Development and validation of a two phase CFD model for tubular biodiesel reactors

The use of biodiesel as an alternative to diesel has gained increasing momentum over the past 15 years. To meet this growing demand there is a need to optimise the transesterification reactor at the heart of the biodiesel production system. Assessing the performance of innovative reactors is difficult due to the liquid–liquid reaction mixture that is affected by mass transfer, reaction kinetics and component solubility. This paper presents a Computational Fluid Dynamic model of a tubular reactor developed in ANSYS CFX that can be used to predict the onset of mixing via turbulent flow. In developing the model an analysis of the reaction mixture is provided before the presentation of experimental data, which includes flow visualisation results and temperature dependant viscosity and density data for each phase. The detailed data and model development procedure represents an advancement in the modelling of the two phase transesterification reaction used in biodiesel production

Maternal undernutrition and the offspring kidney: from fetal to adult life

Maternal dietary protein restriction during pregnancy is associated with low fetal birth weight and leads to renal morphological and physiological changes. Different mechanisms can contribute to this phenotype: exposure to fetal glucocorticoid, alterations in the components of the renin-angiotensin system, apoptosis, and DNA methylation. A low-protein diet during gestation decreases the activity of placental 11ß-hydroxysteroid dehydrogenase, exposing the fetus to glucocorticoids and resetting the hypothalamic-pituitary-adrenal axis in the offspring. The abnormal function/expression of type 1 (AT1R) or type 2 (AT2R) AngII receptors during any period of life may be the consequence or cause of renal adaptation. AT1R is up-regulated, compared with control, on the first day after birth of offspring born to low-protein diet mothers, but this protein appears to be down-regulated by 12 days of age and thereafter. In these offspring, AT2R expression differs from control at 1 day of age, but is also down-regulated thereafter, with low nephron numbers at all ages: from the fetal period, at the end of nephron formation, and during adulthood. However, during adulthood, the glomerular filtration rate is not altered, due to glomerulus and podocyte hypertrophy. Kidney tubule transporters are regulated by physiological mechanisms; Na+/K+-ATPase is inhibited by AngII and, in this model, the down-regulated AngII receptors fail to inhibit Na+/K+-ATPase, leading to increased Na+ reabsorption, contributing to the hypertensive status. We also considered the modulation of pro-apoptotic and anti-apoptotic factors during nephrogenesis, since organogenesis depends upon a tight balance between proliferation, differentiation and cell death.1010101

Development of an optimal biogas system design model for Sub-Saharan Africa with case studies from Kenya and Cameroon

The optimal biogas system design model (OBSDM) described in this paper is intended to be used as a decision-making tool to increase awareness of the potential of biogas technology for different applications in Sub-Saharan Africa (SSA). The decision-making tool identifies the most suitable biodigester design based on user defined inputs, including energy and fertiliser requirements; feedstock (type, amount, and rate of supply); water supply; land use (area, soil type, ground water level); climate (temperature and rainfall); construction materials available locally; and the priorities (based on sustainability criteria) of the intended biogas user. The output of the model provides a recommended design with estimates of the expected costs, energy and fertiliser production, and links to contact biodigester suppliers. In order to test the model, data from household surveys conducted in rural regions of Kenya and Cameroon were used as inputs to the model. An innovative fixed dome biodigester design, which uses stabilised soil blocks instead of bricks, was identified as optimal for both Kenyan and Cameroonian rural households. The expected performance of the optimal biogas system design from the model output was consistent with survey data on existing biogas systems in the region

Investigation of liquid-liquid two phase flow in biodiesel production

Over the past two years the Australian biodiesel industry has faced difficult times causing large scale producers to drastically curtail production with some even ceasing operation. This turn of events has highlighted the advantages of small scale production, which are investigated in depth in a companion paper (de Boer and Bahri 2009a). For small scale production to be viable the transesterification reactor at the heart of the process must provide high conversion levels in short time periods. Assessing the performance of a particular reactor design is difficult due to the complex liquid-liquid reaction mixture that is affected by mass transfer, reaction kinetics and component solubility. This paper presents the first step in the development of a CFD model in ANSYS CFX that encapsulates the liquid-liquid flow phenomena observed in the reaction medium. The paper includes an analysis of the reaction mixture focusing on necessary simplifying assumptions, experimental flow visualisation results and an investigation of different simulation settings

