Influence of pore geometry on motility and trapping of metal reducing bacteria

2020 ◽  
Author(s):  
Lazaro J. Perez ◽  
Nicole L. Sund ◽  
Rishi Parashar ◽  
Andrew E. Plymale ◽  
Dehong Hu ◽  
...  
Keyword(s):  
Porous Medium ◽  
Porous Media ◽  
Large Scale ◽  
Ad Hoc ◽  
Pore Space ◽  
Practical Applications ◽  
Bacterial Migration ◽  
Reducing Bacteria ◽  
The Impact ◽  
Metal Reducing Bacteria

<p>Diverse processes such as bioremediation, biofertilization, and microbial drug delivery<br>rely on bacterial migration in porous media. However, how pore-scale confinement alters<br>bacterial motility is unknown due to the inherent heterogeneity in porous media. As a<br>result, models of migration are limited and often employ ad hoc assumptions.<br>We aim to determine the impact of pore confinement in the spreading dynamics of two<br>populations of motile metal reducing bacteria by directly visualizing individual <em>Acidovorax</em><br>and <em>Pelosinus</em> in an unconfined liquid medium and in a microfluidic chip containing regular<br>placed pillars. We observe that the length of runs of the two species differs from the<br>unconfined and confined medium. Results show that bacteria in the confined medium<br>display a systematic shorter jumps due to grain obstacles when compared to the open<br>porous medium. Close inspection of the trajectories reveals that cells are intermittently<br>and transiently trapped, which produces superdiffusive motion at early and subdiffusion<br>behavior at late times, as they navigate through the confined pore space. While in the open<br>medium, we observe a linearly increasing variance with respect to time for <em>Acidovorax</em>, and<br>for <em>Pelosinus</em> the variance increases at a much faster rate showing super diffusive behavior<br>at early times. At late times, the rate of growth in spreading increases for <em>Acidovorax</em> while<br>it reduces for <em>Pelosinus</em>. We finally discuss that the paradigm of run-and-tumble motility<br>is dramatically altered in the confined porous medium and its practical applications of<br>these effects on large-scale transport.</p>

scholarly journals Quantitative Analysis for the Reconstruction of Porous Media Using Multiple-Point Statistics

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Qing Xie ◽  
Jianping Xu ◽  
Yuanda Yuan ◽  
Cong Niu
Keyword(s):  
Porous Media ◽  
Large Scale ◽  
Pore Space ◽  
Flow In Porous Media ◽  
Template Method ◽  
Multiple Point ◽  
Multiple Point Statistics ◽  
Grid Scheme ◽  
The Impact ◽  
Data Template

The pore structure reconstruction of the porous media is of great importance to the research of mechanisms of fluid flow in porous media. To capture the large-scale patterns in the pore space, the multiple-point statistical technique is generally adopted for porous media reconstruction. Commonly, two different schemes, i.e., the single-grid scheme and the multiple-grid scheme, can be applied for simulation realization. The selection between this two schemes and a proper data template size have thus become a new research issue, and the performance of the characteristic reproduction of the training image using this two schemes must be quantified. In this paper, a series of multiple-point statistics simulation basing on a 2D micro-CT sandstone image are proceeded using both single- and multiple-grid schemes, and different data templates are adapted for porous media reconstruction. Further, to quantify the impact of the computational schemes and setting of the data template to the simulation realizations, a number of measurements considering the pore diameter, porosity, connectivity, and permeability are implemented to fully analyze the results obtained. Results show that by using the single-point statistical method, a large template is necessary to reproduce large-scale structures. The multiple-grid template method may bring great benefits to simulation efficiency over the simple data template method, as well as the recovery of the pore long-range geometric features and seepage characteristics. With the extension of the template for the multiple-grid scheme, the simulation results show lack of variations to some extent.

Pore-scale Mixing and the Evolution from Anomalous to Normal Hydrodynamic Dispersion

2021 ◽  
Author(s):  
Marco Dentz ◽  
Alexandre Puyguiraud ◽  
Philippe Gouze
Keyword(s):  
Porous Media ◽  
Large Scale ◽  
Molecular Diffusion ◽  
Pore Space ◽  
Breakthrough Curves ◽  
Heterogeneous Porous Media ◽  
Hydrodynamic Dispersion ◽  
Pore Scale ◽  
Sandstone Sample ◽  
Flow Variability

