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Revised NHS guidance has relaxed infection prevention and control (IPC) requirements for hospitals and GP practices. These authors question why airborne transmission is not more clearly acknowledged and why healthcare workers still do not have access to appropriate personal protective equipment

Organic photovoltaic (OPV) devices provide an opportunity for low cost, printable solar cells. This thesis focuses upon improving power conversion efficiencies (PCE) and lifetimes of OPV devices, with an emphasis on studying materials made from cyclopentadithiophene (CPDT) and benzothiadiazole (BT) monomers. The first part of the work focuses on characterising the optical and electrical properties of new materials based on this material system. A donor-acceptor-donor (D-A-D) small molecule, with the monomer order of CPDTBT-CPDT (C2B1) was trialled and demonstrated an optical band gap of 1.8 eV. OFET mobility was measured as 5 x 10-3 cm 2 .V-1.s-1 in the saturation region, and when blended with phenyl-C71-butyric acid methyl ester (PC71BM), gave a PCE of 1.54% under AM1.5G illumination. The moderate performance directed research towards donor-acceptor (D-A) polymers (PCPDTBT), synthesised using direct heterolytic arylation. OPV devices made with this material blended with PC71BM gave a maximum PCE of 4.23%, when tested under AM1.5G. OPV device performance is slightly higher than for PCPDTBT synthesised using more established techniques. This is the first known report of a working device with an active layer polymer synthesised using the direct heterolytic arylation route. The stability of the PCPDTBT material was tested using a combination of OPV device data and analytical instruments. From device data, PCPDTBT was shown to be less stable than the more commonly reported P3HT material. Significantly, processing additives used to optimise the active layer morphology, are shown to be detrimental to long-term performance, approximately halving the device half-life (T50%). The physical changes are examined using Atomic Force Microscopy (AFM) and Grazing-Incidence Small-Angle X-ray Scattering (GISAXS) and show that the inclusion of processing additives leads to greater morphological changes during ageing experiments. The chemical changes occurring in PCPDTBT were examined using XPS and show that light soaking leads to observations of severe oxidation, with a break-up of the aromatic rings, formation of sulphates at the thiophene ring, chain scission in the polymer backbone and loss of side chains. However, it is concluded that morphological changes are mostly responsible for the observed decrease in OPV device PCE. PCPDTBT with thermally initiated cross-linking behaviour is characterised and used to fabricate OPV cells. Cross-linkable PCPDTBT demonstrates a PCE of 3.65%, which is similar to its non-cross-linkable analogue, however, improved stability is observed from ageing experiments. This increase in stability, investigated further using AFM and GISAXS, is a result of fewer morphological changes in the active layer. While the work has focussed on PCPDTBT, many of the conclusions regarding the analysis of material degradation could be of wider interest to the field. The analysis could provide some new insights, on the degradation and stability of conjugated polymers and fullerene derivatives.

Genotoxins cause DNA damage, which can result in genomic instability. The genetic changes induced have far-reaching consequences, often leading to diseases such as cancer. A wide range of genotoxins exists, including radiations and chemicals found naturally in the environment and in man-made forms created by human activity across a variety of industries. Genomic technologies offer the possibility of unravelling the mechanisms of genotoxicity, including the repair of genetic damage, enhancing our ability to develop, test and safely use existing and novel materials. We have developed 3D-DIP-Chip, a microarray-based method to measure the prevalence of genomic genotoxin-induced DNA damage. We demonstrate the measurement of both physical and chemical induced DNA damage spectra, integrating the analysis of these with the associated changes in histone acetylation induced in the epigenome. We discuss the application of the method in the context of basic and translational sciences.

The rates at which lesions are removed by DNA repair can vary widely throughout the genome with important implications for genomic stability. To study this, we measured the distribution of nucleotide excision repair (NER) rates for UV-induced lesions throughout the budding yeast genome. By plotting these repair rates in relation to genes and their associated flanking sequences, we reveal that in normal cells, genomic repair rates display a distinctive pattern, suggesting that DNA repair is highly organised within the genome. Furthermore, by comparing genome-wide DNA repair rates in wild-type cells, and cells defective in the global genome-NER (GG-NER) sub-pathway, we establish how this alters the distribution of NER rates throughout the genome. We also examined the genomic locations of GG-NER factor binding to chromatin before and after UV irradiation revealing that GG-NER is organised and initiated from specific genomic locations. At these sites, chromatin occupancy of the histone acetyl transferase Gcn5 is controlled by the GG-NER complex, which regulates histone H3 acetylation and chromatin structure, thereby promoting efficient DNA repair of UV-induced lesions. Chromatin remodeling during the GG-NER process is therefore organized into these genomic domains. Importantly, loss of Gcn5, significantly alters the genomic distribution of NER rates, a finding that has important implications for the effects of chromatin modifiers on the distribution of mutations that arise throughout the genome.