Collaborative Research: Investigation of Chemotaxis in Porous Media -- Visualization Experiments and Modeling

合作研究：研究多孔介质中的趋化性？可视化实验和模型该奖项是根据2009年美国复苏和再投资法案(公法111-5)资助的。了解地下细菌的传输对于防止饮用水供应中的微生物污染和成功实施生物修复计划都是至关重要的。许多地下微生物群落是能动的，由于它们的鞭毛可以活跃地游泳。许多游动细菌对趋化剂表现出趋化性，然而，趋化性常常被排除在细菌转运模型之外。我们的假设解决了两种情况，从理论上预测趋化性是相关的，但没有实验证明：(A)理论上预测的趋化性细菌的旅行带可以在实验上观察到，并且对应于细菌消耗底物所产生的化学梯度。(B)趋化性细菌根据自由流动介质中产生的化学梯度迁移到低渗透性区域。我们的具体目标是：1.优化一种新的可视化系统，用于同时观察表面标记有传感器分子的2D微观模型中的细菌传输和水中化学浓度。利用可视化系统在以下情况下对假设a和b进行实验研究：(A)可消耗的化学吸引剂浓度最初是均匀的多孔介质，其中应出现移动细菌带；以及(B)其中化学吸引剂从低渗透区扩散的双渗透性多孔介质。发展一个孔洞尺度的数值模型来描述观察到的输运现象。具体地说，格子-玻尔兹曼模型将被推广到考虑细胞附着和努森扩散。开发达西规模的趋化性分析解决方案，并评估达西规模流动-固定区的概念。我们将使用这项提案中使用的视觉吸引力成像技术来改善本科教育和社区推广，包括为中学女孩举办的科学博览会和为高中教师提供的研究经验。我们还将为数学专业的学生提供一个研究机会，让他们从事建模任务。

Collaborative Research: Investigation of Chemotaxis in Porous Media ? Visualization Experiments and ModelingThis award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). Understanding bacterial transport in the subsurface is critical both in preventing microbial contamination of drinking-water supplies and in successful implementation of bioremediation schemes. Much of the subsurface microbial community is motile and can actively swim due to their flagella. Many motile bacterial species exhibit chemotaxis to chemoattractants, however, chemotaxis is often excluded from bacterial transport models. Our hypotheses address two scenarios in which chemotaxis has been theoretically predicted to be relevant, but not proven experimentally: (a) Theoretically predicted traveling bands of chemotactic bacteria can be observed experimentally, and correspond to chemical gradients created by bacterial consumption of substrate. (b) Chemotactic bacteria migrate into regions of low permeability in response to chemical gradients created in the freely-flowing media. Our specific objectives are:1. To optimize a novel visualization system for simultaneously observing bacterial transport and aqueous chemical concentrations in 2D micromodels whose surfaces are labeled with sensor molecules.2. To experimentally investigate Hypotheses a and b with the visualization system in the following scenarios: (a) a homogeneous porous medium where the consumable chemoattractant concentration is initially uniform and where traveling bacterial bands should occur; and (b) a dual permeability porous medium in which chemoattractant diffuses from the low permeability region.3. To develop a pore-scale numerical model to describe the observed transport phenomena. Specifically, a Lattice-Boltzmann model will be generalized to account for cell attachment and Knudsen diffusion.4. To develop Darcy-scale analytical solutions for chemotaxis and to evaluate the Darcy-scale mobile-immobile zone concept.We will use the visually appealing imaging techniques employed in this proposal to improve undergraduate education and community outreach, including a science fair for middle school girls and research experience for high school teachers. We will also offer a research opportunity for a mathematics major to work on modeling tasks.