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Sample records for prevent pore formation

  1. 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...... 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...

  2. Seismic attributes and advanced computer algorithm to predict formation pore pressure: Qalibah formation of Northwest Saudi Arabia

    Science.gov (United States)

    Nour, Abdoulshakour M.

    Oil and gas exploration professionals have long recognized the importance of predicting pore pressure before drilling wells. Pre-drill pore pressure estimation not only helps with drilling wells safely but also aids in the determination of formation fluids migration and seal integrity. With respect to the hydrocarbon reservoirs, the appropriate drilling mud weight is directly related to the estimated pore pressure in the formation. If the mud weight is lower than the formation pressure, a blowout may occur, and conversely, if it is higher than the formation pressure, the formation may suffer irreparable damage due to the invasion of drilling fluids into the formation. A simple definition of pore pressure is the pressure of the pore fluids in excess of the hydrostatic pressure. In this thesis, I investigated the utility of advance computer algorithm called Support Vector Machine (SVM) to learn the pattern of high pore pressure regime, using seismic attributes such as Instantaneous phase, t*Attenuation, Cosine of Phase, Vp/Vs ratio, P-Impedance, Reflection Acoustic Impedance, Dominant frequency and one well attribute (Mud-Weigh) as the learning dataset. I applied this technique to the over pressured Qalibah formation of Northwest Saudi Arabia. The results of my research revealed that in the Qalibah formation of Northwest Saudi Arabia, the pore pressure trend can be predicted using SVM with seismic and well attributes as the learning dataset. I was able to show the pore pressure trend at any given point within the geographical extent of the 3D seismic data from which the seismic attributes were derived. In addition, my results surprisingly showed the subtle variation of pressure within the thick succession of shale units of the Qalibah formation.

  3. Formation and decay of rudimentary penumbra around a pore

    Energy Technology Data Exchange (ETDEWEB)

    Watanabe, Hiroko [Unit of Synergetic Studies for Space, Kyoto University, Yamashina-ku, Kyoto 607-8417 (Japan); Kitai, Reizaburo [Kwasan and Hida Observatories, Kyoto University, Yamashina-ku, Kyoto 607-8417 (Japan); Otsuji, Kenichi, E-mail: watanabe@kwasan.kyoto-u.ac.jp [Solar Observatory, National Astronomical Observatory, Mitaka, Tokyo 181-8588 (Japan)

    2014-12-01

    We analyze the evolution of a pore in the active region NOAA 10940 using the data obtained by the Hinode satellite on 2007 February 3. The pore we analyzed showed the formation of a rudimentary penumbra structure, succeeded by an abrupt disappearance after about 5 hr. The pore had an approximate radius of 3.5 Mm and a total magnetic flux of 3.0 × 10{sup 19} Mx, which is a little smaller than the necessary magnetic flux for penumbral formation supposed by Rucklidge et al. (1-1.5 × 10{sup 20} Mx). Our observation describes a rare phenomenon which was in the unstable phase between a pore and a sunspot. The area of the dark umbra gradually decreased when the rudimentary penumbral filaments formed the penumbral structure, meaning that the penumbra develops at the expense of the umbral magnetic flux. This statement was confirmed by a rough estimation of the magnetic flux variation observed by the Hinode Fe I magnetogram. Five hours after the formation phase, the decay phase began. In this decaying phase, multiple opposite polarity patches are found to appear in the exterior of the pore (a different location from the penumbra formation site). We interpret these opposite polarities as signatures of the horizontal magnetic field, which preferably appears in the course of the unstable reconfiguration of the magnetic field structure. During the course of the disappearance of the penumbra, the horizontal penumbral field seems to become vertical because of the dark umbral area that recovered by about 10%.

  4. Nucleation in mesoscopic systems under transient conditions: Peptide-induced pore formation in vesicles

    Science.gov (United States)

    Zhdanov, Vladimir P.; Höök, Fredrik

    2013-04-01

    Attachment of lytic peptides to the lipid membrane of virions or bacteria is often accompanied by their aggregation and pore formation, resulting eventually in membrane rupture and pathogen neutralization. The membrane rupture may occur gradually via formation of many pores or abruptly after the formation of the first pore. In academic studies, this process is observed during interaction of peptides with lipid vesicles. We present an analytical model and the corresponding Monte Carlo simulations focused on the pore formation in such situations. Specifically, we calculate the time of the first nucleation-limited pore-formation event and show the distribution of this time in the regime when the fluctuations of the number of peptides attached to a vesicle are appreciable. The results obtained are used to clarify the mechanism of the pore formation and membrane destabilization observed recently during interaction of highly active α-helical peptide with sub-100-nm lipid vesicles that mimic enveloped viruses with nanoscale membrane curvature. The model proposed and the analysis presented are generic and may be applicable to other meso- and nanosystems.

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

    Science.gov (United States)

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

    2016-03-01

    Actinoporins (APs) from sea anemones are ~20 kDa pore forming toxins with a β-sandwich structure flanked by two α-helices. The molecular mechanism of APs pore formation is composed of several well-defined steps. APs bind to membrane by interfacial binding site composed of several aromatic amino acid residues that allow binding to phosphatidylcholine and specific recognition of sphingomyelin. Subsequently, the N-terminal α-helix from the β-sandwich has to be inserted into the lipid/water interphase in order to form a functional pore. Functional studies and single molecule imaging revealed that only several monomers, 3-4, oligomerise to form a functional pore. In this model the α-helices and surrounding lipid molecules build toroidal pore. In agreement, AP pores are transient and electrically heterogeneous. On the contrary, crystallized oligomers of actinoporin fragaceatoxin C were found to be composed of eight monomers with no lipids present between the adjacent α-helices. This article is part of a Special Issue entitled: Pore-Forming Toxins edited by Maur Dalla Serra and Franco Gambale. Copyright © 2015 Elsevier B.V. All rights reserved.

  6. Pore formation during C.W.Nd: YAG laser welding of aluminum alloys for automotive applications

    International Nuclear Information System (INIS)

    Pastor, M.; Zhao, H.; DebRoy, T.

    2000-01-01

    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

  7. 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

  8. Pore formation mechanism of porous poly(DL-lactic acid) matrix membrane

    Energy Technology Data Exchange (ETDEWEB)

    Phaechamud, Thawatchai, E-mail: tphaechamud011@yahoo.com; Chitrattha, Sasiprapa, E-mail: sasi_toey@hotmail.com

    2016-04-01

    Porous PLA structure has been widely used in cell transplantation, drug carrier and wound dressing. The porous structure can be controlled depending on the choice of the polymer, solvent, nonsolvent and preparation parameters. In this study, the porous PLA matrix membranes were prepared by adding PEG 400 in PLA solution using dichloromethane (DCM) as solvent prior to casting. The influence of other liquids as co-solvent on pore formation and the structural change during membrane formation were evaluated. The co-solvents affected both porous topography and mechanical properties of PLA membrane. The porous matrix were produced when the non-solvent of PLA was used as co-solvent. Cryo-SEM micrographs revealed that PEG 400 still remained in the PLA porous matrix membrane. From the tracking of the structural change during film formation, the PLA–PEG solution changed into porous structure by liquid liquid phase separation and solidification processes, respectively. Thermogravimetric analysis revealed that PLA–PEG in DCM solution exhibited the two-step of weight loss, the first step occurred from DCM evaporation and the second step occurred from the degradation of PLA–PEG matrix. The liquid–liquid phase separation and solidification started when the amount of DCM was higher than PEG 400 for 2.67 folds and DCM amount was equal to that of PEG 400, respectively. These results could clarify the pore formation mechanism of porous PLA membrane and will be useful for the further investigation and application. - Highlights: • Pore formation mechanism of PLA matrix membrane inducing by PEG 400 addition was investigated. • Cryo-scanning electron microscopy revealed the embedded PEG 400 in matrix membrane. • Tracking of structural change during membrane formation with stereomicroscope and thermogravimetric analysis could explain the pore formation mechanism. • Liquid-liquid phase separation of PLA-PEG 400 solution started when the amount of dichloromethane remained 2

  9. Pore formation mechanism of porous poly(DL-lactic acid) matrix membrane

    International Nuclear Information System (INIS)

    Phaechamud, Thawatchai; Chitrattha, Sasiprapa

    2016-01-01

    Porous PLA structure has been widely used in cell transplantation, drug carrier and wound dressing. The porous structure can be controlled depending on the choice of the polymer, solvent, nonsolvent and preparation parameters. In this study, the porous PLA matrix membranes were prepared by adding PEG 400 in PLA solution using dichloromethane (DCM) as solvent prior to casting. The influence of other liquids as co-solvent on pore formation and the structural change during membrane formation were evaluated. The co-solvents affected both porous topography and mechanical properties of PLA membrane. The porous matrix were produced when the non-solvent of PLA was used as co-solvent. Cryo-SEM micrographs revealed that PEG 400 still remained in the PLA porous matrix membrane. From the tracking of the structural change during film formation, the PLA–PEG solution changed into porous structure by liquid liquid phase separation and solidification processes, respectively. Thermogravimetric analysis revealed that PLA–PEG in DCM solution exhibited the two-step of weight loss, the first step occurred from DCM evaporation and the second step occurred from the degradation of PLA–PEG matrix. The liquid–liquid phase separation and solidification started when the amount of DCM was higher than PEG 400 for 2.67 folds and DCM amount was equal to that of PEG 400, respectively. These results could clarify the pore formation mechanism of porous PLA membrane and will be useful for the further investigation and application. - Highlights: • Pore formation mechanism of PLA matrix membrane inducing by PEG 400 addition was investigated. • Cryo-scanning electron microscopy revealed the embedded PEG 400 in matrix membrane. • Tracking of structural change during membrane formation with stereomicroscope and thermogravimetric analysis could explain the pore formation mechanism. • Liquid-liquid phase separation of PLA-PEG 400 solution started when the amount of dichloromethane remained 2

  10. Optimization of hybrid laser arc welding of 42CrMo steel to suppress pore formation

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Yan [Hunan University, State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body, Changsha (China); Hunan Institute of Science and Technology, College of Mechanical Engineering, Yueyang (China); Chen, Genyu; Mao, Shuai; Zhou, Cong; Chen, Fei [Hunan University, State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body, Changsha (China)

    2017-06-15

    The hybrid laser arc welding (HLAW) of 42CrMo quenched and tempered steel was conducted. The effect of the processing parameters, such as the relative positions of the laser and the arc, the shielding gas flow rate, the defocusing distance, the laser power, the wire feed rate and the welding speed, on the pore formation was analyzed, the morphological characteristics of the pores were analyzed using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The results showed that the majority of the pores were invasive. The pores formed at the leading a laser (LA) welding process were fewer than those at the leading a arc (AL) welding process. Increasing the shielding gas flow rate could also facilitate the reduction of pores. The laser power and the welding speed were two key process parameters to reduce the pores. The flow of the molten pool, the weld cooling rate and the pore escaping rate as a result of different parameters could all affect pore formation. An ideal pore-free weld was obtained for the optimal welding process parameters. (orig.)

  11. Biofilm formation on a TiO2 nanotube with controlled pore diameter and surface wettability

    International Nuclear Information System (INIS)

    Anitha, V C; Narayan Banerjee, Arghya; Woo Joo, Sang; Lee, Jin-Hyung; Lee, Jintae; Ki Min, Bong

    2015-01-01

    Titania (TiO 2 ) nanotube arrays (TNAs) with different pore diameters (140 − 20 nm) are fabricated via anodization using hydrofluoric acid (HF) containing ethylene glycol (EG) by changing the HF-to-EG volume ratio and the anodization voltage. To evaluate the effects of different pore diameters of TiO 2 nanotubes on bacterial biofilm formation, Shewanella oneidensis (S. oneidensis) MR-1 cells and a crystal-violet biofilm assay are used. The surface roughness and wettability of the TNA surfaces as a function of pore diameter, measured via the contact angle and AFM techniques, are correlated with the controlled biofilm formation. Biofilm formation increases with the decreasing nanotube pore diameter, and a 20 nm TiO 2 nanotube shows the maximum biofilm formation. The measurements revealed that 20 nm surfaces have the least hydrophilicity with the highest surface roughness of ∼17 nm and that they show almost a 90% increase in the effective surface area relative to the 140 nm TNAs, which stimulate the cells more effectively to produce the pili to attach to the surface for more biofilm formation. The results demonstrate that bacterial cell adhesion (and hence, biofilm formation) can effectively be controlled by tuning the roughness and wettability of TNAs via controlling the pore diameters of TNA surfaces. This biofilm formation as a function of the surface properties of TNAs can be a potential candidate for both medical applications and as electrodes in microbial fuel cells. (paper)

  12. Pore formation and occurrence in the organic-rich shales of the Triassic Chang-7 Member, Yanchang Formation, Ordos Basin, China

    Directory of Open Access Journals (Sweden)

    Chuang Er

    2016-12-01

    Full Text Available Shale-reservoir appraisal depends greatly on its pore characteristics (e.g., diameter, geometry, connectivity. Using a new pore-classification scheme based on the matrix type and occurrence state, four types of pores are identified in the organic-rich shales of the Triassic Chang-7 Member: intergranular, intragranular, organic pore, and microfracture. The intergranular pores are subdivided into primary pores between clastic grains, clay-mineral aggregates, and secondary dissolution pores between clastic grains or clay-mineral aggregates based on their origins, respectively. The intragranular pores are subdivided into secondary dissolved pores in feldspars, intra-clay-mineral aggregates and inter-pyrite. Organic pores include primarily microfractures in the organic matter and isolated organic pores. Microfracture is mainly developed along sandy and muddy laminations. Analysis by integration of data from pore imaging, low-temperature liquid nitrogen absorption, relationships between pore geometry and mineral components and between TOC and maturity of organic matter indicates that depositional environment, diagenesis, and thermal evolution of organic matter controlled the formation and preservation of pores. Organic-rich shales deposited in a deep and semi-deep lake environment contains thinly bedded turbidite sandstones, which are characterized by high content of clastic particles and thus favor the development of primary intergranular and intragranular pores, as well as microfractures along sandy laminations. During the early diagenesis process, precipitation of pyrite favors the development of inter-pyrite pores. However, compaction reduced the diameter and bulk pore volume. Organic pore has been greatly reduced under compaction. Dissolution led to formation of both inter and intra-feldspar pores, which has improved reservoir quality to some extent. Organic pore started to develop after shale maturity reaches a threshold (RO = 0

  13. Pore-scale studies of multiphase flow and reaction involving CO2 sequestration in geologic formations

    Science.gov (United States)

    Kang, Q.; Wang, M.; Lichtner, P. C.

    2008-12-01

    In geologic CO2 sequestration, pore-scale interfacial phenomena ultimately govern the key processes of fluid mobility, chemical transport, adsorption, and reaction. However, spatial heterogeneity at the pore scale cannot be resolved at the continuum scale, where averaging occurs over length scales much larger than typical pore sizes. Natural porous media, such as sedimentary rocks and other geological media encountered in subsurface formations, are inherently heterogeneous. This pore-scale heterogeneity can produce variabilities in flow, transport, and reaction processes that take place within a porous medium, and can result in spatial variations in fluid velocity, aqueous concentrations, and reaction rates. Consequently, the unresolved spatial heterogeneity at the pore scale may be important for reactive transport modeling at the larger scale. In addition, current continuum models of surface complexation reactions ignore a fundamental property of physical systems, namely conservation of charge. Therefore, to better understand multiphase flow and reaction involving CO2 sequestration in geologic formations, it is necessary to quantitatively investigate the influence of the pore-scale heterogeneity on the emergent behavior at the field scale. We have applied the lattice Boltzmann method to simulating the injection of CO2 saturated brine or supercritical CO2 into geological formations at the pore scale. Multiple pore-scale processes, including advection, diffusion, homogeneous reactions among multiple aqueous species, heterogeneous reactions between the aqueous solution and minerals, ion exchange and surface complexation, as well as changes in solid and pore geometry are all taken into account. The rich pore scale information will provide a basis for upscaling to the continuum scale.

  14. Type IIA photosensitivity and formation of pores in optical fibers under intense ultraviolet irradiation

    International Nuclear Information System (INIS)

    Kukushkin, S. A.; Shlyagin, M. G.; Swart, P. L.; Chtcherbakov, A. A.; Osipov, A. V.

    2007-01-01

    Formation of the type IIA Bragg gratings in germanosilicate optical fibers is studied. We report the observation of such a type of gratings in the standard single-mode fiber (Corning SMF-28) under different experimental conditions. A mechanism for the type IIA photosensitivity in optical fibers is proposed which is based on nucleation and evolution of pores from vacancy-type defects in fiber areas where a high level of mechanical stress is induced under intense ultraviolet (UV) light. Evolution of fiber core temperature under influence of a single 20 ns light pulse from a KrF excimer laser was measured and compared with theoretical calculations. It was shown that transient thermoinduced stress in the fiber core can achieve a level sufficient for effective nucleation of pores. A theory describing formation of pores in optical fibers has been developed and was used to estimate the pore nucleation rate, concentration, and other parameters of pore evolution for different levels of UV fluence and fiber core stress

  15. FORMATION OF PORES ASSOCIATED WITH THE INFLOW OF MOVING MAGNETIC FEATURES

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xiaobo; Yang, Zhiliang [Department of Astronomy, Beijing Normal University, No. 19, XinJieKouWai St., HaiDian District, Beijing 100875 (China); Zhang, Hongqi, E-mail: zlyang@bnu.edu.cn [Key Laboratory of Solar Activity, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China)

    2015-07-10

    We investigate the formation of pores in NOAA AR 10930 associated with the inflow of moving magnetic features (MMFs) using simultaneous Hinode/Solar Optical Telescope filtergrams and magnetograms. The main results are outlined as follows: (1) the existence of MMFs around pores is a fairly common phenomenon. Around the four innate and one residue pores investigated, there are obvious inflows of MMFs during the pores’ growth phase. (2) The observed magnetic flux transport conveyed by MMFs is strongly correlated with the change in the pore’s flux content, and therefore reflects the pore’s growth and decay. The concentration and dissolution of the pores are direct results of the local convergence and convection of sunspots’ magnetic outflow. (3) The most common source of MMF flows into pores are produced near sunspots and move along the connection lines between the sunspots’ penumbrae and the pores. These monopolar and bipolar magnetic elements are either fragments from the penumbra or continuations of penumbral fibrils. Pores also merge dissociated elements and receive flows produced by small-scale bipolar emergence. MMF inflows that diminish a pore’s magnetic flux often trigger chromospheric bright points. (4) In their decay phase, the pores release outflows of magnetic elements. The distribution of flows around pores is asymmetrical: the inflow is concentrated on the side facing the parent sunspot, while the outflow is generally concentrated on the opposite side. A pore’s outflow is also part of the process of decomposing and removing of the active region’s magnetic field.

  16. Positron lifetimes at the initial stage of pore formation in Vycor glass

    CERN Document Server

    Jasinska, B; Goworek, T

    2000-01-01

    The formation of narrow pores during leaching of Vycor glass by sulphuric acid was investigated using the positron lifetime technique. During the leaching process the pore diameter remained roughly constant (except for the case of cold leaching). The time of processing changed the total length of capillaries, but not their number; at the temperature 50 deg. C during 20 min of leaching the average leaching depth was 24 mu m.

  17. Numerical investigation of micro-pore formation during substrate impact of molten droplets in spraying processes

    International Nuclear Information System (INIS)

    Liu, H.; Lavernia, E.J.; Rangel, R.H.; Muehlberger, E.; Sickinger, A.

    1994-01-01

    The porosity that is commonly associated with discrete droplet processes, such as plasma spraying and spray deposition, effectively degrades the quality of the sprayed material. In the present study, micro-pore formation during the deformation and interaction of molten tungsten droplets impinging onto a flat substrate in spraying processes is numerically investigated. The numerical simulation is accomplished on the basis of the full Navier-Stokes equations and the Volume Of Fluid (VOF) function by using a 2-domain method for the thermal field and solidification problem and a two-phase flow continuum model for the flow problem with a growing solid layer. The possible mechanisms governing the formation of micro-pores are discussed. The effects of important processing parameters, such as droplet impact velocity, droplet temperature, substrate temperature, and droplet viscosity, on the micro-pore formation are addressed

  18. Two-Step Mechanism of Membrane Disruption by Aβ through Membrane Fragmentation and Pore Formation

    Science.gov (United States)

    Sciacca, Michele F.M.; Kotler, Samuel A.; Brender, Jeffrey R.; Chen, Jennifer; Lee, Dong-kuk; Ramamoorthy, Ayyalusamy

    2012-01-01

    Disruption of cell membranes by Aβ is believed to be one of the key components of Aβ toxicity. However, the mechanism by which this occurs is not fully understood. Here, we demonstrate that membrane disruption by Aβ occurs by a two-step process, with the initial formation of ion-selective pores followed by nonspecific fragmentation of the lipid membrane during amyloid fiber formation. Immediately after the addition of freshly dissolved Aβ1–40, defects form on the membrane that share many of the properties of Aβ channels originally reported from single-channel electrical recording, such as cation selectivity and the ability to be blockaded by zinc. By contrast, subsequent amyloid fiber formation on the surface of the membrane fragments the membrane in a way that is not cation selective and cannot be stopped by zinc ions. Moreover, we observed that the presence of ganglioside enhances both the initial pore formation and the fiber-dependent membrane fragmentation process. Whereas pore formation by freshly dissolved Aβ1–40 is weakly observed in the absence of gangliosides, fiber-dependent membrane fragmentation can only be observed in their presence. These results provide insights into the toxicity of Aβ and may aid in the design of specific compounds to alleviate the neurodegeneration of Alzheimer’s disease. PMID:22947931

  19. Effect of pores formation process and oxygen plasma treatment to hydroxyapatite formation on bioactive PEEK prepared by incorporation of precursor of apatite.

    Science.gov (United States)

    Yabutsuka, Takeshi; Fukushima, Keito; Hiruta, Tomoko; Takai, Shigeomi; Yao, Takeshi

    2017-12-01

    When bioinert substrates with fine-sized pores are immersed in a simulated body fluid (SBF) and the pH value or the temperature is increased, fine particles of calcium phosphate, which the authors denoted as 'precursor of apatite' (PrA), are formed in the pores. By this method, hydroxyapatite formation ability can be provided to various kinds of bioinert materials. In this study, the authors studied fabrication methods of bioactive PEEK by using the above-mentioned process. First, the fine-sized pores were formed on the surface of the PEEK substrate by H 2 SO 4 treatment. Next, to provide hydrophilic property to the PEEK, the surfaces of the PEEK were treated with O 2 plasma. Finally, PrA were formed in the pores by the above-mentioned process, which is denoted as 'Alkaline SBF' treatment, and the bioactive PEEK was obtained. By immersing in SBF with the physiological condition, hydroxyapatite formation was induced on the whole surface of the substrate within 1day. The formation of PrA directly contributed to hydroxyapatite formation ability. By applying the O 2 plasma treatment, hydroxyapatite formation was uniformly performed on the whole surface of the substrate. The H 2 SO 4 treatment contributed to a considerable enhancement of adhesive strength of the formed hydroxyapatite layer formed in SBF because of the increase of surface areas of the substrate. As a comparative study, the sandblasting method was applied as the pores formation process instead of the H 2 SO 4 treatment. Although hydroxyapatite formation was provided also in this case, however, the adhesion of the formed hydroxyapatite layer to the substrate was not sufficient even if the O 2 plasma treatment was conducted. This result indicates that the fine-sized pores should be formed on the whole surface of the substrate uniformly to achieve high adhesive strength of the hydroxyapatite layer. Therefore, it is considered that the H 2 SO 4 treatment before the O 2 plasma and the 'Alkaline SBF' treatment

  20. Controls of Ca/Mg/Fe activity ratios in pore water chemistry models of the Callovian-Oxfordian clay formation

    International Nuclear Information System (INIS)

    Lerouge, C.; Grangeon, S.; Wille, G.; Flehoc, C.; Gailhanou, H.; Gaucher, E.C.; Tournassat, C.; Vinsot, A.; Made, B.; Altmann, S.

    2013-01-01

    In the pore water chemistry model of the Callovian-Oxfordian clay formation, the divalent cations Ca, Mg, and Fe are controlled by equilibrium reactions with pure carbonates: calcite for Ca, dolomite for Mg, and siderite for Fe. Results of a petrological study and computing of the Ca/Mg and Ca/Fe activity ratios based on natural pore water chemistry provide evidence that equilibrium with pure calcite and pure dolomite is a reasonable assumption for undisturbed pore waters; on the other hand, siderite cannot be considered at equilibrium with pore waters at the formation scale. (authors)

  1. Controls of Ca/Mg/Fe activity ratios in pore water chemistry models of the Callovian-Oxfordian clay formation

    Energy Technology Data Exchange (ETDEWEB)

    Lerouge, C.; Grangeon, S.; Wille, G.; Flehoc, C.; Gailhanou, H.; Gaucher, E.C.; Tournassat, C. [BRGM av. Claude Guillemin BP6009 45060 Orleans cedex 2 (France); Vinsot, A. [ANDRA Meuse/Haute-Marne Underground research Laboratory (URL), RD 960, 55290 Bure (France); Made, B.; Altmann, S. [ANDRA - Parc de la Croix Blanche, 1-7 rue Jean Monnet, 92298 Chatenay-Malabry Cedex (France)

    2013-07-01

    In the pore water chemistry model of the Callovian-Oxfordian clay formation, the divalent cations Ca, Mg, and Fe are controlled by equilibrium reactions with pure carbonates: calcite for Ca, dolomite for Mg, and siderite for Fe. Results of a petrological study and computing of the Ca/Mg and Ca/Fe activity ratios based on natural pore water chemistry provide evidence that equilibrium with pure calcite and pure dolomite is a reasonable assumption for undisturbed pore waters; on the other hand, siderite cannot be considered at equilibrium with pore waters at the formation scale. (authors)

  2. A model of lipid rearrangements during pore formation in the DPPC lipid bilayer.

    Science.gov (United States)

    Wrona, Artur; Kubica, Krystian

    2017-07-10

    The molecular bases of pore formation in the lipid bilayer remain unclear, as do the exact characteristics of their sizes and distributions. To understand this process, numerous studies have been performed on model lipid membranes including cell-sized giant unilamellar vesicles (GUV). The effect of an electric field on DPPC GUV depends on the lipid membrane state: in the liquid crystalline phase the created pores have a cylinder-like shape, whereas in the gel phase a crack has been observed. The aim of the study was to investigate the geometry of pores created in a lipid bilayer in gel and liquid crystalline phases in reference to literature experimental data. A mathematical model of the pore in a DPPC lipid bilayer developed based on the law of conservation of mass and the assumption of constant volume of lipid molecules, independent of their conformation, allows for analysis of pore shape and accompanying molecular rearrangements. The membrane area occupied by the pore of a cylinder-like shape is greater than the membrane area occupied by lipid molecules creating the pore structure (before pore appearance). Creation of such pores requires more space, which can be achieved by conformational changes of lipid chains toward a more compact state. This process is impossible for a membrane in the most compact, gel phase. We show that the geometry of the pores formed in the lipid bilayer in the gel phase must be different from the cylinder shape formed in the lipid bilayer in a liquid crystalline state, confirming experimental studies. Furthermore, we characterize the occurrence of the 'buffer' zone surrounding pores in the liquid crystalline phase as a mechanism of separation of neighbouring pores.

  3. 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.

  4. A new model for pore formation by cholesterol-dependent cytolysins.

    Directory of Open Access Journals (Sweden)

    Cyril F Reboul

    2014-08-01

    Full Text Available Cholesterol Dependent Cytolysins (CDCs are important bacterial virulence factors that form large (200-300 Å membrane embedded pores in target cells. Currently, insights from X-ray crystallography, biophysical and single particle cryo-Electron Microscopy (cryo-EM experiments suggest that soluble monomers first interact with the membrane surface via a C-terminal Immunoglobulin-like domain (Ig; Domain 4. Membrane bound oligomers then assemble into a prepore oligomeric form, following which the prepore assembly collapses towards the membrane surface, with concomitant release and insertion of the membrane spanning subunits. During this rearrangement it is proposed that Domain 2, a region comprising three β-strands that links the pore forming region (Domains 1 and 3 and the Ig domain, must undergo a significant yet currently undetermined, conformational change. Here we address this problem through a systematic molecular modeling and structural bioinformatics approach. Our work shows that simple rigid body rotations may account for the observed collapse of the prepore towards the membrane surface. Support for this idea comes from analysis of published cryo-EM maps of the pneumolysin pore, available crystal structures and molecular dynamics simulations. The latter data in particular reveal that Domains 1, 2 and 4 are able to undergo significant rotational movements with respect to each other. Together, our data provide new and testable insights into the mechanism of pore formation by CDCs.

  5. Proton Tracks and Formation of Pores in Poly[Diethylene Glycol Bis-(Allyl Carbonate)

    CERN Document Server

    Oganesyan, V R; Danziger, M; Hermsdorf, D; Orelovich, O L

    2004-01-01

    Modern dosimetry needs effective detectors to register light ions, especially those having energies down to 10 MeV/a.m.u. That is why in the research in hand we pay attention to development of materials for such a task. In this work the most effective detector CR-39 irradiated with low-energy protons was applied. A full analysis from opening to final formation of a pore was made with the help of sensitive electrolytic ething and electron scanning microscopy. Successive process of track breakthroughs was observed. The shape of the pore and corresponding parameters of its formation provide simulation of the process. Etching rates and factor of selectivity were determined. The influence of energy losses on geometry was noted.

  6. Proton tracks and formation of pores in poly[diethylene glycol bis-(allyl carbonate)

    International Nuclear Information System (INIS)

    Oganesyan, V.R.; Trofimov, V.V.; Orelovich, O.L.; Danziger, M.; Hermsdorf, D.

    2004-01-01

    Modern dosimetry needs effective detectors to register light ions, especially those having energies down to 10 MeV/a.m.a. That is why in the research in hand we pay attention to development of materials for such a task. In this work the most effective detector CR-39 irradiated with low-energy protons was applied. A full analysis from opening to final formation of a pore was made with the help of sensitive electrolytic etching and electron scanning microscopy. Successive process of track breakthroughs was observed. The shape of the pore and corresponding parameters of its formation provide simulation of the process. Etching rates and factor of selectivity were determined. The influence of energy losses on geometry was noted

  7. Fractal Characteristics of Pores in Taiyuan Formation Shale from Hedong Coal Field, China

    Science.gov (United States)

    Li, Kunjie; Zeng, Fangui; Cai, Jianchao; Sheng, Guanglong; Xia, Peng; Zhang, Kun

    For the purpose of investigating the fractal characteristics of pores in Taiyuan formation shale, a series of qualitative and quantitative experiments were conducted on 17 shale samples from well HD-1 in Hedong coal field of North China. The results of geochemical experiments show that Total organic carbon (TOC) varies from 0.67% to 5.32% and the organic matters are in the high mature or over mature stage. The shale samples consist mainly of clay minerals and quartz with minor pyrite and carbonates. The FE-SEM images indicate that three types of pores, organic-related pores, inorganic-related pores and micro-fractures related pores, are developed well, and a certain number of intragranular pores are found inside quartz and carbonates formed by acid liquid corrosion. The pore size distributions (PSDs) broadly range from several to hundreds nanometers, but most pores are smaller than 10nm. As the result of different adsorption features at relative pressure (0-0.5) and (0.5-1) on the N2 adsorption isotherm, two fractal dimensions D1 and D2 were obtained with the Frenkel-Halsey-Hill (FHH) model. D1 and D2 vary from 2.4227 to 2.6219 and from 2.6049 to 2.7877, respectively. Both TOC and brittle minerals have positive effect on D1 and D2, whereas clay minerals, have a negative influence on them. The fractal dimensions are also influenced by the pore structure parameters, such as the specific surface area, BJH pore volume, etc. Shale samples with higher D1 could provide more adsorption sites leading to a greater methane adsorption capacity, whereas shale samples with higher D2 have little influence on methane adsorption capacity.

  8. An inverse-source problem for maximization of pore-fluid oscillation within poroelastic formations

    KAUST Repository

    Jeong, C.; Kallivokas, L. F.

    2016-01-01

    This paper discusses a mathematical and numerical modeling approach for identification of an unknown optimal loading time signal of a wave source, atop the ground surface, that can maximize the relative wave motion of a single-phase pore fluid within fluid-saturated porous permeable (poroelastic) rock formations, surrounded by non-permeable semi-infinite elastic solid rock formations, in a one-dimensional setting. The motivation stems from a set of field observations, following seismic events and vibrational tests, suggesting that shaking an oil reservoir is likely to improve oil production rates. This maximization problem is cast into an inverse-source problem, seeking an optimal loading signal that minimizes an objective functional – the reciprocal of kinetic energy in terms of relative pore-fluid wave motion within target poroelastic layers. We use the finite element method to obtain the solution of the governing wave physics of a multi-layered system, where the wave equations for the target poroelastic layers and the elastic wave equation for the surrounding non-permeable layers are coupled with each other. We use a partial-differential-equation-constrained-optimization framework (a state-adjoint-control problem approach) to tackle the minimization problem. The numerical results show that the numerical optimizer recovers optimal loading signals, whose dominant frequencies correspond to amplification frequencies, which can also be obtained by a frequency sweep, leading to larger amplitudes of relative pore-fluid wave motion within the target hydrocarbon formation than other signals.

  9. An inverse-source problem for maximization of pore-fluid oscillation within poroelastic formations

    KAUST Repository

    Jeong, C.

    2016-07-04

    This paper discusses a mathematical and numerical modeling approach for identification of an unknown optimal loading time signal of a wave source, atop the ground surface, that can maximize the relative wave motion of a single-phase pore fluid within fluid-saturated porous permeable (poroelastic) rock formations, surrounded by non-permeable semi-infinite elastic solid rock formations, in a one-dimensional setting. The motivation stems from a set of field observations, following seismic events and vibrational tests, suggesting that shaking an oil reservoir is likely to improve oil production rates. This maximization problem is cast into an inverse-source problem, seeking an optimal loading signal that minimizes an objective functional – the reciprocal of kinetic energy in terms of relative pore-fluid wave motion within target poroelastic layers. We use the finite element method to obtain the solution of the governing wave physics of a multi-layered system, where the wave equations for the target poroelastic layers and the elastic wave equation for the surrounding non-permeable layers are coupled with each other. We use a partial-differential-equation-constrained-optimization framework (a state-adjoint-control problem approach) to tackle the minimization problem. The numerical results show that the numerical optimizer recovers optimal loading signals, whose dominant frequencies correspond to amplification frequencies, which can also be obtained by a frequency sweep, leading to larger amplitudes of relative pore-fluid wave motion within the target hydrocarbon formation than other signals.

  10. Pore Formation Process of Porous Ti3SiC2 Fabricated by Reactive Sintering

    Directory of Open Access Journals (Sweden)

    Huibin Zhang

    2017-02-01

    Full Text Available Porous Ti3SiC2 was fabricated with high purity, 99.4 vol %, through reactive sintering of titanium hydride (TiH2, silicon (Si and graphite (C elemental powders. The reaction procedures and the pore structure evolution during the sintering process were systematically studied by X-ray diffraction (XRD and scanning electron microscope (SEM. Our results show that the formation of Ti3SiC2 from TiH2/Si/C powders experienced the following steps: firstly, TiH2 decomposed into Ti; secondly, TiC and Ti5Si3 intermediate phases were generated; finally, Ti3SiC2 was produced through the reaction of TiC, Ti5Si3 and Si. The pores formed in the synthesis procedure of porous Ti3SiC2 ceramics are derived from the following aspects: interstitial pores left during the pressing procedure; pores formed because of the TiH2 decomposition; pores formed through the reactions between Ti and Si and Ti and C powders; and the pores produced accompanying the final phase synthesized during the high temperature sintering process.

  11. Cell-fusion method to visualize interphase nuclear pore formation.

    Science.gov (United States)

    Maeshima, Kazuhiro; Funakoshi, Tomoko; Imamoto, Naoko

    2014-01-01

    In eukaryotic cells, the nucleus is a complex and sophisticated organelle that organizes genomic DNA to support essential cellular functions. The nuclear surface contains many nuclear pore complexes (NPCs), channels for macromolecular transport between the cytoplasm and nucleus. It is well known that the number of NPCs almost doubles during interphase in cycling cells. However, the mechanism of NPC formation is poorly understood, presumably because a practical system for analysis does not exist. The most difficult obstacle in the visualization of interphase NPC formation is that NPCs already exist after nuclear envelope formation, and these existing NPCs interfere with the observation of nascent NPCs. To overcome this obstacle, we developed a novel system using the cell-fusion technique (heterokaryon method), previously also used to analyze the shuttling of macromolecules between the cytoplasm and the nucleus, to visualize the newly synthesized interphase NPCs. In addition, we used a photobleaching approach that validated the cell-fusion method. We recently used these methods to demonstrate the role of cyclin-dependent protein kinases and of Pom121 in interphase NPC formation in cycling human cells. Here, we describe the details of the cell-fusion approach and compare the system with other NPC formation visualization methods. Copyright © 2014 Elsevier Inc. All rights reserved.

  12. Reovirus FAST Proteins Drive Pore Formation and Syncytiogenesis Using a Novel Helix-Loop-Helix Fusion-Inducing Lipid Packing Sensor.

    Directory of Open Access Journals (Sweden)

    Jolene Read

    2015-06-01

    Full Text Available Pore formation is the most energy-demanding step during virus-induced membrane fusion, where high curvature of the fusion pore rim increases the spacing between lipid headgroups, exposing the hydrophobic interior of the membrane to water. How protein fusogens breach this thermodynamic barrier to pore formation is unclear. We identified a novel fusion-inducing lipid packing sensor (FLiPS in the cytosolic endodomain of the baboon reovirus p15 fusion-associated small transmembrane (FAST protein that is essential for pore formation during cell-cell fusion and syncytiogenesis. NMR spectroscopy and mutational studies indicate the dependence of this FLiPS on a hydrophobic helix-loop-helix structure. Biochemical and biophysical assays reveal the p15 FLiPS preferentially partitions into membranes with high positive curvature, and this partitioning is impeded by bis-ANS, a small molecule that inserts into hydrophobic defects in membranes. Most notably, the p15 FLiPS can be functionally replaced by heterologous amphipathic lipid packing sensors (ALPS but not by other membrane-interactive amphipathic helices. Furthermore, a previously unrecognized amphipathic helix in the cytosolic domain of the reptilian reovirus p14 FAST protein can functionally replace the p15 FLiPS, and is itself replaceable by a heterologous ALPS motif. Anchored near the cytoplasmic leaflet by the FAST protein transmembrane domain, the FLiPS is perfectly positioned to insert into hydrophobic defects that begin to appear in the highly curved rim of nascent fusion pores, thereby lowering the energy barrier to stable pore formation.

  13. Effect of Fe- and Si-Enriched Secondary Precipitates and Surface Roughness on Pore Formation on Aluminum Plate Surfaces During Anodizing

    Science.gov (United States)

    Zhu, Yuanzhi; Wang, Shizhi; Yang, Qingda; Zhou, Feng

    2014-09-01

    Two twin roll casts (TRCs) and one hot rolled (HR) AA 1235 aluminum alloy plates with different microstructures are prepared. The plates were electrolyzed in a 1.2 wt% HCl solution with a voltage of 21 V and a current of 1.9 mA. The shape, size, and number of pores formed on the surfaces of these plates were analyzed and correlated with the microstructures of the plates. It is found that pores are easier to form on the alloy plates containing subgrains with a lower dislocation density inside the subgrains, rather than along the grain boundaries. Furthermore, Fe- and Si-enriched particles in the AA1235 aluminum alloys lead to the formation of pores on the surface during electrolyzing; the average precipitate sizes of 4, 3.5, and 2 μm in Alloy 1#, Alloy 2# and Alloy 3# result in the average pore sizes of 3.78, 2.76, and 1.9 μm on the surfaces of the three alloys, respectively; The G.P zone in the alloy also facilitates the surface pore formation. High-surface roughness enhances the possibility of entrapping more lubricants into the plate surface, which eventually blocks the formation of the pores on the surface of the aluminum plates in the following electrolyzing process.

  14. Characterization of lacustrine shale pore structure: The Upper-Triassic Yanchang Formation, Ordos Basin, China

    Directory of Open Access Journals (Sweden)

    Yuxi Yu

    2016-08-01

    Full Text Available Amounts of silty laminae in continental shale gas reservoir were investigated in the Zhangjiatan shale of the Yanchang Formation, Ordos Basin. The purpose of this study is to provide awareness in terms of the nature and discrepancies in pore structure between silty laminae and clayey laminae. By mechanically separating the silty laminae from the shale core, a combination measurement series of mercury injection capillary pressure, N2 adsorption, and carbon dioxide adsorption were performed on the aforementioned two parts. An integrated pore size distribution, with a pore diameter range of 0.1 nm-100 μm, was obtained by using appropriate sample particle size and calculation model. The comparative analysis of the pore structure shows that the clayey laminae are dominated by mesopore and micropore; meanwhile, the silty laminae are dominated by macropore alone. The pore volume distribution in clayey laminae is sorted as mesopore volume > micropore volume > macropore volume, on the other hand, for silty laminae it is macropore volume > mesopore volume > micropore volume. The averaged total pore volume of silty laminae is 2.02 cc/100 g, and for clayey laminae, it is 1.41 cc/100 g. The porosity of silty laminae is 5.40%, which is greater than that of clayey laminae's 3.67%. Since silty laminae have larger pore width and pore space, they are more permeable and porous than the clayey laminae; it also acts as a favorable conduit and reservoir for shale gas.

  15. An alternative explanation for evidence that xenon depletion, pore formation, and grain subdivision begin at different local burnups

    International Nuclear Information System (INIS)

    Rest, J.; Hofman, G.L.

    2000-01-01

    In order to interpret the recent observation that xenon depletion, pore formation, and grain subdivision occur successively at increasing local burnups, a rate-theory-based model is used to investigate the nucleation and growth of cavities during low-temperature irradiation of UO 2 in the presence of irradiation-induced interstitial-loop formation and growth. Consolidation of the dislocation structure takes into account the generation of forest dislocations and capture of interstitial dislocation loops. The loops accumulate and ultimately evolve into a low-energy cellular dislocation structure. The cell walls have been previously identified as recrystallization nuclei. The calculations indicate that nanometer-size bubbles are associated with this cellular dislocation structure while the observed micron-size bubbles are presumed to be either preexisting pores deformed by adjacent grains and/or new pores formed in the new recrystallized grain-boundary junctions. Subsequent to recrystallization, gas released from the recrystallized grains feeds the preexisting pores and the recrystallized grains may appear to form a preferential concentration of subdivided grains around the growing pores. This picture is illustrated in a sequence of photomicrographs of irradiated U 3 O 8

  16. High Structural Stability of Textile Implants Prevents Pore Collapse and Preserves Effective Porosity at Strain

    Directory of Open Access Journals (Sweden)

    Uwe Klinge

    2015-01-01

    Full Text Available Reinforcement of tissues by use of textiles is encouraged by the reduced rate of recurrent tissue dehiscence but for the price of an inflammatory and fibrotic tissue reaction to the implant. The latter mainly is affected by the size of the pores, whereas only sufficiently large pores are effective in preventing a complete scar entrapment. Comparing two different sling implants (TVT and SIS, which are used for the treatment of urinary incontinence, we can demonstrate that the measurement of the effective porosity reveals considerable differences in the textile construction. Furthermore the changes of porosity after application of a tensile load can indicate a structural instability, favouring pore collapse at stress and questioning the use for purposes that are not “tension-free.”

  17. Experimental on moisture migration and pore pressure formation of concrete members subjected to high temperature

    International Nuclear Information System (INIS)

    Nagao, Kakuhiro; Nakane, Sunao

    1993-01-01

    The experimental studies concerning temperature, moisture migration, and pore pressure of mass concrete mock-up specimens heated up to high temperature at 110degC to 600degC, were performed, so as to correctly estimate the moisture migration behaviour of concrete members subjected to high temperature, which is considered significantly influenced on physical properties of concrete. As a results, it is confirmed that the moisture migration behavior of concrete members can be explained by temperature and pore pressure, and indicate the characteristics both sealed condition (dissipation of moisture is prevented) and unsealed condition (dissipation of moisture occur). (author)

  18. Inner/Outer nuclear membrane fusion in nuclear pore assembly: biochemical demonstration and molecular analysis.

    Science.gov (United States)

    Fichtman, Boris; Ramos, Corinne; Rasala, Beth; Harel, Amnon; Forbes, Douglass J

    2010-12-01

    Nuclear pore complexes (NPCs) are large proteinaceous channels embedded in double nuclear membranes, which carry out nucleocytoplasmic exchange. The mechanism of nuclear pore assembly involves a unique challenge, as it requires creation of a long-lived membrane-lined channel connecting the inner and outer nuclear membranes. This stabilized membrane channel has little evolutionary precedent. Here we mapped inner/outer nuclear membrane fusion in NPC assembly biochemically by using novel assembly intermediates and membrane fusion inhibitors. Incubation of a Xenopus in vitro nuclear assembly system at 14°C revealed an early pore intermediate where nucleoporin subunits POM121 and the Nup107-160 complex were organized in a punctate pattern on the inner nuclear membrane. With time, this intermediate progressed to diffusion channel formation and finally to complete nuclear pore assembly. Correct channel formation was blocked by the hemifusion inhibitor lysophosphatidylcholine (LPC), but not if a complementary-shaped lipid, oleic acid (OA), was simultaneously added, as determined with a novel fluorescent dextran-quenching assay. Importantly, recruitment of the bulk of FG nucleoporins, characteristic of mature nuclear pores, was not observed before diffusion channel formation and was prevented by LPC or OA, but not by LPC+OA. These results map the crucial inner/outer nuclear membrane fusion event of NPC assembly downstream of POM121/Nup107-160 complex interaction and upstream or at the time of FG nucleoporin recruitment.

  19. Optical study of the ultrasonic formation process of noble metal nanoparticles dispersed inside the pores of monolithic mesoporous silica

    CERN Document Server

    Fu Gan Hua; Kan Cai Xia; Li Cun Cheng; Fang Qi

    2003-01-01

    Gold nanoparticles dispersed inside the pores of monolithic mesoporous silica were prepared by soaking the silica in a gold (III) ion solution and subsequent ultrasound irradiation. The formation process of gold nanoparticles in the pores of mesoporous silica was investigated based on optical measurements of wrapped and naked soaked silica after ultrasonic irradiation, and the reduction rate effect in solution and pre-soaking effect. It has been shown that acoustic cavitation cannot occur in nano-sized pores. The gold nanoparticles in silica are not formed in situ within the pores but produced mainly by diffusion of the gold clusters formed in the solution during irradiation into the pores. The radicals formed in solution are exhausted before entering the pores of silica. There exists a critical reduction rate in solution, at which the yield of gold nanoparticles in silica reaches a maximum, and above which there is a decrease in the yield. This is attributed to too quick a growth or aggregation of gold clust...

  20. Study of shale reservoir nanometer-sized pores in Member 1 of Shahejie Formation in JX area, Liaozhong sag

    Science.gov (United States)

    Cheng, Yong; Zhang, Yu; Wen, Yiming

    2018-02-01

    The microscopic pore structure is the key of the shale reservoir study; however, traditional Scanning Electron Microscopy (SEM) methods cannot identify the irregular morphology caused by mechanical polishing. In this work, Scanning Electron Microscopy combined argon ion polishing technology was taken to study the characteristics of shale reservoir pores of Member 1 of Shahejie Formation (E3s1) located in JX1-1 area of Liaozhong Sag. The results show that pores between clay platelets, intraplatelet pores within clay aggregates and organic-matter pores are very rich in the area and with good pore connectivity, so these types of pores are of great significance for oil-gas exporation. Pores between clay platelets are formed by directional or semi-directional contact between edge and surface, edge and edge or surface and surface of laminated clay minerals, whose shapes are linear, mesh, and irregular with the size of 500 nm to 5 μm. The intraplatelet pores within clay aggregates are formed in the process of the transformation and compaction of clay minerals, whose shapes are usually linear with the width of 30 to 500 nm and the length of 2 to 50 μm. The organic-matter pores are from the process of the conversion from organic matters to the hydrocarbon under thermal evolution, whose shapes are gneissic, irregular, pitted and elliptical with the size of 100 nm to 2 μm. This study is of certain guiding significance to selecting target zones, evaluating resource potential and exploring & developing of shale gas in this region.

  1. Measuring kinetic drivers of pneumolysin pore structure.

    Science.gov (United States)

    Gilbert, Robert J C; Sonnen, Andreas F-P

    2016-05-01

    Most membrane attack complex-perforin/cholesterol-dependent cytolysin (MACPF/CDC) proteins are thought to form pores in target membranes by assembling into pre-pore oligomers before undergoing a pre-pore to pore transition. Assembly during pore formation is into both full rings of subunits and incomplete rings (arcs). The balance between arcs and full rings is determined by a mechanism dependent on protein concentration in which arc pores arise due to kinetic trapping of the pre-pore forms by the depletion of free protein subunits during oligomerization. Here we describe the use of a kinetic assay to study pore formation in red blood cells by the MACPF/CDC pneumolysin from Streptococcus pneumoniae. We show that cell lysis displays two kinds of dependence on protein concentration. At lower concentrations, it is dependent on the pre-pore to pore transition of arc oligomers, which we show to be a cooperative process. At higher concentrations, it is dependent on the amount of pneumolysin bound to the membrane and reflects the affinity of the protein for its receptor, cholesterol. A lag occurs before cell lysis begins; this is dependent on oligomerization of pneumolysin. Kinetic dissection of cell lysis by pneumolysin demonstrates the capacity of MACPF/CDCs to generate pore-forming oligomeric structures of variable size with, most likely, different functional roles in biology.

  2. Pore Effect on the Occurrence and Formation of Gas Hydrate in Permafrost of Qilian Mountain, Qinghai-Tibet Plateau, China

    Science.gov (United States)

    Gao, H.; Lu, H.; Lu, Z.

    2014-12-01

    Gas hydrates were found in the permafrost of Qilian Mountain, Qinghai- Tibet Plateau, China in 2008. It has been found that gas hydrates occur in Jurassic sedimentary rocks, and the hydrated gases are mainly thermogenic. Different from the gas hydrates existing in loose sands in Mallik, Mackenzie Delta, Canada and North Slope, Alaska, USA, the gas hydrates in Qilian Mountain occurred in hard rocks. For understanding the occurrence and formation mechanism of gas hydrate in hard rcok, extensive experimental investigations have been conducted to study the pore features and hydrate formation in the rocks recovered from the hydrate layers in Qilian Mountain. The structures of sedimentary rock were observed by high-resolution X-ray CT, and pore size distribution of a rock specimen was measured with the mercury-injection method. Methane hydrate was synthesized in water-saturated rocks, and the saturations of hydrate in sedimentary rocks of various types were estimated from the amount of gas released from certain volume of rock. X-ray CT observation revealed that fractures were developed in the rocks associated with faults, while those away from faults were generally with massive structure. The mercury-injection analysis of pore features found that the porosities of the hydrate-existing rocks were generally less than 3%, and the pore sizes were generally smaller than 100 nm. The synthesizing experiments found that the saturation of methane hydrate were generally lower than 6% of pore space in rocks, but up to 16% when fractures developed. The low hydrate saturation in Qilian sedimentary rocks has been found mainly due to the small pore size of rock. The low hydrate saturation in the rocks might be the reason for the failure of regional seismic and logging detections of gas hydrates in Qilian Mountain.

  3. Estimation of pore pressure from seismic velocities

    International Nuclear Information System (INIS)

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

    2009-01-01

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

  4. Anodic processes in the chemical and electrochemical etching of Si crystals in acid-fluoride solutions: Pore formation mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Ulin, V. P.; Ulin, N. V.; Soldatenkov, F. Yu., E-mail: f.soldatenkov@mail.ioffe.ru [Ioffe Physical–Technical Institute (Russian Federation)

    2017-04-15

    The interaction of heavily doped p- and n-type Si crystals with hydrofluoric acid in the dark with and without contact with metals having greatly differing work functions (Ag and Pd) is studied. The dependences of the dissolution rates of Si crystals in HF solutions that contain oxidizing agents with different redox potentials (FeCl{sub 3}, V{sub 2}O{sub 5} and CrO{sub 3}) on the type and level of silicon doping are determined. Analysis of the experimental data suggests that valence-band holes in silicon are not directly involved in the anodic reactions of silicon oxidation and dissolution and their generation in crystals does not limit the rate of these processes. It is also shown that the character and rate of the chemical process leading to silicon dissolution in HF-containing electrolytes are determined by the interfacial potential attained at the semiconductor–electrolyte interface. The mechanism of electrochemical pore formation in silicon crystals is discussed in terms of selfconsistent cooperative reactions of nucleophilic substitution between chemisorbed fluorine anions and coordination- saturated silicon atoms in the crystal subsurface layer. A specific feature of these reactions for silicon crystals is that vacant nonbonding d{sup 2}sp{sup 3} orbitals of Si atoms, associated with sixfold degenerate states corresponding to the Δ valley of the conduction band, are involved in the formation of intermediate complexes. According to the suggested model, the pore-formation process spontaneously develops in local regions of the interface under the action of the interfacial potential in the adsorption layer and occurs as a result of the detachment of (SiF{sub 2}){sub n} polymer chains from the crystal. Just this process leads to the preferential propagation of pores along the <100> crystallographic directions. The thermodynamic aspects of pore nucleation and the effect of the potential drop across the interface, conduction type, and free-carrier concentration

  5. Amino acid residues involved in membrane insertion and pore formation of Clostridium botulinum C2 toxin.

    Science.gov (United States)

    Lang, Alexander E; Neumeyer, Tobias; Sun, Jianjun; Collier, R John; Benz, Roland; Aktories, Klaus

    2008-08-12

    The actin-ADP-ribosylating Clostridium botulinum C2 toxin consists of the enzymatic component C2I and the binding component C2II. C2II forms heptameric channels involved in translocation of the enzymatic component into the target cell. On the basis of the heptameric toxin channel, we studied functional consequences of mutagenesis of amino acid residues probably lining the lumen of the toxin channel. Substitution of glutamate-399 of C2II with alanine blocked channel formation and cytotoxicity of the holotoxin. Although cytotoxicity and rounding up of cells by C2I were completely blocked by exchange of phenylalanine-428 with alanine, the mutation increased potassium conductance caused by C2II in artificial membranes by about 2-3-fold over that of wild-type toxin. In contrast to its effects on single-channel potassium conductance in artificial membranes, the F428A mutation delayed the kinetics of pore formation in lipid vesicles and inhibited the activity of C2II in promoting (86)Rb (+) release from preloaded intact cells after pH shift of the medium. Moreover, F428A C2II exhibited delayed and diminished formation of C2II aggregates at low pH, indicating major changes of the biophysical properties of the toxin. The data indicate that phenylalanine-428 of C2II plays a major role in conformational changes occurring during pore formation of the binding component of C2II.

  6. Pore characteristics of shale gas reservoirs from the Lower Paleozoic in the southern Sichuan Basin, China

    Directory of Open Access Journals (Sweden)

    Xianqing Li

    2016-06-01

    Full Text Available Data was acquired from both the drillings and core samples of the Lower Paleozoic Qiongzhusi and Longmaxi Formations' marine shale gas reservoirs in the southern Sichuan Basin by means of numerous specific experimental methods such as organic geochemistry, organic petrology, and pore analyses. Findings helped determine the characteristics of organic matter, total porosity, microscopic pore, and pore structure. The results show that the Lower Paleozoic marine shale in the south of the Sichuan Basin are characterized by high total organic carbon content (most TOC>2.0%, high thermal maturity level (RO = 2.3%–3.8%, and low total porosity (1.16%–6.87%. The total organic carbon content and thermal maturity level of the Qiongzhusi Formation shale are higher than those of the Longmaxi Formation shale, while the total porosity of the Qiongzhusi Formation shale is lower than that of the Longmaxi Formation shale. There exists intergranular pore, dissolved pore, crystal particle pore, particle edge pore, and organic matter pore in the Lower Paleozoic Qiongzhusi Formation and Longmaxi Formation shale. There are more micro-nano pores developed in the Longmaxi Formation shales than those in the Qiongzhusi Formation shales. Intergranular pores, dissolved pores, as well as organic matter pores, are the most abundant, these are primary storage spaces for shale gas. The microscopic pores in the Lower Paleozoic shales are mainly composed of micropores, mesopores, and a small amount of macropores. The micropore and mesopore in the Qiongzhusi Formation shale account for 83.92% of the total pore volume. The micropore and mesopore in the Longmaxi Formation shale accounts for 78.17% of the total pore volume. Thus, the micropores and mesopores are the chief components of microscopic pores in the Lower Paleozoic shale gas reservoirs in the southern Sichuan Basin.

  7. Mechanical constraint and release generates long, ordered horizontal pores in anodic alumina templates

    International Nuclear Information System (INIS)

    Bolger, Ciara T; Petkov, Nikolay; Holmes, Justin D; Fois, Giovanni; Cross, Graham L W; Sassiat, Nicolas; Burke, Micheál; Quinn, Aidan J

    2012-01-01

    We describe the formation of long, highly ordered arrays of planar oriented anodic aluminum oxide (AAO) pores during plane parallel anodization of thin aluminum ‘finger’ microstructures fabricated on thermally oxidized silicon substrates and capped with a silicon oxide layer. The pore morphology was found to be strongly influenced by mechanical constraint imposed by the oxide layers surrounding the Al fingers. Tractions induced by the SiO 2 substrate and capping layer led to frustrated volume expansion and restricted oxide flow along the interface, with extrusion of oxide into the primary pore volume, leading to the formation of dendritic pore structures and meandering pore growth. However, partial relief of the constraint by a delaminating interfacial fracture, with its tip closely following the anodization front, led to pore growth that was highly ordered with regular, hexagonally packed arrays of straight horizontal pores up to 3 µm long. Detailed characterization of both straight and dendritic planar pores over a range of formation conditions using advanced microscopy techniques is reported, including volume reconstruction, enabling high quality 3D visualization of pore formation. (paper)

  8. Broad neutralization of calcium-permeable amyloid pore channels with a chimeric Alzheimer/Parkinson peptide targeting brain gangliosides.

    Science.gov (United States)

    Di Scala, Coralie; Yahi, Nouara; Flores, Alessandra; Boutemeur, Sonia; Kourdougli, Nazim; Chahinian, Henri; Fantini, Jacques

    2016-02-01

    Growing evidence supports a role for brain gangliosides in the pathogenesis of neurodegenerative diseases including Alzheimer's and Parkinson's. Recently we deciphered the ganglioside-recognition code controlling specific ganglioside binding to Alzheimer's β-amyloid (Aβ1-42) peptide and Parkinson's disease-associated protein α-synuclein. Cracking this code allowed us to engineer a short chimeric Aβ/α-synuclein peptide that recognizes all brain gangliosides. Here we show that ganglioside-deprived neural cells do no longer sustain the formation of zinc-sensitive amyloid pore channels induced by either Aβ1-42 or α-synuclein, as assessed by single-cell Ca(2+) fluorescence microscopy. Thus, amyloid channel formation, now considered a key step in neurodegeneration, is a ganglioside-dependent process. Nanomolar concentrations of chimeric peptide competitively inhibited amyloid pore formation induced by Aβ1-42 or α-synuclein in cultured neural cells. Moreover, this peptide abrogated the intracellular calcium increases induced by Parkinson's-associated mutant forms of α-synuclein (A30P, E46K and A53T). The chimeric peptide also prevented the deleterious effects of Aβ1-42 on synaptic vesicle trafficking and decreased the Aβ1-42-induced impairment of spontaneous activity in rat hippocampal slices. Taken together, these data show that the chimeric peptide has broad anti-amyloid pore activity, suggesting that a common therapeutic strategy based on the prevention of amyloid-ganglioside interactions is a reachable goal for both Alzheimer's and Parkinson's diseases. Copyright © 2015 Elsevier B.V. All rights reserved.

  9. From Cell to Tissue Properties-Modeling Skin Electroporation With Pore and Local Transport Region Formation.

    Science.gov (United States)

    Dermol-Cerne, Janja; Miklavcic, Damijan

    2018-02-01

    Current models of tissue electroporation either describe tissue with its bulk properties or include cell level properties, but model only a few cells of simple shapes in low-volume fractions or are in two dimensions. We constructed a three-dimensional model of realistically shaped cells in realistic volume fractions. By using a 'unit cell' model, the equivalent dielectric properties of whole tissue could be calculated. We calculated the dielectric properties of electroporated skin. We modeled electroporation of single cells by pore formation on keratinocytes and on the papillary dermis which gave dielectric properties of the electroporated epidermis and papillary dermis. During skin electroporation, local transport regions are formed in the stratum corneum. We modeled local transport regions and increase in their radii or density which affected the dielectric properties of the stratum corneum. The final model of skin electroporation accurately describes measured electric current and voltage drop on the skin during electroporation with long low-voltage pulses. The model also accurately describes voltage drop on the skin during electroporation with short high-voltage pulses. However, our results indicate that during application of short high-voltage pulses additional processes may occur which increase the electric current. Our model connects the processes occurring at the level of cell membranes (pore formation), at the level of a skin layer (formation of local transport region in the stratum corneum) with the tissue (skin layers) and even level of organs (skin). Using a similar approach, electroporation of any tissue can be modeled, if the morphology of the tissue is known.

  10. Tension-induced vesicle fusion: pathways and pore dynamics

    DEFF Research Database (Denmark)

    Shillcock, Julian C.

    2008-01-01

    and eventually opens a pore to complete the fusion process. In pathway II, at higher tension, a stalk is formed during the fusion process that is then transformed by transmembrane pore formation into a fusion pore. Whereas the latter pathway II resembles stalk pathways as observed in other simulation studies......, fusion pathway I, which does not involve any stalk formation, has not been described previously to the best of our knowledge. A statistical analysis of the various processes shows that fusion is the dominant pathway for releasing the tension of the vesicles. The functional dependence of the observed...

  11. Formation factor in Bentheimer and Fontainebleau sandstones: Theory compared with pore-scale numerical simulations

    Science.gov (United States)

    Ghanbarian, Behzad; Berg, Carl F.

    2017-09-01

    Accurate quantification of formation resistivity factor F (also called formation factor) provides useful insight into connectivity and pore space topology in fully saturated porous media. In particular the formation factor has been extensively used to estimate permeability in reservoir rocks. One of the widely applied models to estimate F is Archie's law (F = ϕ- m in which ϕ is total porosity and m is cementation exponent) that is known to be valid in rocks with negligible clay content, such as clean sandstones. In this study we compare formation factors determined by percolation and effective-medium theories as well as Archie's law with numerical simulations of electrical resistivity on digital rock models. These digital models represent Bentheimer and Fontainebleau sandstones and are derived either by reconstruction or directly from micro-tomographic images. Results show that the universal quadratic power law from percolation theory accurately estimates the calculated formation factor values in network models over the entire range of porosity. However, it crosses over to the linear scaling from the effective-medium approximation at the porosity of 0.75 in grid models. We also show that the effect of critical porosity, disregarded in Archie's law, is nontrivial, and the Archie model inaccurately estimates the formation factor in low-porosity homogeneous sandstones.

  12. Porosity and pore size distribution determination of Tumblagooda formation sandstone by X-ray microtomography

    International Nuclear Information System (INIS)

    Fernandes, Jaquiel S.; Appoloni, Carlos R.; Moreira, Anderson C.

