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Sample records for non-isothermal pore network

  1. Particle diffusion in complex nanoscale pore networks

    DEFF Research Database (Denmark)

    Müter, Dirk; Sørensen, Henning Osholm; Bock, H.

    2015-01-01

    We studied the diffusion of particles in the highly irregular pore networks of chalk, a very fine-grained rock, by combining three-dimensional X-ray imaging and dissipative particle dynamics (DPD) simulations. X-ray imaging data were collected at 25 nm voxel dimension for two chalk samples...... with very different porosities (4% and 26%). The three-dimensional pore systems derived from the tomograms were imported into DPD simulations and filled with spherical particles of variable diameter and with an optional attractive interaction to the pore surfaces. We found that diffusion significantly...

  2. A hybrid optimization approach in non-isothermal glass molding

    Science.gov (United States)

    Vu, Anh-Tuan; Kreilkamp, Holger; Krishnamoorthi, Bharathwaj Janaki; Dambon, Olaf; Klocke, Fritz

    2016-10-01

    Intensively growing demands on complex yet low-cost precision glass optics from the today's photonic market motivate the development of an efficient and economically viable manufacturing technology for complex shaped optics. Against the state-of-the-art replication-based methods, Non-isothermal Glass Molding turns out to be a promising innovative technology for cost-efficient manufacturing because of increased mold lifetime, less energy consumption and high throughput from a fast process chain. However, the selection of parameters for the molding process usually requires a huge effort to satisfy precious requirements of the molded optics and to avoid negative effects on the expensive tool molds. Therefore, to reduce experimental work at the beginning, a coupling CFD/FEM numerical modeling was developed to study the molding process. This research focuses on the development of a hybrid optimization approach in Non-isothermal glass molding. To this end, an optimal configuration with two optimization stages for multiple quality characteristics of the glass optics is addressed. The hybrid Back-Propagation Neural Network (BPNN)-Genetic Algorithm (GA) is first carried out to realize the optimal process parameters and the stability of the process. The second stage continues with the optimization of glass preform using those optimal parameters to guarantee the accuracy of the molded optics. Experiments are performed to evaluate the effectiveness and feasibility of the model for the process development in Non-isothermal glass molding.

  3. Pore Structure Characterization of Indiana Limestone and Pink Dolomite from Pore Network Reconstructions

    Directory of Open Access Journals (Sweden)

    Freire-Gormaly Marina

    2016-05-01

    Full Text Available Carbon sequestration in deep underground saline aquifers holds significant promise for reducing atmospheric carbon dioxide emissions (CO2. However, challenges remain in predicting the long term migration of injected CO2. Addressing these challenges requires an understanding of pore-scale transport of CO2 within existing brine-filled geological reservoirs. Studies on the transport of fluids through geological porous media have predominantly focused on oil-bearing formations such as sandstone. However, few studies have considered pore-scale transport within limestone and other carbonate formations, which are found in potential storage sites. In this work, high-resolution micro-Computed Tomography (microCT was used to obtain pore-scale structural information of two model carbonates: Indiana Limestone and Pink Dolomite. A modified watershed algorithm was applied to extract pore network from the reconstructed microCT volumetric images of rock samples and compile a list of pore-scale characteristics from the extracted networks. These include statistical distributions of pore size and radius, pore-pore separation, throat radius, and network coordination. Finally, invasion percolation algorithms were applied to determine saturation-pressure curves for the rock samples. The statistical distributions were comparable to literature values for the Indiana Limestone. This served as validation for the network extraction approach for Pink Dolomite, which has not been considered previously. Based on the connectivity and the pore-pore separation, formations such as Pink Dolomite may present suitable storage sites for carbon storage. The pore structural distributions and saturation curves obtained in this study can be used to inform core- and reservoir-scale modeling and experimental studies of sequestration feasibility.

  4. Synthesis, non-isothermal crystallization and magnetic properties of ...

    Indian Academy of Sciences (India)

    A non-isothermal study of the crystallization kinetic of ferrite/PEVA nanocomposite was carried out by differential scanning calorimetry (DSC), scanning electron microscope (SEM) and X-ray diffraction (XRD) techniques. It was observed that the Ozawa equation describes perfectly the primary process of non-isothermal ...

  5. Non-isothermal crystallization kinetics of polyethylene–clay ...

    Indian Academy of Sciences (India)

    Administrator

    Abstract. Non-isothermal crystallization kinetics of pure medium density polyethylene (MDPE) and MDPE– clay nanocomposites have been investigated by differential scanning calorimeter. The modified Avrami,. Ozawa, Liu and Ziabicki equations have been applied to describe non-isothermal crystallization process. The.

  6. A new way to parameterize hydraulic conductances of pore elements: A step towards creating pore-networks without pore shape simplifications

    Science.gov (United States)

    Miao, Xiuxiu; Gerke, Kirill M.; Sizonenko, Timofey O.

    2017-07-01

    Pore-network models were found useful in describing important flow and transport mechanisms and in predicting flow properties of different porous media relevant to numerous fundamental and industrial applications. Pore-networks provide very fast computational framework and permit simulations on large volumes of pores. This is possible due to significant pore space simplifications and linear/exponential relationships between effective properties and geometrical characteristics of the pore elements. To make such relationships work, pore-network elements are usually simplified by circular, triangular, square and other basic shapes. However, such assumptions result in inaccurate prediction of transport properties. In this paper, we propose that pore-networks can be constructed without pore shape simplifications. To test this hypothesize we extracted 3292 2D pore element cross-sections from 3D X-ray microtomography images of sandstone and carbonate rock samples. Based on the circularity, convexity and elongation of each pore element we trained neural networks to predict the dimensionless hydraulic conductance. The optimal neural network provides 90% of predictions lying within the 20% error bounds compared against direct numerical simulation results. Our novel approach opens a new way to parameterize pore-networks and we outlined future improvements to create a new class of pore-network models without pore shape simplifications.

  7. Non-isothermal crystallization kinetics of polyethylene–clay ...

    Indian Academy of Sciences (India)

    MDPE) and MDPE–clay nanocomposites have been investigated by differential scanning calorimeter. The modified Avrami, Ozawa, Liu and Ziabicki equations have been applied to describe non-isothermal crystallization process. The results of ...

  8. Reactive transport in porous media: Pore-network model approach compared to pore-scale model

    Science.gov (United States)

    Varloteaux, Clément; Vu, Minh Tan; Békri, Samir; Adler, Pierre M.

    2013-02-01

    Accurate determination of three macroscopic parameters governing reactive transport in porous media, namely, the apparent solute velocity, the dispersion, and the apparent reaction rate, is of key importance for predicting solute migration through reservoir aquifers. Two methods are proposed to calculate these parameters as functions of the Péclet and the Péclet-Dahmköhler numbers. In the first method called the pore-scale model (PSM), the porous medium is discretized by the level set method; the Stokes and convection-diffusion equations with reaction at the wall are solved by a finite-difference scheme. In the second method, called the pore-network model (PNM), the void space of the porous medium is represented by an idealized geometry of pore bodies joined by pore throats; the flow field is computed by solving Kirchhoff's laws and transport calculations are performed in the asymptotic regime where the solute concentration undergoes an exponential evolution with time. Two synthetic geometries of porous media are addressed by using both numerical codes. The first geometry is constructed in order to validate the hypotheses implemented in PNM. PSM is also used for a better understanding of the various reaction patterns observed in the asymptotic regime. Despite the PNM approximations, a very good agreement between the models is obtained, which shows that PNM is an accurate description of reactive transport. PNM, which can address much larger pore volumes than PSM, is used to evaluate the influence of the concentration distribution on macroscopic properties of a large irregular network reconstructed from microtomography images. The role of the dimensionless numbers and of the location and size of the largest pore bodies is highlighted.

  9. Pore morphologies of root induced biopores from single pore to network scale investigated by XRCT

    Science.gov (United States)

    Peth, Stephan; Wittig, Marlen C.; Uteau Puschmann, Daniel; Pagenkemper, Sebastian; Haas, Christoph; Holthusen, Dörthe; Horn, Rainer

    2015-04-01

    Biopores are assumed to be an important factor for nutrient acquisition by providing biologically highly active soil-root interfaces to re-colonizing roots and controlling oxygen and water flows at the pedon scale and within the rhizosphere through the formation of branching channel networks which potentially enhance microbial turnover processes. Characteristic differences in pore morphologies are to be expected depending on the genesis of biopores which, for example, can be earthworm-induced or root-induced or subsequently modified by one of the two. Our understanding of biophysical interactions between plants and soil can be significantly improved by quantifying 3D biopore architectures across scales ranging from single biopores to pedon scale pore networks and linking pore morphologies to microscale measurements of transport processes (e.g. oxygen diffusion). While a few studies in the past have investigated biopore networks on a larger scale yet little is known on the micro-morphology of root-induces biopores and their associated rhizosphere. Also little data is available on lateral transport of oxygen through the rhizosphere which will strongly influence microbial turnover processes and consequently control the release and uptake of nutrients. This paper highlights results gathered within a research unit on nutrient acquisition from the subsoil. Here we focus on X-ray microtomography (XRCT) studies ranging from large soil columns (70 cm length and 20 cm diameter) to individual biopores and its surrounding rhizosphere. Samples were collected from sites with different preceding crops (fescue, chicory, alfalfa) and various cropping durations (1-3 years). We will present an approach for quantitative image analysis combined with micro-sensor measurements of oxygen diffusion and spatial gradients of O2 partial pressures to relate pore structure with transport functions. Implications of various biopore architectures for the accessibility of nutrient resources in

  10. Calorimetric studies of non-isothermal crystallization in amorphous

    Indian Academy of Sciences (India)

    Administrator

    The applicability of Meyer–Neldel relation between the pre-exponential factor and activation energy of non-isothermal crystallization for amorphous alloys of Cu–Ti system was verified. Keywords. Amorphous materials; differential scanning calorimetry (DSC); phase transitions. 1. Introduction. There is a significant attention ...

  11. Non-isothermal gas absorption with reversible chemical reaction

    NARCIS (Netherlands)

    Vas Bhat, R.D.; Swaaij, W.P.M. van; Benes, N.E.; Kuipers, J.A.M.; Versteeg, G.F.

    1997-01-01

    A fundamental description of non-isothermal mass transfer accompanied by a single reversible chemical reaction has been presented. The description is based on the Higbie penetration theory. Arrhenius type dependence of solubility, reaction rates and diffusivities on temperature has been assumed.

  12. Non-isothermal gas absorption with reversible chemical reaction.

    NARCIS (Netherlands)

    Vas bhat, R.D.; van Swaaij, Willibrordus Petrus Maria; Benes, Nieck Edwin; Kuipers, J.A.M.; Versteeg, Geert

    1997-01-01

    A fundamental description of non-isothermal mass transfer accompanied by a single reversible chemical reaction has been presented. The description is based on the Higbie penetration theory. Arrhenius type dependence of solubility, reaction rates and diffusivities on temperature has been assumed.

  13. Non-isothermal Moisture Transport Through Insulation Materials

    DEFF Research Database (Denmark)

    Peuhkuri, Ruut Hannele; Rode, Carsten; Hansen, Kurt Kielsgaard

    2008-01-01

    An experimental investigation was conducted in order to draw some conclusions on the magnitude of moisture transport due to temperature gradient on a range of porous light-weight building materials. A special constructed non-isothermal set-up allowed the creation of a temperature gradient of 10K...... and given humidity gradient over the sample. The resulting moisture ux as well as the hygrothermal states around and within the material were monitored. The hypothesis of relative humidity being a driving force for non-isothermal moisture transport already in the hygroscopic range could not be confirmed....... On the contrary, indications exist that the temperature gradient itself is driving the moisture from the warm side towards the cold side. An attempt to identify and quantify the single contributions of the different transport forms involved is also presented. The diferent results gave, however, diverging...

  14. Non-isothermal Diffusion of Water Vapour in Porous Building Materials

    Directory of Open Access Journals (Sweden)

    T. Ficker

    2002-01-01

    Full Text Available Non-isothermal diffusion is analysed using Fick's laws. The exact relations for non-isothermal diffusion flux and partial pressure profiles in porous building materials are derived and discussed.

  15. Soil Pore Network Visualisation and Quantification using ImageJ

    DEFF Research Database (Denmark)

    Garbout, Amin; Pajor, Radoslaw; Otten, Wilfred

    Abstract Soil is one of the most complex materials on the earth, within which many biological, physical and chemical processes that support life and affect climate change take place. A much more detailed knowledge of the soil system is required to improve our ability to develop soil management...... strategies to preserve this limited resource. Many of those processes occur at micro scales. For long our ability to study soils non-destructively at microscopic scales has been limited, but recent developments in the use of X-ray Computed Tomography has offered great opportunities to quantify the 3-D...... geometry of soil pores. In this study we look at how networks that summarize the geometry of pores in soil are affected by soil structure. One of the objectives is to develop a robust and reproducible image analysis technique to produce quantitative knowledge on soil architecture from high resolution 3D...

  16. Non-Isothermal Constitutive Relations and Heat Transfer Equations of a Two-Phase Medium

    Directory of Open Access Journals (Sweden)

    Uciechowska-Grakowicz Anna

    2017-09-01

    Full Text Available In the case of a two-phase medium – such as the soil, which consists of an elastic skeleton and is filled with pore fluids – stress and strain within the medium are dependent on both phases. Similarly, in the case of heat transfer, heat is conducted through the two phases at different rates, with an additional heat transfer between the phases. In the classical approach to modelling a porous medium, it is assumed that the fluid filling the pore space is water, which is incompressible. In the case of gas, the volume of which is strongly dependent on temperature and pressure, one should take this behavior into account in the constitutive relations for the medium. This work defines the physical relations of a two-phase medium and provides heat transfer equations, constructed for a porous, elastic skeleton with fluid-filled pores, which may be: liquid, gas, or mixture of liquid and a gas in non-isothermal conditions. The paper will present constitutive relations derived from the laws of irreversible thermodynamics, assuming that pores are filled with either a liquid or a gas. These relations, in the opinion of the authors, may be used as the basis for the construction of a model of the medium filled partly with a liquid and partly with a gas. It includes the possibility of independent heat transfer through any given two-phase medium phase, with the transfer of heat between the phases.

  17. Quantification of soil pore network complexity with X-ray computed tomography and gas transport measurements

    DEFF Research Database (Denmark)

    Katuwal, Sheela; Arthur, Emmanuel; Tuller, M.

    2015-01-01

    Flow and transport of gases through soils are largely controlled by pore structural attributes. The quantification of pore network characteristics is therefore essential for accurate prediction of air permeability and gas diffusivity. In this study, the pore network characteristics of seven diffe...

  18. A Microfluidic Pore Network Approach to Investigate Water Transport in Fuel Cell Porous Transport Layers

    OpenAIRE

    Bazylak, A.; Berejnov, V.; Markicevic, B.; Sinton, D.; Djilali, N.

    2008-01-01

    Pore network modelling has traditionally been used to study displacement processes in idealized porous media related to geological flows, with applications ranging from groundwater hydrology to enhanced oil recovery. Very recently, pore network modelling has been applied to model the gas diffusion layer (GDL) of a polymer electrolyte membrane (PEM) fuel cell. Discrete pore network models have the potential to elucidate transport phenomena in the GDL with high computational efficiency, in cont...

  19. Pore network properties of sandstones in a fault damage zone

    Science.gov (United States)

    Bossennec, Claire; Géraud, Yves; Moretti, Isabelle; Mattioni, Luca; Stemmelen, Didier

    2018-05-01

    The understanding of fluid flow in faulted sandstones is based on a wide range of techniques. These depend on the multi-method determination of petrological and structural features, porous network properties and both spatial and temporal variations and interactions of these features. The question of the multi-parameter analysis on fluid flow controlling properties is addressed for an outcrop damage zone in the hanging wall of a normal fault zone on the western border of the Upper Rhine Graben, affecting the Buntsandstein Group (Early Triassic). Diagenetic processes may alter the original pore type and geometry in fractured and faulted sandstones. Therefore, these may control the ultimate porosity and permeability of the damage zone. The classical model of evolution of hydraulic properties with distance from the major fault core is nuanced here. The hydraulic behavior of the rock media is better described by a pluri-scale model including: 1) The grain scale, where the hydraulic properties are controlled by sedimentary features, the distance from the fracture, and the impact of diagenetic processes. These result in the ultimate porous network characteristics observed. 2) A larger scale, where the structural position and characteristics (density, connectivity) of the fracture corridors are strongly correlated with both geo-mechanical and hydraulic properties within the damage zone.

  20. Pore-network modeling of solute transport and biofilm growth in porous media

    NARCIS (Netherlands)

    Qin, Chao Zhong; Hassanizadeh, S. Majid

    2015-01-01

    In this work, a pore-network (PN) model for solute transport and biofilm growth in porous media was developed. Compared to previous studies of biofilm growth, it has two new features. First, the constructed pore network gives a better representation of a porous medium. Second, instead of using a

  1. Micro/Nano-pore Network Analysis of Gas Flow in Shale Matrix.

    Science.gov (United States)

    Zhang, Pengwei; Hu, Liming; Meegoda, Jay N; Gao, Shengyan

    2015-08-27

    The gas flow in shale matrix is of great research interests for optimized shale gas extraction. The gas flow in the nano-scale pore may fall in flow regimes such as viscous flow, slip flow and Knudsen diffusion. A 3-dimensional nano-scale pore network model was developed to simulate dynamic gas flow, and to describe the transient properties of flow regimes. The proposed pore network model accounts for the various size distributions and low connectivity of shale pores. The pore size, pore throat size and coordination number obey normal distribution, and the average values can be obtained from shale reservoir data. The gas flow regimes were simulated using an extracted pore network backbone. The numerical results show that apparent permeability is strongly dependent on pore pressure in the reservoir and pore throat size, which is overestimated by low-pressure laboratory tests. With the decrease of reservoir pressure, viscous flow is weakening, then slip flow and Knudsen diffusion are gradually becoming dominant flow regimes. The fingering phenomenon can be predicted by micro/nano-pore network for gas flow, which provides an effective way to capture heterogeneity of shale gas reservoir.

  2. Modeling of Non-isothermal Austenite Formation in Spring Steel

    Science.gov (United States)

    Huang, He; Wang, Baoyu; Tang, Xuefeng; Li, Junling

    2017-12-01

    The austenitization kinetics description of spring steel 60Si2CrA plays an important role in providing guidelines for industrial production. The dilatometric curves of 60Si2CrA steel were measured using a dilatometer DIL805A at heating rates of 0.3 K to 50 K/s (0.3 °C/s to 50 °C/s). Based on the dilatometric curves, a unified kinetics model using the internal state variable (ISV) method was derived to describe the non-isothermal austenitization kinetics of 60Si2CrA, and the abovementioned model models the incubation and transition periods. The material constants in the model were determined using a genetic algorithm-based optimization technique. Additionally, good agreement between predicted and experimental volume fractions of transformed austenite was obtained, indicating that the model is effective for describing the austenitization kinetics of 60Si2CrA steel. Compared with other modeling methods of austenitization kinetics, this model, which uses the ISV method, has some advantages, such as a simple formula and explicit physics meaning, and can be probably used in engineering practice.

  3. A numerical study of non-isothermal turbulent coaxial jets

    Energy Technology Data Exchange (ETDEWEB)

    Kriaa, Wassim; Abderrazak, Kamel; Mhiri, Hatem [Ecole Nationale d' Ingenieurs de Monastir, Laboratoire de Mecanique des Fluides et Thermique, Monastir (Tunisia); Palec, Georges le; Bournot, Philippe [Institut de Mecanique de Marseille, Marseille (France)

    2008-07-15

    In this work, we propose to study non isothermal air-air coaxial jets with two different approaches: parabolic and elliptic approaches. The standard k-{epsilon} model and the RSM model were applied in this study. The numerical resolution of the equations governing this flow type was carried out for: the parabolic approach, by a ''home-made'' CFD code based on a finite difference method, and the elliptic approach by an industrial code (FLUENT) based on a finite volume method. In forced convection mode (Fr={infinity}), the two turbulence models are valid for the prediction of the mean flow. But for turbulent sizes, k-{epsilon} model gives results closer to those achieved in experiments compared to RSM Model. Concerning the limit of validity of the parabolic and elliptic approaches, we showed that for velocities ratio r lower than 1, the results of the two approaches were satisfactory. On the other hand, for r>1, the difference between the results became increasingly significant. In mixed convection mode (Fr{approx_equal}20), the results obtained by the two turbulence models for the mean axial velocity were very different even in the plume region. For the temperature and the turbulent sizes the two models give satisfactory results which agree well with the correlations suggested by the experimenters for X{>=}20. Thus, the second order model with {sigma}{sub t}=0.85 is more effective for a coaxial jet study in a mixed convection mode. (orig.)

  4. Review of pore network modelling of porous media: experimental characterisations, network constructions and applications to reactive transport

    OpenAIRE

    Xiong, Qingrong; Baychev, Todor; Jivkov, Andrey

    2016-01-01

    Pore network models have been applied widely for simulating a variety of different physical and chemical processes, including phase exchange, non-Newtonian displacement, non-Darcy flow, reactive transport and thermodynamically consistent oil layers. The realism of such modelling, i.e. the credibility of their predictions, depends to a large extent on the quality of the correspondence between the pore space of a given medium and the pore network constructed as its representation. The main expe...

  5. Br2 induced oxidative pore modification of a porous coordination network.

    Science.gov (United States)

    Ohtsu, Hiroyoshi; Kawano, Masaki

    2016-01-14

    Iodinated pores of a Zn-based coordination network were modified by Br2 oxidation to produce brominated pores in a polycrystalline-to-polycrystalline manner while maintaining the same network topology. Ab initio X-ray powder diffraction analysis and Raman spectroscopy revealed that the brominated pore can trap Br2 or I2 by strong σ/π-type interactions. A kinetic study in solution revealed that the pore modification by Br2 oxidation is much faster than the Br2 encapsulation process.

  6. Review of pore network modelling of porous media: Experimental characterisations, network constructions and applications to reactive transport

    Science.gov (United States)

    Xiong, Qingrong; Baychev, Todor G.; Jivkov, Andrey P.

    2016-09-01

    Pore network models have been applied widely for simulating a variety of different physical and chemical processes, including phase exchange, non-Newtonian displacement, non-Darcy flow, reactive transport and thermodynamically consistent oil layers. The realism of such modelling, i.e. the credibility of their predictions, depends to a large extent on the quality of the correspondence between the pore space of a given medium and the pore network constructed as its representation. The main experimental techniques for pore space characterisation, including direct imaging, mercury intrusion porosimetry and gas adsorption, are firstly summarised. A review of the main pore network construction techniques is then presented. Particular focus is given on how such constructions are adapted to the data from experimentally characterised pore systems. Current applications of pore network models are considered, with special emphasis on the effects of adsorption, dissolution and precipitation, as well as biomass growth, on transport coefficients. Pore network models are found to be a valuable tool for understanding and predicting meso-scale phenomena, linking single pore processes, where other techniques are more accurate, and the homogenised continuum porous media, used by engineering community.

  7. Impact of pore size variability and network coupling on electrokinetic transport in porous media

    Science.gov (United States)

    Alizadeh, Shima; Bazant, Martin Z.; Mani, Ali

    2016-11-01

    We have developed and validated an efficient and robust computational model to study the coupled fluid and ion transport through electrokinetic porous media, which are exposed to external gradients of pressure, electric potential, and concentration. In our approach a porous media is modeled as a network of many pores through which the transport is described by the coupled Poisson-Nernst-Planck-Stokes equations. When the pore sizes are random, the interactions between various modes of transport may provoke complexities such as concentration polarization shocks and internal flow circulations. These phenomena impact mixing and transport in various systems including deionization and filtration systems, supercapacitors, and lab-on-a-chip devices. In this work, we present simulations of massive networks of pores and we demonstrate the impact of pore size variation, and pore-pore coupling on the overall electrokinetic transport in porous media.

  8. Effect of morphology on water sorption in cellular solid foods. Part I: Pore scale network model

    NARCIS (Netherlands)

    Esveld, D.C.; Sman, van der R.G.M.; Dalen, van G.; Duynhoven, van J.P.M.; Meinders, M.B.J.

    2012-01-01

    A pore scale network model is developed to predict the dynamics of moisture diffusion into complex cellular solid foods like bread, crackers, and cereals. The morphological characteristics of the sample, including the characteristics of each cellular void and the open pore connections between them

  9. Development of a pore network simulation model to study nonaqueous phase liquid dissolution

    Science.gov (United States)

    Dillard, Leslie A.; Blunt, Martin J.

    2000-01-01

    A pore network simulation model was developed to investigate the fundamental physics of nonequilibrium nonaqueous phase liquid (NAPL) dissolution. The network model is a lattice of cubic chambers and rectangular tubes that represent pore bodies and pore throats, respectively. Experimental data obtained by Powers [1992] were used to develop and validate the model. To ensure the network model was representative of a real porous medium, the pore size distribution of the network was calibrated by matching simulated and experimental drainage and imbibition capillary pressure-saturation curves. The predicted network residual styrene blob-size distribution was nearly identical to the observed distribution. The network model reproduced the observed hydraulic conductivity and produced relative permeability curves that were representative of a poorly consolidated sand. Aqueous-phase transport was represented by applying the equation for solute flux to the network tubes and solving for solute concentrations in the network chambers. Complete mixing was found to be an appropriate approximation for calculation of chamber concentrations. Mass transfer from NAPL blobs was represented using a corner diffusion model. Predicted results of solute concentration versus Peclet number and of modified Sherwood number versus Peclet number for the network model compare favorably with experimental data for the case in which NAPL blob dissolution was negligible. Predicted results of normalized effluent concentration versus pore volume for the network were similar to the experimental data for the case in which NAPL blob dissolution occurred with time.

  10. Multiple stable isotope fronts during non-isothermal fluid flow

    Science.gov (United States)

    Fekete, Szandra; Weis, Philipp; Scott, Samuel; Driesner, Thomas

    2018-02-01

    Stable isotope signatures of oxygen, hydrogen and other elements in minerals from hydrothermal veins and metasomatized host rocks are widely used to investigate fluid sources and paths. Previous theoretical studies mostly focused on analyzing stable isotope fronts developing during single-phase, isothermal fluid flow. In this study, numerical simulations were performed to assess how temperature changes, transport phenomena, kinetic vs. equilibrium isotope exchange, and isotopic source signals determine mineral oxygen isotopic compositions during fluid-rock interaction. The simulations focus on one-dimensional scenarios, with non-isothermal single- and two-phase fluid flow, and include the effects of quartz precipitation and dissolution. If isotope exchange between fluid and mineral is fast, a previously unrecognized, significant enrichment in heavy oxygen isotopes of fluids and minerals occurs at the thermal front. The maximum enrichment depends on the initial isotopic composition of fluid and mineral, the fluid-rock ratio and the maximum change in temperature, but is independent of the isotopic composition of the incoming fluid. This thermally induced isotope front propagates faster than the signal related to the initial isotopic composition of the incoming fluid, which forms a trailing front behind the zone of transient heavy oxygen isotope enrichment. Temperature-dependent kinetic rates of isotope exchange between fluid and rock strongly influence the degree of enrichment at the thermal front. In systems where initial isotope values of fluids and rocks are far from equilibrium and isotope fractionation is controlled by kinetics, the temperature increase accelerates the approach of the fluid to equilibrium conditions with the host rock. Consequently, the increase at the thermal front can be less dominant and can even generate fluid values below the initial isotopic composition of the input fluid. As kinetics limit the degree of isotope exchange, a third front may

  11. Water retention, gas transport, and pore network complexity during short-term regeneration of soil structure

    DEFF Research Database (Denmark)

    Arthur, Emmanuel; Møldrup, Per; Schjønning, Per

    2013-01-01

    Human activities such as mining, grading, and filling results in physical disturbance of soil structure and associated functions, and knowledge on structure recovery after such activities is vital. This study quantifies the newly-formed structure of 22-month field-incubated physically-disturbed (2...... was done using water retention (pore size distribution), soil gas diffusivity, air permeability, and derived pore network complexity parameters. Significant decreases in bulk density (increased total porosity) and increases in pores > 100 1m was observed for incubated samples compared with SR samples......, incubated samples had lower water content, higher air filled porosity, and air permeability than natural intact samples at matric potential of –10 kPa. Despite this, soil pore organization was similar among the two groups but pore network complexity increased in order: SR

  12. Effects of the soil pore network architecture on the soil's physical functionalities

    Science.gov (United States)

    Smet, Sarah; Beckers, Eléonore; Léonard, Angélique; Degré, Aurore

    2017-04-01

    The soil fluid movement's prediction is of major interest within an agricultural or environmental scope because many processes depend ultimately on the soil fluids dynamic. It is common knowledge that the soil microscopic pore network structure governs the inner-soil convective fluids flow. There isn't, however, a general methodthat consider the pore network structure as a variable in the prediction of thecore scale soil's physical functionalities. There are various possible representations of the microscopic pore network: sample scale averaged structural parameters, extrapolation of theoretic pore network, or use of all the information available by modeling within the observed pore network. Different representations implydifferent analyzing methodologies. To our knowledge, few studies have compared the micro-and macroscopic soil's characteristics for the same soil core sample. The objective of our study is to explore the relationship between macroscopic physical properties and microscopic pore network structure. The saturated hydraulic conductivity, the air permeability, the retention curve, and others classical physical parameters were measured for ten soil samples from an agricultural field. The pore network characteristics were quantified through the analyses of X-ray micro-computed tomographic images(micro-CT system Skyscan-1172) with a voxel size of 22 µm3. Some of the first results confirmed what others studies had reported. Then, the comparison between macroscopic properties and microscopic parameters suggested that the air movements depended mostly on the pore connectivity and tortuosity than on the total porosity volume. We have also found that the fractal dimension calculated from the X-ray images and the fractal dimension calculated from the retention curve were significantly different. Our communication will detailthose results and discuss the methodology: would the results be similar with a different voxel size? What are the calculated and measured

  13. Model-free method for isothermal and non-isothermal decomposition kinetics analysis of PET sample

    International Nuclear Information System (INIS)

    Saha, B.; Maiti, A.K.; Ghoshal, A.K.

    2006-01-01

    Pyrolysis, one possible alternative to recover valuable products from waste plastics, has recently been the subject of renewed interest. In the present study, the isoconversion methods, i.e., Vyazovkin model-free approach is applied to study non-isothermal decomposition kinetics of waste PET samples using various temperature integral approximations such as Coats and Redfern, Gorbachev, and Agrawal and Sivasubramanian approximation and direct integration (recursive adaptive Simpson quadrature scheme) to analyze the decomposition kinetics. The results show that activation energy (E α ) is a weak but increasing function of conversion (α) in case of non-isothermal decomposition and strong and decreasing function of conversion in case of isothermal decomposition. This indicates possible existence of nucleation, nuclei growth and gas diffusion mechanism during non-isothermal pyrolysis and nucleation and gas diffusion mechanism during isothermal pyrolysis. Optimum E α dependencies on α obtained for non-isothermal data showed similar nature for all the types of temperature integral approximations

  14. Simulating drainage and imbibition experiments in a high-porosity micromodel using an unstructured pore network model

    NARCIS (Netherlands)

    Joekar Niasar, V.; Hassanizadeh, S.M.; Pyrak-Nolte, L.J.; Berentsen, C.W.J.

    2009-01-01

    Development of pore network models based on detailed topological data of the pore space is essential for predicting multiphase flow in porous media. In this work, an unstructured pore network model has been developed to simulate a set of drainage and imbibition laboratory experiments performed on a

  15. A computational geometry approach to pore network construction for granular packings

    Science.gov (United States)

    van der Linden, Joost H.; Sufian, Adnan; Narsilio, Guillermo A.; Russell, Adrian R.; Tordesillas, Antoinette

    2018-03-01

    Pore network construction provides the ability to characterize and study the pore space of inhomogeneous and geometrically complex granular media in a range of scientific and engineering applications. Various approaches to the construction have been proposed, however subtle implementational details are frequently omitted, open access to source code is limited, and few studies compare multiple algorithms in the context of a specific application. This study presents, in detail, a new pore network construction algorithm, and provides a comprehensive comparison with two other, well-established Delaunay triangulation-based pore network construction methods. Source code is provided to encourage further development. The proposed algorithm avoids the expensive non-linear optimization procedure in existing Delaunay approaches, and is robust in the presence of polydispersity. Algorithms are compared in terms of structural, geometrical and advanced connectivity parameters, focusing on the application of fluid flow characteristics. Sensitivity of the various networks to permeability is assessed through network (Stokes) simulations and finite-element (Navier-Stokes) simulations. Results highlight strong dependencies of pore volume, pore connectivity, throat geometry and fluid conductance on the degree of tetrahedra merging and the specific characteristics of the throats targeted by the merging algorithm. The paper concludes with practical recommendations on the applicability of the three investigated algorithms.

  16. Understanding fluid transport through the multiscale pore network of a natural shale

    Directory of Open Access Journals (Sweden)

    Davy Catherine A.

    2017-01-01

    Full Text Available The pore structure of a natural shale is obtained by three imaging means. Micro-tomography results are extended to provide the spatial arrangement of the minerals and pores present at a voxel size of 700 nm (the macroscopic scale. FIB/SEM provides a 3D representation of the porous clay matrix on the so-called mesoscopic scale (10-20 nm; a connected pore network, devoid of cracks, is obtained for two samples out of five, while the pore network is connected through cracks for two other samples out of five. Transmission Electron Microscopy (TEM is used to visualize the pore space with a typical pixel size of less than 1 nm and a porosity ranging from 0.12 to 0.25. On this scale, in the absence of 3D images, the pore structure is reconstructed by using a classical technique, which is based on truncated Gaussian fields. Permeability calculations are performed with the Lattice Boltzmann Method on the nanoscale, on the mesoscale, and on the combination of the two. Upscaling is finally done (by a finite volume approach on the bigger macroscopic scale. Calculations show that, in the absence of cracks, the contribution of the nanoscale pore structure on the overall permeability is similar to that of the mesoscale. Complementarily, the macroscopic permeability is measured on a centimetric sample with a neutral fluid (ethanol. The upscaled permeability on the macroscopic scale is in good agreement with the experimental results.

  17. A kinetic Monte Carlo approach to study fluid transport in pore networks

    Science.gov (United States)

    Apostolopoulou, M.; Day, R.; Hull, R.; Stamatakis, M.; Striolo, A.

    2017-10-01

    The mechanism of fluid migration in porous networks continues to attract great interest. Darcy's law (phenomenological continuum theory), which is often used to describe macroscopically fluid flow through a porous material, is thought to fail in nano-channels. Transport through heterogeneous and anisotropic systems, characterized by a broad distribution of pores, occurs via a contribution of different transport mechanisms, all of which need to be accounted for. The situation is likely more complicated when immiscible fluid mixtures are present. To generalize the study of fluid transport through a porous network, we developed a stochastic kinetic Monte Carlo (KMC) model. In our lattice model, the pore network is represented as a set of connected finite volumes (voxels), and transport is simulated as a random walk of molecules, which "hop" from voxel to voxel. We simulated fluid transport along an effectively 1D pore and we compared the results to those expected by solving analytically the diffusion equation. The KMC model was then implemented to quantify the transport of methane through hydrated micropores, in which case atomistic molecular dynamic simulation results were reproduced. The model was then used to study flow through pore networks, where it was able to quantify the effect of the pore length and the effect of the network's connectivity. The results are consistent with experiments but also provide additional physical insights. Extension of the model will be useful to better understand fluid transport in shale rocks.

  18. Coupling root architecture and pore network modeling - an attempt towards better understanding root-soil interactions

    Science.gov (United States)

    Leitner, Daniel; Bodner, Gernot; Raoof, Amir

    2013-04-01

    Understanding root-soil interactions is of high importance for environmental and agricultural management. Root uptake is an essential component in water and solute transport modeling. The amount of groundwater recharge and solute leaching significantly depends on the demand based plant extraction via its root system. Plant uptake however not only responds to the potential demand, but in most situations is limited by supply form the soil. The ability of the plant to access water and solutes in the soil is governed mainly by root distribution. Particularly under conditions of heterogeneous distribution of water and solutes in the soil, it is essential to capture the interaction between soil and roots. Root architecture models allow studying plant uptake from soil by describing growth and branching of root axes in the soil. Currently root architecture models are able to respond dynamically to water and nutrient distribution in the soil by directed growth (tropism), modified branching and enhanced exudation. The porous soil medium as rooting environment in these models is generally described by classical macroscopic water retention and sorption models, average over the pore scale. In our opinion this simplified description of the root growth medium implies several shortcomings for better understanding root-soil interactions: (i) It is well known that roots grow preferentially in preexisting pores, particularly in more rigid/dry soil. Thus the pore network contributes to the architectural form of the root system; (ii) roots themselves can influence the pore network by creating preferential flow paths (biopores) which are an essential element of structural porosity with strong impact on transport processes; (iii) plant uptake depend on both the spatial location of water/solutes in the pore network as well as the spatial distribution of roots. We therefore consider that for advancing our understanding in root-soil interactions, we need not only to extend our root models

  19. A general approach for defining the macroscopic free energy density of saturated porous media at finite strains under non-isothermal conditions

    International Nuclear Information System (INIS)

    Gajo, A.

    2011-01-01

    A general approach is proposed for defining the macroscopic free energy density function (and its complement, the free enthalpy) of a saturated porous medium submitted to finite deformations under non-isothermal conditions, in the case of compressible fluid and solid constituents. Reference is made to an elementary volume treated as an 'open system', moving with the solid skeleton. The proposed free energy depends on the generalised strains (namely an appropriate measure of the strain of the solid skeleton and the variation in fluid mass content) and the absolute temperatures of the solid and fluid phases (which are assumed to differ from each other for the sake of generality). This macroscopic energy proves to be a potential for the generalised stresses (namely the associated measure of the total stress and the free enthalpy of the pore fluid per unit mass) and the entropies of the solid and fluid phases. In contrast with mixture theories, the resulting free energy is not the simple sum of the free energies of the single constituents. Two simplified cases are examined in detail, i.e. the semi-linear theory (originally proposed for isothermal conditions and extended here to non-isothermal problems) and the linear theory. The proposed approach paves the way to the consistent non-isothermal-hyper-elastic-plastic modelling of saturated porous media with a compressible fluid and solid constituents. (authors)

  20. Multiscale pore networks and their effect on deformation and transport property alteration associated with hydraulic fracturing

    Science.gov (United States)

    Daigle, Hugh; Hayman, Nicholas; Jiang, Han; Tian, Xiao; Jiang, Chunbi

    2017-04-01

    Multiple lines of evidence indicate that, during a hydraulic fracture stimulation, the permeability of the unfractured matrix far from the main, induced tensile fracture increases by one to two orders of magnitude. This permeability enhancement is associated with pervasive shear failure in a large region surrounding the main induced fracture. We have performed low-pressure gas sorption, mercury intrusion, and nuclear magnetic resonance measurements along with high-resolution scanning electron microscope imaging on several preserved and unpreserved shale samples from North American basins before and after inducing failure in confined compressive strength tests. We have observed that the pore structure in intact samples exhibits multiscale behavior, with sub-micron-scale pores in organic matter connected in isolated, micron-scale clusters which themselves are connected to each other through a network of microcracks. The organic-hosted pore networks are poorly connected due to a significant number of dead-end pores within the organic matter. Following shear failure, we often observe an increase in pore volume in the sub-micron range, which appears to be related to the formation of microcracks that propagate along grain boundaries and other planes of mechanical strength contrast. This is consistent with other experimental and field evidence. In some cases these microcracks cross or terminate in organic matter, intersecting the organic-hosted pores. The induced microcrack networks typically have low connectivity and do not appreciably increase the connectivity of the overall pore network. However, in other cases the shear deformation results in an overall pore volume decrease; samples which exhibit this behavior tend to have more clay minerals. Our interpretation of these phenomena is as follows. As organic matter is converted to hydrocarbons, organic-hosted pores develop, and the hydrocarbons contained in these pores are overpressured. The disconnected nature of these

  1. Pore Network Modeling: Alternative Methods to Account for Trapping and Spatial Correlation

    KAUST Repository

    De La Garza Martinez, Pablo

    2016-05-01

    Pore network models have served as a predictive tool for soil and rock properties with a broad range of applications, particularly in oil recovery, geothermal energy from underground reservoirs, and pollutant transport in soils and aquifers [39]. They rely on the representation of the void space within porous materials as a network of interconnected pores with idealised geometries. Typically, a two-phase flow simulation of a drainage (or imbibition) process is employed, and by averaging the physical properties at the pore scale, macroscopic parameters such as capillary pressure and relative permeability can be estimated. One of the most demanding tasks in these models is to include the possibility of fluids to remain trapped inside the pore space. In this work I proposed a trapping rule which uses the information of neighboring pores instead of a search algorithm. This approximation reduces the simulation time significantly and does not perturb the accuracy of results. Additionally, I included spatial correlation to generate the pore sizes using a matrix decomposition method. Results show higher relative permeabilities and smaller values for irreducible saturation, which emphasizes the effects of ignoring the intrinsic correlation seen in pore sizes from actual porous media. Finally, I implemented the algorithm from Raoof et al. (2010) [38] to generate the topology of a Fontainebleau sandstone by solving an optimization problem using the steepest descent algorithm with a stochastic approximation for the gradient. A drainage simulation is performed on this representative network and relative permeability is compared with published results. The limitations of this algorithm are discussed and other methods are suggested to create a more faithful representation of the pore space.

  2. Percolating macropore networks in tilled topsoil: effects of sample size, minimum pore thickness and soil type

    Science.gov (United States)

    Jarvis, Nicholas; Larsbo, Mats; Koestel, John; Keck, Hannes

    2017-04-01

    The long-range connectivity of macropore networks may exert a strong control on near-saturated and saturated hydraulic conductivity and the occurrence of preferential flow through soil. It has been suggested that percolation concepts may provide a suitable theoretical framework to characterize and quantify macropore connectivity, although this idea has not yet been thoroughly investigated. We tested the applicability of percolation concepts to describe macropore networks quantified by X-ray scanning at a resolution of 0.24 mm in eighteen cylinders (20 cm diameter and height) sampled from the ploughed layer of four soils of contrasting texture in east-central Sweden. The analyses were performed for sample sizes ("regions of interest", ROI) varying between 3 and 12 cm in cube side-length and for minimum pore thicknesses ranging between image resolution and 1 mm. Finite sample size effects were clearly found for ROI's of cube side-length smaller than ca. 6 cm. For larger sample sizes, the results showed the relevance of percolation concepts to soil macropore networks, with a close relationship found between imaged porosity and the fraction of the pore space which percolated (i.e. was connected from top to bottom of the ROI). The percolating fraction increased rapidly as a function of porosity above a small percolation threshold (1-4%). This reflects the ordered nature of the pore networks. The percolation relationships were similar for all four soils. Although pores larger than 1 mm appeared to be somewhat better connected, only small effects of minimum pore thickness were noted across the range of tested pore sizes. The utility of percolation concepts to describe the connectivity of more anisotropic macropore networks (e.g. in subsoil horizons) should also be tested, although with current X-ray scanning equipment it may prove difficult in many cases to analyze sufficiently large samples that would avoid finite size effects.

  3. Non-isothermal effects on multi-phase flow in porous medium

    DEFF Research Database (Denmark)

    Singh, Ashok; Wang, W; Park, C. H.

    2010-01-01

    In this paper a ppT -formulation for non-isothermal multi-phase flow is given including diffusion and latent heat effects. Temperature and pressure dependencies of governing parameters are considered, in particular surface tension variation on phase interfaces along with temperature changes. A we...... geotechnical areas. The classic benchmark for two-phase flow by McWhorter and Sunada1 is used as a reference case on which non-isothermal effects and non-linear material behavior are studied.......In this paper a ppT -formulation for non-isothermal multi-phase flow is given including diffusion and latent heat effects. Temperature and pressure dependencies of governing parameters are considered, in particular surface tension variation on phase interfaces along with temperature changes. A weak...

  4. Reconstruction of chalk pore networks from 2D backscatter electron micrographs using a simulated annealing technique

    Energy Technology Data Exchange (ETDEWEB)

    Talukdar, M.S.; Torsaeter, O. [Department of Petroleum Engineering and Applied Geophysics, Norwegian University of Science and Technology, Trondheim (Norway)

    2002-05-01

    We report the stochastic reconstruction of chalk pore networks from limited morphological information that may be readily extracted from 2D backscatter electron (BSE) images of the pore space. The reconstruction technique employs a simulated annealing (SA) algorithm, which can be constrained by an arbitrary number of morphological descriptors. Backscatter electron images of a high-porosity North Sea chalk sample are analyzed and the morphological descriptors of the pore space are determined. The morphological descriptors considered are the void-phase two-point probability function and lineal path function computed with or without the application of periodic boundary conditions (PBC). 2D and 3D samples have been reconstructed with different combinations of the descriptors and the reconstructed pore networks have been analyzed quantitatively to evaluate the quality of reconstructions. The results demonstrate that simulated annealing technique may be used to reconstruct chalk pore networks with reasonable accuracy using the void-phase two-point probability function and/or void-phase lineal path function. Void-phase two-point probability function produces slightly better reconstruction than the void-phase lineal path function. Imposing void-phase lineal path function results in slight improvement over what is achieved by using the void-phase two-point probability function as the only constraint. Application of periodic boundary conditions appears to be not critically important when reasonably large samples are reconstructed.

  5. New insight into non-isothermal crystallization of PVA-graphene composites.

    Science.gov (United States)

    Li, Chengpeng; Vongsvivut, Jitraporn; She, Xiaodong; Li, Yongzhen; She, Fenghua; Kong, Lingxue

    2014-10-28

    The melt crystallization of poly(vinyl alcohol) (PVA) and PVA composites has been a controversial subject due to inconclusive evidence and different opinions for its decomposition during crystallization. Using graphene as a model, the melt crystallization of PVA and PVA-graphene composites occurring during single-cycle and multiple-cycle non-isothermal annealing processes was systematically analyzed using different characterization techniques. The results obtained using single-cycle non-isothermal annealing indicated that the entire crystallization process took place through two main stages. The graphene in the PVA matrix regulates the nucleation and crystal growth manner of the PVA, yet resulting in retardation of the entire crystallization. The FTIR and Raman spectroscopic results particularly demonstrated that the annealing process not only improved the crystallinity but also led to clear decomposition in PVA and PVA-graphene composites, such as the elimination of hydroxyl groups and the production of C=C double bonds. The newly produced C=C double bonds were found to be responsible for the retardation of PVA macromolecule crystallization and the breaking of hydrogen bonds among the hydroxyl groups in the PVA chains. In addition, the morphological observation and multi-cycle non-isothermal crystallization further confirmed the existence of decomposition based on the surface damage as well as decreased crystallization enthalpy and crystallization peak temperature. Therefore, the non-isothermal crystallizations of the pure PVA and the PVA-graphene composites were in fact the combination of non-isothermal crystallization and non-isothermal degradation processes.

  6. To the theory of non-local non-isothermal filtration in porous medium

    Science.gov (United States)

    Meilanov, R. R.; Akhmedov, E. N.; Beybalaev, V. D.; Magomedov, R. A.; Ragimkhanov, G. B.; Aliverdiev, A. A.

    2018-01-01

    A new approach to the theory of non-local and non-isothermal filtration based on the mathematical apparatus of fractional order derivatives is developing. A solution of the Cauchy problem for the system of equations of non-local non-isothermal filtration in fractional calculus is obtained. Some applications of the solutions obtained to the problems of underground hydrodynamics (fracturing and explosion) are considered. A computational experiment was carried out to analyze the solutions obtained. Graphs of pressure and temperature dependences are plotted against time.

  7. Percolation properties of 3-D multiscale pore networks: how connectivity controls soil filtration processes

    Directory of Open Access Journals (Sweden)

    E. M. A. Perrier

    2010-10-01

    Full Text Available Quantifying the connectivity of pore networks is a key issue not only for modelling fluid flow and solute transport in porous media but also for assessing the ability of soil ecosystems to filter bacteria, viruses and any type of living microorganisms as well inert particles which pose a contamination risk. Straining is the main mechanical component of filtration processes: it is due to size effects, when a given soil retains a conveyed entity larger than the pores through which it is attempting to pass. We postulate that the range of sizes of entities which can be trapped inside soils has to be associated with the large range of scales involved in natural soil structures and that information on the pore size distribution has to be complemented by information on a critical filtration size (CFS delimiting the transition between percolating and non percolating regimes in multiscale pore networks. We show that the mass fractal dimensions which are classically used in soil science to quantify scaling laws in observed pore size distributions can also be used to build 3-D multiscale models of pore networks exhibiting such a critical transition. We extend to the 3-D case a new theoretical approach recently developed to address the connectivity of 2-D fractal networks (Bird and Perrier, 2009. Theoretical arguments based on renormalisation functions provide insight into multi-scale connectivity and a first estimation of CFS. Numerical experiments on 3-D prefractal media confirm the qualitative theory. These results open the way towards a new methodology to estimate soil filtration efficiency from the construction of soil structural models to be calibrated on available multiscale data.

  8. Typical parameters of the plasma chemical similarity in non-isothermal reactive plasmas

    International Nuclear Information System (INIS)

    Gundermann, S.; Jacobs, H.; Miethke, F.; Rutsher, A.; Wagner, H.E.

    1996-01-01

    The substance of physical similarity principles is contained in parameters which govern the comparison of different realizations of a model device. Because similarity parameters for non-isothermal plasma chemical reactors are unknown to a great extent, an analysis of relevant equations is given together with some experimental results. Modelling of the reactor and experimental results for the ozone synthesis are presented

  9. Non-isothermal compositional gas flow during carbon dioxide storage and enhanced gas recovery

    DEFF Research Database (Denmark)

    Singh, Ashok; Böettcher, N.; Wang, W.

    2011-01-01

    In this work we present the conceptual modeling and the numerical scheme for carbon dioxide storage into nearly depleted gas reservoirs for enhanced gas recovery reasons. For this we develop non-isothermal compositional gas flow model. We used a combined monolithic / staggered coupling scheme to ...

  10. A simple method of evaluating non-isothermal crystallization kinetics in multicomponent polymer systems

    Czech Academy of Sciences Publication Activity Database

    Kratochvíl, Jaroslav; Kelnar, Ivan

    2015-01-01

    Roč. 47, October (2015), s. 79-86 ISSN 0142-9418 R&D Projects: GA ČR(CZ) GA13-15255S Institutional support: RVO:61389013 Keywords : non-isothermal crystallization kinetics * cumulative curves * inflection point Subject RIV: JI - Composite Materials Impact factor: 2.350, year: 2015

  11. Non-local temperature-dependent phase-field models for non-isothermal phase transitions

    Czech Academy of Sciences Publication Activity Database

    Krejčí, Pavel; Rocca, E.; Sprekels, J.

    2007-01-01

    Roč. 76, č. 1 (2007), s. 197-210 ISSN 0024-6107 Institutional research plan: CEZ:AV0Z10190503 Keywords : non-isothermal phase transitions * free energy * thermodynamic consistency Subject RIV: BA - General Mathematics Impact factor: 0.733, year: 2007 http://jlms.oxfordjournals.org/content/76/1/197.short

  12. Multiscale Pore Throat Network Reconstruction of Tight Porous Media Constrained by Mercury Intrusion Capillary Pressure and Nuclear Magnetic Resonance Measurements

    Science.gov (United States)

    Xu, R.; Prodanovic, M.

    2017-12-01

    Due to the low porosity and permeability of tight porous media, hydrocarbon productivity strongly depends on the pore structure. Effective characterization of pore/throat sizes and reconstruction of their connectivity in tight porous media remains challenging. Having a representative pore throat network, however, is valuable for calculation of other petrophysical properties such as permeability, which is time-consuming and costly to obtain by experimental measurements. Due to a wide range of length scales encountered, a combination of experimental methods is usually required to obtain a comprehensive picture of the pore-body and pore-throat size distributions. In this work, we combine mercury intrusion capillary pressure (MICP) and nuclear magnetic resonance (NMR) measurements by percolation theory to derive pore-body size distribution, following the work by Daigle et al. (2015). However, in their work, the actual pore-throat sizes and the distribution of coordination numbers are not well-defined. To compensate for that, we build a 3D unstructured two-scale pore throat network model initialized by the measured porosity and the calculated pore-body size distributions, with a tunable pore-throat size and coordination number distribution, which we further determine by matching the capillary pressure vs. saturation curve from MICP measurement, based on the fact that the mercury intrusion process is controlled by both the pore/throat size distributions and the connectivity of the pore system. We validate our model by characterizing several core samples from tight Middle East carbonate, and use the network model to predict the apparent permeability of the samples under single phase fluid flow condition. Results show that the permeability we get is in reasonable agreement with the Coreval experimental measurements. The pore throat network we get can be used to further calculate relative permeability curves and simulate multiphase flow behavior, which will provide valuable

  13. Dynamic pore network model of surface heterogeneity in brine-filled porous media for carbon sequestration.

    Science.gov (United States)

    Ellis, Jonathan S; Bazylak, Aimy

    2012-06-21

    Trapping of carbon in deep underground brine-filled reservoirs is a promising approach for the reduction of atmospheric greenhouse gas emissions. However, estimation of the amount of carbon dioxide (CO(2)) that can be captured in a given reservoir and the long-term storage stability remain a challenge. One difficulty lies in the estimation of local capillary pressure effects that arise from mineral surface heterogeneity inherent in underground geological formations. As a preliminary step to address this issue, we have performed dynamic pore network modelling (PNM) simulations of two-phase immiscible flow in two-dimensional structured porous media with contact angle heterogeneity under typical reservoir conditions. We begin by characterizing the network with a single, uniform contact angle. We then present saturation patterns for networks with homogeneous and heterogeneous contact angles distributions, based on two common reservoir minerals: quartz and mica, both of which have been well-characterized experimentally for their brine-CO(2) contact angles. At lower flow rates, we found moderately higher saturations for the heterogeneous networks than for the homogeneous ones. To characterize the fingering patterns, we have introduced R as the ratio of filled throats to the total network saturation. Based on this measure, the heterogeneous networks demonstrated thicker fingering patterns than the homogeneous networks. The computed saturation patterns demonstrate the importance of considering surface heterogeneity in pore-scale modelling of deep saline aquifers.

  14. Pyrolysis kinetics of perfusion tubes under non-isothermal and isothermal conditions

    International Nuclear Information System (INIS)

    Wang, Jinxing; Zhao, Haibo

    2015-01-01

    Highlights: • TGA and fluidized bed were selected to study perfusion tube pyrolysis. • The isothermal and non-isothermal pyrolysis kinetics were comparatively studied. • The contracting volume (R3) model describes isothermal pyrolysis most probably. - Abstract: The waste-to-energy (WTE) conversion of solid waste including perfusion tubes becomes interesting, with potential advantages of reducing the volume and mass of solid waste, and exploiting new energy sources. First, the non-isothermal pyrolysis experiments of perfusion tubes with the heating rates (β) of 5, 10, 20, 40 °C min −1 were conducted in a thermogravimetric analyzer (TGA) under nitrogen atmosphere. The TGA results indicated that the pyrolysis temperature of perfusion tubes is mainly between 200 °C and 500 °C, and the pyrolysis process of perfusion tubes under non-isothermal conditions can be divided into two stages. Next, the isothermal pyrolysis experiments of perfusion tubes were carried out on a batch fluidized bed at four temperatures (850, 875, 900, 925 °C), which is close to the practical pyrolysis processes of perfusion tubes. The batch fluidized bed results demonstrated that the pyrolysis process of perfusion tubes under isothermal conditions only has a rapid conversion stage, which is dissimilar to that under non-isothermal conditions (two-stage conversion). Last, the pyrolysis kinetic parameters of perfusion tubes under non-isothermal and isothermal conditions were calculated, respectively by the isoconversional methods (the Flynn–Wall–Ozawa (FWO) method and the Kissinger–Akahira–Sunose (KAS) method) and the isothermal model fitting methods. Noted that the isothermal pyrolysis kinetics of perfusion tubes were for the first time investigated according to the gas compositions at different isothermal conditions, and the contracting volume (R3) mechanism model was determined as the most probable model to describe the pyrolysis process of perfusion tubes among six potential

  15. Inertial forces affect fluid front displacement dynamics in a pore-throat network model.

    Science.gov (United States)

    Moebius, Franziska; Or, Dani

    2014-08-01

    The seemingly regular and continuous motion of fluid displacement fronts in porous media at the macroscopic scale is propelled by numerous (largely invisible) pore-scale abrupt interfacial jumps and pressure bursts. Fluid fronts in porous media are characterized by sharp phase discontinuities and by rapid pore-scale dynamics that underlie their motion; both attributes challenge standard continuum theories of these flow processes. Moreover, details of pore-scale dynamics affect front morphology and subsequent phase entrapment behind a front and thereby shape key macroscopic transport properties of the unsaturated zone. The study presents a pore-throat network model that focuses on quantifying interfacial dynamics and interactions along fluid displacement fronts. The porous medium is represented by a lattice of connected pore throats capable of detaining menisci and giving rise to fluid-fluid interfacial jumps (the study focuses on flow rate controlled drainage). For each meniscus along the displacement front we formulate a local inertial, capillary, viscous, and hydrostatic force balance that is then solved simultaneously for the entire front. The model enables systematic evaluation of the role of inertia and boundary conditions. Results show that while displacement patterns are affected by inertial forces mainly by invasion of throats with higher capillary resistance, phase entrapment (residual saturation) is largely unaffected by inertia, limiting inertial effects on hydrological properties behind a front. Interfacial jump velocities are often an order of magnitude larger than mean front velocity, are strongly dependent on geometrical throat dimensions, and become less predictable (more scattered) when inertia is considered. Model simulations of the distributions of capillary pressure fluctuations and waiting times between invasion events follow an exponential distribution and are in good agreement with experimental results. The modeling approach provides insights

  16. Measure of pore size in micro filtration polymeric membrane using ultrasonic technique and artificial neural networks

    International Nuclear Information System (INIS)

    Lucas, Carla de Souza

    2009-01-01

    This work presents a study of the pore size in micro filtration polymeric membranes, used in the nuclear area for the filtration of radioactive liquid effluent, in the residual water treatment of the petrochemical industry, in the electronic industry for the ultrapure water production for the manufacture of conductors and laundering of microcircuits and in many other processes of separation. Diverse processes for measures of pores sizes in membranes exist, amongst these, electronic microscopy, of bubble point and mercury intrusion porosimetry, however the majority of these uses destructive techniques, of high cost or great time of analysis. The proposal of this work is to measure so great of pore being used ultrasonic technique in the time domain of the frequency and artificial neural networks. A receiving/generator of ultrasonic pulses, a immersion transducer of 25 MHz was used, a tank of immersion and microporous membranes of pores sizes of 0,2 μm, 0,4 μm, 0,6 μm, 8 μm, 10 μm and 12 μm. The ultrasonic signals after to cover the membrane, come back to the transducer (emitting/receiving) bringing information of the interaction of the signal with the membranes. These signals had been used for the training of neural networks, and these had supplied the necessary precision the distinction of the same ones. Soon after, technique with the one of electronic microscopy of sweepings was made the comparison of this. The experiment showed very resulted next to the results gotten with the MEV, what it indicated that the studied technique is ideal for measure of pore size in membranes for being not destructive and of this form to be able to be used also on-line of production. (author)

  17. Oscillations of non-isothermal N/S boundary with a high frequency and large amplitude

    International Nuclear Information System (INIS)

    Bezuglyj, A.I.; Shklovskij, V.A.

    2016-01-01

    Within the framework of the phenomenological approach based on the heat balance equation and the dependence of the critical temperature of the superconductor on the current value theoretically investigated the impact of high-frequency current of high amplitude and arbitrary shape on the non-isothermal balance of the oscillating N/S interface in a long superconductor. We introduce a self-consistent average temperature field of rapidly oscillating non-isothermal N/S boundary (heat kink), which allows to go beyond the well-known concept of mean-square heating and consider the impact of current waveform. With regard to experiments on the effects of microwave high-power radiation on the current-voltage characteristics (CVC) of superconducting films, we give the classification of the families of the CVC for inhomogeneous superconductors which carry a current containing a high frequency component of large amplitude. Several characteristics have hysteresis of thermal nature.

  18. Pyrolysis kinetics of coking coal mixed with biomass under non-isothermal and isothermal conditions.

    Science.gov (United States)

    Jeong, Ha Myung; Seo, Myung Won; Jeong, Sang Mun; Na, Byung Ki; Yoon, Sang Jun; Lee, Jae Goo; Lee, Woon Jae

    2014-03-01

    To investigate the kinetic characteristics of coking coal mixed with biomass during pyrolysis, thermogravimetric (TG) and thermo-balance reactor (TBR) analyses were conducted under non-isothermal and isothermal condition. Yellow poplar as a biomass (B) was mixed with weak coking coal (WC) and hard coking coal (HC), respectively. The calculated activation energies of WC/B blends were higher than those of HC/B blends under non-isothermal and isothermal conditions. The coal/biomass blends show increased reactivity and decreased activation energy with increasing biomass blend ratio, regardless of the coking properties of the coal. The different char structures of the WC/B and HC/B blends were analyzed by BET and SEM. Copyright © 2014 Elsevier Ltd. All rights reserved.

  19. In Situ Study of Phase Transformations during Non-Isothermal Tempering of Bainitic and Martensitic Microstructures

    Directory of Open Access Journals (Sweden)

    S. Hesamodin Talebi

    2017-09-01

    Full Text Available Phase transformations during non-isothermal tempering of bainitic or martensitic microstructures obtained after quenching of a medium-carbon low-alloy steel was studied. The microstructures correspond to different locations of an as-quenched large-sized forged ingot used as a die material in the automotive industry. High-resolution dilatometry experiments were conducted to simulate the heat treatment process, as well as to investigate different phenomena occurring during non-isothermal tempering. The microstructures were characterized using optical and scanning electron microscopy. Dilatometry analyses demonstrated that tempering behavior varied significantly from bainitic to martensitic microstructures. Retained austenite, which exists between bainitic ferrite sheaves, decomposes to lower bainite causing a remarkable volume increase. It was found that this decomposition finishes below 386 °C. By contrast, martensite tempering was accompanied with a volume decrease due to the decomposition of medium-carbon martensite to low carbon martensite and carbides.

  20. Influence of rare earth oxides on the non-isothermal crystallization of phosphosilicate melts during cooling

    DEFF Research Database (Denmark)

    Liu, S.J.; Shan, Z.T.; Fu, G.Z.

    2014-01-01

    We report a detailed calorimetric study concerning the influence of Yb2O3 and Er2O3 on the non-isothermal crystallization in phosphosilicate melts. The results show that Yb3+/Er3+ ions promote the Zn2SiO4 crystal formation, but suppress the Na3PO4 and AlPO4 formation during cooling. The non-isoth...

  1. A new approach to non-isothermal models for nematic liquid crystals

    Czech Academy of Sciences Publication Activity Database

    Feireisl, Eduard; Frémond, M.; Rocca, E.; Schimperna, G.

    2012-01-01

    Roč. 205, č. 2 (2012), s. 651-672 ISSN 0003-9527 R&D Projects: GA ČR GA201/09/0917 Institutional research plan: CEZ:AV0Z10190503 Keywords : liquid crystals * non-isothermal model * flows Subject RIV: BA - General Mathematics Impact factor: 2.292, year: 2012 http://www.springerlink.com/content/cl205h73077jr810/

  2. Water transport in the gas diffusion layer of a polymer electrolyte fuel cell : Dynamic Pore-Network Modeling

    NARCIS (Netherlands)

    Qin, C.

    2015-01-01

    The pore-scale modeling is a powerful tool for increasing our understanding of water transport in the fibrous gas diffusion layer (GDL) of a polymer electrolyte fuel cell (PEFC). In this work, a new dynamic pore-network model for air-water flow in the GDL is developed. It incorporates water vapor

  3. Insights into the relationships among capillary pressure, saturation, interfacial area and relative permeability using pore-network modeling

    NARCIS (Netherlands)

    Joekar-Niasar, V.; Hassanizadeh, S.M.; Leijnse, A.

    2008-01-01

    To gain insight in relationships among capillary pressure, interfacial area, saturation, and relative permeability in two-phase flow in porous media, we have developed two types of pore-network models. The first one, called tube model, has only one element type, namely pore throats. The second one

  4. Insights into the Relationships Among Capillary Pressure, Saturation, Interfacial Area and Relative Permeability Using Pore-Network Modeling

    NARCIS (Netherlands)

    Joekar-Niasar, V.; Hassanizadeh, S.M.; Leijnse, A.

    To gain insight in relationships among capillary pressure, interfacial area, saturation, and relative permeability in two-phase flow in porous media, we have developed two types of pore-network models. The first one, called tube model, has only one element type, namely pore throats. The second one

  5. Modeling of the non-isothermal crystallization kinetics of polyamide 6 composites during thermoforming

    Science.gov (United States)

    Kugele, Daniel; Dörr, Dominik; Wittemann, Florian; Hangs, Benjamin; Rausch, Julius; Kärger, Luise; Henning, Frank

    2017-10-01

    The combination of thermoforming processes of continuous-fiber reinforced thermoplastics and injection molding offers a high potential for cost-effective use in automobile mass production. During manufacturing, the thermoplastic laminates are initially heated up to a temperature above the melting point. This is followed by continuous cooling of the material during the forming process, which leads to crystallization under non-isothermal conditions. To account for phase change effects in thermoforming simulation, an accurate modeling of the crystallization kinetics is required. In this context, it is important to consider the wide range of cooling rates, which are observed during processing. Consequently, this paper deals with the experimental investigation of the crystallization at cooling rates varying from 0.16 K/s to 100 K/s using standard differential scanning calorimetry (DSC) and fast scanning calorimetry (Flash DSC). Two different modeling approaches (Nakamura model, modified Nakamura-Ziabicki model) for predicting crystallization kinetics are parameterized according to DSC measurements. It turns out that only the modified Nakamura-Ziabicki model is capable of predicting crystallization kinetics for all investigated cooling rates. Finally, the modified Nakamura-Ziabicki model is validated by cooling experiments using PA6-CF laminates with embedded temperature sensors. It is shown that the modified Nakamura-Ziabicki model predicts crystallization at non-isothermal conditions and varying cooling rates with a good accuracy. Thus, the study contributes to a deeper understanding of the non-isothermal crystallization and presents an overall method for modeling crystallization under process conditions.

  6. Upper-bound and finite-element analyses of non-isothermal ECAP

    International Nuclear Information System (INIS)

    Silva, F.R.F.; Medeiros, N.; Moreira, L.P.; Lins, J.F.C.; Gouvêa, J.P.

    2012-01-01

    Highlights: ► We analytically modeled the non-isothermal temperature rising during single pass of ECAP. ► We modeled non-isothermal plane strain finite models to reproduce the sample heating. ► The proposed analytical model can represent the material heating during single pass of ECAP. - Abstract: In this paper, the thermomechanical properties of pure tantalum described by Liang and Khan [Int. J. Plast. 15 (1999) 963] through Johnson–Cook hardening law were used to propose a non-isothermal solution for estimating the temperature increasing during single-pass equal channel angular pressed metallic materials. The pressing force was determined with the upper-bound models developed by Pérez and Luri [Mech. Mater. 40 (2008) 617] extended for elastic-plastic materials with the isotropic criteria of von Mises and Drucker. The von Mises plane-strain finite-element models were done with the program ABAQUS/Explicit to provide the pressing force, P, effective plastic strain, ε ¯p , and temperature along the workpiece and also to validate the proposed analytical solutions. By using Drucker's criterion, theoretical analyses showed that the decreasing of the sample temperature increment, ΔT, was primarily affected by higher values of die channels intersection angle, Φ, and moderately for its initial temperature and the tooling outer fillet radius, R outer . Also, the increasing of ΔT was more sensible for greater die inner fillet radii, R inner , and superior velocities, V 0 . In addition, the force dropped for elevated sample initial temperatures. For Φ = 90°, the finite-element models confirmed the decreasing of ΔT and P for 0 mm ≤ R outer ≤ 5 mm and their increasing for 10 mm/s ≤ V 0 ≤ 20 mm/s. Lastly, by comparing the numerical and theoretical results of P, ε ¯p and ΔT, the proposed solutions could be validated.

  7. Wall modeling for the simulation of highly non-isothermal unsteady flows; Modelisation de paroi pour la simulation d'ecoulements instationnaires non-isothermes

    Energy Technology Data Exchange (ETDEWEB)

    Devesa, A

    2006-12-15

    Nuclear industry flows are most of the time characterized by their high Reynolds number, density variations (at low Mach numbers) and a highly unsteady behaviour (low to moderate frequencies). High Reynolds numbers are un-affordable by direct simulation (DNS), and simulations must either be performed by solving averaged equations (RANS), or by solving only the large eddies (LES), both using a wall model. A first investigation of this thesis dealt with the derivation and test of two variable density wall models: an algebraic law (CWM) and a zonal approach dedicated to LES (TBLE-{rho}). These models were validated in quasi-isothermal cases, before being used in academic and industrial non-isothermal flows with satisfactory results. Then, a numerical experiment of pulsed passive scalars was performed by DNS, were two forcing conditions were considered: oscillations are imposed in the outer flow; oscillations come from the wall. Several frequencies and amplitudes of oscillations were taken into account in order to gain insights in unsteady effects in the boundary layer, and to create a database for validating wall models in such context. The temporal behaviour of two wall models (algebraic and zonal wall models) were studied and showed that a zonal model produced better results when used in the simulation of unsteady flows. (author)

  8. Pore network modeling of drainage process in patterned porous media: a quasi-static study

    KAUST Repository

    Zhang, Tao

    2015-04-17

    This work represents a preliminary investigation on the role of wettability conditions on the flow of a two-phase system in porous media. Since such effects have been lumped implicitly in relative permeability-saturation and capillary pressure-saturation relationships, it is quite challenging to isolate its effects explicitly in real porous media applications. However, within the framework of pore network models, it is easy to highlight the effects of wettability conditions on the transport of two-phase systems. We employ quasi-static investigation in which the system undergo slow movement based on slight increment of the imposed pressure. Several numerical experiments of the drainage process are conducted to displace a wetting fluid with a non-wetting one. In all these experiments the network is assigned different scenarios of various wettability patterns. The aim is to show that the drainage process is very much affected by the imposed pattern of wettability. The wettability conditions are imposed by assigning the value of contact angle to each pore throat according to predefined patterns.

  9. Functional thermo-dynamics: a generalization of dynamic density functional theory to non-isothermal situations.

    Science.gov (United States)

    Anero, Jesús G; Español, Pep; Tarazona, Pedro

    2013-07-21

    We present a generalization of Density Functional Theory (DFT) to non-equilibrium non-isothermal situations. By using the original approach set forth by Gibbs in his consideration of Macroscopic Thermodynamics (MT), we consider a Functional Thermo-Dynamics (FTD) description based on the density field and the energy density field. A crucial ingredient of the theory is an entropy functional, which is a concave functional. Therefore, there is a one to one connection between the density and energy fields with the conjugate thermodynamic fields. The connection between the three levels of description (MT, DFT, FTD) is clarified through a bridge theorem that relates the entropy of different levels of description and that constitutes a generalization of Mermin's theorem to arbitrary levels of description whose relevant variables are connected linearly. Although the FTD level of description does not provide any new information about averages and correlations at equilibrium, it is a crucial ingredient for the dynamics in non-equilibrium states. We obtain with the technique of projection operators the set of dynamic equations that describe the evolution of the density and energy density fields from an initial non-equilibrium state towards equilibrium. These equations generalize time dependent density functional theory to non-isothermal situations. We also present an explicit model for the entropy functional for hard spheres.

