications. Electrostatic actuation was also demonstrated with a nanoprobe in close proximity to a single CNF and suggests that such structures are attractive for nonvolatile memory applications. Since the magnitude of the actuation voltage is intimately dictated by the physical characteristics of the CNFs, such as diameter and length, we also addressed the ability to tune these parameters, to some extent, by adjusting the plasma-enhanced chemical vapor deposition growth parameters with this bottom-up synthesis approach

Sol-gel coatings for subaquatic self-cleaning windows

Self-cleaning windows are well known for their ability to function with airborne pollutants, but there is a growing industry for semi-permanent subaquatic optical devices, where the performance of such windows should be considered. Here sol-gel technology is explored as a means of producing self-cleaning, subaquatic, sapphire windows. We demonstrate removal of marine bacteria and, in the worst-case contamination scenario, dead North Sea crude oil (API 35). This greasy contaminant was smeared across the windows to effectively reduce optical transmission strength to just 54%. The titania-based sol-gel-coated windows can restore transmission to within 10% of the clean value in less than one day, unlike standard sapphire windows, which lose 68% transmission following contamination and aquatic submergence over the same duration. A range of theories to enhance the self-cleaning performance of the sol-gel coating were explored, but none of the tested variables were able to provide any enhancement for subaquatic performance

Self-folding nano- and micropatterned hydrogel tissue engineering scaffolds by single step photolithographic process

Current progress in tissue engineering is focused on the creation of environments in which cultures of relevant cells can adhere, grow and form functional tissue. We propose a method for controlled chemical and topographical cues through surface patterning of self-folding hydrogel films. This provides a conversion of 2D patterning techniques into a viable method of manufacturing a 3D scaffold. While similar bilayers have previously been demonstrated, here we present a faster and high throughput process for fabricating self-folding hydrogel devices incorporating controllable surface nanotopographies by serial hot embossing of sacrificial layers and photolithography

Interpretation, Imagination, and Discipline in Hindu Trinidad

xi, 249 p. : ill. (some col.)Globalization has inaugurated many rapid changes in local communities throughout the world. The globalization of media, both electronic and print, has introduced new pressures for local communities to confront while also opening up new imaginative possibilities. As many observers have noted, transnational media transform local public cultures, or shared imaginative spaces, but never in predictable, totally hegemonic ways. This dissertation focuses on the efforts of a small Hindu community called the Hindu Prachar Kendra located in Trinidad, West Indies, as they develop critical strategies that help their children read, negotiate, and in some cases contribute to local and global public cultures. I argue that though many Hindu parents and teachers of the Kendra share anxieties about the effects of local and global popular cultures on their children, they also use many features, ideas, and texts emerging from imaginative media in creative ways. Furthermore, their concerns about media shape their interpretation and instruction of Hindu practice.Committee in charge: Philip Scher, Chair; Lynn Stephen, Member; Lamia Karim, Member; Deborah Green, Outside Membe