Reactive Flow and Transport Through Complex Systems

The meeting focused on mathematical aspects of reactive flow, diffusion and transport through complex systems. The research interest of the participants varied from physical modeling using PDEs, mathematical modeling using upscaling and homogenization, numerical analysis of PDEs describing reactive transport, PDEs from fluid mechanics, computational methods for random media and computational multiscale methods

ToScA North America (6 – 8 June 2017, The University of Texas, Austin, TX) Program

ToScA North America will address key areas of science, including Multi-modal Imaging, Geosciences, Forensics, Increasing Contrast, Educational Outreach, Data, Materials Science and Medical and Biological Science.University of Texas High-Resolution X-ray CT Facility (UTCT); Jackson School of Geosciences, The University of Texas at Austin; Natural History Museum (London); Royal Microscopical Society (Oxford, UK)Geological Science

Pore-Scale Investigations of Rock and Fluid Microstructure and Fluid Displacement Processes in Geological Porous Media

This study evaluates the super critical carbon dioxide trapping capacity of oil-wet formations at reservoir conditions via x-ray micro-computed tomography. The CO2 clusters and their morphologies were analysed statistically, and it is clear that residual saturations are approximately halved in oil-wet rock, while cluster morphology also changes into flatter clusters

Movement Effects on the Flow Physics and Nutrient Delivery in Engineered Valvular Tissues

Mechanical conditioning has been shown to promote tissue formation in a wide variety of tissue engineering efforts. However the underlying mechanisms by which external mechanical stimuli regulate cells and tissues are not known. This is particularly relevant in the area of heart valve tissue engineering (HVTE) owing to the intense hemodynamic environments that surround native valves. Some studies suggest that oscillatory shear stress (OSS) caused by steady flow and scaffold flexure play a critical role in engineered tissue formation derived from bone marrow derived stem cells (BMSCs). In addition, scaffold flexure may enhance nutrient (e.g. oxygen, glucose) transport. In this study, we computationally quantified the i) magnitude of fluid-induced shear stresses; ii) the extent of temporal fluid oscillations in the flow field using the oscillatory shear index (OSI) parameter, and iii) glucose and oxygen mass transport profiles. Noting that sample cyclic flexure induces a high degree of oscillatory shear stress (OSS), we incorporated moving boundary computational fluid dynamic simulations of samples housed within a bioreactor to consider the effects of: 1) no flow, no flexure (control group), 2) steady flow-alone, 3) cyclic flexure-alone and 4) combined steady flow and cyclic flexure environments. We also coupled a diffusion and convention mass transport equation to the simulated system. We found that the coexistence of both OSS and appreciable shear stress magnitudes, described by the newly introduced parameter OSI-t , explained the high levels of engineered collagen previously observed from combining cyclic flexure and steady flow states. On the other hand, each of these metrics on its own showed no association. This finding suggests that cyclic flexure and steady flow synergistically promote engineered heart valve tissue production via OSS, so long as the oscillations are accompanied by a critical magnitude of shear stress. In addition, our simulations showed that mass transport of glucose and oxygen is enhanced by sample movement at low sample porosities, but did not play a role in highly porous scaffolds. Preliminary in-house in vitro experiments showed that cell proliferation and phenotype is enhanced in OSI-t environments

Shear-promoted drug encapsulation into red blood cells: a CFD model and μ-PIV analysis

The present work focuses on the main parameters that influence shear-promoted encapsulation of drugs into erythrocytes. A CFD model was built to investigate the fluid dynamics of a suspension of particles flowing in a commercial micro channel. Micro Particle Image Velocimetry (μ-PIV) allowed to take into account for the real properties of the red blood cell (RBC), thus having a deeper understanding of the process. Coupling these results with an analytical diffusion model, suitable working conditions were defined for different values of haematocrit

GiD 2008. 4th Conference on advances and applications of GiD

The extended use of simulation programs has leaned on the advances in user-friendly interfaces and in the capability to generate meshes for any generic complex geometry. More than ten years of development have made Gid grow to become one of the more popular pre ans postprocessing systems at international level. The constant dialogue between the GiD development team and the users has guided the development of giD to cover the pre-post needs of many disciplines in science and engineering. Following gthis philosophy, the biannual GiD Conference has become an important forum for discussion and interchange of experiences among the GiD community. This monograph includes the contributions of the participants to the fourth edition of the GiD Conference held in the island of Ibiza from 8-9 May 2008

MICROPOLYHEDRA AND THEIR APPLICATIONS AS A CHEMICAL DISPLAY

Inspired by the readily observed phenomenon of self-assembly in nature, multiple self-assembling microfabrication techniques have been developed to fabricate various 3D structures in both micro and nanoscale. Among the structures that can be fabricated via self-assembly are polyhedra, an attractive model system for studying a wide range of disciplines including mathematics, chemistry and biology. While polyhedra have been considered as an attractive model system with a wide range of implications in multiple fields of study, they are also an effective choice of encapsulant in particle technology to enable spatially controlled chemical reactions. From the formation of milk from fat globules to the development of the central nervous system (CNS) through diffusible chemoattractants, nature has benefitted from selecting and fine-tuning particles to enable spatially controlled chemistry. In past studies, scientists have mainly utilized particle technology to develop an effective system of drug delivery in micro and nanoscale. However, the potential application of particle technology is unlimited; we were inspired to develop a novel application of a chemical display in addition to other existing applications of particle technology. We herein describe a concept of a chemical display system that can generate a dynamic pattern based on a controlled chemical release from an array of porous self-assembled micropolyhedra with various tunable properties such as dimensions, pore sizes, chemical concentrations and arrangements. Based on the idea of controlled chemical release via particle technology, our goal is to develop a chemical display system that would be able to address an inherent limitation that exists in conventional electronic display. A concept of a chemical display would benefit from the absence of components or interfaces that connect each pixel, allowing increased freedom in both design and utility. We fabricated our chemical display system based on an array of self-assembled micropolyhedra, a structure that can be produced in parallel at high efficiency. In this study, we have successfully demonstrated the viability of a chemical display system by loading porous self-folded metallic cubes with chemicals and by precisely controlling the porosity, volume and chemical concentration. We expect that our highly tunable chemical display system based on a self-assembled micropolyhedra would be able to benefit current display systems by complementing currently existing electronic displays. We also anticipate that the technology could open up new possibilities in other fields such as biotechnology, benefitting from a sequential release of chemicals, cells and more. Advisor: Dr. David H. Gracias Reader: Dr. Honggang Cu

Linking Morphology and Multi-Physical Transport in Structured Photoelectrodes

Semiconductors with complex anisotropic morphologies in solar to chemical energy conversion devices enhance light absorption and overcome limiting charge transport in the solid. However, structuring the solid-liquid interface has also implications on concentration distributions and diffusive charge transport in the electrolyte. Quantifying the link between morphology and those multi-physical transport processes remains a challenge. Here we develop a coupled experimental-numerical approach to digitalize the photoelectrodes by high resolution FIB-SEM tomography, quantitatively characterize their morphologies and calculate multi-physical transport processes on the exact geometries. We demonstrate the extraction of the specific surface, shape, orientation and dimension of the building blocks and the multi-scale pore features from the digital model. Local current densities at the solid-liquid interface and ion concentration distributions in the electrolyte have been computed by direct pore-level simulations. We have identified morphology-dependent parameters to link the incident-light-to-charge-transfer-rate-conversion to the material bulk properties. In the case of a structured lanthanum titanium oxynitride photoelectrode (Eg = 2.1 eV), with an absorptance of 77%, morphology-induced mass transport performance limitations have been found for low bulk ion concentrations and diffusion coefficients