Review of tailoring ZnO for optoelectronics through atomic layer deposition experimental variables

Atomic layer deposition (ALD) is an increasingly popular thin film deposition technique which offers unique large area capability combined with excellent conformality, thus ALD will likely be important in the development of next generation optoelectronic devices. Such device platforms include solar cells, thin film transistors and light emitting diodes, and in all of these technologies one material is frequently used – zinc oxide (ZnO) – owing to its excellent electrical and optical properties combined with earth abundance. The approaches and achievements in tailoring the properties of ALD ZnO are discussed. Key process variables include deposition temperature and purge times as well dopant incorporation, with particular attention paid to tuning band alignment and carrier concentrations (focusing on lower carrier concentration applications).

This review was submitted as part of the 2016 Materials Literature Review Prize of the Institute of Materials, Minerals and Mining run by the Editorial Board of MST. Sponsorship of the prize by TWI Ltd is gratefully acknowledged.     

Automation of cell-based drug absorption assays in 96-well format using permeable support systems

Cell-based drug absorption assays, such as Caco-2 and MDCK-MDR1, are an essential component of lead compound ADME/Tox testing. The permeability and transport data they provide can determine whether a compound continues in the drug discovery process. Current methods typically incorporate 24-well microplates and are performed manually. Yet the need to generate absorption data earlier in the drug discovery process, on an increasing number of compounds, is driving the use of higher density plates. A simple, more efficient process that incorporates 96-well permeable supports and proper instrumentation in an automated process provides more reproducible data compared to manual methods. Here we demonstrate the ability to perform drug permeability and transport assays using Caco-2 or MDCKII-MDR1 cells. The assay procedure was automated in a 96-well format, including cell seeding, media and buffer exchanges, compound dispense, and sample removal using simple robotic instrumentation. Cell monolayer integrity was confirmed via transepithelial electrical resistance and Lucifer yellow measurements. Proper cell function was validated by analyzing apical-to-basolateral and basolateral-to-apical movement of rhodamine 123, a known P-glycoprotein substrate. Apparent permeability and efflux data demonstrate how the automated procedure provides a less variable method than manual processing, and delivers a more accurate assessment of a compound's absorption characteristics.     

Gas absorption in the plunging liquid jet reactor

A pseudo first-order gas absorption survey has been made of the contacting system formed when a coherent liquid jet plunges through an ambient reactive gaseous atmosphere into a bath of jet liquid. Using the hypochlorite ion catalysed reaction between pure carbon dioxide and a carbonate ion-bicarbonate ion buffer solution, the reactor has been found to be analogous to a gas sparged stirred tank contactor with the plunging jet acting as both the reactor agitator and gas bubble generator. Resolution of the gas—liquid interfacial area and rate of surface renewal absorption parameters was thus made possible. Specific interfacial areas in the range 20–110 m^?1 and rates of surface renewal in the range 40–160 sec^?1 for the subsurface reactor have been related to the plunging jet surface roughness and velocity or the entrainment rate of the plunging jet.     

SIMD algorithm for curved object recognition using Grimson and Lozano-Pérez matching

The complexity of many computer-recognition problems is such that speed of processing is an important factor that cannot be overlooked, especially when real-time applications are sought. In order to reduce the processing time of matching, our work is implemented in parallel on SIMD architecture. We describe an extension of the Holder and Buxton algorithm (1989) using the surface normal and axis of rotation of objects as edge features to increase the object-recognition scope to objects containing developable surfaces. In addition, we implement an improved data-sorting algorithm that gives impressive speed ups compared with the earlier sorting technique. We show the method to be highly effective in the fast determination of scene interpretations with tests using artificial scenes generated efficiently by a parallel ray caster incorporating constructive solid geometry (CSG). Accuracy and robustness are further tested by application to a real-world scene.     

Assessment of Microbial Populations in Activated Sludge Using an Organism Diversity Index

An organism diversity index for use with mixed liquor or wastewater samples was developed to assess the species richness and diversity of activated sludge. The index was used in several studies and was found to be fast and simple to perform using basic laboratory equipment. Two bench-scale and two pilot-scale studies found that the resulting 'organism diversity index'value was a good indicator of process performance and was not influenced by the total concentration of the mixed-liquor suspended solids but by their nature alone. The technique rapidly yielded pertinent information about the health of the sludge and could be used instead of genetic investigations to obtain population information quickly enough for wastewater-treatment plant process control.     

River landscapes: changing the concrete overcoat?

