The Role of Learning in Construction Technology Transfer: A 'SCOT' Perspective

Technology transfer has been given increasing importance since the formulation of the international code of conduct for technology transfer by the UNCTAD in 1985, and has become a preferred medium to bridge development gaps between developed and developing countries. In this development, international joint ventures have been but forward as vehicle for change in the belief that contractors in developing countries can position themselves to receive technology from their developed counterparts. So far, Technology Transfer has been studied through a variety of theoretical lenses. However, predominantly, the perspectives taken have assumed a linear process, viewing technology as an object and effectively disregarding the multiple social interactions that contribute to the process. In this paper, we argue that such perspectives only provide partial explanations of how technology is transferred across organisational boundaries, and that this has consequences for its broader uptake. A counter-argument is put forward to instead view Technology Transfer as a process of socio-technical interactions that is reliant on learning within a context. Adopting the theoretical lens of the Social Construction of Technological Systems (SCOT) as put forward by Bijker et al. (1987; 2012), we explicate the role learning plays in Technology Transfer in construction projects under IJV arrangements in developing countries. Drawing on an extensive literature review and the initial findings from case study research on oil and gas projects in Ghana, we show how the SCOT framework allows for examination of the socio-technical interactions between the human actors and the construction technology at hand. In particular, how the component of learning is an integral element of the construct of ‘closure and stabilisation’ under SCOT. Conclusions are drawn highlighting the importance of studying technology transfer as a product of socio-technical interactions within a context, in order to obtain a better understanding of the process.published_or_final_versio

Biophysical evidence for intrinsic disorder in the C-terminal tails of the epidermal growth factor receptor (EGFR) and HER3 receptor tyrosine kinases

The epidermal growth factor receptor (EGFR)/ErbB family of receptor tyrosine kinases includes oncogenes important in the progression of breast and other cancers, and they are targets for many drug development strategies. Each member of the ErbB family possesses a unique, structurally uncharacterized C-terminal tail that plays an important role in autophosphorylation and signal propagation. To determine whether these C-terminal tails are intrinsically disordered regions, we conducted a battery of biophysical experiments on the EGFR and HER3 tails. Using hydrogen/deuterium exchange mass spectrometry, we measured the conformational dynamics of intracellular half constructs and compared the tails with the ordered kinase domains. The C-terminal tails demonstrate more rapid deuterium exchange behavior when compared with the kinase domains. Next, we expressed and purified EGFR and HER3 tail-only constructs. Results from circular dichroism spectroscopy, size exclusion chromatography with multiangle light scattering, dynamic light scattering, analytical ultracentrifugation, and small angle X-ray scattering each provide evidence that the EGFR and HER3 C-terminal tails are intrinsically disordered with extended, non-globular structure in solution. The intrinsic disorder and extended conformation of these tails may be important for their function by increasing the capture radius and reducing the thermodynamic barriers for binding of downstream signaling proteins

Network-analysis-guided synthesis of weisaconitine D and liljestrandinine.

General strategies for the chemical synthesis of organic compounds, especially of architecturally complex natural products, are not easily identified. Here we present a method to establish a strategy for such syntheses, which uses network analysis. This approach has led to the identification of a versatile synthetic intermediate that facilitated syntheses of the diterpenoid alkaloids weisaconitine D and liljestrandinine, and the core of gomandonine. We also developed a web-based graphing program that allows network analysis to be easily performed on molecules with complex frameworks. The diterpenoid alkaloids comprise some of the most architecturally complex and functional-group-dense secondary metabolites isolated. Consequently, they present a substantial challenge for chemical synthesis. The synthesis approach described here is a notable departure from other single-target-focused strategies adopted for the syntheses of related structures. Specifically, it affords not only the targeted natural products, but also intermediates and derivatives in the three families of diterpenoid alkaloids (C-18, C-19 and C-20), and so provides a unified synthetic strategy for these natural products. This work validates the utility of network analysis as a starting point for identifying strategies for the syntheses of architecturally complex secondary metabolites

The Growth Performance of Triplochiton scleroxylon, Terminalia superba and Ceiba pentandra in Pure and Mixed Stands.

Plantation developers mostly prefer exotic to indigenous tree species in restoration of degraded forests due, perhaps to, inadequate information on indigenous tree plantations to enable them change in that direction. The study was conducted at the Jimira Forest Reserve in the Nkawie Forest District to compare the growth performance of Ceiba pentandra, Terminalia superba and Triplochiton scleroxylonin their pure and mixed stands. Four plots, each divided into four subplots measuring 50m x 50m, of one hectare demarcated represented three pure stands of Ceiba pentandra, Terminalia superba and Triplochiton scleroxylon and one mixed stand of the three species. Simple random sampling was used to a subplot from each plotand diameter and height measurements were taken. The mean growth rates in diameter of Ceiba pentandra, Terminalia superba, and Triplochiton scleroxylon in the pure stands and the mixed stand were 1.73 and 1.61cm/year; 1.77 and 2.02 cm/year; and 2.70 and 2.57 cm/year respectively and those in height were 1.06 and 0.80 m/year; 1.16 and 1.25 m/year; and 1.98 and 1.59 m/year respectively. The statistical analysis carried out to determine the variations in tree diameter and height in the pure and mixed stands indicated no significant differences. Keywords: Growth Performance, Triplochiton scleroxylon, Terminalia superba, Ceiba pentandra, Pure and Mixed Stands. DOI: 10.7176/JNSR/9-4-0

