Mechanistic studies of photoelectrochemical systems

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Primary Primers: Observing the Iowa caucus reveals heartening goodwill and candidate engagement

With only days to go before the Iowa caucuses begin the 2020 US presidential election season, Phillip Davies gives an outsider's view of the campaigning now going on in the Hawkeye State. He writes that while caucusers are engaged with the political messages of the various Democratic candidates, there is growing tension over choosing their preferred candidate compared to one they think is most likely to beat Donald Trump in November

Alternative filter media in rapid gravity filtration of potable water

Sand has been the main filter media used in rapid gravity filtration since their emergence in the 19th century. This dominance is due to its low cost, availability and extensive experience which has led to dependable and predictable performance. Over recent years multi-media filters have become the typical filter arrangement. Sand still remains the preferred filter medium in the lower layer with typically anthracite used in the upper layer. A limitation to match previous work has been the emphasis on overall performance but mechanistic analysis as to the reasons for the variations compared to sand has been rare. The fundamental effects of particle size and consolidation on filtration performance and headloss are known but were not often accounted for in the reported research. This has limited the academic contribution of previous work and made it more difficult to compare with the data for this thesis. At an average treatment works the highest costs are associated with the use of chemicals (30 %) and power (60 %) required mainly for pumping. Rapid gravity filters are one of the least energy demanding stages in this system, only requiring pumping for backwashing and air scour, assuming gravity feed was incorporated into the design. Energy efficiency of water treatment has become more important and the research was conducted to determine if the use of novel new media could be used to improve the performance of the filters with regards to turbidity and headloss. For example, the result presented within this thesis demonstrates through the use of angular media improved performance to benefit both turbidity and headloss performance. This was obtained from slate having a sphericity of 0.49 compared to sand at 0.88. In addition the use of novel materials with different physical properties has allowed an extension to analysis of performance using fundamental filtration mechanisms. The greater range of properties available from the novel media used in this thesis compared to sand has suggested additions to this theory. The use of surface reactive materials, including limestone, has shown the removal of additional contaminants such as phosphorus, iron, aluminium and manganese not typically associated with rapid gravity filtration. An assessment of the impact these reactions had on typical filter performance criteria, for example turbidity, headloss and life expectancy. The results showed an 97 % removal of Fe in the limestone compared to 13 % for sand. This was brought about by the precipitation of hydroxide, coagulation, a pH change and consequent co-precipitation. In the case of iron and aluminium removal this pH induced change was theorized as the most likely cause of coagulation within the filter bed itself leading to improved turbidity removal performance. Filter media chosen for laboratory and pilot study in this work was firstly assessed using British Standards tests, but additional tests were added that could provide additional characterisation data. The media were selected based on an individual fundamental property that differed from the other media selected whilst retaining the standard RGF size. Filtralite for example offered a high surface area, limestone a more active surface and slate a plate-like particle shape. Glass had a very smooth surface texture and as a recycled material better sustainability. Four of these filter media (Sand (control), Glass, Filtralite and Slate) were then selected for further on-site pilot plant studies, based on results from the laboratory work. Both the laboratory and pilot study suggested that turbidity and headloss performance could be improved by changes in media specification. The results showed that after particle size, angularity of the media was the most important factor affecting turbidity and headloss performance. A greater angularity led to improvements in filter run time with for example a doubling of filter run time with the slate compared to sand for the same turbidity removal in the pilot plant. Previous literature had suggested an improvement in turbidity performance but that head loss would deteriorate but this was not seen in the data from this research, with slate (sphericity of 0.49) offering improved headloss performance. This improvement was attributed to the varied packing of the filter bed and associated porosity variations throughout the filter. The objectives of the pilot study were to provide understanding of scale-up factors and adjust these theories with real variable clarified water. Real water chemistry is too complex to model and enabled experiments more typical of the variation that a rapid gravity filter would encounter. The pilot plant is 0.07 % the plan area of a full scale filter compared to the 0.01 % of the laboratory columns. Results corroborated the laboratory work on the effect of extreme particle shapes on filter performance. The pilot study also highlighted problems from floc carry over with the use of clarified water and quantified the impact it had on filtration performance. In this case floc carryover changed the performance of the pilot plant results significantly. Thus an overall conclusion from the work was that an integrated design approach to filters, to account for the clarifier type the likelihood of floc carryover and raw water anticipated could be further researched. There were also limitations to the current monitoring equipment that could not quantitatively measure the floc carryover because of large particle size

Development of a data model for an Adaptive Multimedia Presentation System (AMPS)

We investigate the requirements and nature of data models for a multimedia learning system that presents adaptable learning objects based on a range of stimuli provided by the student and tutor. A conceptual model is explored together with a proposal for an implementation using the well-known relational data model. We also investigate how to describe the learning objects in the form of hierarchical subject ontology. An ontological calculus is created to allow knowledge metrics to be constructed for evaluation within data models. We further consider the limitations of the relational abstract data model to accurately represent the meaning and understanding of learning objects and contrast this with less structured data models implicit in ontological hierarchies. Our findings indicate that more consideration is needed into how to match traditional data models with ontological structures, especially in the area of database integrity constraints