  10. Non-isothermal cold crystallization kinetics of poly(3-hydoxybutyrate) filled with zinc oxide

    Energy Technology Data Exchange (ETDEWEB)

    Ries, Andreas, E-mail: ries750@yahoo.com.br [Electrical Engineering Department, Federal University of Paraíba, João Pessoa, PB 58051-900 (Brazil); Canedo, Eduardo L. [Materials Engineering Department, Federal University of Campina Grande, Campina Grande, PB 58429-900 (Brazil); Souto, Cícero R. [Electrical Engineering Department, Federal University of Paraíba, João Pessoa, PB 58051-900 (Brazil); Wellen, Renate M.R. [Materials Engineering Department, Federal University of Paraíba, João Pessoa, PB 58051-900 (Brazil)

    2016-08-10

    Highlights: • Non-isothermal cold crystallization kinetics of PHB filled with ZnO is presented. • Pseudo-Avrami model is best for describing an individual crystallization condition. • Mo model is allows to judge the kinetics of a condition untested in this work. • ZnO affects the kinetics irregularly. - Abstract: The non-isothermal cold crystallization kinetics of poly(3-hydroxybutyrate) (PHB) and PHB-ZnO composites, with ZnO content of 1%, 5% and 10% per weight, was investigated at different heating rates (5, 7.5, 10, 15, 20 and 30 °C/min) using differential scanning calorimetry. Both, Kissinger and Friedman activation energies predict correctly the slowest and fastest crystallizing composition. It was further found, that ZnO can neither be classified as a crystallization accelerator, nor as a crystallization inhibitor; its action is strongly concentration dependent. The empirical Pseudo-Avrami model has the best overall capability for fitting the experimental kinetic data. However, since the Pseudo-Avrami exponent was found to vary irregularly with heating rate and filler content, this model should not be applied for kinetic predictions of an arbitrary composition or an untested heating rate. In such cases, Mo's model should be used.

  11. Kinetic analysis for non-isothermal decomposition of unirradiated and γ-irradiated indium acetyl acetonate

    Directory of Open Access Journals (Sweden)

    Refaat Mohammed Mahfouz

    2011-03-01

    Full Text Available Kinetic studies for the non-isothermal decomposition of un-irradiated and γ-irradiated indium acetyl acetonate In(acac3 with 10² kGy total γ-ray dose were carried out in static air. The results showed that the decomposition proceeds in one major step in the temperature range of 150-250 °C with the formation of In2O3 as solid residue. The non-isothermal data for un-irradiated and γ-irradiated In(acac3 were analysed using linear Flynn-Wall-Ozawa (FWO and nonlinear Vyazovkin (VYZ iso-conversional methods. The results of application of these free models on the investigated data showed a systematic dependence of Ea on α indicating a simple decomposition process. No significant changes were observed in both decomposition behaviour and (Eα-α dependency between unirradiated and γ-irradiated In(acac3. Calcination of In(acac3 at 400 °C for 5 hours led to the formation of In2O3 monodispersed nanoparticles. X-ray diffraction, FTIR and SEM techniques were employed for characterization of the synthesised nanoparticles. This is the first attempt to prepare In2O3 nanoparticles by solid state thermal decomposition of In(acac3.

  12. Non-isothermal cure and exfoliation of tri-functional epoxy-clay nanocomposites

    Directory of Open Access Journals (Sweden)

    F. Shiravand

    2015-08-01

    Full Text Available The non-isothermal cure kinetics of polymer silicate layered nanocomposites based on a tri-functional epoxy resin has been investigated by differential scanning calorimetry. From an analysis of the kinetics as a function of the clay content, it can be concluded that the non-isothermal cure reaction can be considered to consist of four different processes: the reaction of epoxy groups with the diamine curing agent; an intra-gallery homopolymerisation reaction which occurs concurrently with the epoxy-amine reaction; and two extra-gallery homopolymerisation reactions, catalysed by the onium ion of the organically modified clay and by the tertiary amines resulting from the epoxy-amine reaction. The final nanostructure displays a similar quality of exfoliation as that observed for the isothermal cure of the same nanocomposite system. This implies that the intra-gallery reaction, which is responsible for the exfoliation, is not significantly inhibited by the extra-gallery epoxy-amine cross-linking reaction.

  13. Pore-network model of evaporation-induced salt precipitation in porous media: The effect of correlations and heterogeneity

    Science.gov (United States)

    Dashtian, Hassan; Shokri, Nima; Sahimi, Muhammad

    2018-02-01

    Salt transport and precipitation in porous media constitute a set of complex and fascinating phenomena that are of considerable interest to several important problems, ranging from storage of CO2 in geological formations, to soil fertility, and protection of pavements and roads, as well as historical monuments. The phenomena occur at the pore scale and are greatly influenced by the heterogeneity of the pore space morphology. We present a pore-network (PN) model to study the phenomena. Vapor diffusion, capillary effect at the brine-vapor interface, flow of brine, and transport of salt and its precipitation in the pores that plug the pores partially or completely are all accounted for. The drying process is modeled by the invasion percolation, while transport of salt in brine is accounted for by the convective-diffusion equation. We demonstrate that the drying patterns, the clustering and connectivity of the pore throats in which salt precipitation occurs, the saturation distribution, and the drying rate are all strongly dependent upon the pore-size distribution, the correlations among the pore sizes, and the anisotropy of the pore space caused by stratification that most natural porous media contain. In particular, if the strata are more or less parallel to the direction of injection of the gas that dries out the pore space (air, for example) and/or causes salt precipitation (CO2, for example), the drying rate increases significantly. Moreover, salt tends to precipitate in clusters of neighboring pores that are parallel to the open surface of the porous medium.

  14. Hydro-mechanical behaviour of two reference Belgian clay formations under non-isothermal conditions

    International Nuclear Information System (INIS)

    Lima, A.; Romero, E.; Gens, A.; Li, X.L.

    2012-01-01

    Document available in extended abstract form only. Two deep clay formations are being investigated in Belgium in connection with the design of a repository for 'High-Level Radioactive Waste': Boom clay BC at Mol (located between 160 and 270 m depths), considered the reference host formation, and Ypresian clay YC at Kallo (located between 300 and 450 m depths) as an alternative one. A comprehensive experimental programme has been carried out on these materials to explore water permeability at different temperatures and sample orientations, as well as to analyse volume change behaviour on loading/unloading at different temperatures and sample orientations (including pre and post-yield compressibility, yield properties and volume changes on drained thermal loading). Table 1 summarises some properties of BC and YC. Figure 1 presents the pore size distribution PSD curves of both clays obtained by mercury intrusion porosimetry. They display contrasting features (bi-modal pore network in YP with larger dominant pore sizes). Larger water permeability values are expected on YC as indicated in Table 1 and Figure 2, not only as a consequence of its higher void ratio but also due to these double porosity features. Water retention properties, of particular concern on sample retrieval from large depths, are also affected due to desaturation processes that are associated with the double porosity network of YP and its effects on air-entry value (a lower initial suction is measured on YP, despite being retrieved from larger depths). Figure 2 shows vertical and horizontal water permeability results under constant volume conditions and different temperatures. BC and YC display small anisotropy at sample scale - permeability is slightly larger on horizontal direction-. With regard to temperature effects, the figure shows that water permeability dependency on temperature in YC is slightly higher than the water viscosity prediction for both orientations. Instead BC displayed a thermal

  15. Upper-bound and finite-element analyses of non-isothermal ECAP

    Energy Technology Data Exchange (ETDEWEB)

    Silva, F.R.F. [Programa de Pos-graduacao em Engenharia Metalurgica, Universidade Federal Fluminense, Av. dos Trabalhadores, 420, CEP 27255-125, Volta Redonda, RJ (Brazil); Medeiros, N., E-mail: neil@metal.eeimvr.uff.br [Programa de Pos-graduacao em Engenharia Metalurgica, Universidade Federal Fluminense, Av. dos Trabalhadores, 420, CEP 27255-125, Volta Redonda, RJ (Brazil); Moreira, L.P.; Lins, J.F.C.; Gouvea, J.P. [Programa de Pos-graduacao em Engenharia Metalurgica, Universidade Federal Fluminense, Av. dos Trabalhadores, 420, CEP 27255-125, Volta Redonda, RJ (Brazil)

    2012-06-01

    Highlights: Black-Right-Pointing-Pointer We analytically modeled the non-isothermal temperature rising during single pass of ECAP. Black-Right-Pointing-Pointer We modeled non-isothermal plane strain finite models to reproduce the sample heating. Black-Right-Pointing-Pointer The proposed analytical model can represent the material heating during single pass of ECAP. - Abstract: In this paper, the thermomechanical properties of pure tantalum described by Liang and Khan [Int. J. Plast. 15 (1999) 963] through Johnson-Cook hardening law were used to propose a non-isothermal solution for estimating the temperature increasing during single-pass equal channel angular pressed metallic materials. The pressing force was determined with the upper-bound models developed by Perez and Luri [Mech. Mater. 40 (2008) 617] extended for elastic-plastic materials with the isotropic criteria of von Mises and Drucker. The von Mises plane-strain finite-element models were done with the program ABAQUS/Explicit to provide the pressing force, P, effective plastic strain, {epsilon}{sup Macron p}, and temperature along the workpiece and also to validate the proposed analytical solutions. By using Drucker's criterion, theoretical analyses showed that the decreasing of the sample temperature increment, {Delta}T, was primarily affected by higher values of die channels intersection angle, {Phi}, and moderately for its initial temperature and the tooling outer fillet radius, R{sub outer}. Also, the increasing of {Delta}T was more sensible for greater die inner fillet radii, R{sub inner}, and superior velocities, V{sub 0}. In addition, the force dropped for elevated sample initial temperatures. For {Phi} = 90 Degree-Sign , the finite-element models confirmed the decreasing of {Delta}T and P for 0 mm {<=} R{sub outer} {<=} 5 mm and their increasing for 10 mm/s {<=} V{sub 0} {<=} 20 mm/s. Lastly, by comparing the numerical and theoretical results of P, {epsilon}{sup Macron p} and {Delta}T, the

  16. Kink Waves in Non-isothermal Stratified Solar Waveguides: Effect of the External Magnetic Field

    Energy Technology Data Exchange (ETDEWEB)

    Lopin, I. [Ussuriisk Astrophysical Observatory, Russian Academy of Sciences (Russian Federation); Nagorny, I., E-mail: lopin78@mail.ru [Institute of Automation and Control Processes FEB RAS, Vladivostok (Russian Federation)

    2017-10-01

    We study the effect of an external magnetic field on the properties of kink waves, propagating along a thin non-isothermal stratified and diverging magnetic flux tube. A wave equation, governing the propagation of kink waves under the adopted model is derived. It is shown that the vertical gradient of temperature introduces a spatially local cut-off frequency ω {sub c}. The vertical distribution of the cut-off frequency is calculated for the reference VAL-C model of the solar atmosphere and for different values of a ratio of external to internal magnetic fields. The results show that the cut-off frequency is negative below the temperature minimum due to the negative temperature gradient. In the chromosphere the cut-off frequency at a given height is smaller for a stronger external magnetic field. For the appropriate range of a ratio B{sub e} / B{sub i}  ≈ 0–0.8, the cutoff lies in the range ω{sub c}  ≈ 0.003–0.010 s{sup −1} (periods 600 < P{sub c} < 2000 s). The estimate of the cut-off frequency in the transition region is provided as well. In the propagating wave regime, the effective wave energy flux in the non-isothermal diverging flux tubes is the same as in the straight and homogeneous cylindrical waveguides. The obtained wave equation in the limit β  = 0 is used to study the kink oscillations of non-isothermal coronal loops. It is found that the gradient of temperature along the coronal loops reduces the frequency ratio of the first overtone to the fundamental mode, i.e., ω{sub 2}/ ω{sub 1} < 2. This reduction grows for a larger ratio of temperature at the loop top to the temperature at the footpoints. Moreover, the effect of reduction is most pronounced for the steeper temperature profiles.

  17. Effect of Initial Hydraulic Conditions on Capillary Rise in a Porous Medium: Pore-Network Modeling

    KAUST Repository

    Joekar-Niasar, V.

    2012-01-01

    The dynamics of capillary rise in a porous medium have been mostly studied in initially dry systems. As initial saturation and initial hydraulic conditions in many natural and industrial porous media can be variable, it is important to investigate the influence of initial conditions on the dynamics of the process. In this study, using dynamic pore-network modeling, we simulated capillary rise in a porous medium for different initial saturations (and consequently initial capillary pressures). Furthermore, the effect of hydraulic connectivity of the wetting phase in corners on the height and velocity of the wetting front was studied. Our simulation results show that there is a trade-off between capillary forces and trapping due to snap-off, which leads to a nonlinear dependence of wetting front velocity on initial saturation at the pore scale. This analysis may provide a possible answer to the experimental observations in the literature showing a non-monotonic dependency between initial saturation and the macroscopic front velocity. © Soil Science Society of America.

  18. Online monitoring method of degree of cure during non-isothermal microwave curing process

    Science.gov (United States)

    He, Yongxi; Li, Yingguang; Li, Nanya; Hao, Xiaozhong

    2018-02-01

    Curing rate is the variation rate of degree of cure with time, which is a crucial issue in the curing process of composite structures since it has a significant influence on the generation of voids and residual stresses. In this paper, an online monitoring method of degree of cure was presented based on refractive index measurement. The influence of cure and temperature variation on the refractive index of composite was separated in real time with a step-temperature refractive index separation method. Non-isothermal microwave curing process of carbon fiber/epoxy composite was monitored, and the degree of cure was obtained with a low measurement error of ±1.5% compared with that determined by off-line DSC measurement. The online monitoring method is a promising technology for smart manufacturing of composite structures.

  19. Energy dissipation in non-isothermal molecular dynamics simulations of confined liquids under shear.

    Science.gov (United States)

    Berro, Hassan; Fillot, Nicolas; Vergne, Philippe; Tokumasu, Takashi; Ohara, Taku; Kikugawa, Gota

    2011-10-07

    Energy is commonly dissipated in molecular dynamics simulations by using a thermostat. In non-isothermal shear simulations of confined liquids, the choice of the thermostat is very delicate. We show in this paper that under certain conditions, the use of classical thermostats can lead to an erroneous description of the dynamics in the confined system. This occurs when a critical shear rate is surpassed as the thermo-viscous effects become prominent. In this high-shear-high-dissipation regime, advanced dissipation methods including a novel one are introduced and compared. The MD results show that the physical modeling of both the accommodation of the surface temperature to liquid heating and the heat conduction through the confining solids is essential. The novel method offers several advantages on existing ones including computational efficiency and easiness of application for complex systems. © 2011 American Institute of Physics

  20. Synthesis and Non-isothermal Thermal Decomposition of Polydiphenyl(diphenylethynylSilane

    Directory of Open Access Journals (Sweden)

    TAN De-xin

    2017-07-01

    Full Text Available Diphenyldiphenylethynylsilane monomer (DPDPES was synthesized with ethyl bromide, diphenyldichlorosilane and phenylacetylene by Grignard reaction. The molecular structure was characterized by FTIR and 1H-NMR spectroscopy. The polymer of polydiphenyl(diphenylethynylsilane (PDPDPES was also prepared by thermal polymerization. Non-isothermal thermal decomposition process of PDPDPES was studied with TG-DTG technology via model method to get thermal decomposition function and the corresponding mechanism which was further verified by model-free method. Results show that the apparent activation energy and the pre-exponential factor are about Ea=245.37kJ/mol and lgA=13.78s-1 obtained by six different kinetic methods, respectively. The mechanism of functions are f(α= 10/23 ·(1-α·[-ln(1-α]-1.3 and g(α=[-ln(1-α]2.3。

  1. Non-isothermal processes during the drying of bare soil: Model Development and Validation

    Science.gov (United States)

    Sleep, B.; Talebi, A.; O'Carrol, D. M.

    2017-12-01

    Several coupled liquid water, water vapor, and heat transfer models have been developed either to study non-isothermal processes in the subsurface immediately below the ground surface, or to predict the evaporative flux from the ground surface. Equilibrium phase change between water and gas phases is typically assumed in these models. Recently, a few studies have questioned this assumption and proposed a coupled model considering kinetic phase change. However, none of these models were validated against real field data. In this study, a non-isothermal coupled model incorporating kinetic phase change was developed and examined against the measured data from a green roof test module. The model also incorporated a new surface boundary condition for water vapor transport at the ground surface. The measured field data included soil moisture content and temperature at different depths up to the depth of 15 cm below the ground surface. Lysimeter data were collected to determine the evaporation rates. Short and long wave radiation, wind velocity, air ambient temperature and relative humidity were measured and used as model input. Field data were collected for a period of three months during the warm seasons in south eastern Canada. The model was calibrated using one drying period and then several other drying periods were simulated. In general, the model underestimated the evaporation rates in the early stage of the drying period, however, the cumulative evaporation was in good agreement with the field data. The model predicted the trends in temperature and moisture content at the different depths in the green roof module. The simulated temperature was lower than the measured temperature for most of the simulation time with the maximum difference of 5 ° C. The simulated moisture content changes had the same temporal trend as the lysimeter data for the events simulated.

  2. Non-isothermal curing kinetics and physical properties of MMT-reinforced unsaturated polyester (UP) resins

    Energy Technology Data Exchange (ETDEWEB)

    Vargas, María A., E-mail: angelesvh@yahoo.com [Tecnológico de Estudios Superiores de Ecatepec, Av. Tecnológico S/N, Valle de Anáhuac, 55210 Ecatepec de Morelos (Mexico); Vázquez, H. [Universidad Autónoma Metropolitana-Iztapalapa, Departamento de Física, Av. San Rafael Atlixco 186, col. Vicentina, Mexico, D.F. 09340 (Mexico); Guthausen, G. [KIT, Pro2NMR at MVM and IBG, Karlsruhe (Germany)

    2015-07-10

    Highlights: • Non-isothermal DSC analysis results have shown that the addition of MMT to a UP resin produces a delay in the cure reaction. • The shape of experimental heat-flow DSC curves showed two exothermic peaks for all the samples at different heating rates. • The overall kinetic analysis was performed by isoconversional methods. • It was found that the dependence of the activation energy (E{sub a}) on degree of reaction (α) is complex. - Abstract: Cure behavior of unsaturated polyester (UP)/montmorillonite (MMT)/methyl ethyl ketone peroxide (MEKP)/cobalt octoate intercalated nanocomposites with various MMT loadings was investigated by dynamic differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and transmission electron microscopy (TEM). UP/MMT nanocomposites were prepared by sequential mixing. Non-isothermal DSC curves were obtained by applying heating rates ranging from 5 to 20 °C/min. They presented two exothermic peaks, which should correspond to two independent cure reactions. The effective activation energy E{sub a}, was determined by applying both the Kissinger’s and Starink’s methods. The results showed slightly higher activation energy for nanocomposites, except for UP/10-MMT. It was found that the dependence of E{sub a} on α is complex. All the systems in this study fitted Sesták–Berggren (SB) model in overall reaction controlled kinetics and the corresponding model parameters, n, m, A were obtained, but it was insufficient in depicting the complex reaction kinetics. Transmission electron microscopy data support the formation of a partially delaminated nanocomposite material. UP and nanocomposites showed similar behavior on thermal stability.

  3. Lagrangian finite element method for 3D time-dependent non-isothermal flow of K-BKZ fluids

    DEFF Research Database (Denmark)

    Román Marín, José Manuel; Rasmussen, Henrik K.

    2009-01-01

    A new numerical approach for the simulation of non-isothermal three-dimensional time-dependent flow of viscoelastic fluids is presented. The viscoelastic fluids are of the K-BKZ integral type and the method is based on a Lagrangian kinematics description of the fluid flow. The K-BKZ fluid...... is assumed to be a thermorheological simple material using the extended Morland and Lee hypothesis by Crochet and Naghdi [M.J. Crochet, P.M. Naghdi, A class of non-isothermal viscoelastic fluids, International Journal of Engineering Science 10 (1972) 755–800], where the real time in the K-BKZ constitutive...

  4. Non-isothermal kinetics of phase transformations in magnetron sputtered alumina films with metastable structure

    International Nuclear Information System (INIS)

    Zuzjaková, Š.; Zeman, P.; Kos, Š.

    2013-01-01

    Highlights: • Non-isothermal kinetics of phase transformations in alumina films was investigated. • The structure of alumina films affects kinetics of the transformation processes. • Kinetic triplets of all transformation processes were determined. • The KAS, FWO, FR and IKP methods for determination of E a and A were used. • The Málek method for determination of the kinetic model was used. - Abstract: The paper reports on non-isothermal kinetics of transformation processes in magnetron sputtered alumina thin films with an amorphous and γ-phase structure leading ultimately to the formation of the thermodynamically stable α-Al 2 O 3 phase. Phase transformation sequences in the alumina films were investigated using differential scanning calorimetry (DSC) at four different heating rates (10, 20, 30, 40 °C/min). Three isoconversional methods (Kissinger–Akahira–Sunose (KAS), Flynn–Wall–Ozawa (FWO) and Friedman (FR) method) as well as the invariant kinetic parameters (IKP) method were used to determine the activation energies for transformation processes. Moreover, the pre-exponential factors were determined using the IKP method. The kinetic models of the transformation processes were determined using the Málek method. It was found that the as-deposited structure of alumina films affects kinetics of the transformation processes. The film with the amorphous as-deposited structure heated at 40 °C/min transforms to the crystalline γ phase at a temperature of ∼930 °C (E a,IKP = 463 ± 10 kJ/mol) and subsequently to the crystalline α phase at a temperature of ∼1200 °C (E a,IKP = 589 ± 10 kJ/mol). The film with the crystalline γ-phase structure heated at 40 °C/min is thermally stable up to ∼1100 °C and transforms to the crystalline α phase (E a,IKP = 511 ± 16 kJ/mol) at a temperature of ∼1195 °C. The empirical two-parameter Šesták–Berggren kinetic model was found to be the most adequate one to describe all transformation processes

  5. Rarefied gas flow in a rectangular enclosure induced by non-isothermal walls

    Energy Technology Data Exchange (ETDEWEB)

    Vargas, Manuel; Tatsios, Giorgos; Valougeorgis, Dimitris, E-mail: diva@mie.uth.gr [Department of Mechanical Engineering, University of Thessaly, 38334 Volos (Greece); Stefanov, Stefan [Institute of Mechanics, Bulgarian Academy of Sciences, Sofia (Bulgaria)

    2014-05-15

    The flow of a rarefied gas in a rectangular enclosure due to the non-isothermal walls with no synergetic contributions from external force fields is investigated. The top and bottom walls are maintained at constant but different temperatures and along the lateral walls a linear temperature profile is assumed. Modeling is based on the direct numerical solution of the Shakhov kinetic equation and the Direct Simulation Monte Carlo (DSMC) method. Solving the problem both deterministically and stochastically allows a systematic comparison and verification of the results as well as the exploitation of the numerical advantages of each approach in the investigation of the involved flow and heat transfer phenomena. The thermally induced flow is simulated in terms of three dimensionless parameters characterizing the problem, namely, the reference Knudsen number, the temperature ratio of the bottom over the top plates, and the enclosure aspect ratio. Their effect on the flow configuration and bulk quantities is thoroughly examined. Along the side walls, the gas flows at small Knudsen numbers from cold-to-hot, while as the Knudsen number is increased the gas flows from hot-to-cold and the thermally induced flow configuration becomes more complex. These flow patterns with the hot-to-cold flow to be extended to the whole length of the non-isothermal side walls may exist even at small temperature differences and then, they are enhanced as the temperature difference between the top and bottom plates is increased. The cavity aspect ratio also influences this flow configuration and the hot-to-cold flow is becoming more dominant as the depth compared to the width of the cavity is increased. To further analyze the flow patterns a novel solution decomposition into ballistic and collision parts is introduced. This is achieved by accordingly modifying the indexing process of the typical DSMC algorithm. The contribution of each part of the solution is separately examined and a physical

  6. Non-Isothermic Chemical Kinetics in the Undergraduate Laboratory: Arrhenius Parameters from Experiments with Hyperbolic Temperature Variation.

    Science.gov (United States)

    Salvador, F.; And Others

    1984-01-01

    Describes a method which adapts itself to the characteristics of the kinetics of a chemical reaction in solution, enabling students to determine the Arrhenius parameters with satisfactory accuracy by means of a single non-isothermic experiment. Both activation energy and the preexponential factor values can be obtained by the method. (JN)

  7. Incorporating Embedded Microporous Layers into Topologically Equivalent Pore Network Models for Oxygen Diffusivity Calculations in Polymer Electrolyte Membrane Fuel Cell Gas Diffusion Layers

    International Nuclear Information System (INIS)

    Fazeli, Mohammadreza; Hinebaugh, James; Bazylak, Aimy

    2016-01-01

    Highlights: • Pore network model for modeling PEMFC MPL-coated GDL effective diffusivity. • Bilayered GDL (substrate and MPL) is modeled with a hybrid network of block MPL elements combined with discrete substrate pores. • Diffusivities of MPL-coated GDLs agree with analytical solutions. - Abstract: In this work, a voxel-based methodology is introduced for the hybridization of a pore network with interspersed nano-porous material elements allowing pore network based oxygen diffusivity calculations in a 3D image of a polymer electrolyte membrane (PEM) fuel cell gas diffusion layer (GDL) with an embedded microporous layer (MPL). The composite GDL is modeled by combining a hybrid network of block MPL elements with prescribed bulk material properties and a topologically equivalent network of larger discrete pores and throats that are directly derived from the 3D image of the GDL substrate. This hybrid network was incorporated into a pore network model, and effective diffusivity predictions of GDL materials with MPL coatings were obtained. Stochastically generated numerical models of carbon paper substrates with and without MPLs were used, and the pore space was directly extracted from this realistic geometry as the input for the pore network model. The effective diffusion coefficient of MPL-coated GDL materials was predicted from 3D images in a pore network modeling environment without resolving the nano-scale structure of the MPL. This method is particularly useful due to the disparate length scales that are involved when attempting to capture pore-scale transport in the GDL. Validation was performed by comparing our predicted diffusivity values to analytical predictions, and excellent agreement was observed. Upon conducting a mesh sensitivity study, it was determined that an MPL element size of 7 μm provided sufficiently high resolution for accurately describing the MPL nano-structure.

  8. Replicative manufacturing of complex lighting optics by non-isothermal glass molding

    Science.gov (United States)

    Kreilkamp, Holger; Vu, Anh Tuan; Dambon, Olaf; Klocke, Fritz

    2016-09-01

    The advantages of LED lighting, especially its energy efficiency and the long service life have led to a wide distribution of LED technology in the world. However, in order to make fully use of the great potential that LED lighting offers, complex optics are required to distribute the emitted light from the LED efficiently. Nowadays, many applications use polymer optics which can be manufactured at low costs. However, due to ever increasing luminous power, polymer optics reach their technological limits. Due to its outstanding properties, especially its temperature resistance, resistance against UV radiation and its long term stability, glass is the alternative material of choice for the use in LED optics. This research is introducing a new replicative glass manufacturing approach, namely non-isothermal glass molding (NGM) which is able to manufacture complex lighting optics in high volumes at competitive prices. The integration of FEM simulation at the early stage of the process development is presented and helps to guarantee a fast development cycle. A coupled thermo-mechanical model is used to define the geometry of the glass preform as well as to define the mold surface geometry. Furthermore, simulation is used to predict main process outcomes, especially in terms of resulting form accuracy of the molded optics. Experiments conducted on a commercially available molding machine are presented to validate the developed simulation model. Finally, the influence of distinct parameters on important process outcomes like form accuracy, surface roughness, birefringence, etc. is discussed.

  9. Gravitational instability of filamentary molecular clouds, including ambipolar diffusion; non-isothermal filament

    Science.gov (United States)

    Hosseinirad, Mohammad; Abbassi, Shahram; Roshan, Mahmood; Naficy, Kazem

    2018-04-01

    Recent observations of the filamentary molecular clouds show that their properties deviate from the isothermal equation of state. Theoretical investigations proposed that the logatropic and the polytropic equations of state with negative indexes can provide a better description for these filamentary structures. Here, we aim to compare the effects of these softer non-isothermal equations of state with their isothermal counterpart on the global gravitational instability of a filamentary molecular cloud. By incorporating the ambipolar diffusion, we use the non-ideal magnetohydrodynamics framework for a filament that is threaded by a uniform axial magnetic field. We perturb the fluid and obtain the dispersion relation both for the logatropic and polytropic equations of state by taking the effects of magnetic field and ambipolar diffusion into account. Our results suggest that, in absence of the magnetic field, a softer equation of state makes the system more prone to gravitational instability. We also observed that a moderate magnetic field is able to enhance the stability of the filament in a way that is sensitive to the equation of state in general. However, when the magnetic field is strong, this effect is suppressed and all the equations of state have almost the same stability properties. Moreover, we find that for all the considered equations of state, the ambipolar diffusion has destabilizing effects on the filament.

  10. Non-isothermal oxidation of aluminum nanopowder coated by hydrocarbons and fluorohydrocarbons

    Science.gov (United States)

    Sossi, A.; Duranti, E.; Paravan, C.; DeLuca, L. T.; Vorozhtsov, A. B.; Gromov, A. A.; Pautova, Yu. I.; Lerner, M. I.; Rodkevich, N. G.

    2013-04-01

    Aluminum nanopowder (nAl) obtained by electrical explosion of wires and passivated/coated with hydrocarbons and fluorohydrocarbons is comprehensively characterized. Coatings of different natures (octadecanoic and hexadecanoic acid, (1,1,11) trihydroperfluoro-undecan-1-ol, Fluorel™ + ester from esterification of (1,1,11) trihydroperfluoro-undecan-1-ol with furan-2,5-dione) were applied on the particle surface. The powders were studied by TEM, SEM, DSC-TGA, and BET specific surface area. The active aluminum content was determined by volumetric analyses. Coated nAl particles were compared to non-coated powder by the corresponding reactivity parameters obtained from DSC-TGA. It was found that while fatty acids have a weak effect on the non-isothermal oxidation behavior, fluoroelastomers shift the oxidation onset of nAl to higher temperatures by ˜20 °C for the first oxidation stage and by ˜100 °C for the second oxidation stage.

  11. Non-isothermal kinetics studies on the thermal decomposition of zinc hydroxide carbonate

    International Nuclear Information System (INIS)

    Li Zhongjun; Shen Xiaoqing; Feng Xun; Wang Peiyuan; Wu Zhishen

    2005-01-01

    Zinc hydroxide carbonate precursor, Zn 4 CO 3 (OH) 6 .H 2 O, was synthesized from zinc sulfate using ammonium carbonate as a precipitating agent. Thermogravimetry (TG), differential scanning calorimetry (DSC), transmission electronic microscopy (TEM), infrared spectrum (IR) and X-ray diffraction (XRD) were used to characterize the precursor and the decomposed product. Non-isothermal kinetics of the thermal decomposition of zinc hydroxide carbonate were studied in nitrogen. Based on which, the kinetic parameters were obtained through mode-free method and the thermal decomposition mechanism was derived by mains of non-linear regression. The results show that the decomposition of zinc hydroxide carbonate acts as a double-step reaction, A-bar D2B-bar FnC: a reversible reaction of two-dimensional diffusion (D2), with E1=202kJmol -1 , lg(A1/s -1 )=22.1, is followed by an irreversible one of nth-order reaction (Fn) with n=0.51, E2=129kJmol -1 , lg(A2/s -1 )=10.5, and the decomposition of Zn 4 CO 3 (OH) 6 .H 2 O to ZnO is accompanied by the change in particle morphology and particle size

  12. Evaluating the Energy Recovery Potential of Nigerian Coals under Non-Isothermal Thermogravimetry

    Science.gov (United States)

    Bevan Nyakuma, Bemgba; Oladokun, Olagoke; Jauro, Aliyu; Damian Nyakuma, Denen

    2017-07-01

    This study investigated the fuel properties and energy recovery potential of two coal samples from Ihioma (IHM) and Ogboligbo (OGB) environs in Nigeria. The ultimate, proximate, and bomb calorimetric analyses of the coal were examined. Next, the rank classification and potential application of the coals were evaluated according to the ASTM standard D388. Lastly, thermal decomposition behaviour was examined by non-isothermal thermogravimetry (TG) under pyrolysis conditions from 30 - 900 °C. The results indicated IHM and OGB contain high proportions of combustible elements for potential thermal conversion. The higher heating value (HHV) of IHM was 20.37 MJ/kg whereas OGB was 16.33 MJ/kg. TG analysis revealed 55% weight loss for OGB and 76% for IHM. The residual mass was 23% for IHM and 44% for OGB. Based on the temperature profile characteristics (TPCs); Ton , Tmax , and Toff , IHM was more reactive than OGB due to its higher volatile matter (VM). Overall, results revealed the coals are Lignite (Brown) low-rank coals (LRCs) with potential for electric power generation.

  13. Non-isothermal precipitation behaviors of Al-Mg-Si-Cu alloys with different Zn contents

    Energy Technology Data Exchange (ETDEWEB)

    Guo, M.X., E-mail: mingxingguo@skl.ustb.edu.cn; Zhang, Y.; Zhang, X.K.; Zhang, J.S.; Zhuang, L.Z.

    2016-07-04

    The non-isothermal precipitation behaviors of Al–Mg–Si–Cu alloys with different Zn contents were investigated by differential scanning calorimetry (DSC) analysis, hardness measurement and high resolution transmission electron microscope characterization. The results show that Zn addition has a significant effect on the GP zone dissolution and precipitation of Al-Mg-Si-Cu alloys. And their activation energies change with the changes of Zn content and aging conditions. Precipitation kinetics can be improved by adding 0.5 wt% or 3.0 wt%Zn, while be suppressed after adding 1.5 wt%Zn. The Mg-Si precipitates (GP zones and β″) are still the main precipitates in the Al-Mg-Si-Cu alloys after heated up to 250 °C, and no Mg-Zn precipitates are observed in the Zn-added alloy due to the occurrence of Mg-Zn precipitates reversion. The measured age-hardening responses of the alloys are corresponding to the predicted results by the established precipitation kinetic equations. Additionally, a double-hump phenomenon of hardness appears in the artificial aging of pre-aged alloy with 3.0 wt% Zn addition, which resulted from the formation of pre-β″ and β″ precipitates. Finally, the precipitation mechanism of Al-Mg-Si-Cu alloys with different Zn contents was proposed based on the microstructure evolution and interaction forces between Mg, Si and Zn atoms.

  14. Evaluation of agricultural residues pyrolysis under non-isothermal conditions: Thermal behaviors, kinetics, and thermodynamics.

    Science.gov (United States)

    Chen, Jianbiao; Wang, Yanhong; Lang, Xuemei; Ren, Xiu'e; Fan, Shuanshi

    2017-10-01

    The thermal conversion characteristics, kinetics, and thermodynamics of agricultural residues, rape straw (RS) and wheat bran (WB), were investigated under non-isothermal conditions. TGA experiments showed that the pyrolysis characteristics of RS were quite different from those of WB. As reflected by the comprehensive devolatilization index, when the heating rate increased from 10 to 30Kmin -1 , the pyrolysis performance of RS and WB were improved 5.27 and 5.96 times, respectively. The kinetic triplets of the main pyrolysis process of agricultural residues were calculated by the Starink method and the integral master-plots method. Kinetic analysis results indicated that the most potential kinetic models for the pyrolysis of RS and WB were D 2 and F 2.7 , respectively. The thermodynamic parameters (ΔH, ΔG, and ΔS) were determined by the activated complex theory. The positive ΔH, positive ΔG, and negative ΔS at characteristic temperatures validated that the pyrolysis of agricultural residues was endothermic and non-spontaneous. Copyright © 2017 Elsevier Ltd. All rights reserved.

  15. A quadrature-based kinetic model for a dilute non-isothermal granular gas

    Science.gov (United States)

    Passalacqua, Alberto; Galvin, Janine; Vedula, Prakash; Hrenya, Christine; Fox, Rodney

    2009-11-01

    A dilute non-isothermal inelastic granular gas between two stationary Maxwellian walls is studied by means of numerical simulations of the Boltzmann kinetic equation with hard-sphere collisions. The behavior of a granular gas in these conditions is influenced by the thickness of the wall Knudsen layer: if its thickness is not negligible, the traditional description based on the Navier-Stokes-Fourier equations is invalid, and it is necessary to account for the presence of rarefaction effects using high-order solutions of the Boltzmann equation. The system is described by solving the full Boltzmann equation using a quadrature-based moment method (QMOM), with different orders of accuracy in terms of the moments of the distribution function, considering moments up to the seventh order. Four different inelastic collision models (BGK, ES-BGK, Maxwell hard-sphere, Boltzmann hard-sphere) are employed. QMOM results are compared with the predictions of molecular dynamics (MD) simulations of a nearly equivalent system with finite-size particles, showing the agreement of constitutive quantities such as heat flux and stress tensor.

  16. Characterizing two-phase flow relative permeabilities in chemicalflooding using a pore-scale network model

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Qingjie; Shen, Pingping; Wu, Yu-Shu

    2004-03-15

    A dynamic pore-scale network model is presented for investigating the effects of interfacial tension and oil-water viscosity on relative permeability during chemical flooding. This model takes into account both viscous and capillary forces in analyzing the impact of chemical properties on flow behavior or displacement configuration, as opposed to the conventional or invasion percolation algorithm which incorporates capillary pressure only. The study results indicate that both water and oil relative-permeability curves are dependent strongly on interfacial tension as well as an oil-water viscosity ratio. In particular, water and oil relative-permeability curves are both found to shift upward as interfacial tension is reduced, and they both tend to become linear versus saturation once interfacial tension is at low values. In addition, the oil-water viscosity ratio appears to have only a small effect under conditions of high interfacial tension. When the interfacial tension is low, however, water relative permeability decreases more rapidly (with the increase in the aqueous-phase viscosity) than oil relative permeability. The breakthrough saturation of the aqueous phase during chemical flooding tends to decrease with the reduction of interfacial tension and may also be affected by the oil-water viscosity ratio.

  17. Micro-CT scan reveals an unexpected high-volume and interconnected pore network in a Cretaceous Sanagasta dinosaur eggshell.

    Science.gov (United States)

    Hechenleitner, E Martín; Grellet-Tinner, Gerald; Foley, Matthew; Fiorelli, Lucas E; Thompson, Michael B

    2016-03-01

    The Cretaceous Sanagasta neosauropod nesting site (La Rioja, Argentina) was the first confirmed instance of extinct dinosaurs using geothermal-generated heat to incubate their eggs. The nesting strategy and hydrothermal activities at this site led to the conclusion that the surprisingly 7 mm thick-shelled eggs were adapted to harsh hydrothermal microenvironments. We used micro-CT scans in this study to obtain the first three-dimensional microcharacterization of these eggshells. Micro-CT-based analyses provide a robust assessment of gas conductance in fossil dinosaur eggshells with complex pore canal systems, allowing calculation, for the first time, of the shell conductance through its thickness. This novel approach suggests that the shell conductance could have risen during incubation to seven times more than previously estimated as the eggshell erodes. In addition, micro-CT observations reveal that the constant widening and branching of pore canals form a complex funnel-like pore canal system. Furthermore, the high density of pore canals and the presence of a lateral canal network in the shell reduce the risks of pore obstruction during the extended incubation of these eggs in a relatively highly humid and muddy nesting environment. © 2016 The Author(s).

  18. Thermal behavior and decomposition kinetics of rifampicin polymorphs under isothermal and non-isothermal conditions

    Directory of Open Access Journals (Sweden)

    Ricardo Alves

    2010-06-01

    Full Text Available The thermal behavior of two polymorphic forms of rifampicin was studied by DSC and TG/DTG. The thermoanalytical results clearly showed the differences between the two crystalline forms. Polymorph I was the most thermally stable form, the DSC curve showed no fusion for this species and the thermal decomposition process occurred around 245 ºC. The DSC curve of polymorph II showed two consecutive events, an endothermic event (Tpeak = 193.9 ºC and one exothermic event (Tpeak = 209.4 ºC, due to a melting process followed by recrystallization, which was attributed to the conversion of form II to form I. Isothermal and non-isothermal thermogravimetric methods were used to determine the kinetic parameters of the thermal decomposition process. For non-isothermal experiments, the activation energy (Ea was derived from the plot of Log β vs 1/T, yielding values for polymorph form I and II of 154 and 123 kJ mol-1, respectively. In the isothermal experiments, the Ea was obtained from the plot of lnt vs 1/T at a constant conversion level. The mean values found for form I and form II were 137 and 144 kJ mol-1, respectively.O comportamento térmico de duas formas polimórficas da rifampicina foi estudado por DSC e TG/DTG. Os resultados termoanalíticos mostraram claramente as diferenças entre as duas formas cristalinas. O polimorfo I é a forma mais estável termicamente, a curva DSC não mostrou a fusão dessa espécie e o processo de decomposição térmica ocorreu próximo a 245 ºC. A curva DSC do Polimorfo II apresentou dois eventos consecutivos, um endotérmico (Tpico = 193,9 ºC e outro exotérmico (Tpico = 209,4 ºC, devido à fusão seguida de recristalização, a qual foi atribuída à conversão da forma II à forma I. Métodos termogravimétricos isotérmicos e não-isotérmicos foram empregados para determinar os parâmetros cinéticos do processo de decomposição térmica. Para experimentos não-isotérmicos, a energia de ativação (Ea foi

  19. Cinetique de la nucleation binaire non-isotherme et de la condensation binaire aux conditions dynamiques

    Science.gov (United States)

    Djikaev, Yuri

    La présente thèse est consacrée à la théorie de la condensation binaire. Premièrement, nous considérons la thermodynamique de la nucléation binaire, en nous concentrant sur l'énergie libre de formation d'une goutte et la distribution d'équilibre des gouttes, qui est essentielle pour la vitesse théorique de nucléation et dont le choix n'est toutefois pas unique. Une nouvelle distribution d'équilibre est proposée. Deuxièmement, nous développons la théorie cinétique de la nucléation binaire non-isotherme. Cette théorie traite de l'influence des effets thermiques sur la condensation binaire qui sont causés par la chaleur de condensation. Les molécules du mélange de vapeurs absorbées par une goutte de solution binaire lui transmettent de la chaleur de condensation, tandis que les molécules émises par la goutte lui enlèvent une telle chaleur. La température moyenne de la goutte s'accroît au fur et à mesure qu'elle grandit. Cet échauffement des gouttes croissantes diminue la vitesse de nucléation et influence d'autres caractéristiques du processus. Dans le cas où les chaleurs de condensation sont très petites par rapport à la fluctuation efficace de l'énergie d'une goutte l'équation cinétique peut être réduite à celle de Fokker et Planck. L'analyse de l'équation cinétique permet de déterminer la hiérarchie des échelles de temps de la nucléation binaire non-isotherme. Cela rend possible de séparer et décrire analytiquement l'étape de relaxation thermique pendant laquelle la distribution des gouttes selon la température s'approche d'une gaussienne, alors que leur distribution selon les nombres de molécules ne change guère. Finalement, nous étudions la condensation binaire isotherme aux conditions dynamiques. Dans ce cas la formation et la croissance des gouttes se passent en même temps que la métastabilité du mélange de vapeurs croît graduellement, atteint son maximum et décroît. C'est ainsi que la condensation

  20. Pyrolysis of olive residue and sugar cane bagasse: non-isothermal thermogravimetric kinetic analysis.

    Science.gov (United States)

    Ounas, A; Aboulkas, A; El Harfi, K; Bacaoui, A; Yaacoubi, A

    2011-12-01

    Thermal degradation and kinetics for olive residue and sugar cane bagasse have been evaluated under dynamic conditions in the presence of nitrogen atmosphere, using a non-isothermal thermogravimetric method (TGA). The effect of heating rate was evaluated in the range of 2-50 K min(-1) providing significant parameters for the fingerprinting of the biomass. The DTG plot for the olive residue and sugar cane bagasse clearly shows that the bagasse begins to degrade at 473 K and exhibits two major peaks. The initial mass-loss was associated with hemicellulose pyrolysis and responsible for the first peak (538-543 K) whereas cellulose pyrolysis was initiated at higher temperatures and responsible for the second peak (600-607 K). The two biomass mainly devolatilized around 473-673 K, with total volatile yield of about 70-75%. The char in final residue was about 19-26%. Mass loss and mass loss rates were strongly affected by heating rate. It was found that an increase in heating rate resulted in a shift of thermograms to higher temperatures. Ozawa-Flynn-Wall and Vyazovkin methods were applied to determine apparent activation energy to the olive residue and sugar cane bagasse. Two different steps were detected with apparent activation energies in the 10-40% conversion range have a value of 153-162 kJ mol(-1) and 168-180 kJ mol(-1) for the hemicellulose degradation of olive residue and sugar cane bagasse, respectively. In the 50-80% conversion range, this value is 204-215 kJ mol(-1) and 231-240 kJ mol(-1) for the cellulose degradation of olive residue and sugar cane bagasse, respectively. Copyright © 2011 Elsevier Ltd. All rights reserved.

  1. Glass transition and crystallization kinetics of a barium borosilicate glass by a non-isothermal method

    International Nuclear Information System (INIS)

    Lopes, Andreia A. S.; Soares, Roque S.; Lima, Maria M. A.; Monteiro, Regina C. C.

    2014-01-01

    The glass transition and crystallization kinetics of a glass with a molar composition 60BaO-30B 2 O 3 -10SiO 2 were investigated by differential scanning calorimetry (DSC) under non-isothermal conditions. DSC curves exhibited an endothermic peak associated with the glass transition and two partially overlapped exothermic peaks associated with the crystallization of the glass. The dependence of the glass transition temperature (T g ) and of the maximum crystallization temperature (T p ) on the heating rate was used to determine the activation energy associated with the glass transition (E g ), the activation energy for crystallization (E c ), and the Avrami exponent (n). X-ray diffraction (XRD) revealed that barium borate (β-BaB 2 O 4 ) was the first crystalline phase to be formed followed by the formation of barium silicate (Ba 5 Si 8 O 21 ). The variations of activation energy for crystallization and of Avrami exponent with the fraction of crystallization (χ) were also examined. When the crystallization fraction (χ) increased from 0.1 to 0.9, the value of local activation energy (E c (χ)) decreased from 554 to 458 kJ/mol for the first exothermic peak and from 1104 to 831 kJ/mol for the second exothermic peak. The value determined for the Avrami exponent was near 2 indicating a similar one-dimensional crystallization mechanism for both crystalline phases. This was confirmed by the morphological studies performed by scanning electron microscopy (SEM) on glass samples heat-treated at the first and at the second crystallization temperatures

  2. Isothermal and non-isothermal infiltration and deuterium transport: a case study in a soil column from a headwater catchment

    Czech Academy of Sciences Publication Activity Database

    Sobotková, M.; Sněhota, M.; Budínová, E.; Tesař, Miroslav

    2017-01-01

    Roč. 65, č. 3 (2017), s. 234-243 ISSN 0042-790X Grant - others:GA ČR(CZ) GA14-03691S Institutional support: RVO:67985874 Keywords : isothermal infiltration * non-isothermal infiltration * column leaching * breakthrough curve * deuterium * viscosity * capillary trapping * entrapped air * permeability Subject RIV: DA - Hydrology ; Limnology OBOR OECD: Environmental sciences (social aspects to be 5.7) Impact factor: 1.654, year: 2016

  3. Influence of Selectively Localised Nanoclay Particles on Non-Isothermal Crystallisation and Degradation Behaviour of PP/LDPE Blend Composites

    Directory of Open Access Journals (Sweden)

    Tladi Gideon Mofokeng

    2018-02-01

    Full Text Available In immiscible polymer blend nanocomposites, nanoparticles can be localised either in polymer matrices or at the interface, invoking the simple question of how the spatial distribution of the nanoparticles and the resulting morphological changes affect the non-isothermal crystallisation and degradation kinetics. In this study, the non-isothermal crystallisation of polypropylene in polypropylene (PP-rich compatibilised and non-compatibilised PP/low-density polyethylene (LDPE/clay composites and their degradation are investigated. The non-isothermal crystallisation analyses show that the localisation of the clay particles in the blend composites has two opposing effects. First, the poorly dispersed clay particles at the PP/LDPE interface in the non-compatibilised blend composite has no significant effect on the crystallisation temperature of PP but allows the free movement of PP chains, resulting in a higher crystallinity of PP than that of PP in the neat blend. Second, the well-dispersed clay particles in the compatibilised blend composites disrupt the free movement of PP chains, resulting in a lower crystallisation temperature and crystallinity than that of PP in the neat blend. The influences of different selective localisations of clay particles on the activation energies of degradation are studied. The presence of maleated compatibilisers, clay, and the distribution of clay in the blend composite play important roles in determining the activation energies of degradation.

  4. Production of valuable pyrolytic oils from mixed Municipal Solid Waste (MSW in Indonesia using non-isothermal and isothermal experimental

    Directory of Open Access Journals (Sweden)

    Indra Mamad Gandidi

    2017-09-01

    Full Text Available Municipal solid waste (MSW, disposed of at open dumping sites, poses health risks, contaminates surface water, and releases greenhouse gasses such as methane. However, pyrolysis offers the opportunity to convert MSW into Bio-Oil (BO for clean energy resource. In this paper, an MSW sample consisting of plastic, paper and cardboard, rubber and textiles, and vegetable waste is pyrolysed on a laboratory scale in a fixed-bed vacuum reactor. In the non-isothermal process, the sample was fed into the reactor and then heated. In the isothermal process, the reactor is first heated and then the sample is added. The non-isothermal process created greater BO in both quality and quantity. The BO had a larger amount of gasoline species than diesel-48 fuel, with at 33.44%the BO produced by isothermal pyrolysis and 36.42% in non-isothermal pyrolysis. However the product of isothermal pyrolysis had a higher acid content that reduced its heating value.

  5. Non-isothermal crystallization and melting of ethylene-vinyl acetate copolymers with different vinyl acetate contents

    Directory of Open Access Journals (Sweden)

    2008-09-01

    Full Text Available Non-isothermal crystallization and subsequent melting of three grades of ethylene-vinyl acetate copolymer were investigated by differential scanning calorimetry (DSC technique. The DSC crystallization curves show that vinyl acetate (VAc content has the same effect on the onset, peak and final crystallization temperatures, and these copolymers have almost the same spacing of thermal windows under identical crystallization condition. Subsequent melting DSC results suggest that EVA14 (14 wt% VAc has the narrowest distribution of lamellar thickness and the most perfect crystals. Though the instantaneous nucleation was preferred, non-isothermal crystallization kinetics shows that EVA14 could form tridimensional crystallites, whereas EVA18 (18 wt% VAc and EVA28 (28 wt% VAc are prone to crystallize two-dimensionally, as a result of more noncrystallizable VAc co-monomers introduced in the crystallizable ethylene segments. The growth rate falls on the following sequence: EVA14>EVA18>EVA28. Moreover, the kinetic crystallizability G also well characterizes the variation of the non-isothermal crystallization of these EVA materials, in the view of structural impediment caused by the VAc content.

  6. Single- and two-phase flow simulation based on equivalent pore network extracted from micro-CT images of sandstone core.

    Science.gov (United States)

    Song, Rui; Liu, Jianjun; Cui, Mengmeng

    2016-01-01

    Due to the intricate structure of porous rocks, relationships between porosity or saturation and petrophysical transport properties classically used for reservoir evaluation and recovery strategies are either very complex or nonexistent. Thus, the pore network model extracted from the natural porous media is emphasized as a breakthrough to predict the fluid transport properties in the complex micro pore structure. This paper presents a modified method of extracting the equivalent pore network model from the three-dimensional micro computed tomography images based on the maximum ball algorithm. The partition of pore and throat are improved to avoid tremendous memory usage when extracting the equivalent pore network model. The porosity calculated by the extracted pore network model agrees well with the original sandstone sample. Instead of the Poiseuille's law used in the original work, the Lattice-Boltzmann method is employed to simulate the single- and two- phase flow in the extracted pore network. Good agreements are acquired on relative permeability saturation curves of the simulation against the experiment results.

  7. Non-isothermal kinetics of the thermal desorption of mercury from a contaminated soil

    Directory of Open Access Journals (Sweden)

    López, Félix A.

    2014-03-01

    Full Text Available The Almadén mining district (Ciudad Real, Spain was the largest cinnabar (mercury sulphide mine in the world. Its soils have high levels of mercury a consequence of its natural lithology, but often made much worse by its mining history. The present work examines the thermal desorption of two contaminated soils from the Almadén area under non-isothermal conditions in a N2 atmosphere, using differential scanning calorimetry (DSC. DSC was performed at different heating rates between room temperature and 600 °C. Desorption temperatures for different mercury species were determined. The Friedman, Flynn-Wall-Ozawa and Coasts–Redfern methods were employed to determine the reaction kinetics from the DSC data. The activation energy and pre-exponential factor for mercury desorption were calculated.El distrito minero de Almadén (Ciudad Real, España tiene la mayor mina de cinabrio (sulfuro de mercurio del mundo. Sus suelos tienen altos niveles de mercurio como consecuencia de su litología natural, pero a menudo su contenido en mercurio es mucho más alto debido a la historia minera de la zona. Este trabajo examina la desorción térmica de dos suelos contaminados procedentes de Almadén bajo condiciones isotérmicas en atmósfera de N2, empleando calorimetría diferencial de barrido (DSC. La calorimetría se llevó a cabo a diferentes velocidades de calentamiento desde temperatura ambiente hasta 600 °C. Se determinaron las diferentes temperaturas de desorción de las especies de mercurio presentes en los suelos. Para determinar la cinética de reacción a partir de los datos de DSC se utilizaron los métodos de Friedman, Flynn-Wall-Ozawa y Coasts–Redfern. Además se calcularon las energías de activación y los factores pre-exponenciales para la desorción del mercurio.

  8. Connectivity and percolation of pore networks in a cultivated silt loam soil quantified by X-ray tomography

    Science.gov (United States)

    Jarvis, Nicholas; Koestel, John; Larsbo, Mats

    2016-04-01

    The connectivity of macropore networks is thought to exert an important control on transport processes in soil. However, little progress has been made towards quantifying these effects for natural soils in the field, partly because of the experimental difficulties but also because the concept of connectivity lacks a unique mathematical definition. To investigate this question, X-ray tomography was used to measure pore volume, size distribution and connectivity at an image resolution of 65 microns for 64 samples taken in two consecutive years in the harrowed and ploughed layers of a silt loam soil a few weeks after spring cultivation. Three different connectivity metrics were evaluated and compared: one local metric, the Euler number, and two global measures, the connection probability and the probability of percolation (the fraction of the porosity which is continuous across the sample). The connection probability was found to be a good measure of the long-range connectivity (i.e. continuity) of the pore networks. In contrast, the Euler number was not a sensitive measure of global connectivity, although all samples with negative Euler numbers did percolate. We also found that the way connection is defined in the image analysis (either by 6 or 26 nearest neighbours) did not influence the calculations of percolating porosity. The results also demonstrate that harrowing has a clear homogenizing effect on the distribution of the pore space. However, a comparison with random field simulations and the evidence of small percolation thresholds shows that the macropore system developed in the recently harrowed soil was far from completely random or disordered. In some samples, more than one pore cluster percolated, while in others the percolating cluster was not the largest one. Nevertheless, the macropore networks in this cultivated silt loam soil displayed some key features predicted by percolation theory: a strong relationship was found between the percolating fraction

  9. Microbial dispersal in unsaturated porous media: Characteristics of motile bacterial cell motions in unsaturated angular pore networks

    Science.gov (United States)

    Ebrahimi, Ali N.; Or, Dani

    2014-09-01

    The dispersal rates of self-propelled microorganisms affect their spatial interactions and the ecological functioning of microbial communities. Microbial dispersal rates affect risk of contamination of water resources by soil-borne pathogens, the inoculation of plant roots, or the rates of spoilage of food products. In contrast with the wealth of information on microbial dispersal in water replete systems, very little is known about their dispersal rates in unsaturated porous media. The fragmented aqueous phase occupying complex soil pore spaces suppress motility and limits dispersal ranges in unsaturated soil. The primary objective of this study was to systematically evaluate key factors that shape microbial dispersal in model unsaturated porous media to quantify effects of saturation, pore space geometry, and chemotaxis on characteristics of principles that govern motile microbial dispersion in unsaturated soil. We constructed a novel 3-D angular pore network model (PNM) to mimic aqueous pathways in soil for different hydration conditions; within the PNM, we employed an individual-based model that considers physiological and biophysical properties of motile and chemotactic bacteria. The effects of hydration conditions on first passage times in different pore networks were studied showing that fragmentation of aquatic habitats under dry conditions sharply suppresses nutrient transport and microbial dispersal rates in good agreement with limited experimental data. Chemotactically biased mean travel speed of microbial cells across 9 mm saturated PNM was ˜3 mm/h decreasing exponentially to 0.45 mm/h for the PNM at matric potential of -15 kPa (for -35 kPa, dispersal practically ceases and the mean travel time to traverse the 9 mm PNM exceeds 1 year). Results indicate that chemotaxis enhances dispersal rates by orders of magnitude relative to random (diffusive) motions. Model predictions considering microbial cell sizes relative to available liquid pathways sizes were

  10. Solving the non-isothermal kinetic curves of gas-solid reactions by non-linear fitting method

    International Nuclear Information System (INIS)

    Ge Qingren

    1987-01-01

    Solving the non-isothermal kinetic curves of gas-solid reactions is a subject in question up-to-date. This paper presents a non-linear fitting method on the basis of reviewing the previous methods. The computer programs have been compiled. The solutions may be obtained within five minutes with 441B-III Computer, and graphs of experimental curves and fitting curves can be printed simultaneously. More satisfactory results have been obtained for solving the twenty-eight typical theoretically calculated kinetic curves. The application and limitation of the method are discussed

  11. Study on the non-isothermal curing kinetics of a polyfurfuryl alcohol bioresin by DSC using different amounts of catalyst

    DEFF Research Database (Denmark)

    Dominguez Toribio, Juan Carlos; Grivel, Jean-Claude; Madsen, Bo

    2012-01-01

    The curing kinetics of a biomass-based polyfurfuryl alcohol resin with three different amounts of catalyst was studied by DSC non-isothermal measurements using seven heating rates. The change of the activation energy of the curing process was obtained by the isoconversional methods of Kissinger......–Akahira–Sunone, Flynn–Wall–Ozawa and Vyazovkin. The latter method provided maximum values of the activation energy of about 115, 95 and 80 kJ mol−1 before the gelation point for 2%, 4%, and 6% (w/w) amounts of catalyst, respectively. Based on a purely kinetic criterion, the most suitable amount of catalyst is assessed...

  12. Approximations to the Non-Isothermal Distributed Activation Energy Model for Biomass Pyrolysis Using the Rayleigh Distribution

    Directory of Open Access Journals (Sweden)

    Dhaundiyal Alok

    2017-09-01

    Full Text Available This paper deals with the influence of some parameters relevant to biomass pyrolysis on the numerical solutions of the nonisothermal nth order distributed activation energy model using the Rayleigh distribution. Investigated parameters are the integral upper limit, the frequency factor, the heating rate, the reaction order and the scale parameters of the Rayleigh distribution. The influence of these parameters has been considered for the determination of the kinetic parameters of the non-isothermal nth order Rayleigh distribution from the experimentally derived thermoanalytical data of biomass pyrolysis.

  13. Tuning Pore Size in Square-Lattice Coordination Networks for Size-Selective Sieving of CO2.

    Science.gov (United States)

    Chen, Kai-Jie; Madden, David G; Pham, Tony; Forrest, Katherine A; Kumar, Amrit; Yang, Qing-Yuan; Xue, Wei; Space, Brian; Perry, John J; Zhang, Jie-Peng; Chen, Xiao-Ming; Zaworotko, Michael J

    2016-08-22

    Porous materials capable of selectively capturing CO2 from flue-gases or natural gas are of interest in terms of rising atmospheric CO2 levels and methane purification. Size-exclusive sieving of CO2 over CH4 and N2 has rarely been achieved. Herein we show that a crystal engineering approach to tuning of pore-size in a coordination network, [Cu(quinoline-5-carboxyate)2 ]n (Qc-5-Cu) ena+bles ultra-high selectivity for CO2 over N2 (SCN ≈40 000) and CH4 (SCM ≈3300). Qc-5-Cu-sql-β, a narrow pore polymorph of the square lattice (sql) coordination network Qc-5-Cu-sql-α, adsorbs CO2 while excluding both CH4 and N2 . Experimental measurements and molecular modeling validate and explain the performance. Qc-5-Cu-sql-β is stable to moisture and its separation performance is unaffected by humidity. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. EFFECT OF POLY (N- VINYPYRROLIDONE ON THE NON-ISOTHERMAL CRYSTALLIZATION KINETICS AND VISCOELASTIC PROPERTIES OF PVDF FILMS

    Directory of Open Access Journals (Sweden)

    A. Mashak

    Full Text Available Abstract Poly(vinylidene fluoride (PVDF and PVDF blends with various molecular weights of poly (N- vinylpyrrolidone (PVP films were prepared in dimethyl formamide through the solution casting method. Non-isothermal melt crystallization studies of PVDF films were carried out by cooling the molten samples at different temperatures using differential scanning calorimetry (DSC. The obtained films have been characterized by dynamic mechanical thermal analysis (DMTA. Crystallization kinetics of PVDF films were successfully described by the Jeziorney, Mo and Ziabicki models. The Ozawa equation was found to be invalid for describing the crystallization kinetics. Kinetic parameters such as t1/2, Zc and F(T indicated that the crystallization rate decreased for PVDF/PVP films as compared to neat PVDF films and was affected by the molecular weight of PVP. The results based on Ziabicki's model revealed that the addition of PVP decreased the ability of PVDF to crystallize under non-isothermal melt crystallization conditions. The activation energy was calculated through Friedman and advanced isoconversional methods. Results showed that the addition of PVP to PVDF films caused an increase in activation energy. By comparing DMTA results of PVDF/PVP blends with neat PVDF films, it could be concluded that blending PVDF with PVP caused an increase in the glass transition temperature (Tg while the storage modulus was decreased.

  15. Experimental and Numerical Studies on Isothermal and Non-isothermal Deep Drawing of IS 513 CR3 Steel Sheets

    Science.gov (United States)

    Mayavan, T.; Karthikeyan, L.; Senthilkumar, V. S.

    2016-11-01

    The present work aims to investigate the effects of the temperature gradient developed within the tool profiles on the formability of IS 513 CR3-grade steel sheets using the cup drawing test. The deformation characteristics of steel sheets were analyzed by comparing the thicknesses in various regions of the formed cup and also the limiting drawing ratios (LDR). Finite element simulations were carried out to predict the behavior of the steel sheets in isothermal and non-isothermal forming using Abaqus/Standard 6.12-1. An analytical model created by Kim was used to validate the experimental and finite element analysis (FEA) results on identical process parameters. Both the FEA and analytical modeling results showed that formability improvement is possible in warm forming; the findings are in good agreement with the experimental results in determining the locations and values of excessive thinning. The results also indicated that formability improvement cannot be achieved by keeping the tooling temperature at the same level. The LDR increased by around 9.5% in isothermal forming and by 19% in non-isothermal forming (with the punch maintained at a lower temperature compared with the die and blank holder). In addition, the fractured surfaces of unsuccessfully formed samples were analyzed using scanning electron microscopy. Metallographic investigations confirmed that the fracture mechanism during the forming of IS 513 CR3-grade steel sheets depends on the brittleness, strain hardening value, forming temperature, and magnitude of stresses developed.

  16. Non-isothermal crystallization kinetics of As{sub 30}Te{sub 60}Ga{sub 10} glass

    Energy Technology Data Exchange (ETDEWEB)

    Mohamed, Mansour; Abd-Elnaiem, Alaa M.; Abdel-Rahim, M.A.; Hafiz, M.M. [Assiut University, Physics Department, Faculty of Science, Assiut (Egypt); Hassan, R.M. [Assiut University, Physics Department, Faculty of Science, Assiut (Egypt); Aden University, Physics Department, Faculty of Education-Zingiber, Aden (Yemen)

    2017-08-15

    The crystallization study under non-isothermal conditions of As{sub 30}Te{sub 60}Ga{sub 10} glass was investigated. The studied composition was synthesized by melt-quenching technique and characterized by different techniques such as X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The XRD analysis revealed that the as-prepared and annealed bulk glass of As{sub 30}Te{sub 60}Ga{sub 10} exhibit the amorphous, and polycrystalline nature, respectively. The DSC results showed that the heating rate affects the characteristic temperatures, for instance, the glass transition, onset, and peak crystallization temperatures. Furthermore, some thermal analysis methods such as the Kissinger and Matusita et al., approximations were employed to determine the crystallization parameters: for example Avrami exponent and the activation energies for glass transition and crystallization process. In addition, we have compared the experimental DSC data with the calculated ones based on the Johnson-Mehl-Avrami (JMA) and Sestak-Berggren SB(M,N) models. The results indicated that the SB(M,N) model is more suitable for describing the non-isothermal crystallization kinetics of the investigated composition. (orig.)

  17. Evolutionarily Conserved Sequence Features Regulate the Formation of the FG Network at the Center of the Nuclear Pore Complex.

    Science.gov (United States)

    Peyro, M; Soheilypour, M; Lee, B L; Mofrad, M R K

    2015-11-06

    The nuclear pore complex (NPC) is the portal for bidirectional transportation of cargos between the nucleus and the cytoplasm. While most of the structural elements of the NPC, i.e. nucleoporins (Nups), are well characterized, the exact transport mechanism is still under much debate. Many of the functional Nups are rich in phenylalanine-glycine (FG) repeats and are believed to play the key role in nucleocytoplasmic transport. We present a bioinformatics study conducted on more than a thousand FG Nups across 252 species. Our results reveal the regulatory role of polar residues and specific sequences of charged residues, named 'like charge regions' (LCRs), in the formation of the FG network at the center of the NPC. Positively charged LCRs prepare the environment for negatively charged cargo complexes and regulate the size of the FG network. The low number density of charged residues in these regions prevents FG domains from forming a relaxed coil structure. Our results highlight the significant role of polar interactions in FG network formation at the center of the NPC and demonstrate that the specific localization of LCRs, FG motifs, charged, and polar residues regulate the formation of the FG network at the center of the NPC.

  18. Study of Non-Isothermal Crystallization Kinetics of Biodegradable Poly(ethylene adipate/SiO2 Nanocomposites

    Directory of Open Access Journals (Sweden)

    M. R. Memarzadeh

    2013-09-01

    Full Text Available Poly(ethylene adipte and poly(ethylene adipate/silica nanocomposite (PEAd/SiO2 containing 3 wt. % SiO2  were prepared by an in situ method. The examinations on the non-isothermal crystallization kinetic behavior have been conducted by means of differential scanning calorimeter (DSC. The Avrami, Ozawa, and combined Avrami and Ozawa equations were applied to describe the crystallization kinetics and to determine the crystallization parameters of the prepared PEAd/SiO2 nanocomposites. It is found that the inclusion of the silica nanoparticles can accelerate the nucleation rate due to heterogeneous nucleation effect of silica on the polymer matrix. According to the obtained results, the combined Avrami and Ozawa equation shown that the better model for examination of this system.

  19. Morphology, melting behavior, and non-isothermal crystallization of poly(butylene terephthalate)/poly(ethylene-co-methacrylic acid) blends

    Energy Technology Data Exchange (ETDEWEB)

    Huang, J.-W. [Department of Styling and Cosmetology, Tainan University of Technology, 529 Chung Cheng Rd., Yung Kang City 710, Taiwan (China)], E-mail: jw.huang@msa.hinet.net; Wen, Y.-L. [Department of Nursing, Meiho Institute of Technology, 23 Ping Kuang Rd., Neipu Hsiang, Pingtung 912, Taiwan (China); Department of Resources Engineering, National Cheng Kung University, No. 1, University Rd., Tainan City 701, Taiwan (China); Kang, C.-C. [R and D Center, Hi-End Polymer Film Co., Ltd. 15-1 Sin Jhong Rd., Sin Ying City 730, Taiwan (China); Yeh, M.-Y. [Department of Chemistry, National Cheng Kung University, No. 1, University Rd., Tainan City 701, Taiwan (China); Sustainable Environment Research Centre, National Cheng Kung University, Taiwan (China); Wen, S.-B. [Department of Nursing, Meiho Institute of Technology, 23 Ping Kuang Rd., Neipu Hsiang, Pingtung 912, Taiwan (China); Department of Resources Engineering, National Cheng Kung University, No. 1, University Rd., Tainan City 701, Taiwan (China)

    2007-12-15

    The morphology, melting behavior, and non-isothermal crystallization of poly(butylene terephthalate) (PBT) and poly(ethylene-co-methacrylic acid) (PEMA) blends were studied with scanning electron microscopy, X-ray diffraction and differential scanning calorimetry (DSC). PEMA forms immiscible, yet compatible, blends with PBT. Subsequent DSC scans on melt-crystallized samples exhibited two melting endotherms (T{sub mI} and T{sub mII}). The presence of PEMA would facilitate the recrystallization during heating scan and retard PBT molecular chains to form a perfect crystal in cooling crystallization. The dispersion phases of molten PEMA acts as nucleating agents to enhance the crystallization rate of PBT. The solidified PBT could act as nucleating agents to enhance the crystallization of PEMA, but also retard the molecular mobility to reduce crystallization rate. The U* and K{sub g} of Hoffman-Lauritzen theory were also determined by Vyazovkin's methods to support the interpretation.

  20. On the integrability of a Hamiltonian reduction of a 2+1-dimensional non-isothermal rotating gas cloud system

    Science.gov (United States)

    Rogers, C.; Schief, W. K.

    2011-11-01

    A 2+1-dimensional version of a non-isothermal gas dynamic system with origins in the work of Ovsiannikov and Dyson on spinning gas clouds is shown to admit a Hamiltonian reduction which is completely integrable when the adiabatic index γ = 2. This nonlinear dynamical subsystem is obtained via an elliptic vortex ansatz which is intimately related to the construction of a Lax pair in the integrable case. The general solution of the gas dynamic system is derived in terms of Weierstrass (elliptic) functions. The latter derivation makes use of a connection with a stationary nonlinear Schrödinger equation and a Steen-Ermakov-Pinney equation, the superposition principle of which is based on the classical Lamé equation.

  1. On the integrability of a Hamiltonian reduction of a 2+1-dimensional non-isothermal rotating gas cloud system

    International Nuclear Information System (INIS)

    Rogers, C; Schief, W K

    2011-01-01

    A 2+1-dimensional version of a non-isothermal gas dynamic system with origins in the work of Ovsiannikov and Dyson on spinning gas clouds is shown to admit a Hamiltonian reduction which is completely integrable when the adiabatic index γ = 2. This nonlinear dynamical subsystem is obtained via an elliptic vortex ansatz which is intimately related to the construction of a Lax pair in the integrable case. The general solution of the gas dynamic system is derived in terms of Weierstrass (elliptic) functions. The latter derivation makes use of a connection with a stationary nonlinear Schrödinger equation and a Steen–Ermakov–Pinney equation, the superposition principle of which is based on the classical Lamé equation

  2. A study by non-isothermal thermal methods of spruce wood bark materialss after their application for dye removal

    Directory of Open Access Journals (Sweden)

    VIORICA DULMAN

    2005-11-01

    Full Text Available This paper deals with a study of some materials obtained from spruce bark (Picea abies, Romania, after retention of some dyes frequently used in dyeing processes in the textile industry and waste water treatment. These materials obtained by dye retention exhibit a particular thermal behavior which is different from that of the blank sample (spruce bark. The characteristic temperatures, weight losses, the residue remaining after thermo-oxidative degradation, as well as the activation energies of the significant thermo-destruction stages, estimated from non-isothermal thermogravimetric data, together with the thermal quantities calculated from DTAdata support the conclusion presented in a previous study on dye retention from aqueous solution. The obtained results made evident that, under optimal retention conditions, spruce bark shows the highest retention capacity for the Basic Blue dye, followed by Direct Brown 95 and Direct Brown 2.

  3. Impact of thermal radiation on MHD slip flow of a ferrofluid over a non-isothermal wedge

    Science.gov (United States)

    Rashad, A. M.

    2017-01-01

    This article is concerned with the problem of magnetohydrodynamic (MHD) mixed convection flow of Cobalt-kerosene ferrofluid adjacent a non-isothermal wedge under the influence of thermal radiation and partial slip. Such type of problems are posed by electric generators and biomedical enforcement. The governing equations are solved using the Thomas algorithm with finite-difference type and solutions for a wide range of magnet parameter are presented. It is found that local Nusselt number manifests a considerable diminishing for magnetic parameter and magnifies intensively in case of slip factor, thermal radiation and surface temperature parameters. Further, the skin friction coefficient visualizes a sufficient enhancement for the parameters thermal radiation, surface temperature and magnetic field, but a huge reduction is recorded by promoting the slip factor.