Geometallurgical Studies on Gold Ore for Enhanced Comminution and Leaching

Many gold processing plants are experiencing challenges as mining pits are becoming deeper, rocks are getting harder and more complex polymetallic and refractory ores are being encountered. The variations in the characteristics of ores lead to deviations from the established parameters, and these affect gold extraction efficiency. This paper presents a study where geological characteristics of the ore types from some mining pits were used to ascertain the influence of ore blends on improving the performances of comminution and leaching circuits. To achieve this, mineralogical, comminution, gravity recoverable gold and leaching investigations were conducted on fresh and weathered ore samples and their blends. Mineralogical study showed that the main rock types associated with the mine pits were dolerite, phyllites, conglomerates and sandstone. The dominant minerals were quartz, plagioclase, with traces of pyrites. The Crushability Work Indices of the rocks were between 30 and 37 KWh/t, which are generally higher than the maximum design value of 31.9 kWh/t, and this situation will pose throughput challenges in that section. The Bond Ball Mill Work Indices of the blends tested were between 16.4 kWh/t and 9.6 kWh/t and a blend ratio of 85% fresh and 15% weathered was found to have a Bond Ball Work Index almost equal to the design value of 14 kWh/t. With gold assays of 2.5 g/t for dolerite, 2.1 g/t for phyllite, 3.7 g/t for sandstone and 3.4 g/t for conglomerate, the gravity recoverable gold was in the order of sandstone 36% > phyllite (31.5%) > dolerite (29.5%) > conglomerate (18%). The overall gold recoveries were in the sequence of conglomerate (95%), sandstone (94%), phyllite (92%) and dolerite (87%). This information could be utilised in developing a proactive plant operations strategies for an operating plant in order to ultimately manage the plant and enhance achievement of set targets. Keywords: Geometallurgy; Ore Blends; Characterisation; Communition Circuit Performance; Gold Recover

Oxidation Behaviour and Bio-oxidation of Gold-bearing Sulphide Ores: Oxygen Capabilities and Challenges

The paper presents an overview of bio-oxidation of sulphidic refractory gold ores prior to gold cyanidation. This review discusses several factors, more importantly, oxygen requirements and oxygen limitations in biological oxidation of various sulphide minerals associated with gold ores. The availability of sufficient oxygen in bio-oxidation systems can speed up and enhance the oxidation of sulphide minerals, allowing the gold to be liberated for further extraction. However, oxygen supply and its low solubility in water have been the major limiting factors in bio-oxidation processes. More importantly, oxygen limitations are found to affect the rate of sulphide oxidation and the volume of materials that can be treated for gold leaching. First, the paper discusses the influence of dissolved oxygen on the oxidation behaviour of various sulphide minerals found in refractory gold ores or concentrates. Further discussed are the limiting factors in relation to dissolved oxygen during bio-oxidation of refractory gold ores. This review demonstrates that oxygen availability is a major challenge and therefore, oxygen enhancement techniques or strategies are vitally needed. As well, the review serves to inspire new research into efficient strategies to enhance oxygen availability

Fungal-Transformation of Surrogate Sulphides and Carbonaceous Matter in Refractory Gold Ores: Revisited

In the recovery of gold from refractory gold ores, pretreatment is required to decompose sulphides and liberate occluded gold before cyanidation, and to deactivate carbonaceous matter and prevent it from adsorbing dissolved gold. Until the past three decades, most commercial pretreatment processes had been by abiotic means. Biological pretreatment methods on commercial basis is therefore a recent phenomenon, and several researches are underway to assess the ability of different biological agents in the breakdown of sulphur and carbonaceous matter (CM) in gold ores. This paper, which is a revisit of an earlier one, presents an overview of on-going research aimed at assessing the capability of the fungus, Phanerochaete chrysosporium, to degrade sulphides and CM. Surrogate carbonaceous materials (lignite, bituminous and anthracite coals) and pure sulphides (pyrite and arsenopyrite) were used to model the behavior of CM and sulphides in refractory gold ores. To monitor the extent of biotransformation, preg-robbing test was conducted on the as-received and treated CM, and sulphide sulphur in the residual sulphidic materials was also determined. From an initial preg-robbing effect of 125 µg of gold per gram of CM, the ability of CM to preg-rob gold reduced by 70-95% in the order of lignite<bituminous <anthracite within 21 days of treatment, whereas there were 18% and 39% oxidation of sulphide sulphur in pyrite and arsenopyrite respectively. XRD examination of the treated anthracite confirmed reduction in the graphitic structure of carbon following fungal transformation. Similarly, there was a decline in the major sulphide peak after microbial pretreatment. The results indicate that the fungus biotransforms through destruction of the ordered structure, followed by introduction of oxygen groups. The amorphous nature, thus generated, inhibits the uptake of aurocyanide ions by CM, while enhancing the affinity of cyanide for the oxidised sulphide material in subsequent cyanidation treatment. The findings contribute to knowledge on novel and technically viable alternative methods for oxidative pretreatment of refractory gold ores. Keywords: Phanerochaete Chrysosporium, Carbonaceous Matter, Metal Sulphides, Biotransformatio