    2007-01-01

    Microstructural parameters evaluations of reservoir rocks are very important to petroleum industry. This work presents total porosity and pore size distribution measurement of a sandstone sample from the Tumblagooda formation, collected at Kalbarri National Park in Australia. Porosity and pores size distribution were determined using X-Ray microtomography and imaging techniques. For these measurements, it was employed a micro-CT (μ-CT) Skyscan system model 1172 with conical beam, operated with a 1 mm Al filter at 80 kV and 125 μA, respectively, and a 2000 x 1048 pixels CCD camera. The sample was rotated from 0 deg to 180 deg, in step of 0.5 deg. For the considered sample, this equipment provided images with 2.9 μm spatial resolution. Six hundreds 2-D images where reconstructed with the Skyscan NRecon software, which were analyzed with the aid of Imago software, developed at the Laboratory of Porous Media and Thermophysical Properties (LMPT), Department of Mechanical Engineering, Federal University of Santa Catarina, Brazil, in association with the Brazilian software company Engineering Simulation and Scientific Software (ESSS), and Petroleo Brasileiro SA (PETROBRAS) Research and Development Center (CENPES). The determined average porosity was 11.45 ±1.53 %. Ninety five percent of the porous phase refers to pores with radius ranging from 2.9 to 85.2 μm, presenting the larger frequency (7.7 %) at 11.7 μm radius. (author)

  13. Biophysical and biochemical strategies to understand membrane binding and pore formation by sticholysins, pore-forming proteins from a sea anemone.

    Science.gov (United States)

    Alvarez, Carlos; Ros, Uris; Valle, Aisel; Pedrera, Lohans; Soto, Carmen; Hervis, Yadira P; Cabezas, Sheila; Valiente, Pedro A; Pazos, Fabiola; Lanio, Maria E

    2017-10-01

    Actinoporins constitute a unique class of pore-forming toxins found in sea anemones that are able to bind and oligomerize in membranes, leading to cell swelling, impairment of ionic gradients and, eventually, to cell death. In this review we summarize the knowledge generated from the combination of biochemical and biophysical approaches to the study of sticholysins I and II (Sts, StI/II), two actinoporins largely characterized by the Center of Protein Studies at the University of Havana during the last 20 years. These approaches include strategies for understanding the toxin structure-function relationship, the protein-membrane association process leading to pore formation and the interaction of toxin with cells. The rational combination of experimental and theoretical tools have allowed unraveling, at least partially, of the complex mechanisms involved in toxin-membrane interaction and of the molecular pathways triggered upon this interaction. The study of actinoporins is important not only to gain an understanding of their biological roles in anemone venom but also to investigate basic molecular mechanisms of protein insertion into membranes, protein-lipid interactions and the modulation of protein conformation by lipid binding. A deeper knowledge of the basic molecular mechanisms involved in Sts-cell interaction, as described in this review, will support the current investigations conducted by our group which focus on the design of immunotoxins against tumor cells and antigen-releasing systems to cell cytosol as Sts-based vaccine platforms.

  14. The Rapid Formation of Localized Compaction Bands Under Hydrostatic Load Leading to Pore-pressure Transients in Compacting Rocks

    Science.gov (United States)

    Faulkner, D.; Leclere, H.; Bedford, J. D.; Behnsen, J.; Wheeler, J.

    2017-12-01

    Compaction of porous rocks can occur uniformly or within localized deformation bands. The formation of compaction bands and their effects on deformation behaviour are poorly understood. Porosity may be primary and compaction can occur with burial, or it can be produced by metamorphic reactions with a solid volume reduction, that can then undergo collapse. We report results from hydrostatic compaction experiments on porous bassanite (CaSO4.0.5H2O) aggregates. Gypsum (CaSO4.2H2O) is first dehydrated under low effective pressure, 4 MPa, to produce a bassanite aggregate with a porosity of 27%. Compaction is induced by increasing confining pressure at rates from 0.001 MPa/s to 0.02 MPa/s while the sample is maintained at a temperature of 115°C. At slow compaction rates, porosity collapse proceeds smoothly. At higher compaction rates, sudden increases in the pore-fluid pressure occur with a magnitude of 5 MPa. Microstructural investigations using X-ray microtomography and SEM observations show that randomly oriented localized compaction features occur in all samples, where the bulk porosity of 18% outside the band is reduced to 5% inside the band. Previous work on deformation bands has suggested that localized compactive features only form under an elevated differential stress and not under a hydrostatic stress state. The magnitude of the pore-pressure pulses can be explained by the formation of compaction bands. The results indicate that the compaction bands can form by rapid (unstable) propagation across the sample above a critical strain rate, or quasi-statically at low compaction rates without pore-fluid pressure bursts. The absence of pore-fluid pressure bursts at slow compaction rates can be explained by viscous deformation of the bassanite aggregate around the tip of a propagating compaction band, relaxing stress, and promoting stable propagation. Conversely, at higher compaction rates, viscous deformation cannot relax the stress sufficiently and unstable

  15. Role of scaffold mean pore size in meniscus regeneration.

    Science.gov (United States)

    Zhang, Zheng-Zheng; Jiang, Dong; Ding, Jian-Xun; Wang, Shao-Jie; Zhang, Lei; Zhang, Ji-Ying; Qi, Yan-Song; Chen, Xue-Si; Yu, Jia-Kuo

    2016-10-01

    Recently, meniscus tissue engineering offers a promising management for meniscus regeneration. Although rarely reported, the microarchitectures of scaffolds can deeply influence the behaviors of endogenous or exogenous stem/progenitor cells and subsequent tissue formation in meniscus tissue engineering. Herein, a series of three-dimensional (3D) poly(ε-caprolactone) (PCL) scaffolds with three distinct mean pore sizes (i.e., 215, 320, and 515μm) were fabricated via fused deposition modeling. The scaffold with the mean pore size of 215μm significantly improved both the proliferation and extracellular matrix (ECM) production/deposition of mesenchymal stem cells compared to all other groups in vitro. Moreover, scaffolds with mean pore size of 215μm exhibited the greatest tensile and compressive moduli in all the acellular and cellular studies. In addition, the relatively better results of fibrocartilaginous tissue formation and chondroprotection were observed in the 215μm scaffold group after substituting the rabbit medial meniscectomy for 12weeks. Overall, the mean pore size of 3D-printed PCL scaffold could affect cell behavior, ECM production, biomechanics, and repair effect significantly. The PCL scaffold with mean pore size of 215μm presented superior results both in vitro and in vivo, which could be an alternative for meniscus tissue engineering. Meniscus tissue engineering provides a promising strategy for meniscus regeneration. In this regard, the microarchitectures (e.g., mean pore size) of scaffolds remarkably impact the behaviors of cells and subsequent tissue formation, which has been rarely reported. Herein, three three-dimensional poly(ε-caprolactone) scaffolds with different mean pore sizes (i.e., 215, 320, and 515μm) were fabricated via fused deposition modeling. The results suggested that the mean pore size significantly affected the behaviors of endogenous or exogenous stem/progenitor cells and subsequent tissue formation. This study furthers

  16. NSF- and SNARE-mediated membrane fusion is required for nuclear envelope formation and completion of nuclear pore complex assembly in Xenopus laevis egg extracts.

    Science.gov (United States)

    Baur, Tina; Ramadan, Kristijan; Schlundt, Andreas; Kartenbeck, Jürgen; Meyer, Hemmo H

    2007-08-15

    Despite the progress in understanding nuclear envelope (NE) reformation after mitosis, it has remained unclear what drives the required membrane fusion and how exactly this is coordinated with nuclear pore complex (NPC) assembly. Here, we show that, like other intracellular fusion reactions, NE fusion in Xenopus laevis egg extracts is mediated by SNARE proteins that require activation by NSF. Antibodies against Xenopus NSF, depletion of NSF or the dominant-negative NSF(E329Q) variant specifically inhibited NE formation. Staging experiments further revealed that NSF was required until sealing of the envelope was completed. Moreover, excess exogenous alpha-SNAP that blocks SNARE function prevented membrane fusion and caused accumulation of non-flattened vesicles on the chromatin surface. Under these conditions, the nucleoporins Nup107 and gp210 were fully recruited, whereas assembly of FxFG-repeat-containing nucleoporins was blocked. Together, we define NSF- and SNARE-mediated membrane fusion events as essential steps during NE formation downstream of Nup107 recruitment, and upstream of membrane flattening and completion of NPC assembly.

  17. Characterization of Bc1-2, Bc1-xL, and Bax Pore Formation and Their Role in Apoptosis Regulation

    Science.gov (United States)

    2002-01-01

    Bcl-2, Bcl-xL, and Bax Pore Formation and Their Role in Apoptosis Regulation PRINCIPAL INVESTIGATOR: Frank Stenner -Liewen, Ph.D. Sharon Schendel, Ph.D...AUTHOR(S) Frank Stenner -Liewen, Ph.D. Sharon Schendel, Ph.D. John C. Reed, M.D., Ph.D. 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING

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

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Yeon Soo, E-mail: yskim@anl.gov [Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (United States); Jeong, G.Y.; Sohn, D.-S. [Ulsan National Institute of Science and Technology, 50 UNIST-gil, Eonyang-eup, Ulju-gun, Ulsan, 689-798 (Korea, Republic of); Jamison, L.M. [Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (United States)

    2016-09-15

    U-Mo/Al dispersion fuel is currently under development in the DOE’s Material Management and Minimization program to convert HEU-fueled research reactors to LEU-fueled reactors. In some demanding conditions in high-power and high-performance reactors, large pores form in the interaction layers between the U-Mo fuel particles and the Al matrix, which pose a potential to cause fuel failure. In this study, comprehension of the formation and growth of these pores was explored. As a product, a model to predict pore growth and porosity increase was developed. The model includes three major topics: fission gas release from the U-Mo and the IL to the pores, stress evolution in the fuel meat, and the effect of amorphous IL growth. Well-characterized in-pile data from reduced-size plates were used to fit the model parameters. A data set from full-sized plates, independent and distinctively different from those used to fit the model parameters, was used to examine the accuracy of the model. The model showed fair agreement with the measured data. The model suggested that the growth of the IL has a critical effect on pore growth, as both its material properties and energetics are favorable to pore formation. Therefore, one area of the current effort, focused on suppressing IL growth, appears to be on the right track to improve the performance of this fuel.

  19. Crack formation and prevention in colloidal drops

    Science.gov (United States)

    Kim, Jin Young; Cho, Kun; Ryu, Seul-A.; Kim, So Youn; Weon, Byung Mook

    2015-08-01

    Crack formation is a frequent result of residual stress release from colloidal films made by the evaporation of colloidal droplets containing nanoparticles. Crack prevention is a significant task in industrial applications such as painting and inkjet printing with colloidal nanoparticles. Here, we illustrate how colloidal drops evaporate and how crack generation is dependent on the particle size and initial volume fraction, through direct visualization of the individual colloids with confocal laser microscopy. To prevent crack formation, we suggest use of a versatile method to control the colloid-polymer interactions by mixing a nonadsorbing polymer with the colloidal suspension, which is known to drive gelation of the particles with short-range attraction. Gelation-driven crack prevention is a feasible and simple method to obtain crack-free, uniform coatings through drying-mediated assembly of colloidal nanoparticles.

  20. Synthesis and characterization of nanoparticulate MnS within the pores of mesoporous silica

    International Nuclear Information System (INIS)

    Barry, Louse; Copley, Mark; Holmes, Justin D.; Otway, David J.; Kazakova, Olga; Morris, Michael A.

    2007-01-01

    Mesoporous silica was loaded with nanoparticulate MnS via a simple post-synthesis treatment. The mesoporous material that still contained surfactant was passivated to prevent MnS formation at the surface. The surfactant was extracted and a novel manganese ethylxanthate was used to impregnate the pore network. This precursor thermally decomposes to yield MnS particles that are smaller or equal to the pore size. The particles exhibit all three common polymorphs. The passivation treatment is most effective at lower loadings because at the highest loadings (SiO 2 :MnS molar ratio of 6:1) large particles (>50 nm) form at the exterior of the mesoporous particles. The integrity of the mesoporous network is maintained through the preparation and high order is maintained. The MnS particles exhibit unexpected ferromagnetism at low temperatures. Strong luminescence of these samples is observed and this suggests that they may have a range of important application areas. - Graphical abstract: A novel manganese ethylxanthate precursor was used to impregnate the pore network of mesoporous silica and was decomposed to yield MnS particles smaller or equal to the pore size. The particles exhibit all three common polymorphs, demonstrate unexpected ferromagnetism at low temperatures and display a strong luminescence

  1. Control of pore size in epoxy systems.

    Energy Technology Data Exchange (ETDEWEB)

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

    2009-01-01

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

  2. Numerical estimates of the maximum sustainable pore pressure in anticline formations using the tensor based concept of pore pressure-stress coupling

    Directory of Open Access Journals (Sweden)

    Andreas Eckert

    2015-02-01

    Full Text Available The advanced tensor based concept of pore pressure-stress coupling is used to provide pre-injection analytical estimates of the maximum sustainable pore pressure change, ΔPc, for fluid injection scenarios into generic anticline geometries. The heterogeneous stress distribution for different prevailing stress regimes in combination with the Young's modulus (E contrast between the injection layer and the cap rock and the interbedding friction coefficient, μ, may result in large spatial and directional differences of ΔPc. A single value characterizing the cap rock as for horizontal layered injection scenarios is not obtained. It is observed that a higher Young's modulus in the cap rock and/or a weak mechanical coupling between layers amplifies the maximum and minimum ΔPc values in the valley and limb, respectively. These differences in ΔPc imposed by E and μ are further amplified by different stress regimes. The more compressional the stress regime is, the larger the differences between the maximum and minimum ΔPc values become. The results of this study show that, in general compressional stress regimes yield the largest magnitudes of ΔPc and extensional stress regimes provide the lowest values of ΔPc for anticline formations. Yet this conclusion has to be considered with care when folded anticline layers are characterized by flexural slip and the friction coefficient between layers is low, i.e. μ = 0.1. For such cases of weak mechanical coupling, ΔPc magnitudes may range from 0 MPa to 27 MPa, indicating imminent risk of fault reactivation in the cap rock.

  3. Combined use of rheometry and microscopy to understand pore structure development during coal carbonisation

    Energy Technology Data Exchange (ETDEWEB)

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

    2007-07-01

    The viscoelastic behaviour of coal during carbonisation plays a role in the formation, growth and coalescence of pores. While viscosity is considered to govern pore formation and growth, the coalescence of pores or stabilisation of pores is considered to be governed by elasticity, and these two factors need to be considered in tandem when investigating pore network formation. The properties of the pore network, such as the connectivity of the pores, is hypothesised to be a factor controlling the degree of pressure that the carbonising mass exerts on its surrounding walls, called oven wall pressure (OWP). When volatiles are unable to pass out through the newly formed semi-coke due to low permeability, they travel instead to the centre of the charge, possibly condense as it is cooler, and build-up to high levels, causing high OWPs. Possible causes for low permeability on the semi-coke side could include poor connectivity between pores in the resolidifying material due to lack of connections, tortuous flow paths or narrow necks between pores. Low OWPs are thought to be largely due to a reduction in the elasticity of the fluid phase which allows a greater degree of pore coalescence and ultimately pore connectivity. This paper presents viscoelastic measurements for coals exhibiting different OWPs and scanning electron microscopy (SEM) images of the coal, quenched at various temperatures during carbonisation to show the development of their pore networks. 12 refs., 5 figs., 1 tab.

  4. Effect of Aluminum Purity on the Pore Formation of Porous Anodic Alumina

    International Nuclear Information System (INIS)

    Kim, Byeol; Lee, Jin Seok

    2014-01-01

    Anodic alumina oxide (AAO), a self-ordered hexagonal array, has various applications in nanofabrication such as the fabrication of nanotemplates and other nanostructures. In order to obtain highly ordered porous alumina membranes, a two-step anodization or prepatterning of aluminum are mainly conducted with straight electric field. Electric field is the main driving force for pore growth during anodization. However, impurities in aluminum can disturb the direction of the electric field. To confirm this, we anodized two different aluminum foil samples with high purity (99.999%) and relatively low purity (99.8%), and compared the differences in the surface morphologies of the respective aluminum oxide membranes produced in different electric fields. Branched pores observed in porous alumina surface which was anodized in low-purity aluminum and the size; dimensions of the pores were found to be usually smaller than those obtained from high-purity aluminum. Moreover, anodization at high voltage proceeds to a significant level of conversion because of the high speed of the directional electric field. Consequently, anodic alumina membrane of a specific morphology, i. e., meshed pore, was produced

  5. Effect of Aluminum Purity on the Pore Formation of Porous Anodic Alumina

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Byeol; Lee, Jin Seok [Sookmyung Women' s Univ., Seoul (Korea, Republic of)

    2014-02-15

    Anodic alumina oxide (AAO), a self-ordered hexagonal array, has various applications in nanofabrication such as the fabrication of nanotemplates and other nanostructures. In order to obtain highly ordered porous alumina membranes, a two-step anodization or prepatterning of aluminum are mainly conducted with straight electric field. Electric field is the main driving force for pore growth during anodization. However, impurities in aluminum can disturb the direction of the electric field. To confirm this, we anodized two different aluminum foil samples with high purity (99.999%) and relatively low purity (99.8%), and compared the differences in the surface morphologies of the respective aluminum oxide membranes produced in different electric fields. Branched pores observed in porous alumina surface which was anodized in low-purity aluminum and the size; dimensions of the pores were found to be usually smaller than those obtained from high-purity aluminum. Moreover, anodization at high voltage proceeds to a significant level of conversion because of the high speed of the directional electric field. Consequently, anodic alumina membrane of a specific morphology, i. e., meshed pore, was produced.

  6. Spontaneous formation of structurally diverse membrane channel architectures from a single antimicrobial peptide

    Science.gov (United States)

    Wang, Yukun; Chen, Charles H.; Hu, Dan; Ulmschneider, Martin B.; Ulmschneider, Jakob P.

    2016-11-01

    Many antimicrobial peptides (AMPs) selectively target and form pores in microbial membranes. However, the mechanisms of membrane targeting, pore formation and function remain elusive. Here we report an experimentally guided unbiased simulation methodology that yields the mechanism of spontaneous pore assembly for the AMP maculatin at atomic resolution. Rather than a single pore, maculatin forms an ensemble of structurally diverse temporarily functional low-oligomeric pores, which mimic integral membrane protein channels in structure. These pores continuously form and dissociate in the membrane. Membrane permeabilization is dominated by hexa-, hepta- and octamers, which conduct water, ions and small dyes. Pores form by consecutive addition of individual helices to a transmembrane helix or helix bundle, in contrast to current poration models. The diversity of the pore architectures--formed by a single sequence--may be a key feature in preventing bacterial resistance and could explain why sequence-function relationships in AMPs remain elusive.

  7. Functions of phenylalanine residues within the beta-barrel stem of the anthrax toxin pore.

    Directory of Open Access Journals (Sweden)

    Jie Wang

    2009-07-01

    Full Text Available A key step of anthrax toxin action involves the formation of a protein-translocating pore within the endosomal membrane by the Protective Antigen (PA moiety. Formation of this transmembrane pore by PA involves interaction of the seven 2beta2-2beta3 loops of the heptameric precursor to generate a 14-strand transmembrane beta barrel.We examined the effects on pore formation, protein translocation, and cytotoxicity, of mutating two phenylalanines, F313 and F314, that lie at the tip the beta barrel, and a third one, F324, that lies part way up the barrel.Our results show that the function of these phenylalanine residues is to mediate membrane insertion and formation of stable transmembrane channels. Unlike F427, a key luminal residue in the cap of the pore, F313, F314, and F324 do not directly affect protein translocation through the pore. Our findings add to our knowledge of structure-function relationships of a key virulence factor of the anthrax bacillus.

  8. Stable silicon isotope signatures of marine pore waters - Biogenic opal dissolution versus authigenic clay mineral formation

    Science.gov (United States)

    Ehlert, Claudia; Doering, Kristin; Wallmann, Klaus; Scholz, Florian; Sommer, Stefan; Grasse, Patricia; Geilert, Sonja; Frank, Martin

    2016-10-01

    Dissolved silicon isotope compositions have been analysed for the first time in pore waters (δ30SiPW) of three short sediment cores from the Peruvian margin upwelling region with distinctly different biogenic opal content in order to investigate silicon isotope fractionation behaviour during early diagenetic turnover of biogenic opal in marine sediments. The δ30SiPW varies between +1.1‰ and +1.9‰ with the highest values occurring in the uppermost part close to the sediment-water interface. These values are of the same order or higher than the δ30Si of the biogenic opal extracted from the same sediments (+0.3‰ to +1.2‰) and of the overlying bottom waters (+1.1‰ to +1.5‰). Together with dissolved silicic acid concentrations well below biogenic opal saturation, our collective observations are consistent with the formation of authigenic alumino-silicates from the dissolving biogenic opal. Using a numerical transport-reaction model we find that approximately 24% of the dissolving biogenic opal is re-precipitated in the sediments in the form of these authigenic phases at a relatively low precipitation rate of 56 μmol Si cm-2 yr-1. The fractionation factor between the precipitates and the pore waters is estimated at -2.0‰. Dissolved and solid cation concentrations further indicate that off Peru, where biogenic opal concentrations in the sediments are high, the availability of reactive terrigenous material is the limiting factor for the formation of authigenic alumino-silicate phases.

  9. Pore development of thermosetting phenol resin derived mesoporous carbon through a commercially nanosized template

    Energy Technology Data Exchange (ETDEWEB)

    Tang Zhihong [Key Laboratory of Carbon Materials, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001 (China); Graduate University of Chinese Academy of Sciences, Beijing 100039 (China); Song Yan [Key Laboratory of Carbon Materials, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001 (China)], E-mail: yansong1026@126.com; Tian Yongming [Key Laboratory of Carbon Materials, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001 (China); Graduate University of Chinese Academy of Sciences, Beijing 100039 (China); Liu Lang; Guo Quangui [Key Laboratory of Carbon Materials, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001 (China)

    2008-01-25

    Mesoporous carbons (MCs) with high specific surface area and pore volume were synthesized from thermosetting phenol resin (TPR) by using commercial nanosized silica particles as template. Based on the results of thermogravimetric analysis, nitrogen adsorption, mercury adsorption and high-resolution transmission electron microscopy (HRTEM), mechanism of the pore formation of MCs was proposed. Silica particles not only participated in the pore formation of MCs but also influenced the thermosetting process of the carbon precursor. The mechanism of pore formation in the MCs may be described as follows: mesopores were introduced by the removal of silica particles; small mesopores were created by the combination of aperture between TPR and silica particles and opened pores in the matrix generated by the release of small molecules in the carbon during carbonization process; macropores were produced by the aggregation of silica particles and the collapse of carbon wall.

  10. Pore development of thermosetting phenol resin derived mesoporous carbon through a commercially nanosized template

    International Nuclear Information System (INIS)

    Tang Zhihong; Song Yan; Tian Yongming; Liu Lang; Guo Quangui

    2008-01-01

    Mesoporous carbons (MCs) with high specific surface area and pore volume were synthesized from thermosetting phenol resin (TPR) by using commercial nanosized silica particles as template. Based on the results of thermogravimetric analysis, nitrogen adsorption, mercury adsorption and high-resolution transmission electron microscopy (HRTEM), mechanism of the pore formation of MCs was proposed. Silica particles not only participated in the pore formation of MCs but also influenced the thermosetting process of the carbon precursor. The mechanism of pore formation in the MCs may be described as follows: mesopores were introduced by the removal of silica particles; small mesopores were created by the combination of aperture between TPR and silica particles and opened pores in the matrix generated by the release of small molecules in the carbon during carbonization process; macropores were produced by the aggregation of silica particles and the collapse of carbon wall

  11. Physical Property Changes During CO2 Injection into Sandstone from Pukpyeong Formation, South Korea: Pore-scale Approach

    Science.gov (United States)

    Han, J.; Keehm, Y.

    2010-12-01

    Carbon dioxide is believed to be responsible for global warming and climate change, and Korea government puts a great effort in CCS (Carbon Capture and Storage). The geological sequestration is regarded as one viable option and we are looking for prospecting formations for carbon storage. In this paper, we present a new approach to determine physical property changes during CO2 injection and preliminary results from applying the method to one of prospective Tertiary formation in South Korea. The so-called computational rock physics method is composed of three steps: 1) acquisition of high-resolution pore microstructures by X-ray micro-tomography; 2) CO2 injection simulation using lattice-Boltzmann (LB) two-phase flow simulation; and 3) FEM property simulations (electrical and elastic) at different CO2 saturations during the injection. We have been shown the viability of the method last year. This year we applied this method to one of CS (carbon storage) target area, Pukpyeong formation located in north-eastern part of South Korea. From thin section analysis, we found that the formation is composed of mudstone, sandstone and conglomerate, and most of them are poorly consolidated. The mudstone and poorly-sorted conglomerate are believed to have very low permeability, and the effect of CO2 injection would be significant. Thus we focus on sandstone units and get pore microstructure of those units. We then performed the computational rock physics analysis, and present the relations of Vp - CO2 saturation, and electrical conductivity - CO2 saturation for a few sand units. We also present the preliminary upscaling results by putting combined sandstone and mudstone units into FEM modeling. The modeling results implies that the new computational approach can be very useful to characterizing the CS sites especially in early stage. Acknowledgement: This work was supported by the Energy R&D program of the Korea Institute of Energy Technology Evaluation and Planning (KETEP

  12. Multiple Approaches to Characterizing Pore Structure in Natural Rock

    Science.gov (United States)

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

    2012-12-01

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

  13. A modified approach to predict pore pressure using the D exponent method: An example from the Carbonera Formation, Colombia

    International Nuclear Information System (INIS)

    Solano, Yully P; Uribe, Rodolfo; Frydman, Marcelo; Saavedra, Nestor F; Calderon, Zuly H

    2007-01-01

    The methodology for the pore pressure prediction known as an exponent is o function of an exponent of adjustment that was originally defined for the Gulf of Mexico (Jorden and Shirley, 1966; Eaton, 1972). A limiting factor of this methodology is the definition of the normal compaction trend (NCT), which needs to be interpreted from the data (Mouchet and Mitchell, 1989). In this study, the D exponent methodology was modified to make it applicable to the Oligocene Carbonera Formation in an oil field of the llanos foothills Colombia. The approach consisted of calculating the ratio between affective stress and the D exponent of each wall, in order to find a robust NCT for the entire field, thus reducing subjectivity in the traditional d exponent methodology. Pore pressure determinations from Measured Direct Tests (MDT) at one wall confirm the predictive capability of our approach

  14. Simulations of Skin Barrier Function: Free Energies of Hydrophobic and Hydrophilic Transmembrane Pores in Ceramide Bilayers

    OpenAIRE

    Notman, Rebecca; Anwar, Jamshed; Briels, W. J.; Noro, Massimo G.; den Otter, Wouter K.

    2008-01-01

    Transmembrane pore formation is central to many biological processes such as ion transport, cell fusion, and viral infection. Furthermore, pore formation in the ceramide bilayers of the stratum corneum may be an important mechanism by which penetration enhancers such as dimethylsulfoxide (DMSO) weaken the barrier function of the skin. We have used the potential of mean constraint force (PMCF) method to calculate the free energy of pore formation in ceramide bilayers in both the innate gel pha...

  15. Free energies of stable and metastable pores in lipid membranes under tension.

    Science.gov (United States)

    den Otter, Wouter K

    2009-11-28

    The free energy profile of pore formation in a lipid membrane, covering the entire range from a density fluctuation in an intact bilayer to a large tension-stabilized pore, has been calculated by molecular dynamics simulations with a coarse-grained lipid model. Several fixed elongations are used to obtain the Helmholtz free energy as a function of pore size for thermodynamically stable, metastable, and unstable pores, and the system-size dependence of these elongations is discussed. A link to the Gibbs free energy at constant tension, commonly known as the Litster model, is established by a Legendre transformation. The change of genus upon pore formation is exploited to estimate the saddle-splay modulus or Gaussian curvature modulus of the membrane leaflets. Details are provided of the simulation approach, which combines the potential of mean constraint force method with a reaction coordinate based on the local lipid density.

  16. Anomalous or regular capacitance? The influence of pore size dispersity on double-layer formation

    Science.gov (United States)

    Jäckel, N.; Rodner, M.; Schreiber, A.; Jeongwook, J.; Zeiger, M.; Aslan, M.; Weingarth, D.; Presser, V.

    2016-09-01

    The energy storage mechanism of electric double-layer capacitors is governed by ion electrosorption at the electrode surface. This process requires high surface area electrodes, typically highly porous carbons. In common organic electrolytes, bare ion sizes are below one nanometer but they are larger when we consider their solvation shell. In contrast, ionic liquid electrolytes are free of solvent molecules, but cation-anion coordination requires special consideration. By matching pore size and ion size, two seemingly conflicting views have emerged: either an increase in specific capacitance with smaller pore size or a constant capacitance contribution of all micro- and mesopores. In our work, we revisit this issue by using a comprehensive set of electrochemical data and a pore size incremental analysis to identify the influence of certain ranges in the pore size distribution to the ion electrosorption capacity. We see a difference in solvation of ions in organic electrolytes depending on the applied voltage and a cation-anion interaction of ionic liquids in nanometer sized pores.

  17. Stepwise visualization of membrane pore formation by suilysin, a bacterial cholesterol-dependent cytolysin.

    Science.gov (United States)

    Leung, Carl; Dudkina, Natalya V; Lukoyanova, Natalya; Hodel, Adrian W; Farabella, Irene; Pandurangan, Arun P; Jahan, Nasrin; Pires Damaso, Mafalda; Osmanović, Dino; Reboul, Cyril F; Dunstone, Michelle A; Andrew, Peter W; Lonnen, Rana; Topf, Maya; Saibil, Helen R; Hoogenboom, Bart W

    2014-12-02

    Membrane attack complex/perforin/cholesterol-dependent cytolysin (MACPF/CDC) proteins constitute a major superfamily of pore-forming proteins that act as bacterial virulence factors and effectors in immune defence. Upon binding to the membrane, they convert from the soluble monomeric form to oligomeric, membrane-inserted pores. Using real-time atomic force microscopy (AFM), electron microscopy (EM), and atomic structure fitting, we have mapped the structure and assembly pathways of a bacterial CDC in unprecedented detail and accuracy, focussing on suilysin from Streptococcus suis. We show that suilysin assembly is a noncooperative process that is terminated before the protein inserts into the membrane. The resulting ring-shaped pores and kinetically trapped arc-shaped assemblies are all seen to perforate the membrane, as also visible by the ejection of its lipids. Membrane insertion requires a concerted conformational change of the monomeric subunits, with a marked expansion in pore diameter due to large changes in subunit structure and packing.

  18. Determination of Pore Pressure from Sonic Log: a Case Study on One of Iran Carbonate Reservoir Rocks

    Directory of Open Access Journals (Sweden)

    Morteza Azadpour

    2015-07-01

    Full Text Available Pore pressureis defined as the pressure of the fluid inside the pore space of the formation, which is also known as the formation pressure. When the pore pressure is higher than hydrostatic pressure, it is referred to as overpressure. Knowledge of this pressure is essential for cost-effective drilling, safe well planning, and efficient reservoir modeling. The main objective of this study is to estimate the formation pore pressure as a reliable mud weight pressure using well log data at one of oil fields in the south of Iran. To obtain this goal, the formation pore pressure is estimated from well logging data by applying Eaton’s prediction method with some modifications. In this way, sonic transient time trend line is separated by lithology changes and recalibrated by Weakley’s approach. The created sonic transient time is used to create an overlay pore pressure based on Eaton’s method and is led to pore pressure determination. The results are compared with the pore pressure estimated from commonly used methods such as Eaton’s and Bowers’s methods. The determined pore pressure from Weakley’s approach shows some improvements in comparison with Eaton’s method. However, the results of Bowers’s method, in comparison with the other two methods, show relatively better agreement with the mud weight pressure values.

  19. [Pharmacotherapy for preventing calcium containing stone formation].

    Science.gov (United States)

    Nagata, Masao; Takayama, Tatsuya; Mugiya, Souichi; Ohzono, Seiichiro

    2011-10-01

    Many urinary tract stones consist of calcium, and has high relapse rate. Accordingly, it is very important to prevent calcium-containing stone formation. This paper describes about effects and mechanisms for Xanthine oxidase inhibitor, citrate formulation, magnesium formulation, thiazides, vitamin B(6), extract of Quercus salicina Blume and chorei-to (medical herb) . Recent new drugs and the elucidation of new metabolic pathways may lead to the development of prevention of urolithiasis.

  20. Valve seat pores sealed with thermosetting monomer

    Science.gov (United States)

    Olmore, A. B.

    1966-01-01

    Hard anodic coating provides a smooth wear resistant value seating surface on a cast aluminum alloy valve body. Vacuum impregnation with a thermosetting monomer, diallyl phthalate, seals the pores on the coating to prevent galvanic corrosion.

  1. Simulations of skin barrier function: free energies of hydrophobic and hydrophilic transmembrane pores in ceramide bilayers.

    Science.gov (United States)

    Notman, Rebecca; Anwar, Jamshed; Briels, W J; Noro, Massimo G; den Otter, Wouter K

    2008-11-15

    Transmembrane pore formation is central to many biological processes such as ion transport, cell fusion, and viral infection. Furthermore, pore formation in the ceramide bilayers of the stratum corneum may be an important mechanism by which penetration enhancers such as dimethylsulfoxide (DMSO) weaken the barrier function of the skin. We have used the potential of mean constraint force (PMCF) method to calculate the free energy of pore formation in ceramide bilayers in both the innate gel phase and in the DMSO-induced fluidized state. Our simulations show that the fluid phase bilayers form archetypal water-filled hydrophilic pores similar to those observed in phospholipid bilayers. In contrast, the rigid gel-phase bilayers develop hydrophobic pores. At the relatively small pore diameters studied here, the hydrophobic pores are empty rather than filled with bulk water, suggesting that they do not compromise the barrier function of ceramide membranes. A phenomenological analysis suggests that these vapor pores are stable, below a critical radius, because the penalty of creating water-vapor and tail-vapor interfaces is lower than that of directly exposing the strongly hydrophobic tails to water. The PMCF free energy profile of the vapor pore supports this analysis. The simulations indicate that high DMSO concentrations drastically impair the barrier function of the skin by strongly reducing the free energy required for pore opening.

  2. Molecular mechanism of pore creation in bacterial membranes by amyloid proteins

    International Nuclear Information System (INIS)

    Tsigelny, I F; Sharikov, Y; Miller, M A; Masliah, E

    2009-01-01

    This study explores the mechanism of pore creation in cellular membranes by MccE92 bacterial proteins. The results of this study are then compared with the mechanism of alpha-synuclein (aS)-based pore formation in mammalian cells, and its role in Parkinson's disease.

  3. Formation and pore structure of boron nitride aerogels

    International Nuclear Information System (INIS)

    Lindquist, D.H.; Borek, T.T.; Kramer, S.J.; Kramer, S.J.; Naruta, C.K.; Johnson, G.; Schaeffer, R.; Smith, D.M.; Paine, R.T.

    1990-01-01

    This paper reports gels containing a poly(borazinyl amine) and tetrahydrofuran processed by CO 2 supercritical drying techniques followed by pyrolysis. The resulting BN ceramic aerogels are highly porous, and the microstructure, porosity, and surface area characteristics have been examined. The aerogels show excellent thermal stability exhibiting surface areas in excess of 350 m 2 /g and porosities greater than 0.8 even when heated in argon at 1500 degrees C for 8 h. By removing solvent via evaporation before supercritical drying, the mean pore radius can be varied between 3.6 and 10 nm

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

    International Nuclear Information System (INIS)

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

    1985-06-01

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

  5. Simulations of Skin Barrier Function: Free Energies of Hydrophobic and Hydrophilic Transmembrane Pores in Ceramide Bilayers

    NARCIS (Netherlands)

    Notman, Rebecca; Anwar, Jamshed; Briels, Willem J.; Noro, Massimo G.; den Otter, Wouter K.

    2008-01-01

    Transmembrane pore formation is central to many biological processes such as ion transport, cell fusion, and viral infection. Furthermore, pore formation in the ceramide bilayers of the stratum corneum may be an important mechanism by which penetration enhancers such as dimethylsulfoxide (DMSO)

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

    International Nuclear Information System (INIS)

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

    2000-01-01

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

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

    Science.gov (United States)

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

    2017-08-01

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

  8. Cu(II) promotes amyloid pore formation

    International Nuclear Information System (INIS)

    Zhang, Hangyu; Rochet, Jean-Christophe; Stanciu, Lia A.

    2015-01-01

    The aggregation of α-synuclein is associated with dopamine neuron death in Parkinson's disease. There is controversy in the field over the question of which species of the aggregates, fibrils or protofibrils, are toxic. Moreover, compelling evidence suggested the exposure to heavy metals to be a risk of PD. Nevertheless, the mechanism of metal ions in promoting PD remains unclear. In this research, we investigated the structural basis of Cu(II) induced aggregation of α-synuclein. Using transmission electron microscopy experiments, Cu(II) was found to promote in vitro aggregation of α-synuclein by facilitating annular protofibril formation rather than fibril formation. Furthermore, neuroprotective baicalein disaggregated annular protofibrils accompanied by considerable decrease of β-sheet content. These results strongly support the hypothesis that annular protofibrils are the toxic species, rather than fibrils, thereby inspiring us to search novel therapeutic strategies for the suppression of the toxic annular protofibril formation. - Highlights: • Cu(II) promoted the annular protofibril formation of α-synuclein in vitro. • Cu(II) postponed the in vitro fibrillization of α-synuclein. • Neuroprotective baicalein disaggregated annular protofibrils

  9. Cu(II) promotes amyloid pore formation

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Hangyu, E-mail: hangyuz@uw.edu [Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN 47907 (United States); Rochet, Jean-Christophe [Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN 47907 (United States); Stanciu, Lia A. [Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN 47907 (United States); School of Materials Engineering, Purdue University, West Lafayette, IN 47907 (United States)

    2015-08-14

    The aggregation of α-synuclein is associated with dopamine neuron death in Parkinson's disease. There is controversy in the field over the question of which species of the aggregates, fibrils or protofibrils, are toxic. Moreover, compelling evidence suggested the exposure to heavy metals to be a risk of PD. Nevertheless, the mechanism of metal ions in promoting PD remains unclear. In this research, we investigated the structural basis of Cu(II) induced aggregation of α-synuclein. Using transmission electron microscopy experiments, Cu(II) was found to promote in vitro aggregation of α-synuclein by facilitating annular protofibril formation rather than fibril formation. Furthermore, neuroprotective baicalein disaggregated annular protofibrils accompanied by considerable decrease of β-sheet content. These results strongly support the hypothesis that annular protofibrils are the toxic species, rather than fibrils, thereby inspiring us to search novel therapeutic strategies for the suppression of the toxic annular protofibril formation. - Highlights: • Cu(II) promoted the annular protofibril formation of α-synuclein in vitro. • Cu(II) postponed the in vitro fibrillization of α-synuclein. • Neuroprotective baicalein disaggregated annular protofibrils.

  10. Free energies of stable and metastable pores in lipid membranes under tension

    NARCIS (Netherlands)

    den Otter, Wouter K.

    2009-01-01

    The free energy profile of pore formation in a lipid membrane, covering the entire range from a density fluctuation in an intact bilayer to a large tension-stabilized pore, has been calculated by molecular dynamics simulations with a coarse-grained lipid model. Several fixed elongations are used to

  11. Bacteroides fragilis interferes with iNOS activity and leads to pore formation in macrophage surface

    International Nuclear Information System (INIS)

    Vieira, Jessica Manya B.D.; Vallim, Deyse C.; Ferreira, Eliane O.; Seabra, Sergio H.; Vommaro, Rossiane C.; Avelar, Katia E.S.; De Souza, Wanderley; Ferreira, Maria Ca-hat ndida S.; Domingues, Regina M.C.P.

    2005-01-01

    Bacteroides fragilis is the anaerobe most commonly recoverable from clinical specimens. The wide genetic diversity of this bacterium related with virulence potential is still an open question. In this study, we analyzed the morphological aspects and microbicide action of MO during interactions with B. fragilis. A filamentous cytoplasm content release and a different actin organization colocalized with iNOS were detected. It was also possible to observe the reduction of NO production in the same conditions. The scanning electron microscopy showed the formation of pore-like structures in the surface of macrophages in the bacterial presence and by transmission electron microscopy we could observe the extrusion of cytoplasm contents as well as the condensation of chromatin in the nucleus periphery. These data suggest the existence of an inhibitory mechanism developed by B. fragilis strains for one of the macrophage microbicide actions

  12. Pore Formation and Mobility Investigation (PFMI): Concept, Hardware Development and Initial Analysis of Experiments

    Science.gov (United States)

    Grugel, Richard N.

    2004-01-01

    Porosity in the form of "bubbles and pipes" can occur during controlled directional solidification processing of metal alloys. This is a consequence that 1) precludes obtaining any meaningful scientific results and 2) is detrimental to desired material properties. Unfortunately, several Microgravity experiments have been compromised by porosity. The intent of the PFMI investigation is to conduct a systematic effort directed towards understanding porosity formation and mobility during controlled directional solidification (DS) in a microgravity environment. PFMI uses a pure transparent material, succinonitrile (SCN), as well as SCN "alloyed" with water, in conjunction with a translating temperature gradient stage so that direct observation and recording of pore generation and mobility can be made. PFMI is investigating the role of thermocapillary forces and temperature gradients in affecting bubble dynamics as well as other solidification processes in a microgravity Environment. This presentation will cover the concept, hardware development, operations, and the initial results from experiments conducted aboard the International Space Station. .

  13. Killing machines: three pore-forming proteins of the immune system

    Science.gov (United States)

    McCormack, Ryan; de Armas, Lesley; Shiratsuchi, Motoaki

    2014-01-01

    The evolution of early multicellular eukaryotes 400–500 million years ago required a defensive strategy against microbial invasion. Pore-forming proteins containing the membrane-attack-complex-perforin (MACPF) domain were selected as the most efficient means to destroy bacteria or virally infected cells. The mechanism of pore formation by the MACPF domain is distinctive in that pore formation is purely physical and unspecific. The MACPF domain polymerizes, refolds, and inserts itself into bilayer membranes or bacterial outer cell walls. The displacement of surface lipid/carbohydrate molecules by the polymerizing MACPF domain creates clusters of large, water-filled holes that destabilize the barrier function and provide access for additional anti-bacterial or anti-viral effectors to sensitive sites that complete the destruction of the invader via enzymatic or chemical attack. The highly efficient mechanism of anti-microbial defense by a combined physical and chemical strategy using pore-forming MACPF-proteins has been retargeted during evolution of vertebrates and mammals for three purposes: (1) to kill extracellular bacteria C9/polyC9 evolved in conjunction with complement, (2) to kill virus infected and cancer cells perforin-1/polyperforin-1 CTL evolved targeted by NK and CTL, and (3) to kill intracellular bacteria transmembrane perforin-2/putative polyperforin-2 evolved targeted by phagocytic and nonphagocytic cells. Our laboratory has been involved in the discovery and description of each of the three pore-formers that will be reviewed here. PMID:24293008

  14. Evaluation of the influence of sulfur-based functional groups on the embedding of silver nanoparticles into the pores of MCM-41

    International Nuclear Information System (INIS)

    Oliveira, Roselaine da S.; Camilo, Fernanda F.; Bizeto, Marcos A.

    2016-01-01

    The incorporation of noble metals in the pores of mesoporous silicas might produce materials with interesting catalytic and sensing capabilities, but the proper control of pore filling and the avoidance of nanoparticles migration to outside the pores are processes not yet completely understood. In this work, we evaluated the role of –SH and –SO_3H groups post-grafted into MCM-41 on the production of silver nanoparticles by using 1-butanol as reducing agent. Thiol groups were the most efficient on promoting the formation of nanoparticles within the pores. Conversely, sulfonic groups establish electrostatic interactions with silver cations that preclude the formation of nanoparticle in yields comparable to thiol groups. MCM-41 without functional groups did not have good affinity to silver and the nanoparticles are produced outside the pores. This study showed the importance on selecting an adequate surface functional group in order to obtain silver nanoparticles filling the pores of MCM-41. - Graphical abstract: Silver nanoparticles formation inside the pores of sulfur-groups functionalized mesoporous silica. - Highlights: • Silver nanoparticles formation inside the pores of mesoporous silica. • n-butanol as reducing agent of impregnated silver cations. • Tuning the silica surface properties by grafting sulfur-based functional groups. • Influence on the loading and distribution of the nanoparticles through the pores.

  15. 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.

  16. Induction of nano pore in Agrobacterial hemoglobin

    Directory of Open Access Journals (Sweden)

    Mojtaba Tousheh

    2014-01-01

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

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

    Science.gov (United States)

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

    2014-11-01

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

  18. Dependence of cell adhesion on extracellular matrix materials formed on pore bridge boundaries by nanopore opening and closing geometry.

    Science.gov (United States)

    Kim, Sueon; Han, Dong Yeol; Chen, Zhenzhong; Lee, Won Gu

    2018-04-30

    In this study, we report experimental results for characterization of the growth and formation of pore bridge materials that modified the adhesion structures of cells cultured on nanomembranes with opening and closing geometry. To perform the proof-of-concept experiments, we fabricated two types of anodized alumina oxide substrates with single-sided opening (i.e., one side open, but closed at the other side) and double-sided opening (i.e., both sides open). In our experiment, we compared the densities of pores formed and of bridge materials which differently act as connective proteins depending on the size of pores. The results show that the pore opening geometry can be used to promote the net contact force between pores, resulting in the growth and formation of pore bridge materials before and after cell culture. The results also imply that the bridge materials can be used to attract the structural protrusion of filopodia that can promote the adhesion of cell-to-cell and cell-to-pore bridge. It is observed that the shape and size of cellular structures of filopodia depend on the presence of pore bridge materials. Overall, this observation brought us a significant clue that cells cultured on nanopore substrates would change the adhesion property depending on not only the formation of nanopores formed on the surface of topological substrates, but also that of pore bridge materials by its morphological growth.

  19. Synthesis of mesoporous carbon nanoparticles with large and tunable pore sizes

    Science.gov (United States)

    Liu, Chao; Yu, Meihua; Li, Yang; Li, Jiansheng; Wang, Jing; Yu, Chengzhong; Wang, Lianjun

    2015-07-01

    Mesoporous carbon nanoparticles (MCNs) with large and adjustable pores have been synthesized by using poly(ethylene oxide)-b-polystyrene (PEO-b-PS) as a template and resorcinol-formaldehyde (RF) as a carbon precursor. The resulting MCNs possess small diameters (100-126 nm) and high BET surface areas (up to 646 m2 g-1). By using home-designed block copolymers, the pore size of MCNs can be tuned in the range of 13-32 nm. Importantly, the pore size of 32 nm is the largest among the MCNs prepared by the soft-templating route. The formation mechanism and structure evolution of MCNs were studied by TEM and DLS measurements, based on which a soft-templating/sphere packing mechanism was proposed. Because of the large pores and small particle sizes, the resulting MCNs were excellent nano-carriers to deliver biomolecules into cancer cells. MCNs were further demonstrated with negligible toxicity. It is anticipated that this carbon material with large pores and small particle sizes may have excellent potential in drug/gene delivery.Mesoporous carbon nanoparticles (MCNs) with large and adjustable pores have been synthesized by using poly(ethylene oxide)-b-polystyrene (PEO-b-PS) as a template and resorcinol-formaldehyde (RF) as a carbon precursor. The resulting MCNs possess small diameters (100-126 nm) and high BET surface areas (up to 646 m2 g-1). By using home-designed block copolymers, the pore size of MCNs can be tuned in the range of 13-32 nm. Importantly, the pore size of 32 nm is the largest among the MCNs prepared by the soft-templating route. The formation mechanism and structure evolution of MCNs were studied by TEM and DLS measurements, based on which a soft-templating/sphere packing mechanism was proposed. Because of the large pores and small particle sizes, the resulting MCNs were excellent nano-carriers to deliver biomolecules into cancer cells. MCNs were further demonstrated with negligible toxicity. It is anticipated that this carbon material with large pores and

  20. Numerical modeling of pore-scale phenomena during CO2 sequestration in oceanic sediments

    International Nuclear Information System (INIS)

    Kang, Qinjun; Tsimpanogiannis, Ioannis N.; Zhang, Dongxiao; Lichtner, Peter C.

    2005-01-01

    Direct disposal of liquid CO 2 on the ocean floor is one of the approaches considered for sequestering CO 2 in order to reduce its concentration in the atmosphere. At oceanic depths deeper than approximately 3000 m, liquid CO 2 density is higher than the density of seawater and CO 2 is expected to sink and form a pool at the ocean floor. In addition to chemical reactions between CO 2 and seawater to form hydrate, fluid displacement is also expected to occur within the ocean floor sediments. In this work, we consider two different numerical models for hydrate formation at the pore scale. The first model consists of the Lattice Boltzmann (LB) method applied to a single-phase supersaturated solution in a constructed porous medium. The second model is based on the Invasion Percolation (IP) in pore networks, applied to two-phase immiscible displacement of seawater by liquid CO 2 . The pore-scale results are upscaled to obtain constitutive relations for porosity, both transverse and for the entire domain, and for permeability. We examine deposition and displacement patterns, and changes in porosity and permeability due to hydrate formation, and how these properties depend on various parameters including a parametric study of the effect of hydrate formation kinetics. According to the simulations, the depth of CO 2 invasion in the sediments is controlled by changes in the pore-scale porosity close to the hydrate formation front. (author)

  1. Relationship between petrographic pore types and core measurements in sandstones of the Monserrate Formation, upper Magdalena Valley, Colombia

    International Nuclear Information System (INIS)

    Ehrlich, R; Cobaleda, G; Barclay, Ferm

    1997-01-01

    Patterns of porosity in sandstones of the Monserrate Formation (Upper Magdalena Valley) exposed in polished blocks have been digitally recorded using an image processor coupled to a scanning electron microscope operated in back scatter electron mode. Additionally, porosity, permeability and response to mercury injection-capillary pressure tests were measured on some of the imaged samples. Porosity pattern were evaluated via an erosion/dilation-differencing image-processing algorithm and then classified by the self-training classifier, SAWVEC. Changes in the resulting pore type proportions were strongly associated with changes in the mercury porosimetry curves. From the image processing data, five pore types, sufficient to include all of the variability in size and shape of the patterns of porosity, were identified. Variations in the number of pares of each type per unit cross sectional area were related to variations in permeability. The resultant relationships with mercury porosimetry demonstrated that pares of the same type tends to form microcircuits characterized by a limited throat size range. Permeability modeling showed that intergranular Pare Types 2 and 4 (secondary porosity resulting from carbonate dissolution) are responsible for permeability in the 0,01 - 0,1 0 Darcy range. Type 5 pares (large molds) slightly contribute to permeability, except in coarse grained rocks where they are efficiently connected by micro fractures

  2. Analysis of the effect of pore geometry in the physical properties of rocks

    Directory of Open Access Journals (Sweden)

    Luiz Alberto Oliveira Lima Roque

    2012-12-01

    Full Text Available Pore geometry is one of the main factors influencing the flow of reservoir fluids under pressure. Pores with narrower formats are more easily compressed when subject to pressure. Pressure modifies pore geometry by opening or closing cracks, causing increase or decrease in the elastic modulus, porosity, permeability, and other parameters. Rock physical properties depend on the size and shape of pores. Thus, in order to analyze changes on the physical properties behavior according to the pores geometry, it is necessary to study and improve mathematical models of the porous media by taking into account the pore shape factor for estimating rock elastic properties. Differential effective medium model (DEM, Hertz-Mindlin theory and coherent potential approximation (CPA are some of the theoretical paradigms that take into account pore geometry in changes in elastic moduli. Given the importance of the pore structure effect on the behavior of physical parameters, this article proposes an analysis of some mathematical models that consider the influence of pore shapes in the physical properties of rocks.

  3. Effects of Pore Size on the Osteoconductivity and Mechanical Properties of Calcium Phosphate Cement in a Rabbit Model.

    Science.gov (United States)

    Zhao, Yi-Nan; Fan, Jun-Jun; Li, Zhi-Quan; Liu, Yan-Wu; Wu, Yao-Ping; Liu, Jian

    2017-02-01

    Calcium phosphate cement (CPC) porous scaffold is widely used as a suitable bone substitute to repair bone defect, but the optimal pore size is unclear yet. The current study aimed to evaluate the effect of different pore sizes on the processing of bone formation in repairing segmental bone defect of rabbits using CPC porous scaffolds. Three kinds of CPC porous scaffolds with 5 mm diameters and 12 mm length were prepared with the same porosity but different pore sizes (Group A: 200-300 µm, Group B: 300-450 µm, Group C: 450-600 µm, respectively). Twelve millimeter segmental bone defects were created in the middle of the radius bone and filled with different kinds of CPC cylindrical scaffolds. After 4, 12, and 24 weeks, alkaline phosphatase (ALP), histological assessment, and mechanical properties evaluation were performed in all three groups. After 4 weeks, ALP activity increased in all groups but was highest in Group A with smallest pore size. The new bone formation within the scaffolds was not obvious in all groups. After 12 weeks, the new bone formation within the scaffolds was obvious in each group and highest in Group A. At 24 weeks, no significant difference in new bone formation was observed among different groups. Besides the osteoconductive effect, Group A with smallest pore size also had the best mechanical properties in vivo at 12 weeks. We demonstrate that pore size has a significant effect on the osteoconductivity and mechanical properties of calcium phosphate cement porous scaffold in vivo. Small pore size favors the bone formation in the early stage and may be more suitable for repairing segmental bone defect in vivo. © 2016 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.

  4. Optimal Pile Arrangement for Minimizing Excess Pore Water Pressure Build-Up

    DEFF Research Database (Denmark)

    Barari, Amin; Saadati, Meysam; Ibsen, Lars Bo

    2013-01-01

    Numerical analysis of pile group in a liquefiable soil was considered to investigate the influence of pile spacing on excess pore pressure distribution and liquefaction potential. The analysis is conducted using a two-dimensional plain strain finite difference program considering a nonlinear...... constitutive model for sandy soil, strength and stiffness reduction, and pile-soil interaction. The Mohr-Coulomb constitutive model coupled with Byrne pore pressure build-up model have been employed in the analysis. Numerical analysis results show that pile groups have significant influence on the dynamic...... response of sandy soil as they reduce the amount of excess pore pressure development during seismic shaking and may even prevent liquefaction....

  5. Pore shape of honeycomb-patterned films: modulation and interfacial behavior.

    Science.gov (United States)

    Wan, Ling-Shu; Ke, Bei-Bei; Zhang, Jing; Xu, Zhi-Kang

    2012-01-12

    The control of the pore size of honeycomb-patterned films has been more or less involved in most work on the topic of breath figures. Modulation of the pore shape was largely ignored, although it is important to applications in replica molding, filtration, particle assembly, and cell culture. This article reports a tunable pore shape for patterned films prepared from commercially available polystyrene (PS). We investigated the effects of solvents including tetrahydrofuran (THF) and chloroform (CF) and hydrophilic additives including poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA), poly(ethylene glycol) (PEG), and poly(N-vinyl pyrrolidone) (PVP). Water droplets on/in the polymer solutions were observed and analyzed for simulating the formation and stabilization of breath figures. Interfacial tensions of the studied systems were measured and considered as a main factor to modulate the pore shape. Results indicate that the pores gradually change from near-spherical to ellipsoidal with the increase of additive content when using CF as the solvent; however, only ellipsoidal pores are formed from the THF solution. It is demonstrated that the aggregation of the additives at the water/polymer solution interface is more efficient in the THF solution than that in the CF solution. This aggregation decreases the interfacial tension, stabilizes the condensed water droplets, and shapes the pores of the films. The results may facilitate our understanding of the dynamic breath figure process and provide a new pathway to prepare patterned films with different pore structures.

  6. Mitochondrial permeability transition pore inhibitors prevent ethanol-induced neuronal death in mice.

    Science.gov (United States)

    Lamarche, Frederic; Carcenac, Carole; Gonthier, Brigitte; Cottet-Rousselle, Cecile; Chauvin, Christiane; Barret, Luc; Leverve, Xavier; Savasta, Marc; Fontaine, Eric

    2013-01-18

    Ethanol induces brain injury by a mechanism that remains partly unknown. Mitochondria play a key role in cell death processes, notably through the opening of the permeability transition pore (PTP). Here, we tested the effect of ethanol and PTP inhibitors on mitochondrial physiology and cell viability both in vitro and in vivo. Direct addition of ethanol up to 100 mM on isolated mouse brain mitochondria slightly decreased oxygen consumption but did not affect PTP regulation. In comparison, when isolated from ethanol-treated (two doses of 2 g/kg, 2 h apart) 7-day-old mouse pups, brain mitochondria displayed a transient decrease in oxygen consumption but no change in PTP regulation or H2O2 production. Conversely, exposure of primary cultured astrocytes and neurons to 20 mM ethanol for 3 days led to a transient PTP opening in astrocytes without affecting cell viability and to a permanent PTP opening in 10 to 20% neurons with the same percentage of cell death. Ethanol-treated mouse pups displayed a widespread caspase-3 activation in neurons but not in astrocytes and dramatic behavioral alterations. Interestingly, two different PTP inhibitors (namely, cyclosporin A and nortriptyline) prevented both ethanol-induced neuronal death in vivo and ethanol-induced behavioral modifications. We conclude that PTP opening is involved in ethanol-induced neurotoxicity in the mouse.

  7. Understanding chemical-potential-related transient pore-pressure response to improve real-time borehole (in)stability predictions

    Energy Technology Data Exchange (ETDEWEB)

    Tare, U. A.; Mody, F. K.; Mese, A. I. [Haliburton Energy Services, TX (United States)

    2002-07-01

    In order to develop a real-time wellbore (in)stability modelling capability, experimental work was carried out to investigate the role of the chemical potential of drilling fluids on transient pore pressure and time-dependent rock property alterations of shale formations. Time-dependent alterations in the pore pressure, acoustic and rock properties of formations subjected to compressive tri-axial test were recorded during the experiments involving the Pore Pressure Transmission (PPT) test. Based on the transient pore pressure of shale exposed to the test fluid presented here, the 20 per cent calcium chloride showed a very low membrane efficiency of 4.45 per cent. The need for a thorough understanding of the drilling fluid/shale interaction prior to applying any chemical potential wellbore (in)stability model to real-time drilling operations was emphasized. 9 refs., 5 figs.

  8. Oligomerization is involved in pore formation by Bordetella adenylate cyclase toxin

    Czech Academy of Sciences Publication Activity Database

    Vojtová, Jana; Basler, Marek; Osička, Radim; Knapp, O.; Maier, E.; Černý, J.; Benada, Oldřich; Benz, R.; Šebo, Peter

    2009-01-01

    Roč. 23, - (2009), s. 2831-2843 ISSN 0892-6638 R&D Projects: GA AV ČR IAA500200914; GA MŠk 1M0506 Grant - others:-(XE) LSHB-CT-2003-503582 THERAVAC Institutional research plan: CEZ:AV0Z50200510 Keywords : blue native electrophoresis * planar lipid bilayer membranes * pore-forming activity Subject RIV: EE - Microbiology, Virology Impact factor: 6.401, year: 2009

  9. TIG Dressing Effects on Weld Pores and Pore Cracking of Titanium Weldments

    Directory of Open Access Journals (Sweden)

    Hui-Jun Yi

    2016-10-01

    Full Text Available Weld pores redistribution, the effectiveness of using tungsten inert gas (TIG dressing to remove weld pores, and changes in the mechanical properties due to the TIG dressing of Ti-3Al-2.5V weldments were studied. Moreover, weld cracks due to pores were investigated. The results show that weld pores less than 300 μm in size are redistributed or removed via remelting due to TIG dressing. Regardless of the temperature condition, TIG dressing welding showed ductility, and there was a loss of 7% tensile strength of the weldments. Additionally, it was considered that porosity redistribution by TIG dressing was due to fluid flow during the remelting of the weld pool. Weld cracks in titanium weldment create branch cracks around pores that propagate via the intragranular fracture, and oxygen is dispersed around the pores. It is suggested that the pore locations around the LBZ (local brittle zone and stress concentration due to the pores have significant effects on crack initiation and propagation.

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

    Science.gov (United States)

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

    2017-04-01

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

  11. Conductometric determination of single pores in polyethyleneterephthalate irradiated by heavy ions

    International Nuclear Information System (INIS)

    Oganesyan, V.R.; Trofimov, V.V.; Doerschel, B.; Hermsdorf, D.; Vetter, J.; Danziger, M.

    2002-01-01

    Most of the previous works devoted to the problem of track formation processes did not pay enough attention to direct measurement of the appearance of every individual pore in an array of many pores induced by the irradiation of polymer films with ions. Such measurements are not easy to carry out due to the extremely high electric resistance in the moment of pore opening. In this work the analysis of films irradiated with low particle fluences up to 3.7·10 3 ions/cm 2 is described. Polyethyleneterephthalate (PET) Hostaphan with a thickness of 20μm was used. The samples were irradiated with Bi ions of 11.4 MeV/amu energy. Using optimized etching conditions and computer aided data evaluation, we obtained results, which are in good agreement with theoretical predictions and model calculations. The measured increase of conductivity beginning from the breakthrough of a single track up to the next pore opening in dependence on the etching time and the number of opened pores confirm the assumed model. Thus, the developed 'track-by-track' method can be used effectively for description of the sequential appearance of individual pores in an electrolytic etching process

  12. Effects of Coke Calcination Level on Pore Structure in Carbon Anodes

    Science.gov (United States)

    Fang, Ning; Xue, Jilai; Lang, Guanghui; Bao, Chongai; Gao, Shoulei

    2016-02-01

    Effects of coke calcination levels on pore structure of carbon anodes have been investigated. Bench anodes were prepared by 3 types of cokes with 4 calcination temperatures (800°C, 900°C, 1000°C and 1100°C). The cokes and anodes were characterized using hydrostatic method, air permeability determination, mercury porosimetry, image analysis and confocal microscopy (CSLM). The cokes with different calcination levels are almost the same in LC values (19-20 Å) and real density (1.967-1.985 g/cm3), while the anode containing coke calcined at 900°C has the lowest open porosity and air permeability. Pore size distribution (represented by Anode H sample) can be roughly divided into two ranges: small and medium pores in diameter of 10-400 μm and large pores of 400-580 μm. For the anode containing coke calcined at 800°C, a number of long, narrow pores in the pore size range of 400-580 μm are presented among cokes particles. Formation of these elongated pores may be attributed to coke shrinkages during the anode baking process, which may develop cracking in the anode under cell operations. More small or medium rounded pores with pore size range of 10-400 μm emerge in the anodes with coke calcination temperatures of 900°C, 1000°C and 1100°C, which may be generated due to release of volatiles from the carbon anode during baking. For the anode containing coke calcined at 1100°C, it is found that many rounded pores often closely surround large coke particles, which have potential to form elongated, narrow pores.

  13. Pore Structure and Fractal Characteristics of Niutitang Shale from China

    Directory of Open Access Journals (Sweden)

    Zhaodong Xi

    2018-04-01

    Full Text Available A suite of shale samples from the Lower Cambrian Niutitang Formation in northwestern Hunan Province, China, were investigated to better understand the pore structure and fractal characteristics of marine shale. Organic geochemistry, mineralogy by X-ray diffraction, porosity, permeability, mercury intrusion and nitrogen adsorption and methane adsorption experiments were conducted for each sample. Fractal dimension D was obtained from the nitrogen adsorption data using the fractal Frenkel-Halsey-Hill (FHH model. The relationships between total organic carbon (TOC content, mineral compositions, pore structure parameters and fractal dimension are discussed, along with the contributions of fractal dimension to shale gas reservoir evaluation. Analysis of the results showed that Niutitang shale samples featured high TOC content (2.51% on average, high thermal maturity (3.0% on average, low permeability and complex pore structures, which are highly fractal. TOC content and mineral compositions are two major factors affecting pore structure but they have different impacts on the fractal dimension. Shale samples with higher TOC content had a larger specific surface area (SSA, pore volume (PV and fractal dimension, which enhanced the heterogeneity of the pore structure. Quartz content had a relatively weak influence on shale pore structure, whereas SSA, PV and fractal dimension decreased with increasing clay mineral content. Shale with a higher clay content weakened pore structure heterogeneity. The permeability and Langmuir volume of methane adsorption were affected by fractal dimension. Shale samples with higher fractal dimension had higher adsorption capacity but lower permeability, which is favorable for shale gas adsorption but adverse to shale gas seepage and diffusion.

