WorldWideScience

Sample records for surface pore structure

  1. 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.

  2. Permeation Properties and Pore Structure of Surface Layer of Fly Ash Concrete.

    Science.gov (United States)

    Liu, Jun; Qiu, Qiwen; Xing, Feng; Pan, Dong

    2014-05-30

    This paper presents an experimental study on the nature of permeation properties and pore structure of concrete surface layers containing fly ash. Concretes containing different dosages of fly ash as a replacement for cement (15% and 30% by weight of total cement materials, respectively) were investigated. Concrete without any fly ash added was also employed as the reference specimen. Laboratory tests were conducted to determine the surface layer properties of concrete including chloride transport, apparent water permeability and pore structure. The results demonstrate that incorporation of fly ash, for the early test period, promotes the chloride ingress at the surface layer of concrete but substituting proportions of fly ash may have little impact on it. With the process of chloride immersion, the chloride concentration at the surface layer of concrete with or without fly ash was found to be nearly the same. In addition, it is suggested that the water permeability at the concrete surface area is closely related to the fly ash contents as well as the chloride exposure time. Pore structure was characterized by means of mercury intrusion porosimetry (MIP) test and the scanning electron microscopy (SEM) images. The modification of pore structure of concrete submersed in distilled water is determined by the pozzolanic reaction of fly ash and the calcium leaching effect. The pozzolanic reaction was more dominant at the immersion time of 180 days while the calcium leaching effect became more evident after 270 days.

  3. Pore-scale water dynamics during drying and the impacts of structure and surface wettability

    Science.gov (United States)

    Cruz, Brian C.; Furrer, Jessica M.; Guo, Yi-Syuan; Dougherty, Daniel; Hinestroza, Hector F.; Hernandez, Jhoan S.; Gage, Daniel J.; Cho, Yong Ku; Shor, Leslie M.

    2017-07-01

    Plants and microbes secrete mucilage into soil during dry conditions, which can alter soil structure and increase contact angle. Structured soils exhibit a broad pore size distribution with many small and many large pores, and strong capillary forces in narrow pores can retain moisture in soil aggregates. Meanwhile, contact angle determines the water repellency of soils, which can result in suppressed evaporation rates. Although they are often studied independently, both structure and contact angle influence water movement, distribution, and retention in soils. Here drying experiments were conducted using soil micromodels patterned to emulate different aggregation states of a sandy loam soil. Micromodels were treated to exhibit contact angles representative of those in bulk soil (8.4° ± 1.9°) and the rhizosphere (65° ± 9.2°). Drying was simulated using a lattice Boltzmann single-component, multiphase model. In our experiments, micromodels with higher contact angle surfaces took 4 times longer to completely dry versus micromodels with lower contact angle surfaces. Microstructure influenced drying rate as a function of saturation and controlled the spatial distribution of moisture within micromodels. Lattice Boltzmann simulations accurately predicted pore-scale moisture retention patterns within micromodels with different structures and contact angles.

  4. 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

  5. Vertical structure of pore pressure under surface gravity waves on a steep, megatidal, mixed sand-gravel-cobble beach

    Science.gov (United States)

    Guest, Tristan B.; Hay, Alex E.

    2017-01-01

    The vertical structure of surface gravity wave-induced pore pressure is investigated within the intertidal zone of a natural, steeply sloping, megatidal, mixed sand-gravel-cobble beach. Results from a coherent vertical array of buried pore pressure sensors are presented in terms of signal phase lag and attenuation as functions of oscillatory forcing frequency and burial depth. Comparison of the observations with the predictions of a theoretical poro-elastic bed response model indicates that the large observed phase lags and attenuation are attributable to interstitial trapped air. In addition to the dependence on entrapped air volume, the pore pressure phase and attenuation are shown to be sensitive to the hydraulic conductivity of the sediment, to the changing mean water depth during the tidal cycle, and to the redistribution/rearrangement of beach face material by energetic wave action during storm events. The latter result indicates that the effects on pore pressure of sediment column disturbance during instrument burial can persist for days to weeks, depending upon wave forcing conditions. Taken together, these results raise serious questions as to the practicality of using pore pressure measurements to estimate the kinematic properties of surface gravity waves on steep, mixed sand-gravel beaches.

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

    International Nuclear Information System (INIS)

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

    2017-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2017-07-01

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

  8. Effects of steam activation on the pore structure and surface chemistry of activated carbon derived from bamboo waste

    Science.gov (United States)

    Zhang, Yan-Juan; Xing, Zhen-Jiao; Duan, Zheng-Kang; Li, Meng; Wang, Yin

    2014-10-01

    The effects of steam activation on the pore structure evolution and surface chemistry of activated carbon (AC) obtained from bamboo waste were investigated. Nitrogen adsorption-desorption isotherms revealed that higher steam activation temperatures and/or times promoted the creation of new micropores and widened the existing micropores, consequently decreasing the surface area and total pore volume. Optimum conditions included an activation temperature of 850 °C, activation time of 120 min, and steam flush generated from deionized water of 0.2 cm3 min-1. Under these conditions, AC with a BET surface area of 1210 m2 g-1 and total pore volume of 0.542 cm-3 g-1was obtained. Changes in surface chemistry were determined through Boehm titration, pH measurement, Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). Results revealed the presence of a large number of basic groups on the surface of the pyrolyzed char and AC. Steam activation did not affect the species of oxygen-containing groups but changed the contents of these species when compared with pyrolyzed char. Scanning electron microscopy was used to observe the surface morphology of the products. AC obtained under optimum conditions showed a monolayer adsorption capacity of 330 mg g-1 for methylene blue (MB), which demonstrates its excellent potential for MB adsorption applications.

