Numerical Investigation of the Layer-Inversion Phenomenon in Binary Solid Liquid Fluidized Beds

Layer inversion behaviour in binary-solid liquid fluidized beds is examined using a Combined Continuum and Discrete Model. A suitable bidisperse system was selected from information in the literature. By simulating the fluidization of the system at a range of liquid velocities, varying degrees of segregation and mixing have been observed

Healthy Placemaking - Revitalizing Springfield\u27s Medical District

Healthy Placemaking - Revitalizing Springfield’s Medical District Healthy Placemaking for the North End Medical District was a community engagement urban design studio for Springfield, MA to propose a new vision for the Medical District as an exemplary model of healthy place-making. WHAT IS HEALTHY PLACE-MAKING? Healthy place-making is a creative process that generates an interconnected mixture of amenities that activate the public realm, creating a livelihood that builds upon sense of place. Urban design strategies consider the ecological relationship between people and the environment in order to provide design interventions that improve the mental, physical, social, and economic wellbeing of inhabitants. Contextually rooted in the history of the area, new and adapted development illustrates environmentally responsible initiatives. EXISTING CONDITIONS 1. No Sense of Place 2. Weak Connections 3. No Mix of Uses and Amenities 4. Unhealthy Environment STUDIO PROCESS AND COMMUNITY ENGAGEMENT Meetings with diverse stakeholders – residents, community leaders, employees in the medical industry- led to a better understanding of assets, challenges and goals from different perspectives. Listening to their ideas was influential for developing the design program. DESIGN STRATEGIES AND OBJECTIVES 1. Enhance the Sense of Place The designs create a sense of place through Landscape Architecture for playing and gathering and the enjoyment of the beauty and healing of plants. 2. Increase Connections The designs create new green connections to work, school and nature in the city. 3. Provide a Balance of Amenities A variety of amenities are introduced into the urban fabric to activate the street life while also stimulating the local economy. 4. Green Infrastructure as a Framework for Public Health Green infrastructure and public health are intrinsically linked: stormwater management, tree canopy, pervious surface cover, and public open space. PLACE-ORIENTED DESIGN PROPOSALS The work explores design proposals for three different places: DESTINATION WASON RIVERSIDE creates two new destinations on the edge of the Connecticut River that engage people and plants, BRIGHTWOOD’S MEDICAL EDGE designs a livable neighborhood with a mix of amenities, gathering places, infill for housing and a remodeled industrial edge to mitigate the impact for residents and to improve the services, and HEALTHY SPACES FOR HEALTHY PEOPLE designs a walkable, green Medical Campus with the framework of the healing landscape

Numerical simulation of CO2 dispersion from punctures and ruptures of buried high-pressure dense phase CO2 pipelines with experimental validation

Carbon capture and storage (CCS) presents an option for significantly reducing the amount of carbon dioxide (CO2) released into the atmosphere and mitigating the effects of climate change. Pipelines are considered to be the most likely method for transporting captured CO2 and their safe operation is of paramount importance as their contents are likely to be in the region of several thousand tonnes and CO2 poses a number of concerns upon release due to its unusual physical properties. To this end, National Grid initiated the COOLTRANS (CO2 Liquid Pipeline Transportation) research programme to consider the pipeline transportation of high-pressure dense phase CO2. Part of this work involved the development of a mathematical model for predicting the dispersion of pure CO2 following the venting, puncture, or rupture, of such a transportation pipeline during normal operational conditions. In this paper, we describe the use of a computational fluid dynamic (CFD) tool that can be used to numerically simulate the near-field sonic dispersion from such releases, above and below ground. The model is shown to qualitatively and quantitatively reproduce observed experimental results. Validated flows at the top of the crater formed by below ground releases presented here for a range of scenarios provide the basis for developing robust source conditions for use in CFD studies of far-field dispersion, and for use with pragmatic quantified risk assessment (QRA) models

Single-chain Fv phage display propensity exhibits strong positive correlation with overall expression levels