Accelerating topical anaesthesia using microneedles

Background/Aims: Topical anaesthetics reduce pain during venous access procedures in children. However, clinical use is hindered by a significant anaesthetic onset time. Restricted diffusion of the topical anaesthetic through the stratum corneum barrier is the principal reason for the delayed onset. Microneedles can painlessly pierce the skin. This study evaluated microneedle pre-treatment of ex vivo human skin as a means to increase the rate of tetracaine permeation, in order to accelerate the onset of anaesthesia. Methods: Franz-type diffusion cells were used to determine permeation of a commercial tetracaine formulation, Ametop gel, through human skin epidermis. Microneedle-assisted permeation was compared to untreated epidermis. Upon completion of permeation studies the epidermal membranes were visually characterised. Results: At 30 minutes 5.43 μg/cm2 of tetracaine had permeated through untreated membrane compared to 12.13 μg/cm2 in microneedle treated membrane. Insertion of a hypodermic needle created a large single channel in the epidermis (approximately 4250μm2) whilst the punctured surface area following microneedle treatments was estimated to be 75,000μm2. Conclusion: Pre-treatment of skin with microneedles significantly enhances the permeation of tetracaine. Microneedles have the potential to more than halve the onset time for anaesthesia when applying Ametop gel

Crime in Public Housing: Clarifying Research Issues

In recent years, crime and public housing have been closely linked in our political and popular cultures. Tragic episodes of violence have reinforced the notion that public housing is a milieu with rates of victimization and offending far greater than other locales. However, these recent developments belie the complex social and political evolution of public housing from its origins in the 1930s, through urban renewal, and into the present. Stereotypes abound about public housing, its management, residents, and crime rates. In reality, variation is the norm, and it is these variations that affect crime. The study of crime in public housing is in its earliest phase, and there is much to learn. A few studies suggest that crime rates are higher in public housing complexes than in their immediate surroundings; other studies suggest quite the opposite. Still others suggest a process of diffusion and exchange of violent crimes between public housing and the surrounding neighborhood contexts

Investigating Client In their Relationships with Advertising

This study examines how characteristics of performance, relationship investments, general beliefs about relationships and conditions about the internal and external environment are associated with client tolerance toward their experiences in client-advertising agency relationships (CAR), particularly at the service encounter. A critical incident technique is adopted, collecting both negative incidents and positive incidents. The generic aspects of CAR above were conceptualised from a literature review incorporating buyer-seller behaviour, interorganisational relationships, and CAR research. The literature review was refined by qualitative research, involving depth interviews with 14 agencies and 11 client organisations. Respondents were key informants who had decision-making responsibility for their relationships. The depth interviews collectively sought to identify the range of negative and positive critical incidents experienced by clients and their agencies. Additionally, the points of contact between client and agency were identified from which critical incidents were experienced, together with characteristics considered to influence tolerance. These characteristics were screened to identify 32 independent variables and 5 investment variables for a postal survey of clients. The purpose was to identify the main predictors of tolerance. A unique feature of the study was the development of grouping variables designed to measure tolerance, based on seven dependent variables. The amount of incidents experienced per respondent were accounted for in making decisions about tolerance. Discriminant analysis was used to identify predictor variables for each set of grouping variables. This showed that a number of performance variables, investment criteria, client beliefs and environmental conditions were associated with tolerance. Performance predictors included consistent work processes, proactivity and stability of key account management. Additional predictors included beliefs in compatible working styles and less effort in making changes by clients, supporting the view that processes may become more important under stressful times because they facilitate governance. Procedures and processes might also reflect the need to ensure fairness in relationships

In Silico Screening and In Vitro Evaluation of GSK-3β Type I and II Inhibitors: Potential Treatment for Alzheimer’s Disease?

Alzheimer’s disease is a neurodegenerative disorder, and the most common form of dementia. The disease is becoming increasingly prevalent in our aging population, and as there are no effective methods of treating the condition, there is an increasing need for the development of new treatments. In this project, the in silico design, screening and in vitro validation of a selection of potential type I and type II inhibitors of GSK-3β as a possible pathway to a new treatment for Alzheimer’s disease is presented. The screening of compounds for possible type I activity was carried out using a newly designed docking consensus scoring method, first employing a benchmarking database to assess various different combinations of docking algorithms to be used in a virtual screening of 157,238 compounds. The final consensus scoring method was a Simple Sum Rank combination of Glide-SP and –XP, AutoDock Vina and GOLD ASP, chosen based on its superior statistical metrics produced for EF (24), EF’ (33) and BEDROC α=160.9 (0.345), all of which were higher than those of the individual programs. Pharmacophore models were applied to improve the overall accuracy of the results. Once the virtual screening had finished 10 diverse final compounds were selected fit for in vitro validation, based on a wide variety of different protein-ligand interactions. The best type I inhibitor compound 6 (ZINC000072152229) with an IC50 of 24.69 ± 0.73 μM. For the investigation of type II inhibition of GSK-3β, two different type II DFG-out models were developed for the virtual screening of a natural product database (27,286 Compounds). The first model was created using DOLPHIN docking, involving the deletion of 5 residues (201-205) to create the type II consistent binding site, and the second model was designed using a combination of Prime loop refinement, induced fit docking and molecular dynamics. Both models were validated using a selection of analogues of type II ligands with known experimental inhibition data. Both of the models produced experimentally consistent data, which indicated they were both accurate at predicting type II binding. Once the type II virtual screening was completed, the resultant ranks of the compounds for each model were combined into a simple sum consensus score, and 20 compounds were selected for biological validation. The three type II ligands that performed the best in the biological validation were Sorafenib (one of the known type II inhibitors) with an IC50 of 32.64 ± 0.76 µM, compound 2 (ZINC000008299930) with 26.96 ± 1.77 µM and compound 4 (ZINC000008297322) with 9.75 ± 2.2 µM, a promising result for the first ever screening of human GSK-3β for type II inhibition, validating such an approach in the future