N-type organic semiconductors and conductors for plastic electronics

Organic semiconductors have begun to find a place as viable active materials for a new generation of devices. Throughout the development of this relatively new class of materials, it has been apparent that optimising the performance of n-type semiconductors and dopants has been a challenge compared to their p-type counterparts. Many applications in photovoltaics, thermoelectrics, light-emitting diodes and more, require or can benefit from n-type components. To really benefit from the processability and scalability of organic semiconductors in industry it is therefore necessary to develop stable and high-performing n-type materials. This thesis aims to advance the understanding of promising n-type semiconductor and dopant pairs through structural characterisation. A new “self-doping” naphthalene diimide conductor, NDI-OH, was designed and synthesised based on previously made structures which exhibited surprisingly stable radical anions. A full spectroscopic characterisation of the self-dopant revealed that it is the product of hydrolysis after ion-exchange in basic conditions. This was found to have a profound effect on the mechanism of charge transfer between dopant and semiconducting moieties and on the lifetime of charge carriers. It was postulated that the mixture of compounds present in doped films is likely to contribute to charge transport pathways and the electronic conductivity. The interactions between n-type semiconductors and fluoride anions was also explored. Reactions between solvent and fluoride salt were found to have an impact on the efficiency and nature of the subsequent charge transfer on to BDOPV semiconductors. The mechanism of doping relied on factors including the acidity of solvent and the presence of water. Spectroscopic characterisation was carried out in order to determine the active compounds involved in charge transfer between tetrabutylammonium fluoride and BDOPV. Finally, two new n-type polymers, PbTzTT and PbTz3, were designed with the aim of exhibiting a high degree of long-range order in the solid-state. The reactivity of thiazoles and fused thiazolo[5,4-d]thiazole heterocycles was explored at length. The ring-opening of these compounds on metalation and the possibilities of electrophilic substitution were especially of interest. The eventual successful synthesis of the polymer PbTzTT is described via a Stille cross-coupling polymerisation. The PbTz3 macromonomer was also obtained through a double ring-closing condensation. A comparison of the optoelectronic properties of PbTzTT with the structurally analogous p-type polymer PbTTT was also made

Integrated pest management portfolios in UK arable farming: results of a farmer survey.

Farmers are faced with a wide range of pest management (PM) options that can be adopted in isolation or alongside complementary or substitute strategies. This paper presents the results of a survey of UK cereal producers, focusing on the character and diversity of PM strategies currently used by, or available to, farmers. In addition, the survey asked various questions pertaining to agricultural policy participation, attitude towards environmental issues, sources of PM advice and information and the important characteristics of PM technologies. The results indicate that many farmers do make use of a suite of PM techniques, and that their choice of integrated PM (IPM) portfolio appears to be jointly dictated by farm characteristics and government policy. Results also indicate that portfolio choice does affect the number of subsequent insecticide applications per crop. These results help to identify the type of IPM portfolios considered to be adoptable by farmers and highlight the importance of substitution in IPM portfolios. As such, these results will help to direct R&D effort towards the realisation of more sustainable PM approaches and aid the identification of potential portfolio adopters. These findings highlight the opportunity that a revised agri-environmental policy design could generate in terms of enhancing coherent IPM portfolio adoption

Hsp21potentiates antifungal drug tolerance in Candida albicans

Peer reviewedPublisher PD

Critical analysis of self-doping and water-soluble n-type organic semiconductors: structures and mechanisms

Self-doping organic semiconductors provide a promising route to avoid instabilities and morphological issues associated with molecular n-type dopants. Structural characterization of a naphthalenetetracarboxylic diimide (NDI) semiconductor covalently bound to an ammonium hydroxide group is presented. The dopant precursor was found to be the product of an unexpected base catalyzed hydrolysis, which was reversible. The reversible hydrolysis had profound consequences on the chemical composition, morphology, and electronic performance of the doped films. In addition, we investigated the degradation mechanism of the quaternary ammonium group and the subsequent doping of NDI. These findings reveal that the products of more than one chemical reaction during processing of films must be considered when utilizing this promising class of water-soluble semiconductors