  4. Non-isothermal kinetics model to predict accurate phase transformation and hardness of 22MnB5 boron steel

    Energy Technology Data Exchange (ETDEWEB)

    Bok, H.-H.; Kim, S.N.; Suh, D.W. [Graduate Institute of Ferrous Technology, POSTECH, San 31, Hyoja-dong, Nam-gu, Pohang, Gyeongsangbuk-do (Korea, Republic of); Barlat, F., E-mail: f.barlat@postech.ac.kr [Graduate Institute of Ferrous Technology, POSTECH, San 31, Hyoja-dong, Nam-gu, Pohang, Gyeongsangbuk-do (Korea, Republic of); Lee, M.-G., E-mail: myounglee@korea.ac.kr [Department of Materials Science and Engineering, Korea University, Anam-dong, Seongbuk-gu, Seoul (Korea, Republic of)

    2015-02-25

    A non-isothermal phase transformation kinetics model obtained by modifying the well-known JMAK approach is proposed for application to a low carbon boron steel (22MnB5) sheet. In the modified kinetics model, the parameters are functions of both temperature and cooling rate, and can be identified by a numerical optimization method. Moreover, in this approach the transformation start and finish temperatures are variable instead of the constants that depend on chemical composition. These variable reference temperatures are determined from the measured CCT diagram using dilatation experiments. The kinetics model developed in this work captures the complex transformation behavior of the boron steel sheet sample accurately. In particular, the predicted hardness and phase fractions in the specimens subjected to a wide range of cooling rates were validated by experiments.

  5. Non-isothermal kinetics model to predict accurate phase transformation and hardness of 22MnB5 boron steel

    International Nuclear Information System (INIS)

    Bok, H.-H.; Kim, S.N.; Suh, D.W.; Barlat, F.; Lee, M.-G.

    2015-01-01

    A non-isothermal phase transformation kinetics model obtained by modifying the well-known JMAK approach is proposed for application to a low carbon boron steel (22MnB5) sheet. In the modified kinetics model, the parameters are functions of both temperature and cooling rate, and can be identified by a numerical optimization method. Moreover, in this approach the transformation start and finish temperatures are variable instead of the constants that depend on chemical composition. These variable reference temperatures are determined from the measured CCT diagram using dilatation experiments. The kinetics model developed in this work captures the complex transformation behavior of the boron steel sheet sample accurately. In particular, the predicted hardness and phase fractions in the specimens subjected to a wide range of cooling rates were validated by experiments

  6. A two-phase flow and non-isothermal agglomerate model for a proton exchange membrane (PEM) fuel cell

    International Nuclear Information System (INIS)

    Xing, Lei; Liu, Xiaoteng; Alaje, Taiwo; Kumar, Ravi; Mamlouk, Mohamed; Scott, Keith

    2014-01-01

    A two dimensional, across the channel, steady-state model for a proton exchange membrane fuel cell (PEMFC) is presented in which the non-isothermal model for temperature distribution, the two-phase flow model for liquid water transport and the agglomerate model for oxygen reduction reaction are fully coupled. This model is used to investigate thermal transport within the membrane electrode assembly (MEA) associated with the combinational water phase-transfer and transport mechanisms. Effective temperature distribution strategies are established aim to enhance the cell performance. Agglomerate assumption is adopted in which the ionomer and liquid water in turn cover the agglomerate to form the ionomer and liquid water films. Ionomer swelling is associated with the non-uniform distribution of the water content. The modelling results show that heat accumulates within the cathode catalyst layer under the channel. Higher operating temperature improves the cell performance by increasing the kinetics, reducing the liquid water saturation on the cathode and increasing the water carrying capacity of the anode gas. Applying higher temperature on the anode and enlarging the width ratio of the channel/rib could improve the cell performance. Higher cathode temperature decreases the oxygen mole fraction, resulting in an insufficient oxygen supply and a limitation of the cell performance. - Highlights: • The two-phase flow and non-isothermal model couple with the agglomerate model. • Oxygen diffusivity and solubility in Nafion ® relate to water content and temperature. • Higher anode operating temperature improves the fuel cell performance. • Insufficient oxygen supply limits cell performance at higher current densities

  7. Non-isothermal kinetics study on synthesis of LiFePO4 via carbothermal reduction method

    International Nuclear Information System (INIS)

    He, Lihua; Liu, Xuheng; Zhao, Zhongwei

    2013-01-01

    Highlights: • Non-isothermal kinetics of LiFePO 4 synthesis is studied. • LiFePO 4 synthesis can be divided into dehydration and LiFePO 4 formation stages. • Dehydration process is controlled by product layer diffusion. • LiFePO 4 crystallization is controlled by random nucleation and subsequent growth. • Kinetic equations of dehydration and LiFePO 4 formation are Avrami's A 1.5 and A 4 . - Abstract: Non-isothermal kinetics of lithium ion phosphate synthesis via carbothermal reduction method with raw materials Li 2 CO 3 , FePO 4 ·2H 2 O and C 6 H 12 O 6 ·2H 2 O is studied by thermogravimetry-differential scanning calorimetry (TG–DSC) technology. The results indicate the synthesis process can be divided into two stages: dehydration and LiFePO 4 formation. The apparent activation energy and natural logarithm frequency factor (ln A-value) for dehydration reaction is respectively 83.4 ± 4.7 kJ mol −1 and 22.1 ± 1.5 s −1 , and that for LiFePO 4 formation reaction is in turn 184.2 ± 10.4 kJ mol −1 and 28.3 ± 1.9 s −1 . Additionally, the mechanism for dehydration and LiFePO 4 formation stages is Avrami's A 1.5 and A 4 , respectively. Furthermore, the dehydration process is diffusion controlled, and the crystallization of LiFePO 4 formation is controlled by nuclei being formed randomly and growing in three-dimensions, and the kinetic equations for each stage are shown as follows: (table) where α is the fractional conversion, T the calcination temperature (K), t the calcination time (s), R the gas constant (8.314 J mol −1 K −1 )

  8. A combined viscous-vortex, thermal-blob and Lagrangian method for non-isothermal, two-phase flow modelling

    International Nuclear Information System (INIS)

    Rybdylova, O.; Osiptsov, A.N.; Sazhin, S.S.; Begg, S.; Heikal, M.

    2016-01-01

    Highlights: • A meshless method for modelling two-phase flows with phase transition is developed. • Carrier phase parameters are calculated using the vortex and thermal blob methods. • Droplet parameters are calculated using the Lagrangian approach. • The method is verified against the analytical solution for the Lamb vortex. • The method is used to model an impulse two-phase cold jet injected into hot gas. - Abstract: A meshless method for modelling of 2D transient, non-isothermal, gas-droplet flows with phase transitions, based on a combination of the viscous-vortex and thermal-blob methods for the carrier phase with the Lagrangian approach for the dispersed phase, is developed. The one-way coupled, two-fluid approach is used in the analysis. The method makes it possible to avoid the ‘remeshing’ procedure (recalculation of flow parameters from Eulerian to Lagrangian grids) and reduces the problem to the solution of three systems of ordinary differential equations, describing the motion of viscous-vortex blobs, thermal blobs, and evaporating droplets. The gas velocity field is restored using the Biot–Savart integral. The numerical algorithm is verified against the analytical solution for a non-isothermal Lamb vortex and some asymptotic results known in the literature. The method is applied to modelling of an impulse two-phase cold jet injected into a quiescent hot gas, taking into account droplet evaporation. Various flow patterns are obtained in the calculations, depending on the initial droplet size: (i) low-inertia droplets, evaporating at a higher rate, form ring-like structures and are accumulated only behind the vortex pair; (ii) large droplets move closer to the jet axis, with their sizes remaining almost unchanged; and (iii) intermediate-size droplets are accumulated in a curved band whose ends trail in the periphery behind the head of the cloud, with larger droplets being collected at the front of the two-phase region.

  9. Non isothermal decomposition of lanthanum titanates precursors prepared by sol gel process: A kinetic and thermodynamic study

    Energy Technology Data Exchange (ETDEWEB)

    Bassil, S. [Université Lyon 1, CNRS, UMR 5256, IRCELYON, Institut de recherches sur la catalyse et l’environnement de Lyon, 2 avenue Albert Einstein, F-69626 Villeurbanne (France); Kaddouri, A., E-mail: akim.kaddouri@ircelyon.univ-lyon1.fr [Université Lyon 1, CNRS, UMR 5256, IRCELYON, Institut de recherches sur la catalyse et l’environnement de Lyon, 2 avenue Albert Einstein, F-69626 Villeurbanne (France); Béguin, B.; Gélin, P. [Université Lyon 1, CNRS, UMR 5256, IRCELYON, Institut de recherches sur la catalyse et l’environnement de Lyon, 2 avenue Albert Einstein, F-69626 Villeurbanne (France)

    2013-09-10

    Highlights: ► Metal-propionates is a most promising route for the preparation of La{sub 0.8}Sr{sub 0.2}TiO{sub 3+δ} (LST) at a temperature substantially lower than that used for the preparation of the same solid by traditional methods. ► Activation energy and isothermal thermodynamic parameters calculated for the decomposition process are close to those observed for metal organic compounds. ► Sol gel-prepared LST presented low propensity to coke deposition and high stability with time during the critical long term exposure to methane and steam at high temperatures. - Abstract: The single phase La{sub 0.8}Sr{sub 0.2}TiO{sub 3+δ} was prepared via the sol gel process using propionic acid. Kinetics of the thermal decomposition of the precursors has been studied using differential thermogravimetry under non-isothermal conditions in different atmospheres (air and helium). Non isothermal kinetic (A and ΔE) and thermodynamic parameters (ΔH, ΔS and Cp) were determined using different heating rates. La{sub 2}O{sub 3}, SrO and TiO{sub 2} products crystallized at temperatures of ca. 730, 960 and 470 °C respectively while pure La{sub 0.8}Sr{sub 0.2}TiO{sub 3+δ} phase was obtained at 1200 °C, temperature substantially lower than that used for the preparation of La{sub 0.8}Sr{sub 0.2}TiO{sub 3+δ} by conventional solid state method. Precursors and/or final solids were characterized by thermogravimetric analysis (TG), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction, diffuse reflectance ultraviolet–visible spectroscopy (DR-UV–vis) and methane steam reforming under water deficient conditions.

  10. Pore-Network Modeling of Water and Vapor Transport in the Micro Porous Layer and Gas Diffusion Layer of a Polymer Electrolyte Fuel Cell

    NARCIS (Netherlands)

    Qin, C.; Hassanizadeh, S.M.; van Oosterhout, L.M.

    2016-01-01

    In the cathode side of a polymer electrolyte fuel cell (PEFC), a micro porous layer (MPL) added between the catalyst layer (CL) and the gas diffusion layer (GDL) plays an important role in water management. In this work, by using both quasi-static and dynamic pore-network models, water and vapor

  11. Spatially orthogonal chemical functionalization of a hierarchical pore network for catalytic cascade reactions

    Science.gov (United States)

    Parlett, Christopher M. A.; Isaacs, Mark A.; Beaumont, Simon K.; Bingham, Laura M.; Hondow, Nicole S.; Wilson, Karen; Lee, Adam F.

    2016-02-01

    The chemical functionality within porous architectures dictates their performance as heterogeneous catalysts; however, synthetic routes to control the spatial distribution of individual functions within porous solids are limited. Here we report the fabrication of spatially orthogonal bifunctional porous catalysts, through the stepwise template removal and chemical functionalization of an interconnected silica framework. Selective removal of polystyrene nanosphere templates from a lyotropic liquid crystal-templated silica sol-gel matrix, followed by extraction of the liquid crystal template, affords a hierarchical macroporous-mesoporous architecture. Decoupling of the individual template extractions allows independent functionalization of macropore and mesopore networks on the basis of chemical and/or size specificity. Spatial compartmentalization of, and directed molecular transport between, chemical functionalities affords control over the reaction sequence in catalytic cascades; herein illustrated by the Pd/Pt-catalysed oxidation of cinnamyl alcohol to cinnamic acid. We anticipate that our methodology will prompt further design of multifunctional materials comprising spatially compartmentalized functions.

  12. Technical Assessment of Isothermal and Non-Isothermal Modelings of Natural Gas Pipeline Operational Conditions Évaluation technique de modélisations isothermes et non isothermes de conditions opérationnelles de conduites de gaz naturel

    Directory of Open Access Journals (Sweden)

    Sanaye S.

    2012-05-01

    Full Text Available Modeling of equipment in a gas pipeline was performed here by deriving a new form of conservation equation set for compressible flow. Then a section of the third Iranian gas transmission pipeline (Nourabad-Pataveh-Dorahan, N-P-D was investigated by isothermal (IT and non-isothermal (NIT modeling approaches taking into account the effects of ground temperature. In the first part, the steady state operation of the N-P-D pipeline including a compressor station at Pataveh was studied. For the known values of natural gas mass flow rate, and inlet/outlet gas pressures at Nourabad/Dorahan points, the IT and NIT modelings showed about 33.7%, 16.6% and 23% maximum difference percent points for the compressors head, compressors rotational speed and fuel consumption rates respectively. In the second part, the unsteady operation of the N-P-D pipeline due to the shutdown of a compressor at Pataveh Compressor Station (PCS was studied. The results confirmed that at lower ground temperatures (0 and 20°C, the remaining compressors could compensate the loss of one compressor. However, at higher ground temperatures (40 and 50°C, the compressors had to run faster than the highest permissible speed to be able to deliver a certain mass flow rate without reducing the required pipeline pressure. In all above studied cases, the computing time for the non-isothermal modeling was about three times longer than that for the isothermal one. Une modélisation d'équipement au sein d'un gazoduc a été réalisée en dérivant une nouvelle forme d'ensemble d'équations de conservation pour un écoulement compressible. Une section du troisième réseau de distribution de gaz iranien (Nourabad-Pataveh-Dorahan, N-P-D a été ensuite étudiée selon des approches de modélisation isotherme (IT et non isotherme (NIT en prenant en compte les effets de la température du sol. Dans la première partie, le fonctionnement en régime stationnaire du gazoduc N-P-D, comprenant une station

  13. Non-isothermal kinetics study on synthesis of LiFePO{sub 4} via carbothermal reduction method

    Energy Technology Data Exchange (ETDEWEB)

    He, Lihua; Liu, Xuheng; Zhao, Zhongwei, E-mail: zhaozw@csu.edu.cn

    2013-08-20

    Highlights: • Non-isothermal kinetics of LiFePO{sub 4} synthesis is studied. • LiFePO{sub 4} synthesis can be divided into dehydration and LiFePO{sub 4} formation stages. • Dehydration process is controlled by product layer diffusion. • LiFePO{sub 4} crystallization is controlled by random nucleation and subsequent growth. • Kinetic equations of dehydration and LiFePO{sub 4} formation are Avrami's A{sub 1.5} and A{sub 4}. - Abstract: Non-isothermal kinetics of lithium ion phosphate synthesis via carbothermal reduction method with raw materials Li{sub 2}CO{sub 3}, FePO{sub 4}·2H{sub 2}O and C{sub 6}H{sub 12}O{sub 6}·2H{sub 2}O is studied by thermogravimetry-differential scanning calorimetry (TG–DSC) technology. The results indicate the synthesis process can be divided into two stages: dehydration and LiFePO{sub 4} formation. The apparent activation energy and natural logarithm frequency factor (ln A-value) for dehydration reaction is respectively 83.4 ± 4.7 kJ mol{sup −1} and 22.1 ± 1.5 s{sup −1}, and that for LiFePO{sub 4} formation reaction is in turn 184.2 ± 10.4 kJ mol{sup −1} and 28.3 ± 1.9 s{sup −1}. Additionally, the mechanism for dehydration and LiFePO{sub 4} formation stages is Avrami's A{sub 1.5} and A{sub 4}, respectively. Furthermore, the dehydration process is diffusion controlled, and the crystallization of LiFePO{sub 4} formation is controlled by nuclei being formed randomly and growing in three-dimensions, and the kinetic equations for each stage are shown as follows: (table) where α is the fractional conversion, T the calcination temperature (K), t the calcination time (s), R the gas constant (8.314 J mol{sup −1} K{sup −1})

  14. TOURGHREACT: A Simulation Program for Non-isothermal MultiphaseReactive Geochemical Transport in Variably Saturated GeologicMedia

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Tianfu; Sonnenthal, Eric; Spycher, Nicolas; Pruess, Karsten

    2004-12-07

    TOUGHREACT is a numerical simulation program for chemically reactive non-isothermal flows of multiphase fluids in porous and fractured media. The program was written in Fortran 77 and developed by introducing reactive geochemistry into the multiphase fluid and heat flow simulator TOUGH2. A variety of subsurface thermo-physical-chemical processes are considered under a wide range of conditions of pressure, temperature, water saturation, ionic strength, and pH and Eh. Interactions between mineral assemblages and fluids can occur under local equilibrium or kinetic rates. The gas phase can be chemically active. Precipitation and dissolution reactions can change formation porosity and permeability. The program can be applied to many geologic systems and environmental problems, including geothermal systems, diagenetic and weathering processes, subsurface waste disposal, acid mine drainage remediation, contaminant transport, and groundwater quality. Here we present two examples to illustrate applicability of the program: (1) injectivity effects of mineral scaling in a fractured geothermal reservoir and (2) CO2 disposal in a deep saline aquifer.

  15. Oxidative synthesis of a novel polyphenol having pendant Schiff base group: Synthesis, characterization, non-isothermal decomposition kinetics

    Energy Technology Data Exchange (ETDEWEB)

    Dilek, Deniz [Faculty of Education, Secondary Science and Mathematics Education, Canakkale Onsekiz Mart University, 17100 Canakkale (Turkey); Dogan, Fatih, E-mail: fatihdogan@comu.edu.tr [Faculty of Education, Secondary Science and Mathematics Education, Canakkale Onsekiz Mart University, 17100 Canakkale (Turkey); Bilici, Ali, E-mail: alibilici66@hotmail.com [Control Laboratory of Agricultural and Forestry Ministry, 34153 Istanbul (Turkey); Kaya, Ismet [Department of Chemistry, Faculty of Science and Arts, Canakkale Onsekiz Mart University, Canakkale (Turkey)

    2011-05-10

    Research highlights: {yields} In this study, the synthesis and thermal characterization of a new functional polyphenol are reported. {yields} Non-isothermal methods were used to evaluate the thermal decomposition kinetics of resulting polymer. {yields} Thermal decomposition of polymer follows a diffusion type kinetic model. {yields} It is noted that this kinetic model is quite rare in polymer degradation studies. - Abstract: In here, the facile synthesis and thermal characterization of a novel polyphenol containing Schiff base pendant group, poly(4-{l_brace}[(4-hydroxyphenyl)imino]methyl{r_brace}benzene-1,2,3-triol) [PHPIMB], are reported. UV-vis, FT-IR, {sup 1}H NMR, {sup 13}C NMR, GPC, TG/DTG-DTA, CV (cyclic voltammetry) and solid state conductivity measurements were utilized to characterize the obtained monomer and polymer. The spectral analyses results showed that PHPIMB was composed of polyphenol main chains containing Schiff base pendant side groups. Thermal properties of the polymer were investigated by thermogravimetric analyses under a nitrogen atmosphere. Five methods were used to study the thermal decomposition of PHPIMB at different heating rate and the results obtained by using all the kinetic methods were compared with each other. The thermal decomposition of PHPIMB was found to be a simple process composed of three stages. These investigated methods were those of Flynn-Wall-Ozawa (FWO), Tang, Kissinger-Akahira-Sunose (KAS), Friedman and Kissinger methods.

  16. Matrix assisted pulsed laser evaporation of zinc benzoate for ZnO thin films and non-isothermal decomposition kinetics

    International Nuclear Information System (INIS)

    Rotaru, A.; Constantinescu, C.; Mandruleanu, Anca; Rotaru, P.; Moldovan, A.; Gyoryova, Katarina; Dinescu, Maria; Balek, V.

    2010-01-01

    Zinc(II) coordination compounds may provide a better source for ZnO thin films obtaining, since ZnO was found as the final product of their thermal decomposition. Thin films of zinc benzoate have been obtained on silicon substrates by matrix assisted pulsed laser evaporation (MAPLE) technique, using a Nd:YAG laser working at 266 nm. A comparative study of 1% zinc benzoate frozen solution in methanol at different fulences was carried out for 20,000 laser pulses; for the best deposition fluence a double deposition time was employed. Comparative thermal analysis and non-isothermal kinetic investigation of Zn(C 6 H 5 COO) 2 .2H 2 O dehydration and decomposition was performed. Thin films of ZnO have been obtained by thermal treatment of the MAPLE obtained thin films, according to the thermal analysis and decomposition kinetics of zinc benzoate. The obtained morphologies, before and after thermal treatment, have been investigated by atomic force microscopy (AFM).

  17. Non-isothermal kinetic studies on the formation of Al{sub 2}O{sub 3}/Nb composite

    Energy Technology Data Exchange (ETDEWEB)

    Mostaan, H. [Department of Materials Engineering, Nanotechnology and Advanced Materials Institute, Isfahan University of Technology, Isfahan, 84156-83111 (Iran, Islamic Republic of); Karimzadeh, F., E-mail: Karimzadeh_f@cc.iut.ac.ir [Department of Materials Engineering, Nanotechnology and Advanced Materials Institute, Isfahan University of Technology, Isfahan, 84156-83111 (Iran, Islamic Republic of); Abbasi, M.H. [Department of Materials Engineering, Nanotechnology and Advanced Materials Institute, Isfahan University of Technology, Isfahan, 84156-83111 (Iran, Islamic Republic of)

    2010-11-20

    The reaction mechanism and activation energy (E{sub {alpha}}) of aluminothermic reaction between Al and Nb{sub 2}O{sub 5} were investigated under non-isothermal conditions using X-ray diffractometry (XRD) and differential thermal analysis (DTA). It was found that the mechanically alloyed Al-Nb{sub 2}O{sub 5} powder mixture was converted to Al{sub 2}O{sub 3}/Nb composite in three stages and during the reduction, intermediate Nb oxides (NbO{sub 2} and NbO) were formed. Four isoconversional methods, of Kissinger-Akahira-Sunose (KAS), Flynn-Wall-Ozawa (FWO), Tang and Starink, were used to determine the value of E on a conversion fraction of {alpha} = 0.5 for these three exothermic reactions. The results showed that all methods lead to similar values of E and have a good agreement with one another. Also, the isoconversional method of Starink was used to determine the variation of the activation energy, E{sub {alpha}}, for three exothermic reactions with degree of conversion ({alpha}). It was revealed that the E{sub {alpha}} for the first and third reactions are independent from {alpha} while different behavior was observed for the second reaction, where a decrease of E{sub {alpha}} occurred in the conversion range of 0.6 {<=} {alpha} {<=} 0.95.

  18. Non-isothermal crystallization kinetics of partially miscible ethylene-vinyl acetate copolymer/low density polyethylene blends

    Directory of Open Access Journals (Sweden)

    2010-03-01

    Full Text Available The non-isothermal crystallization kinetics of ethylene-vinyl acetate copolymer (EVA, 14 wt% vinyl acetate content, low density polyethylene (LDPE and their binary blends with different blending ratio were investigated via differential scanning calorimetry. Jeziorny theory and Mo’s method were utilized in evaluating the crystallization behavior of both neat materials successfully. In the primary crystallization stage both EVA and LDPE had three-dimensional spherulitic growth mechanism. Apparently the crystallization rate of LDPE was faster than that of EVA at a low cooling rate. Increase in cooling rate limited the spherulites’ growth, which narrowed their rate difference. Influences from blending on the crystallization kinetics of each component in EVA/LDPE mixture were evaluated by Kissinger’s activation energy (∆E and Khanna’s crystallization rate coefficient (CRC. Inter-molecular interaction in the melt increased the ∆E of both EVA and LDPE components at the beginning of cooling. During the primary crystallization stage of LDPE, dilution effect from EVA facilitated the crystal growth in LDPE. Co-crystallization between EVA component and the secondary crystallization stage of LDPE component also increased the CRC of EVA. In blend of EVA/LDPE = 7/3, LDPE obtained the maximal CRC value of 174.2 h–1. Results obtained from various approaches accorded well with each other, which insured the rationality of conclusion.

  19. Three dimensional analysis of the pore space in fine-grained Boom Clay, using BIB-SEM (broad-ion beam scanning electron microscopy), combined with FIB (focused ion-beam) serial cross-sectioning, pore network modeling and Wood's metal injection

    Science.gov (United States)

    Hemes, Susanne; Klaver, Jop; Desbois, Guillaume; Urai, Janos

    2014-05-01

    The Boom Clay is, besides the Ypresian clays, one of the potential host rock materials for radioactive waste disposal in Belgium (Gens et al., 2003; Van Marcke & Laenen, 2005; Verhoef et al., 2011). To access parameters, which are relevant for the diffusion controlled transport of radionuclides in the material, such as porosity, pore connectivity and permeability, it is crucial to characterize the pore space at high resolution (nm-scale) and in 3D. Focused-ion-beam (FIB) serial cross-sectioning in combination with high resolution scanning electron microscopy (SEM), pore network modeling, Wood's metal injection and broad-ion-beam (BIB) milling, constitute a superior set of methods to characterize the 3D pore space in fine-grained, clayey materials, down to the nm-scale resolution. In the present study, we identified characteristic 3D pore space morphologies, determined the 3D volume porosity of the material and applied pore network extraction modeling (Dong and Blunt, 2009), to access the connectivity of the pore space and to discriminate between pore bodies and pore throats. Moreover, we used Wood's metal injection (WMI) in combination with BIB-SEM imaging to assess the pore connectivity at a larger scale and even higher resolution. The FIB-SEM results show a highly (~ 90 %) interconnected pore space in Boom Clay, down to the resolution of ~ 3E+03 nm³ (voxel-size), with a total volume porosity of ~ 20 %. Pore morphologies of large (> 5E+08 nm³), highly interconnected pores are complex, with high surface area to volume ratios (shape factors G ~ 0.01), whereas small (< 1E+06 nm³), often isolated pores are much more compact and show higher shape factors (G) up to 0.03. WMI in combination with BIB-SEM, down to a resolution of ~ 50 nm² pixel-size, indicates an interconnected porosity fraction of ~ 80 %, of a total measured 2D porosity of ~ 20 %. Determining and distinguishing between pore bodies and pore throats enables us to compare 3D FIB-SEM pore

  20. TOUGHREACT User's Guide: A Simulation Program for Non-isothermal Multiphase Reactive geochemical Transport in Variably Saturated Geologic Media

    International Nuclear Information System (INIS)

    Xu, Tianfu; Sonnenthal, Eric; Spycher, Nicolas; Pruess, Karsten

    2004-01-01

    Coupled modeling of subsurface multiphase fluid and heat flow, solute transport and chemical reactions can be used for the assessment of mineral alteration in hydrothermal systems, waste disposal sites, acid mine drainage remediation, contaminant transport, and groundwater quality. A comprehensive non-isothermal multi-component reactive fluid flow and geochemical transport simulator, TOUGHREACT, has been developed. A wide range of subsurface thermo-physical-chemical processes is considered under various thermohydrological and geochemical conditions of pressure, temperature, water saturation, and ionic strength. The program can be applied to one-, two- or three-dimensional porous and fractured media with physical and chemical heterogeneity. The model can accommodate any number of chemical species present in liquid, gas and solid phases. A variety of equilibrium chemical reactions are considered, such as aqueous complexation, gas dissolution/exsolution, and cation exchange. Mineral dissolution/precipitation can proceed either subject to local equilibrium or kinetic conditions. Changes in porosity and permeability due to mineral dissolution and precipitation can be considered. Linear adsorption and decay can be included. For the purpose of future extensions, surface complexation by double layer model is coded in the program. Xu and Pruess (1998) developed a first version of a non-isothermal reactive geochemical transport model, TOUGHREACT, by introducing reactive geochemistry into the framework of the existing multi-phase fluid and heat flow code TOUGH2 (Pruess, 1991). Xu, Pruess, and their colleagues have applied the program to a variety of problems such as: (1) supergene copper enrichment (Xu et al, 2001), (2) caprock mineral alteration in a hydrothermal system (Xu and Pruess, 2001a), and (3) mineral trapping for CO 2 disposal in deep saline aquifers (Xu et al, 2003b and 2004a). For modeling the coupled thermal, hydrological, and chemical processes during heater

  1. A comparison of results obtained with two subsurface non-isothermal multiphase reactive transport simulators, FADES-CORE and TOUGHREACT

    Energy Technology Data Exchange (ETDEWEB)

    Juncosa Rivera, Ricardo; Xu, Tianfu; Pruess, Karsten

    2001-01-01

    FADES-CORE and TOUGHREACT are codes used to model the non-isothermal multiphase flow with multicomponent reactive transport in porous media. Different flow and reactive transport problems were used to compare the FADES-CORE and TOUGHREACT codes. These problems take into account the different cases of multiphase flow with and without heat transport, conservative transport, and reactive transport. Consistent results were obtained from both codes, which use different numerical methods to solve the differential equations resulting from the various physicochemical processes. Here we present the results obtained from both codes for various cases. Some results are slightly different with minor discrepancies, which have been remedied, so that both codes would be able to reproduce the same processes using the same parameters. One of the discrepancies found is related to the different calculation for thermal conductivity in heat transport, which affects the calculation of the temperatures, as well as the pH of the reaction of calcite dissolution problem modeled. Therefore it is possible to affirm that the pH is highly sensitive to temperature. Generally speaking, the comparison was concluded to be highly satisfactory, leading to the complete verification of the FADES-CORE code. However, we must keep in mind that, as there are no analytical solutions available with which to verify the codes, the TOUGHREACT code has been thoroughly corroborated, given that the only possible way to prove that the code simulation is correct, is by comparing the results obtained with both codes for the identical problems, or to validate the simulation results with actual measured data.

  2. Effects of Soil Bulk Density on Gas Transport Parameters and Pore-Network Properties across a Sandy Field Site

    DEFF Research Database (Denmark)

    Masis Melendez, Federico; de Jonge, Lis Wollesen; Chamindu, T K K Deepagoda

    2015-01-01

    investigated. Interactions with soil organic matter, sand and clay fractions were also examined. Six parameters including Campbell b, the air entry pressure, the diffusive and convective percolation thresholds, and the diffusivity- and air permeability-based pore connectivity indices were determined......The gas diffusion coefficient, air permeability, and their interrelations with air-filled porosity are crucial for characterization of diffusive and convective transport of gases in soils. Variations in soil bulk density can affect water retention, air-filled pore space, pore tortuosity...

  3. Nuclear routing networks span between nuclear pore complexes and genomic DNA to guide nucleoplasmic trafficking of biomolecules

    Science.gov (United States)

    Malecki, Marek; Malecki, Bianca

    2012-01-01

    In health and disease, biomolecules, which are involved in gene expression, recombination, or reprogramming have to traffic through the nucleoplasm, between nuclear pore complexes (NPCs) and genomic DNA (gDNA). This trafficking is guided by the recently revealed nuclear routing networks (NRNs). In this study, we aimed to investigate, if the NRNs have established associations with the genomic DNA in situ and if the NRNs have capabilities to bind the DNA de novo. Moreover, we aimed to study further, if nucleoplasmic trafficking of the histones, rRNA, and transgenes’ vectors, between the NPCs and gDNA, is guided by the NRNs. We used Xenopus laevis oocytes as the model system. We engineered the transgenes’ DNA vectors equipped with the SV40 LTA nuclear localization signals (NLS) and/or HIV Rev nuclear export signals (NES). We purified histones, 5S rRNA, and gDNA. We rendered all these molecules superparamagnetic and fluorescent for detection with nuclear magnetic resonance (NMR), total reflection x-ray fluorescence (TXRF), energy dispersive x-ray spectroscopy (EDXS), and electron energy loss spectroscopy (EELS). The NRNs span between the NPCs and genomic DNA. They form firm bonds with the gDNA in situ. After complete digestion of the nucleic acids with the RNases and DNases, the newly added DNA - modified with the dNTP analogs, bonds firmly to the NRNs. Moreover, the NRNs guide the trafficking of the DNA transgenes’ vectors - modified with the SV40 LTA NLS, following their import into the nuclei through the NPCs. The pathway is identical to that of histones. The NRNs also guide the trafficking of the DNA transgenes’ vectors, modified with the HIV Rev NES, to the NPCs, followed by their export out of the nuclei. Ribosomal RNAs follow the same pathway. To summarize, the NRNs are the structures connecting the NPCs and the gDNA. They guide the trafficking of the biomolecules between the NPCs and the gDNA. PMID:23275893

  4. The Effect of Heat Transfer and Polymer Concentration on Non-Newtonian Fluid from Pore-Scale Simulation of Rock X-ray Micro-CT

    Directory of Open Access Journals (Sweden)

    Moussa Tembely

    2017-10-01

    Full Text Available Most of the pore-scale imaging and simulations of non-Newtonian fluid are based on the simplifying geometry of network modeling and overlook the fluid rheology and heat transfer. In the present paper, we developed a non-isothermal and non-Newtonian numerical model of the flow properties at pore-scale by simulation of the 3D micro-CT images using a Finite Volume Method (FVM. The numerical model is based on the resolution of the momentum and energy conservation equations. Owing to an adaptive mesh generation technique and appropriate boundary conditions, rock permeability and mobility are accurately computed. A temperature and concentration-dependent power-law viscosity model in line with the experimental measurement of the fluid rheology is adopted. The model is first applied at isothermal condition to 2 benchmark samples, namely Fontainebleau sandstone and Grosmont carbonate, and is found to be in good agreement with the Lattice Boltzmann method (LBM. Finally, at non-isothermal conditions, an effective mobility is introduced that enables to perform a numerical sensitivity study to fluid rheology, heat transfer, and operating conditions. While the mobility seems to evolve linearly with polymer concentration in agreement with a derived theoretical model, the effect of the temperature seems negligible by comparison. However, a sharp contrast is found between carbonate and sandstone under the effect of a constant temperature gradient. Besides concerning the flow index and consistency factor, a master curve is derived when normalizing the mobility for both the carbonate and the sandstone.

  5. TOUGHREACT User's Guide: A Simulation Program for Non-isothermal Multiphase Reactive Geochemical Transport in Variably Saturated Geologic Media, V1.2.1

    International Nuclear Information System (INIS)

    Xu, Tianfu; Sonnenthal, Eric; Spycher, Nicolas; Pruess, Karsten

    2008-01-01

    Coupled modeling of subsurface multiphase fluid and heat flow, solute transport, and chemical reactions can be applied to many geologic systems and environmental problems, including geothermal systems, diagenetic and weathering processes, subsurface waste disposal, acid mine drainage remediation, contaminant transport, and groundwater quality. TOUGHREACT has been developed as a comprehensive non-isothermal multi-component reactive fluid flow and geochemical transport simulator to investigate these and other problems. A number of subsurface thermo-physical-chemical processes are considered under various thermohydrological and geochemical conditions of pressure, temperature, water saturation, and ionic strength. TOUGHREACT can be applied to one-, two- or three-dimensional porous and fractured media with physical and chemical heterogeneity. The code can accommodate any number of chemical species present in liquid, gas and solid phases. A variety of equilibrium chemical reactions are considered, such as aqueous complexation, gas dissolution/exsolution, and cation exchange. Mineral dissolution/precipitation can take place subject to either local equilibrium or kinetic controls, with coupling to changes in porosity and permeability and capillary pressure in unsaturated systems. Chemical components can also be treated by linear adsorption and radioactive decay. The first version of the non-isothermal reactive geochemical transport code TOUGHREACT was developed (Xu and Pruess, 1998) by introducing reactive geochemistry into the framework of the existing multi-phase fluid and heat flow code TOUGH2 (Pruess, 1991). TOUGHREACT was further enhanced with the addition of (1) treatment of mineral-water-gas reactive-transport under boiling conditions, (2) an improved HKF activity model for aqueous species, (3) gas species diffusion coefficients calculated as a function of pressure, temperature, and molecular properties, (4) mineral reactive surface area formulations for fractured

  6. TOUGHREACT User's Guide: A Simulation Program for Non-isothermal Multiphase Reactive Geochemical Transport in Variably Saturated Geologic Media, V1.2.1

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Tianfu; Sonnenthal, Eric; Spycher, Nicolas; Pruess, Karsten

    2008-09-29

    Coupled modeling of subsurface multiphase fluid and heat flow, solute transport, and chemical reactions can be applied to many geologic systems and environmental problems, including geothermal systems, diagenetic and weathering processes, subsurface waste disposal, acid mine drainage remediation, contaminant transport, and groundwater quality. TOUGHREACT has been developed as a comprehensive non-isothermal multi-component reactive fluid flow and geochemical transport simulator to investigate these and other problems. A number of subsurface thermo-physical-chemical processes are considered under various thermohydrological and geochemical conditions of pressure, temperature, water saturation, and ionic strength. TOUGHREACT can be applied to one-, two- or three-dimensional porous and fractured media with physical and chemical heterogeneity. The code can accommodate any number of chemical species present in liquid, gas and solid phases. A variety of equilibrium chemical reactions are considered, such as aqueous complexation, gas dissolution/exsolution, and cation exchange. Mineral dissolution/precipitation can take place subject to either local equilibrium or kinetic controls, with coupling to changes in porosity and permeability and capillary pressure in unsaturated systems. Chemical components can also be treated by linear adsorption and radioactive decay. The first version of the non-isothermal reactive geochemical transport code TOUGHREACT was developed (Xu and Pruess, 1998) by introducing reactive geochemistry into the framework of the existing multi-phase fluid and heat flow code TOUGH2 (Pruess, 1991). TOUGHREACT was further enhanced with the addition of (1) treatment of mineral-water-gas reactive-transport under boiling conditions, (2) an improved HKF activity model for aqueous species, (3) gas species diffusion coefficients calculated as a function of pressure, temperature, and molecular properties, (4) mineral reactive surface area formulations for fractured

  7. Hydrodynamic boundary conditions for one-component liquid-gas flows on non-isothermal solid substrates

    KAUST Repository

    Xu, Xinpeng

    2012-01-01

    Recently, liquid-gas flows related to droplets, bubbles, and thin films on solid surfaces with thermal and wettability gradients have attracted widespread attention because of the many physical processes involved and their promising potential applications in biology, chemistry, and industry. Various new physical effects have been discovered at fluid-solid interfaces by experiments and molecular dynamics simulations, e.g., fluid velocity slip, temperature slip (Kapitza resistance), mechanical-thermal cross coupling, etc. There have been various models and theories proposed to explain these experimental and numerical observations. However, to the best of our knowledge,a continuum hydrodynamic model capable of predicting the temperature and velocity profiles of liquid-gas flows on non-isothermal, heterogeneous solid substrates is still absent. The purpose of this work is to construct a continuum model for simulating the liquid-gas flows on solid surfaces that are flat and rigid, and may involve wettability gradients and thermal gradients. This model is able to describe fluid velocity slip, temperature slip, and mechanical-thermal coupling that may occur at fluid-solid interfaces. For this purpose, we first employ the diffuse interface modeling to formulate the hydrodynamic equations for one-component liquid-gas flows in the bulk region. This reproduces the dynamic van der Waals theory of Onuki [Phys. Rev. Lett., 94: 054501, 2005]. We then extendWaldmann\\'s method [Z. Naturforsch. A, 22: 1269-1280, 1967] to formulate the boundary conditions at the fluid-solid interface that match the hydrodynamic equations in the bulk. The effects of the solid surface curvature are also briefly discussed in the appendix. The guiding principles of our model derivation are the conservation laws and the positive definiteness of entropy production together with the Onsager reciprocal relation. The derived model is self-consistent in the sense that the boundary conditions are

  8. Experimental study on corrosion and precipitation in non-isothermal Pb-17Li system for development of liquid breeder blanket of fusion reactor

    Science.gov (United States)

    Kondo, Masatoshi; Ishii, Masaomi; Norimatsu, Takayoshi; Muroga, Takeo

    2017-07-01

    The corrosion characteristics of RAFM steel JLF-1 in a non-isothermal Pb-17Li flowing system were investigated by means of the corrosion test using a non-isothermal mixing pot. The corrosion test was performed at 739K with a temperature gradient of 14K for 500 hours. The corrosion tests at a static and a flowing conditions in an isothermal Pb-17Li system were also performed at the same temperature for the same duration with the non-isothermal test. Then, the effect of mass transfer both by the flow and the temperature gradient on the corrosion behaviors was featured by the comparison of these results. The corrosion was caused by the dissolution of Fe and Cr from the steel surface into the flowing Pb-17Li. The specimen surface revealed a fine granular microstructure after the corrosion tests. A large number of pebbleshaped protrusions were observed on the specimen surface. This microstructure was different from the original martensite microstructure of the steel, and might be formed by the influence of the reaction with Li component in the alloy. The formation of the granular microstructure was accelerated by the flow and the temperature gradient. Some pebble-shaped protrusions had gaps at their bases. The removal of these pebble-shaped granules by the flowing Pb-17Li might cause a small-scale corrosion-erosion. The results of metallurgical analysis indicated that a large-scale corrosion-erosion was also caused by their destruction of the corroded layer on the surface. The non-isothermal mixing pot equipped a cold trap by a metal mesh in the low temperature region. The metal elements of Fe and Cr were recovered as they precipitated on the surface of the metal mesh. It was found that a Fe-Cr binary intermetallic compound was formed in the precipitation procedure. The overall mass transfer coefficient for the dissolution type corrosion in the non-isothermal system was much bigger than that in the isothermal system. This model evaluation indicated that the temperature

  9. Effects of network dissolution changes on pore-to-core upscaled reaction rates for kaolinite and anorthite reactions under acidic conditions

    KAUST Repository

    Kim, Daesang

    2013-11-01

    We have extended reactive flow simulation in pore-network models to include geometric changes in the medium from dissolution effects. These effects include changes in pore volume and reactive surface area, as well as topological changes that open new connections. The computed changes were based upon a mineral map from an X-ray computed tomography image of a sandstone core. We studied the effect of these changes on upscaled (pore-scale to core-scale) reaction rates and compared against the predictions of a continuum model. Specifically, we modeled anorthite and kaolinite reactions under acidic flow conditions during which the anorthite reactions remain far from equilibrium (dissolution only), while the kaolinite reactions can be near-equilibrium. Under dissolution changes, core-scale reaction rates continuously and nonlinearly evolved in time. At higher injection rates, agreement with predictions of the continuum model degraded significantly. For the far-from-equilibrium reaction, our results indicate that the ability to correctly capture the heterogeneity in dissolution changes in the reactive mineral surface area is critical to accurately predict upscaled reaction rates. For the near-equilibrium reaction, the ability to correctly capture the heterogeneity in the saturation state remains critical. Inclusion of a Nernst-Planck term to ensure neutral ionic currents under differential diffusion resulted in at most a 9% correction in upscaled rates.

  10. The kinetic of mass loss of grades A and B of melted TNT by isothermal and non-isothermal gravimetric methods

    Directory of Open Access Journals (Sweden)

    Hamid Reza Pouretedal

    2018-04-01

    Full Text Available The kinetic and activation energy of mass loss of two grades of melted TNT explosive, grade A and grade B, with freezing points of 80.57 and 78.15 °C, respectively, were studied by isothermal and non-isothermal gravimetric methods. In isothermal method, the mass loss of samples in containers of glass and aluminum was followed in temperatures of 80, 90 and 100 °C. The kinetic of the mass loss of the samples in the aluminum container was higher than the kinetic of it in the glass container that can be related to the effects of heat transfer and catalytic of aluminum metal. Also, the presence of impurities in grade B was due to increasing of kinetic of mass loss of it versus grade A. The non-isothermal curves were obtained in range of 30–330 °C at heating rates of 10, 15 and 20 °C⋅min−1. The TG/DTG data were used for determination of activation energy (Ea of mass loss of TNT samples upon degradation by using Ozawa, Kissinger, Ozawa-Flynn-Wall (OFW and Kissinger-Akahira-Sunose (KAS methods as model free methods. The activation energies of grades of A and B of TNT was obtained 99–120 and 66–70 kJ mol−1, respectively. The lower values of activation energy of the degradation reaction of grade B confirm the effect of impurities in the kinetics of mass loss of this grade. Keywords: TNT, Isothermal, Non-isothermal, Kinetic, Mass loss

  11. Assessment of Salmonella spp. and Escherichia coli O157:H7 growth on lettuce exposed to isothermal and non-isothermal conditions.

    Science.gov (United States)

    de Oliveira Elias, Susana; Noronha, Tiago Baptista; Tondo, Eduardo Cesar

    2018-06-01

    This study aimed to assess the growth of Salmonella and Escherichia coli O157:H7 on lettuce exposed to isothermal and non-isothermal conditions. Pathogens were inoculated on lettuce separately and stored under isothermal condition at 5 °C, 10 °C, 25 °C, 37 °C for both bacteria, at 40 °C for Salmonella and 42 °C for E. coli O157:H7. Growth curves were built by fitting the data to the Baranyi's DMFit, generating R 2 values greater than 0.92 for primary models. Secondary models were fitted with Ratkowsky equations, generating R 2 values higher than 0.91 and RMSE lower than 0.1. Experimental data showed that both bacteria could grow at all temperatures. Also, the growth of both pathogens under non-isothermal conditions was studied simulating temperatures found from harvest to supermarkets in Brazil. Models were analysed by R 2 , RMSE, bias factor (Bf) and accuracy factor (Af). Salmonella and E. coli O157:H7 were able to grow in this temperature profile and the models could predict the behavior of these microorganisms on lettuce under isothermal and non-isothermal conditions. Based on the results, a negligible growth time (ς) was proposed to provide the time which lettuce could be exposed to a specific temperature and do not present an expressive growth of bacteria. The ς was developed based on Baranyi's primary model equation and on growth potential concept. ς is the value of lag phase added of the time necessary to population grow 0.5 log CFU/g. The ς of lettuce exposed to 37 °C was 1.3 h, while at 5 °C was 3.3 days. Copyright © 2017 Elsevier Ltd. All rights reserved.

  12. Characterizing precipitate evolution of an Al–Zn–Mg–Cu-based commercial alloy during artificial aging and non-isothermal heat treatments by in situ electrical resistivity monitoring

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Fulin [College of Materials Science and Engineering, Hunan University, Changsha 410082 (China); Department of Materials Science and Engineering, McMaster University, 1280 Main Street West, Hamilton, Ontario L8S 4L7 (Canada); Zurob, Hatem S., E-mail: zurobh@mcmaster.ca [Department of Materials Science and Engineering, McMaster University, 1280 Main Street West, Hamilton, Ontario L8S 4L7 (Canada); Purdy, Gary R. [Department of Materials Science and Engineering, McMaster University, 1280 Main Street West, Hamilton, Ontario L8S 4L7 (Canada); Zhang, Hui, E-mail: zhanghui63hunu@163.com [College of Materials Science and Engineering, Hunan University, Changsha 410082 (China); Hunan Province Key Laboratory for Spray Deposition Technology and Application, Hunan University, Changsha 410082 (China)

    2016-07-15

    In situ electrical resistivity monitoring technique was employed to continuously evaluate the precipitate evolution of an Al–Zn–Mg–Cu-based commercial alloy during typical artificial aging treatments. The effects of artificial aging on the precipitates stability during non-isothermal heat treatments were also explored. Conventional hardness test, transmission electron microscopy and differential scanning calorimetry were also adopted to verify the electrical resistivity results. The results indicated that both the precipitation process and its timely rate could be followed by the monitored electrical resistivity during artificial aging treatments. The electrical resistivity results gave overall information on continuous precipitation and dissolution processes, especially under high heating rates. Samples artificial aging heat treated at 120 °C for 24 h followed by aging at 150 °C for 24 h presented more stable state and coarser precipitates than the samples only artificial aging heat treated at 120 °C for 24 h or triple artificial aging heat treated at 120 °C/24 h + 195 °C/15 min + 120 °/24 h. While the incoherent η precipitates in the samples artificial aging heat treated at 120 °C for 24 h followed by aging at 150 °C for 24 h were more easiness to coarsening and dissolve during non-isothermal heat treatments as well. - Highlights: • In situ electrical resistivity monitoring technique was employed on an Al-Zn-Mg-Cu alloy. • The precipitate evolution during typical artificial aging treatments was studied. • The precipitate stability during non-isothermal heat treatments was explored. • The electrical resistivity wonderfully monitored continuous precipitation and dissolution. • The alloy submitted to a T7 treatment presents a more stable state during heating due to incoherent η precipitates.

  13. Formulation of strongly non-local, non-isothermal dynamics for heterogeneous solids based on the GENERIC with application to phase-field modeling

    Science.gov (United States)

    Hütter, Markus; Svendsen, Bob

    2017-12-01

    The purpose of the current work is the formulation of models for conservative and non-conservative dynamics in solid systems with the help of the General Equation for the Non-Equilibrium Reversible-Irreversible Coupling (GENERIC: e.g., Grmela and Öttinger, Phys. Rev. E 56(6), 6620 (1997); Öttinger and Grmela, Phys. Rev. E 56(6), 6633 (1997)). In this context, the resulting models are inherently spatially strongly non-local (i.e., functional) and non-isothermal in character. They are applicable in particular to the modeling of phase transitions as well as mass and heat transport in multiphase, multicomponent solids. In the last part of the work, the strongly non-local model formulation is reduced to weakly non-local form with the help of generalized gradient approximation of the energy and entropy functionals. On this basis, the current model formulation is shown to be consistent with and reduce to a recent non-isothermal generalization (Gladkov et al., J. Non-Equilib. Thermodyn. 41(2), 131 (2016)) of the well-known phase-field models of Cahn and Hilliard (J. Chem. Phys. 28(2), 258 (1958)) for conservative dynamics and of Allen and Cahn (Acta Metall. 27(6), 1085 (1979)) for non-conservative dynamics. Finally, the current approach is applied to derive a non-isothermal generalization of a phase-field crystal model for binary alloys (see, e.g., Elder et al., Phys. Rev. B 75(6), 064107 (2007)).

  14. Non-Isothermal Gas-Based Direct Reduction Behavior of High Chromium Vanadium-Titanium Magnetite Pellets and the Melting Separation of Metallized Pellets

    Directory of Open Access Journals (Sweden)

    Jue Tang

    2017-04-01

    Full Text Available The non-isothermal reduction behavior of high chromium vanadium-titanium magnetite (HCVTM pellets by gas mixtures was investigated using different heating rates (4, 8, and 12 K/min and varied gas compositions (H2/CO = 2/5, H2/CO = 1/1, and H2/CO = 5/2 volume ratios; the pellets were then used for melting separation. It was observed that the temperature corresponding to the maximum reduction ratio increased with the increasing heating rate. The HCVTM pellets reached the same final reduction ratio under a given reducing gas composition, although the heating rates were different. Under the same heating rate, the gas mixture with more H2 was conducive for obtaining a higher reduction ratio. The phase transformations during the non-isothermal reduction were ordered as follows: Fe2O3 → Fe3O4 → FeO → Fe; Fe9TiO15 + Fe2Ti3O9 → Fe2.75Ti0.25O4 → FeTiO3 → TiO2; V1.7Cr0.3O3 → V2O3 → Fe2VO4; Fe1.2Cr0.8O3 → Cr2O3 → FeCr2O4. The non-isothermal reduction kinetic model was established based on the unreacted core model with multiple reaction interfaces. The correlation coefficients were greater than 0.99, revealing that this kinetic model could properly describe the non-isothermal reduction of the HCVTM pellets by gas mixtures. Iron containing V and Cr along with the Ti-rich slag was obtained through the melting separation of the metallized HCVTM pellets. The mass fractions and recovery rates of Fe, V, and Cr in the iron were 93.87% and 99.45%, 0.91% and 98.83%, and 0.72% and 95.02%, respectively. The mass fraction and recovery rate of TiO2 in the slag were 38.12% and 95.08%, respectively.

  15. An attempt to model the probability of growth and aflatoxin B1 production of Aspergillus flavus under non-isothermal conditions in pistachio nuts.

    Science.gov (United States)

    Aldars-García, Laila; Ramos, Antonio J; Sanchis, Vicente; Marín, Sonia

    2015-10-01

    Human exposure to aflatoxins in foods is of great concern. The aim of this work was to use predictive mycology as a strategy to mitigate the aflatoxin burden in pistachio nuts postharvest. The probability of growth and aflatoxin B1 (AFB1) production of aflatoxigenic Aspergillus flavus, isolated from pistachio nuts, under static and non-isothermal conditions was studied. Four theoretical temperature scenarios, including temperature levels observed in pistachio nuts during shipping and storage, were used. Two types of inoculum were included: a cocktail of 25 A. flavus isolates and a single isolate inoculum. Initial water activity was adjusted to 0.87. Logistic models, with temperature and time as explanatory variables, were fitted to the probability of growth and AFB1 production under a constant temperature. Subsequently, they were used to predict probabilities under non-isothermal scenarios, with levels of concordance from 90 to 100% in most of the cases. Furthermore, the presence of AFB1 in pistachio nuts could be correctly predicted in 70-81 % of the cases from a growth model developed in pistachio nuts, and in 67-81% of the cases from an AFB1 model developed in pistachio agar. The information obtained in the present work could be used by producers and processors to predict the time for AFB1 production by A. flavus on pistachio nuts during transport and storage. Copyright © 2015 Elsevier Ltd. All rights reserved.

  16. Effect of inflow condition on near-field prediction of Large Eddy Simulations of isothermal and non-isothermal turbulent jets

    Science.gov (United States)

    Salkhordeh, Sasan; Kimber, Mark

    2017-11-01

    In order to develop an experimentally validated computational model, turbulent round jets have been studied extensively under both isothermal and non-isothermal conditions using Large Eddy Simulation (LES) methodology. Capturing the near-field physics of a turbulent jet has been a challenge when utilizing LES. To address this concern, the effect of inlet flow profile and turbulent fluctuations on the evolution of both type of jets has been analyzed in detail by performing separate large eddy simulations of the flow in the nozzle upstream of the jet inlet to accurately determine the inlet turbulent spectra. From the precursor simulations, the accurate turbulence fluctuations at the jet nozzle can be sampled and then implement to the inlet boundary of the main jet simulation. Properly specifying the turbulent fluctuations at the jet inlet was found to play a vital role in order to accurately predict key characteristics throughout the computational domain. For isothermal jets, the experimental measurements of Hussein et al. (Journal of Fluid Mechanics. 1994 Jan;258:31-75) has been simulated computationally using LES. The experimental measurement of Mi et al. (Journal of Fluid Mechanics. 2001 Apr;432:91-125) has been chosen for performing LES for a non-isothermal jet at the same Reynolds number and identical temperature difference. The LES results show good agreement for first and higher order statistics of velocities and temperatures in both near field and far-field data.

  17. Design of a Seismic Reflection Multi-Attribute Workflow for Delineating Karst Pore Systems Using Neural Networks and Statistical Dimensionality Reduction Techniques

    Science.gov (United States)

    Ebuna, D. R.; Kluesner, J.; Cunningham, K. J.; Edwards, J. H.

    2016-12-01

    An effective method for determining the approximate spatial extent of karst pore systems is critical for hydrological modeling in such environments. When using geophysical techniques, karst features are especially challenging to constrain due to their inherent heterogeneity and complex seismic signatures. We present a method for mapping these systems using three-dimensional seismic reflection data by combining applications of machine learning and modern data science. Supervised neural networks (NN) have been successfully implemented in seismic reflection studies to produce multi-attributes (or meta-attributes) for delineating faults, chimneys, salt domes, and slumps. Using a seismic reflection dataset from southeast Florida, we develop an objective multi-attribute workflow for mapping karst in which potential interpreter bias is minimized by applying linear and non-linear data transformations for dimensionality reduction. This statistical approach yields a reduced set of input seismic attributes to the NN by eliminating irrelevant and overly correlated variables, while still preserving the vast majority of the observed data variance. By initiating the supervised NN from an eigenspace that maximizes the separation between classes, the convergence time and accuracy of the computations are improved since the NN only needs to recognize small perturbations to the provided decision boundaries. We contend that this 3D seismic reflection, data-driven method for defining the spatial bounds of karst pore systems provides great value as a standardized preliminary step for hydrological characterization and modeling in these complex geological environments.

  18. Pore network modeling to explore the effects of compression on multiphase transport in polymer electrolyte membrane fuel cell gas diffusion layers

    Science.gov (United States)

    Fazeli, Mohammadreza; Hinebaugh, James; Fishman, Zachary; Tötzke, Christian; Lehnert, Werner; Manke, Ingo; Bazylak, Aimy

    2016-12-01

    Understanding how compression affects the distribution of liquid water and gaseous oxygen in the polymer electrolyte membrane fuel cell gas diffusion layer (GDL) is vital for informing the design of improved porous materials for effective water management strategies. Pore networks extracted from synchrotron-based micro-computed tomography images of compressed GDLs were employed to simulate liquid water transport in GDL materials over a range of compression pressures. The oxygen transport resistance was predicted for each sample under dry and partially saturated conditions. A favorable GDL compression value for a preferred liquid water distribution and oxygen diffusion was found for Toray TGP-H-090 (10%), yet an optimum compression value was not recognized for SGL Sigracet 25BC. SGL Sigracet 25BC exhibited lower transport resistance values compared to Toray TGP-H-090, and this is attributed to the additional diffusion pathways provided by the microporous layer (MPL), an effect that is particularly significant under partially saturated conditions.

  19. Rigorous derivation of the effective model describing a non-isothermal fluid flow in a vertical pipe filled with porous medium

    Science.gov (United States)

    Beneš, Michal; Pažanin, Igor

    2017-11-01

    This paper reports an analytical investigation of non-isothermal fluid flow in a thin (or long) vertical pipe filled with porous medium via asymptotic analysis. We assume that the fluid inside the pipe is cooled (or heated) by the surrounding medium and that the flow is governed by the prescribed pressure drop between pipe's ends. Starting from the dimensionless Darcy-Brinkman-Boussinesq system, we formally derive a macroscopic model describing the effective flow at small Brinkman-Darcy number. The asymptotic approximation is given by the explicit formulae for the velocity, pressure and temperature clearly acknowledging the effects of the cooling (heating) and porous structure. The theoretical error analysis is carried out to indicate the order of accuracy and to provide a rigorous justification of the effective model.

  20. Kinetic Parameters of Non-Isothermal Thermogravimetric Non-Catalytic and Catalytic Pyrolysis of Empty Fruit Bunch with Alumina by Kissinger and Ozawa Methods

    Science.gov (United States)

    Rahayu Mohamed, Alina; Li, Nurfahani; Sohaimi, Khairunissa Syairah Ahmad; Izzati Iberahim, Nur; Munirah Rohaizad, Nor; Hamzah, Rosniza

    2018-03-01

    The non-isothermal thermogravimetric non-catalytic and catalytic empty fruit bunch (EFB) pyrolysis with alumina were performed at different heating rates of 10, 15, 20, 25, 30 and 40 K/min under nitrogen atmosphere at a flow rate of 100 ml/min under dynamic conditions from 301 K to 1273 K. The activation energy were calculated based on Kissinger and Ozawa methods. Both reactions followed first order reactions. By Kissinger method, the activation energy and Ln A values for non-catalytic and catalytic EFB pyrolysis with alumina were 188.69 kJ mol-1 and 201.67 kJ/mol respectively. By Ozawa method, the activation energy values for non-catalytic and catalytic EFB pyrolysis with alumina were 189.13 kJ/mol and 201.44 kJ/mol respectively. The presence of catalyst increased the activation energy values for EFB pyrolysis as calculated by Kissinger and Ozawa methods.

  1. Non-isothermal crystallization kinetics and fragility of (Cu46Zr47Al7)97Ti3 bulk metallic glass investigated by differential scanning calorimetry

    International Nuclear Information System (INIS)

    Zhu, Man; Li, Junjie; Yao, Lijuan; Jian, Zengyun; Chang, Fang’e; Yang, Gencang

    2013-01-01

    Highlights: • Non-isothermal crystallization kinetics of (Cu 46 Zr 47 Al 7 ) 97 Ti 3 BMGs was studied. • Two-stage of crystallization process is confirmed by DSC. • The nucleation process is difficult than growth process during crystallization. • The second crystallization process is the most sensitive to heating rate. • Kinetic fragility index is evaluated suggesting it is an intermediate glass. - Abstract: In this paper, bulk metallic glasses with the composition of (Cu 46 Zr 47 Al 7 ) 97 Ti 3 were prepared by copper mold casting technique. X-ray diffraction (XRD) and differential scanning calorimetry (DSC) were used to investigate its structure and non-isothermal crystallization kinetics. DSC traces revealed that it undergoes two-stage crystallization. The activation energies corresponding to the characteristic temperatures have been calculated, and the results reveal that the as-cast alloys have a good thermal stability in thermodynamics. Based on Kissinger equation, the activation energies for glass transition, the first and second crystallization processes were obtained as 485 ± 16 kJ/mol, 331 ± 7 kJ/mol and 210 ± 3 kJ/mol, respectively, suggesting that the nucleation process is more difficult than the grain growth process. The fitting curves using Lasocka's empirical relation show that the influence of the heating rate for crystallization is larger than glass transition. Furthermore, the kinetic fragility for (Cu 46 Zr 47 Al 7 ) 97 Ti 3 bulk metallic glasses is evaluated. Depending on the fragility index, (Cu 46 Zr 47 Al 7 ) 97 Ti 3 bulk metallic glasses should be considered as “intermediate glasses”

  2. Experimental study on imbibition displacement mechanisms of two-phase fluid using micromodel: Fracture network, distribution of pore size, and matrix construction

    Science.gov (United States)

    Jafari, Iman; Masihi, Mohsen; Nasiri Zarandi, Masoud

    2017-12-01

    In this study, the effect of different parameters on the fluid transport in a fractured micromodel has been investigated. All experiments in this study have been conducted in a glass micromodel. Since the state of wetting is important in the micromodel, the wetting experiments have been conducted to determine the state of wetting in the micromodel. The used micromodel was wet by water and non-wet regarding normal decane. The fracture network, distribution of pore size, matrix construction, and injection rate are the most important parameters affecting the process. Therefore, the influence of these parameters was studied using five different patterns (A to E). The obtained results from pattern A showed that increasing water injection the flow rate results in both higher rate of imbibition and higher ultimate recovery. Pattern B, which was characterized with higher porosity and permeability, was employed to study the effect of matrix pore size distribution on the imbibition process. Compared to pattern A, a higher normal decane production was observed in this pattern. Patterns C and D were designed to understand the impact of lateral fractures on the displacement process. Higher ultimate recoveries were obtained in these patterns. A system of matrix-fracture was designed (pattern E) to evaluate water injection performance in a multi-block system. Injection of water with the flow rate of 0.01 cc/min could produce 15% of the oil available in the system. While in the test with the flow rate of 0.1 cc/min, a normal decane recovery of 0.28 was achieved.

  3. Wet winter pore pressures in railway embankments

    OpenAIRE

    Briggs, Kevin M; Smethurst, Joel A; Powrie, William; O'Brien, Anthony S

    2013-01-01

    This paper demonstrates the influence of extreme wet winter weather on pore water pressures within clay fill railway embankments, using field monitoring data and numerical modelling. Piezometer readings taken across the London Underground Ltd network following the wet winter of 2000/2001 were examined, and showed occurrences of hydrostatic pore water pressure within embankments but also many readings below this. A correlation was found between the maximum pore water pressures and the permeabi...

  4. Monte Carlo modelling of non-isothermal degradation of two cyanidin-based anthocyanins in aqueous system at high temperatures and its impact on antioxidant capacities.

    Science.gov (United States)

    Sui, Xiaonan; Zhou, Weibiao

    2014-04-01

    The non-isothermal degradation of two cyanidin-based anthocyanins, cyanidin-3-glucoside and cyanidin-3-rutinoside, was investigated in aqueous system within the temperature range from 100 to 165 °C, and the degradation kinetics was modelled using Monte Carlo simulation. The two anthocyanins showed different stability, with cyanidin-3-glucoside exhibiting a higher degradation rate than cyanidin-3-rutinoside. The derived degradation rate at the reference temperature of 132.5 °C and activation energy of cyanidin-3-glucoside and cyanidin-3-rutinoside were 0.0047 and 0.0023 s(-1), and 87 and 104 kJ/mol, respectively. The antioxidant capacity of the thermally processed anthocyanins solutions was measured by using ABTS and DPPH assays. Results showed that the antioxidant capacity of the samples remained at the same level during the thermal treatment process under various conditions, i.e., there was no significant difference (P>0.05) in the antioxidant capacity amongst the samples despite their significantly different contents of the two anthocyanins. Copyright © 2013 Elsevier Ltd. All rights reserved.

  5. Entropy stable modeling of non-isothermal multi-component diffuse-interface two-phase flows with realistic equations of state

    KAUST Repository

    Kou, Jisheng

    2018-02-25

    In this paper, we consider mathematical modeling and numerical simulation of non-isothermal compressible multi-component diffuse-interface two-phase flows with realistic equations of state. A general model with general reference velocity is derived rigorously through thermodynamical laws and Onsager\\'s reciprocal principle, and it is capable of characterizing compressibility and partial miscibility between multiple fluids. We prove a novel relation among the pressure, temperature and chemical potentials, which results in a new formulation of the momentum conservation equation indicating that the gradients of chemical potentials and temperature become the primary driving force of the fluid motion except for the external forces. A key challenge in numerical simulation is to develop entropy stable numerical schemes preserving the laws of thermodynamics. Based on the convex-concave splitting of Helmholtz free energy density with respect to molar densities and temperature, we propose an entropy stable numerical method, which solves the total energy balance equation directly, and thus, naturally satisfies the first law of thermodynamics. Unconditional entropy stability (the second law of thermodynamics) of the proposed method is proved by estimating the variations of Helmholtz free energy and kinetic energy with time steps. Numerical results validate the proposed method.

  6. Characterization, non-isothermal decomposition kinetics and photocatalytic water splitting of green chemically synthesized polyoxoanions of molybdenum containing phosphorus as hetero atom

    International Nuclear Information System (INIS)

    D’Cruz, Bessy; Samuel, Jadu; George, Leena

    2014-01-01

    Highlights: • CPM nanorods were synthesized by applying the principles of green chemistry. • The isoconversional method was used to analyze the effective activation energy. • The appropriate reaction models of the two decomposition stages were determined. • Photocatalytic water splitting was investigated in the presence of platinum co-catalyst. - Abstract: In here, the green synthesis and thermal characterization of a novel polyoxoanions of molybdenum containing phosphorus as hetero atom are reported. The composition and morphology of the nanorods were established by fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA) and inductively coupled plasma atomic emission spectroscopic (ICP-AES) techniques. Thermal properties of the nanoparticles were investigated by non-isothermal analysis under nitrogen atmosphere. The values activation energy of each stage of thermal decomposition for all heating rates was calculated by Flynn–Wall–Ozawa (FWO) and Kissinger–Akahira–Sunnose (KAS) methods. Invariant kinetic parameter (IKP) method and master plot method were also used to evaluate the kinetic parameters and mechanism for the thermal decomposition of cetylpyridinium phosphomolybdate (CPM). Photocatalytic water oxidation mechanism using CPM catalyst in the presence of platinum (Pt) co-catalyst enhances the H 2 evolution and was found to be 1.514 mmol/g/h

  7. Non-isothermal crystallization kinetics of Fe2O3-CaO-SiO2 glass containing nucleation agent P2O5/TiO2

    Science.gov (United States)

    Li, Bin; Wang, Yongya; Luo, Wenqin; Li, Jingfen; Li, Jianyou

    2017-03-01

    Fe2O3-CaO-SiO2 glass ceramics containing nucleation agent P2O5/TiO2 were prepared by sol-gel method. The samples were characterized by X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The activation energy and kinetic parameters for crystallization of the samples were calculated by the Johnson-Mehi-Avrami (JMA) model and Augis-Bennett method according to the results of DSC. The results showed that the crystallization mechanism of Fe2O3-CaO-SiO2 glass, whose non-isothermal kinetic parameter n = 2.3, was consistent with surface crystallization of the JMA model. The kinetics model function of Fe2O3-CaO-SiO2 glass, f(α) = 2.3(1-α)[-ln(1-α)]0.57, was also obtained. The addition of nucleation agent P2O5/TiO2 could reduce the activation energy, which made the crystal growth modes change from onedimensional to three-dimensional.

  8. Multivariate data analysis as a tool to investigate the reaction kinetics of intramolecular cyclization of enalapril maleate studied by isothermal and non-isothermal FT-IR microscopy.

    Science.gov (United States)

    Widjaja, Effendi; Lim, Geok Hong; Chow, Pui Shan; Tan, Selvi

    2007-12-01

    In this paper, the use of multivariate data analysis approach to investigate the kinetics of solid-state reaction monitored via FT-IR thermal microscopy is discussed. The solid-state degradation of enalapril maleate was monitored non-isothermally at temperature range from 25 to 200 degrees C and isothermally at various temperatures (115, 120, 125, 130, and 135 degrees C) for a few hours. The collected FT-IR spectra were subjected to self-modeling curve resolution (SMCR) in order to elucidate the pure component spectral estimates. Subsequently, the relative contributions from the observed species could be obtained by projecting the pure component spectral estimates onto the collected FT-IR spectra. Accordingly, the conversion factors from enalapril maleate to diketopiperazine were calculated and were fitted to various solid-state reaction models. The activation energy values (E(a)) calculated from seven nucleation models were ranging from 176.4 to 193.9 kJ/mol. This multivariate data analysis approach proves to be an effective tool for analyzing the kinetic spectroscopic data having a high degree of overlap between original compound and its degradation product since the information from the whole spectral range is used.

  9. Effects of pressure, temperature, and treatment time on oscillatory rheological properties and non-isothermal gelatinization kinetics of chickpea (Cicer arietinum L.) flour slurry

    Science.gov (United States)

    Canet, W.; Cuesta, F. J.; Fuentes, R.; Alvarez, M. D.

    2017-10-01

    The effect of high hydrostatic pressure (HHP), temperature at pressurization, and treatment time at three levels (200, 400, 600 MPa; 10, 25, 50 °C 5, 15, 25 min) on the gelatinization of chickpea flour (CF) slurry during non-isothermal heating from 25 to 95 °C and gel rheological properties after subsequent cooling to 25 °C was investigated. CF gelatinization kinetics from the cross-over of elastic modulus (G’) and viscous modulus (G″) to 95 °C were considered for rate estimation. Zero-order reaction kinetics adequately described the CF gelatinization process. Structure development rate (dG‧/dt) is described by two exponential functions with activation energies ranging from 51.2 to 576.6 and -128.9 to 538.9 kJ mol-1 for downward and upward gelatinization curves, respectively. Changes in dG‧/dt vs. temperature seem to be closely related to the degree of gelatinization induced by HHP pre-treatment.

  10. Rheometric Non-Isothermal Gelatinization Kinetics of Chickpea Flour-Based Gluten-Free Muffin Batters with Added Biopolymers

    Directory of Open Access Journals (Sweden)

    María Dolores Alvarez

    2017-01-01

    Full Text Available An attempt was made to analyze the elastic modulus (G0 of chickpea flour (CF-based muffin batters made with CF alone and with added biopolymers (whey protein (WP, xanthan gum (XG, inulin (INL, and their blends in order to evaluate their suitability to be a wheat flour (WF substitute in muffins, and to model the heat-induced gelatinization of batters under non-isothermal heating condition from 25 ◦C to 90 ◦C. A rheological approach is proposed to determine the kinetic parameters (reaction order (n, frequency factor (k0, and activation energy (Ea using linearly-increasing temperature. Zero-order reaction kinetics adequately described batter gelatinization process, therefore assuming a constant rate independent of the initial G0 value. The change of the derivative of G0 with respect to time (dG0/dt versus temperature is described by one exponential function with activation energies ranging from 118 to 180 kJ·mol−1. Control wheat gluten batter, with higher and lower starch and protein contents, respectively, than CF-based batters, exhibited the highest Ea value. Formulation of CF-based gluten-free batters with starch and protein contents closer to the levels of WF-based batter could be a strategy to decrease differences in kinetic parameters of muffin batters and, therefore, in technological characteristics of baked muffins.

