Synthesis and Characterisation of Initiators and Amphiphilic Miktoarm Star Polymers

This project involves the development of several novel heterofunctional initiators with a calix[4]arene centre that can facilitate a “core” first method for the synthesis of miktoarm star polymers. Chapter 1 introduces main concepts on calixarenes, single electron transfer living radical polymerisation and the ring opening polymerisation of ε-caprolactone. Chapter 2 describes the synthetic strategy employed for the synthesis of a novel A2B2 heterofunctional initiator that incorporated an alkyl halogen moiety and a primary hydroxyl. p-tert-butylcalix[4]arene was modified via a six step process to introduce the required functionality and was fully characterised at each stage using 1D and 2D NMR spectroscopy, ASAP MS and IR spectroscopy. Chapter 3 describes how the A2B2 heterofunctional initiator was used to synthesise a novel 2-armed PCL polymer centred on a calixarene core. This was further used for copper(0) mediated polymerisation of 2-hydroxyethylacrylate due to the alkyl halide moieties remaining in the calixarene core, leading to the formation of several amphiphilic A2B2 miktoarm star polymers. Both polymers were fully characterised using 1D and 2D NMR spectroscopy, SEC, DSC, TGA and IR spectroscopy. Chapter 4 describes the synthetic strategy employed for the synthesis of a novel A4B4 heterofunctional initiator that incorporated an alkyl halogen moiety and a primary hydroxyl. p-tert-butylcalix[4]arene was modified via a seven step process to introduce the required functionality and was fully characterised at each stage using 1D and 2D NMR spectroscopy, ASAP MS and IR spectroscopy. Chapter 5 describes how the A4B4 heterofunctional initiator was used to synthesise a novel 4-armed star PCL polymer centred on a calixarene core. This was further used for copper(0) mediated polymerisation of 2-hydroxyethylacrylate due to the alkyl halide moieties remaining in the calixarene core, leading to the formation of several amphiphilic A4B4 miktoarm star polymers. Both polymers were fully characterised using 1D and 2D NMR spectroscopy, SEC, DSC, TGA and IR spectroscopy. Chapter 6 described the self-assembly of A2B2 and A4B4 amphiphilic miktoarm star polymers calixarene-A2B2starPCL100PHEAm, 8-10, where m = 75, 100 and 270, respectively and calixarene-A4B4starPCL20PHEAm, 18, 19 and 20 where m = 10, 25 and 48, respectively). The TEM analysis on polymer systems 8 - 10 and 18 - 20, revealed spherical micelles, with the size of the micelle decreasing as the proportion of hydrophilic PHEA increased. The CMC determinations for polymers 8 – 10 revealed that the length of the hydrophilic chain does not appear to have a significant effect on the CMC. For polymers 18 – 20, the CMC increases as the length of the hydrophilic polymer chain increases. For both polymeric systems 8 - 10 and 18 - 20, low CMC values were calculated. This work showed the system has a potential in medical applications, with their ability to form micelles in the range of 5 to 110 nm and have the ability to encapsulate highly hydrophobic material, such as the fluorescent probe pyrene. In chapter 7 general conclusions and future perspectives for the work are discussed

Multiframe Adaptive Wiener Filter Super-Resolution with JPEG2000-Compressed Images

Historically, Joint Photographic Experts Group 2000 (JPEG2000) image compression and multiframe super-resolution (SR) image processing techniques have evolved separately. In this paper, we propose and compare novel processing architectures for applying multiframe SR with JPEG2000 compression. We propose a modified adaptive Wiener filter (AWF) SR method and study its performance as JPEG2000 is incorporated in different ways. In particular, we perform compression prior to SR and compare this to compression after SR. We also compare both independent-frame compression and difference-frame compression approaches. We find that some of the SR artifacts that result from compression can be reduced by decreasing the assumed global signal-to-noise ratio (SNR) for the AWF SR method. We also propose a novel spatially adaptive SNR estimate for the AWF designed to compensate for the spatially varying compression artifacts in the input frames. The experimental results include the use of simulated imagery for quantitative analysis. We also include real-video results for subjective analysis

