Next-generation organic blend semiconductors for high performance solution-processable field Effect Transistors

Ambitions for transparent, lightweight, flexible and inexpensive electronic technologies that can be printed over large area substrates have driven substantial advances in the field of organic/printed electronics in recent years. Amongst the various technologies investigated, solution-processed, organic thin-film transistors (OTFTs) have received extraordinary attention, primarily due to the enormous potential for simple, cost-effective manufacturing. Two exciting research areas relevant to OTFT development that offer tremendous potential are those of the small molecule/polymer organic semiconducting blends and the science and engineering of molecular doping. However, the lack of organic semiconducting blends that surpass the benchmark charge carrier mobility of 10 cm2/Vs, and the numerous challenges associated with the practical utilisation of molecular doping, have prevented adaptation of OTFTs as a viable technology for application in the emerging sector of plastic electronics. The work in this thesis focuses on an organic semiconducting system for OTFTs that addresses these two points. The first part of this thesis describes the development of advanced organic semiconducting blends, the so-called 3rd generation (3G) blend systems. Specifically, a new blend based on the small-molecule C8-BTBT and the conjugated polymer C16DT-BT is introduced. A third component, the molecular p-dopant, C60F48, is then added to the blend system and it is found to have remarkably positive effects on OTFT performance. The ternary blend system is then combined with a solvent-mixing approach, resulting in devices with an exceptional hole mobility value exceeding 13 cm2/Vs. Through the use of complementary characterisation techniques, it is shown that key to this achievement is the unusual three-component material distribution, hinting at the existence of an unconventional doping mechanism. Furthermore, by considering alternative processing techniques, the maximum mobility of the resulting OTFTs is improved further to a value in excess of 23 cm2/Vs. The second part of the thesis focuses on the impact of p-doping in the ternary C8 BTBT:C16IDT BT:C60F48 blend on other important operating characteristics of the OTFTs. The intentional and simple to implement doping process is shown to improve key device parameters such as bias-stress stability, parasitic contact resistance, threshold voltage and the overall device-to-device parameter variation (i.e. narrowing of the parameter spread). Importantly, the inclusion of the dopant is not found to adversely affect the nature of the C8 BTBT crystal packing at the OTFT channel. The final part of this thesis describes the incorporation of 3G blend-based OTFTs into fully functional logic electronic circuits. Hybrid inverter circuits (i.e. NOT gates) are fabricated at low temperatures from solution-phase by combining the high hole mobility C8-BTBT:C16IDT-BT:C60F48 blend OTFTs as the p-channel device and a novel In2O3/ZnO heterojunction metal oxide semiconducting system as the n-channel transistor. The resulting complementary inverters exhibit excellent signal gain and high noise margins, making this hybrid circuitry a promising contender for application in the emerging field of printed microelectronics.Open Acces

The Role of Angiopoietin-2 in Vascular Calcification

Cardiovascular disease (CVD) is a leading cause of mortality in paediatric patients with chronic kidney disease (CKD), particularly in those undergoing dialysis. One of the earliest events in CVD is endothelial damage, which may result from changes in levels of vascular growth factors that control blood vessel function and stability. Markers of endothelial dysfunction and vascular calcification are observed during CKD, and are documented as early as the first decade of life. Previous research indicates that growth factors controlling blood vessel function and stability are altered in CKD patients; circulating levels of the pro-inflammatory/anti-angiogenic molecule angiopoietin-2 (Angpt2) are notably increased in children on dialysis and correlate with surrogate markers of vascular calcification. I therefore hypothesise that Angpt2 may promote medial calcification in CKD. Through in vitro studies using intact vessel rings and explanted vascular smooth muscle cells (VSMCs) from paediatric pre-dialysis and dialysis patients, I have shown that addition of exogenous Angpt2 in a pro-calcaemic environment (medium supplemented with 2.7 mM calcium, and 2.0 mM phosphate) increases calcium deposition within vessels from dialysis patients, but has no effect on control or predialysis vessels. In endothelial cells, Angpt2 acts through the receptor tyrosine kinase with immunoglobulin-like and EGF-like domains-2 (Tie2); this receptor was detected through immunofluorescence in the media layer of the intact vessels and by protein and RNA analyses of explanted VSMCs. The calcifying effect of Angpt2 in VSMCs could be blocked by downregulating Tie2 expression by small interfering ribonucleic acid (siRNA), but was not prevented by addition of the Angpt2 antagonist, vascular stabiliser and anti-inflammatory molecule, Angpt1. Vascular calcification is driven through several pathophysiological mechanisms including osteogenic gene expression, apoptosis and vesicle release; these have been investigated in both vascular rings and explanted VSMCs. While the full mechanism has yet to be elucidated, this thesis provides evidence to suggest that manipulation of Tie2 and angiopoietin pathways may have potential to decrease the rate of vascular calcification in patients with CKD

Soil contamination in urban Tyneside : a chemical and biological risk assessment.