  9. Influence of the pore structure and surface chemical properties of activated carbon on the adsorption of mercury from aqueous solutions

    International Nuclear Information System (INIS)

    Lu, Xincheng; Jiang, Jianchun; Sun, Kang; Wang, Jinbiao; Zhang, Yanping

    2014-01-01

    Highlights: • Activated carbons with different pore structure and surface chemical properties were prepared by modification process. • HgCl 2 as a pollution target to evaluate the adsorption performance. • Influence of pore structure and surface chemical properties of activated carbon on adsorption of mercury was investigated. -- Abstract: Reactivation and chemical modification were used to obtain modified activated carbons with different pore structure and surface chemical properties. The samples were characterized by nitrogen absorption–desorption, Fourier transform infrared spectroscopy and the Bothem method. Using mercury chloride as the target pollutant, the Hg 2+ adsorption ability of samples was investigated. The results show that the Hg 2+ adsorption capacity of samples increased significantly with increases in micropores and acidic functional groups and that the adsorption process was exothermic. Different models and thermodynamic parameters were evaluated to establish the mechanisms. It was concluded that the adsorption occurred through a monolayer mechanism by a two-speed process involving both rapid adsorption and slow adsorption. The adsorption rate was determined by chemical reaction

  10. Effect of elemental sulfur in precursors on the pore structure and surface chemical characteristics of high-surface area activated carbon

    Directory of Open Access Journals (Sweden)

    Jing Zhao

    2017-09-01

    Full Text Available Analog sulfur-containing precursors (ASCPs have been prepared by adding a certain amount of elemental sulfur (ES into petroleum coke (PC for synthesis of high-surface area activated carbon (HAC. ASCPs make it feasible to control the speciation and content of sulfur in ASCPs, so as to accurately investigate the influence of ES on the pore structure and surface chemical characteristics of the resultant HAC. The results indicate that ES in ASCPs can react with activator KOH and consume a part of KOH amount, thus leading to the deficiency of actual KOH amount for PC activation, eventually making a decrease in the specific surface area and pore volume of HAC. Interestingly, some of ES in ASCPs is transformed into organic sulfur thioether (C–S–C and sulfate (C–SO4–C or sulfonate (C–SO3–C on HAC surface during the activation process. Therefore, the surface chemical characteristics of HAC are modified correspondingly.

  11. Cross-cutting High Surface Area Graphene-based Frameworks with Controlled Pore Structure/Dopants

    Energy Technology Data Exchange (ETDEWEB)

    Gaillard, J. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2017-09-28

    The goal of this project is to enhance the performance of graphene-based materials by manufacturing specific 3D architectures. The materials have global applications regarding fuel cell catalysts, gas adsorbents, supercapacitor/battery electrodes, ion (e.g., actinide) capture, gas separation, oil adsorption, and catalysis. This research focuses on hydrogen storage for hydrogen fuel cell vehicles with a potential transformational impact on hydrogen adsorbents that exhibit high gravimetric and volumetric density, a clean energy application sought by the Department of Energy. The development of an adsorbent material would enable broad commercial opportunities in hydrogen-fueled vehicles, promote new advanced nanomanufacturing scale-up, and open other opportunities at Savannah River National Laboratory to utilize a high surface area material that is robust, chemically stable, and radiation resistant.

  12. Metal structures with parallel pores

    Science.gov (United States)

    Sherfey, J. M.

    1976-01-01

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

  13. Nuclear pore structure: warming up the core.

    Science.gov (United States)

    Harel, Amnon; Gruenbaum, Yosef

    2011-07-22

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

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

    Science.gov (United States)

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

    2008-02-01

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

  15. Pore structure and growth kinetics in carbon materials

    Energy Technology Data Exchange (ETDEWEB)

    Bose, S.

    1978-04-01

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

  16. Block copolymer structures in nano-pores

    Science.gov (United States)

    Pinna, Marco; Guo, Xiaohu; Zvelindovsky, Andrei

    2010-03-01

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

  17. Pore structure in blended cement pastes

    DEFF Research Database (Denmark)

    Canut, Mariana Moreira Cavalcanti

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

  18. 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

  19. Modeling branching pore structures in membrane filters

    Science.gov (United States)

    Sanaei, Pejman; Cummings, Linda J.

    2016-11-01

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

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

    Science.gov (United States)

    Baradari, Mehdi Gholipour

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

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

    International Nuclear Information System (INIS)

    Deo, Omkar; Neithalath, Narayanan

    2010-01-01

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

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

    Directory of Open Access Journals (Sweden)

    Freire-Gormaly Marina

    2016-05-01

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

  3. The Pore Structure of Direct Methanol Fuel Cell Electrodes

    DEFF Research Database (Denmark)

    Lund, Peter Brilner

    2005-01-01

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

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

    Science.gov (United States)

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

    2017-06-19

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

  5. Multi-tests for pore structure characterization-A case study using lamprophyre

    Science.gov (United States)

    Li, Zhen; Feng, Guorui; Luo, Yi; Hu, Shengyong; Qi, Tingye; Jiang, Haina; Guo, Jun; Bai, Jinwen; Du, Xianjie; Kang, Lixun

    2017-08-01

    The pore structure plays an important role to understand methane adsorption, storage and flow behavior of geological materials. In this paper, the multi-tests including N2 adsorption, mercury intrusion porosimetry (MIP) and CT reconstruction have been proposed on Tashan lamprophyre samples. The main findings are listed: (1) The pore size distribution has a broad range ranging from 2-100000nm, among which the adsorption pores (100nm) only account for 34% of total pore volume. (2) The lamprophyre open pores are mainly slit-like/plate-like and ink-bottle-shaped pores on a two-dimensional level. The lamprophyre 3D pore structure shows more stochastic and anisotropic extension on the z axis to form a complex pore system on a three-dimensional level. (3) The closed pores (>647nm) occupy averaged 74.86% and 72.75% of total pores (>647nm) volume and specific surface area indicating a poor connectivity pore system. The revealed results provide basic information for understanding the abnormal methane emission reasons in similar geological conditions with lamprophyre invasions.

  6. Multi-tests for pore structure characterization-A case study using lamprophyre

    Directory of Open Access Journals (Sweden)

    Zhen Li

    2017-08-01

    Full Text Available The pore structure plays an important role to understand methane adsorption, storage and flow behavior of geological materials. In this paper, the multi-tests including N2 adsorption, mercury intrusion porosimetry (MIP and CT reconstruction have been proposed on Tashan lamprophyre samples. The main findings are listed: (1 The pore size distribution has a broad range ranging from 2-100000nm, among which the adsorption pores (100nm only account for 34% of total pore volume. (2 The lamprophyre open pores are mainly slit-like/plate-like and ink-bottle-shaped pores on a two-dimensional level. The lamprophyre 3D pore structure shows more stochastic and anisotropic extension on the z axis to form a complex pore system on a three-dimensional level. (3 The closed pores (>647nm occupy averaged 74.86% and 72.75% of total pores (>647nm volume and specific surface area indicating a poor connectivity pore system. The revealed results provide basic information for understanding the abnormal methane emission reasons in similar geological conditions with lamprophyre invasions.

  7. Open pore structure analysis of lithium bearing ceramics

    International Nuclear Information System (INIS)

    Elbel, H.

