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Sample records for alamethicin pore reconstructed

  1. Lipid-alamethicin interactions influence alamethicin orientation

    OpenAIRE

    Huang, Huey W.; Wu, Yili

    1991-01-01

    Whereas the barrel-stave configuration is accepted by most investigators as a good description of the conducting state of alamethicin, there are conflicting interpretations on its nonconducting state; in the absence of an applied field, some found alamethicin molecules on the membrane surface, but others found them incorporated in the hydrophobic core of the membrane. This problem is resolved by the discovery of a phase-transitionlike behavior of alamethicin in the membrane. As a function of ...

  2. Lipid-alamethicin interactions influence alamethicin orientation.

    Science.gov (United States)

    Huang, H W; Wu, Y

    1991-11-01

    Whereas the barrel-stave configuration is accepted by most investigators as a good description of the conducting state of alamethicin, there are conflicting interpretations on its nonconducting state; in the absence of an applied field, some found alamethicin molecules on the membrane surface, but others found them incorporated in the hydrophobic core of the membrane. This problem is resolved by the discovery of a phase-transitionlike behavior of alamethicin in the membrane. As a function of lipid/peptide ratio L/P and the chemical potential of water mu, alamethicin molecules were observed to switch between two states: in one, the majority of the peptide molecules bind parallel to the membrane surface; in another, the majority of the peptide molecules insert perpendicularly into the membrane. The state of alamethicin was monitored by the method of oriented circular dichroism (OCD; Wu, Y., H. W. Huang, and G. A. Olah, 1990, Biophys. J. 57:797-806) using aligned multilayer samples in the liquid crystalline L(alpha) phase. If L/P exceeds a critical value, most of the peptide molecules are on the membrane surface. If L/P is below the critical value, most of the peptide molecules are incorporated in the membrane when mu is high; when mu is low, most of them are again on the membrane surface. In a typical conduction experiment of voltage dependence, alamethicin molecules are in a partition equilibrium between the aqueous phase and the lipid phase before the application of voltage; in the lipid phase, the lipid/peptide ratio is such that most of alamethicin molecules are on the membrane surface. This is the nonconducting state of alamethicin. The OCD analysis showed that there is essentially no change in the secondary structure when alamethicin changes between the surface state and the inserted state. The voltage-gating mechanism can be explained if we assume that these surface peptide molecules probabilistically turn into the membrane core to form channels due to the

  3. 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.

  4. Antimicrobial Peptides in Toroidal and Cylindrical Pores

    OpenAIRE

    Mihajlovic, Maja; Lazaridis, Themis

    2010-01-01

    Antimicrobial peptides (AMPs) are small, usually cationic peptides, which permeabilize biological membranes. Their mechanism of action is still not well understood. Here we investigate the preference of alamethicin and melittin for pores of different shapes, using molecular dynamics (MD) simulations of the peptides in pre-formed toroidal and cylindrical pores. When an alamethicin hexamer is initially embedded in a cylindrical pore, at the end of the simulation the pore remains cylindrical or ...

  5. Analysis and evaluation of channel models : Simulations of alamethicin

    NARCIS (Netherlands)

    Tieleman, DP; Hess, B; Sansom, MSP

    2002-01-01

    Alamethicin is an antimicrobial peptide that forms stable channels with well-defined conductance levels. We have used extended molecular dynamics simulations of alamethicin bundles consisting of 4, 5, 6, 7, and 8 helices in a palmitoyl-oleolyl-phosphatidylcholine bilayer to evaluate and analyze chan

  6. Alamethicin Suppresses Methanogenesis and Promotes Acetogenesis in Bioelectrochemical Systems

    KAUST Repository

    Zhu, Xiuping

    2015-03-27

    Microbial electrosynthesis (MES) systems with mixed cultures often generate a variety of gaseous and soluble chemicals. Methane is the primary end product in mixed-culture MES because it is the thermodynamically most favorable reduction product of CO2. Here, we show that the peptaibol alamethicin selectively suppressed the growth of methanogens in mixed-culture MES systems, resulting in a shift of the solution and cathode communities to an acetate-producing system dominated by Sporomusa, a known acetogenic genus in MES systems. Archaea in the methane-producing control were dominated by Methanobrevibacter species, but no Archaea were detected in the alamethicin-treated reactors. No methane was detected in the mixed-culture reactors treated with alamethicin over 10 cycles (∼ 3 days each). Instead, acetate was produced at an average rate of 115 nmol ml(-1) day(-1), similar to the rate reported previously for pure cultures of Sporomusa ovata on biocathodes. Mixed-culture control reactors without alamethicin generated methane at nearly 100% coulombic recovery, and no acetate was detected. These results show that alamethicin is effective for the suppression of methanogen growth in MES systems and that its use enables the production of industrially relevant organic compounds by the inhibition of methanogenesis.

  7. Numerical Simulation of Two Phase Flow in Reconstructed Pore Network Based on Lattice Boltzmann Method

    OpenAIRE

    Song Rui; Liu Jianjun; Qin Dahui

    2013-01-01

    Accurate prediction and understanding of the disorder microstructures in the porous media contribute to acquiring the macroscopic physical properties such as conductivity, permeability, formation factor, elastic moduli etc. Based on the rock serial sectioning images of Berea sandstone acquired by the core scanning system developed by our research group, the reconstructed rock model is established in the Mimics software and the extracted pore network of the porous rock is accomplished by the s...

  8. Asymmetric distribution of charged lipids between the leaflets of a vesicle bilayer induced by melittin and alamethicin

    Energy Technology Data Exchange (ETDEWEB)

    Qian, Shuo [ORNL; Heller, William T [ORNL

    2011-01-01

    Cellular membranes are complex mixtures of lipids, proteins, and other small molecules that provide functional, dynamic barriers between the cell and its environment, as well as between environments within the cell. The lipid composition of the membrane is highly specific and controlled in terms of both content and lipid localization. The membrane structure results from the complex interplay between the wide varieties of molecules present. Here, small-angle neutron scattering and selective deuterium labeling were used to probe the impact of the membrane-active peptides melittin and alamethicin on the structure of lipid bilayers composed of a mixture of the lipids dimyristoyl phosphatidylglycerol (DMPG) and chain-perdeuterated dimyristoyl phosphatidylcholine (DMPC). We found that both peptides enriched the outer leaflet of the bilayer with the negatively charged DMPG, creating an asymmetric distribution of lipids. The level of enrichment is peptide concentration-dependent and is stronger for melittin than it is for alamethicin. The enrichment between the inner and outer bilayer leaflets occurs at very low peptide concentrations and increases with peptide concentration, including when the peptide adopts a membrane-spanning, pore-forming state. The results suggest that these membrane-active peptides may have a secondary stressful effect on target cells at low concentrations that results from a disruption of the lipid distribution between the inner and outer leaflets of the bilayer that is independent of the formation of transmembrane pores.

  9. Numerical Simulation of Two Phase Flow in Reconstructed Pore Network Based on Lattice Boltzmann Method

    Directory of Open Access Journals (Sweden)

    Song Rui

    2013-01-01

    Full Text Available Accurate prediction and understanding of the disorder microstructures in the porous media contribute to acquiring the macroscopic physical properties such as conductivity, permeability, formation factor, elastic moduli etc. Based on the rock serial sectioning images of Berea sandstone acquired by the core scanning system developed by our research group, the reconstructed rock model is established in the Mimics software and the extracted pore network of the porous rock is accomplished by the self-programming software in C++ programming language based on the revised Medial axis based algorithm and the Maximal ball algorithm. Using a lattice Boltzmann method, the single and two C phase flow are accomplished. Both of the pore-scale networks and the seepage mechanism of the single- and two Cphase flow are identical with the benchmark experimental data.

  10. Reconstruction of Berea sandstone and pore-scale modelling of wettability effects

    Energy Technology Data Exchange (ETDEWEB)

    Oeren, Pal-Eric; Bakke, Stig [Statoil Research Centre, N-7005 Trondheim (Norway)

    2003-09-01

    We present an integrated procedure for estimating permeability, conductivity, capillary pressure, and relative permeability of porous media. Although the method is general, we demonstrate its power and versatility on samples of Berea sandstone. The method utilizes petrographical information obtained from 2D thin sections to reconstruct 3D porous media. The permeability and conductivity are determined by solving numerically the local equations governing the transport. The reconstructed microstructure is transformed into a topologically equivalent network that is used directly as input to a network model. Computed two-phase and three-phase relative permeabilities for water wet conditions are in good agreement with experimental data. We present a method for characterizing wettability on the pore-scale from measured Amott wettability indices. Simulated effects of wettability on waterflood relative permeabilities and oil recovery compare favourably with experimental results.

  11. Defect formation of lytic peptides in lipid membranes and their influence on the thermodynamic properties of the pore environment

    CERN Document Server

    Oliynyk, V; Heimburg, T; Oliynyk, Vitaliy; Kaatze, Udo; Heimburg, Thomas

    2006-01-01

    We present an experimental study of the pore formation processes of small amphipathic peptides in model phosphocholine lipid membranes. We used atomic force microscopy to characterize the spatial organization and structure of alamethicin- and melittin- induced defects in lipid bilayer membranes and the influence of the peptide on local membrane properties. Alamethicin induced holes in gel DPPC membranes were directly visualized at different peptide concentrations. We found that the thermodynamic state of lipids in gel membranes can be influenced by the presence of alamethicin such that nanoscopic domains of fluid lipids form close to the peptide pores, and that the elastic constants of the membrane are altered in their vicinity. Melittin-induced holes were visualized in DPPC and DLPC membranes at room temperature in order to study the influence of the membrane state on the peptide induced hole formation. Also differential scanning calorimetry was used to investigate the effect of alamethicin on the lipid memb...

  12. Assessing permeability impairment due to scale in tri dimensional reconstructed reservoir rocks: pore-lining, pore-filing and dendritic algorithms; Estudo das representacoes tridimensionais incrustadas com os algotitmos pore-lining, porefiling e dentritico

    Energy Technology Data Exchange (ETDEWEB)

    Schaewer, T.R.; Bueno, A.D.; Bedrikovetsky, P. [Universidade Estadual do Norte Fluminense Darcy Ribeiro (LENEP/UENF), Macae, RJ (Brazil). Lab. de Engenharia e Exploracao de Petroleo], e-mail: tschaewer@lenep.uenf.br, e-mail: bueno@lenep.uenf.br, e-mail: pavel@lenep.uenf.br

    2006-07-01

    Barium sulphate scaling is a chronicle problem in the Campos Basin, where the most usual secondary recovery technic is waterooding (which corresponds to 85% of total oil volume produced). BaSO{sub 4} scale deposition occurs when the injected water, rich in sulphate ions, is mixed with the formation water, rich in barium ions, resulting in solid precipitate accumulation in the well bore, well tubing and near well bore formation. The problem is further aggravated by the hardness and low solubility of the salt, as well as the formation damage which occurs near the production well, where the mixing between the incompatible waters is more intense. Other sulphates, such as SrSO{sub 4}, also cause the same problem. In this wok, new models and algorithms to simulate sulphate scaling in reconstructed reservoir rocks are tested. Tridimensional reconstructed rocks are obtained from high resolution images of thin sections of rocks found in brazilian basins (contributed by CENPES). These reconstructed rocks are numerically scaled and permeability is then calculated by the serial connection graph, allowing the determination of the injectivity index impairment as a function of the total volume precipitated and the estimation of the formation damage coefficient. The tested models consider the influence of the geometric and topological organization of the porous media, as well as the morphology of the scaling phase itself. Three different scaling models were designed: pore-lining, pore-filling and dendritic. Analysis of the simulation results made it possible to assess the: effects on the scaled reconstructed rock (porosity, specific surface and connectivity), and the effects over permeability reduction (formation damage). The main advantage of the proposed approach is the possibility to use small rock samples, like drill cuttings and sidewall samples, which can be obtained by a small fraction of the of a full core. Another benefit is that destructive laboratory experiments are

  13. Barrel-stave model or toroidal model? A case study on melittin pores.

    OpenAIRE

    Yang, L; Harroun, T A; Weiss, T M; Ding, L; Huang, H W

    2001-01-01

    Transmembrane pores induced by amphiphilic peptides, including melittin, are often modeled with the barrel-stave model after the alamethicin pore. We examine this assumption on melittin by using two methods, oriented circular dichroism (OCD) for detecting the orientation of melittin helix and neutron scattering for detecting transmembrane pores. OCD spectra of melittin were systematically measured. Melittin can orient either perpendicularly or parallel to a lipid bilayer, depending on the phy...

  14. Mechanical properties of collagen membranes modified with pores--are they still sufficient for orbital floor reconstruction?

    Science.gov (United States)

    Birkenfeld, F; Flörke, C; Behrens, E; Rohnen, M; Kern, M; Gassling, V; Wiltfang, J

    2015-12-01

    Adequate mechanical strength is essential for materials used to reconstruct the orbital floor, and collagen membranes have recently been suggested for the repair of isolated fractures of the orbital floor. However, their mechanical properties after modification with pores for increased drainage of blood into the sinus have not been sufficiently investigated. We have tested the mechanical resistance of polydioxanone foils (PDS) to distortion and compared it with that of 3 resorbable collagen membranes (Smartbrane(®), Bio-Gide(®), and Creos(®)) in mint condition and when artificially aged (3 weeks, 6 weeks, and 8 weeks) after modification with pores (diameter 2mm) in a standard configuration (n=12 in each group). PDS and Creos(®) had comparable initial values for mechanical resistance of about 2.3N/mm(2), and Bio-Gide(®) and Smartbrane(®) had about 20% and 80% lower initial mechanical resistance, respectively. All materials tested had lower values after artificial ageing. After eight weeks of ageing, PDS lost about 99% of its initial mechanical resistance, Creos(®) about 66%, Bio-Gide(®) about 30%, and Smartbrane(®) about 95%. After 3 weeks the mechanical resistance in all groups was significantly less than the initial values (p=0.05), but there was no difference between samples aged artificially for 6 compared with 8 weeks. The mechanical resistance of the tested materials was not influenced by the presence of pores in a standard configuration and was in the appropriate range for moderate fractures of the orbital floor. We recommend further clinical investigations of collagen membranes modified with pores. PMID:26255542

  15. Stochastic Reconstruction of Particulate Media Using Simulated Annealing: Improving Pore Connectivity

    Czech Academy of Sciences Publication Activity Database

    Čapek, P.; Hejtmánek, Vladimír; Brabec, Libor; Zikánová, Arlette; Kočiřík, Milan

    2009-01-01

    Roč. 76, č. 2 (2009), s. 179-198. ISSN 0169-3913 R&D Projects: GA ČR GA203/05/0347 Institutional research plan: CEZ:AV0Z40720504; CEZ:AV0Z40400503 Keywords : stochastic reconstruction * simulated annealing * two-point cluster function Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 0.966, year: 2009

  16. Transport Properties of Stochastically Reconstructed Porous Media with Improved Pore Connectivity

    Czech Academy of Sciences Publication Activity Database

    Čapek, P.; Hejtmánek, Vladimír; Kolafa, J.; Brabec, Libor

    2011-01-01

    Roč. 88, č. 1 (2011), s. 87-106. ISSN 0169-3913 R&D Projects: GA ČR GA203/09/1353; GA ČR GA203/05/0347 Institutional research plan: CEZ:AV0Z40720504; CEZ:AV0Z40400503 Keywords : viscous flow * simulated annealing * stochastic reconstruction Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 1.811, year: 2011

  17. Reconstructing input for artificial neural networks based on embedding theory and mutual information to simulate soil pore water salinity in tidal floodplain

    Science.gov (United States)

    Zheng, Fawen; Wan, Yongshan; Song, Keunyea; Sun, Detong; Hedgepeth, Marion

    2016-01-01

    Soil pore water salinity plays an important role in the distribution of vegetation and biogeochemical processes in coastal floodplain ecosystems. In this study, artificial neural networks (ANNs) were applied to simulate the pore water salinity of a tidal floodplain in Florida. We present an approach based on embedding theory with mutual information to reconstruct ANN model input time series from one system state variable. Mutual information between system output and input was computed and the local minimum mutual information points were used to determine a time lag vector for time series embedding and reconstruction, with which the mutual information weighted average method was developed to compute the components of reconstructed time series. The optimal embedding dimension was obtained by optimizing model performance. The method was applied to simulate soil pore water salinity dynamics at 12 probe locations in the tidal floodplain influenced by saltwater intrusion using 4 years (2005-2008) data, in which adjacent river water salinity was used to reconstruct model input. The simulated electrical conductivity of the pore water showed close agreement with field observations (RMSE and ), suggesting the reconstructed input by the proposed approach provided adequate input information for ANN modeling. Multiple linear regression model, partial mutual information algorithm for input variable selection, k-NN algorithm, and simple time delay embedding were also used to further verify the merit of the proposed approach.

  18. Oxidation and reduction of pyridine nucleotides in alamethicin-permeabilized plant mitochondria

    DEFF Research Database (Denmark)

    Johansson, F.I.; Michalecka, A.M.; Møller, I.M.;

    2004-01-01

    The inner mitochondrial membrane is selectively permeable, which limits the transport of solutes and metabolites across the membrane. This constitutes a problem when intramitochondrial enzymes are studied. The channel-forming antibiotic AlaM (alamethicin) was used as a potentially less invasive...... method to permearbilize mitochondria and study the highly branched electron-transport chain in potato tuber (Solanum tuberosum) and pea leaf (Pisum sativum) mitochondria. We show that AlaM permeabilized the inner membrane of plant mitochondria to NAD(P)H, allowing the quantification of internal NAD......(P)H dehydrogenarses as well as matrix enzymes in situ. AlaM was found to inhibit the electron-tran sport chain at the external Ca2+-dependent rotenone-insensitive NADH dehydrogenase and around complexes III and IV. Nevertheless, under optimal conditions, especially complex I-mediated NADH oxidation in Ala...

  19. Influence of pore structures on the mechanical behavior of low-permeability sandstones:numerical reconstruction and analysis

    Institute of Scientific and Technical Information of China (English)

    Jiangtao Zheng; Yang Ju; Xi Zhao

    2014-01-01

    The research of rock properties based on its inherent microscopic to mesoscopic porous structure has drawn great attention for its potential in predicting the macroscopic behavior of rocks. An accurate reconstruction of the three-dimensional porous structure is a premise for the related studies of hydraulic and mechanical properties of rocks, such as the transport properties and mechanical responses under pressures. In this paper, we present a computer procedure for reconstructing the 3D porous structure of low-permeability sandstone. Two large-size 3D models are reconstructed based on the information of a reference model which is established from computed tomography (CT) images. A self-developed finite element method is applied to analyze the nonlinear mechanical behavior of the sandstone based on its reconstructed model and to compare the results with those based on the reference model. The good consistency of the obtained mechanical responses indicates the potential of using reconstruction models to predict the influences of porous structure on the mechanical properties of low-permeability sandstone.

  20. Rapid Brownian Motion Primes Ultrafast Reconstruction of Intrinsically Disordered Phe-Gly Repeats Inside the Nuclear Pore Complex.

    Science.gov (United States)

    Moussavi-Baygi, R; Mofrad, M R K

    2016-01-01

    Conformational behavior of intrinsically disordered proteins, such as Phe-Gly repeat domains, alters drastically when they are confined in, and tethered to, nan channels. This has challenged our understanding of how they serve to selectively facilitate translocation of nuclear transport receptor (NTR)-bearing macromolecules. Heterogeneous FG-repeats, tethered to the NPC interior, nonuniformly fill the channel in a diameter-dependent manner and adopt a rapid Brownian motion, thereby forming a porous and highly dynamic polymeric meshwork that percolates in radial and axial directions and features two distinguishable zones: a dense hydrophobic rod-like zone located in the center, and a peripheral low-density shell-like zone. The FG-meshwork is locally disrupted upon interacting with NTR-bearing macromolecules, but immediately reconstructs itself between 0.44 μs and 7.0 μs, depending on cargo size and shape. This confers a perpetually-sealed state to the NPC, and is solely due to rapid Brownian motion of FG-repeats, not FG-repeat hydrophobic bonds. Elongated-shaped macromolecules, both in the presence and absence of NTRs, penetrate more readily into the FG-meshwork compared to their globular counterparts of identical volume and surface chemistry, highlighting the importance of the shape effects in nucleocytoplasmic transport. These results can help our understanding of geometrical effects in, and the design of, intelligent and responsive biopolymer-based materials in nanofiltration and artificial nanopores. PMID:27470900

  1. Rapid Brownian Motion Primes Ultrafast Reconstruction of Intrinsically Disordered Phe-Gly Repeats Inside the Nuclear Pore Complex

    Science.gov (United States)

    Moussavi-Baygi, R.; Mofrad, M. R. K.

    2016-01-01

    Conformational behavior of intrinsically disordered proteins, such as Phe-Gly repeat domains, alters drastically when they are confined in, and tethered to, nan channels. This has challenged our understanding of how they serve to selectively facilitate translocation of nuclear transport receptor (NTR)-bearing macromolecules. Heterogeneous FG-repeats, tethered to the NPC interior, nonuniformly fill the channel in a diameter-dependent manner and adopt a rapid Brownian motion, thereby forming a porous and highly dynamic polymeric meshwork that percolates in radial and axial directions and features two distinguishable zones: a dense hydrophobic rod-like zone located in the center, and a peripheral low-density shell-like zone. The FG-meshwork is locally disrupted upon interacting with NTR-bearing macromolecules, but immediately reconstructs itself between 0.44 μs and 7.0 μs, depending on cargo size and shape. This confers a perpetually-sealed state to the NPC, and is solely due to rapid Brownian motion of FG-repeats, not FG-repeat hydrophobic bonds. Elongated-shaped macromolecules, both in the presence and absence of NTRs, penetrate more readily into the FG-meshwork compared to their globular counterparts of identical volume and surface chemistry, highlighting the importance of the shape effects in nucleocytoplasmic transport. These results can help our understanding of geometrical effects in, and the design of, intelligent and responsive biopolymer-based materials in nanofiltration and artificial nanopores. PMID:27470900

  2. Backbone Dynamics of Alamethicin Bound to Lipid Membranes: Spin-Echo Electron Paramagnetic Resonance of TOAC-Spin Labels

    Science.gov (United States)

    Bartucci, Rosa; Guzzi, Rita; De Zotti, Marta; Toniolo, Claudio; Sportelli, Luigi; Marsh, Derek

    2008-01-01

    Alamethicin F50/5 is a hydrophobic peptide that is devoid of charged residues and that induces voltage-dependent ion channels in lipid membranes. The peptide backbone is likely to be involved in the ion conduction pathway. Electron spin-echo spectroscopy of alamethicin F50/5 analogs in which a selected Aib residue (at position n = 1, 8, or 16) is replaced by the TOAC amino-acid spin label was used to study torsional dynamics of the peptide backbone in association with phosphatidylcholine bilayer membranes. Rapid librational motions of limited angular amplitude were observed at each of the three TOAC sites by recording echo-detected spectra as a function of echo delay time, 2τ. Simulation of the time-resolved spectra, combined with conventional EPR measurements of the librational amplitude, shows that torsional fluctuations of the peptide backbone take place on the subnanosecond to nanosecond timescale, with little temperature dependence. Associated fluctuations in polar fields from the peptide could facilitate ion permeation. PMID:18096632

  3. Reconstruction and analysis of fuel cell gas diffusion layers using fiber spacing rather than pore size data: Questioned validity of widely-used porosity-based thermal conductivity models

    Science.gov (United States)

    Sadeghifar, Hamidreza

    2016-03-01

    Porosity and pore size data have long been used for reconstructing (two directional) fibrous materials. The present study is aimed to explain the overlooked fact that pore size parameter, bundling several other geometric parameters together, cannot be directly used for the reconstruction and geometrical modeling of gas diffusion layers (GDLs) of fuel cells. Instead, it has to be converted to fiber spacing, for which purpose it is a useful parameter. A technical approach is presented on how to reach fiber spacing from pore size (diameter) data. The reason why GDLs with the same porosity, fiber diameter and angle, but with unequal fiber spacing, may have different properties is also explained by providing physical evidence. The present study clearly demonstrates that the traditional notion that fibrous materials with lower porosity have higher thermal conductivity does not necessary hold. In addition, it is shown that GDLs with the same porosity and the same pore size may have different fiber spacing and thus, distinct properties. It is found that the thermal conductivity models based solely upon porosity can be off by several hundred percent and must be either discarded or used over the narrow range of conditions under which they have been formulated.

  4. Pore Forming Properties of Cecropin-Melittin Hybrid Peptide in a Natural Membrane

    Directory of Open Access Journals (Sweden)

    Giorgio Rispoli

    2009-12-01

    Full Text Available The pore forming properties of synthetic cecropin-melittin hybrid peptide (Acetyl-KWKLFKKIGAVLKVL-CONH2; CM15 were investigated by using photoreceptor rod outer segments (OS isolated from frog retinae obtained by using the whole-cell configuration of the patch-clamp technique. CM15 was applied (and removed to (from the OS in ~50 ms with a computer-controlled microperfusion system. Once the main OS endogenous conductance was blocked with light, the OS membrane resistance was ≥1 GΩ, allowing high resolution, low-noise recordings. Different to alamethicines, CM15 produced voltage-independent membrane permeabilisation, repetitive peptide application caused a progressive permeabilisation increase, and no single-channel events were detected at low peptide concentrations. Collectively, these results indicate a toroidal mechanism of pore formation by CM15.

  5. Alamethicin permeabilizes the plasma membrane and mitochondria but not the tonoplast in tobacco (Nicotiana tabacum L. cv Bright Yellow) suspension cells

    DEFF Research Database (Denmark)

    Matic, S.; Geisler, D.A.; Møller, I.M.;

    2005-01-01

    The ion channel-forming peptide AlaM (alamethicin) is known to permeabilize isolated mitochondria as well as animal cells. When intact tobacco (Nicotiana tabacum L.) Bright Yellow-2 cells were treated with AlaM, the cells became permeable for low-molecular-mass molecules as shown by induced leakage...... cofactor concentrations. Possible uses and limitations of this method for plant cell research are discussed....... of NAD(P)(+). After the addition of cofactors and substrates, activities of cytosolic as well as mitochondrial respiratory enzymes could be directly determined inside the permeabilized cells. However, at an AlaM concentration at which the cytoplasmic enzymes were maximally accessible, the vacuole...

  6. Pore Velocity Estimation Uncertainties

    Science.gov (United States)

    Devary, J. L.; Doctor, P. G.

    1982-08-01

    Geostatistical data analysis techniques were used to stochastically model the spatial variability of groundwater pore velocity in a potential waste repository site. Kriging algorithms were applied to Hanford Reservation data to estimate hydraulic conductivities, hydraulic head gradients, and pore velocities. A first-order Taylor series expansion for pore velocity was used to statistically combine hydraulic conductivity, hydraulic head gradient, and effective porosity surfaces and uncertainties to characterize the pore velocity uncertainty. Use of these techniques permits the estimation of pore velocity uncertainties when pore velocity measurements do not exist. Large pore velocity estimation uncertainties were found to be located in the region where the hydraulic head gradient relative uncertainty was maximal.

  7. In vivo Quantification of the Effects of Radiation and Presence of Hair Follicle Pores on the Proliferation of Fibroblasts in an Acellular Human Dermis in a Dorsal Skinfold Chamber: Relevance for Tissue Reconstruction following Neoadjuvant Therapy

    OpenAIRE

    Vitacolonna, Mario; Belharazem, Djeda; Maier, Patrick; Hohenberger, Peter; Roessner, Eric Dominic

    2015-01-01

    Introduction In neoadjuvant therapy, irradiation has a deleterious effect on neoangiogenesis. The aim of this study was to examine the post-implantation effects of neoadjuvant irradiation on the survival and proliferation of autologous cells seeded onto an acellular human dermis (hAD; Epiflex). Additionally, we examined the influence of dermal hair follicle pores on viability and proliferation. We used dorsal skinfold chambers implanted in rats and in-situ microscopy to quantify cell numbers ...

  8. Pore-scale simulation of laminar flow through porous media

    International Nuclear Information System (INIS)

    The experimental investigation of flow through porous media is inherently difficult due to the lack of optical access. The recent developments in the fields of X-ray micro-tomography (micro-CT hereafter), digital sample reconstruction by image-processing techniques and fluid-dynamics simulation, together with the increasing power of super-computers, allow to carry out pore-scale simulations through digitally-reconstructed porous samples. The scientific relevance of pore-scale simulations lies in the possibility of upscaling the pore-level data, yielding volume-averaged quantities useful for practical purposes. One of the best-known examples of upscaling is the calculation of absolute and relative permeability of reservoir rocks. This contribution presents a complete work-flow for setting up pore-scale simulations, starting from the micro-CT of a (in general small) porous sample. Relevant applications are discussed in order to reveal the potential of the proposed methodology.

  9. Pore-scale simulation of laminar flow through porous media

    Science.gov (United States)

    Piller, M.; Casagrande, D.; Schena, G.; Santini, M.

    2014-04-01

    The experimental investigation of flow through porous media is inherently difficult due to the lack of optical access. The recent developments in the fields of X-ray micro-tomography (micro-CT hereafter), digital sample reconstruction by image-processing techniques and fluid-dynamics simulation, together with the increasing power of super-computers, allow to carry out pore-scale simulations through digitally-reconstructed porous samples. The scientific relevance of pore-scale simulations lies in the possibility of upscaling the pore-level data, yielding volume-averaged quantities useful for practical purposes. One of the best-known examples of upscaling is the calculation of absolute and relative permeability of reservoir rocks. This contribution presents a complete work-flow for setting up pore-scale simulations, starting from the micro-CT of a (in general small) porous sample. Relevant applications are discussed in order to reveal the potential of the proposed methodology.

  10. Chemotherapy Drugs Thiocolchicoside and Taxol Permeabilize Lipid Bilayer Membranes by Forming Ion Pores

    Science.gov (United States)

    Ashrafuzzaman, Md; Duszyk, M.; Tuszynski, J. A.

    2011-12-01

    We report ion channel formation by chemotherapy drugs: thiocolchicoside (TCC) and taxol (TXL) which primarily target tubulin but not only. For example, TCC has been shown to interact with GABAA, nuclear envelope and strychnine-sensitive glycine receptors. TXL interferes with the normal breakdown of microtubules inducing mitotic block and apoptosis. It also interacts with mitochondria and found significant chemotherapeutic applications for breast, ovarian and lung cancer. In order to better understand the mechanisms of TCC and TXL actions, we examined their effects on phospholipid bilayer membranes. Our electrophysiological recordings across membranes constructed in NaCl aqueous phases consisting of TCC or TXL under the influence of an applied transmembrane potential (V) indicate that both molecules induce stable ion flowing pores/channels in membranes. Their discrete current versus time plots exhibit triangular shapes which is consistent with a spontaneous time-dependent change of the pore conductance in contrast to rectangular conductance events usually induced by ion channels. These events exhibit conductance (~0.01-0.1 pA/mV) and lifetimes (~5-30 ms) within the ranges observed in e.g., gramicidin A and alamethicin channels. The channel formation probability increases linearly with TCC/TXL concentration and V and is not affected by pH (5.7 - 8.4). A theoretical explanation on the causes of chemotherapy drug induced ion pore formation and the pore stability has also been found using our recently discovered binding energy between lipid bilayer and the bilayer embedded ion channels using gramicidin A channels as tools. This picture of energetics suggests that as the channel forming agents approach to the lipids on bilayer the localized charge properties in the constituents of both channel forming agents (e.g., chemotherapy drugs in this study) and the lipids determine the electrostatic drug-lipid coupling energy through screened Coulomb interactions between the drug

  11. Chemotherapy Drugs Thiocolchicoside and Taxol Permeabilize Lipid Bilayer Membranes by Forming Ion Pores

    International Nuclear Information System (INIS)

    We report ion channel formation by chemotherapy drugs: thiocolchicoside (TCC) and taxol (TXL) which primarily target tubulin but not only. For example, TCC has been shown to interact with GABAA, nuclear envelope and strychnine-sensitive glycine receptors. TXL interferes with the normal breakdown of microtubules inducing mitotic block and apoptosis. It also interacts with mitochondria and found significant chemotherapeutic applications for breast, ovarian and lung cancer. In order to better understand the mechanisms of TCC and TXL actions, we examined their effects on phospholipid bilayer membranes. Our electrophysiological recordings across membranes constructed in NaCl aqueous phases consisting of TCC or TXL under the influence of an applied transmembrane potential (V) indicate that both molecules induce stable ion flowing pores/channels in membranes. Their discrete current versus time plots exhibit triangular shapes which is consistent with a spontaneous time-dependent change of the pore conductance in contrast to rectangular conductance events usually induced by ion channels. These events exhibit conductance (∼0.01-0.1 pA/mV) and lifetimes (∼5-30 ms) within the ranges observed in e.g., gramicidin A and alamethicin channels. The channel formation probability increases linearly with TCC/TXL concentration and V and is not affected by pH (5.7 - 8.4). A theoretical explanation on the causes of chemotherapy drug induced ion pore formation and the pore stability has also been found using our recently discovered binding energy between lipid bilayer and the bilayer embedded ion channels using gramicidin A channels as tools. This picture of energetics suggests that as the channel forming agents approach to the lipids on bilayer the localized charge properties in the constituents of both channel forming agents (e.g., chemotherapy drugs in this study) and the lipids determine the electrostatic drug-lipid coupling energy through screened Coulomb interactions between the

  12. Stochastic reconstruction of sandstones

    International Nuclear Information System (INIS)

    A simulated annealing algorithm is employed to generate a stochastic model for a Berea sandstone and a Fontainebleau sandstone, with each a prescribed two-point probability function, lineal-path function, and ''pore size'' distribution function, respectively. We find that the temperature decrease of the annealing has to be rather quick to yield isotropic and percolating configurations. A comparison of simple morphological quantities indicates good agreement between the reconstructions and the original sandstones. Also, the mean survival time of a random walker in the pore space is reproduced with good accuracy. However, a more detailed investigation by means of local porosity theory shows that there may be significant differences of the geometrical connectivity between the reconstructed and the experimental samples. (c) 2000 The American Physical Society

  13. Stochastic reconstruction of sandstones

    Science.gov (United States)

    Manwart; Torquato; Hilfer

    2000-07-01

    A simulated annealing algorithm is employed to generate a stochastic model for a Berea sandstone and a Fontainebleau sandstone, with each a prescribed two-point probability function, lineal-path function, and "pore size" distribution function, respectively. We find that the temperature decrease of the annealing has to be rather quick to yield isotropic and percolating configurations. A comparison of simple morphological quantities indicates good agreement between the reconstructions and the original sandstones. Also, the mean survival time of a random walker in the pore space is reproduced with good accuracy. However, a more detailed investigation by means of local porosity theory shows that there may be significant differences of the geometrical connectivity between the reconstructed and the experimental samples. PMID:11088546

  14. Stochastic reconstruction of sandstones

    OpenAIRE

    Manwart, C.; Torquato, S.; Hilfer, R.

    2000-01-01

    A simulated annealing algorithm is employed to generate a stochastic model for a Berea and a Fontainebleau sandstone with prescribed two-point probability function, lineal path function, and ``pore size'' distribution function, respectively. We find that the temperature decrease of the annealing has to be rather quick to yield isotropic and percolating configurations. A comparison of simple morphological quantities indicates good agreement between the reconstructions and the original sandston...

  15. NUCLEAR PORE COMPLEX BIOGENESIS

    OpenAIRE

    Fernandez-Martinez, Javier; Rout, Michael P.

    2009-01-01

    Nuclear pore complexes (NPCs) are the sole mediators of transport between the nucleus and the cytoplasm. NPCs have a life cycle: they assemble, disassemble, turn over and age. The molecular mechanisms governing these different vital steps are beginning to emerge, suggesting key roles for the core structural scaffold of the NPC and auxiliary factors in the assembly of this large macromolecular complex, and connections between NPC maintenance, NPC turnover, and ageing of the cell.

  16. 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

  17. Magnetic-resonance pore imaging of nonsymmetric microscopic pore shapes

    Science.gov (United States)

    Hertel, Stefan Andreas; Wang, Xindi; Hosking, Peter; Simpson, M. Cather; Hunter, Mark; Galvosas, Petrik

    2015-07-01

    Imaging of the microstructure of porous media such as biological tissue or porous solids is of high interest in health science and technology, engineering and material science. Magnetic resonance pore imaging (MRPI) is a recent technique based on nuclear magnetic resonance (NMR) which allows us to acquire images of the average pore shape in a given sample. Here we provide details on the experimental design, challenges, and requirements of MRPI, including its calibration procedures. Utilizing a laser-machined phantom sample, we present images of microscopic pores with a hemiequilateral triangular shape even in the presence of NMR relaxation effects at the pore walls. We therefore show that MRPI is applicable to porous samples without a priori knowledge about their pore shape and symmetry. Furthermore, we introduce "MRPI mapping," which combines MRPI with conventional magnetic resonance imaging (MRI). This enables one to resolve microscopic pore sizes and shapes spatially, thus expanding the application of MRPI to samples with heterogeneous distributions of pores.

  18. Pore-water chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Vinsot, A. [Agence Nationale pour la Gestion des Dechets Radioactifs, Lab. de Souterrain de Meuse/Haute-Marne, 55 - Bure (France); Appelo, C.A.J. [Valeriusstraat 11, Amsterdam (Netherlands); Cailteau, C. [LEM, ENSG/INPL, 54 - Vandoeuvre-les-Nancy (France); Cailteau, C. [G2R-CREGU, UMR 7566 CNRS, 54 - Vandoeuvre-les-Nancy (France); Cailteau, C. [Andra - Agence Nationale pour la Gestion des Dechets Radioactifs, 92 - Chatenay Malabry (France); Mettler, S.; Wersin, P. [NAGRA, CH-5430 Wettingen (Switzerland); Canniere, P. de [Studiecentrum voor Kernenergie - Centre d' Etude de l' Energie Nucleaire, Mol (Belgium); Gabler, H.E. [BGR, Hannover (Germany); Gaucher, E.C.; Tournassat, C. [Bureau de Recherches Geologiques et Minieres (BRGM), 45 - Orleans (France); Jacquot, E.; Altmann, S. [Agence Nationale pour la Gestion des Dechets Radioactifs (DS/TR), 92 - Chatenay Malabry (France); Vinsot, A. [Agence Nationale pour la Gestion des Dechets Radioactifs, Lab. de Recherche Souterrain de Meuse/Haute-Marne, 55 - Bure (France); Courdouan, A.; Christl, I.; Kretzschmar, R. [Institute of Biogeochemistry and Pollutant Dynamics, Dept. of Environmental Sciences, ETH Zurich, CHN (Switzerland); Wersin, P. [National Cooperative for the Disposal of Radioactive Waste (Nagra), Wettingen (Switzerland); Savoye, S.; Matray, J.M.; Wittebroodt, Ch.; Cabrera, J.; Bensenouci, F. [Institut de Radioprotection et de Surete Nucleaire, 92 - Fontenay aux Roses (France); Michelot, J.L.; Bensenouci, F. [Paris-11 Univ., UMR IDES CNRS, 91 - Orsay (France); Waber, H.S. [Rock-Water Interaction (RWI), Inst. of Geological Sciences, Bern (Switzerland); Wittebroodt, Ch. [Montpellier-2 Univ., MSE, 34 (France); Lavielle, B.; Gilabert, E.; Thomas, B.; Lavastre, V. [Bordeaux 1-2 Univ., (GdR FORPRO 0788), Chimie Nucleaire Analytique et Bioenvironnementale (CNAB), CNRS, 33 - Gradignan (France); Lavastre, V. [Nimes Univ., Geochimie Isotopique Environnementale (GIS/CEREGE), CNRS-RANCE, 30 (France)

    2007-07-01

    This session gathers 5 articles dealing with: CO{sub 2} data on gas and pore water sampled in-situ in the Opalinus clay at the Mont Terri rock laboratory (A. Vinsot, C.A.J. Appelo, C. Cailteau, S. Mettler, P. Wersin, P. De Canniere, H.E. Gaebler); the improvements in the modelling of the pore water chemistry of the Callovo-Oxfordian formation (E.C. Gaucher, C. Tournassat, E. Jacquot, S. Altmann, A. Vinsot) the nature and reactivity of dissolved organic matter in the Opalinus clay and Callovo-Oxfordian formations (A. Courdouan, I. Christl, P.Wersin, R. Kretzschmar); PH4: a 250 m deep borehole in Tournemire for assessing the reliability of chloride, helium and water stable isotopes profiles in the Toarcian/ Domerian shales (S. Savoye, J.L. Michelot, H.N. Waber, J.M. Matray, F. Bensenouci, Ch. Wittebroodt, J. Cabrera); and the development of a new facility for dating old groundwaters by using {sup 81}Kr (B. Lavielle, E. Gilabert, B. Thomas, V. Lavastre)

  19. Pore dynamics in lipid membranes

    Science.gov (United States)

    Gozen, I.; Dommersnes, P.

    2014-09-01

    Transient circular pores can open in plasma membrane of cells due to mechanical stress, and failure to repair such pores lead to cell death. Similar pores in the form of defects also exist among smectic membranes, such as in myelin sheaths or mitochondrial membranes. The formation and growth of membrane defects are associated with diseases, for example multiple sclerosis. A deeper understanding of membrane pore dynamics can provide a more refined picture of membrane integrity-related disease development, and possibly also treatment options and strategies. Pore dynamics is also of great importance regarding healthcare applications such as drug delivery, gene or as recently been implied, cancer therapy. The dynamics of pores significantly differ in stacks which are confined in 2D compared to those in cells or vesicles. In this short review, we will summarize the dynamics of different types of pores that can be observed in biological membranes, which include circular transient, fusion and hemi-fusion pores. We will dedicate a section to floral and fractal pores which were discovered a few years ago and have highly peculiar characteristics. Finally, we will discuss the repair mechanisms of large area pores in conjunction with the current cell membrane repair hypotheses.

  20. Soils, Pores, and NMR

    Science.gov (United States)

    Pohlmeier, Andreas; Haber-Pohlmeier, Sabina; Haber, Agnes; Sucre, Oscar; Stingaciu, Laura; Stapf, Siegfried; Blümich, Bernhard

    2010-05-01

    Within Cluster A, Partial Project A1, the pore space exploration by means of Nuclear Magnetic Resonance (NMR) plays a central role. NMR is especially convenient since it probes directly the state and dynamics of the substance of interest: water. First, NMR is applied as relaxometry, where the degree of saturation but also the pore geometry controls the NMR signature of natural porous systems. Examples are presented where soil samples from the Selhausen, Merzenhausen (silt loams), and Kaldenkirchen (sandy loam) test sites are investigated by means of Fast Field Cycling Relaxometry at different degrees of saturation. From the change of the relaxation time distributions with decreasing water content and by comparison with conventional water retention curves we conclude that the fraction of immobile water is characterized by T1 samples (Haber-Pohlmeier et al. 2010). Third, relaxometric information forms the basis of understanding magnetic resonance imaging (MRI) results. The general difficulty of imaging in soils are the inherent fast T2 relaxation times due to i) the small pore sizes, ii) presence of paramagnetic ions in the solid matrix, and iii) diffusion in internal gradients. The last point is important, since echo times can not set shorter than about 1ms for imaging purposes. The way out is either the usage of low fields for imaging in soils or special ultra-short pulse sequences, which do not create echoes. In this presentation we will give examples on conventional imaging of macropore fluxes in soil cores (Haber-Pohlmeier et al. 2010), and the combination with relaxometric imaging, as well as the advantages and drawbacks of low-field and ultra-fast pulse imaging. Also first results on the imaging of soil columns measured by SIP in Project A3 are given. Haber-Pohlmeier, S., S. Stapf, et al. (2010). "Waterflow Monitored by Tracer Transport in Natural Porous Media Using MRI." Vadose Zone J.: submitted. Haber-Pohlmeier, S., S. Stapf, et al. (2010). "Relaxation in a

  1. Boom clay pore water chemistry

    International Nuclear Information System (INIS)

    In Belgium, geological disposal in clay is the primary option for the isolation of high-level radioactive waste and spent fuel from the biosphere. The Boom Clay is studied as the potential host rock for methodological studies on the geological disposal of radioactive waste. It is present under the facilities of the SCK-CEN at Mol, at a depth of 190 to 293 m. The current R and D programme focuses on the feasibility and safety of radioactive waste disposal in the Boom Clay. In this framework, a detailed characterisation of the clay is performed (mechanical, physico-chemical and hydrogeological properties, variability, role of organic matter,...). In addition, high priority is given to the understanding of the basic phenomena which control the retention o f radionuclides in the clay. Therefore, it is very important to characterise and understand the pore water composition in the host rock. All the available information from previous studies on the Boom Clay pore water chemistry was synthesise d in a 'state of the art' report, status 2004. This report describes the pore water sampling and analytical techniques, the results, and interpretation of a series of studies carried out in-situ in the HADES URF and in the laboratories. The objective of this study was to evaluate the most reliable technique(s) to obtain representative pore water samples, to determine the variation of the pore water composition in the Boom Clay, to present a coherent geochemical model for explaining the mechanisms controlling the Boom Clay pore water composition, and to propose a reference pore water composition to be used in the laboratory experiments, for speciation calculations, and for assessments of perturbation that might influence the Boom Clay pore water. The main conclusions will be presented here. (authors)

  2. Can ash clog soil pores?

    Science.gov (United States)

    Stoof, Cathelijne; Stoof, Cathelijne; Gevaert, Anouk; Gevaert, Anouk; Baver, Christine; Baver, Christine; Hassanpour, Bahareh; Hassanpour, Bahareh; Morales, Veronica; Morales, Veronica; Zhang, Wei; Zhang, Wei; Martin, Deborah; Martin, Deborah; Steenhuis, Tammo; Steenhuis, Tammo

    2015-04-01

    Wildfire can greatly increase a landscape's vulnerability to flooding and erosion events, and ash is thought to play a large role in controlling runoff and erosion processes after wildfire. Although ash can store rainfall and thereby reduce runoff and erosion for a limited period after wildfires, it has also been hypothesized to clog soil pores and reduce infiltration. Several researchers have attributed the commonly observed increase in runoff and erosion after fire to the potential pore-clogging effect of ash. Evidence is however incomplete, as to date, research has solely focused on identifying the presence of ash in the soil, with the actual flow processes associated with the infiltration and pore-clogging of ash remaining a major unknown. In several laboratory experiments, we tested the hypothesis that ash causes pore clogging to the point that infiltration is hampered and ponding occurs. We first visualized and quantified pore-scale infiltration of water and ash in sand of a range of textures and at various infiltration rates, using a digital bright field microscope capturing both photo and video. While these visualization experiments confirm field and lab observation of ash washing into soil pores, we did not observe any clogging of pores, and have not been able to create conditions for which this does occur. Additional electrochemical analysis and measurement of saturated hydraulic conductivity indicate that pore clogging by ash is not plausible. Electrochemical analysis showed that ash and sand are both negatively charged, showing that attachment of ash to sand and any resulting clogging is unlikely. Ash also had quite high saturated conductivity, and systems where ash was mixed in or lying on top of sand had similarly high hydraulic conductivity. Based on these various experiments, we cannot confirm the hypothesis that pore clogging by ash contributes to the frequently observed increase in post-fire runoff, at least for the medium to coarse sands

  3. The Description of Shale Reservoir Pore Structure Based on Method of Moments Estimation.

    Science.gov (United States)

    Li, Wenjie; Wang, Changcheng; Shi, Zejin; Wei, Yi; Zhou, Huailai; Deng, Kun

    2016-01-01

    Shale has been considered as good gas reservoir due to its abundant interior nanoscale pores. Thus, the study of the pore structure of shale is of great significance for the evaluation and development of shale oil and gas. To date, the most widely used approaches for studying the shale pore structure include image analysis, radiation and fluid invasion methods. The detailed pore structures can be studied intuitively by image analysis and radiation methods, but the results obtained are quite sensitive to sample preparation, equipment performance and experimental operation. In contrast, the fluid invasion method can be used to obtain information on pore size distribution and pore structure, but the relative simple parameters derived cannot be used to evaluate the pore structure of shale comprehensively and quantitatively. To characterize the nanoscale pore structure of shale reservoir more effectively and expand the current research techniques, we proposed a new method based on gas adsorption experimental data and the method of moments to describe the pore structure parameters of shale reservoir. Combined with the geological mixture empirical distribution and the method of moments estimation principle, the new method calculates the characteristic parameters of shale, including the mean pore size ([Formula: see text]), standard deviation (σ), skewness (Sk) and variation coefficient (c). These values are found by reconstructing the grouping intervals of observation values and optimizing algorithms for eigenvalues. This approach assures a more effective description of the characteristics of nanoscale pore structures. Finally, the new method has been applied to analyze the Yanchang shale in the Ordos Basin (China) and Longmaxi shale from the Sichuan Basin (China). The results obtained well reveal the pore characteristics of shale, indicating the feasibility of this new method in the study of the pore structure of shale reservoir. PMID:26992168

  4. Geostatistical Modeling of Pore Velocity

    Energy Technology Data Exchange (ETDEWEB)

    Devary, J.L.; Doctor, P.G.

    1981-06-01

    A significant part of evaluating a geologic formation as a nuclear waste repository involves the modeling of contaminant transport in the surrounding media in the event the repository is breached. The commonly used contaminant transport models are deterministic. However, the spatial variability of hydrologic field parameters introduces uncertainties into contaminant transport predictions. This paper discusses the application of geostatistical techniques to the modeling of spatially varying hydrologic field parameters required as input to contaminant transport analyses. Kriging estimation techniques were applied to Hanford Reservation field data to calculate hydraulic conductivity and the ground-water potential gradients. These quantities were statistically combined to estimate the groundwater pore velocity and to characterize the pore velocity estimation error. Combining geostatistical modeling techniques with product error propagation techniques results in an effective stochastic characterization of groundwater pore velocity, a hydrologic parameter required for contaminant transport analyses.

  5. Penile reconstruction

    OpenAIRE

    Garaffa, Giulio; Sansalone, Salvatore; Ralph, David J.

    2012-01-01

    During the most recent years, a variety of new techniques of penile reconstruction have been described in the literature. This paper focuses on the most recent advances in male genital reconstruction after trauma, excision of benign and malignant disease, in gender reassignment surgery and aphallia with emphasis on surgical technique, cosmetic and functional outcome.

  6. Penile reconstruction

    Institute of Scientific and Technical Information of China (English)

    Giulio Garaffa; Salvatore Sansalone; David J Ralph

    2013-01-01

    During the most recent years,a variety of new techniques of penile reconstruction have been described in the literature.This paper focuses on the most recent advances in male genital reconstruction after trauma,excision of benign and malignant disease,in gender reassignment surgery and aphallia with emphasis on surgical technique,cosmetic and functional outcome.

  7. Pore structure of ore granular media by computerized tomography image processing

    Institute of Scientific and Technical Information of China (English)

    WU Ai-xiang; YANG Bao-hua; XI Yong; JIANG Huai-chun

    2007-01-01

    The pore structure images of ore particles located at different heights of leaching column were scanned with X-ray computerized tomography (CT) scanner, the porosity and pore size distribution were calculated and the geometrical shape and connectivity of pores were analyzed based on image process method, and the three dimensional reconstruction of pore structure images was realized. The results show that the porosity of ore particles bed in leaching column is 42.92%, 41.72%, 39.34% at top,middle and bottom zone, respectively. Obviously it has spatial variability and decreases appreciably along the height of the column.The overall average porosity obtained by image processing is 41.33% while the porosity gotten from general measurement method in laboratory is 42.77% showing the results of both methods are consistent well. The pore structure of ore granular media is characterized as a dynamical space network composed of interconnected pore bodies and pore throats. The ratio of throats with equivalent diameter less than 1.91 mm to the total pores is 29.31%, and that of the large pores with equivalent diameter more than 5.73 mm is 2.90%.

  8. Climate Reconstructions

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The NOAA Paleoclimatology Program archives reconstructions of past climatic conditions derived from paleoclimate proxies, in addition to the Program's large...

  9. Laryngopharyngeal reconstruction

    OpenAIRE

    Kazi, Rehan A

    2006-01-01

    There is a high incidence of hypopharyngeal cancer is our country due to the habits of tobacco and alcohol. Moreover these cases are often detected in the late stages thereby making the issue of reconstruction very tedious and unpredictable. There are a number of options for laryngopharyngeal reconstruction available now including the use of microvascular flaps depending upon the patient’s fitness, motivation, technical expertise, size and extent of the defect. This article reviews the differ...

  10. The Arabidopsis Nuclear Pore and Nuclear Envelope

    OpenAIRE

    Meier, Iris; Brkljacic, Jelena

    2010-01-01

    The nuclear envelope is a double membrane structure that separates the eukaryotic cytoplasm from the nucleoplasm. The nuclear pores embedded in the nuclear envelope are the sole gateways for macromolecular trafficking in and out of the nucleus. The nuclear pore complexes assembled at the nuclear pores are large protein conglomerates composed of multiple units of about 30 different nucleoporins. Proteins and RNAs traffic through the nuclear pore complexes, enabled by the interacting activities...

  11. Project Reconstruct.

    Science.gov (United States)

    Helisek, Harriet; Pratt, Donald

    1994-01-01

    Presents a project in which students monitor their use of trash, input and analyze information via a database and computerized graphs, and "reconstruct" extinct or endangered animals from recyclable materials. The activity was done with second-grade students over a period of three to four weeks. (PR)

  12. Vaginal reconstruction

    Energy Technology Data Exchange (ETDEWEB)

    Lesavoy, M.A.