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

    International Nuclear Information System (INIS)

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

    2015-01-01

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

  15. The potential of medium-pore zeolites for improved propene yields from catalytic cracking

    Energy Technology Data Exchange (ETDEWEB)

    Bager, F.; Salas, N.; Ernst, S. [Technische Univ. Kaiserslautern (Germany). Dept. of Chemistry, Chemical Technology

    2011-07-01

    The medium-pore zeolites ZSM-5 (MFI), ZSM-22 (TON), ZSM-23 (MTT), and EU-1 (EUO) were synthesized under hydrothermal conditions and modified by ion exchange to obtain the Broensted-acid forms. The activity and selectivity of these catalysts in catalytic cracking of a model compound, viz. n-octane, was studied in a fixed-bed flow-type reactor. The catalytic results clearly reflect the differences in the pore architectures of the tested zeolites on n-octane conversion and on the product selectivities. Over the zeolites with one-dimensional pore systems and without large intracrystalline cavities, a remarkable increase of the contribution of the monomolecular cracking mechanism could be observed as compared to the standard catalyst zeolite ZSM-5. This is indicated by a high selectivity for unsaturated products and, hence, increasing yields of propene. Large cavities in the pore system, viz. in the case of zeolite EU-1, increase the conversion in particular at lower temperatures. However, the large cavities also favor the formation of large transition states required for the classical bimolecular cracking mechanism, resulting in decreased selectivities for unsaturated products, increased selectivities for aromatics formation and faster deactivation. (orig.)

  16. Conductometric Determination of Single Pores in Polyethyleneterephthalate Irradiated by Heavy Ions

    CERN Document Server

    Oganesyan, V R; Dörschel, B; Vetter, J E; Danziger, M; Hermsdorf, D

    2002-01-01

    Most of previous works devoted to the problem of track formation processes did not pay enough attention to direct measurement of the appearance of every individual pore in an array of many pores induced by the irradiation of polymer films with ions. Such measurements are not easy to carry out due to the extremely high electric resistance in the moment of pore opening. In this work the analysis of films irradiated with low particle fluences up to 3.7\\cdot 10^{3} ions/cm^2 is described. Polyethyleneterephthalate (PET) Hostaphan with a thickness of 20 m was used. The samples were irradiated with Bi ions of 11.4 MeV/amu energy. Using optimized etching conditions and computer aided data evaluation we obtained results, which are in good agreement with theoretical predictions and model calculations. The measured increase of conductivity beginning from the breakthrough of a single track up to the next pore opening in dependence on the etching time and the number of opened pores confirm the assumed model. Thus, the de...

  17. Conductometric determination of single pores in polyethyleneterephthalate irradiated by heavy ions

    CERN Document Server

    Oganesyan, V R; Dörschel, B; Hermsdorf, D; Trofimov, V V; Vetter, J

    2002-01-01

    Most of the previous works devoted to the problem of track formation processes did not pay enough attention to direct measurement of the appearance of every individual pore in an array of many pores induced by the irradiation of polymer films with ions. Such measurements are not easy to carry out due to the extremely high electric resistance in the moment of pore opening. In this work the analysis of films irradiated with low particle fluences up to 3.7 centre dot 10 sup 3 ions/cm sup 2 is described. Polyethyleneterephthalate (PET) Hostaphan with a thickness of 20 mu m was used. The samples were irradiated with Bi ions of 11.4 MeV/amu energy. Using optimized etching conditions and computer aided data evaluation, we obtained results, which are in good agreement with theoretical predictions and model calculations. The measured increase of conductivity beginning from the breakthrough of a single track up to the next pore opening in dependence on the etching time and the number of opened pores confirm the assumed...

  18. Size Control of Porous Silicon-Based Nanoparticles via Pore-Wall Thinning.

    Science.gov (United States)

    Secret, Emilie; Leonard, Camille; Kelly, Stefan J; Uhl, Amanda; Cozzan, Clayton; Andrew, Jennifer S

    2016-02-02

    Photoluminescent silicon nanocrystals are very attractive for biomedical and electronic applications. Here a new process is presented to synthesize photoluminescent silicon nanocrystals with diameters smaller than 6 nm from a porous silicon template. These nanoparticles are formed using a pore-wall thinning approach, where the as-etched porous silicon layer is partially oxidized to silica, which is dissolved by a hydrofluoric acid solution, decreasing the pore-wall thickness. This decrease in pore-wall thickness leads to a corresponding decrease in the size of the nanocrystals that make up the pore walls, resulting in the formation of smaller nanoparticles during sonication of the porous silicon. Particle diameters were measured using dynamic light scattering, and these values were compared with the nanocrystallite size within the pore wall as determined from X-ray diffraction. Additionally, an increase in the quantum confinement effect is observed for these particles through an increase in the photoluminescence intensity of the nanoparticles compared with the as-etched nanoparticles, without the need for a further activation step by oxidation after synthesis.

  19. Gelatin Scaffolds with Controlled Pore Structure and Mechanical Property for Cartilage Tissue Engineering.

    Science.gov (United States)

    Chen, Shangwu; Zhang, Qin; Nakamoto, Tomoko; Kawazoe, Naoki; Chen, Guoping

    2016-03-01

    Engineering of cartilage tissue in vitro using porous scaffolds and chondrocytes provides a promising approach for cartilage repair. However, nonuniform cell distribution and heterogeneous tissue formation together with weak mechanical property of in vitro engineered cartilage limit their clinical application. In this study, gelatin porous scaffolds with homogeneous and open pores were prepared using ice particulates and freeze-drying. The scaffolds were used to culture bovine articular chondrocytes to engineer cartilage tissue in vitro. The pore structure and mechanical property of gelatin scaffolds could be well controlled by using different ratios of ice particulates to gelatin solution and different concentrations of gelatin. Gelatin scaffolds prepared from ≥70% ice particulates enabled homogeneous seeding of bovine articular chondrocytes throughout the scaffolds and formation of homogeneous cartilage extracellular matrix. While soft scaffolds underwent cellular contraction, stiff scaffolds resisted cellular contraction and had significantly higher cell proliferation and synthesis of sulfated glycosaminoglycan. Compared with the gelatin scaffolds prepared without ice particulates, the gelatin scaffolds prepared with ice particulates facilitated formation of homogeneous cartilage tissue with significantly higher compressive modulus. The gelatin scaffolds with highly open pore structure and good mechanical property can be used to improve in vitro tissue-engineered cartilage.

  20. Facile Synthesis of Gold-Silver Nanocages with Controllable Pores on the Surface

    OpenAIRE

    Chen, Jingyi; McLellan, Joseph M.; Siekkinen, Andrew; Xiong, Yujie; Li, Zhi-Yuan; Xia, Younan

    2006-01-01

    Gold-silver alloy nanocages with controllable pores on the surface have been synthesized via galvanic replacement reaction between truncated Ag nanocubes and aqueous HAuCl4. Unlike the previous studies, the initiation of replacement reaction started in a controllable way, simultaneously from eight corners of the truncated Ag nanocubes where {111} facets were exposed. The formation of cubic nanocages with pores at all the corners was determined by the capping agent, poly(vinyl pyrrolidone) (PV...

  1. Involvement of IGF-1/IGFBP-3 signaling on the conspicuousness of facial pores.

    Science.gov (United States)

    Sugiyama-Nakagiri, Yoriko; Ohuchi, Atsushi; Hachiya, Akira; Kitahara, Takashi

    2010-11-01

    Conspicuous facial pores are one type of serious esthetic defects for many women. We previously reported that the severity of impairment of skin architecture around facial pores correlates well with the appearance of facial pores in several ethnic groups. In our last report, we showed that serum levels of insulin-like growth factor-1 (IGF-1) correlate well with facial pore size and with the severity of impairment of epidermal architecture around facial pores. However, our results could not fully explain the implication between facial pores and IGF signaling. In this study, we conducted a histological analysis of facial skin to determine whether potential changes in IGF-1 availability occur in the skin with or without conspicuous pores. Immunohistochemical observations showed that expression of insulin-like growth factor binding protein-3 (IGFBP-3) is limited to the suprapapillary epidermis around facial pores and to basal cells of rete pegs without tips in epidermis with conspicuous pores. In contrast, in basal cells of skin without conspicuous pores, IGFBP-3 expression is very low. Ki-67 and IGF-1 receptor-positive cells are abundant in basal cells in the tips of the rete pegs in skin with typical epidermal architecture around facial pores. No obvious differences were observed in the expression of filaggrin, involucrin, K1, K6 or K17 in skin with or without conspicuous pores. However, increased expression of K16 was observed in skin with conspicuous pores suggesting hyperproliferation. These results suggest that the IGF-1/IGFBP-3 signaling pathway is involved in the formation of conspicuous facial pores due to the epidermal architecture around facial pores.

  2. The educative prevention of the early stage of educationist’s formation.

    Directory of Open Access Journals (Sweden)

    Marta Alfonso Nazco

    2010-04-01

    Full Text Available The article introduces a characterization of the educative prevention stage at the early professional formation process of educacionist in Sancti Spìritus province. The study is done by the indication analysis of assistant, learning, permanence and behavior at youths who course pedagogical carrers, and haven’t expressed a desire stage yet. The main shown results dealt with the assumption of the searching variables and its indicators, the construction of instruments and the definition of aspects concerning the educative prevention at the early stage of educationist’s formation in the selected choosing. Theoretical, empirical and statistical- math, methods were used which were helped by the constructed instruments and the triangulations among them thus arriving to generalizations for the caracterization. The results have better the work at the area project of the educative prevention in adolescents and youths in the territory, witch mainly concern the desing and implementation of actions withing the pedagogical process, foccuse in the integration of institutions, socializer and educative agents functioning to eductive prevention.

  3. Lattice density functional theory investigation of pore shape effects. I. Adsorption in single nonperiodic pores.

    Science.gov (United States)

    Malanoski, A P; van Swol, Frank

    2002-10-01

    A fully explicit in three dimensions lattice density functional theory is used to investigate adsorption in single nonperiodic pores. The effect of varying pore shape from the slits and cylinders that are normally simulated was our primary interest. A secondary concern was the results for pores with very large diameters. The shapes investigated were square pores with or without surface roughness, cylinders, right triangle pores, and trapezoidal pores. It was found that pores with very similar shape factors gave similar results but that the introduction of acute angled corners or very large side ratio lengths in rectangular pores gave results that were significantly different. Further, a rectangular pore going towards the limit of infinite side ratio does not approach the results of a slit pore. In all of these cases, the importance of features that are present for only a small portion of the pore is demonstrated.

  4. Separating attoliter-sized compartments using fluid pore-spanning lipid bilayers.

    Science.gov (United States)

    Lazzara, Thomas D; Carnarius, Christian; Kocun, Marta; Janshoff, Andreas; Steinem, Claudia

    2011-09-27

    Anodic aluminum oxide (AAO) is a porous material having aligned cylindrical compartments with 55-60 nm diameter pores, and being several micrometers deep. A protocol was developed to generate pore-spanning fluid lipid bilayers separating the attoliter-sized compartments of the nanoporous material from the bulk solution, while preserving the optical transparency of the AAO. The AAO was selectively functionalized by silane chemistry to spread giant unilamellar vesicles (GUVs) resulting in large continuous membrane patches covering the pores. Formation of fluid single lipid bilayers through GUV rupture could be readily observed by fluorescence microscopy and further supported by conservation of membrane surface area, before and after GUV rupture. Fluorescence recovery after photobleaching gave low immobile fractions (5-15%) and lipid diffusion coefficients similar to those found for bilayers on silica. The entrapment of molecules within the porous underlying cylindrical compartments, as well as the exclusion of macromolecules from the nanopores, demonstrate the barrier function of the pore-spanning membranes and could be investigated in three-dimensions using confocal laser scanning fluorescence imaging. © 2011 American Chemical Society

  5. The Pore Collapse “Hot-Spots” Model Coupled with Brittle Damage for Solid Explosives

    Directory of Open Access Journals (Sweden)

    L. R. Cheng

    2014-01-01

    Full Text Available This paper is devoted to the building of a numerical pore collapse model with “hot-spots” formation for the impacted damage explosives. According to damage mechanical evolution of brittle material, the one-dimensional elastic-viscoplastic collapse model was improved to incorporate the impact damage during the dynamic collapse of pores. The damage of explosives was studied using the statistical crack mechanics (SCRAM. The effects of the heat conduction and the chemical reaction were taken into account in the formation of “hot-spots.” To verify the improved model, numerical simulations were carried out for different pressure states and used to model a multiple-impact experiment. The results show that repeated weak impacts can lead to the collapse of pores and the “hot-spots” may occur due to the accumulation of internal defects accompanied by the softening of explosives.

  6. Studies of in Situ Pore Pressure Fluctuations At Various Scales Études des fluctuations in situ de la pression de pore à différentes échelles

    Directory of Open Access Journals (Sweden)

    Kümpel H. J.

    2006-12-01

    Full Text Available Pore pressure fluctuations in fluid saturated geological formations, either of natural or anthropogenic origin, can be observed at different scales. Natural fluctuations, e. g. , due to tidal, barometric or seismogenic forcing, or man-made effects as through use of underground fluid reservoirs, or initial filling and cyclic loading of lake reservoirs may have wavelengths from meters to kilometers. In situ monitoring of processes, in which both rock deformation and pore pressure changes are significant, improves our knowledge on the mechanical behaviour and the role of pore pressure in porous rocks and sedimentary layers. Pressure transducers for continuous recording of fluid level variations in wells, reflecting pore pressure changes at depth, or borehole tiltmeters that are sensitive to ground deformation caused by gradients of pore pressure fluctuations are relatively simple means to trace the dynamics of such rock-fluid interactions. The obtained data series are usually interpreted in two ways: by application of analytical solutions-adopting homogeneous poroelastic conditions or single fracture models in a uniform, elastic medium-and by simulation through numerical calculations allowing for some heterogeneity in the model volume. Field cases presented in this article include tilt measurements in the vicinity of pumped wells (1 to 100 m scale, fluid level monitoring in wells (borehole scale, and studies of pore pressure effects induced by seismic events (1 to 100 km scale. Specific rock parameters that can be constrained are the Skempton ratio, the hydraulic diffusivity, and the type of the effective rheology. In cases of tiltmeter studies, anisotropy of pore fluid flow can also be detected. Keywords: fluids in rocks, pore pressure, poroelasticity, hydrology. Les fluctuations de la pression de pore dans les formations géologiques saturées en fluides, d'origine naturelle ou anthropogéniques, peuvent être observées à différentes

  7. Effect of pore structure on chemico-osmotic, diffusion and hydraulic properties of mud-stones

    International Nuclear Information System (INIS)

    Takeda, M.; Manaka, M.; Ito, K.; Miyoshi, S.; Tokunaga, T.

    2012-01-01

    Document available in extended abstract form only. An in-situ experiment by Neuzil (2000) has obtained the substantial proof of chemical osmosis in natural clayey formation. Chemical osmosis in clayey formations has thus received attention in recent years in the context of geological disposal of radioactive waste. Chemical osmosis is the diffusion of water through a semi-permeable membrane driven by the difference of chemical potentials between solutions to compensate the difference of water potentials, increasing the other potential differences, such as the pressure difference. Accordingly, the chemical osmosis could generate localized, abnormal fluid pressures in geological formations where formation media act as semi-permeable membranes and groundwater salinity is not uniform. Without taking account of the chemical osmosis, groundwater flow modeling may mislead the prediction of the groundwater flow direction. Therefore the possibility of chemical osmosis needs to be identified for potential host formations for radioactive waste repositories. The chemico-osmotic property of formation media is an essential parameter to identify the possibility of chemical osmosis in the formation; however, the diffusion and hydraulic properties are also fundamental parameters to estimate the duration of chemical osmosis since they control the spatial variation of salinity and the dissipation of osmotically induced pressures. In order to obtain the chemico-osmotic, diffusion and hydraulic parameters from a rock sample, this study developed a laboratory experimental system capable of performing chemical osmosis and permeability experiments. A series of experiments were performed on mud-stones. The chemico-osmotic parameter of each rock sample was further interpreted by the osmotic efficiency model proposed by Bresler (1973) to examine the pore structure inherent in rocks. Diatomaceous and siliceous mud-stone samples were obtained from drill cores taken from the Koetoi and Wakkanai

  8. 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

  9. Biogeochemical processes in a clay formation in situ experiment: Part E - Equilibrium controls on chemistry of pore water from the Opalinus Clay, Mont Terri Underground Research Laboratory, Switzerland

    Energy Technology Data Exchange (ETDEWEB)

    Pearson, F.J., E-mail: fjpearson@gmail.com [Ground-Water Geochemistry, 5108 Trent Woods Dr., New Bern, NC 28562 (United States); Tournassat, Christophe; Gaucher, Eric C. [BRGM, B.P. 36009, 45060 Orleans Cedex 2 (France)

    2011-06-15

    -examination of the measured Ca/Mg activity ratios and consideration of the mineralogical composition of the Opalinus Clay suggested that Ca/Mg cation exchange rather than dolomite saturation may control the ratio of these ions in solution. This re-examination also suggests that the Ca/Mg ratio decreases with increasing pore-water salinity. Several possible reasons for this are proposed. Moreover, it is demonstrated that feldspar equilibria must not be included in Opalinus Clay modelling because feldspars are present only in very small quantities in the formation and because Na/K ratios measured in pore water samples are inconsistent with feldspar saturation. The principal need to improve future modelling is additional or better data on rock properties, in particular: (i) a more detailed identification of phases in the Opalinus Clay that include redox-sensitive elements together with evaluation of their thermodynamic properties; (ii) an improved understanding of the distribution of celestite throughout the Opalinus Clay for Sr/SO{sub 4} concentrations control; (iii) improvements in analytic and thermodynamic data for Ca-Mg rock cation exchange and mineral chemical properties and (iv) the measurement of composition and stability constants of clay minerals actually present in the formation.

  10. 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.

  11. Facile synthesis of gold-silver nanocages with controllable pores on the surface.

    Science.gov (United States)

    Chen, Jingyi; McLellan, Joseph M; Siekkinen, Andrew; Xiong, Yujie; Li, Zhi-Yuan; Xia, Younan

    2006-11-22

    Gold-silver alloy nanocages with controllable pores on the surface have been synthesized via galvanic replacement reaction between truncated Ag nanocubes and aqueous HAuCl4. Unlike in the previous studies, the initiation of replacement reaction started in a controllable way, simultaneously from eight corners of the truncated Ag nanocubes where {111} facets were exposed. The formation of cubic nanocages with pores at all the corners was determined by the capping agent, poly(vinyl pyrrolidone) (PVP), which preferentially covered the {100} facets of a truncated Ag nanocube.

  12. 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)

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

    Science.gov (United States)

    Delavari, Armin; Baltus, Ruth

    2017-08-10

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

  14. Hydration properties of mechanosensitive channel pores define the energetics of gating

    International Nuclear Information System (INIS)

    Anishkin, A; Akitake, B; Kamaraju, K; Chiang, C-S; Sukharev, S

    2010-01-01

    Opening of ion channels directly by tension in the surrounding membrane appears to be the most ancient and simple mechanism of gating. Bacterial mechanosensitive channels MscL and MscS are the best-studied tension-gated nanopores, yet the key physical factors that define their gating are still hotly debated. Here we present estimations, simulations and experimental results showing that hydration of the pore might be one of the major parameters defining the thermodynamics and kinetics of mechanosensitive channel gating. We associate closing of channel pores with complete dehydration of the hydrophobic gate (occlusion by 'vapor lock') and formation of two water-vapor interfaces above and below the constriction. The opening path is the expansion of these interfaces, ultimately leading to wetting of the hydrophobic pore, which does not appear to be the exact reverse of the closing path, thus producing hysteresis. We discuss specifically the role of polar groups (glycines) buried in narrow closed conformations but exposed in the open states that change the wetting characteristics of the pore lining and stabilize conductive states of the channels.

  15. Prevention of H-Aggregates Formation in Cy5 Labeled Macromolecules

    Directory of Open Access Journals (Sweden)

    Jing Kang

    2010-01-01

    Full Text Available H-aggregates of the cyanine dye Cy5 are formed during covalent linkage to the cationic macromolecule Poly(allylamine (PAH. The nonfluorescent H-aggregates strongly restrict the usage of the dye for analytical purposes and prevent a quantitative determination of the labeled macromolecules. The behavior of the H-aggregates has been studied by investigation of the absorption and fluorescence spectra of the dye polymer in dependence on solvent, label degree and additional sulfonate groups. H-aggregate formation is caused by an inhomogeneous distribution of the Cy5 molecules on the polymer chain. The H-aggregates can be destroyed by conformational changes of the PAH induced by interactions with polyanions or in organic solvents. It has been found that the polymer labeling process in high content of organic solvents can prevent the formation of H-aggregates. The results offer a better understanding and improvement of the use of the Cy5 dye for labeling purposes in fluorescence detection of macromolecules.

  16. Diffusion in the pore water of compacted crushed salt

    Energy Technology Data Exchange (ETDEWEB)

    Fluegge, Judith; Herr, Sebastian; Lauke, Thomas; Meleshyn, Artur; Miehe, Ruediger; Ruebel, Andre

    2016-07-15

    Diffusion of dissolved radionuclides in the pore water of compacted crushed salt in the long-term is the most relevant process for the release of radionuclides from a dedicated repository for high-level waste in a salt formation as has been shown in latest safety assessments and research projects /BUH 16/. So far, diffusion coefficients for free water have been applied for the diffusion in pore water in models for long-term safety assessments. This conservative assumption was used, because data on the diffusion coefficient of dissolved substances in crushed salt have been missing. Furthermore, the diffusion coefficient in the pore water was assumed to be constant and independent from the degree of compaction of the crushed salt. The work presented in this report was intended to contribute to fill this gap of knowledge about how the diffusion of radionuclides takes place in the compacted backfill of a repository in salt. For the first time, the pore diffusion coefficient as well as its dependence on the porosity of the crushed salt was determined experimentally by means of through-diffusion experiments using caesium as tracer. The results achieved in this project suggest that the diffusion in compacted crushed salt is not fully comparable to that in a homogeneous, temporally stable porous medium like sand or clay. The results obtained from four diffusion experiments show a remarkably different behaviour and all yield unique concentration versus time plots which includes highly temporal variable tracer fluxes with even full interruptions of the flux for longer periods of time. This effect cannot be explained by assuming a tracer transport by diffusion in a temporarily invariant pore space and / or under temporally invariant experimental conditions. From our point of view, a restructuring of the pore space seems to lead to closed areas of pore water in the sample which may open up again after some time, leading to a variable pore space and hence variable diffusive

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

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, Suk Bon; Choi, Wang Kyu; Choi, Byung Seon; Moon, Jei Kwon [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2012-05-15

    Porous materials with various pore sizes in the range of micropore (< 2 nm), mesopore (2-50 nm), and macropore (> 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 m{sup 2}/g and total pore volume of ca 0.64-0.74 cm{sup 3}/g and showed a narrow pore size distribution (PSD) due to the removal of the organic surfactant molecules

  18. Studying the influence of pore water electrical conductivity on the formation factor, as estimated based on electrical methods

    Energy Technology Data Exchange (ETDEWEB)

    Loefgren, Martin (Kemakta Konsult AB, Stockholm (Sweden)); Vecernik, Petr; Havlova, Vaclava (Waste Disposal Dept., Nuclear Research Institute Rez plc. (Czech Republic))

    2009-11-15

    factors and generic surface conductivities, and fairly good agreement was obtained. Part 1 suffered from methodology problems, which ultimately lead to poor reproducibility and accuracy. Here a single sample was in sequence saturated with the 0.001, 0.03, 0.5, 0.1 and 1.0 M NaCl electrolytes. The aim was to see if the apparent formation factor increasingly overestimates the formation factor with decreasing electrical conductivity of the pore water. Notwithstanding the experimental problems and errors, it was shown that this is clearly the case. For the electrolyte 0.001 M NaCl, and for this particular sample, the apparent formation factor overestimates the formation factor by at least one order of magnitude. The measured apparent formation factors were compared with modelled apparent formation factors, where input data were the sample's measured formation factor and surface conductivity, and fairly good agreement was obtained. The formation factors obtained by the TEM method were comparable with those obtained in the previous through diffusion experiments on the same samples. Especially for the Forsmark samples of part 2, the TEM results agreed with the through diffusion results, indicating that anion exclusion is not a major issue. From comparison of the TEM formation factors, obtained with anionic tracer iodide, and estimated formation factors based on the resistivity methods, it is indicated that anion exclusion should not reduce the effective diffusivity by more than a few factors

  19. Studying the influence of pore water electrical conductivity on the formation factor, as estimated based on electrical methods

    International Nuclear Information System (INIS)

    Loefgren, Martin; Vecernik, Petr; Havlova, Vaclava

    2009-11-01

    factors and generic surface conductivities, and fairly good agreement was obtained. Part 1 suffered from methodology problems, which ultimately lead to poor reproducibility and accuracy. Here a single sample was in sequence saturated with the 0.001, 0.03, 0.5, 0.1 and 1.0 M NaCl electrolytes. The aim was to see if the apparent formation factor increasingly overestimates the formation factor with decreasing electrical conductivity of the pore water. Notwithstanding the experimental problems and errors, it was shown that this is clearly the case. For the electrolyte 0.001 M NaCl, and for this particular sample, the apparent formation factor overestimates the formation factor by at least one order of magnitude. The measured apparent formation factors were compared with modelled apparent formation factors, where input data were the sample's measured formation factor and surface conductivity, and fairly good agreement was obtained. The formation factors obtained by the TEM method were comparable with those obtained in the previous through diffusion experiments on the same samples. Especially for the Forsmark samples of part 2, the TEM results agreed with the through diffusion results, indicating that anion exclusion is not a major issue. From comparison of the TEM formation factors, obtained with anionic tracer iodide, and estimated formation factors based on the resistivity methods, it is indicated that anion exclusion should not reduce the effective diffusivity by more than a few factors

  20. Earthworm-Derived Pore-Forming Toxin Lysenin and Screening of Its Inhibitors

    Directory of Open Access Journals (Sweden)

    Neelanun Sukumwang

    2013-08-01

    Full Text Available Lysenin is a pore-forming toxin from the coelomic fluid of earthworm Eisenia foetida. This protein specifically binds to sphingomyelin and induces erythrocyte lysis. Lysenin consists of 297 amino acids with a molecular weight of 41 kDa. We screened for cellular signal transduction inhibitors of low molecular weight from microorganisms and plants. The purpose of the screening was to study the mechanism of diseases using the obtained inhibitors and to develop new chemotherapeutic agents acting in the new mechanism. Therefore, our aim was to screen for inhibitors of Lysenin-induced hemolysis from plant extracts and microbial culture filtrates. As a result, we isolated all-E-lutein from an extract of Dalbergia latifolia leaves. All-E-lutein is likely to inhibit the process of Lysenin-membrane binding and/or oligomer formation rather than pore formation. Additionally, we isolated tyrosylproline anhydride from the culture filtrate of Streptomyces as an inhibitor of Lysenin-induced hemolysis.

  1. Nicorandil prevents sirolimus-induced production of reactive oxygen species, endothelial dysfunction, and thrombus formation

    Directory of Open Access Journals (Sweden)

    Ken Aizawa

    2015-03-01

    Full Text Available Sirolimus (SRL is widely used to prevent restenosis after percutaneous coronary intervention. However, its beneficial effect is hampered by complications of thrombosis. Several studies imply that reactive oxygen species (ROS play a critical role in endothelial dysfunction and thrombus formation. The present study investigated the protective effect of nicorandil (NIC, an anti-angina agent, on SRL-associated thrombosis. In human coronary artery endothelial cells (HCAECs, SRL stimulated ROS production, which was prevented by co-treatment with NIC. The preventive effect of NIC on ROS was abolished by 5-hydroxydecanoate but not by 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one. NIC also inhibited SRL-induced up-regulation of NADPH oxidase subunit p22phox mRNA. Co-treatment with NIC and SRL significantly up-regulated superoxide dismutase 2. NIC treatment significantly improved SRL-induced decrease in viability of HCAECs. The functional relevance of the preventive effects of NIC on SRL-induced ROS production and impairment of endothelial viability was investigated in a mouse model of thrombosis. Pretreatment with NIC inhibited the SRL-induced acceleration of FeCl3-initiated thrombus formation and ROS production in the testicular arteries of mice. In conclusion, NIC prevented SRL-induced thrombus formation, presumably due to the reduction of ROS and to endothelial protection. The therapeutic efficacy of NIC could represent an additional option in the prevention of SRL-related thrombosis.

  2. 1.9 μm superficially porous packing material with radially oriented pores and tailored pore size for ultra-fast separation of small molecules and biomolecules.

    Science.gov (United States)

    Min, Yi; Jiang, Bo; Wu, Ci; Xia, Simin; Zhang, Xiaodan; Liang, Zhen; Zhang, Lihua; Zhang, Yukui

    2014-08-22

    In this work, 1.9 μm reversed-phase packing materials with superficially porous structure were prepared to achieve the rapid and high efficient separation of peptides and proteins. The silica particles were synthesized via three steps, nonporous silica particle preparation by a modified seeded growth method, mesoporous shell formation by a one pot templated dissolution and redeposition strategy, and pore size expansion via acid-refluxing. By such a method, 1.9 μm superficially porous materials with 0.18 μm shell thickness and tailored pore diameter (10 nm, 15 nm) were obtained. After pore enlargement, the formerly dense arrays of mesoporous structure changed, the radially oriented pores dominated the superficially porous structure. The chromatographic performance of such particles was investigated after C18 derivatization. For packing materials with 1.9 μm diameter and 10 nm pore size, the column efficiency could reach 211,300 plates per m for naphthalene. To achieve the high resolution separation of peptides and proteins, particles with pore diameter of 15 nm were tailored, by which the baseline separation of 5 peptides and 5 intact proteins could be respectively achieved within 1 min, demonstrating the superiority in the high efficiency and high throughput analysis of biomolecules. Furthermore, BSA digests were well separated with peak capacity of 120 in 30 min on a 15 cm-long column. Finally, we compared our columns with a 1.7 μm Kinetex C18 column under the same conditions, our particles with 10nm pore size demonstrated similar performance for separation of the large intact proteins. Moreover, the particles with 15 nm pore size showed more symmetrical peaks for the separation of large proteins (BSA, OVA and IgG) and provided rapid separation of protein extracts from Escherichia coli in 5 min. All these results indicated that the synthesized 1.9 μm superficially porous silica packing materials would be promising in the ultra-fast and high

  3. Active pore space utilization in nanoporous carbon-based supercapacitors: Effects of conductivity and pore accessibility

    Science.gov (United States)

    Seredych, Mykola; Koscinski, Mikolaj; Sliwinska-Bartkowiak, Malgorzata; Bandosz, Teresa J.

    2012-12-01

    Composites of commercial graphene and nanoporous sodium-salt-polymer-derived carbons were prepared with 5 or 20 weight% graphene. The materials were characterized using the adsorption of nitrogen, SEM/EDX, thermal analysis, Raman spectroscopy and potentiometric titration. The samples' conductivity was also measured. The performance of the carbon composites in energy storage was linked to their porosity and electronic conductivity. The small pores (<0.7) were found as very active for double layer capacitance. It was demonstrated that when double layer capacitance is a predominant mechanism of charge storage, the degree of the pore space utilization for that storage can be increased by increasing the conductivity of the carbons. That active pore space utilization is defined as gravimetric capacitance per unit pore volume in pores smaller than 0.7 nm. Its magnitude is affected by conductivity of the carbon materials. The functional groups, besides pseudocapacitive contribution, increased the wettability and thus the degree of the pore space utilization. Graphene phase, owing to its conductivity, also took part in an insitu increase of the small pore accessibility and thus the capacitance of the composites via enhancing an electron transfer to small pores and thus imposing the reduction of groups blocking the pores for electrolyte ions.

  4. Fabrication of three-dimensional poly(ε-caprolactone) scaffolds with hierarchical pore structures for tissue engineering

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Qingchun [Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 (China); Luo, Houyong [State Key Laboratory of Bioreactor Engineering, School of Bioengineering, East China University of Science and Technology, Shanghai 200237 (China); Zhang, Yan [Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 (China); Zhou, Yan [State Key Laboratory of Bioreactor Engineering, School of Bioengineering, East China University of Science and Technology, Shanghai 200237 (China); Ye, Zhaoyang, E-mail: zhaoyangye@ecust.edu.cn [State Key Laboratory of Bioreactor Engineering, School of Bioengineering, East China University of Science and Technology, Shanghai 200237 (China); Tan, Wensong [State Key Laboratory of Bioreactor Engineering, School of Bioengineering, East China University of Science and Technology, Shanghai 200237 (China); Lang, Meidong, E-mail: mdlang@ecust.edu.cn [Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 (China)

    2013-05-01

    The physical properties of tissue engineering scaffolds such as microstructures play important roles in controlling cellular behaviors and neotissue formation. Among them, the pore size stands out as a key determinant factor. In the present study, we aimed to fabricate porous scaffolds with pre-defined hierarchical pore sizes, followed by examining cell growth in these scaffolds. This hierarchical porous microstructure was implemented via integrating different pore-generating methodologies, including salt leaching and thermal induced phase separation (TIPS). Specifically, large (L, 200–300 μm), medium (M, 40–50 μm) and small (S, < 10 μm) pores were able to be generated. As such, three kinds of porous scaffolds with a similar porosity of ∼ 90% creating pores of either two (LS or MS) or three (LMS) different sizes were successfully prepared. The number fractions of different pores in these scaffolds were determined to confirm the hierarchical organization of pores. It was found that the interconnectivity varied due to the different pore structures. Besides, these scaffolds demonstrated similar compressive moduli under dry and hydrated states. The adhesion, proliferation, and spatial distribution of human fibroblasts within the scaffolds during a 14-day culture were evaluated with MTT assay and fluorescence microscopy. While all three scaffolds well supported the cell attachment and proliferation, the best cell spatial distribution inside scaffolds was achieved with LMS, implicating that such a controlled hierarchical microstructure would be advantageous in tissue engineering applications. Highlights: ► The scaffolds with dual-pore and triple-pore structures were fabricated. ► Triple-pore structure had better interconnectivity than dual-pore structures. ► Better cell migration and distribution were found on the triple-pore structures. ► The medium pore size (45–50 μm) was appropriate for cell migration. ► Scaffolds with triple-pore structure

  5. Growth and microstructure of iron nitride layers and pore formation in {epsilon}-Fe{sub 3}N

    Energy Technology Data Exchange (ETDEWEB)

    Middendorf, C.; Mader, W. [Univ. Bonn, Inst. fuer Anorganische Chemie, Bonn (Germany)

    2003-03-01

    Layers of {epsilon}-Fe{sub 3}N and {gamma}'-Fe{sub 4}N on ferrite were produced by nitriding iron single crystals or rolled sheets of iron in flowing ammonia at 520 C. The nitride layers were characterised using X-ray diffraction, light microscopy as well as scanning and transmission electron microscopy. The compound layer consists of {epsilon}-Fe{sub 3}N at the surface and of {gamma}'-Fe{sub 4}N facing the ferrite. After 4 h of nitriding, pores develop in the near surface region of {epsilon}-Fe{sub 3}N showing more or less open porosity. Growth of the entire compound layer as well as of the massive and the porous {epsilon}-Fe{sub 3}N sublayer is diffusion-controlled and follows a parabolic growth rate. The {gamma}'-Fe{sub 4}N layer is formed as a transition phase within a narrow interval of nitrogen activity, and it shows little growth in thickness. The transformation of {gamma}'-Fe{sub 4}N to {epsilon}-Fe{sub 3}N is topotactic, where the orientation of the closed-packed iron layers of the crystal structures is preserved. Determination of lattice plane spacings was possible by X-ray diffraction, and this was correlated to the nitrogen content of {epsilon}-Fe{sub 3}N. While the porous layer exhibits an enhanced nitrogen content corresponding to the chemical composition Fe{sub 3}N{sub 1.1}, the massive e Fe{sub 3}N layer corresponds to Fe{sub 3}N{sub 1.0}. The pore formation in {epsilon}-Fe{sub 3}N{sub 1.1} is concluded to be the result of excess nitrogen atoms on non-structural sites, which have a high mobility. Therefore, recombination of excess nitrogen to molecular N{sub 2} at lattice defects is preferred in {epsilon}-Fe{sub 3}N with high nitrogen content compared to stoichiometric {epsilon}-Fe{sub 3}N{sub 1.0} with nitrogen on only structural sites. (orig.)

  6. A novel approach to particle track etching: surfactant enhanced control of pore morphology

    International Nuclear Information System (INIS)

    Apel', P.Yu.; Dmitriev, S.N.; Vutsadakis, V.A.; Root, D.

    2000-01-01

    Based on the understanding of the mechanism behind a long observed but thus far unexplained effect, a new method to control the geometry of nano- and micropores is described. Surfactant molecules added to an etching solution used for etching out ion tracks, create a steric-hindrance effect which is responsible for the formation of 'bottleneck' or 'cigar-like' pores. Filtration membranes thus obtained exhibit significantly improved flow rates without deterioration in the retention properties. New applications are made possible with these new pore geometries

  7. The Drainage Consolidation Modeling of Sand Drain in Red Mud Tailing and Analysis on the Change Law of the Pore Water Pressure

    Directory of Open Access Journals (Sweden)

    Chuan-sheng Wu

    2014-01-01

    Full Text Available In order to prevent the occurring of dam failure and leakage, sand-well drainages systems were designed and constructed in red mud tailing. It is critical to focus on the change law of the pore water pressure. The calculation model of single well drainage pore water pressure was established. The pore water pressure differential equation was deduced and the analytical solution of differential equation using Bessel function and Laplace transform was given out. The impact of parameters such as diameter d, separation distance l, loading rate q, and coefficient of consolidation Cv in the function on the pore water pressure is analyzed by control variable method. This research is significant and has great reference for preventing red mud tailings leakage and the follow-up studies on the tailings stability.

  8. Membranes with functionalized carbon nanotube pores for selective transport

    Science.gov (United States)

    Bakajin, Olgica; Noy, Aleksandr; Fornasiero, Francesco; Park, Hyung Gyu; Holt, Jason K; Kim, Sangil

    2015-01-27

    Provided herein composition and methods for nanoporous membranes comprising single walled, double walled, or multi-walled carbon nanotubes embedded in a matrix material. Average pore size of the carbon nanotube can be 6 nm or less. These membranes are a robust platform for the study of confined molecular transport, with applications in liquid and gas separations and chemical sensing including desalination, dialysis, and fabric formation.

  9. Assessment of effectiveness of geologic isolation systems: geostatistical modeling of pore velocity

    International Nuclear Information System (INIS)

    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

  10. Quantitative Study of Porosity and Pore Features in Moldavites by Means of X-ray Micro-CT

    Directory of Open Access Journals (Sweden)

    Giovanni Pratesi

    2014-04-01

    Full Text Available X-ray micro-computer aided tomography (μ-CT, together with optical microscopy and imaging, have been applied to the study of six moldavite samples. These techniques enabled a complete characterization to be made of the textural features of both Muong Nong-type and common splashform moldavites. A detailed study of the size and distribution of pores or bubbles confirmed the marked variability in pore size among the samples, as well as within each sample, and indicated in the Muong Nong-type moldavites the presence of at least two deformation stages which occurred before and after pore formation.

  11. Antera 3D capabilities for pore measurements.

    Science.gov (United States)

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

    2018-04-29

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

  12. Development of pore interconnectivity/morphology in porous silica films investigated by cyclic voltammetry and slow positron annihilation spectroscopy

    International Nuclear Information System (INIS)

    Tang, Xiuqin; Xiong, Bangyun; Li, Qichao; Mao, Wenfeng; Xiao, Wei; Fang, Pengfei; He, Chunqing

    2015-01-01

    Highlights: •Porous silica films were studied by cyclic voltammetry and positron annihilation. •Highly interconnected pores were formed in the film fabricated with more CTAB. •Aligned nanochannels were observed in the porous flim prepared with 25 wt.% CTAB. •I − and Ps diffusion in the films was governed by pore interconnectivity/morphology. •Cyclic voltammetry is feasible to explore pore interconnectivity/morphology. -- Abstract: Cyclic voltammetry and positronium (Ps) 3γ-annihilation spectroscopy were applied to investigate pore interconnectivity/morphology of porous silica films fabricated with various loading of cetyltrimethyl ammonium bromide (CTAB). With increasing the ratio of CTAB up to 15 wt.%, the total charge Q, resulted from I − diffusion across the silica films, increased remarkably, indicative of formation of highly interconnected pores in the films prepared with more porogen. However, it decreased dramatically with further loading CTAB of 25 wt.%. Interestingly, 3γ-annihilation fraction I 3γ due to a triplet-state Ps (ortho-positronium, o-Ps) emission from the silica films showed a similar behavior as a function of CTAB loading. The abnormal decrement in Q and I 3γ in the film fabricated with 25 wt.% CTAB was well explained by formation of long nanochannels aligning parallel to the film surface. The results indicated that the total charge Q and Ps 3γ-annihilation fraction were closely associated with I − and Ps diffusion governed by the pore interconnectivity/morphology of the silica films, which made cyclic voltammetry possible to be a feasible tool to characterize pore interconnectivity/morphology of porous thin films

  13. Synthesis of metal-organic framework films by pore diffusion method

    Science.gov (United States)

    Murayama, Naohiro; Nishimura, Yuki; Kajiro, Hiroshi; Kishida, Satoru; Kinoshita, Kentaro; Tottori Univ Team; Nippon Steel; Sumitomo Metal Co. Collaboration; Tottori Integrated Frontier Resaerch Center (Tifrec) Collaboration; Tottori University Electronic Display Resaerch Center (Tedrec) Collaboration

    Metal-organic frameworks (MOFs) presents high controllability in designing the nano-scale pore, and this enable molecular storages, catalysts, gas sensors, gas separation membranes, and electronic devices for next-generation. Therefore, a simple method for film synthesis of MOFs compared with conventional methods [1] is strongly required. In this paper, we provide pore diffusion method, in which a substrate containing constituent metals of MOF is inserted in solution that includes only linker molecules of MOF. As a result, 2D growth of MOF was effectively enhanced, and the formation of flat and dense MOF films was attained. The growth time, t, dependence of film thickness, d, can be expressed by the relation of d = Aln(t + 1) + B, where A and B are constants. It means that ionized coppers diffuse through the pores of MOFs and the synthesis reaction proceeds at the MOF/solvent interface. We demonstrated the fabrication of a HKUST-1/Cu-TPA hetero structure by synthesizing a Cu-TPA film continuously after the growth of a HKUST-1 film on the CuOx substrate.

  14. Electroosmotic pore transport in human skin.

    Science.gov (United States)

    Uitto, Olivia D; White, Henry S

    2003-04-01

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

  15. Forming and control of pores by capsule-free hot isostatic pressing in NiTi shape memory alloys

    International Nuclear Information System (INIS)

    Yuan, B; Zhu, M; Gao, Y; Li, X; Chung, C Y

    2008-01-01

    In this study, the pore evolution process of porous NiTi shape memory alloys (SMAs) fabricated by capsule-free hot isostatic pressing (CF-HIP) was investigated by adopting different fabricating parameters. It is shown that porous NiTi SMAs with homogeneous pore distribution and nearly spherical pore shape can be prepared by CF-HIP under suitable conditions. In addition, two novel pore structures were produced, one with a sandwich-like structure, and another with controlled gradient of porosity along the radial direction, with pore size increasing from the outside towards the center of the specimen. The former was obtained by balancing the pressure in the HIP chamber and the gas pressure resulting from the gas expansion in the green sample. The latter resulted from the formation of air bubbles in the liquid phase during the sintering

  16. Microfluidic Experiments Studying Pore Scale Interactions of Microbes and Geochemistry

    Science.gov (United States)

    Chen, M.; Kocar, B. D.

    2016-12-01

    Understanding how physical phenomena, chemical reactions, and microbial behavior interact at the pore-scale is crucial to understanding larger scale trends in groundwater chemistry. Recent studies illustrate the utility of microfluidic devices for illuminating pore-scale physical-biogeochemical processes and their control(s) on the cycling of iron, uranium, and other important elements 1-3. These experimental systems are ideal for examining geochemical reactions mediated by microbes, which include processes governed by complex biological phenomenon (e.g. biofilm formation, etc.)4. We present results of microfluidic experiments using a model metal reducing bacteria and varying pore geometries, exploring the limitations of the microorganisms' ability to access tight pore spaces, and examining coupled biogeochemical-physical controls on the cycling of redox sensitive metals. Experimental results will provide an enhanced understanding of coupled physical-biogeochemical processes transpiring at the pore-scale, and will constrain and compliment continuum models used to predict and describe the subsurface cycling of redox-sensitive elements5. 1. Vrionis, H. A. et al. Microbiological and geochemical heterogeneity in an in situ uranium bioremediation field site. Appl. Environ. Microbiol. 71, 6308-6318 (2005). 2. Pearce, C. I. et al. Pore-scale characterization of biogeochemical controls on iron and uranium speciation under flow conditions. Environ. Sci. Technol. 46, 7992-8000 (2012). 3. Zhang, C., Liu, C. & Shi, Z. Micromodel investigation of transport effect on the kinetics of reductive dissolution of hematite. Environ. Sci. Technol. 47, 4131-4139 (2013). 4. Ginn, T. R. et al. Processes in microbial transport in the natural subsurface. Adv. Water Resour. 25, 1017-1042 (2002). 5. Scheibe, T. D. et al. Coupling a genome-scale metabolic model with a reactive transport model to describe in situ uranium bioremediation. Microb. Biotechnol. 2, 274-286 (2009).

  17. A new method for calculating gas content of coal reservoirs with consideration of a micro-pore overpressure environment

    Directory of Open Access Journals (Sweden)

    Jinxing Song

    2017-05-01

    Full Text Available When the gas content of a coal reservoir is calculated, the reservoir pressure measured by well logging and well testing is generally used for inversion calculation instead of gas pressure. However, the calculation result is not accurate because the reservoir pressure is not equal to the gas pressure in overpressure environments. In this paper, coal samples of different ranks in Shanxi and Henan are collected for testing the capillary pressure of coal pores. Based on the formation process of CBM reservoirs and the hydrocarbon generation and expulsion history of coal beds, the forming mechanisms of micro-pore overpressure environments in coal reservoirs were analyzed. Accordingly, a new method for calculating the gas content of coal reservoirs with consideration of a micro-pore overpressure environment was developed. And it was used to calculate the gas content of No. 1 coal bed of the 2nd member of Lower Permian Shanxi Fm in the Zhongmacun Coal Mine in Jiaozuo, Henan. It is indicated that during the formation and evolution of coals, some solid organic matters were converted into gas and water, and gas–water contact is surely formed in pores. In the end, capillary pressure is generated, so the gas pressure in micro-pores is much higher than the hydrostatic column pressure, which results in a micro-pore overpressure environment. Under such an environment, gas pressure is higher than reservoir pressure, so the gas content of coal reservoirs calculated previously based on the conventional reservoir pressure evaluation are usually underestimated. It is also found that the micro-pore overpressure environment exerts a dominating effect on the CBM content calculation of 3–100 nm pores, especially that of 3–10 nm pores, but a little effect on that of pores >100 nm. In conclusion, this new method clarifies the pressure environment of CBM gas reservoirs, thereby ensuring the calculation accuracy of gas content of coal reservoirs.

  18. Transport of water molecules through noncylindrical pores in multilayer nanoporous graphene.

    Science.gov (United States)

    Shahbabaei, Majid; Kim, Daejoong

    2017-08-09

    In this study, molecular dynamics (MD) simulations are used to examine the water transport properties through asymmetric hourglass-shaped pores in multilayer nanoporous graphene with a constant interlayer separation of 6 Å. The properties of the tested asymmetric hourglass-shaped pores [with the models having long cone (l 1 , -P) and short cone (l 2 , +P) entrances] are compared to a symmetric pore model. The study findings indicate that the water occupancy increases across the asymmetric pore (l 1 , -P) compared to (l 2 , +P), because of the length effect. The asymmetric pore, (l 1 , -P), yields higher flux compared to (l 2 , +P) and even the symmetric model, which can be attributed to the increase in the hydrogen bonds. In addition, the single-file water molecules across the narrowest pore diameter inside the (l 2 , +P) pore exhibit higher viscosity compared to those in the (l 1 , -P) pore because of the increase in the water layering effect. Moreover, it is found that the permeability inside the multilayer hourglass-shaped pore depends on the length of the flow path of the water molecules before approaching the layer with the smallest pore diameter. The probability of dipole orientation exhibits wider distribution inside the (l 1 , -P) system compared to (l 2 , +P), implying an enhanced formation of hydrogen bonding of water molecules. This results in the fast flow of water molecules. The MD trajectory shows that the dipole orientation across the single-layer graphene has frequently flipped compared to the dipole orientation across the pores in multilayer graphene, which is maintained during the whole simulation time (although the dipole orientation has flipped for a few picoseconds at the beginning of the simulation). This can be attributed to the energy barrier induced by the individual layer. The diffusion coefficient of water molecules inside the (l 2 , +P) system increases with pressure difference, however, it decreases inside the (l 1 , -P) system because

  19. Ir catalysts: Preventing CH3COOH formation in ethanol oxidation

    Science.gov (United States)

    Miao, Bei; Wu, Zhipeng; Xu, Han; Zhang, Minhua; Chen, Yifei; Wang, Lichang

    2017-11-01

    Current catalysts used for ethanol oxidation reaction (EOR) cannot effectively prevent CH3COOH formation, and thus become a major hindrance for direct ethanol fuel cell applications. We report an Ir catalyst that shows great promise for a complete EOR based on density functional theory calculations using PBE functional. The reaction barrier on Ir(1 0 0) was found to be 2.10 eV for CH3COOH formation, which is much higher than currently used Pd and Pt, and 0.57 eV for Csbnd C bond cleavage in CHCO species, which are comparable to Pd and Pt. The result suggests future directions for studying optimal complete EOR catalysts.

  20. Laboratory characterization of shale pores

    Science.gov (United States)

    Nur Listiyowati, Lina

    2018-02-01

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

  1. Long-term Differences in Tillage and Land Use Affect Intra-aggregate Pore Heterogeneity

    International Nuclear Information System (INIS)

    Kravchenko, A.N.; Wang, A.N.W.; Smucker, A.J.M.; Rivers, M.L.

    2011-01-01

    very large pores associated with former root channels in NT and NS aggregates. Our findings indicate that mechanisms of macro-aggregate formation might differ in their importance in different land use and management practices.

  2. 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.)

  3. Development of eco-friendly porous fired clay bricks using pore-forming agents: a review.

    Science.gov (United States)

    Bories, Cecile; Borredon, Marie-Elisabeth; Vedrenne, Emeline; Vilarem, Gerard

    2014-10-01

    Today, clay bricks are facing technological challenges and are uncompetitive compared to materials such as concrete. Their performance must be improved if they are to stand up to the competition. Increasing environmental concerns over the accumulation of unmanaged wastes from agricultural or industrial productions have made these good candidates for incorporation into building materials to improve their performance. This process leads to the formation of pores in the bricks, producing lightweight and sustainable building materials. This paper reviews the different pore-forming agents from renewable or mineral resources as described in the literature. It also presents the impact of pore-forming agents on the physical, mechanical and thermal properties of clay bricks. Copyright © 2014 Elsevier Ltd. All rights reserved.

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

    Science.gov (United States)

    Grégoire, David; Malheiro, Carine; Miqueu, Christelle

    2018-03-01

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

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

    Science.gov (United States)

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

    2016-03-01

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

  6. Phosphatidylinositol 4,5-Bisphosphate (PI(4,5)P2)-dependent Oligomerization of Fibroblast Growth Factor 2 (FGF2) Triggers the Formation of a Lipidic Membrane Pore Implicated in Unconventional Secretion*

    Science.gov (United States)

    Steringer, Julia P.; Bleicken, Stephanie; Andreas, Helena; Zacherl, Sonja; Laussmann, Mareike; Temmerman, Koen; Contreras, F. Xabier; Bharat, Tanmay A. M.; Lechner, Johannes; Müller, Hans-Michael; Briggs, John A. G.; García-Sáez, Ana J.; Nickel, Walter

    2012-01-01

    Fibroblast growth factor 2 (FGF2) is a critical mitogen with a central role in specific steps of tumor-induced angiogenesis. It is known to be secreted by unconventional means bypassing the endoplasmic reticulum/Golgi-dependent secretory pathway. However, the mechanism of FGF2 membrane translocation into the extracellular space has remained elusive. Here, we show that phosphatidylinositol 4,5-bisphosphate-dependent membrane recruitment causes FGF2 to oligomerize, which in turn triggers the formation of a lipidic membrane pore with a putative toroidal structure. This process is strongly up-regulated by tyrosine phosphorylation of FGF2. Our findings explain key requirements of FGF2 secretion from living cells and suggest a novel self-sustained mechanism of protein translocation across membranes with a lipidic membrane pore being a transient translocation intermediate. PMID:22730382

  7. Structure formation control of foam concrete

    Science.gov (United States)

    Steshenko, Aleksei; Kudyakov, Aleksander; Konusheva, Viktoriya; Syrkin, Oleg

    2017-01-01

    The process of predetermined foam concrete structure formation is considered to be a crucial issue from the point of process control and it is currently understudied thus defining the need for additional research. One of the effective ways of structure formation control in naturally hardening foam concrete is reinforcement with dispersed fibers or introduction of plasticizers. The paper aims at studying the patterns of influence of microreinforcing and plasticizing additives on the structure and performance properties of foam concrete. Preparation of foam concrete mix has been conducted using one-step technology. The structure of modified foam concrete has been studied by means of electron microscopy. The cellular structure of foam concrete samples with the additives is homogeneous; the pores are uniformly distributed over the total volume. It has been revealed that introduction of the Neolas 5.2 plasticizer and microreinforcing fibers in the foam concrete mixture in the amount of 0.4 - 0.1 % by weight of cement leads to reduction of the average pore diameter in the range of 45.3 to 30.2 microns and the standard deviation of the pore average diameter from 23.6 to 9.2 in comparison with the sample without additive. Introduction of modifying additives has stimulated formation of a large number of closed pores. Thus porosity of conditionally closed pores has increased from 16.06 % to 34.48 %, which has lead to increase of frost resistance brand of foam concrete from F15 to F50 and to reduction of its water absorption by weight by 20 %.

  8. A study of formation of iron nanoparticles in aluminium matrix with helium pores

    Czech Academy of Sciences Publication Activity Database

    Kichanov, S.E.; Kozlenko, D. P.; Belushkin, A.V.; Reutov, V.F.; Samoilenko, S.O.; Jirák, Zdeněk; Savenko, B. N.; Bulavin, L. A.; Zubavichus, Y.V.

    2012-01-01

    Roč. 351, č. 1 (2012), "012013-1"-"012013-5" ISSN 1742-6588. [International Workshop on SANS-YuMO User Meeting at the Start-up of Scientific Experiments on the IBR-2M Reactor - Devoted to the 75th anniversary of Yu M Ostanevich's Birth /2./. Dubna, 27.05.2011-30.05.2011] Institutional research plan: CEZ:AV0Z10100521 Keywords : iron nanoparticles * aluminium matrix * helium pores Subject RIV: BM - Solid Matter Physics ; Magnetism

  9. Advanced Technologies for Monitoring CO2 Saturation and Pore Pressure in Geologic Formations: Linking the Chemical and Physical Effects to Elastic and Transport Properties

    Energy Technology Data Exchange (ETDEWEB)

    Mavko, G.; Vanorio, T.; Vialle, S.; Saxena, N.

    2014-03-31

    advection: because of an efficient mass transfer of reactants and products, the fluid remains acidic, far from thermodynamical equilibrium and the dissolution of calcite is important. These conclusions are consistent with the lab observations. Sandstones from the Tuscaloosa formation in Mississippi were also subjected to injection under representative in situ stress and pore pressure conditions. Again, both P- and S-wave velocities decreased with injection. Time-lapse SEM images indicated permanent changes induced in the sandstone microstructure by chamosite dissolution upon injection of CO2-rich brine. After injection, the sandstone showed an overall cleaner microstructure. Two main changes are involved: (a) clay dissolution between grains and at the grain contact and (b) rearrangement of grains due to compaction under pressure Theoretical and empirical models were developed to quantify the elastic changes associated with injection. Permanent changes to the rock frame resulted in seismic velocity-porosity trends that mimic natural diagenetic changes. Hence, when laboratory measurments are not available for a candidate site, these trends can be estimated from depth trends in well logs. New theoretical equations were developed to predict the changes in elastic moduli upon substitution of pore-filling material. These equations reduce to Gassmann’s equations for the case of constant frame properties, low seismic frequencies, and fluid changes in the pore space. The new models also predict the change dissolution or precipitation of mineral, which cannot be described with the conventional Gassmann theory.

  10. Preventing disulfide bond formation weakens non-covalent forces among lysozyme aggregates.

    Directory of Open Access Journals (Sweden)

    Vijay Kumar Ravi

    Full Text Available Nonnative disulfide bonds have been observed among protein aggregates in several diseases like amyotrophic lateral sclerosis, cataract and so on. The molecular mechanism by which formation of such bonds promotes protein aggregation is poorly understood. Here in this work we employ previously well characterized aggregation of hen eggwhite lysozyme (HEWL at alkaline pH to dissect the molecular role of nonnative disulfide bonds on growth of HEWL aggregates. We employed time-resolved fluorescence anisotropy, atomic force microscopy and single-molecule force spectroscopy to quantify the size, morphology and non-covalent interaction forces among the aggregates, respectively. These measurements were performed under conditions when disulfide bond formation was allowed (control and alternatively when it was prevented by alkylation of free thiols using iodoacetamide. Blocking disulfide bond formation affected growth but not growth kinetics of aggregates which were ∼50% reduced in volume, flatter in vertical dimension and non-fibrillar in comparison to control. Interestingly, single-molecule force spectroscopy data revealed that preventing disulfide bond formation weakened the non-covalent interaction forces among monomers in the aggregate by at least ten fold, thereby stalling their growth and yielding smaller aggregates in comparison to control. We conclude that while constrained protein chain dynamics in correctly disulfide bonded amyloidogenic proteins may protect them from venturing into partial folded conformations that can trigger entry into aggregation pathways, aberrant disulfide bonds in non-amyloidogenic proteins (like HEWL on the other hand, may strengthen non-covalent intermolecular forces among monomers and promote their aggregation.

  11. The connectivity of pore space in mudstones: insights from high-pressure Wood's metal injection, BIB-SEM imaging, and mercury intrusion porosimetry

    NARCIS (Netherlands)

    Klaver, J.; Hemes, S.; Houben, M.; Desbois, G.; Radi, Z.; Urai, J.L.

    2015-01-01

    Study of the pore space in mudstones by mercury intrusion porosimetry is a common but indirect technique and it is not clear which part of the pore space is actually filled with mercury. We studied samples from the Opalinus Clay, Boom Clay, Haynesville Shale, and Bossier Shale Formations using

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

    Science.gov (United States)

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

    2010-09-01

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

  13. Investigating the pore-water chemistry effects on the volume change behaviour of Boom clay

    Science.gov (United States)

    Deng, Y. F.; Cui, Y. J.; Tang, A. M.; Nguyen, X. P.; Li, X. L.; Van Geet, M.

    The Essen site has been chosen as an alternative site for nuclear waste disposal in Belgium. The soil formation involved at this site is the same as at Mol site: Boom clay. However, owing to its geographical situation closer to the sea, Boom clay at Essen presents a pore water salinity 4-5 times higher than Boom clay at Mol. This study aims at studying the effects of pore water salinity on the hydro-mechanical behaviour of Boom clay. Specific oedometer cells were used allowing “flushing” the pore water in soil specimen by synthetic pore water or distilled water. The synthetic pore water used was prepared with the chemistry as that for the site water: 5.037 g/L for core Ess83 and 5.578 g/L for core Ess96. Mechanical loading was then carried out on the soil specimen after flushing. The results show that water salinity effect on the liquid limit is negligible. The saturation or pore water replacement under the in situ effective stress of 2.4 MPa does not induce significant volume change. For Ess83, hydro-mechanical behaviour was found to be slightly influenced by the water salinity; on the contrary, no obvious effect was identified on the hydro-mechanical behaviour of Ess96. This can be attributed to the higher smectite content in Ess83 than in Ess96.

  14. A statistical image analysis framework for pore-free islands derived from heterogeneity distribution of nuclear pore complexes.

    Science.gov (United States)

    Mimura, Yasuhiro; Takemoto, Satoko; Tachibana, Taro; Ogawa, Yutaka; Nishimura, Masaomi; Yokota, Hideo; Imamoto, Naoko

    2017-11-24

    Nuclear pore complexes (NPCs) maintain cellular homeostasis by mediating nucleocytoplasmic transport. Although cyclin-dependent kinases (CDKs) regulate NPC assembly in interphase, the location of NPC assembly on the nuclear envelope is not clear. CDKs also regulate the disappearance of pore-free islands, which are nuclear envelope subdomains; this subdomain gradually disappears with increase in homogeneity of the NPC in response to CDK activity. However, a causal relationship between pore-free islands and NPC assembly remains unclear. Here, we elucidated mechanisms underlying NPC assembly from a new perspective by focusing on pore-free islands. We proposed a novel framework for image-based analysis to automatically determine the detailed 'landscape' of pore-free islands from a large quantity of images, leading to the identification of NPC intermediates that appear in pore-free islands with increased frequency in response to CDK activity. Comparison of the spatial distribution between simulated and the observed NPC intermediates within pore-free islands showed that their distribution was spatially biased. These results suggested that the disappearance of pore-free islands is highly related to de novo NPC assembly and indicated the existence of specific regulatory mechanisms for the spatial arrangement of NPC assembly on nuclear envelopes.

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

    Science.gov (United States)

    Dashtian, Hassan; Shokri, Nima; Sahimi, Muhammad

    2018-02-01

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

  16. Contribution of formative research to design an environmental program for obesity prevention in schools in Mexico City.

    Science.gov (United States)

    Bonvecchio, Anabelle; Théodore, Florence L; Safdie, Margarita; Duque, Tiffany; Villanueva, María Ángeles; Torres, Catalina; Rivera, Juan

    2014-01-01

    This paper describes the methods and key findings of formative research conducted to design a school-based program for obesity prevention. Formative research was based on the ecological model and the principles of social marketing. A mixed method approach was used. Qualitative (direct observation, indepth interviews, focus group discussions and photo-voice) and quantitative (closed ended surveys, checklists, anthropometry) methods were employed. Formative research key findings, including barriers by levels of the ecological model, were used for designing a program including environmental strategies to discourage the consumption of energy dense foods and sugar beverages. Formative research was fundamental to developing a context specific obesity prevention program in schools that seeks environment modification and behavior change.