Multistep π dimerization of tetrakis(n-decyl)heptathienoacene radical cations: a combined experimental and theoretical study

Radical cations of a heptathienoacene a,b-substituted with four n-decyl side groups (D4T7C+) form exceptionally stable p-dimer dications already at ambient temperature (Chem. Comm. 2011, 47, 12622). This extraordinary p-dimerization process is investigated here with a focus on the ultimate[D4T7C+]2 p-dimer dication and yet-unreported transitoryspecies formed during and after the oxidation. To this end, we use a joint experimental and theoretical approach that combines cyclic voltammetry, in situ spectrochemistry and spectroelectrochemistry, EPR spectroscopy, and DFT calculations. The impact of temperature, thienoacene concentration, and the nature and concentration of counteranions on the p-dimerization process is also investigated in detail. Two different transitory species were detected in the course of the one-electron oxidation: 1) a different transient conformation of the ultimate [D4T7C+]2 p-dimer dications, the stability of which is strongly affected by the applied experimental conditions, and 2) intermediate [D4T7]2C+ p-dimer radical cations formed prior to the fully oxidized [D4T7]2C+ p-dimer dications. Thus, this comprehensive work demonstrates the formation of peculiar supramolecular species of heptathienoacene radical cations, the stability, nature, and structure of which have been successfully analyzed. We therefore believe that this study leads to a deeper fundamental understanding of the mechanism of dimer formation between conjugated aromatic systems

A Broadly Implementable Research Course in Phage Discovery and Genomics for First-Year Undergraduate Students

Engaging large numbers of undergraduates in authentic scientific discovery is desirable but difficult to achieve. We have developed a general model in which faculty and teaching assistants from diverse academic institutions are trained to teach a research course for first-year undergraduate students focused on bacteriophage discovery and genomics. The course is situated within a broader scientific context aimed at understanding viral diversity, such that faculty and students are collaborators with established researchers in the field. The Howard Hughes Medical Institute (HHMI) Science Education Alliance Phage Hunters Advancing Genomics and Evolutionary Science (SEA-PHAGES) course has been widely implemented and has been taken by over 4,800 students at 73 institutions. We show here that this alliance-sourced model not only substantially advances the field of phage genomics but also stimulates students’ interest in science, positively influences academic achievement, and enhances persistence in science, technology, engineering, and mathematics (STEM) disciplines. Broad application of this model by integrating other research areas with large numbers of early-career undergraduate students has the potential to be transformative in science education and research training

The neurocircuitry of addiction: an overview

Drug addiction presents as a chronic relapsing disorder characterized by persistent drug-seeking and drug-taking behaviours. Given the significant detrimental effects of this disease both socially and economically, a considerable amount of research has been dedicated to understanding a number of issues in addiction, including behavioural and neuropharmacological factors that contribute to the development, loss of control and persistence of compulsive addictive behaviours. In this review, we will give a broad overview of various theories of addiction, animal models of addiction and relapse, drugs of abuse, and the neurobiology of drug dependence and relapse. Although drugs of abuse possess diverse neuropharmacological profiles, activation of the mesocorticolimbic system, particularly the ventral tegmental area, nucleus accumbens, amygdala and prefrontal cortex via dopaminergic and glutamatergic pathways, constitutes a common pathway by which various drugs of abuse mediate their acute reinforcing effects. However, long-term neuroadaptations in this circuitry likely underlie the transition to drug dependence and cycles of relapse. As further elucidated in more comprehensive reviews of various subtopics on addiction in later sections of this special issue, it is anticipated that continued basic neuroscience research will aid in the development of effective therapeutic interventions for the long-term treatment of drug-dependent individuals