PhD ThesisThe extent of soil contamination with organic and inorganic pollutants in most urban areas in the UK is largely unknown but due to past and present industrial activity it is likely that pollutant levels are high. Such contamination could have a serious impact on human health. Therefore this thesis set out to examine the extent of soil contamination within Newcastle upon Tyne with a focus on the contribution of an incinerator (Byker) to contamination levels of urban soils. The Byker incinerator is situated in central Newcastle and has been the subject of much media controversy due to the disposal of incinerator ash on local allotments. The current work extended past investigations to see if the incinerator had contributed to general urban soil pollution (heavy metals and dioxins) by aerial deposition and allowed a useful investigation into levels of urban soil contamination in Newcastle. In addition to examining metal and dioxin levels the bioaccessibility (human and bacterial) of pollutants in selected soil samples was estimated and an attempt to develop a human cell based soil toxicity assay made. These measurements permit a preliminary assessment of risk to human health from soil contamination. A total of 163 soil samples were collected based on predicted aerial deposition from the Byker incinerator and analysed for dioxins and heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb & Zn) content (mg pollutant /kg soil). A high proportion of samples (90/163) had contamination levels above soil guideline values (as proscribed in current UK regulations; CLEA). The highest dioxin levels were South West of the incinerator (1911 ng I-TEQ/kg) and the congener profiles coupled with a detailed historical survey demonstrated that the source of contamination was likely to be an old alkali works and not the incinerator. Overall it was found that the incinerator did not contribute significantly to dioxins found in the urban soils except those in the incinerator plant grounds. Soil metal contamination levels varied but were not related to incinerator deposition. Many samples contained levels of heavy metals well over soil guideline values with the highest values being found for Cu (12,108 mg/kg), Pb (4,134 mg/kg) and Zn (4,625 mg/kg) To determine the potential human health risk associated with heavy metal contaminated soils, selected samples (16) were subjected to two in vitro digestion techniques which simulate the bioaccessibility of metals (Cu, Ni, Pb & Zn) to humans in case of soil ingestion. Only three samples had high levels of metal availability (over SGV's) indicating that these soils should be subjected to further risk assessment. All other samples tested had low metal availability most likely due to a combination of metal speciation, and complexation to soil particles over time. An attempt was made to develop a human cell based system to determine the toxicity of contaminated soil. Using an in vitro system, human liver cells (HepG2's) were exposed to extracts from soils; cytotoxic effects (membrane integrity, metabolic capability and oxidative stress status) and genotoxicity potential (DNA damage) of Cu and Zn were first investigated in order to standardise the biological assays used. Between 0.1 and 10 mg/L Cu caused DNA damage and higher concentrations caused cytotoxicity. Zn was also proven to cause genotoxic effects from O. lmg/L. From 10 mg/L cytotoxic responses occurred and DNA damage could be attributed to cell death. Due to difficulties in sterilising soil extracts and physical damage caused to HepG2 cells by the abrasive nature of soil, it was not possible to elucidate whether metal contaminated soil extracts were capable of causing a cytotoxic or genotoxic response in human liver cells. Finally, the same soil samples were then subjected to a bacterial (lux) biosensor technique to examine soil toxicity. Interestingly, despite the high levels of contamination found, none of the soil samples were found to be toxic to the two Pseudomonas strains used which again indicates a low level of ecosystem risk and suggests that most of the contaminants present are either in a form that is unavailable to living microbes or are complexed to soil particles. In summary, this research has shown that the high level of soil contamination of urban areas in Newcastle is due to past industrial activity and a similar situation is likely in most other urban areas of the UK and internationally. The high cost of remediation means that if contaminated sites are shown to be a potential risk then bioaccessibility of contaminants should be examined in order to provide a more realistic assessment of the need for remediation. This work demonstrates that only a small proportion of urban contaminated sites are likely to require remediation based on bioaccessibility determination measurements

The Index of Medieval Art

Maintained and hosted by Princeton University, the Index is a comprehensive database of iconography from the Middle Ages that has been cataloged and indexed to allow users to browse and search images based on subject, location, medium, and other facets. While the Index’s original emphasis on the Western European canon of early Christian art is evident in the collection’s relative strength in that area, its scope now encompasses the entirety of the long Middle Ages, up to the mid-sixteenth century

Extreme temperature events on Greenland in observations and the MAR regional climate model