  17. Regulation of Exocytotic Fusion Pores by SNARE Protein Transmembrane Domains

    Directory of Open Access Journals (Sweden)

    Zhenyong Wu

    2017-10-01

    Full Text Available Calcium-triggered exocytotic release of neurotransmitters and hormones from neurons and neuroendocrine cells underlies neuronal communication, motor activity and endocrine functions. The core of the neuronal exocytotic machinery is composed of soluble N-ethyl maleimide sensitive factor attachment protein receptors (SNAREs. Formation of complexes between vesicle-attached v- and plasma-membrane anchored t-SNAREs in a highly regulated fashion brings the membranes into close apposition. Small, soluble proteins called Complexins (Cpx and calcium-sensing Synaptotagmins cooperate to block fusion at low resting calcium concentrations, but trigger release upon calcium increase. A growing body of evidence suggests that the transmembrane domains (TMDs of SNARE proteins play important roles in regulating the processes of fusion and release, but the mechanisms involved are only starting to be uncovered. Here we review recent evidence that SNARE TMDs exert influence by regulating the dynamics of the fusion pore, the initial aqueous connection between the vesicular lumen and the extracellular space. Even after the fusion pore is established, hormone release by neuroendocrine cells is tightly controlled, and the same may be true of neurotransmitter release by neurons. The dynamics of the fusion pore can regulate the kinetics of cargo release and the net amount released, and can determine the mode of vesicle recycling. Manipulations of SNARE TMDs were found to affect fusion pore properties profoundly, both during exocytosis and in biochemical reconstitutions. To explain these effects, TMD flexibility, and interactions among TMDs or between TMDs and lipids have been invoked. Exocytosis has provided the best setting in which to unravel the underlying mechanisms, being unique among membrane fusion reactions in that single fusion pores can be probed using high-resolution methods. An important role will likely be played by methods that can probe single fusion pores

  18. Monitoring the kinetics of the pH-driven transition of the anthrax toxin prepore to the pore by biolayer interferometry and surface plasmon resonance.

    Science.gov (United States)

    Naik, Subhashchandra; Brock, Susan; Akkaladevi, Narahari; Tally, Jon; McGinn-Straub, Wesley; Zhang, Na; Gao, Phillip; Gogol, E P; Pentelute, B L; Collier, R John; Fisher, Mark T

    2013-09-17

    Domain 2 of the anthrax protective antigen (PA) prepore heptamer unfolds and refolds during endosome acidification to generate an extended 100 Å β barrel pore that inserts into the endosomal membrane. The PA pore facilitates the pH-dependent unfolding and translocation of bound toxin enzymic components, lethal factor (LF) and/or edema factor, from the endosome to the cytoplasm. We constructed immobilized complexes of the prepore with the PA-binding domain of LF (LFN) to monitor the real-time prepore to pore kinetic transition using surface plasmon resonance and biolayer interferometry (BLI). The kinetics of this transition increased as the solution pH was decreased from 7.5 to 5.0, mirroring acidification of the endosome. Once it had undergone the transition, the LFN-PA pore complex was removed from the BLI biosensor tip and deposited onto electron microscopy grids, where PA pore formation was confirmed by negative stain electron microscopy. When the soluble receptor domain (ANTRX2/CMG2) binds the immobilized PA prepore, the transition to the pore state was observed only after the pH was lowered to early (pH 5.5) or late (pH 5.0) endosomal pH conditions. Once the pore formed, the soluble receptor readily dissociated from the PA pore. Separate binding experiments with immobilized PA pores and the soluble receptor indicate that the receptor has a weakened propensity to bind to the transitioned pore. This immobilized anthrax toxin platform can be used to identify or validate potential antimicrobial lead compounds capable of regulating and/or inhibiting anthrax toxin complex formation or pore transitions.

  19. Monitoring the kinetics of the pH driven transition of the anthrax toxin prepore to the pore by biolayer interferometry and surface plasmon resonance

    Science.gov (United States)

    Naik, Subhashchandra; Brock, Susan; Akkaladevi, Narahari; Tally, Jon; Mcginn-Straub, Wesley; Zhang, Na; Gao, Phillip; Gogol, E. P.; Pentelute, B. L.; Collier, R. John; Fisher, Mark T.

    2013-01-01

    Domain 2 of the anthrax protective antigen (PA) prepore heptamer unfolds and refolds during endosome acidification to generate an extended 100 Å beta barrel pore that inserts into the endosomal membrane. The PA pore facilitates the pH dependent unfolding and translocation of bound toxin enzymic components, lethal factor (LF) and/or edema factor (EF), from the endosome into the cytoplasm. We constructed immobilized complexes of the prepore with the PA-binding domain of LF (LFN) to monitor the real-time prepore to pore kinetic transition using surface plasmon resonance (SPR) and bio-layer interferometry (BLI). The kinetics of this transition increased as the solution pH was decreased from pH 7.5 to pH 5.0, mirroring acidification of the endosome. Once transitioned, the LFN-PA pore complex was removed from the BLI biosensor tip and deposited onto EM grids, where the PA pore formation was confirmed by negative stain electron microscopy. When the soluble receptor domain (ANTRX2/CMG2) binds the immobilized PA prepore, the transition to the pore state was observed only after the pH was lowered to early or late endosomal pH conditions (5.5 to 5.0 respectively). Once the pore formed, the soluble receptor readily dissociated from the PA pore. Separate binding experiments with immobilized PA pores and soluble receptor indicate that the receptor has a weakened propensity to bind to the transitioned pore. This immobilized anthrax toxin platform can be used to identify or validate potential antimicrobial lead compounds capable of regulating and/or inhibiting anthrax toxin complex formation or pore transitions. PMID:23964683

  20. Laser-induced micropore formation and modification of cartilage structure in osteoarthritis healing

    Science.gov (United States)

    Sobol, Emil; Baum, Olga; Shekhter, Anatoly; Wachsmann-Hogiu, Sebastian; Shnirelman, Alexander; Alexandrovskaya, Yulia; Sadovskyy, Ivan; Vinokur, Valerii

    2017-09-01

    Pores are vital for functioning of avascular tissues. Laser-induced pores play an important role in the process of cartilage regeneration. The aim of any treatment for osteoarthritis is to repair hyaline-type cartilage. The aims of this study are to answer two questions: (1) How do laser-assisted pores affect the cartilaginous cells to synthesize hyaline cartilage (HC)? and (2) How can the size distribution of pores arising in the course of laser radiation be controlled? We have shown that in cartilage, the pores arise predominately near chondrocytes, which promote nutrition of cells and signal molecular transfer that activates regeneration of cartilage. In vivo laser treatment of damaged cartilage of miniature pig joints provides cellular transformation and formation of HC. We propose a simple model of pore formation in biopolymers that paves the way for going beyond the trial-and-error approach when choosing an optimal laser treatment regime. Our findings support the approach toward laser healing of osteoarthritis.

  1. Laser-induced micropore formation and modification of cartilage structure in osteoarthritis healing.

    Science.gov (United States)

    Sobol, Emil; Baum, Olga; Shekhter, Anatoly; Wachsmann-Hogiu, Sebastian; Shnirelman, Alexander; Alexandrovskaya, Yulia; Sadovskyy, Ivan; Vinokur, Valerii

    2017-09-01

    Pores are vital for functioning of avascular tissues. Laser-induced pores play an important role in the process of cartilage regeneration. The aim of any treatment for osteoarthritis is to repair hyaline-type cartilage. The aims of this study are to answer two questions: (1) How do laser-assisted pores affect the cartilaginous cells to synthesize hyaline cartilage (HC)? and (2) How can the size distribution of pores arising in the course of laser radiation be controlled? We have shown that in cartilage, the pores arise predominately near chondrocytes, which promote nutrition of cells and signal molecular transfer that activates regeneration of cartilage. In vivo laser treatment of damaged cartilage of miniature pig joints provides cellular transformation and formation of HC. We propose a simple model of pore formation in biopolymers that paves the way for going beyond the trial-and-error approach when choosing an optimal laser treatment regime. Our findings support the approach toward laser healing of osteoarthritis.

  2. Laser-induced micropore formation and modification of cartilage structure in osteoarthritis healing

    Energy Technology Data Exchange (ETDEWEB)

    Sobol, Emil [Institute of Applied Physics of the Russian Academy of Sciences, Nizhny Novgorod, RussiabFederal Scientific Research Centre “Crystallography and Photonics” of the Russian Academy of Sciences, Institute of Photonic Technologies, Moscow, Russia; Baum, Olga [Federal Scientific Research Centre “Crystallography and Photonics” of the Russian Academy of Sciences, Institute of Photonic Technologies, Moscow, Russia; Shekhter, Anatoly [Sechenov First Medical University of Moscow, Institute of Regenerative Medicine, Moscow, Russia; Wachsmann-Hogiu, Sebastian [University of California, Center for Biophotonics, Department of Pathology and Laboratory Medicine, Sacramento, California, United StateseMcGill University, Department of Bioengineering, Montreal, Canada; Shnirelman, Alexander [Concordia University, Department of Mathematics and Statistics, Montreal, Canada; Alexandrovskaya, Yulia [Institute of Applied Physics of the Russian Academy of Sciences, Nizhny Novgorod, RussiabFederal Scientific Research Centre “Crystallography and Photonics” of the Russian Academy of Sciences, Institute of Photonic Technologies, Moscow, Russia; Sadovskyy, Ivan [Argonne National Laboratory, Materials Science Division, Argonne, Illinois, United States; Vinokur, Valerii [Argonne National Laboratory, Materials Science Division, Argonne, Illinois, United States

    2017-05-31

    Pores are vital for functioning of avascular tissues. Laser-induced pores play an important role in the process of cartilage regeneration. The aim of any treatment for osteoarthritis is to repair hyaline-type cartilage. The aims of this study are to answer two questions: (1) How do laser-assisted pores affect the cartilaginous cells to synthesize hyaline cartilage (HC)? and (2) How can the size distribution of pores arising in the course of laser radiation be controlled? We have shown that in cartilage, the pores arise predominately near chondrocytes, which promote nutrition of cells and signal molecular transfer that activates regeneration of cartilage. In vivo laser treatment of damaged cartilage of miniature pig joints provides cellular transformation and formation of HC. We propose a simple model of pore formation in biopolymers that paves the way for going beyond the trial-anderror approach when choosing an optimal laser treatment regime. Our findings support the approach toward laser healing of osteoarthritis.

  3. Pore Formation and Mobility Investigation (PFMI): Concept, Hardware Development, and Initial Analysis of Experiments Conducted Aboard the International Space Station

    Science.gov (United States)

    Grugel, Richard N.

    2003-01-01

    Porosity in the form of "bubbles and pipes" can occur during controlled directional solidification processing of metal alloys. This is a consequence that 1) precludes obtaining any meaningful scientific results and 2) is detrimental to desired material properties. Unfortunately, several Microgravity experiments have been compromised by porosity. The intent of the PFMl investigation is to conduct a systematic effort directed towards understanding porosity formation and mobility during controlled directional solidification (DS) in a microgravity environment. PFMl uses a pure transparent material, succinonitrile (SCN), as well as SCN "alloyed" with water, in conjunction with a translating temperature gradient stage so that direct observation and recording of pore generation and mobility can be made. PFMl is investigating the role of thermocapillary forces and temperature gradients in affecting bubble dynamics as well as other solidification processes in a microgravity environment. This presentation will cover the concept, hardware development, operations, and the initial results from experiments conducted aboard the International Space Station.

  4. 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

  5. [Pollution prevention and control of aqueous extract of astragali radix processed with ZrO2 inorganic ceramic membrane micro-filtration].

    Science.gov (United States)

    Pan, Lin-Men; Huang, Min-Yan; Guo, Li-Wei

    2012-11-01

    To study the measures for preventing and controlling the pollution of aqueous extract of Astragali Radix proceeded with inorganic ceramic membrane micro-filtration, in order to find effective measures for preventing and controlling the membrane pollution. The resistance distribution, polymer removal and changes in physical and chemical parameters of the zirconium oxide film of different pore diameters were determined to analyze the state or location of pollutants as well as the regularity of formation. Meanwhile, recoil and ultrasonic physical measures were adopted to strengthen the membrane process, in order to explore the methods for preventing and controlling the membrane pollution. When 0.2 microm of ZrO2 micro-filtrated aqueous extract of Astragali Radix, the rate of pollution was as high as 44.9%. The hole blocking resistance and the concentration polarization resistance were the main filtration resistances, while the surface deposit resistance decreased with the increase in the membrane's hold diameter; after micro-filtration, the liquid turbidity significantly reduced, with slight changes in both pH and viscosity. The 0.2 microm ZrO2 micro-filtration membrane performed better than the 0.05 microm pore size membrane in terms of conductivity. The 0. 2 microm and 0.05 microm pore diameter membranes showed better performance in the removal of pectin. The ultrasonic measure to strengthen membranes is more suitable to this system, with a flux rate up by 41.7%. The membrane optimization process adopts appropriate measures for preventing and controlling the membrane pollution, in order to reduce the membrane pollution, recover membrane performance and increase filtration efficiency.

  6. Enhanced membrane pore formation through high-affinity targeted antimicrobial peptides.

    Directory of Open Access Journals (Sweden)

    Christopher J Arnusch

    Full Text Available Many cationic antimicrobial peptides (AMPs target the unique lipid composition of the prokaryotic cell membrane. However, the micromolar activities common for these peptides are considered weak in comparison to nisin, which follows a targeted, pore-forming mode of action. Here we show that AMPs can be modified with a high-affinity targeting module, which enables membrane permeabilization at low concentration. Magainin 2 and a truncated peptide analog were conjugated to vancomycin using click chemistry, and could be directed towards specific membrane embedded receptors both in model membrane systems and whole cells. Compared with untargeted vesicles, a gain in permeabilization efficacy of two orders of magnitude was reached with large unilamellar vesicles that included lipid II, the target of vancomycin. The truncated vancomycin-peptide conjugate showed an increased activity against vancomycin resistant Enterococci, whereas the full-length conjugate was more active against a targeted eukaryotic cell model: lipid II containing erythrocytes. This study highlights that AMPs can be made more selective and more potent against biological membranes that contain structures that can be targeted.

  7. Ethylene formation by dehydration of ethanol over medium pore zeolites

    Science.gov (United States)

    Gołąbek, Kinga; Tarach, Karolina A.; Filek, Urszula; Góra-Marek, Kinga

    2018-03-01

    In this work, the role of pore arrangement of 10-ring zeolites ZSM-5, TNU-9 and IM-5 on their catalytic properties in ethanol transformation were investigated. Among all the studied catalysts, the zeolite IM-5, characterized by limited 3-dimensionality, presented the highest conversion of ethanol and the highest yields of diethyl ether (DEE) and ethylene. The least active and selective to ethylene and C3 + products was zeolite TNU-9 with the largest cavities formed on the intersection of 10-ring channels. The catalysts varied, however, in lifetime, and their deactivation followed the order: IM-5 > TNU-9 > ZSM-5. The processes taking place in the microporous zeolite environment were tracked by IR spectroscopy and analysed by the 2D correlation analysis (2D COS) allowing for an insight into the nature of chemisorbed adducts and transition products of the reaction. The cage dimension was found as a decisive factor influencing the tendency for coke deposition, herein identified as polymethylated benzenes, mainly 1,2,4-trimethyl-benzene.

  8. Pore water colloid properties in argillaceous sedimentary rocks

    Energy Technology Data Exchange (ETDEWEB)

    Degueldre, Claude, E-mail: c.degueldre@lancaster.ac.uk [Engineering Department, University of Lancaster, LA1 4YW Lancaster (United Kingdom); ChiAM & Institute of Environment, University of Geneva, 1211 Genève 4, Swizerland (Switzerland); Earlier, NES, Paul Scherrer Institute, 5232 Villigen (Switzerland); Cloet, Veerle [NAGRA, Hardstrasse 73, 5430 Wettingen (Switzerland)

    2016-11-01

    The focus of this work is to evaluate the colloid nature, concentration and size distribution in the pore water of Opalinus Clay and other sedimentary host rocks identified for a potential radioactive waste repository in Switzerland. Because colloids could not be measured in representative undisturbed porewater of these host rocks, predictive modelling based on data from field and laboratory studies is applied. This approach allowed estimating the nature, concentration and size distributions of the colloids in the pore water of these host rocks. As a result of field campaigns, groundwater colloid concentrations are investigated on the basis of their size distribution quantified experimentally using single particle counting techniques. The colloid properties are estimated considering data gained from analogue hydrogeochemical systems ranging from mylonite features in crystalline fissures to sedimentary formations. The colloid concentrations were analysed as a function of the alkaline and alkaline earth element concentrations. Laboratory batch results on clay colloid generation from compacted pellets in quasi-stagnant water are also reported. Experiments with colloids in batch containers indicate that the size distribution of a colloidal suspension evolves toward a common particle size distribution independently of initial conditions. The final suspension size distribution was found to be a function of the attachment factor of the colloids. Finally, calculations were performed using a novel colloid distribution model based on colloid generation, aggregation and sedimentation rates to predict under in-situ conditions what makes colloid concentrations and size distributions batch- or fracture-size dependent. The data presented so far are compared with the field and laboratory data. The colloid occurrence, stability and mobility have been evaluated for the water of the considered potential host rocks. In the pore water of the considered sedimentary host rocks, the clay

  9. Pore formation during dehydration of a polycrystalline gypsum sample observed and quantified in a time-series synchrotron X-ray micro-tomography experiment

    Directory of Open Access Journals (Sweden)

    F. Fusseis

    2012-03-01

    Full Text Available We conducted an in-situ X-ray micro-computed tomography heating experiment at the Advanced Photon Source (USA to dehydrate an unconfined 2.3 mm diameter cylinder of Volterra Gypsum. We used a purpose-built X-ray transparent furnace to heat the sample to 388 K for a total of 310 min to acquire a three-dimensional time-series tomography dataset comprising nine time steps. The voxel size of 2.2 μm3 proved sufficient to pinpoint reaction initiation and the organization of drainage architecture in space and time.

    We observed that dehydration commences across a narrow front, which propagates from the margins to the centre of the sample in more than four hours. The advance of this front can be fitted with a square-root function, implying that the initiation of the reaction in the sample can be described as a diffusion process.

    Novel parallelized computer codes allow quantifying the geometry of the porosity and the drainage architecture from the very large tomographic datasets (20483 voxels in unprecedented detail. We determined position, volume, shape and orientation of each resolvable pore and tracked these properties over the duration of the experiment. We found that the pore-size distribution follows a power law. Pores tend to be anisotropic but rarely crack-shaped and have a preferred orientation, likely controlled by a pre-existing fabric in the sample. With on-going dehydration, pores coalesce into a single interconnected pore cluster that is connected to the surface of the sample cylinder and provides an effective drainage pathway.

    Our observations can be summarized in a model in which gypsum is stabilized by thermal expansion stresses and locally increased pore fluid pressures until the dehydration front approaches to within about 100 μm. Then, the internal stresses are released and dehydration happens efficiently, resulting in new pore space. Pressure release, the production of pores and the

  10. Pore formation during dehydration of polycrystalline gypsum observed and quantified in a time-series synchrotron radiation based X-ray micro-tomography experiment

    Science.gov (United States)

    Fusseis, F.; Schrank, C.; Liu, J.; Karrech, A.; Llana-Fúnez, S.; Xiao, X.; Regenauer-Lieb, K.

    2011-10-01

    We conducted an in-situ X-ray micro-computed tomography heating experiment at the Advanced Photon Source (USA) to dehydrate an unconfined 2.3 mm diameter cylinder of Volterra Gypsum. We used a purpose-built X-ray transparent furnace to heat the sample to 388 K for a total of 310 min to acquire a three-dimensional time-series tomography dataset comprising nine time steps. The voxel size of 2.2 μm3 proved sufficient to pinpoint reaction initiation and the organization of drainage architecture in space and time. We observed that dehydration commences across a narrow front, which propagates from the margins to the centre of the sample in more than four hours. The advance of this front can be fitted with a square-root function, implying that the initiation of the reaction in the sample can be described as a diffusion process. Novel parallelized computer codes allow quantifying the geometry of the porosity and the drainage architecture from the very large tomographic datasets (6.4 × 109 voxel each) in unprecedented detail. We determined position, volume, shape and orientation of each resolvable pore and tracked these properties over the duration of the experiment. We found that the pore-size distribution follows a power law. Pores tend to be anisotropic but rarely crack-shaped and have a preferred orientation, likely controlled by a pre-existing fabric in the sample. With on-going dehydration, pores coalesce into a single interconnected pore cluster that is connected to the surface of the sample cylinder and provides an effective drainage pathway. Our observations can be summarized in a model in which gypsum is stabilized by thermal expansion stresses and locally increased pore fluid pressures until the dehydration front approaches to within about 100 μm. Then, the internal stresses are released and dehydration happens efficiently, resulting in new pore space. Pressure release, the production of pores and the advance of the front are coupled in a feedback loop. We

  11. Pore formation during dehydration of a polycrystalline gypsum sample observed and quantified in a time-series synchrotron X-ray micro-tomography experiment

    Science.gov (United States)

    Fusseis, F.; Schrank, C.; Liu, J.; Karrech, A.; Llana-Fúnez, S.; Xiao, X.; Regenauer-Lieb, K.

    2012-03-01

    We conducted an in-situ X-ray micro-computed tomography heating experiment at the Advanced Photon Source (USA) to dehydrate an unconfined 2.3 mm diameter cylinder of Volterra Gypsum. We used a purpose-built X-ray transparent furnace to heat the sample to 388 K for a total of 310 min to acquire a three-dimensional time-series tomography dataset comprising nine time steps. The voxel size of 2.2 μm3 proved sufficient to pinpoint reaction initiation and the organization of drainage architecture in space and time. We observed that dehydration commences across a narrow front, which propagates from the margins to the centre of the sample in more than four hours. The advance of this front can be fitted with a square-root function, implying that the initiation of the reaction in the sample can be described as a diffusion process. Novel parallelized computer codes allow quantifying the geometry of the porosity and the drainage architecture from the very large tomographic datasets (20483 voxels) in unprecedented detail. We determined position, volume, shape and orientation of each resolvable pore and tracked these properties over the duration of the experiment. We found that the pore-size distribution follows a power law. Pores tend to be anisotropic but rarely crack-shaped and have a preferred orientation, likely controlled by a pre-existing fabric in the sample. With on-going dehydration, pores coalesce into a single interconnected pore cluster that is connected to the surface of the sample cylinder and provides an effective drainage pathway. Our observations can be summarized in a model in which gypsum is stabilized by thermal expansion stresses and locally increased pore fluid pressures until the dehydration front approaches to within about 100 μm. Then, the internal stresses are released and dehydration happens efficiently, resulting in new pore space. Pressure release, the production of pores and the advance of the front are coupled in a feedback loop.

  12. Influence of hydrological regime on pore water metal concentrations in a contaminated sediment-derived soil

    International Nuclear Information System (INIS)

    Du Laing, G.; Vanthuyne, D.R.J.; Vandecasteele, B.; Tack, F.M.G.; Verloo, M.G.

    2007-01-01

    Options for wetland creation or restoration might be limited because of the presence of contaminants in the soil. The influence of hydrological management on the pore water concentrations of Cd, Cr, Cu, Fe, Mn, Ni and Zn in the upper soil layer of a contaminated overbank sedimentation zone was investigated in a greenhouse experiment. Flooding conditions led to increased Fe, Mn, Ni and Cr concentrations and decreased Cd, Cu and Zn concentrations in the pore water of the upper soil layer. Keeping the soil at field capacity resulted in a low pore water concentration of Fe, Mn and Ni while the Cd, Cu, Cr and Zn concentrations increased. Alternating hydrological conditions caused metal concentrations in the pore water to fluctuate. Formation and re-oxidation of small amounts of sulphides appeared dominant in determining the mobility of Cd, Cu, and to a lesser extent Zn, while Ni behaviour was consistent with Fe/Mn oxidation and reduction. These effects were strongly dependent on the duration of the flooded periods. The shorter the flooded periods, the better the metal concentrations could be linked to the mobility of Ca in the pore water, which is attributed to a fluctuating CO 2 pressure. - The hydrological regime is a key factor in determining the metal concentration in the pore water of a contaminated sediment-derived soil

  13. Dissolution at porous interfaces VI: Multiple pore systems.

    Science.gov (United States)

    Grijseels, H; Crommelin, D J; De Blaey, C J

    1984-12-01

    With the aid of rapidly dissolving sodium chloride particles, cubic pores were made in the surface of a theophylline tablet. The influence of the pores on the dissolution rate of the surface was investigated in a rotating disk apparatus. Like the drilled pores used in earlier studies, downstream on the surface they caused a turbulent flow regimen with the development of a trough due to enhanced erosion. The phenomenon of a critical pore diameter, discovered with single, drilled pores, seems to be applicable to the cubic pores investigated in this study, although a higher degree of surface coverage with pores caused complications, probably due to particles bordering one another and forming larger pores. The behavior of the porous surfaces at different rotation speeds was studied. Due to the presence of pores the laminar character of the boundary layer flow changes to turbulent, which induces locally an increased dissolution flux in the wake of a pore.

  14. Molecular basis of usher pore gating in Escherichia coli pilus biogenesis.

    Science.gov (United States)

    Volkan, Ender; Kalas, Vasilios; Pinkner, Jerome S; Dodson, Karen W; Henderson, Nadine S; Pham, Thieng; Waksman, Gabriel; Delcour, Anne H; Thanassi, David G; Hultgren, Scott J

    2013-12-17

    Extracellular fibers called chaperone-usher pathway pili are critical virulence factors in a wide range of Gram-negative pathogenic bacteria that facilitate binding and invasion into host tissues and mediate biofilm formation. Chaperone-usher pathway ushers, which catalyze pilus assembly, contain five functional domains: a 24-stranded transmembrane β-barrel translocation domain (TD), a β-sandwich plug domain (PLUG), an N-terminal periplasmic domain, and two C-terminal periplasmic domains (CTD1 and 2). Pore gating occurs by a mechanism whereby the PLUG resides stably within the TD pore when the usher is inactive and then upon activation is translocated into the periplasmic space, where it functions in pilus assembly. Using antibiotic sensitivity and electrophysiology experiments, a single salt bridge was shown to function in maintaining the PLUG in the TD channel of the P pilus usher PapC, and a loop between the 12th and 13th beta strands of the TD (β12-13 loop) was found to facilitate pore opening. Mutation of the β12-13 loop resulted in a closed PapC pore, which was unable to efficiently mediate pilus assembly. Deletion of the PapH terminator/anchor resulted in increased OM permeability, suggesting a role for the proper anchoring of pili in retaining OM integrity. Further, we introduced cysteine residues in the PLUG and N-terminal periplasmic domains that resulted in a FimD usher with a greater propensity to exist in an open conformation, resulting in increased OM permeability but no loss in type 1 pilus assembly. These studies provide insights into the molecular basis of usher pore gating and its roles in pilus biogenesis and OM permeability.

  15. Wormholes propagation for fractured-vuggy formation: Laboratory tests, numerical simulation and field application

    Directory of Open Access Journals (Sweden)

    Fei Liu

    2017-12-01

    Full Text Available The propagation of wormhole is vital important for matrix acidizing and acid fracturing in carbonate reservoirs. While the formation of acid dissolved wormhole is derived from heterogeneous physical and chemical transportations and reactions. Alveolate dissolved pores, krast caves, and natural fissures are the major reservoir spaces for the Sinian dolomite formation in the Anyue gas field of the Sichuan Basin. There were four categories of formation, which are matrix dominated, inter-breccia dissolved pore dominated, dissolved pore and cave dominated, and fissure and cave dominated, based on the development intensity and connectedness of caves and fissures. The caves and fissures make the wormhole formation and propagation particularly complicated. Firstly, the 3-D topological structure of dissolved pores, vugs, fissures and throats inside cores is quantitatively scanned by CT imaging technology for its feature of vivid and damage-free. Secondly, 3-D patterns of wormhole are obtained with CT scanning after core flooding by acid. Additionally, the pore-throat network model is reconstructed with digital cores technology. Then, the size and ratio of pore and throat before and after core flooding by acid is analyzed and the absolute permeability of pore scale flow is numerically simulated to understand the fundamental influence of pores and vugs distribution and connectedness on wormhole propagation. Lastly, the wormhole pattern gained by CT scanning and simulating with two-scale model is compared. Meanwhile, the corrected two-scale model is utilized to simulate the wormhole propagation for matrix acidizing and acid fracturing of Sinian fractured-vuggy dolomite in Anyue gas field, Sichuan Basin. The optimized injection rate and volume were in agreement with the characteristic matrix acidizing operating curve, which indicates that the two-scale model was suitable for matrix acidizing optimization design of such formations. In addition, the simulated

  16. Creating Hierarchical Pores by Controlled Linker Thermolysis in Multivariate Metal-Organic Frameworks.

    Science.gov (United States)

    Feng, Liang; Yuan, Shuai; Zhang, Liang-Liang; Tan, Kui; Li, Jia-Luo; Kirchon, Angelo; Liu, Ling-Mei; Zhang, Peng; Han, Yu; Chabal, Yves J; Zhou, Hong-Cai

    2018-02-14

    Sufficient pore size, appropriate stability, and hierarchical porosity are three prerequisites for open frameworks designed for drug delivery, enzyme immobilization, and catalysis involving large molecules. Herein, we report a powerful and general strategy, linker thermolysis, to construct ultrastable hierarchically porous metal-organic frameworks (HP-MOFs) with tunable pore size distribution. Linker instability, usually an undesirable trait of MOFs, was exploited to create mesopores by generating crystal defects throughout a microporous MOF crystal via thermolysis. The crystallinity and stability of HP-MOFs remain after thermolabile linkers are selectively removed from multivariate metal-organic frameworks (MTV-MOFs) through a decarboxylation process. A domain-based linker spatial distribution was found to be critical for creating hierarchical pores inside MTV-MOFs. Furthermore, linker thermolysis promotes the formation of ultrasmall metal oxide nanoparticles immobilized in an open framework that exhibits high catalytic activity for Lewis acid-catalyzed reactions. Most importantly, this work provides fresh insights into the connection between linker apportionment and vacancy distribution, which may shed light on probing the disordered linker apportionment in multivariate systems, a long-standing challenge in the study of MTV-MOFs.

  17. Pore development in anodic alumina in sulphuric acid and borax electrolytes

    International Nuclear Information System (INIS)

    Garcia-Vergara, S.J.; Skeldon, P.; Thompson, G.E.; Habakaki, H.

    2007-01-01

    The formation of porous anodic films on an Al-3.5 at.%W alloy is compared in sulphuric acid and borax electrolytes in order to investigate pore development processes. The findings disclose that for anodizing in sulphuric acid, the pores develop mainly due to the influences of field-induced plasticity of the film and growth stresses; in borax, field-assisted dissolution dominates. The films formed in sulphuric acid are consequently much thicker than the layer of oxidized alloy and tungsten species are retained in the film. In contrast, with borax, the films and oxidized alloy layers are of similar thickness and tungsten species are lost to the electrolyte. Efficiencies of film growth are also significantly different, about 65% in sulphuric acid and about 52% in borax. The retention of tungsten species during anodizing in sulphuric acid is due to the localization of tungsten in the inner regions of the barrier layer and cell walls, with a layer of anodic alumina separating the tungsten-containing regions from the electrolyte. For borax, the tungsten is distributed more uniformly through the film material, enabling loss of tungsten species to the electrolyte from the pore base

  18. Mechanism of formation of a zone without vacancy pores along a surface under electron irradiation of a metal in the high-volt electron microscope

    International Nuclear Information System (INIS)

    Golubov, S.I.; Konobeev, Yu.V.; Ryabov, V.A.

    1981-01-01

    Formation mechanism of zones free of vacancy pores near the vacant surface of a metal preliminary irradiated at a high neutron dose when irradiating with electrons in a high-voltage electron microscope has been suggested. It was assumed to explain experimentally observed values of width and time of such zone formation that interstitial atoms are reflected from foil surface while boundary serves as an ideal sink for the vacancies. The carried out calculation of stationary equations of vacancy and interstitial diffusion with the mentioned boundary condition has shown that determination of a stable zone width is possible only in assumption on a variable in a depth of dislocation density. Theoretical evaluations of a zone width being in good agreement with an experiment and with the results of numerical calculations have been obtained in negligence of recombination of point defects as well as for the case of total reflection of interstitials. Discussed are different mechanisms of weak capture of proper interstitial atoms diffusing to it with the metal surface [ru

  19. Pore-Scale Investigation of Micron-Size Polyacrylamide Elastic Microspheres (MPEMs) Transport and Retention in Saturated Porous Media

    KAUST Repository

    Yao, Chuanjin

    2014-05-06

    Knowledge of micrometer-size polyacrylamide elastic microsphere (MPEM) transport and retention mechanisms in porous media is essential for the application of MPEMs as a smart sweep improvement and profile modification agent in improving oil recovery. A transparent micromodel packed with translucent quartz sand was constructed and used to investigate the pore-scale transport, surface deposition-release, and plugging deposition-remigration mechanisms of MPEMs in porous media. The results indicate that the combination of colloidal and hydrodynamic forces controls the deposition and release of MPEMs on pore-surfaces; the reduction of fluid salinity and the increase of Darcy velocity are beneficial to the MPEM release from pore-surfaces; the hydrodynamic forces also influence the remigration of MPEMs in pore-throats. MPEMs can plug pore-throats through the mechanisms of capture-plugging, superposition-plugging, and bridge-plugging, which produces resistance to water flow; the interception with MPEM particulate filters occurring in the interior of porous media can enhance the plugging effect of MPEMs; while the interception with MPEM particulate filters occurring at the surface of low-permeability layer can prevent the low-permeability layer from being damaged by MPEMs. MPEMs can remigrate in pore-throats depending on their elasticity through four steps of capture-plugging, elastic deformation, steady migration, and deformation recovery. © 2014 American Chemical Society.

  20. Positronium formation in porous materials for antihydrogen production

    International Nuclear Information System (INIS)

    Ferragut, R; Calloni, A; Dupasquier, A; Consolati, G; Giammarchi, M G; Quasso, F; Trezzi, D; Egger, W; Ravelli, L; Petkov, M P; Jones, S M; Wang, B; Yaghi, O M; Jasinska, B; Chiodini, N; Paleari, A

    2010-01-01

    Positronium (Ps) formation measurements in several porous materials as: Vycor, germanate Xerogel, Metal-Organic Frameworks MOF-177 and Aerogel with two densities (20 and 150 mg/cm 3 ), were performed by means of a variable energy positron beam provided with a Ge detector and a positron lifetime spectrometer. An efficient formation of cooled Ps atoms is a requisite for the production of antihydrogen, with the aim of a direct measurement of the Earth gravitational acceleration g of antimatter, which is a primary scientific goal of AEGIS (Antimatter Experiment: Gravity, Interferometry, Spectroscopy). Porous materials are necessary to form a high yield of Ps atoms as well as to cool Ps through collisions with the inner walls of the pores. The different materials were characterized and produce Ps into the pores. Lifetime measurements give an estimation of the typical pores dimension of the substances. A comparative study of the positron lifetime and the Ps fraction values in the above mentioned materials indicates that silica Aerogel, with the appropriate density, is an excellent candidate for an efficient formation of cold Ps atoms for the AEGIS project.

  1. Control and Prevention of Ice Formation on the Surface of an Aluminum Alloy

    DEFF Research Database (Denmark)

    Rahimi, Maral

    modified with (3-aminopropyl) triethoxy silane (APTES) exhibited longer freezing delays as compared to both more hydrophilic and more hydrophobic substrates. This is attributed to a particular surface chemistry of the APTES modification that prevents ice formation at the interface of the substrate due...

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

    Science.gov (United States)

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

    2017-10-01

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

  3. 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.

  4. Cavitation and pore blocking in nanoporous glasses.

    Science.gov (United States)

    Reichenbach, C; Kalies, G; Enke, D; Klank, D

    2011-09-06

    In gas adsorption studies, porous glasses are frequently referred to as model materials for highly disordered mesopore systems. Numerous works suggest that an accurate interpretation of physisorption isotherms requires a complete understanding of network effects upon adsorption and desorption, respectively. The present article deals with nitrogen and argon adsorption at different temperatures (77 and 87 K) performed on a series of novel nanoporous glasses (NPG) with different mean pore widths. NPG samples contain smaller mesopores and significantly higher microporosity than porous Vycor glass or controlled pore glass. Since the mean pore width of NPG can be tuned sensitively, the evolution of adsorption characteristics with respect to a broadening pore network can be investigated starting from the narrowest nanopore width. With an increasing mean pore width, a H2-type hysteresis develops gradually which finally transforms into a H1-type. In this connection, a transition from a cavitation-induced desorption toward desorption controlled by pore blocking can be observed. Furthermore, we find concrete hints for a pore size dependence of the relative pressure of cavitation in highly disordered pore systems. By comparing nitrogen and argon adsorption, a comprehensive insight into adsorption mechanisms in novel disordered materials is provided. © 2011 American Chemical Society

  5. 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...

  6. Pore facies analysis: incorporation of rock properties into pore geometry based classes in a Permo-Triassic carbonate reservoir in the Persian Gulf

    International Nuclear Information System (INIS)

    Rahimpour-Bonab, H; Aliakbardoust, E

    2014-01-01

    Pore facies analysis is a useful method for the classification of reservoir rocks according to pore geometry characteristics. The importance of this method is related to the dependence of the dynamic behaviour of the reservoir rock on the pore geometry. In this study, pore facies analysis was performed by the quantification and classification of the mercury injection capillary pressure (MICP) curves applying the multi-resolution graph-based clustering (MRGC) method. Each pore facies includes a limited variety of rock samples with different depositional fabrics and diagenetic histories, which are representative of one type of pore geometry. The present pore geometry is the result of the interaction between the primary rock fabric and its diagenetic overprint. Thus the variations in petrographic properties can be correlated with the pore geometry characteristics. Accordingly, the controlling parameters in the pore geometry characteristics were revealed by detailed petrographic analysis in each pore facies. The reservoir rock samples were then classified using the determined petrographic properties which control the pore system quality. This method is proposed for the classification of reservoir rocks in complicated carbonate reservoirs, in order to reduce the incompatibility of traditional facies analysis with pore system characteristics. The method is applicable where enough capillary pressure data is not available. (papers)

  7. Pore surface engineering in covalent organic frameworks.

    Science.gov (United States)

    Nagai, Atsushi; Guo, Zhaoqi; Feng, Xiao; Jin, Shangbin; Chen, Xiong; Ding, Xuesong; Jiang, Donglin

    2011-11-15

    Covalent organic frameworks (COFs) are a class of important porous materials that allow atomically precise integration of building blocks to achieve pre-designable pore size and geometry; however, pore surface engineering in COFs remains challenging. Here we introduce pore surface engineering to COF chemistry, which allows the controlled functionalization of COF pore walls with organic groups. This functionalization is made possible by the use of azide-appended building blocks for the synthesis of COFs with walls to which a designable content of azide units is anchored. The azide units can then undergo a quantitative click reaction with alkynes to produce pore surfaces with desired groups and preferred densities. The diversity of click reactions performed shows that the protocol is compatible with the development of various specific surfaces in COFs. Therefore, this methodology constitutes a step in the pore surface engineering of COFs to realize pre-designed compositions, components and functions.

  8. Relationship between pore structure and compressive strength

    Indian Academy of Sciences (India)

    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 ...

  9. Randomized clinical trial of prevention of seroma formation after mastectomy by local methylprednisolone injection

    DEFF Research Database (Denmark)

    Qvamme, G; Axelsson, C. K.; Lanng, C

    2015-01-01

    : This was a double-blind randomized placebo-controlled intervention study of a single dose of 80 mg methylprednisolone versus saline on seroma formation after mastectomy. Patients were further classified according to the surgical axillary procedure: mastectomy with sentinel lymph node biopsy (M + SLNB) or mastectomy......BACKGROUND: Seroma formation, the most prevalent postoperative complication after mastectomy, is an inflammatory process that is potentially preventable via local steroid administration. This study investigated the effect of local steroid administration on seroma formation. METHODS...... with level I-II axillary lymph node dissection (M + ALND). Treatments were administered into the wound cavity via the drain orifice following removal of the drain on the first day after surgery. The primary endpoint was seroma formation; secondary endpoints included the frequency of side...

  10. A pore water conductivity sensor

    NARCIS (Netherlands)

    Hilhorst, M.A.

    2001-01-01

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

  11. Damage development - effects of multiaxial loads on creep pore formation and fatigue damage in typical power plant steels. Final report

    International Nuclear Information System (INIS)

    Lenk, P.; Proft, D.; Kussmaul, A.; Fischer, R.

    2000-01-01

    The influence of multiaxial stress on creep pore formation in the steels 14MoV6-3 10CrMo9-10 and X10CrMoVNb9-1 was investigated on the basis of internal pressure experiments on smooth and notched hollow cylinders. In some cases, additional axial forces were applied in order to reproduce component-relevant multiaxial stresses. Local elongation during loading was investigated and analyzed using applied HT-DMS. When different strain levels had been reached, the samples were removed, analyzed, and characterized with regard to different damage parameters. It was found that no interdependence between the surface damage pattern and the deep damage pattern can be derived across the wall thickness if no information on the load state is available. Parallel to the experiments, inelastic FEA were carried out using the ABAQUS program system. The creep law of Graham and Walles was used for calculating flow and creep via a user-defined subroutine CREEP. The parameters of the creep law could be identified by adaptation to monoaxial creep tests [de

  12. Creating Hierarchical Pores by Controlled Linker Thermolysis in Multivariate Metal-Organic Frameworks

    KAUST Repository

    Feng, Liang

    2018-01-18

    Sufficient pore size, appropriate stability and hierarchical porosity are three prerequisites for open frameworks designed for drug delivery, enzyme immobilization and catalysis involving large molecules. Herein, we report a powerful and general strate-gy, linker thermolysis, to construct ultra-stable hierarchically porous metal−organic frameworks (HP-MOFs) with tunable pore size distribution. Linker instability, usually an undesirable trait of MOFs, was exploited to create mesopores by generating crystal defects throughout a microporous MOF crystal via thermolysis. The crystallinity and stability of HP-MOFs remain after thermolabile linkers are selectively removed from multivariate metal-organic frameworks (MTV-MOFs) through a decarboxyla-tion process. A domain-based linker spatial distribution was found to be critical for creating hierarchical pores inside MTV-MOFs. Furthermore, linker thermolysis promotes the formation of ultra-small metal oxide (MO) nanoparticles immobilized in an open framework that exhibits high catalytic activity for Lewis acid catalyzed reactions. Most importantly, this work pro-vides fresh insights into the connection between linker apportionment and vacancy distribution, which may shed light on prob-ing the disordered linker apportionment in multivariate systems, a long-standing challenge in the study of MTV-MOFs.

  13. Thermal Instability Induced Oriented 2D Pores for Enhanced Sodium Storage.

    Science.gov (United States)

    Kong, Lingjun; Xie, Chen-Chao; Gu, Haichen; Wang, Chao-Peng; Zhou, Xianlong; Liu, Jian; Zhou, Zhen; Li, Zhao-Yang; Zhu, Jian; Bu, Xian-He

    2018-04-19

    Hierarchical porous structures are highly desired for various applications. However, it is still challenging to obtain such materials with tunable architectures. Here, this paper reports hierarchical nanomaterials with oriented 2D pores by taking advantages of thermally instable bonds in vanadium-based metal-organic frameworks (MOFs). High-temperature calcination of these MOFs accompanied by the loss of coordinated water molecules and other components enables the formation of orderly slit-like 2D pores in vanadium oxide/porous carbon nanorods (VO x /PCs). This unique combination leads to an increase of the reactive surface area. In addition, optimized VO x /PCs demonstrate high-rate capability and ultralong cycling life for sodium storage. The assembled full cells also show high capacity and cycling stability. This report provides an effective strategy for producing MOFs-derived composites with hierarchical porous architectures for energy storage. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Activation of P2X7-mediated apoptosis Inhibits DMBA/TPA-induced formation of skin papillomas and cancer in mice

    International Nuclear Information System (INIS)

    Fu, Wen; Gorodeski, George I; McCormick, Tom; Qi, Xiaoping; Luo, Liping; Zhou, Lingyin; Li, Xin; Wang, Bing-Cheng; Gibbons, Heidi E; Abdul-Karim, Fadi W

    2009-01-01

    The study tested the hypothesis that apoptosis can prevent and control growth of neoplastic cells. Previous studies in-vitro have shown that the pro-apoptotic P2X 7 receptor regulates growth of epithelial cells. The specific objective of the present study was to understand to what degree the P2X 7 system controls development and growth of skin cancer in vivo, and what cellular and molecular mechanisms are involved in the P2X 7 action. Skin neoplasias in mice (papillomas, followed by squamous spindle-cell carcinomas) were induced by local application of DMBA/TPA. Experiments in-vitro utilized cultured epidermal keratinocytes generated from wild-type or from P2X 7 -null mice. Assays involved protein immunostaining and Western blots; mRNA real-time qPCR; and apoptosis (evaluated in situ by TUNEL and quantified in cultured keratinocytes as solubilized DNA or by ELISA). Changes in cytosolic calcium or in ethidium bromide influx (P2X 7 pore formation) were determined by confocal laser microscopy. (a) Co-application on the skin of the P2X 7 specific agonist BzATP inhibited formation of DMBA/TPA-induced skin papillomas and carcinomas. At the completion of study (week 28) the proportion of living animals with cancers in the DMBA/TPA group was 100% compared to 43% in the DMBA/TPA+BzATP group. (b) In the normal skin BzATP affected mainly P2X 7 -receptor – expressing proliferating keratinocytes, where it augmented apoptosis without evoking inflammatory changes. (c) In BzATP-treated mice the degree of apoptosis was lesser in cancer than in normal or papilloma keratinocytes. (d) Levels of P2X 7 receptor, protein and mRNA were 4–5 fold lower in cancer tissues than in normal mouse tissues. (e) In cultured mouse keratinocytes BzATP induced apoptosis, formation of pores in the plasma membrane, and facilitated prolonged calcium influx. (f) The BzATP-induced apoptosis, pore-formation and augmented calcium influx had similar dose-dependence for BzATP. (g) Pore formation and the

  15. Mesoscale Simulations of Pore Migration in a Nuclear Fuel

    International Nuclear Information System (INIS)

    Radhakrishnan, Balasubramaniam; Gorti, Sarma B.

    2010-01-01

    The evolution of pore and grain structure in a nuclear fuel environment is strongly influenced by the local temperature, and the temperature gradient. The evolution of pore and grain structure in an externally imposed temperature gradient is simulated for a hypothetical material using a Potts model approach that allows for porosity migration by mechanisms similar to surface, grain boundary and volume diffusion, as well as the interaction of migrating pores with stationary grain boundaries. First, the migration of a single pore in a single crystal in the presence of the temperature gradient is simulated. Next, the interaction of a pore moving in a temperature gradient with a grain boundary that is perpendicular to the pore migration direction is simulated in order to capture the force exerted by the pore on the grain boundary. The simulations reproduce the expected variation of pore velocity with pore size as well as the variation of the grain boundary force with pore size.

  16. Bithermal and isothermal experimental test design and resulting influence on the pore formation during high-temperature-induced fatigue of the alloy 800 H

    International Nuclear Information System (INIS)

    Hurta, S.

    1991-01-01

    For investigating the damaging mechanism, bithermal TMF tests have been carried out with the alloy 800H, applying fast pressure half-cycles at low temperature (e.g. 300 C) and slow tensile phases at high temperature (e.g. 700 C). The experimental data thus obtained have been compared with the results of isothermal tests performed at 700 C. Most of the experiments have been performed stress-controlled and with a constant range of plastic strain. Under this regime, deformation is induced in the case of asymmetric test design within the tensile load phase, at various constant tensile stresses each, wheras in the compressive load phase, the stress is constantly increased for compressive stress-governed testing. The results obtained from both test types show that the type of compressive load phase is the factor governing the efficiency of pore formation. (orig.) [de

  17. Drying-induced deformation of Horonobe sedimentary rock in the Koetoi and Wakkanai formations

    International Nuclear Information System (INIS)

    Illankoon, Thilini Nuwanradha; Yee, Suu Mon; Osada, Masahiko; Maekawa, Keisuke; Tada, Hiroyuki; Kumasaka, Hiroo

    2013-01-01

    In order to increase the long-term safety of geological disposal sites, knowledge of the drying-induced deformation characteristics of the rock mass in underground ventilated galleries is necessary to understand its cracking susceptibility and the chance of further propagation of the excavation damaged zone. Hence, strain was measured in ten cylindrical mudstone specimens (4 from Koetoi formation and 6 from Wakkanai formation respectively) cored at Horonobe Underground Research Laboratory (URL), an off-site (generic) URL, to examine deformation behavior during desiccation. The specimens were prepared in one-dimensional drying conditions in a 25degC or 40degC climatic chamber with 50% relative humidity. Mercury intrusion porosimetry (MIP) was also conducted to measure the pore size distributions of each formation. The recorded data showed that the Koetoi formation specimens generated smaller maximum shrinkage values (10,000 μ) compared to those from the Wakkanai formation (13,000 μ and 24,000 μ for Wakkanai groups I and II respectively). Wakkanai formation specimens were divided into two groups (Wakkanai groups I and II) according to their strain behavior. The porosity of the Koetoi formation was 54% whereas that of the Wakkanai formation was 27 - 38%. MIP results clearly indicate that the Wakkanai formation has a greater mesopore volume (63% and 73% of porosity for Wakkanai groups I and II respectively) than the Koetoi formation (8% of porosity) which contributes to its greater shrinkage. In addition, Wakkanai groups I and II have different pore size distribution patterns. Therefore, Wakkanai groups I and II exhibit distinct strain behaviors during drying. Similarities in grain density, a decrease in porosity and a gradual increase in mesopore volume with depth confirm the progressive hardening of Horonobe sedimentary rock. The pore volume in the 0.013 - 0.025 μm pore radius range exerts a strong influence on shrinkage generation in the Wakkanai formation

  18. Prevention of organic iodide formation in BWR's

    International Nuclear Information System (INIS)

    Karjunen, T.; Laitinen, T.; Piippo, J.; Sirkiae, P.

    1996-01-01

    During an accident, many different forms of iodine may emerge. Organic iodides, such as methyl iodide and ethyl iodide, are relatively volatile, and thus their appearance leads to increased concentration of gaseous iodine. Since organic iodides are also relatively immune to most accident mitigation measures, such as sprays and filters, they can affect the accident source term significantly even when only a small portion of iodine is in organic form. Formation of organic iodides may not be limited by the amount of organic substances available. Excessive amounts of methane can be produced, for example, during oxidation of boron carbide, which is used in BWR's as a neutron absorber material. Another important source is cable insulation. In a BWR, a large quantity of cables is placed below the pressure vessel. Thus a large quantity of pyrolyse gases will be produced, should the vessel fail. Organic iodides can be formed as a result of many different reactions, but at least in certain conditions the main reaction takes place between an organic radical produced by radiolysis and elemental iodine. A necessary requirement for prevention of organic iodide production is therefore that the pH in the containment water pools is kept high enough to eliminate formation of elemental iodine. In a typical BWR the suppression pool water is usually unbuffered. As a result, the pH may be dominated by chemicals introduced during an accident. If no system for adding basic chemicals is operable, the main factor affecting pool water pH may be hydrochloric acid released during cable degradation. Should this occur, the conditions could be very favorable for production of elemental iodine and, consequently, formation of organic iodides. Although high pH is necessary for iodine retention, it could have also adverse effects. High pH may, for example, accelerate corrosion of containment materials and alter the characteristics of the solid corrosion products. (author) 6 figs., 1 tab., 13 refs

  19. Can Dietary Polyphenols Prevent the Formation of Toxic Compounds from Maillard Reaction?

    Science.gov (United States)

    Del Turco, Serena; Basta, Giuseppina

    2016-01-01

    Polyphenols are functional compounds in edible vegetable and food such as tea, coffee and red wine and increasing evidence demonstrates a positive link between consumption of polyphenol-rich foods and disease prevention. In this review we have focused on the current knowledge of the potential anti-glycation effects of polyphenols, particularly in regard to their influence on Maillard reaction, a non-enzymatic reaction between amino acids and reducing sugars that contributes to the production of toxic compounds, mainly reactive carbonyl species, advanced glycation end-products (AGEs) and other toxicants. The Maillard reaction occurs in the human body during hyperglycemic condition, but it is well known as browning reaction in thermally processed foods and it is responsible for flavor and toxicant formation. Dietary polyphenols can have anti-glycation effects and actively participate in Maillard reaction, mitigating the AGE formation and the heat-induced production of toxic compounds. In a time in which the role of a healthy diet in the prevention of chronic diseases is welcome and the borderline between food and medicine is becoming very thin, an improved mechanistic knowledge of how polyphenols can function to reduce harmful and unhealthy substances is mandatory.

  20. Concerning a mechanism for removing clay particles of washing liquids from pores

    Energy Technology Data Exchange (ETDEWEB)

    Badzhurak, R F

    1982-01-01

    Examined is a mechanism for removing the clay particles of washing liquids from a pore space. All the experiments are conducted in 1-% clay, water and polymer solutions (with a viscosity of 120 in accordance with SPV-5), made of clay powder of the Makharadz'ye deposit with a particle size of 40-60 mkm, sorted by a screen method. The polymer solutions were made on the basis of hypane, metas, polyacrylamide, KMTs-500, KhS-1 biopolymer, modified and clusterized by an alkaline (NaOH) of cornstarch. Studied is the process of removal of the solid phase from an ''ideal pore'', that is, a quartz capillary. It is demonstrated that the break away of the basic mass of the bentonite particles sedimented from the washing liquids on the quartz surface from the capillary and the formation by them of ''suspended flocules'' occurs at a water current speed in the pore equal to 2.5-4.0 times 10/sup -3/m/s. The carry away of the particles sedimented from the polymer solutions of metase, hypane, clusterized and modified starch, KMTs-500 and water occurs at a stream speed above 5.4 times 10/sup -3/m/s. The greatest speeds are required for the removal of clay particles more than 15 mkm in size from the pore space. The complete removal of these particles from the capillary is observed at a current speed above 40 times 10/sup -3/m/s.

  1. The one-dimensional compression method for extraction of pore water from unsaturated tuff and effects on pore-water chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Higgins, J.D.; Burger, P.A. [Colorado School of Mines, Golden, CO (United States); Yang, L.C. [Geological Survey, Denver, CO (United States)

    1997-12-31

    Study of the hydrologic system at Yucca Mountain, Nevada, requires extraction of pore-water samples from unsaturated tuff bedrock. Two generations of compression cells have been designed and tested for extracting representative, unaltered pore-water samples from unsaturated tuff cores. The one-dimensional compression cell has a maximum compressive stress rating of 552 MPa. Results from 86 tests show that the minimum degree of saturation for successful extraction of pore water was about 14% for non welded tuff and about 61% for densely welded tuff. The high-pressure, one-dimensional compression cell has a maximum compressive stress rating of 827 MPa. Results from 109 tests show that the minimum degree of saturation for successful extraction of pore water was about 7.5% for non welded tuff and about 34% for densely welded tuff. Geochemical analyses show that, in general, there is a decrease in ion concentration of pore waters as extraction pressures increase. Only small changes in pore-water composition occur during the one-dimensional extraction test.

  2. Novel thermosensitive hydrogel for preventing formation of abdominal adhesions

    Directory of Open Access Journals (Sweden)

    Gao X

    2013-07-01

    Full Text Available Xiang Gao,1,2 Xiaohui Deng,3 Xiawei Wei,2 Huashan Shi,2 Fengtian Wang,2 Tinghong Ye,2 Bin Shao,2 Wen Nie,2 Yuli Li,2 Min Luo,2 Changyang Gong,2 Ning Huang1 1Department of Pathophysiology, College of Preclinical and Forensic Medical Sciences, Sichuan University, Chengdu, 2State Key Laboratory of Biotherapy and Cancer Center, West China Hospital, West China Medical School, Sichuan University, Chengdu, 3Department of Human Anatomy, Xinxiang Medical University, Xinxiang, People’s Republic of China Abstract: Adhesions can form after almost any type of abdominal surgery. Postoperative adhesions can be prevented by improved surgical techniques, such as reducing surgical trauma, preventing ischemia, and avoiding exposure of the peritoneal cavity to foreign materials. Although improved surgical techniques can potentially reduce formation of adhesions, they cannot be eliminated completely. Therefore, finding more effective methods to prevent postoperative adhesions is imperative. Recently, we found that a novel thermosensitive hydrogel, ie, poly(ε-caprolactone-poly(ethylene glycol-poly(ε-caprolactone (PCEC had the potential to prevent postoperative adhesions. Using the ring-opening polymerization method, we prepared a PCEC copolymer which could be dissolved and assembled at 55°C into PCEC micelles with mean size of 25 nm. At body temperature, a solution containing PCEC micelles could convert into a hydrogel. The PCEC copolymer was biodegradable and had low toxicity in vitro and in vivo. We found that most animals in a hydrogel-treated group (n = 10 did not develop adhesions. In contrast, 10 untreated animals developed adhesions that could only be separated by sharp dissection (P < 0.001. The hydrogel could adhere to peritoneal wounds and degraded gradually over 7–9 days, transforming into a viscous fluid that was completely absorbed within 12 days. The injured parietal and visceral peritoneum remesothelialized over about seven and nine days

  3. Propagation of a plasma streamer in catalyst pores

    Science.gov (United States)

    Zhang, Quan-Zhi; Bogaerts, Annemie

    2018-03-01

    Although plasma catalysis is gaining increasing interest for various environmental applications, the underlying mechanisms are still far from understood. For instance, it is not yet clear whether and how plasma streamers can propagate in catalyst pores, and what is the minimum pore size to make this happen. As this is crucial information to ensure good plasma-catalyst interaction, we study here the mechanism of plasma streamer propagation in a catalyst pore, by means of a two-dimensional particle-in-cell/Monte Carlo collision model, for various pore diameters in the nm-range to μm-range. The so-called Debye length is an important criterion for plasma penetration into catalyst pores, i.e. a plasma streamer can penetrate into pores when their diameter is larger than the Debye length. The Debye length is typically in the order of a few 100 nm up to 1 μm at the conditions under study, depending on electron density and temperature in the plasma streamer. For pores in the range of ∼50 nm, plasma can thus only penetrate to some extent and at very short times, i.e. at the beginning of a micro-discharge, before the actual plasma streamer reaches the catalyst surface and a sheath is formed in front of the surface. We can make plasma streamers penetrate into smaller pores (down to ca. 500 nm at the conditions under study) by increasing the applied voltage, which yields a higher plasma density, and thus reduces the Debye length. Our simulations also reveal that the plasma streamers induce surface charging of the catalyst pore sidewalls, causing discharge enhancement inside the pore, depending on pore diameter and depth.

  4. Facial skin pores: a multiethnic study.

    Science.gov (United States)

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

    2015-01-01

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

  5. Visualization of enzyme activities inside earthworm pores

    Science.gov (United States)

    Hoang, Duyen; Razavi, Bahar S.

    2015-04-01

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

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

    Directory of Open Access Journals (Sweden)

    Jincai Zhang

    2017-01-01

    Full Text Available High uncertainties may exist in the predrill pore pressure prediction in new prospects and deepwater subsalt wells; therefore, real-time pore pressure detection is highly needed to reduce drilling risks. The methods for pore pressure detection (the resistivity, sonic, and corrected d-exponent methods are improved using the depth-dependent normal compaction equations to adapt to the requirements of the real-time monitoring. A new method is proposed to calculate pore pressure from the connection gas or elevated background gas, which can be used for real-time pore pressure detection. The pore pressure detection using the logging-while-drilling, measurement-while-drilling, and mud logging data is also implemented and evaluated. Abnormal pore pressure indicators from the well logs, mud logs, and wellbore instability events are identified and analyzed to interpret abnormal pore pressures for guiding real-time drilling decisions. The principles for identifying abnormal pressure indicators are proposed to improve real-time pore pressure monitoring.

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

    Science.gov (United States)

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

    2017-12-01

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

  8. Pore Pressure Distribution and Flank Instability in Hydrothermally Altered Stratovolcanoes

    Science.gov (United States)

    Ball, J. L.; Taron, J.; Hurwitz, S.; Reid, M. E.

    2015-12-01

    Field and geophysical investigations of stratovolcanoes with long-lived hydrothermal systems commonly reveal that initially permeable regions (such as brecciated layers of pyroclastic material) can become both altered and water-bearing. Hydrothermal alteration in these regions, including clay formation, can turn them into low-permeability barriers to fluid flow, which could increase pore fluid pressures resulting in flank slope instability. We examined elevated pore pressure conditions using numerical models of hydrothermal flow in stratovolcanoes, informed by geophysical data about internal structures and deposits. Idealized radially symmetric meshes were developed based on cross-sectional profiles and alteration/permeability structures of Cascade Range stratovolcanoes. We used the OpenGeoSys model to simulate variably saturated conditions in volcanoes heated only by regional heat fluxes, as well as 650°C intrusions at two km depth below the surface. Meteoric recharge was estimated from precipitation rates in the Cascade Range. Preliminary results indicate zones of elevated pore pressures form: 1) where slopes are underlain by continuous low-permeability altered layers, or 2) when the edifice has an altered core with saturated, less permeable limbs. The first scenario might control shallow collapses on the slopes above the altered layers. The second could promote deeper flank collapses that are initially limited to the summit and upper slopes, but could progress to the core of an edifice. In both scenarios, pore pressures can be further elevated by shallow intrusions, or evolve over longer time scales under forcing from regional heat flux. Geometries without confining low-permeability layers do not show these pressure effects. Our initial scenarios use radially symmetric models, but we are also simulating hydrothermal flow under real 3D geometries with asymmetric subsurface structures (Mount Adams). Simulation results will be used to inform 3D slope

  9. Inorganic polyphosphate (polyP) as an activator and structural component of the mitochondrial permeability transition pore.

    Science.gov (United States)

    Solesio, Maria E; Elustondo, Pia A; Zakharian, Eleonora; Pavlov, Evgeny V

    2016-02-01

    Mitochondrial permeability transition pore (mPTP) is a large channel located in the mitochondrial inner membrane. The opening of mPTP during pathological calcium overload leads to the membrane depolarization and disruption of ATP production. mPTP activation has been implicated as a central event during the process of stress-induced cell death. mPTP is a supramolecular complex composed of many proteins. Recent studies suggest that mitochondrial ATPase plays the central role in the formation of mPTP. However, the structure of the central conducting pore part of mPTP (mPTPore) remains elusive. Here we review current models proposed for the mPTPore and involvement of polyP in its formation and regulation. We discuss the underestimated role of polyP as an effector and a putative structural component of the mPTPore. We propose the hypothesis that inclusion of polyP can explain such properties of mPTP activity as calcium activation, selectivity and voltage-dependence. © 2016 Authors; published by Portland Press Limited.

  10. Pore Pressure and Field stress variation from Salt Water Injection; A case Study from Beaver Lodge Field in Williston Basin

    Science.gov (United States)

    Mohammed, R. A.; Khatibi, S.

    2017-12-01

    One of the major concerns in producing from oil and gas reservoirs in North American Basins is the disposal of high salinity salt water. It is a misconception that Hydro frack triggers Earthquakes, but due to the high salinity and density of water being pumped to the formation that has pore space of the rock already filled, which is not the case in Hydro-frack or Enhanced Oil Recovery in which fracturing fluid is pumped into empty pore space of rocks in depleted reservoirs. A review on the Bakken history showed that the concerns related to induce seismicity has increased over time due to variations in Pore pressure and In-situ stress that have shown steep changes in the region over the time. In this study, we focused on Pore pressure and field Stress variations in lower Cretaceous Inyan Kara and Mississippian Devonian Bakken, Inyan Kara is the major source for class-II salt-water disposal in the basin. Salt-water disposal is the major cause for induced seismicity. A full field study was done on Beaver Lodge Field, which has many salt-water disposal wells Adjacent to Oil and Gas Wells. We analyzed formation properties, stresses, pore-pressure, and fracture gradient profile in the field and. The constructed Mechanical Earth Model (MEM) revealed changes in pore pressure and stresses over time due to saltwater injection. Well drilled in the past were compared to recently drilled wells, which showed much stress variations. Safe mud weight Window of wells near proximity of injection wells was examined which showed many cases of wellbore instabilities. Results of this study will have tremendous impact in studying environmental issues and the future drilling and Fracking operations.