River landscapes are increasingly important components of rural and urban environments but many river locations have become degraded by 'over-engineering' and neglect. They now need careful resuscitation using the range of relevant disciplines such that their values are enhanced in a sustainable way. The 'cultural' turn taken by landscape studies in the past decade or so will help, by adding interpretive skills and a deeper analysis of shared values and of the differences in understandings of nature and landscape by different individuals and groups. The river landscape of the 'every-day', and its associations and characteristics, will increase in importance as the emphasis in river and catchment management moves away from reliance on a land use planning or an engineering approach and towards enhancing what the common person finds important and valuable in their local river scene.     

PRACTICAL METHODOLOGY FOR DETERMINING THE SIGNIFICANCE OF IMPACTS ON THE WATER ENVIRONMENT

There is currently limited guidance available in the UK for predicting the significance of the impacts of developments on the water environment. This may be partly due to the disparate nature of the components of the water environment, which are covered by a range of scientific and engineering disciplines. This paper reviews the current status of Environmental Impact Assessment for the water environment in the UK and identifies key methodologies and guidance. Proposals are made for a more detailed approach to determining the significance of impacts on rivers, stillwaters (lakes and ponds), groundwater and floodplains, building on methodologies previously developed for highways schemes. Account is taken of the Environment Agency's ongoing work to classify water features to meet the requirements of the Water Framework Directive.     

On developing indicators with text analytics: exploring concept vectors applied to English and Chinese texts

This paper investigates how high-quality, vocabulary-based classifiers, useful for competitive intelligence, can be found for relatively small corpora of publicly available documents. Two corpora of recent annual reports are examined and compared, one in English and one in Chinese. The paper tests whether vocabularies can predict whether firms are relatively innovative or not, examining vocabularies of both content words and function words. We find that indeed the tested vocabularies do produce effective indicators or classifiers and, surprisingly, that function words are especially effective. The paper also provides extensive conceptual and theoretical background to frame the investigation in the context of an EMCUT problematic, that of mapping entities to classification schemes using information derived from text.     

Exploratory Analysis of the Effects of Particulate Characteristics on the Variation in Partitioning of Nonpolar Organic Contaminants to Marine Sediments

The partitioning of nonpolar organic contaminants to marine sediments is considered to be controlled by the amount of organic carbon present. However, several studies propose that other characteristics of sediments may affect the partitioning of contaminants. For this exploratory analysis, we measured 19 sediment characteristics from five marine sediments and 11 characteristics of humic acids extracted from the sediments. These characteristics included elemental composition, grain size, soot carbon, polarity indices and molar ratios. Each individual characteristic and combinations of these characteristics were then used to normalize partition coefficients (K_p) generated for three organic contaminants: lindane, fluoranthene and a tetrachlorinated biphenyl (PCB). A coefficient of variation (CV) was then calculated for each contaminant to determine which normalization characteristic (individually or in combination) resulted in the lowest variability in partitioning between study sediments. For lindane and the PCB, normalization by the amount of sediment organic carbon resulted in the lowest variability in partition coefficients with CVs of 16.2% and 37.7%, respectively. However, normalization of fluoranthene by silt content resulted in lower CVs than those generated by organic carbon normalization: 31.0% vs. 37.6%. Normalization of contaminants K_p's by combined values of sediment characteristics resulted in lower CVs but only by a few percent. Using humic acid characteristics, humic organic carbon reduced variability between sediments most effectively. But only the normalized fluoranthene values had a CV (i.e., 25.4%) lower than the one based on normalization by sediment characteristics. When combined, humic acid characteristics resulted in lower CVs than normalization by individual or combinations of sediment characteristics for fluoranthene and the PCB with CVs of 19.3% and 28.7%, respectively. This analysis indicates variability associated with the partitioning of some organic contaminants to marine sediments can be further reduced when normalization by sediment characteristics other than organic carbon are utilized.     

The Potential use of Silicon Isotope Composition of Biogenic Silica as a Proxy for Environmental Change

Silicon isotope geochemistry is a relatively new branch of environmental change research. Here we review the recent developments in the preparation of materials, analytical methods and applications of stable silicon isotope geochemistry in the most common types of biogenic silica currently being analysed. These materials are: diatom, radiolarian and siliceous sponges in lake and ocean sediments and plant phytoliths which are preserved in soils. Despite analyses of Si isotopes being carried out on rocks and minerals since the 1950's and the increasingly widespread use of Si isotopes since the 1990's, to date only a relatively small number of studies have applied Si isotope ratios to environmental change. In lake and ocean sediments the analysis of Si isotope ratios from biogenic materials has the potential to provide an important source of palaeoenvironmental information, especially where carbonates are not preserved. In plants and soils few studies have used Si isotopes, but important advances have recently been made in the understanding within plant fractionations. These may be useful in the application of Si isotopes in phytoliths to archaeological and palaeoenvironmental contexts.