<p>Transport of dissolved substances through porous media is determined by the complexity of the pore space and diffusive mass transfer within and between pores. The interplay of diffusive pore-scale mixing and spatial flow variability are key for the understanding of transport and reaction phenomena in porous media. We study the interplay of pore-scale mixing and network-scale advection through heterogeneous porous media, and its role for the evolution and asymptotic behavior of hydrodynamic dispersion. In a Lagrangian framework, we identify three fundamental mechanisms of pore-scale mixing that determine large scale particle motion: (i) The smoothing of intra-pore velocity contrasts, (ii) the increase of the tortuosity of particle paths, and (iii) the setting of a maximum time for particle transitions. Based on these mechanisms, we derive an upscaled approach that predicts anomalous and normal hydrodynamic dispersion based on the characteristic pore length, Eulerian velocity distribution and Péclet number. The theoretical developments are supported and validated by direct numerical flow and transport simulations in a three-dimensional digitized Berea sandstone sample obtained using X-Ray microtomography. Solute breakthrough curves, are characterized by an intermediate power-law behavior and exponential cut-off, which reflect pore-scale velocity variability and intra-pore solute mixing. Similarly, dispersion evolves from molecular diffusion at early times to asymptotic hydrodynamics dispersion via an intermediate superdiffusive regime. The theory captures the full evolution form anomalous to normal transport behavior at different Péclet numbers as well as the Péclet-dependence of asymptotic dispersion. It sheds light on hydrodynamic dispersion behaviors as a consequence of the interaction between pore-scale mixing and Eulerian flow variability. </p>

scholarly journals Assessing the Impact of Crowd Tasking Apps on Resuscitation Success

2016 ◽  
Vol 8 (2) ◽  
pp. 1-16
Author(s):  
Simone Wurster ◽  
Michael Klafft ◽  
Frank Fiedrich ◽  
Andreas Bohn
Keyword(s):  
Large Scale ◽  
Causes Of Death ◽  
Ad Hoc ◽  
Emergency Services ◽  
Sudden Cardiac Arrest ◽  
Crisis Response ◽  
Smartphone Apps ◽  
It Systems ◽  
Industrialized Nations ◽  
The Impact

Sudden cardiac arrest (SCA) is among the three most prominent causes of death in industrialized nations. Therefore, experts are calling for solutions, including IT-systems to mobilize volunteers. SCA emergencies require immediate action and advanced first aid skills. As of today, emergency services are often unable to arrive at the victim in time, and laypeople on the scene frequently fail to conduct resuscitation properly. One approach to solve this problem is to rely on skilled volunteers, who are alerted by smartphone apps. Among others, German researchers are currently developing a crisis response system with a crowd tasking app. It aims to help reduce the effects of large-scale events, but also of ad-hoc incidents including SCA. This paper describes an approach to determine the potential of the system to increase the survival rate of SCA illustrated based upon data from Germany. Its concept was analyzed by experts and benefited from their feedback.

scholarly journals A homogenised model for flow, transport and sorption in a heterogeneous porous medium

2021 ◽  
Vol 932 ◽  
Author(s):  
L.C. Auton ◽  
S. Pramanik ◽  
M.P. Dalwadi ◽  
C.W. MacMinn ◽  
I.M. Griffiths
Keyword(s):  
Porous Medium ◽  
Porous Media ◽  
Multiple Scales ◽  
Effective Diffusivity ◽  
Rectangular Lattice ◽  
Mathematical Framework ◽  
Anisotropic Flow ◽  
Flow And Transport ◽  
Soft Porous Media ◽  
The Impact

A major challenge in flow through porous media is to better understand the link between microstructure and macroscale flow and transport. For idealised microstructures, the mathematical framework of homogenisation theory can be used for this purpose. Here, we consider a two-dimensional microstructure comprising an array of obstacles of smooth but arbitrary shape, the size and spacing of which can vary along the length of the porous medium. We use homogenisation via the method of multiple scales to systematically upscale a novel problem involving cells of varying area to obtain effective continuum equations for macroscale flow and transport. The equations are characterised by the local porosity, a local anisotropic flow permeability, an effective local anisotropic solute diffusivity and an effective local adsorption rate. These macroscale properties depend non-trivially on the two degrees of microstructural geometric freedom in our problem: obstacle size and obstacle spacing. We exploit this dependence to construct and compare scenarios where the same porosity profile results from different combinations of obstacle size and spacing. We focus on a simple example geometry comprising circular obstacles on a rectangular lattice, for which we numerically determine the macroscale permeability and effective diffusivity. We investigate scenarios where the porosity is spatially uniform but the permeability and diffusivity are not. Our results may be useful in the design of filters or for studying the impact of deformation on transport in soft porous media.