  11. Pore structure of natural and regenerated soil aggregates

    DEFF Research Database (Denmark)

    Naveed, Muhammad; Arthur, Emmanuel; de Jonge, Lis Wollesen

    2014-01-01

    Quantitative characterization of aggregate pore structure can reveal the evolution of aggregates under different land use and management practices and their effects on soil processes and functions. Advances in X-ray Computed Tomography (CT) provide powerful means to conduct such characterization....... This study examined aggregate pore structure of three differently managed same textured Danish soils (mixed forage cropping, MFC; mixed cash cropping, MCC; cereal cash cropping, CCC) for (i) natural aggregates, and (ii) aggregates regenerated after 20 months of incubation. In total, 27 aggregates (8-16 mm...... pore diameter of 200 and 170 Hm, respectively. Pore shape analysis indicated that CCC and MFC aggregates had an abundance of rounded and elongated pores, respectively, and those of MCC were in-between CCC and MFC. Aggregate pore structure development in the lysimeters was nearly similar irrespective...

  12. UV-Induced prevention of biofilm formation inside medical tubes and catheters

    DEFF Research Database (Denmark)

    Pedersen, Jens Kristian Mølgaard; Nielsen, Kristian; Bang, Ole

    2014-01-01

    Biofilm formation inside medical tubes and catheters may often cause unwanted infections, illness andimpaired wound healing during medical treatment, resulting in extended hospitalization and - in worst case– life threatening conditions of the patients. In fact, it is estimated, that the infection...... of multi resistant bacteriacultures. Prevention of biofilm formation inside the tube or catheter, without risk of developing multiresistance, may be achieved by creating a UV-exposed environment in the interior. This may be realized bytransforming the tube itself into an optical waveguide supporting UV...... risk connected withthe use of medical tubes and catheters is the direct cause of more than 60% of all infections acquired inEuropean hospitals. Once formed, the biofilm is generally very tough to suppress by either the body’simmunity system or by use of antibiotics, which may even favor the population...

  13. Enhancement of plasma generation in catalyst pores with different shapes

    Science.gov (United States)

    Zhang, Yu-Ru; Neyts, Erik C.; Bogaerts, Annemie

    2018-05-01

    Plasma generation inside catalyst pores is of utmost importance for plasma catalysis, as the existence of plasma species inside the pores affects the active surface area of the catalyst available to the plasma species for catalytic reactions. In this paper, the electric field enhancement, and thus the plasma production inside catalyst pores with different pore shapes is studied with a two-dimensional fluid model. The results indicate that the electric field will be significantly enhanced near tip-like structures. In a conical pore with small opening, the strongest electric field appears at the opening and bottom corners of the pore, giving rise to a prominent ionization rate throughout the pore. For a cylindrical pore, the electric field is only enhanced at the bottom corners of the pore, with lower absolute value, and thus the ionization rate inside the pore is only slightly enhanced. Finally, in a conical pore with large opening, the electric field is characterized by a maximum at the bottom of the pore, yielding a similar behavior for the ionization rate. These results demonstrate that the shape of the pore has a significantly influence on the electric field enhancement, and thus modifies the plasma properties.

  14. Dynamic Pore-Scale Imaging of Reactive Transport in Heterogeneous Carbonates at Reservoir Conditions Across Multiple Dissolution Regimes

    Science.gov (United States)

    Menke, H. P.; Bijeljic, B.; Andrew, M. G.; Blunt, M. J.

    2014-12-01

    Sequestering carbon in deep geologic formations is one way of reducing anthropogenic CO2 emissions. When supercritical CO2 mixes with brine in a reservoir, the acid generated has the potential to dissolve the surrounding pore structure. However, the magnitude and type of dissolution are condition dependent. Understanding how small changes in the pore structure, chemistry, and flow properties affect dissolution is paramount for successful predictive modelling. Both 'Pink Beam' synchrotron radiation and a Micro-CT lab source are used in dynamic X-ray microtomography to investigate the pore structure changes during supercritical CO2 injection in carbonate rocks of varying heterogeneity at high temperatures and pressures and various flow-rates. Three carbonate rock types were studied, one with a homogeneous pore structure and two heterogeneous carbonates. All samples are practically pure calcium carbonate, but have widely varying rock structures. Flow-rate was varied in three successive experiments by over an order of magnitude whlie keeping all other experimental conditions constant. A 4-mm carbonate core was injected with CO2-saturated brine at 10 MPa and 50oC. Tomographic images were taken at 30-second to 20-minute time-resolutions during a 2 to 4-hour injection period. A pore network was extracted using a topological analysis of the pore space and pore-scale flow modelling was performed directly on the binarized images with connected pathways and used to track the altering velocity distributions. Significant differences in dissolution type and magnitude were found for each rock type and flowrate. At the highest flow-rates, the homogeneous carbonate was seen to have predominately uniform dissolution with minor dissolution rate differences between the pores and pore throats. Alternatively, the heterogeneous carbonates which formed wormholes at high flow rates. At low flow rates the homogeneous rock developed wormholes, while the heterogeneous samples showed evidence

  15. Ursodeoxycholic Acid in the Prevention of Gallstone Formation After Bariatric Surgery: an Updated Systematic Review and Meta-analysis.

    Science.gov (United States)

    Magouliotis, Dimitrios E; Tasiopoulou, Vasiliki S; Svokos, Alexis A; Svokos, Konstantina A; Chatedaki, Christina; Sioka, Eleni; Zacharoulis, Dimitris

    2017-11-01

    We aim to review the available literature on obese patients treated with ursodeoxycholic acid (UDCA) in order to prevent gallstone formation after bariatric surgery. A systematic literature search was performed in PubMed, Cochrane library, and Scopus databases, in accordance with the PRISMA guidelines. Eight studies met the inclusion criteria incorporating 1355 patients. Random-effects meta-analysis showed a lower incidence of gallstone formation in patients taking UDCA. Subgroup analysis reported fewer cases of gallstone disease in the UDCA group in relation to different bariatric procedures, doses of administered UDCA, and time from bariatric surgery. Adverse events were similar in both groups. Fewer patients required cholecystectomy in UDCA group. No deaths were reported. The administration of UDCA after bariatric surgery seems to prevent gallstone formation.

  16. Disturbances to metal partitioning during toxicity testing of iron(II)-rich estuarine pore waters and whole sediments.

    Science.gov (United States)

    Simpson, Stuart L; Batley, Graeme E

    2003-02-01

    Metal partitioning is altered when suboxic estuarine sediments containing Fe(II)-rich pore waters are disturbed during collection, preparation, and toxicity testing. Experiments with model Fe(II)-rich pore waters demonstrated the rates at which adsorptive losses of Cd, Cu, Ni, Mn, Pb, and Zn occur upon exposure to air. Experiments with Zn-contaminated estuarine sediments demonstrated large and often unpredictable changes to metal partitioning during sediment storage, removal of organisms, and homogenization before testing. Small modifications to conditions, such as aeration of overlying waters, caused large changes to the metal partitioning. Disturbances caused by sediment collection required many weeks for reestablishment of equilibrium. Bioturbation by benthic organisms led to oxidation of pore-water Fe(II) and lower Zn fluxes because of the formation of Fe hydroxide precipitates that adsorb pore-water Zn. For five weeks after the addition of organisms to sediments, Zn fluxes increased slowly as the organisms established themselves in the sediments, indicating that the establishment of equilibrium was not rapid. The results are discussed in terms of the dynamic nature of suboxic, Fe(II)-rich estuarine sediments, how organisms perturb their environment, and the importance of understanding chemistry in toxicity testing with whole sediments or pore water. Recommendations are provided for the handling of sediments for toxicity testing.

  17. A method of evaluating facial pores using optical 2D images and analysis of age-dependent changes in facial pores in Koreans.

    Science.gov (United States)

    Jang, S I; Kim, E J; Lee, H K

    2018-05-01

    Enlarged facial pores and changes in pore area are of concern for cosmetic reasons. To evaluate pores, measuring tools based on 3D methodology are used. Yet, these methods are limited by their measuring ranges. In this study, we performed pore analysis by measuring the whole face using 2D optical images. We further sought to understand how the pores of Korean women change with age. One hundred sixteen Korean female subjects aged 20-60 years were recruited for this study. Facial images were taken using the VISIA-CR ® adjusted light source. Images were processed using Image-Pro Plus 9.2. Statistical significance was assumed when P pore area, as indicated by pixel count, gradually increased in patients through their 40s, but decreased through their 50s and 60s. Facial pores generally exhibited directionality through the patients' 30s, but this isotropic feature was more prominent in their 50s. Pore elongation increased stepwise. The first increase occurred during the transition from patients' 30s to their 40s and the second increase occurred during the transition from patients' 50s to their 60s. This indicated that the pores deformed from a circular shape to a long elliptic shape over time. A new evaluation method using 2D optical images facilitates the analysis of pore distribution and elongation throughout the entire cheek. This is an improvement over an analysis of pores over a narrow region of interest. © 2018 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  18. Formation of Molecular Networks: Tailored Quantum Boxes and Behavior of Adsorbed CO in Them

    Science.gov (United States)

    Wyrick, Jon; Sun, Dezheng; Kim, Dae-Ho; Cheng, Zhihai; Lu, Wenhao; Zhu, Yeming; Luo, Miaomiao; Kim, Yong Su; Rotenberg, Eli; Kim, Kwangmoo; Einstein, T. L.; Bartels, Ludwig

    2011-03-01

    We show that the behavior of CO adsorbed into the pores of large regular networks on Cu(111) is significantly affected by their nano-scale lateral confinement and that formation of the networks themselves is directed by the Shockley surface state. Saturation coverages of CO are found to exhibit persistent dislocation lines; at lower coverages their mobility increases. Individual CO within the pores titrate the surface state, providing crucial information for understanding formation of the network as a result of optimization of the number N of electrons bound within each pore. Determination of N is based on quinone-coverage-dependent UPS data and an analysis of states of particles in a pore-shaped box (verified by CO's titration); a wide range of possible pore shapes and sizes has been considered. Work at UCR supported by NSF CHE 07-49949; at UMD by NSF CHE 07-50334 & UMD NSF-MRSEC DMR 05-20471.

  19. Nuclear Pore-Like Structures in a Compartmentalized Bacterium.

    Directory of Open Access Journals (Sweden)

    Evgeny Sagulenko

    Full Text Available Planctomycetes are distinguished from other Bacteria by compartmentalization of cells via internal membranes, interpretation of which has been subject to recent debate regarding potential relations to Gram-negative cell structure. In our interpretation of the available data, the planctomycete Gemmata obscuriglobus contains a nuclear body compartment, and thus possesses a type of cell organization with parallels to the eukaryote nucleus. Here we show that pore-like structures occur in internal membranes of G.obscuriglobus and that they have elements structurally similar to eukaryote nuclear pores, including a basket, ring-spoke structure, and eight-fold rotational symmetry. Bioinformatic analysis of proteomic data reveals that some of the G. obscuriglobus proteins associated with pore-containing membranes possess structural domains found in eukaryote nuclear pore complexes. Moreover, immunogold labelling demonstrates localization of one such protein, containing a β-propeller domain, specifically to the G. obscuriglobus pore-like structures. Finding bacterial pores within internal cell membranes and with structural similarities to eukaryote nuclear pore complexes raises the dual possibilities of either hitherto undetected homology or stunning evolutionary convergence.

  20. YaxAB, a Yersinia enterocolitica Pore-Forming Toxin Regulated by RovA

    Science.gov (United States)

    Wagner, Nikki J.; Lin, Carolina P.; Borst, Luke B.

    2013-01-01

    The transcriptional regulator RovA positively regulates transcription of the Yersinia enterocolitica virulence gene inv. Invasin, encoded by inv, is important for establishment of Y. enterocolitica infection. However, a rovA mutant is more attenuated for virulence than an inv mutant, implying that RovA regulates additional virulence genes. When the Y. enterocolitica RovA regulon was defined by microarray analysis, YE1984 and YE1985 were among the genes identified as being upregulated by RovA. Since these genes are homologous to Xenorhabdus nematophila cytotoxin genes xaxA and xaxB, we named them yaxA and yaxB, respectively. In this work, we demonstrate the effects of YaxAB on the course of infection in the murine model. While a yaxAB mutant (ΔyaxAB) is capable of colonizing mice at the same level as the wild type, it slightly delays the course of infection and results in differing pathology in the spleen. Further, we found that yaxAB encode a probable cytotoxin capable of lysing mammalian cells, that both YaxA and YaxB are required for cytotoxic activity, and that the two proteins associate. YaxAB-mediated cell death occurs via osmotic lysis through the formation of distinct membrane pores. In silico tertiary structural analysis identified predicted structural homology between YaxA and proteins in pore-forming toxin complexes from Bacillus cereus (HBL-B) and Escherichia coli (HlyE). Thus, it appears that YaxAB function as virulence factors by inducing cell lysis through the formation of pores in the host cell membrane. This characterization of YaxAB supports the hypothesis that RovA regulates expression of multiple virulence factors in Y. enterocolitica. PMID:24002058

  1. Transmembrane helical interactions in the CFTR channel pore.

    Directory of Open Access Journals (Sweden)

    Jhuma Das

    2017-06-01

    Full Text Available Mutations in the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR gene affect CFTR protein biogenesis or its function as a chloride channel, resulting in dysregulation of epithelial fluid transport in the lung, pancreas and other organs in cystic fibrosis (CF. Development of pharmaceutical strategies to treat CF requires understanding of the mechanisms underlying channel function. However, incomplete 3D structural information on the unique ABC ion channel, CFTR, hinders elucidation of its functional mechanism and correction of cystic fibrosis causing mutants. Several CFTR homology models have been developed using bacterial ABC transporters as templates but these have low sequence similarity to CFTR and are not ion channels. Here, we refine an earlier model in an outward (OWF and develop an inward (IWF facing model employing an integrated experimental-molecular dynamics simulation (200 ns approach. Our IWF structure agrees well with a recently solved cryo-EM structure of a CFTR IWF state. We utilize cysteine cross-linking to verify positions and orientations of residues within trans-membrane helices (TMHs of the OWF conformation and to reconstruct a physiologically relevant pore structure. Comparison of pore profiles of the two conformations reveal a radius sufficient to permit passage of hydrated Cl- ions in the OWF but not the IWF model. To identify structural determinants that distinguish the two conformations and possible rearrangements of TMHs within them responsible for channel gating, we perform cross-linking by bifunctional reagents of multiple predicted pairs of cysteines in TMH 6 and 12 and 6 and 9. To determine whether the effects of cross-linking on gating observed are the result of switching of the channel from open to close state, we also treat the same residue pairs with monofunctional reagents in separate experiments. Both types of reagents prevent ion currents indicating that pore blockage is primarily responsible.

  2. Investigating Multiphase Flow Phenomena in Fine-Grained Reservoir Rocks: Insights from Using Ethane Permeability Measurements over a Range of Pore Pressures

    Directory of Open Access Journals (Sweden)

    Eric Aidan Letham

    2018-01-01

    Full Text Available The ability to quantify effective permeability at the various fluid saturations and stress states experienced during production from shale oil and shale gas reservoirs is required for efficient exploitation of the resources, but to date experimental challenges prevent measurement of the effective permeability of these materials over a range of fluid saturations. To work towards overcoming these challenges, we measured effective permeability of a suite of gas shales to gaseous ethane over a range of pore pressures up to the saturated vapour pressure. Liquid/semiliquid ethane saturation increases due to adsorption and capillary condensation with increasing pore pressure resulting in decreasing effective permeability to ethane gas. By how much effective permeability to ethane gas decreases with adsorption and capillary condensation depends on the pore size distribution of each sample and the stress state that effective permeability is measured at. Effective permeability decreases more at higher stress states because the pores are smaller at higher stress states. The largest effective permeability drops occur in samples with dominant pore sizes in the mesopore range. These pores are completely blocked due to capillary condensation at pore pressures near the saturated vapour pressure of ethane. Blockage of these pores cuts off the main fluid flow pathways in the rock, thereby drastically decreasing effective permeability to ethane gas.

  3. Synthesis and Characterization of Wooden Magnetic Activated Carbon Fibers with Hierarchical Pore Structures

    Directory of Open Access Journals (Sweden)

    Dongna Li

    2018-04-01

    Full Text Available Wooden magnetic activated carbon fibers (WMACFs with hierarchical pore structures were obtained by adding magnetic iron oxide (Fe3O4 nanoparticles into the liquefied wood. The structures and properties of WMACFs were analyzed by scanning electronmicroscopy (SEM, X-ray diffraction (XRD, Fourier transform infrared spectroscopy (FTIR, N2 adsorption, and vibrating sample magnetometer (VSM. The results showed that WMACFs had high Brunauer-Emmett-Teller (BET surface area (1578 m2/g and total pore volume (0.929 cm3/g, of which 45% was the contribution of small mesopores of 2–3 nm. It is believed that Fe3O4 nanoparticles play an important role in the formation of hierarchical pores. With the Fe3O4 content increasing, the yield rate of WMACFs decreased, and the Fe3O4 crystal plane diffraction peaks and characteristic adsorption peaks were obviously observed. At the same time, it was also found that WMACFs had favorable magnetic properties when the Fe3O4 content was above 1.5%. As a result, WMACFs could be a promising candidate for high efficiency, low cost, and convenient separation for the magnetic field.

  4. Efficacy of cimetidin in the prevention of ulcer formation in the stomach during immobilization stress

    Science.gov (United States)

    Dorofeyev, G. I.; Litovskiy, I. A.; Gavrovskaya, L. K.; Ivashkin, V. T.

    1982-01-01

    The effect of stress on the formation of ulcers in the mucous membrane of the stomach, the increase in cyclic adenosine monophosphate level in the gastric tissues, and parietal cell structure alteration. Use of cimetidin prevents these effects

  5. Monalysin, a novel ß-pore-forming toxin from the Drosophila pathogen Pseudomonas entomophila, contributes to host intestinal damage and lethality.

    Directory of Open Access Journals (Sweden)

    Onya Opota

    2011-09-01

    Full Text Available Pseudomonas entomophila is an entomopathogenic bacterium that infects and kills Drosophila. P. entomophila pathogenicity is linked to its ability to cause irreversible damages to the Drosophila gut, preventing epithelium renewal and repair. Here we report the identification of a novel pore-forming toxin (PFT, Monalysin, which contributes to the virulence of P. entomophila against Drosophila. Our data show that Monalysin requires N-terminal cleavage to become fully active, forms oligomers in vitro, and induces pore-formation in artificial lipid membranes. The prediction of the secondary structure of the membrane-spanning domain indicates that Monalysin is a PFT of the ß-type. The expression of Monalysin is regulated by both the GacS/GacA two-component system and the Pvf regulator, two signaling systems that control P. entomophila pathogenicity. In addition, AprA, a metallo-protease secreted by P. entomophila, can induce the rapid cleavage of pro-Monalysin into its active form. Reduced cell death is observed upon infection with a mutant deficient in Monalysin production showing that Monalysin plays a role in P. entomophila ability to induce intestinal cell damages, which is consistent with its activity as a PFT. Our study together with the well-established action of Bacillus thuringiensis Cry toxins suggests that production of PFTs is a common strategy of entomopathogens to disrupt insect gut homeostasis.

  6. Mechanical behavior of cellular borosilicate glass with pressurized Ar-filled closed pores

    International Nuclear Information System (INIS)

    Wang Bo; Matsumaru, Koji; Yang Jianfeng; Fu Zhengyi; Ishizaki, Kozo

    2012-01-01

    High strength borosilicate foams were fabricated by melting glass powder under high-pressure argon gas and subsequent heat treatment of the glass bulk at atmospheric pressure. In the first step, borosilicate glass powder was melted at 1100 °C for 1 h by capsule-free hot isostatic pressing (HIPing) under a high gas pressure of 10–70 MPa. Pressurized Ar-filled spherical pores were introduced into the glass, and argon atoms were dissolved in the glass network structure. The expansion of argon-filled pores and the release of the dissolved Ar gas resulted in the formation of pressurized Ar-filled closed pores by isothermal heat treatment at 800 °C for 10 min. A high porosity of up to 80% with a bimodal distribution of micro-size cells was obtained for the resultant cellular borosilicate glass. By increasing the total gas pressure from 10 to 70 MPa, the compressive strength and the Young’s modulus were increased considerably from 15 to 52 MPa and from 4.1 to 12.6 GPa, respectively, which can be substantially attributed to the high collapse stress from the high enclosed gas pressure. The cellular glass with a high porosity showed a large failure strain under uniaxial compression.

  7. Radiative magnetohydrodynamic simulations of solar pores

    NARCIS (Netherlands)

    Cameron, R.; Schuessler, M.; Vögler, A.; Zakharov, V.

    2007-01-01

    Context. Solar pores represent a class of magnetic structures intermediate between small-scale magnetic flux concentrations in intergranular lanes and fully developed sunspots with penumbrae. Aims. We study the structure, energetics, and internal dynamics of pore-like magnetic structures by means of

  8. Pore-water chemistry effects on the compressibility behaviour of Boom Clay

    International Nuclear Information System (INIS)

    Deng, Y.F.; Cui, Y.J.; Tang, A.M.; Nguyen, X.P.; Li, X.L.; Maarten, V.G.

    2010-01-01

    Document available in extended abstract form only. Boom clay is a thick deposit of over-consolidated marine clay, and belongs to the Oligocene series. Its hydraulic conductivity has been investigated since many years in Belgium within the site characterization program related to the performance assessment of potential geological disposal of high-level radioactive waste in this formation. Recently, the work of Wemaere et al. (2008) shows a significant variability of the hydraulic conductivity of the Boom clay. Indeed, they performed measurements on soil cores taken from four distant boreholes at various depths. The vertical hydraulic conductivity was found to vary from 3 x 10 -12 to 10 x 10 -12 m/s. It is suspected that this variability would be partly related to the water chemistry effects. Indeed, De Craen et al. (2006) shows that the pore-water chemical composition of soil cores taken from the Essen site is significantly different from that at the Mol site. If the pore water chemistry has strong effect on the hydraulic conductivity, its effect on the mechanical behaviour needs to be investigated too. The aim of this paper is to verify whether there are significant effects of pore-water chemistry on the soil compressibility. This study would be helpful to transpose the knowledge obtained from the Mol site to other sites of Boom clay formation where the geochemical components are different from the former site, as the hydro-mechanical characteristics of Boom clay at the Mol site has been widely investigated since the last decades. Two soil cores were taken from the Essen site at a depth of 227 m (Ess83) and 240 m (Ess96). Based on the geochemical analysis presented by De Craen et al. (2006), synthetic water having similar chemical composition of the in-situ pore-water was prepared. The identification geotechnical characteristics of these cores are shown in Table 2. It can be observed that the clay content (particle size < 2 μm) is relatively high (more than 50

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

    International Nuclear Information System (INIS)

    Gauden, Piotr A; Terzyk, Artur P; Furmaniak, Sylwester; Zieliński, Wojciech; Włoch, Jerzy; Kowalczyk, Piotr

    2014-01-01

    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)

  10. Lipid intermediates in membrane fusion: formation, structure, and decay of hemifusion diaphragm.

    Science.gov (United States)

    Kozlovsky, Yonathan; Chernomordik, Leonid V; Kozlov, Michael M

    2002-11-01

    Lipid bilayer fusion is thought to involve formation of a local hemifusion connection, referred to as a fusion stalk. The subsequent fusion stages leading to the opening of a fusion pore remain unknown. The earliest fusion pore could represent a bilayer connection between the membranes and could be formed directly from the stalk. Alternatively, fusion pore can form in a single bilayer, referred to as hemifusion diaphragm (HD), generated by stalk expansion. To analyze the plausibility of stalk expansion, we studied the pathway of hemifusion theoretically, using a recently developed elastic model. We show that the stalk has a tendency to expand into an HD for lipids with sufficiently negative spontaneous splay, (~)J(s)action of an external force pulling the diaphragm rim apart. We calculate the dependence of the HD radius on this force. To address the mechanism of fusion pore formation, we analyze the distribution of the lateral tension emerging in the HD due to the establishment of lateral equilibrium between the deformed and relaxed portions of lipid monolayers. We show that this tension concentrates along the HD rim and reaches high values sufficient to rupture the bilayer and form the fusion pore. Our analysis supports the hypothesis that transition from a hemifusion to a fusion pore involves radial expansion of the stalk.

  11. Measurements of pore-scale flow through apertures

    Energy Technology Data Exchange (ETDEWEB)

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

    2017-09-01

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

  12. A Functional DNase I Coating to Prevent Adhesion of Bacteria and the Formation of Biofilm

    NARCIS (Netherlands)

    Swartjes, Jan J. T. M.; Das, Theerthankar; Sharifi, Shahriar; Subbiahdoss, Guruprakash; Sharma, Prashant K.; Krom, Bastiaan P.; Busscher, Henk J.; van der Mei, Henny C.

    2013-01-01

    Biofilms are detrimental in many industrial and biomedical applications and prevention of biofilm formation has been a prime challenge for decades. Biofilms consist of communities of adhering bacteria, supported and protected by extracellular-polymeric-substances (EPS), the so-called house of

  13. Material science studies on the formation and growth of pores in the production and creep of single-crystal nickel-based superalloys; Werkstoffwissenschaftliche Untersuchungen zur Bildung und zum Wachstum von Poren bei der Herstellung und beim Kriechen einkristalliner Nickelbasis-Superlegierungen

    Energy Technology Data Exchange (ETDEWEB)

    Buck, Heinrich Joergen

    2015-02-20

    results, presented in this work, suggest that creep rupture is associated with the formation of microcracks at larger solidification and heat treatment pores, which can grow, interlink and initiate final creep rupture. Creep pores appear, due to their size, to be less important with respect to creep rupture. The alignment of pores along the dendrites and their relative position to the loading direction are the key factors, that can limit creep life. Finally, the influence of the crystallographic orientation on the evolution of porosity was investigated. It has been shown, that there are no fundamental differences of the size and shape factor distributions, when [001] and [110] oriented specimens are compared, but there are differences in the appearance of crystallographic facets and an orientation dependency of pore growth is suggested.

  14. The effect of swelling agent on the pore characteristics of mesoporous hydroxyapatite nanoparticles

    Directory of Open Access Journals (Sweden)

    L. Bakhtiari

    2015-06-01

    Full Text Available The effect of swelling agent on the physicochemical properties of mesoporous hydroxyapatite particles synthesized by self-assembly process has been investigated. Cetyl trimethylammonium bromide (CTAB and 1-dodecanethiol were used as soft template and swelling agent respectively. The results of the field emission scanning electron microscopy (FESEM, X-ray diffraction (XRD, simultaneous thermal analysis (STA, Brunauer-Emmett-Teller (BET surface area, small-angle X-ray diffraction and Fourier transform infrared spectroscopy (FTIR assessments revealed that in the case of low concentration, 1-dodecanethiol performed as swelling agent and caused an increase in the pore size. However, at higher concentrations it led to the formation of microemulsion and foamy structures. The optimum swelling agent: surfactant mass ratio in synthesis of mesoporous hydroxyapatite particles with high pore volume was determined to be around 2.1 in this study.

  15. The effect of swelling agent on the pore characteristics of mesoporous hydroxyapatite nanoparticles

    Institute of Scientific and Technical Information of China (English)

    L. Bakhtiari; J. Javadpour; H.R. Rezaie; M. Erfan; M.A. Shokrgozar

    2015-01-01

    The effect of swelling agent on the physicochemical properties of mesoporous hydroxyapatite particles synthesized by self-assembly process has been investigated. Cetyl trimethylammonium bromide (CTAB) and 1-dodecanethiol were used as soft template and swelling agent respectively. The results of the field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), simultaneous thermal analysis (STA), Brunauer-Emmett-Teller (BET) surface area, small-angle X-ray diffraction and Fourier transform infrared spectroscopy (FTIR) assessments revealed that in the case of low concentration, 1-dodecanethiol performed as swelling agent and caused an increase in the pore size. However, at higher concentrations it led to the formation of microemulsion and foamy structures. The optimum swelling agent:surfactant mass ratio in synthesis of mesoporous hydroxyapatite particles with high pore volume was determined to be around 2.1 in this study.

  16. Capillary pressure-saturation relationships for porous granular materials: Pore morphology method vs. pore unit assembly method

    Science.gov (United States)

    Sweijen, Thomas; Aslannejad, Hamed; Hassanizadeh, S. Majid

    2017-09-01

    In studies of two-phase flow in complex porous media it is often desirable to have an estimation of the capillary pressure-saturation curve prior to measurements. Therefore, we compare in this research the capability of three pore-scale approaches in reproducing experimentally measured capillary pressure-saturation curves. To do so, we have generated 12 packings of spheres that are representative of four different glass-bead packings and eight different sand packings, for which we have found experimental data on the capillary pressure-saturation curve in the literature. In generating the packings, we matched the particle size distributions and porosity values of the granular materials. We have used three different pore-scale approaches for generating the capillary pressure-saturation curves of each packing: i) the Pore Unit Assembly (PUA) method in combination with the Mayer and Stowe-Princen (MS-P) approximation for estimating the entry pressures of pore throats, ii) the PUA method in combination with the hemisphere approximation, and iii) the Pore Morphology Method (PMM) in combination with the hemisphere approximation. The three approaches were also used to produce capillary pressure-saturation curves for the coating layer of paper, used in inkjet printing. Curves for such layers are extremely difficult to determine experimentally, due to their very small thickness and the presence of extremely small pores (less than one micrometer in size). Results indicate that the PMM and PUA-hemisphere method give similar capillary pressure-saturation curves, because both methods rely on a hemisphere to represent the air-water interface. The ability of the hemisphere approximation and the MS-P approximation to reproduce correct capillary pressure seems to depend on the type of particle size distribution, with the hemisphere approximation working well for narrowly distributed granular materials.

  17. Pore-Width-Dependent Preferential Interaction of sp2 Carbon Atoms in Cyclohexene with Graphitic Slit Pores by GCMC Simulation

    Directory of Open Access Journals (Sweden)

    Natsuko Kojima

    2011-01-01

    Full Text Available The adsorption of cyclohexene with two sp2 and four sp3 carbon atoms in graphitic slit pores was studied by performing grand canonical Monte Carlo simulation. The molecular arrangement of the cyclohexene on the graphitic carbon wall depends on the pore width. The distribution peak of the sp2 carbon is closer to the pore wall than that of the sp3 carbon except for the pore width of 0.7 nm, even though the Lennard-Jones size of the sp2 carbon is larger than that of the sp3 carbon. Thus, the difference in the interactions of the sp2 and sp3 carbon atoms of cyclohexene with the carbon pore walls is clearly observed in this study. The preferential interaction of sp2 carbon gives rise to a slight tilting of the cyclohexene molecule against the graphitic wall. This is suggestive of a π-π interaction between the sp2 carbon in the cyclohexene molecule and graphitic carbon.

  18. Activation of P2X7-mediated apoptosis Inhibits DMBA/TPA-induced formation of skin papillomas and cancer in mice

    Directory of Open Access Journals (Sweden)

    Fu Wen

    2009-04-01

    Full Text Available Abstract Background The study tested the hypothesis that apoptosis can prevent and control growth of neoplastic cells. Previous studies in-vitro have shown that the pro-apoptotic P2X7 receptor regulates growth of epithelial cells. The specific objective of the present study was to understand to what degree the P2X7 system controls development and growth of skin cancer in vivo, and what cellular and molecular mechanisms are involved in the P2X7 action. Methods Skin neoplasias in mice (papillomas, followed by squamous spindle-cell carcinomas were induced by local application of DMBA/TPA. Experiments in-vitro utilized cultured epidermal keratinocytes generated from wild-type or from P2X7-null mice. Assays involved protein immunostaining and Western blots; mRNA real-time qPCR; and apoptosis (evaluated in situ by TUNEL and quantified in cultured keratinocytes as solubilized DNA or by ELISA. Changes in cytosolic calcium or in ethidium bromide influx (P2X7 pore formation were determined by confocal laser microscopy. Results (a Co-application on the skin of the P2X7 specific agonist BzATP inhibited formation of DMBA/TPA-induced skin papillomas and carcinomas. At the completion of study (week 28 the proportion of living animals with cancers in the DMBA/TPA group was 100% compared to 43% in the DMBA/TPA+BzATP group. (b In the normal skin BzATP affected mainly P2X7-receptor – expressing proliferating keratinocytes, where it augmented apoptosis without evoking inflammatory changes. (c In BzATP-treated mice the degree of apoptosis was lesser in cancer than in normal or papilloma keratinocytes. (d Levels of P2X7 receptor, protein and mRNA were 4–5 fold lower in cancer tissues than in normal mouse tissues. (e In cultured mouse keratinocytes BzATP induced apoptosis, formation of pores in the plasma membrane, and facilitated prolonged calcium influx. (f The BzATP-induced apoptosis, pore-formation and augmented calcium influx had similar dose-dependence for

  19. X-ray pore optic developments

    Science.gov (United States)

    Wallace, Kotska; Bavdaz, Marcos; Collon, Maximilien; Beijersbergen, Marco; Kraft, Stefan; Fairbend, Ray; Séguy, Julien; Blanquer, Pascal; Graue, Roland; Kampf, Dirk

    2017-11-01

    In support of future x-ray telescopes ESA is developing new optics for the x-ray regime. To date, mass and volume have made x-ray imaging technology prohibitive to planetary remote sensing imaging missions. And although highly successful, the mirror technology used on ESA's XMM-Newton is not sufficient for future, large, x-ray observatories, since physical limits on the mirror packing density mean that aperture size becomes prohibitive. To reduce telescope mass and volume the packing density of mirror shells must be reduced, whilst maintaining alignment and rigidity. Structures can also benefit from a modular optic arrangement. Pore optics are shown to meet these requirements. This paper will discuss two pore optic technologies under development, with examples of results from measurement campaigns on samples. One activity has centred on the use of coated, silicon wafers, patterned with ribs, that are integrated onto a mandrel whose form has been polished to the required shape. The wafers follow the shape precisely, forming pore sizes in the sub-mm region. Individual stacks of mirrors can be manufactured without risk to, or dependency on, each other and aligned in a structure from which they can also be removed without hazard. A breadboard is currently being built to demonstrate this technology. A second activity centres on glass pore optics. However an adaptation of micro channel plate technology to form square pores has resulted in a monolithic material that can be slumped into an optic form. Alignment and coating of two such plates produces an x-ray focusing optic. A breadboard 20cm aperture optic is currently being built.

  20. Distribution of B, Cl and Their Isotopes in Pore Waters Separated from Gas Hydrate Potential Areas, Offshore Southwestern Taiwan

    Directory of Open Access Journals (Sweden)

    Hung-Chun Chao Chen-Feng You

    2006-01-01

    Full Text Available Boron (B and chlorine (Cl are widely distributed on the Earth’s surface and show distinctive geochemical behaviors. Cl behaves rather conservatively in oceanic environments while B is an excess-volatile and its distribution is sensitive to sediment absorption and organic matter degradation. The distribution of B, Cl and their isotopes in pore waters provide useful information for distinguishing between shallow circulation and deep origin fluid sources. Thirty-six sediment cores 0 - 5 m in length were sampled from a foreland accretionary prism offshore Southwestern Taiwan where strong bottom simulating reflectors (BSRs and an abundance of mud diapirs were discovered. More than 350 pore water samples were separated and analyzed for B, Cl and other major ions. Four long cores were selected for B and Cl isotopic analysis. We found that the Cl in all cores varied less than 10%, suggesting no major hydrate dissolution or formation involvement at shallow depths in the study area. However, the B concentration changed greatly, ranging between 360 and 650 μM, indicating a possible sedimentary contribution during the early diagenesis stage. The B isotopic compositions were relatively depleted (~25 to 37‰ in these pore waters, implying the addition of sedimentary exchangeable B with low δ11B. The Cl isotopes showed rather large variations, more than 8‰, possibly related to the addition of deep situated fluids. In summary, the chemical and isotopic characteristics of pore waters separated from piston cores off Southwestern Taiwan suggest strong influence from organic matter degradation during diagenesis at shallow depths and the possible addition of deep fluids advecting through mud diapir channels at greater depths, causing a minor degree of hydrate dissolution / formation to occur at shallow depths. Further systematic investigation of pore waters δ18O and δD are needed in a future study.

  1. The equivalent pore aspect ratio as a tool for pore type prediction in carbonate reservoirs

    OpenAIRE

    FOURNIER , François; Pellerin , Matthieu; Villeneuve , Quentin; Teillet , Thomas; Hong , Fei; Poli , Emmanuelle; Borgomano , Jean; Léonide , Philippe; Hairabian , Alex

    2018-01-01

    International audience; The equivalent pore aspect ratios (EPAR) provide a tool to detect pore types by combining P-and S-wave velocities, porosity, bulk density and mineralogical composition of carbonate rocks. The integration of laboratory measurements, well log data and petrographic analysis of 468 carbonate samples from various depositional and diagenetic settings (Lower Cretaceous pre-salt non-marine carbonates from offshore Brazil, Lower Cretaceous shallow-water platform carbonates from...

  2. An instrument to measure differential pore pressures in deep ocean sediments: Pop-Up-Pore-Pressure-Instrument (PUPPI)

    International Nuclear Information System (INIS)

    Schultheiss, P.J.; McPhail, S.D.; Packwood, A.R.; Hart, B.

    1985-01-01

    A Pop-Up-Pore-Pressure-Instrument (PUPPI) has been developed to measure differential pore pressures in sediments. The differential pressure is the pressure above or below normal hydrostatic pressure at the depth of the measurement. It is designed to operate in water depths up to 6000 metres for periods of weeks or months, if required, and measures differential pore pressures at depths of up to 3 metres into the sediments with a resolution of 0.05 kPa. It is a free-fall device with a lance which penetrates the sediments. This lance and the ballast weight is disposed when the PUPPI is acoustically released from the sea floor. When combined with permeability and porosity values of deep-sea sediments the pore pressure measurements made using the PUPPI suggest advection velocities as low as 8.8 mm/yr. The mechanical, electrical and acoustic systems are described together with data obtained from both shallow and deep water trials. (author)

  3. 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.

  4. Research progress in formation mechanism of anodizing aluminum oxide

    Science.gov (United States)

    Lv, Yudong

    2017-12-01

    The self-ordering porous anodizing aluminum oxide (AAO) has attracted much attention because of its potential value of application. Valve metals (Al, Ti, Zr etc.) anodic studies have been conducted for more than 80 years, but the mechanism of the formation of hexagonal prismatic cell structure has so far been different. In this paper, the research results of AAO film formation mechanism are reviewed, and the growth models of several AAO films are summarized, including the field-assisted dissolution (FAD), the viscous flow model, the critical current density effect model, the bulk expansion stress model and the steady-state pore growth model and so on. It analyzed the principle of each model and its rationality. This paper will be of great help to reveal the nature of pore formation and self-ordering, and with the hope that through the study of AAO film formation mechanism, the specific effects of various oxidation parameters on AAO film morphology can be obtained.

  5. Nanometer-Scale Pore Characteristics of Lacustrine Shale, Songliao Basin, NE China.

    Directory of Open Access Journals (Sweden)

    Min Wang

    Full Text Available In shale, liquid hydrocarbons are accumulated mainly in nanometer-scale pores or fractures, so the pore types and PSDs (pore size distributions play a major role in the shale oil occurrence (free or absorbed state, amount of oil, and flow features. The pore types and PSDs of marine shale have been well studied; however, research on lacustrine shale is rare, especially for shale in the oil generation window, although lacustrine shale is deposited widely around the world. To investigate the relationship between nanometer-scale pores and oil occurrence in the lacustrine shale, 10 lacustrine shale core samples from Songliao Basin, NE China were analyzed. Analyses of these samples included geochemical measurements, SEM (scanning electron microscope observations, low pressure CO2 and N2 adsorption, and high-pressure mercury injection experiments. Analysis results indicate that: (1 Pore types in the lacustrine shale include inter-matrix pores, intergranular pores, organic matter pores, and dissolution pores, and these pores are dominated by mesopores and micropores; (2 There is no apparent correlation between pore volumes and clay content, however, a weak negative correlation is present between total pore volume and carbonate content; (3 Pores in lacustrine shale are well developed when the organic matter maturity (Ro is >1.0% and the pore volume is positively correlated with the TOC (total organic carbon content. The statistical results suggest that oil in lacustrine shale mainly occurs in pores with diameters larger than 40 nm. However, more research is needed to determine whether this minimum pore diameter for oil occurrence in lacustrine shale is widely applicable.

  6. Thermal conductivity of high-porosity cellular-pore biocarbon prepared from sapele wood

    Science.gov (United States)

    Parfen'eva, L. S.; Orlova, T. S.; Kartenko, N. F.; Sharenkova, N. V.; Smirnov, B. I.; Smirnov, I. A.; Misiorek, H.; Jezowski, A.; Mucha, J.; de Arellano-Lopez, A. R.; Martinez-Fernandez, J.

    2009-10-01

    This paper reports on measurements (in the temperature range T = 5-300 K) of the thermal conductivity κ( T) and electrical conductivity σ( T) of the high-porosity (˜63 vol %) amorphous biocarbon preform with cellular pores, prepared by pyrolysis of sapele wood at the carbonization temperature 1000°C. The preform at 300 K was characterized using X-ray diffraction analysis. Nanocrystallites 11-30 Å in ize were shown to participate in the formation of the carbon network of sapele wood preforms. The dependences κ( T) and σ( T) were measured for the samples cut across and along empty cellular pore channels, which are aligned with the tree growth direction. Thermal conductivity measurements performed on the biocarbon sapele wood preform revealed a temperature dependence of the phonon thermal conductivity that is not typical of amorphous (and X-ray amorphous) materials. The electrical conductivity σ was found to increase with the temperature increasing from 5 to 300 K. The results obtained were analyzed.

  7. Pore size determination from charged particle energy loss measurement

    International Nuclear Information System (INIS)

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

    1977-01-01

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

  8. Accurate relations between pore size and the pressure of capillary condensation and the evaporation of nitrogen in cylindrical pores.

    Science.gov (United States)

    Morishige, Kunimitsu; Tateishi, Masayoshi

    2006-04-25

    To examine the theoretical and semiempirical relations between pore size and the pressure of capillary condensation or evaporation proposed so far, we constructed an accurate relation between the pore radius and the capillary condensation and evaporation pressure of nitrogen at 77 K for the cylindrical pores of the ordered mesoporous MCM-41 and SBA-15 silicas. Here, the pore size was determined from a comparison between the experimental and calculated X-ray diffraction patterns due to X-ray structural modeling recently developed. Among the many theoretical relations that differ from each other in the degree of theoretical improvements, a macroscopic thermodynamic approach based on Broekhoff-de Boer equations was found to be in fair agreement with the experimental relation obtained in the present study.

  9. Pore-water indicators of rainwater-dominated versus groundwater-dominated peat bog profiles (Jura Mountains, Switzerland)

    International Nuclear Information System (INIS)

    Shotyk, W.; Steinmann, P.

    1994-01-01

    The dominant inorganic anions and cations, and dissolved organic carbon have been measured in the pore waters expressed from peat cores taken from two Sphagnum bogs in the Jura Mountains of Switzerland: Etang de la Gruyere (EGr) consists of > 6 m of peat representing more than 12,000 yr of peat formation while at La Tourbiere de Genevez (TGe) approximately 1.5 m of peat have accumulated over the past 5,000 yr. The pore-water analyses of the core taken at EGr show that the first 100 cm of the core are influenced only by atmospheric inputs. Relative to the average composition of rainwater in this area, Na + is enriched throughout the pore-water profiles, K 2+ is neither enriched nor depleted, Mg 2+ is significantly depleted in the deeper pore waters and Ca 2+ strongly depleted through the profile. The dominant process affecting the cations in these waters is ion exchange, with the peats behaving like a simple cation exchanger with ion preference decreasing in the order Ca 2+ >Mg 2+ >H + >K + much-greater than Na + . In contrast, at TGe the pH increases from pH approximately 4 at the surface to pH 5 at 80 cm. The Cl - and K + concentrations are up to 10 times higher than rainwater values because of mixing of the bog pore water with nearby groundwaters. The Mg 2+ and Ca 2+ concentrations increase with depth to concentrations up to 10 times higher than rainwater values, mainly because of the increasing importance of mineral dissolution within the profile

  10. Understanding chemical-potential-related transient pore-pressure response to improve real-time borehole (in)stability predictions

    Energy Technology Data Exchange (ETDEWEB)

    Tare, U.A.; Mody, F.K.; Mese, A.I. [Halliburton Energy Services, Cairo (Egypt)

    2000-11-01

    Experimental studies were conducted to explain the concept of a real-time wellbore (in)stability logging methodology. The role of the chemical potential of drilling fluids on transient pore pressure and time-dependent rock property alterations of shale formations was examined by providing details about a pore pressure transmission (PPT) test. The PPT experiments exposed formation (shale) cores under simulated downhole conditions to various salt solutions and drilling fluids. The main objective was to translate the results of the PPT tests to actual drilling conditions. A 20 per cent w/w calcium chloride solution was exposed to a Pierre II shale under high pressure in the PPT apparatus. The PPT test was used to estimate the impact of a drilling fluid on shale pore pressure. The efficiency of the salt solution/shale system was also estimated. Estimates of the dynamic rock properties were made based on the obtained acoustic data. It was determined that in order to accurately model time-dependent wellbore (in)stability in the field, it is important to calibrate representative shale core response to drilling fluids under realistic in-situ conditions. The 20 per cent w/w calcium chloride solution showed very low membrane efficiency of 4.45 per cent. It was concluded that changes in the shale dynamic rock properties as a function of test fluid exposure can be obtained from the simultaneous acquisition of sonic compression and shear wave velocity data. 12 refs., 5 figs.

  11. 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.

  12. On the corrosion behaviour of phosphoric irons in simulated concrete pore solution

    International Nuclear Information System (INIS)

    Sahoo, Gadadhar; Balasubramaniam, R.

    2008-01-01

    The corrosion behaviour of three phosphoric irons P 1 (Fe-0.11P-0.028C), P 2 (Fe-0.32P-0.026C) and P 3 (Fe-0.49P-0.022C) has been studied in simulated concrete pore solution (saturated Ca(OH) 2 solution) containing different chloride concentration. This has been compared with that of two commercial concrete reinforcement steels, a low carbon steel TN (Fe-0.148C-0.542Mn-0.128Si) and a microalloyed corrosion resistant steel CS (Fe-0.151C-0.088P-0.197Si-0.149Cr-0.417Cu). The beneficial aspect of phosphoric irons was revealed from potentiodynamic polarization experiments. The pitting potentials and pitting nucleation resistances for phosphoric irons and CS were higher than that for TN. Electrochemical impedance spectroscopy (EIS) studies revealed thickening and growth of passive film as a function of time in case of phosphoric irons and CS in saturated Ca(OH) 2 pore solutions without chloride and in the same solution with 0.05% Cl - and 0.1% Cl - . In case of TN, breakdown of passive film resulted in active corrosion in simulated pore solution containing 0.1% Cl - . Linear polarization resistance measurements complemented EIS results. Visual observations indicated that phosphoric iron P 3 was immune to corrosion even after 125 days of immersion in saturated Ca(OH) 2 solution containing 5% NaCl. The good corrosion resistance of phosphoric irons in simulated concrete pore solution containing chloride ions has been related to the formation of phosphate, based on ultraviolet spectrophotometric analysis and Pourbaix diagram of phosphorus-water system

  13. Effect of a Traveling Magnetic Field on Micropore Formation in Al-Cu Alloys

    Directory of Open Access Journals (Sweden)

    Yanjin Xu

    2018-06-01

    Full Text Available The effect of traveling magnetic fields (TMFs on the grain and micro-pore formation in an Al alloy was studied by scanning electron microscope and X-ray microtomography in this work. The results show that with the increasing magnetic flux density, the three-dimensional morphology of the micro-pores transformed from dendrite to a relatively equiaxed structure. Quantified results show that both the micro-pore volume fraction and the average grain size of the primary phase decreased as the TMF density increased. The analyses show that the forced convection induced by TMF can break the dendrites, refine the grain size, and promote the liquid feeding, leading to the decrease in the volume fraction of the porosity and improved mechanical property. The TMF performed at different stages during solidification reveal that the maximum effect of TMF on reducing the micro-pore formation was found when TMF was applied in the stage of nucleation and the early stage of grain growth during solidification.

  14. Hydrology and Hydraulic Properties of a Bedded Evaporite Formation

    International Nuclear Information System (INIS)

    BEAUHEIM, RICHARD L.; ROBERTS, RANDALL M.

    2000-01-01

    The Permian Salado Formation in the Delaware Basin of New Mexico is an extensively studied evaporite deposit because it is the host formation for the Waste Isolation Pilot Plant, a repository for transuranic wastes. Geologic and hydrologic studies of the Salado conducted since the mid-1970's have led to the development of a conceptual model of the hydrogeology of the formation that involves far-field permeability in anhydrite layers and at least some impure halite layers. Pure halite layers and some impure halite layers may not possess an interconnected pore network adequate to provide permeability. Pore pressures are probably very close to lithostatic pressure. In the near field around an excavation, dilation, creep, and shear have created and/or enhanced permeability and decreased pore pressure. Whether flow occurs in the far field under natural gradients or only after some threshold gradient is reached is unknown. If far-field flow does occur, mean pore velocities are probably on the order of a meter per hundreds of thousands to tens of millions of years. Flow dimensions inferred from most hydraulic-test responses are subradial, which is believed to reflect channeling of flow through fracture networks, or portions of fractures, that occupy a diminishing proportion of the radially available space, or through percolation networks that are not ''saturated'' (fully interconnected). This is probably related to the directional nature of the permeability created or enhanced by excavation effects. Inferred values of permeability cannot be separated from their associated flow dimensions. Therefore, numerical models of flow and transport should include heterogeneity that is structured to provide the same flow dimensions as are observed in hydraulic tests. Modeling of the Salado Formation around the WIPP repository should also include coupling between hydraulic properties and the evolving stress field because hydraulic properties change as the stress field changes

  15. Cationic osteogenic peptide P15-CSP coatings promote 3-D osteogenesis in poly(epsilon-caprolactone) scaffolds of distinct pore size.

    Science.gov (United States)

    Li, Xian; Ghavidel Mehr, Nima; Guzmán-Morales, Jessica; Favis, Basil D; De Crescenzo, Gregory; Yakandawala, Nandadeva; Hoemann, Caroline D

    2017-08-01

    P15-CSP is a biomimetic cationic fusion peptide that stimulates osteogenesis and inhibits bacterial biofilm formation when coated on 2-D surfaces. This study tested the hypothesis that P15-CSP coatings enhance 3-D osteogenesis in a porous but otherwise hydrophobic poly-(ɛ-caprolactone) (PCL) scaffold. Scaffolds of 84 µm and 141 µm average pore size were coated or not with Layer-by-Layer polyelectrolytes followed by P15-CSP, seeded with adult primary human mesenchymal stem cells (MSCs), and cultured 10 days in proliferation medium, then 21 days in osteogenic medium. Atomic analyses showed that P15-CSP was successfully captured by LbL. After 2 days of culture, MSCs adhered and spread more on P15-CSP coated pores than PCL-only. At day 10, all constructs contained nonmineralized tissue. At day 31, all constructs became enveloped in a "skin" of tissue that, like 2-D cultures, underwent sporadic mineralization in areas of high cell density that extended into some 141 µm edge pores. By quantitative histomorphometry, 2.5-fold more tissue and biomineral accumulated in edge pores versus inner pores. P15-CSP specifically promoted tissue-scaffold integration, fourfold higher overall biomineralization, and more mineral deposits in the outer 84 µm and inner 141 µm pores than PCL-only (p pore surfaces with 3-D topography. Biomineralization deeper than 150 µm from the scaffold edge was optimally attained with the larger 141 µm peptide-coated pores. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 2171-2181, 2017. © 2017 Wiley Periodicals, Inc.

  16. The Role of Ion Selectivity of the Fusion Pore on Transmission and the Exocytosis of Neurotransmitters and Hormones

    Science.gov (United States)

    Delacruz, Joannalyn Bongar

    Healthy nervous system function depends on proper transmission. Synaptic transmission occurs by the release of transmitters from vesicles that fuse to the plasma membrane of a pre-synaptic cell. Regulated release of neurotransmitters, neuropeptides, and hormones occurs by exocytosis, initiated by the formation of the fusion pore. The initial fusion pore has molecular dimensions with a diameter of 1-2 nm and a rapid lifetime on the millisecond time scale. It connects the vesicular lumen and extracellular space, serving as an important step for regulating the release of charged transmitters. Comprehending the molecular structure and biophysical properties of the fusion pore is essential for a mechanistic understanding of vesicle-plasma membrane fusion and transmitter release. Release of charged transmitter molecules such as glutamate, acetylcholine, dopamine, or noradrenaline through a narrow fusion pore requires compensation of change in charge. Transmitter release through the fusion pore is therefore an electrodiffusion process. If the fusion pore is selective for specific ions, then its selectivity will affect the rate of transmitter release via the voltage gradient that develops across the fusion pore. The elucidation of these mechanisms can lead to a better understanding of nervous system cell biology, neural and endocrine signaling, learning, memory, motor control, sensory function and integration, and in particular synaptic transmission. This investigation can advance our understanding of neurological disorders in which noradrenergic and dopaminergic exocytosis is disturbed, leading to neurological consequences of developmental disorders, epilepsy, Parkinson's disease, and other neurodegenerative diseases. Ultimately, understanding the role of selectivity in the fusion pore and its effects on exocytosis can contribute to the development of more effective therapies. This study investigates the selectivity of the fusion pore by observing the effects of ion

  17. Prevention of organic iodide formation in BWR`s

    Energy Technology Data Exchange (ETDEWEB)

    Karjunen, T [Finnish Centre for Radiation and Nuclear Safety, Helsinki (Finland); Laitinen, T; Piippo, J; Sirkiae, P [VTT Manufacturing Technology (Finland)

    1996-12-01

    During an accident, many different forms of iodine may emerge. Organic iodides, such as methyl iodide and ethyl iodide, are relatively volatile, and thus their appearance leads to increased concentration of gaseous iodine. Since organic iodides are also relatively immune to most accident mitigation measures, such as sprays and filters, they can affect the accident source term significantly even when only a small portion of iodine is in organic form. Formation of organic iodides may not be limited by the amount of organic substances available. Excessive amounts of methane can be produced, for example, during oxidation of boron carbide, which is used in BWR`s as a neutron absorber material. Another important source is cable insulation. In a BWR, a large quantity of cables is placed below the pressure vessel. Thus a large quantity of pyrolyse gases will be produced, should the vessel fail. Organic iodides can be formed as a result of many different reactions, but at least in certain conditions the main reaction takes place between an organic radical produced by radiolysis and elemental iodine. A necessary requirement for prevention of organic iodide production is therefore that the pH in the containment water pools is kept high enough to eliminate formation of elemental iodine. In a typical BWR the suppression pool water is usually unbuffered. As a result, the pH may be dominated by chemicals introduced during an accident. If no system for adding basic chemicals is operable, the main factor affecting pool water pH may be hydrochloric acid released during cable degradation. Should this occur, the conditions could be very favorable for production of elemental iodine and, consequently, formation of organic iodides. Although high pH is necessary for iodine retention, it could have also adverse effects. High pH may, for example, accelerate corrosion of containment materials and alter the characteristics of the solid corrosion products. (author) 6 figs., 1 tab., 13 refs.

  18. Methylene blue 1% solution on the prevention of intraperitoneal adhesion formation in a dog model

    Directory of Open Access Journals (Sweden)

    Marco Augusto Machado Silva

    Full Text Available Intraperitoneal adhesions usually are formed after abdominal surgeries and may cause technical difficulties during surgical intervention, chronic abdominal pain and severe obstructions of the gastrointestinal tract. The current study aimed to evaluate the efficacy of methylene blue (MB 1% solution on the prevention of intraperitoneal postsurgical adhesion formation in a canine surgical trauma model. Twenty bitches were submitted to falciform ligament resection, omentectomy, ovariohysterectomy and scarification of a colonic segment. Prior to abdominal closure, 10 bitches received 1mg kg-1 MB intraperitoneally (MB group and 10 bitches received no treatment (control group, CT. On the 15th postoperative day the bitches were submitted to laparoscopy to assess adhesions. The mean adhesion scores were 13.9 (±5.6 for MB group and 20.5 (±6.4 for the CT group (P=0,043. In conclusion, the 1% MB solution was efficient on the prevention of intraperitoneal postoperative adhesion formation in bitches, especially those involving the colonic serosa.

  19. Gas transport and subsoil pore characteristics

    DEFF Research Database (Denmark)

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

    2013-01-01

    Arrangements of elementary soil particles during soil deposition and subsequent biological and physical processes in long-term pedogenesis are expected to lead to anisotropy of the non-tilled subsoil pore system. Soil compaction by agricultural machinery is known to affect soil pore characteristics...... were sampled in vertical and horizontal directions from 0.3, 0.5, 0.7 and 0.9 m depth (the two lower depths only in Sweden). In the laboratory, water retention, air permeability (ka) and gas diffusivity (Ds/D0) were determined. For the sandy clay loam, morphological characteristics of pores (effective......). In the sandy clay loam soil, dB and nB displayed significant anisotropy (FAcharacteristics because of its origin...

  20. MRI of the transplanted endothelial progenitor cells for prevent atherosclerotic plaque formation

    International Nuclear Information System (INIS)

    Ma Zhanlong; Teng Gaojun; Mai Xiaoli; Chen Jun; Sun Junhui; Zhang Hongying; Yu Hui; Li Guozhao

    2007-01-01

    Objective: To evaluate the 1.5 T magnetic resonance imaging system to depict and track in vivo of magnetically labeled endothelial progenitor cells (EPCs), and to study the possibility for preventing the atherosclerotic plaque formation in New Zealand rabbit model of carotid arterial injury after transplantation. Methods: New Zealand rabbit EPCs were isolated, confirmed, expanded and then incubated with home synthesized Fe 2 O 3 -PLL, Prussian blue stain was performed for showing intracellular irons. The model of carotid arterial injury was performed by 2.5F balloons, the group A of 8 rabbits received magnetically labeled EPCs, group B of 3 rabbits received fluorescent-labeled EPCs and the group C of 5 rabbits were given same volume saline injection after endothelial injury of the carotid artery. MR imaging and histology were performed and compared 4 days later for randomly chosen three rabbit, each from one of the three group; all the other rabbits were fed with high lipid diet and examed using MR imaging and histology after 15 weeks. Results: Epcs labeling efficiency was more than 95% by Prussian blue stain, 4 days after transplantation of EPCs, only in group A, the injured endothelium of carotid artery had signal intensity loss in T 2 * WI, which were correlated well with the area where the most Prussian blue staining positive cells were found in histopathology analyses. The rabbits of group A and B which received EPCs transplantation exhibited fewer plaques formation than those of the group C (P 2 O 3 -PLL. The 1.5 T magnetic resonance imaging system could depict and monitor the magnetically labeled endothelial progenitor cells homing to the injured endothelium of the artery, and EPCs contribute to preventing atherosclerotic plaque formation in New Zealand rabbit model of atherosclerosis. (authors)

  1. Using pore-scale imaging and modeling to provide new insights in multi-phase flow, transport and reaction phenomena in porous media (Invited)

    Science.gov (United States)

    Bijeljic, B.; Andrew, M. G.; Menke, H. P.; Blunt, M. J.

    2013-12-01

    to formation of more larger ganglia; on the other hand, pore structures characterised by smaller, poorly connected pores, lead to the formation of more smaller blobs. Implications for scCO2 storage security are discussed. Finally, probably the most exciting capability of X ray imaging technique lies in its ability to image pore-scale displacements in real time. The first in-situ multiphase flow dynamic experiments during injection of supercritical CO2 in natural rock with the scanning interval of 30 seconds will be presented. Using reservoir-condition micro-flow test rig, pore-scale displacements including individual pore filling events in drainage (water/scCO2) in a carbonate rock were imaged at the Diamond Light Source synchrotron. Furthermore, the in-situ heterogeneous reaction between brine-equilibrated scCO2 and Ketton limestone at reservoir conditions has been imaged at the hours scale (with the same time resolution), where slow reaction regime was observed. The changes in porosity, permeability and, most importantly, PDFs of velocity have been characterized from the experiment and enable us to fully describe structural, flow and transport changes induced by reaction in this regime.

  2. 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.

  3. Cinnamon Oil and Chitosan Coating on Orthopaedic Implant Surface for Prevention of Staphylococcus Epidermidis Biofilm Formation

    OpenAIRE

    R Magetsari; P Dewo; BK Saputro; Z Lanodiyu

    2014-01-01

    S. Epidermidis is among the most frequently isolated microorganisms found in -infection related to implanted devices and the formation of biofilm will be more resistantcompared to the planktonic form. This study was carried out determine the effect of coating on stainless steel orthopaedic implants surfaces with cinnamon oil and chitosan as bioadhesive to prevent biofilms formation of S. Epidermidis.The rod shaped stainless steel 316 L orthopaedic implant with 5 mm diameters was coated 2 t...

  4. 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.

  5. Formation factor of regular porous pattern in poly-α-methylstyrene film

    International Nuclear Information System (INIS)

    Yang Ruizhuang; Xu Jiajing; Gao Cong; Ma Shuang; Chen Sufen; Luo Xuan; Fang Yu; Li Bo

    2015-01-01

    Regular poly-α-methylstyrene (PAMS) porous film with macron-sized cells was prepared by casting the solution in the condition with high humidity. In this paper, the effects of the molecular weight of PAMS, PAMS concentration, humidity, temperature, volatile solvents and the thickness of liquid of solution on formation of regular porous pattern in PAMS film were discussed. The results show that these factors significantly affect the pore size and the pore distribution. The capillary force and Benard-Marangoni convection are main driving forces for the water droplet moving and making pores regular arrangement. (authors)

  6. Visualization of soil structure and pore structure modifications by pioneering ground beetles (Cicindelidae) in surface sediments of an artificial catchment

    Science.gov (United States)

    Badorreck, Annika; Gerke, Horst H.; Weller, Ulrich; Vontobel, Peter

    2010-05-01

    An artificial catchment was constructed to study initial soil and ecosystem development. As a key process, the pore structure dynamics in the soil at the surface strongly influences erosion, infiltration, matter dynamics, and vegetation establishment. Little is known, however, about the first macropore formation in the very early stage. This presentation focuses on observations of soil pore geometry and its effect on water flow at the surface comparing samples from three sites in the catchment and in an adjacent "younger" site composed of comparable sediments. The surface soil was sampled in cylindrical plastic rings (10 cm³) down to 2 cm depth in three replicates each site and six where caves from pioneering ground-dwelling beetles Cicindelidae were found. The samples were scanned with micro-X-ray computed tomography (at UFZ-Halle, Germany) with a resolution of 0.084 mm. The infiltration dynamics were visualized with neutronradiography (at Paul-Scherer-Institute, Switzerland) on slab-type soil samples in 2D. The micro-tomographies exhibit formation of surface sealing whose thickness and intensity vary with silt and clay content. The CT images show several coarser- and finer-textured micro-layers at the sample surfaces that were formed as a consequence of repeated washing in of finer particles in underlying coarser sediment. In micro-depressions, the uppermost layers consist of sorted fine sand and silt due to wind erosion. Similar as for desert pavements, a vesicular pore structure developed in these sediments on top, but also scattered in fine sand- and silt-enriched micro-layers. The ground-dwelling activity of Cicindelidae beetles greatly modifies the soil structure through forming caves in the first centimetres of the soil. Older collapsed caves, which form isolated pores within mixed zones, were also found. The infiltration rates were severely affected both, by surface crusts and activity of ground-dwelling beetles. The observations demonstrate relatively

  7. Pore Scale Analysis of Oil Shale/Sands Pyrolysis

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Chen-Luh [Univ. of Utah, Salt Lake City, UT (United States); Miller, Jan [Univ. of Utah, Salt Lake City, UT (United States)

    2011-03-01

    There are important questions concerning the quality and volume of pore space that is created when oil shale is pyrolyzed for the purpose of producing shale oil. In this report, 1.9 cm diameter cores of Mahogany oil shale were pyrolyzed at different temperatures and heating rates. Detailed 3D imaging of core samples was done using multiscale X-ray computed tomography (CT) before and after pyrolysis to establish the pore structure. The pore structure of the unreacted material was not clear. Selected images of a core pyrolyzed at 400oC were obtained at voxel resolutions from 39 microns (Οm) to 60 nanometers (nm). Some of the pore space created during pyrolysis was clearly visible at these resolutions and it was possible to distinguish between the reaction products and the host shale rock. The pore structure deduced from the images was used in Lattice Boltzmann simulations to calculate the permeability in the pore space. The permeabilities of the pyrolyzed samples of the silicate-rich zone were on the order of millidarcies, while the permeabilities of the kerogen-rich zone after pyrolysis were very anisotropic and about four orders of magnitude higher.