    1988-01-01

    The analysis of the open pore structure includes mercury porosimetry, helium stereopycnometry, gas permeability and specific surface area measurements. These methods were used in the analysis of different types of Li 2 SiO 3 and Li j SiO 4 specimens whose behaviour is tested under operation conditions in various irradiation experiments. Mercury porosimetry yielded density of the specimens, size distribution of the channels and amount of the open porosity. The correlation between mercury pressure and channel diameter was approximated by the Washburn equation. Density determinations by means of helium stereopycnometry demonstrated the existence of open pore volume below the mercury porosimetry detection. Additional information about the structure of open porosity was obtained by gas permeability measurements evaluated using the Carman relation, which is a generalization of the Hagen-Poiseuille law. This approach correlates structure parameters of the open porosity with permeability coefficients. The specific surface area was determined by applying the BET theory to volumetric nitrogen gas adsorption. (orig.)

  8. 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.

  9. A tri-continuous mesoporous material with a silica pore wall following a hexagonal minimal surface

    KAUST Repository

    Han, Yu

    2009-04-06

    Ordered porous materials with unique pore structures and pore sizes in the mesoporous range (2-50nm) have many applications in catalysis, separation and drug delivery. Extensive research has resulted in mesoporous materials with one-dimensional, cage-like and bi-continuous pore structures. Three families of bi-continuous mesoporous materials have been made, with two interwoven but unconnected channels, corresponding to the liquid crystal phases used as templates. Here we report a three-dimensional hexagonal mesoporous silica, IBN-9, with a tri-continuous pore structure that is synthesized using a specially designed cationic surfactant template. IBN-9 consists of three identical continuous interpenetrating channels, which are separated by a silica wall that follows a hexagonal minimal surface. Such a tri-continuous mesostructure was predicted mathematically, but until now has not been observed in real materials. © 2009 Macmillan Publishers Limited. All rights reserved.

  10. Hierarchically templated beads with tailored pore structure for phosphopeptide capture and phosphoproteomics

    DEFF Research Database (Denmark)

    Wierzbicka, Celina; Torsetnes, Silje B.; Jensen, Ole N.

    2017-01-01

    Two templating approaches to produce imprinted phosphotyrosine capture beads with a controllable pore structure are reported and compared with respect to their ability to enrich phosphopeptides from a tryptic peptide mixture. The beads were prepared by the polymerization of urea-based host monomers...... and crosslinkers inside the pores of macroporous silica beads with both free and immobilized template. In the final step the silica was removed by fluoride etching resulting in mesoporous polymer replicas with narrow pore size distributions, pore diameters ≈ 10 nm and surface area > 260 m2 g-1. The beads displayed...

  11. 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.

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

    Science.gov (United States)

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

    2015-01-01

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

  13. Tailor-Made Pore Surface Engineering in Covalent Organic Frameworks: Systematic Functionalization for Performance Screening.

    Science.gov (United States)

    Huang, Ning; Krishna, Rajamani; Jiang, Donglin

    2015-06-10

    Imine-linked covalent organic frameworks (COFs) were synthesized to bear content-tunable, accessible, and reactive ethynyl groups on the walls of one-dimensional pores. These COFs offer an ideal platform for pore-wall surface engineering aimed at anchoring diverse functional groups ranging from hydrophobic to hydrophilic units and from basic to acidic moieties with controllable loading contents. This approach enables the development of various tailor-made COFs with systematically tuned porosities and functionalities while retaining the crystallinity. We demonstrate that this strategy can be used to efficiently screen for suitable pore structures for use as CO2 adsorbents. The pore-surface-engineered walls exhibit an enhanced affinity for CO2, resulting in COFs that can capture and separate CO2 with high performance.

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

    Indian Academy of Sciences (India)

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

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

    Indian Academy of Sciences (India)

    Administrator

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

  16. Influence of carbonization conditions on micro-pore structure of foundry formed coke produced with char

    Energy Technology Data Exchange (ETDEWEB)

    Jun Qiao; Jianjun Wu; Jingru Zu; Zhiyuan Gao; Guoli Zhou

    2009-07-01

    There are few studies on coke's micro-pore structure in recent years, however, micro-pore structure of foundry coke determines its macroscopically quality index and reactivity in cupola furnace. Effect of such factors on micro-pore structure were investigated under different carbonization conditions with certain ratio of raw materials and material forming process in this article as charging temperature (A); braised furnace time (B); heating rate of the first stage (C)and the second stage (D) and holding time of ultimate temperature (E). Research showed that charging temperature was the most influential factor on the coke porosity, pore volume, pore size and specific surface area. It is suggested that formation of plastic mass and releasing rate of volatile during carbonization period are two main factors on microstructure of foundry coke while charging temperature contributes most to the above factors. 6 refs., 4 figs., 9 tabs.

  17. Relationship between pore structure and compressive strength of ...

    Indian Academy of Sciences (India)

    Keywords. Pore structure; compressive strength; concrete; statistical model; mercury intrusion porosimetry (MIP) ... Author Affiliations. J BU1 Z TIAN. College of Water Conservancy and Hydropower Engineering, Hohai University, Nanjing, Jiangsu 210098, People's Republic of China ...

  18. Crystalline mesoporous zirconia catalysts having stable tetragonal pore wall structure

    Science.gov (United States)

    Sachtler, Wolfgang M. H.; Huang, Yin-Yan

    1998-01-01

    Methods for the preparation of new sulfated mesoporous zirconia materials/catalysts with crystalline pore walls of predominantly tetragonal crystal structure, characterized by nitrogen physisorption measurement, X-ray diffraction, transmission electron microscopy and catalytic tests using n-butane isomerization to iso-butane and alkylation of 1-naphthol with 4-tert-butylstyrene as probe reactions. Sulfate deposition is preferred for the transformation of a mesoporous precursor with amorphous pore walls into a material with crystalline pore walls maintaining the mesoporous characteristics.

  19. Relationship between pore structure and compressive strength of ...

    Indian Academy of Sciences (India)

    J BU

    [16] Shi C 1996 Strength, pore structure and permeability of alkali-activated slag mortars. Cem. Concr. Res. 26(10): 1789–. 1799. [17] O'Farrell M, Wild S and Sabir B B 2001 Pore size distribution and compressive strength of waste clay brick mortar. Cem. Concr. Res. 23(1): 81–91. [18] Wen C E, Yamada Y, Shimojima K, ...

