Extraction of three-dimensional soil pore space from microtomography images using a geometrical approach

Geoderma ◽  
2011 ◽  
Vol 163 (1-2) ◽  
pp. 127-134 ◽  
Author(s):  
Ndeye Fatou Ngom ◽  
Patricia Garnier ◽  
Olivier Monga ◽  
Stephan Peth
Keyword(s):  
Pore Space ◽  
Three Dimensional ◽  
Geometrical Approach ◽  
Soil Pore Space

scholarly journals Physical Processes Affecting Microbial Habitats and Activity in Unsaturated Porous Media

2002 ◽  
Vol 7 (2) ◽  
pp. 39 ◽  
Author(s):  
D. Or
Keyword(s):  
Pore Space ◽  
Three Dimensional ◽  
Interfacial Area ◽  
Spatial Arrangement ◽  
Transport Processes ◽  
Solid Surfaces ◽  
Solid Matrix ◽  
Extracellular Polysaccharides ◽  
Structural Stabilization ◽  
Soil Pore Space

Recent advances in soil pore space visualization and geometrical characterization coupled with improved models for liquid and gaseous behaviour provide the impetus for examination of physical influences on microbial habitats and activity. Desaturation of a porous medium is accompanied by marked changes in liquid-vapour interfacial configurations, which result in confinement and fragmentation of aquatic habitats, alteration of liquid and gaseous diffusion pathways, and introduction of mechanical stresses exerted by films and receding menisci. At the pore scale, we examine relationships between liquid element size (at a given potential) and typical organism or colony size, in an attempt to explain physical triggers for enhanced biological production of extracellular polysaccharides (EPS) coating. The role of EPS in habitat alteration is deduced from its structural, mechanical and transport characteristics. The interplay between increasing liquid-vapour interfacial area and decreasing liquid diffusion pathways with decreasing water content can be formulated as a function of pore space geometry. Such relationships are potentially important for optimal biological control of various bioremediation activities taking place at the soil profile scale. Interactions between microorganisms and solid surfaces are investigated in the context of adhesion and formation of biofilms. In such prevailing microbial communities, EPS forms complex three-dimensional structures that facilitate efficient transport processes and support a rich spatial arrangement of microorganisms with different affinities to oxygen and various nutrients. Effects of microbial activity on properties of solid surfaces including weathering and wettability, and structural stabilization of the solid matrix by biological products are examined. 

scholarly journals Gamma-Ray Attenuation to Evaluate Soil Porosity: An Analysis of Methods

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Luiz F. Pires ◽  
André B. Pereira
Keyword(s):  
Gamma Ray ◽  
Particle Density ◽  
Pore Space ◽  
Physical Property ◽  
Soil Bulk Density ◽  
Soil Porosity ◽  
Porous System ◽  
Soil Pore Space ◽  
Gamma Ray Attenuation ◽  
Dry Soil

Soil porosity (ϕ) is of a great deal for environmental studies due to the fact that water infiltrates and suffers redistribution in the soil pore space. Many physical and biochemical processes related to environmental quality occur in the soil porous system. Representative determinations ofϕare necessary due to the importance of this physical property in several fields of natural sciences. In the current work, two methods to evaluateϕwere analyzed by means of gamma-ray attenuation technique. The first method uses the soil attenuation approach through dry soil and saturated samples, whereas the second one utilizes the same approach but taking into account dry soil samples to assess soil bulk density and soil particle density to determineϕ. The results obtained point out a good correlation between both methods. However, whenϕis obtained through soil water content at saturation and a 4 mm collimator is used to collimate the gamma-ray beam the first method also shows good correlations with the traditional one.

scholarly journals A microscopic approach to investigate bacteria under in situ conditions in sea-ice samples