    1985-05-01

    Vaginal reconstruction can be an uncomplicated and straightforward procedure when attention to detail is maintained. The Abbe-McIndoe procedure of lining the neovaginal canal with split-thickness skin grafts has become standard. The use of the inflatable Heyer-Schulte vaginal stent provides comfort to the patient and ease to the surgeon in maintaining approximation of the skin graft. For large vaginal and perineal defects, myocutaneous flaps such as the gracilis island have been extremely useful for correction of radiation-damaged tissue of the perineum or for the reconstruction of large ablative defects. Minimal morbidity and scarring ensue because the donor site can be closed primarily. With all vaginal reconstruction, a compliant patient is a necessity. The patient must wear a vaginal obturator for a minimum of 3 to 6 months postoperatively and is encouraged to use intercourse as an excellent obturator. In general, vaginal reconstruction can be an extremely gratifying procedure for both the functional and emotional well-being of patients.

  13. Vaginal reconstruction

    International Nuclear Information System (INIS)

    Vaginal reconstruction can be an uncomplicated and straightforward procedure when attention to detail is maintained. The Abbe-McIndoe procedure of lining the neovaginal canal with split-thickness skin grafts has become standard. The use of the inflatable Heyer-Schulte vaginal stent provides comfort to the patient and ease to the surgeon in maintaining approximation of the skin graft. For large vaginal and perineal defects, myocutaneous flaps such as the gracilis island have been extremely useful for correction of radiation-damaged tissue of the perineum or for the reconstruction of large ablative defects. Minimal morbidity and scarring ensue because the donor site can be closed primarily. With all vaginal reconstruction, a compliant patient is a necessity. The patient must wear a vaginal obturator for a minimum of 3 to 6 months postoperatively and is encouraged to use intercourse as an excellent obturator. In general, vaginal reconstruction can be an extremely gratifying procedure for both the functional and emotional well-being of patients

  14. ACL reconstruction - discharge

    Science.gov (United States)

    Anterior cruciate ligament reconstruction - discharge; ACL reconstruction - discharge ... had surgery to reconstruct your anterior cruciate ligament (ACL). The surgeon drilled holes in the bones of ...

  15. Radio Reconstructions

    OpenAIRE

    Bulley, James; Jones, Daniel

    2013-01-01

    Radio Reconstructions is a sound installation which use indeterminate radio broadcasts as its raw material. Each piece is structured by a notated score, which controls its rhythm, dynamics and melodic contour over time. The audio elements used to enact this score are selected in real-time from unknown radio transmissions, by an autonomous software system which is continuously scanning the radio waves in search of similar fragments of audio. Using a technique known as audio mosaicing, hund...

  16. Microlens arrays with integrated pores

    Directory of Open Access Journals (Sweden)

    Shu Yang

    2005-12-01

    Full Text Available Microlenses are important optical components that image, detect, and couple light. But most synthetic microlenses have fixed position and shape once they are fabricated, so their possible range of tunability and complexity is rather limited. By comparison, biology provides many varied, new paradigms for the development of adaptive optical networks. Here, we discuss inspirational examples of biological lenses and their synthetic analogs. We focus on the fabrication and characterization of biomimetic microlens arrays with integrated pores, whose appearance and function are similar to highly efficient optical elements formed by brittlestars. The complex design can be created by three-beam interference lithography. The synthetic lens has strong focusing ability for use as an adjustable lithographic mask and a tunable optical device coupled with the microfluidic system. Replacing rigid microlenses with soft hydrogels provides a way of changing the lens geometry and refractive index continuously in response to external stimuli, resulting in intelligent, multifunctional, tunable optics.

  17. 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...

  18. Effects of fractal pore on coal devolatilization

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Yongli; He, Rong [Tsinghua Univ., Beijing (China). Dept. of Thermal Engineering; Wang, Xiaoliang; Cao, Liyong [Dongfang Electric Corporation, Chengdu (China). Centre New Energy Inst.

    2013-07-01

    Coal devolatilization is numerically investigated by drop tube furnace and a coal pyrolysis model (Fragmentation and Diffusion Model). The fractal characteristics of coal and char pores are investigated. Gas diffusion and secondary reactions in fractal pores are considered in the numerical simulations of coal devolatilization, and the results show that the fractal dimension is increased firstly and then decreased later with increased coal conversions during devolatilization. The mechanisms of effects of fractal pores on coal devolatilization are analyzed.

  19. Minimum Membrane Bending Energies of Fusion Pores

    OpenAIRE

    Jackson, Meyer B.

    2009-01-01

    Membranes fuse by forming highly curved intermediates, culminating in structures described as fusion pores. These hourglass-like figures that join two fusing membranes have high bending energies, which can be estimated using continuum elasticity models. Fusion pore bending energies depend strongly on shape, and the present study developed a method for determining the shape that minimizes bending energy. This was first applied to a fusion pore modeled as a single surface and then extended to a...

  20. Nanofiltration membranes with narrowed pore size distribution via pore wall modification.

    Science.gov (United States)

    Du, Yong; Lv, Yan; Qiu, Wen-Ze; Wu, Jian; Xu, Zhi-Kang

    2016-06-30

    We propose a novel strategy for narrowing down the pore size distribution of ready-made nanofiltration membranes (NFMs) via pore wall modification. NFMs were subjected to the filtration of a highly reactive molecule solution, during which large pores were selectively reduced in size. The as-treated NFMs have high monovalent ion/divalent ion selectivity. PMID:27321407

  1. Tracheal reconstructions.

    Science.gov (United States)

    Srikrishna, S V; Shekar, P S; Shetty, N

    1998-12-01

    Surgical reconstruction of the trachea is a relatively complex procedure. We had 20 cases of tracheal stenosis. We have a modest experience of 16 tracheal reconstructions for acquired tracheal stenosis. Two patients underwent laser treatment while another two died before any intervention. The majority of these cases were a result of prolonged ventilation (14 cases), following organophosphorous poisoning (11 cases), Guillain-Barré syndrome, bullet injury, fat embolism and surprisingly only one tumor, a case of mucoepidermoid carcinoma, who had a very unusual presentation. There were 12 males and 4 females in this series, age ranging from 12-35 years. The duration of ventilation ranged from 1-21 days and the interval from decannulation to development of stridor was between 5-34 days. Six of them were approached by the cervical route, 5 by thoracotomy and cervical approach, 2 via median sternotomy and 3 by thoracotomy alone. Five of them required an additional laryngeal drop and 1 required pericardiotomy and release of pulmonary veins to gain additional length. The excised segments of trachea measured 3 to 5 cms in length. All were end to end anastomosis with interrupted Vicryl sutures. We have had no experience with stents or prosthetic tubes. Three patients developed anastomotic leaks which were controlled conservatively. Almost all of them required postoperative tracheo-bronchial suctioning with fibreoptic bronchoscope. We had one death in this series due to sepsis. PMID:9914459

  2. The Pivotal Role of Alumina Pore Structure in HF Capture and Fluoride Return in Aluminum Reduction

    Science.gov (United States)

    McIntosh, Grant J.; Agbenyegah, Gordon E. K.; Hyland, Margaret M.; Metson, James B.

    2016-07-01

    Fluoride emissions during primary aluminum production are mitigated by dry scrubbing on alumina which, as the metal feedstock, also returns fluoride to the pots. This ensures stable pot operation and maintains process efficiency but requires careful optimization of alumina for both fluoride capture and solubility. The Brunauer-Emmett-Teller (BET) surface area of 70-80 m2 g-1 is currently accepted. However, this does not account for pore accessibility. We demonstrate using industry-sourced data that pores <3.5 nm are not correlated with fluoride return. Reconstructing alumina pore size distributions (PSDs) following hydrogen fluoride (HF) adsorption shows surface area is not lost by pore diameter shrinkage, but by blocking the internal porosity. However, this alone cannot explain this 3.5 nm threshold. We show this is a consequence of surface diffusion-based inhibition with surface chemistry probably playing an integral role. We advocate new surface area estimates for alumina which account for pore accessibility by explicitly ignoring <3.5 nm pores.

  3. Pore Narrowing of Mesoporous Silica Materials

    Directory of Open Access Journals (Sweden)

    Christophe Detavernier

    2013-02-01

    Full Text Available To use mesoporous silicas as low-k materials, the pore entrances must be really small to avoid diffusion of metals that can increase the dielectric constant of the low-k dielectric. In this paper we present a new method to narrow the pores of mesoporous materials through grafting of a cyclic-bridged organosilane precursor. As mesoporous material, the well-studied MCM-41 powder was selected to allow an easy characterization of the grafting reactions. Firstly, the successful grafting of the cyclic-bridged organosilane precursor on MCM-41 is presented. Secondly, it is demonstrated that pore narrowing can be obtained without losing porosity by removing the porogen template after grafting. The remaining silanols in the pores can then be end-capped with hexamethyl disilazane (HMDS to make the material completely hydrophobic. Finally, we applied the pore narrowing method on organosilica films to prove that this method is also successful on existing low-k materials.

  4. Gas transport and subsoil pore characteristics

    DEFF Research Database (Denmark)

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

    2013-01-01

    a range of matric potentials. Factor of anisotropy (FA) was determined as the ratio of a given property measured in the horizontal direction to that in the vertical direction. For both soils, ka was anisotropic at some depths (FA<1), while Ds/D0 displayed anisotropy only for the clay soil (FA<1). In...... pore diameter, dB; tortuosity, τ; the number of effective pores per unit area, nB) were calculated using a tortuous tube model at -100 hPa matric potential and blocked air-filled porosity (εb) and pore continuity index (N) were estimated from the relationship between ka and air-filled porosity (εa) for......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 characteristics...

  5. 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.

  6. Influence of pore pressure to the development of a hydraulic fracture in poroelastic medium

    CERN Document Server

    Golovin, Sergey V

    2016-01-01

    In this paper we demonstrate the influence of the pore pressure to the development of a hydraulically-driven fracture in a poroelastic medium. We present a novel numerical model for propagation of a planar hydraulic fracture and prove its correctness by demonstration of the numerical convergence and by comparison with known solutions. The advantage of the algorithm is that it does not require the distinguishing of the fracture's tips and reconstruction of the numerical mesh according to the fracture propagation. Next, we perform a thorough analysis of the interplay of fluid filtration and redistribution of stresses near the fracture. We demonstrate that the fracture length decreases with the increase of the Biot's number (the parameter that determines the contribution of the pore pressure to the stress) and explain this effect by analysing the near-fracture pore pressure, rock deformation and stresses. We conclude, that the correct account for the fluid exchange between the fracture and the rock should be bas...

  7. High temperature ion channels and pores

    Science.gov (United States)

    Kang, Xiaofeng (Inventor); Gu, Li Qun (Inventor); Cheley, Stephen (Inventor); Bayley, Hagan (Inventor)

    2011-01-01

    The present invention includes an apparatus, system and method for stochastic sensing of an analyte to a protein pore. The protein pore may be an engineer protein pore, such as an ion channel at temperatures above 55.degree. C. and even as high as near 100.degree. C. The analyte may be any reactive analyte, including chemical weapons, environmental toxins and pharmaceuticals. The analyte covalently bonds to the sensor element to produce a detectable electrical current signal. Possible signals include change in electrical current. Detection of the signal allows identification of the analyte and determination of its concentration in a sample solution. Multiple analytes present in the same solution may also be detected.

  8. 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. PMID:27529707

  9. Membrane-mediated repulsion between gramicidin pores

    OpenAIRE

    Constantin, Doru

    2015-01-01

    International audience We investigated the X-ray scattering signal of highly aligned multilayers of the zwitterionic lipid 1,2-dilauroyl-sn-glycero-3-phosphatidylcholine containing pores formed by the antimicrobial peptide gramicidin as a function of the peptide/lipid ratio. We are able to obtain information on the structure factor of the pore fluid, which then yields the interaction potential between pores in the plane of the bilayers. Aside from a hard core with a radius close to the geo...

  10. 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 Christopher; 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.

  11. Breast Reconstruction and Prosthesis

    Science.gov (United States)

    ... have breast reconstruction If you choose to have reconstructive surgery, follow these steps: STEP 1 — Ask your doctor to refer you to a plastic surgeon who is an expert in breast reconstruction. ...

  12. DESIGN MANUAL: FINE PORE AERATION SYSTEMS

    Science.gov (United States)

    This manual presents the best current practices for selecting, designing, operating, maintaining, and controlling fine pore aeration systems used in the treatment of municipal wastewater. It was prepared by the American Society of Civil Engineers Committee on Oxygen Transfer unde...

  13. Straight Pore Microfilter with Efficient Regeneration Project

    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...

  14. Straight Pore Microfilter with Efficient Regeneration Project

    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...

  15. OBSERVATIONS OF SAUSAGE MODES IN MAGNETIC PORES

    International Nuclear Information System (INIS)

    We present here evidence for the observation of the magnetohydrodynamic (MHD) sausage modes in magnetic pores in the solar photosphere. Further evidence for the omnipresent nature of acoustic global modes is also found. The empirical decomposition method of wave analysis is used to identify the oscillations detected through a 4170 A 'blue continuum' filter observed with the Rapid Oscillations in the Solar Atmosphere (ROSA) instrument. Out of phase, periodic behavior in pore size and intensity is used as an indicator of the presence of magnetoacoustic sausage oscillations. Multiple signatures of the magnetoacoustic sausage mode are found in a number of pores. The periods range from as short as 30 s up to 450 s. A number of the magnetoacoustic sausage mode oscillations found have periods of 3 and 5 minutes, similar to the acoustic global modes of the solar interior. It is proposed that these global oscillations could be the driver of the sausage-type magnetoacoustic MHD wave modes in pores.

  16. Analysis of a spatially deconvolved solar pore

    CERN Document Server

    Noda, C Quintero; Cobo, B Ruiz; Suematsu, Y; Katsukawa, Y; Ichimoto, K

    2016-01-01

    Solar pores are active regions with large magnetic field strengths and apparent simple magnetic configurations. Their properties resemble the ones found for the sunspot umbra although pores do not show penumbra. Therefore, solar pores present themselves as an intriguing phenomenon that is not completely understood. We examine in this work a solar pore observed with Hinode/SP using two state of the art techniques. The first one is the spatial deconvolution of the spectropolarimetric data that allows removing the stray light contamination induced by the spatial point spread function of the telescope. The second one is the inversion of the Stokes profiles assuming local thermodynamic equilibrium that let us to infer the atmospheric physical parameters. After applying these techniques, we found that the spatial deconvolution method does not introduce artefacts, even at the edges of the magnetic structure, where large horizontal gradients are detected on the atmospheric parameters. Moreover, we also describe the p...

  17. Low Pore Connectivity in Natural Rock

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Qinhong; Ewing, Robert P.; Dultz, Stefan

    2012-05-15

    As repositories for CO₂ and radioactive waste, as oil and gas reservoirs, and as contaminated sites needing remediation, rock formations play a central role in energy and environmental management. The connectivity of the rock's porespace strongly affects fluid flow and solute transport. This work examines pore connectivity and its implications for fluid flow and chemical transport. Three experimental approaches (imbibition, tracer concentration profiles, and imaging) were used in combination with network modeling. In the imbibition results, three types of imbibition slope [log (cumulative imbibition) vs. log (imbibition time)] were found: the classical 0.5, plus 0.26, and 0.26 transitioning to 0.5. The imbibition slope of 0.26 seen in Indiana sandstone, metagraywacke, and Barnett shale indicates low pore connectivity, in contrast to the slope of 0.5 seen in the well-connected Berea sandstone. In the tracer profile work, rocks exhibited different distances to the plateau porosity, consistent with the pore connectivity from the imbibition tests. Injection of a molten metal into connected pore spaces, followed by 2-D imaging of the solidified alloy in polished thin sections, allowed direct assessment of pore structure and lateral connection in the rock samples. Pore-scale network modeling gave results consistent with measurements, confirming pore connectivity as the underlying cause of both anomalous behaviors: imbibition slope not having the classical value of 0.5, and accessible porosity being a function of distance from the edge. A poorly connected porespace will exhibit anomalous behavior in fluid flow and chemical transport, such as a lower imbibition slope (in air–water system) and diffusion rate than expected from classical behavior.

  18. Low pore connectivity in natural rock.

    Science.gov (United States)

    Hu, Qinhong; Ewing, Robert P; Dultz, Stefan

    2012-05-15

    As repositories for CO(2) and radioactive waste, as oil and gas reservoirs, and as contaminated sites needing remediation, rock formations play a central role in energy and environmental management. The connectivity of the rock's porespace strongly affects fluid flow and solute transport. This work examines pore connectivity and its implications for fluid flow and chemical transport. Three experimental approaches (imbibition, tracer concentration profiles, and imaging) were used in combination with network modeling. In the imbibition results, three types of imbibition slope [log (cumulative imbibition) vs. log (imbibition time)] were found: the classical 0.5, plus 0.26, and 0.26 transitioning to 0.5. The imbibition slope of 0.26 seen in Indiana sandstone, metagraywacke, and Barnett shale indicates low pore connectivity, in contrast to the slope of 0.5 seen in the well-connected Berea sandstone. In the tracer profile work, rocks exhibited different distances to the plateau porosity, consistent with the pore connectivity from the imbibition tests. Injection of a molten metal into connected pore spaces, followed by 2-D imaging of the solidified alloy in polished thin sections, allowed direct assessment of pore structure and lateral connection in the rock samples. Pore-scale network modeling gave results consistent with measurements, confirming pore connectivity as the underlying cause of both anomalous behaviors: imbibition slope not having the classical value of 0.5, and accessible porosity being a function of distance from the edge. A poorly connected porespace will exhibit anomalous behavior in fluid flow and chemical transport, such as a lower imbibition slope (in air-water system) and diffusion rate than expected from classical behavior. PMID:22507286

  19. Low pore connectivity in natural rock

    Science.gov (United States)

    Hu, Qinhong; Ewing, Robert P.; Dultz, Stefan

    2012-05-01

    As repositories for CO2 and radioactive waste, as oil and gas reservoirs, and as contaminated sites needing remediation, rock formations play a central role in energy and environmental management. The connectivity of the rock's porespace strongly affects fluid flow and solute transport. This work examines pore connectivity and its implications for fluid flow and chemical transport. Three experimental approaches (imbibition, tracer concentration profiles, and imaging) were used in combination with network modeling. In the imbibition results, three types of imbibition slope [log (cumulative imbibition) vs. log (imbibition time)] were found: the classical 0.5, plus 0.26, and 0.26 transitioning to 0.5. The imbibition slope of 0.26 seen in Indiana sandstone, metagraywacke, and Barnett shale indicates low pore connectivity, in contrast to the slope of 0.5 seen in the well-connected Berea sandstone. In the tracer profile work, rocks exhibited different distances to the plateau porosity, consistent with the pore connectivity from the imbibition tests. Injection of a molten metal into connected pore spaces, followed by 2-D imaging of the solidified alloy in polished thin sections, allowed direct assessment of pore structure and lateral connection in the rock samples. Pore-scale network modeling gave results consistent with measurements, confirming pore connectivity as the underlying cause of both anomalous behaviors: imbibition slope not having the classical value of 0.5, and accessible porosity being a function of distance from the edge. A poorly connected porespace will exhibit anomalous behavior in fluid flow and chemical transport, such as a lower imbibition slope (in air-water system) and diffusion rate than expected from classical behavior.

  20. Hydrochromic Approaches to Mapping Human Sweat Pores.

    Science.gov (United States)

    Park, Dong-Hoon; Park, Bum Jun; Kim, Jong-Man

    2016-06-21

    Hydrochromic materials, which undergo changes in their light absorption and/or emission properties in response to water, have been extensively investigated as humidity sensors. Recent advances in the design of these materials have led to novel applications, including monitoring the water content of organic solvents, water-jet-based rewritable printing on paper, and hydrochromic mapping of human sweat pores. Our interest in this area has focused on the design of hydrochromic materials for human sweat pore mapping. We recognized that materials appropriate for this purpose must have balanced sensitivities to water. Specifically, while they should not undergo light absorption and/or emission transitions under ambient moisture conditions, the materials must have sufficiently high hydrochromic sensitivities that they display responses to water secreted from human sweat pores. In this Account, we describe investigations that we have carried out to develop hydrochromic substances that are suitable for human sweat pore mapping. Polydiacetylenes (PDAs) have been extensively investigated as sensor matrices because of their stimulus-responsive color change property. We found that incorporation of headgroups composed of hygroscopic ions such as cesium or rubidium and carboxylate counterions enables PDAs to undergo a blue-to-red colorimetric transition as well as a fluorescence turn-on response to water. Very intriguingly, the small quantities of water secreted from human sweat pores were found to be sufficient to trigger fluorescence turn-on responses of the hydrochromic PDAs, allowing precise mapping of human sweat pores. Since the hygroscopic ion-containing PDAs developed in the initial stage display a colorimetric transition under ambient conditions that exist during humid summer periods, a new system was designed. A PDA containing an imidazolium ion was found to be stable under all ambient conditions and showed temperature-dependent hydrochromism corresponding to a

  1. Analysis of a spatially deconvolved solar pore

    Science.gov (United States)

    Quintero Noda, C.; Shimizu, T.; Cobo, B. Ruiz; Suematsu, Y.; Katsukawa, Y.; Ichimoto, K.

    2016-05-01

    Solar pores are active regions with large magnetic field strengths and apparent simple magnetic configurations. Their properties resemble the ones found for the sunspot umbra although pores do not show penumbra. Therefore, solar pores present themselves as an intriguing phenomenon that is not completely understood. We examine in this work a solar pore observed with Hinode/SP using two state of the art techniques. The first one is the spatial deconvolution of the spectropolarimetric data that allows removing the stray light contamination induced by the spatial point spread function of the telescope. The second one is the inversion of the Stokes profiles assuming local thermodynamic equilibrium that let us to infer the atmospheric physical parameters. After applying these techniques, we found that the spatial deconvolution method does not introduce artefacts, even at the edges of the magnetic structure, where large horizontal gradients are detected on the atmospheric parameters. Moreover, we also describe the physical properties of the magnetic structure at different heights finding that, in the inner part of the solar pore, the temperature is lower than outside, the magnetic field strength is larger than 2 kG and unipolar, and the LOS velocity is almost null. At neighbouring pixels, we found low magnetic field strengths of same polarity and strong downward motions that only occur at the low photosphere, below the continuum optical depth log τ = -1. Finally, we studied the spatial relation between different atmospheric parameters at different heights corroborating the physical properties described before.

  2. Analysis of a spatially deconvolved solar pore

    Science.gov (United States)

    Quintero Noda, C.; Shimizu, T.; Ruiz Cobo, B.; Suematsu, Y.; Katsukawa, Y.; Ichimoto, K.

    2016-08-01

    Solar pores are active regions with large magnetic field strengths and apparent simple magnetic configurations. Their properties resemble the ones found for the sunspot umbra although pores do not show penumbra. Therefore, solar pores present themselves as an intriguing phenomenon that is not completely understood. We examine in this work a solar pore observed with Hinode/SP using two state of the art techniques. The first one is the spatial deconvolution of the spectropolarimetric data that allows removing the stray light contamination induced by the spatial point spread function of the telescope. The second one is the inversion of the Stokes profiles assuming local thermodynamic equilibrium that let us to infer the atmospheric physical parameters. After applying these techniques, we found that the spatial deconvolution method does not introduce artefacts, even at the edges of the magnetic structure, where large horizontal gradients are detected on the atmospheric parameters. Moreover, we also describe the physical properties of the magnetic structure at different heights finding that, in the inner part of the solar pore, the temperature is lower than outside, the magnetic field strength is larger than 2 kG and unipolar, and the line-of-sight velocity is almost null. At neighbouring pixels, we found low magnetic field strengths of same polarity and strong downward motions that only occur at the low photosphere, below the continuum optical depth log τ = -1. Finally, we studied the spatial relation between different atmospheric parameters at different heights corroborating the physical properties described before.

  3. Using BIB-SEM to determine pore morphology and pore size distributions in coal macerals

    Energy Technology Data Exchange (ETDEWEB)

    Giffin, S.; Littke, R. [RWTH Aachen Univ. (Germany). Inst. of Geology and Geochemistry of Petroleum and Coal; Klaver, J.; Urai, J.L. [RWTH Aachen Univ. (Germany). Structural Geology, Tectonics and Geomechanics

    2013-08-01

    The composition of coalbeds is considerably heterogeneous, affecting the transport pathways for fluids within the coal. Transport pathways include cleats and larger pores. However, only a few clues exist as the nature of these pores. This study examines the morphology and distribution of macro- and mesopores in coal samples, using broad ion beam (BIB) milling to prepare relief- and damage-free polished surfaces of coal samples for high-resolution SEM imaging. Broad ion beam milling is advantageous to focused ion beam milling in that a larger surface area can be milled. Combining that with SEM imaging results in a useful tool to study pore morphology and distributions in the size range between 10 nm and 10 {mu}m. Since BIB-sections of a few square millimeters are not large enough to be statistically representative, results cannot be easily interpreted from a coal seam standpoint. Therefore, porosity was investigated as a function of maceral type to characterize pore morphologies. Macerals from the vitrinite and inertinite groups were selected with a known relationship to bedding. BIB-sections were milled parallel to bedding and perpendicular to bedding, and the pores were evaluated in each section. The goal of this study is to (1) qualitatively describe pore morphology with respect to maceral type and (2) quantitatively characterize pore size distributions with respect to maceral and in relationship to bedding. Our results lead to a better understanding of bulk coal porosity due to the visual, spatial representation and quantification of pores in individual macerals. (orig.)

  4. PORE STRUCTURE MODEL OF CEMENT HYDRATES CONSIDERING PORE WATER CONTENT AND REACTION PROCESS UNDER ARBITRARY HUMIDITY

    Science.gov (United States)

    Fujikura, Yusuke; Oshita, Hideki

    A simulation model to estimate the pore structure of cement hydrates by curing in arbitrary relative humidity is presented. This paper describes procedures for predicting phase compositions based on the classical hydration model of Portland cement, calculating the particle size distribution of constituent phases and evaluating the pore size distribution by stereological and statistical considerations. And to estimate the water content in pore structure under any relative humidity, we proposed the simulation model of adsorption isotherm model based on the pore structure. To evaluate the effectiveness of this model, simulation results were compared with experimental results of the pore size distribution measured by mercury porosimetry. As a result, it was found that the experimental and simulated results were in close agreement, and the simulated results indicated characterization of the po re structure of cement hydrates.

  5. Optical detection of pores in adipocyte membrane

    Science.gov (United States)

    Yanina, I. Yu.; Doubrovski, V. A.; Tuchin, V. V.

    2013-08-01

    Structures that can be interpreted as cytoplasm droplets leaking through the membrane are experimentally detected on the membranes of adipocytes using optical digital microscopy. The effect of an aqueous alcohol solution of brilliant green on the amount and sizes of structures is studied. It is demonstrated that the optical irradiation of the adipocytes that are sensitized with the aid of the brilliant green leads to an increase in the amount of structures (pores) after the irradiation. The experimental results confirm the existence of an earlier-proposed effect of photochemical action on the sensitized cells of adipose tissue that involves additional formation of pores in the membrane of the sensitized cell under selective optical irradiation. The proposed method for the detection of micropores in the membrane of adipose tissue based on the detection of the cytoplasm droplets leaking from the cell can be considered as a method for the optical detection of nanosized pores.

  6. Pore pressure enhancements observed on Rio Blanco

    International Nuclear Information System (INIS)

    Measurements were made of the change of in situ pore pressures and the associated accelerations in the saturated clayey silts (ML) of Fawn Creek and Black Sulphur Valleys at 2.1, 4, 7, and 10 km from surface zero. The early pore pressure changes correlated well with accelerations while the later values correlated better with velocities. The pressure changes ranged from 17.1 to 0.36 psi for the peak pressures and from 1.7 to 0.10 psi for the average pressure increases 10 sec after the detonation. Pretest estimates indicated that liquefaction was considered probable but it was not observed and the pore pressure increases were one-quarter or less than those associated with this phenomenon. (auth)

  7. Pore water chemistry of the febex bentonite

    International Nuclear Information System (INIS)

    The knowledge of pore water chemistry in the clay barrier is essential for performance assessment purposes in a nuclear waste repository, since the pore water composition controls the processes involved in the release and transport of the radionuclides. The methodology followed to define the representative composition of the FEBEX bentonite pore water is presented in this paper. A series of bentonite-water interaction tests have been performed with the aim of providing a database on the main chemical parameters of the bentonite. These tests were carried out both with high solid to liquid (s:l) ratios (squeezing tests) and low s:l ratios (aqueous extracts tests). The exchangeable cations have also been analyzed to determine the selectivity coefficient of the exchange reactions. To complete the data set, a physical and mineralogical characterization of the bentonite was made. The most significant bentonite-water interaction processes controlling the chemistry of the system was identified. The ion concentrations basically depend on the s:l ratio of the system, and the pore water composition is controlled by the dissolution of chlorides, dissolution/precipitation of carbonates and sulphates and the cation exchange reactions in the smectite. The bentonite/water system was modelled with the PHREEQC2 program to obtain the best possible estimation of the pore water composition for initial conditions of water content (=14%), after checking the conceptual model with the experimental results. The model predictions fitted satisfactorily with the experimental data at low s:l ratios. At high s:l ratios, the modelled results agree adequately, except for the sulphate content, which could be affected by the effective porosity, anion exclusion or stagnant zones not taken into account in the model. According to the model, the FEBEX bentonite pore water at 14% moisture is a sodium-chloride type, with an ionic strength of 0.25 M and pH of 7.78. Copyright (2001) Material Research

  8. 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

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

    Directory of Open Access Journals (Sweden)

    Zizhen Wang

    Full Text Available 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.

  10. 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 H...

  11. 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...

  12. Observations of sausage modes in magnetic pores

    CERN Document Server

    Morton, R J; Jess, D B; Mathioudakis, M

    2010-01-01

    We present here evidence for the observation of the magneto-hydrodynamic (MHD) sausage modes in magnetic pores in the solar photosphere. Further evidence for the omnipresent nature of acoustic global modes is also found. The empirical decomposition method of wave analysis is used to identify the oscillations detected through a 4170 {\\AA} 'blue continuum' filter observed with the Rapid Oscillations in the Solar Atmosphere (ROSA) instrument. Out of phase, periodic behavior in pore size and intensity is used as an indicator of the presence of magneto-acoustic sausage oscillations. Multiple signatures of the magneto-acoustic sausage mode are found in a number of pores. The periods range from as short as 30 s up to 450 s. A number of the magneto-acoustic sausage mode oscillations found have periods of 3 and 5 minutes, similar to the acoustic global modes of the solar interior. It is proposed that these global oscillations could be the driver of the sausage type magneto-acoustic MHD wave modes in pores.

  13. Silicon Pore Optics development for ATHENA

    DEFF Research Database (Denmark)

    Collon, Maximilien J.; Vacanti, Giuseppe; Guenther, Ramses;

    2015-01-01

    meet the science requirements of large effective area (1-2 m(2) at a few keV) at a focal length of 12 m. To meet the high angular resolution (5 arc seconds) requirement the X-ray lens will also need to be very accurate. Silicon Pore Optics (SPO) technology has been invented to enable building such a...

  14. Multi-scale simulation of capillary pores and gel pores in Portland cement paste

    OpenAIRE

    Gao, Peng; YE, guang; Wei, Jiangxiong; Yu, Qijun

    2015-01-01

    The microstructures of Portland cement paste (water to cement ratio is 0.4, curing time is from 1 day to 28 days) are simulated based on the numerical cement hydration model, HUMOSTRUC3D (van Breugel, 1991; Koenders, 1997; Ye, 2003). The nanostructures of inner and outer C-S-H are simulated by the packing of monosized (5 nm) spheres. The pore structures (capillary pores and gel pores) of Portland cement paste are established by upgrading the simulated nanostructures of C-S-H to th...

  15. Breast Reconstruction After Mastectomy

    Science.gov (United States)

    ... reconstruction with or without radiotherapy. Current Opinion in Obstetrics and Gynecology 2011;23(1):44–50. [PubMed Abstract] Barry M, Kell MR. Radiotherapy and breast reconstruction: a meta-analysis. Breast ...

  16. Pore Structure of Cement Pastes Blended with Volcanic Rock

    Institute of Scientific and Technical Information of China (English)

    YU Lehua; ZHOU Shuangxi; LI Liling

    2016-01-01

    The pore parameters of cement pastes blended with volcanic rock at the curing age of 1, 28 and 90 d were de-termined by a mercury intrusion porosimetry. The pore structure of the pastes was characterized through the analysis of porosity, average pore diameter, the most probable pore aperture, pore size distribution, as well as total pore volume. For the improvement of mechanical property and durability of cement-based material, the correlation of the formed pore structure with hydration time and replacement level of volcanic rock for cement was revealed. The results indicate that volcanic rock can diminish porosity and reduce pore size in cement paste when curing time prolongs, which is particu-larly prominent with replacement level of less than 20% in late period. The more harmful pores (i.e., capillary pore) are gradually transformed into harmless pore (i.e., gel pores or micropore), even fully filled and disappeared when hydration products increase. The pore structure of the cement paste is thus refined. The beneficial effect of volcanic rock on the pore structure of cement paste could enhance the mechanical property and durability of cement-based material.

  17. Freeze-cast alumina pore networks: Effects of freezing conditions and dispersion medium

    Energy Technology Data Exchange (ETDEWEB)

    Miller, S. M.; Xiao, X.; Faber, K. T.

    2015-11-01

    Alumina ceramics were freeze-cast from water- and camphene-based slurries under varying freezing conditions and examined using X-ray computed tomography (XCT). Pore network characteristics, i.e., porosity, pore size, geometric surface area, and tortuosity, were measured from XCT reconstructions and the data were used to develop a model to predict feature size from processing conditions. Classical solidification theory was used to examine relationships between pore size, temperature gradients, and freezing front velocity. Freezing front velocity was subsequently predicted from casting conditions via the two-phase Stefan problem. Resulting models for water-based samples agreed with solidification-based theories predicting lamellar spacing of binary eutectic alloys, and models for camphene-based samples concurred with those for dendritic growth. Relationships between freezing conditions and geometric surface area were also modeled by considering the inverse relationship between pore size and surface area. Tortuosity was determined to be dependent primarily on the type of dispersion medium. (C) 2015 Elsevier Ltd. All rights reserved.

  18. Lattice Boltzmann simulation of gas-solid adsorption processes at pore scale level

    Science.gov (United States)

    Zhou, L.; Qu, Z. G.; Chen, L.; Tao, W. Q.

    2015-11-01

    A two-dimensional lattice Boltzmann (LB) approach was established to implement kinetic concentration boundary conditions in interfacial mass-transfer processes and to simulate the adsorption process in porous media at pore scale and mesoscopic levels. A general treatment was applied to conduct three types of concentration boundary conditions effectively and accurately. Applicability for adsorption was verified by two benchmark examples, which were representative of the interparticle mass transport and intraparticle mass transport in the adsorption system, respectively. The gas-solid adsorption process in reconstructed porous media at the pore scale level was numerically investigated. Mass-transfer processes of the adsorption reaction were simulated by executing Langmuir adsorption kinetics on surfaces of adsorbent particles. Meanwhile, the homogeneous solid diffusion model (HSDM) was used for mass transport in interior particles. The transient adsorbed amount was obtained in detail, and the impact of flow condition, porosity, and adsorbent particle size on the entire dynamic adsorption performance was investigated. The time needed to approach steady state decreased with increased fluid velocity. Transient adsorption capability and time consumption to equilibrium were nearly independent of porosity, whereas increasing pore size led to a moderating adsorption rate and more time was consumed to approach the saturation adsorption. Benefiting from the advantages of the LB method, both bulk and intraparticle mass transfer performances during adsorption can be obtained using the present pore scale approach. Thus, interparticle mass transfer and intraparticle mass transfer are the two primary segments, and intraparticle diffusion has the dominant role.

  19. Surfaces, Digitisations and Reconstructions

    DEFF Research Database (Denmark)

    Christensen, Sabrina Tang

    2015-01-01

    We present a new digital reconstruction of r-regular sets in three-dimensional Euclidean space. We introduce a vector field and analyse the relation between the topologies of the boundaries of the r-regular set and its reconstruction. This reconstruction can be carried out faster than prior model...

  20. 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 and...... wave damping in the core and important for the scaling of core materials in small scale hydraulic models. The main objectives are to study and examine the wave damping in the core of rubble mound breakwater models. the acquired test results are compared with results available from the literature, and...... compared to a damping model presented by Burcharth et al. (1999). Reasonable agreement is found when considering the difference in the grading and uniformity of the model core materials. Comparison between results obtained from small and large scale model tests showed no clear evidence of scale effects....

  1. 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

  2. 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 by a...... valuable knowledge of SCMs, which is relevant for performance based design of concrete structures. In addition, the thesis provides guidelines for porosity investigations with focus on the applicability of the methods and sources of error. Pore structure was here determined by several methods, mercury...... 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, the...

  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. Active Pore Volume in Danish Peat Soils

    DEFF Research Database (Denmark)

    Forsmann, Ditte M.; Kjærgaard, Charlotte

    2012-01-01

    environment. Lowland soils are primarily peat soils, and only a minor part of the total soil volume of peat soils is occupied by macropores (>30 µm). Since water primarily flows in these macropores, the majority of the soil matrix is bypassed (the immobile domain). Phosphorus released in the immobile domain...... is not actively transported out of the system, but is only transported via diffusion, which is a very slow process. Thus it is interesting to investigate the size of the active pore volume in peat soils. The hypothesis of this study is that the active pores volume of a peat soil can be expressed using bulk...... density as a key parameter. This hypothesis is investigated using intact soil cores (d:6 cm; h: 15 cm) from 20 Danish peat soil locations. The volume of macropores was determined for samples, drained to a matrix potential of pF 2, using a pycnometer. Furthermore, retention curves were conducted using 100...

  5. The Nuclear Pore Complex and Nuclear Transport

    OpenAIRE

    Wente, Susan R.; Rout, Michael P

    2010-01-01

    Internal membrane bound structures sequester all genetic material in eukaryotic cells. The most prominent of these structures is the nucleus, which is bounded by a double membrane termed the nuclear envelope (NE). Though this NE separates the nucleoplasm and genetic material within the nucleus from the surrounding cytoplasm, it is studded throughout with portals called nuclear pore complexes (NPCs). The NPC is a highly selective, bidirectional transporter for a tremendous range of protein and...

  6. Pores and Void in Asclepiades’ Physical Theory

    OpenAIRE

    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 f...

  7. The pore dimensions of gramicidin A.

    OpenAIRE

    Smart, O S; Goodfellow, J. M.; Wallace, B.A.

    1993-01-01

    The ion channel forming peptide gramicidin A adopts a number of distinct conformations in different environments. We have developed a new method to analyze and display the pore dimensions of ion channels. The procedure is applied to two x-ray crystal structures of gramicidin that adopt distinct antiparallel double helical dimer conformations and a nuclear magnetic resonance (NMR) structure for the beta6.3 NH2-terminal to NH2-terminal dimer. The results are discussed with reference to ion cond...

  8. Temperature induced pore fluid pressurization in geomaterials

    OpenAIRE

    Ghabezloo, Siavash; Sulem, Jean

    2010-01-01

    International audience The theoretical basis of the thermal response of the fluid-saturated porous materials in undrained condition is presented. It has been demonstrated that the thermal pressurization phenomenon is controlled by the discrepancy between the thermal expansion of the pore fluid and of the solid phase, the stress-dependency of the compressibility and the non-elastic volume changes of the porous material. For evaluation of the undrained thermo-poro-elastic properties of satur...

  9. Morphology of the pore space in claystones – evidence from BIB/FIB ion beam sectioning and cryo-SEM observations

    Directory of Open Access Journals (Sweden)

    G. Desbois

    2009-02-01

    Full Text Available The morphology of pore space has a strong effect on mechanical and transport properties of mudrocks and clay-rich fault gouge, but its characterization has been mostly indirect. We report on a study of Boom clay from a proposed disposal site of radioactive waste (Mol site, Belgium using high resolution SEM at cryogenic temperature, with ion beam cutting to prepare smooth, damage free surfaces. Pores commonly have crack-like tips, preferred orientation parallel to bedding and power law size distribution. We define a number of pore types depending on shape and location in the microstructure: large jagged pores in strain shadows of clastic grains, high aspect ratio pores between similarly oriented phyllosilicate grains and crescent-shaped pores in saddle reefs of folded phyllosilicates. 3-D reconstruction by serial sectioning shows 3-D connectivity of the pore space. These findings call for reinterpretation of traditional pore size distributions calculated from mercury Injection experiments, explain slaking of clays by successive wetting and drying and provide the basis for microstructure-based models of transport in clays.

  10. 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

  11. The Structure of a Melittin-Stabilized Pore

    OpenAIRE

    Leveritt, John M.; Pino-Angeles, Almudena; Lazaridis, Themis

    2015-01-01

    Melittin has been reported to form toroidal pores under certain conditions, but the atomic-resolution structure of these pores is unknown. A 9-μs all-atom molecular-dynamics simulation starting from a closely packed transmembrane melittin tetramer in DMPC shows formation of a toroidal pore after 1 μs. The pore remains stable with a roughly constant radius for the rest of the simulation. Surprisingly, one or two melittin monomers frequently transition between transmembrane and surface states. ...

  12. Atomistic Simulations of Pore Formation and Closure in Lipid Bilayers

    OpenAIRE

    Bennett, W. F. Drew; Sapay, Nicolas; Tieleman, D. Peter

    2014-01-01

    Cellular membranes separate distinct aqueous compartments, but can be breached by transient hydrophilic pores. A large energetic cost prevents pore formation, which is largely dependent on the composition and structure of the lipid bilayer. The softness of bilayers and the disordered structure of pores make their characterization difficult. We use molecular-dynamics simulations with atomistic detail to study the thermodynamics, kinetics, and mechanism of pore formation and closure in DLPC, DM...

  13. Pore Scale View of Fluid Displacement Fronts in Porous Media

    Science.gov (United States)

    Or, D.; Moebius, F.

    2014-12-01

    The macroscopically smooth and regular motion of fluid fronts in porous media is composed of abrupt pore-scale interfacial jumps involving intense interfacial energy release marked by pressure bursts and acoustic emissions. The characteristics of these pore scale events affect residual phase entrapment and the resulting unsaturated transport properties behind the front. Experimental studies using acoustic emissions technique (AE), rapid imaging, and pressure measurements help characterize pore scale processes during drainage and imbibition in model porous media. Imbibition and drainage produce different AE signatures (obeying a power law). For rapid drainage, AE signals persist long after cessation of front motion indicative of redistribution and interfacial relaxation. Rapid imaging revealed that interfacial jumps exceed mean front velocity and are highly inertial (Re>1000). Imaged pore invasion volumes and pore volumes deduced from waiting times between pressure fluctuations were in remarkable agreement with geometric pores. Differences between invaded volumes and geometrical pores increase with increasing capillary numbers due to shorter pore evacuation times and onset of simultaneous invasion events. A new mechanistic model for interfacial motions through a pore-throat network enabled systematic evaluation of inertia in interfacial dynamics. Results suggest that in contrast to great sensitivity of pore scale dynamics to variations in pore geometry and boundary conditions, inertia exerts only a minor effect on average phase entrapment. Pore scale invasion events paint a complex picture of rapid and inertial motions and provide new insights on mechanisms at displacement fronts essential for improving the macroscopic description of multiphase flow in porous media.

  14. Effective Diffusivities of Gases in a Reconstructed Porous Body.

    Czech Academy of Sciences Publication Activity Database

    Čapek, P.; Hejtmánek, Vladimír; Brabec, Libor; Zikánová, Arlette; Kočiřík, Milan

    - : Norhaven Book, 2007 - (Gani, R.; Dam-Johansen, K.), s. 389-390 ISBN 978-87-91435-56-0. [European Congress of Chemical Engineering ECCE-6. Copenhagen (DK), 16.09.2007-20.09.2007] R&D Projects: GA ČR(CZ) GA203/05/0347 Institutional research plan: CEZ:AV0Z40720504; CEZ:AV0Z40400503 Keywords : stochastic reconstruction * pore network * random walk Subject RIV: CF - Physical ; Theoretical Chemistry

  15. New ultrasonic technique for the study of the pore shape of track-etched pores in polymer films

    Energy Technology Data Exchange (ETDEWEB)

    Gomez Alvarez-Arenas, T.E., E-mail: tgomez@ia.cetef.csic.e [Instituto de Acustica, CSIC, Serrano 144, 28006 Madrid (Spain); Apel, P.Yu.; Orelovitch, O.L. [Flerov Lab. of Nuclear Reactions, JINR, Dubna (Russian Federation); Munoz, M. [Institute of Applied Physics, CSIC, Serrano 144, Madrid (Spain)

    2009-10-15

    A new technique for the study of the pore shape of track-etched pores in polymer films is presented. This technique is based on the use of air-coupled ultrasounds and phase and magnitude spectral analysis. Transmission of ultrasounds through these membranes is made up of two contributions: propagation through the solid part and propagation along the pore channels. A time-domain procedure to separate these to contributions is presented. Sensitivity of ultrasounds propagation in the pore channels to variations of pore shape is studied. Membranes with similar properties (gas flow rate values) but slight differences in the pore shape are studied. The proposed technique reveals to be sensitive to such differences; unlike other techniques, it is capable to provide information in a separate way about pore aperture at the surface and pore diameter inside the membrane, in addition the technique is non-destructive.

  16. Cosmic Tidal Reconstruction

    CERN Document Server

    Zhu, Hong-Ming; Yu, Yu; Er, Xinzhong; Chen, Xuelei

    2015-01-01

    The gravitational coupling of a long wavelength tidal field with small scale density fluctuations leads to anisotropic distortions of the locally measured small scale matter correlation function. Since the local correlation function is statistically isotropic in the absence of such tidal interactions, the tidal distortions can be used to reconstruct the long wavelength tidal field and large scale density field in analogy with the cosmic microwave background lensing reconstruction. In this paper we present in detail a formalism for the cosmic tidal reconstruction and test the reconstruction in numerical simulations. We find that the density field on large scales can be reconstructed with good accuracy and the cross correlation coefficient between the reconstructed density field and the original density field is greater than 0.9 on large scales ($k\\lesssim0.1h/\\mathrm{Mpc}$). This is useful in the 21cm intensity mapping survey, where the long wavelength radial modes are lost due to foreground subtraction proces...

  17. 2D and 3D imaging resolution trade-offs in quantifying pore throats for prediction of permeability

    Energy Technology Data Exchange (ETDEWEB)

    Beckingham, Lauren E.; Peters, Catherine A.; Um, Wooyong; Jones, Keith W.; Lindquist, W.Brent

    2013-09-03

    Although the impact of subsurface geochemical reactions on porosity is relatively well understood, changes in permeability remain difficult to estimate. In this work, pore-network modeling was used to predict permeability based on pore- and pore-throat size distributions determined from analysis of 2D scanning electron microscopy (SEM) images of thin sections and 3D X-ray computed microtomography (CMT) data. The analyzed specimens were a Viking sandstone sample from the Alberta sedimentary basin and an experimental column of reacted Hanford sediments. For the column, a decrease in permeability due to mineral precipitation was estimated, but the permeability estimates were dependent on imaging technique and resolution. X-ray CT imaging has the advantage of reconstructing a 3D pore network while 2D SEM imaging can easily analyze sub-grain and intragranular variations in mineralogy. Pore network models informed by analyses of 2D and 3D images at comparable resolutions produced permeability esti- mates with relatively good agreement. Large discrepancies in predicted permeabilities resulted from small variations in image resolution. Images with resolutions 0.4 to 4 lm predicted permeabilities differ- ing by orders of magnitude. While lower-resolution scans can analyze larger specimens, small pore throats may be missed due to resolution limitations, which in turn overestimates permeability in a pore-network model in which pore-to-pore conductances are statistically assigned. Conversely, high-res- olution scans are capable of capturing small pore throats, but if they are not actually flow-conducting predicted permeabilities will be below expected values. In addition, permeability is underestimated due to misinterpreting surface-roughness features as small pore throats. Comparison of permeability pre- dictions with expected and measured permeability values showed that the largest discrepancies resulted from the highest resolution images and the best predictions of

  18. Re-construction

    OpenAIRE

    Bernadette Marie Devilat

    2013-01-01

    Re-construct: to build again. The necessary reconstruction process after an earthquake can be seen as an opportunity to improve previous conditions. All damaged buildings undergo a renovation process in which every piece is carefully returned to its original place. The photograph shows roof reconstruction work in San Pedro de Alcántara, a heritage area in the central valley of Chile, which was particularly affected by the 2010 earthquake. 

  19. Flexor pulley reconstruction.

    Science.gov (United States)

    Dy, Christopher J; Daluiski, Aaron

    2013-05-01

    Flexor pulley reconstruction is a challenging surgery. Injuries often occur after traumatic lacerations or forceful extension applied to an acutely flexed finger. Surgical treatment is reserved for patients with multiple closed pulley ruptures, persistent pain, or dysfunction after attempted nonoperative management of a single pulley rupture, or during concurrent or staged flexor tendon repair or reconstruction. If the pulley cannot be repaired primarily, pulley reconstruction can be performed using graft woven into remnant pulley rim or looping graft around the phalanx. Regardless of the reconstructive technique, the surgeon should emulate the length, tension, and glide of the native pulley. PMID:23660059

  20. 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.

  1. Visualization of pore space in the rocks

    Czech Academy of Sciences Publication Activity Database

    Staš, Lubomír; Zajícová, Vendula; Georgiovská, Lucie; Souček, Kamil

    Krakow: Akademia górniczo-hutnicza Im. Stanislawa Staszica w Krakowie, 2015 - (Tomach, P.), s. 44-51 ISBN 978-83-930353-5-9. [Międzynarodowa Konferencja - TECHNIKI URABIANIA /9./. Krynica (PL), 29.09.2015-02.10.2015] R&D Projects: GA MŠk ED2.1.00/03.0082; GA MŠk(CZ) LO1406 Institutional support: RVO:68145535 Keywords : X-ray CT analysis * pore space * rocks Subject RIV: DH - Mining, incl. Coal Mining

  2. Cephalic sensorial pores in galaxiid fishes from Chile (Osmeriformes: Galaxiidae

    Directory of Open Access Journals (Sweden)

    Sylvia Sáez

    2014-11-01

    Full Text Available The number and arrangement of the cephalic pores of the lateral line in Chilean fishes of the family Galaxiidae, were studied. The study showed that Brachygalaxias differs from Galaxias, in the absence of mandibular pores and in pore number reductions in the preopeopercular series. The most important variations were recorded in Galaxias globiceps and G. platei. The former species differed from the other species in the absence of a pore in the preopercular series, while in G. platei the supraorbital pore situated behind the eye was the main distinctive feature observed, in contrast to the upper position observed in the other species studied. A taxonomic key using cephalic sensory pores is proposed. These results indicate that the cephalic sensorial pores of the lateral line are a useful taxonomic character in the improvement of the diagnosis of galaxiid fishes -and in taxonomic and systematic studies among family Galaxiidae members.

  3. Different Routes to the Pore Engineering of Spherical MCM-41

    Institute of Scientific and Technical Information of China (English)

    LIU Shi-quan; E F Vansant; JIANG Min-hua

    2003-01-01

    Different routes,including the replacements of the template,addition of pore expander and hydrothermal post-synthesis treatment have been used for the pore engineering of spherical MCM-41.A comparison among the pore engineering effects of these methods has been made.The results show that the hydrothermal post-synthesis treatment affords the synthesized material with a larger pore size and narrow pore size distribution without changing the spherical morphology.As far as the pore-size expansion is concerned,the addition of DMTA is the most effective one,but this might be limited by the spherical morphology.Combining the replacement of C16TMABr with the Gemini surfactant GEM 16-8-16 with an addition of DMTA gives rise to the largest pore volume and surface area.

  4. Wave-induced pore water pressure in marine cohesive soils

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    Cyclic triaxial tests and numerical analyses were undertaken, in order to evaluate the wave-induced pore water pressure in seabed sediments in the Hangzhou Bay. The cyclic triaxial tests indicate that the rate of pore water pressure generation in cohesive soils decreases with time, and the development of the pore water pressure can be represented by a hyperbolic curve. Numerical analyses, taking into account the generation and dissipation of pore water pressure simultaneously, suggest that the pore water pressure buildup in cohesive soils may increase with time continuously until the pore water pressure ratio approaches to 1, or it may decrease after a certain time, which is controlled by drain conditions. These phenomena are different from those in sands. For waves with a return period of 100 a in the Hangzhou Bay, ifthe wave duration is more than 60 h, then the pore water pressure ratio will be close to 1 and soil fabric failure will take place.

  5. Bimodal mesoporous silica with bottleneck pores.

    Science.gov (United States)

    Reber, M J; Brühwiler, D

    2015-11-01

    Bimodal mesoporous silica consisting of two sets of well-defined mesopores is synthesized by a partial pseudomorphic transformation of an ordered mesoporous starting material (SBA-15 type). The introduction of a second set of smaller mesopores (MCM-41 type) establishes a pore system with bottlenecks that restricts the access to the core of the bimodal mesoporous silica particles. The particle size and shape of the starting material are retained, but micropores present in the starting material disappear during the transformation, leading to a true bimodal mesoporous product. A varying degree of transformation allows the adjustment of the pore volume contribution of the two mesopore domains. Information on the accessibility of the mesopores is obtained by the adsorption of fluorescence-labeled poly(amidoamine) dendrimers and imaging by confocal laser scanning microscopy. This information is correlated with nitrogen sorption data to provide insights regarding the spatial distribution of the two mesopore domains. The bimodal mesoporous materials are excellent model systems for the investigation of cavitation effects in nitrogen desorption isotherms. PMID:26399172

  6. Self-healing of pores in PLGAs.

    Science.gov (United States)

    Huang, J; Mazzara, J M; Schwendeman, S P; Thouless, M D

    2015-05-28

    Self-healing of pores in Poly(lactic-co-glycolic acid)s (PLGA) plays an important role in the encapsulation and controlled release of drugs from PLGA microparticles. Despite the importance of this phenomenon, neither the mechanics of the deformation nor the material properties that control it have been fully studied. In this study, the material properties of PLGA have been characterized using mechanical tests, and a finite-element model has been developed to predict how pores heal. This model assumes that the healing process occurs by viscous flow resulting from the deviatoric stress field induced by the interaction between the surface curvature and the surface tension of the PLGA. The simulations, which incorporate measured material properties, show good agreement with experimental observations. However, annealing processes that occur over prolonged times increase the viscosity and slow the healing times of PLGA films at intermediate temperatures above the glass-transition temperature. These findings may be reasonably applied towards the prediction of healing processes in PLGA and in related biomaterials for important biomedical applications such as drug delivery. PMID:25701611

  7. Temperature induced pore fluid pressurization in geomaterials

    CERN Document Server

    Ghabezloo, Siavash

    2010-01-01

    The theoretical basis of the thermal response of the fluid-saturated porous materials in undrained condition is presented. It has been demonstrated that the thermal pressurization phenomenon is controlled by the discrepancy between the thermal expansion of the pore fluid and of the solid phase, the stress-dependency of the compressibility and the non-elastic volume changes of the porous material. For evaluation of the undrained thermo-poro-elastic properties of saturated porous materials in conventional triaxial cells, it is important to take into account the effect of the dead volume of the drainage system. A simple correction method is presented to correct the measured pore pressure change and also the measured volumetric strain during an undrained heating test. It is shown that the porosity of the tested material, its drained compressibility and the ratio of the volume of the drainage system to the one of the tested sample, are the key parameters which influence the most the error induced on the measuremen...

