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Investigation of the Performance of Donor-Acceptor Conjugated Polymers in Electrolyte-Gated Organic Field-Effect Transistors
No full textElectrolyte-gated organic field-effect transistors (EGOFETs) are low-power thin-film electronic device that is gaining interest for application in healthcare and environmental science. However, robust performance in terms of charge-carrier mobility, on-to-off drain current ratio, and turn-on speed are required for real application. Here, donor-acceptor (D-A) conjugated polymers, namely poly[2,5-(2-octyldodecyl)-3,6-diketopyrrolopyrrole-alt-5,5-(2,5-di(thien-2-yl)thieno [3,2-b]thiophene)] (PDPPDTT) and indacenodithiophene-co-benzothiadiazole (PIDTBT), are evaluated in EGOFETs. The operational performance of these materials is compared to that of the well-established liquid crystalline poly[2,5-bis(3-hexadecylthiophen-2-yl)thieno[3,2-b]thiophene] (PBTTT). The effective mobility extracted for the PDPPDTT (0.18 cm2.V-1.s-1), and PIDTBT (0.16 cm2.V-1.s-1) devices was almost double that of the PBTTT (0.10 cm2.V-1.s-1) based device and the on-to-off current ratio was one ((PDPPDTT): 3 × 103) or two ((PIDTBT): 2 × 104) order of magnitude higher than that of PBTTT (2 × 102) devices. The extracted values compare favourably to those of the highest performing EGOFETs presented in the literature and EGOFETs based on the D-A polymers turn from off to on state two to ten times faster the analogous PBTTT device with an improved subthreshold swing. These results show that D-A polymers with a planar conjugated backbone enable the development of robust EGOFETs that are well appropriate for applications in bioelectronic and environmental science
Approximate models for the lattice thermal conductivity of alloy thermoelectrics
No full textThermoelectric generators (TEGs) convert waste heat to electricity and are a leading contender for improving energy efficiency at a range of scales. Ideal TE materials show a large Seebeck effect, high electrical conductivity, and low thermal conductivity. Alloying is a widely-used approach to engineering the heat transport in TEs, but despite many successes the underlying mechanisms are poorly understood. In previous work, first-principles modelling has successfully been used to study the thermodynamics of alloy formation and to investigate its effect on the electronic structure and phonon spectrum. However, it has so far only been possible to examine qualitatively the impact of alloying on the lattice thermal conductivity. In this work, we develop and test two new approaches to addressing this. The constant relaxation-time approximation (CRTA) assumes the primary effect of alloying is on the phonon group velocities, and allows the thermal conductivity to be calculated assuming a suitable constant lifetime. Alternatively, setting the three-phonon interaction strengths to a constant further enables an assessment of how changes to the phonon frequency spectrum influence the lifetimes. We test both approaches for the Pnma Sn(S1-xSex) alloy system and are able to account for the substantially-reduced thermal conductivity measured in experiments
Natural Language Inference over Tables: Enabling Explainable Data Exploration on Data Lakes
No full textData lakes are repositories of data with potential for analysis. Data lakes aim to liberate data from silos, thereby enabling cross-cutting analyses that were hitherto out of reach. This gives rise to significant challenges for data scientists simply discovering what data sets may be relevant to a task-in-hand. Given a data set of interest, several proposals have been made for indexing schemes that can identify related data sets. However, such schemes tend to build on similarity metrics that stop short of providing a clear explanation as to how an identified data set relates to a provided target. We address this problem by applying Natural Language Inference (NLI) to providing explanations as to how the attributes of discovered data sets relate to those of the target, in terms of a collection of semantic relations. We provide two approaches to inferring semantic relations: (a) by performing unsupervised intensional and extensional analysis of the data sources using Natural Language Processing techniques; and (b) by performing supervised learning of semantic relations by applying BERT over source schema information. The contributions of this paper are: an NLI strategy for providing explicit characterisation of semantic relations between data sets; two approaches to inferring the semantic relations; and an empirical evaluation of the approaches using open government data
Understanding the sources of medication safety incidents in mental health hospitals: A mixed methods analysis of incidents reported to the National Reporting and Learning System
No full textBackground Medication safety incidents commonly occur in mental health hospitals. There is a need to improve understanding of the circumstances, actions or influences which are thought to have played a part in the origin of these medication incidents in order to design safer systems to improve patient safety. Aim To undertake a mixed-methods analysis of medication safety incidents reported to the National Reporting and Learning System (NRLS) in England and Wales during 2010-2017. Method Descriptive analyses were undertaken of all anonymised medication safety incidents reported to the NRLS over an eight-year period to characterise their type, severity, and the medication(s) involved. Secondly, a thematic analysis of the free-text reports for incidents reported with moderate or more serious outcomes was undertaken to identify the underlying contributory factors. ResultIn total, 93,727 medication incident reports were identified and 10.4% (n=9,755) described harmful outcomes. Administration errors accounted for the majority of medication incidents reported (50,314; 53.6%), followed by prescribing (15,480; 16.5%) and dispensing errors (10,871; 11.6%). Omission of medication (17,210; 18.3%), wrong frequency (11,860; 12.6%) and wrong/unclear dose of medication (10,251; 10.9%) were most frequently reported. The most frequent drug classes involved were antipsychotics (14,934; 15.5%) and anxiolytics/hypnotics (8,129; 8.4%) and antidepressants (5,776; 6.0%). Failure to follow protocols (n=93), lack of continuity of care (n=92), patient behaviours (n=62) and lack of stock (n=51) were frequently reported as contributory factors associated with moderate, severe and death outcomes. ConclusionMedication incidents pose an enduring threat to patient safety in mental health hospitals. This study has identified important targets which can guide the development of remedial interventions that are tailored to the mental health inpatient setting
Views and experiences of pregnant women and their partners regarding reduced fetal movements: A narrative literature review from a low resource setting perspective.