2001 ◽  
Vol 33 ◽  
pp. 304-310 ◽  
Author(s):  
Karen Junge ◽  
Christopher Krembs ◽  
Jody Deming ◽  
Aaron Stierle ◽  
Hajo Eicken
Keyword(s):  
Sea Ice ◽  
Pore Space ◽  
Three Dimensional ◽  
Epifluorescence Microscopy ◽  
Microbial Populations ◽  
Microbial Life ◽  
Dimensional Network ◽  
In Situ Conditions ◽  
Fluorescent Stain

AbstractMicrobial populations and activity within sea ice have been well described based on bulk measurements from melted sea-ice samples. However, melting destroys the micro-environments within the ice matrix and does not allow for examination of microbial populations at a spatial scale relevant to the organism. Here, we describe the development of a new method allowing for microscopic observations of bacteria localized within the three-dimensional network of brine inclusions in sea ice under in situ conditions. Conventional bacterial staining procedures, using the DNA-specific fluorescent stain DAPI, epifluorescence microscopy and image analysis, were adapted to examine bacteria and their associations with various surfaces within microtomed sections of sea ice at temperatures from −2° to −15°C. The utility and sensitivity of the method were demonstrated by analyzing artificial sea-ice preparations of decimal dilutions of a known bacterial culture. When applied to natural, particle-rich sea ice, the method allowed distinction between bacteria and particles at high magnification. At lower magnifications, observations of bacteria could be combined with those of other organisms and with morphology and particle content of the pore space. The method described here may ultimately aid in discerning constraints on microbial life at extremely low temperatures.

scholarly journals Scale effect in a fluid-conducting fault network

2019 ◽  
Vol 61 (4) ◽  
pp. 3-14
Author(s):  
V. A. Petrov ◽  
M. Lespinasse ◽  
V. V. Poluektov ◽  
S. A. Ustinov ◽  
V. A. Minaev
Keyword(s):  
Pore Space ◽  
Three Dimensional ◽  
Transport Processes ◽  
Geometrical Parameters ◽  
Fluid Filtration ◽  
Ore Formation ◽  
Fracture Systems ◽  
Eastern Transbaikalia ◽  
Scale Levels ◽  
Fault Network

The data presented in the article consistently outlines the methodology for studying the orientation and morphogenetic characteristics of fracture systems of four scale levels including kilometers, meters, centimeters and millimeters. The Urtuisky granite massif, located in the South-Eastern Transbaikalia to the west of the Streltsovsky caldera, containing uranium deposits unique in their reserves was chosen as the object of the research. The massif is composed of Late Riphean granites and granite-gneisses, affected by dynamometamorphic and hydrothermal-metasomatic transformations in various degrees, and dissected by numerous faults with traces of fluid activity of various tectogenesis episodes. The interrelation between such geometrical parameters of fractures systems as specific density and specific length was established. It is shown that such geostructural data should be used for conceptual and numerical modeling of fluid filtration and radionuclides transport processes occurring in a three-dimensional fractured-pore space of crystalline rocks, as applied to the reconstruction and modeling of uranium ore formation and use of geological space for radioactive materials isolation.

Characteristics of turbulence in a face-centred cubic porous unit cell

2019 ◽  
Vol 873 ◽  
pp. 608-645 ◽  
Author(s):  
Xiaoliang He ◽  
Sourabh V. Apte ◽  
Justin R. Finn ◽  
Brian D. Wood
Keyword(s):  
Pore Space ◽  
Three Dimensional ◽  
Jet Impingement ◽  
Unit Cell ◽  
Mean Flow ◽  
Flow Topology ◽  
Turbulence Structures ◽  
Integral Scales ◽  
Flow Features ◽  
Acceleration And Deceleration