  11. Isothermal and Non-Isothermal Crystallization Studies of Long Chain Branched Polypropylene Containing Poly(ethylene-co-octene under Quiescent and Shear Conditions

    Directory of Open Access Journals (Sweden)

    Zinan Zhang

    2017-06-01

    Full Text Available Isothermal and non-isothermal crystallization behaviours of the blends of long chain branched polypropylene (LCB PP and poly(ethylene-co-octene (PEOc with different weight ratios were studied under quiescent and shear flow using polarized optical microscopy (POM, differential scanning calorimetry (DSC, and rheological measurements. Experimental results showed that the crystallization of the LCB PP/PEOc blends were significantly accelerated due to the existence of the long chain branches (LCBs, the blends being able to rapidly crystallize even at 146 °C. The addition of PEOc that acts as a nucleating agent, could also increase the crystallization rate of LCB PP. However, the crystallization rate of LCB PP was reduced when the PEOc concentration was more than 60 wt %, showing a retarded crystallization growth mechanism. The morphology of the binary blend was changed from a sea-island structure to a co-continuous phase structure when the PEOc concentration was increased from 40 to 60 wt %. In comparison with linear isotactic iPP/PEOc, the interfacial tension between LCB PP and PEOc was increased. In addition, flow-induced crystallization of LCB PP/PEOc blends was observed. Possible crystallization mechanisms for both LCB PP/PEOc and iPP/PEOc blends were proposed.

  12. Computational solutions for non-isothermal, nonlinear magneto-convection in porous media with hall/ionslip currents and ohmic dissipation

    Directory of Open Access Journals (Sweden)

    O. Anwar Bég

    2016-03-01

    Full Text Available A theoretical and numerical study is presented to analyze the nonlinear, non-isothermal, magnetohydrodynamic (MHD free convection boundary layer flow and heat transfer in a non-Darcian, isotropic, homogenous porous medium, in the presence of Hall currents, Ionslip currents, viscous heating and Joule heating. A power-law variation is used for the temperature at the wall. The governing nonlinear coupled partial differential equations for momentum conservation in the x and z directions and heat conservation, in the flow regime are transformed from an (x, y, z coordinate system to a (ξ,η coordinate system in terms of dimensionless x-direction velocity (∂F/∂η and z-direction velocity (G and dimensionless temperature function (H under appropriate boundary conditions. Both Darcian and Forchheimer porous impedances are incorporated in both momentum equations. Computations are also provided for the variation of the x and z direction shear stress components and also local Nusselt number. Excellent correlation is achieved with a Nakamura tridiagonal finite difference scheme (NTM. The model finds applications in magnetic materials processing, MHD power generators and purification of crude oils.

  13. Prediction of capillary hysteresis in a porous material using lattice-Boltzmann methods and comparison to experimental data and a morphological pore network model

    Science.gov (United States)

    Ahrenholz, B.; Tölke, J.; Lehmann, P.; Peters, A.; Kaestner, A.; Krafczyk, M.; Durner, W.

    2008-09-01

    In this work we use two numerical methods which rely only on the geometry and material parameters to predict capillary hysteresis in a porous material. The first numerical method is a morphological pore network (MPN) model, where structural elements are inserted into the imaged pore space to quantify the local capillary forces. Then, based on an invasion-percolation mechanism, the fluid distribution is computed. The second numerical method is a lattice-Boltzmann (LB) approach which solves the coupled Navier-Stokes equations for both fluid phases and describes the dynamics of the fluid/fluid interface. We have developed an optimized version of the model proposed in [Tölke J, Freudiger S, Krafczyk M. An adaptive scheme for LBE multiphase flow simulations on hierarchical grids, Comput. Fluids 2006;35:820-30] for the type of flow problems encountered in this work. A detailed description of the model and an extensive validation of different multiphase test cases have been carried out. We investigated pendular rings in a sphere packing, static and dynamic capillary bundle models and the residual saturation in a sphere packing. A sample of 15 mm in diameter filled with sand particles ranging from 100 to 500 μm was scanned using X-rays from a synchrotron source with a spatial resolution of 11 μm. Based on this geometry we computed the primary drainage, the first imbibition and the secondary drainage branch of the hysteresis loop using both approaches. For the LB approach, we investigated the dependence of the hysteresis loop on the speed of the drainage and the imbibition process. Furthermore we carried out a sensitivity analysis by simulating the hysteretic effect in several subcubes of the whole geometry with extremal characteristic properties. The predicted hysteretic water retention curves were compared to the results of laboratory experiments using inverse modeling based on the Richards equation. A good agreement for the hysteresis loop between the LB and MPN model

  14. Modeling of the non isothermal and non isobaric transformations kinetics. Application to the kaolinite de-hydroxylation and to the tri-uranium octo-oxide reduction by hydrogen; Modelisation de la cinetique de transformations non isothermes et (ou) non isobares. Application a la deshydroxylation de la kaolinite et a la reduction de l'octooxyde de triuranium par l'hydrogene

    Energy Technology Data Exchange (ETDEWEB)

    Perrin, St

    2002-12-15

    The aim of this work is to be able to describe transformations, occurring when solids and gases are in non isothermal and non isobaric conditions, with kinetic models. A methodology has been used. Two essential processes have to be taken into account: the germination and the growth. The germs are supposed to be formed (at constant temperature and pressure) in the grains surface with a constant velocity by surface unit, (gamma), called germination surface frequency (number of germs.m{sup -2}.s{sup -1}. The growth velocity is characterized by a growth surface reactivity, (phi) (in mol.m{sup -2}.s{sup -1}). With an appropriate transformation model, it is possible to obtain the variations of (gamma) and (phi) in terms of the temperature and pressure which are then used in the calculation of the velocity in non isothermal and non isobaric conditions. In order to validate the developed method, two reactions have been studied. For the first one, the kaolinite de-hydroxylation, an anisotropic germination-growth model, where the step limiting the growth is a diffusion step, has been developed in order to explain the experimental kinetic curves. Nevertheless the velocity curves calculated from this model do not allow to describe the reaction for some temperature variations. This result shows the difficulty to precisely determine the germination surface frequency what induces an important approximation on the kinetic curves. The second reaction is the tri-uranium octo-oxide reduction by hydrogen. It has been shown that this reaction occurs according to three successive transformations. A kinetic model has been developed for each of these reactions considering germination as instantaneous. At last, in comparing this model with the experimental velocity curves, a very good agreement has been verified as well as for a temperature variation than for a hydrogen partial pressure change during the reaction. (O.M.)

  15. TOUGHREACT User's Guide: A Simulation Program for Non-isothermal Multiphase Reactive geochemical Transport in Variable Saturated Geologic Media

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Tianfu; Sonnenthal, Eric; Spycher, Nicolas; Pruess, Karsten

    2004-05-24

    Coupled modeling of subsurface multiphase fluid and heat flow, solute transport and chemical reactions can be used for the assessment of mineral alteration in hydrothermal systems, waste disposal sites, acid mine drainage remediation, contaminant transport, and groundwater quality. A comprehensive non-isothermal multi-component reactive fluid flow and geochemical transport simulator, TOUGHREACT, has been developed. A wide range of subsurface thermo-physical-chemical processes is considered under various thermohydrological and geochemical conditions of pressure, temperature, water saturation, and ionic strength. The program can be applied to one-, two- or three-dimensional porous and fractured media with physical and chemical heterogeneity. The model can accommodate any number of chemical species present in liquid, gas and solid phases. A variety of equilibrium chemical reactions are considered, such as aqueous complexation, gas dissolution/exsolution, and cation exchange. Mineral dissolution/precipitation can proceed either subject to local equilibrium or kinetic conditions. Changes in porosity and permeability due to mineral dissolution and precipitation can be considered. Linear adsorption and decay can be included. For the purpose of future extensions, surface complexation by double layer model is coded in the program. Xu and Pruess (1998) developed a first version of a non-isothermal reactive geochemical transport model, TOUGHREACT, by introducing reactive geochemistry into the framework of the existing multi-phase fluid and heat flow code TOUGH2 (Pruess, 1991). Xu, Pruess, and their colleagues have applied the program to a variety of problems such as: (1) supergene copper enrichment (Xu et al, 2001), (2) caprock mineral alteration in a hydrothermal system (Xu and Pruess, 2001a), and (3) mineral trapping for CO{sub 2} disposal in deep saline aquifers (Xu et al, 2003b and 2004a). For modeling the coupled thermal, hydrological, and chemical processes during

  16. Preparation, characterization, non-isothermal reaction kinetics, thermodynamic properties, and safety performances of high nitrogen compound: hydrazine 3-nitro-1,2,4-triazol-5-one complex.

    Science.gov (United States)

    Yi, Jian-Hua; Zhao, Feng-Qi; Gao, Hong-Xu; Xu, Si-Yu; Wang, Min-Chang; Hu, Rong-Zu

    2008-05-01

    A new high nitrogen compound hydrazine 3-nitro-1,2,4-triazol-5-one complex (HNTO) was prepared by the reaction of 3-nitro-1,2,4-triazol-5-one with hydrazine hydrate, and its structure was characterized by means of organic elemental analyzer, FT-IR, XRD, (13)C NMR and (15)N NMR. The non-isothermal reaction kinetics of the main exothermic decomposition reaction of HNTO was investigated by means of DSC. The thermodynamic properties of HNTO were calculated. The results showed that the formation of HNTO is achieved by proton transfer of N(4) atom, and it makes a higher nitrogen content and lower acidity. The reaction mechanism of HNTO is classified as nucleation and growth, and the mechanism function is Avramo-Erofeev equation with n=2/5. The kinetic parameters of the reaction are E(a)=195.29 kJ mol(-1), lg(A (s(-1)))=19.37, respectively. The kinetic equation can be expressed as: d(alpha)/d(t) = 10(18.97)(1 - alpha)[-ln(1 - alpha)](3/5) e(-2.35 x 10(4)/T). The safety performances of HNTO were carried out. The critical temperature of thermal explosion are 464.26 and 474.37 K, the adiabatic time-to-explosion is 262s, the impact sensitivity H(50)=45.7 cm, the friction sensitivity P=20% and the electrostatic spark sensitivity E(50)>5.4J (no ignition). It shows that HNTO has an insensitive nature as RDX and NTO, etc.

  17. Evaluation of the Weibull and log normal distribution functions as survival models of Escherichia coli under isothermal and non isothermal conditions.

    Science.gov (United States)

    Aragao, Glaucia M F; Corradini, Maria G; Normand, Mark D; Peleg, Micha

    2007-11-01

    Published survival curves of Escherichia coli in two growth media, with and without the presence of salt, at various temperatures and in a Greek eggplant salad having various levels of essential oil, all had a characteristic downward concavity when plotted on semi logarithmic coordinates. Some also exhibited what appeared as a 'shoulder' of considerable length. Regardless of whether a shoulder was noticed, the survival pattern could be considered as a manifestation of an underlying unimodal distribution of the cells' death times. Mathematically, the data could be described equally well by the Weibull and log normal distribution functions, which had similar modes, means, standard deviations and coefficients of skewness. When plotted in their probability density function (PDF) form, the curves also appeared very similar visually. This enabled us to quantify and compare the effect of temperature or essential oil concentration on the organism's survival in terms of these temporal distributions' characteristics. Increased lethality was generally expressed in a shorter mean and mode, a smaller standard deviation and increased overall symmetry as judged by the distributions' degree of skewness. The 'shoulder', as expected, simply indicated that the distribution's standard deviation was much smaller than its mode. Rate models based on the two distribution functions could be used to predict non isothermal survival patterns. They were derived on the assumption that the momentary inactivation rate is the isothermal rate at the momentary temperature at a time that corresponds to the momentary survival ratio. In this application, however, the Weibullian model with a fixed power was not only simpler and more convenient mathematically than the one based on the log normal distribution, but it also provided more accurate estimates of the dynamic inactivation patterns.

  18. 3D imaging using X-Ray tomography and SEM combined FIB to study non isothermal creep damage of (111) oriented samples of γ / γ ′ nickel base single crystal superalloy MC2

    KAUST Repository

    Jouiad, Mustapha

    2012-01-01

    An unprecedented investigation consisting of the association of X-Ray tomography and Scanning Electron Microscopy combined with Focus Ion Beam (SEM-FIB) is conducted to perform a 3D reconstruction imaging. These techniques are applied to study the non-isothermal creep behavior of close (111) oriented samples of MC2 nickel base superalloys single crystal. The issue here is to develop a strategy to come out with the 3D rafting of γ\\' particles and its interaction whether with dislocation structures or/and with the preexisting voids. This characterization is uncommonly performed away from the conventional studied orientation [001] in order to feed the viscoplastic modeling leading to its improvement by taking into account the crystal anisotropy. The creep tests were performed at two different conditions: classical isothermal tests at 1050°C under 140 MPa and a non isothermal creep test consisting of one overheating at 1200°C and 30 seconds dwell time during the isothermal creep life. The X-Ray tomography shows a great deformation heterogeneity that is pronounced for the non-isothermal tested samples. This deformation localization seems to be linked to the preexisting voids. Nevertheless, for both tested samples, the voids coalescence is the precursor of the observed damage leading to failure. SEM-FIB investigation by means of slice and view technique gives 3D views of the rafted γ\\' particles and shows that γ corridors evolution seems to be the main creep rate controlling parameter. © 2012 Trans Tech Publications, Switzerland.

  19. Quantification and Prediction of the 3D Pore Network Evolution in Carbonate Reservoir Rocks Quantification et prédiction de l’évolution d’un réseau 3D de pores dans des roches réservoir de carbonates

    Directory of Open Access Journals (Sweden)

    De Boever E.

    2012-02-01

    Full Text Available This study presents an integrated approach that allows the reconstruction and prediction of 3D pore structure modifications and porosity/permeability development throughout carbonate diagenesis. Reactive Pore Network Models (PNM-R can predict changes in the transport properties of porous media, resulting from dissolution/cementation phenomena. The validity and predictability of these models however depend on the representativeness of the equivalent pore networks used and on the equations and parameters used to model the diagenetic events. The developed approach is applied to a real case of a dolostone rock of the Middle East Arab Formation. Standard 2D microscopy shows that the main process affecting the reservoir quality is dolomitisation, followed by porosity enhancement due to dolomite dissolution and secondary porosity destruction by cementation of late diagenetic anhydrite. X-ray μ-CT allows quantifying the 3D volume and distribution of the different sample constituents. Results are compared with lab measurements. Equivalent pore networks before dolomite dissolution and prior to late anhydrite precipitation are reconstructed and used to simulate the porosity, permeability characteristics at these diagenetic steps. Using these 3D pore structures, PNM-R can trace plausible porosity-permeability evolution paths between these steps. The flow conditions and reaction rates obtained by geochemical reaction path modeling can be used as reference to define PNM-R model parameters. The approach can be used in dynamic rock typing and the upscaling of petrophysical properties, necessary for reservoir modeling. Cette étude présente une approche intégrée qui permet la reconstruction et la prédiction des modifications de structure 3D de pores ainsi que le développement de la porosité/perméabilité tout au long de la diagenèse des carbonates. Des modèles de réseau de pores réactifs peuvent prédire les changements en matière de propriétés de

  20. Laboratory Investigation of Rheology and Infiltration Process of Non-Newtonian Fluids through Porous Media in a Non-Isothermal Flow Regime for Effective Remediation of Contaminants

    Science.gov (United States)

    Naseer, F.

    2017-12-01

    Contamination of soil and groundwater by adsorbent (persistent) contaminants have been a major concern. Mine tailings, Acid mine drainage, waste disposal areas, active or abandoned surface and underground mines are some major causes of soil and water contamination. It is need of the hour to develop cost effective and efficient remediation techniques for clean-up of soil and aquifers. The objective of this research is to study a methodology of using non-Newtonian fluids for effective remediation of adsorbent contaminants in porous media under non-isothermal flow regimes. The research comprises of three components. Since, non-Newtonian fluid rheology has not been well studied in cold temperatures, the first component of the objective is to expose a non-Newtonian fluid (Guar gum solution) to different temperatures ranging from 30 °C through -5 °C to understand the change in viscosity, shear strength and contact angle of the fluid. Study of the flow characteristic of non-Newtonian fluids in complex porous media has been limited. Hence, the second component of this study will focus on a comparison of flow characteristics of a Newtonian fluid, non-Newtonian fluid and a combination of both fluids in a glass-tube-bundle setup that will act as a synthetic porous media. The study of flow characteristics will also be done for different thermal regimes ranging from -5 °C to 30 °C. The third component of the research will be to compare the effectiveness Guar gum to remediate a surrogate adsorbed contaminant at a certain temperature from the synthetic porous media. Guar gum is biodegradable and hence it is benign to the environment. Through these experiments, the mobility and behavior of Guar gum under varying temperature ranges will be characterized and its effectiveness in removing contaminants from soils will be understood. The impact of temperature change on the fluid and flow stability in the porous medium will be examined in this research. Guar gum is good suspension

  1. Analytical solutions for non-linear conversion of a porous solid particle in a gas–II. Non-isothermal conversion and numerical verification

    NARCIS (Netherlands)

    Brem, Gerrit; Brouwers, J.J.H.

    1990-01-01

    In Part I, analytical solutions were given for the non-linear isothermal heterogeneous conversion of a porous solid particle. Account was taken of a reaction rate of general order with respect to the gas reactant, intrinsic reaction surface area and effective pore diffusion, which change with solid

  2. Eulerian-Lagrangian simulation of non-isothermal gas-solid flows: particle-turbulence interactions in pipe flows; Simulation eulerienne-lagrangienne d'ecoulements gaz-solide non isothermes: interactions particules-turbulence, application aux ecoulements en conduite

    Energy Technology Data Exchange (ETDEWEB)

    Chagras, V.

    2004-03-15

    The aim of this work is to contribute to the numerical modeling of turbulent gas-solid flows in vertical or horizontal non isothermal pipes, which can be found in many industrial processes (pneumatic transport, drying, etc). The model is based on an Eulerian-Lagrangian approach allowing a fine description of the interactions between the two phases (action of the fluid upon the particles (dispersion), action of the particles upon the fluid (two way coupling) and between particles (collisions)), more or less influential according to the characteristics of the flow. The influence of the gas phase turbulence on the particle motion is taken into account using a non-isotropic dispersion model, which allows the generation of velocity and temperature fluctuations of the fluid seen by the particles. The numerical developments brought to the model for vertical and horizontal pipe flow have been validated by comparison with available experimental results from the literature. The sensitivity tests highlight the influence of the dispersion model, collisions and turbulence modulation (direct and non direct modifications ) on the dynamic and thermal behavior of the suspension. The model is able to predict the heat exchanges in the presence of particles for a wide range of flows in vertical and horizontal pipes. However numerical problems still exist in two-way coupling for very small particles and loading ratios above one. This is related to the problems encountered when modeling the coupling terms between the two phases (parameters C{sub {epsilon}}{sub 2} and C{sub {epsilon}}{sub 3} ) involved in the turbulence dissipation balance. (author)

  3. Reconstituted Fusion Pore

    OpenAIRE

    Jeremic, Aleksandar; Kelly, Marie; Cho, Sang-Joon; Stromer, Marvin H.; Jena, Bhanu P.

    2003-01-01

    Fusion pores or porosomes are basket-like structures at the cell plasma membrane, at the base of which, membrane-bound secretory vesicles dock and fuse to release vesicular contents. Earlier studies using atomic force microscopy (AFM) demonstrated the presence of fusion pores at the cell plasma membrane in a number of live secretory cells, revealing their morphology and dynamics at nm resolution and in real time. ImmunoAFM studies demonstrated the release of vesicular contents through the por...

  4. Nuclear pore complex tethers to the cytoskeleton.

    Science.gov (United States)

    Goldberg, Martin W

    2017-08-01

    The nuclear envelope is tethered to the cytoskeleton. The best known attachments of all elements of the cytoskeleton are via the so-called LINC complex. However, the nuclear pore complexes, which mediate the transport of soluble and membrane bound molecules, are also linked to the microtubule network, primarily via motor proteins (dynein and kinesins) which are linked, most importantly, to the cytoplasmic filament protein of the nuclear pore complex, Nup358, by the adaptor BicD2. The evidence for such linkages and possible roles in nuclear migration, cell cycle control, nuclear transport and cell architecture are discussed. Copyright © 2017. Published by Elsevier Ltd.

  5. Modeling of the non isothermal and non isobaric transformations kinetics. Application to the kaolinite de-hydroxylation and to the tri-uranium octo-oxide reduction by hydrogen

    International Nuclear Information System (INIS)

    Perrin, St.

    2002-12-01

    The aim of this work is to be able to describe transformations, occurring when solids and gases are in non isothermal and non isobaric conditions, with kinetic models. A methodology has been used. Two essential processes have to be taken into account: the germination and the growth. The germs are supposed to be formed (at constant temperature and pressure) in the grains surface with a constant velocity by surface unit, (gamma), called germination surface frequency (number of germs.m -2 .s -1 . The growth velocity is characterized by a growth surface reactivity, (phi) (in mol.m -2 .s -1 ). With an appropriate transformation model, it is possible to obtain the variations of (gamma) and (phi) in terms of the temperature and pressure which are then used in the calculation of the velocity in non isothermal and non isobaric conditions. In order to validate the developed method, two reactions have been studied. For the first one, the kaolinite de-hydroxylation, an anisotropic germination-growth model, where the step limiting the growth is a diffusion step, has been developed in order to explain the experimental kinetic curves. Nevertheless the velocity curves calculated from this model do not allow to describe the reaction for some temperature variations. This result shows the difficulty to precisely determine the germination surface frequency what induces an important approximation on the kinetic curves. The second reaction is the tri-uranium octo-oxide reduction by hydrogen. It has been shown that this reaction occurs according to three successive transformations. A kinetic model has been developed for each of these reactions considering germination as instantaneous. At last, in comparing this model with the experimental velocity curves, a very good agreement has been verified as well as for a temperature variation than for a hydrogen partial pressure change during the reaction. (O.M.)

  6. Capillary pressure at irregularly shaped pore throats: Implications for water retention characteristics

    Science.gov (United States)

    Suh, Hyoung Suk; Kang, Dong Hun; Jang, Jaewon; Kim, Kwang Yeom; Yun, Tae Sup

    2017-12-01

    The random shapes of pore throats in geomaterials hinder accurate estimation of capillary pressure, and conventional pore network models that simply use the Young-Laplace equation assuming circular pore throats overestimate the capillary pressure. As a solution to this problem that does not complicate the pore network model or slow its implementation, we propose a new morphological analysis method to correlate the capillary pressure at an irregular pore channel with its cross-sectional geometry using lattice Boltzmann (LB) simulation and Mayer and Stowe-Princen theory. Geometry-based shape factors for pore throats are shown here to correlate strongly with the capillary pressure obtained by LB simulation. Water retention curves obtained by incorporating the morphological calibration into conventional pore network simulation and their correlative scheme agree well with experimental data. The suggested method is relevant to pore-scale processes such as geological CO2 sequestration, methane bubbling from wetlands, and enhanced carbon recovery.

  7. Measurements of pore-scale flow through apertures

    Energy Technology Data Exchange (ETDEWEB)

    Chojnicki, Kirsten [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2017-09-01

    Pore-scale aperture effects on flow in pore networks was studied in the laboratory to provide a parameterization for use in transport models. Four cases were considered: regular and irregular pillar/pore alignment with and without an aperture. The velocity field of each case was measured and simulated, providing quantitatively comparable results. Two aperture effect parameterizations were considered: permeability and transmission. Permeability values varied by an order of magnitude between the cases with and without apertures. However, transmission did not correlate with permeability. Despite having much greater permeability the regular aperture case permitted less transmission than the regular case. Moreover, both irregular cases had greater transmission than the regular cases, a difference not supported by the permeabilities. Overall, these findings suggest that pore-scale aperture effects on flow though a pore-network may not be adequately captured by properties such as permeability for applications that are interested in determining particle transport volume and timing.

  8. The pore space scramble

    Science.gov (United States)

    Gormally, Alexandra; Bentham, Michelle; Vermeylen, Saskia; Markusson, Nils

    2015-04-01

    Climate change and energy security continue to be the context of the transition to a secure, affordable and low carbon energy future, both in the UK and beyond. This is reflected in for example, binding climate policy targets at the EU level, the introduction of renewable energy targets, and has also led to an increasing interest in Carbon Capture and Storage (CCS) technology with its potential to help mitigate against the effects of CO2 emissions from fossil fuel burning. The UK has proposed a three phase strategy to integrate CCS into its energy system in the long term focussing on off-shore subsurface storage (DECC, 2014). The potential of CCS therefore, raises a number of challenging questions and issues surrounding the long-term storage of CO2 captured and injected into underground spaces and, alongside other novel uses of the subsurface, contributes to opening a new field for discussion on the governance of the subsurface. Such 'novel' uses of the subsurface have lead to it becoming an increasingly contested space in terms of its governance, with issues emerging around the role of ownership, liability and property rights of subsurface pore space. For instance, questions over the legal ownership of pore space have arisen with ambiguity over the legal standpoint of the surface owner and those wanting to utilise the pore space for gas storage, and suggestions of whether there are depths at which legal 'ownership' becomes obsolete (Barton, 2014). Here we propose to discuss this 'pore space scramble' and provide examples of the competing trajectories of different stakeholders, particularly in the off-shore context given its priority in the UK. We also propose to highlight the current ambiguity around property law of pore space in the UK with reference to approaches currently taken in different national contexts. Ultimately we delineate contrasting models of governance to illustrate the choices we face and consider the ethics of these models for the common good

  9. Studying Pore Structure of Nonwovens with 3D Imaging and Modeling Permeability

    Science.gov (United States)

    Baradari, Mehdi Gholipour

    Nonwovens are classified as a porous material and pore structure is named as the most important and complex feature of them. Since pore structure is out of control during any nonwovens manufacturing processes, many attempts have been made to measure the major characteristics of a pore network including: pore size, pore volume, pore surface area and pore shape. Among all pore characteristics, pore size due to its significant influence on many nonwovens applications such as filtration is counted as the most significant one. Generally, experiment, theoretical modeling and image analysis are the most common methods to measure pore size of nonwovens. Normally, pores in nonwovens make many convergences and divergences along the length and for this reason, many pore diameters could be assigned for a media. Due to inefficiency of the aforementioned techniques to measure all these diameters, they are not precise enough to study pore structure. The initial objective of this research is obtaining information of the pore structure, especially pore sizes, by applying image analysis techniques to a 3D image of nonwovens obtained through 3D imaging techniques such as DVI and micro CT. This 3D structure of the nonwoven media will be transformed to a graph, employing skeletonization through AvizoRTM software. The obtained graph exhibits topology, shape and connectivity of the pore structure for the utilized nonwoven. In this graph, each node and link would be a representative for pores intersection and body of pore, respectively. Saving the information of this graph results to some matrices/vectors including nodes coordinated, connectivity and nodes thickness, which exhibits the pore size. Therefore, all the pore sizes available in the structure will be extracted through this method. As expected, the information obtained from pore network is very complex consisting many numbers, so analyse them would be very difficult. Therefore, it was tried to use the saved information to model

  10. Non-isothermal crystallization kinetics of Fe{sub 2}O{sub 3}–CaO–SiO{sub 2} glass containing nucleation agent P{sub 2}O{sub 5}/TiO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Li, Bin, E-mail: stra-ceo@163.com; Wang, Yongya; Luo, Wenqin; Li, Jingfen [Huzhou University, Department of Material Chemistry (China); Li, Jianyou [Huzhou Central Hospital, Orthopedic Department (China)

    2017-03-15

    Fe{sub 2}O{sub 3}–CaO–SiO{sub 2} glass ceramics containing nucleation agent P{sub 2}O{sub 5}/TiO{sub 2} were prepared by sol-gel method. The samples were characterized by X-ray diffraction (XRD) and differential scanning calorimetry (DSC). The activation energy and kinetic parameters for crystallization of the samples were calculated by the Johnson-Mehi-Avrami (JMA) model and Augis-Bennett method according to the results of DSC. The results showed that the crystallization mechanism of Fe{sub 2}O{sub 3}–CaO–SiO{sub 2} glass, whose non-isothermal kinetic parameter n = 2.3, was consistent with surface crystallization of the JMA model. The kinetics model function of Fe{sub 2}O{sub 3}–CaO–SiO{sub 2} glass, f(α) = 2.3(1–α)[–ln(1–α)]{sup 0.57}, was also obtained. The addition of nucleation agent P{sub 2}O{sub 5}/TiO{sub 2} could reduce the activation energy, which made the crystal growth modes change from onedimensional to three-dimensional.

  11. Pore roller filtration apparatus

    DEFF Research Database (Denmark)

    2014-01-01

    The present invention relates to the field of filtering, more precisely the present invention concerns an apparatus and a method for the separation of dry matter from a medium and the use of said apparatus. One embodiment discloses an apparatus for the separation of dry matter from a medium, comp...... of a pore roller and one other roller, means for establishing a pressure difference across the filter, means for passing filter and filter cake through the set of rollers, and a closure mechanism configured to control the transverse tension between the rollers......., comprising a pressure regulated separation chamber defined, in cross section, by a plurality of rollers mounted between opposing sidewalls, each of said rollers having a shaft adapted to be engaged with the sidewalls, a filter arranged so that it passes between at least one set of said rollers consisting...

  12. Experiments on non-isothermal spreading

    International Nuclear Information System (INIS)

    Ehrhard, P.

    1992-09-01

    Experiments are performed on axisymmetric spreading of viscous drops on glass plates. Two liquids are investigated: silicone oil (M-100) spreads to 'infinity' and paraffin oil spreads to a finite-radius steady state. The experiments with silicone oil partly recover the behaviour of previous workers data; those experiments with paraffin oil provide new data. It is found that gravitational forces dominate at long enough times while at shorter times capillary forces dominate. When the plate is heated or cooled with respect to the ambient gas, thermocapillary forces generate flows that alter the spreading dynamics. Heating (cooling) the plate is found to retard (augment) the streading. Moreover, in case of partial wetting, the finally-approached drop radius is smaller (larger) for a heated (cooled) plate. These data are all new. All these observations are in excellent quantitative agreement with the related model predictions of Ehrhard and Davis (1991). A breakdown of the axisymmetric character of the flow is observed only for very long times and/or very thin liquid layers. (orig.) [de

  13. Pore shapes, volume distribution and orientations in monodisperse granular assemblies

    OpenAIRE

    Sufian, Adnan; Russell, Adrian R.; Saadatfar, Mohammad; Whittle, Andrew

    2015-01-01

    The complex mechanical behaviour of granular materials is commonly studied by considering the evolving particle contact network. An often overlooked feature is the influence of micro-scale geometric configuration of pores on the macroscopic response. This paper presents a series of tools to quantify the shape, volume distribution and orientation characteristics of the pore space. The proposed approach is compared against data extracted from physical and numerical experiments with monodisperse...

  14. Impact of pore and pore-throat distributions on porosity-permeability evolution in heterogeneous mineral dissolution and precipitation scenarios

    Science.gov (United States)

    Beckingham, L. E.; Bensinger, J.; Steinwinder, J.

    2017-12-01

    Porosity and permeability in porous media can be altered by mineral dissolution and precipitation reactions, such as those following CO2 injection in saline aquifers. While the extent of reaction controls changes in porosity, the spatial location of geochemical reactions in individual pores and throats and in the greater pore network controls the evolution of permeability. Geochemical reactions have been observed to occur uniformly on all grain surfaces and non-uniformly, controlled by pore size, PeDa, or mineral distribution, for example. These discrete reaction patterns result in variations in pore scale porosity and corresponding differences in permeability. Macroscopic porosity-permeability relationships are often used to predict the evolution of permeability. These relationships, however, are unable to reflect non-uniform structure modifications. Using pore network modeling simulations, the permeability evolution for a range of uniform and non-uniform mineral reaction scenarios and the applicability of common macroscopic porosity—permeability relationships is investigated. The impact of variations in pore and pore-throat size distributions is evaluated using distributions for real sandstone samples complemented with synthetic distributions. Simulated permeability varies greatly for different reaction patterns. For an Alberta basin sandstone sample, macroscopic relationships are only able to reflect permeability alteration given a uniform reaction scenario where the extent of reaction is related to pore and pore-throat size. For this same sample, simulated permeability for uniform reactions with a fixed reaction thickness and all non-uniform reaction scenarios are unable to be captured using common porosity-permeability relationships. Size-dependent reaction scenarios, where reactions initiate in small or large pores, have the largest disagreement with the porosity-permeability relationships. In these scenarios, porosity-permeability resembles a step function

  15. A pore water conductivity sensor

    NARCIS (Netherlands)

    Hilhorst, M.A.

    2001-01-01

    The electrical permittivity and conductivity of the bulk soil are a function of the permittivity and conductivity of the pore water. For soil water contents higher than 0.10 both functions are equal, facilitating in situ conductivity measurements of the pore water. A novel method is described, based

  16. EOS7Cm: An improved TOUGH2 module for simulating non-isothermal multiphase and multicomponent flow in CO2-H2S-CH4-brine systems with high pressure, temperature and salinity

    Science.gov (United States)

    Lei, Hongwu; Li, Jun; Li, Xiaochun; Jiang, Zhenjiao

    2016-09-01

    Understanding the non-isothermal multiphase and multicomponent flow in a CO2-H2S-CH4-brine system is of critical importance in projects such as CO2 storage in deep saline aquifers, natural gas extraction using CO2 as the displacement fluid, and heat extraction from hot dry rocks using CO2 as the working fluid. Numerical simulation is a necessary tool to evaluate the chemical evolution in these systems. However, an accurate thermodynamic model for CO2-H2S-CH4-brine systems appropriate for high pressure, temperature, and salinity is still lacking. This study establishes the mutual solubility model for CO2-H2S-CH4-brine systems based on the fugacity-activity method for phase equilibrium. The model can predict mutual solubilities for pressure up to 1000 bar for CO2 and CH4, and 200 bar for H2S, for temperature up to 200 °C, and for salinity up to 6 mol/kg water. We incorporated the new model into TOUGH2/EOS7C, forming a new improved module we call EOS7Cm. Compared to the original EOS7C, EOS7Cm considers the effects of H2S and covers a larger range of temperature and salinity. EOS7Cm is employed in five examples, including CO2 injection with and without impurities (CH4 and/or H2S) into deep aquifers, CH4 extraction from aquifers by CO2 injection, and heat extraction from hot dry rock. The results are compared to those from TOUGH2/ECO2N, EOS7C and CMG, agreement among which serves to verify EOS7Cm.

  17. Laboratory characterization of shale pores

    Science.gov (United States)

    Nur Listiyowati, Lina

    2018-02-01

    To estimate the potential of shale gas reservoir, one needs to understand the characteristics of pore structures. Characterization of shale gas reservoir microstructure is still a challenge due to ultra-fine grained micro-fabric and micro level heterogeneity of these sedimentary rocks. The sample used in the analysis is a small portion of any reservoir. Thus, each measurement technique has a different result. It raises the question which methods are suitable for characterizing pore shale. The goal of this paper is to summarize some of the microstructure analysis tools of shale rock to get near-real results. The two analyzing pore structure methods are indirect measurement (MIP, He, NMR, LTNA) and direct observation (SEM, TEM, Xray CT). Shale rocks have a high heterogeneity; thus, it needs multiscale quantification techniques to understand their pore structures. To describe the complex pore system of shale, several measurement techniques are needed to characterize the surface area and pore size distribution (LTNA, MIP), shapes, size and distribution of pore (FIB-SEM, TEM, Xray CT), and total porosity (He pycnometer, NMR). The choice of techniques and methods should take into account the purpose of the analysis and also the time and budget.

  18. Upscaling of nanoparticle transport in porous media under unfavorable conditions: Pore scale to Darcy scale

    Science.gov (United States)

    Seetha, N.; Raoof, Amir; Mohan Kumar, M. S.; Majid Hassanizadeh, S.

    2017-05-01

    Transport and deposition of nanoparticles in porous media is a multi-scale problem governed by several pore-scale processes, and hence, it is critical to link the processes at pore scale to the Darcy-scale behavior. In this study, using pore network modeling, we develop correlation equations for deposition rate coefficients for nanoparticle transport under unfavorable conditions at the Darcy scale based on pore-scale mechanisms. The upscaling tool is a multi-directional pore-network model consisting of an interconnected network of pores with variable connectivities. Correlation equations describing the pore-averaged deposition rate coefficients under unfavorable conditions in a cylindrical pore, developed in our earlier studies, are employed for each pore element. Pore-network simulations are performed for a wide range of parameter values to obtain the breakthrough curves of nanoparticle concentration. The latter is fitted with macroscopic 1-D advection-dispersion equation with a two-site linear reversible deposition accounting for both equilibrium and kinetic sorption. This leads to the estimation of three Darcy-scale deposition coefficients: distribution coefficient, kinetic rate constant, and the fraction of equilibrium sites. The correlation equations for the Darcy-scale deposition coefficients, under unfavorable conditions, are provided as a function of measurable Darcy-scale parameters, including: porosity, mean pore throat radius, mean pore water velocity, nanoparticle radius, ionic strength, dielectric constant, viscosity, temperature, and surface potentials of the particle and grain surfaces. The correlation equations are found to be consistent with the available experimental results, and in qualitative agreement with Colloid Filtration Theory for all parameters, except for the mean pore water velocity and nanoparticle radius.

  19. Upscaling of nanoparticle transport in porous media under unfavorable conditions: Pore scale to Darcy scale.

    Science.gov (United States)

    Seetha, N; Raoof, Amir; Mohan Kumar, M S; Majid Hassanizadeh, S

    2017-05-01

    Transport and deposition of nanoparticles in porous media is a multi-scale problem governed by several pore-scale processes, and hence, it is critical to link the processes at pore scale to the Darcy-scale behavior. In this study, using pore network modeling, we develop correlation equations for deposition rate coefficients for nanoparticle transport under unfavorable conditions at the Darcy scale based on pore-scale mechanisms. The upscaling tool is a multi-directional pore-network model consisting of an interconnected network of pores with variable connectivities. Correlation equations describing the pore-averaged deposition rate coefficients under unfavorable conditions in a cylindrical pore, developed in our earlier studies, are employed for each pore element. Pore-network simulations are performed for a wide range of parameter values to obtain the breakthrough curves of nanoparticle concentration. The latter is fitted with macroscopic 1-D advection-dispersion equation with a two-site linear reversible deposition accounting for both equilibrium and kinetic sorption. This leads to the estimation of three Darcy-scale deposition coefficients: distribution coefficient, kinetic rate constant, and the fraction of equilibrium sites. The correlation equations for the Darcy-scale deposition coefficients, under unfavorable conditions, are provided as a function of measurable Darcy-scale parameters, including: porosity, mean pore throat radius, mean pore water velocity, nanoparticle radius, ionic strength, dielectric constant, viscosity, temperature, and surface potentials of the particle and grain surfaces. The correlation equations are found to be consistent with the available experimental results, and in qualitative agreement with Colloid Filtration Theory for all parameters, except for the mean pore water velocity and nanoparticle radius. Copyright © 2017. Published by Elsevier B.V.

  20. Metal structures with parallel pores

    Science.gov (United States)

    Sherfey, J. M.

    1976-01-01

    Four methods of fabricating metal plates having uniformly sized parallel pores are studied: elongate bundle, wind and sinter, extrude and sinter, and corrugate stack. Such plates are suitable for electrodes for electrochemical and fuel cells.

  1. Effects of La{sup 3+}–Nd{sup 3+} ions and pre-calcination on the growth of hexaferrite nanoparticles prepared by gel to crystallization technique: Non-isothermal crystallization kinetics analysis

    Energy Technology Data Exchange (ETDEWEB)

    Thakur, Ankush [Department of Physics, Jaipur Engineering College and Research Centre, Jaipur (India); Barman, P.B. [Department of Physics and Materials Science, Jaypee University of Information Technology, Waknaghat (India); Singh, R.R., E-mail: raginirajsingh@gmail.com [Department of Physics and Materials Science, Jaypee University of Information Technology, Waknaghat (India)

    2015-04-15

    This is the first report ever on La{sup 3+}–Nd{sup 3+} doped M-type hexaferrite nanoparticles: SrNd{sub x}La{sub y}Fe{sub 12−x−y}O{sub 19} (0 ≤ x ≤ 1) prepared by citrate precursor using the sol–gel technique followed by gel to crystallization. The substitution effects of ions and molar ratio of Fe{sup 3+}/Sr{sup 2+} on the formation of ferrite phase were examined using powder differential thermal analysis (DTA) technique, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (Mid-IR) and vibrating sample magnetometer (VSM). The present work aim to study the crystallization of binary La{sup 3+}- Nd{sup 3+} doped hexaferrite nanoparticles. DTA technique was employed to investigate the formation of nanocrystalline SrNd{sub 0.4}La{sub 0.4}Fe{sub 11.2}O{sub 19} and revealed that the formation of ferrite phase was occurred in steps and crystallization take place by the means of endothermic reactions. The value of activation energy and crystallization temperature has been obtained from DTA data using different non-isothermal methods. XRD and Mid-IR studies have confirmed the formation of ferrite phase. Through this work an optimum calcination condition was established for the synthesis of single phase hexaferrite nanoparticles even after the substitution of binary rare earth elements. Magnetic properties were determined by using a vibrating sample magnetometer. The magnetic results revealed that the synthesized nanoparticles are suitable for perpendicular recording media due to their high coercivity value. - Highlights: • First report of studies on Nd{sup 3+}–La{sup 3+} doped M-type strontium hexaferrite nanoparticles. • Studied the crystallization of binary (Nd{sup 3+}–La{sup 3+}) doped hexaferrite nanoparticles. • Studied the effects of La{sup 3+}–Nd{sup 3+} & molar ratio of Fe{sup 3+}/Sr{sup 2+} on the formation of ferrite phase. • Established an optimum condition to obtain single phase hexaferrite nanoparticles. • Magnetic

  2. TOGA: A TOUGH code for modeling three-phase, multi-component, and non-isothermal processes involved in CO2-based Enhanced Oil Recovery

    Energy Technology Data Exchange (ETDEWEB)

    Pan, Lehua [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of California, Berkeley, CA (United States); Oldenburg, Curtis M. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of California, Berkeley, CA (United States)

    2016-10-10

    TOGA is a numerical reservoir simulator for modeling non-isothermal flow and transport of water, CO2, multicomponent oil, and related gas components for applications including CO2-enhanced oil recovery (CO2-EOR) and geologic carbon sequestration in depleted oil and gas reservoirs. TOGA uses an approach based on the Peng-Robinson equation of state (PR-EOS) to calculate the thermophysical properties of the gas and oil phases including the gas/oil components dissolved in the aqueous phase, and uses a mixing model to estimate the thermophysical properties of the aqueous phase. The phase behavior (e.g., occurrence and disappearance of the three phases, gas + oil + aqueous) and the partitioning of non-aqueous components (e.g., CO2, CH4, and n-oil components) between coexisting phases are modeled using K-values derived from assumptions of equal-fugacity that have been demonstrated to be very accurate as shown by comparison to measured data. Models for saturated (water) vapor pressure and water solubility (in the oil phase) are used to calculate the partitioning of the water (H2O) component between the gas and oil phases. All components (e.g., CO2, H2O, and n hydrocarbon components) are allowed to be present in all phases (aqueous, gaseous, and oil). TOGA uses a multiphase version of Darcy’s Law to model flow and transport through porous media of mixtures with up to three phases over a range of pressures and temperatures appropriate to hydrocarbon recovery and geologic carbon sequestration systems. Transport of the gaseous and dissolved components is by advection and Fickian molecular diffusion. New methods for phase partitioning and thermophysical property modeling in TOGA have been validated against experimental data published in the literature for describing phase partitioning and phase behavior. Flow and transport has been verified by testing against related TOUGH2 EOS modules and

  3. Septal Pore Caps in Basidiomycetes, Composition and Ultrastructure

    NARCIS (Netherlands)

    Driel, K.G.A. van

    2007-01-01

    Filamentous fungi, including Ascomycota and Basidiomycota, form mycelia that consist of a network of apical growing hyphae. These hyphae are separated into cellular compartments by septa that have pores of about 70 to 500 nm in diameter. The cytoplasm within the mycelium is thus continuous

  4. Evaluation of Colloid Retention Site Dominance in Variably Saturated Porous Media: An All Pores Pore-Scale Analysis

    Science.gov (United States)

    Morales, Veronica; Perez-Reche, Francisco; Holzner, Markus; Kinzelbach, Wolfgang

    2016-04-01

    It is well accepted that colloid and nanoparticle transport processes in porous media differ substantially between water saturated and unsaturated conditions. Differences are frequently ascribed to particle immobilization by association with interfaces with the gas, as well as to restrictions of the liquid medium through which colloids are transported. Yet, the current understanding of the importance of particle retention at gas interfaces is based on observations of single pores or two-dimensional pore network representations, leaving open the question of their statistical significance when all pores in the medium are considered. In order to address this question, column experiments were performed using a model porous medium of glass beads through which Silver particles were transported for conditions of varying water content and water chemistry. X-ray microtomography was subsequently employed as a non-destructive imaging technique to obtain pore-scale information of the entire column regarding: i) the presence and distribution of the main locations where colloids can become retained (interfaces with the water-solid, air-water, air-solid, and air-water-solid, grain-grain contacts, and the bulk liquid), ii) deposition profiles of colloids along the column classified by the available retention location, and iii) channel widths of 3-dimensional pore-water network representations. The results presented provide a direct statistical evaluation on the significance of colloid retention by attachment to interfaces or by strainig at contact points where multiple interfaces meet.

  5. Antera 3D capabilities for pore measurements.

    Science.gov (United States)

    Messaraa, C; Metois, A; Walsh, M; Flynn, J; Doyle, L; Robertson, N; Mansfield, A; O'Connor, C; Mavon, A

    2018-04-29

    The cause of enlarged pores remains obscure but still remains of concern for women. To complement subjective methods, bioengineered methods are needed for quantification of pores visibility following treatments. The study objective was to demonstrate the suitability of pore measurements from the Antera 3D. Pore measurements were collected on 22 female volunteers aged 18-65 years with the Antera 3D, the DermaTOP and image analysis on photographs. Additionally, 4 raters graded pore size on photographs on a scale 0-5. Repeatability of Antera 3D parameters was ascertained and the benefit of a pore minimizer product on the cheek was assessed on a sub panel of seven female volunteers. Pore parameters using the Antera were shown to depict pore severity similar to raters on photographs, except for Max Depth. Mean pore volume, mean pore area and count were moderately correlated with DermaTOP parameters (up to r = .50). No relationship was seen between the Antera 3D and pore visibility analysis on photographs. The most repeatable parameters were found to be mean pore volume, mean pore area and max depth, especially for the small and medium filters. The benefits of a pore minimizer product were the most striking for mean pore volume and mean pore area when using the small filter for analysis, rather than the medium/large ones. Pore measurements with the Antera 3D represent a reliable tool for efficacy and field studies, with an emphasis of the small filter for analysis for the mean pore volume/mean pore area parameters. © 2018 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  6. Pore-scale modeling of capillary trapping in water-wet porous media: A new cooperative pore-body filling model

    Science.gov (United States)

    Ruspini, L. C.; Farokhpoor, R.; Øren, P. E.

    2017-10-01

    We present a pore-network model study of capillary trapping in water-wet porous media. The amount and distribution of trapped non-wetting phase is determined by the competition between two trapping mechanisms - snap-off and cooperative pore-body filling. We develop a new model to describe the pore-body filling mechanism in geologically realistic pore-networks. The model accounts for the geometrical characteristics of the pore, the spatial location of the connecting throats and the local fluid topology at the time of the displacement. We validate the model by comparing computed capillary trapping curves with published data for four different water-wet rocks. Computations are performed on pore-networks extracted from micro-CT images and process-based reconstructions of the actual rocks used in the experiments. Compared with commonly used stochastic models, the new model describes more accurately the experimental measurements, especially for well connected porous systems where trapping is controlled by subtleties of the pore structure. The new model successfully predicts relative permeabilities and residual saturation for Bentheimer sandstone using in-situ measured contact angles as input to the simulations. The simulated trapped cluster size distributions are compared with predictions from percolation theory.

  7. Preferential flow from pore to landscape scales

    Science.gov (United States)

    Koestel, J. K.; Jarvis, N.; Larsbo, M.

    2017-12-01

    In this presentation, we give a brief personal overview of some recent progress in quantifying preferential flow in the vadose zone, based on our own work and those of other researchers. One key challenge is to bridge the gap between the scales at which preferential flow occurs (i.e. pore to Darcy scales) and the scales of interest for management (i.e. fields, catchments, regions). We present results of recent studies that exemplify the potential of 3-D non-invasive imaging techniques to visualize and quantify flow processes at the pore scale. These studies should lead to a better understanding of how the topology of macropore networks control key state variables like matric potential and thus the strength of preferential flow under variable initial and boundary conditions. Extrapolation of this process knowledge to larger scales will remain difficult, since measurement technologies to quantify macropore networks at these larger scales are lacking. Recent work suggests that the application of key concepts from percolation theory could be useful in this context. Investigation of the larger Darcy-scale heterogeneities that generate preferential flow patterns at the soil profile, hillslope and field scales has been facilitated by hydro-geophysical measurement techniques that produce highly spatially and temporally resolved data. At larger regional and global scales, improved methods of data-mining and analyses of large datasets (machine learning) may help to parameterize models as well as lead to new insights into the relationships between soil susceptibility to preferential flow and site attributes (climate, land uses, soil types).

  8. Pore-scale supercritical CO2 dissolution and mass transfer under drainage conditions

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Chun; Zhou, Quanlin; Oostrom, Mart; Kneafsey, Timothy J.; Mehta, Hardeep

    2017-02-01

    Abstract: Recently, both core- and pore-scale imbibition experiments have shown non-equilibrium dissolution of supercritical CO2 (scCO2) and a prolonged depletion of residual scCO2. In this study, pore-scale scCO2 dissolution and mass transfer under drainage conditions were investigated using a two-dimensional heterogeneous micromodel and a novel fluorescent water dye with a sensitive pH range between 3.7 and 6.5. Drainage experiments were conducted at 9 MPa and 40 °C by injecting scCO2 into the sandstone-analogue pore network initially saturated by water without dissolved CO2 (dsCO2). During the experiments, time-lapse images of dye intensity, reflecting water pH, were obtained. These images show non-uniform pH in individual pores and pore clusters, with average pH levels gradually decreasing with time. Further analysis on selected pores and pore clusters shows that (1) rate-limited mass transfer prevails with slowly decreasing pH over time when the scCO2-water interface area is low with respect to the volume of water-filled pores and pore clusters, (2) fast scCO2 dissolution and phase equilibrium occurs when scCO2 bubbles invade into water-filled pores, significantly enhancing the area-to-volume ratio, and (3) a transition from rate-limited to diffusion-limited mass transfer occurs in a single pore when a medium area-to-volume ratio is prevalent. The analysis also shows that two fundamental processes – scCO2 dissolution at phase interfaces and diffusion of dsCO2 at the pore scale (10-100 µm) observed after scCO2 bubble invasion into water-filled pores without pore throat constraints – are relatively fast. The overall slow dissolution of scCO2 in the millimeter-scale micromodel can be attributed to the small area-to-volume ratios that represent pore-throat configurations and characteristics of phase

  9. Pore volume is most highly correlated with the visual assessment of skin pores.

    Science.gov (United States)

    Kim, S J; Shin, M K; Back, J H; Koh, J S

    2014-11-01

    Many studies have been focused on evaluating assessment techniques for facial pores amid growing attention on skin care. Ubiquitous techniques used to assess the size of facial pores include visual assessment, cross-section images of the skin surface, and profilometric analysis of silicone replica of the facial skin. In addition, there are indirect assessment methods, including observation of pores based on confocal laser scanning microscopy and the analysis of sebum secretion and skin elasticity. The aim of this study was to identify parameters useful in estimating pore of surface in normal skin. The severity of pores on the cheek area by frontal optical images was divided on a 0-6 scale with '0' being faint and small pore and '6' being obvious and large pore. After the photos of the frontal cheek of 32 women aged between 35 and 49 were taken, the size of their pores was measured on a 0-6 scale; and the correlation between visual grading of pore and various evaluations (pore volume by 3-D image, pore area and number by Optical Image Analyzer) contributing to pore severity investigated using direct, objective, and noninvasive evaluations. The visual score revealed that the size of pores was graded on a 1-6 scale. Visual grading of pore was highly correlated with pore volume measured from 3-D images and pore area measured from 2-D optical images in the order (P pore was also slightly correlated with the number of pores in size of over 0.04 mm(2) (P pore score and pore volume can be explained by 3-D structural characteristics of pores. It is concluded that pore volume and area serve as useful parameters in estimating pore of skin surface. © 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  10. Pore Pressure Measurements Inside Rubble Mound Breakwaters

    DEFF Research Database (Denmark)

    Helgason, Einar; Burcharth, H. F.; Grüne, Joachim

    2004-01-01

    The present paper presents pore pressure measurements from large scale model tests performed at the Large Wave Channel, Hannover, Germany and small scale model test performed at the Hydraulic & Coastal Engineering Laboratory, Aalborg University, Denmark. Information on pore pressure attenuation...

  11. Multifractal Characterization of Soil Pore Shapes

    Science.gov (United States)

    Gimenez, Daniel; Posadas, Adolfo; Cooper, Miguel

    2010-05-01

    Two dimensional (2-D) images representing pores and solids are used for direct quantification of soil structure using tools that are sensitive to the spatial arrangement of pores or by grouping pores by morphological properties such as shape and size. Pore shapes and sizes are related and have been used to interpret soil processes. Fractal and multifractal methods of pore characterization have been applied separately to spatial arrangement of soil pores and to pore size distributions derived from 2-D images. The objective of this work was to estimate fractal dimensions of spatial arrangement of soil pores of predetermined shapes. Images covering a range of soil structures were analyzed. Pore shape was classified using a shape factor S that quantifies the circularity of pores (S=1 for circular pores). Images containing only pores with S values smaller than 0.1, between 0.1 and 0.2, 0.2 and 0.5, 0.5 and 0.7 and greater than 0.7 were derived from the initial images and analyzed with a multifractal algorithm. The findings of this work will be discussed in relation to models of soil hydraulic properties.

  12. Facial Pores: Definition, Causes, and Treatment Options.

    Science.gov (United States)

    Lee, Sang Ju; Seok, Joon; Jeong, Se Yeong; Park, Kui Young; Li, Kapsok; Seo, Seong Jun

    2016-03-01

    Enlarged skin pores refer to conditions that present with visible topographic changes of skin surfaces. Although not a medical concern, enlarged pores are a cosmetic concern for a large number of individuals. Moreover, clear definition and possible causes of enlarged pores have not been elucidated. To review the possible causes and treatment options for skin pores. This article is based on a review of the medical literature and the authors' clinical experience in investigating and treating skin pores. There are 3 major clinical causes of enlarged facial pores, namely high sebum excretion, decreased elasticity around pores, and increased hair follicle volume. In addition, chronic recurrent acne, sex hormones, and skin care regimen can affect pore size. Given the different possible causes for enlarged pores, therapeutic modalities must be individualized for each patient. Potential factors that contribute to enlarged skin pores include excessive sebum, decreased elasticity around pores, and increased hair follicle volume. Because various factors cause enlarged facial pores, it might be useful to identify the underlying causes to be able to select the appropriate treatment.

  13. Determinação da constante cinética de cristalização não-isotérmica de polipropilenos modificados com ácido acrílico e anidrido maleico Determination of the non-isothermal crystallization rate constant of grafted maleic anhydride and grafted acrylic acid polypropylenes

    Directory of Open Access Journals (Sweden)

    Benjamim de M. Carvalho

    2006-12-01

    Full Text Available O propósito do presente trabalho foi testar a validade do Método da Curva Mestre para a determinação da constante de cristalização não-isotérmica de polipropilenos modificados com anidrido maleico e ácido acrílico. Experimentos de cristalização não-isotérmica foram realizados a diversas taxas de resfriamento por meio de Calorimetria Exploratória Diferencial (DSC. Para serem usadas no Método da Curva Mestre, as curvas originais obtidas em DSC foram corrigidas em termos da defasagem de temperatura entre a amostra polimérica e o forno do equipamento. A equação de Nakamura e a constante de cristalização determinada foram utilizadas para simular as curvas de cristalinidade relativa em função da temperatura para as diversas taxas de resfriamento. As curvas simuladas apresentaram boa concordância com as curvas experimentais para ambas as amostras de polipropileno modificado, mostrando que o Método da Curva Mestre pode ser empregado com sucesso para este polímero.The purpose of the present work was to evaluate the Master Curve Approach in the determination of the non-isothermal crystallization constant, for samples of two modified polypropylenes (grafted maleic anhydride and grafted acrylic acid polypropylenes. Non-isothermal crystallization experiments were carried out in a differential scanning calorimeter, DSC, at several cooling rates. The original DSC curves were corrected for the temperature lag between the sample and the DSC furnace. The Nakamura equation and the non-isothermal crystallization constant obtained by the Master Curve Approach were employed to simulate the curves of relative crystallinity as a function of temperature, for the different cooling rates. The generated curves presented good agreement with the experimental data for both samples of grafted polypropylene, showing that the Master Curve Approach can be successfully employed for these polymers.

  14. Pore-scale Modelling of Capillarity in Swelling Granular Materials

    Science.gov (United States)

    Hassanizadeh, S. M.; Sweijen, T.; Nikooee, E.; Chareyre, B.

    2015-12-01

    Capillarity in granular porous media is a common and important phenomenon in earth materials and industrial products, and therefore has been studied extensively. To model capillarity in granular porous media, one needs to go beyond current models which simulate either two-phase flow in porous media or mechanical behaviour in granular media. Current pore-scale models for two-phase flow such as pore-network models are tailored for rigid pore-skeletons, even though in many applications, namely hydro-mechanical coupling in soils, printing, and hygienic products, the porous structure does change during two-phase flow. On the other hand, models such as Discrete Element Method (DEM), which simulate the deformable porous media, have mostly been employed for dry or saturated granular media. Here, the effects of porosity change and swelling on the retention properties was studied, for swelling granular materials. A pore-unit model that was capable to construct the capillary pressure - saturation curve was coupled to DEM. Such that the capillary pressure - saturation curve could be constructed for varying porosities and amounts of absorbed water. The study material was super absorbent polymer particles, which are capable to absorb water 10's to 200 times their initial weight. We have simulated quasi-static primary imbibition for different porosities and amounts of absorbed water. The results reveal a 3 dimensional surface between capillary pressure, saturation, and porosity, which can be normalized by means of the entry pressure and the effective water saturation to a unique curve.

  15. Evaluation of the capacity of mosaic-like porous ceramics with designed pores to support osteoconduction.

    Science.gov (United States)

    Teraoka, Kay; Kato, Tomotaka; Hattori, Koji; Ohgushi, Hajime

    2013-12-01

    Under osteoconductive conditions, porous calcium phosphate ceramics are known to induce new bone formation within their pores. A critical aspect of the design of porous ceramics is the geometrical features of their pores, with regard to promoting bone formation and mass transfer management in pore networks. However, the pore geometries of common porous ceramics lack clear details. Further, the connections between pores are hard to characterize and thus have not been thoroughly researched. To address these issues, we have developed an original method for fabricating porous ceramics, which we have termed "mosaic-like ceramics fabrication (MLCF)." Using MLCF, pore geometries can be designed and fabricated by each unit, and a network covering all the pores can be fabricated. Furthermore, MLCF can be used to build porous ceramics with custom-made shapes. In this study, we assessed the osteogenic influences of MLCF products (MLPC) composed of hydroxyapatite units on the differentiation of rat bone-marrow-derived mesenchymal stem cells (MSCs) in vitro and in vivo. Two types of commercial porous artificial bone were used as positive controls. MLPC was superior in osteogenic potential, and proved to be a reliable scaffold for bone tissue engineering. Furthermore, this study succeeded in defining the important geometries for osteoconduction. Copyright © 2013 Wiley Periodicals, Inc.

  16. Coating of silicon pore optics

    DEFF Research Database (Denmark)

    Cooper-Jensen, Carsten P.; Ackermann, M.; Christensen, Finn Erland

    2009-01-01

    For the International X-ray observatory (IXO), a mirror module with an effective area of 3 m2 at 1.25 keV and at least 0.65 m2 at 6 keV has to be realized. To achieve this goal, coated silicon pore optics has been developed over the last years. One of the challenges is to coat the Si plates...... and still to realize Si-Si bonding. It has been demonstrated that ribbed silicon plates can be produced and assembled into stacks. All previously work has been done using uncoated Si plates. In this paper we describe how to coat the ribbed Si plates with an Ir coating and a top C coating through a mask so...

  17. Geometry-driven cell organization determines tissue growths in scaffold pores: consequences for fibronectin organization.

    Directory of Open Access Journals (Sweden)

    Pascal Joly

    Full Text Available To heal tissue defects, cells have to bridge gaps and generate new extracellular matrix (ECM. Macroporous scaffolds are frequently used to support the process of defect filling and thus foster tissue regeneration. Such biomaterials contain micro-voids (pores that the cells fill with their own ECM over time. There is only limited knowledge on how pore geometry influences cell organization and matrix production, even though it is highly relevant for scaffold design. This study hypothesized that 1 a simple geometric description predicts cellular organization during pore filling at the cell level and that 2 pore closure results in a reorganization of ECM. Scaffolds with a broad distribution of pore sizes (macroporous starPEG-heparin cryogel were used as a model system and seeded with primary fibroblasts. The strategies of cells to fill pores could be explained by a simple geometrical model considering cells as tensioned chords. The model matched qualitatively as well as quantitatively by means of cell number vs. open cross-sectional area for all pore sizes. The correlation between ECM location and cell position was higher when the pores were not filled with tissue (Pearson's coefficient ρ = 0.45±0.01 and reduced once the pores were closed (ρ = 0.26±0.04 indicating a reorganization of the cell/ECM network. Scaffold pore size directed the time required for pore closure and furthermore impacted the organization of the fibronectin matrix. Understanding how cells fill micro-voids will help to design biomaterial scaffolds that support the endogenous healing process and thus allow a fast filling of tissue defects.

  18. The role of pore space morphology in multi-phase flow in porous media

    Science.gov (United States)

    Wildenschild, D.; Prodanovic, M.; Jansik, D. P.

    2008-12-01

    Porous medium morphology can play an important role when we use numerical models to predict subsurface flow and transport behavior at larger scales. Yet, understanding the role that pore structure plays at smaller scales is a necessary first step. Fluid-fluid configuration in particular is highly influenced by the surface characteristics of the porous medium. Fluid configurations vary significantly between drainage and imbibiton (due to spontaneous, irreversible changes of the interface between fluids). We specifically measure large differences in wetting-nonwetting interfacial area as a function of different pore space morphology: as observed for a crushed volcanic tuff with high surface area and affinity for fluid films, and for smooth glass beads. The observed imbibition process for the glass beads resembles a piston-flow situation, whereas imbibition into the tuff appears dominated by fluid film connectivity with growth from pendular rings in spatially distant locations of the imaged system. The latter process leads to a very different distribution of fluids and overall lower saturations and interfacial areas than in the glass bead system. Characteristics such as pore- scale Pc-S curves and related interfacial area per volume have been quantified using computed microtomography. In addition, we present pore network characterization (pore connectivity, pore throats to pore body aspect ratio, pore body volumes and throat areas) of the two porous media.

  19. Changes in pore structure of coal caused by coal-to-gas bioconversion.

    Science.gov (United States)

    Zhang, Rui; Liu, Shimin; Bahadur, Jitendra; Elsworth, Derek; Wang, Yi; Hu, Guanglong; Liang, Yanna

    2017-06-19

    Microbial enhanced coalbed methane (ME-CBM) recovery is critically examined as a viable technology for natural gas recovery from coalbed methane (CBM) reservoirs. Since the majority of gas-in-place (GIP) is stored as an adsorbed phase in fine pores of coal matrix, the nano-pore structure directly influences gas storage and transport properties. Only limited studies have quantified the alteration of the nano-pore structure due to ME-CBM treatment. This study examines the evolution of the pore structure using a combination of small angle X-ray scattering (SAXS), low-pressure N 2 and CO 2 adsorption (LPGA) and high-pressure methane adsorption methods. The results show that the surface fractal dimension decreases for the two bioconverted coals compared to the untreated coal. After bio-treatment, the mesopore surface area and pore volume decrease with the average pore diameter increases, while the micropore surface area increases with pore volume decreases. Both inaccessible meso-/micropore size distributions decrease after bioconversion, while the accessible micropore size distribution increases, making a portion of closed micropore network accessible. In addition, the methane adsorption capacities increase after bio-treatment, which is confirmed by the increase of micropore surface area. A conceptual physical model of methanogenesis is proposed based on the evolution of the pore structure.

  20. Electroosmotic pore transport in human skin.

    Science.gov (United States)

    Uitto, Olivia D; White, Henry S

    2003-04-01

    To determine the pathways and origin of electroosmotic flow in human skin. Iontophoretic transport of acetaminophen in full thickness human cadaver skin was visualized and quantified by scanning electrochemical microscopy. Electroosmotic flow in the shunt pathways of full thickness skin was compared to flow in the pores of excised stratum corneum and a synthetic membrane pore. The penetration of rhodamine 6G into pore structures was investigated by laser scanning confocal microscopy. Electroosmotic transport is observed in shunt pathways in full thickness human skin (e.g., hair follicles and sweat glands), but not in pore openings of freestanding stratum corneum. Absolute values of the diffusive and iontophoretic pore fluxes of acetaminophen in full thickness human skin are also reported. Rhodamine 6G is observed to penetrate to significant depths (approximately 200 microm) along pore pathways. Iontophoresis in human cadaver skin induces localized electroosmotic flow along pore shunt paths. Electroosmotic forces arise from the passage of current through negatively charged mesoor nanoscale pores (e.g., gap functions) within cellular regions that define the pore structure beneath the stratum corneum.

  1. Water nanodroplets confined in zeolite pores.

    Science.gov (United States)

    Coudert, François-Xavier; Cailliez, Fabien; Vuilleumier, Rodolphe; Fuchs, Alain H; Boutin, Anne

    2009-01-01

    We provide a comprehensive depiction of the behaviour of a nanodroplet of approximately equal to 20 water molecules confined in the pores of a series of 3D-connected isostructural zeolites with varying acidity, by means of molecular simulations. Both grand canonical Monte Carlo simulations using classical interatomic forcefields and first-principles Car-Parrinello molecular dynamics were used in order to characterise the behaviour of confined water by computing a range of properties, from thermodynamic quantities to electronic properties such as dipole moment, including structural and dynamical information. From the thermodynamic point of view, we have identified the all-silica zeolite as hydrophobic, and the cationic zeolites as hydrophilic; the condensation transition in the first case was demonstrated to be of first order. Furthermore, in-depth analysis of the dynamical and electronic properties of water showed that water in the hydrophobic zeolite behaves as a nanodroplet trying to close its hydrogen-bond network onto itself, with a few short-lived dangling OH groups, while water in hydrophilic zeolites "opens up" to form weak hydrogen bonds with the zeolite oxygen atoms. Finally, the dipole moment of confined water is studied and the contributions of water self-polarisation and the zeolite electric field are discussed.

  2. Automatic facial pore analysis system using multi-scale pore detection.

    Science.gov (United States)

    Sun, J Y; Kim, S W; Lee, S H; Choi, J E; Ko, S J

    2017-08-01

    As facial pore widening and its treatments have become common concerns in the beauty care field, the necessity for an objective pore-analyzing system has been increased. Conventional apparatuses lack in usability requiring strong light sources and a cumbersome photographing process, and they often yield unsatisfactory analysis results. This study was conducted to develop an image processing technique for automatic facial pore analysis. The proposed method detects facial pores using multi-scale detection and optimal scale selection scheme and then extracts pore-related features such as total area, average size, depth, and the number of pores. Facial photographs of 50 subjects were graded by two expert dermatologists, and correlation analyses between the features and clinical grading were conducted. We also compared our analysis result with those of conventional pore-analyzing devices. The number of large pores and the average pore size were highly correlated with the severity of pore enlargement. In comparison with the conventional devices, the proposed analysis system achieved better performance showing stronger correlation with the clinical grading. The proposed system is highly accurate and reliable for measuring the severity of skin pore enlargement. It can be suitably used for objective assessment of the pore tightening treatments. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  3. The Effect of the Pore Entrance on Particle Motion in Slit Pores: Implications for Ultrathin Membranes.

    Science.gov (United States)

    Delavari, Armin; Baltus, Ruth

    2017-08-10

    Membrane rejection models generally neglect the effect of the pore entrance on intrapore particle transport. However, entrance effects are expected to be particularly important with ultrathin membranes, where membrane thickness is typically comparable to pore size. In this work, a 2D model was developed to simulate particle motion for spherical particles moving at small Re and infinite Pe from the reservoir outside the pore into a slit pore. Using a finite element method, particles were tracked as they accelerated across the pore entrance until they reached a steady velocity in the pore. The axial position in the pore where particle motion becomes steady is defined as the particle entrance length (PEL). PELs were found to be comparable to the fluid entrance length, larger than the pore size and larger than the thickness typical of many ultrathin membranes. Results also show that, in the absence of particle diffusion, hydrodynamic particle-membrane interactions at the pore mouth result in particle "funneling" in the pore, yielding cross-pore particle concentration profiles focused at the pore centerline. The implications of these phenomena on rejection from ultrathin membranes are examined.

  4. Unlocking the Physiochemical Controls on Organic Carbon Dynamics from the Soil Pore- to Core-Scale

    Science.gov (United States)

    Smith, A. P.; Tfaily, M. M.; Bond-Lamberty, B. P.; Todd-Brown, K. E.; Bailey, V. L.

    2015-12-01

    The physical organization of soil includes pore networks of varying size and connectivity. These networks control microbial access to soil organic carbon (C) by spatially separating microorganisms and C by both distance and size exclusion. The extent to which this spatially isolated C is vulnerable to microbial transformation under hydrologically dynamic conditions is unknown, and limits our ability to predict the source and sink capacity of soils. We investigated the effects of shifting hydrologic connectivity and soil structure on greenhouse gas C emissions from surface soils collected from the Disney Wilderness Preserve (Florida, USA). We subjected intact soil cores and re-packed homogenized soil cores to simulated groundwater rise or precipitation, monitoring their CO2 and CH4 emissions over 24 hours. Soil pore water was then extracted from each core using different suctions to sample water retained by pore throats of different sizes and then characterized by Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry. Greater respiration rates were observed from homogenized cores compared to intact cores, and from soils wet from below, in which the wetting front is driven by capillary forces, filling fine pores first. This suggests that C located in fine pores may turn over via diffusion processes that lead to the colocation of this C with other resources and microorganisms. Both the complexity and concentration of soluble-C increased with decreasing pore size domains. Pore water extracted from homogenized cores had greater C concentrations than from intact cores, with the greatest concentrations in pore waters sampled from very fine pores, highlighting the importance of soil structure in physically protecting C. These results suggest that the spatial separation of decomposers from C is a key mechanism stabilizing C in these soils. Further research is ongoing to accurately represent this protection mechanism, and the conditions under which it breaks

  5. Gas transport and subsoil pore characteristics

    DEFF Research Database (Denmark)

    Berisso, Feto Esimo; Schjønning, Per; Keller, Thomas

    2013-01-01

    Arrangements of elementary soil particles during soil deposition and subsequent biological and physical processes in long-term pedogenesis are expected to lead to anisotropy of the non-tilled subsoil pore system. Soil compaction by agricultural machinery is known to affect soil pore characteristi...

  6. Nuclear pore structure: warming up the core.

    Science.gov (United States)

    Harel, Amnon; Gruenbaum, Yosef

    2011-07-22

    Structural determination of the nuclear pore complex has been limited by the complexity and size of this cellular megalith. By taking advantage of exceptionally stable nucleoporins from the thermophilic fungus Chaetomium thermophilum, Amlacher et al. (2011) provide new insight into a core element of the nuclear pore scaffold. Copyright © 2011 Elsevier Inc. All rights reserved.

  7. Networking

    OpenAIRE

    Rauno Lindholm, Daniel; Boisen Devantier, Lykke; Nyborg, Karoline Lykke; Høgsbro, Andreas; Fries, de; Skovlund, Louise

    2016-01-01

    The purpose of this project was to examine what influencing factor that has had an impact on the presumed increasement of the use of networking among academics on the labour market and how it is expressed. On the basis of the influence from globalization on the labour market it can be concluded that the globalization has transformed the labour market into a market based on the organization of networks. In this new organization there is a greater emphasis on employees having social qualificati...