No full textBackground: Globally there are 2 million stillbirths annually, 98 % of which occur in low-income settings (LICs). Stillbirth may be associated with the maternal perception of reduced fetal movements (RFM) in LICs. However, little is known about maternal experiences of RFM and subsequent engagement with health services in LICs.Aim: This narrative literature review aimed to improve understanding of views and experiences of RFM in pregnant women in LICs using information synthesized from international studies.Methodology: The literature reviewed qualitative, quantitative, and mixed-method studies guided by a systematic approach. The findings were discussed narratively.Findings: Forty studies were identified, only four of which were from LICs. The four main themes identified were:- Maternal perception of fetal movements, facilitators and barriers to seeking health care, RFM as a predictor of fetal outcomes, knowledge of fetal movements and management strategies.Conclusion: A variety of factors may influence the maternal perception of RFM and experience of care. As most studies were conducted in HICs, it is imperative to describe women’s experiences of RFM in LIC settings
The developmental course of loneliness in adolescence: Implications for mental health, educational attainment and psychosocial functioning
No full textThe present study examined patterns of stability and change in loneliness across adolescence. Data were drawn from the Environmental Risk (E-Risk) Longitudinal Twin Study, a UK population-representative cohort of 2,232 individuals born in 1994 and 1995. Loneliness was assessed when participants were aged 12 and 18. Loneliness showed modest stability across these ages (r = .25). Behavioural genetic modelling indicated that stability in loneliness was explained largely by genetic influences (66%), while change was explained by non-shared environmental effects (58%). Individuals who reported loneliness at both ages were broadly similar to individuals who only reported it at age 18, with both groups at elevated risk of mental health problems, physical health risk behaviours, and education and employment difficulties. Individuals who were lonely only at age 12 generally fared better; however, they were still more likely to finish school with lower qualifications. Positive family influences in childhood predicted reduced risk of loneliness at age 12, while negative peer experiences increased the risk. Together, the findings show that while early adolescent loneliness does not appear to exert a cumulative burden when it persists, it is nonetheless a risk for a range of concomitant impairments, some of which can endure
Distribution coefficient model for zirconium and technetium extraction from nitric acid solution
No full textTechnetium and zirconium are two of the most problematic fission products in the PUREX process due to their complex extraction behaviours. Although there are several published works related to the calculation of Tc and Zr distribution coefficients, the reliability of those methods have to be validated carefully, and further knowledge in this area is still needed. This work is, therefore, devoted to developing technetium and zirconium distribution coefficient models for predicting their distribution between nitric acid solution and tri-butyl phosphate in diluent for solutions containing uranium, technetium and zirconium. The distribution coefficient model for zirconium is based on the organic nitric acid concentration, rather than the free TBP concentration. An improved technetium distribution coefficient model, in the absence of other metals, is also developed. The co-extraction of technetium and zirconium or uranium is calculated by ligand exchange mechanisms. The validation results demonstrate that the distribution coefficient models developed in this work are more accurate than established models
Integral effects of initial fluids configuration and wettability alteration on remaining saturation: characterization with X-ray micro-computed tomography
No full textWettability alteration is the key process in low salinity waterflooding to enhance oil recovery. However, wettability alteration cannot necessarily lead to better oil recovery as other factors such as initial fluids morphology plays critical roles. We used Micro-CT X-ray imaging to investigate the effects of initial water morphology and wettability alteration on final remaining oil saturation and oil ganglia size distribution. The results show that presence of percolating water pathways impedes the oil recovery and oil can be produced mostly from large pores at tertiary mode, whereas the secondary low salinity waterflooding unlocks oil from a much broader range of pores. Moreover, the in-situ contact angles decrease towards less oil-wet regardless of initial water saturation, suggesting that wettability alteration is not dependent on the initial water saturation. We observed that at the end of secondary low salinity water flooding, larger trapped ganglia were identified which is in agreement with the ganglia mobilisation theory. This work provided novel insights into the source of additional oil recovery during low salinity waterflooding and addressed the unrecognized role of initial fluids morphology in hydrocarbon recovery and multiphase flow
Noise Source Analysis in Counter Rotating Open Rotors
No full textDue to their potential to reduce aircraft emissions, Counter Rotating Open Rotors (CROR) have seen a renewed interest in applications, from civil aviation to urban air mobility. However, there are concerns surrounding their acoustic emissions. In thework presented, we investigated the noise sources for a range of CROR configurations for a general aviation class aircraft. Numerical models are used to compute the aerodynamic and aeroacoustic performance of these configurations. Further dissection of the various CROR noise sources is then carried out in order to better understand their contribution to CROR noise, and to direct the design of future low-noise CROR. Noise reductions were observed when the rotor-rotor spacing was increased. Increased contraction of the wake requires the need for increased clipping to reduce the tip vortex interaction source. Noise reductions were also observed in the case of asynchronous rotational speeds. However, this was accompanied by a reduction in propulsive efficiency. Analysis of the CROR in non-axial flight demonstrated the need to evaluate noisereducing strategies at off-design conditions. Whilst the analysis proved the ability to reduce various CROR noise sources, it highlighted that trade-offs with aerodynamic performance is necessary