  8. Atmosphere above a large solar pore

    CERN Document Server

    Sobotka, M; Jurcak, J; Heinzel, P; Del Moro, D

    2013-01-01

    A large solar pore with a granular light bridge was observed on October 15, 2008 with the IBIS spectrometer at the Dunn Solar Telescope and a 69-min long time series of spectral scans in the lines Ca II 854.2 nm and Fe I 617.3 nm was obtained. The intensity and Doppler signals in the Ca II line were separated. This line samples the middle chromosphere in the core and the middle photosphere in the wings. Although no indication of a penumbra is seen in the photosphere, an extended filamentary structure, both in intensity and Doppler signals, is observed in the Ca II line core. An analysis of morphological and dynamical properties of the structure shows a close similarity to a superpenumbra of a sunspot with developed penumbra. A special attention is paid to the light bridge, which is the brightest feature in the pore seen in the Ca II line centre and shows an enhanced power of chromospheric oscillations at 3-5 mHz. Although the acoustic power flux in the light bridge is five times higher than in the "quiet" chr...

  9. Image Reconstruction. Chapter 13

    International Nuclear Information System (INIS)

    This chapter discusses how 2‑D or 3‑D images of tracer distribution can be reconstructed from a series of so-called projection images acquired with a gamma camera or a positron emission tomography (PET) system [13.1]. This is often called an ‘inverse problem’. The reconstruction is the inverse of the acquisition. The reconstruction is called an inverse problem because making software to compute the true tracer distribution from the acquired data turns out to be more difficult than the ‘forward’ direction, i.e. making software to simulate the acquisition. There are basically two approaches to image reconstruction: analytical reconstruction and iterative reconstruction. The analytical approach is based on mathematical inversion, yielding efficient, non-iterative reconstruction algorithms. In the iterative approach, the reconstruction problem is reduced to computing a finite number of image values from a finite number of measurements. That simplification enables the use of iterative instead of mathematical inversion. Iterative inversion tends to require more computer power, but it can cope with more complex (and hopefully more accurate) models of the acquisition process

  10. Bitzer's Model Reconstructed.

    Science.gov (United States)

    Lybarger, Scott; Smith, Craig R.

    1996-01-01

    Reconstructs Lloyd Bitzer's situational model to serve as a guide for the generation of multiperspectival critical assessments of rhetorical discourse. Uses two of President Bush's speeches on the drug crisis to illustrate how the reconstructed model can account for such modern problems as multiple audiences, perceptions, and exigencies. (PA)

  11. Geochemistry of Lake Van pore water and sediment, or How to distinguish climatic from diagenetic signals?

    Science.gov (United States)

    Kwiecien, Ola; Tomonaga, Yama; Brennwald, Matthias S.; Randlett, Marie-Eve; Peterse, Francien; Bechtel, Achim; van der Meer, Marcel; Stockhecke, Mona; Bucher, Stefan; Anselmetti, Flavio; Litt, Thomas; Schubert, Carsten J.; Kipfer, Rolf

    2014-05-01

    Lake Van is a terminal soda lake located in a semiarid region (eastern Anatolia, Turkey). Its geographical setting makes Lake Van a superb archive of paleoenvironmental changes. One of the aims of the ICDP PALEOVAN project is the reconstruction of the hydrological and climatic variability in the eastern Mediterranean region and the Near East on glacial/interglacial and millennial time scales. We applied a multi-proxy approach to distinguish the environmental synsedimentary imprint and the postsedimentary diagenetic changes. Microfaunal evidence, carbonate isotopic composition (d18O, d13C), molecular proxies (BIT, ACE) and isotopic composition of lipid biomarkers (dD) are matched with isotopic and elemental composition (d18O, dD, Mg, Ca, Sr, Cl, salinity) of sediment pore-water. An excellent correspondence between these proxies indicates that the elemental composition of pore water in Lake Van does not result from diagenetic changes, but, unlike in many cases known from marine environment, represents to some extent relicts of 'paleolake-water'. On the contrary, the stable isotopic composition of the pore water (d18O, dD) seems to reflect more recent hydrological regime dominated by precipitation/evaporation changes. As salinity and chlorine concentration changes mimic the isotopic composition of biomarkers for the last 140 ka, we use pore-water data to quantify changes in the lake level. Our reconstruction (Tomonaga et al., in review) is in line with previous studies on lake terraces (Kuzucuoglu et al., 2010) and seismic surveys (Cukur et al., 2012) showing a major transgression of up to 105 m with respect to the current lake level during the last interglacial (MIS5e), and a major regression of ~145 m at ~30 ka BP during the last glacial. Kuzucuoglu et al. (2010) Formation of the Upper Pleistocene terraces of Lake Van (Turkey). Journal of Quaternary Science 25, 1124-1137. Cukur et al. (2012) Sedimentary evolution of Lake Van (Eastern Turkey) reconstructed from high

  12. Scaffolds and cells for tissue regeneration: different scaffold pore sizes-different cell effects.

    Science.gov (United States)

    Bružauskaitė, Ieva; Bironaitė, Daiva; Bagdonas, Edvardas; Bernotienė, Eiva

    2016-05-01

    During the last decade biomaterial sciences and tissue engineering have become new scientific fields supplying rising demand of regenerative therapy. Tissue engineering requires consolidation of a broad knowledge of cell biology and modern biotechnology investigating biocompatibility of materials and their application for the reconstruction of damaged organs and tissues. Stem cell-based tissue regeneration started from the direct cell transplantation into damaged tissues or blood vessels. However, it is difficult to track transplanted cells and keep them in one particular place of diseased organ. Recently, new technologies such as cultivation of stem cell on the scaffolds and subsequently their implantation into injured tissue have been extensively developed. Successful tissue regeneration requires scaffolds with particular mechanical stability or biodegradability, appropriate size, surface roughness and porosity to provide a suitable microenvironment for the sufficient cell-cell interaction, cell migration, proliferation and differentiation. Further functioning of implanted cells highly depends on the scaffold pore sizes that play an essential role in nutrient and oxygen diffusion and waste removal. In addition, pore sizes strongly influence cell adhesion, cell-cell interaction and cell transmigration across the membrane depending on the various purposes of tissue regeneration. Therefore, this review will highlight contemporary tendencies in application of non-degradable scaffolds and stem cells in regenerative medicine with a particular focus on the pore sizes significantly affecting final recover of diseased organs. PMID:26091616

  13. The CMS Reconstruction Software

    Science.gov (United States)

    Lange, David J.; CMS Collaboration

    2011-12-01

    We report on the status and plans for the event reconstruction software of the CMS experiment. The CMS reconstruction algorithms are the basis for a wide range of data analysis approaches currently under study by the CMS collaboration using the first high-energy run of the LHC. These algorithms have been primarily developed and validated using simulated data samples, and are now being commissioned with LHC proton-proton collision data samples. The CMS reconstruction is now operated routinely on all events triggered by the CMS detector, both in a close to real-time prompt reconstruction processing and in frequent passes over the full recorded CMS data set. We discuss the overall software design, development cycle, computational requirements and performance, recent operational performance, and planned improvements of the CMS reconstruction software.

  14. Computational modeling of electrokinetic transport in random networks of micro-pores and nano-pores

    Science.gov (United States)

    Alizadeh, Shima; Mani, Ali

    2014-11-01

    A reduced order model has been developed to study the nonlinear electrokinetic behaviors emerging in the transport of ionic species through micro-scale and nano-scale porous media. In this approach a porous structure is modeled as a network of long and thin pores. By assuming transport equilibrium in the thin dimensions for each pore, a 1D transport equation is developed in the longitudinal direction covering a wide range of conditions including extreme limits of thick and thin electric double layers. This 1D model includes transport via diffusion, electromigration and wide range of advection mechanisms including pressure driven flow, electroosmosis, and diffusion osmosis. The area-averaged equations governing the axial transport from different pores are coupled at the pore intersections using the proper conservation laws. Moreover, an asymptotic treatment has been included in order to remove singularities in the limit of small concentration. The proposed method provides an efficient framework for insightful simulations of porous electrokinetic systems with applications in water desalination and energy storage. PhD student in Mechanical Engineering, Stanford University. She received her Master's degree in Mechanical Engineering from Stanford at 2013. Her research interests include CFD, high performance computing, and optimization.

  15. Electrokinetic induced solute dispersion in porous media; pore network modeling

    Science.gov (United States)

    Li, Shuai; Schotting, Ruud; Raoof, Amir

    2013-04-01

    Electrokinetic flow plays an important role in remediation process, separation technique, and chromatography. The solute dispersion is a key parameter to determine transport efficiency. In this study, we present the electrokinetic effects on solute dispersion in porous media at the pore scale, using a pore network model. The analytical solution of the electrokinetic coupling coefficient was obtained to quantity the fluid flow velocity in a cylinder capillary. The effect of electrical double layer on the electrokinetic coupling coefficient was investigated by applying different ionic concentration. By averaging the velocity over cross section within a single pore, the average flux was obtained. Applying such single pore relationships, in the thin electrical double layer limit, to each and every pore within the pore network, potential distribution and the induced fluid flow was calculated for the whole domain. The resulting pore velocities were used to simulate solute transport within the pore network. By averaging the results, we obtained the breakthrough curve (BTC) of the average concentration at the outlet of the pore network. Optimizing the solution of continuum scale advection-dispersion equation to such a BTC, solute dispersion coefficient was estimated. We have compared the dispersion caused by electrokinetic flow and pure pressure driven flow under different Peclet number values. In addition, the effect of microstructure and topological properties of porous media on fluid flow and solute dispersion is presented, mainly based on different pore coordination numbers.

  16. Characterization of Reconstructed Basins Using Pattern Spectrum Procedure

    Directory of Open Access Journals (Sweden)

    P. Radhakrishnan

    2005-01-01

    Full Text Available Several classical and Fractal binary shapes, which are akin to geophysical shapes such as basins, lakes, and pore-grain spruce, are analyzed and characterized by employing various mathematical morphological transformations, and methods. By employing rhombus, square and octagon structuring elements, these shapes are decomposed into their skeletal networks and their corresponding skeletal network subsets are dilated to the respective degree by these structuring elements in order to reconstruct the original shapes. Furthermore, to test the reconstruction accuracy, the pattern spectrum procedure is applied and sharpness indices were computed. These shapiness indices were considered as a basis to test the reconstruction accuracy in a quantitative manner. A general trend is observed while characterizing the shape-size complexity of these surface water bodies.

  17. Distributed Pore Chemistry in Porous Organic Polymers

    Science.gov (United States)

    Koontz, Steven L. (Inventor)

    1999-01-01

    A method for making a biocompatible polymer article using a uniform atomic oxygen treatment is disclosed. The substrate may be subsequently optionally grated with a compatibilizing compound. Compatibilizing compounds may include proteins, phosphorylcholine groups, platelet adhesion preventing polymers, albumin adhesion promoters, and the like. The compatibilized substrate may also have a living cell layer adhered thereto. The atomic oxygen is preferably produced by a flowing afterglow microwave discharge. wherein the substrate resides in a sidearm out of the plasma. Also, methods for culturing cells for various purposes using the various membranes are disclosed as well. Also disclosed are porous organic polymers having a distributed pore chemistry (DPC) comprising hydrophilic and hydrophobic regions. and a method for making the DPC by exposing the polymer to atomic oxygen wherein the rate of hydrophilization is greater than the rate of mass loss.

  18. Conservation agriculture effects on soil pore characteristics

    DEFF Research Database (Denmark)

    Munkholm, Lars Juhl; Abdollahi, Lotfollah

    Conservation tillage in combination with crop rotation, residue management and cover crops are key components of conservation agriculture. A positive long-term effect of applying all components of conservation agriculture on soil structural quality is expected. However, there is a lack of...... quantitative knowledge to support this statement. This study examines the long-term effects of crop rotations, residue management and tillage on soil pore characteristics of two sandy loam soils in Denmark. Results are reported from a split plot field experiment rotation as main plot factor and tillage as...... -1000 cm. Air permeability and gas diffusivity were measured at matric potentials ranging from -30 to -300 cm for 4-8 and 12-16 cm depth (100 cm3 cores). At 18-27 cm depth (250 cm3 cores) air permeability was determined at matric potentials ranging from -10 cm to -100 cm. Tillage systems clearly...

  19. 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.

  20. Factors governing the behaviour of aqueous methane in narrow pores.

    Science.gov (United States)

    Phan, Anh; Cole, David R; Striolo, Alberto

    2016-02-13

    All-atom equilibrium molecular dynamics simulations were employed to investigate the behaviour of aqueous methane confined in 1-nm-wide pores obtained from different materials. Models for silica, alumina and magnesium oxide were used to construct the slit-shaped pores. The results show that methane solubility in confined water strongly depends on the confining material, with silica yielding the highest solubility in the systems considered here. The molecular structure of confined water differs within the three pores, and density fluctuations reveal that the silica pore is effectively less 'hydrophilic' than the other two pores considered. Comparing the water fluctuation autocorrelation function with local diffusion coefficients of methane across the hydrated pores we observed a direct proportional coupling between methane and water dynamics. These simulation results help to understand the behaviour of gas in water confined within narrow subsurface formations, with possible implications for fluid transport. PMID:26712646

  1. Experimental study on pore water pressure dissipation of mucky soil

    Institute of Scientific and Technical Information of China (English)

    Xianwei ZHANG; Changming WANG; Junxia LI; Bin WANG

    2008-01-01

    Pore water pressure has an important influence on mechanical properties of soil. The authors studied the characteristics of pore water pressure dissipating of mucky soil under consolidated-drained condition by using refitted triaxial instrument and analyzed the variation of pore pressure coefficient with consolidation pressure. The results show that the dissipating of pore water pressure behaves in different ways depends on different styles of loading. What is more, the pore water pressure coefficient of mucky soil is less than 1. As the compactness of soil increases and moisture content reduces, the value of B reduces. There is a staggered dissipating in the process of consolidation, in which it is a mutate point when U/P is 80%. It is helpful to establish the pore water pressure model and study the strength-deformation of soil in process of consolidation.

  2. Delayed breast implant reconstruction

    DEFF Research Database (Denmark)

    Hvilsom, Gitte B.; Hölmich, Lisbet R.; Steding-Jessen, Marianne;

    2011-01-01

    -stage procedures. From the Danish Registry for Plastic Surgery of the Breast, which has prospectively registered data for women undergoing breast implantations since 1999, we identified 559 women without a history of radiation therapy undergoing 592 delayed breast reconstructions following breast cancer during the......Studies of complications following reconstructive surgery with implants among women with breast cancer are needed. As the, to our knowledge, first prospective long-term study we evaluated the occurrence of complications following delayed breast reconstruction separately for one- and two...

  3. Process of inducing pores in membranes by melittin

    OpenAIRE

    Lee, Ming-Tao; Sun, Tzu-Lin; Hung, Wei-Chin; Huang, Huey W.

    2013-01-01

    Melittin is a prototype of the ubiquitous antimicrobial peptides that induce pores in membranes. It is commonly used as a molecular device for membrane permeabilization. Even at concentrations in the nanomolar range, melittin can induce transient pores that allow transmembrane conduction of atomic ions but not leakage of glucose or larger molecules. At micromolar concentrations, melittin induces stable pores allowing transmembrane leakage of molecules up to tens of kilodaltons, corresponding ...

  4. On the Mechanism of Pore Formation by Melittin*

    OpenAIRE

    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 only forms pores but also inhibits pore formation. We propose that these two modes of action are the result of two competing reactions: direct insertion into the membrane and b...

  5. X-ray CT analysis of pore structure in sand

    OpenAIRE

    Mukunoki, Toshifumi; Miyata, Yoshihisa; Mikami, Kazuaki; Shiota, Erika

    2016-01-01

    The development of a micro-focused X-ray CT device enables digital imaging analysis at the pore-scale. The applications have been diverse, for instance, in soil mechanics, geotechnical and geoenvironmental engineering, petroleum engineering, and agricultural engineering. In particular, imaging of the pore space of porous media has contributed to numerical simulations for single and multi-phase flow, or contaminant transport, through the pore structure as three-dimensional image data. These...

  6. Ion exclusion by sub-2-nm carbon nanotube pores

    OpenAIRE

    Fornasiero, Francesco; Park, Hyung Gyu; Holt, Jason K.; Stadermann, Michael; Grigoropoulos, Costas P.; Noy, Aleksandr; Bakajin, Olgica

    2008-01-01

    Biological pores regulate the cellular traffic of a large variety of solutes, often with high selectivity and fast flow rates. These pores share several common structural features: the inner surface of the pore is frequently lined with hydrophobic residues, and the selectivity filter regions often contain charged functional groups. Hydrophobic, narrow-diameter carbon nanotubes can provide a simplified model of membrane channels by reproducing these critical features in a simpler and more robu...

  7. Regulation of the assembly and function of the nuclear pore

    OpenAIRE

    Delmar, Valerie Anne

    2008-01-01

    The nucleus is the defining structure of eukaryotic cells. The nuclear envelope acts as a barrier between nucleus and cytoplasm. Nuclear pore complexes perforating the envelope control all traffic into and out of the nucleus, and thus act to regulate transcription, translation, and other essential cellular processes. During mitosis, the nuclear envelope from flies to mammals disassembles into its component parts, with the nuclear pore breaking into multiple subunits. The pore then reassembles...

  8. Enhanced membrane pore information by multimeric/oligomeric antimicrobial peptides

    OpenAIRE

    Arnusch, C.J.; Branderhorst, H.M.; de Kruijff, B.; Liskamp, R. M. J.; Breukink, E.J.; Pieters, R. J.

    2007-01-01

    The pore-forming antibacterial peptide magainin 2 was made divalent, tetravalent, and octavalent via a copper(I)-mediated 1-3 dipolar cycloaddition reaction (“click” chemistry). This series of poreforming compounds was tested in vitro for their ability to form pores in large unilamillar vesicles (LUVs). A large increase in the pore-forming capability was especially observed with the tetravalent and octavalent magainin compounds in the LUVs consisting of DOPC, and the octavalent magainin compo...

  9. Influence of Pore Structure on Compressive Strength of Cement Mortar

    OpenAIRE

    Haitao Zhao; Qi Xiao; Donghui Huang; Shiping Zhang

    2014-01-01

    This paper describes an experimental investigation into the pore structure of cement mortar using mercury porosimeter. Ordinary Portland cement, manufactured sand, and natural sand were used. The porosity of the manufactured sand mortar is higher than that of natural sand at the same mix proportion; on the contrary, the probable pore size and threshold radius of manufactured sand mortar are finer. Besides, the probable pore size and threshold radius increased with increasing water to cement r...

  10. Optimization of a pressurization methodology for extracting pore-water

    OpenAIRE

    Lopes, Isabel; Ribeiro, Rui

    2005-01-01

    Sediment toxicity can be assessed by conducting pore-water toxicity assays with standard water column organisms. Several methods have been developed for sampling pore-water. Centrifugation and pressurization methods are recommended when large volumes of pore-water are required to perform toxicity assays. Nevertheless, these methods involve sediment transportation and storage in laboratory, which can alter sediment toxicity. Therefore, an extraction method for large volumes that could be emplo...

  11. Ultrafast laser fabrication of submicrometer pores in borosilicate glass

    OpenAIRE

    An, Ran; Uram, Jeffrey D.; Yusko, Erik C.; Ke, Kevin; Mayer, Michael; Hunt, Alan J.

    2008-01-01

    We demonstrate rapid fabrication of submicrometer-diameter pores in borosilicate glass using femtosecond laser machining and subsequent wet-etch techniques. This approach allows direct and repeatable fabrication of high-quality pores with diameters of 400–800 nm. Such small pores coupled with the desirable electrical and chemical properties of glass enable sensitive resistive-pulse analysis to determine the size and concentration of macromolecules and nanoparticles. Plasma-enhanced chemical v...

  12. Enhanced membrane pore formation by multimeric/oligomeric antimicrobial peptides.

    Science.gov (United States)

    Arnusch, Christopher J; Branderhorst, Hilbert; de Kruijff, Ben; Liskamp, Rob M J; Breukink, Eefjan; Pieters, Roland J

    2007-11-20

    The pore-forming antibacterial peptide magainin 2 was made divalent, tetravalent, and octavalent via a copper(I)-mediated 1-3 dipolar cycloaddition reaction ("click" chemistry). This series of pore-forming compounds was tested in vitro for their ability to form pores in large unilamillar vesicles (LUVs). A large increase in the pore-forming capability was especially observed with the tetravalent and octavalent magainin compounds in the LUVs consisting of DOPC, and the octavalent magainin compound showed a marked increase with the DOPC/DOPG LUVs. Activity was observed in the low nanomolar range for these compounds. PMID:17944489

  13. 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. PMID:22264795

  14. 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.

  15. Surgical Ventricular Reconstruction

    Medline Plus

    Full Text Available SURGICAL VENTRICULAR RECONSTRUCTION MONTEFIORE-EINSTEIN HEART CENTER NEW YORK CITY, NEW YORK February 13, 2008 00:00:09 NARRATOR: Welcome to the Montefiore-Einstein Heart Center in ...

  16. Surgical Ventricular Reconstruction

    Medline Plus

    Full Text Available SURGICAL VENTRICULAR RECONSTRUCTION MONTEFIORE-EINSTEIN HEART CENTER NEW YORK CITY, NEW YORK February 13, 2008 00:00:09 NARRATOR: Welcome to the Montefiore-Einstein Heart Center in New York City. In ...

  17. Prairie Reconstruction Initiative

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The purpose of the Prairie Reconstruction Initiative Advisory Team (PRIAT) is to identify and take steps to resolve uncertainties in the process of prairie...

  18. Overview of Image Reconstruction

    Energy Technology Data Exchange (ETDEWEB)

    Marr, R. B.

    1980-04-01

    Image reconstruction (or computerized tomography, etc.) is any process whereby a function, f, on Rn is estimated from empirical data pertaining to its integrals, ∫f(x) dx, for some collection of hyperplanes of dimension k < n. The paper begins with background information on how image reconstruction problems have arisen in practice, and describes some of the application areas of past or current interest; these include radioastronomy, optics, radiology and nuclear medicine, electron microscopy, acoustical imaging, geophysical tomography, nondestructive testing, and NMR zeugmatography. Then the various reconstruction algorithms are discussed in five classes: summation, or simple back-projection; convolution, or filtered back-projection; Fourier and other functional transforms; orthogonal function series expansion; and iterative methods. Certain more technical mathematical aspects of image reconstruction are considered from the standpoint of uniqueness, consistency, and stability of solution. The paper concludes by presenting certain open problems. 73 references. (RWR)

  19. Surgical Ventricular Reconstruction

    Medline Plus

    Full Text Available ... reconstruction. This study is going to be a land…landmark study. And in all likelihood will influence ... improve postoperatively. But, nevertheless, this is an acute change and may take some time for the myocardium ...

  20. Overview of image reconstruction

    International Nuclear Information System (INIS)

    Image reconstruction (or computerized tomography, etc.) is any process whereby a function, f, on R/sup n/ is estimated from empirical data pertaining to its integrals, ∫f(x) dx, for some collection of hyperplanes of dimension k < n. The paper begins with background information on how image reconstruction problems have arisen in practice, and describes some of the application areas of past or current interest; these include radioastronomy, optics, radiology and nuclear medicine, electron microscopy, acoustical imaging, geophysical tomography, nondestructive testing, and NMR zeugmatography. Then the various reconstruction algorithms are discussed in five classes: summation, or simple back-projection; convolution, or filtered back-projection; Fourier and other functional transforms; orthogonal function series expansion; and iterative methods. Certain more technical mathematical aspects of image reconstruction are considered from the standpoint of uniqueness, consistency, and stability of solution. The paper concludes by presenting certain open problems. 73 references

  1. Breast reconstruction - natural tissue

    Science.gov (United States)

    After a mastectomy , some women choose to have cosmetic surgery to remake their breast. This type of surgery ... Risks of anesthesia and surgery are: Reactions to medicines Breathing problems Bleeding, blood clots , or infection Risks of breast reconstruction with ...

  2. Permutationally invariant state reconstruction

    CERN Document Server

    Moroder, Tobias; Toth, Geza; Schwemmer, Christian; Niggebaum, Alexander; Gaile, Stefanie; Gühne, Otfried; Weinfurter, Harald

    2012-01-01

    Feasible tomography schemes for large particle numbers must possess, besides an appropriate data acquisition protocol, also an efficient way to reconstruct the density operator from the observed finite data set. Since state reconstruction typically requires the solution of a non-linear large-scale optimization problem, this is a major challenge in the design of scalable tomography schemes. Here we present an efficient state reconstruction scheme for permutationally invariant quantum state tomography. It works for all common state-of-the-art reconstruction principles, including, in particular, maximum likelihood and least squares methods, which are the preferred choices in today's experiments. This high efficiency is achieved by greatly reducing the dimensionality of the problem employing a particular representation of permutationally invariant states known from spin coupling combined with convex optimization, which has clear advantages regarding speed, control and accuracy in comparison to commonly employed n...

  3. Surgical Ventricular Reconstruction

    Medline Plus

    Full Text Available ... a better procedure, the ventricular reconstruction or heart transplantation. This particular viewer actually saw our previous video on heart transplantation. And to answer that question, they are both ...

  4. On TPC cluster reconstruction

    CERN Document Server

    Dydak, F; Nefedov, Y; Wotschack, J; Zhemchugov, A

    2004-01-01

    For a bias-free momentum measurement of TPC tracks, the correct determination of cluster positions is mandatory. We argue in particular that (i) the reconstruction of the entire longitudinal signal shape in view of longitudinal diffusion, electronic pulse shaping, and track inclination is important both for the polar angle reconstruction and for optimum r phi resolution; and that (ii) self-crosstalk of pad signals calls for special measures for the reconstruction of the z coordinate. The problem of 'shadow clusters' is resolved. Algorithms are presented for accepting clusters as 'good' clusters, and for the reconstruction of the r phi and z cluster coordinates, including provisions for 'bad' pads and pads next to sector boundaries, respectively.

  5. Surgical Ventricular Reconstruction

    Medline Plus

    Full Text Available ... He has not been readmitted for any reasons related to heart failure. 00:41:57 ROBERT E. ... question, because it really deals with whether anything related to surgical ventricular reconstruction would add to the ...

  6. 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.

  7. Chalet. Reconstruction from Memory

    OpenAIRE

    Gheysen, Eva

    2015-01-01

    In the research project several design tactics are developed in order to counteract the phenomenon of experiential erosion. This particular project explored one of the tactics: Reconstruction from Memory. When reconstructing space from memory, isolated spatial fragments from the past are reformed into a new, decontextualized construct that represents the most memorable experiences evoked by that space. These memories give insight in which architectural features strongly affect our experience ...

  8. Reconstructing baryon oscillations

    OpenAIRE

    Noh, Yookyung; White, Martin; Padmanabhan, Nikhil

    2009-01-01

    The baryon acoustic oscillation (BAO) method for constraining the expansion history is adversely affected by non-linear structure formation, which washes out the correlation function peak created at decoupling. To increase the constraining power of low z BAO experiments, it has been proposed that one use the observed distribution of galaxies to "reconstruct'' the acoustic peak. Recently Padmanabhan, White and Cohn provided an analytic formalism for understanding how reconstruction works withi...

  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. Ekofisk chalk: core measurements, stochastic reconstruction, network modeling and simulation

    Energy Technology Data Exchange (ETDEWEB)

    Talukdar, Saifullah

    2002-07-01

    This dissertation deals with (1) experimental measurements on petrophysical, reservoir engineering and morphological properties of Ekofisk chalk, (2) numerical simulation of core flood experiments to analyze and improve relative permeability data, (3) stochastic reconstruction of chalk samples from limited morphological information, (4) extraction of pore space parameters from the reconstructed samples, development of network model using pore space information, and computation of petrophysical and reservoir engineering properties from network model, and (5) development of 2D and 3D idealized fractured reservoir models and verification of the applicability of several widely used conventional up scaling techniques in fractured reservoir simulation. Experiments have been conducted on eight Ekofisk chalk samples and porosity, absolute permeability, formation factor, and oil-water relative permeability, capillary pressure and resistivity index are measured at laboratory conditions. Mercury porosimetry data and backscatter scanning electron microscope images have also been acquired for the samples. A numerical simulation technique involving history matching of the production profiles is employed to improve the relative permeability curves and to analyze hysteresis of the Ekofisk chalk samples. The technique was found to be a powerful tool to supplement the uncertainties in experimental measurements. Porosity and correlation statistics obtained from backscatter scanning electron microscope images are used to reconstruct microstructures of chalk and particulate media. The reconstruction technique involves a simulated annealing algorithm, which can be constrained by an arbitrary number of morphological parameters. This flexibility of the algorithm is exploited to successfully reconstruct particulate media and chalk samples using more than one correlation functions. A technique based on conditional simulated annealing has been introduced for exact reproduction of vuggy

  11. Cosmic tidal reconstruction

    Science.gov (United States)

    Zhu, Hong-Ming; Pen, Ue-Li; Yu, Yu; Er, Xinzhong; Chen, Xuelei

    2016-05-01

    The gravitational coupling of a long-wavelength tidal field with small-scale density fluctuations leads to anisotropic distortions of the locally measured small-scale matter correlation function. Since the local correlation function is known to be statistically isotropic in the absence of such tidal interactions, the tidal distortions can be used to reconstruct the long-wavelength tidal field and large-scale density field in analogy with the cosmic microwave background lensing reconstruction. In this paper we present the theoretical framework of cosmic tidal reconstruction and test the reconstruction in numerical simulations. We find that the density field on large scales can be reconstructed with good accuracy and the cross-correlation coefficient between the reconstructed density field and the original density field is greater than 0.9 on large scales (k ≲0.1 h /Mpc ), with the filter scale ˜1.25 Mpc /h . This is useful in the 21 cm intensity mapping survey, where the long-wavelength radial modes are lost due to a foreground subtraction process.

  12. Permutationally invariant state reconstruction

    DEFF Research Database (Denmark)

    Moroder, Tobias; Hyllus, Philipp; Tóth, Géza;

    2012-01-01

    Feasible tomography schemes for large particle numbers must possess, besides an appropriate data acquisition protocol, an efficient way to reconstruct the density operator from the observed finite data set. Since state reconstruction typically requires the solution of a nonlinear large-scale opti......Feasible tomography schemes for large particle numbers must possess, besides an appropriate data acquisition protocol, an efficient way to reconstruct the density operator from the observed finite data set. Since state reconstruction typically requires the solution of a nonlinear large......-scale optimization problem, this is a major challenge in the design of scalable tomography schemes. Here we present an efficient state reconstruction scheme for permutationally invariant quantum state tomography. It works for all common state-of-the-art reconstruction principles, including, in particular, maximum...... likelihood and least squares methods, which are the preferred choices in today's experiments. This high efficiency is achieved by greatly reducing the dimensionality of the problem employing a particular representation of permutationally invariant states known from spin coupling combined with convex...

  13. The CMS Muon Reconstruction Software

    CERN Document Server

    Trocino, Daniele

    2009-01-01

    Muonic final states will provide clean signatures for many physics processes at the LHC. One of the main goals of the Compact Muon Solenoid (CMS) design is thus to ensure efficient and accurate identification and reconstruction of muons. A sophisticated muon system is used for muon identification and stand-alone reconstruction and the inner silicon tracker exploits the high magnetic field to ensure a very precise transverse momentum resolution. The global reconstruction algorithms combine muons reconstructed in the dedicated spectrometer with tracks reconstructed in the inner detector. The CMS reconstruction software is well suited for both offline reconstruction and online event selection (HLT) and its performance has been studied in detail using Monte Carlo simulations. The muon reconstruction has also been employed successfully to reconstruct cosmic muons traversing the CMS detector. The design of the CMS muon identification and reconstruction is presented, as well as its performance on simulated and cosmi...

  14. Interface engineering of synthetic pores: towards hypersensitive biosensors.

    Science.gov (United States)

    Mora, Federico; Tran, Duy-Hien; Oudry, Natalie; Hopfgartner, Gerard; Jeannerat, Damien; Sakai, Naomi; Matile, Stefan

    2008-01-01

    Hydrophilic anchoring is introduced as a promising strategy to constructively control the various interactions of synthetic pore sensors with the surrounding biphasic environment. Artificial rigid-rod beta barrels are selected as classical synthetic multifunctional pores and random-coil tetralysines are attached as hydrophilic anchors. The synthesis of this advanced pore is accomplished in 32 steps from commercially available starting materials. With regard to pore activity as such, the key impact of hydrophilic anchoring is a change from a Hill coefficient nEC(50)). These results not only reveal stoichiometric binding as the expected origin of the sensitivity limit of synthetic pore sensors, they also provide promising solutions for this problem. The combination of hydrophilic anchoring with targeted pore formation emerges as a particularly promising strategy to further reduce effective pore concentrations. The scope and limitations of this approach are exemplified with pertinent analyte pairs that are essential for the sensing of sucrose, lactose, acetate, and glutamate with synthetic pores in samples from the supermarket. PMID:18067110

  15. 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 permeabi...

  16. Pore pressure calculation of the UO2 high burnup structure

    International Nuclear Information System (INIS)

    Highlights: • Pore pressure is calculated based on local burnup, density and porosity. • Ronchi's equations of state are used instead of van der Waals’ equation. • Pore pressure increases as HBS transformation begins and then stays constant. • A best approximated parameter used for pore pressure calculation is recommended. -- Abstract: UO2 high burnup structure has an important impact on fuel behavior, especially in case of reactivity initiated accident (RIA). Pore relaxation enhances local fuel swelling and puts additional load to the fuel cladding, which makes fuel more susceptible to pellet–cladding mechanical interaction induced failure. Therefore, pore pressure calculation becomes vital when evaluating the fuel failure. In this paper pore pressure is calculated as a function of pellet radial local burnup based on the basic characteristics of HBS using Ronchi's correlation. The results indicate that pore pressure will approach a stable value as HBS is developing. A best approximated C value of 55 N/m is recommended for pore pressure calculation

  17. Improving the ruggedness of silicon pore optics

    Science.gov (United States)

    Ackermann, Marcelo D.; Collon, Maximilien J.; Günther, Ramses; Partapsing, Rakesh; Bavdaz, Marcos; Wallace, Kotska; Wille, Eric; van Baren, Coen; Kampf, Dirk; Erhard, Markus

    2010-07-01

    In this paper we present the latest developments on the ruggedisation of the Silicon Pore Optics (SPO) mirror modules. SPO is one of the candidate technologies for producing the X-ray optics for the future space based Xray telescope, the International X-ray Observatory (IXO). To produce SPO mirror modules, Si mirrors are first bonded together using direct Si bonding to form a stack. These stacks are the glued into brackets, which then connect to the supporting optical bench by invar pins. The combination of brackets and invar pins now forms a full isostatic mount, and is rugged enough to allow the mirror module to survive the high loads of a launch. The mounting system furthermore allows for a certain level of manufacturing tolerances for the support structure, and ensures interchangeability of the mirror modules within one single ring of the optical bench. To prove this, a test interface has been designed and manufactured, on which a single, full fledged mirror module will be mounted to be exposed to environmental tests.

  18. 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. PMID:19227366

  19. Nipple-areola complex reconstruction

    OpenAIRE

    Nimboriboonporn, Anongporn; Chuthapisith, Suebwong

    2014-01-01

    Nipple areolar reconstruction (NAC) was introduced since 1940s and evolved as parallel with breast reconstruction since era of breast cancer treatment. It consists of nipple and areolar reconstruction. Ideal reconstruction of the NAC requires symmetry in position, size, shape, texture, and pigmentation and permanent projection. There are many innovative ways to create a nipple and each method has its unique characteristics that apply to certain breast types. NAC reconstruction techniques comp...

  20. Surface pore tension and adsorption characteristics of polluted sediment

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Most natural sediment particles have numerous pores and a complex surface texture which facilitates their adsorption of contaminants. Particle surface structure,therefore,is an important instrumental factor in the transport of contaminants,especially in water environments. This paper reports on the results of adsorption-desorption experiments to analyze polluted sediment surface pore tension characteristics performed on samples from the bottom of Guanting Reservoir. In our analysis,the Frenkel-Halsey-Hill(FHH) equation is applied to calculate the fractal dimensions of particles to quantify the surface roughness and pore tension characteristics. The results show that the surface fractal dimensions of sediment particle surfaces normally measure from 2.6 to 2.85. The volume of pores smaller than 10 nm changes significantly after being contaminated with pollutants and the fractal dimension decreases because the pores adsorb the contaminants.

  1. Influence of pore structure on compressive strength of cement mortar.

    Science.gov (United States)

    Zhao, Haitao; Xiao, Qi; Huang, Donghui; Zhang, Shiping

    2014-01-01

    This paper describes an experimental investigation into the pore structure of cement mortar using mercury porosimeter. Ordinary Portland cement, manufactured sand, and natural sand were used. The porosity of the manufactured sand mortar is higher than that of natural sand at the same mix proportion; on the contrary, the probable pore size and threshold radius of manufactured sand mortar are finer. Besides, the probable pore size and threshold radius increased with increasing water to cement ratio and sand to cement ratio. In addition, the existing models of pore size distribution of cement-based materials have been reviewed and compared with test results in this paper. Finally, the extended Bhattacharjee model was built to examine the relationship between compressive strength and pore structure. PMID:24757414

  2. Influence of Pore Structure on Compressive Strength of Cement Mortar

    Directory of Open Access Journals (Sweden)

    Haitao Zhao

    2014-01-01

    Full Text Available This paper describes an experimental investigation into the pore structure of cement mortar using mercury porosimeter. Ordinary Portland cement, manufactured sand, and natural sand were used. The porosity of the manufactured sand mortar is higher than that of natural sand at the same mix proportion; on the contrary, the probable pore size and threshold radius of manufactured sand mortar are finer. Besides, the probable pore size and threshold radius increased with increasing water to cement ratio and sand to cement ratio. In addition, the existing models of pore size distribution of cement-based materials have been reviewed and compared with test results in this paper. Finally, the extended Bhattacharjee model was built to examine the relationship between compressive strength and pore structure.

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

    International Nuclear Information System (INIS)

    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. - Highlights: ► This study is about porosity parameter in carbonate rocks by 3D X-Ray Microtomography. ► This study has become useful as data input for modeling reservoir characterization. ► This technique was able to provide pores, grains and mineralogical differences among the samples.

  4. Pore capillary pressure and saturation of methane hydrate bearing sediments

    Institute of Scientific and Technical Information of China (English)

    SUN Shicai; LIU Changling; YE Yuguang; LIU Yufeng

    2014-01-01

    To better understand the relationship between the pore capillary pressure and hydrate saturation in sedi-ments, a new method was proposed. First, the phase equilibria of methane hydrate in fine-grained silica sands were measured. As to the equilibrium data, the pore capillary pressure and saturation of methane hydrate were calculated. The results showed that the phase equilibria of methane hydrates in fine-grained silica sands changed due to the depressed activity of pore water caused by the surface group and negatively charged characteristic of silica particles as well as the capillary pressure in small pores together. The capil-lary pressure increased with the increase of methane hydrate saturation due to the decrease of the available pore space. However, the capillary-saturation relationship could not yet be described quantitatively because of the stochastic habit of hydrate growth.

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

    International Nuclear Information System (INIS)

    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

  6. X-ray CT analysis of pore structure in sand

    Science.gov (United States)

    Mukunoki, Toshifumi; Miyata, Yoshihisa; Mikami, Kazuaki; Shiota, Erika

    2016-06-01

    The development of microfocused X-ray computed tomography (CT) devices enables digital imaging analysis at the pore scale. The applications of these devices are diverse in soil mechanics, geotechnical and geoenvironmental engineering, petroleum engineering, and agricultural engineering. In particular, the imaging of the pore space in porous media has contributed to numerical simulations for single-phase and multiphase flows or contaminant transport through the pore structure as three-dimensional image data. These obtained results are affected by the pore diameter; therefore, it is necessary to verify the image preprocessing for the image analysis and to validate the pore diameters obtained from the CT image data. Moreover, it is meaningful to produce the physical parameters in a representative element volume (REV) and significant to define the dimension of the REV. This paper describes the underlying method of image processing and analysis and discusses the physical properties of Toyoura sand for the verification of the image analysis based on the definition of the REV. On the basis of the obtained verification results, a pore-diameter analysis can be conducted and validated by a comparison with the experimental work and image analysis. The pore diameter is deduced from Young-Laplace's law and a water retention test for the drainage process. The results from previous study and perforated-pore diameter originally proposed in this study, called the voxel-percolation method (VPM), are compared in this paper. In addition, the limitations of the REV, the definition of the pore diameter, and the effectiveness of the VPM for an assessment of the pore diameter are discussed.

  7. Alternative reconstruction after pancreaticoduodenectomy

    Directory of Open Access Journals (Sweden)

    Cooperman Avram M

    2008-01-01

    Full Text Available Abstract Background Pancreaticoduodenectomy is the procedure of choice for tumors of the head of the pancreas and periampulla. Despite advances in surgical technique and postoperative care, the procedure continues to carry a high morbidity rate. One of the most common morbidities is delayed gastric emptying with rates of 15%–40%. Following two prolonged cases of delayed gastric emptying, we altered our reconstruction to avoid this complication altogether. Subsequently, our patients underwent a classic pancreaticoduodenectomy with an undivided Roux-en-Y technique for reconstruction. Methods We reviewed the charts of our last 13 Whipple procedures evaluating them for complications, specifically delayed gastric emptying. We compared the outcomes of those patients to a control group of 15 patients who underwent the Whipple procedure with standard reconstruction. Results No instances of delayed gastric emptying occurred in patients who underwent an undivided Roux-en-Y technique for reconstruction. There was 1 wound infection (8%, 1 instance of pneumonia (8%, and 1 instance of bleeding from the gastrojejunal staple line (8%. There was no operative mortality. Conclusion Use of the undivided Roux-en-Y technique for reconstruction following the Whipple procedure may decrease the incidence of delayed gastric emptying. In addition, it has the added benefit of eliminating bile reflux gastritis. Future randomized control trials are recommended to further evaluate the efficacy of the procedure.

  8. STATISTICAL ANALYSIS OF TOMOGRAPHIC RECONSTRUCTION ALGORITHMS BY MORPHOLOGICAL IMAGE CHARACTERISTICS

    Directory of Open Access Journals (Sweden)

    Sebastian Lǖck

    2011-05-01

    Full Text Available We suggest a procedure for quantitative quality control of tomographic reconstruction algorithms. Our task-oriented evaluation focuses on the correct reproduction of phase boundary length and has thus a clear implication for morphological image analysis of tomographic data. Indirectly the method monitors accurate reproduction of a variety of locally defined critical image features within tomograms such as interface positions and microstructures, debonding, cracks and pores. Tomographic errors of such local nature are neglected if only global integral characteristics such as mean squared deviation are considered for the evaluation of an algorithm. The significance of differences in reconstruction quality between algorithms is assessed using a sample of independent random scenes to be reconstructed. These are generated by a Boolean model and thus exhibit a substantial stochastic variability with respect to image morphology. It is demonstrated that phase boundaries in standard reconstructions by filtered backprojection exhibit substantial errors. In the setting of our simulations, these could be significantly reduced by the use of the innovative reconstruction algorithm DIRECTT.

  9. Breast Reconstruction with Microvascular

    Directory of Open Access Journals (Sweden)

    David W. Chang

    2012-01-01

    Full Text Available The free muscle-sparing transverse rectus abdominis myocutaneous (MS-TRAM and deepinferior epigastric perforator (DIEP flaps involve transferring skin and subcutaneous tissuefrom the lower abdominal area and have many features that make them well suited forbreast reconstruction. The robust blood supply of the free flap reduces the risk of fat necrosisand also enables aggressive shaping of the flap for breast reconstruction to optimize theaesthetic outcome. In addition, the free MS-TRAM flap and DIEP flap require minimal donorsitesacrifice in most cases. With proper patient selection and safe surgical technique, the freeMS-TRAM flap and DIEP flap can transfer the lower abdominal skin and subcutaneous tissueto provide an aesthetically pleasing breast reconstruction with minimal donor-site morbidity.

  10. Reconstructing random media

    International Nuclear Information System (INIS)

    We formulate a procedure to reconstruct the structure of general random heterogeneous media from limited morphological information by extending the methodology of Rintoul and Torquato [J. Colloid Interface Sci. 186, 467 (1997)] developed for dispersions. The procedure has the advantages that it is simple to implement and generally applicable to multidimensional, multiphase, and anisotropic structures. Furthermore, an extremely useful feature is that it can incorporate any type and number of correlation functions in order to provide as much morphological information as is necessary for accurate reconstruction. We consider a variety of one- and two-dimensional reconstructions, including periodic and random arrays of rods, various distribution of disks, Debye random media, and a Fontainebleau sandstone sample. We also use our algorithm to construct heterogeneous media from specified hypothetical correlation functions, including an exponentially damped, oscillating function as well as physically unrealizable ones. copyright 1998 The American Physical Society

  11. Reconstructed Jets at RHIC

    CERN Document Server

    Salur, Sevil

    2010-01-01

    To precisely measure jets over a large background such as pile up in high luminosity p+p collisions at LHC, a new generation of jet reconstruction algorithms is developed. These algorithms are also applicable to reconstruct jets in the heavy ion environment where large event multiplicities are produced. Energy loss in the medium created in heavy ion collisions are already observed indirectly via inclusive hadron distributions and di-hadron correlations. Jets can be used to study this energy loss in detail with reduced biases. We review the latest results on jet-medium interactions as seen in A+A collisions at RHIC, focusing on the recent progress on jet reconstruction in heavy ion collisions.

  12. Pore Scale Dynamics of Microemulsion Formation.

    Science.gov (United States)

    Unsal, Evren; Broens, Marc; Armstrong, Ryan T

    2016-07-19

    Experiments in various porous media have shown that multiple parameters come into play when an oleic phase is displaced by an aqueous solution of surfactant. In general, the displacement efficiency is improved when the fluids become quasi-miscible. Understanding the phase behavior oil/water/surfactant systems is important because microemulsion has the ability to generate ultralow interfacial tension (microemulsion formation and the resulting properties under equilibrium conditions. However, the majority of applications where microemulsion is present also involve flow, which has received relatively less attention. It is commonly assumed that the characteristics of an oil/water/surfactant system under flowing conditions are identical to the one under equilibrium conditions. Here, we show that this is not necessarily the case. We studied the equilibrium phase behavior of a model system consisting of n-decane and an aqueous solution of olefin sulfonate surfactant, which has practical applications for enhanced oil recovery. The salt content of the aqueous solution was varied to provide a range of different microemulsion compositions and oil-water interfacial tensions. We then performed microfluidic flow experiments to study the dynamic in situ formation of microemulsion by coinjecting bulk fluids of n-decane and surfactant solution into a T-junction capillary geometry. A solvatochromatic fluorescent dye was used to obtain spatially resolved compositional information. In this way, we visualized the microemulsion formation and the flow of it along with the excess phases. A complex interaction between the flow patterns and the microemulsion properties was observed. The formation of microemulsion influenced the flow regimes, and the flow regimes affected the characteristics of the microemulsion formation. In particular, at low flow rates, slug flow was observed, which had profound consequences on the pore scale mixing behavior and resulting microemulsion properties. PMID

  13. A Relationship between Pore Shapes and Mercury Porosimetry Curves as Revealed by a Random Pore Networks

    Czech Academy of Sciences Publication Activity Database

    Čapek, P.; Hejtmánek, Vladimír

    Cambridge : Royal Society of Chemistry Publishing, 2009 - (Kaskel, S.; Rodriguez-Reinoso, F.; Seaton, N.), s. 385-393 ISBN 978-1-84755-904-3. ISSN 0260-6291. [International Symposium on the Characterization of Porous Solids /8./. Edinburg (GB), 10.06.2008-13.06.2008] R&D Projects: GA ČR GA203/05/0347 Institutional research plan: CEZ:AV0Z40720504 Keywords : pore network model * mercury porosimetry * external pressure Subject RIV: CF - Physical ; Theoretical Chemistry

  14. Vertex Reconstruction in CMS

    CERN Document Server

    Chabanat, E; D'Hondt, J; Vanlaer, P; Prokofiev, K; Speer, T; Frühwirth, R; Waltenberger, W

    2005-01-01

    Because of the high track multiplicity in the final states expected in proton collisions at the LHC experiments, novel vertex reconstruction algorithms are required. The vertex reconstruction problem can be decomposed into a pattern recognition problem ("vertex finding") and an estimation problem ("vertex fitting"). Starting from least-square methods, ways to render the classical algorithms more robust are discussed and the statistical properties of the novel methods are shown. A whole set of different approaches for the vertex finding problem is presented and compared in relevant physics channels.

  15. The evolving breast reconstruction

    DEFF Research Database (Denmark)

    Thomsen, Jørn Bo; Gunnarsson, Gudjon Leifur

    2014-01-01

    The aim of this editorial is to give an update on the use of the propeller thoracodorsal artery perforator flap (TAP/TDAP-flap) within the field of breast reconstruction. The TAP-flap can be dissected by a combined use of a monopolar cautery and a scalpel. Microsurgical instruments are generally...... not needed. The propeller TAP-flap can be designed in different ways, three of these have been published: (I) an oblique upwards design; (II) a horizontal design; (III) an oblique downward design. The latissimus dorsi-flap is a good and reliable option for breast reconstruction, but has been...

  16. Reconstruction of inflation models

    Energy Technology Data Exchange (ETDEWEB)

    Myrzakulov, Ratbay; Sebastiani, Lorenzo [Eurasian National University, Department of General and Theoretical Physics and Eurasian Center for Theoretical Physics, Astana (Kazakhstan); Zerbini, Sergio [Universita di Trento, Dipartimento di Fisica, Trento (Italy); TIFPA, Istituto Nazionale di Fisica Nucleare, Trento (Italy)

    2015-05-15

    In this paper, we reconstruct viable inflationary models by starting from spectral index and tensor-to-scalar ratio from Planck observations. We analyze three different kinds of models: scalar field theories, fluid cosmology, and f(R)-modified gravity. We recover the well-known R{sup 2} inflation in Jordan-frame and Einstein-frame representation, the massive scalar inflaton models and two models of inhomogeneous fluid. A model of R{sup 2} correction to Einstein's gravity plus a ''cosmological constant'' with an exact solution for early-time acceleration is reconstructed. (orig.)

  17. Hetero-oligomeric MspA pores in Mycobacterium smegmatis.

    Science.gov (United States)

    Pavlenok, Mikhail; Niederweis, Michael

    2016-04-01

    The porin MspA of Mycobacterium smegmatis is a biological nanopore used for DNA sequencing. The octameric MspA pore can be isolated from M. smegmatis in milligram quantities, is extremely stable against denaturation and rapidly inserts into lipid membranes. Here, we show that MspA pores composed of different Msp subunits are formed in M. smegmatis and that hetero-oligomers of different Msp monomers increase the heterogeneity of MspA pores designed for DNA sequencing. To improve the quality of preparations of mutant MspA proteins, all four msp genes were deleted from the M. smegmatis genome after insertion of an inducible porin gene from M. tuberculosis. In the msp quadruple mutant M. smegmatis ML712 no Msp porins were detected and mutant MspA proteins were produced at wild-type levels. Lipid bilayer experiments demonstrated that MspA pores isolated from ML712 formed functional channels and had a narrower conductance distribution than pores purified from M. smegmatis with background msp expression. Thus, the M. smegmatis msp quadruple mutant improves the homogeneity of MspA pores designed for DNA sequencing and might also facilitate the identification and functional characterization of other mycobacterial pore proteins. PMID:26912121

  18. Assembly and stability of nisin-lipid II pores.

    Science.gov (United States)

    Hasper, Hester Emilie; de Kruijff, Ben; Breukink, Eefjan

    2004-09-14

    The peptide antibiotic nisin was the first reported example of an antibiotic that kills bacteria via targeted pore formation. The specific target of nisin is Lipid II, an essential intermediate in the bacterial cell-wall synthesis. High-affinity binding of the antibiotic to Lipid II is followed by rapid permeabilization of the membrane. Here, we investigated the assembly and stability of nisin-Lipid II pore complexes by means of pyrene fluorescence and circular dichroism. We demonstrated that nisin uses all available Lipid II molecules in the membrane to form pore complexes. The pore complexes have a uniform structure and consist of 8 nisin and 4 Lipid II molecules. Moreover, the pores displayed a remarkable stability, because they were able to resist the solubilization of the membrane environment by mild detergents. Similar experiments with [N20P/M21P]nisin showed that the hinge region is essential for the assembly into stable pore complexes. The new insights were used to propose a refined model for nisin pore formation. PMID:15350143

  19. Pore geometry controls on porosity and permeability in the Tirrawarre Sandstone reservoir, Cooper basin, South Australia

    Energy Technology Data Exchange (ETDEWEB)

    Rezaee, M.R.; Griffiths, C.M. [Univ. of Adelaide (Australia)

    1996-12-31

    Pore geometry is a major control on hydraulic conductivity in a porous medium. Pore geometry may be defined in terms of pore and pore throat size, pore diameter, and pore shape (pore surface area, pore perimeter). Petrographic image analysis, and mercury injection data were employed to group fluvio-deltaic Tirrawarra Sandstone samples in the Moorari and Fly Lake fields into eight classes. The classes are separated according to the relative proportions of different kinds of porosity (microporosity, and primary and secondary macroporosity), size of pore spaces, size of pore throats, and pore diameter. The reservoir quality increases from class eight to class one and the classes have a predictable relationship to sedimentary environment. Class one samples, associated with meander, aeolian or beach-barrier environments, have primary macroporosity with partial quartz cement. Pore throats mostly exceed 10 micron. Mean pore space area is about 6300 micron. Mean pore diameter and mean pore perimeter are respectively 66 and 275 micron. Class eight, on the other hand, associated with a braid-delta environment, is dominated by microporosity. Mean pore space area is about 436 micron. Mean pore diameter and mean pore perimeter are respectively 25 and 76 micron. In addition the pore-throat distribution shows poor sorting with a pore throat ranging from 0.1 to 0.5 micron.