BABY BOOM target genes provide diverse entry points into cell proliferation and cell growth pathways

Ectopic expression of the Brassica napus BABY BOOM (BBM) AP2/ERF transcription factor is sufficient to induce spontaneous cell proliferation leading primarily to somatic embryogenesis, but also to organogenesis and callus formation. We used DNA microarray analysis in combination with a post-translationally regulated BBM:GR protein and cycloheximide to identify target genes that are directly activated by BBM expression in Arabidopsis seedlings. We show that BBM activated the expression of a largely uncharacterized set of genes encoding proteins with potential roles in transcription, cellular signaling, cell wall biosynthesis and targeted protein turnover. A number of the target genes have been shown to be expressed in meristems or to be involved in cell wall modifications associated with dividing/growing cells. One of the BBM target genes encodes an ADF/cofilin protein, ACTIN DEPOLYMERIZING FACTOR9 (ADF9). The consequences of BBM:GR activation on the actin cytoskeleton were followed using the GFP:FIMBRIN ACTIN BINDING DOMAIN2 (GFP:FABD) actin marker. Dexamethasone-mediated BBM:GR activation induced dramatic changes in actin organization resulting in the formation of dense actin networks with high turnover rates, a phenotype that is consistent with cells that are rapidly undergoing cytoplasmic reorganization. Together the data suggest that the BBM transcription factor activates a complex network of developmental pathways associated with cell proliferation and growth

Membranes for Topological M-Theory

We formulate a theory of topological membranes on manifolds with G_2 holonomy. The BRST charges of the theories are the superspace Killing vectors (the generators of global supersymmetry) on the background with reduced holonomy G_2. In the absence of spinning formulations of supermembranes, the starting point is an N=2 target space supersymmetric membrane in seven euclidean dimensions. The reduction of the holonomy group implies a twisting of the rotations in the tangent bundle of the branes with ``R-symmetry'' rotations in the normal bundle, in contrast to the ordinary spinning formulation of topological strings, where twisting is performed with internal U(1) currents of the N=(2,2) superconformal algebra. The double dimensional reduction on a circle of the topological membrane gives the strings of the topological A-model (a by-product of this reduction is a Green-Schwarz formulation of topological strings). We conclude that the action is BRST-exact modulo topological terms and fermionic equations of motion. We discuss the role of topological membranes in topological M-theory and the relation of our work to recent work by Hitchin and by Dijkgraaf et al.Comment: 22 pp, plain tex. v2: refs. adde

Forging ahead with small scale production technology

Over the past three years the Australian biodiesel industry has struggled with rapidly increasing feedstock prices and an unfavourable taxation environment. These tough times have caused large scale producers to drastically curtail production with some even ceasing operation. Instead of sounding the end of the biodiesel industry in Australia, this can act as a stimulus for refocusing the scale of production. In this paper a new model of production is proposed that maintains the benefits of large production scales while taking advantage of the agility, low risk and decentralised nature of small scale production. This model consists of optimised small scale (1-5 million L/yr) production technology incorporated into a regional industry hub. The regional industry hub provides existing infrastructure as well as significant synergies with other industries to provide guaranteed product markets and reduced transport costs. A case study at Macco Feeds PTY LTD (Western Australia) is provided to examine the viability of this model in an industrial setting

Non-commutative superspace from string theory

Turning on background fields in string theory sometimes has an alternative interpretation as a deformation of the target space geometry. A particularly well-known case is the NS-NS two form B, which gives rise to space-time non-commutativity. In this note we point out that this phenomenon extends to ten-dimensional superspace when employing a covariant quantization of the superstring, generalizing an observation by Ooguri and Vafa in four dimensions. In particular, we will find that RR field strengths give rise to a non-zero $\{\theta,\theta\}$ anti-commutator, just as in four dimensions, whereas the gravitino yields a non-zero value for $[x,\theta]$.Comment: LaTex, 12 page

Drivers of CO2 emissions from electricity generation in the European Union 2000–2015

Industrial EcologyGlobal Challenges (FGGA