<p>Abstract</p> <p>Background</p> <p>Single chain Fvs (scFvs) are widely applied in research, diagnostics and therapeutic settings. Display and selection from combinatorial libraries is the main route to their discovery and many factors influence the success of this process. They exhibit low thermodynamic stability, resulting in low levels of premature cytosolic folding or aggregation which facilitates <it>sec </it>YEG-mediated translocation and phage in <it>E. coli</it>. However, there is little data analysing how this is related to and influenced by scFv protein expression.</p> <p>Results</p> <p>We characterised the relationship between overall scFv expression and display propensity for a panel of 15 anti-tetanus toxin scFvs and found a strong positive correlation (Rho = 0.88, p < 0.005) between the two parameters. Display propensity, overall expression and soluble localisation to the periplasm and extracellular fractions were clone specific characteristics which varied despite high levels of sequence homology. There was no correlation between display of scFv or its expression in non-fused (free) form with soluble scFv localisation to the periplasm or culture supernatant. This suggests that divergence in the fate of scFv-pIII and non-fused scFv after translocation to the periplasm accounts for the observed disparity. Differential degrees of periplasmic aggregation of non-fused scFv between clones may affect the partitioning of scFv in the periplasm and culture supernatant abrogating any correlation. We suggest that these factors do not apply to the scFv-pIII fusion since it remains anchored to the bacterial inner membrane as part of the innate phage packaging and budding process.</p> <p>Conclusion</p> <p>We conclude that in the absence of premature cytosolic aggregation or folding, the propensity of a scFv to be displayed on phage is directly related to its overall expression level and is thus indirectly influenced by factors such as codon bias, mRNA abundance or putative DNA motifs affecting expression. This suggests that scFvs capable of high overall expression and display levels may not produce high yields of non phage-fused soluble protein in either the periplasmic or extracellular fractions of <it>E. coli</it>. This should be considered when screening clones selected from combinatorial libraries for further study.</p> <p>The nucleotide and amino acid sequences of the anti-tetanus toxin scFvs have been deposited in the EMBL data base: accession numbers-C1: <ext-link ext-link-type="embl" ext-link-id="AM749134">AM749134</ext-link>, C2: <ext-link ext-link-type="embl" ext-link-id="AM749135">AM749135</ext-link>, C3: <ext-link ext-link-type="embl" ext-link-id="AM749136">AM749136</ext-link>, C4: <ext-link ext-link-type="embl" ext-link-id="AM749137">AM749137</ext-link>, C5: <ext-link ext-link-type="embl" ext-link-id="AM749138">AM749138</ext-link>, N1: <ext-link ext-link-type="embl" ext-link-id="AM749139">AM749139</ext-link>, N2: <ext-link ext-link-type="embl" ext-link-id="AM749140">AM749140</ext-link>, N3: <ext-link ext-link-type="embl" ext-link-id="AM749141">AM749141</ext-link>, N4: <ext-link ext-link-type="embl" ext-link-id="AM749142">AM749142</ext-link>, N5: <ext-link ext-link-type="embl" ext-link-id="AM749143">AM749143</ext-link> J1; <ext-link ext-link-type="embl" ext-link-id="AM749144">AM749144</ext-link>, J2: <ext-link ext-link-type="embl" ext-link-id="AM749145">AM749145</ext-link>, J3: <ext-link ext-link-type="embl" ext-link-id="AM749146">AM749146</ext-link>, J4: <ext-link ext-link-type="embl" ext-link-id="AM749147">AM749147</ext-link>, J5: <ext-link ext-link-type="embl" ext-link-id="AM749148">AM749148</ext-link>.</p

Characterisation of multiple hindered settling regimes in aggregated mineral suspensions

Aqueous suspensions of magnesium hydroxide are shown to exhibit low ζ-potential behavior and highly complex settling dynamics. Two distinct regimes of hindered settling behavior are observed on either side of a threshold concentration, ϕ*, of 2.38% v/v, which is considerably below the gel point, ϕg, observed at 5.4 ± 1.6% v/v. The low-concentration regime was characterized by a very large Richardson and Zaki exponent of 146, a factor of 10 larger than that of the high-concentration regime. Michaels and Bolger analysis of the low-concentration regime implies settling governed by large, low-density macroaggregates of 138–147 μm diameter and low intraaggregate packing fractions on the order of 0.05, which is in good agreement with in situ particle characterization undertaken using particle vision and measurement (PVM) and focused-beam reflectance measurements (FBRM). The large macroaggregates must undergo some shear densification within the higher-concentration hindered settling regime in order for the suspension to gel at a concentration of 5.4% v/v. Consequently, fluid flow past small, shear-resistant primary agglomerates, observed within the aggregates using scanning electron microscopy and flow particle image analysis, during aggregate densification may represent the limiting step for dewatering within the high-concentration regime

Simulation of deterministic energy-balance particle agglomeration in turbulent liquid-solid flows

An efficient technique to simulate turbulent particle-laden flow at high mass loadings within the four-way coupled simulation regime is presented. The technique implements large-eddy simulation, discrete particle simulation, a deterministic treatment of inter-particle collisions, and an energy-balanced particle agglomeration model. The algorithm to detect inter-particle collisions is such that the computational costs scale linearly with the number of particles present in the computational domain. On detection of a collision, particle agglomeration is tested based on the pre-collision kinetic energy, restitution coefficient, and van der Waals’ interactions. The performance of the technique developed is tested by performing parametric studies on the influence of the restitution coefficient (en = 0.2, 0.4, 0.6, and 0.8), particle size (dp = 60, 120, 200, and 316 μm), Reynolds number (Reτ = 150, 300, and 590), and particle concentration (αp = 5.0 × 10−4, 1.0 × 10−3, and 5.0 × 10−3) on particle-particle interaction events (collision and agglomeration). The results demonstrate that the collision frequency shows a linear dependency on the restitution coefficient, while the agglomeration rate shows an inverse dependence. Collisions among smaller particles are more frequent and efficient in forming agglomerates than those of coarser particles. The particle-particle interaction events show a strong dependency on the shear Reynolds number Reτ, while increasing the particle concentration effectively enhances particle collision and agglomeration whilst having only a minor influence on the agglomeration rate. Overall, the sensitivity of the particle-particle interaction events to the selected simulation parameters is found to influence the population and distribution of the primary particles and agglomerates formed

Large Eddy Simulation of Particle Agglomeration with Shear Breakup in Turbulent Channel Flow

A systematic technique is developed for studying particle dynamics as induced by a turbulent liquid flow, in which transport, agglomeration, and breakup are considered. An Eulerian description of the carrier phase obtained using large eddy simulation is adopted and fully coupled to a Lagrangian definition of the particle phase using a pointwise discrete particle simulation. An efficient hard-sphere interaction model with deterministic collision detection enhanced with an energy-balance agglomeration model was implemented in an existing computational fluid dynamic code for turbulent multiphase flow. The breakup model adopted allows instantaneous breakup to occur once the transmitted hydrodynamic stress within an agglomerate exceeds a critical value, characterised by a fractal dimension and the size of the agglomerate. The results from the developed technique support the conclusion that the local turbulence kinetic energy, its dissipation rate, and the agglomerate fractal dimension control the kinetics of the agglomeration and de-agglomeration processes, and as well as defining with time the morphology of the particles and their resultant transport. Overall, the results are credible and consistent with the expected physical behavior and with known theories