  20. Three-dimensional image analysis of plugging at the septal pore by Woronin body during hypotonic shock inducing hyphal tip bursting in the filamentous fungus Aspergillus oryzae

    International Nuclear Information System (INIS)

    We observed that the filamentous fungus, Aspergillus oryzae, grown on agar media burst out cytoplasmic constituents from the hyphal tip soon after flooding with water. Woronin body is a specialized organelle known to plug the septal pore adjacent to the lysed compartment to prevent extensive loss of cytoplasm. A. oryzae Aohex1 gene homologous to Neurospora crassa HEX1 gene encoding a major protein in Woronin body was expressed as a fusion with DsRed2, resulting in visualization of Woronin body. Confocal microscopy and three-dimensional reconstruction of images visualized the septal pore as a dark region surrounded by green fluorescence of EGFP-fused secretory protein, RNase T1, on the septum. Dual fluorescent labeling revealed the plugging of the septal pores adjacent to the lysed apical compartments by Woronin bodies during hypotonic shock. Disruption of Aohex1 gene caused disappearance of Woronin bodies and the defect to prevent extensive loss of cytoplasm during hypotonic shock

  1. 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.

  2. 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.

  3. Surgical Ventricular Reconstruction

    Medline Plus

    Full Text Available ... VENTRICULAR RECONSTRUCTION MONTEFIORE-EINSTEIN HEART CENTER NEW YORK CITY, NEW YORK February 13, 2008 00:00:09 ... the Montefiore-Einstein Heart Center in New York City. In just moments, you'll see an expert ...

  4. Impact of pore size and pore surface composition on the dynamics of confined water in highly ordered porous silica

    International Nuclear Information System (INIS)

    The impact of pore size and pore surface composition on water dynamics confined in highly ordered porous silica material (MCM-41) was investigated using neutron scattering for correlation times in the picosecond range. Samples were synthesized by the hydrothermal route and grafted via the hydrolytic surface sol-gel method to obtain pore wall surfaces with Si-OH, Al-OH, or Zr-OH terminations and pore sizes from 2 to 2.7 nm. The samples were characterized after grafting using nitrogen adsorption-desorption isotherms and small-angle X-ray scattering. At room temperature, the analysis of the quasi-elastic neutron scattering data shows a decrease of mean square displacement of the mobile protons with the pore size and when Si-OH surface termination is replaced by Al-OH and Zr-OH. The water translational diffusion coefficients are close to the bulk value whatever the samples. The amounts of fixed protons depend on the pore size and the ability of the grafted layers to immobilize the water molecules which were determined also from thermogravimetric and differential thermal analysis. This last result highlights that pore surface composition could be the predominant parameter affecting the fixed proton content at this time scale. (authors)

  5. Breast Reconstruction with Tissue Expansion

    Medline Plus

    Full Text Available ... planning to do a left breast reconstruction, so lift up the flaps here and go underneath the ... breast reconstruction. In this case, we would usually lift the skin flap and the pectoralis major muscle ...

  6. Theory of electroporation of planar bilayer membranes: predictions of the aqueous area, change in capacitance, and pore-pore separation.

    OpenAIRE

    Freeman, S. A.; Wang, M. A.; Weaver, J C

    1994-01-01

    A large increase in the transmembrane voltage, U(t), of a fluid bilayer membrane is believed to result in the occurrence of temporary aqueous pathways ("pores") across the membrane. The number, size, and evolution dynamics of these pores are expected to be crucial to the transport of water-soluble species ranging from small ions to macromolecules such as proteins and nucleic acids. In this paper we use a transient aqueous pore theory to estimate the fraction of the membrane area, Fw(t), which...

  7. The Pore Structure and Hydration Performance of Sulphoaluminate MDF Cement

    Institute of Scientific and Technical Information of China (English)

    HUANG Cong-yun; YUAN Run-zhang; LONG Shi-zong

    2004-01-01

    The hydration and pore structure of sulphoaluminate MDF cement were studied by X-ray diffractometer ( XRD ), scanning electron microscope (SEM) and mercury intrusion porosimeter ( MIP ) etc. The ex-perimental results indicate that hydration products of the materials are entringites ( Aft ), aluminium hydroxide andCSH (Ⅰ) gel etc. Due to its very low water-cement ratio, hydration function is only confined to the surfaces of ce-ment grains, and there is a lot of sulphoaluminate cement in the hardenite which is unhydrated yet. Hydration re-action was rapidly carried under the condition of the heat-pressing. Therefore cement hydrates Aft, CSH (Ⅰ) andaluminium hydroxide gel fill in pores. The expansibility of Aft makes the porosity of MDF cement lower ( less than1 percent ) and the size of pore smaller (80 percent pore was less than 250A), and enhances its strength.

  8. 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.

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

    DEFF Research Database (Denmark)

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

    2010-01-01

    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...... remains elusive. Here we show that the ability of sybII to support exocytosis is inhibited by addition of one or two residues to the sybII C terminus depending on their energy of transfer from water to the membrane interface, following a Boltzmann distribution. These results suggest that following...... 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...

  10. Comparative squamation of the lateral line canal pores in sharks.

    Science.gov (United States)

    McKenzie, R W; Motta, P J; Rohr, J R

    2014-05-01

    The current study collected the first quantitative data on lateral line pore squamation patterns in sharks and assessed whether divergent squamation patterns are similar to experimental models that cause reduction in boundary layer turbulence. In addition, the hypothesis that divergent orientation angles are exclusively found in fast-swimming shark species was tested. The posterior lateral line and supraorbital lateral line pore squamation of the fast-swimming pelagic shortfin mako shark Isurus oxyrinchus and the slow-swimming epi-benthic spiny dogfish shark Squalus acanthias was examined. Pore scale morphology and pore coverage were qualitatively analysed and compared. In addition, pore squamation orientation patterns were quantified for four regions along the posterior lateral line and compared for both species. Isurus oxyrinchus possessed consistent pore scale coverage among sampled regions and had a divergent squamation pattern with multiple scale rows directed dorsally and ventrally away from the anterior margin of the pore with an average divergent angle of 13° for the first row of scales. Squalus acanthias possessed variable amounts of scale coverage among the sampled regions and had a divergent squamation pattern with multiple scale rows directed ventrally away from the anterior margin of the pore with an average angle of 19° for the first row of scales. Overall, the squamation pattern measured in I. oxyrinchus fell within the parameters used in the fluid flow analysis, which suggests that this pattern may reduce boundary layer turbulence and affect lateral line sensitivity. The exclusively ventral oriented scale pattern seen in S. acanthias possessed a high degree of divergence but the pattern did not match that of the fluid flow models. Given current knowledge, it is unclear how this would affect boundary layer flow. By studying the relationship between squamation patterns and the lateral line, new insights are provided into sensory biology that warrant

  11. Phase-Field Modeling of Lipid Vesicles With Pores

    Science.gov (United States)

    Seifi, Saman; Salac, David

    2013-11-01

    The formation and annihilation of pores in a lipid vesicle membrane is critical to a number of biotechnologies, such as drug delivery. Previous models of vesicle behavior have ignored the influence of topological changes in the vesicle membrane. Here the entire Helfrich model of a vesicle membrane is considered. Topological changes in the vesicle membrane, such as the formation of a pore, are captured through the use of an embedded phase-field model. The numerical method and sample results will be presented.

  12. Accumulation of formamide in hydrothermal pores to form prebiotic nucleobases

    OpenAIRE

    Niether, Doreen; Afanasenkau, Dzmitry; Dhont, Jan K.G.; Wiegand, Simone

    2016-01-01

    Formamide is one of the important compounds from which prebiotic molecules can be synthesized, provided that its concentration is sufficiently high. For nucleotides and short DNA strands, it has been shown that a high degree of accumulation in hydrothermal pores occurs, so that temperature gradients might play a role in the origin of life [Baaske P, et al. (2007) Proc Natl Acad Sci USA 104(22):9346−9351]. We show that the same combination of thermophoresis and convection in hydrothermal pores...

  13. Kaolinite Mobilisation in Sandstone:Pore Plugging vs. Suspended Particles

    OpenAIRE

    Rosenbrand, Esther; Fabricius, Ida Lykke; Kets, Frans

    2013-01-01

    The effect of temperature and salinity on sandstone permeability is critical to the feasibility of heat storage in geothermal aquifers. Permeability reduction has been observed in Berea sandstone when the salinity of the pore water is reduced as well as when the sample is heated. Several authors suggest that this effect is due to kaolinite clay mobilisation from the quartz grain surface; the mobilised particles subsequently plug the pore throats and reduce the permeability irreversibly. The e...

  14. RNase A Does Not Translocate the Alpha-Hemolysin Pore

    OpenAIRE

    Besnik Krasniqi; Lee, Jeremy S

    2014-01-01

    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 i...

  15. Low Pore Connectivity Increases Bacterial Diversity in Soil▿

    OpenAIRE

    Carson, Jennifer K.; Gonzalez-Quiñones, Vanesa; Murphy, Daniel V.; Hinz, Christoph; Shaw, Jeremy A.; Gleeson, Deirdre B.

    2010-01-01

    One of soil microbiology's most intriguing puzzles is how so many different bacterial species can coexist in small volumes of soil when competition theory predicts that less competitive species should decline and eventually disappear. We provide evidence supporting the theory that low pore connectivity caused by low water potential (and therefore low water content) increases the diversity of a complex bacterial community in soil. We altered the pore connectivity of a soil by decreasing water ...

  16. Collective dynamics of flowing colloids during pore clogging

    OpenAIRE

    Agbangla, Gbedo Constant; Bacchin, Patrice; Climent, Eric

    2014-01-01

    Based on direct numerical simulations of the coupled motion of particles and fluid, this study analyzes the collective hydrodynamic and colloidal effects of flowing microparticles during the formation of different 3D clogging patterns at a pore entrance. Simulations of flowing suspensions through a pore with various simulation conditions show that particle concentration and surface interactions play a major role on the occurrence of the bridging phenomenon (simultaneous adhesion of many parti...

  17. Relationship between pore structure and compressive strength of concrete: Experiments and statistical modeling

    Indian Academy of Sciences (India)

    J BU; Z TIAN

    2016-03-01

    Properties of concrete are strongly dependent on its pore structure features, porosity being an important one among them. This study deals with developing an understanding of the pore structure-compressive strength relationship in concrete. Several concrete mixtures with different pore structures are proportioned and subjected to static compressive tests. The pore structure features such as porosity, pore size distribution are extracted using mercury intrusion porosimetry technique. A statistical model is developed to relate thecompressive strength to relevant pore structure features.

  18. Pore volume and pore size distribution of cement samples measured by a modified mercury intrusion porosimeter

    International Nuclear Information System (INIS)

    Important parameters for the characterization of cement specimens are mechanical properties and porosity. This work is carried out at the Ispra Establishment of the Joint Research Centre in the scope of the Radioactive Waste Management programme. A commercial Mercury Intrusion Porosimeter was modified in an attempt to improve the performance of the instrument and to provide fast processing of the recorded values: pressure-volume of pores. The dead volume of the instrument was reduced and the possibility of leakage from the moving parts eliminated. In addition, the modification allows an improvement of data acquisition thus increasing data accuracy and reproducibility. In order to test the improved performance of the modified instrument, physical characterizations of cement forms were carried out. Experimental procedures and results are reported

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

    International Nuclear Information System (INIS)

    A central concept for the geological barrier at the proposed Yucca Mountain radioactive waste repository is 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. The original concept of diffusive retardation required knowledge only of the fracture conductivity and the matrix diffusion. But that simple concept is unavoidably complicated by 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. Some of these issues have been examined by other projects. This particular project is motivated by a simple fact: Yucca Mountain tuff has low pore connectivity. This fact is not widely recognized, nor are its implications widely appreciated. Because low pore connectivity affects many processes, it may invalidate many assumptions that are basic (though perhaps not stated) to other investigations. The overall project's objective statement (from the proposal) was: This proposal aims to improve our understanding of diffusive retardation of radionuclides due to fracture/matrix interactions. Results from this combined experimental/modeling work will (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) evaluate the impact on diffusive retardation of episodic fracture flow and pore connectivity in Yucca Mountain tuffs. An obvious data gap addressed by the project was that there were only a few limited measurements of the diffusion coefficient of the rock at the repository level. That is, at the time we wrote

  20. On the Minimum Energy Path to Membrane Pore Formation

    Science.gov (United States)

    Ting, Christina; Wang, Zhen-Gang

    2011-03-01

    Several experimental methods have been developed to study the mechanical response of vesicles under an applied tension. Of particular note are the micropipette aspiration techniques and the use of a viscous solution to extend the lifetime of pores. MD simulations have also been used to study the energetic and structural properties of these transient pores on a molecular level. However, they often require extremely high tensions beyond the regime where pore formation is a thermally-activated event. We approach the nucleation problem by combining the string method with dynamic self-consistent field (DSCF) theory to obtain the full minimum energy path (MEP) to pore formation for a range of surface tensions γ . We compare our results with classical nucleation theory (CNT). Near the coexistence (γ --> 0) the rim of the pore is well-defined and the line tension is well approximated by the macroscopic definition given by CNT. However, when the free energy barrier is within ~ 10 kT , the transition state is somewhere between a stalk-like structure and a thinned membrane leading to a hole that is partially exposed to solvents. These molecular rearrangements involved in the formation of a pore are not captured by CNT.

  1. Smooth DNA transport through a narrowed pore geometry.

    Science.gov (United States)

    Carson, Spencer; Wilson, James; Aksimentiev, Aleksei; Wanunu, Meni

    2014-11-18

    Voltage-driven transport of double-stranded DNA through nanoscale pores holds much potential for applications in quantitative molecular biology and biotechnology, yet the microscopic details of translocation have proven to be challenging to decipher. Earlier experiments showed strong dependence of transport kinetics on pore size: fast regular transport in large pores (> 5 nm diameter), and slower yet heterogeneous transport time distributions in sub-5 nm pores, which imply a large positional uncertainty of the DNA in the pore as a function of the translocation time. In this work, we show that this anomalous transport is a result of DNA self-interaction, a phenomenon that is strictly pore-diameter dependent. We identify a regime in which DNA transport is regular, producing narrow and well-behaved dwell-time distributions that fit a simple drift-diffusion theory. Furthermore, a systematic study of the dependence of dwell time on DNA length reveals a single power-law scaling of 1.37 in the range of 35-20,000 bp. We highlight the resolution of our nanopore device by discriminating via single pulses 100 and 500 bp fragments in a mixture with >98% accuracy. When coupled to an appropriate sequence labeling method, our observation of smooth DNA translocation can pave the way for high-resolution DNA mapping and sizing applications in genomics. PMID:25418307

  2. Pore growth in U-Mo/Al dispersion fuel

    Science.gov (United States)

    Kim, Yeon Soo; Jeong, G. Y.; Sohn, D.-S.; Jamison, L. M.

    2016-09-01

    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.

  3. Accumulation of formamide in hydrothermal pores to form prebiotic nucleobases

    Science.gov (United States)

    Niether, Doreen; Afanasenkau, Dzmitry; Dhont, Jan K. G.

    2016-04-01

    Formamide is one of the important compounds from which prebiotic molecules can be synthesized, provided that its concentration is sufficiently high. For nucleotides and short DNA strands, it has been shown that a high degree of accumulation in hydrothermal pores occurs, so that temperature gradients might play a role in the origin of life [Baaske P, et al. (2007) Proc Natl Acad Sci USA 104(22):9346-9351]. We show that the same combination of thermophoresis and convection in hydrothermal pores leads to accumulation of formamide up to concentrations where nucleobases are formed. The thermophoretic properties of aqueous formamide solutions are studied by means of Infrared Thermal Diffusion Forced Rayleigh Scattering. These data are used in numerical finite element calculations in hydrothermal pores for various initial concentrations, ambient temperatures, and pore sizes. The high degree of formamide accumulation is due to an unusual temperature and concentration dependence of the thermophoretic behavior of formamide. The accumulation fold in part of the pores increases strongly with increasing aspect ratio of the pores, and saturates to highly concentrated aqueous formamide solutions of ˜85 wt% at large aspect ratios. Time-dependent studies show that these high concentrations are reached after 45-90 d, starting with an initial formamide weight fraction of 10-310-3 wt % that is typical for concentrations in shallow lakes on early Earth.

  4. 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.

  5. Pore size and the lab-field reaction rate riddle

    Science.gov (United States)

    Emmanuel, S.; Ague, J. J.; Walderhaug, O.

    2009-12-01

    Pore size is usually thought to influence the rate of crystal growth during diagenesis and metamorphism by controlling the ratio of surface area to fluid volume. However, theory suggests that in micron-scale to nanometer-scale pores, interfacial energy effects can also become important. We used mercury porosimetry to investigate the pore-size distributions in naturally cemented sandstone adjacent to stylolites and found that quartz precipitation was inhibited in pores smaller than 10 microns in diameter. We demonstrate that standard kinetic models cannot reproduce the observed pore-size patterns in mineralized samples; by contrast, excellent fits with the data are obtained when interfacial energy effects are taken into account. Moreover, as such micron-scale pores comprise the overwhelming majority of surface area in the sandstone, average reaction rates for the rock are significantly reduced. Reaction rates in geological media determined in field studies can be orders of magnitude lower than those measured in laboratory experiments, and we propose that reduced reaction rates in rocks with micron-scale porosity could account for the apparent paradox.

  6. Pore Scale Analysis of Oil Shale/Sands Pyrolysis

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Chen-Luh; Miller, Jan

    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 (❍m) 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.

  7. Accumulation of formamide in hydrothermal pores to form prebiotic nucleobases.

    Science.gov (United States)

    Niether, Doreen; Afanasenkau, Dzmitry; Dhont, Jan K G; Wiegand, Simone

    2016-04-19

    Formamide is one of the important compounds from which prebiotic molecules can be synthesized, provided that its concentration is sufficiently high. For nucleotides and short DNA strands, it has been shown that a high degree of accumulation in hydrothermal pores occurs, so that temperature gradients might play a role in the origin of life [Baaske P, et al. (2007)Proc Natl Acad Sci USA104(22):9346-9351]. We show that the same combination of thermophoresis and convection in hydrothermal pores leads to accumulation of formamide up to concentrations where nucleobases are formed. The thermophoretic properties of aqueous formamide solutions are studied by means of Infrared Thermal Diffusion Forced Rayleigh Scattering. These data are used in numerical finite element calculations in hydrothermal pores for various initial concentrations, ambient temperatures, and pore sizes. The high degree of formamide accumulation is due to an unusual temperature and concentration dependence of the thermophoretic behavior of formamide. The accumulation fold in part of the pores increases strongly with increasing aspect ratio of the pores, and saturates to highly concentrated aqueous formamide solutions of ∼85 wt% at large aspect ratios. Time-dependent studies show that these high concentrations are reached after 45-90 d, starting with an initial formamide weight fraction of[Formula: see text]wt % that is typical for concentrations in shallow lakes on early Earth. PMID:27044100

  8. [Pore structure and desulfurization characteristics of organic calcium].

    Science.gov (United States)

    Xiao, Hai-ping; Li, Jing-tao; Zhou, Jun-hu; Sun, Bao-min; Ye, Li-ping

    2008-08-01

    Calcination of oganic calcium was carried out in fixed bed, pore structure of tested sample was analyzed with auto-adsorption analyzer, and desulfurization experiment was studied by intelligent sulfur determination analyzer. Specific surface area of calcium magnesium acetate (CMA) was 46.6 m2/g after calcination at 900 degrees C, almost four times of that of limestone. Specific surface area of calcium acetate (CA) were mainly made up of pore of diameter less than 5 nm, and those of CMA was chiefly contributed by middle pore of diameter about 5 nm. Agglomeration of CA occurred in pore of diameter less than 5 nm, while CMA was sintered in whole range of pore size distribution. Agglomeration of organic calcium were slighter. Desulfurization efficiency of organic calcium ranged from 62.28% to 75.55% at 1000 degrees C as calcium/sulfur ratio being one, which was one time more than that of limestone. Perfect pore structure of organic calcium contributes to higher desulfurization efficiency. PMID:18839601

  9. Membrane pore formation in atomistic and coarse-grained simulations.

    Science.gov (United States)

    Kirsch, Sonja A; Böckmann, Rainer A

    2016-10-01

    Biological cells and their organelles are protected by ultra thin membranes. These membranes accomplish a broad variety of important tasks like separating the cell content from the outer environment, they are the site for cell-cell interactions and many enzymatic reactions, and control the in- and efflux of metabolites. For certain physiological functions e.g. in the fusion of membranes and also in a number of biotechnological applications like gene transfection the membrane integrity needs to be compromised to allow for instance for the exchange of polar molecules across the membrane barrier. Mechanisms enabling the transport of molecules across the membrane involve membrane proteins that form specific pores or act as transporters, but also so-called lipid pores induced by external fields, stress, or peptides. Recent progress in the simulation field enabled to closely mimic pore formation as supposed to occur in vivo or in vitro. Here, we review different simulation-based approaches in the study of membrane pores with a focus on lipid pore properties such as their size and energetics, poration mechanisms based on the application of external fields, charge imbalances, or surface tension, and on pores that are induced by small molecules, peptides, and lipids. This article is part of a Special Issue entitled: Biosimulations edited by Ilpo Vattulainen and Tomasz Róg. PMID:26748016

  10. Mangrove pore water exchange across a latitudinal gradient

    Science.gov (United States)

    Tait, Douglas R.; Maher, Damien T.; Macklin, Paul A.; Santos, Isaac R.

    2016-04-01

    We combined observations of the natural tracer radon (222Rn) with hydrodynamic models across a broad latitudinal gradient covering several climate zones to estimate pore water exchange rates in mangroves. Pore water exchange ranged from 2.1 to 35.5 cm d-1 from temperate to tropical regions and averaged 16.3 ± 5.1 cm d-1. If upscaled to the global weighted mangrove area, pore water exchange in mangroves would recirculate the entire volume of water overlying the continental shelf in less than 153 years. Although pore water exchange (recirculated seawater) and river discharge represent different pathways for water entering the coastal ocean, the estimated global mangrove pore water exchange would be equal to approximately one third of annual global river discharge to the ocean (3.84 × 1013 m3 yr-1). Because biogeochemical processes in mangroves are largely dependent on pore water exchange, these large exchange rates have major implications for coastal nutrient, carbon, and greenhouse gas cycling in tropical marine systems.

  11. Local membrane mechanics of pore-spanning bilayers.

    Science.gov (United States)

    Mey, Ingo; Stephan, Milena; Schmitt, Eva K; Müller, Martin Michael; Ben Amar, Martine; Steinem, Claudia; Janshoff, Andreas

    2009-05-27

    The mechanical behavior of lipid bilayers spanning the pores of highly ordered porous silicon substrates was scrutinized by local indentation experiments as a function of surface functionalization, lipid composition, solvent content, indentation velocity, and pore radius. Solvent-containing nano black lipid membranes (nano-BLMs) as well as solvent-free pore-spanning bilayers were imaged by fluorescence and atomic force microscopy prior to force curve acquisition, which allows distinguishing between membrane-covered and uncovered pores. Force indentation curves on pore-spanning bilayers attached to functionalized hydrophobic porous silicon substrates reveal a predominately linear response that is mainly attributed to prestress in the membranes. This is in agreement with the observation that indentation leads to membrane lysis well below 5% area dilatation. However, membrane bending and lateral tension dominate over prestress and stretching if solvent-free supported membranes obtained from spreading giant liposomes on hydrophilic porous silicon are indented. An elastic regime diagram is presented that readily allows determining the dominant contribution to the mechanical response upon indentation as a function of load and pore radius. PMID:19453196

  12. Pore scale definition and computation from tomography data

    Science.gov (United States)

    Dupuy, P. M.; Austin, P.; Delaney, G. W.; Schwarz, M. P.

    2011-10-01

    During recent years characterisation capabilities of porous media have been transformed by advances in computation and visualisation technologies. It is now possible to obtain detailed topological and hydrodynamic information of porous media by combining tomographic and computational fluid dynamic studies. Despite the existence of these new capabilities, the characterisation process itself is based on the same antiquated experimental macroscopic concepts. We are interested in an up-scaling process where we can keep key information for every pore size present in the media in order to feed multi-scale transport models. Hydrometallurgical, environmental, food, pharmaceutical and chemical engineering are industries with process outcomes based on homogeneous and heterogeneous reactions and therefore sensitive to the reaction and transport processes happening at different pore scales. The present work addresses a key step in the information up-scaling process, i.e. a pore identification algorithm similar to alternating sequential filters. In a preliminary study, topological and hydrodynamic variables are correlated with the pore size. Micrometre and millimetre resolution tomographies are used to characterise the pore size distribution of a packed column and different rocks. Finally, we compute the inter-pore-scale redistribution function which is a measure of the heterogeneity of the media and magnitude needed in multi-scale modelling.

  13. Quantification of subsurface pore pressure through IODP drilling

    Science.gov (United States)

    Saffer, D. M.; Flemings, P. B.

    2010-12-01

    It is critical to understand the magnitude and distribution of subsurface pore fluid pressure: it controls effective stress and thus mechanical strength, slope stability, and sediment compaction. Elevated pore pressures also drive fluid flows that serve as agents of mass, solute, and heat fluxes. The Ocean Drilling Program (ODP) and Integrated Ocean Drilling Program (IODP) have provided important avenues to quantify pore pressure in a range of geologic and tectonic settings. These approaches include 1) analysis of continuous downhole logs and shipboard physical properties data to infer compaction state and in situ pressure and stress, 2) laboratory consolidation testing of core samples collected by drilling, 3) direct downhole measurements using pore pressure probes, 3) pore pressure and stress measurements using downhole tools that can be deployed in wide diameter pipe recently acquired for riser drilling, and 4) long-term monitoring of formation pore pressure in sealed boreholes within hydraulically isolated intervals. Here, we summarize key advances in quantification of subsurface pore pressure rooted in scientific drilling, highlighting with examples from subduction zones, the Gulf of Mexico, and the New Jersey continental shelf. At the Nankai, Costa Rican, and Barbados subduction zones, consolidation testing of cores samples, combined with analysis of physical properties data, indicates that even within a few km landward of the trench, pore pressures in and below plate boundary décollement zones reach a significant fraction of the lithostatic load (λ*=0.25-0.91). These results document a viable and quantifiable mechanism to explain the mechanical weakness of subduction décollements, and are corroborated by a small number of direct measurements in sealed boreholes and by inferences from seismic reflection data. Recent downhole measurements conducted during riser drilling using the modular formation dynamics tester wireline tool (MDT) in a forearc basin ~50

  14. Impact of Nano-Pore Structure in Harden Non-Sintering Cement.

    Science.gov (United States)

    Seo, Seong-Gyu; Kim, Sang-Chai; Kim, Eun-Sik; Mun, Kyoung-Ju; Park, Won-Chun; Eum, Hyun-Mi; Yoon, Hyung-Sun

    2015-07-01

    This study investigates the nano pore structure of non-sintering cement (NSC) matrix. The result of pore structure properties showed no considerable difference in the total pore volume, but presented a large distinction in distribution of pore diameter by cement mixing ratio. The pore-diameter of NSC paste shows that occupation ratio of pore diameter below 10 nm was larger and was smaller than ordinary Portland cement (OPC) and blast-furnace slag cement (BSC) at pore diameter of over 10 nm. The reasons are due to the hydrate such as C-S-H gel and ettringite which formed dense nano pore structure of NSC matrix. PMID:26373159

  15. Modeling of seismic field in porous medium:Simulation study of single pore and pore ensemble effects

    Science.gov (United States)

    Shatskaya, A. A.; Nemirovich-Danchenko, M. M.; Terre, D. A.

    2015-11-01

    The article considers the effect of porous media on elastic wave field. Based on numerical modeling, diffraction pattern of the wave propagating through a single pore in carbonates has been produced. Matrix properties (calcite and dolomite) and fluid (water) are modeled based on thin core section image. The qualitative comparison with the available computational data has been performed. Provided that ensemble of pores is involved, the effect of porous medium on seismic field has been studied. For comparison with experimental data the model of porous sintered aluminum Al-6061 has been considered. The processing of numerical modeling results made it possible to estimate average velocities in the model of porous aluminum and compare them with physical modeling data. The provided estimates have indicated qualitative (single pore) and quantitative (ensemble of pores) correlation of simulation and experiment results.

  16. Morphology of the pore space in claystones - evidence from BIB/FIB ion beam sectioning and cryo-SEM observations

    Science.gov (United States)

    Desbois, G.; Urai, J. L.; Kukla, P. A.

    2009-12-01

    microstructure. 3-D reconstruction by serial cross-sectioning shows 3-D connectivity of the pore space. These findings offer a new insight into the morphology of pores down to nano-scale and provide the basis for microstructure-based models of transport in clays. SEM image (SE) of a Broad Ion Beam polished cross-section performed on dry Boom clay (Mol site, Belgium) showing the 2D apparent porosity (26.3%). The cross-section is perpendicular to the bedding.

  17. Anterior cruciate ligament reconstruction

    International Nuclear Information System (INIS)

    This paper determines the efficacy of MR imaging in evaluation of the anterior cruciate ligament (ACL) following reconstructive surgery. Forty-three MR examinations were performed in 33 patients who had undergone previous arthroscopic ACL reconstruction with patellar bone-tendon- bone autografts (postoperative period, 1-24 months; mean, 5.2 months). Of the 40 studies performed in clinically stable knees (30 patients), MR demonstrated a well-defined, signal void ACL graft in 36. Of the three studies performed in three patients with clinical ACL laxity or suspected tear, the neoligament was of intermediate definition in one and nondiscernible in the other two. As in the native knee, buckling of the PCL was suggestive of ACL insufficiency. Bone tunnel placement, patellar tendon changes, and joint effusions were also evaluated

  18. Reconstructing the Tengger calendar

    Directory of Open Access Journals (Sweden)

    Ian Proudfoot

    2008-12-01

    Full Text Available The survival of an Indic calendar among the Tengger people of the Brama highlands in east Java opens a window on Java’s calendar history. Its hybrid form reflects accommodations between this non-Muslim Javanese group and the increasingly dominant Muslim Javanese culture. Reconstruction is challenging because of this hybridity, because of inconsistencies in practice, and because the historical evidence is sketchy and often difficult to interpret.

  19. Reconstructing the Tengger calendar

    OpenAIRE

    Ian Proudfoot

    2008-01-01

    The survival of an Indic calendar among the Tengger people of the Brama highlands in east Java opens a window on Java’s calendar history. Its hybrid form reflects accommodations between this non-Muslim Javanese group and the increasingly dominant Muslim Javanese culture. Reconstruction is challenging because of this hybridity, because of inconsistencies in practice, and because the historical evidence is sketchy and often difficult to interpret.

  20. Reconstructing holographic quintessence

    OpenAIRE

    Zhang, Xin

    2006-01-01

    The holographic dark energy model is an attempt for probing the nature of dark energy within the framework of quantum gravity. The dimensionless parameter $c$ determines the main property of the holographic dark energy. With the choice of $c\\geq 1$, the holographic dark energy can be described completely by a quintessence scalar field. In this paper, we show this quintessential description of the holographic dark energy with $c\\geq 1$ and reconstruct the potential of the quintessence as well ...

  1. LOFAR sparse image reconstruction

    Science.gov (United States)

    Garsden, H.; Girard, J. N.; Starck, J. L.; Corbel, S.; Tasse, C.; Woiselle, A.; McKean, J. P.; van Amesfoort, A. S.; Anderson, J.; Avruch, I. M.; Beck, R.; Bentum, M. J.; Best, P.; Breitling, F.; Broderick, J.; Brüggen, M.; Butcher, H. R.; Ciardi, B.; de Gasperin, F.; de Geus, E.; de Vos, M.; Duscha, S.; Eislöffel, J.; Engels, D.; Falcke, H.; Fallows, R. A.; Fender, R.; Ferrari, C.; Frieswijk, W.; Garrett, M. A.; Grießmeier, J.; Gunst, A. W.; Hassall, T. E.; Heald, G.; Hoeft, M.; Hörandel, J.; van der Horst, A.; Juette, E.; Karastergiou, A.; Kondratiev, V. I.; Kramer, M.; Kuniyoshi, M.; Kuper, G.; Mann, G.; Markoff, S.; McFadden, R.; McKay-Bukowski, D.; Mulcahy, D. D.; Munk, H.; Norden, M. J.; Orru, E.; Paas, H.; Pandey-Pommier, M.; Pandey, V. N.; Pietka, G.; Pizzo, R.; Polatidis, A. G.; Renting, A.; Röttgering, H.; Rowlinson, A.; Schwarz, D.; Sluman, J.; Smirnov, O.; Stappers, B. W.; Steinmetz, M.; Stewart, A.; Swinbank, J.; Tagger, M.; Tang, Y.; Tasse, C.; Thoudam, S.; Toribio, C.; Vermeulen, R.; Vocks, C.; van Weeren, R. J.; Wijnholds, S. J.; Wise, M. W.; Wucknitz, O.; Yatawatta, S.; Zarka, P.; Zensus, A.

    2015-03-01

    Context. The LOw Frequency ARray (LOFAR) radio telescope is a giant digital phased array interferometer with multiple antennas distributed in Europe. It provides discrete sets of Fourier components of the sky brightness. Recovering the original brightness distribution with aperture synthesis forms an inverse problem that can be solved by various deconvolution and minimization methods. Aims: Recent papers have established a clear link between the discrete nature of radio interferometry measurement and the "compressed sensing" (CS) theory, which supports sparse reconstruction methods to form an image from the measured visibilities. Empowered by proximal theory, CS offers a sound framework for efficient global minimization and sparse data representation using fast algorithms. Combined with instrumental direction-dependent effects (DDE) in the scope of a real instrument, we developed and validated a new method based on this framework. Methods: We implemented a sparse reconstruction method in the standard LOFAR imaging tool and compared the photometric and resolution performance of this new imager with that of CLEAN-based methods (CLEAN and MS-CLEAN) with simulated and real LOFAR data. Results: We show that i) sparse reconstruction performs as well as CLEAN in recovering the flux of point sources; ii) performs much better on extended objects (the root mean square error is reduced by a factor of up to 10); and iii) provides a solution with an effective angular resolution 2-3 times better than the CLEAN images. Conclusions: Sparse recovery gives a correct photometry on high dynamic and wide-field images and improved realistic structures of extended sources (of simulated and real LOFAR datasets). This sparse reconstruction method is compatible with modern interferometric imagers that handle DDE corrections (A- and W-projections) required for current and future instruments such as LOFAR and SKA.

  2. The art of reconstruction

    OpenAIRE

    Healey, Michael; Esson, Michael

    2011-01-01

    The ‘Art of Reconstruction Research Project’ is where re-skilling of plastic surgeons by artists is already in an embryonic phase. In integrating the required network of associated skills, expertise and experience, the research collaboration brings together artists within The Drawing Research Group of The Faculty of Art, Architecture and Design (AAD) and the distinguished work of Professor Mike Esson, Director, The International Drawing Research Institute (IDRI). Th...

  3. Reconstruction of vaginal agenesis.

    Science.gov (United States)

    Ozkan, Ozlenen; Erman Akar, Münire; Ozkan, Omer; Doğan, N Utku

    2011-06-01

    Vaginal ageneses are by no means rare anomalies. Complete Mullerian agenesis is the most common reason for vaginal agenesis requiring reconstruction. Patients usually present with pain, hematocolpos, or hematometra in puberty, and later with amenorrhea and dyspareunia. Detailed information is given here regarding etiologies, timing of surgery, and current treatment options for vaginal agenesis. Outcomes and short- and long-term complications of recent treatment options are also discussed. PMID:21372677

  4. Orthotopic neobladder reconstruction

    OpenAIRE

    Chang, Dwayne T. S.; Nathan Lawrentschuk

    2015-01-01

    Orthotopic neobladder reconstruction is becoming an increasingly common urinary diversion following cystectomy for bladder cancer. This is in recognition of the potential benefits of neobladder surgery over creation of an ileal conduit related to quality of life (QoL), such as avoiding the need to form a stoma with its cosmetic, psychological and other potential complications. The PubMed database was searched using relevant search terms for articles published electronically between January 19...

  5. MD simulation of organics adsorption from aqueous solution in carbon slit-like pores. Foundations of the pore blocking effect

    International Nuclear Information System (INIS)

    The results of systematic studies of organics adsorption from aqueous solutions (at the neutral pH level) in a system of slit-like carbon pores having different sizes and oxygen groups located at the pore mouth are reported. Using molecular dynamics simulations (GROMACS package) the properties of adsorbent–adsorbate (benzene, phenol or paracetamol) as well as adsorbent–water systems are discussed. After the introduction of surface oxygen functionalities, adsorption of organic compounds decreases (in accordance with experimental data) and this is caused by the accumulation of water molecules at pore entrances. The pore blocking effect decreases with the diameter of slits and practically vanishes for widths larger than approx. 0.68 nm. We observed the increase in phenol adsorption with the rise in temperature. Moreover, adsorbed molecules occupy the external surface of the slit pores (the entrances) in the case of oxidized adsorbents. Among the studied molecules benzene, phenol and paracetamol prefer an almost flat orientation and with the rise in the pore width the number of molecules oriented in parallel decreases. The decrease or increase in temperature (with respect to 298 K) leads to insignificant changes of angular orientation of adsorbed molecules. (paper)

  6. Unified method for the total pore volume and pore size distribution of hierarchical zeolites from argon adsorption and mercury intrusion.

    Science.gov (United States)

    Kenvin, Jeffrey; Jagiello, Jacek; Mitchell, Sharon; Pérez-Ramírez, Javier

    2015-02-01

    A generalized approach to determine the complete distribution of macropores, mesopores, and micropores from argon adsorption and mercury porosimetry is developed and validated for advanced zeolite catalysts with hierarchically structured pore systems in powder and shaped forms. Rather than using a fragmented approach of simple overlays from individual techniques, a unified approach that utilizes a kernel constructed from model isotherms and model intrusion curves is used to calculate the complete pore size distribution and the total pore volume of the material. An added benefit of a single full-range pore size distribution is that the cumulative pore area and the area distribution are also obtained without the need for additional modeling. The resulting complete pore size distribution and the kernel accurately model both the adsorption isotherm and the mercury porosimetry. By bridging the data analysis of two primary characterization tools, this methodology fills an existing gap in the library of familiar methods for porosity assessment in the design of materials with multilevel porosity for novel technological applications. PMID:25603366

  7. Determination of the pore size distribution of micro porous layer in PEMFC using pore forming agents under various drying conditions

    Energy Technology Data Exchange (ETDEWEB)

    Chun, Jeong Hwan; Park, Ki Tae; Jo, Dong Hyun; Lee, Ji Young; Kim, Sang Gon; Kim, Sung Hyun [Department of Chemical and Biological Engineering, Korea University, 1 Anam-Dong, Seongbuk-Ku, Seoul 136-713 (Korea); Lee, Eun Sook; Jyoung, Jy-Young [Energy Research Center, HyupJin I and C Co., LTD, 143-1 Gwelang-Ri, Jungnam-Myun, Hwasung-Si, Kyunggi-Do (Korea)

    2010-10-15

    In this paper, the effect of the pore size distribution of a micro-porous layer (MPL) on the performance of polymer electrolyte membrane fuel cells (PEMFC) was investigated using self-made gas diffusion layers (GDLs) with different MPLs for which the pore size distribution was modified using pore forming agents under different drying conditions. When MPL dried at high temperature, more macro pores, approximately 1,000-20,000 nm in diameter, and less micro pores, below 100 nm, were observed relative to when MPL was dried at low temperature. Self-made GDLs were characterized by a field-emission scanning electron microscope (FE-SEM), mercury porosimetry and self-made gas permeability measurement equipment. The performance of the single cells was measured under two different humidification conditions. The results demonstrate that the optimum pore size distribution of MPL depended on the cell operating humidification condition. The MPL dried at high temperature performed better than the MPL dried at low temperature under a low humidification condition; however, MPL dried at low temperature performed better under a high humidification condition. (author)

  8. Canal Wall Reconstruction Mastoidectomy

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Objective To investigate the advantages of canal wall reconstruction (CWR) mastoidectomy, a single-stage technique for cholesteatoma removal and posterior external canal wall reconstruction, over the open and closed procedures in terms of cholesteatoma recurrence. Methods: Between June 2002 and December 2005, 38 patients (40 ears) with cholesteatoma were admited to Sun Yat-Sen Memorial Hospital and received surgical treatments. Of these patients, 25 were male with ages ranging between 11 and 60 years (mean = 31.6 years) and 13 were female with ages ranging between 20 and 65 years (mean = 38.8 years). Canal wall reconstruction (CWR)mastoidectomy was performed in 31 ears and canal wall down (CWD) mastoidectomy in 9 ears. Concha cartilage was used for ear canal wall reconstruction in 22 of the 31 CWR procedures and cortical mastoid bone was used in the remaining 9 cases. Results At 0.5 to 4 years follow up, all but one patients remained free of signs of cholesteatoma recurrence, i.e., no retraction pocket or cholesteatoma matrix. One patient, a smoker, needed revision surgery due to cholesteatoma recurrence 1.5 year after the initial operation. The recurrence rate was therefore 3.2% (1/31). Cholesteatoma recurrence was monitored using postoperative CT scans whenever possible. In the case that needed a revision procedure, a retraction pocket was identified by otoendoscopy in the pars flacida area that eventually evolved into a cholesteatoma. A pocket extending to the epitympanum filled with cholesteatoma matrix was confirmed during the revision operation, A decision to perform a modified mastoidectomy was made as the patient refused to quit smoking. The mean air-bone gap in pure tone threshold was 45 dB before surgery and 25 dB after (p < 0.05). There was no difference between using concha cartilage and cortical mastoid bone for the reconstruction regarding air-bone gap improvement, CT findings and otoendoscopic results. Conclusion CWR mastoidectomy can be used for

  9. Fractal classification and natural classification of coal pore structure based on migration of coal bed methane

    Institute of Scientific and Technical Information of China (English)

    FU Xuehai; QIN Yong; ZHANG Wanhong; WEI Chongtao; ZHOU Rongfu

    2005-01-01

    According to the data of 146 coal samples measured by mercury penetration, coal pores are classified into two levels of <65 nm diffusion pore and >65 nm seeping pore by fractal method based on the characteristics of diffusion, seepage of coal bed methane(CBM) and on the research results of specific pore volume and pore structure. The diffusion pores are further divided into three categories: <8 nm micropore, 8-20 nm transitional pore, and 20-65 nm minipore based on the relationship between increment of specific surface area and diameter of pores, while seepage pores are further divided into three categories: 65-325 nm mesopore,325-1000 nm transitional pore, and >1000 nm macropore based on the abrupt change in the increment of specific pore volume.

  10. 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/.

  11. Synthesis of Novel Mesoporous Silica Materials with Hierarchical Pore Structures

    International Nuclear Information System (INIS)

    Porous materials with various pore sizes in the range of micropore ( 50 nm) are attractive due to their many emerging applications such as catalysts, separation systems, and low dielectric constant materials. The discovery of new M41S mesoporous silica families with pore sizes larger than 2 nm in diameter in 1992 extended the applications into much wider pore ranges, bringing in a new prosperous era in porous material research. The synthesis of these silica materials has been mainly accomplished through a self-assembly between surfactant molecules and inorganic species under various pH conditions. Recently, core-shell nanoparticles with a silica core and mesoporous shell under basic conditions were synthesized using the silica nanoparticles as a core, and a silica precursor (TEOS) and cationic surfactant (CTABr) as a material for the formation of the mesoporous shell. The resultant materials were very monodispersive in size and showed a narrow pore size distribution in the range of ca 2-3 nm in diameter, depending on the alkyl-chain length of the surfactants used. In this work, the mesoporous shell coated-fumed silicas (denoted as MS M-5s) were synthesized by using fumed silica instead of the silica nanoparticle as a core based on previous reports. Also, the structural properties of the MS M-5s such as the specific surface area and pore volume were easily controlled by varying the amount of the silica precursor and surfactant. The resultant materials exhibited a BET surface area of ca 279-446 m2/g and total pore volume of ca 0.64-0.74 cm3/g and showed a narrow pore size distribution (PSD) due to the removal of the organic surfactant molecules

  12. A robust model for pore-water chemistry of clayrock

    Science.gov (United States)

    Gaucher, E. C.; Tournassat, C.; Pearson, F. J.; Blanc, P.; Crouzet, C.; Lerouge, C.; Altmann, S.

    2009-11-01

    The chemistry of pore water is an important property of clayrocks being considered as host rocks for long-term storage of radioactive waste. It may be difficult, if not impossible, to obtain water samples for chemical analysis from such rocks because of their low hydraulic conductivity. This paper presents an approach for calculating the pore-water compositions of clayrocks from laboratory-measured properties of core samples, including their leachable Cl and SO 4 concentrations and analysed exchangeable cations, and from mineral and cation exchange equilibria based on the formation mineralogy. New core sampling and analysis procedures are presented that reduce or quantify side reactions such as sample oxidation (e.g. pyrite) and soluble mineral dissolution (celestite, SrSO 4) that affect measured SO 4 concentrations and exchangeable cation distributions. The model considers phase equilibria only with minerals that are observed in the formation including the principal clay phases. The model has been used to calculate the composition of mobile pore water in the Callovo-Oxfordian clayrock and validated against measurements of water chemistry made in an underground research laboratory in that formation. The model reproduces the measured, in situ pore-water composition without any estimated parameters. All required parameters can be obtained from core sample analysis. We highlight the need to consider only those mineral phases which can be shown to be in equilibrium with contacting pore water. The consequence of this is that some conceptual models available in the literature appear not to be appropriate for modelling clayrocks, particularly those considering high temperature and/or high pressure detrital phases as chemical buffers of pore water. The robustness of our model with respect to uncertainties in the log K values of clay phases is also demonstrated. Large uncertainties in log K values for clay minerals have relatively small effects on modelled pore

  13. Assessment of Image Processing and Resolution on Permeability and Drainage Simulations Through 3D Pore-networks Obtained Using X-ray Computed Tomography

    Science.gov (United States)

    Mills, G.; Willson, C. S.; Thompson, K. E.; Rivers, M. L.

    2013-12-01

    Typically, continuum-scale flow parameters are obtained through laboratory experiments. Over the past several years, image-based modeling, which is a direct simulation of flow through the structural arrangements of the voids and solids obtained using X-ray computed tomography (XCT) in a sample porous medium, has become a reliable technique for predicting certain flow parameters. Even though XCT is capable of resolving micron-level details, the voxel resolution of the reconstructed image is still dependent upon a number of factors, including the sample size, X-ray energy and XCT beamline setup. Thus, each imaging experiment requires a tradeoff between the sample size that can be imaged, the voxel resolution, and the length scale of the pore space that can be extracted. In addition, the geometric and topological properties of the void space and 3D pore network structure are dictated by the image processing and the choice of pore network generation method. In this research, image-based pore network models are used to quantitatively assess the impact of image resolution, image processing and the choice of pore network generation methods on simulated parameters. A 5 mm diameter and ~15 mm in length Berea sandstone core was scanned two times. First, a ~12 mm long section of the entire cross-section was scanned at 4.1 micron voxel resolution; next, a ~1.4 mm diameter and ~4.12 mm length section within the 1st domain was scanned at 1 micron voxel resolution. The resulting 3D datasets were filtered and segmented into solid and void space. The low resolution image was filtered and segmented using two different approaches in order to evaluate the potential of each approach in identifying the different solid phases in the original 16 bit dataset. A set of networks were created by varying the pore density on both the high and low resolution datasets in order to assess the impact of these factors on flow simulations. Single-phase permeability and a two-phase drainage pore

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

    International Nuclear Information System (INIS)

    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

  15. 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

  16. Combination of SANS and 3D stochastic reconstruction techniques for the study of nanostructured materials

    CERN Document Server

    Kikkinides, E S; Steriotis, T A; Kanellopoulos, N K; Mitropoulos, A C; Treimer, W

    2002-01-01

    Ceramic nanostructured materials have recently received scientific and industrial interest due to their unique properties. A series of such nanoporous structures were characterised by SANS techniques. The resulting scattering curves were analysed to obtain basic structural information regarding the pore size distribution and autocorrelation function of each material. Furthermore, stochastic reconstruction models were employed to generate 3D images with the same basic structural characteristics obtained from SANS. Finally, simulation results of permeation on the reconstructed images provide very good agreement with experimental data. (orig.)

  17. Impacts of simulated drought on pore water chemistry of peatlands

    International Nuclear Information System (INIS)

    Northern peatlands are increasingly threatened by climate change and industrial activities. This study examined the impact of simulated droughts on pore water chemistry at six peatlands in Sudbury, Ontario, that differ in copper (Cu), nickel (Ni) and cobalt (Co) contamination, including a site that had been previously limed. All sites responded similarly to simulated drought: pore water pH declined significantly following the 30 day drought and the decline was greater following the 60 day drought treatment. The decline in pore water pH was due to increasing sulphate concentrations, whereas nitrate increased more in the 60 day drought treatment. Decreases in pH were accompanied by large increases in Ni and Co that greatly exceeded provincial water quality guidelines. In contrast, dissolved organic carbon (DOC) concentrations decreased significantly following drought, along with concentrations of Cu and Al, which are strongly complexed by organic acids. -- Highlights: • Assessed impact of simulated 30 and 60 day droughts on peatland pore water chemistry. • Release of SO4 and NO3 induces peatland acidification. • Release of Ni and Co increases with drought duration. • Dissolved organic carbon decreases with drought along with Cu and Al. • Historical liming does not greatly reduce drought impact. -- Simulated drought acidifies pore water of peatlands and increases Ni and Co but decreases DOC, Cu and Al concentration

  18. SCAM analysis of Panx1 suggests a peculiar pore structure.

    Science.gov (United States)

    Wang, Junjie; Dahl, Gerhard

    2010-11-01

    Vertebrates express two families of gap junction proteins: the well-characterized connexins and the pannexins. In contrast to connexins, pannexins do not appear to form gap junction channels but instead function as unpaired membrane channels. Pannexins have no sequence homology to connexins but are distantly related to the invertebrate gap junction proteins, innexins. Despite the sequence diversity, pannexins and connexins form channels with similar permeability properties and exhibit similar membrane topology, with two extracellular loops, four transmembrane (TM) segments, and cytoplasmic localization of amino and carboxy termini. To test whether the similarities extend to the pore structure of the channels, pannexin 1 (Panx1) was subjected to analysis with the substituted cysteine accessibility method (SCAM). The thiol reagents maleimidobutyryl-biocytin and 2-trimethylammonioethyl-methanethiosulfonate reacted with several cysteines positioned in the external portion of the first TM segment (TM1) and the first extracellular loop. These data suggest that portions of TM1 and the first extracellular loop line the outer part of the pore of Panx1 channels. In this aspect, the pore structures of Panx1 and connexin channels are similar. However, although the inner part of the pore is lined by amino-terminal amino acids in connexin channels, thiol modification was detected in carboxyterminal amino acids in Panx1 channels by SCAM analysis. Thus, it appears that the inner portion of the pores of Panx1 and connexin channels may be distinct. PMID:20937692

  19. Regulation of soil organic C mineralisation at the pore scale.

    Science.gov (United States)

    Ruamps, Léo S; Nunan, Naoise; Pouteau, Valérie; Leloup, Julie; Raynaud, Xavier; Roy, Virginie; Chenu, Claire

    2013-10-01

    Little is known about the factors that regulate C mineralisation at the soil pore scale or how these factors vary throughout the pore network. This study sought to understand how the decomposition of organic carbon varies within the soil pore network and to determine the relative importance of local environmental properties relative to biological properties as controlling factors. This was achieved by sterilising samples of soil and reinoculating them with axenic bacterial suspensions using the matric potential to target different locations in the pore network. Carbon mineralisation curves were described with two-compartment first-order models to distinguish CO2 derived from the labile organic carbon released during sterilisation from CO2 derived from organic C unaffected by sterilisation. The data indicated that the size of the labile pool of organic C, possibly of microbial origin, varied as a function of location in the pore network but that the organic carbon unaffected by sterilisation did not. The mineralisation rate of the labile C varied with the bacterial type inoculated, but the mineralisation rate of the organic C unaffected by sterilisation was insensitive to bacterial type. Taken together, the results suggest that microbial metabolism is a less significant regulator of soil organic carbon decomposition than are microbial habitat properties. PMID:23346944

  20. Phase Transitions of 2-Decanol in Nano Pores

    Science.gov (United States)

    Amanuel, Samuel; Turner, Jason; Novins, Caleb; Clain, Alexander

    We studied the melting of 2-decanol confined in nano pores, 10-100 nm, using a power-compensated Differential Scanning Calorimeter (DSC). The melting temperature of the nano confined 2-decanol decreases as pore size decreases and a linear relationship is observed between the melting temperature and the inverse of the pore size. This is in agreement with the Gibbs-Thomson prediction. In addition, the apparent heat of fusion of the 2-decanol confined in the nano pores appears to decrease as the size of the pores decreases. However, the apparent heat of fusion of the nano confined 2-decanol may not necessarily be its true heat of fusion. Annealing, for instance, increases the apparent heat of fusion by as much as 26%. A correction or alternate procedure should be employed to extract the true heat of fusion from DSC measurements, especially when the physical size of the sample is in nano scale or the sample possesses a large surface area to volume ratio. This work was partially supported by NSF-DMR: 1229142.