  8. Protein crystal nucleation in pores.

    Science.gov (United States)

    Nanev, Christo N; Saridakis, Emmanuel; Chayen, Naomi E

    2017-01-16

    The most powerful method for protein structure determination is X-ray crystallography which relies on the availability of high quality crystals. Obtaining protein crystals is a major bottleneck, and inducing their nucleation is of crucial importance in this field. An effective method to form crystals is to introduce nucleation-inducing heterologous materials into the crystallization solution. Porous materials are exceptionally effective at inducing nucleation. It is shown here that a combined diffusion-adsorption effect can increase protein concentration inside pores, which enables crystal nucleation even under conditions where heterogeneous nucleation on flat surfaces is absent. Provided the pore is sufficiently narrow, protein molecules approach its walls and adsorb more frequently than they can escape. The decrease in the nucleation energy barrier is calculated, exhibiting its quantitative dependence on the confinement space and the energy of interaction with the pore walls. These results provide a detailed explanation of the effectiveness of porous materials for nucleation of protein crystals, and will be useful for optimal design of such materials.

  9. Control and prevention of ice formation and accretion on heat exchangers for ventilation systems

    DEFF Research Database (Denmark)

    Rahimi, Maral; Afshari, Alireza

    2015-01-01

    In cold climates, the application of mechanical ventilation systems with heat recovery like are airto-air exchangers is used for reducing energy consumption for heating buildings by transferring heat exhausted air to supply air. However, increase efficiency of heat exchanger results in lower...... exhaust air temperatures and Ice formation on heat exchanger fins, which can cause problem and is not favourable. Therefore, prevention and control of ice formation on heat exchangers is necessary. The existing methods are divided into two different methods: active and passive ice control methods....... The active methods are e.g. bypass, recirculation, preheating. The passive methods relate to the surface characteristics of the heat exchanger fins as they have effect on ice formation in initial phase. All these methods have varying levels of success, cost, and effectiveness, which are depending on the heat...

  10. A casting based process to fabricate 3D alginate scaffolds and to investigate the influence of heat transfer on pore architecture during fabrication

    International Nuclear Information System (INIS)

    Parks, W.M.; Guo, Y.B.

    2008-01-01

    The fabrication of 3-dimensional (3D) tissue scaffolds is a competitive approach to engineered tissues. An ideal tissue scaffold must be highly porous, biocompatible, biodegradable, easily processed and cost-effective, and have adequate mechanical properties. A casting based process has been developed in this study to fabricate 3D alginate tissue scaffolds. The alginate/calcium gluconate hydrogel was quenched in a glass mold and freeze dried to form a highly porous tissue scaffold whose tiny pores retain the shape of the ice crystals during quenching. Knowing that the water in the alginate hydrogel would form ice crystals if frozen and that different cooling conditions may dramatically influence the pore architecture, the speed and direction of the heat transfer in freeze drying hydrogel were examined with regard to pore size and orientation. The pore architecture at the different locations of the fabricated scaffolds was characterized using scanning electron microscopy. The fabricated scaffolds consist of pores that are highly interconnected, with a diameter about 200 μm (average diameter of a capillary) to permit blood vessel penetration. It also has been found that the pore size, orientation, and uniformity are significantly affected by the condition of heat transfer during freeze drying. Tailoring the pore architecture of the scaffolds is feasible by controlling heat transfer. This study provides an insight on pore architecture formation and control by altered process parameters

  11. 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.

  12. Determination of geochemical characters of insterstitial waters of pleistocene Italian clay formations

    International Nuclear Information System (INIS)

    Fontanive, A.; Gragnani, R.; Mignuzzi, C.; Spat, G.

    1985-01-01

    The geochemical characters of clay formations and of their pore water are fundamental with regards to the mobility of the radionuclides as well as to the corrosion processes on enginered barriers. Experimental researches have been carried out in different types of clay, which represent Italian formations, for the characterization of pore water. A squeezer system, which reaches 1500 Kg/cm 2 in pressure, and an analytical micro-scale methodology, for the determination of dissolved constituents in pore water, were set up. The extracted pore water ranges from 60% to 85% in relation to consolidation state of clay. The chemical composition of the extracted fluid has been checked during the squeezing. During this step the observed variations were smaller than those between the different specimens of the same sample. The comparison between the results obtained by squeezing and by a multiple washing technique, using increasing water/sediment ratios, shows that the last one does not give reliable results on the chemical composition of pore water. This is due to the presence of easily weatherable minerals and to the exchange processes between the clayey minerals and the solution. Nevertheless both these techniques have supplied complementary information about geochemical processes in water-rock interaction. The salinity of pore water ranges from 0.45 g/l to 24.5 g/l and the chemism always shows a high content of calcium-magnesium sulfate, or sodium chloride or calcium-magnesium-sulfate with sodium chloride. The correlation between geochemical composition of pore water and mineralogical composition of clay is not significant

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

    Science.gov (United States)

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

    2016-04-01

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

  14. Halogens in pore water of peat bogs – the role of peat decomposition and dissolved organic matter

    Directory of Open Access Journals (Sweden)

    H. Biester

    2006-01-01

    Full Text Available Halogens are strongly enriched in peat and peatlands and such they are one of their largest active terrestrial reservoir. The enrichment of halogens in peat is mainly attributed to the formation of organohalogens and climatically controlled humification processes. However, little is known about release of halogens from the peat substrate and the distribution of halogens in the peat pore water. In this study we have investigated the distribution of chlorine, bromine and iodine in pore water of three pristine peat bogs located in the Magellanic Moorlands, southern Chile. Peat pore waters were collected using a sipping technique, which allows in situ sampling down to a depth greater than 6m. Halogens and halogen species in pore water were determined by ion-chromatography (IC (chlorine and IC-ICP-MS (bromine and iodine. Results show that halogen concentrations in pore water are 15–30 times higher than in rainwater. Mean concentrations of chlorine, bromine and iodine in pore water were 7–15 mg l−1, 56–123 μg l−1, and 10–20 μg l−1, which correspond to mean proportions of 10–15%, 1–2.3% and 0.5–2.2% of total concentrations in peat, respectively. Organobromine and organoiodine were the predominant species in pore waters, whereas chlorine in pore water was mostly chloride. Advection and diffusion of halogens were found to be generally low and halogen concentrations appear to reflect release from the peat substrate. Release of bromine and iodine from peat depend on the degree of peat degradation, whereas this relationship is weak for chlorine. Relatively higher release of bromine and iodine was observed in less degraded peat sections, where the release of dissolved organic carbon (DOC was also the most intensive. It has been concluded that the release of halogenated dissolved organic matter (DOM is the predominant mechanism of iodine and bromine release from peat.

  15. HYDROXYETHYL METHACRYLATE BASED NANOCOMPOSITE HYDROGELS WITH TUNABLE PORE ARCHITECTURE

    Directory of Open Access Journals (Sweden)

    Erhan Bat

    2016-10-01

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

  16. Nanothin Coculture Membranes with Tunable Pore Architecture and Thermoresponsive Functionality for Transfer-Printable Stem Cell-Derived Cardiac Sheets.

    Science.gov (United States)

    Ryu, Seungmi; Yoo, Jin; Jang, Yeongseon; Han, Jin; Yu, Seung Jung; Park, Jooyeon; Jung, Seon Yeop; Ahn, Kyung Hyun; Im, Sung Gap; Char, Kookheon; Kim, Byung-Soo

    2015-10-27

    Coculturing stem cells with the desired cell type is an effective method to promote the differentiation of stem cells. The features of the membrane used for coculturing are crucial to achieving the best outcome. Not only should the membrane act as a physical barrier that prevents the mixing of the cocultured cell populations, but it should also allow effective interactions between the cells. Unfortunately, conventional membranes used for coculture do not sufficiently meet these requirements. In addition, cell harvesting using proteolytic enzymes following coculture impairs cell viability and the extracellular matrix (ECM) produced by the cultured cells. To overcome these limitations, we developed nanothin and highly porous (NTHP) membranes, which are ∼20-fold thinner and ∼25-fold more porous than the conventional coculture membranes. The tunable pore size of NTHP membranes at the nanoscale level was found crucial for the formation of direct gap junctions-mediated contacts between the cocultured cells. Differentiation of the cocultured stem cells was dramatically enhanced with the pore size-customized NTHP membrane system compared to conventional coculture methods. This was likely due to effective physical contacts between the cocultured cells and the fast diffusion of bioactive molecules across the membrane. Also, the thermoresponsive functionality of the NTHP membranes enabled the efficient generation of homogeneous, ECM-preserved, highly viable, and transfer-printable sheets of cardiomyogenically differentiated cells. The coculture platform developed in this study would be effective for producing various types of therapeutic multilayered cell sheets that can be differentiated from stem cells.

  17. 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

  18. 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)

    Maruyama, Jun-ichi; Juvvadi, Praveen Rao; Ishi, Kazutomo; Kitamoto, Katsuhiko

    2005-01-01

    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

  19. The pore structure and fractal characteristics of shales with low thermal maturity from the Yuqia Coalfield, northern Qaidam Basin, northwestern China

    Science.gov (United States)

    Hou, Haihai; Shao, Longyi; Li, Yonghong; Li, Zhen; Zhang, Wenlong; Wen, Huaijun

    2018-03-01

    The continental shales from the Middle Jurassic Shimengou Formation of the northern Qaidam Basin, northwestern China, have been investigated in recent years because of their shale gas potential. In this study, a total of twenty-two shale samples were collected from the YQ-1 borehole in the Yuqia Coalfield, northern Qaidam Basin. The total organic carbon (TOC) contents, pore structure parameters, and fractal characteristics of the samples were investigated using TOC analysis, low-temperature nitrogen adsorption experiments, and fractal analysis. The results show that the average pore size of the Shimengou shales varied from 8.149 nm to 20.635 nm with a mean value of 10.74 nm, which is considered mesopore-sized. The pores of the shales are mainly inkbottle- and slit-shaped. The sedimentary environment plays an essential role in controlling the TOC contents of the low maturity shales, with the TOC values of shales from deep to semi-deep lake facies (mean: 5.23%) being notably higher than those of the shore-shallow lake facies (mean: 0.65%). The fractal dimensions range from 2.4639 to 2.6857 with a mean of 2.6122, higher than those of marine shales, which indicates that the pore surface was rougher and the pore structure more complex in these continental shales. The fractal dimensions increase with increasing total pore volume and total specific surface area, and with decreasing average pore size. With increasing TOC contents in shales, the fractal dimensions increase first and then decrease, with the highest value occurring at 2% of TOC content, which is in accordance with the trends between the TOC and both total specific surface area and total pore volume. The pore structure complexity and pore surface roughness of these low-maturity shales would be controlled by the combined effects of both sedimentary environments and the TOC contents.

  20. Deviation of the typical AAA substrate-threading pore prevents fatal protein degradation in yeast Cdc48.

    Science.gov (United States)

    Esaki, Masatoshi; Islam, Md Tanvir; Tani, Naoki; Ogura, Teru

    2017-07-14

    Yeast Cdc48 is a well-conserved, essential chaperone of ATPases associated with diverse cellular activity (AAA) proteins, which recognizes substrate proteins and modulates their conformations to carry out many cellular processes. However, the fundamental mechanisms underlying the diverse pivotal roles of Cdc48 remain unknown. Almost all AAA proteins form a ring-shaped structure with a conserved aromatic amino acid residue that is essential for proper function. The threading mechanism hypothesis suggests that this residue guides the intrusion of substrate proteins into a narrow pore of the AAA ring, thereby becoming unfolded. By contrast, the aromatic residue in one of the two AAA rings of Cdc48 has been eliminated through evolution. Here, we show that artificial retrieval of this aromatic residue in Cdc48 is lethal, and essential features to support the threading mechanism are required to exhibit the lethal phenotype. In particular, genetic and biochemical analyses of the Cdc48 lethal mutant strongly suggested that when in complex with the 20S proteasome, essential proteins are abnormally forced to thread through the Cdc48 pore to become degraded, which was not detected in wild-type Cdc48. Thus, the widely applicable threading model is less effective for wild-type Cdc48; rather, Cdc48 might function predominantly through an as-yet-undetermined mechanism.

  1. Interaction between Proppant Packing, Reservoir Depletion, and Fluid Flow in Pore Space

    Science.gov (United States)

    Fan, M.; McClure, J. E.; Han, Y.; Chen, C.

    2016-12-01

    In the oil and gas industry, the performance of proppant pack in hydraulically created fractures has a significant influence on fracture conductivity. A better understanding of proppant transport and deposition pattern in a hydraulic fracture is vital for effective and economical production within oil and gas reservoirs. In this research, a numerical modeling approach, combining Particle Flow Code (PFC) and GPU-enhanced lattice Boltzmann simulator (GELBS), is adopted to advance the understanding of the interaction between proppant particle packing, depletion of reservoir formation, and transport of reservoir flow through the pore space. In this numerical work flow, PFC is used to simulate effective stress increase and proppant particle movement and rearrangement under increasing mechanical loading. The pore structure of the proppant pack evolves subsequently and the geometrical data are output for lattice Boltzmann (LB) simulation of proppant pack permeability. Three different proppant packs with fixed particle concentration and 12/18, 16/30, and 20/40 mesh sizes are generated. These proppant packs are compressed with specified loading stress and their subsequent geometries are used for fluid flow simulations. The simulation results are in good agreement with experimental observations, e.g., the conductivity of proppant packs decreases with increasing effective stress. Three proppant packs with the same average diameter were generated using different coefficients of variation (COVs) for the proppant diameter (namely cov5%, cov20%, and cov30%). By using the coupled PFC-LBM work flow, the proppant pack permeability as functions of effective stress and porosity is investigated. The results show that the proppant pack with a higher proppant diameter COV has lower permeability and porosity under the same effective stress, because smaller particles fill in the pore space between bigger particles. The relationship between porosity and permeability is also consistent with

  2. Prevention of Risky Sexual Behaviour through the Formation of Psychological Readiness to Parenthood

    Directory of Open Access Journals (Sweden)

    Krysko A.A.,

    2018-04-01

    Full Text Available In the world there are tendencies of early entering into sexual relations and simultaneous withdrawal of the age of marriage, an increase in the number of early pregnancies and abortions among minors. Existing programs for the prevention of risky sexual behavior are ineffective, since they are one-time, narrowly focused. The author presents the results of an experiment on the prevention of risky sexual behavior in adolescents based on the formation of their ideas of parenting and child-parent relations, and through the prism of this topic, allowing to build an image of reproductive behavior in the present and future. The program is designed taking into account the psychology of modern adolescents, in accordance with the principles of awareness and responsibility, is based on a restorative approach and resource approach to the formation of psychological readiness for parenthood M.E. Lantsburg. The program for the development of psychological preparedness for parenting in adolescents has two targets: the nearest: preventing adolescent pregnancy and reducing its negative consequences in the event of an early pregnancy, and strategic - preparing for the planning and birth of the coveted child in the future. The results prove that the adolescents' views about the family depend both on the experiences they experienced in their own childhood and on the trends in the social and political space discussed in this topic. The study showed that adolescents' views on sexual relations, family and parenthood can be purposefully influenced through a program based on the knowledge of age-related psychology, resource and recovery approaches and using interactive methods of teaching relevant to this age group.

  3. 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

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

    International Nuclear Information System (INIS)

    Gao Xiaoling; Gu Mei; Xie Xubing; Huang Wei

    2013-01-01

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

  5. Antibiotic-Loaded Synthetic Calcium Sulfate Beads for Prevention of Bacterial Colonization and Biofilm Formation in Periprosthetic Infections

    Science.gov (United States)

    Howlin, R. P.; Brayford, M. J.; Webb, J. S.; Cooper, J. J.; Aiken, S. S.

    2014-01-01

    Periprosthetic infection (PI) causes significant morbidity and mortality after fixation and joint arthroplasty and has been extensively linked to the formation of bacterial biofilms. Poly(methyl methacrylate) (PMMA), as a cement or as beads, is commonly used for antibiotic release to the site of infection but displays variable elution kinetics and also represents a potential nidus for infection, therefore requiring surgical removal once antibiotics have eluted. Absorbable cements have shown improved elution of a wider range of antibiotics and, crucially, complete biodegradation, but limited data exist as to their antimicrobial and antibiofilm efficacy. Synthetic calcium sulfate beads loaded with tobramycin, vancomycin, or vancomycin-tobramycin dual treatment (in a 1:0.24 [wt/wt] ratio) were assessed for their abilities to eradicate planktonic methicillin-resistant Staphylococcus aureus (MRSA) and Staphylococcus epidermidis relative to that of PMMA beads. The ability of the calcium sulfate beads to prevent biofilm formation over multiple days and to eradicate preformed biofilms was studied using a combination of viable cell counts, confocal microscopy, and scanning electron microscopy of the bead surface. Biofilm bacteria displayed a greater tolerance to the antibiotics than their planktonic counterparts. Antibiotic-loaded beads were able to kill planktonic cultures of 106 CFU/ml, prevent bacterial colonization, and significantly reduce biofilm formation over multiple days. However, established biofilms were harder to eradicate. These data further demonstrate the difficulty in clearing established biofilms; therefore, early preventive measures are key to reducing the risk of PI. Synthetic calcium sulfate loaded with antibiotics has the potential to reduce or eliminate biofilm formation on adjacent periprosthetic tissue and prosthesis material and, thus, to reduce the rates of periprosthetic infection. PMID:25313221

  6. Isolation and characterization of dissolved organic matter from the Callovo-Oxfordian formation

    International Nuclear Information System (INIS)

    Courdouan, Amandine; Christl, Iso; Meylan, Sebastien; Wersin, Paul; Kretzschmar, Ruben

    2007-01-01

    Characterizing dissolved organic matter (DOM) in the pore water of the Callovo-Oxfordian formation, a potential host rock for the disposal of radioactive waste, is important to estimate its potential influence on the mobility of radionuclides in the rock. To isolate DOM, crushed rock material was extracted under anoxic conditions with deionized water, 0.1 M NaOH and synthetic pore water (SPW, water containing all major ions at pore water concentrations but no organic matter), respectively. The effects of extraction parameters on the extracted DOM including the solid-to-liquid ratio, extraction time, exposure to O 2 and acid pretreatment of the rock material prior to the anoxic extraction were evaluated. In addition, DOM in one of the first pore water samples collected in the underground rock laboratory at Bure (France) was characterized for comparison. The size distribution and the low molecular weight organic acid contents of the extracts and pore water DOM were determined by liquid chromatography coupled with an organic C detector (LC-OCD) and by ion chromatography. The results revealed that only a fraction of less than 1.2% of the total organic C present in the rock was extractable. Maximum dissolved organic C (DOC) concentrations in the anoxic extracts ranged from 5.5 ± 0.3 mg/L for SPW extracts to 14.2 ± 1.1 mg/L for 0.1 M NaOH extracts. The major portion of the DOC in the anoxic extracts consisted of hydrophilic compounds (48-78%) having a molecular weight of less than 500 Da. Up to 21% of DOC in the anoxic extracts was identified as acetate, formate, lactate and malate. The short-term exposure of rock material to O 2 during rock crushing strongly increased DOC concentrations and led to a shift towards smaller molecular weight compounds and to a higher low molecular weight organic acid (LMWOA) content as compared to the strictly anoxic extraction. The pore water sampled from a packed-off borehole exhibited a higher DOC concentration (56.7 mg/L) than the

  7. Pore water colloid properties in argillaceous sedimentary rocks.

    Science.gov (United States)

    Degueldre, Claude; Cloet, Veerle

    2016-11-01

    The focus of this work is to evaluate the colloid nature, concentration and size distribution in the pore water of Opalinus Clay and other sedimentary host rocks identified for a potential radioactive waste repository in Switzerland. Because colloids could not be measured in representative undisturbed porewater of these host rocks, predictive modelling based on data from field and laboratory studies is applied. This approach allowed estimating the nature, concentration and size distributions of the colloids in the pore water of these host rocks. As a result of field campaigns, groundwater colloid concentrations are investigated on the basis of their size distribution quantified experimentally using single particle counting techniques. The colloid properties are estimated considering data gained from analogue hydrogeochemical systems ranging from mylonite features in crystalline fissures to sedimentary formations. The colloid concentrations were analysed as a function of the alkaline and alkaline earth element concentrations. Laboratory batch results on clay colloid generation from compacted pellets in quasi-stagnant water are also reported. Experiments with colloids in batch containers indicate that the size distribution of a colloidal suspension evolves toward a common particle size distribution independently of initial conditions. The final suspension size distribution was found to be a function of the attachment factor of the colloids. Finally, calculations were performed using a novel colloid distribution model based on colloid generation, aggregation and sedimentation rates to predict under in-situ conditions what makes colloid concentrations and size distributions batch- or fracture-size dependent. The data presented so far are compared with the field and laboratory data. The colloid occurrence, stability and mobility have been evaluated for the water of the considered potential host rocks. In the pore water of the considered sedimentary host rocks, the clay

  8. Influence of Solutocapillary Convection on Macrovoid Defect Formation in Polymeric Membranes

    Science.gov (United States)

    Greenberg, Alan R.; Krantz, William B.; Todd, Paul

    2003-01-01

    The focus of this research project involved the dry-cast process for polymeric membrane formation, whereby evaporation of solvent from an initially homogeneous polymer/solvent/ nonsolvent solution results in phase separation and the formation of polymer-rich and polymer-lean phases. Under certain conditions the polymer-lean phase gives rise to very large and usually undesirable, tear-drop-shaped pores (size approx. 10 - 50 microns) termed macrovoids (MVs). Although in many cases the presence of MV pores has deleterious effects on membrane performance, there are a number of innovative applications where the presence of such pores is highly desirable. Although researchers have proposed a variety of mechanisms for MV formation over the past three decades, two main hypotheses are currently favored: one asserts that MV growth can be attributed solely to diffusion (the diffusive growth hypothesis), whereas the other states that solutocapillary convection (the SC hypothesis) at the MV interface contributes to growth. The overall goal of this research was to obtain a more comprehensive understanding of the fundamental mechanism of MV growth. This research incorporates a coupled modeling and experimental approach to test a solutocapillary convection hypothesis for the growth of macrovoid pores in polymeric membranes. Specifically, we utilized a modification of the first principles model developed by two of the PIs (ARG and WBK) for dry-cast CA membranes. For the experimental component, two separate and mutually complementary approaches were used to study MV growth. In the first, membranes cast in a zero-g environment aboard the NASA KC-135 aircraft were compared with those cast on the ground to assess the effect of the buoyancy force on membrane morphology and MV size and shape. In the second approach, videomicroscopy flow visualization (VMFV) was utilized to observe MV formation and growth in real time and to assess the effect of surface tension on the MV growth dynamics

  9. Evaluation of pore structures and cracking in cement paste exposed to elevated temperatures by X-ray computed tomography

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Kwang Yeom, E-mail: kimky@kict.re.kr [Korea Institute of Construction Technology, 283 Goyangdae-ro, Ilsanseo-gu, Goyang 411-712 (Korea, Republic of); Yun, Tae Sup, E-mail: taesup@yonsei.ac.kr [School of Civil and Environmental Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 120-749 (Korea, Republic of); Park, Kwang Pil, E-mail: bamtol97@kict.re.kr [Korea Institute of Construction Technology, 283 Goyangdae-ro, Ilsanseo-gu, Goyang 411-712 (Korea, Republic of)

    2013-08-15

    When cement-based materials are exposed to the high temperatures induced by fire, which can rapidly cause temperatures of over 1000 °C, the changes in pore structure and density prevail. In the present study, mortar specimens were subjected to a series of increasing temperatures to explore the temperature-dependent evolution of internal pore structure. High-performance X-ray computed tomography (CT) was used to observe the evolution of temperature-induced discontinuities at the sub-millimeter level. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were employed to investigate the cause of physical changes in the heated mortar specimens. Results exhibit the changes in pore structure caused by elevated temperatures, and thermally induced fractures. We discuss the progressive formation of thermally induced fracture networks, which is a prerequisite for spalling failure of cement-based materials by fire, based on visual observations of the 3D internal structures revealed by X-ray CT.

  10. Evaluation of pore structures and cracking in cement paste exposed to elevated temperatures by X-ray computed tomography

    International Nuclear Information System (INIS)

    Kim, Kwang Yeom; Yun, Tae Sup; Park, Kwang Pil

    2013-01-01

    When cement-based materials are exposed to the high temperatures induced by fire, which can rapidly cause temperatures of over 1000 °C, the changes in pore structure and density prevail. In the present study, mortar specimens were subjected to a series of increasing temperatures to explore the temperature-dependent evolution of internal pore structure. High-performance X-ray computed tomography (CT) was used to observe the evolution of temperature-induced discontinuities at the sub-millimeter level. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were employed to investigate the cause of physical changes in the heated mortar specimens. Results exhibit the changes in pore structure caused by elevated temperatures, and thermally induced fractures. We discuss the progressive formation of thermally induced fracture networks, which is a prerequisite for spalling failure of cement-based materials by fire, based on visual observations of the 3D internal structures revealed by X-ray CT

  11. Novel Techniques to Characterize Pore Size of Porous Materials

    KAUST Repository

    Alabdulghani, Ali J.

    2016-01-01

    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.

  12. 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.

  13. Development of a smoking prevention mass media program using diagnostic and formative research.

    Science.gov (United States)

    Worden, J K; Flynn, B S; Geller, B M; Chen, M; Shelton, L G; Secker-Walker, R H; Solomon, D S; Solomon, L J; Couchey, S; Costanza, M C

    1988-09-01

    The process of developing a mass media campaign to prevent smoking among adolescents is described in detail. This campaign supplements a school smoking prevention program and shares educational objectives with the school program but is otherwise independent. It comprises various television and radio 30- and 60-sec "spot" messages. The campaign development process includes identifying educational objectives and strategies for appealing to young people; conducting diagnostic surveys and focus groups to determine target audience interests and perceptions about smoking and media content; suggesting approaches to producers to create preliminary television and radio messages for testing; conducting formative pretests with target groups to select optimal messages and suggest improvements to those messages; producing final messages for media presentation; and developing a media exposure plan to place messages in local media at optimal times for reception by target audiences. The media campaign is being evaluated in a 5-year project with 5,500 adolescents in four communities to determine the additional effect of mass media over a school program alone in preventing smoking.

  14. OBSERVATIONS OF SAUSAGE MODES IN MAGNETIC PORES

    International Nuclear Information System (INIS)

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

    2011-01-01

    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.

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

    Science.gov (United States)

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

    2012-07-01

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

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

    Science.gov (United States)

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

    2014-03-07

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

  17. A mathematical study of the influence of pore geometry on diffusion

    International Nuclear Information System (INIS)

    Melnyk, T.W.; Skeet, A.M.M.

    1987-01-01

    Diffusion into the pore space of plutonic rock matrices is an important phenomenon that can affect the migration of radionuclides and other contaminants in groundwater systems. The effects of irregular pore geometry on rates of diffusive transport are examined in this report. Approximate equations describing steady-state diffusive transport in pores of variable geometry are presented and indicate a strong dependence of the diffusion rates on the geometry of the pore space. Finite-element diffusion calculations were carried out for a series of pores containing storage spaces with rectangular cross-sections. The calculations showed the time taken to reach steady-state is affected by the pore geometry. The results of these calculations were used to simulate typical laboratory diffusion experiments and to evaluate the interpretation of effective diffusion parameters obtained from analysis of the simulated experiments using both capillary and dead-end pore models of the pore space. A capillary model of the pore space requires two independent parameters to characterize the pore space, and is shown, in general, to be inadequate to describe the pre-steady-state regime. The diffusion of radionuclides in groundwater systems lies in this non-steady-state regime. More complex mathematical descriptions of the pore space, using more variables and parameters, can accurately describe the non-steady-state transport. The capillary model, with effective parameter values, gives reasonable results when the size of the dead-end pore space is small relative to the overall diffusion distance under consideration

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

    Science.gov (United States)

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

    2015-08-27

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

  19. NF-κB inhibitors that prevent foam cell formation and atherosclerotic plaque accumulation.

    Science.gov (United States)

    Plotkin, Jesse D; Elias, Michael G; Dellinger, Anthony L; Kepley, Christopher L

    2017-08-01

    The transformation of monocyte-derived macrophages into lipid-laden foam cells is one inflammatory process underlying atherosclerotic disease. Previous studies have demonstrated that fullerene derivatives (FDs) have inflammation-blunting properties. Thus, it was hypothesized that FD could inhibit the transformation process underlying foam cell formation. Fullerene derivatives inhibited the phorbol myristic acid/oxidized low-density lipoprotein-induced differentiation of macrophages into foam cells as determined by lipid staining and morphology.Lipoprotein-induced generation of TNF-α, C5a-induced MC activation, ICAM-1 driven adhesion, and CD36 expression were significantly inhibited in FD treated cells compared to non-treated cells. Inhibition appeared to be mediated through the NF-κB pathway as FD reduced expression of NF-κB and atherosclerosis-associated genes. Compared to controls, FD dramatically inhibited plaque formation in arteries of apolipoprotein E null mice. Thus, FD may be an unrecognized therapy to prevent atherosclerotic lesions via inhibition of foam cell formation and MC stabilization. Copyright © 2017 Elsevier Inc. All rights reserved.

  20. Cranberry-derived proanthocyanidins prevent formation of Candida albicans biofilms in artificial urine through biofilm- and adherence-specific mechanisms.

    Science.gov (United States)

    Rane, Hallie S; Bernardo, Stella M; Howell, Amy B; Lee, Samuel A

    2014-02-01

    Candida albicans is a common cause of nosocomial urinary tract infections (UTIs) and is responsible for increased morbidity and healthcare costs. Moreover, the US Centers for Medicare & Medicaid Services no longer reimburse for hospital-acquired catheter-associated UTIs. Thus, development of specific approaches for the prevention of Candida urinary infections is needed. Cranberry juice-derived proanthocyanidins (PACs) have efficacy in the prevention of bacterial UTIs, partially due to anti-adherence properties, but there are limited data on their use for the prevention and/or treatment of Candida UTIs. Therefore, we sought to systematically assess the in vitro effect of cranberry-derived PACs on C. albicans biofilm formation in artificial urine. C. albicans biofilms in artificial urine were coincubated with cranberry PACs at serially increasing concentrations and biofilm metabolic activity was assessed using the XTT assay in static microplate and silicone disc models. Cranberry PAC concentrations of ≥16 mg/L significantly reduced biofilm formation in all C. albicans strains tested, with a paradoxical effect observed at high concentrations in two clinical isolates. Further, cranberry PACs were additive in combination with traditional antifungals. Cranberry PACs reduced C. albicans adherence to both polystyrene and silicone. Supplementation of the medium with iron reduced the efficacy of cranberry PACs against biofilms. These findings indicate that cranberry PACs have excellent in vitro activity against C. albicans biofilm formation in artificial urine. We present preliminary evidence that cranberry PAC activity against C. albicans biofilm formation is due to anti-adherence properties and/or iron chelation.

  1. Contribution of liver mitochondrial membrane-bound glutathione transferase to mitochondrial permeability transition pores

    International Nuclear Information System (INIS)

    Hossain, Quazi Sohel; Ulziikhishig, Enkhbaatar; Lee, Kang Kwang; Yamamoto, Hideyuki; Aniya, Yoko

    2009-01-01

    We recently reported that the glutathione transferase in rat liver mitochondrial membranes (mtMGST1) is activated by S-glutathionylation and the activated mtMGST1 contributes to the mitochondrial permeability transition (MPT) pore and cytochrome c release from mitochondria [Lee, K.K., Shimoji, M., Quazi, S.H., Sunakawa, H., Aniya, Y., 2008. Novel function of glutathione transferase in rat liver mitochondrial membrane: role for cytochrome c release from mitochondria. Toxcol. Appl. Pharmacol. 232, 109-118]. In the present study we investigated the effect of reactive oxygen species (ROS), generator gallic acid (GA) and GST inhibitors on mtMGST1 and the MPT. When rat liver mitochondria were incubated with GA, mtMGST1 activity was increased to about 3 fold and the increase was inhibited with antioxidant enzymes and singlet oxygen quenchers including 1,4-diazabicyclo [2,2,2] octane (DABCO). GA-mediated mtMGST1 activation was prevented by GST inhibitors such as tannic acid, hematin, and cibacron blue and also by cyclosporin A (CsA). In addition, GA induced the mitochondrial swelling which was also inhibited by GST inhibitors, but not by MPT inhibitors CsA, ADP, and bongkrekic acid. GA also released cytochrome c from the mitochondria which was inhibited completely by DABCO, moderately by GST inhibitors, and somewhat by CsA. Ca 2+ -mediated mitochondrial swelling and cytochrome c release were inhibited by MPT inhibitors but not by GST inhibitors. When the outer mitochondrial membrane was isolated after treatment of mitochondria with GA, mtMGST1 activity was markedly increased and oligomer/aggregate of mtMGST1 was observed. These results indicate that mtMGST1 in the outer mitochondrial membrane is activated by GA through thiol oxidation leading to protein oligomerization/aggregation, which may contribute to the formation of ROS-mediated, CsA-insensitive MPT pore, suggesting a novel mechanism for regulation of the MPT by mtMGST1

  2. Silver Nanoparticle Transport Through Soil: Illuminating the Pore-Scale Processes

    Science.gov (United States)

    Molnar, I. L.; Willson, C. S.; Gerhard, J.; O'Carroll, D. M.

    2015-12-01

    For nanoparticle transport through soil, the pore-scale (i.e., tens to hundreds of grains and pores) is a crucial intermediate scale which links nanoparticle-surface interactions with field-scale transport behaviour. However, very little information exists on how nanoparticles behave within real three-dimensional pore spaces. As a result, pore-scale processes are poorly characterized for nanoparticle systems and, subsequently, continuum-scale transport models struggle to describe commonly observed 'anomalous' behaviour such as extended tailing. This knowledge gap is due to two primary factors: an inability to experimentally observe nanoparticles within real pore spaces, and the computationally expensive models required to simulate nanoparticle movement. However, due to recent advances in Synchrotron X-Ray Computed Microtomography (SXCMT), it is now possible to quantify in-situ pore-scale nanoparticle concentrations during transport through real 3-dimensional porous media [1]. Employing this SXCMT quantification method to examine real nanoparticle/soil transport experiments has yielded new insights into the pore-scale processes governing nanoparticle transport. By coupling SXCMT nanoparticle quantification method with Computational Fluid Dynamics (CFD) simulations we are able to construct a better picture of how nanoparticles flow through real pore spaces. This talk presents SXCMT/CFD analyses of three silver nanoparticle transport experiments. Silver nanoparticles were flushed through three different sands to characterize the influence of grain distribution and retention rates on pore-scale flow and transport processes. These CFD/SXCMT analyses illuminate how processes such as temporary hydraulic retention govern nanoparticle transport. In addition, the observed distributions of pore water velocities and nanoparticle mass flow rates challenge the standard conceptual model of nanoparticle transport, suggesting that pore-scale processes require explicit consideration

  3. Bioactive glass-poly (ε-caprolactone) composite scaffolds with 3 dimensionally hierarchical pore networks

    International Nuclear Information System (INIS)

    Yun, Hui-suk; Kim, Seung-eon; Park, Eui Kyun

    2011-01-01

    Hierarchically mesoporous-macroporous-giant-porous bioactive glass/poly ε-caprolactone (PCL) composite scaffolds were prepared using a combination of the sol-gel method, evaporation-induced self-assembly process in the presence of nonionic triblock copolymer, EO 100 PO 65 EO 100 (F127), as template, salt leaching method, and rapid prototyping techniques. F127 acts as a template, inducing the formation of mesopores, NaCl with sizes between 25 and 33 μm provides macro-pores after leaching, and rapid prototyping produces giant-pores. The structure and morphology of the scaffolds were characterized by the field emission scanning electron microscopy, transmission electron microscopy, and Hg porosimetry. The mechanical properties of the scaffolds were examined by the dynamic mechanical analysis. Their in vitro bioactivities were confirmed by immersing the scaffolds in simulated body fluid. Their biocompatibilities were also evaluated by culturing human bone marrow stromal cells on the scaffolds. The scaffolds show good molding capabilities, mechanical properties, 3 dimensionally well-interconnected pore structures, bioactivities, and biocompatibilities in vitro. Depending on the amount of NaCl, the scaffolds also show unique sponge-like properties, but still retain better mechanical properties than general salt leaching derived PCL scaffolds. All of the data provide good evidence that the obtained scaffolds possess excellent potential for applications in the fields of tissue engineering and drug storage.

  4. Molecular Properties of Globin Channels and Pores: Role of Cholesterol in Ligand Binding and Movement

    Directory of Open Access Journals (Sweden)

    Gene A Morrill

    2016-09-01

    Full Text Available ABSTRACT: Globins contain one or more cavities that control or affect such functions as ligand movement and ligand binding. Here we report that the extended globin family [cytoglobin (Cygb; neuroglobin (Ngb; myoglobin (Mb; hemoglobin (Hb subunits Hba(α and Hbb(β] contain either a transmembrane (TM helix or pore-lining region as well as internal cavities. Protein motif/domain analyses indicate that Ngb and Hbb each contain 5 cholesterol-binding (CRAC/CARC domains and 1 caveolin binding motif, whereas the Cygb dimer has 6 cholesterol-binding domains but lacks caveolin-binding motifs. Mb and Hba each exhibit 2 cholesterol-binding domains and also lack caveolin-binding motifs. The Hb αβ-tetramer contains 14 cholesterol-binding domains. Computer algorithms indicate that Cygb and Ngb cavities display multiple partitions and C-terminal pore-lining regions, whereas Mb has three major cavities plus a C-terminal pore-lining region. The Hb tetramer exhibits a large internal cavity but the subunits differ in that they contain a C-terminal TM helix (Hba and pore-lining region (Hbb. The cavities include 43 of 190 Cygb residues, 38 of 151 of Ngb residues, 55 of 154 Mb residues and 137 of 688 residues in the Hb tetramer. Each cavity complex includes 6 to 8 residues of the TM helix or pore-lining region and CRAC/CARC domains exist within all cavities. Erythrocyte Hb αβ-tetramers are largely cytosolic but also bind to a membrane anion exchange protein, band 3, which contains a large internal cavity and 12 TM helices (5 being pore-lining regions. The Hba TM helix may be the erythrocyte membrane band 3 attachment site. Band 3 contributes 4 caveolin binding motifs and 10 CRAC/CARC domains. Cholesterol binding may create lipid-disordered phases that alter globin cavities and facilitate ligand movement, permitting ion channel formation and conformational changes that orchestrate anion and ligand (O2, CO2, NO movement within the large internal cavities and

  5. Atomistic Insight on the Charging Energetics in Sub-nanometer Pore Supercacitors

    Energy Technology Data Exchange (ETDEWEB)

    Qiao, Rui [ORNL; Huang, Jingsong [ORNL; Sumpter, Bobby G [ORNL; Meunier, Vincent [ORNL; Feng, Guang [Clemson University

    2010-01-01

    Electrodes featuring sub-nanometer pores can significantly enhance the capacitance and energy density of supercapacitors. However, ions must pay an energy penalty to enter sub-nanometer pores as they have to shed part of their solvation shell. The magnitude of such energy penalty plays a key role in determining the accessibility and charging/discharging of these sub-nanometer pores. Here we report on the atomistic simulation of Na+ and Cl ions entering a polarizable slit pore with a width of 0.82 nm. We show that the free energy penalty for these ions to enter the pore is less than 14 kJ/mol for both Na+ and Cl ions. The surprisingly small energy penalty is caused by the van der Waals attractions between ion and pore walls, the image charge effects, the moderate (19-26%) de-hydration of the ions inside the pore, and the strengthened interactions between ions and their hydration water molecules in the sub-nanometer pore. The results provide strong impetus for further developing nanoporous electrodes featuring sub- nanometer pores.

  6. Moving Magnetic Features Around a Pore

    Energy Technology Data Exchange (ETDEWEB)

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

    2017-03-01

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

  7. Effect of the biodegradation rate controlled by pore structures in magnesium phosphate ceramic scaffolds on bone tissue regeneration in vivo.

    Science.gov (United States)

    Kim, Ju-Ang; Lim, Jiwon; Naren, Raja; Yun, Hui-Suk; Park, Eui Kyun

    2016-10-15

    Similar to calcium phosphates, magnesium phosphate (MgP) ceramics have been shown to be biocompatible and support favorable conditions for bone cells. Micropores below 25μm (MgP25), between 25 and 53μm (MgP53), or no micropores (MgP0) were introduced into MgP scaffolds using different sizes of an NaCl template. The porosities of MgP25 and MgP53 were found to be higher than that of MgP0 because of their micro-sized pores. Both in vitro and in vivo analysis showed that MgP scaffolds with high porosity promoted rapid biodegradation. Implantation of the MgP0, MgP25, and MgP53 scaffolds into rabbit calvarial defects (with 4- and 6-mm diameters) was assessed at two times points (4 and 8weeks), followed by analysis of bone regeneration. The micro-CT and histologic analyses of the 4-mm defect showed that the MgP25 and MgP53 scaffolds were degraded completely at 4weeks with simultaneous bone and marrow-like structure regeneration. For the 6-mm defect, a similar pattern of regeneration was observed. These results indicate that the rate of degradation is associated with bone regeneration. The MgP25 and MgP53 scaffold-implanted bone showed a better lamellar structure and enhanced calcification compared to the MgP0 scaffold because of their porosity and degradation rate. Tartrate-resistant acid phosphatase (TRAP) staining indicated that the newly formed bone was undergoing maturation and remodeling. Overall, these data suggest that the pore architecture of MgP ceramic scaffolds greatly influence bone formation and remodeling activities and thus should be considered in the design of new scaffolds for long-term bone tissue regeneration. The pore structural conditions of scaffold, including porosity, pore size, pore morphology, and pore interconnectivity affect cell ingrowth, mechanical properties and biodegradabilities, which are key components of scaffold in bone tissue regeneration. In this study, we designed hierarchical pore structure of the magnesium phosphate (Mg

  8. Modelling of tracer profiles in pore water of argillaceous rocks in the Benken borehole

    International Nuclear Information System (INIS)

    Gimmi, T.; Waber, H. N.

    2004-12-01

    Isotope tracers offer unique possibilities for analysing flow and transport processes over large scales of time and space. This is especially relevant for low-permeability media like clay stones, where transport is typically very slow and, consequently, difficult to investigate. Such lithologies are currently being investigated in several countries as potential host rocks for the disposal of radioactive or other hazardous waste. In the deep borehole at Benken (north-eastern Switzerland), a sequence of aquifers and argillaceous aquitards was investigated. Water samples were obtained from four formations (Malm, Keuper, Muschelkalk, and Buntsandstein). The Malm and the Keuper aquifer delimit a sequence of clay stones and marls at depth from about 400 to 700 m with hydraulic conductivities generally below 10 -13 m s -1 . Profiles of δ 18 O, δ 2 H, chloride, and δ 37 Cl in pore fluids of these formations were obtained. The chemical, isotopic, and noble gas composition of the ground water samples indicated that no cross-formation flow occurred, but that - with the exception of the Malm - the waters evolved geochemically within the formation from which they were sampled. Infiltration conditions could also be inferred from the data. The pore water profiles in the low-permeability zone show clear trends that hint at diffusion-dominated transport processes. To evaluate possible mechanisms and time scales of evolution of the profiles, a series of advective-dispersive model calculations was performed. Varying initial conditions as well as the type and concentration values of boundary conditions revealed the following: (i), molecular diffusion to the underlying aquifer can explain the general features of the isotope profiles, (ii), no signatures of advective flow could be detected, (iii), the evolution time is in the order of 0.5 to 1 Ma (relying on laboratory diffusion coefficients) with a possible range of about 0.2 to 2 Ma, which is geologically plausible, and, (iv

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

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, M.F.S.; Lima, I. [Nuclear Instrumentation Laboratory, COPPE/UFRJ, P.O. Box 68509, 21.941-972, Rio de Janeiro (Brazil); Borghi, L. [Geology Department, Geosciences Institute, Federal University of Rio de Janeiro, Brazil. (Brazil); Lopes, R.T., E-mail: ricardo@lin.ufrj.br [Nuclear Instrumentation Laboratory, COPPE/UFRJ, P.O. Box 68509, 21.941-972, Rio de Janeiro (Brazil)

    2012-07-15

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

  10. PZ, PT and PZT formation from metal citrates

    International Nuclear Information System (INIS)

    Bastos, C.M.R.; Zaghette, M.A.; Jafelicci Junior, M.; Varela, J.A.

    1990-01-01

    Lead zirconate, lead titanate and lead titanate-zirconate were obtained by mechanical mixing of lead, titanium and zirconium citrates in ether and by calcination. The process was analyzed by DTA, TGA, IR, pore size distribution and surface area measurements. The results indicate that the decomposition reaction and formation of PZ, PT occur simultaneaously without formation of intermediate compounds. PZT was formed from 500 0 C. (author) [pt

  11. Microtomography and pore-scale modeling of two-phase Fluid Distribution

    Energy Technology Data Exchange (ETDEWEB)

    Silin, D.; Tomutsa, L.; Benson, S.; Patzek, T.

    2010-10-19

    Synchrotron-based X-ray microtomography (micro CT) at the Advanced Light Source (ALS) line 8.3.2 at the Lawrence Berkeley National Laboratory produces three-dimensional micron-scale-resolution digital images of the pore space of the reservoir rock along with the spacial distribution of the fluids. Pore-scale visualization of carbon dioxide flooding experiments performed at a reservoir pressure demonstrates that the injected gas fills some pores and pore clusters, and entirely bypasses the others. Using 3D digital images of the pore space as input data, the method of maximal inscribed spheres (MIS) predicts two-phase fluid distribution in capillary equilibrium. Verification against the tomography images shows a good agreement between the computed fluid distribution in the pores and the experimental data. The model-predicted capillary pressure curves and tomography-based porosimetry distributions compared favorably with the mercury injection data. Thus, micro CT in combination with modeling based on the MIS is a viable approach to study the pore-scale mechanisms of CO{sub 2} injection into an aquifer, as well as more general multi-phase flows.

  12. Formation of Dense Pore Structure by Te Addition in Bi0.5Sb1.5Te3: An Approach to Minimize Lattice Thermal Conductivity

    Directory of Open Access Journals (Sweden)

    Syed Waqar Hasan

    2013-01-01

    Full Text Available We herein report the electronic and thermal transport properties of p-type Bi0.5Sb1.5Te3 polycrystalline bulks with dense pore structure. Dense pore structure was fabricated by vaporization of residual Te during the pressureless annealing of spark plasma sintered bulks of Te coated Bi0.5Sb1.5Te3 powders. The lattice thermal conductivity was effectively reduced to the value of 0.35 W m−1 K−1 at 300 K mainly due to the phonon scattering by pores, while the power factor was not significantly affected. An enhanced ZT of 1.24 at 300 K was obtained in spark plasma sintered and annealed bulks of 3 wt.% Te coated Bi0.5Sb1.5Te3 by these synergetic effects.

  13. First assessment of the pore water composition of Rupel Clay in the Netherlands and the characterisation of its reactive solids

    NARCIS (Netherlands)

    Behrends, T.; Veen, I. van der; Hoving, A.; Griffioen, J.

    2016-01-01

    The Rupel Clay member in the Netherlands largely corresponds to the Boom Formation in Belgium, and this marine, clay-rich deposit is a potential candidate to host radioactive waste disposal facilities. Prediction of the speciation of radionuclides in Rupel Clay pore water and their retardation by

  14. Pore-Fractal Structure in Porous Carbons Made from Corn and Wheat

    Science.gov (United States)

    Kapoor, Y. M.; Schmidt, P. W.; Rice, Randall D.; Shulse, Laural; Voss, D. J.; Venkatraman, A.; Fan, L. T.; Walawender, W. P.; Rieker, T. P.

    1998-03-01

    Small-angle X-ray scattering has been used in a study of the pore structure of some porous and activated carbons on length scales between about 5 and 10^4 ÅThe carbons were obtained by pyrolysis and activation of wheat and American corn (maize). The scattering data showed that in each carbon there are at least two of the following four types of pores: (1) pores with diameters of at least 10^4 Åpores with smooth or fractal surfaces and diameters of at least 5 x 10^3 Åpore-fractals with diameters of no more than about 10^3 Åand (4) pores with diameters no larger than 100 ÅThe relation between the pore structure and the procedure used to obtain the carbon and will be discussed.

  15. Effect of etching current density on microstructure and NH3-sensing properties of porous silicon with intermediate-sized pores

    International Nuclear Information System (INIS)

    Li, Mingda; Hu, Ming; Zeng, Peng; Ma, Shuangyun; Yan, Wenjun; Qin, Yuxiang

    2013-01-01

    In this work, porous silicon with intermediate-sized pores (intermediate–PS) was prepared by using galvanostatic electrochemical etching method and the effect toward sensing response characteristics of NH 3 gas was also studied. The morphology and surface chemical bonds of intermediate–PS were characterized by using field emission scanning electron microscope (FESEM) and Fourier transform infrared spectroscopy (FTIR), respectively. The results showed the intermediate–PS microstructure can be significantly modulated by the etching current density. Moreover, the freshly prepared intermediate–PS surface could achieve reliable passivation after storage in ethanol. Furthermore, the gas-sensing measurements of the intermediate–PS sensors were carried out versus different concentrations of NH 3 . The PS sensor exhibited good NH 3 -sensing performances at room temperature owing to its unique microstructure features, including large specific surface area and highly ordered pore channels. In addition, the conceivable pore formation mechanism as well as gas sensing mechanism was also discussed

  16. Monte-Carlo simulation of crystallographical pore growth in III-V-semiconductors

    International Nuclear Information System (INIS)

    Leisner, Malte; Carstensen, Juergen; Foell, Helmut

    2011-01-01

    The growth of crystallographical pores in III-V-semiconductors can be understood in the framework of a simple model, which is based on the assumption that the branching of pores is proportional to the current density at the pore tips. The stochastic nature of this model allows its implementation into a three-dimensional Monte-Carlo-simulation of pore growth. The simulation is able to reproduce the experimentally observed crysto pore structures in III-V-semiconductors in full quantitative detail. The different branching probabilities for different semiconductors, as well as doping levels, can be deduced from the specific passivation behavior of the semiconductor-electrolyte-interface at the pore tips.

  17. 3D Textural and Geochemical Analyses on Carbonado Diamond: Insights from Pores and the Minerals within Them

    Science.gov (United States)

    Eckley, S. A.; Ketcham, R. A.

    2017-12-01

    Carbonado is an enigmatic variety of polycrystalline diamond found only in placer deposits and Proterozoic metaconglomerates in Brazil and the Central African Republic with unknown primary origin. These highly porous black nodules possess a narrow range of isotopically light carbon (δ13C -31 to -24 ‰), a primarily crustal inclusion suite unusually enriched in REEs and actinides filling the pore spaces, a crystallization age from 2.6 to 3.8 Ga, and other atypical features which have led to a variety of formation theories from extra-solar to deep mantle. We have completed the first multi-sample 3D textural analysis on nine carbonados using high resolution X-ray CT (XCT), with follow-up geochemical work. We have documented a variety of textures in both pore structure and mineralogy within pores. All pore textures feature a preferred orientation. Spatial coherence in pore fillings in some specimens suggest that secondary minerals formed by in-situ breakdown of primary inclusion phases. This, combined with the presence of pseudomorphs, support the hypothesis that elements comprising the secondary minerals within the pore spaces are actually primary. SEM-EDS analysis of one carbonado's exterior revealed the presence of zircon; XCT analysis of the complete volume indicates zircon is present only on the exterior of that specimen, but may be interior to others. Anticipated follow-up work will include LA-ICP-MS U-Pb dating and REE analysis of the zircon, and step-leaching and ICP analysis of some specimens. Periodic XCT imaging will allow us to trace leaching progress and effectiveness. To provide further context for our observed pore fabrics, we also analyzed a framesite, a less porous polycrystalline diamond found in kimberlites thought to crystallize shortly before eruption. Both diamond varieties have bladed/elongated pores forming a foliation with a moderate lineation. The similarity in fabrics suggests a similar process could have formed both carbonados and

  18. Long-pore Electrostatics in Inward-rectifier Potassium Channels

    Science.gov (United States)

    Robertson, Janice L.; Palmer, Lawrence G.; Roux, Benoît

    2008-01-01

    Inward-rectifier potassium (Kir) channels differ from the canonical K+ channel structure in that they possess a long extended pore (∼85 Å) for ion conduction that reaches deeply into the cytoplasm. This unique structural feature is presumably involved in regulating functional properties specific to Kir channels, such as conductance, rectification block, and ligand-dependent gating. To elucidate the underpinnings of these functional roles, we examine the electrostatics of an ion along this extended pore. Homology models are constructed based on the open-state model of KirBac1.1 for four mammalian Kir channels: Kir1.1/ROMK, Kir2.1/IRK, Kir3.1/GIRK, and Kir6.2/KATP. By solving the Poisson-Boltzmann equation, the electrostatic free energy of a K+ ion is determined along each pore, revealing that mammalian Kir channels provide a favorable environment for cations and suggesting the existence of high-density regions in the cytoplasmic domain and cavity. The contribution from the reaction field (the self-energy arising from the dielectric polarization induced by the ion's charge in the complex geometry of the pore) is unfavorable inside the long pore. However, this is well compensated by the electrostatic interaction with the static field arising from the protein charges and shielded by the dielectric surrounding. Decomposition of the static field provides a list of residues that display remarkable correspondence with existing mutagenesis data identifying amino acids that affect conduction and rectification. Many of these residues demonstrate interactions with the ion over long distances, up to 40 Å, suggesting that mutations potentially affect ion or blocker energetics over the entire pore. These results provide a foundation for understanding ion interactions in Kir channels and extend to the study of ion permeation, block, and gating in long, cation-specific pores. PMID:19001143

  19. Water vapor weathering of Taurus-Littrow orange soil - A pore-structure analysis

    Science.gov (United States)

    Cadenhead, D. A.; Mikhail, R. S.

    1975-01-01

    A pore-volume analysis was performed on water vapor adsorption data previously obtained on a fresh sample of Taurus-Littrow orange soil, and the analysis was repeated on the same sample after its exposure to moist air for a period of approximately six months. The results indicate that exposure of an outgassed sample to high relative pressures of water vapor can result in the formation of substantial micropore structure, the precise amount being dependent on the sample pretreatment, particularly the outgassing temperature. Micropore formation is explained in terms of water penetration into surface defects. In contrast, long-term exposure to moist air at low relative pressures appears to reverse the process with the elimination of micropores and enlargement of mesopores possibly through surface diffusion of metastable adsorbent material. The results are considered with reference to the storage of lunar samples.

  20. Formative research to develop theory-based messages for a Western Australian child drowning prevention television campaign: study protocol.

    Science.gov (United States)

    Denehy, Mel; Crawford, Gemma; Leavy, Justine; Nimmo, Lauren; Jancey, Jonine

    2016-05-20

    Worldwide, children under the age of 5 years are at particular risk of drowning. Responding to this need requires the development of evidence-informed drowning prevention strategies. Historically, drowning prevention strategies have included denying access, learning survival skills and providing supervision, as well as education and information which includes the use of mass media. Interventions underpinned by behavioural theory and formative evaluation tend to be more effective, yet few practical examples exist in the drowning and/or injury prevention literature. The Health Belief Model and Social Cognitive Theory will be used to explore participants' perspectives regarding proposed mass media messaging. This paper describes a qualitative protocol to undertake formative research to develop theory-based messages for a child drowning prevention campaign. The primary data source will be focus group interviews with parents and caregivers of children under 5 years of age in metropolitan and regional Western Australia. Qualitative content analysis will be used to analyse the data. This study will contribute to the drowning prevention literature to inform the development of future child drowning prevention mass media campaigns. Findings from the study will be disseminated to practitioners, policymakers and researchers via international conferences, peer and non-peer-reviewed journals and evidence summaries. The study was submitted and approved by the Curtin University Human Research Ethics Committee. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/

  1. Impact of Pore-Scale Wettability on Rhizosphere Rewetting

    Directory of Open Access Journals (Sweden)

    Pascal Benard

    2018-04-01

    Full Text Available Vast amounts of water flow through a thin layer of soil around the roots, the rhizosphere, where high microbial activity takes place—an important hydrological and biological hotspot. The rhizosphere was shown to turn water repellent upon drying, which has been interpreted as the effect of mucilage secreted by roots. The effects of such rhizosphere water dynamics on plant and microbial activity are unclear. Furthermore, our understanding of the biophysical mechanisms controlling the rhizosphere water repellency remains largely speculative. Our hypothesis is that the key to describe the emergence of water repellency lies within the microscopic distribution of wettability on the pore-scale. At a critical mucilage content, a sufficient fraction of pores is blocked and the rhizosphere turns water repellent. Here we tested whether a percolation approach is capable to predict the flow behavior near the critical mucilage content. The wettability of glass beads and sand mixed with chia seed mucilage was quantified by measuring the infiltration rate of water drops. Drop infiltration was simulated using a simple pore-network model in which mucilage was distributed heterogeneously throughout the pore space with a preference for small pores. The model approach proved capable to capture the percolation nature of the process, the sudden transition from wettable to water repellent and the high variability in infiltration rates near the percolation threshold. Our study highlights the importance of pore-scale distribution of mucilage in the emergent flow behavior across the rhizosphere.

  2. Software Image J to study soil pore distribution

    Directory of Open Access Journals (Sweden)

    Sabrina Passoni

    2014-04-01

    Full Text Available In the soil science, a direct method that allows the study of soil pore distribution is the bi-dimensional (2D digital image analysis. Such technique provides quantitative results of soil pore shape, number and size. The use of specific softwares for the treatment and processing of images allows a fast and efficient method to quantify the soil porous system. However, due to the high cost of commercial softwares, public ones can be an interesting alternative for soil structure analysis. The objective of this work was to evaluate the quality of data provided by the Image J software (public domain used to characterize the voids of two soils, characterized as Geric Ferralsol and Rhodic Ferralsol, from the southeast region of Brazil. The pore distribution analysis technique from impregnated soil blocks was utilized for this purpose. The 2D image acquisition was carried out by using a CCD camera coupled to a conventional optical microscope. After acquisition and treatment of images, they were processed and analyzed by the software Noesis Visilog 5.4® (chosen as the reference program and ImageJ. The parameters chosen to characterize the soil voids were: shape, number and pore size distribution. For both soils, the results obtained for the image total porosity (%, the total number of pores and the pore size distribution showed that the Image J is a suitable software to be applied in the characterization of the soil sample voids impregnated with resin.

  3. Pore Characterization of Shale Rock and Shale Interaction with Fluids at Reservoir Pressure-Temperature Conditions Using Small-Angle Neutron Scattering

    Science.gov (United States)

    Ding, M.; Hjelm, R.; Watkins, E.; Xu, H.; Pawar, R.

    2015-12-01

    Oil/gas produced from unconventional reservoirs has become strategically important for the US domestic energy independence. In unconventional realm, hydrocarbons are generated and stored in nanopores media ranging from a few to hundreds of nanometers. Fundamental knowledge of coupled thermo-hydro-mechanical-chemical (THMC) processes that control fluid flow and propagation within nano-pore confinement is critical for maximizing unconventional oil/gas production. The size and confinement of the nanometer pores creates many complex rock-fluid interface interactions. It is imperative to promote innovative experimental studies to decipher physical and chemical processes at the nanopore scale that govern hydrocarbon generation and mass transport of hydrocarbon mixtures in tight shale and other low permeability formations at reservoir pressure-temperature conditions. We have carried out laboratory investigations exploring quantitative relationship between pore characteristics of the Wolfcamp shale from Western Texas and the shale interaction with fluids at reservoir P-T conditions using small-angle neutron scattering (SANS). We have performed SANS measurements of the shale rock in single fluid (e.g., H2O and D2O) and multifluid (CH4/(30% H2O+70% D2O)) systems at various pressures up to 20000 psi and temperature up to 150 oF. Figure 1 shows our SANS data at different pressures with H2O as the pressure medium. Our data analysis using IRENA software suggests that the principal changes of pore volume in the shale occurred on smaller than 50 nm pores and pressure at 5000 psi (Figure 2). Our results also suggest that with increasing P, more water flows into pores; with decreasing P, water is retained in the pores.

  4. The effect of the atmosphere and the role of pore filling on the sintering of aluminium

    International Nuclear Information System (INIS)

    Schaffer, G.B.; Hall, B.J.; Bonner, S.J.; Huo, S.H.; Sercombe, T.B.

    2006-01-01

    Alloys of Al-3.8Cu-1Mg-0.7Si, Al-4Cu-0.6Si-0.1Mg, Al-4Cu-1.2Mg and Al-1.9Mg-1.9Si were made using air atomised powder and conventional press-and-sinter powder metallurgy techniques. These were sintered under nitrogen with a controlled water content which varied from 3 to 630 ppm (a dew point of -69 to -25 deg. C), nitrogen-5%hydrogen, argon and argon-5%hydrogen, all at atmospheric pressure, or a vacuum of -2 torr. Dry nitrogen is the most efficacious atmosphere. Vacuum is more effective than argon while hydrogen, and thus water, is extremely prejudicial to sintered density. The minimum dew point for optimum sintering is -60 deg. C (10.5 ppm H 2 O). The key feature in the beneficial effect of nitrogen is the formation of aluminium nitride. This reduces the pressure in the pore spaces relative to the external atmosphere, which induces pore filling at grain sizes that are smaller than those required for sintering in inert atmospheres. It is suggested that pore filling is an important densification mechanism during the sintering of aluminium

  5. Preparation of MgO with High Surface Area, and Modification of Its Pore Characteristics

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Moon Hee; Park, Dong Gon [Sookmyung Women' s University, Seoul (Korea, Republic of)

    2003-10-15

    Thermal decomposition of hydrated surface layer of Mg(OH){sub 2} at 500 .deg. C in vacuum turned non-porous MgO into porous one with high surface area of around 270 m{sup 2}/g. Most of its surface area, 74 %, was from micropores, and rest of it was from mesopores in wedge-shaped slits, exhibiting bimodal size distribution centered around 30 and 90 A. Rehydration followed by subsequent dehydration at 300 .deg. C in dynamic vacuum further raised the surface area to 340 m{sup 2}/g. Fraction of microporous surface area was increased to 93%, and the shape of the mesopores was modified into parallel slits with a specific dimension of 32 A. Application of Fe{sub 2}O{sub 3} over MgO via iron complex formation did not alter the pore characteristics of MgO core, except slightly increased pore dimension. Over the course of the modification, Fe{sub 2}O{sub 3} stayed on the surface possibly via spill-over reaction.

