Urban Land Market in Ghana: A Study of the Wa Municipality

This paper examines the land market in Ghana using the Wa municipality as a study area, an urban land market that is largely underdeveloped. The study employed questionnaires to collect data on how the land market in the municipality functions. It was found that this land market basically comprises undeveloped land and most of the land units are located in areas without basic infrastructure or services. Furthermore, customary land is efficiently allocated to competing uses and users. However, the market is bedevilled with problems such as multiple land sales and boundary disputes as a result of the unavailability of documentation on land transactions in the municipality. It suggests that state policy interventions, and not the institutional bureaucracy of land management, are required to address the inherent market problems.     

Engineering a mammalian super producer

Mammalian cells are the preferred host for the manufacture of a wide range of biopharmaceuticals, but production costs are high owing to low productivity. A range of rational engineering strategies have been pursued in order to increase volumetric product titres from mammalian cells, such as delaying apoptosis, manipulation of the cell cycle, and improving metabolism and protein processing. Unfortunately, outcomes from these strategies have been mixed, with few instances where significant improvements in product yield have been achieved. This article reviews and contrasts many of the engineering strategies attempted to date, highlighting the variability and context specificity in outcome. The paper argues that this is a reflection of the complexity of mammalian cells, and that a deeper understanding of the biology underpinning protein production for biotechnological purposes is required. Copyright © 2011 Society of Chemical Industry     

Performance-driven design of Biocompatible Mg alloys

Magnesium (Mg) and its alloys provide numerous benefits as a resorptive biomaterial and present the very real possibility of replacing current metallic implant materials in a variety of roles. The development of suitable biodegradable implant alloys is a multidisciplinary challenge, since alloy design must be confined to a range of alloying additions that are biologically nontoxic, whilst still providing the requisite mechanical properties. This leaves a small number of compatible elements that can provide benefits when alloyed with Mg, including calcium (Ca) and zinc (Zn). To date, although a range of different Mg alloys have been investigated both in vitro and in vivo, little work has been performed to characterize the relationship between the composition of Mg alloys, their corrosion and resulting mechanical properties over time. Consequently it is crucial to understand how these properties may be related if alloys are to be successfully screened for implantation in the body.     

Electrospun composite poly(lactic acid)/polyaniline nanofibers from low concentrations in CHCl3: Making a biocompatible polyester electro-active

Nanofibers of poly(lactic acid) (PLA) blended with polyaniline (PANi) were fabricated via electrospinning at much lower PLA concentrations (∼1wt%) in CHCl₃ than reported before using a more efficient technique of preparing the solutions. The polymer nanofibers had diameters in the range 10 nm–300 nm. Nanofibers prepared with a 3 wt% PLA/PANi solution were conducting and were used to fabricate a diode which was electrically characterized and exhibited a low turn-on voltage and a rectification ratio of 500. The device characteristics were analyzed using the standard thermionic emission model of a Schottky junction and yielded an ideality factor of 1.6 and a barrier height of 0.49 eV. Using a simple circuit, the diode was able to rectify a low frequency alternating current signal with an efficiency of 10%. The ability to engineer insulating PLA into nanofibers that are electro-active extends the range of applications of this biocompatible and biodegradable polyester to include electronic devices that have reduced toxicity.     

Thermodynamic cycle optimization for pyroelectric energy conversion in the thin film regime

Pyroelectric energy conversion is both simulated and realized on thin film lead zirconate titanate capacitors. The thermodynamics of the energy conversion cycle were explored, and the performance of the Brayton cycle was compared with the conventional Ericsson pyroelectric cycle. Cycle performance was examined using coefficients extracted from measured isothermal polarization hysteresis loops. It was found that the Brayton cycle is slightly more efficient than the Ericsson cycle over the range of temperatures tested and has significant efficiency improvements with increasing pyroelectric coefficients. The results from actual energy conversion cycles differed slightly from simulated performance, confirming the known challenges with synchronizing pyroelectric cycles with realistic thermal excitation. Finally, a one‐dimensional thermal transient model is used to explore the power conversion potential of thin film pyroelectrics. It is shown that the Brayton cycle has a significant performance advantage over the Ericsson cycle at higher operating frequencies. A power density of 8 mW/cm³ was obtained using the Brayton cycle for a thin film system at about 60 °C with an applied field of 5 V and stimulation frequency of 0.2 Hz. Copyright © 2017 John Wiley & Sons, Ltd.     

Neurofuzzy control of a low‐temperature desulphurization plant

Low‐temperature desulphurization (LTD) is a low‐cost alternative to conventional wet scrubbing for removing sulphur dioxide from flue gas produced by power generating plants. A problem in the design of conventional controllers to achieve and maintain process conditions for optimal desulphurisation is the lack of mathematical models to characterise the complex desulphurization process and unexpected environ mental disturbances. The aim of the work reported in this paper was to replace a skilled human operator who could successfully regulate the LTD plant through manipulation of low‐level controllers with a competitive neurofuzzy system, which possesses both the learning ability of neural networks and the structural transparency of fuzzy logic systems. A hierarchical control structure was adopted whereby the competitive neurofuzzy method was used at the top level for co‐ordinating actions of low‐level conventional controllers. This approach would considerably simplify the task of designing the control system and has been shown to yield high‐level controllers with performances at least equalling that of expert operators, as demonstrated in this paper. Copyright © 2001 John Wiley & Sons, Ltd.     

Reprint of “Safe places for pedestrians: Using cognitive work analysis to consider the relationships between the engineering and urban design of footpaths”

Footpaths provide an integral component of our urban environments and have the potential to act as safe places for people and the focus for community life. Despite this, the approach to designing footpaths that are safe while providing this sense of place often occurs in silos. There is often very little consideration given to how designing for sense of place impacts safety and vice versa. The aim of this study was to use a systems analysis and design framework to develop a design template for an ‘ideal’ footpath system that embodies both safety and sense of place. This was achieved through using the first phase of the Cognitive Work Analysis framework, Work Domain Analysis, to specify a model of footpaths as safe places for pedestrians. This model was subsequently used to assess two existing footpath environments to determine the extent to which they meet the design requirements specified. The findings show instances where the existing footpaths both meet and fail to meet the design requirements specified. Through utilising a systems approach for footpaths, this paper has provided a novel design template that can inform new footpath design efforts or be used to evaluate the extent to which existing footpaths achieve their safety and sense of place requirements.