  8. FINGERPRINT MATCHING BASED ON PORE CENTROIDS

    Directory of Open Access Journals (Sweden)

    S. Malathi

    2011-05-01

    Full Text Available In recent years there has been exponential growth in the use of bio- metrics for user authentication applications. Automated Fingerprint Identification systems have become popular tool in many security and law enforcement applications. Most of these systems rely on minutiae (ridge ending and bifurcation features. With the advancement in sensor technology, high resolution fingerprint images (1000 dpi pro- vide micro level of features (pores that have proven to be useful fea- tures for identification. In this paper, we propose a new strategy for fingerprint matching based on pores by reliably extracting the pore features The extraction of pores is done by Marker Controlled Wa- tershed segmentation method and the centroids of each pore are con- sidered as feature vectors for matching of two fingerprint images. Experimental results shows that the proposed method has better per- formance with lower false rates and higher accuracy.

  9. Improvement of endothelial progenitor outgrowth cell (EPOC)-mediated vascularization in gelatin-based hydrogels through pore size manipulation.

    Science.gov (United States)

    Fu, Jiayin; Wiraja, Christian; Muhammad, Hamizan B; Xu, Chenjie; Wang, Dong-An

    2017-08-01

    In addition to chemical compositions, physical properties of scaffolds, such as pore size, can also influence vascularization within the scaffolds. A larger pore has been shown to improve host vascular tissue invasion into scaffolds. However, the influence of pore sizes on vascularization by endothelial cells directly encapsulated in hydrogels remains unknown. In this study, micro-cavitary hydrogels with different pore sizes were created in gelatin-methacrylate hydrogels with dissolvable gelatin microspheres (MS) varying in sizes. The effect of pore sizes on vascular network formation by endothelial progenitor outgrowth cells (EPOCs) encapsulated in hydrogels was then investigated both in vitro and in vivo. When cultured in vitro, vascular networks were formed around pore structures in micro-cavitary hydrogels. The middle pore size supported best differentiation of EPOCs and thus best hydrogel vascularization in vitro. When implantation in vivo, functional connections between encapsulated EPOCs and host vasculature micro-cavitary hydrogels were established. Vascularization in vivo was promoted best in hydrogels with the large pore size due to the increased vascular tissue invasion. These results highlight the difference between in vitro and in vivo culture conditions and indicate that pore sizes shall be designed for in vitro and in vivo hydrogel vascularization respectively. Pore sizes for hydrogel vascularization in vitro shall be middle ones and pore sizes for hydrogel vascularization in vivo shall be large ones. This study reveals that the optimal pore size for hydrogel vascularization in vitro and in vivo is different. The middle pore size supported best differentiation of EPOCs and thus best hydrogel vascularization in vitro, while vascularization in vivo was promoted best in hydrogels with the large pore size due to the increased vascular tissue invasion. These results highlight the difference between in vitro and in vivo culture conditions and indicate that

  10. Large-Pore Mesoporous Silica with Three-Dimensional Wormhole Framework Structures.

    Science.gov (United States)

    Park, In; Pinnavaia, Thomas J

    2009-02-01

    Large-pore mesoporous silica with 3D wormhole framework structures (denoted MSU-J) are prepared through a supramolecular hydrogen-bonding assembly pathway from low-cost sodium silicate as the silica source and commercially available mono- and triamine Jeffamine and Surfonamine surfactants as structure-directing porogens. The calcined mesostructures exhibit large pore sizes (up to 8.2 nm), surface areas (632-1030 m(2)/g) and pore volumes (0.5-2.0 cm(3)/g), depending on the surfactant chain length and synthesis temperature (25-65 °C). The textural properties of these new wormhole mesostructures are comparable to those of hexagonal SBA-15 derivatives and large pore MCM-48. However, unlike the SBA-15 structure type, wherein the 3D pore network is formed by connecting 1D cylindrical mesopores through micropores, MSU-J mesophases have wormhole framework structures containing fully interconnected 3D mesopores that can minimize the diffusion limitations often encountered in adsorption and chemical catalysis. Also, unlike large pore MCM-48, which requires cost-intensive tetraethylorthosilicate as a silica source and the use of a co-surfactant as a pore expander under strong acid conditions, MSU-J mesostructures are assembled from low cost sodium silicate in the presence of a single Jeffamine or Surfonamine porogen at near-neutral pH.

  11. Two sides of a fault: Grain-scale analysis of pore pressure control on fault slip

    Science.gov (United States)

    Yang, Zhibing; Juanes, Ruben

    2018-02-01

    Pore fluid pressure in a fault zone can be altered by natural processes (e.g., mineral dehydration and thermal pressurization) and industrial operations involving subsurface fluid injection and extraction for the development of energy and water resources. However, the effect of pore pressure change on the stability and slip motion of a preexisting geologic fault remains poorly understood; yet, it is critical for the assessment of seismic hazard. Here, we develop a micromechanical model to investigate the effect of pore pressure on fault slip behavior. The model couples fluid flow on the network of pores with mechanical deformation of the skeleton of solid grains. Pore fluid exerts pressure force onto the grains, the motion of which is solved using the discrete element method. We conceptualize the fault zone as a gouge layer sandwiched between two blocks. We study fault stability in the presence of a pressure discontinuity across the gouge layer and compare it with the case of continuous (homogeneous) pore pressure. We focus on the onset of shear failure in the gouge layer and reproduce conditions where the failure plane is parallel to the fault. We show that when the pressure is discontinuous across the fault, the onset of slip occurs on the side with the higher pore pressure, and that this onset is controlled by the maximum pressure on both sides of the fault. The results shed new light on the use of the effective stress principle and the Coulomb failure criterion in evaluating the stability of a complex fault zone.

  12. Two sides of a fault: Grain-scale analysis of pore pressure control on fault slip.

    Science.gov (United States)

    Yang, Zhibing; Juanes, Ruben

    2018-02-01

    Pore fluid pressure in a fault zone can be altered by natural processes (e.g., mineral dehydration and thermal pressurization) and industrial operations involving subsurface fluid injection and extraction for the development of energy and water resources. However, the effect of pore pressure change on the stability and slip motion of a preexisting geologic fault remains poorly understood; yet, it is critical for the assessment of seismic hazard. Here, we develop a micromechanical model to investigate the effect of pore pressure on fault slip behavior. The model couples fluid flow on the network of pores with mechanical deformation of the skeleton of solid grains. Pore fluid exerts pressure force onto the grains, the motion of which is solved using the discrete element method. We conceptualize the fault zone as a gouge layer sandwiched between two blocks. We study fault stability in the presence of a pressure discontinuity across the gouge layer and compare it with the case of continuous (homogeneous) pore pressure. We focus on the onset of shear failure in the gouge layer and reproduce conditions where the failure plane is parallel to the fault. We show that when the pressure is discontinuous across the fault, the onset of slip occurs on the side with the higher pore pressure, and that this onset is controlled by the maximum pressure on both sides of the fault. The results shed new light on the use of the effective stress principle and the Coulomb failure criterion in evaluating the stability of a complex fault zone.

  13. Electroactive Tissue Scaffolds with Aligned Pores as Instructive Platforms for Biomimetic Tissue Engineering

    Directory of Open Access Journals (Sweden)

    John G. Hardy

    2015-01-01

    Full Text Available Tissues in the body are hierarchically structured composite materials with tissue-specific chemical and topographical properties. Here we report the preparation of tissue scaffolds with macroscopic pores generated via the dissolution of a sacrificial supramolecular polymer-based crystal template (urea from a biodegradable polymer-based scaffold (polycaprolactone, PCL. Furthermore, we report a method of aligning the supramolecular polymer-based crystals within the PCL, and that the dissolution of the sacrificial urea yields scaffolds with macroscopic pores that are aligned over long, clinically-relevant distances (i.e., centimeter scale. The pores act as topographical cues to which rat Schwann cells respond by aligning with the long axis of the pores. Generation of an interpenetrating network of polypyrrole (PPy and poly(styrene sulfonate (PSS in the scaffolds yields electroactive tissue scaffolds that allow the electrical stimulation of Schwann cells cultured on the scaffolds which increases the production of nerve growth factor (NGF.

  14. Enlarged facial pores: an update on treatments.

    Science.gov (United States)

    Dong, Joanna; Lanoue, Julien; Goldenberg, Gary

    2016-07-01

    Enlarged facial pores remain a common dermatologic and cosmetic concern from acne and rosacea, among other conditions, that is difficult to treat due to the multifactorial nature of their pathogenesis and negative impact on patients' quality of life. Enlarged facial pores are primarily treated through addressing associative factors, such as increased sebum production and cutaneous aging. We review the current treatment modalities for enlarged or dense facial pores, including topical retinoids, chemical peels, oral antiandrogens, and lasers and devices, with a focus on newer therapies.

  15. Control of pore size in epoxy systems.

    Energy Technology Data Exchange (ETDEWEB)

    Sawyer, Patricia Sue; Lenhart, Joseph Ludlow (North Dakota State University, Fargo, ND); Lee, Elizabeth (North Dakota State University, Fargo, ND); Kallam, Alekhya (North Dakota State University, Fargo, ND); Majumdar, Partha (North Dakota State University, Fargo, ND); Dirk, Shawn M.; Gubbins, Nathan; Chisholm, Bret J. (North Dakota State University, Fargo, ND); Celina, Mathias C.; Bahr, James (North Dakota State University, Fargo, ND); Klein, Robert J.

    2009-01-01

    Both conventional and combinatorial approaches were used to study the pore formation process in epoxy based polymer systems. Sandia National Laboratories conducted the initial work and collaborated with North Dakota State University (NDSU) using a combinatorial research approach to produce a library of novel monomers and crosslinkers capable of forming porous polymers. The library was screened to determine the physical factors that control porosity, such as porogen loading, polymer-porogen interactions, and polymer crosslink density. We have identified the physical and chemical factors that control the average porosity, pore size, and pore size distribution within epoxy based systems.

  16. Pore Space Connectivity and the Transport Properties of Rocks

    Directory of Open Access Journals (Sweden)

    Bernabé Yves

    2016-07-01

    Full Text Available Pore connectivity is likely one of the most important factors affecting the permeability of reservoir rocks. Furthermore, connectivity effects are not restricted to materials approaching a percolation transition but can continuously and gradually occur in rocks undergoing geological processes such as mechanical and chemical diagenesis. In this study, we compiled sets of published measurements of porosity, permeability and formation factor, performed in samples of unconsolidated granular aggregates, in which connectivity does not change, and in two other materials, sintered glass beads and Fontainebleau sandstone, in which connectivity does change. We compared these data to the predictions of a Kozeny-Carman model of permeability, which does not account for variations in connectivity, and to those of Bernabé et al. (2010, 2011 model, which does [Bernabé Y., Li M., Maineult A. (2010 Permeability and pore connectivity: a new model based on network simulations, J. Geophys. Res. 115, B10203; Bernabé Y., Zamora M., Li M., Maineult A., Tang Y.B. (2011 Pore connectivity, permeability and electrical formation factor: a new model and comparison to experimental data, J. Geophys. Res. 116, B11204]. Both models agreed equally well with experimental data obtained in unconsolidated granular media. But, in the other materials, especially in the low porosity samples that had undergone the greatest amount of sintering or diagenesis, only Bernabé et al. model matched the experimental data satisfactorily. In comparison, predictions of the Kozeny-Carman model differed by orders of magnitude. The advantage of the Bernabé et al. model was its ability to account for a continuous, gradual reduction in pore connectivity during sintering or diagenesis. Although we can only speculate at this juncture about the mechanisms responsible for the connectivity reduction, we propose two possible mechanisms, likely to be active at different stages of sintering and diagenesis

  17. Understanding the mechanisms behind coking pressure: Relationship to pore structure

    Energy Technology Data Exchange (ETDEWEB)

    John J. Duffy; M. Castro Diaz; Colin E. Snape; Karen M. Steel; Merrick R. Mahoney [University of Nottingham, Nottingham (United Kingdom). Nottingham Fuel and Energy Centre, School of Chemical, Environmental and Mining Engineering

    2007-09-15

    Three low volatile coals A, B and C with oven wall pressures of 100 kPa, 60 kPa and 20 kPa respectively were investigated using high-temperature rheometry, {sup 1}H NMR, thermogravimetric analysis and SEM, with the primary aim to better understand the mechanisms behind the coking pressure phenomenon. Rheometer plate displacement measurements ({Delta}L) have shown differences in the expansion and contraction behaviour of the three coals, which seem to correlate with changes in rheological properties; while SEM images have shown that the expansion process coincides with development of pore structure. It is considered that the point of maximum plate height ({Delta}L{sub max}) prior to contraction may be indicative of a cell opening or pore network forming process, based on analogies with other foam systems. Such a process may be considered important for coking pressure since it provides a potential mechanism for volatile escape, relieving internal gas pressure and inducing charge contraction. For coal C, which has the highest fluidity {delta}L{sub max} occurs quite early in the softening process and consequently a large degree of contraction is observed; while for the lower fluidity coal B, the process is delayed since pore development and consequently wall thinning progress at a slower rate. When {Delta}L{sub max} is attained, a lower degree of contraction is observed because the event occurs closer to resolidification where the increasing viscosity/elasticity can stabilise the expanded pore structure. For coal A which is relatively high fluidity, but also high coking pressure, a greater degree of swelling is observed prior to cell rupture, which may be due to greater fluid elasticity during the expansion process. This excessive expansion is considered to be a potential reason for its high coking pressure. 58 refs., 15 figs., 1 tab.

  18. Estimation of pore pressure from seismic velocities

    International Nuclear Information System (INIS)

    Perez, Zayra; Ojeda, German Y; Mateus, Darwin

    2009-01-01

    On pore pressure calculations it is common to obtain a profile in a well bore, which is then extrapolated toward offset wells. This practice might generate mistakes on pore pressure measurements, since geological conditions may change from a well bore to another, even into the same basin. Therefore, it is important to use other tools which allow engineers not only to detect and estimate in an indirect way overpressure zones, but also to keep a lateral tracking of possible changes that may affect those values in the different formations. Taking into account this situation, we applied a methodology that estimates formation pressure from 3D seismic velocities by using the Eaton method. First, we estimated formation pore pressure; then, we identified possible overpressure zones. Finally, those results obtained from seismic information were analyzed involving well logs and pore pressure tests, in order to compare real data with prediction based on seismic information from the Colombian foothill.

  19. Block copolymer structures in nano-pores

    Science.gov (United States)

    Pinna, Marco; Guo, Xiaohu; Zvelindovsky, Andrei

    2010-03-01

    We present results of coarse-grained computer modelling of block copolymer systems in cylindrical and spherical nanopores on Cell Dynamics Simulation. We study both cylindrical and spherical pores and systematically investigate structures formed by lamellar, cylinders and spherical block copolymer systems for various pore radii and affinity of block copolymer blocks to the pore walls. The obtained structures include: standing lamellae and cylinders, ``onions,'' cylinder ``knitting balls,'' ``golf-ball,'' layered spherical, ``virus''-like and mixed morphologies with T-junctions and U-type defects [1]. Kinetics of the structure formation and the differences with planar films are discussed. Our simulations suggest that novel porous nano-containers can be formed by confining block copolymers in pores of different geometries [1,2]. [4pt] [1] M. Pinna, X. Guo, A.V. Zvelindovsky, Polymer 49, 2797 (2008).[0pt] [2] M. Pinna, X. Guo, A.V. Zvelindovsky, J. Chem. Phys. 131, 214902 (2009).

  20. Pore structure in blended cement pastes

    DEFF Research Database (Denmark)

    Canut, Mariana Moreira Cavalcanti

    Supplementary cementitious materials (SCMs), such as slag and fly ash, are increasingly used as a substitute for Portland cement in the interests of improvement of engineering properties and sustainability of concrete. According to studies improvement of engineering properties can be explained...... supplement each other. Cement pastes (w/b=0.4) with and without slag and fly ash cured at two moisture (sealed and saturated) and temperature (20 and 55ºC) conditions were used to investigate the combined impact of SCMs addition and curing on the pore structure of pastes cured up to two years. Also...... volume and threshold pore size were found when comparing with plain cement paste at the same curing conditions. The porosity methods MIP, LTC and SEM have been shown to be suitable to characterise pore parameters of the pastes. MIP is a simple and fast method which covers a large range of pore sizes...

  1. Visualization of enzyme activities inside earthworm pores

    Science.gov (United States)

    Hoang, Duyen; Razavi, Bahar S.

    2015-04-01

    In extremely dynamic microhabitats as bio-pores made by earthworm, the in situ enzyme activities are assumed as a footprint of complex biotic interactions. Our study focused on the effect of earthworm on the enzyme activities inside bio-pores and visualizing the differences between bio-pores and earthworm-free soil by zymography technique (Spohn and Kuzyakov, 2013). For the first time, we aimed at quantitative imaging of enzyme activities in bio-pores. Lumbricus terrestris L. was placed into transparent box (15×20×15cm). After two weeks when bio-pore systems were formed by earthworms, we visualized in situ enzyme activities of five hydrolytic enzymes (β-glucosidase, cellobiohydrolase, chitinase, xylanase, leucine-aminopeptidase, and phosphatase. Zymography showed higher activity of β-glucosidase, chitinase, xylanase and phosphatase in biopores comparing to bulk soil. However, the differences in activity of cellobiohydrolase and leucine aminopeptidase between bio-pore and bulk soil were less pronounced. This demonstrated an applicability of zymography approach to monitor and to distinguish the in situ activity of hydrolytic enzymes in soil biopores.

  2. Single Particle Tracking to Characterize the Mechanism of Pore Formation by Pore Forming Proteins

    OpenAIRE

    Subburaj, Yamunadevi

    2014-01-01

    Pore formation is a common natural mechanism occurring in large number of organisms where proteins are involved as toxins, effectors in immune response or apoptosis. Despite intense research, the structural and dynamic aspects of oligomerization and membrane permeabilization by pore forming proteins remains poorly understood. In this work we have aimed to provide a better understanding on dynamics, oligomerization and pore forming process of two proteins; a) Equinatoxin II, b) Bax (Bcl2 famil...

  3. A Dynamic Pore-Scale Model of Imbibition

    DEFF Research Database (Denmark)

    Mogensen, Kristian; Stenby, Erling Halfdan

    1998-01-01

    We present a dynamic pore-scale network model of imbibition, capable of calculating residual oil saturation for any given capillary number, viscosity ratio, contact angle and aspect ratio. Our goal is not to predict the outcome of core floods, but rather to perform a sensitivity analysis of the a......We present a dynamic pore-scale network model of imbibition, capable of calculating residual oil saturation for any given capillary number, viscosity ratio, contact angle and aspect ratio. Our goal is not to predict the outcome of core floods, but rather to perform a sensitivity analysis...... of the above-mentioned parameters, except the viscosity ratio. We find that contact angle, aspect ratio and capillary number all have a significant influence on the competition between piston-like advance, leading to high recovery, and snap-off, causing oil entrapment. Due to enormous CPU-time requirements we...... been entirely inhibited, in agreement with results obtained by Blunt using a quasi-static model. For higher aspect ratios, the effect of rate and contact angle is more pronounced. Many core floods are conducted at capillary numbers in the range 10 to10.6. We believe that the excellent recoveries...

  4. Pore REconstruction and Segmentation (PORES) method for improved porosity quantification of nanoporous materials

    Energy Technology Data Exchange (ETDEWEB)

    Van Eyndhoven, G., E-mail: geert.vaneyndhoven@uantwerpen.be [iMinds-Vision Lab, University of Antwerp, Universiteitsplein 1, B-2610 Wilrijk (Belgium); Kurttepeli, M. [EMAT, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp (Belgium); Van Oers, C.J.; Cool, P. [Laboratory of Adsorption and Catalysis, University of Antwerp, Universiteitsplein 1, B-2610 Wilrijk (Belgium); Bals, S. [EMAT, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp (Belgium); Batenburg, K.J. [iMinds-Vision Lab, University of Antwerp, Universiteitsplein 1, B-2610 Wilrijk (Belgium); Centrum Wiskunde and Informatica, Science Park 123, NL-1090 GB Amsterdam (Netherlands); Mathematical Institute, Universiteit Leiden, Niels Bohrweg 1, NL-2333 CA Leiden (Netherlands); Sijbers, J. [iMinds-Vision Lab, University of Antwerp, Universiteitsplein 1, B-2610 Wilrijk (Belgium)

    2015-01-15

    Electron tomography is currently a versatile tool to investigate the connection between the structure and properties of nanomaterials. However, a quantitative interpretation of electron tomography results is still far from straightforward. Especially accurate quantification of pore-space is hampered by artifacts introduced in all steps of the processing chain, i.e., acquisition, reconstruction, segmentation and quantification. Furthermore, most common approaches require subjective manual user input. In this paper, the PORES algorithm “POre REconstruction and Segmentation” is introduced; it is a tailor-made, integral approach, for the reconstruction, segmentation, and quantification of porous nanomaterials. The PORES processing chain starts by calculating a reconstruction with a nanoporous-specific reconstruction algorithm: the Simultaneous Update of Pore Pixels by iterative REconstruction and Simple Segmentation algorithm (SUPPRESS). It classifies the interior region to the pores during reconstruction, while reconstructing the remaining region by reducing the error with respect to the acquired electron microscopy data. The SUPPRESS reconstruction can be directly plugged into the remaining processing chain of the PORES algorithm, resulting in accurate individual pore quantification and full sample pore statistics. The proposed approach was extensively validated on both simulated and experimental data, indicating its ability to generate accurate statistics of nanoporous materials. - Highlights: • An electron tomography reconstruction/segmentation method for nanoporous materials. • The method exploits the porous nature of the scanned material. • Validated extensively on both simulation and real data experiments. • Results in increased image resolution and improved porosity quantification.

  5. Effect of pore size on the calculated pressure at biological cells pore wall.

    Science.gov (United States)

    El-Hag, Ayman H; Zheng, Zhong; Boggs, Steven A; Jayaram, Shesha H

    2006-09-01

    A transient nonlinear finite-element program has been used to calculate the electric field distribution as a function of time for a spherical cell with a pore in a conducting medium during application of a subnanosecond rise time "step" wave, including the effects of dipolar saturation in the water-based cytoplasm and cell medium. The time-dependent pressure on the pore wall has been computed as a function of time as the system polarizes from the change of the energy in the electric field to the left (inside the pore) and to the right (inside the membrane) of the pore wall. The computations suggest that dipolar saturation, while significant, has little effect on the time-dependent electric field distribution but a substantial effect on the field-induced pore wall pressure. Also, the effect of pore size on both the computed electric field and field-induced pressure was studied. As the pore size increases, a collapse in both the electric field and field-induced pressure has been noticed. This suggests that as the pore size increases, the driving force for further opening the pore is not electrical.

  6. New bimodal pore catalysts for Fischer-Tropsch synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Shinoda, Misao; Zhang, Yi; Yoneyama, Yoshiharu; Hasegawa, Kiyoshi; Tsubaki, Noritatsu [Department of Material System and Life Science, School of Engineering, Toyama University, Gofuku 3190, Toyama 930-8555 (Japan)

    2004-11-15

    A simple preparation method of bimodal pore supports was developed by introducing SiO{sub 2} or ZrO{sub 2} sols into large pores of SiO{sub 2} gel pellets directly. The pores of the obtained bimodal pore supports distributed distinctly as two kinds of main pores. On the other hand, the increased BET surface area and decreased pore volume, compared to those of original silica gel, indicated that the obtained bimodal pore supports formed according to the designed route. The obtained bimodal pore supports were applied in liquid-phase Fischer-Tropsch synthesis (FTS) where cobalt was supported. The bimodal pore catalysts presented the best reaction performance in liquid-phase Fischer-Tropsch synthesis (FTS) as higher reaction rate and lower methane selectivities, because the spatial promotional effect of bimodal pore structure and chemical effect of the porous zirconia behaved inside the large pores of original silica gel.

  7. A Novel Nano/Micro-Fluidic Reactor for Evaluation of Pore-Scale Reactive Transport

    Science.gov (United States)

    Werth, C. J.; Alcalde, R.; Ghazvini, S.; Sanford, R. A.; Fouke, B. W.; Valocchi, A. J.

    2017-12-01

    The reactive transport of pollutants in groundwater can be affected by the presence of stressor chemicals, which inhibit microbial functions. The stressor can be a primary reactant (e.g., trichloroethene), a reaction product (e.g., nitrite from nitrate), or some other chemical present in groundwater (e.g., antibiotic). In this work, a novel nano/microfluidic cell was developed to examine the effect of the antibiotic ciprofloxacin on nitrate reduction coupled to lactate oxidation. The reactor contains parallel boundary channels that deliver flow and solutes on either side of a pore network. The boundary channels are separated from the pore network by one centimeter-long, one micrometer-thick walls perforated by hundreds of nanoslits. The nanoslits allow solute mass transfer from the boundary channels to the pore network, but not microbial passage. The pore network was inoculated with a pure culture of Shewanella oneidensis MR-1, and this was allowed to grow on lactate and nitrate in the presence of ciprofloxacin, all delivered through the boundary channels. Microbial growth patterns suggest inhibition from ciprofloxacin and the nitrate reduction product nitrite, and a dependence on nitrate and lactate mass transfer rates from the boundary channels. A numerical model was developed to interpret the controlling mechanisms, and results indicate cell chemotaxis also affects nitrate reduction and microbial growth. The results are broadly relevant to bioremediation efforts where one or more chemicals that inhibit microbial growth are present and inhibit pollutant degradation rates.

  8. Facial skin pores: a multiethnic study.

    Science.gov (United States)

    Flament, Frederic; Francois, Ghislain; Qiu, Huixia; Ye, Chengda; Hanaya, Tomoo; Batisse, Dominique; Cointereau-Chardon, Suzy; Seixas, Mirela Donato Gianeti; Dal Belo, Susi Elaine; Bazin, Roland

    2015-01-01

    Skin pores (SP), as they are called by laymen, are common and benign features mostly located on the face (nose, cheeks, etc) that generate many aesthetic concerns or complaints. Despite the prevalence of skin pores, related literature is scarce. With the aim of describing the prevalence of skin pores and anatomic features among ethnic groups, a dermatoscopic instrument, using polarized lighting, coupled to a digital camera recorded the major features of skin pores (size, density, coverage) on the cheeks of 2,585 women in different countries and continents. A detection threshold of 250 μm, correlated to clinical scorings by experts, was input into a specific software to further allow for automatic counting of the SP density (N/cm(2)) and determination of their respective sizes in mm(2). Integrating both criteria also led to establishing the relative part of the skin surface (as a percentage) that is actually covered by SP on cheeks. The results showed that the values of respective sizes, densities, and skin coverage: 1) were recorded in all studied subjects; 2) varied greatly with ethnicity; 3) plateaued with age in most cases; and 4) globally refected self-assessment by subjects, in particular those who self-declare having "enlarged pores" like Brazilian women. Inversely, Chinese women were clearly distinct from other ethnicities in having very low density and sizes. Analyzing the present results suggests that facial skin pore's morphology as perceived by human eye less result from functional criteria of associated appendages such as sebaceous glands. To what extent skin pores may be viewed as additional criteria of a photo-altered skin is an issue to be further addressed.

  9. Pore fluid pressure and the seismic cycle

    Science.gov (United States)

    French, M. E.; Zhu, W.; Hirth, G.; Belzer, B.

    2017-12-01

    In the brittle crust, the critical shear stress required for fault slip decreases with increasing pore fluid pressures according to the effective stress criterion. As a result, higher pore fluid pressures are thought to promote fault slip and seismogenesis, consistent with observations that increasing fluid pressure as a result of wastewater injection is correlated with increased seismicity. On the other hand, elevated pore fluid pressure is also proposed to promote slow stable failure rather than seismicity along some fault zones, including during slow slip in subduction zones. Here we review recent experimental evidence for the roles that pore fluid pressure and the effective stress play in controlling fault slip behavior. Using two sets of experiments on serpentine fault gouge, we show that increasing fluid pressure does decrease the shear stress for reactivation under brittle conditions. However, under semi-brittle conditions as expected near the base of the seismogenic zone, high pore fluid pressures are much less effective at reducing the shear stress of reactivation even though deformation is localized and frictional. We use an additional study on serpentinite to show that cohesive fault rocks, potentially the product of healing and cementation, experience an increase in fracture energy during faulting as fluid pressures approach lithostatic, which can lead to more stable failure. Structural observations show that the increased fracture energy is associated with a greater intensity of transgranular fracturing and delocalization of deformation. Experiments on several lithologies indicate that the stabilizing effect of fluid pressure occurs independent of rock composition and hydraulic properties. Thus, high pore fluid pressures have the potential to either enhance seismicity or promote stable faulting depending on pressure, temperature, and fluid pressure conditions. Together, the results of these studies indicate that pore fluid pressure promotes

  10. Modeling branching pore structures in membrane filters

    Science.gov (United States)

    Sanaei, Pejman; Cummings, Linda J.

    2016-11-01

    Membrane filters are in widespread industrial use, and mathematical models to predict their efficacy are potentially very useful, as such models can suggest design modifications to improve filter performance and lifetime. Many models have been proposed to describe particle capture by membrane filters and the associated fluid dynamics, but most such models are based on a very simple structure in which the pores of the membrane are assumed to be simple circularly-cylindrical tubes spanning the depth of the membrane. Real membranes used in applications usually have much more complex geometry, with interconnected pores which may branch and bifurcate. Pores are also typically larger on the upstream side of the membrane than on the downstream side. We present an idealized mathematical model, in which a membrane consists of a series of bifurcating pores, which decrease in size as the membrane is traversed. Feed solution is forced through the membrane by applied pressure, and particles are removed from the feed either by sieving, or by particle adsorption within pores (which shrinks them). Thus the membrane's permeability decreases as the filtration progresses, ultimately falling to zero. We discuss how filtration efficiency depends on the characteristics of the branching structure. Partial support from NSF DMS 1261596 is gratefully acknowledged.

  11. Modeling Tissue Growth Within Nonwoven Scaffolds Pores

    Science.gov (United States)

    Church, Jeffrey S.; Alexander, David L.J.; Russell, Stephen J.; Ingham, Eileen; Ramshaw, John A.M.; Werkmeister, Jerome A.

    2011-01-01

    In this study we present a novel approach for predicting tissue growth within the pores of fibrous tissue engineering scaffolds. Thin nonwoven polyethylene terephthalate scaffolds were prepared to characterize tissue growth within scaffold pores, by mouse NR6 fibroblast cells. On the basis of measurements of tissue lengths at fiber crossovers and along fiber segments, mathematical models were determined during the proliferative phase of cell growth. Tissue growth at fiber crossovers decreased with increasing interfiber angle, with exponential relationships determined on day 6 and 10 of culture. Analysis of tissue growth along fiber segments determined two growth profiles, one with enhanced growth as a result of increased tissue lengths near the fiber crossover, achieved in the latter stage of culture. Derived mathematical models were used in the development of a software program to visualize predicted tissue growth within a pore. This study identifies key pore parameters that contribute toward tissue growth, and suggests models for predicting this growth, based on fibroblast cells. Such models may be used in aiding scaffold design, for optimum pore infiltration during the tissue engineering process. PMID:20687775

  12. Pore to core scale simulation of the mass transfer with mineral reaction in porous media

    International Nuclear Information System (INIS)

    Bekri, S.; Renard, S.; Delprat-Jannaud, F.

    2015-01-01

    Pore Network Model (PNM) is used to simulate mass transfer with mineral reaction in a single phase flow through porous medium which is here a sandstone sample from the reservoir formation of the Pakoslaw gas field. The void space of the porous medium is represented by an idealized geometry of pore-bodies joined by pore-throats. Parameters defining the pore-bodies and the pore-throats distribution are determined by an optimization process aiming to match the experimental Mercury Intrusion Capillary Pressure (MICP) curve and petrophysical properties of the rock such as intrinsic permeability and formation factor. The generated network is used first to simulate the multiphase flow by solving Kirchhoff's laws. The capillary pressure and relative permeability curves are derived. Then, reactive transport is addressed under asymptotic regime where the solute concentration undergoes an exponential evolution with time. The porosity/ permeability relationship and the three phenomenological coefficients of transport, namely the solute velocity, the dispersion and the mean reaction rate are determined as functions of Peclet and Peclet-Damkohler dimensionless numbers. Finally, the role of the dimensionless numbers on the reactive flow properties is highlighted. (authors)

  13. The water-induced linear reduction gas diffusivity model extended to three pore regions

    DEFF Research Database (Denmark)

    Chamindu, Deepagoda; De Jonge, Lis Wollesen; Kawamoto, Ken

    2015-01-01

    An existing gas diffusivity model developed originally for sieved, repacked soils was extended to characterize gas diffusion in differently structured soils and functional pore networks. A gas diffusivity-derived pore connectivity index was used as a measure of soil structure development. Charact......An existing gas diffusivity model developed originally for sieved, repacked soils was extended to characterize gas diffusion in differently structured soils and functional pore networks. A gas diffusivity-derived pore connectivity index was used as a measure of soil structure development....... Characterization of soil functional pore structure is an essential prerequisite to understand key gas transport processes in variably saturated soils in relation to soil ecosystems, climate, and environmental services. In this study, the water-induced linear reduction (WLR) soil gas diffusivity model originally...... gas diffusivity from moist to dry conditions across differently structured porous media, including narrow soil size fractions, perforated plastic blocks, fractured limestone, peaty soils, aggregated volcanic ash soils, and particulate substrates for Earth- or space-based applications. The new Cip...

  14. Non-isothermal crystallization kinetics and thermal behaviour of ...

    Indian Academy of Sciences (India)

    Administrator

    neering applications. The thermal property and crystalli- zation behaviour of these blends greatly influence the polymer properties through the crystal structure and mor- phology generated. Hence, it is desirable to study the thermal behaviour and crystallization kinetics of. PA/elastomer blends in both the isothermal and non-.

  15. Film condensation on non-isothermal vertical plates

    NARCIS (Netherlands)

    Brouwers, Jos

    1989-01-01

    An analytical study is presented of the condensation of a pure saturated vapour on a cooled channel plate, including the interaction between the cooling liquid, the condensate and the vapour. The governing equations of co-, counter- and cross-current condensation are derived, set dimensionless and

  16. Synthesis, characterisation and non-isothermal degradation kinetics ...

    Indian Academy of Sciences (India)

    Synthesis of a novel co-polymer made by the addition polymerisation between MEGDMA and 4-AB by aza-Michael addition (AMA) polymerisation method is a fascinating field of research. The present investigationyielded a hazardous metal catalyst-free and toxic solvent-free methodology. The AMA polymerisation was ...

  17. Synthesis, non-isothermal crystallization and magnetic properties of ...

    Indian Academy of Sciences (India)

    eral investigations were reported on morphology and crys- tallinity behaviour of this copolymer or that blended with other polymers, but no investigations were reported on the study of PEVA/ferrite nanocomposites. To achieve such a goal we have chosen the. Co0·75Zn0·25Fe2O4 as ferrite nanoparticles with magnetiza-.

  18. Synthesis, non-isothermal crystallization and magnetic properties of ...

    Indian Academy of Sciences (India)

    perties and harmlessness to health. PEVA, in their different compositions, are essentially randomic and semicrystalline, over the entire range of composition, despite the irregular- ity and non-steriospecificity of the vinyl alcohol units dis- tributed on the PEVA copolymer chain (Keskin and Elliot. 2003). No doubt that blending ...

  19. On a non-isothermal model for nematic liquid crystals

    Czech Academy of Sciences Publication Activity Database

    Feireisl, Eduard; Rocca, E.; Schimperna, G.

    2011-01-01

    Roč. 24, č. 1 (2011), s. 243-257 ISSN 0951-7715 R&D Projects: GA ČR GA201/09/0917; GA MŠk LC06052 Institutional research plan: CEZ:AV0Z10190503 Keywords : Navier-Stokes equation s * system * flows Subject RIV: BA - General Mathematics Impact factor: 1.386, year: 2011 http://iopscience.iop.org/0951-7715/24/1/012/

  20. Non-isothermal spreading of liquid drops on horizontal plates

    International Nuclear Information System (INIS)

    Ehrhard, P.; Davis, S.H.

    1990-05-01

    A viscous-liquid drop spreads on a smooth horizontal surface, which is uniformly heated or cooled. Lubrication theory is used to study thin drops subject to capillary, thermocapillary and gravity forces, and a variety of contact-angle-versus-speed conditions. It is found for isothermal drops that gravity is very important at large times and determines the power law for unlimited spreading. Predictions compare well with the experimental data on isothermal spreading for both two-dimensional and axisymmetric configurations. It is found that heating (cooling) retards (augments) the spreading process. When the advancing contact angle is zero, heating will cause the drop to spread only finitely far. For positive advancing contact angles, sufficient cooling will cause unlimited spreading. Thus, the heat transfer serves as a sentitive control on the spreading. (orig.) [de

  1. A benchmark study on non-isothermal compositional fluid flow

    DEFF Research Database (Denmark)

    Singh, Ashok; Böttcher, Norbert; Görke, U. J.

    2013-01-01

    CO2 capture and storage technology is often hampered by CO2 leakage through natural occurring fractures in the overlying caprock. This work suggests a two-dimensional test case of typical CO2 injection with possible leakage into freshwater resource. By using this test case in combination with a 1D...

  2. Modeling of Non-Isothermal Cryogenic Fluid Sloshing

    Science.gov (United States)

    Agui, Juan H.; Moder, Jeffrey P.

    2015-01-01

    A computational fluid dynamic model was used to simulate the thermal destratification in an upright self-pressurized cryostat approximately half-filled with liquid nitrogen and subjected to forced sinusoidal lateral shaking. A full three-dimensional computational grid was used to model the tank dynamics, fluid flow and thermodynamics using the ANSYS Fluent code. A non-inertial grid was used which required the addition of momentum and energy source terms to account for the inertial forces, energy transfer and wall reaction forces produced by the shaken tank. The kinetics-based Schrage mass transfer model provided the interfacial mass transfer due to evaporation and condensation at the sloshing interface. The dynamic behavior of the sloshing interface, its amplitude and transition to different wave modes, provided insight into the fluid process at the interface. The tank pressure evolution and temperature profiles compared relatively well with the shaken cryostat experimental test data provided by the Centre National D'Etudes Spatiales.

  3. Non-isothermal crystallization kinetics and thermal behaviour of ...

    Indian Academy of Sciences (India)

    Administrator

    engineering applications particularly in automotive and electrical industries.5–7 A major limitation of PA is its inherently low impact strength, especially at low tempera- ture. Hence, blending of PA with elastomers has been extensively used to make them suitable for versatile engi- neering applications. The thermal property ...

  4. Abareshi Maryam Non-isothermal crystallization kinetics of ...

    Indian Academy of Sciences (India)

    Administrator

    Alfaramawi K. Electric-field dependence of the electron mobility in bulk wurtzite ZnO. 1603. Altindal Ahmet .... Characterization of neutrophil adhesion to different titanium surfaces. 157. Canbay Erhan. Ionic liquid modified ... Processing, structure and flexural strength of CNT and carbon fibre reinforced, epoxy-matrix hybrid ...

  5. Synthesis, characterisation and non-isothermal degradation kinetics ...

    Indian Academy of Sciences (India)

    between MEGDMA and aromatic primary amine leads to. AMA polymerisation. The slope value declared that, 0.31 mol of monomer is required to form 1 mol of the co-polymer. 3.2 UV–visible reflectance study. The above-synthesised polymer was characterised by UV– visible reflectance study. The co-polymer contains both.

  6. Abareshi Maryam Non-isothermal crystallization kinetics of ...

    Indian Academy of Sciences (India)

    Administrator

    ing (FSP) of Al–TiC in situ composite. 571. Bechir M Ben ..... carbide–cobalt bounded inserts. 327. Kamariah see Kartini I. 1419. Kanagaraj S .... see Yuan Changlai. 263. Liu Yanyun. A simple and efficient electrochemical reductive method for graphene oxide. 1529. Liu Zi Xuan see Chen Chang Chun. 1725. Logan Philip J.

  7. Synthesis, characterisation and non-isothermal degradation kinetics ...

    Indian Academy of Sciences (India)

    out at five different [M1/M2] values under N2 atmosphere at 100◦C for 2 h. Thus, obtained co-polymer was charac- terized by .... the slope value one can calculate the apparent activation energy. 2.5b Friedman method: ..... [4] Escalante J, Morales M C and Linzaga I 2008 Molecules 13. 340. [5] Kou J P, Lu Y J, Luo X Y and Li ...

  8. Non-isothermal crystallization kinetics of polyethylene–clay ...

    Indian Academy of Sciences (India)

    Administrator

    received much attention because of their significant prop- erties with respect to the neat polymer such as better mechanical properties, higher thermal stability, reduced thermal expansion coefficient and gas permeability. (Xu et al 2005). Crystallization kinetics of semi-crystalline polymers have been continuously the subject ...

  9. Synthesis, characterisation and non-isothermal degradation kinetics ...

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 39; Issue 7 ... Synthesis of a novel co-polymer made by the addition polymerisation between MEGDMA and 4-AB by aza-Michael addition (AMA) polymerisation method is a ... Among the modelsused, the Kissinger method yielded the lowest degradation kinetics.

  10. Calorimetric studies of non-isothermal crystallization in amorphous

    Indian Academy of Sciences (India)

    Administrator

    congruently melting compound, which should allow static under-cooling experiments. Several works on the mecha- nical properties and microstructures of copper– ..... Koga and Sestak (1991) have shown that the kinetic compensation effect mathematically results from the exponential form of the rate constant. A change of ...

  11. Final Report for Subcontract B541028, Pore-Scale Modeling to Support 'Pore Connectivity' Research Work

    International Nuclear Information System (INIS)

    Ewing, R.P.

    2009-01-01

    This report covers modeling aspects of a combined experimental and modeling task in support of the DOE Science and Technology Program (formerly OSTI) within the Office of Civilian Radioactive Waste Management (OCRWM). Research Objectives The research for this project dealt with diffusive retardation: solute moving through a fracture diffuses into and out of the rock matrix. This diffusive exchange retards overall solute movement, and retardation both dilutes waste being released, and allows additional decay. Diffusive retardation involves not only fracture conductivity and matrix diffusion, but also other issues and processes: contaminants may sorb to the rock matrix, fracture flow may be episodic, a given fracture may or may not flow depending on the volume of flow and the fracture's connection to the overall fracture network, the matrix imbibes water during flow episodes and dries between episodes, and so on. The objective of the project was to improve understanding of diffusive retardation of radionuclides due to fracture / matrix interactions. Results from combined experimental/modeling work were to (1) determine whether the current understanding and model representation of matrix diffusion is valid, (2) provide insights into the upscaling of laboratory-scale diffusion experiments, and (3) help in evaluating the impact on diffusive retardation of episodic fracture flow and pore connectivity in Yucca Mountain tuffs. Questions explored included the following: (1) What is the relationship between the diffusion coefficient measured at one scale, to that measured or observed at a different scale? In classical materials this relationship is trivial; in low-connectivity materials it is not. (2) Is the measured diffusivity insensitive to the shape of the sample? Again, in classical materials there should be no sample shape effect. (3) Does sorption affect diffusive exchange in low-connectivity media differently than in classical media? (4) What is the effect of matrix

  12. Final Report for Subcontract B541028, Pore-Scale Modeling to Support "Pore Connectivity" Research Work

    Energy Technology Data Exchange (ETDEWEB)

    Ewing, R P

    2009-02-25

    This report covers modeling aspects of a combined experimental and modeling task in support of the DOE Science and Technology Program (formerly OSTI) within the Office of Civilian Radioactive Waste Management (OCRWM). Research Objectives The research for this project dealt with diffusive retardation: solute moving through a fracture diffuses into and out of the rock matrix. This diffusive exchange retards overall solute movement, and retardation both dilutes waste being released, and allows additional decay. Diffusive retardation involves not only fracture conductivity and matrix diffusion, but also other issues and processes: contaminants may sorb to the rock matrix, fracture flow may be episodic, a given fracture may or may not flow depending on the volume of flow and the fracture's connection to the overall fracture network, the matrix imbibes water during flow episodes and dries between episodes, and so on. The objective of the project was to improve understanding of diffusive retardation of radionuclides due to fracture / matrix interactions. Results from combined experimental/modeling work were to (1) determine whether the current understanding and model representation of matrix diffusion is valid, (2) provide insights into the upscaling of laboratory-scale diffusion experiments, and (3) help in evaluating the impact on diffusive retardation of episodic fracture flow and pore connectivity in Yucca Mountain tuffs. Questions explored included the following: (1) What is the relationship between the diffusion coefficient measured at one scale, to that measured or observed at a different scale? In classical materials this relationship is trivial; in low-connectivity materials it is not. (2) Is the measured diffusivity insensitive to the shape of the sample? Again, in classical materials there should be no sample shape effect. (3) Does sorption affect diffusive exchange in low-connectivity media differently than in classical media? (4) What is the effect of

  13. Unplugging the callose plug from sieve pores.

    Science.gov (United States)

    Xie, Bo; Hong, Zonglie

    2011-04-01

    The presence of callose in sieve plates has been known for a long time, but how this polysaccharide plug is synthesized has remained unsolved. Two independent laboratories have recently reported the identification of callose synthase 7 (CalS7), also known as glucan synthase-like 7 (GSL7), as the enzyme responsible for callose deposition in sieve plates. Mutant plants defective in this enzyme failed to synthesize callose in developing sieve plates during phloem formation and were unable to accumulate callose in sieve pores in response to stress treatments. The mutant plants developed less open pores per sieve plate and the pores were smaller in diameter. As a result, phloem conductivity was reduced significantly and the mutant plants were shorter and set fewer seeds.

  14. Pore-forming toxins in Cnidaria.

    Science.gov (United States)

    Podobnik, Marjetka; Anderluh, Gregor

    2017-12-01

    The ancient phylum of Cnidaria contains many aquatic species with peculiar lifestyle. In order to survive, these organisms have evolved attack and defense mechanisms that are enabled by specialized cells and highly developed venoms. Pore-forming toxins are an important part of their venomous arsenal. Along some other types, the most representative are examples of four protein families that are commonly found in other kingdoms of life: actinoporins, Cry-like proteins, aerolysin-like toxins and MACPF/CDC toxins. Some of the homologues of pore-forming toxins may serve other functions, such as in food digestion, development and response against pathogenic organisms. Due to their interesting physico-chemical properties, the cnidarian pore-forming toxins may also serve as tools in medical research and nanobiotechnological applications. Copyright © 2017 Elsevier Ltd. All rights reserved.

  15. Moving Magnetic Features Around a Pore

    Energy Technology Data Exchange (ETDEWEB)

    Kaithakkal, A. J.; Riethmüller, T. L.; Solanki, S. K.; Lagg, A.; Barthol, P.; Gandorfer, A.; Gizon, L.; Hirzberger, J.; VanNoort, M. [Max Planck Institute for Solar System Research, Justus-von-Liebig-Weg 3, Göttingen D-37077 (Germany); Rodríguez, J. Blanco [Grupo de Astronomía y Ciencias del Espacio, Universidad de Valencia, E-46980 Paterna, Valencia (Spain); Iniesta, J. C. Del Toro; Suárez, D. Orozco [Instituto de Astrofísica de Andalucía (CSIC), Apartado de Correos 3004, E-18080 Granada (Spain); Schmidt, W. [Kiepenheuer-Institut für Sonnenphysik, Schöneckstr. 6, D-79104 Freiburg (Germany); Pillet, V. Martínez [National Solar Observatory, 3665 Discovery Drive, Boulder, CO 80303 (United States); Knölker, M., E-mail: anjali@mps.mpg.de [High Altitude Observatory, National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307-3000 (United States)

    2017-03-01

    Spectropolarimetric observations from Sunrise/IMaX, obtained in 2013 June, are used for a statistical analysis to determine the physical properties of moving magnetic features (MMFs) observed near a pore. MMFs of the same and opposite polarity, with respect to the pore, are found to stream from its border at an average speed of 1.3 km s{sup −1} and 1.2 km s{sup −1}, respectively, with mainly same-polarity MMFs found further away from the pore. MMFs of both polarities are found to harbor rather weak, inclined magnetic fields. Opposite-polarity MMFs are blueshifted, whereas same-polarity MMFs do not show any preference for up- or downflows. Most of the MMFs are found to be of sub-arcsecond size and carry a mean flux of ∼1.2 × 10{sup 17} Mx.

  16. Porous media fluid transport and pore structure

    CERN Document Server

    Dullien, F A L

    1992-01-01

    This book examines the relationship between transport properties and pore structure of porous material. Models of pore structure are presented with a discussion of how such models can be used to predict the transport properties of porous media. Portions of the book are devoted to interpretations of experimental results in this area and directions for future research. Practical applications are given where applicable, and are expected to be useful for a large number of different fields, including reservoir engineering, geology, hydrogeology, soil science, chemical process engineering, biomedica

  17. Pore-scale modeling of pore structure effects on P-wave scattering attenuation in dry rocks.

    Science.gov (United States)

    Wang, Zizhen; Wang, Ruihe; Li, Tianyang; Qiu, Hao; Wang, Feifei

    2015-01-01

    Underground rocks usually have complex pore system with a variety of pore types and a wide range of pore size. The effects of pore structure on elastic wave attenuation cannot be neglected. We investigated the pore structure effects on P-wave scattering attenuation in dry rocks by pore-scale modeling based on the wave theory and the similarity principle. Our modeling results indicate that pore size, pore shape (such as aspect ratio), and pore density are important factors influencing P-wave scattering attenuation in porous rocks, and can explain the variation of scattering attenuation at the same porosity. From the perspective of scattering attenuation, porous rocks can safely suit to the long wavelength assumption when the ratio of wavelength to pore size is larger than 15. Under the long wavelength condition, the scattering attenuation coefficient increases as a power function as the pore density increases, and it increases exponentially with the increase in aspect ratio. For a certain porosity, rocks with smaller aspect ratio and/or larger pore size have stronger scattering attenuation. When the pore aspect ratio is larger than 0.5, the variation of scattering attenuation at the same porosity is dominantly caused by pore size and almost independent of the pore aspect ratio. These results lay a foundation for pore structure inversion from elastic wave responses in porous rocks.

  18. Double urine circulation: importance of pores.

    Science.gov (United States)

    Antonello, Augusto; D'Angelo, Angela; Nalesso, Federico; Capezzi, Maria; Malagoli, Andrea; Pastori, Giordano; Lazzarin, Roberta; Calò, Lorenzo; Bonfante, Luciana; Gambaro, Giovanni

    2003-01-01

    The authors examine a presentation to the Royal Academy of Sciences of Paris by L. Morin, French physician and meteorologist. In this communication the presence of "pores" in the stomach and the bladder, which would allow a quick elimination of the urines on the occasion of an abundant fluid intake.

  19. Mimicking the nuclear pore complex using nanopores

    NARCIS (Netherlands)

    Ananth, A.N.

    2018-01-01

    Nuclear pore complexes acts as a gatekeeper for molecular transport between the nucleus and the cytoplasm in eukaryotic cells. The central NPC channel is filled with intrinsically disordered FG domains (phenylalanine (F), glycine (G)) that are responsible for the fascinating selectivity of NPCs, for

  20. Induction of nano pore in Agrobacterial hemoglobin

    Directory of Open Access Journals (Sweden)

    Mojtaba Tousheh

    2014-01-01

    Full Text Available Introduction: A variety of oxygen-transport and -binding proteins exist in organisms including bacteria, protozoans, and fungi all have hemoglobin-like proteins. In addition to dealing with transport and sensing of oxygen, they may also deal with NO2, CO2, sulfide compounds, and even O2 scavenging in environments. Also they detoxified chlorinated materials like P450 enzymes and peroxidases and use as a detector of nitrate and hydrogen peroxide. Pore-forming bacterial globins are interested for filtration. Materials and methods: Although there are data for bacterial toxin as a filter, here we used Agrobacterial hem to induce nano pore in the heme structure using point mutation. Results: Investigations showed that three amino acids leucine 76, alanine 83 and histidine 80 are important for pore formation in Agrobacterium hemoglobin. A point mutation on leucine 76 to glycine, histidine 80 to asparagine and alanine 83 to lysine step by step led to create the nano pore 0.7- 0.8 nm in the globin. Discussion and conclusion: These mutations in bacterial hemoglobin increase the stability when mutation is with it’s at pH7. This mutation decreases the aliphatic index however increase the stability index.

  1. Temperature and Pressure from Collapsing Pores in HMX

    Science.gov (United States)

    Hardin, D. Barrett

    2017-06-01

    The thermal and mechanical response of collapsing voids in HMX is analyzed. In this work, the focus is simulating the temperature and pressure fields arising from isolated, idealized pores as they collapse in the presence of a shock. HMX slabs are numerically generated which contain a single pore, isolated from the boundaries to remove all wave reflections. In order to understand the primary pore characteristics leading to temperature rise, a series of 2D, plane strain simulations are conducted on HMX slabs containing both cylindrical and elliptical pores of constant size equal to the area of a circular pore with a 1 micron diameter. Each of these pore types is then subjected to shock pressures ranging from a weak shock that is unable to fully collapse the pore to a strong shock which overwhelms the tendency for localization. Results indicate that as shock strength increases, pore collapse phenomenology for a cylindrical pore transitions from a mode dominated by localized melt cracking to an idealized hydrodynamic pore collapse. For the case of elliptical pores, the orientation causing maximum temperature and pressure rise is found. The relative heating in elliptical pores is then quantified as a function of pore orientation and aspect ratio for a pore of a given area. Distribution A: Distribution unlimited. (96TW 2017-0036).

  2. Variable pore connectivity model linking gas diffusivity and air-phase tortuosity to soil matric potential

    DEFF Research Database (Denmark)

    Chamindu, Deepagoda; Møldrup, Per; Schjønning, Per

    2012-01-01

    - and intraaggregate pore regions of aggregated soils. We further suggest that the new model with parameter values of X* = 1.7 and A = 0 may be used for upper limit Dp/Do predictions in risk assessments of, e.g., fluxes of toxic volatile organics from soil to indoor air at polluted soil sites....... of a variable pore connectivity factor, X, as a function of soil matric potential, expressed as pF (=log |−ψ|), for pF values ranging from 1.0 to 3.5. The new model takes the form of X = X* (F/F*)A with F = 1 + pF−1, where X* is the pore network tortuosity at reference F (F*) and A is a model parameter...... that accounts for water blockage. The X–pF relation can be linked to drained pore size to explain the lower probability of the larger but far fewer air-filled pores at lower pF effectively interconnecting and promoting gas diffusion. The model with X* = 2 and A = 0.5 proved promising for generalizing Dp...

  3. Pores and Void in Asclepiades’ Physical Theory

    Science.gov (United States)

    Leith, David

    2012-01-01

    This paper examines a fundamental, though relatively understudied, aspect of the physical theory of the physician Asclepiades of Bithynia, namely his doctrine of pores. My principal thesis is that this doctrine is dependent on a conception of void taken directly from Epicurean physics. The paper falls into two parts: the first half addresses the evidence for the presence of void in Asclepiades’ theory, and concludes that his conception of void was basically that of Epicurus; the second half focuses on the precise nature of Asclepiadean pores, and seeks to show that they represent void interstices between the primary particles of matter which are the constituents of the human body, and are thus exactly analogous to the void interstices between atoms within solid objects in Epicurus’ theory. PMID:22984299

  4. Hydrophobic polymers modification of mesoporous silica with large pore size for drug release

    Energy Technology Data Exchange (ETDEWEB)

    Zhu Shenmin, E-mail: smzhu@sjtu.edu.c [Shanghai Jiao Tong University, State Key Lab of Metal Matrix Composites (China); Zhang Di; Yang Na [Fudan University, Ministry of Education, Key Lab of Molecular Engineering of Polymers (China)

    2009-04-15

    Mesostructure cellular foam (MCF) materials were modified with hydrophobic polyisoprene (PI) through free radical polymerization in the pores network, and the resulting materials (MCF-PI) were investigated as matrices for drug storage. The successful synthesis of PI inside MCF was characterized by Fourier transform infrared (FT-IR), hydrogen nuclear magnetic resonance ({sup 1}H NMR), X-ray diffraction patterns (XRD) and nitrogen adsorption/desorption measurements. It was interesting to find the resultant system held a relatively large pore size (19.5 nm) and pore volume (1.02 cm{sup 3} g{sup -1}), which would benefit for drug storage. Ibuprofen (IBU) and vancomycin were selected as model drugs and loaded onto unmodified MCF and modified MCF (MCF-PI). The adsorption capacities of these model drugs on MCF-PI were observed increase as compared to that of on pure MCF, due to the trap effects induced by polyisoprene chains inside the pores. The delivery system of MCF-PI was found to be more favorable for the adsorption of IBU (31 wt%, IBU/silica), possibly attributing to the hydrophobic interaction between IBU and PI formed on the internal surface of MCF matrix. The release of drug through the porous network was investigated by measuring uptake and release of IBU.

  5. Effects of pore topology and iron oxide core on doxorubicin loading and release from mesoporous silica nanoparticles

    Science.gov (United States)

    Ronhovde, Cicily J.; Baer, John; Larsen, Sarah C.

    2017-06-01

    Mesoporous silica nanoparticles (MSNs) have a network of pores that give rise to extremely high specific surface areas, making them attractive materials for applications such as adsorption and drug delivery. The pore topology can be readily tuned to achieve a variety of structures such as the hexagonally ordered Mobil Crystalline Material 41 (MCM-41) and the disordered "wormhole" (WO) mesoporous silica (MS) structure. In this work, the effects of pore topology and iron oxide core on doxorubicin loading and release were investigated using MSNs with pore diameters of approximately 3 nm and sub-100 nm particle diameters. The nanoparticles were loaded with doxorubicin, and the drug release into phosphate-buffered saline (PBS, 10 mM, pH 7.4) at 37 °C was monitored by fluorescence spectroscopy. The release profiles were fit using the Peppas model. The results indicated diffusion-controlled release for all samples. Statistically significant differences were observed in the kinetic host-guest parameters for each sample due to the different pore topologies and the inclusion of an iron oxide core. Applying a static magnetic field to the iron oxide core WO-MS shell materials did not have a significant impact on the doxorubicin release. This is the first time that the effects of pore topology and iron oxide core have been isolated from pore diameter and particle size for these materials.

  6. Pore-Scale Model for Microbial Growth

    Science.gov (United States)

    Tartakovsky, G.; Tartakovsky, A. M.; Scheibe, T. D.

    2011-12-01

    A lagrangian particle model based on smoothed particle hydrodynamics (SPH) is used to simulate pore-scale flow, reactive transport and biomass growth which is controlled by the mixing of an electron donor and acceptor, in a microfluidic porous cell. The experimental results described in Ch. Zhang et al "Effects of pore-scale heterogeneity and transverse mixing on bacterial growth in porous media" were used for this study. The model represents the homogeneous pore structure of a uniform array of cylindrical posts with microbes uniformly distributed on the grain surfaces. Each one of the two solutes (electron donor and electron acceptor) enters the domain unmixed through separate inlets. In the model, pair-wise particle-particle interactions are used to simulate interactions within the biomass, and both biomass-fluid and biomass-soil grain interactions. The biomass growth rate is described by double Monod kinetics. For the set of parameters used in the simulations the model predicts that: 1) biomass grows in the shape of bridges connecting soil grains and oriented in the direction of flow so as to minimize resistance to the fluid flow; and 2) the biomass growth occurs only in the mixing zone. Using parameters available in the literature, the biomass growth model agrees qualitatively with the experimental results. In order to achieve quantitative agreement, model calibration is required.

  7. Dendritic silica nanomaterials (KCC-1) with fibrous pore structure possess high DNA adsorption capacity and effectively deliver genes in vitro.

    Science.gov (United States)

    Huang, Xiaoxi; Tao, Zhimin; Praskavich, John C; Goswami, Anandarup; Al-Sharab, Jafar F; Minko, Tamara; Polshettiwar, Vivek; Asefa, Tewodros

    2014-09-16

    The pore size and pore structure of nanoporous materials can affect the materials' physical properties, as well as potential applications in different areas, including catalysis, drug delivery, and biomolecular therapeutics. KCC-1, one of the newest members of silica nanomaterials, possesses fibrous, large pore, dendritic pore networks with wide pore entrances, large pore size distribution, spacious pore volume and large surface area--structural features that are conducive for adsorption and release of large guest molecules and biomacromolecules (e.g., proteins and DNAs). Here, we report the results of our comparative studies of adsorption of salmon DNA in a series of KCC-1-based nanomaterials that are functionalized with different organoamine groups on different parts of their surfaces (channel walls, external surfaces or both). For comparison the results of our studies of adsorption of salmon DNA in similarly functionalized, MCM-41 mesoporous silica nanomaterials with cylindrical pores, some of the most studied silica nanomaterials for drug/gene delivery, are also included. Our results indicate that, despite their relatively lower specific surface area, the KCC-1-based nanomaterials show high adsorption capacity for DNA than the corresponding MCM-41-based nanomaterials, most likely because of KCC-1's large pores, wide pore mouths, fibrous pore network, and thereby more accessible and amenable structure for DNA molecules to diffuse through. Conversely, the MCM-41-based nanomaterials adsorb much less DNA, presumably because their outer surfaces/cylindrical channel pore entrances can get blocked by the DNA molecules, making the inner parts of the materials inaccessible. Moreover, experiments involving fluorescent dye-tagged DNAs suggest that the amine-grafted KCC-1 materials are better suited for delivering the DNAs adsorbed on their surfaces into cellular environments than their MCM-41 counterparts. Finally, cellular toxicity tests show that the KCC-1-based

  8. Real-Time Pore Pressure Detection: Indicators and Improved Methods

    OpenAIRE

    Jincai Zhang; Shangxian Yin

    2017-01-01

    High uncertainties may exist in the predrill pore pressure prediction in new prospects and deepwater subsalt wells; therefore, real-time pore pressure detection is highly needed to reduce drilling risks. The methods for pore pressure detection (the resistivity, sonic, and corrected d-exponent methods) are improved using the depth-dependent normal compaction equations to adapt to the requirements of the real-time monitoring. A new method is proposed to calculate pore pressure from the connecti...

  9. Facial skin pores: a multiethnic study

    Directory of Open Access Journals (Sweden)

    Flament F

    2015-02-01

    Full Text Available Frederic Flament,1 Ghislain Francois,1 Huixia Qiu,2 Chengda Ye,2 Tomoo Hanaya,3 Dominique Batisse,3 Suzy Cointereau-Chardon,1 Mirela Donato Gianeti Seixas,4 Susi Elaine Dal Belo,4 Roland Bazin5 1Department of Applied Research and Development, L’Oreal Research and Innovation, Paris, France; 2Department of Applied Research and Development, L’Oreal Research and Innovation, Shanghai, People’s Republic of China; 3Department of Applied Research and Development, L’Oreal Research and Innovation, Tokyo, Japan; 4Department of Applied Research and Development, L’Oreal Research and Innovation, Rio de Janeiro, Brazil; 5RB Consult, Bievres, France Abstract: Skin pores (SP, as they are called by laymen, are common and benign features mostly located on the face (nose, cheeks, etc that generate many aesthetic concerns or complaints. Despite the prevalence of skin pores, related literature is scarce. With the aim of describing the prevalence of skin pores and anatomic features among ethnic groups, a dermatoscopic instrument, using polarized lighting, coupled to a digital camera recorded the major features of skin pores (size, density, coverage on the cheeks of 2,585 women in different countries and continents. A detection threshold of 250 µm, correlated to clinical scorings by experts, was input into a specific software to further allow for automatic counting of the SP density (N/cm2 and determination of their respective sizes in mm2. Integrating both criteria also led to establishing the relative part of the skin surface (as a percentage that is actually covered by SP on cheeks. The results showed that the values of respective sizes, densities, and skin coverage: 1 were recorded in all studied subjects; 2 varied greatly with ethnicity; 3 plateaued with age in most cases; and 4 globally reflected self-assessment by subjects, in particular those who self-declare having “enlarged pores” like Brazilian women. Inversely, Chinese women were clearly

  10. Estimation of adsorption-induced pore pressure and confinement in a nanoscopic slit pore by a density functional theory

    Science.gov (United States)

    Grégoire, David; Malheiro, Carine; Miqueu, Christelle

    2018-03-01

    This study aims at characterising the adsorption-induced pore pressure and confinement in nanoscopic pores by molecular non-local density functional theory (DFT). Considering its important potential industrial applications, the adsorption of methane in graphitic slit pores has been selected as the test case. While retaining the accuracy of molecular simulations at pore scale, DFT has a very low computational cost that allows obtaining highly resolved pore pressure maps as a function of both pore width and thermodynamic conditions. The dependency of pore pressure on these parameters (pore width, pressure and temperature) is carefully analysed in order to highlight the effect of each parameter on the confined fluid properties that impact the solid matrix.

  11. Capillary pressure in a porous medium with distinct pore surface and pore volume fractal dimensions.

    Science.gov (United States)

    Deinert, M R; Dathe, A; Parlange, J-Y; Cady, K B

    2008-02-01

    The relationship between capillary pressure and saturation in a porous medium often exhibits a power-law dependence. The physical basis for this relation has been substantiated by assuming that capillary pressure is directly related to the pore radius. When the pore space of a medium exhibits fractal structure this approach results in a power-law relation with an exponent of 3-D(v), where D(v) is the pore volume fractal dimension. However, larger values of the exponent than are realistically allowed by this result have long been known to occur. Using a thermodynamic formulation for equilibrium capillary pressure we show that the standard result is a special case of the more general exponent (3-D(v))(3-D(s)) where D(s) is the surface fractal dimension of the pores. The analysis reduces to the standard result when D(s)=2, indicating a Euclidean relationship between a pore's surface area and the volume it encloses, and allows for a larger value for the exponent than the standard result when D(s)>2 .

  12. Nuclear networking.

    Science.gov (United States)

    Xie, Wei; Burke, Brian

    2017-07-04

    Nuclear lamins are intermediate filament proteins that represent important structural components of metazoan nuclear envelopes (NEs). By combining proteomics and superresolution microscopy, we recently reported that both A- and B-type nuclear lamins form spatially distinct filament networks at the nuclear periphery of mouse fibroblasts. In particular, A-type lamins exhibit differential association with nuclear pore complexes (NPCs). Our studies reveal that the nuclear lamina network in mammalian somatic cells is less ordered and more complex than that of amphibian oocytes, the only other system in which the lamina has been visualized at high resolution. In addition, the NPC component Tpr likely links NPCs to the A-type lamin network, an association that appears to be regulated by C-terminal modification of various A-type lamin isoforms. Many questions remain, however, concerning the structure and assembly of lamin filaments, as well as with their mode of association with other nuclear components such as peripheral chromatin.

  13. Energy conversion device with support member having pore channels

    Science.gov (United States)

    Routkevitch, Dmitri [Longmont, CO; Wind, Rikard A [Johnstown, CO

    2014-01-07

    Energy devices such as energy conversion devices and energy storage devices and methods for the manufacture of such devices. The devices include a support member having an array of pore channels having a small average pore channel diameter and having a pore channel length. Material layers that may include energy conversion materials and conductive materials are coaxially disposed within the pore channels to form material rods having a relatively small cross-section and a relatively long length. By varying the structure of the materials in the pore channels, various energy devices can be fabricated, such as photovoltaic (PV) devices, radiation detectors, capacitors, batteries and the like.

  14. High Fidelity Computational Analysis of CO2 Trapping at Pore Scales

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Vinod

    2013-07-13

    With an alarming rise in carbon dioxide (CO2) emission from anthropogenic sources, CO2 sequestration has become an attractive choice to mitigate the emission. Some popular storage media for CO{sub 2} are oil reservoirs, deep coal-bed, and deep oceanic-beds. These have been used for the long term CO{sub 2} storage. Due to special lowering viscosity and surface tension property of CO{sub 2}, it has been widely used for enhanced oil recovery. The sites for CO{sub 2} sequestration or enhanced oil recovery mostly consist of porous rocks. Lack of knowledge of molecular mobility under confinement and molecule-surface interactions between CO2 and natural porous media results in generally governed by unpredictable absorption kinetics and total absorption capacity for injected fluids, and therefore, constitutes barriers to the deployment of this technology. Therefore, it is important to understand the flow dynamics of CO{sub 2} through the porous microstructures at the finest scale (pore-scale) to accurately predict the storage potential and long-term dynamics of the sequestered CO{sub 2}. This report discusses about pore-network flow modeling approach using variational method and analyzes simulated results this method simulations at pore-scales for idealized network and using Berea Sandstone CT scanned images. Variational method provides a promising way to study the kinetic behavior and storage potential at the pore scale in the presence of other phases. The current study validates variational solutions for single and two-phase Newtonian and single phase non-Newtonian flow through angular pores for special geometries whose analytical and/or empirical solutions are known. The hydraulic conductance for single phase flow through a triangular duct was also validated against empirical results derived from lubricant theory.

  15. Quantifying similarity of pore-geometry in nanoporous materials

    Science.gov (United States)

    Lee, Yongjin; Barthel, Senja D.; Dłotko, Paweł; Moosavi, S. Mohamad; Hess, Kathryn; Smit, Berend

    2017-05-01

    In most applications of nanoporous materials the pore structure is as important as the chemical composition as a determinant of performance. For example, one can alter performance in applications like carbon capture or methane storage by orders of magnitude by only modifying the pore structure. For these applications it is therefore important to identify the optimal pore geometry and use this information to find similar materials. However, the mathematical language and tools to identify materials with similar pore structures, but different composition, has been lacking. We develop a pore recognition approach to quantify similarity of pore structures and classify them using topological data analysis. This allows us to identify materials with similar pore geometries, and to screen for materials that are similar to given top-performing structures. Using methane storage as a case study, we also show that materials can be divided into topologically distinct classes requiring different optimization strategies.

  16. Rock Physics of Reservoir Rocks with Varying Pore Water Saturation and Pore Water Salinity

    DEFF Research Database (Denmark)

    Katika, Konstantina

    the mechanical or physical properties of the rock during waterflooding experiments. The phenomena include decreased pore stiffness and subsequent compaction and can be related to a variety of parameters; including precipitation and dissolution reactions, as well as adsorption reactions and changes in wettability...... to understand the potential mechanisms behind the action of ions in high concentration on the chalk surface; such as precipitation and dissolution. The effect of the divalent ions on the elasticity and pore collapse of this rock was observed and validated from the ultrasonic velocity data. Low field NMR...

  17. Silicon pore optics developments and status

    DEFF Research Database (Denmark)

    Bavdaz, Marcos; Wille, Eric; Wallace, Kotska

    2012-01-01

    Silicon Pore Optics (SPO) is a lightweight high performance X-ray optics technology being developed in Europe, driven by applications in observatory class high energy astrophysics missions. An example of such application is the former ESA science mission candidate ATHENA (Advanced Telescope...... for High Energy Astrophysics), which uses the SPO technology for its two telescopes, in order to provide an effective area exceeding 1 m2 at 1 keV, and 0.5 m2 at 6 keV, featuring an angular resolution of 10" or better [1 to 24]. This paper reports on the development activities led by ESA, and the status...

  18. [A photographic scale for evaluating facial pores and analysis of factors associated with pore widening in Chengdu].

    Science.gov (United States)

    Wang, Qing; Zhou, Cheng-xia; Meng, Hui-min; Wang, Xi; Li, Li

    2010-09-01

    To develop a photographic scale for grading widening of pores, and to identify the factors associated with pore widening. People with widened pores were recruited, with photographs taken on their nasal tips, nasal alas and cheeks. A questionnaire survey was undertaken by dermatologists to assess the severity of pore widening. A Cumulative Logit Model was established to identify factors that were associated with pore widening. A total of 115 people participated in the study and 562 photographs were taken. The photographic scale was highly consistent with the clinical judgment. Another 1011 residents aged from 18 to 70 years old in Chengdu were surveyed. The logit model revealed that facial pore widening were associated with gender, age, oily skin, sun protection and anti-aging cosmetic. The photographic scale is reliable and easy to use. Gender, age and oily skin are risk factors, and sun protection and anti-aging cosmetic are protective factors with related to pore widening.