scholarly journals Machine Learning for the Educational Sciences

2021 ◽  
Author(s):  
Sven Hilbert ◽  
Stefan Coors ◽  
Elisabeth Barbara Kraus ◽  
Bernd Bischl ◽  
Mario Frei ◽  
...  
Keyword(s):  
Machine Learning ◽  
Large Scale ◽  
Decisive Role ◽  
Quality Of Data ◽  
Practical Applications ◽  
Educational Sciences ◽  
Complex Relationships ◽  
The Impact ◽  
Analytical Approaches

Classical statistical methods are limited in the analysis of highdimensional datasets. Machine learning (ML) provides a powerful framework for prediction by using complex relationships, often encountered in modern data with a large number of variables, cases and potentially non-linear effects. ML has turned into one of the most influential analytical approaches of this millennium and has recently become popular in the behavioral and social sciences. The impact of ML methods on research and practical applications in the educational sciences is still limited, but continuously grows as larger and more complex datasets become available through massive open online courses (MOOCs) and large scale investigations.The educational sciences are at a crucial pivot point, because of the anticipated impact ML methods hold for the field. Here, we review the opportunities and challenges of ML for the educational sciences, show how a look at related disciplines can help learning from their experiences, and argue for a philosophical shift in model evaluation. We demonstrate how the overall quality of data analysis in educational research can benefit from these methods and show how ML can play a decisive role in the validation of empirical models. In this review, we (1) provide an overview of the types of data suitable for ML, (2) give practical advice for the application of ML methods, and (3) show how ML-based tools and applications can be used to enhance the quality of education. Additionally we provide practical R code with exemplary analyses, available at https: //osf.io/ntre9/?view only=d29ae7cf59d34e8293f4c6bbde3e4ab2.

scholarly journals СONCEPT AND CALCULATION OF THE LIMIT TRANSVERSE SIZE OF CAPILLARIES

Food systems ◽  
2020 ◽  
Vol 3 (2) ◽  
pp. 4-8
Author(s):  
V. G. Zhukov ◽  
N. D. Lukin
Keyword(s):  
Porous Medium ◽  
Porous Media ◽  
Capillary Column ◽  
Moisture Transfer ◽  
Pore Space ◽  
Analytical Calculation ◽  
Transverse Size ◽  
Axial Section ◽  
Complete Wetting ◽  
Transfer Processes

Porous medium are products of processing in food, agricultural, chemical and many other industries. Calculations of processes with wet porous medium are based on capillary properties of the liquid in a pore space. The capillary properties of liquids in porous media are established in pore models in the form of thin tubes of circular or slit transverse sections. The intensity of the processes occurring in it depends on the nature of the filling of the pore space with liquid. Filling with liquid and the formation of a capillary layer is possible only in small pores. However, there is no analytical justification for the transverse pore size, more than which it cannot be filled with liquid by capillary forces. With this in mind, the concept of the limiting transverse size of a capillary for a liquid under conditions of complete wetting is introduced. The limiting size calculation is based on two conditions: the shape of the axial section of the meniscus surface has the appearance of a semicircle and its extremum point is located at the level of the free surface of the fluid supplying the capillary. A capillary column cannot form in larger pores. The absence of formulas for calculating capillaries of the limiting sizes can introduce a significant error into the analytical calculation of the moisture content in the capillary layer of a liquid in porous media and moisture transfer processes. The aim of the study was to obtain formulas for calculating the limiting (largest) sizes of capillaries of a circular, flat slit section and annular transverse sections with complete wetting of their walls. For the conditions above, it was identified that the limiting distance between the walls was independent from annular capillary diameter. The formulas for the limiting transverse sizes of the flat slit and annular capillaries turned out to be the same under the assumptions above. This indicates a weak dependence of the limiting size of a slit capillary on the curvature of its transverse section. Examples of calculations of capillaries of the limiting sizes are performed.

Diffusion limited mixing in heterogeneous porous media

2021 ◽  
Author(s):  
Mayumi Hamada ◽  
Pietro de Anna
Keyword(s):  
Porous Medium ◽  
Porous Media ◽  
Flow Field ◽  
Fast Diffusion ◽  
Pore Scale ◽  
Mixing Processes ◽  
Local Flow ◽  
Gaussian Shape ◽  
Diffusion Limited ◽  
The Impact