  6. The effect of scaffold pore size in cartilage tissue engineering.

    Science.gov (United States)

    Nava, Michele M; Draghi, Lorenza; Giordano, Carmen; Pietrabissa, Riccardo

    2016-07-26

    The effect of scaffold pore size and interconnectivity is undoubtedly a crucial factor for most tissue engineering applications. The aim of this study was to examine the effect of pore size and porosity on cartilage construct development in different scaffolds seeded with articular chondrocytes. We fabricated poly-L-lactide-co-trimethylene carbonate scaffolds with different pore sizes, using a solvent-casting/particulate-leaching technique. We seeded primary bovine articular chondrocytes on these scaffolds, cultured the constructs for 2 weeks and examined cell proliferation, viability and cell-specific production of cartilaginous extracellular matrix proteins, including GAG and collagen. Cell density significantly increased up to 50% with scaffold pore size and porosity, likely facilitated by cell spreading on the internal surface of bigger pores, and by increased mass transport of gases and nutrients to cells, and catabolite removal from cells, allowed by lower diffusion barriers in scaffolds with a higher porosity. However, both the cell metabolic activity and the synthesis of cartilaginous matrix proteins significantly decreased by up to 40% with pore size. We propose that the association of smaller pore diameters, causing 3-dimensional cell aggregation, to a lower oxygenation caused by a lower porosity, could have been the condition that increased the cell-specific synthesis of cartilaginous matrix proteins in the scaffold with the smallest pores and the lowest porosity among those tested. In the initial steps of in vitro cartilage engineering, the combination of small scaffold pores and low porosity is an effective strategy with regard to the promotion of chondrogenesis.

  7. Kinetic models of controllable pore growth of anodic aluminum oxide membrane

    Science.gov (United States)

    Huang, Yan; Zeng, Hong-yan; Zhao, Ce; Qu, Ye-qing; Zhang, Pin

    2012-06-01

    An anodized Al2O3 (AAO) membrane with apertures about 72 nm in diameter was prepared by two-step anodic oxidation. The appearance and pore arrangement of the AAO membrane were characterized by energy dispersive x-ray spectroscopy and scanning electron microscopy. It was confirmed that the pores with high pore aspect ratio were parallel, well-ordered, and uniform. The kinetics of pores growth in the AAO membrane was derived, and the kinetic models showed that pores stopped developing when the pressure ( σ) trended to equal the surface tension at the end of anodic oxidation. During pore expansion, the effects of the oxalic acid concentration and expansion time on the pore size were investigated, and the kinetic behaviors were explained with two kinetic models derived in this study. They showed that the pore size increased with extended time ( r= G· t+ G'), but decreased with increased concentration ( r = - K·ln c- K') through the derived mathematic formula. Also, the values of G, G', K, and K' were derived from our experimental data.

  8. Solubility of hydrogen in metals and its effect of pore-formation and embrittlement. Ph.D. Thesis

    Science.gov (United States)

    Shahani, H. R.

    1984-01-01

    The effect of alloying elements on hydrogen solubility were determined by evaluating solubility equations and interaction coefficients. The solubility of dry hydrogen at one atmosphere was investigated in liquid aluminum, Al-Ti, Al-Si, Al-Fe, liquid gold, Au-Cu, and Au-Pd. The design of rapid heating and high pressure casting furnaces used in meta foam experiments is discussed as well as the mechanism of precipitation of pores in melts, and the effect of hydrogen on the shrinkage porosity of Al-Cu and Al-Si alloys. Hydrogen embrittlement in iron base alloys is also examined.

  9. Natural tracer profiles across argillaceous formations

    International Nuclear Information System (INIS)

    Mazurek, Martin; Alt-Epping, Peter; Bath, Adrian; Gimmi, Thomas; Niklaus Waber, H.; Buschaert, Stephane; Canniere, Pierre De; Craen, Mieke De; Gautschi, Andreas; Savoye, Sebastien; Vinsot, Agnes; Wemaere, Isabelle; Wouters, Laurent

    2011-01-01

    Highlights: → Solute transport processes in clay and shale formations at nine sites are examined. → Conservative pore-water tracers (e.g. Cl - , δ 18 O, δ 2 H, He) show regular profiles. → These indicate the dominance of diffusive transport over times of 10 5 -10 6 years. → The contribution of vertical advection to transport is limited or negligible. → Modelled evolution times are in line with independent palaeo-hydrogeological data. - Abstract: Argillaceous formations generally act as aquitards because of their low hydraulic conductivities. This property, together with the large retention capacity of clays for cationic contaminants, has brought argillaceous formations into focus as potential host rocks for the geological disposal of radioactive and other waste. In several countries, programmes are under way to characterise the detailed transport properties of such formations at depth. In this context, the interpretation of profiles of natural tracers in pore waters across the formations can give valuable information about the large-scale and long-term transport behaviour of these formations. Here, tracer-profile data, obtained by various methods of pore-water extraction for nine sites in central Europe, are compiled. Data at each site comprise some or all of the conservative tracers: anions (Cl - , Br - ), water isotopes (δ 18 O, δ 2 H) and noble gases (mainly He). Based on a careful evaluation of the palaeo-hydrogeological evolution at each site, model scenarios are derived for initial and boundary pore-water compositions and an attempt is made to numerically reproduce the observed tracer distributions in a consistent way for all tracers and sites, using transport parameters derived from laboratory or in situ tests. The comprehensive results from this project have been reported in . Here the results for three sites are presented in detail, but the conclusions are based on model interpretations of the entire data set. In essentially all cases, the

  10. Effect of Pore Size and Pore Connectivity on Unidirectional Capillary Penetration Kinetics in 3-D Porous Media using Direct Numerical Simulation

    Science.gov (United States)

    Fu, An; Palakurthi, Nikhil; Konangi, Santosh; Comer, Ken; Jog, Milind

    2017-11-01

    The physics of capillary flow is used widely in multiple fields. Lucas-Washburn equation is developed by using a single pore-sized capillary tube with continuous pore connection. Although this equation has been extended to describe the penetration kinetics into porous medium, multiple studies have indicated L-W does not accurately predict flow patterns in real porous media. In this study, the penetration kinetics including the effect of pore size and pore connectivity will be closely examined since they are expected to be the key factors effecting the penetration process. The Liquid wicking process is studied from a converging and diverging capillary tube to the complex virtual 3-D porous structures with Direct Numerical Simulation (DNS) using the Volume-Of-Fluid (VOF) method within the OpenFOAM CFD Solver. Additionally Porous Medium properties such as Permeability (k) , Tortuosity (τ) will be also analyzed.

  11. High-resolution 3D X-ray microtomography as tool to investigate size distribution of grain phase and pore space in sandstones

    Science.gov (United States)

    Kahl, Wolf-Achim; Holzheid, Astrid

    2013-04-01

    The geometry and internal structures of sandstone reservoirs, like grain size, sorting, degree of bioturbation, and the history of the diagenetic alterations determine the quantity, flow rates, and recovery of hydrocarbons present in the pore space. In this respect, processes influencing the deep reservoir quality in sandstones are either of depositional, shallow diagenetic, or deep-burial origin. To assess the effect of compaction and cementation on the pore space during diagenesis, we investigated a set of sandstone samples using high-resolution microtomography (µ-CT). By high-resolution µ-CT, size distributions (in 2D and 3D), surface areas and volume fractions of the grain skeleton and pore space of sandstones and - in addition - of mineral powders have been determined. For this study, we analysed aliquots of sandstones that exhibit either complete, partial or no cemententation of the pore space, and sets of mineral powders (quartz, feldspar, calcite). As the resolution of the µ-CT scans is in the µm-range, the surface areas determined for sandstones and powders do detect the geometric surface of the material (Kahl & Holzheid, 2010). Since there are differing approaches to "size" parameters like e.g., long/short particle axes, area equivalent radius, Feret-diameter (2D), and structural thickness (3D), we decided to illustrate the effect of various size determinations for (a) single grains, (b) grain skeletons, and (c) pore space. Therefor, the computer-aided morphometric analysis of the segmented 3D models of the reconstructed scan images comprises versatile calculation algorithms. For example, size distribution of the pore space of partially cemented sandstones can be used to infer the timing of the formation of the cement in respect to tectonic/diagenetic activities. In the case of a late-stage partial cementation of a Bunter sandstone, both pore space and cement phase show identical size distributions. On the contrary, the anhydrite cement of a

  12. Antifungal effect and pore-forming action of lactoferricin B like peptide derived from centipede Scolopendra subspinipes mutilans.

    Science.gov (United States)

    Choi, Hyemin; Hwang, Jae-Sam; Lee, Dong Gun

    2013-11-01

    The centipede Scolopendra subspinipes mutilans has been a medically important arthropod species by using it as a traditional medicine for the treatment of various diseases. In this study, we derived a novel lactoferricin B like peptide (LBLP) from the whole bodies of adult centipedes, S. s. mutilans, and investigated the antifungal effect of LBLP. LBLP exerted an antifungal and fungicidal activity without hemolysis. To investigate the antifungal mechanism of LBLP, a membrane study with propidium iodide was first conducted against Candida albicans. The result showed that LBLP caused fungal membrane permeabilization. The assays of the three dimensional flow cytometric contour plot and membrane potential further showed cell shrinkage and membrane depolarization by the membrane damage. Finally, we confirmed the membrane-active mechanism of LBLP by synthesizing model membranes, calcein and FITC-dextran loaded large unilamellar vesicles. These results showed that the antifungal effect of LBLP on membrane was due to the formation of pores with radii between 0.74nm and 1.4nm. In conclusion, this study suggests that LBLP exerts a potent antifungal activity by pore formation in the membrane, eventually leading to fungal cell death. © 2013.

  13. Characteristics of Pore Structure and Fractal Dimension of Isometamorphic Anthracite

    Directory of Open Access Journals (Sweden)

    Di Gao

    2017-11-01

    Full Text Available The geologic conditions of No. 3 coal seams are similar to Sihe and Zhaozhuang Collieries, however, the gas production is significantly different. To better understand the effect of pores, by means of experimental measurements and quantitative analysis, the pore properties of high-rank isometamorphic anthracite were thoroughly studied. Our study showed that the pore structures were predominantly adsorptive, accounting for more than 88% of the specific surface area. The coal pores showed typical three-stage fractal characteristics at boundary points of 1 nm and 9 nm (7 nm of coal samples from Zhaozhuang Colliery, and the fractal dimension with 1–9 nm (or 1–7 nm, as being significantly larger than those measured outside the given ranges. Pores in samples from Sihe Colliery were mainly open spherical or ellipsoidal pores in shape; conversely, those from Zhaozhuang Colliery were mainly Y-shaped, V-shaped, or ‘ink-bottle’ type.

  14. 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.

  15. Lattice Boltzmann simulation of immiscible fluid displacement in porous media: Homogeneous versus heterogeneous pore network

    International Nuclear Information System (INIS)

    Liu, Haihu; Zhang, Yonghao; Valocchi, Albert J.

    2015-01-01

    Injection of anthropogenic carbon dioxide (CO 2 ) into geological formations is a promising approach to reduce greenhouse gas emissions into the atmosphere. Predicting the amount of CO 2 that can be captured and its long-term storage stability in subsurface requires a fundamental understanding of multiphase displacement phenomena at the pore scale. In this paper, the lattice Boltzmann method is employed to simulate the immiscible displacement of a wetting fluid by a non-wetting one in two microfluidic flow cells, one with a homogeneous pore network and the other with a randomly heterogeneous pore network. We have identified three different displacement patterns, namely, stable displacement, capillary fingering, and viscous fingering, all of which are strongly dependent upon the capillary number (Ca), viscosity ratio (M), and the media heterogeneity. The non-wetting fluid saturation (S nw ) is found to increase nearly linearly with logCa for each constant M. Increasing M (viscosity ratio of non-wetting fluid to wetting fluid) or decreasing the media heterogeneity can enhance the stability of the displacement process, resulting in an increase in S nw . In either pore networks, the specific interfacial length is linearly proportional to S nw during drainage with equal proportionality constant for all cases excluding those revealing considerable viscous fingering. Our numerical results confirm the previous experimental finding that the steady state specific interfacial length exhibits a linear dependence on S nw for either favorable (M ≥ 1) or unfavorable (M < 1) displacement, and the slope is slightly higher for the unfavorable displacement

  16. Lattice Boltzmann simulation of immiscible fluid displacement in porous media: Homogeneous versus heterogeneous pore network

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Haihu, E-mail: haihu.liu@mail.xjtu.edu.cn [School of Energy and Power Engineering, Xi’an Jiaotong University, 28 West Xianning Road, Xi’an 710049 (China); James Weir Fluids Laboratory, Department of Mechanical and Aerospace Engineering, University of Strathclyde, Glasgow G1 1XJ (United Kingdom); Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States); Zhang, Yonghao [James Weir Fluids Laboratory, Department of Mechanical and Aerospace Engineering, University of Strathclyde, Glasgow G1 1XJ (United Kingdom); Valocchi, Albert J. [Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801 (United States)

    2015-05-15

    Injection of anthropogenic carbon dioxide (CO{sub 2}) into geological formations is a promising approach to reduce greenhouse gas emissions into the atmosphere. Predicting the amount of CO{sub 2} that can be captured and its long-term storage stability in subsurface requires a fundamental understanding of multiphase displacement phenomena at the pore scale. In this paper, the lattice Boltzmann method is employed to simulate the immiscible displacement of a wetting fluid by a non-wetting one in two microfluidic flow cells, one with a homogeneous pore network and the other with a randomly heterogeneous pore network. We have identified three different displacement patterns, namely, stable displacement, capillary fingering, and viscous fingering, all of which are strongly dependent upon the capillary number (Ca), viscosity ratio (M), and the media heterogeneity. The non-wetting fluid saturation (S{sub nw}) is found to increase nearly linearly with logCa for each constant M. Increasing M (viscosity ratio of non-wetting fluid to wetting fluid) or decreasing the media heterogeneity can enhance the stability of the displacement process, resulting in an increase in S{sub nw}. In either pore networks, the specific interfacial length is linearly proportional to S{sub nw} during drainage with equal proportionality constant for all cases excluding those revealing considerable viscous fingering. Our numerical results confirm the previous experimental finding that the steady state specific interfacial length exhibits a linear dependence on S{sub nw} for either favorable (M ≥ 1) or unfavorable (M < 1) displacement, and the slope is slightly higher for the unfavorable displacement.

  17. Pore-water evolution and solute-transport mechanisms in Opalinus Clay at Mont Terri and Mont Russelin (Canton Jura, Switzerland)

    Energy Technology Data Exchange (ETDEWEB)

    Mazurek, M. [Institute of Geological Sciences, University of Berne, Berne (Switzerland); Haller de, A. [Earth and Environmental Sciences, University of Geneva, Geneva (Switzerland)

    2017-04-15

    Data pertinent to pore-water composition in Opalinus Clay in the Mont Terri and Mont Russelin anticlines have been collected over the last 20 years from long-term in situ pore-water sampling in dedicated boreholes, from laboratory analyses on drill cores and from the geochemical characteristics of vein infills. Together with independent knowledge on regional geology, an attempt is made here to constrain the geochemical evolution of the pore-waters. Following basin inversion and the establishment of continental conditions in the late Cretaceous, the Malm limestones acted as a fresh-water upper boundary leading to progressive out-diffusion of salinity from the originally marine pore-waters of the Jurassic low-permeability sequence. Model calculations suggest that at the end of the Palaeogene, pore-water salinity in Opalinus Clay was about half the original value. In the Chattian/Aquitanian, partial evaporation of sea-water occurred. It is postulated that brines diffused into the underlying sequence over a period of several Myr, resulting in an increase of salinity in Opalinus Clay to levels observed today. This hypothesis is further supported by the isotopic signatures of SO{sub 4}{sup 2-} and {sup 87}Sr/{sup 86}Sr in current pore-waters. These are not simple binary mixtures of sea and meteoric water, but their Cl{sup -} and stable water-isotope signatures can be potentially explained by a component of partially evaporated sea-water. After the re-establishment of fresh-water conditions on the surface and the formation of the Jura Fold and Thrust Belt, erosion caused the activation of aquifers embedding the low-permeability sequence, leading to the curved profiles of various pore-water tracers that are observed today. Fluid flow triggered by deformation events during thrusting and folding of the anticlines occurred and is documented by infrequent vein infills in major fault structures. However, this flow was spatially focussed and of limited duration and so did not

  18. Keeping a Step Ahead: formative phase of a workplace intervention trial to prevent obesity.

    Science.gov (United States)

    Zapka, Jane; Lemon, Stephenie C; Estabrook, Barbara B; Jolicoeur, Denise G

    2007-11-01

    Ecological interventions hold promise for promoting overweight and obesity prevention in worksites. Given the paucity of evaluative research in the hospital worksite setting, considerable formative work is required for successful implementation and evaluation. This paper describes the formative phases of Step Ahead, a site-randomized controlled trial of a multilevel intervention that promotes physical activity and healthy eating in six hospitals in central Massachusetts. The purpose of the formative research phase was to increase the feasibility, effectiveness, and likelihood of sustainability of the intervention. The Step Ahead ecological intervention approach targets change at the organization, interpersonal work environment, and individual levels. The intervention was developed using fundamental steps of intervention mapping and important tenets of participatory research. Formative research methods were used to engage leadership support and assistance and to develop an intervention plan that is both theoretically and practically grounded. This report uses observational data, program minutes and reports, and process tracking data. Leadership involvement (key informant interviews and advisory boards), employee focus groups and advisory boards, and quantitative environmental assessments cultivated participation and support. Determining multiple foci of change and designing measurable objectives and generic assessment tools to document progress are complex challenges encountered in planning phases. Multilevel trials in diverse organizations require flexibility and balance of theory application and practice-based perspectives to affect impact and outcome objectives. Formative research is an essential component.

  19. Hexadecane trapped in nano-pores of silica-aerogel

    International Nuclear Information System (INIS)

    Slavikova, B.; Jesenak, K.; Iskrova, M.; Majernik, V.; Sausa, O.; Kristiak, J.

    2009-01-01

    Ways of filling of the high-porous silica-aerogel with hydrocarbon C 16 H 34 and its efficient removal from the pores by physical method of the Positron Annihilation Spectroscopy were studied. As the most effective way to fill the SiO 2 aerogel appears through the implementation of a liquid phase, while the most appropriate way of removing of hexadecane is firing at an elevated temperature. Molecular system of hexadecane closed in nano-pores of silica-aerogel behaves otherwise than volume system of the same molecules. In the case of pure hexadecane phase transition was observed at 291 K, while solidification process is gradual with decrease of temperature in cetane trapped in pores of silica-aerogel. The results of the periods of life of o-Ps indicate greater turbidity in the pores of the molecular system compared to the volume sample of hexadecane.

  20. Numerical models of pore pressure and stress changes along basement faults due to wastewater injection: Applications to the 2014 Milan, Kansas Earthquake

    Science.gov (United States)

    Hearn, Elizabeth H.; Koltermann, Christine; Rubinstein, Justin R.

    2018-01-01

    We have developed groundwater flow models to explore the possible relationship between wastewater injection and the 12 November 2014 Mw 4.8 Milan, Kansas earthquake. We calculate pore pressure increases in the uppermost crust using a suite of models in which hydraulic properties of the Arbuckle Formation and the Milan earthquake fault zone, the Milan earthquake hypocenter depth, and fault zone geometry are varied. Given pre‐earthquake injection volumes and reasonable hydrogeologic properties, significantly increasing pore pressure at the Milan hypocenter requires that most flow occur through a conductive channel (i.e., the lower Arbuckle and the fault zone) rather than a conductive 3‐D volume. For a range of reasonable lower Arbuckle and fault zone hydraulic parameters, the modeled pore pressure increase at the Milan hypocenter exceeds a minimum triggering threshold of 0.01 MPa at the time of the earthquake. Critical factors include injection into the base of the Arbuckle Formation and proximity of the injection point to a narrow fault damage zone or conductive fracture in the pre‐Cambrian basement with a hydraulic diffusivity of about 3–30 m2/s. The maximum pore pressure increase we obtain at the Milan hypocenter before the earthquake is 0.06 MPa. This suggests that the Milan earthquake occurred on a fault segment that was critically stressed prior to significant wastewater injection in the area. Given continued wastewater injection into the upper Arbuckle in the Milan region, assessment of the middle Arbuckle as a hydraulic barrier remains an important research priority.

  1. Position-Dependent Dynamics Explain Pore-Averaged Diffusion in Strongly Attractive Adsorptive Systems.

    Science.gov (United States)

    Krekelberg, William P; Siderius, Daniel W; Shen, Vincent K; Truskett, Thomas M; Errington, Jeffrey R

    2017-12-12

    Using molecular simulations, we investigate the relationship between the pore-averaged and position-dependent self-diffusivity of a fluid adsorbed in a strongly attractive pore as a function of loading. Previous work (Krekelberg, W. P.; Siderius, D. W.; Shen, V. K.; Truskett, T. M.; Errington, J. R. Connection between thermodynamics and dynamics of simple fluids in highly attractive pores. Langmuir 2013, 29, 14527-14535, doi: 10.1021/la4037327) established that pore-averaged self-diffusivity in the multilayer adsorption regime, where the fluid exhibits a dense film at the pore surface and a lower density interior pore region, is nearly constant as a function of loading. Here we show that this puzzling behavior can be understood in terms of how loading affects the fraction of particles that reside in the film and interior pore regions as well as their distinct dynamics. Specifically, the insensitivity of pore-averaged diffusivity to loading arises from the approximate cancellation of two factors: an increase in the fraction of particles in the higher diffusivity interior pore region with loading and a corresponding decrease in the particle diffusivity in that region. We also find that the position-dependent self-diffusivities scale with the position-dependent density. We present a model for predicting the pore-average self-diffusivity based on the position-dependent self-diffusivity, which captures the unusual characteristics of pore-averaged self-diffusivity in strongly attractive pores over several orders of magnitude.

  2. Sebum output as a factor contributing to the size of facial pores.

    Science.gov (United States)

    Roh, M; Han, M; Kim, D; Chung, K

    2006-11-01

    Many endogenous and exogenous factors are known to cause enlarged pilosebaceous pores. Such factors include sex, genetic predisposition, ageing, chronic ultraviolet light exposure, comedogenic xenobiotics, acne and seborrhoea. This study was an attempt to determine the factors related to enlarged pores. To assess the relationship of sebum output, age, sex, hormonal factors and severity of acne with pore size. A prospective, randomized, controlled study was designed. A total of 60 volunteers, 30 males and 30 females, were recruited for this study. Magnified images of pores were taken using a dermoscopic video camera and measured using an image analysis program. The sebum output level was measured with a Sebumeter. Using multiple linear regression analysis, increased pore size was significantly associated with increased sebum output level, sex and age. Among the variables, sebum output level correlated most with the pore size followed by male sex. In comparing male and female participants, males had higher correlation between the sebum output level and the pore size (male: r = 0.47, female: r = 0.38). Thus, additional factors seem to influence pore size in females. Pore size was significantly increased during the ovulation phase (P = 0.008), but severity of acne was not significantly associated with the pore size. Enlarged pore sizes are associated with increased sebum output level, age and male sex. In female patients, additional hormonal factors, such as those of the menstrual cycle, affect the pore size.

  3. Scanning electron microscope investigations of nuclear pore filters in polyester foils

    International Nuclear Information System (INIS)

    Hopfe, J.

    1980-01-01

    In order to understand and characterize the action of nuclear pore filters it is necessary to know their surface, as well as their bulk, structure. In the present work, investigations of the surface structure (pore size, pore density, pore distribution) and of the pore geometry, especially in the bulk of the filters, are carried out by scanning electron microscopic (SEM) studies. The preparation technique needed is liquid-nitrogen freeze-fracturing followed by a conductive-coating step. Nuclear pore filters studied in this paper were produced by a track etching technique. Laboratory specimens were obtained by bombarding 10 μm thick polyester foils with Xe-ions and a subsequent etching with 20% NaOH. The SEM results are shown and discussed. (author)

  4. The use of nylon and glass fiber filter separators with different pore sizes in air-cathode single-chamber microbial fuel cells

    KAUST Repository

    Zhang, Xiaoyuan

    2010-01-01

    Separators are needed in microbial fuel cells (MFCs) to reduce electrode spacing and preventing electrode short circuiting. The use of nylon and glass fiber filter separators in single-chamber, air-cathode MFCs was examined for their effect on performance. Larger pore nylon mesh were used that had regular mesh weaves with pores ranging from 10 to 160 μm, while smaller pore-size nylon filters (0.2-0.45 μm) and glass fiber filters (0.7-2.0 μm) had a more random structure. The pore size of both types of nylon filters had a direct and predictable effect on power production, with power increasing from 443 ± 27 to 650 ± 7 mW m-2 for pore sizes of 0.2 and 0.45 μm, and from 769 ± 65 to 941 ± 47 mW m-2 for 10 to 160 μm. In contrast, changes in pore sizes of the glass fiber filters resulted in a relatively narrow change in power (732 ± 48 to 779 ± 43 mW m-2) for pore sizes of 0.7 to 2 μm. An ideal separator should increase both power density and Coulombic efficiency (CE). However, CEs measured for the different separators were inversely correlated with power production, demonstrating that materials which reduced the oxygen diffusion into the reactor also hindered proton transport to the cathode, reducing power production through increased internal resistance. Our results highlight the need to develop separators that control oxygen transfer and facilitate proton transfer to the cathode. © 2010 The Royal Society of Chemistry.

  5. Outer capsid proteins induce the formation of pores in epithelial cells

    International Nuclear Information System (INIS)

    Ruiz, M; Abad M; Michelangely, F; Charpilienne, A; Cohen, J

    1995-01-01

    Two mechanisms of entrance in cell of the rotavirus, during the infection, were proposed: a direct entrance through the plasmatic membrane or by means of endocytosis. In the two cases, a permeabilization mechanism of the membrane (cellular or of the endocytic vesicle, respectively) should occur. It has been shown that the rotavirus induces permeabilization of liposomes and of membrane vesicles. In this work, are studied the changes of intact cells permeability, measuring the entrance of e tide bromides. Viral particles of double capsid of the RF stump produce an increase of the cells membrane MA104 permeability, while the simple capsid ones don't induce effect. This phenomenon requires the particles trypsinization, and occurs in a means where the concentration of free Ca is lower to 1 micromolar. The temporary course of the fluorescence increase is sigmoid. The latency, the speed and the width depend on the relationship of virus / cell, and it can be observed up to 100% of permeabilization in relation to the effect of digitonin. The pores induced in the membrane by the rotavirus are irreversible. The permeabilizer effect of the rotavirus on the membrane was observed in other cellular lines as Hela and HT29, but not in the L929 ones. These results suggest that one or more proteins of the external capsid are responsible s of the effect. These could be involved in the penetration process of the virus towards the cytoplasm and could be one of the restrictive factor of the cell infection by means of the virus [es

  6. Radial distribution of ions in pores with a surface charge

    NARCIS (Netherlands)

    Stegen, J.H.G. van der; Görtzen, J.; Kuipers, J.A.M.; Hogendoorn, J.A.; Versteeg, G.F.

    2001-01-01

    A sorption model applicable to calculate the radial equilibrium concentrations of ions in the pores of ion-selective membranes with a pore structure is developed. The model is called the radial uptake model. Because the model is applied to a Nafion sulfonic layer with very small pores and the radial

  7. Pore structure modification of cement concretes by impregnation with sulfur-containing compounds

    Directory of Open Access Journals (Sweden)

    YANAKHMETOV Marat Rafisovich

    2015-02-01

    Full Text Available The authors study how the impregnation with sulfur-containing compounds changes the concrete pore structure and how it influences on the water absorption and watertightness. The results of this research indicate that impregnation of cement concrete with water-based solution of polysulphide modifies pore structure of cement concrete in such a way that it decreases total and effective porosity, reduces water absorption and increases watertightness. The proposed impregnation based on mineral helps to protect for a long time the most vulnerable parts of buildings – basements, foundations, as well as places on the facades of buildings exposed to rain, snow and groundwater. Application of the new product in the construction industry can increase the durability of materials, preventing the destruction processes caused by weathering, remove excess moisture in damp basements. The surfaces treated by protective compounds acquire antisoiling properties for a long time, and due to reduced thermal conductivity the cost of heating buildings is decreased. The effectiveness of the actions and the relatively low cost of proposed hydrophobizator makes it possible to spread widely the proposed protection method for building structures.

  8. Steps in the design, development and formative evaluation of obesity prevention-related behavior change trials

    OpenAIRE

    Baranowski Janice; Cerin Ester; Baranowski Tom

    2009-01-01

    Abstract Obesity prevention interventions through dietary and physical activity change have generally not been effective. Limitations on possible program effectiveness are herein identified at every step in the mediating variable model, a generic conceptual framework for understanding how interventions may promote behavior change. To minimize these problems, and thereby enhance likely intervention effectiveness, four sequential types of formative studies are proposed: targeted behavior valida...

  9. Toward Understanding Pore Formation and Mobility during Controlled Directional Solidification in a Microgravity Environment Investigation (PFMI)

    Science.gov (United States)

    Grugel, Richard N.; Anilkumar, A. V.; Luz, Paul; Jeter, Linda; Volz, Martin P.; Spivey, Reggie; Smith, G.

    2003-01-01

    The generation and inclusion of detrimental porosity, e.g., pipes and rattails can occur during controlled directional solidification processing. The origin of these defects is generally attributed to gas evolution and entrapment during solidification of the melt. On Earth, owing to buoyancy, an initiated bubble can rapidly rise through the liquid melt and pop at the surface; this is obviously not ensured in a low gravity or microgravity environment. Clearly, porosity generation and inclusion is detrimental to conducting any meaningful solidification-science studies in microgravity. Thus it is essential that model experiments be conducted in microgravity, to understand the details of the generation and mobility of porosity, so that methods can be found to eliminate it. In hindsight, this is particularly relevant given the results of the previous directional solidification experiments conducted in Space. The current International Space Station (ISS) Microgravity Science Glovebox (MSG) investigation addresses the central issue of porosity formation and mobility during controlled directional solidification processing in microgravity. The study will be done using a transparent metal-analogue material, succinonitrile (SCN) and succinonitrile-water 'alloys', so that direct observation and recording of pore generation and mobility can be made during the experiments. Succinonitrile is particularly well suited for the proposed investigation because it is transparent, it solidifies in a manner analogous to most metals, it has a convenient melting point, its material properties are well characterized and, it has been successfully used in previous microgravity experiments. The PFMI experiment will be launched on the UF-2, STS-111 flight. Highlighting the porosity development problem in metal alloys during microgravity processing, the poster will describe: (i) the intent of the proposed experiments, (ii) the theoretical rationale behind using SCN as the study material for

  10. Study of pore pressure reaction on hydraulic fracturing

    Science.gov (United States)

    Trimonova, Mariia; Baryshnikov, Nikolay; Turuntaev, Sergey; Zenchenko, Evgeniy; Zenchenko, Petr

    2017-04-01

    We represent the results of the experimental study of the hydraulic fracture propagation influence on the fluid pore pressure. Initial pore pressure was induced by injection and production wells. The experiments were carried out according to scaling analysis based on the radial model of the fracture. All required geomechanical and hydrodynamical properties of a sample were derived from the scaling laws. So, gypsum was chosen as a sample material and vacuum oil as a fracturing fluid. The laboratory setup allows us to investigate the samples of cylindrical shape. It can be considered as an advantage in comparison with standard cubic samples, because we shouldn't consider the stress field inhomogeneity induced by the corners. Moreover, we can set 3D-loading by this setting. Also the sample diameter is big enough (43cm) for placing several wells: the fracturing well in the center and injection and production wells on two opposite sides of the central well. The experiment consisted of several stages: a) applying the horizontal pressure; b) applying the vertical pressure; c) water solution injection in the injection well with a constant pressure; d) the steady state obtaining; e) the oil injection in the central well with a constant rate. The pore pressure was recorded in the 15 points along bottom side of the sample during the whole experiment. We observe the pore pressure change during all the time of the experiment. First, the pore pressure changed due to water injection. Then we began to inject oil in the central well. We compared the obtained experimental data on the pore pressure changes with the solution of the 2D single-phase equation of pore-elasticity, and we found significant difference. The variation of the equation parameters couldn't help to resolve the discrepancy. After the experiment, we found that oil penetrated into the sample before and after the fracture initiation. This fact encouraged us to consider another physical process - the oil

  11. Extraction of pores from microtomographic reconstructions of intact soil aggregates

    Energy Technology Data Exchange (ETDEWEB)

    Albee, P. B.; Stockman, G. C.; Smucker, A. J. M.

    2000-02-29

    Segmentation of features is often a necessary step in the analysis of volumetric data. The authors have developed a simple technique for extracting voids from irregular volumetric data sets. In this work they look at extracting pores from soil aggregates. First, they identify a threshold that gives good separability of the object from the background. They then segment the object, and perform connected components analysis on the pores within the object. Using their technique pores that break the surface can be segmented along with pores completely contained in the initially segmented object.

  12. Pore-scale Simulation and Imaging of Multi-phase Flow and Transport in Porous Media (Invited)

    Science.gov (United States)

    Crawshaw, J.; Welch, N.; Daher, I.; Yang, J.; Shah, S.; Grey, F.; Boek, E.

    2013-12-01

    We combine multi-scale imaging and computer simulation of multi-phase flow and reactive transport in rock samples to enhance our fundamental understanding of long term CO2 storage in rock formations. The imaging techniques include Confocal Laser Scanning Microscopy (CLSM), micro-CT and medical CT scanning, with spatial resolutions ranging from sub-micron to mm respectively. First, we report a new sample preparation technique to study micro-porosity in carbonates using CLSM in 3 dimensions. Second, we use micro-CT scanning to generate high resolution 3D pore space images of carbonate and cap rock samples. In addition, we employ micro-CT to image the processes of evaporation in fractures and cap rock degradation due to exposure to CO2 flow. Third, we use medical CT scanning to image spontaneous imbibition in carbonate rock samples. Our imaging studies are complemented by computer simulations of multi-phase flow and transport, using the 3D pore space images obtained from the scanning experiments. We have developed a massively parallel lattice-Boltzmann (LB) code to calculate the single phase flow field in these pore space images. The resulting flow fields are then used to calculate hydrodynamic dispersion using a novel scheme to predict probability distributions for molecular displacements using the LB method and a streamline algorithm, modified for optimal solid boundary conditions. We calculate solute transport on pore-space images of rock cores with increasing degree of heterogeneity: a bead pack, Bentheimer sandstone and Portland carbonate. We observe that for homogeneous rock samples, such as bead packs, the displacement distribution remains Gaussian with time increasing. In the more heterogeneous rocks, on the other hand, the displacement distribution develops a stagnant part. We observe that the fraction of trapped solute increases from the beadpack (0 %) to Bentheimer sandstone (1.5 %) to Portland carbonate (8.1 %), in excellent agreement with PFG

  13. Superplastically foaming method to make closed pores inclusive porous ceramics

    International Nuclear Information System (INIS)

    Kishimoto, Akira; Hayashi, Hidetaka

    2011-01-01

    Porous ceramics incorporates pores to improve several properties including thermal insulation maintaining inherenet ceramic properties such as corrosion resistance and large mechanical strength. Conventional porous ceramics is usually fabricated through an insufficient sintering. Since the sintering accompanies the exclusion of pores, it must be terminated at the early stage to maintain the high porosity, leading to degraded strength and durability. Contrary to this, we have innovated superplastically foaming method to make ceramic foams only in the solid state. In this method, the previously inserted foam agent evaporates after the full densification of matrix at around the sintering temperature. Closed pores expand utilizing the superplastic deformation driven by the evolved gas pressure. The typical features of this superplastically foaming method are listed as follows, 1. The pores are introduced after sintering the solid polycrystal. 2. Only closed pores are introduced, improving the insulation of gas and sound in addition to heat. 3. The pore walls are fully densified expecting a large mechanical strength. 4. Compared with the melt foaming method, this method is practical because the fabrication temperature is far below the melting point and it does not need molds. 5. The size and the location pores can be controlled by the amount and position of the foam agent.

  14. Co-Aromatization of Methane with Olefins: The Role of Inner Pore and External Surface Catalytic Sites

    Energy Technology Data Exchange (ETDEWEB)

    Yung, Matthew M [National Renewable Energy Laboratory (NREL), Golden, CO (United States); He, Peng [University of Calgary; Jarvis, Jack [University of Calgary; Meng, Shijun [University of Calgary; Wang, Aiguo [University of Calgary; Kou, Shiyu [University of Calgary; Gatip, Richard [University of Calgary; Liu, Lijia [Soochow University; Song, Hua [University of Calgary

    2018-04-22

    The co-aromatization of methane with olefins is investigated using Ag-Ga/HZSM-5 as the catalyst at 400 degrees C. The presence of methane has a pronounced effect on the product distribution in terms of increased average carbon number and substitution index and decreased aromatic carbon fraction compared with its N2 environment counterpart. The participation of methane during the co-aromatization over the Ag-Ga/HZSM-5 catalyst diminishes as the co-fed olefin feedstock molecule becomes larger, from 1-hexene to 1-octene and 1-decene, in diameter. The effect of suppressed methane participation with larger olefinic molecules is not as significant when Ag-Ga/HY is employed as the catalyst, which might be attributed to the larger pore size of HY that gives more room to hold olefin and methane molecules within the inner pores and reduces the diffusion limitation of olefin molecules. The effect of olefin feedstock on the methane participation during the co-aromatization over Ag-Ga/HZSM-5 is experimentally evidenced by 13C and 2D NMR. The incorporation of the methane carbon atoms into the phenyl ring of product molecules is reduced significantly with larger co-fed olefins, whereas its incorporation into the substitution groups of the formed aromatic molecules is not notably affected, suggesting that the methane participation in the phenyl ring formation might preferably occur within inner pores, while its incorporation into substitution groups may mainly take place on external catalytic sites. This hypothesis is well supported by the product selectivity obtained over Ag-Ga/HZSM-5 catalysts prepared using conventional ZSM-5, ZSM-5 with the external catalytic sites deactivated, nanosize ZSM-5, ZSM-5 with a micro/meso pore structure and ZSM-5 with the inner pores blocked, and further confirmed by the isotopic labeling studies.

  15. Stochastic generation of explicit pore structures by thresholding Gaussian random fields

    Energy Technology Data Exchange (ETDEWEB)

    Hyman, Jeffrey D., E-mail: jhyman@lanl.gov [Program in Applied Mathematics, University of Arizona, Tucson, AZ 85721-0089 (United States); Computational Earth Science, Earth and Environmental Sciences (EES-16), and Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, NM 87544 (United States); Winter, C. Larrabee, E-mail: winter@email.arizona.edu [Program in Applied Mathematics, University of Arizona, Tucson, AZ 85721-0089 (United States); Department of Hydrology and Water Resources, University of Arizona, Tucson, AZ 85721-0011 (United States)

    2014-11-15

    We provide a description and computational investigation of an efficient method to stochastically generate realistic pore structures. Smolarkiewicz and Winter introduced this specific method in pores resolving simulation of Darcy flows (Smolarkiewicz and Winter, 2010 [1]) without giving a complete formal description or analysis of the method, or indicating how to control the parameterization of the ensemble. We address both issues in this paper. The method consists of two steps. First, a realization of a correlated Gaussian field, or topography, is produced by convolving a prescribed kernel with an initial field of independent, identically distributed random variables. The intrinsic length scales of the kernel determine the correlation structure of the topography. Next, a sample pore space is generated by applying a level threshold to the Gaussian field realization: points are assigned to the void phase or the solid phase depending on whether the topography over them is above or below the threshold. Hence, the topology and geometry of the pore space depend on the form of the kernel and the level threshold. Manipulating these two user prescribed quantities allows good control of pore space observables, in particular the Minkowski functionals. Extensions of the method to generate media with multiple pore structures and preferential flow directions are also discussed. To demonstrate its usefulness, the method is used to generate a pore space with physical and hydrological properties similar to a sample of Berea sandstone. -- Graphical abstract: -- Highlights: •An efficient method to stochastically generate realistic pore structures is provided. •Samples are generated by applying a level threshold to a Gaussian field realization. •Two user prescribed quantities determine the topology and geometry of the pore space. •Multiple pore structures and preferential flow directions can be produced. •A pore space based on Berea sandstone is generated.

  16. METHODS FOR PORE WATER EXTRACTION FROM UNSATURATED ZONE TUFF, YUCCA MOUNTAIN, NEVADA

    International Nuclear Information System (INIS)

    K.M. SCOFIELD

    2006-01-01

    Assessing the performance of the proposed high-level radioactive waste repository at Yucca Mountain, Nevada, requires an understanding of the chemistry of the water that moves through the host rock. The uniaxial compression method used to extract pore water from samples of tuffaceous borehole core was successful only for nonwelded tuff. An ultracentrifugation method was adopted to extract pore water from samples of the densely welded tuff of the proposed repository horizon. Tests were performed using both methods to determine the efficiency of pore water extraction and the potential effects on pore water chemistry. Test results indicate that uniaxial compression is most efficient for extracting pore water from nonwelded tuff, while ultracentrifugation is more successful in extracting pore water from densely welded tuff. Pore water splits taken from a single nonwelded tuff core during uniaxial compression tests have shown changes in pore water chemistry with increasing pressure for calcium, chloride, sulfate, and nitrate, while the chemistry of pore water splits from welded and nonwelded tuffs using ultracentrifugation indicates that there is no significant fractionation of solutes

  17. Unstable Pore-Water Flow in Intertidal Wetlands

    Science.gov (United States)

    Barry, D. A.; Shen, C.; Li, L.

    2014-12-01

    Salt marshes are important intertidal wetlands strongly influenced by interactions between surface water and groundwater. Bordered by coastal water, the marsh system undergoes cycles of inundation and exposure driven by the tide. This leads to dynamic, complex pore-water flow and solute transport in the marsh soil. Pore-water circulations occur over vastly different spatial and temporal scales with strong link to the marsh topography. These circulations control solute transport between the marsh soil and the tidal creek, and ultimately affect the overall nutrient exchange between the marsh and coastal water. The pore-water flows also dictate the soil condition, particularly aeration, which influences the marsh plant growth. Numerous studies have been carried out to examine the pore-water flow process in the marsh soil driven by tides, focusing on stable flow with the assumption of homogeneity in soil and fluid properties. This assumption, however, is questionable given the actual inhomogeneous conditions in the field. For example, the salinity of surface water in the tidal creek varies temporally and spatially due to the influence of rainfall and evapotranspiration as well as the freshwater input from upland areas to the estuary, creating density gradients across the marsh surface and within the marsh soil. Many marshes possess soil stratigraphy with low-permeability mud typically overlying high-permeability sandy deposits. Macropores such as crab burrows are commonly distributed in salt marsh sediments. All these conditions are prone to the development of non-uniform, unstable preferential pore-water flow in the marsh soil, for example, funnelling and fingering. Here we present results from laboratory experiments and numerical simulations to explore such unstable flow. In particular, the analysis aims to address how the unstable flow modifies patterns of local pore-water movement and solute transport, as well as the overall exchange between the marsh soil and

  18. Preparation of Porous Stainless Steel Hollow-Fibers through Multi-Modal Particle Size Sintering towards Pore Engineering

    Directory of Open Access Journals (Sweden)

    Francois-Marie Allioux

    2017-08-01

    Full Text Available The sintering of metal powders is an efficient and versatile technique to fabricate porous metal elements such as filters, diffusers, and membranes. Neck formation between particles is, however, critical to tune the porosity and optimize mass transfer in order to minimize the densification process. In this work, macro-porous stainless steel (SS hollow-fibers (HFs were fabricated by the extrusion and sintering of a dope comprised, for the first time, of a bimodal mixture of SS powders. The SS particles of different sizes and shapes were mixed to increase the neck formation between the particles and control the densification process of the structure during sintering. The sintered HFs from particles of two different sizes were shown to be more mechanically stable at lower sintering temperature due to the increased neck area of the small particles sintered to the large ones. In addition, the sintered HFs made from particles of 10 and 44 μm showed a smaller average pore size (<1 μm as compared to the micron-size pores of sintered HFs made from particles of 10 μm only and those of 10 and 20 μm. The novel HFs could be used in a range of applications, from filtration modules to electrochemical membrane reactors.

  19. Pore-scale uncertainty quantification with multilevel Monte Carlo

    KAUST Repository

    Icardi, Matteo

    2014-01-06

    Computational fluid dynamics (CFD) simulations of pore-scale transport processes in porous media have recently gained large popularity. However the geometrical details of the pore structures can be known only in a very low number of samples and the detailed flow computations can be carried out only on a limited number of cases. The explicit introduction of randomness in the geometry and in other setup parameters can be crucial for the optimization of pore-scale investigations for random homogenization. Since there are no generic ways to parametrize the randomness in the porescale structures, Monte Carlo techniques are the most accessible to compute statistics. We propose a multilevel Monte Carlo (MLMC) technique to reduce the computational cost of estimating quantities of interest within a prescribed accuracy constraint. Random samples of pore geometries with a hierarchy of geometrical complexities and grid refinements, are synthetically generated and used to propagate the uncertainties in the flow simulations and compute statistics of macro-scale effective parameters.

  20. Nuclear Track-Etched Pore Membrane Production Using OAEP's Research Reactor

    International Nuclear Information System (INIS)

    Chittrakarn, Thawat; Bhongsuwan, Tripob; Wanichapichart, Pikul; Nuanuin, Paiboon; Chongkum, Somporn; Khonduangkaew, Areerat; Bordeepong, Sunaree

    2003-10-01

    Result of this study shows that the OAEP's nuclear research reactor is a good source of both fast and thermal neutrons for pore piercing process on polycarbonate thin film. With our experimental design, the fast neutron provides better results in pore piercing comparing with thermal neutron bombardment. This can be explained that most of the latent tracks that occur by thermal neutron bombardment do not piercing through the thin film. Chemical etching process using NaOH solution with an appropriated time, concentration and temperature was employed to enlarge the latent tracks in the bombarded film by fast neutrons. Fast neutron bombardment with 5, 10 and 20 minutes bombarding time successfully produces the nuclear track membrane. Pore size and pore density of the produced membranes examined by SEM were 0.24-1.01 μm and 4.67 - 245 x 10 6 pore/cm 2 , respectively. Bubble point test showed the maximum pore diameter of the produced membrane ranged between 1.18 - 3.25 μm. Water permeability was studied and compared between the produced and commercial membranes

  1. Bordetella adenylate cyclase toxin: a unique combination of a pore-forming moiety with a cell-invading adenylate cyclase enzyme

    Czech Academy of Sciences Publication Activity Database

    Mašín, Jiří; Osička, Radim; Bumba, Ladislav; Šebo, Peter

    2015-01-01

    Roč. 73, č. 8 (2015) ISSN 2049-632X R&D Projects: GA ČR GAP302/12/0460; GA ČR GA15-09157S; GA ČR(CZ) GA15-11851S Institutional support: RVO:61388971 Keywords : adenylate cyclase toxin * membrane penetration * pore-formation Subject RIV: EE - Microbiology, Virology Impact factor: 2.483, year: 2015

  2. Petrophysical Properties of the Yeso, Abo and Cisco Formations in the Permian Basin in New Mexico, U.S.A

    Science.gov (United States)

    Mann, Griffin

    The area that comprises the Northwest Shelf in Lea Co., New Mexico has been heavily drilled over the past half century. The main target being shallow reservoirs within the Permian section (San Andres and Grayburg Formations). With a focus shifting towards deeper horizons, there is a need for more petrophysical data pertaining to these formations, which is the focus of this study through a variety of techniques. This study involves the use of contact angle measurements, fluid imbibition tests, Mercury Injection Capillary Pressure (MICP) and log analysis to evaluate the nano-petrophysical properties of the Yeso, Abo and Cisco Formation within the Northwest Shelf area of southeast New Mexico. From contact angle measurements, all of the samples studied were found to be oil-wetting as n-decane spreads on to the rock surface much quicker than the other fluids (deionized water and API brine) tested. Imbibition tests resulted in a well-connected pore network being observed for all of the samples with the highest values of imbibition slopes being recorded for the Abo samples. MICP provided a variety of pore structure data which include porosity, pore-throat size distributions, permeability and tortuosity. The Abo samples saw the highest porosity percentages, which were above 15%, with all the other samples ranging from 4 - 7%. The majority of the pore-throat sizes for most of the samples fell within the 1 - 10 mum range. The only exceptions to this being the Paddock Member within the Yeso Formation, which saw a higher percentage of larger pores (10 - 1000mum) and one of the Cisco Formation samples, which had the majority of its pore sizes fall in the 0.1 - 1 mum range. The log analysis created log calculations and curves for cross-plot porosity and water saturation that were then used to derive a value for permeability. The porosity and permeability values were comparable with those measured from our MICP and literature values.

  3. Controlled synthesis of ordered mesoporous TiO{sub 2}-supported on activated carbon and pore-pore synergistic photocatalytic performance

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Chen; Li, Youji, E-mail: bcclyj@163.com; Xu, Peng; Li, Ming; Zeng, Mengxiong

    2015-01-15

    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

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

    Energy Technology Data Exchange (ETDEWEB)

    Taylor, Joshua E.L., E-mail: joshua.taylor@postgrad.manchester.ac.uk; Hall, Graham N., E-mail: graham.n.hall@manchester.ac.uk; Mummery, Paul M., E-mail: paul.m.mummery@manchester.ac.uk

    2016-03-15

    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. - Highlights: • Effects of stress on pore structures of Gilsocarbon and PGA graphites were studied. • Application of a compressive load was used to generate stresses in graphite. • Inverse linear relationship between stress and pore area was observed. • Mean pore eccentricity increased, clockwise pore rotation observed. • Separation of pores quantified using Voronoi and ‘nearest-neighbour’ methods.

  5. Effect of porosity and pore morphology on the low-frequency ...

    Indian Academy of Sciences (India)

    Effect of porosity and pore size distribution on the low-frequency dielectric response, in the range 0.01-100 kHz, in sintered ZrO2-8 mol% Y2O3 ceramic compacts have been investigated. Small-angle neutron scattering (SANS) technique has been employed to obtain the pore characteristics like pore size distribution, ...

  6. Pore-water chemistry explains zinc phytotoxicity in soil.

    Science.gov (United States)

    Kader, Mohammed; Lamb, Dane T; Correll, Ray; Megharaj, Mallavarapu; Naidu, Ravi

    2015-12-01

    Zinc (Zn) is a widespread soil contaminant arising from a numerous anthropogenic sources. However, adequately predicting toxicity of Zn to ecological receptors remains difficult due to the complexity of soil characteristics. In this study, we examined solid-solution partitioning using pore-water data and toxicity of Zn to cucumber (Cucumis sativus L.) in spiked soils. Pore-water effective concentration (ECx, x=10%, 20% and 50% reduction) values were negatively related to pH, indicating lower Zn pore water concentration were needed to cause phytotoxicity at high pH soils. Total dissolved zinc (Znpw) and free zinc (Zn(2+)) in soil-pore water successfully described 78% and 80.3% of the variation in relative growth (%) in the full dataset. When the complete data set was used (10 soils), the estimated EC50pw was 450 and 79.2 µM for Znpw and Zn(2+), respectively. Total added Zn, soil pore water pH (pHpw) and dissolve organic carbon (DOC) were the best predictors of Znpw and Zn(2+) in pore-water. The EC10 (total loading) values ranged from 179 to 5214 mg/kg, depending on soil type. Only pH measurements in soil were related to ECx total Zn data. The strongest relationship to ECx overall was pHca, although pHw and pHpw were in general related to Zn ECx. Similarly, when a solution-only model was used to predict Zn in shoot, DOC was negatively related to Zn in shoot, indicating a reduction in uptake/ translocation of Zn from solution with increasing DOC. Copyright © 2015 Elsevier Inc. All rights reserved.

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

    Science.gov (United States)

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

    2017-12-01

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

  8. Effects of intermediate wettability on entry capillary pressure in angular pores.

    Science.gov (United States)

    Rabbani, Harris Sajjad; Joekar-Niasar, Vahid; Shokri, Nima

    2016-07-01

    Entry capillary pressure is one of the most important factors controlling drainage and remobilization of the capillary-trapped phases as it is the limiting factor against the two-phase displacement. It is known that the entry capillary pressure is rate dependent such that the inertia forces would enhance entry of the non-wetting phase into the pores. More importantly the entry capillary pressure is wettability dependent. However, while the movement of a meniscus into a strongly water-wet pore is well-defined, the invasion of a meniscus into a weak or intermediate water-wet pore especially in the case of angular pores is ambiguous. In this study using OpenFOAM software, high-resolution direct two-phase flow simulations of movement of a meniscus in a single capillary channel are performed. Interface dynamics in angular pores under drainage conditions have been simulated under constant flow rate boundary condition at different wettability conditions. Our results shows that the relation between the half corner angle of pores and contact angle controls the temporal evolution of capillary pressure during the invasion of a pore. By deviating from pure water-wet conditions, a dip in the temporal evolution of capillary pressure can be observed which will be pronounced in irregular angular cross sections. That enhances the pore invasion with a smaller differential pressure. The interplay between the contact angle and pore geometry can have significant implications for enhanced remobilization of ganglia in intermediate contact angles in real porous media morphologies, where pores are very heterogeneous with small shape factors. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

  9. Comparison of predicted and observed pore pressure increases on Rio Blanco

    International Nuclear Information System (INIS)

    Banister, J.R.; Ellett, D.M.; Pyke, R.; Winters, L.

    1976-01-01

    The RIO BLANCO event presented the opportunity to monitor, under controlled conditions in the field, the increase in pore pressures resulting from ground motion similar to an earthquake. In situ measurements of pore pressure changes were made by Sandia Laboratories and Dames and Moore. This report contains the results of laboratory tests believed to be indicative in assessing the magnitude of pore pressure increases and probability of soil liquefaction. These include triaxial load tests, gradation of grain size, and relative density. No liquefaction was observed in the field, and the increase of in situ pore pressures were much less than expected from laboratory measurements. Allied subjects presented in this report are pore pressure propagation and dissipation profiles, the previously unpublished pore pressure measurements made by Dames and Moore, and the boring logs for the various sites where measurements were taken. It is concluded that methods used to predict pore pressure increases and liquefaction potential are overly conservative, at least for these alluvial and colluvial soils found in Colorado

  10. Effect of diffuse layer and pore shapes in mesoporous carbon supercapacitors

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Jingsong [ORNL; Sumpter, Bobby G [ORNL; Meunier, Vincent [ORNL; Qiao, Rui [ORNL

    2010-01-01

    In the spirit of the theoretical evolution from the Helmholtz model to the Gouy Chapman Stern model for electric double-layer capacitors, we explored the effect of a diffuse layer on the capacitance of mesoporous carbon supercapacitors by solving the Poisson Boltzmann (PB) equation in mesopores of diameters from 2 to 20 nm. To evaluate the effect of pore shape, both slit and cylindrical pores were considered. We found that the diffuse layer does not affect the capacitance significantly. For slit pores, the area-normalized capacitance is nearly independent of pore size, which is not experimentally observed for template carbons. In comparison, for cylindrical pores, PB simulations produce a trend of slightly increasing area-normalized capacitance with pore size, similar to that depicted by the electric double-cylinder capacitor model proposed earlier. These results indicate that it is appropriate to approximate the pore shape of mesoporous carbons as being cylindrical and the electric double-cylinder capacitor model should be used for mesoporous carbons as a replacement of the traditional Helmholtz model.

  11. Diode-like properties of single- and multi-pore asymmetric track membranes

    Science.gov (United States)

    Zielinska, K.; Gapeeva, A. R.; Orelovich, O. L.; Apel, P. Yu.

    2014-05-01

    In this work, we investigated the ionic transport properties of asymmetric polyethylene terephthalate (PET) track membranes with the thickness of 5 μm. The samples containing single pores and arrays of many pores were fabricated by irradiation with accelerated ions and subsequent physicochemical treatment. The method of etching in the presence of a surface-active agent was used to prepare the pores with highly-tapered tip. The transport of monovalent inorganic ions through the nano-scale holes was studied in a conductivity cell. The effective pore radii, electrical conductance and rectification ratios of pores were measured. The geometric characteristics of nanopores were investigated using FESEM.

  12. Dendritic silica particles with center-radial pore channels: promising platforms for catalysis and biomedical applications.

    Science.gov (United States)

    Du, Xin; Qiao, Shi Zhang

    2015-01-27

    Dendritic silica micro-/nanoparticles with center-radial pore structures, a kind of newly created porous material, have attracted considerable attention owing to their unique open three-dimensional dendritic superstructures with large pore channels and highly accessible internal surface areas compared with conventional mesoporous silica nanoparticles (MSNs). They are very promising platforms for a variety of applications in catalysis and nanomedicine. In this review, their unique structural characteristics and properties are first analyzed, then novel and interesting synthesis methods associated with the possible formation mechanisms are summarized to provide material scientists some inspiration for the preparation of this kind of dendritic particles. Subsequently, a few examples of interesting applications are presented, mainly in catalysis, biomedicine, and other important fields such as for sacrificial templates and functional coatings. The review is concluded with an outlook on the prospects and challenges in terms of their controlled synthesis and potential applications. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. New methodology of preparation support for solid oxide fuel cells using different pore forming agent

    Energy Technology Data Exchange (ETDEWEB)

    Fiuza, Raigenis da P.; Guedes, Bruna C.F.; Silva, Marcos A. da; Carvalho, Luiz F.V. de; Boaventura, Jaime S. [Universidade Federal da Bahia (IQ/UFBA), Salvador, BA (Brazil). Inst. de Quimica; Pontes, Luiz A.M. [Universidade Federal da Bahia (EP/UFBA), Salvador, BA (Brazil). Escola Politecnica. Programa de Pos-Graduacao em Engenharia Quimica

    2008-07-01

    The development of environment-friendly energy sources has been of the most important scientific and technological area. Solid oxide fuel cells (SOFC) are very promising alternative for their ability to handle renewable fuels with low emissions and high efficiency. However, this device requires massive improvement before commercial application. This work studies the pore formation in the cell anode and cathode with NaHCO{sub 3} or citric acid, comparing to graphite. The three agents make pore with similar features, but the use of NaHCO{sub 3} and citric acid considerably improves the adhesion of the electrode-electrolyte interface, critical characteristic for good cell efficiency. The prepared anode-electrolyte-cathode structure was studied by SEM technique. The SOFC prepared using citric acid was tested with gaseous ethanol, natural gas and hydrogen. For all these three fuels the SOFC shows virtually no overpotential, indicating the good ionic conductance of the electrodes-electrolyte interface.. (author)

  14. 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.

  15. Pore Structure Model for Predicting Elastic Wavespeeds in Fluid-Saturated Sandstones

    Science.gov (United States)

    Zimmerman, R. W.; David, E. C.

    2011-12-01

    During hydrostatic compression, in the elastic regime, ultrasonic P and S wave velocities measured on rock cores generally increase with pressure, and reach asymptotic values at high pressures. The pressure dependence of seismic velocities is generally thought to be due to the closure of compliant cracks, in which case the high-pressure velocities must reflect only the influence of the non-closable, equant "pores". Assuming that pores can be represented by spheroids, we can relate the elastic properties to the pore structure using an effective medium theory. Moreover, the closure pressure of a thin crack-like pore is directly proportional to its aspect ratio. Hence, our first aim is to use the pressure dependence of seismic velocities to invert the aspect ratio distribution. We use a simple analytical algorithm developed by Zimmerman (Compressibility of Sandstones, 1991), which can be used for any effective medium theory. Previous works have used overly restrictive assumptions, such as assuming that the stiff pores are spherical, or that the interactions between pores can be neglected. Here, we assume that the rock contains an exponential distribution of crack aspect ratios, and one family of stiff pores having an aspect ratio lying somewhere between 0.01 and 1. We develop our model in two versions, using the Differential Scheme, and the Mori-Tanaka scheme. The inversion is done using data obtained in dry experiments, since pore fluids have a strong effect on velocities and tend to mask the effect of the pore geometry. This avoids complicated joint inversion of dry and wet data, such as done by Cheng and Toksoz (JGR, 1979). Our results show that for many sets of data on sandstones, we can fit very well the dry velocities. Our second aim is to predict the saturated velocities from our pore structure model, noting that at a given differential stress, the pore structure should be the same as for a dry test. Our results show that the Biot-Gassmann predictions always

  16. Formate supplementation enhances folate-dependent nucleotide biosynthesis and prevents spina bifida in a mouse model of folic acid-resistant neural tube defects.

    Science.gov (United States)

    Sudiwala, Sonia; De Castro, Sandra C P; Leung, Kit-Yi; Brosnan, John T; Brosnan, Margaret E; Mills, Kevin; Copp, Andrew J; Greene, Nicholas D E

    2016-07-01

    The curly tail mouse provides a model for neural tube defects (spina bifida and exencephaly) that are resistant to prevention by folic acid. The major ct gene, responsible for spina bifida, corresponds to a hypomorphic allele of grainyhead-like 3 (Grhl3) but the frequency of NTDs is strongly influenced by modifiers in the genetic background. Moreover, exencephaly in the curly tail strain is not prevented by reinstatement of Grhl3 expression. In the current study we found that expression of Mthfd1L, encoding a key component of mitochondrial folate one-carbon metabolism (FOCM), is significantly reduced in ct/ct embryos compared to a partially congenic wild-type strain. This expression change is not attributable to regulation by Grhl3 or the genetic background at the Mthfd1L locus. Mitochondrial FOCM provides one-carbon units as formate for FOCM reactions in the cytosol. We found that maternal supplementation with formate prevented NTDs in curly tail embryos and also resulted in increased litter size. Analysis of the folate profile of neurulation-stage embryos showed that formate supplementation resulted in an increased proportion of formyl-THF and THF but a reduction in proportion of 5-methyl THF. In contrast, THF decreased and 5-methyl THF was relatively more abundant in the liver of supplemented dams than in controls. In embryos cultured through the period of spinal neurulation, incorporation of labelled thymidine and adenine into genomic DNA was suppressed by supplemental formate, suggesting that de novo folate-dependent biosynthesis of nucleotides (thymidylate and purines) was enhanced. We hypothesise that reduced Mthfd1L expression may contribute to susceptibility to NTDs in the curly tail strain and that formate acts as a one-carbon donor to prevent NTDs. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

  17. Understanding capillary condensation and hysteresis in porous silicon: network effects within independent pores.

    Science.gov (United States)

    Naumov, Sergej; Khokhlov, Alexey; Valiullin, Rustem; Kärger, Jörg; Monson, Peter A

    2008-12-01

    The ability to exert a significant degree of pore structure control in porous silicon materials has made them attractive materials for the experimental investigation of the relationship between pore structure, capillary condensation, and hysteresis phenomena. Using both experimental measurements and a lattice gas model in mean field theory, we have investigated the role of pore size inhomogeneities and surface roughness on capillary condensation of N2 at 77K in porous silicon with linear pores. Our results resolve some puzzling features of earlier experimental work. We find that this material has more in common with disordered materials such as Vycor glass than the idealized smooth-walled cylindrical pores discussed in the classical adsorption literature. We provide strong evidence that this behavior comes from the complexity of the processes within independent linear pores, arising from the pore size inhomogeneities along the pore axis, rather than from cooperative effects between different pores.

  18. Invariance of single-file water mobility in gramicidin-like peptidic pores as function of pore length.

    Science.gov (United States)

    Portella, Guillem; Pohl, Peter; de Groot, Bert L

    2007-06-01

    We investigated the structural and energetic determinants underlying water permeation through peptidic nanopores, motivated by recent experimental findings that indicate that water mobility in single-file water channels displays nonlinear length dependence. To address the molecular mechanism determining the observed length dependence, we studied water permeability in a series of designed gramicidin-like channels of different length using atomistic molecular dynamics simulations. We found that within the studied range of length the osmotic water permeability is independent of pore length. This result is at variance with textbook models, where the relationship is assumed to be linear. Energetic analysis shows that loss of solvation rather than specific water binding sites in the pore form the main energetic barrier for water permeation, consistent with our dynamics results. For this situation, we propose a modified expression for osmotic permeability that fully takes into account water motion collectivity and does not depend on the pore length. Different schematic barrier profiles are discussed that explain both experimental and computational interpretations, and we propose a set of experiments aimed at validation of the presented results. Implications of the results for the design of peptidic channels with desired permeation characteristics are discussed.