Direct numerical simulations (DNS) are performed in a triply periodic unit cell of a face-centred cubic (FCC) lattice covering the unsteady inertial, to fully turbulent, flow regimes. The DNS data are used to quantify the flow topology, integral scales, turbulent kinetic energy (TKE) transport and anisotropy distribution in the tortuous geometry. Several unique flow features are observed within this low porosity configuration, where the mean flow undergoes strong acceleration and deceleration regions with presence of three-dimensional helical motions, weak wake-like structures behind spheres, stagnation and jet-impingement-like flows together with merging and spreading jets in the main pore space. The jet-impingement and weak wake-like flow structures give rise to regions with negative total TKE production. Unlike flows in complex shaped ducts, the turbulence intensity levels in the cross-stream directions are found to be larger than those in the streamwise direction. Furthermore, due to the compact nature and confined geometry of the FCC packing, the turbulent integral length scales are estimated to be less than 10 % of the bead diameter even for the lowest Reynolds number studied, indicating the absence of macroscale turbulence structures for this configuration. This finding suggests that even for the highly anisotropic flow within the pore, the upscaled flow statistics are captured well by the representative volumes defined by the unit cell.

scholarly journals Reconstruction and Analysis of Tight Sandstone Digital Rock Combined with X-Ray CT Scanning and Multiple-Point Geostatistics Algorithm

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Yun Lei
Keyword(s):  
Pore Space ◽  
Full Range ◽  
Three Dimensional ◽  
Ct Scanning ◽  
Multiple Point ◽  
Tight Sandstone ◽  
Sandstone Sample ◽  
X Ray ◽  
Digital Rock ◽  
Experimental Values

Unconventional rocks such as tight sandstone and shale usually develop multiscale complex pore structures, with dimensions ranging from nanometers to millimeters, and the full range can be difficult to characterize for natural samples. In this paper, we developed a new hybrid digital rock construction approach to mimic the pore space of tight sandstone by combining X-ray CT scanning and multiple-point geostatistics algorithm (MPGA). First, a three-dimensional macropore digital rock describing the macroscopic pore structure of tight sandstone was constructed by micro-CT scanning. Then, high-resolution scanning electron microscopy (SEM) was performed on the tight sandstone sample, and the three-dimensional micropore digital rock was reconstructed by MPGA. Finally, the macropore digital rock and the micropore digital rock were superimposed into the full-pore digital rock. In addition, the nuclear magnetic resonance (NMR) response of digital rocks is simulated using a random walk method, and seepage simulation was performed by the lattice Boltzmann method (LBM). The results show that the full-pore digital rock has the same anisotropy and good connectivity as the actual rock. The porosity, NMR response, and permeability are in good agreement with the experimental values.

HYPERBOLIC PLYKIN ATTRACTOR CAN EXIST IN NEURON MODELS

2005 ◽  
Vol 15 (11) ◽  
pp. 3567-3578 ◽  
Author(s):  
VLADIMIR BELYKH ◽  
IGOR BELYKH ◽  
ERIK MOSEKILDE
Keyword(s):  
Neuron Model ◽  
Three Dimensional ◽  
Geometrical Approach ◽  
Hyperbolic Attractor ◽  
Neuron Models ◽  
Neuron System ◽  
Physical Systems ◽  
System A ◽  
Bursting Neurons ◽  
Hyperbolic Attractors

Strange hyperbolic attractors are hard to find in real physical systems. This paper provides the first example of a realistic system, a canonical three-dimensional (3D) model of bursting neurons, that is likely to have a strange hyperbolic attractor. Using a geometrical approach to the study of the neuron model, we derive a flow-defined Poincaré map giving an accurate account of the system's dynamics. In a parameter region where the neuron system undergoes bifurcations causing transitions between tonic spiking and bursting, this two-dimensional map becomes a map of a disk with several periodic holes. A particular case is the map of a disk with three holes, matching the Plykin example of a planar hyperbolic attractor. The corresponding attractor of the 3D neuron model appears to be hyperbolic (this property is not verified in the present paper) and arises as a result of a two-loop (secondary) homoclinic bifurcation of a saddle. This type of bifurcation, and the complex behavior it can produce, have not been previously examined.

Sign in / Sign up

Export Citation Format

Share Document