<p><span><span>A pore-scale description of the transport and mixing processes is particularly relevant when looking at biological and chemical reactions. For instance, a microbial population growth is controlled by local concentrations of nutrients and oxygen, and chemical reaction are driven by molecular-scale concentration gradients. The heterogeneous flow field typically found in porous media results from the contrast of velocities that deforms and elongates the mixing fronts between solutes that often evolves through a lamella-like topology. For continuous Darcy type flow field a novel framework that describes the statistical distribution of concentration being transported was recently developed (Le Borgne et al., JFM 2015). In this model, concentrations in each lamella are distributed as a Gaussian-like profile which experiences diffusion in the transverse direction while the lamella is elongated by advection along the local flow direction. The evolving concentration field is described as the superposition of each lamella. We hypothesize that this novel view, while perfectly predicting the distribution of concentration for Darcy scale mixing processes, will breakdown when the processes description is at the pore scale. Indeed the presence of solid and impermeable boundaries prevents lamella concentration to diffuse freely according to the a Gaussian shape, and therefore changes the mixing front profile, the lamella superposition and elongation rules. P</span></span><span><span>revious work (Hamada et al, PRF, 2020) demonstrated that </span></span><span><span>the presence of solid boundaries leads to an enhanced diffusion and thus fast homogenization of concentrations. </span></span><span><span>In a purely diffusive process the local mixing time is reduced by a factor of ten with respect to the </span></span><span><span>continuous case and concentration gradient are dissipated exponentially fast while a </span></span><span><span>power law decrease </span></span><span><span>is </span></span><span><span>observed in continuous medium.</span></span><span><span> To investigate the impact of these mechanisms on mixing we developed a</span></span><span><span>n experimental set-up to visualize and quantify the displacement of a conservative tracer in a synthetic porous medium. The designed apparatus allows to obtain high resolution concentration measurement</span></span><span><span>s</span></span><span><span> at the pore scale. We show that the resulting mixing measures, computed in terms of concentration probability density function and dilution index values, diverge </span></span><span><span>qualitatively and quantitatively from what happens in a continuous domain. These observations suggest </span></span><span><span>that description of pore-scale diffusion-limited mixing requires model that takes into account the confined nature of porous medium, </span></span><span><span>otherwise we will tend to overestimate concentration value and neglect the fast diffusion dynamic taking place at microscopic level.</span></span></p>

scholarly journals Modelling and simulation of waves in three-layer porous media

2013 ◽  
Vol 20 (6) ◽  
pp. 1023-1030 ◽  
Author(s):  
S. R. Pudjaprasetya
Keyword(s):  
Porous Medium ◽  
Porous Media ◽  
Gravity Waves ◽  
Wave Reflection ◽  
Single Layer ◽  
Reflection And Transmission ◽  
Weakly Nonlinear ◽  
Model Equations ◽  
The Impact ◽  
Wave Transmission Coefficient

Abstract. The propagation of gravity waves in an emerged three-layer porous medium is considered in this paper. Based on the assumption that the flow can be described by Darcy's Law, an asymptotic theory is developed for small-amplitude long waves. This leads to a weakly nonlinear Boussinesq-type diffusion equation for the wave height, with coefficients dependent on the conductivities and depths of each layer. In the limit of equal conductivities of all layers, the equation reduces to the single-layer result recorded in the literature. The model equations are numerically integrated in the case of an incident monochromatic wave hitting the layers. The results exhibit dissipation and also a downstream net height rise at infinity. Wave transmission coefficient in three-layer porous media with conductivity of mangrove is discussed. Numerically, propagation of an initial solitary wave through a porous medium shows the emergence of wave reflection and transmission that both evolve as permanent waves. Additionally we examine the impact of a solitary gravity wave on a porous medium breakwater.

Adhesion of Colloids and Bacteria to Porous Media: A Critical Review

2019 ◽  
Vol 7 (4) ◽  
pp. 417-460 ◽  
Author(s):  
Runwei Li ◽  
Changfu Wei ◽  
Hefa Cheng ◽  
Gang Chen
Keyword(s):  
Porous Medium ◽  
Porous Media ◽  
Bacterial Adhesion ◽  
Fate And Transport ◽  
Theoretical Models ◽  
Water Interface ◽  
Subsurface Soil ◽  
Air Water Interface ◽  
Surface Physicochemical Properties ◽  
The Impact

Adhesion of colloids and bacteria to various surfaces is important for a variety of environmental phenomena including microbial biofouling and contamination prevention. Under saturated conditions, both colloids and bacteria have the opportunity to attach to porous medium surfaces. Under water unsaturated conditions or in the presence of the air-water interface, besides the porous medium surfaces, colloids and bacteria can also attach to the air-water interface, including the air-water-solid threephase interface. The magnitudes of adhesion of colloids and bacteria are correlated to the interactions of the colloids and bacteria with the surfaces, which are a function of their surface physicochemical properties. In this review, adhesion theories are revisited and adhesion of colloids and bacteria to porous media and the air-water interface is discussed. The interaction forces are quantified using various theoretical models including the DLVO models and used to interpret related adhesion. The impact of surfactants on colloid and bacterial adhesion is also discussed. The review also includes the implementation of the adhesion theory in interpreting colloid and bacterial fate and transport in the subsurface soil.

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