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

    International Nuclear Information System (INIS)

    Boher, Cedric; Frizon, Fabien; Bart, Florence; Lorente, Sylvie

    2013-01-01

    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)

  20. Effective porosity and pore-throat sizes of Conasauga Group mudrock: Application, test and evaluation of petrophysical techniques

    International Nuclear Information System (INIS)

    Dorsch, J.; Katsube, T.J.; Sanford, W.E.; Univ. of Tennessee, Knoxville, TN; Dugan, B.E.; Tourkow, L.M.

    1996-04-01

    Effective porosity (specifically referring to the interconnected pore space) was recently recognized as being essential in determining the effectiveness and extent of matrix diffusion as a transport mechanism within fractured low-permeability rock formations. The research presented in this report was performed to test the applicability of several petrophysical techniques for the determination of effective porosity of fine-grained siliciclastic rocks. In addition, the aim was to gather quantitative data on the effective porosity of Conasauga Group mudrock from the Oak Ridge Reservation (ORR). The quantitative data reported here include not only effective porosities based on diverse measurement techniques, but also data on the sizes of pore throats and their distribution, and specimen bulk and grain densities. The petrophysical techniques employed include the immersion-saturation method, mercury and helium porosimetry, and the radial diffusion-cell method

  1. Characterization of chemical composition, surface area pore, and thermal properties of zeolites from Bayah, Tasikmalaya, and Lampung

    International Nuclear Information System (INIS)

    Ginting, Aslina Br.; Dian Anggraini; Sutri Indaryati; Rosika Kriswarini

    2007-01-01

    Characterization of chemical composition, surface area, pore radius, adsorption, and thermal properties of zeolites from Bayah, Tasikmalaya, and Lampung have been performed. The purpose of the characterization is to understand the characteristics of the three zeolites since different types of zeolite will yield different chemical composition, surface area, pore radius, and adsorption. The analysis shows that zeolites from Bayah, Tasikmalaya, and Lampung consist of chemical elements Al, Si, P, K, Ca, Ti, Fe, and S. The analysis of the surface area indicates that zeolite from Lampung has surface area of 10.0477 m 2 , pore radius of 16.0653 Å, and adsorption of 24.500 ml/g, which are greater than those of zeolite from Tasikmalaya with surface area of 6.3319 m2, pore radius of 16.2350 Å, adsorption of 13.2500 ml/g, zeolite from Bayah with surface area of 8.3528 m2, pore radius of 16.2350 Å, and adsorption of 13.250 ml/g. From of the thermal properties characterization it is shown the three zeolites experienced weight reduction from 5.93% to 8.33%, which results in the formation of new phases as indicated by endothermic reactions from 150 °C to 600 °C and from 850 °C to 1000 °C. The three zeolites experienced a decrease in heat capacity up to temperature of 199.96 °C, whereas at temperatures above 216.66 °C the zeolites experienced an increase in heat capacity up to 437.78 °C. The results of the characterization indicate that different types of zeolite do not yield significant difference in chemical composition and thermal characteristics as proven with F test, however different surface area, pore radius, and adsorption characteristics are observed. The characterization results are expected to be the first step in determining the characteristics of the three zeolites that are to be used for cesium ion exchange in the incoming research. (author)

  2. Direct Numerical Simulation of Low Capillary Number Pore Scale Flows

    Science.gov (United States)

    Esmaeilzadeh, S.; Soulaine, C.; Tchelepi, H.

    2017-12-01

    The arrangement of void spaces and the granular structure of a porous medium determines multiple macroscopic properties of the rock such as porosity, capillary pressure, and relative permeability. Therefore, it is important to study the microscopic structure of the reservoir pores and understand the dynamics of fluid displacements through them. One approach for doing this, is direct numerical simulation of pore-scale flow that requires a robust numerical tool for prediction of fluid dynamics and a detailed understanding of the physical processes occurring at the pore-scale. In pore scale flows with a low capillary number, Eulerian multiphase methods are well-known to produce additional vorticity close to the interface. This is mainly due to discretization errors which lead to an imbalance of capillary pressure and surface tension forces that causes unphysical spurious currents. At the pore scale, these spurious currents can become significantly stronger than the average velocity in the phases, and lead to unphysical displacement of the interface. In this work, we first investigate the capability of the algebraic Volume of Fluid (VOF) method in OpenFOAM for low capillary number pore scale flow simulations. Afterward, we compare VOF results with a Coupled Level-Set Volume of Fluid (CLSVOF) method and Iso-Advector method. It has been shown that the former one reduces the VOF's unphysical spurious currents in some cases, and both are known to capture interfaces sharper than VOF. As the conclusion, we will investigate that whether the use of CLSVOF or Iso-Advector will lead to less spurious velocities and more accurate results for capillary driven pore-scale multiphase flows or not. Keywords: Pore-scale multiphase flow, Capillary driven flows, Spurious currents, OpenFOAM

  3. Inter-subunit interactions across the upper voltage sensing-pore domain interface contribute to the concerted pore opening transition of Kv channels.

    Directory of Open Access Journals (Sweden)

    Tzilhav Shem-Ad

    Full Text Available The tight electro-mechanical coupling between the voltage-sensing and pore domains of Kv channels lies at the heart of their fundamental roles in electrical signaling. Structural data have identified two voltage sensor pore inter-domain interaction surfaces, thus providing a framework to explain the molecular basis for the tight coupling of these domains. While the contribution of the intra-subunit lower domain interface to the electro-mechanical coupling that underlies channel opening is relatively well understood, the contribution of the inter-subunit upper interface to channel gating is not yet clear. Relying on energy perturbation and thermodynamic coupling analyses of tandem-dimeric Shaker Kv channels, we show that mutation of upper interface residues from both sides of the voltage sensor-pore domain interface stabilizes the closed channel state. These mutations, however, do not affect slow inactivation gating. We, moreover, find that upper interface residues form a network of state-dependent interactions that stabilize the open channel state. Finally, we note that the observed residue interaction network does not change during slow inactivation gating. The upper voltage sensing-pore interaction surface thus only undergoes conformational rearrangements during channel activation gating. We suggest that inter-subunit interactions across the upper domain interface mediate allosteric communication between channel subunits that contributes to the concerted nature of the late pore opening transition of Kv channels.

  4. Inter-subunit interactions across the upper voltage sensing-pore domain interface contribute to the concerted pore opening transition of Kv channels.

    Science.gov (United States)

    Shem-Ad, Tzilhav; Irit, Orr; Yifrach, Ofer

    2013-01-01

    The tight electro-mechanical coupling between the voltage-sensing and pore domains of Kv channels lies at the heart of their fundamental roles in electrical signaling. Structural data have identified two voltage sensor pore inter-domain interaction surfaces, thus providing a framework to explain the molecular basis for the tight coupling of these domains. While the contribution of the intra-subunit lower domain interface to the electro-mechanical coupling that underlies channel opening is relatively well understood, the contribution of the inter-subunit upper interface to channel gating is not yet clear. Relying on energy perturbation and thermodynamic coupling analyses of tandem-dimeric Shaker Kv channels, we show that mutation of upper interface residues from both sides of the voltage sensor-pore domain interface stabilizes the closed channel state. These mutations, however, do not affect slow inactivation gating. We, moreover, find that upper interface residues form a network of state-dependent interactions that stabilize the open channel state. Finally, we note that the observed residue interaction network does not change during slow inactivation gating. The upper voltage sensing-pore interaction surface thus only undergoes conformational rearrangements during channel activation gating. We suggest that inter-subunit interactions across the upper domain interface mediate allosteric communication between channel subunits that contributes to the concerted nature of the late pore opening transition of Kv channels.

  5. Confocal pore size measurement based on super-resolution image restoration.

    Science.gov (United States)

    Liu, Dali; Wang, Yun; Qiu, Lirong; Mao, Xinyue; Zhao, Weiqian

    2014-09-01

    A confocal pore size measurement based on super-resolution image restoration is proposed to obtain a fast and accurate measurement for submicrometer pore size of nuclear track-etched membranes (NTEMs). This method facilitates the online inspection of the pore size evolution during etching. Combining confocal microscopy with super-resolution image restoration significantly improves the lateral resolution of the NTEM image, yields a reasonable circle edge-setting criterion of 0.2408, and achieves precise pore edge detection. Theoretical analysis shows that the minimum measuring diameter can reach 0.19 μm, and the root mean square of the residuals is only 1.4 nm. Edge response simulation and experiment reveal that the edge response of the proposed method is better than 80 nm. The NTEM pore size measurement results obtained by the proposed method agree well with that obtained by scanning electron microscopy.

  6. FORMATION OF THE PENUMBRA AND START OF THE EVERSHED FLOW

    Energy Technology Data Exchange (ETDEWEB)

    Murabito, M.; Guglielmino, S. L.; Zuccarello, F. [Dipartimento di Fisica e Astronomia—Sezione Astrofisica, Università degli Studi di Catania, Via S. Sofia 78, I-95123 Catania (Italy); Romano, P. [INAF—Osservatorio Astrofisico di Catania, Via S. Sofia 78, I-95123 Catania (Italy); Solanki, S. K., E-mail: mmurabito@oact.inaf.it [Max-Planck-Institut für Sonnensystemforschung Justus-von-Liebig-Weg 3, D-37077 Göttingen (Germany)

    2016-07-01

    We studied the variations of line of sight photospheric plasma flows during the formation phase of the penumbra around a pore in active region NOAA 11490. We used a high spatial, spectral, and temporal resolution data set acquired by the Interferometric BIdimensional Spectrometer operating at the NSO/Dunn Solar Telescope as well as data taken by the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory satellite ( SDO /HMI). Before the penumbra formed we observed a redshift of the spectral line in the inner part of the annular zone surrounding the pore as well as a blueshift of material associated with opposite magnetic polarity farther away from the pore. We found that the onset of the classical Evershed flow occurs on a very short timescale (1 to 3 hr) while the penumbra is forming. During the same time interval we found changes in the magnetic field inclination in the penumbra, with the vertical field actually changing sign near the penumbral edge, while the total magnetic field showed a significant increase, about 400 G. To explain these and other observations related to the formation of the penumbra and the onset of the Evershed flow we propose a scenario in which the penumbra is formed by magnetic flux dragged down from the canopy surrounding the initial pore. The Evershed flow starts when the sinking magnetic field dips below the solar surface and magnetoconvection sets in.

  7. Preparation by the nano-casting process of novel porous carbons from large pore zeolite templates

    International Nuclear Information System (INIS)

    F Gaslain; J Parmentier; V Valtchev; J Patarin; C Vix Guterl

    2005-01-01

    The development of new growing industrial applications such as gas storage (e.g.: methane or hydrogen) or electric double-layer capacitors has focussed the attention of many research groups. For this kind of application, porous carbons with finely tailored micro-porosity (i.e.: pore size diameter ≤ 1 nm) appear as very promising materials due to their high surface area and their specific pore size distribution. In order to meet these requirements, attention has been paid towards the feasibility of preparing microporous carbons by the nano-casting process. Since the sizes and shapes of the pores and walls respectively become the walls and pores of the resultant carbons, using templates with different framework topologies leads to various carbon replicas. The works performed with commercially available zeolites employed as templates [1-4] showed that the most promising candidate is the FAU-type zeolite, which is a large zeolite with three-dimensional channel system. The promising results obtained on FAU-type matrices encouraged us to study the microporous carbon formation on large pore zeolites synthesized in our laboratory, such as EMC-1 (International Zeolite Association framework type FAU), zeolite β (BEA) or EMC-2 (EMT). The carbon replicas were prepared following largely the nano-casting method proposed for zeolite Y by the Kyotani research group [4]: either by liquid impregnation of furfuryl alcohol (FA) followed by carbonization or by vapour deposition (CVD) of propylene, or by an association of these two processes. Heat treatment of the mixed materials (zeolite / carbon) could also follow in order to improve the structural ordering of the carbon. After removal of the inorganic template by an acidic treatment, the carbon materials obtained were characterised by several analytical techniques (XRD, N 2 and CO 2 adsorption, electron microscopy, etc...). The unique characteristics of these carbons are discussed in details in this paper and compared to those

  8. Capillary condensation hysteresis in overlapping spherical pores: a Monte Carlo simulation study.

    Science.gov (United States)

    Gor, Gennady Yu; Rasmussen, Christopher J; Neimark, Alexander V

    2012-08-21

    The mechanisms of hysteretic phase transformations in fluids confined to porous bodies depend on the size and shape of pores, as well as their connectivity. We present a Monte Carlo simulation study of capillary condensation and evaporation cycles in the course of Lennard-Jones fluid adsorption in the system of overlapping spherical pores. This model system mimics pore shape and connectivity in some mesoporous materials obtained by templating cubic surfactant mesophases or colloidal crystals. We show different mechanisms of capillary hysteresis depending on the size of the window between the pores. For the system with a small window, the hysteresis cycle is similar to that in a single spherical pore: capillary condensation takes place upon achieving the limit of stability of adsorption film and evaporation is triggered by cavitation. When the window is large enough, the capillary condensation shifts to a pressure higher than that of the isolated pore, and the possibility for the equilibrium mechanism of desorption is revealed. These finding may have important implications for practical problems of assessment of the pore size distributions in mesoporous materials with cagelike pore networks.

  9. Sediment pore-water interactions associated with arsenic and uranium transport from the North Cave Hills mining region, South Dakota, USA

    International Nuclear Information System (INIS)

    Larson, Lance N.; Kipp, Gregory G.; Mott, Henry V.; Stone, James J.

    2012-01-01

    increased Fe reduction processes. Geochemical modeling suggests solid-phase Fe reduction promotes the liberation of pore-water As and U via suppressing the formation of thioarsenite. Intermittent hydrological processes facilitate As and U transport and deposition throughout the watershed, while biogeochemical-influenced redox changes cycle As and U between pore and surface water within localized environments.

  10. Pore forming polyalkylpyridinium salts from marine sponges versus synthetic lipofection systems: distinct tools for intracellular delivery of cDNA and siRNA.

    Science.gov (United States)

    McLaggan, Debra; Adjimatera, Noppadon; Sepcić, Kristina; Jaspars, Marcel; MacEwan, David J; Blagbrough, Ian S; Scott, Roderick H

    2006-01-16

    Haplosclerid marine sponges produce pore forming polyalkylpyridinium salts (poly-APS), which can be used to deliver macromolecules into cells. The aim of this study was to investigate the delivery of DNA, siRNA and lucifer yellow into cells mediated by poly-APS and its potential mechanisms as compared with other lipofection systems (lipofectamine and N4,N9-dioleoylspermine (LipoGen)). DNA condensation was evaluated and HEK 293 and HtTA HeLa cells were used to investigate pore formation and intracellular delivery of cDNA, siRNA and lucifer yellow. Poly-APS and LipoGen were both found to be highly efficient DNA condensing agents. Fura-2 calcium imaging was used to measure calcium transients indicative of cell membrane pore forming activity. Calcium transients were evoked by poly-APS but not LipoGen and lipofectamine. The increases in intracellular calcium produced by poly-APS showed temperature sensitivity with greater responses being observed at 12 degrees C compared to 21 degrees C. Similarly, delivery of lucifer yellow into cells with poly-APS was enhanced at lower temperatures. Transfection with cDNA encoding for the expression enhanced green fluorescent protein was also evaluated at 12 degrees C with poly-APS, lipofectamine and LipoGen. Intracellular delivery of siRNA was achieved with knockdown in beta-actin expression when lipofectamine and LipoGen were used as transfection reagents. However, intracellular delivery of siRNA was not achieved with poly-APS. Poly-APS mediated pore formation is critical to its activity as a transfection reagent, but lipofection systems utilise distinct mechanisms to enable delivery of DNA and siRNA into cells.

  11. Pore forming polyalkylpyridinium salts from marine sponges versus synthetic lipofection systems: distinct tools for intracellular delivery of cDNA and siRNA

    Directory of Open Access Journals (Sweden)

    Blagbrough Ian S

    2006-01-01

    Full Text Available Abstract Background Haplosclerid marine sponges produce pore forming polyalkylpyridinium salts (poly-APS, which can be used to deliver macromolecules into cells. The aim of this study was to investigate the delivery of DNA, siRNA and lucifer yellow into cells mediated by poly-APS and its potential mechanisms as compared with other lipofection systems (lipofectamine and N4,N9-dioleoylspermine (LipoGen. DNA condensation was evaluated and HEK 293 and HtTA HeLa cells were used to investigate pore formation and intracellular delivery of cDNA, siRNA and lucifer yellow. Results Poly-APS and LipoGen were both found to be highly efficient DNA condensing agents. Fura-2 calcium imaging was used to measure calcium transients indicative of cell membrane pore forming activity. Calcium transients were evoked by poly-APS but not LipoGen and lipofectamine. The increases in intracellular calcium produced by poly-APS showed temperature sensitivity with greater responses being observed at 12°C compared to 21°C. Similarly, delivery of lucifer yellow into cells with poly-APS was enhanced at lower temperatures. Transfection with cDNA encoding for the expression enhanced green fluorescent protein was also evaluated at 12°C with poly-APS, lipofectamine and LipoGen. Intracellular delivery of siRNA was achieved with knockdown in beta-actin expression when lipofectamine and LipoGen were used as transfection reagents. However, intracellular delivery of siRNA was not achieved with poly-APS. Conclusion Poly-APS mediated pore formation is critical to its activity as a transfection reagent, but lipofection systems utilise distinct mechanisms to enable delivery of DNA and siRNA into cells.

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

    Science.gov (United States)

    Ohtsu, Hiroyoshi; Kawano, Masaki

    2016-01-14

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

  13. Time evolution of pore system in lime - Pozzolana composites

    Science.gov (United States)

    Doleželová, Magdaléna; Čáchová, Monika; Scheinherrová, Lenka; Keppert, Martin

    2017-11-01

    The lime - pozzolana mortars and plasters are used in restoration works on building cultural heritage but these materials are also following the trend of energy - efficient solutions in civil engineering. Porosity and pore size distribution is one of crucial parameters influencing engineering properties of porous materials. The pore size distribution of lime based system is changing in time due to chemical processes occurring in the material. The present paper describes time evolution of pore system in lime - pozzolana composites; the obtained results are useful in prediction of performance of lime - pozzolana systems in building structures.

  14. Effect of Pore Geometry on Gas Adsorption: Grand Canonical Monte Carlo Simulation Studies

    International Nuclear Information System (INIS)

    Lee, Eon Ji; Chang, Rak Woo; Han, Ji Hyung; Chung, Taek Dong

    2012-01-01

    In this study, we investigated the pure geometrical effect of porous materials in gas adsorption using the grand canonical Monte Carlo simulations of primitive gas-pore models with various pore geometries such as planar, cylindrical, and random pore geometries. Although the model does not possess atomistic level details of porous materials, our simulation results provided many insightful information in the effect of pore geometry on the adsorption behavior of gas molecules. First, the surface curvature of porous materials plays a significant role in the amount of adsorbed gas molecules: the concave surface such as in cylindrical pores induces more attraction between gas molecules and pore, which results in the enhanced gas adsorption. On the contrary, the convex surface of random pores gives the opposite effect. Second, this geometrical effect shows a nonmonotonic dependence on the gas-pore interaction strength and length. Third, as the external gas pressure is increased, the change in the gas adsorption due to pore geometry is reduced. Finally, the pore geometry also affects the collision dynamics of gas molecules. Since our model is based on primitive description of fluid molecules, our conclusion can be applied to any fluidic systems including reactant-electrode systems

  15. The hydraulic conductivity of sediments: A pore size perspective

    KAUST Repository

    Ren, X.W.; Santamarina, Carlos

    2017-01-01

    in the void ratio is higher than the theoretical value due to two concurrent phenomena: 1) percolating large pores are responsible for most of the flow, and 2) the larger pores close first during compaction. The prediction of hydraulic conductivity based

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

    Science.gov (United States)

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

    2018-03-01

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

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

    Science.gov (United States)

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

    2018-03-22

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

  18. Coarse and fine root plants affect pore size distributions differently

    OpenAIRE

    Bodner, G.; Leitner, D.; Kaul, H.-P.

    2014-01-01

    Aims Small scale root-pore interactions require validation of their impact on effective hydraulic processes at the field scale. Our objective was to develop an interpretative framework linking root effects on macroscopic pore parameters with knowledge at the rhizosphere scale. Methods A field experiment with twelve species from different families was conducted. Parameters of Kosugi?s pore size distribution (PSD) model were determined inversely from tension infiltrometer data. Measured root tr...

  19. A novel polyethylene microfiltration membrane with highly permeable ordered ‘wine bottle’ shaped through-pore structure fabricated via imprint and thermal field induction

    International Nuclear Information System (INIS)

    Fan, Fan; Wang, Lanlan; Jiang, Weitao; Chen, Bangdao; Liu, Hongzhong

    2016-01-01

    A novel microfiltration membrane with ordered ‘wine bottle’ shaped through-pores from inexpensive thermoplastic linear low-density polyethylene (LLDPE) was fabricated via imprint and thermal field induction. At 110 °C, a softened bilayer with a top LLDPE film on a bottom polymer buffer layer was imprinted by a silicon micropillar array template. Under an optimized imprint pressure of 1.4 MPa, the micropillars penetrated through the LLDPE film and into the buffer layer, forming cylindrical through-pores (pore diameter: 2 μm) in the LLDPE film without damaging the template. The establishment of this bilayer can effectively avoid the problem of residual layer which usually exists in conventional single-layer imprints and hinders the formation of perforation. After the imprint, the LLDPE membrane laid flat on a smooth glass substrate was heated in a homogeneous thermal field of 140 °C and melted. The melt can spread over the substrate, inducing the shrinkage of pores. With the increase of heating time, the shrinkage of the membrane top versus bottom surface and the change of membrane thickness and porosity were studied. At 90 s, a thin membrane with ordered ‘wine bottle’ shaped through-pores (pore size: 1 μm on the top surface and 450 nm on the bottom surface) can be achieved. The experimental results of pure-water permeation and the separation of bacteria–water and oil–water have demonstrated the excellent performance of the membrane. (paper)

  20. Understanding the microscopic moisture migration in pore space using DEM simulation

    Directory of Open Access Journals (Sweden)

    Yuan Guo

    2015-04-01

    Full Text Available The deformation of soil skeleton and migration of pore fluid are the major factors relevant to the triggering of and damages by liquefaction. The influence of pore fluid migration during earthquake has been demonstrated from recent model experiments and field case studies. Most of the current liquefaction assessment models are based on testing of isotropic liquefiable materials. However the recent New Zealand earthquake shows much severer damages than those predicted by existing models. A fundamental cause has been contributed to the embedded layers of low permeability silts. The existence of these silt layers inhibits water migration under seismic loads, which accelerated liquefaction and caused a much larger settlement than that predicted by existing theories. This study intends to understand the process of moisture migration in the pore space of sand using discrete element method (DEM simulation. Simulations were conducted on consolidated undrained triaxial testing of sand where a cylinder sample of sand was built and subjected to a constant confining pressure and axial loading. The porosity distribution was monitored during the axial loading process. The spatial distribution of porosity change was determined, which had a direct relationship with the distribution of excess pore water pressure. The non-uniform distribution of excess pore water pressure causes moisture migration. From this, the migration of pore water during the loading process can be estimated. The results of DEM simulation show a few important observations: (1 External forces are mainly carried and transmitted by the particle chains of the soil sample; (2 Porosity distribution during loading is not uniform due to non-homogeneous soil fabric (i.e. the initial particle arrangement and existence of particle chains; (3 Excess pore water pressure develops differently at different loading stages. At the early stage of loading, zones with a high initial porosity feature higher

  1. A failure of matrix metalloproteinase inhibition in the prevention of rat intracranial aneurysm formation

    International Nuclear Information System (INIS)

    Kaufmann, T.J.; Kallmes, D.F.; Marx, W.F.

    2006-01-01

    We tested the hypothesis that nonspecific matrix metalloproteinase (MMP) inhibition with doxycycline would decrease the incidence of intracranial aneurysm formation in a rat aneurysm model. We performed common carotid artery ligation on 96 Long-Evans rats. A treatment group of 48 animals was chosen at random to receive oral doxycycline (3 mg/kg) in addition to standard rat chow, and the control group of 48 animals received standard rat chow only. The major circle of Willis arteries was dissected at 1 year following carotid ligation, and the proportions of animals with aneurysms were compared between groups using Fisher's exact test. Four animals given oral doxycycline and ten control animals expired before 1 year. Of the examined animals, eight saccular intracranial aneurysms were found in 8 of 45 animals which had received doxycycline (17.8%) and seven saccular intracranial aneurysms were found in 7 of 37 control animals (18.9%). There was no significant difference in aneurysm formation between the doxycycline-treated and control groups (P=0.894). Nonspecific MMP inhibition with doxycycline is not effective in preventing intracranial aneurysm formation in a rat model. (orig.)

  2. An investigation of fractal characteristics of mesoporous carbon electrodes with various pore structures

    International Nuclear Information System (INIS)

    Pyun, Su-Il; Rhee, Chang-Kyu

    2004-01-01

    Fractal characteristics of mesoporous carbon electrodes were investigated with various pore structures using the N 2 gas adsorption method and the transmission electron microscopy (TEM) image analysis method. The mesoporous carbons with various pore structures were prepared by imprinting mesophase pitch used as a carbonaceous precursor with different colloidal silica particles. All imprinted mesoporous carbons were composed of two groups of pores produced from the carbonisation of mesophase pitch and from the silica imprinting. The overall surface fractal dimensions of the carbon specimens were determined from the analyses of the N 2 gas adsorption isotherms. In order to distinguish the surface fractal dimension of the carbonisation-induced pore surface from that fractal dimension of the silica-imprinted pore surface, the individual surface fractal dimensions were determined from the image analyses of the TEM images. From the comparison of the overall surface fractal dimension with the individual surface fractal dimensions, it was recognised that the overall surface fractal dimension is crucially influenced by the individual surface fractal dimension of the silica-imprinted pore surface. Moreover, from the fact that the silica-imprinted pore surface with broad relative pore size distribution (PSD) gave lower value of the individual surface fractal dimension than that pore surface with narrow relative PSD, it is concluded that as the silica-imprinted pores comprising the carbon specimen agglomerate, the individual surface fractal dimension of that pore surface decreases

  3. Influence of the Location of Attractive Polymer-Pore Interactions on Translocation Dynamics.

    Science.gov (United States)

    Ghosh, Bappa; Chaudhury, Srabanti

    2018-01-11

    We probe the influence of polymer-pore interactions on the translocation dynamics using Langevin dynamics simulations. We investigate the effect of the strength and location of the polymer-pore interaction using nanopores that are partially charged either at the entry or the exit or on both sides of the pore. We study the change in the translocation time as a function of the strength of the polymer-pore interaction for a given chain length and under the effect of an externally applied field. Under a moderate driving force and a chain length longer than the length of the pore, the translocation time shows a nonmonotonic increase with an increase in the attractive interaction. Also, an interaction on the cis side of the pore can increase the translocation probability. In the presence of an external field and a strong attractive force, the translocation time for shorter chains is independent of the polymer-pore interaction at the entry side of the pore, whereas an interaction on the trans side dominates the translocation process. Our simulation results are rationalized by a qualitative analysis of the free energy landscape for polymer translocation.

  4. The scavenger activity of the human P2X7 receptor differs from P2X7 pore function by insensitivity to antagonists, genetic variation and sodium concentration: Relevance to inflammatory brain diseases.

    Science.gov (United States)

    Ou, Amber; Gu, Ben J; Wiley, James S

    2018-04-01

    Activation of P2X7 receptors is widely recognised to initiate proinflammatory responses. However P2X7 also has a dual function as a scavenger receptor which is active in the absence of ATP and plasma proteins and may be important in central nervous system (CNS) diseases. Here, we investigated both P2X7 pore formation and its phagocytic function in fresh human monocytes (as a model of microglia) by measuring ATP-induced ethidium dye uptake and fluorescent bead uptake respectively. This was studied in monocytes expressing various polymorphic variants as well as in the presence of different P2X7 antagonists and ionic media. P2X7-mediated phagocytosis was found to account for about half of Latrunculin (or Cytochalasin D)-sensitive bead engulfment by fresh human monocytes. Monocytes harbouring P2X7 Ala348Thr or Glu496Ala polymorphic variants showed increase or loss of ethidium uptake respectively, but these changes in pore formation did not always correspond to the changes in phagocytosis of YG beads. Unlike pore function, P2X7-mediated phagocytosis was not affected by three potent selective P2X7 antagonists and remained identical in Na + and K + media. Taken together, our results show that P2X7 is a scavenger receptor with important function in the CNS but its phagocytic function has features distinct from its pore function. Both P2X7 pore formation and P2X7-mediated phagocytosis should be considered in the design of new P2X7 antagonists for the treatment of CNS diseases. Copyright © 2018 Elsevier B.V. All rights reserved.

  5. Pore pressure control on faulting behavior in a block-gouge system

    Science.gov (United States)

    Yang, Z.; Juanes, R.

    2016-12-01

    Pore fluid pressure in a fault zone can be altered by natural processes (e.g., mineral dehydration and thermal pressurization) and industrial operations involving subsurface fluid injection/extraction for the development of energy and water resources. However, the effect of pore pressure change on the stability and slip motion of a preexisting geologic fault remain poorly understood; yet they are critical for the assessment of seismic risk. In this work, we develop a micromechanical model to investigate the effect of pore pressure on faulting behavior. The model couples pore network fluid flow and mechanics of the solid grains. We conceptualize the fault zone as a gouge layer sandwiched between two blocks; the block material is represented by a group of contact-bonded grains and the gouge is composed of unbonded grains. A pore network is extracted from the particulate pack of the block-gouge system with pore body volumes and pore throat conductivities calculated rigorously based on the geometry of the local pore space. Pore fluid exerts pressure force onto the grains, the motion of which is solved using the discrete element method (DEM). The model updates the pore network regularly in response to deformation of the solid matrix. We study the fault stability in the presence of a pressure inhomogeneity (gradient) across the gouge layer, and compare it with the case of homogeneous pore pressure. We consider both normal and thrust faulting scenarios with a focus on the onset of shear failure along the block-gouge interfaces. Numerical simulations show that the slip behavior is characterized by intermittent dynamics, which is evident in the number of slipping contacts at the block-gouge interfaces and the total kinetic energy of the gouge particles. Numerical results also show that, for the case of pressure inhomogeneity, the onset of slip occurs earlier for the side with higher pressure, and that this onset appears to be controlled by the maximum pressure of both sides

  6. Biological function evaluation and effects of laser micro-pore burn-denatured acellular dermal matrix.

    Science.gov (United States)

    Zhang, Youlai; Zeng, Yuanlin; Xin, Guohua; Zou, Lijin; Ding, Yuewei; Duyin, Jiang

    2018-03-01

    In the field of burns repairs, many problems exist in the shortage of donor skin, the expense of allograft or xenograft skin, temporary substitution and unsatisfactory extremity function after wound healing. Previous studies showed that burn-denatured skin could return to normal dermis formation and function. This study investigates the application of laser micro-pore burn-denatured acellular dermis matrix (DADM) from an escharotomy in the repair of burn wounds and evaluates the biological properties and wound repair effects of DADM in implantation experiments in Kunming mice. Specific-pathogen-free (SPF) Kunming mice were used in this study. A deep II° burn wound was created on the dorsum of the mice by an electric heated water bath. The full-thickness wound tissue was harvested. The necrotic tissue and subcutaneous tissue were removed. The denatured dermis was preserved and treated with 0.25% trypsin, 0.5% Triton X-100. The DADM was drilled by laser micro-pore. The biological properties and grafting effects of laser micro-pore burn-DADM were evaluated by morphology, cytokine expression levels and subcutaneous implantation experiments in Kunming mice. We found statistical significance (Ppore burn-DADM (experimental group) compared to the control group (no laser micro-pore burn-DADM). Cytokine expression level was different in the dermal matrixes harvested at various time points after burn (24h, 48h, 72h and infected wound group). Comparing the dermal matrix from 24h burn tissue to infected wound tissue, the expression level of IL-6, MMP-24, VE-cadherin and VEGF were decreased. We found no inflammatory cells infiltration in the dermal matrix were observed in both experimental and control groups (24h burn group), while the obviously vascular infiltration and fiber fusion were observed in the experimental group after subcutaneous implantation experiments. There was better bio-performance, low immunogenicity and better dermal incorporation after treated by laser

  7. Variation of Pore Water Pressure in Tailing Sand under Dynamic Loading

    Directory of Open Access Journals (Sweden)

    Jia-xu Jin

    2018-01-01

    Full Text Available Intense vibration affects the pore water pressure in a tailing dam, with the tendency to induce dam liquefaction. In this study, experiments were performed wherein model tailing dams were completely liquefied by sustained horizontal dynamic loading to determine the effects of the vibration frequency, vibration amplitude, and tailing density on the pore water pressure. The results revealed four stages in the increase of the tailing pore water pressure under dynamic loading, namely, a slow increase, a rapid increase, inducement of structural failure, and inducement of complete liquefaction. A lower frequency and smaller amplitude of the vibration were found to increase the time required to achieve a given pore water pressure in dense tailings. Under the effect of these three factors—vibration frequency and amplitude and tailing density—the tailing liquefaction time varied nonlinearly with the height from the base of the tailing dam, with an initial decrease followed by an increase. The pore pressure that induced structural failure also gradually decreased with increasing height. The increase in the tailing pore pressure could be described by an S-shaped model. A complementary multivariate nonlinear equation was also derived for predicting the tailing pore water pressure under dynamic loading.

  8. Pore Pressure Response to Groundwater Fluctuations in Saturated Double-Layered Soil

    Directory of Open Access Journals (Sweden)

    Hongwei Ying

    2015-01-01

    Full Text Available Analytical solutions are developed for one-dimensional consolidation of double-layered saturated soil subjected to groundwater fluctuations. The solutions are derived by an explicit mathematical procedure using Duhamel’s theorem in conjunction with a Fourier series, when groundwater fluctuation is described by a general time-dependent function and assumed to be the pore water pressure variations at the upper boundary. Taking as an example the harmonic groundwater fluctuation, the relevant response of the excess pore water pressure is discussed in detail, and the main influencing factors of the excess pore pressure distribution are analyzed. A dimensionless parameter θ has been introduced because it significantly affects the phase and the amplitude of excess pore pressures. The influences of the coefficients of permeability and compressibility of soil on the excess pore pressure distribution are different and cannot be incorporated into the coefficient of consolidation in double-layered soil. The relative permeability ratio of two clayey soils also plays an important role on the curves of the distributions of the excess pore pressures. The effects of the thickness of the soil layer on the excess pore pressure distribution should be considered together with the dimensionless parameter θ and the permeability and compressibility of the double-layered soil system.

  9. Analysis of the number of enlarged pores according to site, age, and sex.

    Science.gov (United States)

    Jung, H J; Ahn, J Y; Lee, J I; Bae, J Y; Kim, H L; Suh, H Y; Youn, J I; Park, M Y

    2018-02-02

    Increasing the number of enlarged pores causes cosmetic problems. The difference in the number of enlarged pores according to facial site, age, and sex is unclear. To analyze the distribution of the number of enlarged pores according to facial site, age, and sex. We analyzed the number of the enlarged pores and the percentage of wrinkles in the nose, forehead, and cheek from 434 polarized images. The measurement results were analyzed according to site, age, and sex. Relationship between enlarged pore counts and wrinkle severity was also analyzed. The study was conducted by using DermaVision,™ which can take cross-polarization, parallel polarization, and ultraviolet light images. The enlarged pores of the nose and forehead were more prominent than in the cheeks. Pore counts were increased with age, and the increment was significant between the 30's and 40's. There was no significant difference by gender. Enlarged pore counts were related to wrinkle severity. The number of enlarged pores differs depending on body site and increased with age. The enlarged pore counts correlate with wrinkle severity and the correlation varies depending on the body site. © 2018 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  10. Modern principles of prevention of anophthalmic syndrome: formation of the locomotor stump, the types of orbital implants

    Directory of Open Access Journals (Sweden)

    I. V. Zapuskalov

    2017-01-01

    Full Text Available This article analyzes the current state of the problem of the correction of anophthalmic syndrome. Evaluated various methods of formation of the locomotor stump after removal of the eyeball, gave a detailed description of different types of materials for the fabrication of orbital implant, as well as reflect the basic principles of prevention of complications.

  11. The Pore Structure of Direct Methanol Fuel Cell Electrodes

    DEFF Research Database (Denmark)

    Lund, Peter Brilner

    2005-01-01

    The pore structure and morphology of direct methanol fuel cell electrodes are characterized using mercury intrusion porosimetry and scanning electron microscopy. It is found that the pore size distributions of printed primer and catalyst layers are largely dictated by the powders used to make...

  12. Pore Structures in the Biomineralized Byssus of Anomia simplex

    DEFF Research Database (Denmark)

    Frølich, Simon; Leemreize, Hanna; Thomsen, Jesper Skovhus

    2016-01-01

    that uses a biomineralized byssus to permanently anchor itself to substrates. The byssus has a highly complex hierarchical structure and contains over 90 wt% CaCO3. The byssus features a complex set of porosities, presumed to be highly important for the function of the attachment system. The pore space...... is the main focus of the present work. We characterize the three dimensional distribution of pore spaces in the byssus using micro-computed tomography (µCT) through a combination of in house CT and high-resolution synchrotron CT. The pore structures are observed to fall into distinct categories in various...

  13. Blocking of Single α-Hemolysin Pore by Rhodamine Derivatives.

    Science.gov (United States)

    Rokitskaya, Tatyana I; Nazarov, Pavel A; Golovin, Andrey V; Antonenko, Yuri N

    2017-06-06

    Measurements of ion conductance through α-hemolysin pore in a bilayer lipid membrane revealed blocking of the ion channel by a series of rhodamine 19 and rhodamine B esters. The longest dwell closed time of the blocking was observed with rhodamine 19 butyl ester (C4R1), whereas the octyl ester (C8R1) was of poor effect. Voltage asymmetry in the binding kinetics indicated that rhodamine derivatives bound to the stem part of the aqueous pore lumen. The binding frequency was proportional to a quadratic function of rhodamine concentrations, thereby showing that the dominant binding species were rhodamine dimers. Two levels of the pore conductance and two dwell closed times of the pore were found. The dwell closed times lengthened as the voltage increased, suggesting impermeability of the channel for the ligands. Molecular docking analysis revealed two distinct binding sites within the lumen of the stem of the α-hemolysin pore for the C4R1 dimer, but only one binding site for the C8R1 dimer. The blocking of the α-hemolysin nanopore by rhodamines could be utilized in DNA sequencing as additional optical sensing owing to bright fluorescence of rhodamines if used for DNA labeling. Copyright © 2017 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  14. Can pore-clogging by ash explain post-fire runoff?

    Science.gov (United States)

    Stoof, Cathelijne R.; Gevaert, Anouk I.; Baver, Christine; Hassanpour, Bahareh; Morales, Veronica L.; Zhang, Wei; Martin, Deborah; Giri, Shree K.; Steenhuis, Tammo S.

    2016-01-01

    Ash plays an important role in controlling runoff and erosion processes after wildfire and has frequently been hypothesised to clog soil pores and reduce infiltration. Yet evidence for clogging is incomplete, as research has focussed on identifying the presence of ash in soil; the actual flow processes remain unknown. We conducted laboratory infiltration experiments coupled with microscope observations in pure sands, saturated hydraulic conductivity analysis, and interaction energy calculations, to test whether ash can clog pores (i.e. block pores such that infiltration is hampered and ponding occurs). Although results confirmed previous observations of ash washing into pores, clogging was not observed in the pure sands tested, nor were conditions found for which this does occur. Clogging by means of strong attachment of ash to sand was deemed unlikely given the negative surface charge of the two materials. Ponding due to washing in of ash was also considered improbable given the high saturated conductivity of pure ash and ash–sand mixtures. This first mechanistic step towards analysing ash transport and attachment processes in field soils therefore suggests that pore clogging by ash is unlikely to occur in sands. Discussion is provided on other mechanisms by which ash can affect post-fire hydrology.

  15. 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.

  16. An investigation into the effects of pore connectivity on T2 NMR relaxation

    Science.gov (United States)

    Ghomeshi, Shahin; Kryuchkov, Sergey; Kantzas, Apostolos

    2018-04-01

    Nuclear Magnetic Resonance (NMR) is a powerful technique used to characterize fluids and flow in porous media. The NMR relaxation curves are closely related to pore geometry, and the inversion of the NMR relaxometry data is known to give useful information with regards to pore size distribution (PSD) through the relative amplitudes of the fluids stored in the small and large pores. While this information is crucial, the main challenge for the successful use of the NMR measurements is the proper interpretation of the measured signals. Natural porous media patterns consist of complex pore structures with many interconnected or "coupled" regions, as well as isolated pores. This connectivity along the throats changes the relaxation distribution and in order to properly interpret this data, a thorough understanding of the effects of pore connectivity on the NMR relaxation distribution is warranted. In this paper we address two main points. The first pertains to the fact that there is a discrepancy between the relaxation distribution obtained from experiments, and the ones obtained from solving the mathematical models of diffusion process in the digitized images of the pore space. There are several reasons that may attribute to this such as the lack of a proper incorporation of surface roughness into the model. However, here we are more interested in the effects of pore connectivity and to understand why the typical NMR relaxation distribution obtained from experiments are wider, while the numerical simulations predict that a wider NMR relaxation distribution may indicate poor connectivity. Secondly, by not taking into account the pore coupling effects, from our experience in interpreting the data, we tend to underestimate the pore volume of small pores and overestimate the amplitudes in the large pores. The role of pore coupling becomes even more prominent in rocks with small pore sizes such as for example in shales, clay in sandstones, and in the microstructures of

  17. Swelling and gas release of grain-boundary pores in uranium dioxide

    International Nuclear Information System (INIS)

    Schrire, D.I.

    1983-12-01

    The swelling and gas release of overpressured grain boundary pores is sintered unirradiated uranium dioxide were investigated under isothermal conditions. The pores became overpressured when the ambient pressure was reduced, and the excess pressure driving force caused growth and interconnection of the pores, leading to eventual gas release. Swelling was measured continuously by a linear variable differential transformer, and open and closed porosity fractions were determined after the tests by immersion density and quantitative microscopy measurements. The sinter porosity consisted of pores situated on grain faces, grain edges, and grain corners. Isolated pores maintained their equilibrium shape while growing, without any measurable change in dihedral angle. Interconnection occurred predominantly along grain edges, without any evidence of pore sharpening or crack propagation at low driving forces. Extensive open porosity occurred at a threshold density of about 85% TD. There was an almost linear dependence of the initial swelling rate on the driving force, with an activation energy of 200+- 8 kJ/mole, in good agreement with published values of the activation energy for grain boundary diffusion

  18. On-Going Bentonite Pore Water Studies by NMR and SAXS

    International Nuclear Information System (INIS)

    Carlsson, Torbjoern; Muurinen, Arto; Root, Andrew

    2013-01-01

    Compacted water-saturated MX-80 bentonite is presently being studied by SAXS and NMR in order to quantify the major pore water phases in the bentonite. The SAXS and NMR measurements gave very similar results indicating that the pore water is mainly distributed between two major phases (interlayer and non-interlayer water) and also indicate how these phases depend on the bentonite dry density. The results from the SAXS and NMR studies at VTT indicate the same thing: - The pore water in water-saturated compacted (?dry = 0.7-1.6 g/cm 3 ) bentonite is divided into two main phases: interlayer water and non-interlayer water. - The amounts of these pore water phases can be determined quantitatively with the above methods. (authors)

  19. A new experimental method to prevent paraffin - wax formation on the crude oil wells: A field case study in Libya

    Directory of Open Access Journals (Sweden)

    Elhaddad Elnori E.

    2015-01-01

    Full Text Available Wax formation and deposition is one of the most common problems in oil producing wells. This problem occurs as a result of the reduction of the produced fluid temperature below the wax appearance temperature (range between 46°C and 50°C and the pour point temperature (range between 42°C and 44°C. In this study, two new methods for preventing wax formation were implemented on three oil wells in Libya, where the surface temperature is, normally, 29°C. In the first method, the gas was injected at a pressure of 83.3 bar and a temperature of 65°C (greater than the pour point temperature during the gas-lift operation. In the second method, wax inhibitors (Trichloroethylene-xylene (TEX, Ethylene copolymers, and Comb polymers were injected down the casings together with the gas. Field observations confirmed that by applying these techniques, the production string was kept clean and no wax was formed. The obtained results show that the wax formation could be prevented by both methods.

  20. Why liquid displacement methods are sometimes wrong in estimating the pore-size distribution

    NARCIS (Netherlands)

    Gijsbertsen-Abrahamse, A.J.; Boom, R.M.; Padt, van der A.

    2004-01-01

    The liquid displacement method is a commonly used method to determine the pore size distribution of micro- and ultrafiltration membranes. One of the assumptions for the calculation of the pore sizes is that the pores are parallel and thus are not interconnected. To show that the estimated pore size

  1. Molecular Dynamics Simulations of Hydrophilic Pores in Lipid Bilayers

    NARCIS (Netherlands)

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

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

  2. Microwave-induced synthesis of highly dispersed gold nanoparticles within the pore channels of mesoporous silica

    International Nuclear Information System (INIS)

    Gu Jinlou; Fan Wei; Shimojima, Atsushi; Okubo, Tatsuya

    2008-01-01

    Highly dispersed gold nanoparticles have been incorporated into the pore channels of SBA-15 mesoporous silica through a newly developed strategy assisted by microwave radiation (MR). The sizes of gold are effectively controlled attributed to the rapid and homogeneous nucleation, simultaneous propagation and termination of gold precursor by MR. Diol moieties with high dielectric and dielectric loss constants, and hence a high microwave activation, were firstly introduced to the pore channels of SBA-15 by a simple addition reaction between amino group and glycidiol and subsequently served as the reduction centers for gold nanoparticles. Extraction of the entrapped gold from the nanocomposite resulted in milligram quantities of gold nanoparticles with low dispersity. The successful assembly process of diol groups and formation of gold nanoparticles were monitored and tracked by solid-state NMR and UV-vis measurements. Characterization by small angle X-ray diffraction (XRD) and transmission electron microscopy (TEM) indicated that the incorporation of gold nanoparticles would not breakup the structural integrity and long-range periodicity of SBA-15. The gold nanoparticles had a narrow size distribution with diameters in the size range of 5-10 nm through TEM observation. The average particles size is 7.9 nm via calculation by the Scherrer formula and TEM measurements. Nitrogen adsorption and desorption isotherms gave further evidence that the employed method was efficient and gold nanoparticles were successfully incorporated into the pore channels of SBA-15. - Graphical abstract: A facile and novel strategy has been developed to incorporate gold nanoparticles into the pore channels of mesoporous SBA-15 assisted by microwave radiation (MR) with mild reaction condition and rapid reaction speed. Due to the rapid and homogeneous nucleation, simultaneous propagation and termination by MR, the size of gold nanoparticles are effectively controlled

  3. Polarization-induced local pore-wall functionalization for biosensing: from micropore to nanopore.

    Science.gov (United States)

    Liu, Jie; Pham, Pascale; Haguet, Vincent; Sauter-Starace, Fabien; Leroy, Loïc; Roget, André; Descamps, Emeline; Bouchet, Aurélie; Buhot, Arnaud; Mailley, Pascal; Livache, Thierry

    2012-04-03

    The use of biological-probe-modified solid-state pores in biosensing is currently hindered by difficulties in pore-wall functionalization. The surface to be functionalized is small and difficult to target and is usually chemically similar to the bulk membrane. Herein, we demonstrate the contactless electrofunctionalization (CLEF) approach and its mechanism. This technique enables the one-step local functionalization of the single pore wall fabricated in a silica-covered silicon membrane. CLEF is induced by polarization of the pore membrane in an electric field and requires a sandwich-like composition and a conducting or semiconducting core for the pore membrane. The defects in the silica layer of the micropore wall enable the creation of an electric pathway through the silica layer, which allows electrochemical reactions to take place locally on the pore wall. The pore diameter is not a limiting factor for local wall modification using CLEF. Nanopores with a diameter of 200 nm fabricated in a silicon membrane and covered with native silica layer have been successfully functionalized with this method, and localized pore-wall modification was obtained. Furthermore, through proof-of-concept experiments using ODN-modified nanopores, we show that functionalized nanopores are suitable for translocation-based biosensing.

  4. 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

  5. The effect of pore-scale geometry and wettability on two-phase relative permeabilities within elementary cells

    Science.gov (United States)

    Bianchi Janetti, Emanuela; Riva, Monica; Guadagnini, Alberto

    2017-04-01

    We study the relative role of the complex pore space geometry and wettability of the solid matrix on the quantification of relative permeabilities characterizing steady state immiscible two-phase flow in porous media. We do so by considering elementary cells, which are typically employed in upscaling frameworks based on, e.g., homogenization or volume averaging. In this context one typically relies on the solution of pore-scale physics at a scale which is much smaller than that of an investigated porous system. Pressure-driven two-phase flow following simultaneous co-current injection of water and oil is numerically solved for a suite of regular and stochastically generated two-dimensional explicit elementary cells with fixed porosity and sharing main topological/morphological features. We show that relative permeabilities of the randomly generated elementary cells are significantly influenced by the formation of preferential percolation paths (principal pathways), giving rise to a strongly nonuniform distribution of fluid fluxes. These pathways are a result of the spatially variable resistance that the random pore structures exert on the fluid. The overall effect on relative permeabilities of the diverse organization of principal pathways, as driven by a given random realization at the scale of the unit cell, is significantly larger than that of the wettability of the host rock. In contrast to what can be observed for the random cells analyzed, relative permeabilities of regular cells display a clear trend with contact angle at the investigated scale. Our findings suggest the need to perform systematic upscaling studies in a stochastic context, to propagate the effects of uncertain pore space geometries to a probabilistic description of relative permeability curves at the continuum scale.

  6. Development of image analysis for graphite pore-structure determination using fluorescence techniques

    International Nuclear Information System (INIS)

    Stephen, W.J.; Bowden, E.A.T.; Wickham, A.J.

    1983-03-01

    The use of image analysis to assess the pore structure of graphite has been developed to the point at which it may be considered available for routine use. A definitive pore structure in terms of the geometry-independent ''characteristic pore dimension'' is derived from the computer analysis of polished specimens whose open-pore structure has been impregnated with bismuth or a fluorescent epoxy resin, with the very small pores identified separately by mercury porosimetry as in the past. The pore-size distributions obtained from these combined techniques have been used successfully to predict the corrosion rates of nine graphites, of widely differing pore structure, in a variety of gas compositions and, indirectly, to confirm appropriate mean ranges and rate constants for the reaction of the oxidising species in these gas mixtures. The development of the fluorescent-impregnant technique is discussed in detail and its use is justified in preference to ''traditional'' methods. Further possible refinements are discussed, including the eventual aim of obtaining a computer prediction of the future oxidation behaviour of the graphite directly from the image analyser. (author)

  7. Use of vhf dielectric measurements for borehole formation analysis

    Energy Technology Data Exchange (ETDEWEB)

    Poley, J.P.; Nooteboom, J.J.; de Waal, P.J.

    1978-01-01

    A study of the dielectric properties of sedimentary rocks at a sufficiently high frequency may provide useful data for the evaluation of borehole wall formations in exploration and production wells. An experimental program carried out between 1960 and 1967 on sandstone and limestone samples lent further support to these expectations. At frequencies above 20 Mc/s both real and imaginary parts of the complex epsilon* = epsilon' - j epsilon'' were measurable. Moreover, at higher frequencies, epsilon' proved to be independent of the salinity of the water filling the pores, and insensitive to the way in which the oil and the water are actually distributed. The value of epsilon'', on the other hand, turned out to be indicative of the prevailing salinity. By combining other logging data (for instance from an electric or porosity log) with a series of such v.h.f. measurements of epsilon' and epsilon'', the oil or water saturation, the effective formation porosity, the pore-filling fluid salinity, and the rock matrix formation factor might be deduced, if the depth of investigation can be made large enough to overcome the invasion effects.

  8. Determination of pore diameter from rejection measurements with a mixture of oligosaccharides

    Energy Technology Data Exchange (ETDEWEB)

    Espinoza-Gomez, Heriberto; Rogel-Hernandez, Eduardo [Universidad Autonoma de Baja California-Tijuana, Facultad de Ciencias Quimicas e Ingenieria, Tijuana, BC (Mexico); Lin, Shui Wai [Centro de Graduados e Investigacion del Instituto Tecnologico de Tijuana, Apdo. Postal 1166, Tijuana, BC (Mexico)

    2005-04-01

    This paper present a method to determine pore diameters and effective transport through membranes using a mixture of oligosaccharides. The results are compared with the Maxwell-Stefan equations. The partition coefficients of the solutes are a function of the pore diameter according to the Ferry equation. Thus, with the pore diameter as the only unknown parameter, rejection is described and the pore diameter is obtained by a Marquardt-Levenberg optimization procedure. (orig.)

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

    DEFF Research Database (Denmark)

    Sumer, B. Mutlu; Cheng, Niang-Sheng

    1999-01-01

    A numerical random-walk model has been developed for the pore-water pressure. The model is based on the analogy between the variation of the pore pressure and the diffusion process of any passive quantity such as concentration. The pore pressure in the former process is analogous...... to the concentration in the latter. In the simulation, particles are released in the soil, and followed as they travel through the statistical field variables. The model has been validated (1) against the Terzaghi consolidation process, and (2) against the process where the pore pressure builds up under progressive...... waves. The model will apparently enable the researcher to handle complex geometries (such as a pipeline buried in a soil) relatively easily. Early results with regard to the latter example, namely the buildup of pore pressure around a buried pipeline subject to a progressive wave, are encouraging....

  10. Effect of crystallographic orientation on the anodic formation of nanoscale pores/tubes in TiO 2 films

    Science.gov (United States)

    Kalantar-zadeh, K.; Sadek, A. Z.; Zheng, H.; Partridge, J. G.; McCulloch, D. G.; Li, Y. X.; Yu, X. F.; Wlodarski, W.

    2009-10-01

    Self-organized nanopores and nanotubes have been produced in thin films of titanium (Ti) prepared using filtered cathodic vacuum arc (FCVA), DC- and RF-sputter deposition systems. The anodization process was performed using a neutral electrolyte containing fluoride ions with an applied potential between 2 and 20 V (for clarity the results are only presented for 5 V). Scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray diffraction (XRD) techniques were used to characterise the films. It was found that the crystallographic orientation of the Ti films played a significant role in determining whether pores or tubes were formed during the anodic etching process.

  11. Quantitative analysis of vascular colonisation and angio-conduction in porous silicon-substituted hydroxyapatite with various pore shapes in a chick chorioallantoic membrane (CAM) model.

    Science.gov (United States)

    Magnaudeix, Amandine; Usseglio, Julie; Lasgorceix, Marie; Lalloue, Fabrice; Damia, Chantal; Brie, Joël; Pascaud-Mathieu, Patricia; Champion, Eric

    2016-07-01

    The development of scaffolds for bone filling of large defects requires an understanding of angiogenesis and vascular guidance, which are crucial processes for bone formation and healing. There are few investigations on the ability of a scaffold to support blood vessel guidance and it this is of great importance because it relates to the quality and dispersion of the blood vessel network. This work reports an analysis of vascularisation of porous silicon-substituted hydroxyapatite (SiHA) bioceramics and the effects of pore shape on vascular guidance using an expedient ex ovo model, the chick embryo chorioallantoic membrane (CAM) assay. Image analysis of vascularised implants assessed the vascular density, fractal dimension and diameter of blood vessels at two different scales (the whole ceramic and pores alone) and was performed on model SiHA ceramics harbouring pores of various cross-sectional geometries (circles, square, rhombus, triangles and stars). SiHA is a biocompatible material which allows the conduction of blood vessels on its surface. The presence of pores did not influence angiogenesis related-parameters (arborisation, fractal dimension) but pore geometry affected the blood vessel guidance and angio-conductive potential (diameter and number of the blood vessels converging toward the pores). The measured angles of pore cross-section modulated the number and diameter of blood vessels converging to pores, with triangular pores appearing of particular interest. This result will be used for shaping ceramic scaffolds with specific porous architecture to promote vascular colonisation and osteointegration. An expedient and efficient method, using chick embryo chorioallantoic membrane (CAM) assays, has been set up to characterise quantitatively the angiogenesis and the vascular conduction in scaffolds. This approach complements the usual cell culture assays and could replace to a certain extent in vivo experiments. It was applied to silicon

  12. Analysis of the skin surface and inner structure around pores on the face.

    Science.gov (United States)

    Mizukoshi, Koji; Takahashi, Kazuhiro

    2014-02-01

    Facial pores do not appear to close again in old skin. Therefore, the tissue structure around the pore has been speculated to keep the pore open. To elucidate the reason for pore enlargement, we examined the relationship between the skin surface and inner skin structural characteristics in the same regions especially around the pore. Samples of the skin surface were obtained from the cheek and examined using a laser image processor to obtain three-dimensional (3D) data. The inner structure of the skin was analyzed using in vivo confocal laser scanning microscopy (CLSM). The conspicuous pore not only had a concave structure but also a discontinuous convex structure on the skin surface surrounding the pore. Furthermore, CLSM image indicated that the skin inner structure developed a discontinuous dermal papilla structure and isotropic dermal fiber structure. There were structural changes in the skin surface around conspicuous pores, including not only a concave structure but also a convex structure with skin inner structure changing. © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  13. Mesoporous Akaganeite of Adjustable Pore Size Synthesized using Mixed Templates

    Science.gov (United States)

    Zhang, Y.; Ge, D. L.; Ren, H. P.; Fan, Y. J.; Wu, L. M.; Sun, Z. X.

    2017-12-01

    Mesoporous akaganeite with large and adjustable pore size was synthesized through a co-template method, which was achieved by the combined interaction between PEG2000 and alkyl amines with different lengths of the straight carbon chain. The characterized results indicate that the synthesized samples show comparatively narrow BJH pore size distributions and centered at 14.3 nm when PEG and HEPA was used, and it could be enlarged to 16.8 and 19.4 nm respectively through changing the alkyl amines to DDA and HDA. Meanwhile, all the synthesized akaganeite possess relativity high specific surface area ranging from 183 to 281 m2/g and high total pore volume of 0.98 to 1.5 cm3/g. A possible mechanism leading to the pore size changing was also proposed.

  14. Passive control of quorum sensing: prevention of Pseudomonas aeruginosa biofilm formation by imprinted polymers.

    Science.gov (United States)

    Piletska, Elena V; Stavroulakis, Georgios; Larcombe, Lee D; Whitcombe, Michael J; Sharma, Anant; Primrose, Sandy; Robinson, Gary K; Piletsky, Sergey A

    2011-04-11

    Here we present the first molecular imprinted polymer (MIP) that is able to attenuate the biofilm formation of the opportunistic human pathogen Pseudomonas aeruginosa through specific sequestration of its signal molecule N-(3-oxododecanoyl)-L-homoserine lactone (3-oxo-C(12)-AHL). The MIP was rationally designed using computational modeling, and its capacity and specificity and that of a corresponding blank polymer toward signal molecule of P. aeruginosa (3-oxo-C(12)-AHL) and its analogue were tested. The biofilm formation in the presence of polymers and without polymers was studied using scanning confocal laser microscopy. Staining with crystal violet dye was used for the quantification of the biofilm formation. A significant reduction of the biofilm growth was observed in the presence of MIP (>80%), which was superior to that of the resin prepared without template, which showed a reduction of 40% in comparison with biofilm, which was grown without polymer addition. It was shown that 3-oxo-C(12)-AHL-specific MIP prevented the development of quorum-sensing-controlled phenotypes (in this case, biofilm formation) from being up-regulated. The developed MIP could be considered as a new tool for the elimination of life-threatening infections in a multitude of practical applications; it could, for example, be grafted on the surface of medical devices such as catheters and lenses, be a component of paints, or be used as a wound adsorbent.

  15. Ring-opening metathesis polymerization based pore-size-selective functionalization of glycidyl methacrylate based monolithic media: access to size-stable nanoparticles for ligand-free metal catalysis.

    Science.gov (United States)

    Bandari, Rajendar; Höche, Thomas; Prager, Andrea; Dirnberger, Klaus; Buchmeiser, Michael R

    2010-04-19

    Monolithic polymeric supports have been prepared by electron-beam-triggered free-radical polymerization using a mixture of glycidyl methacrylate and trimethylolpropane triacrylate in 2-propanol, 1-dodecanol, and toluene. Under appropriate conditions, phase separation occurred, which resulted in the formation of a porous monolithic matrix that was characterized by large (convective) pores in the 30 μm range as well as pores of 7 nm were hydrolyzed by using poly(styrenesulfonic acid) (Mw = 69,400 g mol(-1), PDI=2.4). The remaining epoxy groups inside pores of nanoparticles 2 nm in diameter were formed. The palladium-nanoparticle-loaded monoliths were used in both Heck- and Suzuki-type coupling reactions achieving turnover numbers of up to 167,000 and 63,000, respectively. Copyright © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Fouling layer characterization and pore-blocking mechanisms in an ...

    African Journals Online (AJOL)

    Fouling layer characterization and pore-blocking mechanisms in an UF membrane externally coupled to a UASB reactor. ... Regarding pore-blocking mechanisms, standard blocking was the predominant mechanism at the beginning of filtration, coexisting at the end of it with cake filtration. In the first filtration cycle (1 h), after ...

  17. Pore and surface diffusion in multicomponent adsorption and liquid chromatography systems

    International Nuclear Information System (INIS)

    Ma, Z.; Whitley, R.D.; Wang, N.H.L.

    1996-01-01

    A generalized parallel pore and surface diffusion model for multicomponent adsorption and liquid chromatography is formulated and solved numerically. Analytical solution for first- and second-order central moments for a pulse on a plateau input is used as benchmarks for the numerical solutions. Theoretical predictions are compared with experimental data for two systems: ion-exchange of strontium, sodium, and calcium in a zeolite and competitive adsorption of two organics on activated carbon. In a linear isotherm region of single-component systems, both surface and pore diffusion cause symmetric spreading in breakthrough curves. In a highly nonlinear isotherm region, however, surface diffusion causes pronounced tailing in breakthrough curves; the larger the step change in concentration, the more pronounced tailing, in contrast to relatively symmetric breakthroughs due to pore diffusion. If only a single diffusion mechanism is assumed in analyzing the data of parallel diffusion systems, a concentration-dependent apparent surface diffusivity or pore diffusivity results; for a convex isotherm, the apparent surface diffusivity increases, whereas the apparent pore diffusivity decreases with increasing concentration. For a multicomponent nonlinear system, elution order can change if pore diffusion dominates for a low-affinity solute, whereas surface diffusion dominates for a high-affinity solute

  18. Pore size distribution effect on rarefied gas transport in porous media

    Science.gov (United States)

    Hori, Takuma; Yoshimoto, Yuta; Takagi, Shu; Kinefuchi, Ikuya

    2017-11-01

    Gas transport phenomena in porous media are known to strongly influence the performance of devices such as gas separation membranes and fuel cells. Knudsen diffusion is a dominant flow regime in these devices since they have nanoscale pores. Many experiments have shown that these porous media have complex structures and pore size distributions; thus, the diffusion coefficient in these media cannot be easily assessed. Previous studies have reported that the characteristic pore diameter of porous media can be defined in light of the pore size distribution; however, tortuosity factor, which is necessary for the evaluation of diffusion coefficient, is still unknown without gas transport measurements or simulations. Thus, the relation between pore size distributions and tortuosity factors is required to obtain the gas transport properties. We perform numerical simulations to prove the relation between them. Porous media are numerically constructed while satisfying given pore size distributions. Then, the mean-square displacement simulation is performed to obtain the tortuosity factors of the constructed porous media.. This paper is based on results obtained from a project commissioned by the New Energy and Industrial Development Organization (NEDO).