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

    Science.gov (United States)

    Park, In; Pinnavaia, Thomas J

    2009-02-01

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

  1. Characterization of pore structure of several activated carbons with different radon adsorption capabilities

    International Nuclear Information System (INIS)

    Wang Qingbo; Qu Jingyuan; Cao Jianzhu; Zhu Wenkai; Zhou Baichang; Cheng Jinchang; Zhang Huimin

    2011-01-01

    The radon dynamic adsorption coefficients (DAC) of four types of activated carbons measured in radon room are different from each other. The pore structures (specific surface area, pore size distribution, pore volume, etc.) influence the adsorption ability significantly. Physical adsorption of inert nitrogen was used for evaluation pore structures of those four activated carbon samples. The results show that activated carbon with specific surface area about 800 m 2 /g has the strong adsorption ability to radon and when the specific surface areas are close, the adsorption ability to radon increases with the micropore specific surface's percentage. Pore size distribution (PSD) was calculated by H-K, BJH and density function theory (DFT). The Micropore size distribution calculation by H-K method shows that pore with size between 0.7-2 nm plays the most important role for adsorption of radon. Mesopore size distribution calculated by BJH method and DFT method shows that mesopore distribution with discrete peaks is more useful to help radon adsorption on activated carbons. (authors)

  2. Adsorptive capacity and evolution of the pore structure of alumina on reaction with gaseous hydrogen fluoride.

    Science.gov (United States)

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

    2015-05-19

    Brunauer-Emmet-Teller (BET) specific surface areas are generally used to gauge the propensity of uptake on adsorbents, with less attention paid to kinetic considerations. We explore the importance of such parameters by modeling the pore size distributions of smelter grade aluminas following HF adsorption, an industrially important process in gas cleaning at aluminum smelters. The pore size distributions of industrially fluorinated aluminas, and those contacted with HF in controlled laboratory trials, are reconstructed from the pore structure of the untreated materials when filtered through different models of adsorption. These studies demonstrate the presence of three distinct families of pores: those with uninhibited HF uptake, kinetically limited porosity, and pores that are surface blocked after negligible scrubbing. The surface areas of the inaccessible and blocked pores will overinflate estimates of the adsorption capacity of the adsorbate. We also demonstrate, contrary to conventional understanding, that porosity changes are attributed not to monolayer uptake but more reasonably to pore length attenuation. The model assumes nothing specific regarding the Al2O3-HF system and is therefore likely general to adsorbate/adsorbent phenomena.

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

    Science.gov (United States)

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

    2018-02-01

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

  4. Influence of crosslinking agents on the pore structure of skin.

    Science.gov (United States)

    Fathima, N Nishad; Dhathathreyan, Aruna; Ramasami, T

    2007-05-15

    Analysis of pore structure of skin is important to understand process of diffusion and adsorption involved during any application of the skin matrix. In this study, the effect of thermal shrinkage on the pore structure of chromium and vegetable treated skin has been analyzed as these tanning agents are known to bring about thermal stability to the matrix. The changes brought about in the pore structure have been studied using mercury intrusion porosimetry and scanning electron microscopy. Response of the chromium treated and vegetable tanning treated skin structure to heat has been found to be quite different from each other. About 41% decrease in porosity is observed for chromium treated skin as against 97% decrease for the skin treated with vegetable tannins. This is primarily attributed to the basic nature of these materials and the nature of interaction of them towards skin.

  5. A statistical model for the wettability of surfaces with heterogeneous pore geometries

    Science.gov (United States)

    Brockway, Lance; Taylor, Hayden

    2016-10-01

    We describe a new approach to modeling the wetting behavior of micro- and nano-textured surfaces with varying degrees of geometrical heterogeneity. Surfaces are modeled as pore arrays with a Gaussian distribution of sidewall reentrant angles and a characteristic wall roughness. Unlike conventional wettability models, our model considers the fraction of a surface’s pores that are filled at any time, allowing us to capture more subtle dependences of a liquid’s apparent contact angle on its surface tension. The model has four fitting parameters and is calibrated for a particular surface by measuring the apparent contact angles between the surface and at least four probe liquids. We have calibrated the model for three heterogeneous nanoporous surfaces that we have fabricated: a hydrothermally grown zinc oxide, a film of polyvinylidene fluoride (PVDF) microspheres formed by spinodal decomposition, and a polytetrafluoroethylene (PTFE) film with pores defined by sacrificial polystyrene microspheres. These three surfaces show markedly different dependences of a liquid’s apparent contact angle on the liquid’s surface tension, and the results can be explained by considering geometric variability. The highly variable PTFE pores yield the most gradual variation of apparent contact angle with probe liquid surface tension. The PVDF microspheres are more regular in diameter and, although connected in an irregular manner, result in a much sharper transition from non-wetting to wetting behavior as surface tension reduces. We also demonstrate, by terminating porous zinc oxide with three alternative hydrophobic molecules, that a single geometrical model can capture a structure’s wetting behavior for multiple surface chemistries and liquids. Finally, we contrast our results with those from a highly regular, lithographically-produced structure which shows an extremely sharp dependence of wettability on surface tension. This new model could be valuable in designing and

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

    Indian Academy of Sciences (India)

    Administrator

    *For correspondence. The study of the relationship between pore structure and photocatalysis of mesoporous TiO2. BING GUO a. , HANGYAN SHEN a,. *, KANGYING SHU a. , YAOWU ZENG b and. WENSHENG NING c a. College of Materials Science and Engineering, China Jiliang University, Hangzhou 310018, China b.

  7. Investigation on pore structure and small-scale agglomeration ...

    Indian Academy of Sciences (India)

    Investigation on pore structure and small-scale agglomeration behaviour in liquid phase sintered. SiC using small angle neutron scattering. D SEN1,∗, J BAHADUR1, S MAZUMDER1, T MAHATA2, M SYAMBABU2 and. P K SINHA2. 1Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085, India.

  8. Idealized Shale Sorption Isotherm Measurements to Determine Pore Volume, Pore Size Distribution, and Surface Area

    Science.gov (United States)

    Holmes, R.; Wang, B.; Aljama, H.; Rupp, E.; Wilcox, J.

