Gas-liquid mass transfer in an external airlift loop reactor for syngas fermentation

Converting biomass to useful products through synthesis gas (syngas) fermentation has the potential to replace petroleum based products with biobased ones; however, these process are limited in their application. One of the most significant limiting steps in syngas fermentations is the gas-liquid mass transfer in the bioreactor due to the low solubilities of the major syngas components, CO and H2. Hence, to explore possible solutions for over coming the gas-liquid mass transfer barrier, a non-traditional external airlift loop reactor is considered. This study evaluates the hydrodynamics and gas-liquid mass transfer rates in an external airlift loop reactor with an area ratio of 1:16 operating under different conditions. Two downcomer configurations are investigated consisting of the downcomer vent open or closed to the atmosphere. Experiments for these two configurations are carried out over a range of superficial gas velocities (UG) from UG = 0.5 to 20 cm/s using three aeration plates with open area ratios of 0.66, 0.99 and 2.22%. These results are compared to a bubble column operating under similar conditions. Water quality variations are also investigated over the same range of UG with the downcomer open to the atmosphere. Experimental results show that the gas holdup in the riser does not vary significantly with a change in the downcomer configuration or bubble column operation, while a considerable variation is observed in the downcomer gas holdup. Gas holdup in both the riser and downcomer are found to increase with increasing superficial gas velocity. Test results also show that the maximum gas holdup for the three aeration plates is similar, but that the gas holdup trends are different. The superficial liquid velocity is found to vary considerably for the two downcomer configurations. However, for both cases, the superficial liquid velocity is a function of the superficial gas velocity and/or the flow condition in the downcomer. These observed variations are independent of the aerator plate open area ratio. Gas-liquid mass transfer results indicate that mass transfer rates do vary for oxygen and carbon monoxide gas species. Gas-liquid mass transfer rates are observed to increase linearly with UG in the presence of a surfactant and to increase similarly to riser gas holdup with UG for deionized water and ionic solutions. The gas-liquid mass transfer rates are relatively unaffected by the reactor configuration. The results also show that the addition of a surfactant or ionic compounds has a significant effect on mass transfer, where the surfactant restricts gas-liquid mass transfer and the ionic compounds enhance gas-liquid mass transfer

Are R&D collaborators bound to compete? Experience from Cooperative Research Centres in Australia

Increasingly, research of potential socio-economic value is being conducted within cross-sector (government, university, business) inter-organizational networks. Such networks encourage innovation and learning by breaking down rigidities in existing institutions and by providing for ‘knowledge creation in the context of application’. In the process, new organizational forms for research and development (R&D) are emerging. The Cooperative Research Centre (CRC) is the dominant organizational model for cross-sector collaborative R&D in Australia. Joining a cross-sector collaborative R&D centre poses a significant challenge for public sector research managers. Success depends on cooperation with businesses and other organizations whose interests, objectives, expectations and strategies at various times converge or conflict. The game is a risky one, with the possibility of unforeseen and unwelcome consequences such as partner opportunism and competition for resources. Yet little empirical evidence exists on how researchers perceive and manage the risks and rewards of participation in cross-sector R&D centres. Our study gives voice to the researchers within these inter-organizational networks. We draw evidence from a written survey of 370 respondents from public sector organizations involved in the management and conduct of CRC-based research. The survey questions permit an assessment of the main benefits and problems in CRC participation; the management strategies adopted; and the effect of CRC participation on careers. Responses to open-ended questions in the survey convey the ‘CRC experience’ in the participants own words. We find the concepts of risk common in the management and organizational studies literature inadequate to explain the dynamics of interaction in cross-sector R&D. We therefore extend these through notions of the domains of ‘academic’, ‘scientific’ and ‘organizational’ risk. There are two broad implications of our findings: (1) participants in the CRC need to look beyond the traditionally acknowledged risks of contractual arrangements and consider risks that relate to the nature of scientific knowledge structures and the actual concerns and careers of research scientists; and (2) once these ‘academic’ and ‘scientific’ considerations are properly assessed, government research agencies and universities may need to adopt different management responses to their participation in inter-organizational R&D. We speculate that the way these potentially competing domains are dealt with has implications for (1) the survival of individual CRCs and (2) whether cross-sector collaborative R&D organizations remain ephemeral ‘staging posts’ or become entrenched in the national research system. We argue that cross-sector collaborative R&D organizations are an important component of a dynamic ‘science system’, but that they are inherently unstable organizations. They require organizational management that recognises their differences from business IORs that involve firms alone

How materials can beat a virus

From Springer Nature via Jisc Publications RouterHistory: received 2020-03-25, accepted 2020-04-10, registration 2020-04-11, pub-electronic 2020-05-12, online 2020-05-12, pub-print 2020-08Publication status: Publishe

Simple fluorinated moiety insertion on Aβ 16-23 peptide for stain-free TEM imaging.

Peptide aggregation and fibre formation are one of the major underlying causes of several neurodegenerative disorders such as Alzheimer's disease. During the past decades the characterisation of these fibres has been widely studied in an attempt to further understand the nature of the related diseases and in an effort to develop treatments. Transmission electron microscopy (TEM) is one of the most commonly used techniques to identify these fibres, but requires the use of a radioactive staining agent. The procedure we report overcomes this drawback through simple addition of a fluorinated moiety to a short Amyloid β sequence via solid phase peptide synthesis (SPPS). This method is synthetically straightforward, widely applicable to different aggregation-prone sequences and, above all, allows for stain-free TEM imaging with improved quality compared to standard imaging procedures. The presence of the fluorinated moiety does not cause major changes in the fibre structure or aggregation, but rather serves to dissipate the microscope's electron beam, thus allowing for high contrast and straightforward imaging by TEM.The authors are grateful for funding from the ERC Starting Investigator grant ASPiRe (no. 240629). The authors are also grateful to Dr Marco Di Antonio for assistance with HPLC purification.This is the final published version of the article. It was originally published in Analyst (Sonzini S, Jones ST, Walsh Z, Scherman OA, Analyst, 2015, 140, 2735, doi:10.1039/c4an02278e) http://dx.doi.org/10.1039/c4an02278