Secondary Eclipse Photometry of WASP-4b with Warm Spitzer

We present photometry of the giant extrasolar planet WASP-4b at 3.6 and 4.5 micron taken with the Infrared Array Camera on board the Spitzer Space Telescope as part of Spitzer's extended warm mission. We find secondary eclipse depths of 0.319+/-0.031% and 0.343+/-0.027% for the 3.6 and 4.5 micron bands, respectively and show model emission spectra and pressure-temperature profiles for the planetary atmosphere. These eclipse depths are well fit by model emission spectra with water and other molecules in absorption, similar to those used for TrES-3 and HD 189733b. Depending on our choice of model, these results indicate that this planet has either a weak dayside temperature inversion or no inversion at all. The absence of a strong thermal inversion on this highly irradiated planet is contrary to the idea that highly irradiated planets are expected to have inversions, perhaps due the presence of an unknown absorber in the upper atmosphere. This result might be explained by the modestly enhanced activity level of WASP-4b's G7V host star, which could increase the amount of UV flux received by the planet, therefore reducing the abundance of the unknown stratospheric absorber in the planetary atmosphere as suggested in Knutson et al. (2010). We also find no evidence for an offset in the timing of the secondary eclipse and place a 2 sigma upper limit on |ecos(omega)| of 0.0024, which constrains the range of tidal heating models that could explain this planet's inflated radius.Comment: 8 pages, 7 figures (some in color), accepted for publication in Ap

Credibility and adjustment: gold standards versus currency boards

It is often maintained that currency boards (CBs) and gold standards (GSs) are alike in that they are stringent monetary rules, the two basic features of which are high credibility of monetary authorities and the existence of automatic adjustment (non discretionary) mechanism. This article includes a comparative analysis of these two types of regimes both from the perspective of the sources and mechanisms of generating confidence and credibility, and the elements of operation of the automatic adjustment mechanism. Confidence under the GS is endogenously driven, whereas it is exogenously determined under the CB. CB is a much more asymmetric regime than GS (the adjustment is much to the detriment of peripheral countries) although asymmetry is a typical feature of any monetary regime. The lack of credibility is typical for peripheral countries and cannot be overcome completely even by “hard” monetary regimes.http://deepblue.lib.umich.edu/bitstream/2027.42/40078/3/wp692.pd

PAX-D:study protocol for a randomised placebo-controlled trial evaluating the efficacy and mechanism of pramipexole as add-on treatment for people with treatment resistant depression

Introduction: Clinical depression is usually treated in primary care with psychological therapies and antidepressant medication. However, when patients do not respond to at least two or more antidepressants within a depressive episode, they are considered to have treatment resistant depression (TRD). Previous small randomised controlled trials suggested that pramipexole, a dopamine D2/3 receptor agonist, may be effective for treating patients with unipolar and bipolar depression as it is known to influence motivational drive and reward processing. PAX-D will compare the effects of pramipexole versus placebo when added to current antidepressant medication for people with TRD. Additionally, PAX-D will investigate the mechanistic effect of pramipexole on reward sensitivity using a probabilistic decision-making task. Methods and analysis: PAX-D will assess effectiveness in the short- term (during the first 12 weeks) and in the longer-term (48 weeks) in patients with TRD from the UK. The primary outcome will be change in self-reported depressive symptoms from baseline to Week 12 post-randomisation measured using the QIDS-SR. Performance on the decision-making task will be measured at Week 0, Week 2, and Week 12. Secondary outcomes include anhedonia, anxiety, and health economic measures including quality of life, capability, wellbeing, and costs. PAX-D will also assess the adverse effects of pramipexole including impulse control difficulties. Discussion: Pramipexole is a promising augmentation agent for treatment resistant depression and may be a useful addition to existing treatment regimes. PAX-D will assess its effectiveness and test for a potential mechanism of action in patients with treatment resistant depression