Detoxification of Cyanide Wastewater by Cyanotrophic Organisms: the case of Phanerochaete chrysosporium

Abstract Cyanide, a carbon-nitrogen radical, is a major building block in many industries including pharmaceuticals, petrochemical and gold processing. In the gold extraction industry, cyanide has been the universal lixiviant for over a century due to better understood process chemistry, among others. Industries that discharge cyanide-laden effluents are mandated to keep concentrations below 0.2 mg/L to prevent death by cyanide-intoxification, which occurs when cyanide binds to key iron-containing enzymes and prevent them from supplying oxygen-containing blood to the tissues. Techniques used to attenuate cyanide in wastewater can broadly be grouped into chemical, physical and biological methods.  In recent times, attention has been placed on biotechnological methods, which make use of cyanotrophic microorganisms to clean up cyanide-contaminated environments. This paper reports on studies set out to assess the ability of Phanerochaete chrysosporium to degrade cyanide under different conditions including changes in cyanide concentration, culture mass, time, closed system and open system. At the end of 24-hour contact in an open agitated system with initial pH of 11.5, a control experiment using 100 mg/L cyanide revealed a natural attenuation of 15% with pH decreasing to 9.88, while the best myco-detoxification of 85% was achieved by contacting 100 mg/L cyanide with 0.5 g culture mass, translating into degradation capacity of 17.2 mg/g (milligram of cyanide per gram of culture) with pH reducing to 8.4 in 24 hours. The degradation could be based on a number of mechanisms including hydrolysis to HCN, oxidation to cyanyl radical and cyanate due to natural attenuation through atmospheric contact, and secretion of organic acid, oxidative enzymes, and hydrogen peroxide by the fungus.   Keywords: Cyanotrophic Organism, Myco-Detoxification, Cyanide-Laden Effluents, p

Siltation of Ore Particles in Leaching Tanks: Causative Factors and Mitigation Measures

Siltation involves the accumulation of sediment over a considerable period of time and this may occur in closed systems like leaching tanks. Most mining companies in Ghana experience siltation problems during leaching of gold ore. This paper examines the potential causes and possible mitigation measures of siltation. Particle size analysis, slurry settling rate tests and agitation efficiency analysis were used in identifying causative factors of siltation whiles deflocculation test and grind analysis were conducted to ascertain mitigation measures.  Results from the study indicated that, high settling velocity of particles, inefficient milling and classification, poor slurry agitation and particle flocculation were the major causative factors leading to siltation. Size analysis results revealed P67 of 106 µm instead of P80 of 106 µm, a situation which affects particle suspension by agitators leading to siltation. This study therefore suggests that increase in milling residence time and particle deflocculation are potential remediation measures for curbing siltation. Extended grinding of ball mill feed resulted in 94% passing 106 µm while settling velocity was reduced by 71% after deflocculant addition at 1000 ppm. Keywords: Siltation, Deflloculation, Settling Velocity, Grindin

Preg-robbing of Gold by Carbonaceous Materials Encountered in Gold Processing

Processing of gold from refractory ores containing carbonaceous materials (CM) poses challenges due to the ability of the CM to preg-rob dissolved gold. Depending on the type and maturity of CM encountered, preg-robbing of aurocyanide ion can lead to reduction in gold recovery ranging from a few percentages to more than 50%. Knowledge on the type of CM present, and its capacity for gold adsorption is important in predicting pre-treatment methods that can deactivate the CM and reduce its ability to preg-rob. This paper, as part of an on-going work, presents results on the degree of adsorption by the various carbonaceous materials encountered in gold processing, and estimates the amount of aurocyanide complex preg-robbed by them. To do this, various weights of carbonaceous materials (wood chips, charcoal, barren carbon and fresh activated carbon) were contacted with gold solution for a given period of time. The percentages of gold adsorbed on the various carbons were determined, and the results showed an increasing trend of preg-robbing in favour of wood chips < charcoal < barren carbon < activated carbon. Of all the CMs, wood chips have not undergone any carbonisation and/or activation, and thus exhibited the lowest affinity. The adsorption capacities in grams of gold per tonne of carbon over a 24-hr period were 30-65 for wood chips, 320-370 for charcoal, 410-420 for barren carbon and 580-650 for activated carbon. The trend shows direct correlation with the activities and the degrees of graphitisation and maturity of the various carbonaceous materials. It is thus important to characterise carbonaceous gold ores to know the maturity of the CM present, which will inform on the pre-treatment processes required. Keywords: Preg-Robbing, Wood Chips, Charcoal, Activated Carbo