    2014-12-01

    One method for mitigating the impacts of anthropogenic CO2-related climate change is the sequestration of CO2 in depleted gas and oil reservoirs, including shale. The accurate characterization of the heterogeneous material properties of shale, including pore volume, surface area, pore size distributions (PSDs) and composition is needed to understand the interaction of CO2 with shale. Idealized powdered shale sorption isotherms were created by varying incremental amounts of four essential components by weight. The first two components, organic carbon and clay, have been shown to be the most important components for CO2 uptake in shales. Organic carbon was represented by kerogen isolated from a Silurian shale, and clay groups were represented by illite from the Green River shale formation. The rest of the idealized shale was composed of equal parts by weight of SiO2 to represent quartz and CaCO3 to represent carbonate components. Baltic, Eagle Ford, and Barnett shale sorption measurements were used to validate the idealized samples. The idealized and validation shale sorption isotherms were measured volumetrically using low pressure N2 (77K) and CO2 (273K) adsorbates on a Quantachrome Autosorb IQ2. Gravimetric isotherms were also produced for a subset of these samples using CO2 and CH4adsorbates under subsurface temperature and pressure conditions using a Rubotherm magnetic suspension balance. Preliminary analyses were inconclusive in validating the idealized samples. This could be a result of conflicting reports of total organic carbon (TOC) content in each sample, a problem stemming from the heterogeneity of the samples and different techniques used for measuring TOC content. The TOC content of the validation samples (Eagle Ford and Barnett) was measured by Rock-Eval pyrolysis at Weatherford Laboratories, while the TOC content in the Baltic validation samples was determined by LECO TOC. Development of a uniform process for measuring TOC in the validation samples is

  9. Highly Aminated Mesoporous Silica Nanoparticles with Cubic Pore Structure

    KAUST Repository

    Suteewong, Teeraporn

    2011-01-19

    Mesoporous silica with cubic symmetry has attracted interest from researchers for some time. Here, we present the room temperature synthesis of mesoporous silica nanoparticles possessing cubic Pm3n symmetry with very high molar ratios (>50%) of 3-aminopropyl triethoxysilane. The synthesis is robust allowing, for example, co-condensation of organic dyes without loss of structure. By means of pore expander molecules, the pore size can be enlarged from 2.7 to 5 nm, while particle size decreases. Adding pore expander and co-condensing fluorescent dyes in the same synthesis reduces average particle size further down to 100 nm. After PEGylation, such fluorescent aminated mesoporous silica nanoparticles are spontaneously taken up by cells as demonstrated by fluorescence microscopy.

  10. Structural Insights into Clostridium perfringens Delta Toxin Pore Formation.

    Directory of Open Access Journals (Sweden)

    Jessica Huyet

    Full Text Available Clostridium perfringens Delta toxin is one of the three hemolysin-like proteins produced by C. perfringens type C and possibly type B strains. One of the others, NetB, has been shown to be the major cause of Avian Nectrotic Enteritis, which following the reduction in use of antibiotics as growth promoters, has become an emerging disease of industrial poultry. Delta toxin itself is cytotoxic to the wide range of human and animal macrophages and platelets that present GM2 ganglioside on their membranes. It has sequence similarity with Staphylococcus aureus β-pore forming toxins and is expected to heptamerize and form pores in the lipid bilayer of host cell membranes. Nevertheless, its exact mode of action remains undetermined. Here we report the 2.4 Å crystal structure of monomeric Delta toxin. The superposition of this structure with the structure of the phospholipid-bound F component of S. aureus leucocidin (LukF revealed that the glycerol molecules bound to Delta toxin and the phospholipids in LukF are accommodated in the same hydrophobic clefts, corresponding to where the toxin is expected to latch onto the membrane, though the binding sites show significant differences. From structure-based sequence alignment with the known structure of staphylococcal α-hemolysin, a model of the Delta toxin pore form has been built. Using electron microscopy, we have validated our model and characterized the Delta toxin pore on liposomes. These results highlight both similarities and differences in the mechanism of Delta toxin (and by extension NetB cytotoxicity from that of the staphylococcal pore-forming toxins.

  11. The pore wall structure of porous semi-crystalline anatase TiO2

    International Nuclear Information System (INIS)

    Kim, Man-Ho; Doh, Jeong-Mann; Han, Seong Chul; Chae, Keun Hwa; Yu, Byung-Yong; Hong, Kyung Tae; Jackson, Andrew; Maryland Univ., College Park, MD; Anovitz, Lawrence M.

    2011-01-01

    The structure of porous TiO 2 prepared by electrochemical anodization in a fluoride-containing ethylene glycol electrolyte solution was quantitatively studied using small-angle neutron scattering (SANS) and ultra-small-angle neutron scattering (USANS). The cylindrical pores along the coaxial direction were somewhat irregular in shape, were widely distributed in diameter, and seemed to have a broadly pseudo-hexagonal arrangement. The scattering from the pore wall showed a negative deviation from Porod scattering, indicating that the interface between TiO2 and the pore was not sharp. A density gradient of around 40-60 A at the pore wall (i.e. the interface between the pore and the TiO 2 matrix) was estimated using both constant and semi-sigmoidal interface models. This gradient may be due to the presence of fluorine and carbon partially absorbed by the pore wall from the fluoride-containing electrolyte or to sorbed water molecules on the wall. The neutron contrast-matching point between the TiO 2 matrix and the pores filled with liquid H 2 O/D 2 O mixtures was 51/49%(v/v) H 2 O/D 2 O, yielding an estimated mass density of 3.32 g cm -3 . The specific surface area of the sample derived from the (U)SANS data was around 939-1003 m 2 cm -3 (283-302 m 2 g -1 ). (orig.)

  12. The pore wall structure of porous semi-crystalline anatase TiO2.

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Dr Man-Ho [National Institute of Standards and Technol/University of Maryland, College Park; Doh, Dr. Jeong-Mann [Harbin Institute of Technology & Korea Institute of Science and Technology; Han, Seong Chul [Harbin Institute of Technology & Korea Institute of Science and Technology; Chae, Keun Hwa [Harbin Institute of Technology & Korea Institute of Science and Technology; Yu, Byung-Yong [Harbin Institute of Technology & Korea Institute of Science and Technology; Hong, Kyung Tea [Harbin Institute of Technology & Korea Institute of Science and Technology; Jackson, Andrew [NIST Center for Neutron Research (NCRN), Gaithersburg, MD; Anovitz, Lawrence {Larry} M [ORNL

    2011-01-01

    The structure of porous TiO2 prepared by electrochemical anodization in a fluoride-containing ethylene glycol electrolyte solution was quantitatively studied using small-angle neutron scattering (SANS) and ultra-small-angle neutron scattering (USANS). The cylindrical pores along the coaxial direction were somewhat irregular in shape, were widely distributed in diameter, and seemed to have a broadly pseudo-hexagonal arrangement. The scattering from the pore wall showed a negative deviation from Porod scattering, indicating that the interface between TiO2 and the pore was not sharp. A density gradient of around 40 60 A at the pore wall (i.e. the interface between the pore and the TiO2 matrix) was estimated using both constant and semi-sigmoidal interface models. This gradient may be due to the presence of fluorine and carbon partially absorbed by the pore wall from the fluoride-containing electrolyte or to sorbed water molecules on the wall. The neutron contrast-matching point between the TiO2 matrix and the pores filled with liquid H2O/D2O mixtures was 51/49%(v/v) H2O/D2O, yielding an estimated mass density of 3.32 g cm3. The specific surface area of the sample derived from the (U)SANS data was around 939 1003 m2 cm3 (283 302 m2 g1).