  1. MODERN ROUTES TO EXPLORE CONCRETE’S COMPLEX PORE SPACE

    Directory of Open Access Journals (Sweden)

    Piet Stroeven

    2011-05-01

    Full Text Available This paper concentrates on discrete element computer-simulation of concrete. It is argued on the basis of stochastic heterogeneity theory that modern concurrent-algorithm-based systems should be employed for the assessment of pore characteristics underlying durability performance of cementitious materials. The SPACE system was developed at Delft University of Technology for producing realistic schematizations of realcrete for a wide range of other particle packing problems, involving aggregate and fresh cement, and for the purpose of exploring characteristics in the hardened state of concrete, including of the pore network structure because of obvious durability problems. Since structure-sensitive properties are involved, schematization of reality should explicitly deal with the configuration of the cement particles in the fresh state. The paper concentrates on the stereological and mathematical morphology operations executed to acquire information on particle size, global porosity, and on distribution of porosity and of the connected pore fraction as a result of the near neighbourhood of aggregate grains. Goal is to provide information obtained along different exploration routes of concrete's pore space for setting up a pore network modelling approach. This type of methodological papers is scarce in concrete technology, if not missing at all. Technical publications that report on obtained results in our investigations are systematically referred to.

  2. Role of Pore-Forming Toxins in Neonatal Sepsis

    Directory of Open Access Journals (Sweden)

    Andreas F.-P. Sonnen

    2013-01-01

    Full Text Available Protein toxins are important virulence factors contributing to neonatal sepsis. The major pathogens of neonatal sepsis, group B Streptococci, Escherichia coli, Listeria monocytogenes, and Staphylococcus aureus, secrete toxins of different molecular nature, which are key for defining the disease. Amongst these toxins are pore-forming exotoxins that are expressed as soluble monomers prior to engagement of the target cell membrane with subsequent formation of an aqueous membrane pore. Membrane pore formation is not only a means for immediate lysis of the targeted cell but also a general mechanism that contributes to penetration of epithelial barriers and evasion of the immune system, thus creating survival niches for the pathogens. Pore-forming toxins, however, can also contribute to the induction of inflammation and hence to the manifestation of sepsis. Clearly, pore-forming toxins are not the sole factors that drive sepsis progression, but they often act in concert with other bacterial effectors, especially in the initial stages of neonatal sepsis manifestation.

  3. Pore Water Collection, Analysis and Evolution: The Need for Standardization.

    Science.gov (United States)

    Gruzalski, Jacob G; Markwiese, James T; Carriker, Neil E; Rogers, William J; Vitale, Rock J; Thal, David I

    2016-01-01

    Investigating the ecological impacts of contaminants released into the environment requires integration of multiple lines of evidence. Collection and analysis of interstitial water is an often-used line of evidence for developing benthic exposure estimates in aquatic ecosystems. It is a well-established principle that chemical and toxicity data on interstitial water samples should represent in-situ conditions; i.e., sample integrity must be maintained throughout the sample collection process to avoid alteration of the in-situ geochemical conditions. Unfortunately, collection and processing of pore water is not standardized to address possible geochemical transformations introduced by atmospheric exposure. Furthermore, there are no suitable benchmarks (ecological or human health) against which to evaluate adverse effects from chemicals in pore water; i.e., empirical data is lacking on the toxicity of inorganic contaminants in sediment interstitial water. It is clear that pore water data is best evaluated by considering the bioavailability of trace elements and the partitioning of contaminants between the aqueous and solid phases. It is also evident that there is a need for sediment researchers and regulatory agencies to collaborate in developing a standardized approach for sediment/pore water collection and data evaluation. Without such guidelines, the number of different pore water collection and extraction techniques will continue to expand, and investigators will continue to evaluate potentially questionable data by comparison to inappropriate criteria. PMID:26613987

  4. 3D reconstruction of porous electrodes and microstructure modelling

    Energy Technology Data Exchange (ETDEWEB)

    Joos, Jochen; Rueger, Bernd; Weber, Andre; Ivers-Tiffee, Ellen [Karlsruher Institute fuer Technologie (KIT), Karlsruhe (DE). Inst. fuer Werkstoffe der Elektrotechnik (IWE); Carraro, Thomas [Heidelberg Univ. (Germany). Inst. fuer Angewandte Mathematik

    2010-07-01

    The performance of a solid oxide fuel cell (SOFC) is limited by electrode polarisation processes, depending both on material composition and microstructure characteristics. To understand and improve electrode performance, a detailed knowledge of the electrode microstructure is essential. Recent developments in 3D image reconstruction combined with Focused Ion Beam (FIB) and Scanning Electron Microscopy (SEM) techniques proved a way to achieve highly detailed microstructural data. From this data the determination of valuable microstructural parameters is possible. The microstructure is commonly described by parameters as volume/porosity fraction, tortuosity of pores/materal (or: tortuosity of electronic and ionic transport in 2-phase materials), three-phase boundary length (electronic conducting electrodes) or electrode surface area (mixed conducting electrodes). Based on these parameters and with the help of adequate models, the electrode performance can be estimated. It is obvious that the accurateness of the model prediction depends on the quality of the parameters. Different groups reported first trials in the reconstruction of SOFC electrodes by FIB/SEM methods. They all used the reconstruction to calculate microstructural parameters. But nevertheless a lot of questions remain, primarily questions concerning the accuracy of the reconstruction or the minimum size of the volume that has to be reconstructed to obtain meaningful results. In this contribution, a ZEISS 1540XB CrossBeam {sup registered} was used to provide over 700 consecutive images of a porous LSCF (La{sub 0.58}Sr{sub 0.4}CO{sub 0.2.}Fe{sub 0.8}O{sub 3-{delta}})-cathode. The calculation of the key microstructural parameters (i) volume/porosity fraction (ii) electrode surface area and (iii) tortuosity of pores and material from 3D FIB/SEM-data will be presented. Additionally the influence of the reconstruction-volume on the calculated parameters will be discussed. Also the presented technique is

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

    DEFF Research Database (Denmark)

    Katika, Konstantina

    Advanced waterflooding (injection of water with selective ions in reservoirs) is a method of enhanced oil recovery (EOR) that has attracted the interest of oil and gas companies that exploit the Danish oil and gas reservoirs. This method has been applied successfully in oil reservoirs and in the ......Advanced waterflooding (injection of water with selective ions in reservoirs) is a method of enhanced oil recovery (EOR) that has attracted the interest of oil and gas companies that exploit the Danish oil and gas reservoirs. This method has been applied successfully in oil reservoirs...... 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......‐fluid distribution. While investigating the petrophysical properties of reservoir rocks, information concerning the mineralogy is an important factor for the establishment of a rock physical model. Therefore, additional experiments are performed; X-ray diffraction (XRD), backscatter electron microscopy images (BSEM...

  6. On Stack Reconstruction Problem

    Directory of Open Access Journals (Sweden)

    V. D. Аkeliev

    2014-06-01

    Full Text Available The paper describes analytical investigations that study relation of fuel combustion regimes with concentration values of sulphur anhydride in flue gases and acid dew point. Coefficients of convective heat transfer at internal and external surfaces of stacks have been determined in the paper. The paper reveals the possibility to reconstruct stacks while using gas discharging channel made of composite material on the basis of glass-reinforced plastic which permits to reduce thermo-stressed actions on reinforced concrete and increase volume of released gases due to practically two-fold reduction of gas-dynamic pressure losses along the pipe length.

  7. Evolutionary tree reconstruction

    Science.gov (United States)

    Cheeseman, Peter; Kanefsky, Bob

    1990-01-01

    It is described how Minimum Description Length (MDL) can be applied to the problem of DNA and protein evolutionary tree reconstruction. If there is a set of mutations that transform a common ancestor into a set of the known sequences, and this description is shorter than the information to encode the known sequences directly, then strong evidence for an evolutionary relationship has been found. A heuristic algorithm is described that searches for the simplest tree (smallest MDL) that finds close to optimal trees on the test data. Various ways of extending the MDL theory to more complex evolutionary relationships are discussed.

  8. Environmental implications of the use of sulfidic back-bay sediments for dune reconstruction - Lessons learned post Hurricane Sandy.

    Science.gov (United States)

    Plumlee, Geoffrey S; Benzel, William M; Hoefen, Todd M; Hageman, Philip L; Morman, Suzette A; Reilly, Timothy J; Adams, Monique; Berry, Cyrus J; Fischer, Jeffrey M; Fisher, Irene

    2016-06-30

    Some barrier-island dunes damaged or destroyed by Hurricane Sandy's storm surges in October 2012 have been reconstructed using sediments dredged from back bays. These sand-, clay-, and iron sulfide-rich sediments were used to make berm-like cores for the reconstructed dunes, which were then covered by beach sand. In November 2013, we sampled and analyzed partially weathered materials collected from the cores of reconstructed dunes. There are generally low levels of metal toxicants in the reconstructed dune materials. However oxidation of reactive iron sulfides by percolating rainwater produces acid-sulfate pore waters, which evaporate during dry periods to produce efflorescent gypsum and sodium jarosite salts. The results suggest use of sulfidic sediments in dune reconstruction has both drawbacks (e.g., potential to generate acid runoff from dune cores following rainfall, enhanced corrosion of steel bulwarks) and possible benefits (e.g., efflorescent salts may enhance structural integrity). PMID:27210565

  9. Dislocation and pores in mullite from diphasic gels

    International Nuclear Information System (INIS)

    Stoichiometric mullite prepared from the reactions of nanometer-sized pscudo-bochmite and acidic-catalysed silica gel has non-sinterable pores and dislocations. The formation of the pores is accompanied by densification and reactions of the diphasic alumino-silicate gel matrix. These pores tend to be faceted and show low-index crystallographic planes, (110) and (211). After heat treatment at ≥ 1400 degrees C for 24 hr. Dislocations are identified by weak- beam, dark-field, and 2-beam techniques, that show basically three types: one with Bergers vector 001 and is pure screw or a mix: the others may have 210 or 131 Bergers vector. The possible atomic models near last two dislocations are proposed. But the direct observation needs more TEM work

  10. Translocation of an Incompressible Vesicle through a Pore.

    Science.gov (United States)

    Shojaei, Hamid R; Muthukumar, Murugappan

    2016-07-01

    We have derived the free energy landscape for the translocation of a single vesicle through a narrow pore by accounting for bending and stretching of the vesicle, and the deformation of the vesicle by the pore. Emergence of a free energy barrier for translocation is a general result, and the magnitude of the barrier is calculated in terms of the various material parameters. The extent of the reduction in the barrier by the presence of an external constant force is calculated. Using the Fokker-Planck formalism, we have calculated the average translocation time corresponding to the various free energy landscapes representing different parameter sets. The dependencies of the average translocation time on the strength of the external force, vesicle size, bending and stretching moduli of the vesicle, and radius and length of the pore are derived, and the computed results are discussed. PMID:27089012

  11. 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.

  12. Soil Pore Network Visualisation and Quantification using ImageJ

    DEFF Research Database (Denmark)

    Garbout, Amin; Pajor, Radoslaw; Otten, Wilfred

    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...... in the input image. Several parameters (number of networks, junctions, branches…) were used to describe the networks in the sample, and we discuss how these can be used to describe soil structure. Keywords Soil,networks,pore,X-ray micro Computed Tomography,Skeletonize3D...... 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...

  13. Pore-scale simulation of calcium carbonate precipitation and dissolution under highly supersaturated conditions in a microfludic pore network

    Science.gov (United States)

    Yoon, H.; Dewers, T. A.; Valocchi, A. J.; Werth, C. J.

    2011-12-01

    Dissolved CO2 during geological CO2 storage may react with minerals in fractured rocks or confined aquifers and cause mineral precipitation. The overall rate of reaction can be affected by coupled processes among hydrodynamics, transport, and reactions at pore-scale. Pore-scale models of coupled fluid flow, reactive transport, and CaCO3 precipitation and dissolution are applied to account for transient experimental results of CaCO3 precipitation and dissolution under highly supersaturated conditions in a microfluidic pore network (i.e., micromodel). Pore-scale experiments in the micromodel are used as a basis for understanding coupled physics of systems perturbed by geological CO2 injection. In the micromodel, precipitation is induced by transverse mixing along the centerline in pore bodies. Overall, the pore-scale model qualitatively captured the governing physics of reactions such as precipitate morphology, precipitation rate, and maximum precipitation area in first few pore spaces. In particular, we found that proper estimation of the effective diffusion coefficient and the reactive surface area is necessary to adequately simulate precipitation and dissolution rates. As the model domain increases, the effect of flow patterns affected by precipitation on the overall reaction rate also increases. The model is also applied to account for the effect of different reaction rate laws on mineral precipitation and dissolution at pore-scale. Reaction rate laws tested include the linear rate law, nonlinear power law, and newly-developed rate law based on in-situ measurements at nano scale in the literature. Progress on novel methods for upscaling pore-scale models for reactive transport are discussed, and are being applied to mineral precipitation patterns observed in natural analogues. H.Y. and T. D. were supported as part of the Center for Frontiers of Subsurface Energy Security, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of

  14. Evaluation of methods for determining the pore size distribution and pore-network connectivity of porous carbons.

    Science.gov (United States)

    Cai, Q; Buts, A; Biggs, M J; Seaton, N A

    2007-07-31

    The pore size distribution (PSD) and the pore-network connectivity of a porous material determine its properties in applications such as gas storage, adsorptive separations, and catalysis. Methods for the characterization of the pore structure of porous carbons are widely used, but the relationship between the structural parameters measured and the real structure of the material is not yet clear. We have evaluated two widely used and powerful characterization methods based on adsorption measurements by applying the methods to a model carbon which captures the essential characteristics of real carbons but (unlike a real material) has a structure that is completely known. We used three species (CH4, CF4, and SF6) as adsorptives and analyzed the results using an intersecting capillaries model (ICM) which was modeled using a combination of Monte Carlo simulation and percolation theory to obtain the PSD and the pore-network connectivity. There was broad agreement between the PSDs measured using the ICM and the geometric PSD of the model carbon, as well as some systematic differences which are interpreted in terms of the pore structure of the carbon. The measured PSD and connectivity are shown to be able to predict adsorption in the model carbon, supporting the use of the ICM to characterize real porous carbons. PMID:17602506

  15. Pore-size ion-size correlations for carbon supercapacitors

    Science.gov (United States)

    Chmiola, John

    2009-08-01

    Carbon supercapacitors, which are energy storage devices that use ion adsorption on the surface of highly porous materials to store charge, have numerous advantages over other power-source technologies, but could realize further gains if their electrodes were properly optimized. This could lead to fleet-wide improvements in economy, performance, lifetime and environmental impact of Hybrid Electric Vehicles (HEVs), as well as enable or advance many other applications. To determine correlations between ion-size and pore-size in carbon supercapacitors, we generated a well-characterized set of porous carbide-derived carbons (CDC) with average pore sizes from 0.6 to 2.25 nm and used them to probe the limits of understanding. Performing the first systematic study of the effect of pore size on capacitance showed that, in general, decreasing the pore size below the size of the solvated ion, or to precisely the size of the ionic liquid ion, allowed higher accumulation of charge. Using CDC with properly tuned porosity showed excellent performance in H2SO 4, ˜200 F/g, and performance superior to all prior reported results in organic (CH3CH2)4NBF4 (TEABF 4) electrolytes as well as l-ethyl-3-methyl immidazolium bis-(trifluoromethanesulfonyl)imide (EMI-TFSI) ionic liquid, ˜150 F/g. This work conclusively showed that precisely matching the pore size with the ion size is the key factor for maximizing capacitance. Understanding that pores significantly larger than the effective ion size do not have large contributions to energy storage, work on dense porous CDC films on conductive substrates showed ˜100% larger volumetric capacitance than any previously reported. Depositing patterned films of carbide and electrical contacts could lead to microfabricated energy storage devices directly on a chip, or built up in layers for performances yet unrealized.

  16. 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.

  17. RNase A Does Not Translocate the Alpha-Hemolysin Pore

    Science.gov (United States)

    Krasniqi, Besnik; Lee, Jeremy S.

    2014-01-01

    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. PMID:24505349

  18. Non-microsurgical breast reconstruction

    Directory of Open Access Journals (Sweden)

    Sharma Sheel

    2007-12-01

    Full Text Available Breast reconstruction after mastectomy should aim at resulting in an aesthetic outcome that matches the patient′s expectations and without interfering in the oncologic treatment. Whether the reconstruction is performed immediately or in a delayed fashion depends on various factors, which needs detailed attention. Autologous tissue, implants or both are used in the reconstruction. This article reviews the current concepts in these, with emphasis on non-microsurgical methods of using the autologous tissue for reconstruction. Breast conservation has become an accepted practice of treatment. Reconstruction in these situations as well as in an occasion when the surgery is done for failed breast conservation is discussed in detail. The article also reviews the various methods for nipple reconstruction available.

  19. Inertial effects during irreversible meniscus reconfiguration in angular pores

    Science.gov (United States)

    Ferrari, Andrea; Lunati, Ivan

    2014-12-01

    In porous media, the dynamics of the invading front between two immiscible fluids is often characterized by abrupt reconfigurations caused by local instabilities of the interface. As a prototype of these phenomena we consider the dynamics of a meniscus in a corner as it can be encountered in angular pores. We investigate this process in detail by means of direct numerical simulations that solve the Navier-Stokes equations in the pore space and employ the Volume of Fluid method (VOF) to track the evolution of the interface. We show that for a quasi-static displacement, the numerically calculated surface energy agrees well with the analytical solutions that we have derived for pores with circular and square cross sections. However, the spontaneous reconfigurations are irreversible and cannot be controlled by the injection rate: they are characterized by the amount of surface energy that is spontaneously released and transformed into kinetic energy. The resulting local velocities can be orders of magnitude larger than the injection velocity and they induce damped oscillations of the interface that possess their own time scales and depend only on fluid properties and pore geometry. In complex media (we consider a network of cubic pores) reconfigurations are so frequent and oscillations last long enough that increasing inertial effects leads to a different fluid distribution by influencing the selection of the next pore to be invaded. This calls into question simple pore-filling rules based only on capillary forces. Also, we demonstrate that inertial effects during irreversible reconfigurations can influence the work done by the external forces that is related to the pressure drop in Darcy's law. This suggests that these phenomena have to be considered when upscaling multiphase flow because local oscillations of the menisci affect macroscopic quantities and modify the constitutive relationships to be used in macro-scale models. These results can be extrapolated to other

  20. Effects of pore volume-transmissivity correlation on transport phenomena

    Science.gov (United States)

    Lunati, Ivan; Kinzelbach, Wolfgang; Sørensen, Ivan

    2003-12-01

    The relevant velocity that describes transport phenomena in a porous medium is the pore velocity. For this reason, one needs not only to describe the variability of transmissivity, which fully determines the Darcy velocity field for given source terms and boundary conditions, but also any variability of the pore volume. We demonstrate that hydraulically equivalent media with exactly the same transmissivity field can produce dramatic differences in the displacement of a solute if they have different pore volume distributions. In particular, we demonstrate that correlation between pore volume and transmissivity leads to a much smoother and more homogeneous solute distribution. This was observed in a laboratory experiment performed in artificial fractures made of two plexiglass plates into which a space-dependent aperture distribution was milled. Using visualization by a light transmission technique, we observe that the solute behaviour is much smoother and more regular after the fractures are filled with glass powder, which plays the role of a homogeneous fault gouge material. This is due to a perfect correlation between pore volume and transmissivity that causes pore velocity to be not directly dependent on the transmissivity, but only indirectly through the hydraulic gradient, which is a much smoother function due to the diffusive behaviour of the flow equation acting as a filter. This smoothing property of the pore volume-transmissivity correlation is also supported by numerical simulations of tracer tests in a dipole flow field. Three different conceptual models are used: an empty fracture, a rough-walled fracture filled with a homogeneous material and a parallel-plate fracture with a heterogeneous fault gouge. All three models are hydraulically equivalent, yet they have a different pore volume distribution. Even if piezometric heads and specific flow rates are exactly the same at any point of the domain, the transport process differs dramatically. These

  1. Vpliv vegetacije na vodno bilanco porečja

    OpenAIRE

    Kozakiv, Dejan

    2015-01-01

    Znano je, da imata obseg in vrsta vegetacije vpliv na stanje vodne bilance porečja. S procesom prestrezanja padavin, vegetacija uravnava procese kot sta evapotranspiracija in odtok. Mnoge raziskave kažejo na znatno povečanje odtoka, pretoka in vodnih zalog po sečnji gozdov. To lahko razložimo z manjšo stopnjo izhlapevanja na porečjih, kjer prevladuje trava z nizkim rastlinjem v primerjavi s tistimi, ki so porasla z gozdovi. V želji po boljšem poznavanju odnosa med spremembami vegetacijskeg...

  2. Piecing together nuclear pore complex assembly during interphase

    OpenAIRE

    Rexach, Michael

    2009-01-01

    All nucleocytoplasmic traffic of macromolecules occurs through nuclear pore complexes (NPCs), which function as stents in the nuclear envelope to keep nuclear pores open but gated. Three studies in this issue (Flemming, D., P. Sarges, P. Stelter, A. Hellwig, B. Böttcher, and E. Hurt. 2009. J. Cell Biol. 185:387–395; Makio, T., L.H. Stanton, C.-C. Lin, D.S. Goldfarb, K. Weis, and R.W. Wozniak. 2009. J. Cell Biol. 185:459–491; Onishchenko, E., L.H. Stanton, A.S. Madrid, T. Kieselbach, and K. We...

  3. Modeling and Simulating Asymmetrical Conductance Changes in Gramicidin Pores

    OpenAIRE

    Xu Shixin; Chen Minxin; Majd Sheereen; Yue Xingye; Liu Chun

    2014-01-01

    Gramicidin A is a small and well characterized peptide that forms an ion channel in lipid membranes. An important feature of gramicidin A (gA) pore is that its conductance is affected by the electric charges near the its entrance. This property has led to the application of gramicidin A as a biochemical sensor for monitoring and quantifying a number of chemical and enzymatic reactions. Here, a mathematical model of conductance changes of gramicidin A pores in response to the presence of elect...

  4. Hard Sphere Diffusion Behaviour of Polymer Translocating through Interacting Pores

    International Nuclear Information System (INIS)

    The translocation of polymer chain through a small pore from a high concentration side (cis side) to a low concentration side (trans side) is simulated by using Monte Carlo technique. The effect of the polymer-pore interaction on the translocation is studied. We find a special interaction at which the decay of the number of polymer chain, N, at the cis side obeys Fick's law, i.e. N decreases exponentially with time. The behaviour is analogous to the diffusion of hard sphere. (fundamental areas of phenomenology(including applications))

  5. Diffusion pore imaging with generalized temporal gradient profiles

    CERN Document Server

    Laun, F B

    2012-01-01

    In porous material research, one main interest of nuclear magnetic resonance diffusion (NMR) experiments is the determination of the exact shape of pores. While it has been a longstanding question if this is in principle achievable, it has been shown recently that it is indeed possible to perform NMR-based diffusion pore imaging. In this work we present a generalization of these previous results. We show that the specific temporal gradient profiles that were used so far are not unique as almost arbitrary temporal diffusion gradient profiles may be used.

  6. NMR Based Diffusion Pore Imaging by Double Wave Vector Measurements

    CERN Document Server

    Kuder, Tristan Anselm

    2012-01-01

    In porous material research, one main interest of nuclear magnetic resonance (NMR) diffusion experiments is the determination of the exact shape of pores. It has been a longstanding ques-tion if this is achievable in principle. In this work, we present a method using short diffusion gradient pulses only, which is able to reveal the shape of arbitrary closed pores without rely-ing on a priori knowledge. In comparison to former approaches, the method has reduced de-mands on relaxation times and allows for a more flexible NMR sequence design, since, for example, stimulated echoes can be used.

  7. Dynamics of phase ordering of nematics in a pore

    International Nuclear Information System (INIS)

    We study the kinetics of phase ordering of a nematic liquid crystal, modeled by a spin-rotor Hamiltonian, confined within a parallel piped pore. The dynamics of the rotor obeys the time-dependent Ginzburg-Landau equation. We study the generation and evolution of a variety of defect structures, and the growth of domains, with different anchoring conditions at the pore surface. Unlike in binary fluids, mere confinement with no anchoring field, does not result in slow dynamics. Homeotropic anchoring, however, leads to slow logarithmic growth. Interestingly, homogeneous anchoring dynamically generates wall defects, resulting in an Ising like structure factor at late times. (author). 27 refs, 4 figs

  8. Biomaterials for craniofacial reconstruction

    Directory of Open Access Journals (Sweden)

    Neumann, Andreas

    2009-01-01

    Full Text Available Biomaterials for reconstruction of bony defects of the skull comprise of osteosynthetic materials applied after osteotomies or traumatic fractures and materials to fill bony defects which result from malformation, trauma or tumor resections. Other applications concern functional augmentations for dental implants or aesthetic augmentations in the facial region.For ostheosynthesis, mini- and microplates made from titanium alloys provide major advantages concerning biocompatibility, stability and individual fitting to the implant bed. The necessity of removing asymptomatic plates and screws after fracture healing is still a controversial issue. Risks and costs of secondary surgery for removal face a low rate of complications (due to corrosion products when the material remains in situ. Resorbable osteosynthesis systems have similar mechanical stability and are especially useful in the growing skull.The huge variety of biomaterials for the reconstruction of bony defects makes it difficult to decide which material is adequate for which indication and for which site. The optimal biomaterial that meets every requirement (e.g. biocompatibility, stability, intraoperative fitting, product safety, low costs etc. does not exist. The different material types are (autogenic bone and many alloplastics such as metals (mainly titanium, ceramics, plastics and composites. Future developments aim to improve physical and biological properties, especially regarding surface interactions. To date, tissue engineered bone is far from routine clinical application.

  9. LHCb; LHCb Jet Reconstruction

    CERN Multimedia

    Augusto, O

    2012-01-01

    The Large Hadron Collider (LHC) is the most powerful particle accelerator in the world. It has been designed to collide proton beams at an energy up to 14 TeV in the center of mass. In 2011, the data taking was done with a center of mass energy of 7 TeV, the instant luminosity has reached values greater than $4 \\times 10^{32} cm^{-2} s^{-1}$ and the integrated luminosity reached the value of 1.02 $fb^{-1}$ on the LHCb. The jet reconstruction is fundamental to observe events that can be used to test pertubative QCD (pQCD). It also provides a way to observe standard model channels and searches for new physics like SUSY. The anti-kt algorithm is a jet reconstruction algorithm that is based on the distance of the particles on the space $\\eta \\times \\phi$ and on the transverse momentum of particles. To maximize the energy resolution all information about the trackers and the calo...

  10. Delayed breast implant reconstruction

    DEFF Research Database (Denmark)

    Hvilsom, Gitte B.; Hölmich, Lisbet R.; Steding-Jessen, Marianne;

    2012-01-01

    We evaluated the association between radiation therapy and severe capsular contracture or reoperation after 717 delayed breast implant reconstruction procedures (288 1- and 429 2-stage procedures) identified in the prospective database of the Danish Registry for Plastic Surgery of the Breast during...... the period between 1999 and 2006. A history of radiation therapy was associated with increased risk of severe capsular contracture for 1- and 2-stage procedures, with adjusted hazard ratios (HR) of 3.3 (95% confidence interval [CI]: 0.9-12.4) and 7.2 (95% CI: 2.4-21.4), respectively. Similarly, a...... history of radiation therapy was associated with a non-significantly increased risk of reoperation after both 1-stage (HR = 1.4; 95% CI: 0.7-2.5) and 2-stage (HR = 1.6; 95% CI: 0.9-3.1) procedures. Reconstruction failure was highest (13.2%) in the 2-stage procedures with a history of radiation therapy...

  11. Reconstructing Experiences through Sketching

    CERN Document Server

    Karapanos, Evangelos; Hassenzahl, Marc

    2009-01-01

    This paper presents iScale, a survey tool that aims at eliciting users' experiences with a product from memory. iScale employs sketching in imposing a process in the reconstruction of one's experiences. Two versions of iScale, the Constructive and the Value-Account iScale, were motivated by two distinct theories on how people reconstruct emotional experiences from memory. These two versions were tested in two separate studies. Study 1 aimed at providing qualitative insight into the use of iScale and compared its performance to that of free-hand sketching. Study 2 compared the two iScale versions to a control condition: that of reporting one's experiences without employing any form of sketching. Significant differences between iScale and the "no-sketching" tool were found. Overall, iScale resulted in a) an increase in the number of experience reports that subjects provided, b) an increase in the amount of contextual information for the reported experiences, and c) an increase in subjects' accuracy in recalling...

  12. Three-dimensional ICT reconstruction

    International Nuclear Information System (INIS)

    The three-dimensional ICT reconstruction method is the hot topic of recent ICT technology research. In the context, qualified visual three-dimensional ICT pictures are achieved through multi-piece two-dimensional images accumulation by, combining with thresholding method and linear interpolation. Different direction and different position images of the reconstructed pictures are got by rotation and interception respectively. The convenient and quick method is significantly instructive to more complicated three-dimensional reconstruction of ICT images. (authors)

  13. Phase Retrieval Versus Phaseless Reconstruction

    OpenAIRE

    Botelho-Andrade, Sara; Casazza, Peter G.; Nguyen, Hanh; Tremain, Janet C.

    2015-01-01

    In 2006, Balan/Casazza/Edidin \\cite{BCE} introduced the frame theoretic study of phaseless reconstruction. Since then, this has turned into a very active area of research. Over the years, many people have replaced the term {\\it phaseless reconstruction} with {\\it phase retrieval}. Casazza then asked: {\\it Are these really the same?} In this paper, we will show that phase retrieval is equivalent to phaseless reconstruction. We then show, more generally, that phase retrieval by projections is e...

  14. Reconstruction of symmetric Potts Models

    OpenAIRE

    Sly, Allan

    2008-01-01

    The reconstruction problem on the tree has been studied in numerous contexts including statistical physics, information theory and computational biology. However, rigorous reconstruction thresholds have only been established in a small number of models. We prove the first exact reconstruction threshold in a non-binary model establishing the Kesten-Stigum bound for the 3-state Potts model on regular trees of large degree. We further establish that the Kesten-Stigum bound is not tight for the $...

  15. Unfavourable results in thumb reconstruction

    Directory of Open Access Journals (Sweden)

    Samir M Kumta

    2013-01-01

    Full Text Available The history of thumb reconstruction parallels the history of hand surgery. The attributes that make the thumb unique, and that the reconstructive surgeon must assess and try to restore when reconstructing a thumb, are: Position, stability, strength, length, motion, sensibility and appearance. Deficiency in any of these attributes can reduce the utility of the reconstructed thumb. A detailed assessment of the patient and his requirements needs to be performed before embarking on a thumb reconstruction. Most unsatisfactory results can be attributed to wrong choice of procedure. Component defects of the thumb are commonly treated by tissue from adjacent fingers, hand or forearm. With refinements in microsurgery, the foot has become a major source of tissue for component replacement in the thumb. Bone lengthening, osteoplastic reconstruction, pollicisation, and toe to hand transfers are the commonest methods of thumb reconstruction. Unfavourable results can be classified as functional and aesthetic. Some are common to all types of procedures. However each type of reconstruction has its own unique set of problems. Meticulous planning and execution is essential to give an aesthetic and functionally useful thumb. Secondary surgeries like tendon transfers, bone grafting, debulking, arthrodesis, may be required to correct deficiencies in the reconstruction. Attention needs to be paid to the donor site as well.

  16. Set Reconstruction on the Hypercube

    OpenAIRE

    Pebody, Luke

    2016-01-01

    Given an action of a group $G$ on a set $S$, the $k$-deck of a subset $T$ of $S$ is the multiset of all subsets of $T$ of size $k$, each given up to translation by $G$. For a given subset $T$, the {\\em reconstruction number} of $T$ is the minimum $k$ such that the $k$-deck uniquely identifies $T$ up to translation by $G$, and the {\\em reconstruction number} of the action $G:S$ is the maximum reconstruction number of any subset of $S$. The concept of reconstruction number extends naturally to ...

  17. Virtual 3-D Facial Reconstruction

    Directory of Open Access Journals (Sweden)

    Martin Paul Evison

    2000-06-01

    Full Text Available Facial reconstructions in archaeology allow empathy with people who lived in the past and enjoy considerable popularity with the public. It is a common misconception that facial reconstruction will produce an exact likeness; a resemblance is the best that can be hoped for. Research at Sheffield University is aimed at the development of a computer system for facial reconstruction that will be accurate, rapid, repeatable, accessible and flexible. This research is described and prototypical 3-D facial reconstructions are presented. Interpolation models simulating obesity, ageing and ethnic affiliation are also described. Some strengths and weaknesses in the models, and their potential for application in archaeology are discussed.

  18. 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)

    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)

  19. Controlled synthesis of ordered mesoporous TiO2-supported on activated carbon and pore-pore synergistic photocatalytic performance

    International Nuclear Information System (INIS)

    Ordered mesoporous titania/activated carbon (OMTAC) were prepared by the template technique with the aid of an ultrasonic method. To explore the relationship between the structure and properties of OMTAC, the ultrasonic-sol-gel technique was applied to synthesize titania dioxide/activated carbon (USTAC). The obtained material structure was characterized by X-ray diffraction (XRD), nitrogen adsorption – desorption, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV diffuse reflectance (DRS) and Photoluminescence (PL) emission spectra. OMTAC photocatalytic performance was evaluated by means of acid red B (ARB) degradation. The pore-pore synergistic amplification mechanism of photocatalysis was proposed and the effects of catalytic conditions on synergistic amplification were explored. The results show that compared to OMT, OMTAC has a small particle size, low electron-hole recombination rate and high surface areas, due to the hindering effect of activated carbon on crystalline grain growth and an ordered mesoporous structure of titania. OMTAC has higher catalytic activity than USTAC, OMT and P25, due to pore-pore synergistic amplification effect of photocatalysis. The OMT content is strongly affected OMTAC photocatalytic activity, and OMTAC-3 (loading 3 times of OMT on AC) has the highest photocatalytic activity due to high hydroxyl concentration, surface area and low electron-hole recombination rate. When ARB is degraded by OMTAC-3, the optimum catalytic conditions are a catalyst concentration of 1 g/L, an ARB concentration of 15 mg/L and a pH of 5. - Graphical abstract: We investigate the influence of mesoporous titania content upon the photocatalytic performance of OMTAC in acid red B degradation. - Highlights: • OMTAC were fabricated by a template technique with the aid of an ultrasonic method. • OMTAC show high photoactivity for acid red B (ARB) degradation. • OMTAC also show pore-pore synergistic photocatalytic

  20. Toroidal pores formed by antimicrobial peptides show significant disorder

    NARCIS (Netherlands)

    Sengupta, Durba; Leontiadou, Hari; Mark, Alan E.; Marrink, Siewert-Jan

    2008-01-01

    A large variety of antimicrobial peptides have been shown to act, at least in vitro, by potation of the lipid membrane. The nanometre size of these pores, however, complicates their structural characterization by experimental techniques. Here we use molecular dynamics simulations, to study the inter

  1. Relationship between elastic moduli and pore radius in clay aggregates

    DEFF Research Database (Denmark)

    Fabricius, Ida Lykke

    2011-01-01

    Available experimental data on elastic velocities of clay-air mixtures and clay-brine mixtures as a function of porosity are re-interpreted. Pore radius as calculated from porosity and specific surface measured by BET seems to be the factor controlling stiffness of these un-cemented sediments. For...

  2. Pore water transport of enterococci out of beach sediments

    International Nuclear Information System (INIS)

    Highlights: → Ten percent of total bacteria within sand columns were released in flow experiments. → Majority of the bacteria were released within the first pore water volume. → Positive linear correlation seen with bacteria removed and hydraulic conductivity. → We hypothesize that results were dependent on amount of biofilms in sand. → Results significantly higher in cores collected after a significant rain event. - Abstract: Enterococci are used to evaluate the safety of beach waters and studies have identified beach sands as a source of these bacteria. In order to study and quantify the release of microbes from beach sediments, flow column systems were built to evaluate flow of pore water out of beach sediments. Results show a peak in enterococci (average of 10% of the total microbes in core) released from the sand core within one pore water volume followed by a marked decline to below detection. These results indicate that few enterococci are easily removed and that factors other than simple pore water flow control the release of the majority of enterococci within beach sediments. A significantly larger quantity and release of enterococci were observed in cores collected after a significant rain event suggesting the influx of fresh water can alter the release pattern as compared to cores with no antecedent rainfall.

  3. 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 onl

  4. 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...

  5. 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.

  6. Upscaling of Nonlinear Reactive Transport: from Pore to Core

    NARCIS (Netherlands)

    Acharya, R.C.

    2004-01-01

    The major objective of this research is to gain a better understanding of the heterogeneous interactions between reactive solutes and the solid phase at the pore scale, to scale up to the core scale and compare with the results of experimental observations and analytical equations. In this research

  7. Closed-pore Insulation Thermal Protection System Design Concept Development

    Science.gov (United States)

    Varisco, A.; Harris, H. G.

    1973-01-01

    The development of a unique closed-pore ceramic foam insulation (CPI) produced from low cost fly ash cenospheres is reported for space shuttle external thermal protection. Two basic design approaches were developed: bonded and mechanically fastened. A description of the concepts is presented in addition to fabrication and test results.

  8. Optimal reconstruction angles

    International Nuclear Information System (INIS)

    The question of optimal projection angles has recently become of interest in the field of reconstruction from projections. Here, studies are concentrated on the n x n pixel space, where literative algorithms such as ART and direct matrix techniques due to Katz are considered. The best angles are determined in a Gauss--Markov statistical sense as well as with respect to a function-theoretical error bound. The possibility of making photon intensity a function of angle is also examined. Finally, the best angles to use in an ART-like algorithm are studied. A certain set of unequally spaced angles was found to be preferred in several contexts. 15 figures, 6 tables

  9. Urogenital Reconstructive Surgery

    DEFF Research Database (Denmark)

    Jakobsen, Lotte Kaasgaard

    the lower urinary tract causes voiding disabilities, renal failure and chronic bladder changes. Children with such malformations often require extensive treatment, and will experience side effects and not always satisfactory results. Aim: To develop an animal model of congenital infravesical......Urogenital reconstructive surgery Lotte Kaasgaard Jakobsen1 Professor Henning Olsen1 Overlæge Gitte Hvistendahl1 Professor Karl-Erik Andersson2 1 – Dept. of Urology, Aarhus University Hospital 2 – Dept. of Gynecology and Obstetrics, Aarhus University hospital Background: Congenital obstruction of...... the fetal bladder to those of the bladder from young pigs used in the animal model. Results: By further characterising the effect of congenital obstruction, regarding urodynamic properties of the bladder and structural changes in the bladder tissue and comparing the results after relief of obstruction...

  10. Reconstructing the Alcatraz escape

    Science.gov (United States)

    Baart, F.; Hoes, O.; Hut, R.; Donchyts, G.; van Leeuwen, E.

    2014-12-01

    In the night of June 12, 1962 three inmates used a raft made of raincoatsto escaped the ultimate maximum security prison island Alcatraz in SanFrancisco, United States. History is unclear about what happened tothe escapees. At what time did they step into the water, did theysurvive, if so, where did they reach land? The fate of the escapees has been the subject of much debate: did theymake landfall on Angel Island, or did the current sweep them out ofthe bay and into the cold pacific ocean? In this presentation, we try to shed light on this historic case using avisualization of a high-resolution hydrodynamic simulation of the San Francisco Bay, combined with historical tidal records. By reconstructing the hydrodynamic conditions and using a particle based simulation of the escapees we show possible scenarios. The interactive model is visualized using both a 3D photorealistic and web based visualization. The "Escape from Alcatraz" scenario demonstrates the capabilities of the 3Di platform. This platform is normally used for overland flooding (1D/2D). The model engine uses a quad tree structure, resulting in an order of magnitude speedup. The subgrid approach takes detailed bathymetry information into account. The inter-model variability is tested by comparing the results with the DFlow Flexible Mesh (DFlowFM) San Francisco Bay model. Interactivity is implemented by converting the models from static programs to interactive libraries, adhering to the Basic ModelInterface (BMI). Interactive models are more suitable for answeringexploratory research questions such as this reconstruction effort. Although these hydrodynamic simulations only provide circumstantialevidence for solving the mystery of what happened during the foggy darknight of June 12, 1962, it can be used as a guidance and provides aninteresting testcase to apply interactive modelling.

  11. Gender Mainstreaming and Sustainable Post Disaster Reconstruction,

    OpenAIRE

    Yumarni, Tri; Amaratunga, Dilanthi; Haigh, Richard

    2013-01-01

    Gender inequalities are barriers to achieve sustainable post disaster reconstruction. Mainstreaming gender equality within post disaster reconstruction process can enhance sustainability of reconstruction. Based on a detailed literature review on post disaster reconstruction, this paper identifies pre-requisite conditions for mainstreaming gender within sustainable post disaster reconstruction as ; awareness of gender needs and concerns, a strong gender policy framework, women ...

  12. Breast reconstruction - methods and imaging

    International Nuclear Information System (INIS)

    Silicon implants are used for breast reconstruction or for cosmetic operations. The contribution outlines the role of mammography, sonography and MR for defect assessment, tumour detection and monitoring after prosthesis implantation. Instrument adjustment for mammographic screening of patients with implants is gone into. Autologic reconstruction techniques and protocols of secondary and tertiary early detection are presented. (orig.)

  13. Markov Random Field Surface Reconstruction

    DEFF Research Database (Denmark)

    Paulsen, Rasmus Reinhold; Bærentzen, Jakob Andreas; Larsen, Rasmus

    2010-01-01

    A method for implicit surface reconstruction is proposed. The novelty in this paper is the adaption of Markov Random Field regularization of a distance field. The Markov Random Field formulation allows us to integrate both knowledge about the type of surface we wish to reconstruct (the prior) and...

  14. 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.

  15. Pore size distribution of a deeply excavated Oxisol after 19 years reclamation

    Science.gov (United States)

    dos Santos Batista Bonini, Carolina; de Cássia Marchini, Débora; Alves, Marlene Cristina; García de Arruda, Otton; Paz-Ferreiro, Jorge

    2013-04-01

    Digging of the local soil and using it as a raw material for construction purposes has been identified as a non-negligible source of land degradation. Techniques aimed at soil profile reconstruction and ecological restoration of soils truncated by mechanical excavation using heavy machinery have been investigated Both, total soil porosity and pore size distribution are important properties for soil management as well as for assessing the recovery of soil function after land degradation. In this way, macropores are responsible for aeration, whereas water storage depends on soil meso- and micropores in the soil and the optimal pore-size distribution is also an indicator of soil quality. We investigated the changes in the pore size distribution of a soil that was beheaded to extract raw materials after a 19 year period of reclamation, which involved the use of green manures, gypsum and pasture for the purpose of profile recovery. The studied area is located in Mato Grosso do Sul State, Brzil. A field trial was performed following a completely randomized experimental design with seven treatments and four replications. Starting 1992, the initial treatments were: 1) control (tilled bare soil), 2)Stizolobium aterrium, 3)Cajanus cajan, 4)lime+S. aterrimum, 5) lime+C. cajan, 6) lime + gypsum + S. aterrimum, 7) lime + gypsum+C. cajan. In 1994, all treatments with C. cajan were replaced by Canavalia ensiformis and in 1999, Brachiaria decumbens was implanted in all the experimental plots. Data from vegetated treatments were compared with bare soil (control) and native vegetation (Savannah). Soil samples were collected in 2011 at the 0.00-0.10, 0.10-0.20, and 0.20-0.40 m depths. Treatment differences were assessed by analysis of variance, following the Scott-Knott test (5%) of probability to compare averages. Macroporosity of the 0.00-0.10 m top layer was above the 0.10 m3m-3 threshold considered as critical for plant growth. On the 0.10-0.20 m layer only treatments with C

  16. A characterization of the coupled evolution of grain fabric and pore space using complex networks: Pore connectivity and optimized flows in the presence of shear bands

    Science.gov (United States)

    Russell, Scott; Walker, David M.; Tordesillas, Antoinette

    2016-03-01

    A framework for the multiscale characterization of the coupled evolution of the solid grain fabric and its associated pore space in dense granular media is developed. In this framework, a pseudo-dual graph transformation of the grain contact network produces a graph of pores which can be readily interpreted as a pore space network. Survivability, a new metric succinctly summarizing the connectivity of the solid grain and pore space networks, measures material robustness. The size distribution and the connectivity of pores can be characterized quantitatively through various network properties. Assortativity characterizes the pore space with respect to the parity of the number of particles enclosing the pore. Multiscale clusters of odd parity versus even parity contact cycles alternate spatially along the shear band: these represent, respectively, local jamming and unjamming regions that continually switch positions in time throughout the failure regime. Optimal paths, established using network shortest paths in favor of large pores, provide clues on preferential paths for interstitial matter transport. In systems with higher rolling resistance at contacts, less tortuous shortest paths thread through larger pores in shear bands. Notably the structural patterns uncovered in the pore space suggest that more robust models of interstitial pore flow through deforming granular systems require a proper consideration of the evolution of in situ shear band and fracture patterns - not just globally, but also inside these localized failure zones.

  17. Using X-ray computed tomography in pore structure characterization for a Berea sandstone: Resolution effect

    Science.gov (United States)

    Peng, Sheng; Hu, Qinhong; Dultz, Stefan; Zhang, Ming

    2012-11-01

    SummaryX-ray computed tomography (XCT) is a powerful tool for detecting the micro-scale pore structure and has been applied to many natural and synthetic porous media. However, due to the resolution limitations, either non-representative view of the sample or inaccurate results can be produced from the XCT image processing. In this paper, two XCT (micro-CT and CT with synchrotron radiation) with different resolutions of 12.7 μm and 0.35 μm, as well as mercury intrusion porosimetry (MIP) with a minimum detection limit of 3 nm, were used for Berea sandstone to investigate the effect of detecting resolution on the pore structure. Several key pore structure parameters, including porosity, pore size distribution, pore connectivity, surface area, hydraulic radius, and aspect ratio were analyzed in a manner of quantitative comparison between different resolutions of XCT and MIP. The low resolution XCT can capture the large-pore porosity, while overestimates the pore size and pore connectivity. The high resolution XCT is more accurate in describing the pore shape, porosity, pore size; however, it is not representative since narrower detecting pore size range and small volume represented. A representative element volume related to large-pore porosity and probably large-pore connectivity with diameter and height of 2.8 mm is obtained through scale effect analysis. Therefore, selecting an appropriate resolution should be a compromise between the pore size and the representative element volume for the specific property or process of interest.

  18. Blob-enhanced reconstruction technique

    Science.gov (United States)

    Castrillo, Giusy; Cafiero, Gioacchino; Discetti, Stefano; Astarita, Tommaso

    2016-09-01

    A method to enhance the quality of the tomographic reconstruction and, consequently, the 3D velocity measurement accuracy, is presented. The technique is based on integrating information on the objects to be reconstructed within the algebraic reconstruction process. A first guess intensity distribution is produced with a standard algebraic method, then the distribution is rebuilt as a sum of Gaussian blobs, based on location, intensity and size of agglomerates of light intensity surrounding local maxima. The blobs substitution regularizes the particle shape allowing a reduction of the particles discretization errors and of their elongation in the depth direction. The performances of the blob-enhanced reconstruction technique (BERT) are assessed with a 3D synthetic experiment. The results have been compared with those obtained by applying the standard camera simultaneous multiplicative reconstruction technique (CSMART) to the same volume. Several blob-enhanced reconstruction processes, both substituting the blobs at the end of the CSMART algorithm and during the iterations (i.e. using the blob-enhanced reconstruction as predictor for the following iterations), have been tested. The results confirm the enhancement in the velocity measurements accuracy, demonstrating a reduction of the bias error due to the ghost particles. The improvement is more remarkable at the largest tested seeding densities. Additionally, using the blobs distributions as a predictor enables further improvement of the convergence of the reconstruction algorithm, with the improvement being more considerable when substituting the blobs more than once during the process. The BERT process is also applied to multi resolution (MR) CSMART reconstructions, permitting simultaneously to achieve remarkable improvements in the flow field measurements and to benefit from the reduction in computational time due to the MR approach. Finally, BERT is also tested on experimental data, obtaining an increase of the

  19. Pore Fabric Anisotropy: Testing the Equivalent Pore Concept Using Magnetic Ferrofluid and Synthetic Voids of Known Geometry

    Science.gov (United States)

    Jones, S.; Benson, P.; Meredith, P.

    2005-12-01

    We present results from an experimental and theoretical study of pore fabric anisotropy using the method of anisotropy of magnetic susceptibility (AMS) and synthetic pore spaces of known geometry. AMS has traditionally been used to measure the magnetic anisotropy of a dry rock matrix. Here we use the technique to determine the anisotropy of the void space. We provide the voids with an artificial magnetic susceptibility by saturating them with magnetic ferrofluid. AMS measurements are made in the normal manner, and interpreted using the theoretical equivalent pore concept (EPC) proposed by Hrouda et al. (2000). This theory attempts to relate the magnetic measurements of lineation, foliation and anisotropy to the lineation, foliation and anisotropy of the real, physical pore fabric. Essentially, an average physical pore space shape and alignment is modeled that will produce the same magnetic properties as those measured on the real sample. In order to test the theory, we prepared a range of synthetic samples with known pore geometries from cylindrical polycarbonate blanks 25mm in diameter by 22mm long. Firstly, a set of "special fabrics" were machined axially into the sample blanks: (a) a set of 19 equally spaced holes, 2mm in diameter by 12mm long, (b); a row of 5 holes, 3.3mm in diameter by 16mm long; and (c) a tier of four disks, 18mm in diameter by 1.4mm thick. The total bulk susceptibility of each "special fabric" was approximately the same. Secondly, a set of seven samples were machined with quasi-ellipsoidal voids with axial to radial axis ratios of: 0.75, 0.83, 0.92, 1.0, 1.1, 1.2, and 1.3. All of the special-fabric samples showed high magnetic anisotropy, with a maximum foliation of 1.41 and lineation of 1.29. The results are as expected intuitively, with the 19 hole sample exhibiting a highly prolate fabric and the 5 hole sample exhibiting a highly oblate fabric. For the quasi-ellipsoids, the foliation decreases and the lineation increases as the axial to

  20. 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

  1. AORTOILIAC AND AORTOFEMORAL RECONSTRUCTION OF OBSTRUCTIVE DISEASE

    NARCIS (Netherlands)

    VANDENAKKER, PJ; VANSCHILFGAARDE, R; BRAND, R; VANBOCKEL, JH; TERPSTRA, JL

    1994-01-01

    This retrospective study evaluates our strategy to limit prosthetic reconstructions for aortoiliac obstructive disease to the diseased segments in 518 patients. There were 363 (70%) reconstructions without femoral anastomotic sites (FEM-0), 107 (21%) reconstructions with one femoral anastomotic site

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

    OpenAIRE

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

    2015-01-01

    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 thro...

  3. Anisotropy of Pore Structure and Permeability in Granite: Preliminary Results

    Science.gov (United States)

    Onishi, C. T.; Shimizu, I.; Mizoguchi, K.; Uehara, S.; Shimamoto, T.

