Surface Chemistry Mediated Assembly of Polymer-Grafted Nanorods in Solution and Polymer Matrices

In the dissertation, I investigate ways to assemble nanorods, typically made of gold, in solution and polymer matrices by controlling surface chemistry. Gold nanorods were anisotropically functionalized with polymer on the side and alkane dithiol on the end causing the gold nanorods to spontaneously assemble in solution. The assembly could be tuned by controlling the incubation time which affected the solution absorbance due to plasmon coupling. Linked gold nanorods were cast in polymer thin films and their optical properties were imparted to the film. This anisotropic functionalization method was utilized to placed DNA or peptides on the ends of the gold nanorods allowing for reversibly assembly. In the case of DNA, assembly was reversed upon heating and could be tuned by controlling the concentration of the complimentary DNA strand. In the case of the peptide, assembly was triggered by the presence of Zn2+ ions and could be reversed by adding in a chelater. Anisotropic modification of the nanorods could also be used to assemble organic semiconductors around the nanorods at specific facets. Here, organic semiconductors rhodamine-B, 5(6)-carboxyfluorescein, and cyanine-3 were assembled onto the surface of gold nanorods. By tuning the surface chemistry the organic semiconductors would assemble around the nanorods in different ways which resulted in unique optical properties. The dispersion of PMMA-grafted mesoscopic iron-oxide rods in polymer matrices was studied by varying the PMMA brush molecular weight (N) polymer matrix molecular weight (P), and polymer matrix type. Here, we found that the ratio of P/N and matrix type had little effect on dispersion of iron-oxide mesorods. N was found to be the main factor that determined dispersion, which is attributed to the large size of the mesorods. Long PS and short PMMA brushes were grafted to gold nanorod surfaces and the dispersion of this system in PS and PMMA was investigated by controlling matrix molecular weight. We found that the gold nanorods would disperse in PS matrices 24 times larger than the grafted brush, while in PMMA matrices the nanorods would aggregate. SCFT calculations revealed that the good dispersion is most likely due to the collapse of the short PMMA brush and the enthalpic penalty for the collapse of the PS brush onto the PMMA brush. Finally, PS-grafted gold nanorods were assembled in liquid crystals. Assembly was tuned by controlling temperature and liquid crystal defect structure in the presence of micropillar arrays. The assembly of the nanorods resulted in changes in characteristic absorbance peaks of over 100 nm. From these studies, we are able to predict and control the assembly of nanorods in both solution and polymer matrices allowing us to fine-tune optical properties

The informativeness of stochastic frontier and programming frontier efficiency scores: Cost efficiency and other measures of bank holding company performance

This paper examines the properties of the X-inefficiencies in U.S. bank holding companies derived from both stochastic and linear programming frontiers. This examination allows the robustness of results across methods to be compared. While we find that calculated programming inefficiency scores are two to three times larger than those estimated using a stochastic frontier, the patterns of the scores across banks and time are similar, and there is a relatively high correlation of the rankings of banks' efficiencies under the two methods. However, when we examine the "informativeness" of the efficiency measured by the two different techniques, we find some large differences. We find evidence that the stochastic frontier scores are more closely related to risk-taking behavior, managerial competence, and bank stock returns. Based on these findings, we conclude that while both methods produce informative efficiency scores, for this data set decision makers should put more weight on the stochastic frontier efficiency estimates.Bank holding companies ; Banks and banking - Costs

Issues of scale and scope in bio-physical modelling for natural resource management decision making in New South Wales

Natural resource management decision making by Catchment Management Authorities in NSW is being aided by a project involving bio-physical modelling and the development of an alternative decision-making framework. The objective of the bio-physical modelling process is to generate predictions of environmental or natural resource outcomes rather than project outputs. These outcomes can then be used in an investment framework to help priority setting and project decision making. Questions that arise in bio-physical modelling include those relating to scale and scope. Scale issues include how to address the landscape impacts of particular (or a series of local) on-ground works proposals. Scope issues include assessment of multiple-attribute responses to particular changes. In a multi-disciplinary context the challenge is then to translate this information into units that can be adapted to a decision-support framework. Existing Catchment Management Authorities decisions are often based on scoring and weighting of environmental improvements using an environmental benefits index, however other economic frameworks are possible. We discuss the important context for these questions in the decision making framework.environmental benefits, bio-physical models, scale, scope, investment decisions, Resource /Energy Economics and Policy,

Ecosystem health towards sustainability

Ecosystems are becoming damaged or degraded as a result of stresses especially associated with human activities. A healthy ecosystem is essential to provide the services that humans and the natural environment require and has tremendous social and economic value. Exploration of the definition of ecosystem health includes what constitutes health and what it means to be healthy. To evaluate ecosystem health, it is necessary to quantify ecosystem conditions using a variety of indicators. In this paper, the main principles and criteria for indicator selection, classification of indicators for different kinds of ecosystems, the most appropriate indicators for measuring ecosystem sustainability, and various methods and models for the assessment of ecosystem health are presented. Drivers, sustainability, and resilience are considered to be critical factors for ecosystem health and its assessment. Effective integration of ecological understanding with socioeconomic, biophysical, biogeochemical, and public-policy dimensions is still the primary challenge in this field, and devising workable strategies to achieve and maintain ecosystem health is a key future challenge

SiC Field Effect Transistor Technology Demonstrating Prolonged Stable Operation at 500 C

While there have been numerous reports of short-term transistor operation at 500 degree C or above, these devices have previously not demonstrated sufficient long-term operational durability at 500 degree C to be considered viable for most envisioned applications. This paper reports the development of Silicone Carbi field effect transistors capable of long-term electrical operation at 500 degree C. A 6H-SiC MESFET was packaged and subjected to continuous electrical operation while residing in a 500 degree C oven in oxidizing air atmosphere for over 2400 hours. The transistor gain, saturation current (IDSS), and on-resistance (RDS) changed by less than 20% from initial values throughout the duration of the biased 500 degree C test. Another high-temperature packaged 6H-SiC MESFET was employed to form a simple one-stage high-temperature low-frequency voltage amplifier. This single-stage common-source amplifier demonstrated stable continuous electrical operation (negligible changes to gain and operating biases) for over 600 hours while residing in a 500 degree C air ambient oven. In both cases, increased leakage from annealing of the Schottky gate-to-channel diode was the dominant transistor degradation mechanism that limited the duration of 500 degree C electrical operation

RELEVANCE, RELIABILITY AND LIMITATIONS OF A DROP AND STICK LANDING ANALYSIS

The vertical force data from a drop and stick landing can be used to derive a number of variables. Previous studies have generally focused on the time to stabilization and peak force aspects, and issues related to reliability have been reported. This study investigated reliability for time to stabilisation, peak force, time to peak force, stiffness, rate of force dissipation, impulse and eccentric power (EP) among five professional elite surfing athletes. This data was also compared to data of aerial success in World Championship Tour competitions. The results revealed the best relationship between relative stiffness as well as eccentric power and completion rate of aerial manoeuvres. Further, eccentric power had the best reliability of the variables and may therefore be an interesting variable to study further