  13. Influence of pore shape on the structure of a nanoconfined Gay-Berne liquid crystal

    Science.gov (United States)

    Ji, Qing; Lefort, Ronan; Morineau, Denis

    2009-08-01

    We present results from molecular dynamics simulations of a Gay-Berne mesogenic system GB(4.4,20,1,1) under short scale spatial confinement in a slab, a cylinder and a sphere geometry. The structure adopted by the confined phases is characterized by the density profile and the orientational order parameter as a function of temperature, and compared to the bulk. Though confinement always induces a strong surface ordering, the topological constrain introduced by the different pore shapes results in different molecular arrangements. This first study on pore shape effect on the structure of a nanoconfined Gay-Berne system is relevant to numerous experimental studies performed with different mesoporous matrices.

  14. Hysteresis of boiling for different tunnel-pore surfaces

    Directory of Open Access Journals (Sweden)

    Pastuszko Robert

    2015-01-01

    Full Text Available Analysis of boiling hysteresis on structured surfaces covered with perforated foil is proposed. Hysteresis is an adverse phenomenon, preventing high heat flux systems from thermal stabilization, characterized by a boiling curve variation at an increase and decrease of heat flux density. Experimental data were discussed for three kinds of enhanced surfaces: tunnel structures (TS, narrow tunnel structures (NTS and mini-fins covered with the copper wire net (NTS-L. The experiments were carried out with water, R-123 and FC-72 at atmospheric pressure. A detailed analysis of the measurement results identified several cases of type I, II and III for TS, NTS and NTS-L surfaces.

  15. Predicting Reactive Transport Dynamics in Carbonates using Initial Pore Structure

    Science.gov (United States)

    Menke, H. P.; Nunes, J. P. P.; Blunt, M. J.

    2017-12-01

    Understanding rock-fluid interaction at the pore-scale is imperative for accurate predictive modelling of carbon storage permanence. However, coupled reactive transport models are computationally expensive, requiring either a sacrifice of resolution or high performance computing to solve relatively simple geometries. Many recent studies indicate that initial pore structure many be the dominant mechanism in determining the dissolution regime. Here we investigate how well the initial pore structure is predictive of distribution and amount of dissolution during reactive flow using particle tracking on the initial image. Two samples of carbonate rock with varying initial pore space heterogeneity were reacted with reservoir condition CO2-saturated brine and scanned dynamically during reactive flow at a 4-μm resolution between 4 and 40 times using 4D X-ray micro-tomography over the course of 1.5 hours using μ-CT. Flow was modelled on the initial binarized image using a Navier-Stokes solver. Particle tracking was then run on the velocity fields, the streamlines were traced, and the streamline density was calculated both on a voxel-by-voxel and a channel-by-channel basis. The density of streamlines was then compared to the amount of dissolution in subsequent time steps during reaction. It was found that for the flow and transport regimes studied, the streamline density distribution in the initial image accurately predicted the dominant pathways of dissolution and gave good indicators of the type of dissolution regime that would later develop. This work suggests that the eventual reaction-induced changes in pore structure are deterministic rather than stochastic and can be predicted with high resolution imaging of unreacted rock.

  16. The effect of pore diameter in the arrangement of chelating species grafted onto silica surfaces with application to uranium extraction

    International Nuclear Information System (INIS)

    Charlot, A.; Cuer, F.; Grandjean, A.

    2017-01-01

    A series of five silica supports with different pore diameters were functionalized in two steps by post-grafting, producing three types of material: (1) initial supports with pores smaller than 4 nm are heterogeneously functionalized because of steric effects; (2) when the pores range from 5 to 20 nm in diameter, a homogeneous organic monolayer is grafted onto the silica skeleton; and (3) when the pores are larger than 30 nm, an organic multilayer covalently linked to the surface is obtained. These hybrid materials were then used to extract uranium from a sulphuric solution. Our results show that the efficiency, capacity and selectivity of the extraction can be controlled through the effect the initial pore size has on the organic structures that form therein. After regeneration moreover, these materials can be reused with the same efficiency. (authors)

  17. Hierarchically Porous Carbon Materials for CO 2 Capture: The Role of Pore Structure

    Energy Technology Data Exchange (ETDEWEB)

    Estevez, Luis [Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, Washington 99352, United States; Barpaga, Dushyant [Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, Washington 99352, United States; Zheng, Jian [Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, Washington 99352, United States; Sabale, Sandip [Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, Washington 99352, United States; Patel, Rajankumar L. [Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, Washington 99352, United States; Zhang, Ji-Guang [Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, Washington 99352, United States; McGrail, B. Peter [Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, Washington 99352, United States; Motkuri, Radha Kishan [Pacific Northwest National Laboratory, 902 Battelle Boulevard, Richland, Washington 99352, United States

    2018-01-17

    With advances in porous carbon synthesis techniques, hierarchically porous carbon (HPC) materials are being utilized as relatively new porous carbon sorbents for CO2 capture applications. These HPC materials were used as a platform to prepare samples with differing textural properties and morphologies to elucidate structure-property relationships. It was found that high microporous content, rather than overall surface area was of primary importance for predicting good CO2 capture performance. Two HPC materials were analyzed, each with near identical high surface area (~2700 m2/g) and colossally high pore volume (~10 cm3/g), but with different microporous content and pore size distributions, which led to dramatically different CO2 capture performance. Overall, large pore volumes obtained from distinct mesopores were found to significantly impact adsorption performance. From these results, an optimized HPC material was synthesized that achieved a high CO2 capacity of ~3.7 mmol/g at 25°C and 1 bar.