    2001-12-01

    The permeability of rocks is sensitive to pore structures. In fault zones where brittle deformation dominates, connectivity of cracks is perhaps the most important factor to control the fluid permeability. The relationship between microstructure, porosity-pore structures and permeability were investigated, using drill core samples from the Toki Granite in Gifu Prefecture, Central Japan. Core samples taken from a borehole penetrating a fault strand of the Tsukiyoshi Fault at the depth of 700 m were used for analysis and measurements. The Toki Granite shows textural variations. For example, away from the fault zone, the granite is fresh, massive biotite granite. Toward the fault the granitic texture is largely destroyed, reflecting deformation due to fault movement, with extensive fracturing and development of calcite veins. The central part of the fault zone constitutes foliated ultra-cataclasites with a fine grained matrix. Microstructural observations indicate that fragmentation of crystals is the cause of grain size reduction in the fault zone and anisotropy in micro-crack development. The effective porosity of bulk samples measured by Helium pycnometer varies from 0.54% for unaltered fresh granite to over 5.4% for foliated cataclasite from the central part of the fault zone. The pore structures of the granite samples were visualized by the Laser Scanning Microscope (LSM). The samples were impregnated with low viscosity fluorescent resin under vacuum condition, and then observed by the LSM. Quasi 3-D images of pore structures were constructed from optical slices (confocal images) of thick sections. Micro-cracks in granites were successfully filled with the fluorescent resin. Micro-cracks were mainly observed at grain boundaries, and the intra and inter granular fractures. Permeability measurements were performed by a High Pressure Temperature (HPT) gas apparatus using the pore oscillation technique. Confining pressure was increased and then decreased in the range

  4. Direct Measurements of Pore Fluid Density by Vibrating Tube Densimetry

    Energy Technology Data Exchange (ETDEWEB)

    Gruszkiewicz, Miroslaw {Mirek} S [ORNL; Rother, Gernot [ORNL; Wesolowski, David J [ORNL; Cole, David R [ORNL; Wallacher, Dirk [Helmholtz-Zentrum Berlin

    2012-01-01

    The densities of pore-confined fluids were measured for the first time by means of a vibrating tube method. Isotherms of total adsorption capacity were measured directly making the method complementary to the conventional gravimetric or volumetric/piezometric adsorption techniques, which yield the excess adsorption (the Gibbsian surface excess). A custom-made high-pressure, high-temperature vibrating tube densimeter (VTD) was used to measure the densities of subcritical and supercritical propane (between 35 C and 97 C) and supercritical carbon dioxide (between 32 C and 50 C) saturating hydrophobic silica aerogel (0.2 g/cm3, 90% porosity) synthesized inside Hastelloy U-tubes. Additionally, excess adsorption isotherms for supercritical CO2 and the same porous solid were measured gravimetrically using a precise magnetically-coupled microbalance. Pore fluid densities and total adsorption isotherms increased monotonically with increasing density of the bulk fluid, in contrast to excess adsorption isotherms, which reached a maximum at a subcritical density of the bulk fluid, and then decreased towards zero or negative values at supercritical densities. Compression of the confined fluid significantly beyond the density of the bulk liquid at the same temperature was observed at subcritical temperatures. The features of the isotherms of confined fluid density are interpreted to elucidate the observed behavior of excess adsorption. The maxima of excess adsorption were found to occur below the critical density of the bulk fluid at the conditions corresponding to the beginning of the plateau of total adsorption, marking the end of the transition of pore fluid to a denser, liquid-like pore phase. The results for propane and carbon dioxide showed similarity in the sense of the principle of corresponding states. No measurable effect of pore confinement on the liquid-vapor critical point was found. Quantitative agreement was obtained between excess adsorption isotherms determined

  5. Pore connectivity effects on solute transport in rocks

    International Nuclear Information System (INIS)

    Retardation of nuclear contaminants in rock matrices can lead to long retention times, allowing substantial radionuclide decay prior to eventual release. Imbibition and diffusion into the rock matrix can move contaminants away from an active fracture, thereby contributing to their retardation. However, diffusive transport in some rocks may behave anomalously because of their sparsely connected porespace, in contrast to diffusion in rocks with denser pore connections. We examined imbibition of weakly sorbing tracers into welded tuff and Indiana sandstone, and water imbibition into metagraywacke and Berea sandstone. Tuff samples were initially equilibrated to 12% and 76% water (v/v) within controlled humidity chambers, while the other rocks were air-dried. For imbibition, one face was exposed to water, with or without tracer, and uptake was measured over time. Following imbibition, tracer concentration measurements were made at fine (1 mm) increments. Three anomalous results were observed: (1) Indiana sandstone and metagraywacke showed mass of imbibed water scaling as time0.26, while tuff and Berea sandstone showed the more classical scaling with time0.5; (2) tracer movement into dry (2% initial saturation) Indiana sandstone showed a dispersion pattern similar to that expected during tracer movement into moist (76% initial saturation) tuff; and (3) tracer concentrations at the inlet face of the tuff sample were approximately twice those deeper inside the sample. The experiment was then modeled using random walk methods on a 3-D lattice with different values of pore coordination. Network model simulations that used a pore coordination of 1.49 for Indiana sandstone and 1.56 for metagraywacke showed similar temporal scaling, a result of their porespace being close to the percolation threshold. Tracer concentration profiles in Indiana sandstone and tuff were closely matched by simulations that used pore coordinations of 1.49 and 1.68, respectively, because of how low

  6. Pore Connectivity Effects on Solute Transport in Rocks

    International Nuclear Information System (INIS)

    Retardation of nuclear contaminants in rock matrices can lead to long retention times, allowing substantial radionuclide decay prior to eventual release. Imbibition and diffusion into the rock matrix can move contaminants away from an active fracture, thereby contributing to their retardation. However, diffusive transport in some rocks may behave anomalously because of their sparsely connected porespace, in contrast to diffusion in rocks with denser pore connections. We examined imbibition of weakly sorbing tracers into welded tuff and Indiana sandstone, and water imbibition into metagraywacke and Berea sandstone. Tuff samples were initially equilibrated to 12% and 76% water (v/v) within controlled humidity chambers, while the other rocks were air-dried. For imbibition, one face was exposed to water, with or without tracer, and uptake was measured over time. Following imbibition, tracer concentration measurements were made at fine (1 mm) increments. Three anomalous results were observed: (1) Indiana sandstone and metagraywacke showed mass of imbibed water scaling as time0.26, while tuff and Berea sandstone showed the more classical scaling with time0.05; (2) tracer movement into dry (2% initial saturation) Indiana sandstone showed a dispersion pattern similar to that expected during tracer movement into moist (76% initial saturation) tuft and (3) tracer concentrations at the inlet face of the tuff sample were approximately twice those deeper inside the sample. The experiment was then modeled using random walk methods on a 3-D lattice with different values of pore coordination. Network model simulations that used a pore coordination of 1.49 for Indiana sandstone and 1.56 for metagraywacke showed similar temporal scaling, a result of their porespace being close to the percolation threshold. Tracer concentration profiles in Indiana sandstone and tuff were closely matched by simulations that used pore coordinations of 1.49 and 1.68, respectively, because of how low

  7. An Effect of pore pressure on slip strength of serpentinite

    Science.gov (United States)

    Okazaki, K.; Katayama, I.; Takahashi, M.

    2011-12-01

    Slow earthquakes (e.g. slow slip events, very low frequency earthquakes and non-volcanic tremors) have been detected in subduction zones where young and hot slabs are subducting, such as Cascadia and southwest (SW) Japan. Most slow earthquakes in the subduction zone of SW Japan occur with a depth range from 30 to 40 km located at corner of mantle wedge and at slightly deeper than seismogenic zone of Nankai megathrust earthquake (~25km). In this region of SW Japan, low velocity anomaly and high Poisson's ratio have been reported, suggesting that the region is serpentinized and maintains high pore fluid pressure. Generating mechanisms of slow earthquakes are not fully understood, which is our motivation for this experimental study of deformation styles of serpentinite under hydrothermal condition. This study will report about the slip behaviors of antigorite serpentinite under high pore pressure and hydrothermal conditions. In the experiments, we focus on an effect of the pore pressure to frictional coefficient during triaxial deformation. Stating material used in this study is highly dense and isotopic antigorite serpentinite from Nishisonogi metamorphic belts, Nagasaki, Japan, which porosity is about 0.2 to 0.3 %. Samples are grinded cylindrical shape with precut at an angle of 30 degrees, and one piece of the samples is drilled through to the slip surface. Experiments were conducted using the high-temperature and high-pressure gas confining medium apparatus at Hiroshima University, which is capable to apply confining pressure Pc and pore pressure Pp up to 200 MPa and temperature to 800 °C. Preliminary experiments were performed at Pc of 150 MPa, axial displacement rate of 1 μm/s, temperature of 400 °C and variable range of Pp (50 - 105 MPa). Under relatively low Pp conditions (< 100MPa), values of friction coefficient μ are c.a. 0.4, which are similar to these of dry experiments. However, the friction coefficient is abruptly reduced to μ ~ 0.2 when the pore

  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. Vulvovaginal reconstruction for neoplastic disease.

    Science.gov (United States)

    Höckel, Michael; Dornhöfer, Nadja

    2008-06-01

    Current treatment of neoplastic disease that involves the external female genitalia aims to achieve local disease control, but not to restore form and function of these organs. Despite a growing trend to reduce the extent of surgical resection, impaired quality of life after surgery due to severe sexual dysfunction and disturbed body image is common. We postulate that the integration of surgical techniques for vulvar and vaginal reconstruction into primary treatment would improve aesthetic and functional results and therefore quality of life. We systematically searched the literature for surgical procedures designed and validated for vulvovaginal reconstruction. Various skin flaps, both with random vascularisation and those based on vascular territories (ie, axial pattern, fasciocutaneous, musculocutaneous, and bowel flaps), can restore important parts of vulvovaginal form and function with acceptable morbidity at the donor and recipient sites. Appropriate vulvovaginal reconstruction cannot be achieved by doing a few standardised procedures; rather, it necessitates specialists who are familiar with general principles of reconstructive surgery to master many techniques to select the optimum procedure for the individual patient. Vulvovaginal reconstructive surgery has limitations, particularly achievement of functional restoration in irradiated tissue. Physicians who treat women with neoplastic disease of the external genitalia should be aware of the current state of vulvovaginal reconstructive surgery. Prospective controlled clinical trials are warranted to assess the effect of vulvovaginal reconstruction on morbidity and quality of life after treatment. PMID:18510987

  10. Evidence-Based ACL Reconstruction

    Directory of Open Access Journals (Sweden)

    E. Carlos RODRIGUEZ-MERCHAN

    2015-01-01

    Full Text Available There is controversy in the literature regarding a number of topics related to anterior cruciate ligament (ACLreconstruction. The purpose of this article is to answer the following questions: 1 Bone patellar tendon bone (BPTB reconstruction or hamstring reconstruction (HR; 2 Double bundle or single bundle; 3 Allograft or authograft; 4 Early or late reconstruction; 5 Rate of return to sports after ACL reconstruction; 6 Rate of osteoarthritis after ACL reconstruction. A Cochrane Library and PubMed (MEDLINE search of systematic reviews and meta-analysis related to ACL reconstruction was performed. The key words were: ACL reconstruction, systematic reviews and meta-analysis. The main criteria for selection were that the articles were systematic reviews and meta-analysesfocused on the aforementioned questions. Sixty-nine articles were found, but only 26 were selected and reviewed because they had a high grade (I-II of evidence. BPTB-R was associated with better postoperative knee stability but with a higher rate of morbidity. However, the results of both procedures in terms of functional outcome in the long-term were similar. The double-bundle ACL reconstruction technique showed better outcomes in rotational laxity, although functional recovery was similar between single-bundle and double-bundle. Autograft yielded better results than allograft. There was no difference between early and delayed reconstruction. 82% of patients were able to return to some kind of sport participation. 28% of patients presented radiological signs of osteoarthritis with a follow-up of minimum 10 years.

  11. Facial Reconstruction and Rehabilitation.

    Science.gov (United States)

    Guntinas-Lichius, Orlando; Genther, Dane J; Byrne, Patrick J

    2016-01-01

    Extracranial infiltration of the facial nerve by salivary gland tumors is the most frequent cause of facial palsy secondary to malignancy. Nevertheless, facial palsy related to salivary gland cancer is uncommon. Therefore, reconstructive facial reanimation surgery is not a routine undertaking for most head and neck surgeons. The primary aims of facial reanimation are to restore tone, symmetry, and movement to the paralyzed face. Such restoration should improve the patient's objective motor function and subjective quality of life. The surgical procedures for facial reanimation rely heavily on long-established techniques, but many advances and improvements have been made in recent years. In the past, published experiences on strategies for optimizing functional outcomes in facial paralysis patients were primarily based on small case series and described a wide variety of surgical techniques. However, in the recent years, larger series have been published from high-volume centers with significant and specialized experience in surgical and nonsurgical reanimation of the paralyzed face that have informed modern treatment. This chapter reviews the most important diagnostic methods used for the evaluation of facial paralysis to optimize the planning of each individual's treatment and discusses surgical and nonsurgical techniques for facial rehabilitation based on the contemporary literature. PMID:27093062

  12. Reconstructing human evolution

    CERN Document Server

    Cavalli-Sforza, M

    1999-01-01

    One can reconstruct human evolution using modern genetic data and models based on the mathematical theory of evolution and its four major factors : mutation, natural selection, statistical fluctuations in finite populations (random genetic drift), and migration. Archaeology gives some help on the major dates and events of the process. Chances of studying ancient DNA are very limited but there have been a few successful results. Studying DNA instead of proteins, as was done until a few years ago, and in particular the DNA of mitochondria and of the Y chromosome which are transmitted, respectively, by the maternal line and the paternal line, has greatly simplified the analysis. It is now possible to carry the analysis on individuals, while earlier studies were of necessity based on populations. Also the evolution of ÒcultureÓ (i.e. what we learn from others), in particular that of languages, gives some help and can be greatly enlightened by genetic studies. Even though it is largely based on mechanisms of mut...

  13. Orthotopic neobladder reconstruction

    Directory of Open Access Journals (Sweden)

    Dwayne T. S. Chang

    2015-01-01

    Full Text Available Orthotopic neobladder reconstruction is becoming an increasingly common urinary diversion following cystectomy for bladder cancer. This is in recognition of the potential benefits of neobladder surgery over creation of an ileal conduit related to quality of life (QoL, such as avoiding the need to form a stoma with its cosmetic, psychological and other potential complications. The PubMed database was searched using relevant search terms for articles published electronically between January 1994 and April 2014. Full-text articles in English or with English translation were assessed for relevance to the topic before being included in the review. Patients with neobladders have comparable or better post-operative sexual function than those with ileal conduits. They also have comparable QoL to those with ileal conduits. Orthotopic neobladder is a good alternative to ileal conduit in suitable patients who do not want a stoma and are motivated to comply with neobladder training. However, the selection of a neobladder as the urinary diversion of choice requires that patients have good renal and liver functions and are likely to be compliant with neobladder training. With benefits also come potential risks of neobladder formation. These include electrolyte abnormalities and nocturnal incontinence. This short review highlights current aspects of neobladder formation and its potential advantages.

  14. Multi-scale analysis in carbonates by X-ray microtomography: Characterization of the porosity and pore size distribution

    Science.gov (United States)

    Fernandes, Jaquiel S.; Nagata, Rodrigo; Moreira, Anderson C.; Fernandes, Celso P.; Appoloni, Carlos R.

    2013-05-01

    The porous systems of reservoir rocks present a complex geometry, involving aspects of shape of pores (morphology) and connectivity between the pores (topology). The macroscopic physical properties of these materials are strongly dependent of their microstructures. Based on these aspects, the present study has as main objective the characterization of the porous system geometry and computational determination of petrophysics properties of carbonate reservoir rocks through the X-ray microtomography methodology. Samples were microtomographed with the microtomographs Skyscan model 1172, installed at the PETROBRAS Research and Development Center (CENPES), Rio de Janeiro-RJ, Brazil and model 1173, installed at Sedimentary Geology Laboratory (LAGESD) in the Federal University of Rio de Janeiro (UFRJ). Two samples of carbonates were measured, Travertine and Dolomite, with spatial resolutions of 7 μm and 9.8 μm and 1.3 μm, 7 μm and 17 μm, respectively for the travertine and dolomite. With the data collected in the acquisitions, 900 transversal sections were reconstructed for each one of the referred resolutions. For the sample of dolomite, the average porosity found was 21.64%, 20.92% and 15.97% for resolutions of 1.3 μm, 7 μm and 17 μm, respectively. For the sample of travertine, the average porosity was 7.80 % and 7.52 % for resolutions of 7 μm and 9.8 μm, respectively. For the sample of dolomite, the pore size distribution showed that 50 % of the porous phase has pores with radius up to 37.6 μm, 84.6 μm and 84.4 μm, for the spatial resolutions of 1.3 μm, 7 μm and 17 μm, respectively. For the sample of travertine, 50 % of the pores have radius up to 148.1 μm and 158.1 μm, for the spatial resolutions of 7 μm and 9.8 μm.

  15. Reconstruction tomography from incomplete projections

    International Nuclear Information System (INIS)

    In some instances, reconstruction radionuclide tomography must be carried out from projections that do not include projection values for all portions of the object to be reconstructed. This may occur, for example, when the field of view of the detector is limited, or when an opaque foreign body is present within the object. The effects of such incomplete projections upon reconstructions of computer-simulated phantoms were studied, using iterative and convolution methods. Several methods for reducing the resulting artifacts and inaccuracies are discussed

  16. Methane adsorption behavior on coal having different pore structures

    Institute of Scientific and Technical Information of China (English)

    Zhao; Yi; Jiang; Chengfa; Chu; Wei

    2012-01-01

    The adsorption of methane onto five dry coal samples was measured at 298 K over the pressure range from 0 to 3.5 MPa using a volumetric method.The isotherm data were fitted to the Langmuir and the Freundlich equations.The kinetic data were fitted to a pseudo second order equation,the linear driving force equation(LDF),and an intra-particle diffusion model.These results showed that higher methane adsorption is correlated with larger micro-pore volumes and specific surface areas.The adsorption was related to the narrow micro-pore size distribution when the previous two parameters are large.The kinetics study showed that the kinetics of methane adsorption onto these five dry coal samples followed a pseudo second order model very well.Methane adsorption rates are controlled by intra-particle diffusion.The faster the intra-particle diffusion,the faster the methane adsorption rate will be.

  17. Methane adsorption behavior on coal having different pore structures

    Institute of Scientific and Technical Information of China (English)

    Zhao Yi; Jiang Chengfa; Chu Wei

    2012-01-01

    The adsorption of methane onto five dry coal samples was measured at 298 K over the pressure range from 0 to 3.5 MPa using a volumetric method.The isotherm data were fitted to the Langmuir and the Freundlich equations.The kinetic data were fitted to a pseudo second order equation,the linear driving force equation (LDF),and an intra-particle diffusion model.These results showed that higher methane adsorption is correlated with larger micro-pore volumes and specific surface areas.The adsorption was related to the narrow micro-pore size distribution when the previous two parameters are large.The kinetics study showed that the kinetics of methane adsorption onto these five dry coal samples followed a pseudo second order model very well.Methane adsorption rates are controlled by intra-particle diffusion.The faster the intra-particle diffusion,the faster the methane adsorption rate will be.

  18. Chromatography of humic substances on controlled pore glass

    International Nuclear Information System (INIS)

    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)

  19. Role of the pore fluid in crack propagation in glass

    Science.gov (United States)

    Mallet, Céline; Fortin, Jérôme; Guéguen, Yves; Bouyer, Fréric

    2015-05-01

    We investigate pore fluid effects due to surface energy variation or due to chemical corrosion in cracked glass. Both effects have been documented through experimental tests on cracked borosilicate glass samples. Creep tests have been performed to investigate the slow crack propagation behavior. We compared the dry case (saturated with argon gas), the nonreactive water saturated case (commercial mineralized water), and the distilled and deionized water saturated case (pure water). Chemical corrosion effects have been observed and evidenced from pH and water composition evolution of the pure water. Then, the comparison of the dry case, the mineral water saturated case, and the corrosion case allow to (i) evidence the mechanical effect of the presence of a pore fluid and (ii) show also the chemical effect of a glass dissolution. Both effects enhance subcritical crack propagation.

  20. Anomalous mobility of highly charged particles in pores.

    Science.gov (United States)

    Qiu, Yinghua; Yang, Crystal; Hinkle, Preston; Vlassiouk, Ivan V; Siwy, Zuzanna S

    2015-08-18

    Single micropores in resistive-pulse technique were used to understand a complex dependence of particle mobility on its surface charge density. We show that the mobility of highly charged carboxylated particles decreases with the increase of the solution pH due to an interplay of three effects: (i) ion condensation, (ii) formation of an asymmetric electrical double layer around the particle, and (iii) electroosmotic flow induced by the charges on the pore walls and the particle surfaces. The results are important for applying resistive-pulse technique to determine surface charge density and zeta potential of the particles. The experiments also indicate the presence of condensed ions, which contribute to the measured current if a sufficiently high electric field is applied across the pore. PMID:26177843

  1. Pore Size Distribution of High Performance Metakaolin Concrete

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The Compressive strength, porosity and pore size distribution of high performance metakaolin (MK) concrete were investigated. Concretes containing 0,5%,10% and 20% metakaolin were prepared at a water/cementitious material ratio (W/C) of 0.30. In parallel, concrete mixtures with the replacement of cement by 20% fly ash or 5 and 10% silica fume were prepared for comparison. The specimens were cured in water at 27℃ for 3 to 90 days. The results show that at the early age of curing (3 days and 7 days), metakaolin replacements increase the compressive strength, but silica fume replacement slightly reduces the compressive strength. At the age of and after 28 days, the compressive strength of the concrete with metakaolin and silica fume replacement increases.A strong reduction in the total porosity and average pore diameter were observed in the concrete with MK 20% and 10% in the first 7 days.

  2. 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.

  3. Effects of Quenching Temperature and Time on Pore Diameter of Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) Porous Scaffolds and MC3T3-E1 Osteoblast Response to the Scaffolds

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBHHx) scaffolds were prepared by thermally inducing phase separation (TIPS) for bone reconstruction. Scanning electron microscopy and porosity measurements were used to analyze the structure and properties of the scaffolds. The pore diameter of the scaffolds could be easily controlled by changing the quenching temperature and time. The biocompatibility was assessed by examining the proliferation and morphology of MC 3T3-E1 osteoprogenitor cells seeded on the scaffolds. Cultures grown in the presence of a source of phosphate ions showed the formation of a mineralized extracellular matrix. The results indicate that PHBHHx scaffolds prepared using TIPS are a promising candidate for bone reconstruction.

  4. Assessment of pore size distribution using image analysis

    Czech Academy of Sciences Publication Activity Database

    Doktor, Tomáš; Kytýř, Daniel; Valach, Jaroslav; Jiroušek, Ondřej

    Trieste: Italian Group of Fracture, 2010 - (Iacoviello, F.; Cosmi, F.), s. 155-157 ISBN 978-88-95940-30-4. [Youth Symposium on Experimental Solid Mechanics /9./. Trieste (IT), 07.07.2010-10.07.2010] R&D Projects: GA ČR(CZ) GAP105/10/2305 Institutional research plan: CEZ:AV0Z20710524 Keywords : pore size distribution * image analysis * micro-CT Subject RIV: JJ - Other Materials

  5. Host defenses against bacterial pore-forming toxins

    OpenAIRE

    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 Mycobacterium tuberculosis. A review of primary literature shows PFTs may form a viable target for new antibiotics, warranting their further investigation. This thesis describes three studies on host...

  6. Variations in Fusion Pore Formation in Cholesterol-Treated Platelets.

    Science.gov (United States)

    Finkenstaedt-Quinn, Solaire A; Gruba, Sarah M; Haynes, Christy L

    2016-02-23

    Exocytosis is a highly regulated intercellular communication process involving various membrane proteins, lipids, and cytoskeleton restructuring. These components help control granule fusion with the cell membrane, creating a pore through which granular contents are released into the extracellular environment. Platelets are an ideal model system for studying exocytosis due to their lack of a nucleus, resulting in decreased membrane regulation in response to cellular changes. In addition, platelets contain fewer granules than most other exocytosing cells, allowing straightforward measurement of individual granule release with carbon-fiber microelectrode amperometry. This technique monitors the concentration of serotonin, an electroactive molecule found in the dense-body granules of platelets, released as a function of time, with 50 μs time resolution, revealing biophysical characteristics of the fundamental exocytotic process. Variations in fusion pore formation and closure cause deviations from the classic current versus time spike profile and may influence diffusion of serotonin molecules from the site of granule fusion. Physiologically, the delivery of smaller packets of chemical messengers or the prolonged delivery of chemical messengers may represent how cells/organisms tune biological response. The goals of this work are twofold: 1) to categorize secretion features that deviate from the traditional mode of secretion and 2) to examine how changing the cholesterol composition of the platelet membrane results in changes in the pore formation process. Results herein indicate that the expected traditional mode of release is actually in the minority of granule content release events. In addition, results indicate that as the cholesterol content of the plasma membrane is increased, pore opening is less continuous. PMID:26910428

  7. Pore Characteristics of Chitosan Scaffolds Studied by Electrochemical Impedance Spectroscopy

    OpenAIRE

    Tully-Dartez, Stephanie; Cardenas, Henry E.; Sit, Ping-Fai Sidney

    2009-01-01

    In this study, a novel approach, electrochemical impedance spectroscopy (EIS), was used to examine the pore characteristics of chitosan scaffolds under aqueous conditions. The EIS was run with a constant current of 0.1 mA with the frequency sweep of 106 to 10−4 Hz. The resulting complex impedance measurement was then used to calculate porosity, which was determined to be 71%. Scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP), two commonly used methods for scaffold cha...

  8. 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.

  9. A mechanistic view of mitochondrial death decision pores

    OpenAIRE

    Belizário, J E; Alves, J.; J.M. Occhiucci; M. Garay-Malpartida; Sesso, A.

    2007-01-01

    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 whe...

  10. Pore Distribution and Water Uptake in a Cenosphere–Cement

    OpenAIRE

    Baroniņš, J; Sētiņa, J; Šahmenko, G; Lagzdiņa, S; Šiškins, A

    2015-01-01

    Alumina silicate cenospheres (CS) is a significant waste material from power plants that use a coal. Use CS as Portland cement replacement material gives opportunity to control physical and mechanical properties and makes a product lighter and more cost-effective. In the frame of this study, Portland cement paste samples were produced by adding CS in the concentration range from 0 to 40 volume %. Water uptake of hardened samples was checked and pore ...

  11. Proteins Connecting the Nuclear Pore Complex with the Nuclear Interior

    OpenAIRE

    Strambio-De-Castillia, Caterina; Blobel, Günter; Rout, Michael P

    1999-01-01

    While much has been learned in recent years about the movement of soluble transport factors across the nuclear pore complex (NPC), comparatively little is known about intranuclear trafficking. We isolated the previously identified Saccharomyces protein Mlp1p (myosin-like protein) by an assay designed to find nuclear envelope (NE) associated proteins that are not nucleoporins. We localized both Mlp1p and a closely related protein that we termed Mlp2p to filamentous structures stretching from t...

  12. Optical transmission spectra of porous aluminamembranes with different pore size

    International Nuclear Information System (INIS)

    Membranes of nanoporous aluminum oxide (alumina) have been obtained using the electrochemical etching technique by varying technological regimes. The surface morphology and cleavages of obtained experimental samples are studied using scanning electron microscopy (SEM). The optical transmission measurements were performed on a spectrophotometer in the wavelength range of 190-1000 nm. It is possible to determine the average size and the dispersion of the pore diameter by UV- visible transmittance spectrum measuring

  13. Development of Pore Pressure and Material Damping during Cyclic Loading

    OpenAIRE

    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 a mobilization index M it is possible to describe the strongly hysteretic behaviour during loading and unloading, even if the stress path is complicated.

  14. Fabrication and Visualization of Capillary Bridges in Slit Pore Geometry

    OpenAIRE

    Broesch, David J.; Frechette, Joelle

    2014-01-01

    A procedure for creating and imaging capillary bridges in slit-pore geometry is presented. High aspect ratio hydrophobic pillars are fabricated and functionalized to render their top surfaces hydrophilic. The combination of a physical feature (the pillar) with a chemical boundary (the hydrophilic film on the top of the pillar) provides both a physical and chemical heterogeneity that pins the triple contact line, a necessary feature to create stable long but narrow capillary bridges. The subst...

  15. Membranes with functionalized carbon nanotube pores for selective transport

    Energy Technology Data Exchange (ETDEWEB)

    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.

  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. Electrically tunable pore morphology in nanoporous gold thin films

    Institute of Scientific and Technical Information of China (English)

    Tatiana S. Dorofeeva; Erkin Seker

    2015-01-01

    Nanoporous gold (np-Au) is an emerging nanostructured material that exhibits many desirable properties, including high electrical and thermal conductivity, high surface area-to-volume ratio, tunable pore morphology well-established surface-binding chemistry, and compatibility with microfabrication. These features make np-Au a popular material for use in fuel cells, optical and electrical biosensors, drug delivery vehicles, neural electrode coatings, and as a model system for nanoscale mechanics. In each of its many applications, np-Au morphology plays an essential role in the overall device operation. Therefore, precise morphological control is necessary to attain optimal device performance. Traditionally thermal treatment by furnaces and hot plates is used to obtain np-Au with self-similar but coarser morphologies. However, this approach lacks the ability to create different morphologies on a single substrate and requires high temperatures (〉 250 ℃) incompatible with most plastic substrates. Herein, we report electro-annealing as a novel method that permits control of the extent and location of pore coarsening on a single substrate in one fast treatment step. The electro-annealing entails much lower temperatures (〈 150 ℃) than traditional thermal treatment, putatively due to electrically assisted phenomena contributing to the thermally activated surface diffusion of gold atoms, responsible for coarsening. Overall, this approach is easily scaled to display multiple pore morphologies on a single chip, therefore enabling high-throughput screening of optimal nanostructures for specific applications.

  18. Integrated pore blockage-cake filtration model for crossflow filtration

    International Nuclear Information System (INIS)

    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.

  19. 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.

  20. Hydrogeology and hydrodynamics of coral reef pore waters

    Energy Technology Data Exchange (ETDEWEB)

    Buddemeier, R.W.; Oberdorfer, J.A.

    1988-06-29

    A wide variety of forces can produce head gradients that drive the flow and advective mixing of internal coral reef pore waters. Oscillatory gradients that produce mixing result from wave and tide action. Sustained gradients result from wave and tide-induced setup and ponding, from currents impinging on the reef structure, from groundwater heads, and from density differenced (temperature or salinity gradients). These gradients and the permeabilities and porosities of reef sediments are such that most macropore environments are dominated by advection rather than diffusion. The various driving forces must be analyzed to determine the individual and combined magnitudes of their effects on a specific reef pore-water system. Pore-water movement controls sediment diagenesis, the exchange of nutrients between sediments and benthos, and coastal/island groundwater resources. Because of the complexity of forcing functions, their interactions with specific local reef environments, experimental studies require careful incorporation of these considerations into their design and interpretation. 8 refs., 3 figs., 1 tab.

  1. Analysis of Yucca Mountain Pore-Water Chloride Data

    International Nuclear Information System (INIS)

    Distribution of chemical constituents in the unsaturated zone (UZ) system of Yucca Mountain, Nevada, depends on many factors, such as hydrological and geochemical processes of surface precipitation, evapotranspiration, the water-fracture-matrix interactions, large-scale mixing via lateral flow and transport, and the history of climate changes. This study analyzes pore-water chloride-concentration data and models the transport processes. The model results are then used to calibrate the UZ flow model with the aim of refining the infiltration distribution and percolation fluxes to the potential repository. The major chemical data used in this study were pore-water chloride (Cl) concentrations. The sensitivity of this conservative tracer to the UZ flow system is well known. This constituent was directly incorporated into a three-dimensional dual-permeability flow model. Chemical transport properties were taken into account. The surface flux of chloride was determined by the total amount of precipitation reaching the surface and chemical concentration in the precipitation. The entire flow system was divided into domains based on the distribution of pore-water chemical data, infiltration data, hydrogeological and hydrostructural features. Model calibration proceeded by adjusting the site-scale infiltration map and anisotropy permeabilities to reach a satisfying agreement between the simulated subsurface chloride distribution and measured data

  2. Chemical modelling of pore water composition from PFBC residues

    International Nuclear Information System (INIS)

    The concentration of trace elements varies depending on the source of the coal and also due to the combustion process used. Mercury is one important element among the trace elements in the coal residues, generally recognised as potentially harmful to the biological system. To predict the pore water concentrations of mercury and other important constituents leached from coal combustion residues disposal sites, mechanistic data on chemical reactions are required. The present study is an application of a basially thermodynamical approach using the geochemical code EQ3NR. The presence of discrete solid phases that control the aqueous concentrations of major elements such as aluminium, calcium and silicon are identified. Solid phases are modelled in equilibrium with a hypothetical pore water at a pH range of 7-11. In this study the thermodynamic database of EQ3NR has been complemented with data for cadmium, mercury and lead taken from the OECD/NEA Thermodynamic Database and from a compilation made by Lindsay. Possible solubility limiting phases for the important trace elements arsenic, cadmium, chromium, copper, mercury, nickel and lead have been identified. Concentrations of these trace elements as a function of pH in the hypothetical pore water were calculated using mechanistic thermodynamial data. The thermodynamical approach in this study seems justified because most solid residues that are either present or expected to form during weathering have relatively fast precipitation/dissolution kinetics. (21 refs., 18 figs., 5 tabs.)

  3. Simulation of Multiphase FLOW at the Pore Scale: Doable, Useful?

    Science.gov (United States)

    Tchelepi, H.; Abu AlSaud, M.; Soulaine, C.

    2014-12-01

    We discuss the shotcomings of Darcy-scale formulations and constitutive relations for (unstable) immiscible multiphase flow in natural porous media, and we argue for a more rigorous connection between the Darcy-scale representation and the pore-scale dynamics. We then discuss the challenges associated with so-called Direct Numerical Simulation (DNS) at the pore scale. The emphasis is on contact-line dynamics for non-zero contact angles. We argue that accurate description of the (1) fluid-fluid and (2) fluid-fluid-solid contact lines, as well as, (3) the hysteretic ‎behavior of immiscible displacement processes are needed before claims that Direct Numerical Simulation (DNS) of pore-scale physics is doable. Then, we describe our early attempts to devise a hybrid level-set and volume-of-fluid approach to model the evolution of sharp immiscible interfaces in natural porous media. We also discuss the challenges associated with the translation of two-phase flow dynamics to "Darcy" scales.

  4. Single long-polymer translocation through a long pore

    Institute of Scientific and Technical Information of China (English)

    Ding Ke-Jian; Cai Dong-Qing; Zhan Fu-Ru; Wu Li-Jun; Wu Yue-Jin; Yu Zeng-Liang

    2006-01-01

    This paper theoretically studies the free energy and conformational entropy of a long polymer threading a long nanopore (n0/N ≥0.1) on external electric field. The polymer expanded model is built in this paper, that is, a single long polymer chain with N monomers (each of size a) threading a pore with n0 monomers can be regarded as polymer with N + n0 monomers translocating a 2-dimension hole embedded in membrane. A theoretical approach is presented which explicitly takes into account the nucleation theory. Our calculations imply that, the structure of polymer changes more acutely than other situation, while its leading monomer reaches the second vacuum and its end monomer escapes the first vacuum. And it is also shown that the length scale of polymer and pore play a very important role for polymer translocation dynamics. The present model predicts that the translocation time depends on the chemical potential gradient and the property of the solvent on sides of pore to some extent.

  5. In situ temperature tunable pores of shape memory polyurethane membranes

    International Nuclear Information System (INIS)

    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

  6. Pore-scale study of dissolution-induced changes in hydrologic properties of rocks with binary minerals

    CERN Document Server

    Chen, Li; Viswanathan, Hari S; Tao, Wenquan

    2014-01-01

    A pore-scale numerical model for reactive transport processes based on the Lattice Boltzmann method is used to study the dissolution-induced changes in hydrologic properties of a fractured medium and a porous medium. The solid phase of both media consists of two minerals, and a structure reconstruction method called quartet structure generation set is employed to generate the distributions of both minerals. Emphasis is put on the effects of undissolved minerals on the changes of permeability and porosity under different Peclet and Damkohler numbers. The simulation results show porous layers formed by the undissolved mineral remain behind the dissolution reaction front. Due to the large flow resistance in these porous layers, the permeability increases very slowly or even remains at a small value although the porosity increases by a large amount. Besides, due to the heterogeneous characteristic of the dissolution, the chemical, mechanical and hydraulic apertures are very different from each other. Further, sim...

  7. Evaluation of Optimal Pore Size of (3-Aminopropyltriethoxysilane Grafted MCM-41 for Improved CO2 Adsorption

    Directory of Open Access Journals (Sweden)

    Zhilin Liu

    2015-01-01

    Full Text Available An array of new MCM-41 with substantially larger average pore diameters was synthesized through adding 1,3,5-trimethylbenzene (TMB as the swelling agent to explore the effect of pore size on final adsorbent properties. The pore expanded MCM-41 was also grafted with (3-Aminopropyltriethoxysilane (APTES to determine the optimal pore size for CO2 adsorption. The pore-expanded mesoporous MCM-41s showed relatively less structural regularity but significant increments of pore diameter (4.64 to 7.50 nm; the fraction of mesopore volume also illustrated an increase. The adsorption heat values were correlated with the order of the adsorption capacities for pore expanded MCM-41s. After amine functionalization, the adsorption capacities and heat values showed a significant increase. APTES-grafted pore-expanded MCM-41s depicted a high potential for CO2 capture regardless of the major drawback of the high energy required for regeneration.

  8. 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

    2013-11-01

    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. PMID:24042434

  9. Difficulties of supercurrents in narrow pores of 3He-A

    International Nuclear Information System (INIS)

    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)

  10. Reconstruction techniques for optoacoustic imaging

    Science.gov (United States)

    Frenz, Martin; Koestli, Kornel P.; Paltauf, Guenther; Schmidt-Kloiber, Heinz; Weber, Heinz P.

    2001-06-01

    Optoacoustics is a method to gain information from inside a tissue. This is done by irradiating a tissue with a short light pulse, which generates a pressure distribution inside the tissue that mirrors the absorber distribution. The pressure distribution measured on the tissue-surface allows, by applying a back-projection method, to calculate a tomography image of the absorber distribution. This study presents a novel computational algorithm based on Fourier transform, which, at least in principle, yields an exact 3D reconstruction of the distribution of absorbed energy density inside turbid media. The reconstruction is based on 2D pressure distributions captured outside at different times. The FFT reconstruction algorithm is first tested in the back projection of simulated pressure transients of small model absorbers, and finally applied to reconstruct the distribution of artificial blood vessels in three dimensions.

  11. Breast Reconstruction with Tissue Expansion

    Medline Plus

    Full Text Available ... to go with Tamoxifen. At that point in time she did not want to get a reconstruction, ... her work and she's more comfortable with her time, she said she wanted to pursue the breast ...

  12. Breast Reconstruction with Tissue Expansion

    Medline Plus

    Full Text Available ... come to my practice a few months ago seeking a left breast reconstruction after mastectomy. She had ... Veritas Collagen Matrix sling in order to help support the expansion because there is possible radiation damage ...

  13. Submicron STIM tomography reconstruction techniques

    International Nuclear Information System (INIS)

    One-dimensional projections of ion energy loss have been converted to areal density using tabulated stopping powers in a scanning transmission ion microscopy (STIM) reconstruction of a test object, displaying a spatial resolution of 0.37 μm. Location and registration of the centre of areal mass density in each projection provides a means of overcoming (a) the misalignment of the specimen rotation axis with the centre of the scan path and (b) deviations of the specimen from its precession around the axis of rotation. Multiplicative algebraic reconstruction technique (ART), filtered backprojection and maximum-entropy algorithms for the reconstruction of the object are considered. Maximum entropy is shown to produce an image with the least number of artifacts. However, when time considerations are taken into account, it is found that filtered backprojection is the preferred algorithm for a tomographic reconstruction. (orig.)

  14. Reconstruction within the Zeldovich approximation

    CERN Document Server

    White, Martin

    2015-01-01

    The Zeldovich approximation, 1st order Lagrangian perturbation theory, provides a good description of the clustering of matter and galaxies on large scales. The acoustic feature in the large-scale correlation function of galaxies imprinted by sound waves in the early Universe has been successfully used as a `standard ruler' to constrain the expansion history of the Universe. The standard ruler can be improved if a process known as density field reconstruction is employed. In this paper we develop the Zeldovich formalism to compute the correlation function of biased tracers in both real- and redshift-space using the simplest reconstruction algorithm with a Gaussian kernel and compare to N-body simulations. The model qualitatively describes the effects of reconstruction on the simulations, though its quantitative success depends upon how redshift-space distortions are handled in the reconstruction algorithm.

  15. Vermilion Reconstruction with Genital Mucosa.

    Science.gov (United States)

    Müller-Richter, Urs D A; Weyandt, Gerhard H; Woeckel, Achim; Kübler, Alexander C

    2016-05-01

    Functional and aesthetical reconstruction, especially of the upper lip after ablative tumor surgery, can be very challenging. The skin of the lip might be sufficiently reconstructed by transpositional flaps from the nasolabial or facial area. Large defects of the lip mucosa, including the vestibule, are even more challenging due to the fact that flaps from the inner lining of the oral cavity often lead to functional impairments. We present a case of multiple vermilion and skin resections of the upper lip. At the last step, we had to resect even the whole vermilion mucosa, including parts of the oral mucosa of the vestibule, leaving a bare orbicularis oris muscle. To reconstruct the mucosal layer, we used a mucosal graft from the labia minora and placed it on the compromised lip and the former transpositional flaps for the reconstructed skin of the upper lip with very good functional and aesthetic results. PMID:27579226

  16. Provincial reconstruction teams improving effectiveness

    OpenAIRE

    Sellers, Cameron S.

    2007-01-01

    Provincial Reconstruction Teams (PRTs) are currently prominent constructs for stabilization and reconstruction in Afghanistan and Iraq. PRTs are composed of civil-military teams, including elements from coalition partners and the host-nation, and involve multiple military services and civilian agencies. Their missions are to extend the legitimacy of the central government throughout the country and to use Civil Military Operations (CMO) to counter anti-government forces. PRTs are prominent,...

  17. Current Concepts in ACL Reconstruction

    OpenAIRE

    Fu, Freddie H; Cohen, Steven B.

    2008-01-01

    Current Concepts in ACL Reconstruction is a complete reference text composed of the most thorough collection of topics on the ACL and its surgical reconstruction compiled, with contributions from some of the world's experts and most experienced ACL surgeons. Various procedures mentioned throughout the text are also demonstrated in an accompanying video CD-ROM. PURPOSE Composing a single, comprehensive and complete information source on ACL including basic sciences, clinical issues, latest con...

  18. Equilibrium Reconstruction in EAST Tokamak

    Institute of Scientific and Technical Information of China (English)

    QIAN Jinping; WAN Baonian; L. L. LAO; SHEN Biao; S. A. SABBAGH; SUN Youwen; LIU Dongmei; XIAO Singjia; REN Qilong; GONG Xianzu; LI Jiangang

    2009-01-01

    Reconstruction of experimental axisymmetric equilibria is an important part of toka-mak data analysis. Fourier expansion is applied to reconstruct the vessel current distribution in EFIT code. Benchmarking and testing calculations are performed to evaluate and validate this algorithm. Two cases for circular and non-circular plasma discharges are presented. Fourier ex-pansion used to fit the eddy current is a robust method and the real time EFIT can be introduced to the plasma control system in the coming campaign.

  19. Reconstructing pedigrees: a stochastic perspective

    OpenAIRE

    Thatte, Bhalchandra D.; Steel, Mike

    2007-01-01

    A pedigree is a directed graph that describes how individuals are related through ancestry in a sexually-reproducing population. In this paper we explore the question of whether one can reconstruct a pedigree by just observing sequence data for present day individuals. This is motivated by the increasing availability of genomic sequences, but in this paper we take a more theoretical approach and consider what models of sequence evolution might allow pedigree reconstruction (given sufficiently...

  20. The Description of Shale Reservoir Pore Structure Based on Method of Moments Estimation

    OpenAIRE

    Li, Wenjie; WANG Changcheng; Shi, Zejin; Wei, Yi; Zhou, Huailai; Deng, Kun

    2016-01-01

    Shale has been considered as good gas reservoir due to its abundant interior nanoscale pores. Thus, the study of the pore structure of shale is of great significance for the evaluation and development of shale oil and gas. To date, the most widely used approaches for studying the shale pore structure include image analysis, radiation and fluid invasion methods. The detailed pore structures can be studied intuitively by image analysis and radiation methods, but the results obtained are quite s...

  1. Modelling mass transport through a porous partition: Effect of pore size distribution.

    OpenAIRE

    Khayet Souhaimi, Mohamed; Velázquez, Armando; Mengual, Juan I.

    2004-01-01

    Direct contact membrane distillation process has been studied using microporous polytetrafluoroethylene and polyvinylidene fluoride membranes. The membranes were characterized in terms of their nonwettability, pore size distribution and porosity. The mean pore sizes and pore size distributions were obtained by means of wet/ dry flow method. The mean pore size and the effective porosity of the membranes were also determined from the gas permeation test. A theoretical model that considers the p...

  2. Assembly of the nuclear pore: biochemically distinct steps revealed with NEM, GTP gamma S, and BAPTA

    OpenAIRE

    1996-01-01

    A key event in nuclear formation is the assembly of functional nuclear pores. We have used a nuclear reconstitution system derived from Xenopus eggs to examine the process of nuclear pore assembly in vitro. With this system, we have identified three reagents which interfere with nuclear pore assembly, NEM, GTP gamma S, and the Ca++ chelator, BAPTA. These reagents have allowed us to determine that the assembly of a nuclear pore requires the prior assembly of a double nuclear membrane. Inhibiti...

  3. Diagenetic facies controls on pore structure and rock electrical parameters in tight gas sandstone

    Science.gov (United States)

    Liu, Hongping; Zhao, Yanchao; Luo, Yang; Chen, Zhaoyou; He, Sheng

    2015-08-01

    Rock electrical parameters of tight gas sandstone show large variations in the T2 member in Dingbei Block, Ordos Basin, China. Applying the same rock electrical parameters in water saturation calculations would lead to large errors. Based on casting thin sections, x-ray diffraction, scanning electron microscopy (SEM), cathode luminescence, porosity and permeability, image analysis, and high-pressure mercury intrusion/withdrawal method, identification of the diagenetic facies are first conducted, and then their pore structure and their relationship with rock electrical parameters are investigated. Five diagenetic facies (A-E), which are identified based mainly on pore types and authigenic minerals, have different pore structure and rock electrical parameters. Conceptual models that incorporate the rock properties of each diagenetic facies have been built, before applying the electrical efficiency theory to explain the values of cementation exponent (m) and saturation exponent (n). A conventional network model, a shunt pore model, a netted pore model, and a dotted line model are utilized to mimic the intergranular pores, authigenic kaolinite intercrystal pores, carbonate-cement dissolution pores, and clay-matrix intercrystal pores, respectively. A decrease of the contents of large pores increases electrical efficiency and therefore reduces m. The saturation exponent, which depends on the distribution of water and gas, can be better understood by applying the different pore models. In the shunt and netted pore models, gas displacement starts from the larger pores and smaller pores provide alternative conduction pathways, hence sustaining electrical efficiency and decreasing n. Clay-matrix intercrystal pores are mainly micropores, since the brine in the rocks are isolated after gas displacement, reducing overall electrical efficiency and dramatically increasing the value of n in the diagenetic facies, which is dominated by clay-matrix intercrystal pores.

  4. Formation of the postmitotic nuclear envelope from extended ER cisternae precedes nuclear pore assembly

    OpenAIRE

    Ladinsky, Mark S.; Lu, Lei; Kirchhausen, Tomas Leopold

    2011-01-01

    During mitosis, the nuclear envelope merges with the endoplasmic reticulum (ER), and nuclear pore complexes are disassembled. In a current model for reassembly after mitosis, the nuclear envelope forms by a reshaping of ER tubules. For the assembly of pores, two major models have been proposed. In the insertion model, nuclear pore complexes are embedded in the nuclear envelope after their formation. In the prepore model, nucleoporins assemble on the chromatin as an intermediate nuclear pore c...

  5. Compression Process of Pore inside Explosive Charge in a Warhead under Launching Load

    OpenAIRE

    Li, W; Yan, H; Q. Zhang; Y.H. Ji

    2010-01-01

    In this paper, the compression process of the pore inside explosive charge in a warhead under launching load is simulated and its influence on premature explosion is discussed. The relationship between the pore compression, distortion, and the form of 'igniting hot spot' has been established. The analysis of result indicates that the stress wave in the explosive charge developed due to launching load is a key factor in the pore compression process. The volume change of the pore, which is rela...

  6. Nuclear pore complex assembly studied with a biochemical assay for annulate lamellae formation

    OpenAIRE

    1995-01-01

    Formation of the nuclear pore is an intricate process involving membrane fusion and the ordered assembly of up to 1,000 pore proteins. As such, the study of pore assembly is not a simple one. Interestingly, annulate lamellae, a cytoplasmic organelle consisting of stacks of flattened membrane cisternae perforated by numerous pore complexes, have been found to form spontaneously in a reconstitution system derived from Xenopus egg extracts, as determined by electron microscopy (Dabauvalle et al....

  7. Technical basis for dose reconstruction

    International Nuclear Information System (INIS)

    The purpose of this paper is to consider two general topics: technical considerations of why dose-reconstruction studies should or should not be performed and methods of dose reconstruction. The first topic is of general and growing interest as the number of dose-reconstruction studies increases, and one asks the question whether it is necessary to perform a dose reconstruction for virtually every site at which, for example, the Department of Energy (DOE) has operated a nuclear-related facility. And there is the broader question of how one might logically draw the line at performing or not performing dose-reconstruction (radiological and chemical) studies for virtually every industrial complex in the entire country. The second question is also of general interest. There is no single correct way to perform a dose-reconstruction study, and it is important not to follow blindly a single method to the point that cheaper, faster, more accurate, and more transparent methods might not be developed and applied

  8. Lip Reconstruction after Tumor Ablation

    Science.gov (United States)

    Ebrahimi, Ali; Kalantar Motamedi, Mohammad Hossein; Ebrahimi, Azin; Kazemi, Mohammad; Shams, Amin; Hashemzadeh, Haleh

    2016-01-01

    Approximately 25% of all oral cavity carcinomas involve the lips, and the primary management of these lesions is complete surgical resection. Loss of tissue in the lips after resection is treated with a variety of techniques, depending on the extension and location of the defect. Here we review highly accepted techniques of lip reconstruction and some of new trials with significant clinical results. Reconstruction choice is primarily depend to size of the defect, localization of defect, elasticity of tissues. But patient’s age, comorbidities, and motivation are also important. According to the defect location and size, different reconstruction methods can be used. For defects involved less than 30% of lips, primary closures are sufficient. In defects with 35–70% lip involvement, the Karapandzic, Abbe, Estlander, McGregor or Gillies’ fan flaps or their modifications can be used. When lip remaining tissues are insufficient, cheek tissue can be used in Webster and Bernard advancement flaps and their various modifications. Deltopectoral or radial forearm free flaps can be options for large defects of the lip extending to the Jaws. To achieve best functional and esthetic results, surgeons should be able to choose most appropriate reconstruction method. Considering defects’ size and location, patients’ expects and surgeon’s ability and knowledge, a variety of flaps are presented in order to reconstruct defects resulted from tumor ablation. It’s necessary for surgeons to trace the recent innovations in lip reconstruction to offer best choices to patients. PMID:27308236

  9. Changes of soil pore system due to soil macrofauna: an experimental approach to study the contribution of different taxa

    Science.gov (United States)

    Gargiulo, Laura; Buscemi, Gilda; Mele, Giacomo; Terribile, Fabio

    2015-04-01

    Soil fauna contributes to the ecosystem functioning, for example, by means of its direct influence on soil structure which modifies the physical environment of the microbial community. Changes in habitat structure due to soil fauna activities can influence resource availability, species' abundances, and community composition of soil microorganisms. X-ray tomography has been increasingly used to obtain precise and non-destructive analysis mostly of the macroporosity resulting from earthworm activity in repacked soil cores. However also other macrofauna species contribute in different manner and extent to the modification of soil pore system, and then to the soil functioning, by means of their burrows and bioturbation activity. In this work we have developed an experimental approach based on the use of repacked soil mesocosms specifically constructed for the purpose of distinguish separately the contribution to soil structure changes of different organisms naturally present in field or inoculated in laboratory. Six different orders of macrofauna were studied and after four weeks of fauna activity the cores were imaged using a medical X-ray tomograph. Three-dimensional image processing was used in order to obtain 3D reconstructions and preliminary analysis of the identified biopores. In addition to the earthworms (Haplotaxida, genus Lombricus), among the studied taxa, Embioptera showed the most intense burrowing activity, while Coleoptera larvae (sp. Elater sanguineus) and Julida (class Diplopoda) produced the thickest pore network in our mesocosms. The used experimental approach showed a promising potential to provide new useful information about the widely differentiated contribution of many types of macrofauna to the modification of soil pore system.

  10. Direct pore-to-core up-scaling of displacement processes: Dynamic pore network modeling and experimentation

    Science.gov (United States)

    Aghaei, Arash; Piri, Mohammad

    2015-03-01

    We present a new dynamic pore network model that is capable of up-scaling two-phase flow processes from pore to core. This dynamic model provides a platform to study various flow processes in porous media at the core scale using the pore-scale physics. The most critical features of this platform include (1) the incorporation of viscous, capillary, and gravity pressure drops in pore-scale displacement thresholds, (2) wetting-phase corner flow in capillary elements with angular cross-sections, (3) adjustments of corner interfaces between wetting and non-wetting phases based on changes in local capillary pressure, (4) simultaneous injection of wetting and non-wetting phases from the inlet of the medium at constant flow rates that makes the study of steady-state processes possible, (5) heavy parallelization using a three-dimensional domain decomposition scheme that enables the study of two-phase flow at the core scale, and (6) constant pressure boundary condition at the outlet. For the validation of the dynamic model, three two-phase miniature core-flooding experiments were performed in a state-of-the-art micro core-flooding system integrated with a high-resolution X-ray micro-CT scanner. The dynamic model was rigorously validated by comparing the predicted local saturation profiles, fractional flow curves, relative permeabilities, and residual oil saturations against their experimental counterparts. The validated dynamic model was then used to study low-IFT and high-viscosity two-phase flow processes and investigate the effect of high capillary number on relative permeabilities and residual oil saturation.

  11. Self-assembly, structural, and retrostructural analysis of dendritic dipeptide pores undergoing reversible circular to elliptical shape change.

    Science.gov (United States)

    Peterca, Mihai; Percec, Virgil; Dulcey, Andrés E; Nummelin, Sami; Korey, Stephanie; Ilies, Monica; Heiney, Paul A

    2006-05-24

    The synthesis of dendritic dipeptides (4-3,4-3,5-4)12G2-CH(2)-Boc-L-Tyr-L-Ala-OMe and (4-3, 4-3,5-4)12G2-CH(2)-Boc-D-Tyr-D-Ala-OMe is described. These dendritic dipeptides self-assemble into porous elliptical and circular columns that in turn self-organize into centered rectangular columnar and hexagonal columnar periodic arrays. The transition from porous elliptical to porous circular columns is mediated in a reversible or irreversible way by the thermal history of the sample. A method to determine the dimensions of hollow elliptical and circular columns by the reconstruction of the small-angle powder X-ray diffractograms of the centered rectangular or hexagonal columnar lattices was elaborated. This technique together with wide-angle X-ray experiments performed on aligned fibers provided access to the structural and retrostructural analysis of elliptical supramolecular pores. This procedure is general and can be adapted for the determination of the dimensions of pores of any columnar shape. PMID:16704274

  12. Prediction of Hydraulic Conductivity as Related to Pore Size Distribution in Unsaturated Soils

    Science.gov (United States)

    Soil pore volume as well as pore size, shape, type (i.e. biopore versus crack), continuity, and distribution in soil affect soil water and gas exchange. Vertical and lateral drainage of water by gravitational forces occurs through large, non-capillary soil pores, but redistribution and upward moveme...