  19. Performance characterization of silicon pore optics

    Science.gov (United States)

    Collon, M. J.; Kraft, S.; Günther, R.; Maddox, E.; Beijersbergen, M.; Bavdaz, M.; Lumb, D.; Wallace, K.; Krumrey, M.; Cibik, L.; Freyberg, M.

    2006-06-01

    The characteristics of the latest generation of assembled silicon pore X-ray optics are discussed in this paper. These very light, stiff and modular high performance pore optics (HPO) have been developed [1] for the next generation of astronomical X-ray telescopes, which require large collecting areas whilst achieving angular resolutions better than 5 arcseconds. The suitability of 12 inch silicon wafers as high quality optical mirrors and the automated assembly process are discussed elsewhere in this conference. HPOs with several tens of ribbed silicon plates are assembled by bending the plates into an accurate cylindrical shape and directly bonding them on top of each other. The achievable figure accuracy is measured during assembly and in test campaigns at X-ray testing facilities like BESSY-II and PANTER. Pencil beam measurements allow gaining information on the quality achieved by the production process with high spatial resolution. In combination with full beam illumination a complete picture of the excellent performance of these optics can be derived. Experimental results are presented and discussed in detail. The results of such campaigns are used to further improve the production process in order to match the challenging XEUS requirements [2] for imaging resolution and mass.

  20. Modeling a Conventional Electroporation Pulse Train: Decreased Pore Number, Cumulative Calcium Transport and an Example of Electrosensitization.

    Science.gov (United States)

    Son, Reuben S; Gowrishankar, Thiruvallur R; Smith, Kyle C; Weaver, James C

    2016-03-01

    Pulse trains are widely used in electroporation (EP) for both general biomedical research and clinical applications such as nonthermal tumor ablation. Here we use a computational method based on a meshed transport network to investigate a cell system model's response to a train of identical, evenly spaced electric field pulses. We obtain an unexpected result: the number of membrane pores decreases during the application of twenty 1.0 kV/cm, 100 μs pulses, delivered at 1 Hz. This pulse train initially creates 13,000 membrane pores, but pore number decreases by a factor of 15 to about 830 pores throughout subsequent pulses. We conclude that pore number can greatly diminish during a train of identical pulses, with direct consequences for the transport of solutes across an electroporated membrane. Although application of additional pulses is generally intended to increase the effects of EP, we show that these pulses do not significantly enhance calcium delivery into the cell. Instead, calcium delivery can be significantly increased by varying inter-pulse intervals. We show that inserting a 300-s interruption midway in a widely used eight-pulse train (a protocol for electrosensitization) yields a ∼ twofold delivery increase. Overall, our modeling shows support for electrosensitization, in which multiple pulse protocols that maximize pore number over time can yield significant increase of transport of calcium compared to standard pulse trains.

  1. Multiple Approaches to Characterizing Pore Structure in Natural Rock

    Science.gov (United States)

    Hu, Q.; Dultz, S.; Hamamoto, S.; Ewing, R. P.

    2012-12-01

    Microscopic characteristics of porous media - pore shape, pore-size distribution, and pore connectivity - control fluid flow and chemical transport, and are important in hydrogeological studies of rock formations in the context of energy, environmental, and water resources management. This presentation discusses various approaches to investigating pore structure of rock, with a particular focus on the Barnett Shale in north Texas used for natural gas production. Approaches include imbibition, tracer diffusion, porosimetry (MIP, vapor adsorption/desorption isotherms, NMR cyroporometry), and imaging (μ-tomography, Wood's metal impregnation, FIB/SEM). Results show that the Barnett Shale pores are predominantly in the nm size range, with a measured median pore-throat diameter of 6.5 nm. But small pore size is not the major contributor to low gas recovery; rather, the low gas diffusivity appears to be caused by low pore connectivity. Chemical diffusion in sparsely-connected pore spaces is not well described by classical Fickian behavior; anomalous behavior is suggested by percolation theory, and confirmed by results of imbibition tests. Our evolving complementary approaches, with their several advantages and disadvantages, provide a rich toolbox for tackling the pore structure characteristics in the Barnett Shale and other natural rocks.

  2. Permeability and pore structure connectivity of basic concrete formulations to use in near-surface repositories for radioactive wastes

    International Nuclear Information System (INIS)

    Tolentino, Evandro; Santos, Carlos Eduardo de Oliveira; Tello, Clédola Cássia Oliveira de

    2017-01-01

    The main concern of engineers who prepare concrete specifications for a particular application is to predict the deteriorative exposures that could cause concrete degradation over its intended service life. A durable concrete is able to resist destructive environmental conditions, without requiring excessive maintenance. Durability of cementitious materials largely depends on the possibilities of penetration of hazardous ions into the porous material with water as medium. Therefore, the water permeability of cementitious materials is related to its durability. Permeability and porosity should not instinctively be regarded as manifestations of the same phenomenon. Usually, when permeability increases, porosity increases as well. The connectivity of pore network exerts an important control on preferential flow into cementitious materials. This work presents results of quantitative evaluation of permeability and pore connectivity of Portland cement concretes. Two concrete mixture proportions with limestone and gneiss as coarse aggregate were produced. A modified polycarboxyl ether plasticizer GLENIUM 51 was added to one of the concrete mixtures in order to reduce the water content. Permeability tests were performed on all the specimens and a geometric modeling considering pore with cylindrical shape was applied in order to evaluate the pore network connectivity. The results showed that pore structure connectivity of concrete with plasticizer admixture decreased. The purpose of this research is to expand the knowledge concerning concrete durability and to provide the technical requirements related to the production the Brazilian near-surface repository of radioactive wastes. (author)

  3. Permeability and pore structure connectivity of basic concrete formulations to use in near-surface repositories for radioactive wastes

    Energy Technology Data Exchange (ETDEWEB)

    Tolentino, Evandro; Santos, Carlos Eduardo de Oliveira [Centro Federal de Educação Tecnológica de Minas Gerais (CEFET-MG), Timóteo, MG (Brazil); Tello, Clédola Cássia Oliveira de, E-mail: tolentino@timoteo.cefetmg.br, E-mail: tellocc@cdtn.br [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil)

    2017-07-01

    The main concern of engineers who prepare concrete specifications for a particular application is to predict the deteriorative exposures that could cause concrete degradation over its intended service life. A durable concrete is able to resist destructive environmental conditions, without requiring excessive maintenance. Durability of cementitious materials largely depends on the possibilities of penetration of hazardous ions into the porous material with water as medium. Therefore, the water permeability of cementitious materials is related to its durability. Permeability and porosity should not instinctively be regarded as manifestations of the same phenomenon. Usually, when permeability increases, porosity increases as well. The connectivity of pore network exerts an important control on preferential flow into cementitious materials. This work presents results of quantitative evaluation of permeability and pore connectivity of Portland cement concretes. Two concrete mixture proportions with limestone and gneiss as coarse aggregate were produced. A modified polycarboxyl ether plasticizer GLENIUM 51 was added to one of the concrete mixtures in order to reduce the water content. Permeability tests were performed on all the specimens and a geometric modeling considering pore with cylindrical shape was applied in order to evaluate the pore network connectivity. The results showed that pore structure connectivity of concrete with plasticizer admixture decreased. The purpose of this research is to expand the knowledge concerning concrete durability and to provide the technical requirements related to the production the Brazilian near-surface repository of radioactive wastes. (author)

  4. PBO Borehole Strainmeters and Pore Pressure Sensors: Recording Hydrological Strain Signals

    Science.gov (United States)

    Gottlieb, M. H.; Hodgkinson, K. M.; Mencin, D.; Henderson, D. B.; Johnson, W.; Van Boskirk, E.; Pyatt, C.; Mattioli, G. S.

    2017-12-01

    UNAVCO operates a network of 75 borehole strainmeters along the west coast of the United States and Vancouver Island, Canada as part of the Plate Boundary Observatory (PBO), the geodetic component of the NSF-funded Earthscope program. Borehole strainmeters are designed to detect variations in the strain field at the nanostrain level and can easily detect transient strains caused by aseismic creep events, Episodic Tremor and Slip (ETS) events and seismically induced co- and post-seimic signals. In 2016, one strainmeter was installed in an Oklahoma oil field to characterize in-situ deformation during CO2 injection. Twenty-three strainmeter sites also have pore pressure sensors to measure fluctuations in groundwater pressure. Both the strainmeter network and the pore pressure sensors provide unique data against which those using water-level measurements, GPS time-series or InSAR data can compare possible subsidence signals caused by groundwater withdrawal or fluid re-injection. Operating for 12 years, the PBO strainmeter and pore pressure network provides a long-term, continuous, 1-sps record of deformation. PBO deploys GTSM21 tensor strainmeters from GTSM Technologies, which consist of four horizontal strain gauges stacked vertically, at different orientations, within a single 2 m-long instrument. The strainmeters are typically installed at depths of 200 to 250 m and grouted into the bottom of 15 cm diameter boreholes. The pore pressure sensors are Digiquartz Depth Sensors from Paros Scientific. These sensors are installed in 2" PVC, sampling groundwater through a screened section 15 m above the co-located strainmeter. These sensors are also recording at 1-sps with a resolution in the hundredths of hPa. High-rate local barometric pressure data and low-rate rainfall data also available at all locations. PBO Strainmeter and pore pressure data are available in SEED, SAC-ASCII and time-stamped ASCII format from the IRIS Data Managements Center. Strainmeter data are

  5. A Stereolithography Pore-Throat Model

    Science.gov (United States)

    Crandall, D.; Ahmadi, G.; Ferer, M.; Smith, D. H.

    2007-12-01

    A new experimental, heterogeneous pore-throat model has been designed and fabricated using stereolithography (SL). In SL production, a laser cures a thin layer of photo-sensitive resin on the surface of a vat of liquid resin; a moveable platform then submerges the cured layer and a new layer is cured on top of the previous one, creating a physical model from a computer generated model. This layered fabrication of a computer generated model has enabled the production of an experimental porous medium with improved fluid resistance properties, as compared to previously studied, constant-height etched cells. A uniform distribution of throat widths was randomly placed throughout the pore-throat matrix and the throat height of each throat was assigned to increase the range of viscous and capillary resistances within the physical model. This variation in both throat height and width generated a porous medium with fairly low porosity (43%), permeability (~400 D), and wide range of geometric resistance properties. Experimental, two-phase immiscible drainage studies in the porous flowcell were performed. Analysis of the captured images was performed with open-source image processing software. These analysis techniques utilized the capability of both ImageJ and the Gnu Image Manipulation Program to be customized with ancillary codes. This enabled batch procedures to be created that converted the original grey-scale bitmaps to binary data sets, which were then analyzed with in-house codes. The fractal dimension, Df, (measured with box-counting) and percent saturation of these experiments were calculated and shown to compare favorably to fractal predictions and previous flowcell studies. Additionally, using the computer generated pore-throat geometry, a computational fluid dynamics model of two- phase flow through the porous medium was created. This model was created using FLUENT code and the Volume of Fluid method. The percent saturation of the less-viscous invading fluid

  6. P2X7R large pore is partially blocked by pore forming proteins antagonists in astrocytes.

    Science.gov (United States)

    Faria, Robson X; Reis, Ricardo A M; Ferreira, Leonardo G B; Cezar-de-Mello, Paula F T; Moraes, Milton O

    2016-06-01

    The ATP-gated P2X7R (P2X7R) is a channel, which is involved in events, such as inflammation, cell death, and pain. The most intriguing event concerning P2X7R functions is the phenomenon of pore dilation. Once P2X7R is activated, the permeability of the plasma membrane becomes higher, leading to the permeation of 1000 Da-weight solutes. The mechanisms involved in this process remain unclear. Nevertheless, this event is not exclusively through P2X7R, as other proteins may form large pores in the plasma membrane. Recent evidence concerning pore formation reveals putative P2X7R and other pores-associated protein complexes, revealing cross-interactive pharmacological and biophysical issues. In this work, we showed results that corroborated with cross-interactive aspects with P2X7R and pores in astrocytes. These cells expressed most of the pores, including P2X7R. We discovered that different pore types open with peculiar characteristics, as both anionic and cationic charged solutes permeate the plasma membrane, following P2X7R activation. Moreover, we showed that both synergic and additive relationships are found within P2X7, cationic, and anionic large pores. Therefore, our data suggest that other protein-related pores are assembled following the formation of P2X7R pore.

  7. The Pore Structure of Direct Methanol Fuel Cell Electrodes

    DEFF Research Database (Denmark)

    Lund, Peter Brilner

    2005-01-01

    The pore structure and morphology of direct methanol fuel cell electrodes are characterized using mercury intrusion porosimetry and scanning electron microscopy. It is found that the pore size distributions of printed primer and catalyst layers are largely dictated by the powders used to make...... the printing ink. The extent to which the pore structure is modified by changing several parameters in the membrane electrode assembly MEA manufacturing process is discussed. The pore structure of the printed layers is found to be invariant with respect to changes in powder loading or in choice of printing...... substrate, and is relatively undisturbed by MEA hot-pressing. Changing the source of the primer powder and adding a pore-forming agent to the catalyst ink are found to be successful methods of creating a more open pore structure in the printed layers....

  8. Preparation of micro-pored silicone elastomer through radiation crosslinking

    International Nuclear Information System (INIS)

    Gao Xiaoling; Gu Mei; Xie Xubing; Huang Wei

    2013-01-01

    The radiation crosslinking was adopted to prepare the micro-pored silicone elastomer, which was performed by vulcanization and foaming respectively. Radiation crosslinking is a new method to prepare micro-pored material with high performance by use of radiation technology. Silicon dioxide was used as filler, and silicone elastomer was vulcanized by electron beams, then the micro-pored material was made by heating method at a high temperature. The effects of absorbed dose and filler content on the performance and morphology were investigated. The structure and distribution of pores were observed by SEM. The results show that the micro-pored silicon elastomer can be prepared successfully by controlling the absorbed dose and filler content. It has a smooth surface similar to a rubber meanwhile the pores are round and unconnected to each other with the minimum size of 14 μm. And the good mechanical performance can be suitable for further uses. (authors)

  9. Factors Determining the Pore Shape in Polycarbonate Track Membranes

    CERN Document Server

    Apel, P Yu; Orelovich, O L; Akimenko, S N; Sartowska, B; Dmitriev, S N

    2004-01-01

    The process of pore formation in ion-irradiated polycarbonate films on treatment with alkali solutions in the presence of a surfactant is studied. It is found that the pore shape depends on both the structure of the initial films and the peculiarities of the interaction of the surfactant with the polymer surface and the transport of the surfactant into tracks. Due to heterogeneity of the films the cross-section of a track pore channel changes along its length. The presence of the surfactant results in a further effect. Surfactant molecules adsorb on the polymer surface at the pore entries and reduce the etch rate which leads to formation of cigar-like pore channels. The use of surfactant as a component of chemical etchant enables one to control the pore shape in track membranes thus optimizing their retention and permeation characteristics.

  10. Pore size matters for potassium channel conductance

    Science.gov (United States)

    Moldenhauer, Hans; Pincuntureo, Matías

    2016-01-01

    Ion channels are membrane proteins that mediate efficient ion transport across the hydrophobic core of cell membranes, an unlikely process in their absence. K+ channels discriminate K+ over cations with similar radii with extraordinary selectivity and display a wide diversity of ion transport rates, covering differences of two orders of magnitude in unitary conductance. The pore domains of large- and small-conductance K+ channels share a general architectural design comprising a conserved narrow selectivity filter, which forms intimate interactions with permeant ions, flanked by two wider vestibules toward the internal and external openings. In large-conductance K+ channels, the inner vestibule is wide, whereas in small-conductance channels it is narrow. Here we raise the idea that the physical dimensions of the hydrophobic internal vestibule limit ion transport in K+ channels, accounting for their diversity in unitary conductance. PMID:27619418

  11. Deciphering pore-level precipitation mechanisms.

    Science.gov (United States)

    Prasianakis, N I; Curti, E; Kosakowski, G; Poonoosamy, J; Churakov, S V

    2017-10-23

    Mineral precipitation and dissolution in aqueous solutions has a significant effect on solute transport and structural properties of porous media. The understanding of the involved physical mechanisms, which cover a large range of spatial and temporal scales, plays a key role in several geochemical and industrial processes. Here, by coupling pore scale reactive transport simulations with classical nucleation theory, we demonstrate how the interplay between homogeneous and heterogeneous precipitation kinetics along with the non-linear dependence on solute concentration affects the evolution of the system. Such phenomena are usually neglected in pure macroscopic modelling. Comprehensive parametric analysis and comparison with laboratory experiments confirm that incorporation of detailed microscale physical processes in the models is compulsory. This sheds light on the inherent coupling mechanisms and bridges the gap between atomistic processes and macroscopic observations.

  12. Ion track pores in intelligent films

    International Nuclear Information System (INIS)

    Asano, Masaharu; Yoshida, Masaru; Omichi, Hideki; Nagaoka, Noriyasu; Kubota, Hitoshi; Katakai, Ryoichi; Reber, N.; Spohr, R.

    1996-01-01

    To create an intelligent chemical valve which behaves to biological membranes, we combined the following technologies: (1) creation of intelligent gels based on pendant α-amino acids or their oligomers, (2) preparation of nuclear track films by etching chemically after heavy ion irradiation, especially preparation of cylindrical pores passed through the film, and (3) a combination of (1) and (2). The two factors, REL (Restricted Energy Loss) and radiation sensitivity [(V t /V b )-1] play an important role in formation of such cylindrical track films. In the case of CR-39 film, there were found to be REL>1.6x10 4 MeV cm 2 g -1 and (V t /V b )-1>100, respectively. The cylindrical tracks films with intelligent functions, which consist of a combination of (1) and (2), can be fabricated by two techniques, copolymerization and grafting. (author)

  13. Pore-level determination of spectral reflection behaviors of high-porosity metal foam sheets

    Science.gov (United States)

    Li, Yang; Xia, Xin-Lin; Ai, Qing; Sun, Chuang; Tan, He-Ping

    2018-03-01

    Open cell metal foams are currently attracting attention and their radiative behaviors are of primary importance in high temperature applications. The spectral reflection behaviors of high-porosity metal foam sheets, bidirectional reflectance distribution function (BRDF) and directional-hemispherical reflectivity were numerically investigated. A set of realistic nickel foams with porosity from 0.87 to 0.97 and pore density from 10 to 40 pores per inch were tomographied to obtain their 3-D digital cell network. A Monte Carlo ray-tracing method was employed in order to compute the pore-level radiative transfer inside the network within the limit of geometrical optics. The apparent reflection behaviors and their dependency on the textural parameters and strut optical properties were comprehensively computed and analysed. The results show a backward scattering of the reflected energy at the foam sheet surface. Except in the cases of large incident angles, an energy peak is located almost along the incident direction and increases with increasing incident angles. Through an analytical relation established, the directional-hemispherical reflectivity can be related directly to the porosity of the foam sheet and to the complex refractive index of the solid phase as well as the specularity parameter which characterizes the local reflection model. The computations show that a linear decrease in normal-hemispherical reflectivity occurs with increasing porosity. The rate of this decrease is directly proportional to the strut normal reflectivity. In addition, the hemispherical reflectivity increases as a power function of the incident angle cosine.

  14. X-ray microtomography application in pore space reservoir rock.

    Science.gov (United States)

    Oliveira, M F S; Lima, I; Borghi, L; Lopes, R T

    2012-07-01

    Characterization of porosity in carbonate rocks is important in the oil and gas industry since a major hydrocarbons field is formed by this lithology and they have a complex media porous. In this context, this research presents a study of the pore space in limestones rocks by x-ray microtomography. Total porosity, type of porosity and pore size distribution were evaluated from 3D high resolution images. Results show that carbonate rocks has a complex pore space system with different pores types at the same facies. Copyright © 2011 Elsevier Ltd. All rights reserved.

  15. Role of the synaptobrevin C terminus in fusion pore formation

    DEFF Research Database (Denmark)

    Ngatchou, Annita N; Kisler, Kassandra; Fang, Qinghua

    2010-01-01

    stimulation, the SNARE complex pulls the C terminus of sybII deeper into the vesicle membrane. We propose that this movement disrupts the vesicular membrane continuity leading to fusion pore formation. In contrast to current models, the experiments suggest that fusion pore formation begins with molecular......Neurotransmitter release is mediated by the SNARE proteins synaptobrevin II (sybII, also known as VAMP2), syntaxin, and SNAP-25, generating a force transfer to the membranes and inducing fusion pore formation. However, the molecular mechanism by which this force leads to opening of a fusion pore...

  16. Fusion Pore Diameter Regulation by Cations Modulating Local Membrane Anisotropy

    Directory of Open Access Journals (Sweden)

    Doron Kabaso

    2012-01-01

    Full Text Available The fusion pore is an aqueous channel that is formed upon the fusion of the vesicle membrane with the plasma membrane. Once the pore is open, it may close again (transient fusion or widen completely (full fusion to permit vesicle cargo discharge. While repetitive transient fusion pore openings of the vesicle with the plasma membrane have been observed in the absence of stimulation, their frequency can be further increased using a cAMP-increasing agent that drives the opening of nonspecific cation channels. Our model hypothesis is that the openings and closings of the fusion pore are driven by changes in the local concentration of cations in the connected vesicle. The proposed mechanism of fusion pore dynamics is considered as follows: when the fusion pore is closed or is extremely narrow, the accumulation of cations in the vesicle (increased cation concentration likely leads to lipid demixing at the fusion pore. This process may affect local membrane anisotropy, which reduces the spontaneous curvature and thus leads to the opening of the fusion pore. Based on the theory of membrane elasticity, we used a continuum model to explain the rhythmic opening and closing of the fusion pore.

  17. Evaluation of EOR Processes Using Network Models

    DEFF Research Database (Denmark)

    Winter, Anatol; Larsen, Jens Kjell; Krogsbøll, Anette

    1998-01-01

    The report consists of the following parts: 1) Studies of wetting properties of model fluids and fluid mixtures aimed at an optimal selection of candidates for micromodel experiments. 2) Experimental studies of multiphase transport properties using physical models of porous networks (micromodels......) including estimation of their "petrophysical" properties (e.g. absolute permeability). 3) Mathematical modelling and computer studies of multiphase transport through pore space using mathematical network models. 4) Investigation of link between pore-scale and macroscopic recovery mechanisms....

  18. Experimental study on pore structure and performance of sintered porous wick

    Science.gov (United States)

    He, Da; Wang, Shufan; Liu, Rutie; Wang, Zhubo; Xiong, Xiang; Zou, Jianpeng

    2018-02-01

    Porous wicks were prepared via powder metallurgy using NH4HCO3 powders as pore-forming agent. The pore-forming agent particle size was varied to control the pore structure and equivalent pore size distribution feature of porous wick. The effect of pore-forming agent particle size on the porosity, pore structures, equivalent pore size distribution and capillary pumping performance were investigated. Results show that with the particle size of pore-forming agent decrease, the green density and the volume shrinkage of the porous wicks gradually increase and the porosity reduces slightly. There are two types of pores inside the porous wick, large-sized prefabricated pores and small-sized gap pores. With the particle size of pore-forming agent decrease, the size of the prefabricated pores becomes smaller and the distribution tends to be uniform. Gap pores and prefabricated pores inside the wick can make up different types of pore channels. The equivalent pore size of wick is closely related to the structure of pore channels. Furthermore, the equivalent pore size distribution of wick shows an obvious double-peak feature when the pore-forming agent particle size is large. With the particle size of pore-forming agent decrease, the two peaks of equivalent pore size distribution approach gradually to each other, resulting in a single-peak feature. Porous wick with single-peak feature equivalent pore size distribution possesses the better capillary pumping performances.

  19. Entropy of Shortest Distance (ESD as Pore Detector and Pore-Shape Classifier

    Directory of Open Access Journals (Sweden)

    Klaudia Oleschko

    2013-06-01

    Full Text Available The entropy of shortest distance (ESD between geographic elements (“elliptical intrusions”, “lineaments”, “points” on a map, or between "vugs", "fractures" and "pores" in the macro- or microscopic images of triple porosity naturally fractured vuggy carbonates provides a powerful new tool for the digital processing, analysis, classification and space/time distribution prognostic of mineral resources as well as the void space in carbonates, and in other rocks. The procedure is applicable at all scales, from outcrop photos, FMI, UBI, USI (geophysical imaging techniques to micrographs, as we shall illustrate through some examples. Out of the possible applications of the ESD concept, we discuss in details the sliding window entropy filtering for nonlinear pore boundary enhancement, and propose this procedure as unbiased thresholding technique.

  20. Virus-sized colloid transport in a single pore: model development and sensitivity analysis.

    Science.gov (United States)

    Seetha, N; Mohan Kumar, M S; Majid Hassanizadeh, S; Raoof, Amir

    2014-08-01

    the conditions are favorable for adsorption. The results agree qualitatively with the column-scale experimental observations available in the literature. The current model forms the building block in upscaling colloid transport from pore scale to Darcy scale using Pore-Network Modeling. Copyright © 2014 Elsevier B.V. All rights reserved.

  1. Molecular Dynamics Simulations of Hydrophilic Pores in Lipid Bilayers

    NARCIS (Netherlands)

    Leontiadou, Hari; Mark, Alan E.; Marrink, Siewert J.

    Hydrophilic pores are formed in peptide free lipid bilayers under mechanical stress. It has been proposed that the transport of ionic species across such membranes is largely determined by the existence of such meta-stable hydrophilic pores. To study the properties of these structures and understand

  2. The study of the relationship between pore structure and ...

    Indian Academy of Sciences (India)

    Two kinds of channels, straight channels made of cylindrical capillaries and curved channels made of slit-shaped pores, exist in the bulk materials. The influence of the pore structure of mesoporous TiO2 on its photocatalytic performance was studied. The sample with higher porosity, better textural properties and straight ...

  3. Significant improvement in the pore properties of SBA-15 brought ...

    Indian Academy of Sciences (India)

    WINTEC

    Presence of carboxylic acids as well as hydrothermal treatment improves the pore properties of SBA-15. Keywords. SBA-15; mesoporous; carboxylic acids; adsorption; hydrothermal treatment; morphology. 1. Introduction. Molecular sieves with large pores have been of great use in carrying out reactions and separation proc-.

  4. Pore fluids from the argillaceous rocks of the Harwell region

    International Nuclear Information System (INIS)

    Brightman, M.A.; Bath, A.H.; Cave, M.R.; Darling, W.G.

    1985-06-01

    The aim of this work was to obtain samples of pore water from argillaceous formations in the Harwell area for chemical analysis to provide a background for radionuclide migration studies and regional groundwater flow pattern. This report describes the samples, development of a pore-water squeezing cell and its operation. Chemical and analytical studies are summarized. (UK)

  5. The study of the relationship between pore structure and ...

    Indian Academy of Sciences (India)

    Administrator

    Abstract. Mesoporous titania was synthesized by a sol–gel method using the surfactants Span85 and. X114 as the template. The pore structure was determined by the N2 adsorption/desorption method below. 73 K and calculated using the BJH model. TEM characterizations show that the pores are formed through.

  6. Pore size determination from charged particle energy loss measurement

    International Nuclear Information System (INIS)

    Brady, F.P.; Armitage, B.H.

    1977-01-01

    A new method aimed at measuring porosity and mean pore size in materials has been developed at Harwell. The energy width or variance of a transmitted or backscattered charged particle beam is measured and related to the mean pore size via the assumption that the variance in total path length in the porous material is given by (Δx 2 )=na 2 , where n is the mean number of pores and a the mean pore size. It is shown on the basis of a general and rigorous theory of total path length distribution that this approximation can give rise to large errors in the mean pore size determination particularly in the case of large porosities (epsilon>0.5). In practice it is found that it is not easy to utilize fully the general theory because accurate measurements of the first four moments are required to determine the means and variances of the pore and inter-pore length distributions. Several models for these distributions are proposed. When these are incorporated in the general theory the determinations of mean pore size from experimental measurements on powder samples are in good agreement with values determined by other methods. (Auth.)

  7. Bacteriocins : mechanism of membrane insertion and pore formation

    NARCIS (Netherlands)

    Moll, G.N.; Konings, W.N; Driessen, A.J.M.

    1999-01-01

    Lactic acid bacteria produce several types of pore forming peptides. Class I bacteriocins are lantibiotics that contain (methyl)lanthionine residues that may form intramolecular thioether rings. These peptides generally have a broad spectrum of activity and form unstable pores. Class II bacteriocins

  8. Small angle neutron scattering study of pore microstructure in ceria ...

    Indian Academy of Sciences (India)

    fractal morphology of the pore space with fractal dimensionality lying between 2.70 and. 2.76. Keywords. Ceria; sintering ... This paper deals with SANS investigation of internal pore microstructure of sintered compacts of ceria over ... compaction pressure of 200 MPa and sintered at 1250◦C for 2 h. Pramana – J. Phys., Vol.

  9. Analysis Of Pore Pressure Using Geophysical Methods | Dosumnu ...

    African Journals Online (AJOL)

    Many methods have been devised for predicting and evaluating the values of pore pressure in oil and gas formations. The present work employs geophysical approach for prediction of formation pore pressure in Niger Delta. This involved the use of seismic derived data before drilling operation, which was correlated with ...

  10. Pore structure and growth kinetics in carbon materials

    Energy Technology Data Exchange (ETDEWEB)

    Bose, S.

    1978-04-01

    Pore structure of glassy carbon (GC) and pyrolytic graphite (PG) have been investigated. GC is one of the most impervious of solids finding applications in prosthetic devices and fuel cells while PG is used extensively in the aerospace industry. One third of the microstructure of GC consists of closed pores inaccessible to fluids. The microstructure of this material has been characterized using x-ray diffraction (XRD) and high resolution electron microscopy. Small angle x-ray scattering (SAXS) has been used to measure the angstrom sized pores and to follow the evolution of pore surface area as a function of heat treatment temperature (HTT) and heat treatment time (HTt) at constant temperature. From these measurements an analysis of the surface area kinetics was made to find out if rate processes are involved and to locate graphitization occurring at pore surfaces. PG on the other hand has been found to have larger sized pores that comprise five percent of its volume. In addition to being closed these pores are oriented. Some pore models are proposed for PG and the existing scattering theory from oriented ellipsoids is modified to include the proposed shapes.

  11. Performance of multilayer coated silicon pore optics

    Science.gov (United States)

    Ackermann, M. D.; Collon, M. J.; Jensen, C. P.; Christensen, F. E.; Krumrey, M.; Cibik, L.; Marggraf, S.; Bavdaz, M.; Lumb, D.; Shortt, B.

    2010-07-01

    The requirements for the IXO (International X-ray Observatory) telescope are very challenging in respect of angular resolution and effective area. Within a clear aperture with 1.7 m > R > 0.25 m that is dictated by the spacecraft envelope, the optics technology must be developed to satisfy simultaneously requirements for effective area of 2.5 m2 at 1.25 keV, 0.65 m2 at 6 keV and 150 cm2 at 30 keV. The reflectivity of the bare mirror substrate materials does not allow these requirements to be met. As such the IXO baseline design contains a coating layout that varies as a function of mirror radius and in accordance with the variation in grazing incidence angle. The higher energy photon response is enhanced through the use of depth-graded multilayer coatings on the inner radii mirror modules. In this paper we report on the first reflectivity measurements of wedged ribbed silicon pore optics mirror plates coated with a depth graded W/Si multilayer. The measurements demonstrate that the deposition and performance of the multilayer coatings is compatible with the SPO production process.

  12. Current concepts in nuclear pore electrophysiology.

    Science.gov (United States)

    Bustamante, José Omar

    2006-01-01

    Over 4 decades ago, microelectrode studies of in situ nuclei showed that, under certain conditions, the nuclear envelope (NE) behaves as a barrier opposing the nucleocytoplasmic flow of physiological ions. As the nuclear pore complexes (NPCs) of the NE are the only pathways for direct nucleocytoplasmic flow, those experiments implied that the NPCs are capable of restricting ion flow. These early studies validated electrophysiology as a useful approach to quantify some of the mechanisms by which NPCs mediate gene activity and expression. Since electron microscopy (EM) and other non-electrophysiological investigations, showed that the NPC lumen is a nanochannel, the opinion prevailed that the NPC could not oppose the flow of ions and, therefore, that electrophysiological observations resulted from technical artifacts. Consequently, the initial enthusiasm with nuclear electrophysiology faded out in less than a decade. In 1990, nuclear electrophysiology was revisited with patch-clamp, the most powerful electrophysiological technique to date. Patch-clamp has consistently demonstrated that the NE has intrinsic ion channel activity. Direct demonstrations of the NPC on-off ion channel gating behavior were published for artificial conditions in 1995 and for intact living nuclei in 2002. This on-off switching/gating behavior can be interpreted in terms of a metastable energy barrier. In the hope of advancing nuclear electrophysiology, and to complement the other papers contained in this special issue of the journal, here I review some of the main technical, experimental, and theoretical issues of the field, with special focus on NPCs.

  13. Characterization of pore volume of cumulative water injection distribution

    Directory of Open Access Journals (Sweden)

    Guoqing Feng

    2015-06-01

    Full Text Available Pore volume of Cumulative water injection is one of the factors for evaluating water flood effect in a water flood oil field. In previous study, there were limited lab studies for evaluating oil displacement efficiency. A method to characterize the distribution of pore volume of cumulative water injection is proposed in this paper, and it is verified by a five-spot water flooding streamline simulation model. The logarithmic relation between pore volume of cumulative water injection and water saturation is established by regression. An inflection point and limit point of cumulative water injection pore volume are identified. Current simulation model indicates inflection point appears after 2–5 pore volume (PV injection, and limit point appears after 15–25 PV injection. Both inflection and limit point vary in different regions of reservoir.

  14. Integrative structure and functional anatomy of a nuclear pore complex

    Science.gov (United States)

    Kim, Seung Joong; Fernandez-Martinez, Javier; Nudelman, Ilona; Shi, Yi; Zhang, Wenzhu; Raveh, Barak; Herricks, Thurston; Slaughter, Brian D.; Hogan, Joanna A.; Upla, Paula; Chemmama, Ilan E.; Pellarin, Riccardo; Echeverria, Ignacia; Shivaraju, Manjunatha; Chaudhury, Azraa S.; Wang, Junjie; Williams, Rosemary; Unruh, Jay R.; Greenberg, Charles H.; Jacobs, Erica Y.; Yu, Zhiheng; de La Cruz, M. Jason; Mironska, Roxana; Stokes, David L.; Aitchison, John D.; Jarrold, Martin F.; Gerton, Jennifer L.; Ludtke, Steven J.; Akey, Christopher W.; Chait, Brian T.; Sali, Andrej; Rout, Michael P.

    2018-03-01

    Nuclear pore complexes play central roles as gatekeepers of RNA and protein transport between the cytoplasm and nucleoplasm. However, their large size and dynamic nature have impeded a full structural and functional elucidation. Here we determined the structure of the entire 552-protein nuclear pore complex of the yeast Saccharomyces cerevisiae at sub-nanometre precision by satisfying a wide range of data relating to the molecular arrangement of its constituents. The nuclear pore complex incorporates sturdy diagonal columns and connector cables attached to these columns, imbuing the structure with strength and flexibility. These cables also tie together all other elements of the nuclear pore complex, including membrane-interacting regions, outer rings and RNA-processing platforms. Inwardly directed anchors create a high density of transport factor-docking Phe-Gly repeats in the central channel, organized into distinct functional units. This integrative structure enables us to rationalize the architecture, transport mechanism and evolutionary origins of the nuclear pore complex.

  15. Surfactant-enhanced control of track-etch pore morphology

    International Nuclear Information System (INIS)

    Apel', P.Yu.; Blonskaya, I.V.; Didyk, A.Yu.; Dmitriev, S.N.; Orelovich, O.L.; Samojlova, L.I.; Vutsadakis, V.A.; Root, D.

    2000-01-01

    The influence of surfactants on the process of chemical development of ion tracks in polymers is studied. Based on the experimental data, a mechanism of the surfactant effect on the track-etch pore morphology is proposed. In the beginning of etching the surfactant is adsorbed on the surface and creates a layer that is quasi-solid and partially protects the surface from the etching agent. However, some etchant molecules diffuse through the barrier and react with the polymer surface. This results in the formation of a small hole at the entrance to the ion track. After the hole has attained a few annometers in diameter, the surfactant molecules penetrate into the track and cover its walls. Further diffusion of the surfactant into the growing pore is hindered. The adsorbed surfactant layer is not permeable for large molecules. In contrast, small alkali molecules and water molecules diffuse into the track and provide the etching process enlarging the pore. At this stage the transport of the surfactant into the pore channel can proceed only due to the lateral diffusion in the adsorbed layer. The volume inside the pore is free of surfactant molecules and grows at a higher rate than pore entrance. After a more prolonged etching the bottle-like (or 'cigar-like') pore channels are formed. The bottle-like shape of the pore channels depends on the etching conditions such as alkali and surfactant concentration, temperature, and type of the surfactant. The use of surfactants enables one to produce track-etch membranes with improved flow rate characteristics compared with those having cylindrical pores with the same nominal pore diameters

  16. Biophysics, Pathophysiology and Pharmacology of Ion Channel Gating Pores

    Directory of Open Access Journals (Sweden)

    Adrien eMoreau

    2014-04-01

    Full Text Available Voltage sensor domain (VSDs are a feature of voltage gated ion channel (VGICs and voltage sensitive proteins. They are composed of four transmembrane (TM segments (S1 to S4. Currents leaking through VSDs are called omega or gating pore currents.Gating pores are caused by mutations of the highly conserved positively charged amino acids in the S4 segment that disrupt interactions between the S4 segment and the gating charge transfer center (GCTC. The GCTC separates the intracellular and extracellular water crevices. The disruption of S4–GCTC interactions allows these crevices to communicate and create a fast activating and non-inactivating alternative cation-selective permeation pathway of low conductance, or a gating pore.Gating pore currents have recently been shown to cause periodic paralysis phenotypes. There is also increasing evidence that gating pores are linked to several other familial diseases. For example, gating pores in Nav1.5 and Kv7.2 channels may underlie mixed arrhythmias associated with dilated cardiomyopathy (DCM phenotypes and peripheral nerve hyperexcitability (PNH respectively. There is little evidence for the existence of gating pore blockers. Moreover, it is known that a number of toxins bind to the VSD of a specific domain of Na+ channels. These toxins may thus modulate gating pore currents. This focus on the VSD motif opens up a new area of research centered on developing molecules to treat a number of cell excitability disorders such as epilepsy, cardiac arrhythmias, and pain.The purpose of the present review is to summarize existing knowledge of the pathophysiology, biophysics, and pharmacology of gating pore currents and to serve as a guide for future studies aimed at improving our understanding of gating pores and their pathophysiological roles.

  17. HYDROXYETHYL METHACRYLATE BASED NANOCOMPOSITE HYDROGELS WITH TUNABLE PORE ARCHITECTURE

    Directory of Open Access Journals (Sweden)

    Erhan Bat

    2016-10-01

    Full Text Available Hydroxyethyl methacrylate (HEMA based hydrogels have found increasing number of applications in areas such as chromatographic separations, controlled drug release, biosensing, and membrane separations. In all these applications, the pore size and pore interconnectivity are crucial for successful application of these materials as they determine the rate of diffusion through the matrix. 2-Hydroxyethyl methacrylate is a water soluble monomer but its polymer, polyHEMA, is not soluble in water. Therefore, during polymerization of HEMA in aqueous media, a porous structure is obtained as a result of phase separation. Pore size and interconnectivity in these hydrogels is a function of several variables such as monomer concentration, cross-linker concentration, temperature etc. In this study, we investigated the effect of monomer concentration, graphene oxide addition or clay addition on hydrogel pore size, pore interconnectivity, water uptake, and thermal properties. PolyHEMA hydrogels have been prepared by redox initiated free radical polymerization of the monomer using ethylene glycol dimethacrylate as a cross-linker. As a nanofiller, a synthetic hectorite Laponite® XLG and graphene oxide were used. Graphene oxide was prepared by the Tour Method. Pore morphology of the pristine HEMA based hydrogels and nanocomposite hydrogels were studied by scanning electron microscopy. The formed hydrogels were found to be highly elastic and flexible. A dramatic change in the pore structure and size was observed in the range between 22 to 24 wt/vol monomer at 0.5 % of cross-linker. In this range, the hydrogel morphology changes from typical cauliflower architecture to continuous hydrogel with dispersed water droplets forming the pores where the pores are submicron in size and show an interconnected structure. Such controlled pore structure is highly important when these hydrogels are used for solute diffusion or when there’s flow through monolithic hydrogels

  18. Effects of pore size on the adsorption of hydrogen in slit pores of constant width and varying height

    Energy Technology Data Exchange (ETDEWEB)

    Culp, J.T.; Natesakhawat, S.; Smith, M.R.; Bittner, E.W.; Matranga, C.S.; Bockrath, B.C.

    2007-08-01

    The effects of pore size on the hydrogen storage properties of a series of pillared layered solids were investigated at 77 K and 87 K up to a pressure of 1 atm. The isotherms were fit to the Langmuir-Freundlich equation and extrapolated to determine saturation values. The materials studied are based on the M(L)[M'(CN)4] structural motif, where M = Co or Ni, L = pyrazine (pyz), 4,4'bipyridine (bpy) or 4,4'-dipyridylacetylene (dpac), and M' = Ni, Pd or Pt. The compounds all possess slit like pores with constant inplane dimensions and pore heights that vary as a function of (L). The pyz pillared materials with the smallest pore dimensions store hydrogen at a pore density similar to the bulk liquid. The adsorbed hydrogen density drops by a factor of two as the relative pore size is tripled in the dpac material. The decreased storage efficiency diminishes the expected gravimetric gain in capacity for the larger pore materials. The heats of adsorption were found to range from 6 to 8 kJ/mol in the series, and weakly correlate with pore size.

  19. Small scale laboratory studies of flow and transport phenomena in pores and fractures: Phase 2. Technical completion report

    Energy Technology Data Exchange (ETDEWEB)

    Wilson, J.L.

    1997-01-01

    Pore level laboratory experiments using microscopy permit the in situ visualization of flow and transport phenomena, that can be recorded on film or videotape. One of the principal tools for visualization is the etched glass micromodel, which is composed of a transparent two dimensional network of three dimensional pores. The spatial scale of interest in these models extends from the individual pore, up to a network of pores, perhaps with small scale heterogeneities. Micromodels are best used to help validate concepts and assumptions, and to elucidate new, previously unrecognized phenomena for further study. They are not quantitative tools, but should be used in combination with quantitative tools such as column studies or mathematical models. There are three applications: multi-phase flow, colloid transport, and bacterial transport and colonization. Specifically the authors have examined behavior of relevance to liquid-liquid mass transfer (solubilization of capillary trapped organic liquids); liquid-gas mass transfer (in situ volatilization); mathematical models of multi-phase pressure-saturation relationships; colloid movement, attachment and detachment in the presence of fluid-fluid interfaces, clay interference with multi-phase flow; and heterogeneity effects on multi-phase flow and colloid movement.

  20. Hierarchical Pore Development by Plasma Etching of Zr-Based Metal-Organic Frameworks.

    Science.gov (United States)

    DeCoste, Jared B; Rossin, Joseph A; Peterson, Gregory W

    2015-12-07

    The typically stable Zr-based metal-organic frameworks (MOFs) UiO-66 and UiO-66-NH2 were treated with tetrafluoromethane (CF4 ) and hexafluoroethane (C2 F6 ) plasmas. Through interactions between fluoride radicals from the perfluoroalkane plasma and the zirconium-oxygen bonds of the MOF, the resulting materials showed the development of mesoporosity, creating a hierarchical pore structure. It is anticipated that this strategy can be used as a post-synthetic technique for developing hierarchical networks in a variety of MOFs. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. A Dynamic Two-Phase Pore-Scale Model of Imbibition

    DEFF Research Database (Denmark)

    Mogensen, Kristian; Stenby, Erling Halfdan

    1998-01-01

    We present a dynamic pore-scale network model of imbibition, capable of calculating residual oil saturation for any given capillary number, viscosity ratio, contact angle, and aspect ratio. Our goal is not to predict the outcome of core floods, but rather to perform a sensitivity analysis...... of the above-mentioned parameters, except from the viscosity ratio. We find that contact angle, aspect ratio, and capillary number all have a significant influence on the competition between piston-lice advance, leading to high recovery, and snap-off, causing oil entrapment. Due to significant CPU...

  2. Impedance nanopore biosensor: influence of pore dimensions on biosensing performance.

    Science.gov (United States)

    Kant, Krishna; Yu, Jingxian; Priest, Craig; Shapter, Joe G; Losic, Dusan

    2014-03-07

    Knowledge about electrochemical and electrical properties of nanopore structures and the influence of pore dimensions on these properties is important for the development of nanopore biosensing devices. The aim of this study was to explore the influence of nanopore dimensions (diameter and length) on biosensing performance using non-faradic electrochemical impedance spectroscopy (EIS). Nanoporous alumina membranes (NPAMs) prepared by self-ordered electrochemical anodization of aluminium were used as model nanopore sensing platforms. NPAMs with different pore diameters (25-65 nm) and lengths (4-18 μm) were prepared and the internal pore surface chemistry was modified by covalently attaching streptavidin and biotin. The performance of this antibody nanopore biosensing platform was evaluated using various concentrations of biotin as a model analyte. EIS measurements of pore resistivity and conductivity were carried out for pores with different diameters and lengths. The results showed that smaller pore dimensions of 25 nm and pore lengths up to 10 μm provide better biosensing performance.

  3. Pore formation by actinoporins, cytolysins from sea anemones.

    Science.gov (United States)

    Rojko, Nejc; Dalla Serra, Mauro; Maček, Peter; Anderluh, Gregor

    2016-03-01

    Actinoporins (APs) from sea anemones are ~20 kDa pore forming toxins with a β-sandwich structure flanked by two α-helices. The molecular mechanism of APs pore formation is composed of several well-defined steps. APs bind to membrane by interfacial binding site composed of several aromatic amino acid residues that allow binding to phosphatidylcholine and specific recognition of sphingomyelin. Subsequently, the N-terminal α-helix from the β-sandwich has to be inserted into the lipid/water interphase in order to form a functional pore. Functional studies and single molecule imaging revealed that only several monomers, 3-4, oligomerise to form a functional pore. In this model the α-helices and surrounding lipid molecules build toroidal pore. In agreement, AP pores are transient and electrically heterogeneous. On the contrary, crystallized oligomers of actinoporin fragaceatoxin C were found to be composed of eight monomers with no lipids present between the adjacent α-helices. This article is part of a Special Issue entitled: Pore-Forming Toxins edited by Maur Dalla Serra and Franco Gambale. Copyright © 2015 Elsevier B.V. All rights reserved.

  4. Imaging Slit Pores Under Delaminated Splats by White Light Interference

    Science.gov (United States)

    Chen, Lin; Gao, Li-li; Yang, Guan-Jun

    2018-01-01

    The slit pores under delaminated films significantly contribute to the properties of the film and the coating. In the present study, a novel and practical technique, the white light interference method, is proposed to characterize the slit pores covered by the 8YSZ and LZ splats. In this method, only an ordinary optical microscopy (OM) is used. Interestingly, colorful Newton's rings and parabolic shapes of the slit pores were clearly observed by OM. The crack spacing and the shapes of the slit pores captured by OM were in good agreement with those obtained by scanning electron microscopy and focus ion beam. Moreover, this is the first time when successful quantitative imaging of the slit pores under the thermal spray splats is achieved. Besides, mechanical analyses were carried out, and the results were consistent with those obtained by OM. In addition, the essential fact that the slit pores were mainly caused by transverse cracking/delamination in the thermal spray coatings was clarified. These results indicate that white light interference is an excellent method to characterize the slit pores under smooth and transparent films.

  5. Imaging Slit Pores Under Delaminated Splats by White Light Interference

    Science.gov (United States)

    Chen, Lin; Gao, Li-li; Yang, Guan-Jun

    2018-02-01

    The slit pores under delaminated films significantly contribute to the properties of the film and the coating. In the present study, a novel and practical technique, the white light interference method, is proposed to characterize the slit pores covered by the 8YSZ and LZ splats. In this method, only an ordinary optical microscopy (OM) is used. Interestingly, colorful Newton's rings and parabolic shapes of the slit pores were clearly observed by OM. The crack spacing and the shapes of the slit pores captured by OM were in good agreement with those obtained by scanning electron microscopy and focus ion beam. Moreover, this is the first time when successful quantitative imaging of the slit pores under the thermal spray splats is achieved. Besides, mechanical analyses were carried out, and the results were consistent with those obtained by OM. In addition, the essential fact that the slit pores were mainly caused by transverse cracking/delamination in the thermal spray coatings was clarified. These results indicate that white light interference is an excellent method to characterize the slit pores under smooth and transparent films.

  6. Superplastically foaming method to make closed pores inclusive porous ceramics

    International Nuclear Information System (INIS)

    Kishimoto, Akira; Hayashi, Hidetaka

    2011-01-01

    Porous ceramics incorporates pores to improve several properties including thermal insulation maintaining inherenet ceramic properties such as corrosion resistance and large mechanical strength. Conventional porous ceramics is usually fabricated through an insufficient sintering. Since the sintering accompanies the exclusion of pores, it must be terminated at the early stage to maintain the high porosity, leading to degraded strength and durability. Contrary to this, we have innovated superplastically foaming method to make ceramic foams only in the solid state. In this method, the previously inserted foam agent evaporates after the full densification of matrix at around the sintering temperature. Closed pores expand utilizing the superplastic deformation driven by the evolved gas pressure. The typical features of this superplastically foaming method are listed as follows, 1. The pores are introduced after sintering the solid polycrystal. 2. Only closed pores are introduced, improving the insulation of gas and sound in addition to heat. 3. The pore walls are fully densified expecting a large mechanical strength. 4. Compared with the melt foaming method, this method is practical because the fabrication temperature is far below the melting point and it does not need molds. 5. The size and the location pores can be controlled by the amount and position of the foam agent.

  7. Análisis de la respuesta mecánica de recubrimientos elaborados mediante proyección térmica por plasma usando la medición de esfuerzos residuales y el método de elementos finitos a escala estructural: efecto de la red de poros Mechanical responses of plasma sprayed coatings from residual stress measurements and finite element analysis: effect of the pore network architecture

    Directory of Open Access Journals (Sweden)

    Claudia Constanza Palacio Espinosa

    2011-12-01

    element analyses (FEA can be conducted on domains resulting from the discretization of Scanning Electron Microscopy (SEM high resolution pictures of coating structures. TiO2-Cu and Al2O3-HTiO2 plasma sprayed coatings were considered for demonstrative purposes regarding residual stress measurements and effect of the pore network architecture, respectively. Several operating parameters permitted to manufacture coatings exhibiting different magnitude of residual stress and several porous architectures, in terms of pore content, crack density and crack orientation. Residual stress determined from measurements of deflection during elaboration of TiO2-Cu coatings allow to identify their nature while numerical simulations show the very significant influence of the network architecture on the stress field within the Al2O3-13TiO2 coatings. Based on the same analyzed structures, other theoretical compositions were considered in the finite element analyses by modifying the intrinsic mechanical properties of the phases. For the considered cases, simulations show the poor influence of the nature of the secondary phase on the stress field within the coatings. Beside these results, the paper proposes a generic methodology and points out its advantages and limits, emphasizing in particular the importance of the representative elementary volume (REV.

  8. Novel Techniques to Characterize Pore Size of Porous Materials

    KAUST Repository

    Alabdulghani, Ali J.

    2016-04-24

    Porous materials are implemented in several industrial applications such as water desalination, gas separation and pharmaceutical care which they are mainly governed by the pore size and the PSD. Analyzing shale reservoirs are not excluded from these applications and numerous advantages can be gained by evaluating the PSD of a given shale reservoir. Because of the limitations of the conventional characterization techniques, novel methods for characterizing the PSD have to be proposed in order to obtain better characterization results for the porous materials, in general, and shale rocks in particular. Thus, permporosimetry and evapoporometry (EP) technologies were introduced, designed and utilized for evaluating the two key parameters, pore size and pore size distribution. The pore size and PSD profiles of different shale samples from Norway and Argentina were analyzed using these technologies and then confirmed by mercury intrusion porosimeter (MIP). Norway samples showed an average pore diameter of 12.94 nm and 19.22 nm with an average diameter of 13.77 nm and 23.23 nm for Argentina samples using permporosimetry and EP respectively. Both techniques are therefore indicative of the heterogeneity of the shales. The results from permporosimetry are in good agreement with those obtained from MIP technique, but EP for most part over-estimates the average pore size. The divergence of EP results compared to permporosimetry results is referred to the fact that the latter technique measures only the active pores which is not the case with the former technique. Overall, both techniques are complementary to each other which the results from both techniques seem reasonable and reliable and provide two simple techniques to estimate the pore size and pore size distributions for shale rocks.

  9. Time evolution of pore system in lime - Pozzolana composites

    Science.gov (United States)

    Doleželová, Magdaléna; Čáchová, Monika; Scheinherrová, Lenka; Keppert, Martin

    2017-11-01

    The lime - pozzolana mortars and plasters are used in restoration works on building cultural heritage but these materials are also following the trend of energy - efficient solutions in civil engineering. Porosity and pore size distribution is one of crucial parameters influencing engineering properties of porous materials. The pore size distribution of lime based system is changing in time due to chemical processes occurring in the material. The present paper describes time evolution of pore system in lime - pozzolana composites; the obtained results are useful in prediction of performance of lime - pozzolana systems in building structures.

  10. Crystalline mesoporous zirconia catalysts having stable tetragonal pore wall structure

    Science.gov (United States)

    Sachtler, Wolfgang M. H.; Huang, Yin-Yan

    1998-01-01

    Methods for the preparation of new sulfated mesoporous zirconia materials/catalysts with crystalline pore walls of predominantly tetragonal crystal structure, characterized by nitrogen physisorption measurement, X-ray diffraction, transmission electron microscopy and catalytic tests using n-butane isomerization to iso-butane and alkylation of 1-naphthol with 4-tert-butylstyrene as probe reactions. Sulfate deposition is preferred for the transformation of a mesoporous precursor with amorphous pore walls into a material with crystalline pore walls maintaining the mesoporous characteristics.

  11. A FILTRATION METHOD AND APPARATUS INCLUDING A ROLLER WITH PORES

    DEFF Research Database (Denmark)

    2008-01-01

    The present invention offers a method for separating dry matter from a medium. A separation chamber is at least partly defined by a plurality of rollers (2,7) and is capable of being pressure regulated. At least one of the rollers is a pore roller (7) having a surface with pores allowing...... permeability for the medium covered with a filter (3) and furthermore having at least one' channel in fluid contact with the pores of the surface. A pressure difference is established across the filter (3) and both, the filter (3) and the filter cake is passed through the rollers (2,7), whereby the medium...

  12. Scaling theory of pore growth in a reactive solid

    International Nuclear Information System (INIS)

    Kerstein, A.R.; Bug, A.L.R.

    1986-01-01

    Pores in a reactive solid are modeled as a randomly selected fraction p of the bonds of a lattice. Solid bonds adjacent to the open porosity are consumed, leading to the opening of previously closed pores. Just above the pore percolation threshold p/sub c/, exact analysis of the Bethe lattice indicates that the solid is consumed in a time t 0 --ln[ln(1/epsilon)], where epsilon = p-p/sub c/. A scaling argument, supported by computational results, gives t 0 --ln(1/epsilon) for finite-dimensional lattices. Aspects of the time-varying morphology of the solid are examined analytically and computationally

  13. Formation of conical fractures in sedimentary basins: Experiments involving pore fluids and implications for sandstone intrusion mechanisms

    Science.gov (United States)

    Mourgues, R.; Bureau, D.; Bodet, L.; Gay, A.; Gressier, J. B.

    2012-01-01

    Large sand intrusions often exhibit conical morphologies analogous to magmatic intrusions such as saucer-shaped or cup-shaped sills. Whereas some physical processes may be similar, we show with scaled experiments that the formation of conical sand intrusions may be favoured by the pore-pressure gradients prevailing in the host rock before sand injection. Our experiments involve injecting air into a permeable and cohesive analogue material to produce hydraulic fractures while controlling the pore pressure field. We control the state of overpressure in the overburden by applying homogeneous basal pore pressure, and then adding a second local pore pressure field by injecting air via a central injector to initiate hydraulic fractures near the injection point. In experiments involving small vertical effective stresses (small overburden, or high pore fluid overpressure), the fracturing pressure ( λfract) is supralithostatic and two dipping fractures are initiated at the injection point forming a conical structure. From theoretical considerations, we predict that high values of λfract are due to strong cohesion or high pore fluid overpressure distributed in the overburden. Such conditions are favoured by the pore pressure/stress coupling induced by both pore pressure fields. The dips of cones can be accounted for elastic-stress rotation occurring around the source. Contrary to magmatic chamber models, the aqueous fluid overpressure developed in a parent sandbody (and prevailing before the formation of injectites) may diffuse into the surrounding overburden, thus favouring stress rotation and the formation of inclined sheets far from the parent source. For experiments involving higher vertical effective stresses (thick overburden or low pore fluid overpressure), the fracturing pressure is lower than the lithostatic stress, and a single fracture is opened in mode I which then grows vertically. At a critical depth, the fracture separates into two dilatant branches forming

  14. Relationship between pore structure and compressive strength of ...

    Indian Academy of Sciences (India)

    Keywords. Pore structure; compressive strength; concrete; statistical model; mercury intrusion porosimetry (MIP) ... Author Affiliations. J BU1 Z TIAN. College of Water Conservancy and Hydropower Engineering, Hohai University, Nanjing, Jiangsu 210098, People's Republic of China ...

  15. Microfiltration of distillery stillage: Influence of membrane pore size

    Directory of Open Access Journals (Sweden)

    Vasić Vesna M.

    2012-01-01

    Full Text Available Stillage is one of the most polluted waste products of the food industry. Beside large volume, the stillage contains high amount of suspended solids, high values of chemical oxygen demand and biological oxygen demand, so it should not be discharged in the nature before previous purification. In this work, three ceramic membranes for microfiltration with different pore sizes were tested for stillage purification in order to find the most suitable membrane for the filtration process. Ceramic membranes with a nominal pore size of 200 nm, 450 nm and 800 nm were used for filtration. The influence of pore size on permeate flux and removal efficiency was investigated. A membrane with the pore size of 200 nm showed the best filtration performance so it was chosen for the microfiltration process.

  16. Straight Pore Microfilter with Efficient Regeneration, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — This Small Business Innovation Research Phase I project is directed toward development of a novel microfiltration filter that has distinctively narrow pore size...

  17. Straight Pore Microfilter with Efficient Regeneration, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — This Small Business Innovation Research Phase II project is directed toward development of a novel microfiltration filter that has distinctively narrow pore size...

  18. Nano pores evolution in hydroxyapatite microsphere during spark plasma sintering

    Directory of Open Access Journals (Sweden)

    Lin C.

    2011-01-01

    Full Text Available Micron-spherical granules of hydroxyapatite (HAp nanoparticles were prepared by powder granulation methods. Through subsequent sintering, porous HAp microspheres with tailored pore and grain framework structures were obtained. Detailed microstructure investigation by SEM and TEM revealed the correlation of the pore structure and the necking strength with the sintering profiles that determine the coalescence features of the nanoparticles. The partially sintered porous HAp microspheres containing more than 50% porosity consisting of pores and grains both in nano-scale are active in inducing the precipitation of HAp in simulated body fluid. The nano-porous HAp microspheres with an extensive surface and interconnecting pores thus demonstrate the potential of stimulating the formation of collagen and bone and the integration with the newly formed bones during physiological bone remodeling.

  19. Bilayer Deformation, Pores, and Micellation Induced by Oxidized Lipids.

    Science.gov (United States)

    Boonnoy, Phansiri; Jarerattanachat, Viwan; Karttunen, Mikko; Wong-Ekkabut, Jirasak

    2015-12-17

    The influence of different oxidized lipids on lipid bilayers was investigated with 16 individual 1 μs atomistic molecular dynamics (MD) simulations. Binary mixtures of lipid bilayers of 1-palmitoyl-2-linoleoyl-sn-glycero-3-phosphatidylcholine (PLPC) and its peroxide and aldehyde products were performed at different concentrations. In addition, an asymmetrical short chain lipid, 1-palmitoyl-2-decanoyl-sn-glycero-3-phosphatidylcholine (PDPC), was used to compare the effects of polar/apolar groups in the lipid tail on lipid bilayer. Although water defects occurred with both aldehyde and peroxide lipids, full pore formation was observed only for aldehyde lipids. At medium concentrations the pores were stable. At higher concentrations, however, the pores became unstable and micellation occurred. Data analysis shows that aldehyde lipids' propensity for pore formation is due to their shorter and highly mobile tail. The highly polar peroxide lipids are stabilized by strong hydrogen bonds with interfacial water.

  20. Diffusion in the pore water of compacted crushed salt

    Energy Technology Data Exchange (ETDEWEB)

    Fluegge, Judith; Herr, Sebastian; Lauke, Thomas; Meleshyn, Artur; Miehe, Ruediger; Ruebel, Andre

    2016-07-15

    Diffusion of dissolved radionuclides in the pore water of compacted crushed salt in the long-term is the most relevant process for the release of radionuclides from a dedicated repository for high-level waste in a salt formation as has been shown in latest safety assessments and research projects /BUH 16/. So far, diffusion coefficients for free water have been applied for the diffusion in pore water in models for long-term safety assessments. This conservative assumption was used, because data on the diffusion coefficient of dissolved substances in crushed salt have been missing. Furthermore, the diffusion coefficient in the pore water was assumed to be constant and independent from the degree of compaction of the crushed salt. The work presented in this report was intended to contribute to fill this gap of knowledge about how the diffusion of radionuclides takes place in the compacted backfill of a repository in salt. For the first time, the pore diffusion coefficient as well as its dependence on the porosity of the crushed salt was determined experimentally by means of through-diffusion experiments using caesium as tracer. The results achieved in this project suggest that the diffusion in compacted crushed salt is not fully comparable to that in a homogeneous, temporally stable porous medium like sand or clay. The results obtained from four diffusion experiments show a remarkably different behaviour and all yield unique concentration versus time plots which includes highly temporal variable tracer fluxes with even full interruptions of the flux for longer periods of time. This effect cannot be explained by assuming a tracer transport by diffusion in a temporarily invariant pore space and / or under temporally invariant experimental conditions. From our point of view, a restructuring of the pore space seems to lead to closed areas of pore water in the sample which may open up again after some time, leading to a variable pore space and hence variable diffusive

  1. Relationship between pore structure and compressive strength of ...

    Indian Academy of Sciences (India)

    J BU

    [16] Shi C 1996 Strength, pore structure and permeability of alkali-activated slag mortars. Cem. Concr. Res. 26(10): 1789–. 1799. [17] O'Farrell M, Wild S and Sabir B B 2001 Pore size distribution and compressive strength of waste clay brick mortar. Cem. Concr. Res. 23(1): 81–91. [18] Wen C E, Yamada Y, Shimojima K, ...

  2. Pore Scale Analysis of Oil Shale/Sands Pyrolysis

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Chen-Luh [Univ. of Utah, Salt Lake City, UT (United States); Miller, Jan [Univ. of Utah, Salt Lake City, UT (United States)

    2011-03-01

    There are important questions concerning the quality and volume of pore space that is created when oil shale is pyrolyzed for the purpose of producing shale oil. In this report, 1.9 cm diameter cores of Mahogany oil shale were pyrolyzed at different temperatures and heating rates. Detailed 3D imaging of core samples was done using multiscale X-ray computed tomography (CT) before and after pyrolysis to establish the pore structure. The pore structure of the unreacted material was not clear. Selected images of a core pyrolyzed at 400oC were obtained at voxel resolutions from 39 microns (Οm) to 60 nanometers (nm). Some of the pore space created during pyrolysis was clearly visible at these resolutions and it was possible to distinguish between the reaction products and the host shale rock. The pore structure deduced from the images was used in Lattice Boltzmann simulations to calculate the permeability in the pore space. The permeabilities of the pyrolyzed samples of the silicate-rich zone were on the order of millidarcies, while the permeabilities of the kerogen-rich zone after pyrolysis were very anisotropic and about four orders of magnitude higher.

  3. Pore growth in U-Mo/Al dispersion fuel

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Yeon Soo, E-mail: yskim@anl.gov [Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (United States); Jeong, G.Y.; Sohn, D.-S. [Ulsan National Institute of Science and Technology, 50 UNIST-gil, Eonyang-eup, Ulju-gun, Ulsan, 689-798 (Korea, Republic of); Jamison, L.M. [Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (United States)

    2016-09-15

    U-Mo/Al dispersion fuel is currently under development in the DOE’s Material Management and Minimization program to convert HEU-fueled research reactors to LEU-fueled reactors. In some demanding conditions in high-power and high-performance reactors, large pores form in the interaction layers between the U-Mo fuel particles and the Al matrix, which pose a potential to cause fuel failure. In this study, comprehension of the formation and growth of these pores was explored. As a product, a model to predict pore growth and porosity increase was developed. The model includes three major topics: fission gas release from the U-Mo and the IL to the pores, stress evolution in the fuel meat, and the effect of amorphous IL growth. Well-characterized in-pile data from reduced-size plates were used to fit the model parameters. A data set from full-sized plates, independent and distinctively different from those used to fit the model parameters, was used to examine the accuracy of the model. The model showed fair agreement with the measured data. The model suggested that the growth of the IL has a critical effect on pore growth, as both its material properties and energetics are favorable to pore formation. Therefore, one area of the current effort, focused on suppressing IL growth, appears to be on the right track to improve the performance of this fuel.

  4. Software Image J to study soil pore distribution

    Directory of Open Access Journals (Sweden)

    Sabrina Passoni

    2014-04-01

    Full Text Available In the soil science, a direct method that allows the study of soil pore distribution is the bi-dimensional (2D digital image analysis. Such technique provides quantitative results of soil pore shape, number and size. The use of specific softwares for the treatment and processing of images allows a fast and efficient method to quantify the soil porous system. However, due to the high cost of commercial softwares, public ones can be an interesting alternative for soil structure analysis. The objective of this work was to evaluate the quality of data provided by the Image J software (public domain used to characterize the voids of two soils, characterized as Geric Ferralsol and Rhodic Ferralsol, from the southeast region of Brazil. The pore distribution analysis technique from impregnated soil blocks was utilized for this purpose. The 2D image acquisition was carried out by using a CCD camera coupled to a conventional optical microscope. After acquisition and treatment of images, they were processed and analyzed by the software Noesis Visilog 5.4® (chosen as the reference program and ImageJ. The parameters chosen to characterize the soil voids were: shape, number and pore size distribution. For both soils, the results obtained for the image total porosity (%, the total number of pores and the pore size distribution showed that the Image J is a suitable software to be applied in the characterization of the soil sample voids impregnated with resin.

  5. Pore opening dynamics in the exocytosis of serotonin

    Science.gov (United States)

    Ramirez-Santiago, Guillermo; Cercos, Montserrat G.; Martinez-Valencia, Alejandro; Salinas Hernandez, Israel; Rodríguez-Sosa, Leonardo; de-Miguel, Francisco F.

    2015-03-01

    The current view of the exocytosis of transmitter molecules is that it starts with the formation of a fusion pore that connects the intravesicular and the extracellular spaces, and is completed by the release of the rest of the transmitter contained in the vesicle upon the full fusion and collapse of the vesicle with the plasma membrane. However, under certain circumstances, a rapid closure of the pore before the full vesicle fusion produces only a partial release of the transmitter. Here we show that whole release of the transmitter occurs through fusion pores that remain opened for tens of milliseconds without vesicle collapse. This was demonstrated through amperometric measurements of serotonin release from electrodense vesicles in the axon of leech Retzius neurons and mathematical modelling. By modeling transmitter release with a diffusion equation subjected to boundary conditions that are defined by the experiment, we showed that those pores with a fast half rise time constant remained opened and allowed the full quantum release without vesicle collapse, whereas pores with a slow rise time constant closed rapidly, thus producing partial release. We conclude that a full transmitter release may occur through the fusion pore in the absence of vesicle collapse. This work was founded by a DGAPA-UNAM grants IN200914 and IN118410 CONACYT GRANT 130031, and CONACyT doctoral fellowships.

  6. Pore space quantification of carbonate rocks before-after supercritical CO2 interaction by optical image analysis

    Science.gov (United States)

    Berrezueta, Edgar; José Domínguez-Cuesta, María

    2017-04-01

    The aim of this research is to show an experimental application of an automated quantification process of optical porosity in thin sections. Petrographic studies using scanning electronic microscopy, optical microscopy (OpM) and optical image analysis (OIA) could provide a reproducible pore characterization of carbonate rocks in applications related to the geological storage of CO2. This research is focused on i) the quantification of optical pores in a carbonate rock before and after supercritical CO2-rich brine (P ≈ 7.5 MPa and T ≈ 35 °C) and ii) the description of the process followed to guarantee the reproducibility of the OIA method on images acquired with high-resolution scanner. Mineral images were acquired from thin sections using a high-resolution scanner (HRS). Digital images were geo-referenced by using geographic information system to ensure correct spatial correlation and superposition. The optical measures of porosity by image analysis on the carbonates thin sections showed an effective pore segmentation considering different cross-polarized light conditions (90°/0°; 120°/30°) and plane-polarized light conditions (90°/-) of the same petrographic scene. The pore characterization by OpM and OIA-HRS has allowed a preliminary approximation of pore evolution in carbonate rocks under the supercritical CO2-rich brine. This study shows a fast, effective and reproducible methodology that allowed a preliminary characterization (changes in the pore network) of the samples studied. The procedure carried out could be applied to similar experimental injection tests.

  7. Long-pore Electrostatics in Inward-rectifier Potassium Channels

    Science.gov (United States)

    Robertson, Janice L.; Palmer, Lawrence G.; Roux, Benoît

    2008-01-01

    Inward-rectifier potassium (Kir) channels differ from the canonical K+ channel structure in that they possess a long extended pore (∼85 Å) for ion conduction that reaches deeply into the cytoplasm. This unique structural feature is presumably involved in regulating functional properties specific to Kir channels, such as conductance, rectification block, and ligand-dependent gating. To elucidate the underpinnings of these functional roles, we examine the electrostatics of an ion along this extended pore. Homology models are constructed based on the open-state model of KirBac1.1 for four mammalian Kir channels: Kir1.1/ROMK, Kir2.1/IRK, Kir3.1/GIRK, and Kir6.2/KATP. By solving the Poisson-Boltzmann equation, the electrostatic free energy of a K+ ion is determined along each pore, revealing that mammalian Kir channels provide a favorable environment for cations and suggesting the existence of high-density regions in the cytoplasmic domain and cavity. The contribution from the reaction field (the self-energy arising from the dielectric polarization induced by the ion's charge in the complex geometry of the pore) is unfavorable inside the long pore. However, this is well compensated by the electrostatic interaction with the static field arising from the protein charges and shielded by the dielectric surrounding. Decomposition of the static field provides a list of residues that display remarkable correspondence with existing mutagenesis data identifying amino acids that affect conduction and rectification. Many of these residues demonstrate interactions with the ion over long distances, up to 40 Å, suggesting that mutations potentially affect ion or blocker energetics over the entire pore. These results provide a foundation for understanding ion interactions in Kir channels and extend to the study of ion permeation, block, and gating in long, cation-specific pores. PMID:19001143

  8. Detecting pore-lining regions in transmembrane protein sequences

    Directory of Open Access Journals (Sweden)

    Nugent Timothy

    2012-07-01

    Full Text Available Abstract Background Alpha-helical transmembrane channel and transporter proteins play vital roles in a diverse range of essential biological processes and are crucial in facilitating the passage of ions and molecules across the lipid bilayer. However, the experimental difficulties associated with obtaining high quality crystals has led to their significant under-representation in structural databases. Computational methods that can identify structural features from sequence alone are therefore of high importance. Results We present a method capable of automatically identifying pore-lining regions in transmembrane proteins from sequence information alone, which can then be used to determine the pore stoichiometry. By labelling pore-lining residues in crystal structures using geometric criteria, we have trained a support vector machine classifier to predict the likelihood of a transmembrane helix being involved in pore formation. Results from testing this approach under stringent cross-validation indicate that prediction accuracy of 72% is possible, while a support vector regression model is able to predict the number of subunits participating in the pore with 62% accuracy. Conclusion To our knowledge, this is the first tool capable of identifying pore-lining regions in proteins and we present the results of applying it to a data set of sequences with available crystal structures. Our method provides a way to characterise pores in transmembrane proteins and may even provide a starting point for discovering novel routes of therapeutic intervention in a number of important diseases. This software is freely available as source code from: http://bioinf.cs.ucl.ac.uk/downloads/memsat-svm/.