Meltwater from the Greenland ice sheet contributed 1.7–6.12 mm to global sea level between 1993 and 2010 and is expected to contribute 20–110 mm to future sea level rise by 2100. These estimates were produced by regional climate models which are known to be robust at the ice-sheet scale, but occasionally miss regional and local scale climate variability. To date, the fidelity of these models in the context of short period variability in time has not been assessed, for example their ability to simulate extreme temperature events. We use an event identification algorithm commonly used in Extreme Value Analysis, together with observations from the GC-Net, to assess the ability of the MAR RCM to reproduce observed extreme temperature events at 14 sites around Greenland. We find that MAR is able to accurately simulate the frequency and duration of these events but underestimates their magnitude by more than half a degree, although this bias is much smaller than that exhibited by coarse-scale Era-Interim reanalysis data. As a corollary, melt energy in MAR output is underestimated by between 16 % and 41 % depending on global forcing applied. Further work is needed to precisely determine the drivers of extreme temperature events, and why the model underperforms in this area, but our findings suggest that biases are passed into MAR from forcing data. This is important because these forcings are common between RCMs and their range of predictions of past and future ice sheet melting. We propose that examining extreme events should become a routine part of global and regional climate model evaluation and addressing shortcomings in this area should be a priority for model development

The StO2 non-invasive tissue hypoperfusion monitor as a screening tool for early sepsis detection in the emergency department

Background: Early Recognition of patients with sepsis induced tissue hypoperfusion (SITH) Remains a significant clinical challenge. Non--‐invasive Tissue oxygenation saturation (StO2) Monitors have been developed to provide rapid, low--‐cost, and non--‐invasive bedside assessments of tissue oxygen extraction; they have not been well validated as an initial screening tool for sepsis in the ED. Objectives: To Assess the efficacy of initial bedside StO2 Readings in the early identification of patients with SITH And to compare StO2 Readings with lactate levels. Methods: IRB approved, prospective, observational pilot study of a convenience sample of ED Patients presenting with a sepsis continuum diagnosis. Setting: Urban Tertiary care center with 90k visits/yr. Inclusion criteria: Suspicion Of new infection plus 2 SIRS criteria. Exclusion criteria: \u3c18 Or no suspicion of infection. Study procedures: Demographics, co--‐morbidities, clinical data, treatment, disposition, and mortality were collected. A Portable In--‐Spectra ‘Spot Check’ StO2 Monitor was used totake a StO2 Reading at the thenar eminence; a second reading was taken three hours later. All Investigators were trained with the device to record data with a high degree of accuracy and reliability. Abnormal StO2 Was defined as \u3c80% or\u3e91%. The Study was observational and there were no clinical interventions. Descriptive Statistics were employed and Sensitivity/Specificity, Likelihood ratios, andNPV/PPV Were calculated with 95% Confidence intervals (in parenthesis) where appropriate. Results: 79 Patients were enrolled into the study. Mean Age 63 (range 21--‐96). 61 Were admitted to the hospital, 5 To ICU (100% With St02\u3c74%). 3 Mortalities (100% With St02\u3c72%). 75% (9/12) Of patients with an ED Lactate \u3e2.3 Had an abnormal St02. 80% (4/5) For lactate \u3e3, And 100%(3/3) For Lactate \u3e4. For Any initial SITH (MAP\u3c65 Or Lactate \u3e2.3): Sensitivity: 92% (77.5--‐98.2), Specificity: 82.2% (67.9--‐92), +LR: 5.2 (2.7--‐9.7), --‐LR: 0.1 (0.03--‐0.3), PPV: 80.5% (65.1--‐91.2), NPV: 92.5% (80--‐98.3). Conclusions: StO2 May be a useful, rapid, low--‐cost, and non--‐invasive bedside screening tool for SITH In the ED, Particularly for severely ill patients. Further Studies are needed to determine StO2’s Ability to predict mortality and assess response to therapy

The DIP-approach:Student-staff partnerships as a vital tool for learning developers and educators to develop academic [and digital] literacies

Student-staff partnerships can be used to support the development of contextualised digital learning and teaching practices. This can be done by shifting the focus from IT skills to addressing a priority in learning and teaching using a digital approach that is appropriate for that discipline. The development of a formal ‘Digital Innovation Partnership’ (DIP) scheme at the University of Leicester brings students’ digital confidence, perspectives and motivation to enhance learning and teaching. It also recognises the valuable contribution and expertise of student and staff participants. This draws on the academic literacies work of Lea and Street (1998; 2006) and digital literacies work of Sharpe and Beetham (2010) to appreciate that staff and students are developing social practices that are situated within a discipline and intertwined with social, cultural and political factors, power and identity. The reasons for the success of the scheme are explored here, with recommendations for how the model can be applied more generally to educational design to support students’ academic literacies development