  18. Pore structure of natural and regenerated soil aggregates

    DEFF Research Database (Denmark)

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

    2014-01-01

    Quantitative characterization of aggregate pore structure can reveal the evolution of aggregates under different land use and management practices and their effects on soil processes and functions. Advances in X-ray Computed Tomography (CT) provide powerful means to conduct such characterization....... This study examined aggregate pore structure of three differently managed same textured Danish soils (mixed forage cropping, MFC; mixed cash cropping, MCC; cereal cash cropping, CCC) for (i) natural aggregates, and (ii) aggregates regenerated after 20 months of incubation. In total, 27 aggregates (8-16 mm......) were sampled from nine different treatments; 3 natural soils and 3 repacked lysimeters without and 3 with organic matter (ground rape) amendment. Three dimensional X-ray CT images, tensile strength, and organic carbon were obtained for each aggregate. Aggregate-associated organic carbon differed...

  19. Correlation between gas permeability and pore structure of coal matrix

    Science.gov (United States)

    Zhang, J.; Yang, J.; Gao, F.; Li, Y.; Niu, H.; Gao, H.

    2012-04-01

    The sequestration of CO2 in unminable coal seams represents a promising option for CO2 geologic storage, because the injected CO2 may enhance coalbed methane recovery (CO2-ECBM), which could partly offset the costs of the storage process. The CO2-ECBM technology is based on the relative affinity of CO2 and CH4 to coals under given pressure and temperature conditions. The excess sorption capacity of coals for CO2 is generally higher than the sorption capacity for methane. The coal seams are characterized by a dual porosity structure including cleat and matrix pores. The cleats in the coal seams are considered as highways for gas and water flow, while the matrix is the storage location of gas by adsorption. The slow transport process of gas in coal matrix may constrain the efficiency of the displacement of CH4 by CO2 due to the compacted pore structure of the coal matrix. Therefore, a detailed understanding of the correlation between permeability of gas and pore structure in coal matrix is crucial for the CO2-ECBM processes. Yangquan coals originating from the Qingshui basin, which contains gas-rich coals in China, were selected for the tests in this study. Yangquan coals are classified as anthracite. In order to avoid the influence of coal cleats on fluid flow, small coal plugs (~6 mm in diameter, ~13 mm in length) were selected and fixed in the sample compartment by special glue. A test system for simultaneously measuring adsorption-porosity-permeability on the coal matrix blocks in its free state is constructed. The permeability of gas and porosity in coal plugs to He under different gas pressure and temperature conditions were simultaneously investigated. The permeability and excess sorption capacity of the coal plugs to He, N2, CH4 and CO2 were compared at a constant gas pressure and temperature. It is expected that gas break through a cleat-plug is much faster than that through a coal matrix-plug. Different sample plugs with the different pore structure results

  20. 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

  1. Evaluation of the effect of varying the workability in concrete pore structure by using X-ray microtomography

    Directory of Open Access Journals (Sweden)

    E. E. Bernardes

    Full Text Available The useful life of concrete is associated with the penetrative ability of aggressive agents on their structures. Structural parameters such as porosity, pore distribution and connectivity have great influence on the properties of mass transport in porous solids. In the present study, the effect of varying the workability of concrete in fresh state, produced through the use of additives, on pore structure and on the mechanical compressive strength of hardened concrete was assessed. The pore structure was analyzed with the aid of X-ray microtomography, and the results obtained were compared to the total pore volume calculated from data derived from helium and mercury pycnometry tests. A good approximation between the porosity values obtained through the two techniques was observed, and it was found that, regardless of concrete consistency, the samples from the surface of the specimens showed a percentage of pores higher than those taken from the more inner layers.

  2. Rock Pore Structure as Main Reason of Rock Deterioration

    Science.gov (United States)

    Ondrášik, Martin; Kopecký, Miloslav

    2014-03-01

    Crashed or dimensional rocks have been used as natural construction material, decoration stone or as material for artistic sculptures. Especially old historical towns not only in Slovakia have had experiences with use of stones for construction purposes for centuries. The whole buildings were made from dimensional stone, like sandstone, limestone or rhyolite. Pavements were made especially from basalt, andesite, rhyolite or granite. Also the most common modern construction material - concrete includes large amounts of crashed rock, especially limestone, dolostone and andesite. However, rock as any other material if exposed to exogenous processes starts to deteriorate. Especially mechanical weathering can be very intensive if rock with unsuitable rock properties is used. For long it had been believed that repeated freezing and thawing in relation to high absorption is the main reason of the rock deterioration. In Slovakia for many years the high water absorption was set as exclusion criterion for use of rocks and stones in building industry. Only after 1989 the absorption was accepted as merely informational rock property and not exclusion. The reason of the change was not the understanding of the relationship between the porosity and rock deterioration, but more or less good experiences with some high porous rocks used in constructions exposed to severe weather conditions and proving a lack of relationship between rock freeze-thaw resistivity and water absorption. Results of the recent worldwide research suggest that understanding a resistivity of rocks against deterioration is hidden not in the absorption but in the structure of rock pores in relation to thermodynamic properties of pore water and tensile strength of rocks and rock minerals. Also this article presents some results of research on rock deterioration and pore structure performed on 88 rock samples. The results divide the rocks tested into two groups - group N in which the pore water does not freeze

  3. Structure of Staphylococcal α-Hemolysin, a Heptameric Transmembrane Pore

    Science.gov (United States)

    Song, Langzhou; Hobaugh, Michael R.; Shustak, Christopher; Cheley, Stephen; Bayley, Hagan; Gouaux, J. Eric

    1996-12-01

    The structure of the Staphylococcus aureus α-hemolysin pore has been determined to 1.9 overset{circ}{mathrm A} resolution. Contained within the mushroom-shaped homo-oligomeric heptamer is a solvent-filled channel, 100 overset{circ}{mathrm A} in length, that runs along the sevenfold axis and ranges from 14 overset{circ}{mathrm A} to 46 overset{circ}{mathrm A} in diameter. The lytic, transmembrane domain comprises the lower half of a 14-strand antiparallel β barrel, to which each protomer contributes two β strands, each 65 overset{circ}{mathrm A} long. The interior of the β barrel is primarily hydrophilic, and the exterior has a hydrophobic belt 28 overset{circ}{mathrm A} wide. The structure proves the heptameric subunit stoichiometry of the α-hemolysin oligomer, shows that a glycine-rich and solvent-exposed region of a water-soluble protein can self-assemble to form a transmembrane pore of defined structure, and provides insight into the principles of membrane interaction and transport activity of β barrel pore-forming toxins.