  13. 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 approxima

  14. Performance of slotted pores in particle manufacture using rotating membrane emulsification

    Institute of Scientific and Technical Information of China (English)

    Qingchun Yuan; Nita Aryanti; Ruozhou Hou; Richard A.Williams

    2009-01-01

    This paper addresses the use of different slotted pores in rotating membrane emulsification technology.Pores of square and rectangular shapes were studied to understand the effect of aspect ratio (1-3.5) and their orientation on oil droplet formation.Increasing the membrane rotation speed decreased the droplet size,and the oil droplets produced were more uniform using slotted pores as compared to circular geometry.At a given rotation speed,the droplet size was mainly determined by the pore size and the fluid velocity of oil through the pore (pore fluid velocity).The ratio of droplet diameter to the equivalent diameter of the slotted pore increased with the pore fluid velocity.At a given pore fluid velocity and rotation speed,pore orientation significantly influences the droplet formation rate: horizontally disposed pores (with their longer side perpendicular to the membrane axis) generate droplets at double the rate of vertically disposed pores.This work indicates practical benefits in the use of slotted membranes over conventional methods.

  15. A random-walk model for pore pressure accumulation in marine soils

    DEFF Research Database (Denmark)

    Sumer, B. Mutlu; Cheng, Niang-Sheng

    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...

  16. Nanodisc-cell fusion: control of fusion pore nucleation and lifetimes by SNARE protein transmembrane domains.

    Science.gov (United States)

    Wu, Zhenyong; Auclair, Sarah M; Bello, Oscar; Vennekate, Wensi; Dudzinski, Natasha R; Krishnakumar, Shyam S; Karatekin, Erdem

    2016-01-01

    The initial, nanometer-sized connection between the plasma membrane and a hormone- or neurotransmitter-filled vesicle -the fusion pore- can flicker open and closed repeatedly before dilating or resealing irreversibly. Pore dynamics determine release and vesicle recycling kinetics, but pore properties are poorly known because biochemically defined single-pore assays are lacking. We isolated single flickering pores connecting v-SNARE-reconstituted nanodiscs to cells ectopically expressing cognate, "flipped" t-SNAREs. Conductance through single, voltage-clamped fusion pores directly reported sub-millisecond pore dynamics. Pore currents fluctuated, transiently returned to baseline multiple times, and disappeared ~6 s after initial opening, as if the fusion pore fluctuated in size, flickered, and resealed. We found that interactions between v- and t-SNARE transmembrane domains (TMDs) promote, but are not essential for pore nucleation. Surprisingly, TMD modifications designed to disrupt v- and t-SNARE TMD zippering prolonged pore lifetimes dramatically. We propose that the post-fusion geometry of the proteins contribute to pore stability. PMID:27264104

  17. Semi-empirical formula for large pore-size estimation from o-Ps annihilation lifetime

    International Nuclear Information System (INIS)

    The o-Ps annihilation rate in large pore was investigated by the semi-classical approach. The semi-empirical formula that simply correlates between the pore size and the o-Ps lifetime was proposed. The calculated results agree well with experiment in the range from some angstroms to several ten nanometers size of pore. (author)

  18. On $\\mathfrak{I}$-reconstruction Property

    OpenAIRE

    Vashisht, L. K.; Khattar, Geetika

    2013-01-01

    Reconstruction property in Banach spaces introduced and studied by Casazza and Christensen in [1]. In this paper we introduce reconstruction property in Banach spaces which satisfy $\\mathfrak{I}$-property. A characterization of reconstruction property in Banach spaces which satisfy $\\mathfrak{I}$-property in terms of frames in Banach spaces is obtained. Banach frames associated with reconstruction property are discussed.

  19. Ulnar Collateral Ligament Reconstruction

    Science.gov (United States)

    Erickson, Brandon J.; Bach, Bernard R.; Cohen, Mark S.; Bush-Joseph, Charles A.; Cole, Brian J.; Verma, Nikhil N.; Nicholson, Gregory P.; Romeo, Anthony A.

    2016-01-01

    Background: Ulnar collateral ligament reconstruction (UCLR) is a common surgery performed in professional, collegiate, and high school athletes. Purpose: To report patient demographics, surgical techniques, and outcomes of all UCLRs performed at a single institution from 2004 to 2014. Study Design: Case series; Level of evidence, 4. Methods: All patients who underwent UCLR from January 1, 2004, through December 31, 2014, at a single institution were identified. Charts were reviewed to determine patient age, sex, date of surgery, sport played, athletic level, surgical technique, graft type, and complications. Data were collected prospectively, and patients were contacted via phone calls to obtain the return-to-sport rate, Conway-Jobe score, Andrews-Timmerman score, and Kerlan-Jobe Orthopaedic Clinic (KJOC) Shoulder and Elbow score. Continuous variable data were reported as weighted means, and categorical variable data were reported as frequencies with percentages. Results: A total of 187 patients (188 elbows) underwent UCLR during the study period (92% male; mean age, 19.6 ± 4.7 years; 78.2% right elbows). There were 165 baseball players (87.8% of all patients), 155 of whom were pitchers (82.5% of all patients). Ninety-seven (51.6%) were college athletes, 68 (36.2%) high school athletes, and 7 (3.7%) professional athletes at the time of surgery. The docking technique was used in 110 (58.5%) patients while the double-docking technique was used in 78 (41.5%). An ipsilateral palmaris longus graft was used in 110 (58.5%) patients while a hamstring autograft was used in 48 (25.5%) patients. The ulnar nerve was subcutaneously transposed in 79 (42%) patients. Clinical follow-up data were available on 85 patients. Mean follow-up was 60 ± 30.8 months. Overall, 94.1% of patients were able to return to sport and had a Conway-Jobe score of good/excellent while 4.3% had a score of fair. The mean KJOC score was 90.4 ± 6.7 and mean Andrews-Timmerman score was 92.5 ± 7

  20. Pore Structure and Effective Permeability of Metallic Filters

    Czech Academy of Sciences Publication Activity Database

    Hejtmánek, Vladimír; Veselý, M.; Čapek, P.

    2013-01-01

    Roč. 410, č. 2013 (2013), 012110. ISSN 1742-6588. [International Conference on Mathematical Modelling in Physical Sciences (IC-MSQUARE) /1./. Budapest, 03.09.2012-07.09.2012] R&D Projects: GA ČR(CZ) GAP204/11/1206 Institutional support: RVO:67985858 Keywords : stochastic reconstruction * porous media * effective permeability Subject RIV: CF - Physical ; Theoretical Chemistry

  1. Molecular Characterization and Functional Analysis of Annulate Lamellae Pore Complexes in Nuclear Transport in Mammalian Cells.

    Directory of Open Access Journals (Sweden)

    Sarita Raghunayakula

    Full Text Available Annulate lamellae are cytoplasmic organelles containing stacked sheets of membranes embedded with pore complexes. These cytoplasmic pore complexes at annulate lamellae are morphologically similar to nuclear pore complexes at the nuclear envelope. Although annulate lamellae has been observed in nearly all types of cells, their biological functions are still largely unknown. Here we show that SUMO1-modification of the Ran GTPase-activating protein RanGAP1 not only target RanGAP1 to its known sites at nuclear pore complexes but also to annulate lamellae pore complexes through interactions with the Ran-binding protein RanBP2 and the SUMO-conjugating enzyme Ubc9 in mammalian cells. Furthermore, upregulation of annulate lamellae, which decreases the number of nuclear pore complexes and concurrently increases that of annulate lamellae pore complexes, causes a redistribution of nuclear transport receptors including importin α/β and the exportin CRM1 from nuclear pore complexes to annulate lamellae pore complexes and also reduces the rates of nuclear import and export. Moreover, our results reveal that importin α/β-mediated import complexes initially accumulate at annulate lamellae pore complexes upon the activation of nuclear import and subsequently disassociate for nuclear import through nuclear pore complexes in cells with upregulation of annulate lamellae. Lastly, CRM1-mediated export complexes are concentrated at both nuclear pore complexes and annulate lamellae pore complexes when the disassembly of these export complexes is inhibited by transient expression of a Ran GTPase mutant arrested in its GTP-bound form, suggesting that RanGAP1/RanBP2-activated RanGTP hydrolysis at these pore complexes is required for the dissociation of the export complexes. Hence, our findings provide a foundation for further investigation of how upregulation of annulate lamellae decreases the rates of nuclear transport and also for elucidation of the biological

  2. Pore-linked filaments in anura spermatocyte nuclei

    Directory of Open Access Journals (Sweden)

    Maria Luiza Beçak

    2007-03-01

    Full Text Available Pore-linked filaments were visualized in spreads of anuran spermatocyte nuclei using transmission electron microscope. We used Odontophrynus diplo and tetraploid species having the tetraploid frogs reduced metabolic activities. The filaments with 20-40 nm width are connected to a ring component of the nuclear pore complex with 90-120 nm and extend up to 1µm (or more into the nucleus. The filaments are curved and connect single or neighboring pores. The intranuclear filaments are associated with chromatin fibers and related to RNP particles of 20-25 nm and spheroidal structures of 0.5µm, with variations. The aggregates of several neighboring pores with the filaments are more commonly observed in 4n nuclei. We concluded that the intranuclear filaments may correspond to the fibrillar network described in Xenopus oocyte nucleus being probably related to RNA transport. The molecular basis of this RNA remains elusive. Nevertheless, the morphological aspects of the spheroidal structures indicate they could correspond to nucleolar chromatin or to nucleolus-derived structures. We also speculate whether the complex aggregates of neighboring pores with intranuclear filaments may correspond to pore clustering previously described in these tetraploid animals using freeze-etching experiments.Filamentos ligados a poros foram visualizados em núcleos de espermatócitos de anuros através da técnica de espalhamento para microscopia eletrônica de transmissão. Os animais usados pertencem ao gênero Odontophrynus com espécies cripticas diplo e tetraplóides naturais, tendo os tetraplóides atividade metabólica reduzida. Os filamentos com 20-40 nm de largura são ligados a um anel componente do complexo poro nuclear de 90-120 nm e estendem-se até 1 µm (ou mais para dentro do núcleo. Os filamentos são curvos e ligam poros simples ou poros vizinhos. Os filamentos intranucleares são associados a fibras de cromatina e relacionados a partículas de RNP de 20

  3. Relationship between chloride diffusivity and pore structure of hardened cement paste

    Institute of Scientific and Technical Information of China (English)

    Guo-wen SUN; Wei SUN; Yun-sheng ZHANG; Zhi-yong LIU

    2011-01-01

    Based on effective media theory, a predictive model, relating chloride diffusivity to the capillary pores, gel pores,tortuosity factor, and pore size distribution of hardened cement, is proposed. To verify the proposed model, the diffusion coefficient of chloride ions, the degree of hydration, and peak radius of capillary pores of cement paste specimens were measured. The predicted results for chloride diffusivity were compared with published data. The results showed that the predicted chloride diffusivity of hardened cement paste was in good agreement with the experimental results. The effect of the evolution of pore structures in cement paste on chloride diffusivity could be deduced simultaneously using the proposed model.

  4. In-pore exchange and diffusion of carbonate solvent mixtures in nanoporous carbon

    Science.gov (United States)

    Alam, Todd M.; Osborn Popp, Thomas M.

    2016-08-01

    High resolution magic angle spinning (HRMAS) 1H NMR spectroscopy has been used to resolve different surface and in-pore solvent environments of ethylene carbonate (EC) and dimethyl carbonate (DMC) mixtures absorbed within nanoporous carbon (NPC). Two dimensional (2D) 1H HRMAS NMR exchange measurements revealed that the inhomogeneous broadened in-pore resonances have pore-to-pore exchange rates on the millisecond timescale. Pulsed-field gradient (PFG) NMR diffusometry revealed the in-pore self-diffusion constants for both EC and DMC were reduced by up to a factor of five with respect to the diffusion in the non-absorbed solvent mixtures.

  5. 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

    2009-06-17

    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. PMID:19468168

  6. Experimental study on pore pressure in rock-soil slope during reservoir water level fluctuation

    Institute of Scientific and Technical Information of China (English)

    LIU; Yuewu; CHEN; Huixin; LIU; Qingquan; GONG; Xin; ZHANG

    2005-01-01

    A test system was developed for measuring the pore pressure in porous media, and a new model was devised for the pore pressure testing in both saturated and unsaturated rock-soil. Laboratory experiments were carried out to determine the pore pressure during water level fluctuation. The variations of transient pore pressure vs. time at different locations of the simulated rock-soil system were acquired and processed, and meanwhile the deformation and failure of the model are observed. The experiment results show that whether the porous media are saturated or not, the transient pore pressure is mainly dependent on the water level fluctuation, and coupled with the variation of the stress field.

  7. Influence of pore fluid and frequency on elastic properties of greensand as interpreted using NMR data

    DEFF Research Database (Denmark)

    Hossain, Zakir; Mukerj, Tapan; Fabricius, Ida Lykke

    dispersion. However, Biot’s theory does not fully explain the frequency dispersion of sedimentary rocks. Greensands are composed of a mixture of quartz and micro-porous glauconite grains. In greensand, it is possible that the contrast between flow in macro-pores and micro-pores within glauconites gives rise...... moduli. Biot’s critical frequency and NMR (nuclear magnetic resonance) T2 spectrum were combined to describe the differences in fluid flow within macro-pores and within micro-pores. NMR data show that Biot’s flow should occur only in large pores in the greensand while, Biot’s flow should not occur in...

  8. A stochastic model for filtration of particulate suspensions with incomplete pore plugging

    DEFF Research Database (Denmark)

    Shapiro, Alexander; Santos, A; Bedrikovetsky, P. G.;

    2007-01-01

    through the overall pore space, and for particle flux reduction, due to transport of particles by the fraction of the overall flux. The novel feature of the model is the residual pore conductivity after the particle retention in the pore and the possibility of one pore to capture several particles. A...... closed system of governing stochastic equations determines the evolution of size distributions for suspended particles and pores. Its averaging results in the closed system of hydrodynamic equations accounting for permeability and porosity reduction due to plugging. The problem of deep bed filtration of...

  9. Helium measurements of pore-fluids obtained from SAFOD drillcore

    Energy Technology Data Exchange (ETDEWEB)

    Ali, S.; Stute, M.; Torgersen, T.; Winckler, G.; Kennedy, B.M.

    2010-04-15

    {sup 4}He accumulated in fluids is a well established geochemical tracer used to study crustal fluid dynamics. Direct fluid samples are not always collectable; therefore, a method to extract rare gases from matrix fluids of whole rocks by diffusion has been adapted. Helium was measured on matrix fluids extracted from sandstones and mudstones recovered during the San Andreas Fault Observatory at Depth (SAFOD) drilling in California, USA. Samples were typically collected as subcores or from drillcore fragments. Helium concentration and isotope ratios were measured 4-6 times on each sample, and indicate a bulk {sup 4}He diffusion coefficient of 3.5 {+-} 1.3 x 10{sup -8} cm{sup 2}s{sup -1} at 21 C, compared to previously published diffusion coefficients of 1.2 x 10{sup -18} cm{sup 2}s{sup -1} (21 C) to 3.0 x 10{sup -15} cm{sup 2}s{sup -1} (150 C) in the sands and clays. Correcting the diffusion coefficient of {sup 4}He{sub water} for matrix porosity ({approx}3%) and tortuosity ({approx}6-13) produces effective diffusion coefficients of 1 x 10{sup -8} cm{sup 2}s{sup -1} (21 C) and 1 x 10{sup -7} (120 C), effectively isolating pore fluid {sup 4}He from the {sup 4}He contained in the rock matrix. Model calculations indicate that <6% of helium initially dissolved in pore fluids was lost during the sampling process. Complete and quantitative extraction of the pore fluids provide minimum in situ porosity values for sandstones 2.8 {+-} 0.4% (SD, n=4) and mudstones 3.1 {+-} 0.8% (SD, n=4).

  10. Cadmium trapping in an epithelial sodium channel pore mutant.

    Science.gov (United States)

    Takeda, Armelle-Natsuo; Gautschi, Ivan; van Bemmelen, Miguel X; Schild, Laurent

    2007-11-01

    The putative selectivity filter of the epithelial sodium channel (ENaC) comprises a three-residue sequence G/SXS, but it remains uncertain whether the backbone atoms of this sequence or whether their side chains are lining the pore. It has been reported that the S589C mutation in the selectivity filter of alphaENaC renders the channel sensitive to block by externally applied Cd2+; this was interpreted as evidence for Cd2+ coordination with the thiol group of the side chain of alpha589C, pointing toward the pore lumen. Because the alphaS589C mutation alters the monovalent to divalent cation selectivity ratio of ENaC and because internally applied Cd2+ blocks wild-type ENaC with high affinity, we hypothesized that the inhibition of alphaS589C ENaC by Cd2+ results rather from the coordination of this cation with native cysteine residues located in the internal pore of ENaC. We show here that Cd2+ inhibits not only ENaC alphaS589C and alphaS589D but also alphaS589N mutants and that Ca2+ weakly interacts with the S589D mutant. The block of alphaS589C, -D, and -N mutants is characterized by a slow on-rate, is nearly irreversible, is voltage-dependent, and can be prevented by amiloride. The C546S mutation in the second transmembrane helix of gamma subunit in the background of the ENaC alphaS589C, -D, or -N mutants reduces the sensitivity to block by Cd2+ and renders the block rapidly reversible. We conclude therefore that the block by Cd2+ of the alphaS589C, -D, and -N mutants results from the trapping of Cd2+ ions in the internal pore of the channel and involves Cys-546 in the second transmembrane helix of the gammaENaC subunit. PMID:17804416

  11. 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)

  12. Lipopeptide surfactants: Production, recovery and pore forming capacity.

    Science.gov (United States)

    Inès, Mnif; Dhouha, Ghribi

    2015-09-01

    Lipopeptides are microbial surface active compounds produced by a wide variety of bacteria, fungi and yeast. They are characterized by highly structural diversity and have the ability to decrease the surface and interfacial tension at the surface and interface, respectively. Surfactin, iturin and fengycin of Bacillus subtilis are among the most studied lipopeptides. This review will present the main factors encountering lipopeptides production along with the techniques developed for their extraction and purification. Moreover, we will discuss their ability to form pores and destabilize biological membrane permitting their use as antimicrobial, hemolytic and antitumor agents. These open great potential applications in biomediacal, pharmaceutic and agriculture fields. PMID:26189973

  13. Questioning regulation of two-pore channels by NAADP

    OpenAIRE

    Marchant, Jonathan S; Patel, Sandip

    2013-01-01

    NAADP is a potent Ca2+ mobilizing messenger [1–3]. Since its discovery in 1995 [4] a considerable volume of literature has shown that NAADP couples cell stimulation to endolysosomal Ca2+ release and thereby the regulation of many cellular functions [5]. However definition of its molecular mechanism of action has proved far from easy. Since 2009, a consensus emerged as several independent groups coalesced upon the two-pore channel (TPC) family as NAADP-activated channels essential for Ca2+ rel...

  14. 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.

  15. Dynamics of pore synthesis and degradation in protocells

    International Nuclear Information System (INIS)

    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. (paper)

  16. Titanium template for scaphoid reconstruction.

    Science.gov (United States)

    Haefeli, M; Schaefer, D J; Schumacher, R; Müller-Gerbl, M; Honigmann, P

    2015-06-01

    Reconstruction of a non-united scaphoid with a humpback deformity involves resection of the non-union followed by bone grafting and fixation of the fragments. Intraoperative control of the reconstruction is difficult owing to the complex three-dimensional shape of the scaphoid and the other carpal bones overlying the scaphoid on lateral radiographs. We developed a titanium template that fits exactly to the surfaces of the proximal and distal scaphoid poles to define their position relative to each other after resection of the non-union. The templates were designed on three-dimensional computed tomography reconstructions and manufactured using selective laser melting technology. Ten conserved human wrists were used to simulate the reconstruction. The achieved precision measured as the deviation of the surface of the reconstructed scaphoid from its virtual counterpart was good in five cases (maximal difference 1.5 mm), moderate in one case (maximal difference 3 mm) and inadequate in four cases (difference more than 3 mm). The main problems were attributed to the template design and can be avoided by improved pre-operative planning, as shown in a clinical case. PMID:25167978

  17. Using X-Ray Computed Tomography in Pore Structure Characterization for a Berea Sandstone: Resolution Effect

    Energy Technology Data Exchange (ETDEWEB)

    Peng, Sheng; Hu, Qinhong; Dultz, Stefan; Zhang, Ming

    2012-11-23

    X-raycomputedtomography (XCT) is a powerful tool for detecting the micro-scale porestructure and has been applied to many natural and synthetic porous media. However, due to the resolution limitations, either non-representative view of the sample or inaccurate results can be produced from the XCT image processing. In this paper, two XCT (micro-CT and CT with synchrotron radiation) with different resolutions of 12.7 μm and 0.35 μm, as well as mercury intrusion porosimetry (MIP) with a minimum detection limit of 3 nm, were used for Berea sandstone to investigate the effect of detecting resolution on the porestructure. Several key porestructure parameters, including porosity, pore size distribution, pore connectivity, surface area, hydraulic radius, and aspect ratio were analyzed in a manner of quantitative comparison between different resolutions of XCT and MIP. The low resolution XCT can capture the large-pore porosity, while overestimates the pore size and pore connectivity. The high resolution XCT is more accurate in describing the pore shape, porosity, pore size; however, it is not representative since narrower detecting pore size range and small volume represented. A representative element volume related to large-pore porosity and probably large-pore connectivity with diameter and height of 2.8 mm is obtained through scale effect analysis. Therefore, selecting an appropriate resolution should be a compromise between the pore size and the representative element volume for the specific property or process of interest.

  18. Scale parameter-estimating method for adaptive fingerprint pore extraction model

    Science.gov (United States)

    Yi, Yao; Cao, Liangcai; Guo, Wei; Luo, Yaping; He, Qingsheng; Jin, Guofan

    2011-11-01

    Sweat pores and other level 3 features have been proven to provide more discriminatory information about fingerprint characteristics, which is useful for personal identification especially in law enforcement applications. With the advent of high resolution (>=1000 ppi) fingerprint scanning equipment, sweat pores are attracting increasing attention in automatic fingerprint identification system (AFIS), where the extraction of pores is a critical step. This paper presents a scale parameter-estimating method in filtering-based pore extraction procedure. Pores are manually extracted from a 1000 ppi grey-level fingerprint image. The size and orientation of each detected pore are extracted together with local ridge width and orientation. The quantitative relation between the pore parameters (size and orientation) and local image parameters (ridge width and orientation) is statistically obtained. The pores are extracted by filtering fingerprint image with the new pore model, whose parameters are determined by local image parameters and the statistically established relation. Experiments conducted on high resolution fingerprints indicate that the new pore model gives good performance in pore extraction.

  19. Comparative study of pore structure evolution during solvent and thermal debinding of powder injection molded parts

    Science.gov (United States)

    Hwang, K. S.; Hsieh, Y. M.

    1996-02-01

    The solvent debinding process has been widely accepted in the powder injection molding (PIM) industry due to its short debinding cycle. In the current study, specimens were immersed in a heptane bath for different lengths of time, and the pore structure evolvement in the compact was analyzed. Mercury porosimetry analyses and scanning electron micrographs showed that the binder extraction started from the surface and progressed toward the center of the compacts. As the debinding contin-ued, the pores grew and were widely distributed in size. This pore structure evolvement was different from that of straight thermal debinding in which the pore size distribution was quite narrow and the mean pore diameter shifted toward smaller sizes as debinding time increased. After the soluble binders were extracted, parts were subjected to a subsequent thermal debinding during which these pores served as conduits for decomposed gas to escape. Concurrently, the remaining binder became fluidlike and was redistributed within the compact due to capillarity. This pore structure, as observed from the mercury intrusion curves, showed a sharp increase in the pore volume at the 0.8-µm size, followed by a series of fine pores, which is different from the pore structure of straight thermal debinding. The difference in the pore structure evolvement between solvent and thermal debinding and its effect on the debinding rate are discussed.

  20. Comparative study of pore structure evolution during solvent and thermal debinding of powder injection molded parts

    Energy Technology Data Exchange (ETDEWEB)

    Hwang, K.S.; Hsieh, Y.M. [National Taiwan Univ., Taipei (Taiwan, Province of China). Inst. of Materials Science and Engineering

    1996-02-01

    The solvent debinding process has been widely accepted in the powder injection molding (PIM) industry due to its short debinding cycle. In the current study, specimens were immersed in a heptane bath for different lengths of time, and the pore structure evolvement in the compact was analyzed. Mercury porosimetry analyses and scanning electron micrographs showed that the binder extraction started from the surface and progressed toward the center of the compacts. As the debinding continued, the pores grew and were widely distributed in size. This pore structure evolvement was different from that of straight thermal debinding in which the pore size distribution was quite narrow and the mean pore diameter shifted toward smaller sizes as debinding time increased. After the soluble binders were extracted, parts were subjected to a subsequent thermal debinding during which these pores served as conduits for decomposed gas to escape. Concurrently, the remaining binder became fluidlike and was redistributed within the compact due to capillarity. This pore structure, as observed from the mercury intrusion curves, showed a sharp increase in the pore volume at the 0.8-{micro}m size, followed by a series of fine pores, which is different from the pore structure of straight thermal debinding. The difference in the pore structure evolvement between solvent and thermal debinding and its effect on the debinding rate are discussed.

  1. Investigating the effects of stress on the pore structures of nuclear grade graphites

    Science.gov (United States)

    Taylor, Joshua E. L.; Hall, Graham N.; Mummery, Paul M.

    2016-03-01

    Graphite is used as a moderating material and as a structural component in a number of current generation nuclear reactors. During reactor operation stresses develop in the graphite components, causing them to deform. It is important to understand how the microstructure of graphite affects the material's response to these stresses. A series of experiments were performed to investigate how the pore structures of Pile Grade A and Gilsocarbon graphites respond to loading stresses. A compression rig was used to simulate the build-up of operational stresses in graphite components, and a confocal laser microscope was used to study variation of a number of important pore properties. Values of elastic modulus and Poisson's ratio were calculated and compared to existing literature to confirm the validity of the experimental techniques. Mean pore areas were observed to decrease linearly with increasing applied load, mean pore eccentricity increased linearly, and a small amount of clockwise pore rotation was observed. The response to build-up of stresses was dependent on the orientation of the pores and basal planes and the shapes of the pores with respect to the loading axis. It was proposed that pore closure and pore reorientation were competing processes. Pore separation was quantified using 'nearest neighbour' and Voronoi techniques, and non-pore regions were found to shrink linearly with increasing applied load.

  2. Transport properties of track-etched membranes having variable effective pore-lengths

    Science.gov (United States)

    Nguyen, Quoc Hung; Ali, Mubarak; Nasir, Saima; Ensinger, Wolfgang

    2015-12-01

    The transport rate of molecules through polymeric membranes is normally limited because of their micrometer-scale thickness which restricts their suitability for more practical application. To study the effect of effective pore length on the transport behavior, polymer membranes containing cylindrical and asymmetric-shaped nanopores were prepared through a two-step ion track-etching technique. Permeation experiments were performed separately to investigate the transport properties (molecular flux and selectivity) of these track-etched membranes. The permeation data shows that the molecular flux across membranes containing asymmetric nanopores is higher compared to those having cylindrical pores. On the other hand, the cylindrical pore membranes exhibit higher selectivity than asymmetric pores for the permeation of charged molecules across the membrane. Current-voltage (I-V) measurements of single-pore membranes further verify that asymmetric pores exhibit lower resistance for the flow of ions and therefore show higher currents than cylindrical pores. Moreover, unmodified and polyethyleneimine (PEI) modified asymmetric-shaped pore membranes were successfully used for the separation of cationic and anionic analyte molecules from their mixture, respectively. In this study, two distinct effects (pore geometry and pore density, i.e. number of pores cm-2), which mainly influence membrane selectivity and molecular transport rates, were thoroughly investigated in order to optimize the membrane performance. In this context, we believe that membranes with high molecular transport rates could readily find their application in molecular separation and controlled drug delivery processes.

  3. 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.

  4. Detectability of Pore Defect in Wind Turbine Blade Composites Using Image Correlation Technique

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jong Il; Huh, Yong Hak; Lee, Gun Chang [Korea Research institute of Standard and Science, Daejeon (Korea, Republic of)

    2013-10-15

    Defects that occur during the manufacturing process or operation of a wind turbine blade have a great influence on its life and safety. Typically, defects such as delamination, pore, wrinkle and matrix crack are found in a blade. In this study, the detectability of the pores, a type of defect that frequently occur during manufacturing, was examined from the full field strain distribution determined with the image correlation technique. Pore defects were artificially introduced in four-ply laminated GFRP composites with 0 .deg/{+-}45 .deg fiber direction. The artificial pores were introduced in consideration of their size and location. Three different-sized pores with diameter of 1, 2 and 3 mm were located on the top and bottom surface and embedded. By applying static loads of 0-200 MPa, the strain distributions over the specimen with the pore defects were determined using image correlation technique. It was found the pores with diameter exceeding 2 mm can be detected in diameter.

  5. Formation of spherical stomatocyte of high-genus vesicle under pore-size constraint

    CERN Document Server

    Noguchi, Hiroshi

    2016-01-01

    Nuclear pores have an approximately uniform distribution in the nuclear envelope of most living cells. Hence, the morphology of the nuclear envelope is a spherical stomatocyte with a high genus. We have investigated the morphology of high-genus vesicles under pore-size constraint using dynamically triangulated membrane simulations. Bending-energy minimization without volume or other constraints produces a circular-cage stomatocyte, where the pores are aligned in a circular line on an oblate inner bud. As the pore radius is reduced, the circular-pore alignment is more stabilized than a random pore distribution on a spherical bud. However, we have clarified the conditions for the formation of a spherical stomatocyte: a small reduced volume, osmotic pressure within the inner bud, and repulsion between the pores. When area-difference elasticity is taken into account, the formation of cylindrical or budded tubules from the stomatocyte and discoidal stomatocyte is found.

  6. Influence of the pore network on hydrogen diffusion through blended cement pastes

    International Nuclear Information System (INIS)

    This article presents a study on the influence of the pore size distribution on gas diffusion through CEM V cement pastes, for different water saturation degrees. The numerical results are compared to the experimental hydrogen diffusion coefficients obtained with water saturation levels ranging from 20% to 95%. The model developed in our research group accounts for the various types of transfer through the pore network: Knudsen diffusion or molecular diffusion depending on the pore size, together with hydrogen diffusion through water. The virtual pore network is created from mercury porosimetry data as a result of the combination of different sizes pore families. By testing different combinations, we could propose pore arrangements leading to diffusion coefficients corresponding to the experimental ones, and show how the combinations of the biggest pore family contribute to control the gas diffusion process. (authors)

  7. Construction of Nuclear Envelope Shape by a High-Genus Vesicle with Pore-Size Constraint.

    Science.gov (United States)

    Noguchi, Hiroshi

    2016-08-23

    Nuclear pores have an approximately uniform distribution in the nuclear envelope of most living cells. Hence, the morphology of the nuclear envelope is a spherical stomatocyte with a high genus. We have investigated the morphology of high-genus vesicles under pore-size constraint using dynamically triangulated membrane simulations. Bending-energy minimization without volume or other constraints produces a circular-cage stomatocyte, where the pores are aligned in a circular line on an oblate bud. As the pore radius is reduced, the circular-pore alignment is more stabilized than a random pore distribution on a spherical bud. However, we have clarified the conditions for the formation of a spherical stomatocyte: a small perinuclear volume, osmotic pressure within nucleoplasm, and repulsion between the pores. When area-difference elasticity is taken into account, the formation of cylindrical or budded tubules from the stomatocyte and discoidal stomatocyte is found. PMID:27558725

  8. CURRENT CONCEPTS IN ACL RECONSTRUCTION

    Directory of Open Access Journals (Sweden)

    Freddie H. Fu

    2008-09-01

    Full Text Available Current Concepts in ACL Reconstruction is a complete reference text composed of the most thorough collection of topics on the ACL and its surgical reconstruction compiled, with contributions from some of the world's experts and most experienced ACL surgeons. Various procedures mentioned throughout the text are also demonstrated in an accompanying video CD-ROM. PURPOSE Composing a single, comprehensive and complete information source on ACL including basic sciences, clinical issues, latest concepts and surgical techniques, from evaluation to outcome, from history to future, editors and contributors have targeted to keep the audience pace with the latest concepts and techniques for the evaluation and the treatment of ACL injuries. FEATURES The text is composed of 27 chapters in 6 sections. The first section is mostly about basic sciences, also history of the ACL, imaging, clinical approach to adolescent and pediatric patients are subjected. In the second section, Graft Choices and Arthroscopy Portals for ACL Reconstruction are mentioned. The third section is about the technique and the outcome of the single-bundle ACL reconstruction. The fourth chapter includes the techniques and outcome of the double-bundle ACL reconstruction. In the fifth chapter revision, navigation technology, rehabilitation and the evaluation of the outcome of ACL reconstruction is subjected. The sixth/the last chapter is about the future advances to reach: What We Have Learned and the Future of ACL Reconstruction. AUDIENCE Orthopedic residents, sports traumatology and knee surgery fellows, orthopedic surgeons, also scientists in basic sciences or clinicians who are studying or planning a research on ACL forms the audience group of this book. ASSESSMENT This is the latest, the most complete and comprehensive textbook of ACL reconstruction produced by the editorial work up of two pioneer and masters "Freddie H. Fu MD and Steven B. Cohen MD" with the contribution of world

  9. The reconstruction of inflationary potentials

    Science.gov (United States)

    Lin, Jianmang; Gao, Qing; Gong, Yungui

    2016-07-01

    The observational data on the anisotropy of the cosmic microwave background constraints the scalar spectral tilt ns and the tensor to scalar ratio r which depend on the first and second derivatives of the inflaton potential. The information can be used to reconstruct the inflaton potential in the polynomial form up to some orders. However, for some classes of potentials, ns and r behave as ns(N) and r(N) universally in terms of the number of e-folds N. The universal behaviour of ns(N) can be used to reconstruct a class of inflaton potentials. By parametrizing one of the parameters ns(N), ɛ(N) and φ(N), and fitting the parameters in the models to the observational data, we obtain the constraints on the parameters and reconstruct the classes of the inflationary models which include the chaotic inflation, T-model, hilltop inflation, s-dual inflation, natural inflation and R2 inflation.

  10. Network reconstruction from infection cascades

    CERN Document Server

    Braunstein, Alfredo

    2016-01-01

    Reconstructing propagation networks from observations is a fundamental inverse problem, and it's crucial to understand and control dynamics in complex systems. Here we show that it is possible to reconstruct the whole structure of an interaction network and to simultaneously infer the complete time course of activation spreading, relying just on single snapshots of a small number of activity cascades. The method, that we called Inverse Dynamics Network Reconstruction (IDNR), is shown to work successfully on several synthetic and real networks, inferring the networks and the sources of infection based on sparse observations, including single snapshots. IDNR is built on a Belief Propagation approximation, that has an impressive performance in a wide variety of topological structures. The method can be applied in absence of complete time-series data by providing a detailed modeling of the posterior distribution of trajectories conditioned to the observations. Furthermore, we show by experiments that the informat...

  11. Reconstructing Ancient Forms of Life

    Science.gov (United States)

    Benner, Steven A.

    1998-01-01

    Progress in the past three months has occurred in two areas, reconstruction of ancestral proteins and improved understanding of chemical features that are likely to be universal in generic matter regardless of its genesis. Ancestral ribonucleases have been reconstructed, and an example has been developed that shows how physiological function can be assigned to in vitro behaviors observed in biological systems. Sequence data have been collected to permit the reconstruction of src homology 2 domains that underwent radiative divergence at the time of the radiative divergence of chordates. New studies have been completed that show how genetic matter (or its remnants) might be detected on Mars (or other non-terrean locations.) Last, the first in vitro selection experiments have been completed using a nucleoside library carrying positively charged functionality, illustrating the importance of non-standard nucleotides to those attempting to obtain evidence for an "RNA world" as an early episode of life on earth.

  12. The effect of pore fluid on seismicity: a computer model

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    The influence of fluid on seismicity of a computerized system is analyzed in this paper. The diffusion equation of fluid in a crustal fault area is developed and used in the calculation of a spring-slide-damper model. With mirror imagin boundary condition and three initial conditions, the equation is solved for a dynamic model that consists of six seismic belts and eight seismogenous sources in each belt with both explicit algorithm and implicit algorithm. The analysis of the model with water sources shows that the implicit algorithm is better to be used to calculate the model. Taking a constant proportion of the pore pressure of a broken element to that of its neighboring elements, the seismicity of the model is calculated with mirror boundary condition and no-water-source initial condition. The results shows that the frequency and magnitude of shocks are both higher than those in the model with no water pore pressure, which provides more complexity to earthquake prediction.

  13. Movement of fossil pore fluids in granite basement, Illinois

    International Nuclear Information System (INIS)

    The compositions of pore fluids in granite cores from the Precambrian basement in northern Illinois were determined. The estimated chloride concentration in the aqueous phase increases from near zero at the upper contact with sandstone to 2.7 M at 624 m below the contact. Traces of aliphatic oil are present in the overlying sandstone and the upper 516 m of granite, and oil occupies most of the pore space in one sample of unaltered granite 176 m below the contact. The oil has a Δ13C of -25%, about the same as average petroleum. The high concentrations of salt more than 500 m below the contact imply that little or no fresh water has reached these levels of the granite by flow. Lower concentrations near the contact are consistent with replacement of brine in the sandstone by fresh water at least 11 m.y. ago and subsequent upward diffusion of salt from the granite. Geologic data suggest that the time of replacement was about 130 Ma. The purpose of the investigation is to study the record of movement of intergranular fluids within a granite pluton. The composition and movement of ground waters can determine the extent that hazardous or radioactive wastes disposed in igneous rock will remain isolated

  14. Mechanism of pore formation during keyhole laser spot welding

    Science.gov (United States)

    Kaplan, Alexander F. H.; Mizutani, Masami; Katayama, Seiji; Matsunawa, Akira

    2003-03-01

    Theoretical and experimental studies have been carried out in order to improve the understanding of the mechanism of pore formation in keyhole laser spot welding in a qualitative and also quantitative manner. A semi-analytical mathematical model of the keyhole collapse illustrates the different characteristic time scales of the contributing physical processes: post-vaporization (order of magnitude: 100 ns typically), excess keyhole vapor relaxation flow 10 μs), inertia driven collapse (100 μs), followed by bubble contraction, re-condensation and rising (10 ms), and re-solidification (10 ms). The conditions of the keyhole just before switching off the laser beam, observed by X-ray imaging, are essential for the subsequent collapse mechanism. In case of a bottleneck-shaped keyhole, which can easily form due to the paradox of vapor flow inversion, bubble formation is likely to occur due to necking. When the thermally contracting bubble is trapped by the re-solidification front, a pore is formed. The model is complementary to high speed X-ray observations of the keyhole shape, particularly in liquid Zn that enables investigation of keyhole and bubble formation not constrained by surrounding solid.

  15. Heat of fusion of primary alcohol confined in Nano pores

    Science.gov (United States)

    Griffin, Harrisonn; Amanue, Samuel

    Melting behavior of physically confined 1-decanol in nano porous silica was probed using a Differential Scanning Calorimeter (DSC). In agreement with the Gibbs-Thompson prediction, we observe that the melting temperature of the confined 1-decanol scales inversely with the physical size of the pores. Contrary to the assumption used in developing the Gibbs-Thompson equation, however, the apparent heat of fusion decreases as the the pore size decreases. Previously, several models have been proposed where the interfacial layer/s of molecules do not participate in the phase transition and thereby would not contribute to the heat of fusion. While these could reconcile the seeming contradiction, annealing the nano confined materials enables some of the interfacial layers to be incorporated into an existing crystal. This leads to an increase in the apparent heat of fusion and a systematic relationship exists between the annealing temperature and the increase in the apparent heat of fusion. This work was partially supported by NSF-DMR: 1229142.

  16. Epsilon toxin: a fascinating pore-forming toxin.

    Science.gov (United States)

    Popoff, Michel R

    2011-12-01

    Epsilon toxin (ETX) is produced by strains of Clostridium perfringens classified as type B or type D. ETX belongs to the heptameric β-pore-forming toxins including aerolysin and Clostridium septicum alpha toxin, which are characterized by the formation of a pore through the plasma membrane of eukaryotic cells consisting in a β-barrel of 14 amphipatic β strands. By contrast to aerolysin and C. septicum alpha toxin, ETX is a much more potent toxin and is responsible for enterotoxemia in animals, mainly sheep. ETX induces perivascular edema in various tissues and accumulates in particular in the kidneys and brain, where it causes edema and necrotic lesions. ETX is able to pass through the blood-brain barrier and stimulate the release of glutamate, which accounts for the symptoms of nervous excitation observed in animal enterotoxemia. At the cellular level, ETX causes rapid swelling followed by cell death involving necrosis. The precise mode of action of ETX remains to be determined. ETX is a powerful toxin, however, it also represents a unique tool with which to vehicle drugs into the central nervous system or target glutamatergic neurons. PMID:21535407

  17. Wave-induced stresses and pore pressures near a mudline

    Directory of Open Access Journals (Sweden)

    Andrzej Sawicki

    2008-12-01

    Full Text Available Conventional methods for the determination of water-wave induced stresses inseabeds composed of granular soils are based on Biot-type models, in which the soilskeleton is treated as an elastic medium. Such methods predict effective stressesin the soil that are unacceptable from the physical point of view, as they permittensile stresses to occur near the upper surface of the seabed. Therefore, in thispaper the granular soil is assumed to behave as an elastic-ideally plastic material,with the Coulomb-Mohr yield criterion adopted to bound admissible stress states inthe seabed. The governing equations are solved numerically by a~finite differencemethod. The results of simulations, carried out for the case of time-harmonicwater waves, illustrate the depth distributions of the excess pore pressures and theeffective stresses in the seabed, and show the shapes of zones of soil in the plastic state.~In particular, the effects on the seabed behaviour of suchparameters as the degree of pore water saturation, the soil permeability, and theearth pressure coefficient, are illustrated.

  18. The Pore-Forming Haemolysins of Bacillus Cereus: A Review

    Directory of Open Access Journals (Sweden)

    Vincent Sanchis

    2013-06-01

    Full Text Available The Bacillus cereus sensu lato group contains diverse Gram-positive spore-forming bacteria that can cause gastrointestinal diseases and severe eye infections in humans. They have also been incriminated in a multitude of other severe, and frequently fatal, clinical infections, such as osteomyelitis, septicaemia, pneumonia, liver abscess and meningitis, particularly in immuno-compromised patients and preterm neonates. The pathogenic properties of this organism are mediated by the synergistic effects of a number of virulence products that promote intestinal cell destruction and/or resistance to the host immune system. This review focuses on the pore-forming haemolysins produced by B. cereus: haemolysin I (cereolysin O, haemolysin II, haemolysin III and haemolysin IV (CytK. Haemolysin I belongs to the cholesterol-dependent cytolysin (CDC family whose best known members are listeriolysin O and perfringolysin O, produced by L. monocytogenes and C. perfringens respectively. HlyII and CytK are oligomeric ß-barrel pore-forming toxins related to the α-toxin of S. aureus or the ß-toxin of C. perfringens. The structure of haemolysin III, the least characterized haemolytic toxin from the B. cereus, group has not yet been determined.

  19. In situ structural analysis of the human nuclear pore complex.

    Science.gov (United States)

    von Appen, Alexander; Kosinski, Jan; Sparks, Lenore; Ori, Alessandro; DiGuilio, Amanda L; Vollmer, Benjamin; Mackmull, Marie-Therese; Banterle, Niccolo; Parca, Luca; Kastritis, Panagiotis; Buczak, Katarzyna; Mosalaganti, Shyamal; Hagen, Wim; Andres-Pons, Amparo; Lemke, Edward A; Bork, Peer; Antonin, Wolfram; Glavy, Joseph S; Bui, Khanh Huy; Beck, Martin

    2015-10-01

    Nuclear pore complexes are fundamental components of all eukaryotic cells that mediate nucleocytoplasmic exchange. Determining their 110-megadalton structure imposes a formidable challenge and requires in situ structural biology approaches. Of approximately 30 nucleoporins (Nups), 15 are structured and form the Y and inner-ring complexes. These two major scaffolding modules assemble in multiple copies into an eight-fold rotationally symmetric structure that fuses the inner and outer nuclear membranes to form a central channel of ~60 nm in diameter. The scaffold is decorated with transport-channel Nups that often contain phenylalanine-repeat sequences and mediate the interaction with cargo complexes. Although the architectural arrangement of parts of the Y complex has been elucidated, it is unclear how exactly it oligomerizes in situ. Here we combine cryo-electron tomography with mass spectrometry, biochemical analysis, perturbation experiments and structural modelling to generate, to our knowledge, the most comprehensive architectural model of the human nuclear pore complex to date. Our data suggest previously unknown protein interfaces across Y complexes and to inner-ring complex members. We show that the transport-channel Nup358 (also known as Ranbp2) has a previously unanticipated role in Y-complex oligomerization. Our findings blur the established boundaries between scaffold and transport-channel Nups. We conclude that, similar to coated vesicles, several copies of the same structural building block--although compositionally identical--engage in different local sets of interactions and conformations. PMID:26416747

  20. An Evaluation of Models of Bentonite Pore Water Evolution

    International Nuclear Information System (INIS)

    The determination of a bentonite pore water composition and understanding its evolution of with time underpins many radioactive waste disposal issues, such as buffer erosion, canister corrosion, and radionuclide solubility, sorption, and diffusion, inter alia. The usual approach to modelling clay pore fluids is based primarily around assumed chemical equilibrium between Na+, K+, Ca2+, and Mg2+ aqueous species and ion exchange sites on montmorillonite, but also includes protonation- deprotonation of clay edge surface sites, and dissolution-precipitation of the trace mineral constituents, calcite and gypsum. An essential feature of this modelling approach is that clay hydrolysis reactions (i.e. dissolution of the aluminosilicate octahedral and tetrahedral sheets of montmorillonite) are ignored. A consequence of the omission of clay hydrolysis reactions from bentonite pore fluid models is that montmorillonite is preserved indefinitely in the near-field system, even over million-year timescales. Here, we investigate the applicability of an alternative clay pore fluid model, one that incorporates clay hydrolysis reactions as an integral component and test it against well-characterised laboratory experimental data, where key geochemical parameters, Eh and pH, have been measured directly in compacted bentonite. Simulations have been conducted using a range of computer codes to test the applicability of this alternative model. Thermodynamic data for MX-80 smectite used in the calculations were estimated using two different methods. Simulations of 'end-point' pH measurements in batch bentonite-water slurry experiments showed different pH values according to the complexity of the system studied. The most complete system investigated revealed pH values were a strong function of partial pressure of carbon dioxide, with pH increasing with decreasing PCO2 (log PCO2 values ranging from -3.5 to -7.5 bars produced pH values ranging from 7.9 to 9.6). A second set of calculations

  1. Modeling and Simulating Asymmetrical Conductance Changes in Gramicidin Pores

    Directory of Open Access Journals (Sweden)

    Xu Shixin

    2014-01-01

    Full Text Available Gramicidin A is a small and well characterized peptide that forms an ion channel in lipid membranes. An important feature of gramicidin A (gA pore is that its conductance is affected by the electric charges near the its entrance. This property has led to the application of gramicidin A as a biochemical sensor for monitoring and quantifying a number of chemical and enzymatic reactions. Here, a mathematical model of conductance changes of gramicidin A pores in response to the presence of electrical charges near its entrance, either on membrane surface or attached to gramicidin A itself, is presented. In this numerical simulation, a two dimensional computational domain is set to mimic the structure of a gramicidin A channel in the bilayer surrounded by electrolyte. The transport of ions through the channel is modeled by the Poisson-Nernst-Planck (PNP equations that are solved by Finite Element Method (FEM. Preliminary numerical simulations of this mathematical model are in qualitative agreement with the experimental results in the literature. In addition to the model and simulations, we also present the analysis of the stability of the solution to the boundary conditions and the convergence of FEM method for the two dimensional PNP equations in our model.

  2. The effect of pore structure on ebullition from peat

    Science.gov (United States)

    Ramirez, Jorge A.; Baird, Andy J.; Coulthard, Tom J.

    2016-06-01

    The controls on methane (CH4) bubbling (ebullition) from peatlands are uncertain, but evidence suggests that physical factors related to gas transport and storage within the peat matrix are important. Variability in peat pore size and the permeability of layers within peat can produce ebullition that ranges from steady to erratic in time and can affect the degree to which CH4 bubbles bypass consumption by methanotrophic bacteria and enter the atmosphere. Here we investigate the role of peat structure on ebullition in structurally different peats using a physical model that replicates bubble production using air injection into peat. We find that the frequency distributions of number of ebullition events per time and the magnitude of bubble loss from the physical model were similar in shape to ebullition from peatlands and incubated peats. This indicates that the physical model could be a valid proxy for naturally occurring ebullition from peat. For the first time, data on bubble sizes from peat were collected to conceptualize ebullition, and we find that peat structure affects bubble sizes. Using a new method to measure peat macrostructure, we collected evidence that supports the hypothesis that structural differences in peat determine if bubble release is steady or erratic and extreme. Collected pore size data suggest that erratic ebullition occurs when large amounts of gas stored at depth easily move through shallower layers of open peat. In contrast, steady ebullition occurs when dense shallower layers of peat regulate the flow of gas emitted from peat.

  3. Pore fluids and the LGM ocean salinity-Reconsidered

    Science.gov (United States)

    Wunsch, Carl

    2016-03-01

    Pore fluid chlorinity/salinity data from deep-sea cores related to the salinity maximum of the last glacial maximum (LGM) are analyzed using estimation methods deriving from linear control theory. With conventional diffusion coefficient values and no vertical advection, results show a very strong dependence upon initial conditions at -100 ky. Earlier inferences that the abyssal Southern Ocean was strongly salt-stratified in the LGM with a relatively fresh North Atlantic Ocean are found to be consistent within uncertainties of the salinity determination, which remain of order ±1 g/kg. However, an LGM Southern Ocean abyss with an important relative excess of salt is an assumption, one not required by existing core data. None of the present results show statistically significant abyssal salinity values above the global average, and results remain consistent, apart from a general increase owing to diminished sea level, with a more conventional salinity distribution having deep values lower than the global mean. The Southern Ocean core does show a higher salinity than the North Atlantic one on the Bermuda Rise at different water depths. Although much more sophisticated models of the pore-fluid salinity can be used, they will only increase the resulting uncertainties, unless considerably more data can be obtained. Results are consistent with complex regional variations in abyssal salinity during deglaciation, but none are statistically significant.

  4. The pore-forming haemolysins of bacillus cereus: a review.

    Science.gov (United States)

    Ramarao, Nalini; Sanchis, Vincent

    2013-06-01

    The Bacillus cereus sensu lato group contains diverse Gram-positive spore-forming bacteria that can cause gastrointestinal diseases and severe eye infections in humans. They have also been incriminated in a multitude of other severe, and frequently fatal, clinical infections, such as osteomyelitis, septicaemia, pneumonia, liver abscess and meningitis, particularly in immuno-compromised patients and preterm neonates. The pathogenic properties of this organism are mediated by the synergistic effects of a number of virulence products that promote intestinal cell destruction and/or resistance to the host immune system. This review focuses on the pore-forming haemolysins produced by B. cereus: haemolysin I (cereolysin O), haemolysin II, haemolysin III and haemolysin IV (CytK). Haemolysin I belongs to the cholesterol-dependent cytolysin (CDC) family whose best known members are listeriolysin O and perfringolysin O, produced by L. monocytogenes and C. perfringens respectively. HlyII and CytK are oligomeric ß-barrel pore-forming toxins related to the α-toxin of S. aureus or the ß-toxin of C. perfringens. The structure of haemolysin III, the least characterized haemolytic toxin from the B. cereus, group has not yet been determined. PMID:23748204

  5. Assembly of nuclear pore complexes mediated by major vault protein.

    Science.gov (United States)

    Vollmar, Friederike; Hacker, Christian; Zahedi, René-Peiman; Sickmann, Albert; Ewald, Andrea; Scheer, Ulrich; Dabauvalle, Marie-Christine

    2009-03-15

    During interphase growth of eukaryotic cells, nuclear pore complexes (NPCs) are continuously incorporated into the intact nuclear envelope (NE) by mechanisms that are largely unknown. De novo formation of NPCs involves local fusion events between the inner and outer nuclear membrane, formation of a transcisternal membranous channel of defined diameter and the coordinated assembly of hundreds of nucleoporins into the characteristic NPC structure. Here we have used a cell-free system based on Xenopus egg extract, which allows the experimental separation of nuclear-membrane assembly and NPC formation. Nuclei surrounded by a closed double nuclear membrane, but devoid of NPCs, were first reconstituted from chromatin and a specific membrane fraction. Insertion of NPCs into the preformed pore-free nuclei required cytosol containing soluble nucleoporins or nucleoporin subcomplexes and, quite unexpectedly, major vault protein (MVP). MVP is the main component of vaults, which are ubiquitous barrel-shaped particles of enigmatic function. Our results implicate MVP, and thus also vaults, in NPC biogenesis and provide a functional explanation for the association of a fraction of vaults with the NE and specifically with NPCs in intact cells. PMID:19240118

  6. Shape Reconstruction from Generalized Projections

    Science.gov (United States)

    Viikinkoski, Matti

    2016-01-01

    In this thesis we develop methods for recovering the three-dimensional shape of an object from generalized projections. We particularly focus on the problems encountered when data are presented as discrete image fields. We demonstrate the usefulness of the Fourier transform in transferring the image data and shape model projections to a domain more suitable for gradient based optimization. To substantiate the general applicability of our methods to observational astronomy, we reconstruct shape models for several asteroids observed with adaptive optics, thermal infrared interferometry, or range-Doppler radar. The reconstructions are carried out with the ADAM software package that we have designed for general use.

