Homogenization of two fluid flow in porous media

The macroscopic behavior of air and water in porous media is often approximated using Richards’ equation for the fluid saturation and pressure. This equation is parametrized by the hydraulic conductivity and water release curve. In this paper, we use homogenization to derive a general model for saturation and pressure in porous media based on an underlying periodic porous structure. Under an appropriate set of assumptions, i.e., constant gas pressure, this model is shown to reduce to the simpler form of Richards’ equation. The starting point for this derivation is the Cahn-Hilliard phase field equation coupled with Stokes equations for fluid flow. This approach allows us, for the first time, to rigorously derive the water release curve and hydraulic conductivities through a series of cell problems. The method captures the hysteresis in the water release curve and ties the macroscopic properties of the porous media to the underlying geometrical and material properties

Socio-technical transitions towards environmental sustainability through green ICT

We adopt the broad conceptualisation of Green Information Communication Technology (ICT) used by the Organisation for Economic Cooperation and Development (OECD), incorporating perspectives on Information Technology (IT) and Information Systems (IS) which has currency with both business practitioners and policy makers. The objective of our research is to develop a theory of the institutional mechanisms that underpin socio-technical transitions to environmental sustainability through the direct, indirect and systematic effects of Green ICT in and across organisational fields. We construct our theory by drawing on published research in several disciplines focusing on the organisational field of the ICT industry. We present a mechanism-based theoretical model that explains how institutional change in organisational fields can evoke appropriate socio-technical transitions and organisational responses to Green ICT. Systems researchers agree that Green ICT can help lower GHG emissions directly, through energy efficiencies and indirectly by enabling environmentally sustainable business processes. If this research is to be of theoretical or practical relevance it must recognize that government organizations and business enterprises may not adopt policies and strategies on Green ICT because it is rational or moral to do so rather, a web of social, and institutional mechanisms interact to produce the outcomes observed in practice

Mechanism of droplet-formation in a supersonic microfluidic spray device

Spray drying is an approach employed in automotive, food, and pharmaceutical industries as a robust and cost efficient liquid atomization technique offering direct control over droplet dimensions. The majority of commercially available spray nozzles are designed for large throughput spray drying applications or uniform surface coating, but microfluidic nebulizers have recently been developed as small scale alternatives. Here, we explore the physical parameters that define the droplet size and formation under supersonic flow conditions commonly found in microfluidic spray drying systems. We examined the spray nozzle operation using high speed imaging and laser scattering measurements, which allowed us to describe the spray regimes and droplet size distributions. It was determined that by using this spray nozzle device, droplets with diameters of 4–8 μm could be generated. Moreover, we show that the supersonic de Laval nozzle model can be used to predict the average droplet size. Our approach can be used as a platform for interfacing fluid microprocessing with gas phase detection and characterization

Environmental responsibilty and green IT: An institutional perspective

A recent Gartner Research report found that environmental concerns are increasingly exercising the minds of business and IT executives. This is reflected in the growing interest in the adoption of environmentally responsible approaches to the deployment, operation and use of IT. However, for the majority of firms, issues of cost reduction and energy efficiency appear to predominate. This paper argues that whether it is an interest in Green IT or in cost reduction, the concerns of business and IT managers are modulated by regulative, normative, and cultural-cognitive influences in the institutional environment. The study therefore applies institutional theory to develop a series of theoretical propositions which specify the effect that such influences have in shaping environmental responsibility in organisations. Important as such a theoretical contribution may be, there are, however, the pressing practical imperatives of formulating Green IT strategies, achieving energy efficiencies, and reducing carbon footprints—thus, the study also contributes to a practical understanding of the complex institutional influences at play in shaping such imperatives

Challenges in imaging and predictive modeling of rhizosphere processes

Background Plant-soil interaction is central to human food production and ecosystem function. Thus, it is essential to not only understand, but also to develop predictive mathematical models which can be used to assess how climate and soil management practices will affect these interactions. Scope In this paper we review the current developments in structural and chemical imaging of rhizosphere processes within the context of multiscale mathematical image based modeling. We outline areas that need more research and areas which would benefit from more detailed understanding. Conclusions We conclude that the combination of structural and chemical imaging with modeling is an incredibly powerful tool which is fundamental for understanding how plant roots interact with soil. We emphasize the need for more researchers to be attracted to this area that is so fertile for future discoveries. Finally, model building must go hand in hand with experiments. In particular, there is a real need to integrate rhizosphere structural and chemical imaging with modeling for better understanding of the rhizosphere processes leading to models which explicitly account for pore scale processes

Plant derived cyclic peptides

Cyclic peptides are widespread throughout the plant kingdom, and display diverse sequences, structures and bioactivities. The potential applications attributed to these peptides and their unusual biosynthesis has captivated the attention of researchers for many years. Several gene sequences for plant cyclic peptides have been discovered over the last two decades but it is only recently that we are beginning to understand the intricacies associated with their biosynthesis. Recent studies have focussed on three main classes of plant derived cyclic peptides, namely orbitides, SFTI related peptides and cyclotides. In this mini-review, we discuss the expansion of the known sequence and structural diversity in these families, insights into the enzymes involved in the biosynthesis, the exciting applications which includes a cyclotide currently in clinical trials for the treatment of multiple sclerosis, and new production methods that are being developed to realise the potential of plant cyclic peptides as pharmaceutical or agricultural agents