  9. Three-Dimensional Quantification of Pore Space in Flocculated Sediments

    Science.gov (United States)

    Lawrence, Tom; Spencer, Kate; Bushby, Andy; Manning, Andrew

    2017-04-01

    Flocculated sediment structure plays a vital role in determining sediment dynamics within the water column in fresh and saline water bodies. The porosity of flocs contributes to their specific density and therefore their settling characteristics, and can also affect settling characteristics via through-flow. The process of settling and resuspension of flocculated material causes the formation of larger and more complex individual flocs, about which little is known quantitatively of the internal micro-structure and therefore porosity. Hydrological and sedimentological modelling software currently uses estimations of porosity, because it is difficult to capture and analyse flocs. To combat this, we use a novel microscopy method usually performed on biological material to scan the flocs, the output of which can be used to quantify the dimensions and arrangement of pores. This involves capturing flocculated sediment, staining the sample with heavy metal elements to highlight organic content in the Scanning Electron Microscope later, and finally setting the sample in resin. The overall research aim is to quantitatively characterise the dimensions and distribution of pore space in flocs in three dimensions. In order to gather data, Scanning Electron Microscopy and micro-Computed Tomography have been utilised to produce the necessary images to identify and quantify the pore space. The first objective is to determine the dimensional limits of pores in the structure (i.e. what area do they encapsulate? Are they interconnected or discreet?). This requires a repeatable definition to be established, so that all floc pore spaces can be quantified using the same parameters. The LabSFLOC settling column and dyes will be used as one possible method of determining the outer limits of the discreet pore space. LabSFLOC is a sediment settling column that uses a camera to record the flocs, enabling analysis of settling characteristics. The second objective is to develop a reliable

  10. Idealized Shale Sorption Isotherm Measurements to Determine Pore Volume, Pore Size Distribution, and Surface Area

    Science.gov (United States)

    Holmes, R.; Wang, B.; Aljama, H.; Rupp, E.; Wilcox, J.

    2014-12-01

    One method for mitigating the impacts of anthropogenic CO2-related climate change is the sequestration of CO2 in depleted gas and oil reservoirs, including shale. The accurate characterization of the heterogeneous material properties of shale, including pore volume, surface area, pore size distributions (PSDs) and composition is needed to understand the interaction of CO2 with shale. Idealized powdered shale sorption isotherms were created by varying incremental amounts of four essential components by weight. The first two components, organic carbon and clay, have been shown to be the most important components for CO2 uptake in shales. Organic carbon was represented by kerogen isolated from a Silurian shale, and clay groups were represented by illite from the Green River shale formation. The rest of the idealized shale was composed of equal parts by weight of SiO2 to represent quartz and CaCO3 to represent carbonate components. Baltic, Eagle Ford, and Barnett shale sorption measurements were used to validate the idealized samples. The idealized and validation shale sorption isotherms were measured volumetrically using low pressure N2 (77K) and CO2 (273K) adsorbates on a Quantachrome Autosorb IQ2. Gravimetric isotherms were also produced for a subset of these samples using CO2 and CH4adsorbates under subsurface temperature and pressure conditions using a Rubotherm magnetic suspension balance. Preliminary analyses were inconclusive in validating the idealized samples. This could be a result of conflicting reports of total organic carbon (TOC) content in each sample, a problem stemming from the heterogeneity of the samples and different techniques used for measuring TOC content. The TOC content of the validation samples (Eagle Ford and Barnett) was measured by Rock-Eval pyrolysis at Weatherford Laboratories, while the TOC content in the Baltic validation samples was determined by LECO TOC. Development of a uniform process for measuring TOC in the validation samples is

  11. Multifractal Characteristics of Bimodal Mercury Pore Size Distribution Curves

    Science.gov (United States)

    dos Santos Bonini, C.; Alves, M. C.; Paz González, A.

    2012-04-01

    Characterization of Hg pore size distribution (PSDs) curves by monofractal or multifractal analysis has been demonstrated to be an useful tool, which allows a better understanding of the organization of the soil pore space. There are also evidences that multiscale analysis of different segments found in bimodal pore size distributions measured by Hg intrusion can provide further valuable information. In this study we selected bimodal PSDs from samples taken from an experimental area in São Paulo state, Brazil, where a revegetation trial was set up over saprolitic material. The saprolite was left abandoned after decapitation of an Oxisol for building purposes. The field trial consisted of various treatments with different grass species and amendments. Pore size distribution of the sampled aggregates was measured in the equivalent diameter range from 0.005 to about 50 μm and it was characterized by a bimodal pattern, so that two compartments, i.e. 0.005 to 0.2 μm and 0.2 to 50 μm, could be distinguished. The multifractal theory was used to analyse both segments. The scaling properties of these two segments could be fitted reasonably well with multifractal models. Multifractal parameters obtained for equivalent diameters for the segments > 0.2 and pore size distributions studied.

  12. The Bicomponent Pore-Forming Leucocidins of Staphylococcus aureus

    Science.gov (United States)

    Alonzo, Francis

    2014-01-01

    SUMMARY The ability to produce water-soluble proteins with the capacity to oligomerize and form pores within cellular lipid bilayers is a trait conserved among nearly all forms of life, including humans, single-celled eukaryotes, and numerous bacterial species. In bacteria, some of the most notable pore-forming molecules are protein toxins that interact with mammalian cell membranes to promote lysis, deliver effectors, and modulate cellular homeostasis. Of the bacterial species capable of producing pore-forming toxic molecules, the Gram-positive pathogen Staphylococcus aureus is one of the most notorious. S. aureus can produce seven different pore-forming protein toxins, all of which are believed to play a unique role in promoting the ability of the organism to cause disease in humans and other mammals. The most diverse of these pore-forming toxins, in terms of both functional activity and global representation within S. aureus clinical isolates, are the bicomponent leucocidins. From the first description of their activity on host immune cells over 100 years ago to the detailed investigations of their biochemical function today, the leucocidins remain at the forefront of S. aureus pathogenesis research initiatives. Study of their mode of action is of immediate interest in the realm of therapeutic agent design as well as for studies of bacterial pathogenesis. This review provides an updated perspective on our understanding of the S. aureus leucocidins and their function, specificity, and potential as therapeutic targets. PMID:24847020

  13. Small scale laboratory studies of flow and transport phenomena in pores and fractures: Phase II. Progress report, 3rd year continuation proposal, and work plan

    Energy Technology Data Exchange (ETDEWEB)

    Wilson, J.L.

    1994-05-01

    Small scale laboratory experiments, equipped with an ability to actually observe behavior on the pore level using microscopy, provide an economical and easily understood scientific tool to help us validate concepts and assumptions about the transport of contaminants, and offers the propensity to discover heretofore unrecognized phenomena or behavior. The main technique employs etched glass micromodels, composed of two etched glass plates, sintered together, to form a two dimensional network of three dimensional pores. Flow and transport behavior is observed on a pore or pore network level, and recorder on film and video tape. This technique is coupled with related column studies. These techniques have been used to study multiphase flow, colloid transport and most recently bacteria transport. The project has recently moved to the Bacteria Transport Subprogram, and efforts have been redirected to support that Subprogram and its collaborative field experiment. We proposed to study bacteria transport factors of relevance to the field experiment, using micromodels and other laboratory techniques. Factors that may be addressed include bacteria characteristics (eg, hydrophobicity), pore size and shape, permeability heterogeneity, surface chemistry (eg, iron oxide coatings), surface chemistry heterogeneity, active versus resting cell bacteria, and mixed bacteria populations. In other work we will continue to examine the effects of fluid-fluid interfaces on bacteria transport, and develop a new assay for bacteria hydrophobicity. Finally we will collaborate on characterization of the field site, and the design, operation, and interpretation of the field experiment.

  14. Why liquid displacement methods are sometimes wrong in estimating the pore-size distribution

    NARCIS (Netherlands)

    Gijsbertsen-Abrahamse, A.J.; Boom, R.M.; Padt, van der A.

    2004-01-01

    The liquid displacement method is a commonly used method to determine the pore size distribution of micro- and ultrafiltration membranes. One of the assumptions for the calculation of the pore sizes is that the pores are parallel and thus are not interconnected. To show that the estimated pore size

  15. Investigation of Time Dependent Development of Soil Structure and Formation of Macropore Networks as Affected by Various Precrop Species

    OpenAIRE

    Pagenkemper, Sebastian K.; Puschmann, Daniel Uteau; Peth, Stephan; Horn, Rainer

    2014-01-01

    A well developed macropore network is advantageous in terms of transport processes regarding gas and water, as well as nutrient acquisition and root growth of crops. X-ray computed tomography provides a non-destructive method to visualize and quantify three-dimensional pore networks. Geometrical and morphological parameters of the complex pore system such as connectivity, tortuosity, porosity and pore surface area would be very useful for modeling and simulation of transport and exchange proc...

  16. Multifractal Characterization of Pore Size Distributions of Peat Soil

    Directory of Open Access Journals (Sweden)

    Joko Sampurno

    2016-08-01

    Full Text Available This paper discusses a multifractal analysis of the microscopic structure of peat soil. The aim of this study was to apply the multifractal technique to analyze the properties of five slices of peat soil (L1-L5. Binary images (220 x 220 pixels, with a conversion value of 9.41 μm/pixel were made from the thin slices and then analyzed. This analysis was conducted to obtain the relationship between physical parameters and complexity parameters. The results showed that the spectrum of f(α can describe well the pore size distribution and average size of pores correlated with the value of D(0. A high value of the average pore size is followed by a low D value and vice versa.

  17. Two-phase flow simulations in pore-geometries

    Science.gov (United States)

    Heimann, F.; Engwer, C.; Bastian, P.; Ippisch, O.

    2012-04-01

    Pore scale simulations of multi phase flow in porous media present a promising approach in the development and verification of continuum scale models as well as in the understanding of the underlying processes of flow phenomena like hysteresis or the peculiarities of the capillary fringe. As typical pore geometries involve complicated geometries with peculiar topological properties, the generation of a computational mesh, required by finite element (FE) based simulation approaches, becomes a limiting obstacle. We present a numerical discretization based on discontinuous Galerkin methods which does not require a grid which is fitted to the computational domain. In this approach, the resolution of the domain boundaries may be chosen independent of the FE basis. Furthermore, we will present discretization techniques allowing for an accurate representation of the interface conditions i.e. the jump in the pressure and the velocity derivatives. First results of simulations for two-phase flow in pore geometries are discussed.

  18. Highly Aminated Mesoporous Silica Nanoparticles with Cubic Pore Structure

    KAUST Repository

    Suteewong, Teeraporn

    2011-01-19

    Mesoporous silica with cubic symmetry has attracted interest from researchers for some time. Here, we present the room temperature synthesis of mesoporous silica nanoparticles possessing cubic Pm3n symmetry with very high molar ratios (>50%) of 3-aminopropyl triethoxysilane. The synthesis is robust allowing, for example, co-condensation of organic dyes without loss of structure. By means of pore expander molecules, the pore size can be enlarged from 2.7 to 5 nm, while particle size decreases. Adding pore expander and co-condensing fluorescent dyes in the same synthesis reduces average particle size further down to 100 nm. After PEGylation, such fluorescent aminated mesoporous silica nanoparticles are spontaneously taken up by cells as demonstrated by fluorescence microscopy.

  19. Fines classification based on sensitivity to pore-fluid chemistry

    Science.gov (United States)

    Jang, Junbong; Santamarina, J. Carlos

    2016-01-01

    The 75-μm particle size is used to discriminate between fine and coarse grains. Further analysis of fine grains is typically based on the plasticity chart. Whereas pore-fluid-chemistry-dependent soil response is a salient and distinguishing characteristic of fine grains, pore-fluid chemistry is not addressed in current classification systems. Liquid limits obtained with electrically contrasting pore fluids (deionized water, 2-M NaCl brine, and kerosene) are combined to define the soil “electrical sensitivity.” Liquid limit and electrical sensitivity can be effectively used to classify fine grains according to their fluid-soil response into no-, low-, intermediate-, or high-plasticity fine grains of low, intermediate, or high electrical sensitivity. The proposed methodology benefits from the accumulated experience with liquid limit in the field and addresses the needs of a broader range of geotechnical engineering problems.

  20. Formation of protein induced micro-pores in Chitosan membranes

    Science.gov (United States)

    Begum, S. N. Suraiya; Aswal, V. K.; Ramasamy, Radha Perumal

    2017-05-01

    Polymer based nanocomposites are important class of materials and have wide applications. Blending two biopolymers can lead to the development of new materials with tailored properties. Chitosan is a naturally occurring polysaccharide with useful properties such as biodegradability and excellent film forming capacity. Bovine serum albumin (BSA) is a abundantly available globular protein. In our research the interaction of chitosan with BSA and the effect of formation of Au nanoparticles on chitosan-BSA system were investigated. Scanning electron microscope (SEM) of the films showed formation of micron sized pores and these pores were hindered with formation of Au nanoparticles. Small angle neutron scattering (SANS) analysis showed that BSA interacts with chitosan chain and affects the Rg value of chitosan. The formation of micro pores decreases the conductivity values (σ'), while the formation of Au nanoparticles increases σ'.

  1. Influence of crosslinking agents on the pore structure of skin.

    Science.gov (United States)

    Fathima, N Nishad; Dhathathreyan, Aruna; Ramasami, T

    2007-05-15

    Analysis of pore structure of skin is important to understand process of diffusion and adsorption involved during any application of the skin matrix. In this study, the effect of thermal shrinkage on the pore structure of chromium and vegetable treated skin has been analyzed as these tanning agents are known to bring about thermal stability to the matrix. The changes brought about in the pore structure have been studied using mercury intrusion porosimetry and scanning electron microscopy. Response of the chromium treated and vegetable tanning treated skin structure to heat has been found to be quite different from each other. About 41% decrease in porosity is observed for chromium treated skin as against 97% decrease for the skin treated with vegetable tannins. This is primarily attributed to the basic nature of these materials and the nature of interaction of them towards skin.

  2. Fines Classification Based on Sensitivity to Pore-Fluid Chemistry

    KAUST Repository

    Jang, Junbong

    2015-12-28

    The 75-μm particle size is used to discriminate between fine and coarse grains. Further analysis of fine grains is typically based on the plasticity chart. Whereas pore-fluid-chemistry-dependent soil response is a salient and distinguishing characteristic of fine grains, pore-fluid chemistry is not addressed in current classification systems. Liquid limits obtained with electrically contrasting pore fluids (deionized water, 2-M NaCl brine, and kerosene) are combined to define the soil "electrical sensitivity." Liquid limit and electrical sensitivity can be effectively used to classify fine grains according to their fluid-soil response into no-, low-, intermediate-, or high-plasticity fine grains of low, intermediate, or high electrical sensitivity. The proposed methodology benefits from the accumulated experience with liquid limit in the field and addresses the needs of a broader range of geotechnical engineering problems. © ASCE.

  3. RNase A does not translocate the alpha-hemolysin pore.

    Directory of Open Access Journals (Sweden)

    Besnik Krasniqi

    Full Text Available The application of nanopore sensing utilizing the α-hemolysin pore to probe proteins at single-molecule resolution has expanded rapidly. In some studies protein translocation through the α-hemolysin has been reported. However, there is no direct evidence, as yet, that proteins can translocate the α-hemolysin pore. The biggest challenge to obtaining direct evidence is the lack of a highly sensitive assay to detect very low numbers of protein molecules. Furthermore, if an activity based assay is applied then the proteins translocating by unfolding should refold back to an active confirmation for the assay technique to work. To overcome these challenges we selected a model enzyme, ribonuclease A, that readily refolds to an active conformation even after unfolding it with denaturants. In addition we have developed a highly sensitive reverse transcription polymerase chain reaction based activity assay for ribonuclease A. Initially, ribonuclease A, a protein with a positive net charge and dimensions larger than the smallest diameter of the pore, was subjected to nanopore analysis under different experimental conditions. Surprisingly, although the protein was added to the cis chamber (grounded and a positive potential was applied, the interaction of ribonuclease A with α-hemolysin pore induced small and large blockade events in the presence and the absence of a reducing and/or denaturing agent. Upon measuring the zeta potential, it was found that the protein undergoes a charge reversal under the experimental conditions used for nanopore sensing. From the investigation of the effect of voltage on the interaction of ribonuclease A with the α-hemolysin pore, it was impossible to conclude if the events observed were translocations. However, upon testing for ribonuclease A activity on the trans chamber it was found that ribonuclease A does not translocate the α-hemolysin pore.

  4. Microfluidic Experiments Studying Pore Scale Interactions of Microbes and Geochemistry

    Science.gov (United States)

    Chen, M.; Kocar, B. D.

    2016-12-01

    Understanding how physical phenomena, chemical reactions, and microbial behavior interact at the pore-scale is crucial to understanding larger scale trends in groundwater chemistry. Recent studies illustrate the utility of microfluidic devices for illuminating pore-scale physical-biogeochemical processes and their control(s) on the cycling of iron, uranium, and other important elements 1-3. These experimental systems are ideal for examining geochemical reactions mediated by microbes, which include processes governed by complex biological phenomenon (e.g. biofilm formation, etc.)4. We present results of microfluidic experiments using a model metal reducing bacteria and varying pore geometries, exploring the limitations of the microorganisms' ability to access tight pore spaces, and examining coupled biogeochemical-physical controls on the cycling of redox sensitive metals. Experimental results will provide an enhanced understanding of coupled physical-biogeochemical processes transpiring at the pore-scale, and will constrain and compliment continuum models used to predict and describe the subsurface cycling of redox-sensitive elements5. 1. Vrionis, H. A. et al. Microbiological and geochemical heterogeneity in an in situ uranium bioremediation field site. Appl. Environ. Microbiol. 71, 6308-6318 (2005). 2. Pearce, C. I. et al. Pore-scale characterization of biogeochemical controls on iron and uranium speciation under flow conditions. Environ. Sci. Technol. 46, 7992-8000 (2012). 3. Zhang, C., Liu, C. & Shi, Z. Micromodel investigation of transport effect on the kinetics of reductive dissolution of hematite. Environ. Sci. Technol. 47, 4131-4139 (2013). 4. Ginn, T. R. et al. Processes in microbial transport in the natural subsurface. Adv. Water Resour. 25, 1017-1042 (2002). 5. Scheibe, T. D. et al. Coupling a genome-scale metabolic model with a reactive transport model to describe in situ uranium bioremediation. Microb. Biotechnol. 2, 274-286 (2009).

  5. Hydrochromic conjugated polymers for human sweat pore mapping.

    Science.gov (United States)

    Lee, Joosub; Pyo, Minkyeong; Lee, Sang-hwa; Kim, Jaeyong; Ra, Moonsoo; Kim, Whoi-Yul; Park, Bum Jun; Lee, Chan Woo; Kim, Jong-Man

    2014-04-29

    Hydrochromic materials have been actively investigated in the context of humidity sensing and measuring water contents in organic solvents. Here we report a sensor system that undergoes a brilliant blue-to-red colour transition as well as 'Turn-On' fluorescence upon exposure to water. Introduction of a hygroscopic element into a supramolecularly assembled polydiacetylene results in a hydrochromic conjugated polymer that is rapidly responsive (polymer. As a result, the sensor can be used to construct a precise map of active sweat pores on fingertips. The sensor technology, developed in this study, has the potential of serving as new method for fingerprint analysis and for the clinical diagnosis of malfunctioning sweat pores.

  6. Silicon pore optics for future x-ray telescopes

    DEFF Research Database (Denmark)

    Wille, Eric; Bavdaz, Marcos; Wallace, Kotska

    2017-01-01

    Lightweight X-ray Wolter optics with a high angular resolution will enable the next generation of X-ray telescopes in space. The candidate mission ATHENA (Advanced Telescope for High Energy Astrophysics) required a mirror assembly of 1 m2 effective area (at 1 keV) and an angular resolution of 10...... arcsec or better. These specifications can only be achieved with a novel technology like Silicon Pore Optics, which is being developed by ESA together with a consortium of European industry. Silicon Pore Optics are made of commercial Si wafers using process technology adapted from the semiconductor...

  7. Probing single nanometer-scale pores with polymeric molecular rulers

    Science.gov (United States)

    Henrickson, Sarah E.; DiMarzio, Edmund A.; Wang, Qian; Stanford, Vincent M.; Kasianowicz, John J.

    2010-04-01

    We previously demonstrated that individual molecules of single-stranded DNA can be driven electrophoretically through a single Staphylococcus aureus α-hemolysin ion channel. Polynucleotides thread through the channel as extended chains and the polymer-induced ionic current blockades exhibit stable modes during the interactions. We show here that polynucleotides can be used to probe structural features of the α-hemolysin channel itself. Specifically, both the pore length and channel aperture profile can be estimated. The results are consistent with the channel crystal structure and suggest that polymer-based "molecular rulers" may prove useful in deducing the structures of nanometer-scale pores in general.

  8. Local Pore Size Correlations Determine Flow Distributions in Porous Media.

    Science.gov (United States)

    Alim, Karen; Parsa, Shima; Weitz, David A; Brenner, Michael P

    2017-10-06

    The relationship between the microstructure of a porous medium and the observed flow distribution is still a puzzle. We resolve it with an analytical model, where the local correlations between adjacent pores, which determine the distribution of flows propagated from one pore downstream, predict the flow distribution. Numerical simulations of a two-dimensional porous medium verify the model and clearly show the transition of flow distributions from δ-function-like via Gaussians to exponential with increasing disorder. Comparison to experimental data further verifies our numerical approach.

  9. Role of scaffold mean pore size in meniscus regeneration.

    Science.gov (United States)

    Zhang, Zheng-Zheng; Jiang, Dong; Ding, Jian-Xun; Wang, Shao-Jie; Zhang, Lei; Zhang, Ji-Ying; Qi, Yan-Song; Chen, Xue-Si; Yu, Jia-Kuo

    2016-10-01

    Recently, meniscus tissue engineering offers a promising management for meniscus regeneration. Although rarely reported, the microarchitectures of scaffolds can deeply influence the behaviors of endogenous or exogenous stem/progenitor cells and subsequent tissue formation in meniscus tissue engineering. Herein, a series of three-dimensional (3D) poly(ε-caprolactone) (PCL) scaffolds with three distinct mean pore sizes (i.e., 215, 320, and 515μm) were fabricated via fused deposition modeling. The scaffold with the mean pore size of 215μm significantly improved both the proliferation and extracellular matrix (ECM) production/deposition of mesenchymal stem cells compared to all other groups in vitro. Moreover, scaffolds with mean pore size of 215μm exhibited the greatest tensile and compressive moduli in all the acellular and cellular studies. In addition, the relatively better results of fibrocartilaginous tissue formation and chondroprotection were observed in the 215μm scaffold group after substituting the rabbit medial meniscectomy for 12weeks. Overall, the mean pore size of 3D-printed PCL scaffold could affect cell behavior, ECM production, biomechanics, and repair effect significantly. The PCL scaffold with mean pore size of 215μm presented superior results both in vitro and in vivo, which could be an alternative for meniscus tissue engineering. Meniscus tissue engineering provides a promising strategy for meniscus regeneration. In this regard, the microarchitectures (e.g., mean pore size) of scaffolds remarkably impact the behaviors of cells and subsequent tissue formation, which has been rarely reported. Herein, three three-dimensional poly(ε-caprolactone) scaffolds with different mean pore sizes (i.e., 215, 320, and 515μm) were fabricated via fused deposition modeling. The results suggested that the mean pore size significantly affected the behaviors of endogenous or exogenous stem/progenitor cells and subsequent tissue formation. This study furthers

  10. Pore facies analysis: incorporation of rock properties into pore geometry based classes in a Permo-Triassic carbonate reservoir in the Persian Gulf

    International Nuclear Information System (INIS)

    Rahimpour-Bonab, H; Aliakbardoust, E

    2014-01-01

    Pore facies analysis is a useful method for the classification of reservoir rocks according to pore geometry characteristics. The importance of this method is related to the dependence of the dynamic behaviour of the reservoir rock on the pore geometry. In this study, pore facies analysis was performed by the quantification and classification of the mercury injection capillary pressure (MICP) curves applying the multi-resolution graph-based clustering (MRGC) method. Each pore facies includes a limited variety of rock samples with different depositional fabrics and diagenetic histories, which are representative of one type of pore geometry. The present pore geometry is the result of the interaction between the primary rock fabric and its diagenetic overprint. Thus the variations in petrographic properties can be correlated with the pore geometry characteristics. Accordingly, the controlling parameters in the pore geometry characteristics were revealed by detailed petrographic analysis in each pore facies. The reservoir rock samples were then classified using the determined petrographic properties which control the pore system quality. This method is proposed for the classification of reservoir rocks in complicated carbonate reservoirs, in order to reduce the incompatibility of traditional facies analysis with pore system characteristics. The method is applicable where enough capillary pressure data is not available. (papers)

  11. Capillary pressure-saturation relationships for porous granular materials: Pore morphology method vs. pore unit assembly method

    Science.gov (United States)

    Sweijen, Thomas; Aslannejad, Hamed; Hassanizadeh, S. Majid

    2017-09-01

    In studies of two-phase flow in complex porous media it is often desirable to have an estimation of the capillary pressure-saturation curve prior to measurements. Therefore, we compare in this research the capability of three pore-scale approaches in reproducing experimentally measured capillary pressure-saturation curves. To do so, we have generated 12 packings of spheres that are representative of four different glass-bead packings and eight different sand packings, for which we have found experimental data on the capillary pressure-saturation curve in the literature. In generating the packings, we matched the particle size distributions and porosity values of the granular materials. We have used three different pore-scale approaches for generating the capillary pressure-saturation curves of each packing: i) the Pore Unit Assembly (PUA) method in combination with the Mayer and Stowe-Princen (MS-P) approximation for estimating the entry pressures of pore throats, ii) the PUA method in combination with the hemisphere approximation, and iii) the Pore Morphology Method (PMM) in combination with the hemisphere approximation. The three approaches were also used to produce capillary pressure-saturation curves for the coating layer of paper, used in inkjet printing. Curves for such layers are extremely difficult to determine experimentally, due to their very small thickness and the presence of extremely small pores (less than one micrometer in size). Results indicate that the PMM and PUA-hemisphere method give similar capillary pressure-saturation curves, because both methods rely on a hemisphere to represent the air-water interface. The ability of the hemisphere approximation and the MS-P approximation to reproduce correct capillary pressure seems to depend on the type of particle size distribution, with the hemisphere approximation working well for narrowly distributed granular materials.

  12. Plastic strain caused by contraction of pores in polycrystalline graphites

    International Nuclear Information System (INIS)

    Ioka, Ikuo; Yoda, Shinichi; Konishi, Takashi.

    1989-01-01

    The effects of porosity on mechanical properties and deformation behavior of four isotropic polycrystalline graphites were studied. The pore size distributions of the graphites were measured using a conventional mercury penetration technique. The average pore radius of ISO-88 graphite was about one-tenth of that of ISEM-1, IG-11 or IG-15 graphites. Young's modulus of the graphites decreased with increasing porosity. The stress-strain curve of each graphite was measured in its lateral and axial directions. Young's modulus of graphite decreased with increasing load. The plastic strain at a given compressive load was calculated from the stress-strain curve and the initial gradient of the unloading curve at the load. The ratio of lateral plastic strain to axial plastic strain for the graphites was less than 0.5, indicating that the volume of the graphites decreased during compressive loading. By assuming that the volume change was caused by contraction of pores, plastic strain associated with contraction of pores was calculated from the axial plastic strain and lateral plastic strain by slips along the basal planes. The plastic strain increased with increasing axial plastic strain and porosity of graphite. (author)

  13. The study of the relationship between pore structure and ...

    Indian Academy of Sciences (India)

    Administrator

    *For correspondence. The study of the relationship between pore structure and photocatalysis of mesoporous TiO2. BING GUO a. , HANGYAN SHEN a,. *, KANGYING SHU a. , YAOWU ZENG b and. WENSHENG NING c a. College of Materials Science and Engineering, China Jiliang University, Hangzhou 310018, China b.

  14. Low atomic number coating for XEUS silicon pore optics

    DEFF Research Database (Denmark)

    Lumb, D.H.; Cooper-Jensen, Carsten P.; Krumrey, M.

    2008-01-01

    We describe a set of measurements on coated silicon substrates that are representative of the material to be used for the XEUS High Performance Pore Optics (HPO) technology. X-ray angular reflectance measurements at 2.8 and 8 keV, and energy scans of reflectance at a fixed angle representative of...

  15. Pore formation by T3SS translocators: liposome leakage assay.

    Science.gov (United States)

    Faudry, Eric; Perdu, Caroline; Attrée, Ina

    2013-01-01

    Gram-negative bacteria utilize a dedicated membrane-embedded apparatus, the type III secretion system (T3SS), to inject proteins into host cells. The passage of the proteins across the target membrane is accomplished by a proteinaceous pore-the translocon-formed within the host-cell cytoplasmic membrane. Translocators bound to their chaperones can be expressed in Escherichia coli and subsequently dissociated from the chaperone by guanidine treatment. The pore formation properties of the translocators can then be studied by an in-vitro liposome leakage assay. Sulforhodamine-B is encapsulated within lipid vesicles during liposome preparation. At high concentration, this fluorochrome exhibits self-quenching limiting fluorescence emission. Upon pore formation, liposome leakage leads to the dilution of Sulforhodamine-B in the medium and fluorescence emission increases. Alternatively, fluorochromes coupled to large dextran molecules can be encapsulated in order to estimate pore dimensions. Here we describe protein expression and purification, dye-liposome preparation, and leakage assay conditions.

  16. Investigation on pore structure and small-scale agglomeration ...

    Indian Academy of Sciences (India)

    The increase in the additives results in the modification in the pore size distribution and to some extent the total porosity. SANS revealed a mass fractal nature of the agglomerated matrix microstructure. The fractal dimension of the matrix does not change appreciably with the additives although the upper cut-off value of the ...

  17. Alumina ceramics prepared with new pore-forming agents

    Directory of Open Access Journals (Sweden)

    Zuzana Živcová

    2008-06-01

    Full Text Available Porous ceramics have a wide range of applications at all length scales, ranging from fi ltration membranes and catalyst supports to biomaterials (scaffolds for bone ingrowths and thermally or acoustically insulating bulk materials or coating layers. Organic pore-forming agents (PFAs of biological origin can be used to control porosity, pore size and pore shape. This work concerns the characterization and testing of several less common pore-forming agents (lycopodium, coffee, fl our and semolina, poppy seed, which are of potential interest from the viewpoint of size, shape or availability. The performance of these new PFAs is compared to that of starch, which has become a rather popular PFA for ceramics during the last decade. The PFAs investigated in this work are in the size range from 5 μm (rice starch to approximately 1 mm (poppy seed, all with more or less isometric shape. The burnout behavior of PFAs is studied by thermal analysis, i.e. thermogravimetry and differential thermal analysis. For the preparation of porous alumina ceramics from alumina suspensions containing PFAs traditional slip casting (into plaster molds and starch consolidation casting (using metal molds are used in this work. The resulting microstructures are investigated using optical microscopy, combined with image analysis, as well as other methods (Archimedes method of double-weighing in water, mercury intrusion porosimetry.

  18. Compaction and Porosity Based Pore Pressure Prediction in the ...

    African Journals Online (AJOL)

    2: A reversal in the trend (well 3; 5450-9658ft, r = -0.89) indicated by an increase in porosity as a result of overpressure. A number of factors such as compaction, fluid content and pore pressure affect the porosity-depth trends of the Agbada Formation. A decrease in porosity with depth generally holds true for shales (well 1: ...

  19. Concentration Polarization to Measure Nano-pore Accessibility

    NARCIS (Netherlands)

    Solsona, Miguel; Eijkel, Jan C.T.; Olthuis, Wouter; Papadimitriou, Vasileios; van den Berg, Albert; Abelmann, Leon; Weckhuysen, Bert M.; Nieuwelink, A. E.

    2017-01-01

    Understanding the deactivation process in porous catalysts is of tremendous economic significance. We demonstrate the feasibility of using the concentration polarization method to obtain the pore accessibility distribution at single particle level for the first time. By using this technique we could

  20. A simulation of earthquake induced undrained pore pressure ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Earth System Science; Volume 112; Issue 3. A simulation of earthquake induced undrained pore pressure changes with bearing on some soil liquefaction observations following the 2001 Bhuj earthquake. Irene Sarkar Ramesh Chander. Volume 112 Issue 3 September 2003 pp 471-477 ...

  1. On the Mechanism of Pore Formation by Melittin

    NARCIS (Netherlands)

    van den Bogaart, Geert; Guzman, Jeanette Velasquez; Mika, Jacek T.; Poolman, Bert

    2008-01-01

    The mechanism of pore formation of lytic peptides, such as melittin from bee venom, is thought to involve binding to the membrane surface, followed by insertion at threshold levels of bound peptide. We show that in membranes composed of zwitterionic lipids, i.e. phosphatidylcholine, melittin not

  2. Small angle neutron scattering study of pore microstructure in ceria ...

    Indian Academy of Sciences (India)

    The SANS profiles indicate surface fractal morphology of the pore space with fractal dimensionality lying between 2.70 and 2.76. ... Bedekar2 A K Tyagi2. Solid State Physics Division; Bhabha Atomic Research Centre, Mumbai 400 085, India; Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400 085, India ...

  3. The hydraulic conductivity of sediments: A pore size perspective

    KAUST Repository

    Ren, X.W.

    2017-12-06

    This article presents an analysis of previously published hydraulic conductivity data for a wide range of sediments. All soils exhibit a prevalent power trend between the hydraulic conductivity and void ratio. Data trends span 12 orders of magnitude in hydraulic conductivity and collapse onto a single narrow trend when the hydraulic conductivity data are plotted versus the mean pore size, estimated using void ratio and specific surface area measurements. The sensitivity of hydraulic conductivity to changes in the void ratio is higher than the theoretical value due to two concurrent phenomena: 1) percolating large pores are responsible for most of the flow, and 2) the larger pores close first during compaction. The prediction of hydraulic conductivity based on macroscale index parameters in this and similar previous studies has reached an asymptote in the range of kmeas/5≤kpredict≤5kmeas. The remaining uncertainty underscores the important role of underlying sediment characteristics such as pore size distribution, shape, and connectivity that are not measured with index properties. Furthermore, the anisotropy in hydraulic conductivity cannot be recovered from scalar parameters such as index properties. Overall, results highlight the robustness of the physics inspired data scrutiny based Hagen–Poiseuille and Kozeny-Carman analyses.

  4. Multi-Material Tissue Engineering Scaffold with Hierarchical Pore Architecture.

    Science.gov (United States)

    Morgan, Kathy Ye; Sklaviadis, Demetra; Tochka, Zachary L; Fischer, Kristin M; Hearon, Keith; Morgan, Thomas D; Langer, Robert; Freed, Lisa E

    2016-08-23

    Multi-material polymer scaffolds with multiscale pore architectures were characterized and tested with vascular and heart cells as part of a platform for replacing damaged heart muscle. Vascular and muscle scaffolds were constructed from a new material, poly(limonene thioether) (PLT32i), which met the design criteria of slow biodegradability, elastomeric mechanical properties, and facile processing. The vascular-parenchymal interface was a poly(glycerol sebacate) (PGS) porous membrane that met different criteria of rapid biodegradability, high oxygen permeance, and high porosity. A hierarchical architecture of primary (macroscale) and secondary (microscale) pores was created by casting the PLT32i prepolymer onto sintered spheres of poly(methyl methacrylate) (PMMA) within precisely patterned molds followed by photocuring, de-molding, and leaching out the PMMA. Pre-fabricated polymer templates were cellularized, assembled, and perfused in order to engineer spatially organized, contractile heart tissue. Structural and functional analyses showed that the primary pores guided heart cell alignment and enabled robust perfusion while the secondary pores increased heart cell retention and reduced polymer volume fraction.

  5. SANS investigation on evolution of pore morphology for varying ...

    Indian Academy of Sciences (India)

    application as hosts for catalysts in automobile exhaust. It has been observed that by suitably tailoring the sintering conditions (temperature, time and ... As the distance at which mass transport has to take place during sintering is less for finer pores, the kinetics of their elimination is faster than that of the coarser ones.

  6. Enhanced water transport and salt rejection through hydrophobic zeolite pores

    Science.gov (United States)

    Humplik, Thomas; Lee, Jongho; O’Hern, Sean; Laoui, Tahar; Karnik, Rohit; Wang, Evelyn N.

    2017-12-01

    The potential of improvements to reverse osmosis (RO) desalination by incorporating porous nanostructured materials such as zeolites into the selective layer in the membrane has spurred substantial research efforts over the past decade. However, because of the lack of methods to probe transport across these materials, it is still unclear which pore size or internal surface chemistry is optimal for maximizing permeability and salt rejection. We developed a platform to measure the transport of water and salt across a single layer of zeolite crystals, elucidating the effects of internal wettability on water and salt transport through the ≈5.5 Å pores of MFI zeolites. MFI zeolites with a more hydrophobic (i.e., less attractive) internal surface chemistry facilitated an approximately order of magnitude increase in water permeability compared to more hydrophilic MFI zeolites, while simultaneously fully rejecting both potassium and chlorine ions. However, our results also demonstrated approximately two orders of magnitude lower permeability compared to molecular simulations. This decreased performance suggests that additional transport resistances (such as surface barriers, pore collapse or blockages due to contamination) may be limiting the performance of experimental nanostructured membranes. Nevertheless, the inclusion of hydrophobic sub-nanometer pores into the active layer of RO membranes should improve both the water permeability and salt rejection of future RO membranes (Fasano et al 2016 Nat. Commun. 7 12762).

  7. Host defenses against bacterial pore-forming toxins

    NARCIS (Netherlands)

    Los, F.C.O.

    2011-01-01

    Pore-forming toxins (PFTs), the most common bacterial toxins, contribute to infection by perforating host cell membranes. Excessive use and lack of new development of antibiotics are causing increasing numbers of drug-resistant bacteria, like methicillin-resistant Staphylococcus aureus (MRSA) and

  8. Development of Pore Pressure and Material Damping during Cyclic Loading

    DEFF Research Database (Denmark)

    Ibsen, Lars Bo

    1994-01-01

    The behaviour of sand during cyclic loading can be characterized as "stabilization", "instant stabilization". "pore pressure buildup" and "liquefaction". The terminologies can be defined exactly by a simple mathematical formulation based on the existence of a cyclic stable state. By introducing...

  9. Investigation on pore structure and small-scale agglomeration ...

    Indian Academy of Sciences (India)

    Investigation on pore structure and small-scale agglomeration behaviour in liquid phase sintered. SiC using small angle neutron scattering. D SEN1,∗, J BAHADUR1, S MAZUMDER1, T MAHATA2, M SYAMBABU2 and. P K SINHA2. 1Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085, India.

  10. Pore-scale uncertainty quantification with multilevel Monte Carlo

    KAUST Repository

    Icardi, Matteo

    2014-01-06

    Computational fluid dynamics (CFD) simulations of pore-scale transport processes in porous media have recently gained large popularity. However the geometrical details of the pore structures can be known only in a very low number of samples and the detailed flow computations can be carried out only on a limited number of cases. The explicit introduction of randomness in the geometry and in other setup parameters can be crucial for the optimization of pore-scale investigations for random homogenization. Since there are no generic ways to parametrize the randomness in the porescale structures, Monte Carlo techniques are the most accessible to compute statistics. We propose a multilevel Monte Carlo (MLMC) technique to reduce the computational cost of estimating quantities of interest within a prescribed accuracy constraint. Random samples of pore geometries with a hierarchy of geometrical complexities and grid refinements, are synthetically generated and used to propagate the uncertainties in the flow simulations and compute statistics of macro-scale effective parameters.

  11. Load response of periodontal ligament: assessment of fluid flow, compressibility, and effect of pore pressure.

    Science.gov (United States)

    Bergomi, Marzio; Wiskott, H W Anselm; Botsis, John; Mellal, Aïssa; Belser, Urs C

    2010-01-01

    The periodontal ligament (PDL) functions both in tension and in compression. The presence of an extensive vascular network inside the tissue suggests a significant contribution of the fluid phase to the mechanical response. This study examined the load response of bovine PDL under different pore pressure levels. A custom-made pressure chamber was constructed. Rod-shaped specimens comprising portions of dentine, bone, and intervening layer of PDL were extracted from bovine mandibular molars. The dentine ends of the specimens were secured to the actuator while the bone ends were affixed to the load cell. The entire assemblage was surrounded by the pressure chamber, which was then filled with saline. Specimens loaded at 1.0 Hz sinusoidal displacement were subjected to four different environmental fluid pressures (i.e., pressures of 0.0-1.0 MPa). The video images recorded during the tests were analyzed to determine whether or not fluid exchange between the PDL and the surrounding medium took place during mechanical loading. A value for the tissue's apparent Poisson ratio was also determined. The following observations were made: (1) fluid was squeezed out and pumped into the ligament during the compressive and tensile loading phases, (2) the PDL was highly compressible, and (3) the pore pressure had no influence on the mechanical response of the PDL. The present tests emphasized the biphasic structure of PDL tissue, which should be considered as a porous solid matrix through which fluid can freely flow.

  12. Thermal conductivity of high-porosity cellular-pore biocarbon prepared from sapele wood

    Science.gov (United States)

    Parfen'eva, L. S.; Orlova, T. S.; Kartenko, N. F.; Sharenkova, N. V.; Smirnov, B. I.; Smirnov, I. A.; Misiorek, H.; Jezowski, A.; Mucha, J.; de Arellano-Lopez, A. R.; Martinez-Fernandez, J.

    2009-10-01

    This paper reports on measurements (in the temperature range T = 5-300 K) of the thermal conductivity κ( T) and electrical conductivity σ( T) of the high-porosity (˜63 vol %) amorphous biocarbon preform with cellular pores, prepared by pyrolysis of sapele wood at the carbonization temperature 1000°C. The preform at 300 K was characterized using X-ray diffraction analysis. Nanocrystallites 11-30 Å in ize were shown to participate in the formation of the carbon network of sapele wood preforms. The dependences κ( T) and σ( T) were measured for the samples cut across and along empty cellular pore channels, which are aligned with the tree growth direction. Thermal conductivity measurements performed on the biocarbon sapele wood preform revealed a temperature dependence of the phonon thermal conductivity that is not typical of amorphous (and X-ray amorphous) materials. The electrical conductivity σ was found to increase with the temperature increasing from 5 to 300 K. The results obtained were analyzed.

  13. Structural Insights into Clostridium perfringens Delta Toxin Pore Formation.

    Directory of Open Access Journals (Sweden)

    Jessica Huyet

    Full Text Available Clostridium perfringens Delta toxin is one of the three hemolysin-like proteins produced by C. perfringens type C and possibly type B strains. One of the others, NetB, has been shown to be the major cause of Avian Nectrotic Enteritis, which following the reduction in use of antibiotics as growth promoters, has become an emerging disease of industrial poultry. Delta toxin itself is cytotoxic to the wide range of human and animal macrophages and platelets that present GM2 ganglioside on their membranes. It has sequence similarity with Staphylococcus aureus β-pore forming toxins and is expected to heptamerize and form pores in the lipid bilayer of host cell membranes. Nevertheless, its exact mode of action remains undetermined. Here we report the 2.4 Å crystal structure of monomeric Delta toxin. The superposition of this structure with the structure of the phospholipid-bound F component of S. aureus leucocidin (LukF revealed that the glycerol molecules bound to Delta toxin and the phospholipids in LukF are accommodated in the same hydrophobic clefts, corresponding to where the toxin is expected to latch onto the membrane, though the binding sites show significant differences. From structure-based sequence alignment with the known structure of staphylococcal α-hemolysin, a model of the Delta toxin pore form has been built. Using electron microscopy, we have validated our model and characterized the Delta toxin pore on liposomes. These results highlight both similarities and differences in the mechanism of Delta toxin (and by extension NetB cytotoxicity from that of the staphylococcal pore-forming toxins.

  14. Predicting Reactive Transport Dynamics in Carbonates using Initial Pore Structure

    Science.gov (United States)

    Menke, H. P.; Nunes, J. P. P.; Blunt, M. J.

    2017-12-01

    Understanding rock-fluid interaction at the pore-scale is imperative for accurate predictive modelling of carbon storage permanence. However, coupled reactive transport models are computationally expensive, requiring either a sacrifice of resolution or high performance computing to solve relatively simple geometries. Many recent studies indicate that initial pore structure many be the dominant mechanism in determining the dissolution regime. Here we investigate how well the initial pore structure is predictive of distribution and amount of dissolution during reactive flow using particle tracking on the initial image. Two samples of carbonate rock with varying initial pore space heterogeneity were reacted with reservoir condition CO2-saturated brine and scanned dynamically during reactive flow at a 4-μm resolution between 4 and 40 times using 4D X-ray micro-tomography over the course of 1.5 hours using μ-CT. Flow was modelled on the initial binarized image using a Navier-Stokes solver. Particle tracking was then run on the velocity fields, the streamlines were traced, and the streamline density was calculated both on a voxel-by-voxel and a channel-by-channel basis. The density of streamlines was then compared to the amount of dissolution in subsequent time steps during reaction. It was found that for the flow and transport regimes studied, the streamline density distribution in the initial image accurately predicted the dominant pathways of dissolution and gave good indicators of the type of dissolution regime that would later develop. This work suggests that the eventual reaction-induced changes in pore structure are deterministic rather than stochastic and can be predicted with high resolution imaging of unreacted rock.

  15. Typology, morphology and connectivity of pore space in claystones from reference site for research using BIB, FIB and cryo-SEM methods

    Science.gov (United States)

    Desbois, G.; Urai, J. L.; Houben, M. E.; Sholokhova, Y.

    2010-06-01

    Detailed investigation of the morphology of the pore space in clay is a key factor in understanding the sealing capacity, coupled flows, capillary processes and associated deformation present in mudstones. Actually, the combination of ion milling tools (FIB and BIB), cryogenic techniques and SEM imaging offers a new alternative to study in-situ elusive microstructures in wet geomaterials and has the high potential to make a step change in our understanding of how fluids occur in pore space. By using this range of techniques, it is possible to quantify porosity, stabilize in-situ fluids in pore space, preserve the natural structures at nm-scale, produce high quality polished cross-sections for high resolution SEM imaging and reconstruct accurately microstructure networks in 3D by serial cross sectioning.

  16. Typology, morphology and connectivity of pore space in claystones from reference site for research using BIB, FIB and cryo-SEM methods

    Directory of Open Access Journals (Sweden)

    Houben M.E.

    2010-06-01

    Full Text Available Detailed investigation of the morphology of the pore space in clay is a key factor in understanding the sealing capacity, coupled flows, capillary processes and associated deformation present in mudstones. Actually, the combination of ion milling tools (FIB and BIB, cryogenic techniques and SEM imaging offers a new alternative to study in-situ elusive microstructures in wet geomaterials and has the high potential to make a step change in our understanding of how fluids occur in pore space. By using this range of techniques, it is possible to quantify porosity, stabilize in-situ fluids in pore space, preserve the natural structures at nm-scale, produce high quality polished cross-sections for high resolution SEM imaging and reconstruct accurately microstructure networks in 3D by serial cross sectioning.

  17. Description and Reconstruction of Soil Structure Using Correlation Functions: Morphological and Pore-Scale Modeling Study

    Science.gov (United States)

    Karsanina, M.; Gerke, K.; Vasilyev, R.; Skvortsova, E. B.; Korost, D. V.; Mallants, D.

    2013-12-01

    It is now well-established that structure of porous or composite media (i.e., distribution of different materials or phases) defines all physical properties, including multi-phase flow and solute transport. To characterize soil structure conventional soil science uses such metrics as grain size distribution, morphology or numerous classifications. However, all these descriptors provide only limited and often qualitative information about structural properties, cannot be used to reconstruct real structure or predict physical properties. With the progress of modern non-destructive analysis tools we can obtain detailed 3D structure information and use it for calculation of any physical property. Such 3D data is a valuable verification dataset to check the usefulness of soil structure description using stochastic measures such as correlation functions. Any potential soil structure descriptor should possess two main features: 1) represent structure in some mathematical way, 2) reconstruction based on this mathematical function alone should be statistically equal to the original structure (e.g., have similar pore size distributions, physical properties, etc.). To check the applicability to soil science, we choose different 2D and 3D segmented soil images and calculated their correlation function. The modified Yeong-Torquato procedure was then used to reconstruct images based on calculated correlation functions. This method was applied to three different soil datasets: 1) a set of 2D thin-sections, 2) 3D images of soils with known hydraulic properties (Ksat and WRC), 3) 3D images of soils and aggregates from the same soil profile, but different genetic horizons. In the first case, we use conventional morphological descriptors in 2D original and reconstructed images (pore size, shapes and orientations) to quantify reconstructions quality. In the second case, we use pore-network models extracted from original and reconstructed 3D images to calculate Ksat, WRC and relative

  18. An instrument to measure differential pore pressures in deep ocean sediments: Pop-Up-Pore-Pressure-Instrument (PUPPI)

    International Nuclear Information System (INIS)

    Schultheiss, P.J.; McPhail, S.D.; Packwood, A.R.; Hart, B.

    1985-01-01

    A Pop-Up-Pore-Pressure-Instrument (PUPPI) has been developed to measure differential pore pressures in sediments. The differential pressure is the pressure above or below normal hydrostatic pressure at the depth of the measurement. It is designed to operate in water depths up to 6000 metres for periods of weeks or months, if required, and measures differential pore pressures at depths of up to 3 metres into the sediments with a resolution of 0.05 kPa. It is a free-fall device with a lance which penetrates the sediments. This lance and the ballast weight is disposed when the PUPPI is acoustically released from the sea floor. When combined with permeability and porosity values of deep-sea sediments the pore pressure measurements made using the PUPPI suggest advection velocities as low as 8.8 mm/yr. The mechanical, electrical and acoustic systems are described together with data obtained from both shallow and deep water trials. (author)

  19. Capillary pressure–saturation relationships for porous granular materials : Pore morphology method vs. pore unit assembly method

    NARCIS (Netherlands)

    Sweijen, Thomas; Aslannejad, Hamed; Hassanizadeh, S. Majid

    2017-01-01

    In studies of two-phase flow in complex porous media it is often desirable to have an estimation of the capillary pressure–saturation curve prior to measurements. Therefore, we compare in this research the capability of three pore-scale approaches in reproducing experimentally measured capillary

  20. Pore chemistry and size control in hybrid porous materials for acetylene capture from ethylene

    KAUST Repository

    Cui, X.

    2016-05-20

    The trade-off between physical adsorption capacity and selectivity of porous materials is a major barrier for efficient gas separation and purification through physisorption. We report control over pore chemistry and size in metal coordination networks with hexafluorosilicate and organic linkers for the purpose of preferential binding and orderly assembly of acetylene molecules through cooperative host-guest and/or guest-guest interactions. The specific binding sites for acetylene are validated by modeling and neutron powder diffraction studies. The energies associated with these binding interactions afford high adsorption capacity (2.1 millimoles per gram at 0.025 bar) and selectivity (39.7 to 44.8) for acetylene at ambient conditions. Their efficiency for the separation of acetylene/ethylene mixtures is demonstrated by experimental breakthrough curves (0.73 millimoles per gram from a 1/99 mixture).

  1. Rock Pore Structure as Main Reason of Rock Deterioration

    Science.gov (United States)

    Ondrášik, Martin; Kopecký, Miloslav

    2014-03-01

    Crashed or dimensional rocks have been used as natural construction material, decoration stone or as material for artistic sculptures. Especially old historical towns not only in Slovakia have had experiences with use of stones for construction purposes for centuries. The whole buildings were made from dimensional stone, like sandstone, limestone or rhyolite. Pavements were made especially from basalt, andesite, rhyolite or granite. Also the most common modern construction material - concrete includes large amounts of crashed rock, especially limestone, dolostone and andesite. However, rock as any other material if exposed to exogenous processes starts to deteriorate. Especially mechanical weathering can be very intensive if rock with unsuitable rock properties is used. For long it had been believed that repeated freezing and thawing in relation to high absorption is the main reason of the rock deterioration. In Slovakia for many years the high water absorption was set as exclusion criterion for use of rocks and stones in building industry. Only after 1989 the absorption was accepted as merely informational rock property and not exclusion. The reason of the change was not the understanding of the relationship between the porosity and rock deterioration, but more or less good experiences with some high porous rocks used in constructions exposed to severe weather conditions and proving a lack of relationship between rock freeze-thaw resistivity and water absorption. Results of the recent worldwide research suggest that understanding a resistivity of rocks against deterioration is hidden not in the absorption but in the structure of rock pores in relation to thermodynamic properties of pore water and tensile strength of rocks and rock minerals. Also this article presents some results of research on rock deterioration and pore structure performed on 88 rock samples. The results divide the rocks tested into two groups - group N in which the pore water does not freeze

  2. A Tilt, Soil Moisture, and Pore Water Pressure Sensor System for Slope Monitoring Applications

    Directory of Open Access Journals (Sweden)

    Rosanno de Dios

    2009-06-01

    Full Text Available This paper describes the design, implementation and characterization of a sensor network intended for monitoring of slope deformation and potential failures. The sensor network system consists of a tilt and moisture sensor column, a pore water pressure sensor column and a personal computer for data storage and processing. The tilt sensor column consists of several pipe segments containing tri-axial accelerometers and signal processing electronics. Each segment is joined together by flexible joints to allow for the column to deform and subsequently track underground movement. Capacitive-type sensors for soil moisture measurement are also included in the sensor column, which are used to measure the soil moisture at different depths. The measurements at each segment are transferred via a Controller Area Network (CAN bus, where the CAN master node is located at the top of the column above ground. The CAN master node transmits the collected data from the slave nodes via a wireless connection to a personal computer that performs data storage, processing and display via a Python-based graphical user interface (GUI. The entire system was deployed and characterized on a small-scale slope model. Slope failure was induced via water seepage and the system was demonstrated to ably measure the inclination and soil moisture content throughout the landslide event.

  3. Observations of the Dynamic Connectivity of the Non-Wetting Phase During Steady State Flow at the Pore Scale Using 3D X-ray Microtomography

    Science.gov (United States)

    Reynolds, C. A.; Menke, H. P.; Blunt, M. J.; Krevor, S. C.

    2015-12-01

    We observe a new type of non-wetting phase flow using time-resolved pore scale imaging. The traditional conceptual model of drainage involves a non-wetting phase invading a porous medium saturated with a wetting phase as either a fixed, connected flow path through the centres of pores or as discrete ganglia which move individually through the pore space, depending on the capillary number. We observe a new type of flow behaviour at low capillary number in which the flow of the non-wetting phase occurs through networks of persistent ganglia that occupy the large pores but continuously rearrange their connectivity (Figure 1). Disconnections and reconnections occur randomly to provide short-lived pseudo-steady state flow paths between pores. This process is distinctly different to the notion of flowing ganglia which coalesce and break-up. The size distribution of ganglia is dependent on capillary number. Experiments were performed by co-injecting N2and 25 wt% KI brine into a Bentheimer sandstone core (4mm diameter, 35mm length) at 50°C and 10 MPa. Drainage was performed at three flow rates (0.04, 0.3 and 1 ml/min) at a constant fractional flow of 0.5 and the variation in ganglia populations and connectivity observed. We obtained images of the pore space during steady state flow with a time resolution of 43 s over 1-2 hours. Experiments were performed at the Diamond Light Source synchrotron. Figure 1. The position of N2 in the pore space during steady state flow is summed over 40 time steps. White indicates that N2 occupies the space over >38 time steps and red <5 time steps.

  4. A random-walk model for pore pressure accumulation in marine soils

    DEFF Research Database (Denmark)

    Sumer, B. Mutlu; Cheng, Niang-Sheng

    1999-01-01

    A numerical random-walk model has been developed for the pore-water pressure. The model is based on the analogy between the variation of the pore pressure and the diffusion process of any passive quantity such as concentration. The pore pressure in the former process is analogous to the concentra......A numerical random-walk model has been developed for the pore-water pressure. The model is based on the analogy between the variation of the pore pressure and the diffusion process of any passive quantity such as concentration. The pore pressure in the former process is analogous...

  5. Monte-Carlo simulation of crystallographical pore growth in III-V-semiconductors

    International Nuclear Information System (INIS)

    Leisner, Malte; Carstensen, Juergen; Foell, Helmut

    2011-01-01

    The growth of crystallographical pores in III-V-semiconductors can be understood in the framework of a simple model, which is based on the assumption that the branching of pores is proportional to the current density at the pore tips. The stochastic nature of this model allows its implementation into a three-dimensional Monte-Carlo-simulation of pore growth. The simulation is able to reproduce the experimentally observed crysto pore structures in III-V-semiconductors in full quantitative detail. The different branching probabilities for different semiconductors, as well as doping levels, can be deduced from the specific passivation behavior of the semiconductor-electrolyte-interface at the pore tips.

  6. Synchrotron-based micro and nanotomographic investigations of soil aggregate microbial and pore structure

    Science.gov (United States)

    Kemner, K. M.; O'Brien, S.; Whiteside, M. D.; Sholto-Douglas, D.; Antipova, O.; Bailey, V.; Boyanov, M.; Dohnalkova, A.; Gursoy, D.; Kovarik, L.; Lai, B.; Roehrig, C.; Vogt, S.

    2017-12-01

    Soil is a highly complex network of pore spaces, minerals, and organic matter (e.g., roots, fungi, and bacteria), making it physically heterogeneous over nano- to macro-scales. Such complexity arises from feedbacks between physical processes and biological activity that generate a dynamic, self-organizing 3D complex. Since we first demonstrated the utility of synchrotron-based transmission tomography to image internal soil aggregate structure [Kemner et al., 1998], we and many other researchers have made use of and have advanced the application of this technique. However, our understanding of how microbes and microbial metabolism are distributed throughout soil aggregates is limited, because no technique is available to image the soil pore network and the life that inhabits it. X-ray transmission microtomography can provide highly detailed 3D renderings of soil structure but cannot distinguish cells from other electron-light material such as air or water. However, the use of CdSe quantum dots (QDs) as a reporter of bacterial presence enables us to overcome this constraint, instilling bacterial cells with enough contrast to detect them and their metabolic functions in their opaque soil habitat, with hard x-rays capable of penetrating 3D soil structures at high resolution. Previous transmission tomographic imaging of soil aggregates with high energy synchrotron x-rays has demonstrated 700 nm3 voxel spatial resolution. These and recent results from nanotomographic x-ray transmission imaging of soil aggregates with 30 nm3 voxel resolution will be presented. In addition, results of submicron voxel-sized x-ray fluorescence 3D imaging to determine microbial distributions within soil aggregates and the critical role to be played by the upgrade of the Advanced Photon Source for 100-1000X increases in hard x-ray brilliance will also be presented. *Kemner, et al., SPIE 3449, 45-53, 1998

  7. Regulation of Exocytotic Fusion Pores by SNARE Protein Transmembrane Domains

    Directory of Open Access Journals (Sweden)

    Zhenyong Wu

    2017-10-01

    Full Text Available Calcium-triggered exocytotic release of neurotransmitters and hormones from neurons and neuroendocrine cells underlies neuronal communication, motor activity and endocrine functions. The core of the neuronal exocytotic machinery is composed of soluble N-ethyl maleimide sensitive factor attachment protein receptors (SNAREs. Formation of complexes between vesicle-attached v- and plasma-membrane anchored t-SNAREs in a highly regulated fashion brings the membranes into close apposition. Small, soluble proteins called Complexins (Cpx and calcium-sensing Synaptotagmins cooperate to block fusion at low resting calcium concentrations, but trigger release upon calcium increase. A growing body of evidence suggests that the transmembrane domains (TMDs of SNARE proteins play important roles in regulating the processes of fusion and release, but the mechanisms involved are only starting to be uncovered. Here we review recent evidence that SNARE TMDs exert influence by regulating the dynamics of the fusion pore, the initial aqueous connection between the vesicular lumen and the extracellular space. Even after the fusion pore is established, hormone release by neuroendocrine cells is tightly controlled, and the same may be true of neurotransmitter release by neurons. The dynamics of the fusion pore can regulate the kinetics of cargo release and the net amount released, and can determine the mode of vesicle recycling. Manipulations of SNARE TMDs were found to affect fusion pore properties profoundly, both during exocytosis and in biochemical reconstitutions. To explain these effects, TMD flexibility, and interactions among TMDs or between TMDs and lipids have been invoked. Exocytosis has provided the best setting in which to unravel the underlying mechanisms, being unique among membrane fusion reactions in that single fusion pores can be probed using high-resolution methods. An important role will likely be played by methods that can probe single fusion pores

  8. Correlation between gas permeability and pore structure of coal matrix

    Science.gov (United States)

    Zhang, J.; Yang, J.; Gao, F.; Li, Y.; Niu, H.; Gao, H.

    2012-04-01

    The sequestration of CO2 in unminable coal seams represents a promising option for CO2 geologic storage, because the injected CO2 may enhance coalbed methane recovery (CO2-ECBM), which could partly offset the costs of the storage process. The CO2-ECBM technology is based on the relative affinity of CO2 and CH4 to coals under given pressure and temperature conditions. The excess sorption capacity of coals for CO2 is generally higher than the sorption capacity for methane. The coal seams are characterized by a dual porosity structure including cleat and matrix pores. The cleats in the coal seams are considered as highways for gas and water flow, while the matrix is the storage location of gas by adsorption. The slow transport process of gas in coal matrix may constrain the efficiency of the displacement of CH4 by CO2 due to the compacted pore structure of the coal matrix. Therefore, a detailed understanding of the correlation between permeability of gas and pore structure in coal matrix is crucial for the CO2-ECBM processes. Yangquan coals originating from the Qingshui basin, which contains gas-rich coals in China, were selected for the tests in this study. Yangquan coals are classified as anthracite. In order to avoid the influence of coal cleats on fluid flow, small coal plugs (~6 mm in diameter, ~13 mm in length) were selected and fixed in the sample compartment by special glue. A test system for simultaneously measuring adsorption-porosity-permeability on the coal matrix blocks in its free state is constructed. The permeability of gas and porosity in coal plugs to He under different gas pressure and temperature conditions were simultaneously investigated. The permeability and excess sorption capacity of the coal plugs to He, N2, CH4 and CO2 were compared at a constant gas pressure and temperature. It is expected that gas break through a cleat-plug is much faster than that through a coal matrix-plug. Different sample plugs with the different pore structure results

  9. The Controls of Pore-Throat Structure on Fluid Performance in Tight Clastic Rock Reservoir: A Case from the Upper Triassic of Chang 7 Member, Ordos Basin, China

    Directory of Open Access Journals (Sweden)

    Yunlong Zhang

    2018-01-01

    Full Text Available The characteristics of porosity and permeability in tight clastic rock reservoir have significant difference from those in conventional reservoir. The increased exploitation of tight gas and oil requests further understanding of fluid performance in the nanoscale pore-throat network of the tight reservoir. Typical tight sandstone and siltstone samples from Ordos Basin were investigated, and rate-controlled mercury injection capillary pressure (RMICP and nuclear magnetic resonance (NMR were employed in this paper, combined with helium porosity and air permeability data, to analyze the impact of pore-throat structure on the storage and seepage capacity of these tight oil reservoirs, revealing the control factors of economic petroleum production. The researches indicate that, in the tight clastic rock reservoir, largest throat is the key control on the permeability and potentially dominates the movable water saturation in the reservoir. The storage capacity of the reservoir consists of effective throat and pore space. Although it has a relatively steady and significant proportion that resulted from the throats, its variation is still dominated by the effective pores. A combination parameter (ε that was established to be as an integrated characteristic of pore-throat structure shows effectively prediction of physical capability for hydrocarbon resource of the tight clastic rock reservoir.

  10. Pore structure of natural and regenerated soil aggregates

    DEFF Research Database (Denmark)

    Naveed, Muhammad; Arthur, Emmanuel; de Jonge, Lis Wollesen

    2014-01-01

    Quantitative characterization of aggregate pore structure can reveal the evolution of aggregates under different land use and management practices and their effects on soil processes and functions. Advances in X-ray Computed Tomography (CT) provide powerful means to conduct such characterization....... This study examined aggregate pore structure of three differently managed same textured Danish soils (mixed forage cropping, MFC; mixed cash cropping, MCC; cereal cash cropping, CCC) for (i) natural aggregates, and (ii) aggregates regenerated after 20 months of incubation. In total, 27 aggregates (8-16 mm......) were sampled from nine different treatments; 3 natural soils and 3 repacked lysimeters without and 3 with organic matter (ground rape) amendment. Three dimensional X-ray CT images, tensile strength, and organic carbon were obtained for each aggregate. Aggregate-associated organic carbon differed...

  11. A general route towards defect and pore engineering in graphene.

    Science.gov (United States)

    Xie, Guibai; Yang, Rong; Chen, Peng; Zhang, Jing; Tian, Xuezeng; Wu, Shuang; Zhao, Jing; Cheng, Meng; Yang, Wei; Wang, Duoming; He, Congli; Bai, Xuedong; Shi, Dongxia; Zhang, Guangyu

    2014-06-12

    Defect engineering in graphene is important for tailoring graphene's properties thus applicable in various applications such as porous membranes and ultra-capacitors. In this paper, we report a general route towards defect- and pore- engineering in graphene through remote plasma treatments. Oxygen plasma irradiation was employed to create homogenous defects in graphene with controllable density from a few to ≈10(3) (μm(-2)). The created defects can be further enlarged into nanopores by hydrogen plasma anisotropic etching with well-defined pore size of a few nm or above. The achieved smallest nanopores are ≈2 nm in size, showing the potential for ultra-small graphene nanopores fabrication. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Fabrication, properties, and applications of porous metals with directional pores

    Science.gov (United States)

    NAKAJIMA, Hideo

    2010-01-01

    Lotus-type porous metals with aligned long cylindrical pores are fabricated by unidirectional solidification from the melt with a dissolved gas such as hydrogen, nitrogen, or oxygen. The gas atoms can be dissolved into the melt via a pressurized gas atmosphere or thermal decomposition of gaseous compounds. Three types of solidification techniques have been developed: mold casting, continuous zone melting, and continuous casting techniques. The last method is superior from the viewpoint of mass production of lotus metals. The observed anisotropic behaviors of the mechanical properties, sound absorption, and thermal conductivity are inherent to the anisotropic porous structure. In particular, the remarkable anisotropy in the mechanical strength is attributed to the stress concentration around the pores aligned perpendicular to the loading direction. Heat sinks are a promising application of lotus metals due to the high cooling performance with a large heat transfer. PMID:21084772

  13. Chromatography of humic substances on controlled pore glass

    International Nuclear Information System (INIS)

    Danneberg, O.H.

    1977-01-01

    To check the suitability of controlled pore glass (CPG) for the chromatography of humic substances, a soil extract from an Austrian chernozem and humic fractions prepared from the extract were chromatographed using a column filled with CPG of a pore diameter of 156A. The chromatograms obtained were reproducible, and showed the expected sequence of elution, grey humic acids (GHA) being eluted before brown humic acids (BHA) and fulvic acids (FA). Chromatograms of complex humic systems agreed well with the computed sums of the chromatograms of all its components. This means that all humic substances moved through the column independently of the presence or absence of others. From these findings, the suitability of CPG for chromatography of humic substances was concluded. A structural alteration of GHA during the preparation was detected. This was accompanied by a decrease in molecular weight and an increase in colour intensity. (author)

  14. Pore structure of the activated coconut shell charcoal carbon

    Science.gov (United States)

    Budi, E.; Nasbey, H.; Yuniarti, B. D. P.; Nurmayatri, Y.; Fahdiana, J.; Budi, A. S.

    2014-09-01

    The development of activated carbon from coconut shell charcoal has been investigated by using physical method to determine the influence of activation parameters in term of temperature, argon gas pressure and time period on the pore structure of the activated carbon. The coconut shell charcoal was produced by pyrolisis process at temperature of about 75 - 150 °C for 6 hours. The charcoal was activated at various temperature (532, 700 and 868 °C), argon gas pressure (6.59, 15 and 23.4 kgf/cm2) and time period of (10, 60 and 120 minutes). The results showed that the pores size were reduced and distributed uniformly as the activation parameters are increased.

  15. Gas release from pressurized closed pores in nuclear fuels

    International Nuclear Information System (INIS)

    Bailey, P.; Donnelly, S.E.; Armour, D.G.; Matzke, H.

    1988-01-01

    Gas release from the nuclear fuels UO 2 and UN out of pressurized closed pores produced by autoclave anneals has been studied by Thermal Desorption Spectrometry (TDS). Investigation of gas release during heating and cooling has indicated stress related mechanical effects leading to gas release. This release occurred in a narrow temperature range between about 1000 and 1500 K for UO 2 , but it continued down to ambient temperature for UN. No burst release was observed above 1500 K for UO 2 . (orig.)

  16. A mechanistic view of mitochondrial death decision pores

    Directory of Open Access Journals (Sweden)

    J.E. Belizário

    2007-08-01

    Full Text Available Mitochondria increase their outer and inner membrane permeability to solutes, protons and metabolites in response to a variety of extrinsic and intrinsic signaling events. The maintenance of cellular and intraorganelle ionic homeostasis, particularly for Ca2+, can determine cell survival or death. Mitochondrial death decision is centered on two processes: inner membrane permeabilization, such as that promoted by the mitochondrial permeability transition pore, formed across inner membranes when Ca2+ reaches a critical threshold, and mitochondrial outer membrane permeabilization, in which the pro-apoptotic proteins BID, BAX, and BAK play active roles. Membrane permeabilization leads to the release of apoptogenic proteins: cytochrome c, apoptosis-inducing factor, Smac/Diablo, HtrA2/Omi, and endonuclease G. Cytochrome c initiates the proteolytic activation of caspases, which in turn cleave hundreds of proteins to produce the morphological and biochemical changes of apoptosis. Voltage-dependent anion channel, cyclophilin D, adenine nucleotide translocase, and the pro-apoptotic proteins BID, BAX, and BAK may be part of the molecular composition of membrane pores leading to mitochondrial permeabilization, but this remains a central question to be resolved. Other transporting pores and channels, including the ceramide channel, the mitochondrial apoptosis-induced channel, as well as a non-specific outer membrane rupture may also be potential release pathways for these apoptogenic factors. In this review, we discuss the mechanistic models by which reactive oxygen species and caspases, via structural and conformational changes of membrane lipids and proteins, promote conditions for inner/outer membrane permeabilization, which may be followed by either opening of pores or a rupture of the outer mitochondrial membrane.

  17. Membranes with functionalized carbon nanotube pores for selective transport

    Science.gov (United States)

    Bakajin, Olgica; Noy, Aleksandr; Fornasiero, Francesco; Park, Hyung Gyu; Holt, Jason K; Kim, Sangil

    2015-01-27

    Provided herein composition and methods for nanoporous membranes comprising single walled, double walled, or multi-walled carbon nanotubes embedded in a matrix material. Average pore size of the carbon nanotube can be 6 nm or less. These membranes are a robust platform for the study of confined molecular transport, with applications in liquid and gas separations and chemical sensing including desalination, dialysis, and fabric formation.

  18. compaction and porosity based pore pressure prediction in the

    African Journals Online (AJOL)

    Home

    A number of factors such as compaction, fluid content and pore pressure affect the porosity-depth trends of the Agbada Formation. A decrease in porosity with depth generally holds true for shales (well. 1: r2 = 0.74 and well 2: r2 = 0.81) except for an increase in porosity (r2 = -0.596) observed in well 3. Compaction factor is.

  19. Optimization of transdermal delivery using magainin pore-forming peptide

    OpenAIRE

    Kim, Yeu-Chun; Ludovice, Peter J.; Prausnitz, Mark R.

    2008-01-01

    The skin's outer layer of stratum corneum, which is a thin tissue containing multilamellar lipid bilayers, is the main barrier to drug delivery to the skin. To increase skin permeability, our previous work has shown large enhancement of transdermal permeation using a pore-forming peptide, magainin, which was formulated with N-lauroyl sarcosine (NLS) in 50% ethanol-in-PBS. Mechanistic analysis suggested that magainin and NLS can increase skin permeability by disrupting stratum corneum lipid st...