  7. Reconstructing WKB from topological recursion

    CERN Document Server

    Bouchard, Vincent

    2016-01-01

    We prove that the topological recursion reconstructs the WKB expansion of a quantum curve for all spectral curves whose Newton polygons have no interior point (and that are smooth as affine curves). This includes nearly all previously known cases in the literature, and many more; in particular, it includes many quantum curves of order greater than two. We also explore the connection between the choice of ordering in the quantization of the spectral curve and the choice of integration divisor to reconstruct the WKB expansion.

  8. Pore Structure and Effective Permeability of Metallic Filters

    Czech Academy of Sciences Publication Activity Database

    Hejtmánek, Vladimír; Čapek, P.; Veselý, M.

    Tampa : NANOSMAT, 2012 - (Chipara, M.; Haynie, D.; Stanishevsky, A.), 229* ISBN N. [International Conference on Mathematical Modeling in Physical Sciences IC-MSQUARE 2012 . Budapest (HU), 03.09. 2012 -07.09. 2012 ] R&D Projects: GA ČR(CZ) GAP204/11/1206 Institutional support: RVO:67985858 Keywords : porous media * stochastic reconstruction * effective permeability Subject RIV: CF - Physical ; Theoretical Chemistry

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

    Science.gov (United States)

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

    2015-08-01

    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.

  10. Multiple Approaches to Characterizing Nano-Pore Structure of Barnett Shale

    Science.gov (United States)

    Hu, Q.; Gao, Z.; Ewing, R. P.; Dultz, S.; Kaufmann, J.; Hamamoto, S.; Webber, B.; Ding, M.

    2013-12-01

    Microscopic characteristics of porous media - pore shape, pore-size distribution, and pore connectivity - control fluid flow and mass transport. This presentation discusses various approaches to investigating nano-pore structure of Barnett shale, with its implications in gas production behavior. The innovative approaches include imbibition, tracer diffusion, edge-accessible porosity, porosimetry (mercury intrusion porosimetry, nitrogen and water vapor sorption isotherms, and nuclear magnetic resonance cyroporometry), and imaging (Wood's metal impregnation followed with laser ablation-inductively coupled plasma-mass spectrometry, focused ion beam/scanning electron microscopy, and small angle neutron scattering). Results show that the shale pores are predominantly in the nm size range, with measured median pore-throat diameters about 5 nm. But small pore size is not the major contributor to low gas recovery; rather, the low mass diffusivity appears to be caused by low pore connectivity of Barnett shale. 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 and diffusion tests. Our evolving complementary approaches, with their several advantages and disadvantages, provide a rich toolbox for tackling the nano-pore structure characteristics of shales and other natural rocks.

  11. Compressive behavior of pervious concretes and a quantification of the influence of random pore structure features

    Energy Technology Data Exchange (ETDEWEB)

    Deo, Omkar [Department of Civil and Environmental Engineering, Clarkson University, Potsdam, NY 13699 (United States); Neithalath, Narayanan, E-mail: nneithal@clarkson.edu [Department of Civil and Environmental Engineering, Clarkson University, Potsdam, NY 13699 (United States)

    2010-11-25

    Research highlights: {yields} Identified the relevant pore structure features of pervious concretes, provided methodologies to extract those, and quantified the influence of these features on compressive response. {yields} A model for stress-strain relationship of pervious concretes, and relationship between model parameters and parameters of the stress-strain relationship developed. {yields} Statistical model for compressive strength as a function of pore structure features; and a stochastic model for the sensitivity of pore structure features in strength prediction. - Abstract: Properties of a random porous material such as pervious concrete are strongly dependent on its pore structure features, porosity being an important one among them. This study deals with developing an understanding of the material structure-compressive response relationships in pervious concretes. Several pervious concrete mixtures with different pore structure features are proportioned and subjected to static compression tests. The pore structure features such as pore area fractions, pore sizes, mean free spacing of the pores, specific surface area, and the three-dimensional pore distribution density are extracted using image analysis methods. The compressive stress-strain response of pervious concretes, a model to predict the stress-strain response, and its relationship to several of the pore structure features are outlined. Larger aggregate sizes and increase in paste volume fractions are observed to result in increased compressive strengths. The compressive response is found to be influenced by the pore sizes, their distributions and spacing. A statistical model is used to relate the compressive strength to the relevant pore structure features, which is then used as a base model in a Monte-Carlo simulation to evaluate the sensitivity of the predicted compressive strength to the model terms.

  12. Simulations of Pore Formation in Lipid Membranes: Reaction Coordinates, Convergence, Hysteresis, and Finite-Size Effects.

    Science.gov (United States)

    Awasthi, Neha; Hub, Jochen S

    2016-07-12

    Transmembrane pores play an important role in various biophysical processes such as membrane permeation, membrane fusion, and antimicrobial peptide activity. In principal, all-atom molecular dynamics (MD) simulations provide an accurate model of pore formation in lipid membranes. However, the free energy landscape of transmembrane pore formation remains poorly understood, partly because potential of mean force (PMF) calculations of pore formation strongly depend on the choice of the reaction coordinate. In this study, we used umbrella sampling to compute PMFs for pore formation using three different reaction coordinates, namely, (i) a coordinate that steers the lipids in the lateral direction away from the pore center, (ii) the distance of a single lipid phosphate group from the membrane center, and (iii) the average water density inside a membrane-spanning cylinder. Our results show that while the three reaction coordinates efficiently form pores in membranes, they suffer from strong hysteresis between pore-opening and pore-closing simulations, suggesting that they do not restrain the systems close to the transition state for pore formation. The two reaction coordinates that act via restraining the lipids lead to more pronounced hysteresis compared with the coordinate acting on the water molecules. By comparing PMFs computed from membranes with different numbers of lipids, we observed significant artifacts from the periodic boundary conditions in small simulation systems. Further analysis suggests that the formation and disruption of a continuous hydrogen-bonding network across the membrane corresponds to the transition state for pore formation. Our study provides molecular insights into the critical steps of transmembrane pore formation, and it may guide the development of efficient reaction coordinates for pore formation. PMID:27254744

  13. Paleoenvironmental reconstruction using microfossils : terrestrial

    International Nuclear Information System (INIS)

    The following section provides a brief summary of the use of pollen and chironomids in terrestrial paleoenvironmental reconstruction and lists some key references and general text addressing the history, methods and development of these techniques in Quaternary paleoclimate research and their application in New Zealand. (author). 52 refs., 8 figs

  14. Reconstructing Indo-European Syllabification

    Science.gov (United States)

    Byrd, Andrew Miles

    2010-01-01

    The chief concern of this dissertation is to investigate a fundamental, yet unsolved problem within the phonology of Proto-Indo-European (PIE): the process of syllabification. I show that by analyzing the much more easily reconstructable word-edge clusters we may predict which types of consonant clusters can occur word-medially, provided that we…

  15. A survey of urban reconstruction

    KAUST Repository

    Musialski, Przemyslaw

    2013-05-10

    This paper provides a comprehensive overview of urban reconstruction. While there exists a considerable body of literature, this topic is still under active research. The work reviewed in this survey stems from the following three research communities: computer graphics, computer vision and photogrammetry and remote sensing. Our goal is to provide a survey that will help researchers to better position their own work in the context of existing solutions, and to help newcomers and practitioners in computer graphics to quickly gain an overview of this vast field. Further, we would like to bring the mentioned research communities to even more interdisciplinary work, since the reconstruction problem itself is by far not solved. This paper provides a comprehensive overview of urban reconstruction. While there exists a considerable body of literature, this topic is still under active research. The work reviewed in this survey stems from the following three research communities: computer graphics, computer vision and photogrammetry and remote sensing. Our goal is to provide a survey that will help researchers to better position their own work in the context of existing solutions, and to help newcomers and practitioners in computer graphics to quickly gain an overview of this vast field. Further, we would like to bring the mentioned research communities to even more interdisciplinary work, since the reconstruction problem itself is by far not solved. © 2013 The Eurographics Association and John Wiley & Sons Ltd.

  16. Breast Reconstruction with Tissue Expansion

    Medline Plus

    Full Text Available RECONSTRUCTIVE BREAST SURGERY ALBANY MEDICAL CENTER HOSPITAL ALBANY, NY July 31, 2008 00:00:10 ANNOUNCER: Welcome to this OR-Live webcast presentation, brought to ... webcast screen and open the door to informed medical care. 00:00:28 DIMITRI KOUMANIS, M.D.: ...

  17. Tomographic reconstruction of polar plumes

    Science.gov (United States)

    Auchère, F.; Guennou, C.; Barbey, N.

    2012-06-01

    We present a tomographic reconstruction of polar plumes as observed in the Extreme Ultraviolet in January 2010. Plumes are elusive structures visible in polar coronal holes that may play an important role in the acceleration of the solar wind. However, despite numerous observations, little is irrefutably known about them. Because of line of sight effects, even their geometry is subject to debate. Are they genuine cylindrical features of the corona or are they only chance alignments along the line of sight? Tomography provides a means to reconstruct the volume of an optically thin object from a set of observations taken from different vantage points. In the case of the Sun, these are typically obtained by using a solar rotation worth of images, which limits the ability to reconstruct short lived structures. We present here a tomographic inversion of the solar corona obtained using only 6 days of data. This is achieved by using simultaneously three space telescopes (EUVI/STEREO and SWAP/PROBA2) in a very specific orbital configuration. The result is the shortest possible tomographic snapshot of polar plumes. The 3D reconstruction shows both quasi-cylindrical plumes and a network pattern that can mimic them by line of sight superimpositions. This suggests that the controversy on plume geometry is due to the coexistence of both types of structures.

  18. Real Time Pore Structure Evolution during Olivine Mineral Carbonation

    Science.gov (United States)

    Zhu, W.; Fusseis, F.; Lisabeth, H. P.; Xiao, X.

    2014-12-01

    Aqueous carbonation of ultramafic rocks has been proposed as a promising method for long-term, secure sequestration of carbon dioxide. While chemical kinetics data indicate that carbonation reaction in olivine is one of the fastest among the mg-bearing minerals, in practice, the factors that limit the extent and rate of carbonation in ultramafic rocks are fluid supply and flux. On the one hand, reaction products could produce passivating layer that prohibits further reactions. On the other hand, the increases in solid volume during carbonation could lead to cracking and create new fluid paths. Whether carbonation in ultramafic rocks is self-limiting or self-sustaining has been hotly debated. Experimental evidence of precipitation of reaction products during olivine carbonation was reported. To date, reaction-driven cracking has not been observed. In this paper, we present the first real-time pore structure evolution data using the x-ray synchrotron microtomography. Sodium bicarbonate (NaHCO3) solution was injected into porous olivine aggregates and in-situ pore structure change during olivine carbonation at a constant confining pressure (12 MPa) and a temperature of 200oC was captured at 30 min. interval for ~160 hours. Shortly after the experiment started, filling-in of the existing pores by precipitation of reaction products was visible. The size of the in-fills kept increasing as reactions continued. After ~48 hours, cracking around the in-fill materials became visible. After ~60 hours, these cracks started to show a clear polygonal pattern, similar to the crack patterns usually seen on the surface of drying mud. After ~72 hours, some of the cracks coalesced into large fractures that cut-through the olivine aggregates. New fractures continued to develop and at the end of the experiment, the sample was completely disintegrated by these fractures. We also conducted nanotomography experiments on a sub-volume of the reacted olivine aggregate. Orthogonal sets of

  19. Thermal conductivity of granular porous media: A pore scale modeling approach

    Directory of Open Access Journals (Sweden)

    R. Askari

    2015-09-01

    Full Text Available Pore scale modeling method has been widely used in the petrophysical studies to estimate macroscopic properties (e.g. porosity, permeability, and electrical resistivity of porous media with respect to their micro structures. Although there is a sumptuous literature about the application of the method to study flow in porous media, there are fewer studies regarding its application to thermal conduction characterization, and the estimation of effective thermal conductivity, which is a salient parameter in many engineering surveys (e.g. geothermal resources and heavy oil recovery. By considering thermal contact resistance, we demonstrate the robustness of the method for predicting the effective thermal conductivity. According to our results obtained from Utah oil sand samples simulations, the simulation of thermal contact resistance is pivotal to grant reliable estimates of effective thermal conductivity. Our estimated effective thermal conductivities exhibit a better compatibility with the experimental data in companion with some famous experimental and analytical equations for the calculation of the effective thermal conductivity. In addition, we reconstruct a porous medium for an Alberta oil sand sample. By increasing roughness, we observe the effect of thermal contact resistance in the decrease of the effective thermal conductivity. However, the roughness effect becomes more noticeable when there is a higher thermal conductivity of solid to fluid ratio. Moreover, by considering the thermal resistance in porous media with different grains sizes, we find that the effective thermal conductivity augments with increased grain size. Our observation is in a reasonable accordance with experimental results. This demonstrates the usefulness of our modeling approach for further computational studies of heat transfer in porous media.

  20. Stability indicators in network reconstruction.

    Science.gov (United States)

    Filosi, Michele; Visintainer, Roberto; Riccadonna, Samantha; Jurman, Giuseppe; Furlanello, Cesare

    2014-01-01

    The number of available algorithms to infer a biological network from a dataset of high-throughput measurements is overwhelming and keeps growing. However, evaluating their performance is unfeasible unless a 'gold standard' is available to measure how close the reconstructed network is to the ground truth. One measure of this is the stability of these predictions to data resampling approaches. We introduce NetSI, a family of Network Stability Indicators, to assess quantitatively the stability of a reconstructed network in terms of inference variability due to data subsampling. In order to evaluate network stability, the main NetSI methods use a global/local network metric in combination with a resampling (bootstrap or cross-validation) procedure. In addition, we provide two normalized variability scores over data resampling to measure edge weight stability and node degree stability, and then introduce a stability ranking for edges and nodes. A complete implementation of the NetSI indicators, including the Hamming-Ipsen-Mikhailov (HIM) network distance adopted in this paper is available with the R package nettools. We demonstrate the use of the NetSI family by measuring network stability on four datasets against alternative network reconstruction methods. First, the effect of sample size on stability of inferred networks is studied in a gold standard framework on yeast-like data from the Gene Net Weaver simulator. We also consider the impact of varying modularity on a set of structurally different networks (50 nodes, from 2 to 10 modules), and then of complex feature covariance structure, showing the different behaviours of standard reconstruction methods based on Pearson correlation, Maximum Information Coefficient (MIC) and False Discovery Rate (FDR) strategy. Finally, we demonstrate a strong combined effect of different reconstruction methods and phenotype subgroups on a hepatocellular carcinoma miRNA microarray dataset (240 subjects), and we validate the

  1. Stability indicators in network reconstruction.

    Directory of Open Access Journals (Sweden)

    Michele Filosi

    Full Text Available The number of available algorithms to infer a biological network from a dataset of high-throughput measurements is overwhelming and keeps growing. However, evaluating their performance is unfeasible unless a 'gold standard' is available to measure how close the reconstructed network is to the ground truth. One measure of this is the stability of these predictions to data resampling approaches. We introduce NetSI, a family of Network Stability Indicators, to assess quantitatively the stability of a reconstructed network in terms of inference variability due to data subsampling. In order to evaluate network stability, the main NetSI methods use a global/local network metric in combination with a resampling (bootstrap or cross-validation procedure. In addition, we provide two normalized variability scores over data resampling to measure edge weight stability and node degree stability, and then introduce a stability ranking for edges and nodes. A complete implementation of the NetSI indicators, including the Hamming-Ipsen-Mikhailov (HIM network distance adopted in this paper is available with the R package nettools. We demonstrate the use of the NetSI family by measuring network stability on four datasets against alternative network reconstruction methods. First, the effect of sample size on stability of inferred networks is studied in a gold standard framework on yeast-like data from the Gene Net Weaver simulator. We also consider the impact of varying modularity on a set of structurally different networks (50 nodes, from 2 to 10 modules, and then of complex feature covariance structure, showing the different behaviours of standard reconstruction methods based on Pearson correlation, Maximum Information Coefficient (MIC and False Discovery Rate (FDR strategy. Finally, we demonstrate a strong combined effect of different reconstruction methods and phenotype subgroups on a hepatocellular carcinoma miRNA microarray dataset (240 subjects, and we

  2. Ancestral reconstruction of tick lineages.

    Science.gov (United States)

    Mans, Ben J; de Castro, Minique H; Pienaar, Ronel; de Klerk, Daniel; Gaven, Philasande; Genu, Siyamcela; Latif, Abdalla A

    2016-06-01

    Ancestral reconstruction in its fullest sense aims to describe the complete evolutionary history of a lineage. This depends on accurate phylogenies and an understanding of the key characters of each parental lineage. An attempt is made to delineate our current knowledge with regard to the ancestral reconstruction of the tick (Ixodida) lineage. Tick characters may be assigned to Core of Life, Lineages of Life or Edges of Life phenomena depending on how far back these characters may be assigned in the evolutionary Tree of Life. These include housekeeping genes, sub-cellular systems, heme processing (Core of Life), development, moulting, appendages, nervous and organ systems, homeostasis, respiration (Lineages of Life), specific adaptations to a blood-feeding lifestyle, including the complexities of salivary gland secretions and tick-host interactions (Edges of Life). The phylogenetic relationships of lineages, their origins and importance in ancestral reconstruction are discussed. Uncertainties with respect to systematic relationships, ancestral reconstruction and the challenges faced in comparative transcriptomics (next-generation sequencing approaches) are highlighted. While almost 150 years of information regarding tick biology have been assembled, progress in recent years indicates that we are in the infancy of understanding tick evolution. Even so, broad reconstructions can be made with relation to biological features associated with various lineages. Conservation of characters shared with sister and parent lineages are evident, but appreciable differences are present in the tick lineage indicating modification with descent, as expected for Darwinian evolutionary theory. Many of these differences can be related to the hematophagous lifestyle of ticks. PMID:26868413

  3. Transport and Deposition of Nanoparticles in the Pore Network of a Reservoir Rock: Effects of Pore Surface Heterogeneity and Radial Diffusion

    Science.gov (United States)

    Pham, Ngoc; Papavassiliou, Dimitrios

    2014-03-01

    In this study, transport behavior of nanoparticles under different pore surface conditions of consolidated Berea sandstone is numerically investigated. Micro-CT scanning technique is applied to obtain 3D grayscale images of the rock sample geometry. Quantitative characterization, which is based on image analysis is done to obtain physical properties of the pore network, such as the pore size distribution and the type of each pore (dead-end, isolated, and fully connected pore). Transport of water through the rock is simulated by employing a 3D lattice Boltzmann method. The trajectories of nanopaticles moving under convection in the simulated flow field and due to molecular diffusion are monitored in the Lagrangian framework. It is assumed in the model that the particle adsorption on the pore surface, which is modeled as a pseudo-first order adsorption, is the only factor hindering particle propagation. The effect of pore surface heterogeneity to the particle breakthrough is considered, and the role of particle radial diffusion is also addressed in details. The financial support of the Advanced Energy Consortium (AEC BEG08-022) and the computational support of XSEDE (CTS090017) are acknowledged.

  4. Adsorption hysteresis for a slit-like pore model

    Science.gov (United States)

    Kutarov, V. V.; Tarasevich, Yu. I.; Aksenenko, E. V.; Ivanova, Z. G.

    2011-07-01

    The Frenkel-Halsey-Hill equation is used to describe the adsorption branch of a hysteresis loop upon polylayer adsorption with an H3 loop according to IUPAC nomenclature. The equation for the desorption branch of a hysteresis loop is derived from a combined solution to the equation for the Gibbs potential change, given the adsorbent swelling and pore connectivity function, and the Laplace equation taken for the conditions of infinitely elongated meniscus. This equation is shown to connect the adsorbate relative pressure in a bulk phase for the desorption branch of a hysteresis loop with the key parameters of the adsorption system. The equation obtained was verified by a water adsorption isotherm on natural mineral schungite.

  5. Thermally stable crystalline mesoporous metal oxides with substantially uniform pores

    Energy Technology Data Exchange (ETDEWEB)

    Wiesner, Ulrich; Orilall, Mahendra Christopher; Lee, Jinwoo; DiSalvo, Jr., Francis J

    2015-01-27

    Highly crystalline metal oxide-carbon composites, as precursors to thermally stable mesoporous metal oxides, are coated with a layer of amorphous carbon. Using a `one-pot` method, highly crystalline metal oxide-carbon composites are converted to thermally stable mesoporous metal oxides, having highly crystalline mesopore walls, without causing the concomitant collapse of the mesostructure. The `one-pot` method uses block copolymers with an sp or sp 2 hybridized carbon containing hydrophobic block as structure directing agents which converts to a sturdy, amorphous carbon material under appropriate heating conditions, providing an in-situ rigid support which maintains the pores of the oxides intact while crystallizing at temperatures as high as 1000 deg C. A highly crystalline metal oxide-carbon composite can be heated to produce a thermally stable mesoporous metal oxide consisting of a single polymorph.

  6. Pathophysiological role of omega pore current in channelopathies

    Directory of Open Access Journals (Sweden)

    Karin eJurkat-Rott

    2012-06-01

    Full Text Available In voltage-gated cation channels, a recurrent pattern for mutations is the neutralization of positively charged residues in the voltage-sensing S4 transmembrane segments. These mutations cause dominant ion channelopathies affecting many tissues such as brain, heart, and skeletal muscle. Recent studies suggest that the pathogenesis of associated phenotypes is not limited to alterations in the gating of the ion-conducting alpha pore. Instead, aberrant so-called omega currents facilitated by the movement of the S4 segments during activation and during recovery are thought to cause symptoms. Surprisingly, these omega currents display uni- or bi-directionality and conduct cations with varying ion selectivity. Additionally, the voltage-sensitivity enables the channels to conduct different omega currents in the various voltage ranges. This review gives an overview of voltage sensor channelopathies in general and focuses on pathogenesis of skeletal muscle S4 disorders for which current knowledge is most advanced.

  7. Macroscopic ordering of helical pores for arraying guest molecules noncentrosymmetrically

    Science.gov (United States)

    Li, Chunji; Cho, Joonil; Yamada, Kuniyo; Hashizume, Daisuke; Araoka, Fumito; Takezoe, Hideo; Aida, Takuzo; Ishida, Yasuhiro

    2015-09-01

    Helical nanostructures have attracted continuous attention, not only as media for chiral recognition and synthesis, but also as motifs for studying intriguing physical phenomena that never occur in centrosymmetric systems. To improve the quality of signals from these phenomena, which is a key issue for their further exploration, the most straightforward is the macroscopic orientation of helices. Here as a versatile scaffold to rationally construct this hardly accessible structure, we report a polymer framework with helical pores that unidirectionally orient over a large area (~10 cm2). The framework, prepared by crosslinking a supramolecular liquid crystal preorganized in a magnetic field, is chemically robust, functionalized with carboxyl groups and capable of incorporating various basic or cationic guest molecules. When a nonlinear optical chromophore is incorporated in the framework, the resultant complex displays a markedly efficient nonlinear optical output, owing to the coherence of signals ensured by the macroscopically oriented helical structure.

  8. A melanosomal two-pore sodium channel regulates pigmentation.

    Science.gov (United States)

    Bellono, Nicholas W; Escobar, Iliana E; Oancea, Elena

    2016-01-01

    Intracellular organelles mediate complex cellular functions that often require ion transport across their membranes. Melanosomes are organelles responsible for the synthesis of the major mammalian pigment melanin. Defects in melanin synthesis result in pigmentation defects, visual deficits, and increased susceptibility to skin and eye cancers. Although genes encoding putative melanosomal ion transporters have been identified as key regulators of melanin synthesis, melanosome ion transport and its contribution to pigmentation remain poorly understood. Here we identify two-pore channel 2 (TPC2) as the first reported melanosomal cation conductance by directly patch-clamping skin and eye melanosomes. TPC2 has been implicated in human pigmentation and melanoma, but the molecular mechanism mediating this function was entirely unknown. We demonstrate that the vesicular signaling lipid phosphatidylinositol bisphosphate PI(3,5)P2 modulates TPC2 activity to control melanosomal membrane potential, pH, and regulate pigmentation. PMID:27231233

  9. Thermal Motion of DNA in an MspA Pore.

    Science.gov (United States)

    Lu, Bo; Fleming, Stephen; Szalay, Tamas; Golovchenko, Jene

    2015-10-01

    We report on an experiment and calculations that determine the thermal motion of a voltage-clamped single-stranded DNA-NeutrAvidin complex in a Mycobacterium smegmatis porin A nanopore. The electric force and diffusion constant of DNA inside a Mycobacterium smegmatis porin A pore were determined to evaluate the thermal position fluctuations of DNA. We show that an out-of-equilibrium state returns to equilibrium so quickly that experiments usually measure a weighted average over the equilibrium position distribution. Averaging over the equilibrium position distribution is consistent with results of state-of-the-art nanopore sequencing experiments. It is shown how a reduction in thermal position fluctuations can be achieved by increasing the electrophoretic force used in nanopore sequencing devices. PMID:26445444

  10. Diffusion of Macromolecules across the Nuclear Pore Complex

    CERN Document Server

    Chakrabarti, Rajarshi; Sebastian, K L

    2007-01-01

    Nuclear pore complexes (NPCs) are very selective filters that monitor the transport between the cytoplasm and the nucleoplasm. Two models have been suggested for the plug of the NPC. They are (i) it is a reversible hydrogel or (ii) it is a polymer brush. We propose a mesoscopic model for the transport of a protein through the plug, that is general enough to cover both. The protein stretches the plug and creates a local deformation. The bubble so created (prtoein+deformation) executes random walk in the plug. We find that for faster relaxation of the gel, the diffusion of the bubble is greater. Further, on using parameters appropriate for the brush, we find that the diffusion coefficient is much lower. Hence the gel model seems to be more likely explanation for the workings of the plug.

  11. Tailoring particle translocation via dielectrophoresis in pore channels.

    Science.gov (United States)

    Tanaka, Shoji; Tsutsui, Makusu; Theodore, Hu; Yuhui, He; Arima, Akihide; Tsuji, Tetsuro; Doi, Kentaro; Kawano, Satoyuki; Taniguchi, Masateru; Kawai, Tomoji

    2016-01-01

    Understanding and controlling electrophoretic motions of nanoscopic objects in fluidic channels are a central challenge in developing nanopore technology for molecular analyses. Although progress has been made in slowing the translocation velocity to meet the requirement for electrical detections of analytes via picoampere current measurements, there exists no method useful for regulating particle flows in the transverse directions. Here, we report the use of dielectrophoresis to manipulate the single-particle passage through a solid-state pore. We created a trap field by applying AC voltage between electrodes embedded in a low-aspect-ratio micropore. We demonstrated a traffic control of particles to go through center or near side surface via the voltage frequency. We also found enhanced capture efficiency along with faster escaping speed of particles by virtue of the AC-mediated electroosmosis. This method is compatible with nanopore sensing and would be widely applied for reducing off-axis effects to achieve single-molecule identification. PMID:27527126

  12. Dynamics of polynucleotide transport through nanometre-scale pores

    CERN Document Server

    Meller, A

    2003-01-01

    The transport of biopolymers through large membrane channels is a ubiquitous process in biology. It is central to processes such as gene transfer by transduction and RNA transport through nuclear pore complexes. The transport of polymers through nanoscopic channels is also of interest to physicists and chemists studying the effects of steric, hydrodynamic, and electrostatic interactions between polymers and confining walls. Single-channel ion current measurements have been recently used to study the transport of biopolymers, and in particular single-stranded DNA and RNA molecules, through nanometre-size channels. Under the influence of an electric field, the negatively charged polynucleotides can be captured and drawn through the channel in a process termed 'translocation'. During translocation, the ion current flowing through the channel is mostly blocked, indicating the presence of the polymer inside the channel. The current blockades were found to be sensitive to the properties of the biopolymers such as t...

  13. A Dynamic Pore-Scale Model of Imbibition

    DEFF Research Database (Denmark)

    Mogensen, Kristian; Stenby, Erling Halfdan

    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...

  14. Transient streaming potentials under varying pore-water ionic strength

    Science.gov (United States)

    Malama, B.

    2014-12-01

    Streaming potentials (SP) are generated when polar fluids such as groundwater flow through porous media that have charged mineral surfaces. This is due to the flow-shearing of the diffuse layer of the electric double layer (EDL), which is known to form in the fluid phase at the fluid-rock interface. Previous works have suggested that the EDL vanishes at high pore-fluid ionic strengths resulting in vanishing SP signals. However, recent observations in sea-water intrusion applications by Jackson and coworkers indicate that measurable SP signals are obtainable in flows of fluids with high ionic strengths through silica sand. We demonstrate the repeatability of these observations through a series of laboratory flow experiments performed on 98% silica sand in a falling-head permeameter with brines of concentrations ranging from 0.001M to about 5 M NaCl. The results of the experiments, which clearly show measurable SP signals even at the highest concentration of 5 M NaCl, are reported. They are also used to estimate the hydraulic conductivity and electrokinetic coupling coefficient. The linearity assumption for the relation between pressure and SP differentials is evaluated for high pore-water NaCl concentrations. Additionally, displacement of one brine by another of different NaCl concentration yields dramatic transient SP responses that may be harnessed in the development of early-detection/warning technologies for sea-water intrusion applications. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. This research is funded by WIPP programs administered by the Office of Environmental Management (EM) of the U.S Department of Energy.

  15. Pore pressure profiles in fractured and compliant rocks

    Energy Technology Data Exchange (ETDEWEB)

    Yilmaz, O. (Geco-Prakla, West Sussex (United Kingdom)); Nolen-Hoeksema, R.C.; Nur, A. (Stanford Univ., CA (United States). Geophysics Dept.)

    1994-08-01

    Fluid permeability in fractured rocks is sensitive to pore-pressure changes. This dependence can have large effects on the flow of fluids through rocks. The authors define the permeability compliance [gamma] = 1/k([partial derivative]k/[partial derivative]p[sub p])[sub pc], which is the sensitivity of the permeability k to the pore pressure p[sub p] at a constant confining pressure p[sub c], and solve the specific problems of constant pressure at the boundary of a half-space, a cylindrical cavity and a spherical cavity. The results show that when the magnitude of permeability compliance is large relative to other compliances, diffusion is masked by a piston-like pressure profile. The authors expect this phenomenon to occur in highly fractured and compliant rock systems where [gamma] may be large. The pressure profile moves rapidly when fluids are pumped into the rock and very slowly when fluids are pumped out. Consequently, fluid pressure, its history and distribution around injection and production wells may be significantly different from pressures predicted by the linear diffusion equation. The propagation speed of the pressure profile, marked by the point where [partial derivative]p[sub p]/[partial derivative]x is a maximum, decreases with time approximately as [radical]t, and the amplitude of the profile also dissipates with time (or distance). The effect of permeability compliance can be important for fluid injection into and withdrawal from reservoirs. For example, excessive drawdown could cause near-wellbore flow suffocation. Also, estimates of the storage capacity of reservoirs may be greatly modified when [gamma] is large. The large near-wellbore pressure gradients caused during withdrawal by large [gamma] can cause sanding and wellbore collapse due to excessive production rates.

  16. Pores in the epidermis: aquaporins and tight junctions.

    Science.gov (United States)

    Brandner, J M

    2007-12-01

    Water homeostasis of the epidermis is important for the appearance and physical properties of the skin, as well as for water balance in the body. It depends on several factors, e.g. barrier quality, uptake of water into the epidermis, concentration of water-retaining humectants, and external humidity. Aquaporins (AQPs) are pores in the plasmamembranes of cells. Monomeric AQPs form barrel-like structures that are primarily water selective, some AQPs also transport glycerol and possibly other small solutes. In the epidermis, AQP3 is the predominant AQP. It is localized mainly in basal but also in suprabasal layers of the epidermis and is permeable for water as well as for glycerol, a humectant. Mice deficient in AQP3 exhibit reduced stratum corneum (SC) hydration and impaired SC barrier recovery after SC removal. In skin diseases associated with elevated transepidermal water loss (TEWL) and reduced SC hydration, altered expression of AQP3 was shown. Tight junctions (TJ) are cell-cell junctions, which play a central role in sealing the intercellular space of cell sheets and thereby establishing a paracellular barrier. Within the TJ, pores are postulated to exist, which allow the controlled diffusion of water and solutes via the paracellular pathway. In the epidermis, TJ structures were demonstrated in the stratum granulosum whereas TJ proteins were found in all viable layers. Mice which overexpress or are deficient of key-proteins of TJ die soon after birth because of a tremendous TEWL. In various skin diseases that are accompanied by elevated TEWL and reduced skin hydration, staining patterns of TJ proteins are altered. This review will summarize our current knowledge of the involvement of AQPs and TJ in the water homeostasis of the epidermis. PMID:18489380

  17. Defect evolution and pore collapse in crystalline energetic materials

    Science.gov (United States)

    Barton, Nathan R.; Winter, Nicholas W.; Reaugh, John E.

    2009-04-01

    This work examines the use of crystal based continuum mechanics in the context of dynamic loading. In particular, we examine model forms and simulations which are relevant to pore collapse in crystalline energetic materials. Strain localization and the associated generation of heat are important for the initiation of chemical reactions in this context. The crystal mechanics based model serves as a convenient testbed for the interactions among wave motion, slip kinetics, defect generation kinetics and physical length scale. After calibration to available molecular dynamics and single crystal gas gun data for HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine), the model is used to predict behaviors for the collapse of pores under various conditions. Implications for experimental observations are discussed. This document was prepared as an account of work sponsored by an agency of the United States government. Neither the United States government nor Lawrence Livermore National Security, LLC, nor any of their employees makes any warranty, expressed or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States government or Lawrence Livermore National Security, LLC. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States government or Lawrence Livermore National Security, LLC, and shall not be used for advertising or product endorsement purposes.

  18. pH controlled gating of toxic protein pores by dendrimers

    Science.gov (United States)

    Mandal, Taraknath; Kanchi, Subbarao; Ayappa, K. G.; Maiti, Prabal K.

    2016-06-01

    Designing effective nanoscale blockers for membrane inserted pores formed by pore forming toxins, which are expressed by several virulent bacterial strains, on a target cell membrane is a challenging and active area of research. Here we demonstrate that PAMAM dendrimers can act as effective pH controlled gating devices once the pore has been formed. We have used fully atomistic molecular dynamics (MD) simulations to characterize the cytolysin A (ClyA) protein pores modified with fifth generation (G5) PAMAM dendrimers. Our results show that the PAMAM dendrimer, in either its protonated (P) or non-protonated (NP) states can spontaneously enter the protein lumen. Protonated dendrimers interact strongly with the negatively charged protein pore lumen. As a consequence, P dendrimers assume a more expanded configuration efficiently blocking the pore when compared with the more compact configuration adopted by the neutral NP dendrimers creating a greater void space for the passage of water and ions. To quantify the effective blockage of the protein pore, we have calculated the pore conductance as well as the residence times by applying a weak force on the ions/water. Ionic currents are reduced by 91% for the P dendrimers and 31% for the NP dendrimers. The preferential binding of Cl- counter ions to the P dendrimer creates a zone of high Cl- concentration in the vicinity of the internalized dendrimer and a high concentration of K+ ions in the transmembrane region of the pore lumen. In addition to steric effects, this induced charge segregation for the P dendrimer effectively blocks ionic transport through the pore. Our investigation shows that the bio-compatible PAMAM dendrimers can potentially be used to develop therapeutic protocols based on the pH sensitive gating of pores formed by pore forming toxins to mitigate bacterial infections.Designing effective nanoscale blockers for membrane inserted pores formed by pore forming toxins, which are expressed by several virulent

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

    CERN Document Server

    Bazylak, A; 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 contrast to continuum or molecular dynamics modelling that require extensive computational resources. However, the challenge in studying the GDL with pore network modelling lies in defining the network parameters that accurately describe the porous media as well as the conditions of fluid invasion that represent realistic transport processes. In this work, we discuss the first stage of developing and validating a GDL-representative pore network model. We begin with a two-dimensional pore network model with a single mobile pha...

  20. Synthesis of porous ceramics with unidirectionally aligned-pores by freeze drying process

    International Nuclear Information System (INIS)

    A new fabrication method of porous ceramics with unidirectionally aligned pores was studied. A water-based ceramic slurry was prepared and unidirectionally frozen while controlling the direction of ice formation. By freeze-drying the frozen slurry, columnar pores were generated from sublimation of the ice in the green body. Porous ceramics having a complex pore structure were obtained by sintering the porous green body: aligned macroscopic open pores contained minute pores in their internal walls. This fabrication technique is environmentally friendly and applicable to a variety of ceramics because the pores are already produced before sintering. The examples for alumina and silicon nitride are introduced in this study. Copyright (2000) AD-TECH - International Foundation for the Advancement of Technology Ltd

  1. Analysis of Pore Structures and Their Relations with Strength of Hardened Cement Paste

    Institute of Scientific and Technical Information of China (English)

    ZHANG Wensheng; LI Beixing; WANG Hongxia; WEI Jiangxiong; CHEN Yimin

    2005-01-01

    Three cement samples were prepared, including OPC consisted of 100wt% portland cement, PFA consisted of 70wt% portland cement and 30wt% fly-ash, and CA consisted of 70wt% portland cement and 30wt% modified fly ash. The strength of hardened cement paste of these samples was tested and their pore structures were determined by a mercury intrusion porosimeter. Moreover,the data of the pore structures of three samples were comprehensively analyzed. The relations between the pore structures and the compressive strength of the three samples were studied. The experimental results show that the relations between the porosity determined by the mercury intrusion porosimeter and the compressive strength are not notable, and the total pore surface area, the average pore diameter and the median pore diameter could be used to explain the difference of the strength of the tested samples.

  2. Pore Structure Characteristics after 2 Years of Biochar Application to a Sandy Loam Field

    DEFF Research Database (Denmark)

    Sun, Zhencai; Arthur, Emmanuel; de Jonge, Lis Wollesen;

    2015-01-01

    , where the maximum increment was 12% at 100 Mg ha-1 biochar treatment. A pore size distribution index, B, derived from water retention, indicated a wider soil pore size distribution in biochar-amended soil than in the reference soil, especially for the 100-Mg ha-1 application. At given matric potentials......Soil pore structure comprises the size and shape of soil pores and has a major impact on water retention and gas movement. The porous nature of biochar suggests that its application to soil can potentially alter soil pore structure characteristics, and the purpose of this study was to evaluate the...... effects of birch wood biochar (20, 40, and 100 Mg ha-1) applied to a sandy loam on soil total porosity and pore structure indices. Bulk and intact soil samples were collected for physicochemical analyses and water retention and gas diffusivity measurements between pF 1.0 and pF 3.0. Biochar application...

  3. TAILORING OF PORE SIZE IN MESOPOROUS SILICA WITH STEARIC ACID AND PVP

    Institute of Scientific and Technical Information of China (English)

    Haidi Liu; Shufeng Ye; Yunfa Chen

    2005-01-01

    Mesoporous silica was prepared using tetrathoxysilane (TEOS), cetadecyltrimethylammonium bromide (CTAB), aqueous ammonia, acetone and water as silica source, template agent, precipitator and solvent respectively.Stearic acid and polyvinylpyrrolidone (PVP) were employed as additional templates to tailor the pore size in the resultant porous silica. BET, SAXRD and SEM analyses were used to characterize the surface area, pore size, pore structure,pore regularity and morphology of the sample. BET measurement results showed that PVP could increase the surface area but diminish the pore size while stearic acid could decrease the surface area but enlarge the pore size. SAXRD analysis indicated that more additional template introduction gave rise to less order-structured products. All these various results could be attributed to the differently modified CTAB micelles involving stearic acid and PVP addition.

  4. Reconstructing the inflaton potential: Perturbative reconstruction to second order

    Energy Technology Data Exchange (ETDEWEB)

    Copeland, Edmund J.; Kolb, Edward W.; Liddle, Andrew R.; Lidsey, James E.

    1993-08-01

    One method to reconstruct the scalar field potential of inflation is a perturbative approach, where the values of the potential and its derivatives are calculated as an expansion in departures from the slow-roll approximation. They can then be expressed in terms of observable quantities, such as the square of the ratio of the gravitational wave amplitude to the density perturbation amplitude, the deviation of the spectral index from the Harrison--Zel'dovich value, etc. Here, we calculate complete expressions for the second-order contributions to the coefficients of the expansion by including for the first time corrections to the standard expressions for the perturbation spectra. As well as offering an improved result, these corrections indicate the expected accuracy of the reconstruction. Typically the corrections are only a few percent.

  5. Current Trends in Anterior Cruciate Ligament Reconstruction

    OpenAIRE

    Kim, Ha Sung; Seon, Jong Keun; Jo, Ah Reum

    2013-01-01

    The advances in the knowledge of anatomy, surgical techniques, and fixation devices have led to the improvement of anterior cruciate ligament (ACL) reconstruction over the past 10 years. Nowadays, double bundle and anatomical single bundle ACL reconstruction that more closely restores the normal anatomy of the ACL are becoming popular. Although there is still no definite conclusion whether double bundle ACL reconstruction provides better clinical results than single bundle reconstruction, the...

  6. 3D Reconstruction Technique for Tomographic PIV

    Institute of Scientific and Technical Information of China (English)

    姜楠; 包全; 杨绍琼

    2015-01-01

    Tomographic particle image velocimetry(Tomo-PIV) is a state-of-the-art experimental technique based on a method of optical tomography to achieve the three-dimensional(3D) reconstruction for three-dimensional three-component(3D-3C) flow velocity measurements. 3D reconstruction for Tomo-PIV is carried out herein. Meanwhile, a 3D simplified tomographic reconstruction model reduced from a 3D volume light inten-sity field with 2D projection images into a 2D Tomo-slice plane with 1D projecting lines, i.e., simplifying this 3D reconstruction into a problem of 2D Tomo-slice plane reconstruction, is applied thereafter. Two kinds of the most well-known algebraic reconstruction techniques, algebraic reconstruction technique(ART) and multiple algebraic reconstruction technique(MART), are compared as well. The principles of the two reconstruction algorithms are discussed in detail, which has been performed by a series of simulation images, yielding the corresponding recon-struction images that show different features between the ART and MART algorithm, and then their advantages and disadvantages are discussed. Further discussions are made for the standard particle image reconstruction when the background noise of the pre-initial particle image has been removed. Results show that the particle image recon-struction has been greatly improved. The MART algorithm is much better than the ART. Furthermore, the computa-tional analyses of two parameters(the particle density and the number of cameras), are performed to study their effects on the reconstruction. Lastly, the 3D volume particle field is reconstructed by using the improved algorithm based on the simplified 3D tomographic reconstruction model, which proves that the algorithm simplification is feasible and it can be applied to the reconstruction of 3D volume particle field in a Tomo-PIV system.

  7. Multi-resolution Compressive Sensing Reconstruction

    OpenAIRE

    Gonzalez, Adriana; Jiang, Hong; Huang, Gang; Jacques, Laurent

    2016-01-01

    We consider the problem of reconstructing an image from compressive measurements using a multi-resolution grid. In this context, the reconstructed image is divided into multiple regions, each one with a different resolution. This problem arises in situations where the image to reconstruct contains a certain region of interest (RoI) that is more important than the rest. Through a theoretical analysis and simulation experiments we show that the multi-resolution reconstruction provides a higher ...

  8. Finite Element and Experimental Analysis of Closure and Contact Bonding of Pores During Hot Rolling of Steel

    Science.gov (United States)

    Joo, Soo-Hyun; Jung, Jaimyun; Chun, Myung Sik; Moon, Chang Ho; Lee, Sunghak; Kim, Hyoung Seop

    2014-08-01

    The closure and contact bonding behavior of internal pores in steel slabs during hot rolling was studied using experiments and the finite element method (FEM). Effects of pore size and shape were investigated, and three different cases of pore closure results were observed: no closure, partial closure, and full closure. The FEM results well reproduced various closure events. Bonding strengths of unsuccessfully closed pores, measured by tensile tests, showed critical effects. Also, there was a difference in bonding strengths of several fully closed pores. Fracture surfaces showed that welded regions could be divided into three (not, partially, and perfectly) welded regions. The pressure-time curves obtained from the FEM results indicate that pore surface contact time and deformed surface length are important parameters in pore welding. Pore size, pore shape, time of pressure contact, and deformed surface length should be considered to completely eliminate pores in final products.

  9. Pore former induced porosity in LSM/CGO cathodes for electrochemical cells for flue gas purification

    DEFF Research Database (Denmark)

    Skovgaard, M.; Andersen, Kjeld Bøhm; Kammer Hansen, Kent

    2012-01-01

    and the highest porosity measured was 46.4% with an average pore diameter of 0.98 μm. The air flow through this cathode was measured to 5.8 ml/(min mm2). Also the effect of exposure time to the solvent was tested for the most promising PMMA pore former and it was found that the average pore diameter...

  10. 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...

  11. Probing the intrinsically oil-wet surfaces of pores in North Sea chalk at subpore resolution

    OpenAIRE

    Hassenkam, T.; Skovbjerg, L. L.; Stipp, S. L. S.

    2009-01-01

    Pore surface properties control oil recovery. This is especially true for chalk reservoirs, where pores are particularly small. Wettability, the tendency for a surface to cover itself with fluid, is traditionally defined by the angle a droplet makes with a surface, but this macroscopic definition is meaningless when the particles are smaller than even the smallest droplet. Understanding surface wetting, at the pore scale, will provide clues for more effective oil recovery. We used a special m...

  12. pH controlled gating of toxic protein pores by dendrimers.

    Science.gov (United States)

    Mandal, Taraknath; Kanchi, Subbarao; Ayappa, K G; Maiti, Prabal K

    2016-07-14

    Designing effective nanoscale blockers for membrane inserted pores formed by pore forming toxins, which are expressed by several virulent bacterial strains, on a target cell membrane is a challenging and active area of research. Here we demonstrate that PAMAM dendrimers can act as effective pH controlled gating devices once the pore has been formed. We have used fully atomistic molecular dynamics (MD) simulations to characterize the cytolysin A (ClyA) protein pores modified with fifth generation (G5) PAMAM dendrimers. Our results show that the PAMAM dendrimer, in either its protonated (P) or non-protonated (NP) states can spontaneously enter the protein lumen. Protonated dendrimers interact strongly with the negatively charged protein pore lumen. As a consequence, P dendrimers assume a more expanded configuration efficiently blocking the pore when compared with the more compact configuration adopted by the neutral NP dendrimers creating a greater void space for the passage of water and ions. To quantify the effective blockage of the protein pore, we have calculated the pore conductance as well as the residence times by applying a weak force on the ions/water. Ionic currents are reduced by 91% for the P dendrimers and 31% for the NP dendrimers. The preferential binding of Cl(-) counter ions to the P dendrimer creates a zone of high Cl(-) concentration in the vicinity of the internalized dendrimer and a high concentration of K(+) ions in the transmembrane region of the pore lumen. In addition to steric effects, this induced charge segregation for the P dendrimer effectively blocks ionic transport through the pore. Our investigation shows that the bio-compatible PAMAM dendrimers can potentially be used to develop therapeutic protocols based on the pH sensitive gating of pores formed by pore forming toxins to mitigate bacterial infections. PMID:27328315

  13. Membrane Bending Energy and Fusion Pore Kinetics in Ca2+-Triggered Exocytosis

    OpenAIRE

    Zhang, Zhen; Jackson, Meyer B.

    2010-01-01

    A fusion pore composed of lipid is an obligatory kinetic intermediate of membrane fusion, and its formation requires energy to bend membranes into highly curved shapes. The energetics of such deformations in viral fusion is well established, but the role of membrane bending in Ca2+-triggered exocytosis remains largely untested. Amperometry recording showed that during exocytosis in chromaffin and PC12 cells, fusion pores formed by smaller vesicles dilated more rapidly than fusion pores formed...

  14. Reconstructing Deweyan Pragmatism: A Review Essay

    Science.gov (United States)

    Neubert, Stefan

    2009-01-01

    In this essay Stefan Neubert argues that John Dewey was a philosopher of reconstruction and that the best use we can make of him today is to reconstruct his work in and for our own contexts. Neubert distinguishes three necessary and equally important components of the overall project of reconstructing Deweyan pragmatism: first, to make strong and…

  15. Set-reconstructibility of Post classes

    OpenAIRE

    Couceiro, Miguel; Lehtonen, Erkko; Schölzel, Karsten

    2013-01-01

    The clones of Boolean functions are classified in regard to set-reconstructibility via a strong dichotomy result: the clones containing only affine functions, conjunctions, disjunctions or constant functions are set-reconstructible, whereas the remaing clones are not weakly reconstructible.

  16. Mandibular reconstruction using bone allografts

    International Nuclear Information System (INIS)

    Further understanding of bone healing mechanisms, bone physiology and bone biology, transplantation immunology, and development of Tissue Banking procedures has enabled oral and maxillofacial surgeons to reconstruct even the most difficult bony defects successfully with the preserved allogeneic bone implant. Although it had been known that bone allografts were clinically effective, its application has not been widespread until the reports of Inclan (I 942), Hyatt and Butler (I 950), and Wilson (I 95 1). Tissue Banking provides the surgeon with a readily available, relatively inexpensive, and relatively safe selection of allogeneic bone for clinical use. Now autogenous bone and allogeneic bone implants present a wide variety of surgical options to surgeons, whether used separately or in combination. The surgeons are able to make judicious and fruitful choices, only with a thorough knowledge of the above-mentioned biological principles and skillful techniques. Many kinds of bone grafting techniques have been tried for reconstructing defective osseous tissues of the oral and maxillofacial region, though they have varying degrees of success. The osseous defects which require grafting include those of various size, shape, position, or amount. Unlike autogenous grafts, whose function is to provide osteogenic cells, allografts are purely passive, offering only a matrix for the inductive phase of bone healing. The condition of the recipient bed is of primary importance, because the host must produce all of the essential elements for the bone allograft to become incorporated. Depending on the processing methods of the allogeneic bone, the bone graft materials have different qualities, different healing potentials and different indications. Proper selection of grafts and surgical techniques requires an understanding of graft immunology and the mechanisms of graft healing. The surgeons should know about the biological principles to raise the clinical success rate

  17. High Surface Area of Nano Pores Activated Carbon Derived From Agriculture Waste

    International Nuclear Information System (INIS)

    In this study, the high surface area of nano pores activated carbon rice husk originated from local biomass was investigated. The comparison in terms of surface area, porosity and behavior in electrochemical analysis with commercial activated carbon was studied in details. The nano pores activated carbon rice husk was synthesis using consecutive of carbonization and activation under purified nitrogen and carbon dioxide purge. Interestingly, the surface area and capacity of the nano pores activated carbon rice indicated higher in comparison to commercial activated carbon. This indicated that the nano pores activated carbon has potential to be developed further as an alternative material in reducing suspension on commercial activated carbon. (author)

  18. Modelling mass transport through a porous partition: Effect of pore size distribution

    Science.gov (United States)

    Khayet, Mohamed; Velázquez, Armando; Mengual, Juan I.

    2004-09-01

    Direct contact membrane distillation process has been studied using microporous polytetrafluoroethylene and polyvinylidene fluoride membranes. The membranes were characterized in terms of their non-wettability, pore size distribution and porosity. The mean pore sizes and pore size distributions were obtained by means of wet/dry flow method. The mean pore size and the effective porosity of the membranes were also determined from the gas permeation test. A theoretical model that considers the pore size distribution together with the gas transport mechanisms through the membrane pores was developed for this process. The contribution of each mass transport mechanism was analyzed. It was found that both membranes have pore size distributions in the Knudsen region and in the transition between Knudsen and ordinary diffusion region. The transition region was the major contribution to mass transport. The predicted water vapor permeability of the membranes were compared with the experimental ones. The effect of considering pore size distribution instead of mean pore size to predict the water vapor permeability of the membranes was investigated.

  19. Communication: Activation energy of tension-induced pore formation in lipid membranes

    Science.gov (United States)

    Karal, Mohammad Abu Sayem; Yamazaki, Masahito

    2015-08-01

    Tension plays a vital role in pore formation in biomembranes, but the mechanism of pore formation remains unclear. We investigated the temperature dependence of the rate constant of constant tension (σ)-induced pore formation in giant unilamellar vesicles of lipid membranes using an experimental method we developed. By analyzing this result, we determined the activation energy (Ua) of tension-induced pore formation as a function of tension. A constant (U0) that does not depend on tension was found to contribute significantly to Ua. Analysis of the activation energy clearly indicated that the dependence of Ua on σ in the classical theory is correct, but that the classical theory of pore formation is not entirely correct due to the presence of U0. We can reasonably consider that U0 is a nucleation free energy to form a hydrophilic pre-pore from a hydrophobic pre-pore or a region with lower lateral lipid density. After obtaining U0, the evolution of a pre-pore follows a classical theory. Our data provide valuable information that help explain the mechanism of tension-induced pore formation in biomembranes and lipid membranes.

  20. Pore formation during C.W.Nd: YAG laser welding of aluminum alloys for automotive applications

    International Nuclear Information System (INIS)

    Pore formation is an important concern in laser welding of automotive aluminum alloys. This paper investigates the influence of the laser beam defocusing on pore formation during continuous wave Nd:YAG laser welding of aluminum automotive alloys 5182 and 5754. It was found that the instability of the keyhole during welding was a dominant cause of pore formation while hydrogen rejection played an insignificant role. The defocusing of the laser beam greatly affected the stability of the keyhole. Finally, the mechanism of the collapse of the keyhole and pore formation is proposed. (Author) 45 refs