Transient Optical Characterisation of Donor-Acceptor Block Copolymers for Use in Solar Cells

This thesis presents a study of photo-active, semiconducting block copolymers for use in molecular solar cells. Current state-of-the-art organic devices utilise blends of two (or more) materials that are co-deposited from a common solution; the resulting structures formed are determined by material properties and deposition conditions, but often result in configurations that are detrimental to device performance. An answer to this problem comes in the form of the block copolymer; using these materials, devices can be formed from a single material active layer. In addition, the counterbalance of forces within films of block copolymer can lead to nano-scale self-assembly that allows for a strong degree of control over layer equilibrium morphology. Such control will be an important step forward in the evolution of molecular solar cells. The main body of this work is concerned with the study of the photo-physics of photo-conductive block copolymers, especially the generation of free charge. First, an investigation is made into the inherent structure-function relationship in block copolymers. A varying chain length is seen to drastically affect the photoluminescence quenching and yield of long-lived charges. Photovoltaic devices made using these materials show a peak efficiency of 0.11% and correlate with the spectroscopic results, subject to a trade off between charge generation and transport/collection. In a second investigation, the effects of post-fabrication annealing on block copolymer films are considered; studies on annealed samples lead to the conclusion that domain crystallinity is a significant factor in determining the yields of long-lived charge carriers. It is found that these yields are comparable with those of a standard blend (that achieve 75% photon to electron conversion efficiency). Annealing leads to increases in photovoltaic device performance over unannealed samples, although additional control over active layer morphology is necessary for these materials to attain their potential. Following this, a comparative study is made between a block copolymer and a similarly composed blend formed from well studied polyfluorene copolymers. Further advantages of block copolymers are highlighted, including the stability of morphologies generated under different deposition conditions. Finally, a novel tool set is introduced using a block copolymer sample to emphasise the experiments potential with regard to studying interfacial photophysical effects

Municipal Insolvency: The New Chapter IX of the Bankruptcy Act

In this report we give an introduction to a constructive way of treating systems of polynomial equations and inequalities. We present a method called cylindrical algebraic decomposition (CAD) discovered 1973 by Collins. The method constructs a decomposition of Rn such that a given set of polynomials have constant sign on each component. All concepts needed to understand the algorithm is presented, e.g., polynomial remainder sequences, subresultants, principal subresultant coefficients, Sturm chains and algebraic number representations

Carbon dioxide concentration indicator

Device will provide visual indication of concentration of carbon dioxide. It consists of small amounts of absorbent material contained in semipermeable membrane and device to detect color changes. Material will absorb quantity of carbon dioxide proportional to carbon dioxide concentration in atmosphere. Amount of absorption is indicated by color change

Theme Overview: Local Food - Perceptions, Prospects, and Policies

Local Food, Relocalization, Consumer Perception, Growth Prospects, Policy, Food Consumption/Nutrition/Food Safety,

Supply Chain Design for High Quality Products: Economic Concepts and Examples form the United States

The food system is undergoing significant structural change at local, national, and international levels. As the food system evolves, some segments along the chain between producers and consumers are disappearing. Others are being transformed. Supply chain concepts are useful for identifying and assessing alternative designs for the reconfiguration of food product production systems. Changes in the food system will require farm managers to adopt new ways of thinking and new perspectives on collaboration with trading partners. They also will require farm management economists to draw on a wider set of economic theories and concepts than we have in the past. This paper begins with brief descriptions of emerging supply chains for high quality food products in the U.S.: (i) a branded product chain, (ii) a genetics-based chain, and (iii) a production-practice based chain. These illustrate the variety of emerging supply chain structures and the challenges firms face in designing new supply chains. The next section presents an overview of key elements of four theoretical frameworks that are helpful in supply chain analysis and design: (i) transaction cost economics, (ii) agency theory, (iii) property rights theory, and (iv) the resource based view of the firm. Concepts from these theories are used to explain structural differences in the three illustrative cases. Looking to the future, key challenges include improving system-wide efficiency through information sharing and logistics management, promoting transparency and trust among trading partners, and designing incentive systems that ensure an equitable distribution of costs and returns.Farm Management,

Post-transcriptional regulation of the steady-state levels of mitochondrial tRNAs in HeLa cells

In human mitochondrial DNA (mtDNA), the tRNA genes are located in three different transcription units that are transcribed at three different rates. To analyze the regulation of tRNA formation by the three transcription units, we have examined the steady-state levels and metabolic properties of the tRNAs of HeLa cell mitochondria. DNA excess hybridization experiments utilizing separated strands of mtDNA and purified tRNA samples from exponential cells long term labeled with [32P]orthophosphate have revealed a steady-state level of 6 x 10(5) tRNA molecules/cell, with three-fourths being encoded in the H-strand and one-fourth in the L-strand. Hybridization of the tRNAs with a panel of M13 clones of human mtDNA containing, in most cases, single tRNA genes and a quantitation of two-dimensional electrophoretic fractionations of the tRNAs have shown that the steady-state levels of tRNA(Phe) and tRNA(Val) are two to three times higher than the average level of the other H-strand-encoded tRNAs and three to four times higher than the average level of the L-strand-encoded tRNAs. Similar experiments carried out with tRNAs isolated from cells labeled with very short pulses of [5-3H]uridine have indicated that the rates of formation of the individual tRNA species are proportional to their steady-state amounts. Therefore, the approximately 25-fold higher rate of transcription of the tRNA(Phe) and tRNA(Val) genes relative to the other H-strand tRNA genes and the 10-16-fold higher rate of transcription of the L-strand tRNA genes relative to the H-strand tRNA genes are not reflected in the steady-state levels or the rates of formation of the corresponding tRNAs. A comparison of the steady-state levels of the individual tRNAs with the corresponding codon usage for protein synthesis, as determined from the DNA sequence and the rates of synthesis of the various polypeptides, has not revealed any significant correlation between the two parameters

A DECISION SUPPORT SYSTEM FOR COMMODITY MARKETING MANAGEMENT

Marketing,