  20. Pore water colloid properties in argillaceous sedimentary rocks

    OpenAIRE

    Degueldre, Claude; Cloet, Veerle

    2016-01-01

    The focus of this work is to evaluate the colloid nature, concentration and size distribution in the pore water of Opalinus Clay and other sedimentary host rocks identified for a potential radioactive waste repository in Switzerland. Because colloids could not be measured in representative undisturbed porewater of these host rocks, predictive modelling based on data from field and laboratory studies is applied. This approach allowed estimating the nature, concentration and size distributions ...

  1. Difficulties of supercurrents in narrow pores of 3He-A

    International Nuclear Information System (INIS)

    Thuneberg, E.V.; Kurkijaervi, J.

    1980-01-01

    We consider resistanceless supercurrents through narrow pores and find such currents to vanish in most cases because of end effects at the entries and exists of the pores. Under pressure dc-supercurrents are found to arise. (author)

  2. Pore morphology: a vital factor in determining electrochemical properties of electrical double layer capacitors.

    Science.gov (United States)

    Liang, Yeru; Li, Zhenghui; Yang, Xiaoqing; Fu, Ruowen; Wu, Dingcai

    2013-11-04

    The ordered 2D reverse hexagonal pore morphology facilitates rapid ion diffusion more than the disordered wormhole-like pore morphology, thus leading to superior electrochemical properties such as rate capabilities.

  3. High-pressure alchemy on a small-pore zeolite

    Science.gov (United States)

    Lee, Y.

    2011-12-01

    While an ever-expanding variety of zeolites with a wide range of framework topology is available, it is desirable to have a way to tailor the chemistry of the zeolitic nanopores for a given framework topology via controlling both the coordination-inclusion chemistry and framework distortion/relaxation. This is, however, subjected to the ability of a zeolitic nanopore to allow the redistribution of cations-water assembly and/or insertion of foreign molecules into the pores and channels. Small-pore zeolites such as natrolite (Na16Al16Si24O80x16H2O), however, have been known to show very limited capacity for any changes in the confinement chemistry. We have recently shown that various cation-exchanged natrolites can be prepared under modest conditions from natural sodium natrolite and exhibit cation-dependent volume expansions by up to 18.5% via converting the elliptical channels into progressively circular ones. Here, we show that pressure can be used as a unique and clean tool to further manipulate the chemistry of the natrolite nanopores. Our recent crystallographic and spectroscopic studies of pressure-insertion of foreign molecules, trivalent-cation exchange under pressure, and pressure-induced inversion of cation-water coordination and pore geometry in various cation-exchanged natrolites will be presented.

  4. Through pore diameter in the cell wall of Chara corallina.

    Science.gov (United States)

    Berestovsky, G N; Ternovsky, V I; Kataev, A A

    2001-06-01

    Determination of pore size of the cell wall of Chara corallina has been made by using the polyethylene glycol (PEG) series as the hydrophilic probing molecules. In these experiments, the polydispersity of commercial preparation of PEGs was allowed for. The mass share (gamma(p)) of polyethylene glycol preparation fractions penetrating through the pores was determined using a cellular 'ghost', i.e. fragments of internodal cell walls filled with a 25% solution of non-penetrating PEG 6000 and tied up at the ends. In water, such a 'ghost' developed a hydrostatic pressure close to the cell turgor which persisted for several days. The determination of gamma(p), for polydisperse polyethylene glycols with different average molecular mass (M) was calculated from the degree of pressure restoration after water was replaced by a 5-10% polymer solution. Pressure was recorded using a dynamometer, which measures, in the quasi-isometric mode, the force necessary for the partial compression of the 'ghost' in its small fragment. By utilizing the data on the distribution of PEG 1000, 1450, 2000, and 3350 fractions over molecular mass (M), it was found that gamma(p), for these polyethylene glycols corresponded to the upper limit of ML=800-1100 D (hydrodynamic radius of molecules, r(h)=0.85-1.05 nm). Thus, the effective diameter of the pores in the cell wall of Chara did not exceed 2.1 nm.

  5. Integrated pore blockage-cake filtration model for crossflow filtration

    International Nuclear Information System (INIS)

    Daniel, Richard C.; Billing, Justin M.; Russell, Renee L.; Shimskey, Rick W.; Smith, Harry D.; Peterson, Reid A.

    2011-01-01

    Crossflow filtration is to be a key process in the treatment and disposal of approximately 60,000 metric tons of high-level radioactive waste stored at the Hanford Site in Richland, Washington. Pacific Northwest National Laboratory is assessing filter performance with waste simulant materials that mimic the chemical and physical properties of Hanford tank waste. Prior simulant studies indicated that waste filtration performance may be limited by pore and cake fouling. To limit the shutdown of waste treatment operations, the pre-treatment facility plans to recover filter flux losses from cake formation and filter fouling by frequently backpulsing the filter elements. The objective of the current paper is to develop a simple model of flux decline resulting from cake and pore fouling and potential flux recovery through backpulsing of the filters for Hanford waste filtration operations. To this end, a model capable of characterizing the decline in waste-simulant filter flux as a function of both irreversible pore blockage and reversible cake formation is proposed. This model is used to characterize the filtration behavior of Hanford waste simulants in both continuous and backpulsed operations. The model is then used to infer the optimal backpulse frequency under specific operating conditions.

  6. A user-friendly modified pore-solid fractal model.

    Science.gov (United States)

    Ding, Dian-Yuan; Zhao, Ying; Feng, Hao; Si, Bing-Cheng; Hill, Robert Lee

    2016-12-20

    The primary objective of this study was to evaluate a range of calculation points on water retention curves (WRC) instead of the singularity point at air-entry suction in the pore-solid fractal (PSF) model, which additionally considered the hysteresis effect based on the PSF theory. The modified pore-solid fractal (M-PSF) model was tested using 26 soil samples from Yangling on the Loess Plateau in China and 54 soil samples from the Unsaturated Soil Hydraulic Database. The derivation results showed that the M-PSF model is user-friendly and flexible for a wide range of calculation point options. This model theoretically describes the primary differences between the soil moisture desorption and the adsorption processes by the fractal dimensions. The M-PSF model demonstrated good performance particularly at the calculation points corresponding to the suctions from 100 cm to 1000 cm. Furthermore, the M-PSF model, used the fractal dimension of the particle size distribution, exhibited an accepted performance of WRC predictions for different textured soils when the suction values were ≥100 cm. To fully understand the function of hysteresis in the PSF theory, the role of allowable and accessible pores must be examined.

  7. Influence of pore pressure change on coseismic volumetric strain

    Science.gov (United States)

    Wang, C. Y.; Barbour, A. J.

    2017-12-01

    Coseismic strain is fundamentally important for understanding crustal response to transient changes of stress. The elastic dislocation model has been widely applied to interpreting observed shear deformation caused by earthquakes. The application of this model to interpreting volumetric strain, however, has met with difficulty, especially in the far field of earthquakes. Predicted volumetric strain with dislocation model often differs substantially, and sometimes of opposite signs, from observed coseismic volumetric strains. The disagreement suggests that some processes unaccounted for by the dislocation model may occur during earthquakes. Several hypotheses have been suggested, but none have been tested quantitatively. In this study we first assemble published data to highlight the significant difference between the measured and predicted coseismic volumetric strains from the dislocation theory. We then show that the disagreement may largely be explained by coseismic change of pore pressure in the shallow crust. We provide a quantitative test of the model with the assembled data, which allows us to conclude that coseismic change of pore pressure may be an important mechanism for coseismic crustal strain and, in the far field, may even be the controlling mechanism. Thus in the interpretation of observed coseismic crustal strain, one needs to account not only for the elastic strain due to fault rupture but also for the strain due to coseismic change of pore pressure.

  8. Effects of pore design on mechanical properties of nanoporous silicon

    International Nuclear Information System (INIS)

    Winter, Nicholas; Becton, Matthew; Zhang, Liuyang; Wang, Xianqiao

    2017-01-01

    Nanoporous silicon has been emerging as a powerful building block for next-generation sensors, catalysts, transistors, and tissue scaffolds. The capability to design novel devices with desired mechanical properties is paramount to their reliability and serviceability. In order to bring further resolution to the highly variable mechanical characteristics of nanoporous silicon, here we perform molecular dynamics simulations to study the effects of ligament thickness, relative density, and pore geometry/orientation on the mechanical properties of nanoporous silicon, thereby determining its Young's modulus, ultimate strength, and toughness as well as the scaling laws versus the features of interior ligaments. Results show that pore shape and pattern dictate stress accumulation inside the designed structure, leading to the corresponding failure signature, such as stretching-dominated, bending-dominated, or stochastic failure signatures, in nanoporous silicon. The nanostructure of the material is also seen to drive or mute size effects such as “smaller is stronger” and “smaller is ductile”. This investigation provides useful insight into the behavior of nanoporous silicon and how one might leverage its promising applications. - Graphical abstract: Molecular dynamics simulations are performed to study the effects of ligament thickness, relative density, and pore geometry/orientation on the mechanical properties of nanoporous silicon, thereby determining its Young's modulus, ultimate strength, and toughness as well as the scaling trends versus the features of interior ligaments.

  9. Influence factors on etching rate of PET nuclear pore membrane

    International Nuclear Information System (INIS)

    Zuo Zhenzhong; Wu Zhendong; Liang Haiying; Ju Wei; Chen Dongfeng; Fu Yuanyong; Qu Guopu

    2014-01-01

    Background: The nuclear pore membrane is a kind of liquid filtration material manufactured by irradiation and chemical etching. Various conditions in etch process have a great influence on etch rate. Purpose: The influence factors of concentration and temperature of etch solution and the irradiation energy of heavy ions on etch rate was studied. Methods: Four layers of PET (polyethylene terephthalate) films were stacked together and were irradiated with 140-MeV 32 S ions at room temperature under vacuum conditions. Utilizing conductivity measurement technique, the electrical current changes through the u:radiated PET film were monitored during etching, from which the breakthrough time and therefore the track etching rate was calculated. Results: The results show that there is an exponential correlation between etch rate and temperature, and a linear correlation between etch rate and concentration. The track etching rate increases linearly with energy loss rate. Empirical formula for the bulk etching rate as a function of etchant concentration and temperature was also established via fitting of measurements. Conclusion: It is concluded that by using 1.6-MeV·u -1 32 S ions, PET nuclear pore membrane with cylindrical pore shape can be prepared at 85℃ with etchant concentration of l mol·L -1 . (authors)

  10. Scale and distribution of marine carbonate burial dissolution pores

    Directory of Open Access Journals (Sweden)

    Anjiang Shen

    2016-06-01

    Full Text Available It is gradually accepted that porosity can be created in burial settings via dissolution by organic acid; TSR derived or hydrothermal fluids. The role of deep-buried carbonate reservoirs is becoming more and more important since the degree and difficulty in petroleum exploration of shallow strata are increasing. A profound understanding of the development scale and prediction of the deep-buried carbonate reservoirs is economically crucial. In addition to the formation mechanism, scale and distribution of burial dissolution pores in burial settings are focused on in recent studies. This paper is based on case studies of deep-buried (>4500 m carbonate reservoirs from the Tarim Basin and Sichuan Basin. Case studies mentioned includes dissolution simulation experiments proposes that an open system is of crucial importance in the development of large-scale burial dissolution pores, the distribution pattern of which is controlled by lithology, pre-existing porosity, and pore throat structures. These findings provided the basis for evaluation and prediction of deep-buried carbonate reservoirs.

  11. Structure of Staphylococcal α-Hemolysin, a Heptameric Transmembrane Pore

    Science.gov (United States)

    Song, Langzhou; Hobaugh, Michael R.; Shustak, Christopher; Cheley, Stephen; Bayley, Hagan; Gouaux, J. Eric

    1996-12-01

    The structure of the Staphylococcus aureus α-hemolysin pore has been determined to 1.9 overset{circ}{mathrm A} resolution. Contained within the mushroom-shaped homo-oligomeric heptamer is a solvent-filled channel, 100 overset{circ}{mathrm A} in length, that runs along the sevenfold axis and ranges from 14 overset{circ}{mathrm A} to 46 overset{circ}{mathrm A} in diameter. The lytic, transmembrane domain comprises the lower half of a 14-strand antiparallel β barrel, to which each protomer contributes two β strands, each 65 overset{circ}{mathrm A} long. The interior of the β barrel is primarily hydrophilic, and the exterior has a hydrophobic belt 28 overset{circ}{mathrm A} wide. The structure proves the heptameric subunit stoichiometry of the α-hemolysin oligomer, shows that a glycine-rich and solvent-exposed region of a water-soluble protein can self-assemble to form a transmembrane pore of defined structure, and provides insight into the principles of membrane interaction and transport activity of β barrel pore-forming toxins.

  12. Integration of pore features into the evaluation of fingerprint evidence.

    Science.gov (United States)

    Anthonioz, Alexandre; Champod, Christophe

    2014-01-01

    Fingerprint practitioners rely on level 3 features to make decisions in relation to the source of an unknown friction ridge skin impression. This research proposes to assess the strength of evidence associated with pores when shown in (dis)agreement between a mark and a reference print. Based upon an algorithm designed to automatically detect pores, a metric is defined in order to compare different impressions. From this metric, the weight of the findings is quantified using a likelihood ratio. The results obtained on four configurations and 54 donors show the significant contribution of the pore features and translate into statistical terms what latent fingerprint examiners have developed holistically through experience. The system provides LRs that are indicative of the true state under both the prosecution and the defense propositions. Not only such a system brings transparency regarding the weight to assign to such features, but also forces a discussion in relation to the risks of such a model to mislead. © 2013 American Academy of Forensic Sciences.

  13. In situ temperature tunable pores of shape memory polyurethane membranes

    International Nuclear Information System (INIS)

    Ahn, Joon-Sung; Yu, Woong-Ryeol; Youk, Ji Ho; Ryu, Hee Youk

    2011-01-01

    Conventional shape memory polymers, such as shape memory polyurethanes (SMPU), can exhibit net two-way shape memory behavior (2WSM), i.e., upon heating and subsequent cooling, their macroscopic shapes change reversibly under an applied bias load. This paper is aimed at reporting similar 2WSM behavior, especially by focusing on the size of nanopores/micropores in SMPU membranes, i.e., the size of the pores can be reversibly changed by up to about 300 nm upon repeated heating and cooling. The SMPU membranes were prepared by electrospinning and elongated at temperatures higher than the transition temperature of the SMPU. Under the constant stress, the size change of the pores in the membranes was measured by applying cyclic temperature change. It was observed that the pore size changed from 150 to 440 nm according to the temperature change, demonstrating that the SMPU membrane can be utilized as a smart membrane to selectively separate substances according to their sizes by just controlling temperature

  14. Influence of pore pressure change on coseismic volumetric strain

    Science.gov (United States)

    Wang, Chi-Yuen; Barbour, Andrew J.

    2017-01-01

    Coseismic strain is fundamentally important for understanding crustal response to changes of stress after earthquakes. The elastic dislocation model has been widely applied to interpreting observed shear deformation caused by earthquakes. The application of the same theory to interpreting volumetric strain, however, has met with difficulty, especially in the far field of earthquakes. Predicted volumetric strain with dislocation model often differs substantially, and sometimes of opposite signs, from observed coseismic volumetric strains. The disagreement suggests that some processes unaccounted for by the dislocation model may occur during earthquakes. Several hypotheses have been suggested, but none have been tested quantitatively. In this paper we first examine published data to highlight the difference between the measured and calculated static coseismic volumetric strains; we then use these data to provide quantitative test of the model that the disagreement may be explained by the change of pore pressure in the shallow crust. The test allows us to conclude that coseismic change of pore pressure may be an important mechanism for coseismic crustal strain and, in the far field, may even be the dominant mechanism. Thus in the interpretation of observed coseismic crustal strain, one needs to account not only for the elastic strain due to fault rupture but also for the strain due to coseismic change of pore pressure.

  15. Pore Topology Effects in Positron Annihilation Spectroscopy of Zeolites.

    Science.gov (United States)

    Zubiaga, Asier; Warringham, Robbie; Mitchell, Sharon; Gerchow, Lars; Cooke, David; Crivelli, Paolo; Pérez-Ramírez, Javier

    2017-03-03

    Positron annihilation spectroscopy (PAS) is a powerful method to study the size and connectivity of pores in zeolites. The lifetime of positronium within the host material is commonly described by the Tao-Eldrup model. However, one of its largest limitations arises from the simple geometries considered for the shape of the pores, which cannot describe accurately the complex topologies in zeolites. Here, an atomic model that combines the Tao potential with the crystallographic structure is introduced to calculate the distribution and lifetime of Ps intrinsic to a given framework. A parametrization of the model is undertaken for a set of widely applied zeolite framework types (*BEA, FAU, FER, MFI, MOR, UTL), before extending the model to all known structures. The results are compared to structural and topological descriptors, and to the Tao-Eldrup model adapted for zeolites, demonstrating the intricate dependence of the lifetime on the pore architecture. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. MD simulations of the central pore of ryanodine receptors and sequence comparison with 2B protein from coxsackie virus.

    Science.gov (United States)

    Schilling, Roman; Fink, Rainer H A; Fischer, Wolfgang B

    2014-04-01

    The regulation of intracellular Ca(2+) triggers a multitude of vital processes in biological cells. Ca(2+) permeable ryanodine receptors (RyRs) are the biggest known ion channels and play a key role in the regulation of intracellular calcium concentrations, particularly in muscle cells. In this study, we construct a computational model of the pore region of the skeletal RyR and perform molecular dynamics (MD) simulations. The dynamics and distribution of Ca(2+) around the luminal pore entry of the RyR suggest that Ca(2+) ions are channeled to the pore entry due to the arrangement of (acidic) amino acids at the extramembrane surface of the protein. This efficient mechanism of Ca(2+) supply is thought to be part of the mechanism of Ca(2+) conductance of RyRs. Viral myocarditis is predominantly caused by coxsackie viruses that induce the expression of the protein 2B which is known to affect intracellular Ca(2+) homeostasis in infected cells. From our sequence comparison, it is hypothesized, that modulation of RyR could be due to replacement of its transmembrane domains (TMDs) by those domains of the viral channel forming protein 2B of coxsackie virus. This article is part of a Special Issue entitled: Viral Membrane Proteins - Channels for Cellular Networking. Copyright © 2013 Elsevier B.V. All rights reserved.

  17. Pore characteristics of shale gas reservoirs from the Lower Paleozoic in the southern Sichuan Basin, China

    Directory of Open Access Journals (Sweden)

    Xianqing Li

    2016-06-01

    Full Text Available Data was acquired from both the drillings and core samples of the Lower Paleozoic Qiongzhusi and Longmaxi Formations' marine shale gas reservoirs in the southern Sichuan Basin by means of numerous specific experimental methods such as organic geochemistry, organic petrology, and pore analyses. Findings helped determine the characteristics of organic matter, total porosity, microscopic pore, and pore structure. The results show that the Lower Paleozoic marine shale in the south of the Sichuan Basin are characterized by high total organic carbon content (most TOC>2.0%, high thermal maturity level (RO = 2.3%–3.8%, and low total porosity (1.16%–6.87%. The total organic carbon content and thermal maturity level of the Qiongzhusi Formation shale are higher than those of the Longmaxi Formation shale, while the total porosity of the Qiongzhusi Formation shale is lower than that of the Longmaxi Formation shale. There exists intergranular pore, dissolved pore, crystal particle pore, particle edge pore, and organic matter pore in the Lower Paleozoic Qiongzhusi Formation and Longmaxi Formation shale. There are more micro-nano pores developed in the Longmaxi Formation shales than those in the Qiongzhusi Formation shales. Intergranular pores, dissolved pores, as well as organic matter pores, are the most abundant, these are primary storage spaces for shale gas. The microscopic pores in the Lower Paleozoic shales are mainly composed of micropores, mesopores, and a small amount of macropores. The micropore and mesopore in the Qiongzhusi Formation shale account for 83.92% of the total pore volume. The micropore and mesopore in the Longmaxi Formation shale accounts for 78.17% of the total pore volume. Thus, the micropores and mesopores are the chief components of microscopic pores in the Lower Paleozoic shale gas reservoirs in the southern Sichuan Basin.

  18. Three-dimensional pore structure and ion conductivity of porous ceramic diaphragms

    OpenAIRE

    Wiedenmann, Daniel; Keller, Lukas; Holzer, Lorenz; Stojadinović, Jelena; Münch, Beat; Suarez, Laura; Fumey, Benjamin; Hagendorfer, Harald; Brönnimann, Rolf; Modregger, Peter; Gorbar, Michal; Vogt, Ulrich F.; Züttel, Andreas; Mantia, Fabio La; Wepf, Roger

    2013-01-01

    The ion conductivity of two series of porous ceramic diaphragms impregnated with caustic potash was investigated by electrochemical impedance spectroscopy. To understand the impact of the pore structure on ion conductivity, the three-dimensional (3-D) pore geometry of the diaphragms was characterized with synchrotron x-ray absorption tomography. Ion migration was calculated based on an extended pore structure model, which includes the electrolyte conductivity and geometric pore parameters, fo...

  19. Pore water colloid properties in argillaceous sedimentary rocks

    Energy Technology Data Exchange (ETDEWEB)

    Degueldre, Claude, E-mail: c.degueldre@lancaster.ac.uk [Engineering Department, University of Lancaster, LA1 4YW Lancaster (United Kingdom); ChiAM & Institute of Environment, University of Geneva, 1211 Genève 4, Swizerland (Switzerland); Earlier, NES, Paul Scherrer Institute, 5232 Villigen (Switzerland); Cloet, Veerle [NAGRA, Hardstrasse 73, 5430 Wettingen (Switzerland)

    2016-11-01

    The focus of this work is to evaluate the colloid nature, concentration and size distribution in the pore water of Opalinus Clay and other sedimentary host rocks identified for a potential radioactive waste repository in Switzerland. Because colloids could not be measured in representative undisturbed porewater of these host rocks, predictive modelling based on data from field and laboratory studies is applied. This approach allowed estimating the nature, concentration and size distributions of the colloids in the pore water of these host rocks. As a result of field campaigns, groundwater colloid concentrations are investigated on the basis of their size distribution quantified experimentally using single particle counting techniques. The colloid properties are estimated considering data gained from analogue hydrogeochemical systems ranging from mylonite features in crystalline fissures to sedimentary formations. The colloid concentrations were analysed as a function of the alkaline and alkaline earth element concentrations. Laboratory batch results on clay colloid generation from compacted pellets in quasi-stagnant water are also reported. Experiments with colloids in batch containers indicate that the size distribution of a colloidal suspension evolves toward a common particle size distribution independently of initial conditions. The final suspension size distribution was found to be a function of the attachment factor of the colloids. Finally, calculations were performed using a novel colloid distribution model based on colloid generation, aggregation and sedimentation rates to predict under in-situ conditions what makes colloid concentrations and size distributions batch- or fracture-size dependent. The data presented so far are compared with the field and laboratory data. The colloid occurrence, stability and mobility have been evaluated for the water of the considered potential host rocks. In the pore water of the considered sedimentary host rocks, the clay

  20. Sebum output as a factor contributing to the size of facial pores.

    Science.gov (United States)

    Roh, M; Han, M; Kim, D; Chung, K

    2006-11-01

    Many endogenous and exogenous factors are known to cause enlarged pilosebaceous pores. Such factors include sex, genetic predisposition, ageing, chronic ultraviolet light exposure, comedogenic xenobiotics, acne and seborrhoea. This study was an attempt to determine the factors related to enlarged pores. To assess the relationship of sebum output, age, sex, hormonal factors and severity of acne with pore size. A prospective, randomized, controlled study was designed. A total of 60 volunteers, 30 males and 30 females, were recruited for this study. Magnified images of pores were taken using a dermoscopic video camera and measured using an image analysis program. The sebum output level was measured with a Sebumeter. Using multiple linear regression analysis, increased pore size was significantly associated with increased sebum output level, sex and age. Among the variables, sebum output level correlated most with the pore size followed by male sex. In comparing male and female participants, males had higher correlation between the sebum output level and the pore size (male: r = 0.47, female: r = 0.38). Thus, additional factors seem to influence pore size in females. Pore size was significantly increased during the ovulation phase (P = 0.008), but severity of acne was not significantly associated with the pore size. Enlarged pore sizes are associated with increased sebum output level, age and male sex. In female patients, additional hormonal factors, such as those of the menstrual cycle, affect the pore size.

  1. Sebum, acne, skin elasticity, and gender difference - which is the major influencing factor for facial pores?

    Science.gov (United States)

    Kim, B Y; Choi, J W; Park, K C; Youn, S W

    2013-02-01

    Enlarged facial pores have been esthetic problems and have become a matter of cosmetic concern. Several factors are supposed to be related to the enlargement of facial pores, although scientific evaluations were not performed yet. To assess the correlation between facial pores and possible relating factors such as age, gender, sebum secretion, skin elasticity, and the presence of acne, using objective bioengineering instruments. Sixty volunteers, 30 males and 30 females, participated in this study. Various parameters of facial pores were assessed using the Robo Skin Analyzer. The facial sebum secretion and skin elasticity were measured using the Sebumeter and the Cutometer, respectively. These data were compared and correlated to examine the possible relationship between facial pores and age, sebum secretion and skin elasticity, according to gender and the presence of acne. Male gender and the existence of acne were correlated with higher number of facial pores. Sebum secretion levels showed positive correlation with facial pores. The R7 parameter of skin elasticity was negatively correlated with facial pores, suggesting increased facial pores with decreased skin elasticity. However, the age and the severity of acne did not show a definite relationship with facial pores. Male, increased sebum and decreased skin elasticity were mostly correlated with facial pore development. Further studies on population with various demographic profiles and more severe acne may be helpful to elucidate the potential effect of aging and acne severity on facial pores. © 2011 John Wiley & Sons A/S.

  2. Weakly nonlinear thermoacoustics for stacks with slowly varying pore cross-sections

    NARCIS (Netherlands)

    Panhuis, in 't P.H.M.W.; Rienstra, S.W.; Molenaar, J.; Slot, J.J.M.

    2009-01-01

    A general theory of thermoacoustics is derived for arbitrary stack pores. Previous theoretical treatments of porous media are extended by considering arbitrarily shaped pores with the only restriction that the pore cross-sections vary slowly in the longitudinal direction. No boundary-layer

  3. Effect of pore formers on properties of tape cast porous sheets for electrochemical flue gas purification

    DEFF Research Database (Denmark)

    Schmidt, Cristine Grings; Kammer Hansen, Kent; Andersen, Kjeld Bøhm

    2016-01-01

    permeability measurements, mercury porosimetry and pore orientation measurements, to investigate the role of the different pore formers on the properties after sintering at a temperature of 1250°C. Those tapes prepared from different non-spherical pore formers with comparable porosity of about 43%, showed...

  4. Effect of pore fluid on the cyclic behavior of laterally loaded offshore piles modelled in centrifuge

    NARCIS (Netherlands)

    Askarinejad, A.; Philia Boru Sitanggang, Anggi; Schenkeveld, Ferry; Lee, W.; Lee, J-S.; Kim, H-K.; kim, D-S.

    The common practice in centrifuge modelling of dynamic processes is to use high-viscosity pore fluids to unify the time scaling factors for the generation and dissipation of pore pressures. This paper focuses on the effects of the density and viscosity of the pore fluid on the behaviour of an

  5. The impact of calcium carbonate as pore forming agent and drug entrapment method towards drug dissolution mechanism of amoxicillin trihydrate encapsulated by chitosan-methyl cellulose semi-IPN hydrogel for floating drug delivery system

    Science.gov (United States)

    Dewantara, Fauzi; Budianto, Emil

    2018-04-01

    Chitosan-methyl cellulose semi-IPN hydrogel is used as floating drug delivery system, and calcium carbonate also added as pore forming agent. The hydrogel network arranged by not only using biopolymer chitosan and methyl cellulose, but also the crosslink agent that is glutaraldehyde. Amoxicillin trihydrate entrapped into the polymer network with two different method, in situ loading and post loading. Furthermore both method has been tested for drug entrapment efficiency along with drug dissolution test, and the result for drug entrapment efficiency is in situ loading method has highest value of 100%, compared to post loading method which has value only 71%. Moreover, at the final time of drug dissolution test shows in situ loading method has value of 96% for total accumulative of drug dissolution, meanwhile post loading method has 72%. The value of drug dissolution test from both method is used for analyzing drug dissolution mechanism of amoxicillin trihydrate from hydrogel network with four mathematical drug mechanism models as parameter. The polymer network encounter destructive degradation causes by acid solution which used as dissolution medium, and the level of degradation is observed with optical microscope. However the result shows that degradation of the polymer network doesn't affect drug dissolution mechanism directly. Although the pore forming agent causes the pore inside the hydrogel network create interconnection and it was quite influential to drug dissolution mechanism. Interconnected pore is observed with Scanning Electron Microscope (SEM) and shows that the amount and area of interconnected pore inside the hydrogel network is increasing as drug dissolution goes on.

  6. In situ synthesis of Eu(Tp){sub 3} complex inside the pores of mesoporous silica nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Malba, Chandrashekhar; Bellotto, Luca; Freris, Isidora [Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca' Foscari di Venezia, via Torino 155/b, 30170 Venezia-Mestre (Italy); Enrichi, Francesco [CIVEN, Coordinamento Interuniversitario Veneto per le Nanotecnologie, Via delle Industrie 5, 30175 Marghera (Venezia) (Italy); Cristofori, Davide [Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca' Foscari di Venezia, via Torino 155/b, 30170 Venezia-Mestre (Italy); Riello, Pietro, E-mail: riellop@unive.it [Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca' Foscari di Venezia, via Torino 155/b, 30170 Venezia-Mestre (Italy); Benedetti, Alvise [Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca' Foscari di Venezia, via Torino 155/b, 30170 Venezia-Mestre (Italy)

    2013-10-15

    A route for europium (III) tris-pyrazolyl borate complex [Eu(Tp){sub 3}] formation inside the pores of mesoporous silica nanoparticles (MSNs) has been established to yield a highly luminescent nanostructured hybrid. Two different in situ chemical precipitation techniques have been explored for the nanoencapsulation of the Eu{sup 3+} complex [Eu(Tp){sub 3}] inside the pore channels of mesoporous silica nanoparticles, by varying the sequence order of precursor impregnation. In the first method, the Eu salt is introduced into the pores by wet impregnation and removal of the solvent, followed by wet impregnation of the ligand. In the second approach, the addition sequence is reversed. The importance of the addition sequence was demonstrated by the successful formation of the europium (III) tris-pyrazolyl borate complex in the pore network by following the first approach. The observed pyrazol-1-yl borate (Tp) to Eu{sup 3+} intramolecular energy transfer, i.e., the antenna effect, verified the formation of the complex. Photoluminescence spectroscopy, X-ray diffraction, N{sub 2} adsorption, FTIR spectroscopy, and TEM were used to characterize the material. -- Highlights: • In situ formation of Eu(Tp){sub 3} in mesoporous silica nanoparticles is studied. • Pivotal role of the addition sequence of the reagents is demonstrated. • Eu salt adsorption preceded the addition of the ligand proved effective (route A). • Luminescent material is well characterized by several techniques. • We give a possible mechanism for the formation of Eu(Tp){sub 3} complex via route A.

  7. Development of gelatin-chitosan-hydroxyapatite based bioactive bone scaffold with controlled pore size and mechanical strength.

    Science.gov (United States)

    Maji, Kanchan; Dasgupta, Sudip; Kundu, Biswanath; Bissoyi, Akalabya

    2015-01-01

    Hydroxyapatite-chitosan/gelatin (HA:Chi:Gel) nanocomposite scaffold has potential to serve as a template matrix to regenerate extra cellular matrix of human bone. Scaffolds with varying composition of hydroxyapatite, chitosan, and gelatin were prepared using lyophilization technique where glutaraldehyde (GTA) acted as a cross-linking agent for biopolymers. First, phase pure hydroxyapatite-chitosan nanocrystals were in situ synthesized by coprecipitation method using a solution of 2% acetic acid dissolved chitosan and aqueous solution of calcium nitrate tetrahydrate [Ca(NO3)2,4H2O] and diammonium hydrogen phosphate [(NH4)2H PO4]. Keeping solid loading constant at 30 wt% and changing the composition of the original slurry of gelatin, HA-chitosan allowed control of the pore size, its distribution, and mechanical properties of the scaffolds. Microstructural investigation by scanning electron microscopy revealed the formation of a well interconnected porous scaffold with a pore size in the range of 35-150 μm. The HA granules were uniformly dispersed in the gelatin-chitosan network. An optimal composition in terms of pore size and mechanical properties was obtained from the scaffold with an HA:Chi:Gel ratio of 21:49:30. The composite scaffold having 70% porosity with pore size distribution of 35-150 μm exhibited a compressive strength of 3.3-3.5 MPa, which is within the range of that exhibited by cancellous bone. The bioactivity of the scaffold was evaluated after conducting mesenchymal stem cell (MSC) - materials interaction and MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) assay using MSCs. The scaffold found to be conducive to MSC's adhesion as evident from lamellipodia, filopodia extensions from cell cytoskeleton, proliferation, and differentiation up to 14 days of cell culture.

  8. Droplet networks with incorporated protein diodes show collective properties

    Science.gov (United States)

    Maglia, Giovanni; Heron, Andrew J.; Hwang, William L.; Holden, Matthew A.; Mikhailova, Ellina; Li, Qiuhong; Cheley, Stephen; Bayley, Hagan

    2009-07-01

    Recently, we demonstrated that submicrolitre aqueous droplets submerged in an apolar liquid containing lipid can be tightly connected by means of lipid bilayers to form networks. Droplet interface bilayers have been used for rapid screening of membrane proteins and to form asymmetric bilayers with which to examine the fundamental properties of channels and pores. Networks, meanwhile, have been used to form microscale batteries and to detect light. Here, we develop an engineered protein pore with diode-like properties that can be incorporated into droplet interface bilayers in droplet networks to form devices with electrical properties including those of a current limiter, a half-wave rectifier and a full-wave rectifier. The droplet approach, which uses unsophisticated components (oil, lipid, salt water and a simple pore), can therefore be used to create multidroplet networks with collective properties that cannot be produced by droplet pairs.

  9. Involvement of IGF-1/IGFBP-3 signaling on the conspicuousness of facial pores.

    Science.gov (United States)

    Sugiyama-Nakagiri, Yoriko; Ohuchi, Atsushi; Hachiya, Akira; Kitahara, Takashi

    2010-11-01

    Conspicuous facial pores are one type of serious esthetic defects for many women. We previously reported that the severity of impairment of skin architecture around facial pores correlates well with the appearance of facial pores in several ethnic groups. In our last report, we showed that serum levels of insulin-like growth factor-1 (IGF-1) correlate well with facial pore size and with the severity of impairment of epidermal architecture around facial pores. However, our results could not fully explain the implication between facial pores and IGF signaling. In this study, we conducted a histological analysis of facial skin to determine whether potential changes in IGF-1 availability occur in the skin with or without conspicuous pores. Immunohistochemical observations showed that expression of insulin-like growth factor binding protein-3 (IGFBP-3) is limited to the suprapapillary epidermis around facial pores and to basal cells of rete pegs without tips in epidermis with conspicuous pores. In contrast, in basal cells of skin without conspicuous pores, IGFBP-3 expression is very low. Ki-67 and IGF-1 receptor-positive cells are abundant in basal cells in the tips of the rete pegs in skin with typical epidermal architecture around facial pores. No obvious differences were observed in the expression of filaggrin, involucrin, K1, K6 or K17 in skin with or without conspicuous pores. However, increased expression of K16 was observed in skin with conspicuous pores suggesting hyperproliferation. These results suggest that the IGF-1/IGFBP-3 signaling pathway is involved in the formation of conspicuous facial pores due to the epidermal architecture around facial pores.

  10. Generalized network modeling of capillary-dominated two-phase flow.

    Science.gov (United States)

    Raeini, Ali Q; Bijeljic, Branko; Blunt, Martin J

    2018-02-01

    We present a generalized network model for simulating capillary-dominated two-phase flow through porous media at the pore scale. Three-dimensional images of the pore space are discretized using a generalized network-described in a companion paper [A. Q. Raeini, B. Bijeljic, and M. J. Blunt, Phys. Rev. E 96, 013312 (2017)2470-004510.1103/PhysRevE.96.013312]-which comprises pores that are divided into smaller elements called half-throats and subsequently into corners. Half-throats define the connectivity of the network at the coarsest level, connecting each pore to half-throats of its neighboring pores from their narrower ends, while corners define the connectivity of pore crevices. The corners are discretized at different levels for accurate calculation of entry pressures, fluid volumes, and flow conductivities that are obtained using direct simulation of flow on the underlying image. This paper discusses the two-phase flow model that is used to compute the averaged flow properties of the generalized network, including relative permeability and capillary pressure. We validate the model using direct finite-volume two-phase flow simulations on synthetic geometries, and then present a comparison of the model predictions with a conventional pore-network model and experimental measurements of relative permeability in the literature.

  11. Diode-like properties of single- and multi-pore asymmetric track membranes

    Science.gov (United States)

    Zielinska, K.; Gapeeva, A. R.; Orelovich, O. L.; Apel, P. Yu.

    2014-05-01

    In this work, we investigated the ionic transport properties of asymmetric polyethylene terephthalate (PET) track membranes with the thickness of 5 μm. The samples containing single pores and arrays of many pores were fabricated by irradiation with accelerated ions and subsequent physicochemical treatment. The method of etching in the presence of a surface-active agent was used to prepare the pores with highly-tapered tip. The transport of monovalent inorganic ions through the nano-scale holes was studied in a conductivity cell. The effective pore radii, electrical conductance and rectification ratios of pores were measured. The geometric characteristics of nanopores were investigated using FESEM.

  12. Conical tungsten stamps for the replication of pore arrays in anodic aluminium oxide films

    Science.gov (United States)

    LeClere, D. J.; Thompson, G. E.; Derby, B.

    2009-06-01

    A tungsten master stamp has been generated by applying a novel procedure that includes two-step anodizing, followed by sequential anodizing and pore widening to develop nominally funnelled pores. These conical-shaped pores were filled with tungsten by sputter coating to manufacture a master stamp. Under a pressure of 65 MPa, the master stamp successfully embossed the surface of annealed and electropolished aluminium. The embossed surface was then used to control the position of pores created by anodizing under the conditions used to produce the original pore array.

  13. Pore-forming proteins with built-in triggers and switches

    Science.gov (United States)

    Bayley, Hagan

    1996-02-01

    Genetic engineering and targeted chemical modification are being used to produce polypeptides with pore-forming activity that can be triggered or switched on-and-off by biochemical, chemical or physical stimuli. The principal target of our studies has been the (alpha) -hemolysin ((alpha) HL) from the bacterium Staphylococcus aureus. The remodeled hemolysins include protease-activated pores, metal-regulated pores, pores that are activated by chemical alkylation and pores that are turned on with light. These polypeptides have several potential applications. For example, they might serve as components of sensors or they might be useful for mediating the controlled release of encapsulated drugs.

  14. Experimental Study and Numerical Modeling of Wave Induced Pore Pressure Attenuation Inside a Rubble Mound Breakwater

    DEFF Research Database (Denmark)

    Troch, Peter; Rouck, Julien De; Burcharth, Hans Falk

    2003-01-01

    The main objective of this paper is to study the attenuation of the wave induced pore pressures inside the core of a rubble mound breakwater. The knowledge of the distribution and the attenuation of the pore pressures is important for the design of a stable and safe breakwater. The pore pressure...... and have been re-analysed in detail with respect to the attenuation characteristics. The analysis follows the method by Burcharth et al. (1999) and confirms the practical calculation method for the attenuation of the pore pressure in the core given in this reference. The attenuation of pore pressures...

  15. A method of evaluating facial pores using optical 2D images and analysis of age-dependent changes in facial pores in Koreans.

    Science.gov (United States)

    Jang, S I; Kim, E J; Lee, H K

    2018-05-01

    Enlarged facial pores and changes in pore area are of concern for cosmetic reasons. To evaluate pores, measuring tools based on 3D methodology are used. Yet, these methods are limited by their measuring ranges. In this study, we performed pore analysis by measuring the whole face using 2D optical images. We further sought to understand how the pores of Korean women change with age. One hundred sixteen Korean female subjects aged 20-60 years were recruited for this study. Facial images were taken using the VISIA-CR ® adjusted light source. Images were processed using Image-Pro Plus 9.2. Statistical significance was assumed when P pore area, as indicated by pixel count, gradually increased in patients through their 40s, but decreased through their 50s and 60s. Facial pores generally exhibited directionality through the patients' 30s, but this isotropic feature was more prominent in their 50s. Pore elongation increased stepwise. The first increase occurred during the transition from patients' 30s to their 40s and the second increase occurred during the transition from patients' 50s to their 60s. This indicated that the pores deformed from a circular shape to a long elliptic shape over time. A new evaluation method using 2D optical images facilitates the analysis of pore distribution and elongation throughout the entire cheek. This is an improvement over an analysis of pores over a narrow region of interest. © 2018 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  16. Nucleoporin's Like Charge Regions Are Major Regulators of FG Coverage and Dynamics Inside the Nuclear Pore Complex.

    Science.gov (United States)

    Peyro, Mohaddeseh; Soheilypour, Mohammad; Ghavami, Ali; Mofrad, Mohammad R K

    2015-01-01

    Nucleocytoplasmic transport has been the subject of a large body of research in the past few decades. Recently, the focus of investigations in this field has shifted from studies of the overall function of the nuclear pore complex (NPC) to the examination of the role of different domains of phenylalanine-glycine nucleoporin (FG Nup) sequences on the NPC function. In our recent bioinformatics study, we showed that FG Nups have some evolutionarily conserved sequence-based features that might govern their physical behavior inside the NPC. We proposed the 'like charge regions' (LCRs), sequences of charged residues with only one type of charge, as one of the features that play a significant role in the formation of FG network inside the central channel. In this study, we further explore the role of LCRs in the distribution of FG Nups, using a recently developed coarse-grained molecular dynamics model. Our results demonstrate how LCRs affect the formation of two transport pathways. While some FG Nups locate their FG network at the center of the NPC forming a homogeneous meshwork of FG repeats, other FG Nups cover the space adjacent to the NPC wall. LCRs in the former group, i.e. FG Nups that form an FG domain at the center, tend to regulate the size of the highly dense, doughnut-shaped FG meshwork and leave a small low FG density area at the center of the pore for passive diffusion. On the other hand, LCRs in the latter group of FG Nups enable them to maximize their interactions and cover a larger space inside the NPC to increase its capability to transport numerous cargos at the same time. Finally, a new viewpoint is proposed that reconciles different models for the nuclear pore selective barrier function.

  17. Nucleoporin's Like Charge Regions Are Major Regulators of FG Coverage and Dynamics Inside the Nuclear Pore Complex.

    Directory of Open Access Journals (Sweden)

    Mohaddeseh Peyro

    Full Text Available Nucleocytoplasmic transport has been the subject of a large body of research in the past few decades. Recently, the focus of investigations in this field has shifted from studies of the overall function of the nuclear pore complex (NPC to the examination of the role of different domains of phenylalanine-glycine nucleoporin (FG Nup sequences on the NPC function. In our recent bioinformatics study, we showed that FG Nups have some evolutionarily conserved sequence-based features that might govern their physical behavior inside the NPC. We proposed the 'like charge regions' (LCRs, sequences of charged residues with only one type of charge, as one of the features that play a significant role in the formation of FG network inside the central channel. In this study, we further explore the role of LCRs in the distribution of FG Nups, using a recently developed coarse-grained molecular dynamics model. Our results demonstrate how LCRs affect the formation of two transport pathways. While some FG Nups locate their FG network at the center of the NPC forming a homogeneous meshwork of FG repeats, other FG Nups cover the space adjacent to the NPC wall. LCRs in the former group, i.e. FG Nups that form an FG domain at the center, tend to regulate the size of the highly dense, doughnut-shaped FG meshwork and leave a small low FG density area at the center of the pore for passive diffusion. On the other hand, LCRs in the latter group of FG Nups enable them to maximize their interactions and cover a larger space inside the NPC to increase its capability to transport numerous cargos at the same time. Finally, a new viewpoint is proposed that reconciles different models for the nuclear pore selective barrier function.

  18. Measuring Coupled Rock/Pore-Fluid Interaction in Volcanic Rock under Simulated Volcano- Tectonic Conditions

    Science.gov (United States)

    Benson, P. M.; Vinciguerra, S.; Meredith, P. G.; Young, R. P.

    2009-05-01

    We report a suite of laboratory experiments in which basalt from mount Etna volcano is deformed and fractured using a triaxial deformation apparatus. Experiments were monitored using an array of piezoelectric transducers around the sample to permit full-waveform capture, microseismic (AE) location and analysis. A small conduit of 3.125 mm diameter was drilled axially to allow access of the pore water directly to and from the shear/damage zone. Location of AE events through time shows the formation of a classical ~30 degree fault plane and waveforms exhibit the typical high frequency characteristics of volcano-tectonic (VT) earthquakes when experiments are conducted in dry samples. With water saturated samples, both VT events and some Hybrid events are observed (exhibiting a high frequency initial onset with lower frequency coda). A subsequent rapid decompression of the water-filled pore volume and damage zone triggered swarms of Low Frequency events, analogous to Volcanic Long Period seismicity. Analysis of the frequency component show characteristic low-frequencies (~90 kHz) associated with pore fluid decompression; first motion analysis reveals these events to exhibit a low percent component of shear (double-couple) slip, consistent with recent field data. By repeating these experiments at elevated temperatures (up to 175C), we additionally observe more complex, coupled hydro-mechanical behaviour and long-lasting seismic events analogous to volcanic tremor. Quasi-continuous waveforms are observed during the water steam phase change at approximately 0.8 MPa, as fluid/gas is vented through the damage zone to atmosphere. Frequencies during this stage of the experiment are lower still, at approximately 25 kHz. Using a simple size-frequency scaling relation, our laboratory-measured frequencies and crack dimensions can be shown to scale well to observations of sources of the order of hundred of metres to kilometers, typical of those in volcanic edifices. Our data

  19. Open pore biodegradable matrices formed with gas foaming.

    Science.gov (United States)

    Harris, L D; Kim, B S; Mooney, D J

    1998-12-05

    Engineering tissues utilizing biodegradable polymer matrices is a promising approach to the treatment of a number of diseases. However, processing techniques utilized to fabricate these matrices typically involve organic solvents and/or high temperatures. Here we describe a process for fabricating matrices without the use of organic solvents and/or elevated temperatures. Disks comprised of polymer [e.g., poly (D,L-lactic-co-glycolic acid)] and NaCl particles were compression molded at room temperature and subsequently allowed to equilibrate with high pressure CO2 gas (800 psi). Creation of a thermodynamic instability led to the nucleation and growth of gas pores in the polymer particles, resulting in the expansion of the polymer particles. The polymer particles fused to form a continuous matrix with entrapped salt particles. The NaCl particles subsequently were leached to yield macropores within the polymer matrix. The overall porosity and level of pore connectivity were regulated by the ratio of polymer/salt particles and the size of salt particles. Both the compressive modulus (159+/-130 kPa versus 289+/-25 kPa) and the tensile modulus (334+/-52 kPa versus 1100+/-236 kPa) of the matrices formed with this approach were significantly greater than those formed with a standard solvent casting/particulate leaching process. The utility of these matrices was demonstrated by engineering smooth muscle tissue in vitro with them. This novel process, a combination of high pressure gas foaming and particulate leaching techniques, allows one to fabricate matrices with a well controlled porosity and pore structure. This process avoids the potential negatives associated with the use of high temperatures and/or organic solvents in biomaterials processing.

  20. Arsenic readily released to pore waters from buried mill tailings

    International Nuclear Information System (INIS)

    Mahoney, John; Langmuir, Donald; Gosselin, Neil; Rowson, John

    2005-01-01

    At the McClean Lake Operation in the Athabasca Basin of northern Saskatchewan, the untreated acid raffinate solutions associated with U mill tailings contain up to 700 mg/L dissolved As. To reduce the concentration of As and other contaminants in acid tailing slurries at the JEB mill at McClean Lake, ferric sulfate may be added to the acid raffinates to assure that their molar Fe/As ratio equals or exceeds 3. Tailings slurries are then neutralized with lime to pH 4, and subsequently to pH 7-8. The neutralized tailings contain minerals from the original ore, which are chiefly quartz, illite, kaolinite and chlorite, and precipitated (secondary) minerals that include gypsum, scorodite, annabergite, hydrobasaluminite and ferrihydrite. Most of the As is associated with the secondary arsenate minerals, scorodite and annabergite. However, a few percent is adsorbed and/or co-precipitated, mainly by ferrihydrite. Of major concern to provincial and federal regulators is the risk that significant amounts of As might be released from the tailings to pore waters after their subaqueous disposal in the tailings management facility. A laboratory study was performed to address this issue, measuring readily desorbed As using a method known as equilibrium partitioning in closed systems (EPICS). The EPICS method was selected because it employs a leaching solution that, except for its As concentration, is identical in composition to the neutralized raffinate in contact with the tailings. Laboratory experiments and modeling results demonstrated that the As that could be readily released to pore waters is about 0.2% of the total As in the tailings. Long-term, such releases may contribute no more than a few mg/L of dissolved As to tailings pore waters

  1. NLDFT Pore Size Distribution in Amorphous Microporous Materials.

    Science.gov (United States)

    Kupgan, Grit; Liyana-Arachchi, Thilanga P; Colina, Coray M

    2017-10-24

    The pore size distribution (PSD) is one of the most important properties when characterizing and designing materials for gas storage and separation applications. Experimentally, one of the current standards for determining microscopic PSD is using indirect molecular adsorption methods such as nonlocal density functional theory (NLDFT) and N 2 isotherms at 77 K. Because determining the PSD from NLDFT is an indirect method, the validation can be a nontrivial task for amorphous microporous materials. This is especially crucial since this method is known to produce artifacts. In this work, the accuracy of NLDFT PSD was compared against the exact geometric PSD for 11 different simulated amorphous microporous materials. The geometric surface area and micropore volumes of these materials were between 5 and 1698 m 2 /g and 0.039 and 0.55 cm 3 /g, respectively. N 2 isotherms at 77 K were constructed using Gibbs ensemble Monte Carlo (GEMC) simulations. Our results show that the discrepancies between NLDFT and geometric PSD are significant. NLDFT PSD produced several artificial gaps and peaks that were further confirmed by the coordinates of inserted particles of a specific size. We found that dominant peaks from NLDFT typically reported in the literature do not necessarily represent the truly dominant pore size within the system. The confirmation provides concrete evidence for artifacts that arise from the NLDFT method. Furthermore, a sensitivity analysis was performed to show the high dependency of PSD as a function of the regularization parameter, λ. A higher value of λ produced a broader and smoother PSD that closely resembles geometric PSD. As an alternative, a new criterion for choosing λ, called here the smooth-shift method (SSNLDFT), is proposed that tuned the NLDFT PSD to better match the true geometric PSD. Using the geometric pore size distribution as our reference, the smooth-shift method reduced the root-mean-square deviation by ∼70% when the geometric

  2. Pore water colloid properties in argillaceous sedimentary rocks.

    Science.gov (United States)

    Degueldre, Claude; Cloet, Veerle

    2016-11-01

    The focus of this work is to evaluate the colloid nature, concentration and size distribution in the pore water of Opalinus Clay and other sedimentary host rocks identified for a potential radioactive waste repository in Switzerland. Because colloids could not be measured in representative undisturbed porewater of these host rocks, predictive modelling based on data from field and laboratory studies is applied. This approach allowed estimating the nature, concentration and size distributions of the colloids in the pore water of these host rocks. As a result of field campaigns, groundwater colloid concentrations are investigated on the basis of their size distribution quantified experimentally using single particle counting techniques. The colloid properties are estimated considering data gained from analogue hydrogeochemical systems ranging from mylonite features in crystalline fissures to sedimentary formations. The colloid concentrations were analysed as a function of the alkaline and alkaline earth element concentrations. Laboratory batch results on clay colloid generation from compacted pellets in quasi-stagnant water are also reported. Experiments with colloids in batch containers indicate that the size distribution of a colloidal suspension evolves toward a common particle size distribution independently of initial conditions. The final suspension size distribution was found to be a function of the attachment factor of the colloids. Finally, calculations were performed using a novel colloid distribution model based on colloid generation, aggregation and sedimentation rates to predict under in-situ conditions what makes colloid concentrations and size distributions batch- or fracture-size dependent. The data presented so far are compared with the field and laboratory data. The colloid occurrence, stability and mobility have been evaluated for the water of the considered potential host rocks. In the pore water of the considered sedimentary host rocks, the clay

  3. Automatic measurement of contact angle in pore-space images

    Science.gov (United States)

    AlRatrout, Ahmed; Raeini, Ali Q.; Bijeljic, Branko; Blunt, Martin J.

    2017-11-01

    A new approach is presented to measure the in-situ contact angle (θ) between immiscible fluids, applied to segmented pore-scale X-ray images. We first identify and mesh the fluid/fluid and fluid/solid interfaces. A Gaussian smoothing is applied to this mesh to eliminate artifacts associated with the voxelized nature of the image, while preserving large-scale features of the rock surface. Then, for the fluid/fluid interface we apply an additional smoothing and adjustment of the mesh to impose a constant curvature. We then track the three-phase contact line, and the two vectors that have a direction perpendicular to both surfaces: the contact angle is found from the dot product of these vectors where they meet at the contact line. This calculation can be applied at every point on the mesh at the contact line. We automatically generate contact angle values representing each invaded pore-element in the image with high accuracy. To validate the approach, we first study synthetic three-dimensional images of a spherical droplet of oil residing on a tilted flat solid surface surrounded by brine and show that our results are accurate to within 3° if the sphere diameter is 2 or more voxels. We then apply this method to oil/brine systems imaged at ambient temperature and reservoir pressure (10MPa) using X-ray microtomography (Singh et al., 2016). We analyse an image volume of diameter approximately 4.6 mm and 10.7 mm long, obtaining hundreds of thousands of values from a dataset with around 700 million voxels. We show that in a system of altered wettability, contact angles both less than and greater than 90° can be observed. This work provides a rapid method to provide an accurate characterization of pore-scale wettability, which is important for the design and assessment of hydrocarbon recovery and carbon dioxide storage.

  4. Thermodynamic and kinetic supercooling of liquid in a wedge pore.

    Science.gov (United States)

    Nowak, Dominika; Heuberger, Manfred; Zäch, Michael; Christenson, Hugo K

    2008-10-21

    Cyclohexane allowed to capillary condense from vapor in an annular wedge pore of mica in a surface force apparatus (SFA) remains liquid down to at least 14 K below the bulk melting-point T(m). This is an example of supercooling of a liquid due to confinement, like melting-point depression in porous media. In the wedge pore, however, the supercooled liquid is in equilibrium with vapor, and the amount of liquid (and thereby the radius of curvature r of the liquid-vapor interface) depends on the surface tension gamma(LV) of the liquid, not the interfacial tension between the solid and liquid. At coexistence r is inversely proportional to the temperature depression DeltaT below T(m), in accordance with a recently proposed model [P. Barber, T. Asakawa, and H. K. Christenson, J. Phys. Chem. C 111, 2141 (2007)]. We have now extended this model to include effects due to the temperature dependence of both the surface tension and the enthalpy of melting. The predictions of the improved model have been quantitatively verified in experiments using both a Mark IV SFA and an extended surface force apparatus (eSFA). The three-layer interferometer formed by the two opposing, backsilvered mica surfaces in a SFA was analyzed by conventional means (Mark IV) and by fast spectral correlation of up to 40 fringes (eSFA). We discuss the absence of freezing in the outermost region of the wedge pore down to 14 K below T(m) and attribute it to nonequilibrium (kinetic) supercooling, whereas the inner region of the condensate is thermodynamically supercooled.

  5. Thermodynamic and kinetic supercooling of liquid in a wedge pore

    Science.gov (United States)

    Nowak, Dominika; Heuberger, Manfred; Zäch, Michael; Christenson, Hugo K.

    2008-10-01

    Cyclohexane allowed to capillary condense from vapor in an annular wedge pore of mica in a surface force apparatus (SFA) remains liquid down to at least 14K below the bulk melting-point Tm. This is an example of supercooling of a liquid due to confinement, like melting-point depression in porous media. In the wedge pore, however, the supercooled liquid is in equilibrium with vapor, and the amount of liquid (and thereby the radius of curvature r of the liquid-vapor interface) depends on the surface tension γLV of the liquid, not the interfacial tension between the solid and liquid. At coexistence r is inversely proportional to the temperature depression ΔT below Tm, in accordance with a recently proposed model [P. Barber, T. Asakawa, and H. K. Christenson, J. Phys. Chem. C 111, 2141 (2007)]. We have now extended this model to include effects due to the temperature dependence of both the surface tension and the enthalpy of melting. The predictions of the improved model have been quantitatively verified in experiments using both a Mark IV SFA and an extended surface force apparatus (eSFA). The three-layer interferometer formed by the two opposing, backsilvered mica surfaces in a SFA was analyzed by conventional means (Mark IV) and by fast spectral correlation of up to 40 fringes (eSFA). We discuss the absence of freezing in the outermost region of the wedge pore down to 14K below Tm and attribute it to nonequilibrium (kinetic) supercooling, whereas the inner region of the condensate is thermodynamically supercooled.

  6. Description and reconstruction of the soil pore space using correlation functions

    Science.gov (United States)

    Gerke, K. M.; Karsanina, M. V.; Skvortsova, E. B.

    2012-09-01

    In this paper a method for the description and reconstruction of the soil pore space using correlation functions has been examined. The reconstruction procedure employed here is the best way of verification of the potential descriptor of the soil pore space. Thin sections representing eight major types of pore space in zonal loamy soils and parent materials of the Russian Plain with pores of different shapes and orientations have been chosen for this study. Comparison based on the morphological analysis of the original pore space images and their correlation function reconstructions obtained using simulated annealing technique indicates that this method of reconstruction adequately describes the isometric soil pore space with isometric dissected, isometric slightly dissected, and rounded pores. The two-point correlation functions calculated with the use of the orthogonal method proved to be different for the examined types of soil pore space; they reflect the soil porosity, specific surface, and pore structure correlations at different lengths. The results of this study allow us to conclude that the description of the soil pore space with the help of correlation functions is a promising approach, but requires more development. Further directions of the development of this method for describing the soil pore space and determining the soil physical processes are outlined.

  7. Multi-tests for pore structure characterization-A case study using lamprophyre

    Science.gov (United States)

    Li, Zhen; Feng, Guorui; Luo, Yi; Hu, Shengyong; Qi, Tingye; Jiang, Haina; Guo, Jun; Bai, Jinwen; Du, Xianjie; Kang, Lixun

    2017-08-01

    The pore structure plays an important role to understand methane adsorption, storage and flow behavior of geological materials. In this paper, the multi-tests including N2 adsorption, mercury intrusion porosimetry (MIP) and CT reconstruction have been proposed on Tashan lamprophyre samples. The main findings are listed: (1) The pore size distribution has a broad range ranging from 2-100000nm, among which the adsorption pores (100nm) only account for 34% of total pore volume. (2) The lamprophyre open pores are mainly slit-like/plate-like and ink-bottle-shaped pores on a two-dimensional level. The lamprophyre 3D pore structure shows more stochastic and anisotropic extension on the z axis to form a complex pore system on a three-dimensional level. (3) The closed pores (>647nm) occupy averaged 74.86% and 72.75% of total pores (>647nm) volume and specific surface area indicating a poor connectivity pore system. The revealed results provide basic information for understanding the abnormal methane emission reasons in similar geological conditions with lamprophyre invasions.

  8. Multi-tests for pore structure characterization-A case study using lamprophyre

    Directory of Open Access Journals (Sweden)

    Zhen Li

    2017-08-01

    Full Text Available The pore structure plays an important role to understand methane adsorption, storage and flow behavior of geological materials. In this paper, the multi-tests including N2 adsorption, mercury intrusion porosimetry (MIP and CT reconstruction have been proposed on Tashan lamprophyre samples. The main findings are listed: (1 The pore size distribution has a broad range ranging from 2-100000nm, among which the adsorption pores (100nm only account for 34% of total pore volume. (2 The lamprophyre open pores are mainly slit-like/plate-like and ink-bottle-shaped pores on a two-dimensional level. The lamprophyre 3D pore structure shows more stochastic and anisotropic extension on the z axis to form a complex pore system on a three-dimensional level. (3 The closed pores (>647nm occupy averaged 74.86% and 72.75% of total pores (>647nm volume and specific surface area indicating a poor connectivity pore system. The revealed results provide basic information for understanding the abnormal methane emission reasons in similar geological conditions with lamprophyre invasions.

  9. A new collector for in situ pore water sampling in wetland sediment.

    Science.gov (United States)

    Gao, Feng; Deng, Jiancai; Li, Qinqin; Hu, Liuming; Zhu, Jinge; Hang, Hongjuan; Hu, Weiping

    2012-01-01

    Currently available pore water samplers generally do not allow continuous monitoring of temporal variations in pore water composition. Therefore, a new type of pore water collector was designed and constructed. These collectors were constructed of polyvinyl chloride (PVC) materials, including PVC tubing with one end sealed and another end topped with a removable PVC screw-cap. A row of holes was drilled 10 cm from the sealed end of each collector. These new collectors were deployed in different layers of the sediment in a constructed wetland in Lake Taihu, China, to reveal variations in the nutrient composition of pore water with high spatial and temporal resolution. Specifically, the collectors were driven into the sediment, and the pore water flowed into the tubing via gravity. The pore water was then sampled from the PVC tubing using a portable vacuum pump, and then was taken to the lab within 20 min for analysis of the dissolved oxygen (DO) and nutrient concentration. The DO concentration of the pore water was below the detection limit for all samples, indicating that the pore water was probably not influenced by the air and that the water in the collector tube was representative of the pore water. These findings suggest that the collector is capable of measuring the temporal and spatial variations in the nutrient concentrations in pore water. Furthermore, the inexpensive material, ease of construction, minimal disturbance to the sediment and applicability for wetland sediments are advantages of the collector presented here compared with traditional pore water sampling techniques.

  10. Pore Structure Control of Ordered Mesoporous Silica Film Using Mixed Surfactants

    Directory of Open Access Journals (Sweden)

    Tae-Jung Ha

    2011-01-01

    Full Text Available Materials with nanosized and well-arranged pores have been researched actively in order to be applied to new technology fields. Especially, mesoporous material containing various pore structures is expected to have different pore structure. To form a mixed pore structure, ordered mesoporous silica films were prepared with a mixture of surfactant; Brij-76 and P-123 block copolymer. In mixed surfactant system, mixed pore structure was observed in the region of P-123/(Brij-76 + P-123 with about 50.0 wt.% while a single pore structure was observed in regions which have large difference in ratio between Brij-76 and P-123 through the X-ray diffraction analysis. Regardless of surfactant ratio, porosity was retained almost the same. It is expected that ordered mesoporous silica film with mixed pore structure can be one of the new materials which has distinctive properties.

  11. Nuclear pore complexes as hubs for gene regulation.

    Science.gov (United States)

    D'Angelo, Maximiliano A

    2018-01-01

    Nuclear pore complexes (NPCs), the channels connecting the nucleus with the cytoplasm, are the largest protein structures of the nuclear envelope. In addition to their role in regulating nucleocytoplasmic transport, increasing evidence shows that these multiprotein structures play central roles in the regulation of gene activity. In light of recent discoveries, NPCs are emerging as scaffolds that mediate the regulation of specific gene sets at the nuclear periphery. The function of NPCs as genome organizers and hubs for transcriptional regulation provides additional evidence that the compartmentalization of genes and transcriptional regulators within the nuclear space is an important mechanism of gene expression regulation.

  12. Tension-induced vesicle fusion: pathways and pore dynamics

    DEFF Research Database (Denmark)

    Shillcock, Julian C.

    2008-01-01

    The dynamics of tension-induced fusion of two vesicles is studied using dissipative particle dynamics (DPD) simulations. The vesicle membranes use an improved DPD parameter set that results in their sustaining only a 10–30% relative area stretch before rupturing on the microsecond timescale...... fusion time on membrane tension implies that the fusion process is completed by overcoming two energy barriers with scales of 13kBT and 11kBT. The fusion pore radius as a function of time has also been extracted from the simulations, and provides a quantitative measure of the fusion dynamics which...

  13. Dynamics of pore synthesis and degradation in protocells

    Science.gov (United States)

    Kubitschke, H.; Fütterer, C.

    2012-10-01

    Liposomes have found countless applications as microreactors or for studying the evolution of protocells. However, to keep reactions ongoing, exchange with the environment is required. Based on experiments with nanopores expressed by an enclosed gene expression system, we developed a model describing the observed growth dynamics quantitatively. The model depends on one parameter only and allowed estimations of hitherto unknown parameters: the diffusion coefficient of amino acids through a single pore and the initial amino acid concentration. The long-term consequences of different degradation mechanisms are also discussed: we found a surprisingly sharp threshold deciding on the question of survival of the protocell.

  14. Long n-alkanes isomerization by medium pore zeolites with pore mouth and key lock mechanisms; Isomerisation des paraffines longues par des zeolithes a pores moyens selon les mecanismes ouverture de pore et cle serrure

    Energy Technology Data Exchange (ETDEWEB)

    Claude, M.

    1999-10-01

    Skeletal isomerization of long n-alkanes is practiced to improve cold flow properties of diesel and lubricant fractions. In this work, model long n-alkanes (n-C{sub 10} - n-C{sub 24}) were hydro-isomerized in a fixed bed down flow vapour phase reactor loaded with bifunctional Pt/H-ZSM-22 zeolite catalyst. The skeletal isomers were analysed and identified with GC/MS. High isomer yields were obtained. The distribution of positional mono-methyl-branched isomers obtained from n-C{sub 12} to n-C{sub 24} are typically bimodal. This is explained by adsorption and reaction of the alkanes in pore mouths and locks on the external surface of the zeolite crystals. The pore mouth mode favours branching at C{sub 2} and C{sub 3}. The 'key lock' type proceeds by penetration of the two ends of the hydrocarbon chain into a different pore opening and favours more central mono-branching of the chain. The contribution of the key lock mode increases with increasing chain length and with the reaction temperature. The preferentially formed dimethyl-branched isomers have a separation between branchings of three up to fourteen carbon atoms. The formation of the second methyl-branching occurs preferentially from a centrally branched mono-methyl-branched isomer, so that the second branching is generated always more toward the end of the chain. Owing to the differences in adsorption entropy among the locks, at higher temperatures the largest lock is preferred and the distance between the two branching along the carbon chain in the preferred isomers is biggest. Thus the work resulted in the formulation of structure-selectivity relationships. n-C{sub 18} was hydro-isomerized on other zeolites. The nature and distribution of the isomers obtained suggest that the tubular 10-ring zeolites ZSM-23, ZSM-35 and SAPO-11 also operate according to pore mouth and key lock concepts. Zeolites with 12-rings show typical product patterns for catalysis in absence of steric hindrance. (author)

  15. Explicit Pore Pressure Material Model in Carbon-Cloth Phenolic

    Science.gov (United States)

    Gutierrez-Lemini, Danton; Ehle, Curt

    2003-01-01

    An explicit material model that uses predicted pressure in the pores of a carbon-cloth phenolic (CCP) composite has been developed. This model is intended to be used within a finite-element model to predict phenomena specific to CCP components of solid-fuel-rocket nozzles subjected to high operating temperatures and to mechanical stresses that can be great enough to cause structural failures. Phenomena that can be predicted with the help of this model include failures of specimens in restrained-thermal-growth (RTG) tests, pocketing erosion, and ply lifting

  16. The pore structure in processed Victorian Brown coal.

    Science.gov (United States)

    McMahon, P J; Snook, I K; Treimer, W

    2002-08-01

    Changes in the pore structure of Victorian Brown coal when upgraded with heated gases under pressure are investigated. We show that the results obtained from ultra-small-angle neutron scattering (USANS) measurements agree with previous results using small-angle X-ray scattering results but that USANS may also be used to investigate the meso porosity. Findings from small-angle scattering are confirmed using electron microscopy. We also show evidence from electron diffraction that thermal conditions within the brown coals during the upgrade procedure may be far more extreme than previously thought.

  17. The pore structure in processed Victorian brown coal

    Energy Technology Data Exchange (ETDEWEB)

    McMahon, P.J.; Snook, I.K.; Treimer, W. [University of Melbourne, Melbourne, Vic. (Australia). School of Physics

    2002-07-01

    Changes in the pore structure of Victorian Brown coal when upgraded with heated gases under pressure are investigated. It is shown that the results obtained from ultra-small-angle neutron scattering (USANS) measurements agree with previous results using small-angle X-ray scattering results but that USANS may also be used to investigate the meso porosity. Findings from small-angle scattering are confirmed using electron microscopy. Evidence is given from electron diffraction that thermal conditions within the brown coals during the upgrade procedure may be far more extreme than previously thought.

  18. Characterizing gas permeability and pore properties of Czech granitic rocks

    Czech Academy of Sciences Publication Activity Database

    Konečný, Pavel; Kožušníková, Alena

    2016-01-01

    Roč. 13, č. 4 (2016), s. 331-338 ISSN 1214-9705 R&D Projects: GA ČR GA105/09/0089; GA MŠk(CZ) LO1406; GA MŠk ED2.1.00/03.0082 Institutional support: RVO:68145535 Keywords : granitic rocks * permeability * pore properties Subject RIV: DB - Geology ; Mineralogy Impact factor: 0.699, year: 2016 https://www.irsm.cas.cz/materialy/acta_content/2016_doi/Konecny_AGG_2016_0015.pdf

  19. Formation and pore structure of boron nitride aerogels

    International Nuclear Information System (INIS)

    Lindquist, D.H.; Borek, T.T.; Kramer, S.J.; Kramer, S.J.; Naruta, C.K.; Johnson, G.; Schaeffer, R.; Smith, D.M.; Paine, R.T.

    1990-01-01

    This paper reports gels containing a poly(borazinyl amine) and tetrahydrofuran processed by CO 2 supercritical drying techniques followed by pyrolysis. The resulting BN ceramic aerogels are highly porous, and the microstructure, porosity, and surface area characteristics have been examined. The aerogels show excellent thermal stability exhibiting surface areas in excess of 350 m 2 /g and porosities greater than 0.8 even when heated in argon at 1500 degrees C for 8 h. By removing solvent via evaporation before supercritical drying, the mean pore radius can be varied between 3.6 and 10 nm

  20. Morphology, microstructure, and magnetic properties of ordered large-pore mesoporous cadmium ferrite thin film spin glasses.

    Science.gov (United States)

    Reitz, Christian; Suchomski, Christian; Chakravadhanula, Venkata Sai Kiran; Djerdj, Igor; Jagličić, Zvonko; Brezesinski, Torsten

    2013-04-01

    Herein, we report the synthesis, microstructure, and magnetic properties of cadmium ferrite (CdFe2O4) thin films with both an ordered cubic network of 18 nm diameter pores and single-phase spinel grains averaging 13 nm in diameter. These mesoporous materials were produced through facile polymer templating of hydrated nitrate salt precursors. Both the morphology and the microstructure, including cation site occupancy and electronic bonding configuration, were analyzed in detail by electron microscopy, grazing incidence small-angle X-ray scattering, Raman and X-ray photoelectron spectroscopy, and N2-physisorption. The obtained data demonstrate that the network of pores is retained up to annealing temperatures as high as 650 °C--the onset of crystallization is at ϑ = (590 ± 10) °C. Furthermore, they show that the polymer-templated samples exhibit a "partially" inverted spinel structure with inversion parameter λ = 0.40 ± 0.02. This differs from microcrystalline CdFe2O4 which shows virtually no inversion. Magnetic susceptibility studies reveal ferrimagnetic spin coupling below 147 K and further point to the likelihood of glassy behavior at low temperature (T(f) ≈ 60 K). In addition, analysis of room temperature magnetization data indicates the presence of sub-10 nm diameter superparamagnetic clusters in an otherwise paramagnetic environment.