  4. Pore structure and function of synthetic nanopores with fixed charges: tip shape and rectification properties

    Energy Technology Data Exchange (ETDEWEB)

    RamIrez, Patricio [Departament de Fisica Aplicada, Universitat Politecnica de Valencia, E-46022 Valencia (Spain); Apel, Pavel Yu [Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research, Joliot-Curie street 6, 141980 Dubna (Russian Federation); Cervera, Javier; Mafe, Salvador [Departament de Fisica de la Terra i Termodinamica, Universitat de Valencia, E-46100 Burjassot (Spain)], E-mail: patraho@fis.upv.es

    2008-08-06

    We present a complete theoretical study of the relationship between the structure (tip shape and dimensions) and function (selectivity and rectification) of asymmetric nanopores on the basis of previous experimental studies. The theoretical model uses a continuum approach based on the Nernst-Planck equations. According to our results, the nanopore transport properties, such as current-voltage (I-V) characteristics, conductance, rectification ratio, and selectivity, are dictated mainly by the shape of the pore tip (we have distinguished bullet-like, conical, trumpet-like, and hybrid shapes) and the concentration of pore surface charges. As a consequence, the nanopore performance in practical applications will depend not only on the base and tip openings but also on the pore shape. In particular, we show that the pore opening dimensions estimated from the pore conductance can be very different, depending on the pore shape assumed. The results obtained can also be of practical relevance for the design of nanopores, nanopipettes, and nanoelectrodes, where the electrical interactions between the charges attached to the nanostructure and the mobile charges confined in the reduced volume of the inside solution dictate the device performance in practical applications. Because single tracks are the elementary building blocks for nanoporous membranes, the understanding and control of their individual properties should also be crucial in protein separation, water desalination, and bio-molecule detection using arrays of identical nanopores.

  5. Pore structure of the activated coconut shell charcoal carbon

    Science.gov (United States)

    Budi, E.; Nasbey, H.; Yuniarti, B. D. P.; Nurmayatri, Y.; Fahdiana, J.; Budi, A. S.

    2014-09-01

    The development of activated carbon from coconut shell charcoal has been investigated by using physical method to determine the influence of activation parameters in term of temperature, argon gas pressure and time period on the pore structure of the activated carbon. The coconut shell charcoal was produced by pyrolisis process at temperature of about 75 - 150 °C for 6 hours. The charcoal was activated at various temperature (532, 700 and 868 °C), argon gas pressure (6.59, 15 and 23.4 kgf/cm2) and time period of (10, 60 and 120 minutes). The results showed that the pores size were reduced and distributed uniformly as the activation parameters are increased.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2007-09-15

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

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

    Science.gov (United States)

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

    2015-10-01

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

  8. Characterization of Tight Gas Reservoir Pore Structure Using USANS/SANS and Gas Adsorption Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Clarkson, Christopher R [ORNL; He, Lilin [ORNL; Agamalian, Michael [ORNL; Melnichenko, Yuri B [ORNL; Mastalerz, Maria [Indiana Geological Survey; Bustin, Mark [University of British Columbia, Vancouver; Radlinski, Andrzej Pawell [ORNL; Blach, Tomasz P [ORNL

    2012-01-01

    Small-angle and ultra-small-angle neutron scattering (SANS and USANS) measurements were performed on samples from the Triassic Montney tight gas reservoir in Western Canada in order to determine the applicability of these techniques for characterizing the full pore size spectrum and to gain insight into the nature of the pore structure and its control on permeability. The subject tight gas reservoir consists of a finely laminated siltstone sequence; extensive cementation and moderate clay content are the primary causes of low permeability. SANS/USANS experiments run at ambient pressure and temperature conditions on lithologically-diverse sub-samples of three core plugs demonstrated that a broad pore size distribution could be interpreted from the data. Two interpretation methods were used to evaluate total porosity, pore size distribution and surface area and the results were compared to independent estimates derived from helium porosimetry (connected porosity) and low-pressure N{sub 2} and CO{sub 2} adsorption (accessible surface area and pore size distribution). The pore structure of the three samples as interpreted from SANS/USANS is fairly uniform, with small differences in the small-pore range (< 2000 {angstrom}), possibly related to differences in degree of cementation, and mineralogy, in particular clay content. Total porosity interpreted from USANS/SANS is similar to (but systematically higher than) helium porosities measured on the whole core plug. Both methods were used to estimate the percentage of open porosity expressed here as a ratio of connected porosity, as established from helium adsorption, to the total porosity, as estimated from SANS/USANS techniques. Open porosity appears to control permeability (determined using pressure and pulse-decay techniques), with the highest permeability sample also having the highest percentage of open porosity. Surface area, as calculated from low-pressure N{sub 2} and CO{sub 2} adsorption, is significantly less

  9. Change in pore structure of coals by activation with KOH; KOH fukatsushita sekitan no saiko kozo

    Energy Technology Data Exchange (ETDEWEB)

    Maruyama, K.; Yoshizawa, N.; Ishikawa, E.; Kobayashi, M.; Toda, Y.; Yamada, Y.; Shiraishi, M. [National Institute for Resources and Environment, Tsukuba (Japan)

    1996-10-28

    Three typical Japanese coals of non-coking coal, coking coal and anthracite were heat-treated with KOH, and change in their pore structure was examined by absorption of N2, X-ray diffraction and TEM observation. In addition, the relation between a coal rank and pore structure was also studied by absorption experiment of N2. In experiment, the mixture of coal and KOH in a nickel holder was heat-treated in N2 gas flow at heating rate of 2{degree}C/min, and held at a fixed temperature for one hour. To clarify the pore structure, N2 absorption isotherms were measured at -196{degree}C under nearly 76cmHg using a commercially available full-automatic absorption measurement equipment. Based on the X-ray diffraction and TEM observation results on activated coals, the relation between the N2 absorption and pore structure was studied. The results are summarized as follows: (1) The yield and absorption ability of coals increase with a coal rank, (2) The specific surface area of coals reaches its peak at 800{degree}C in activation temperature regardless of a coal rank, and (3) The activation behavior of coals is dependent on a coal rank. 5 refs., 7 figs., 1 tab.

  10. The pore structure in processed Victorian Brown coal.

    Science.gov (United States)

    McMahon, P J; Snook, I K; Treimer, W

    2002-08-01

    Changes in the pore structure of Victorian Brown coal when upgraded with heated gases under pressure are investigated. We show that the results obtained from ultra-small-angle neutron scattering (USANS) measurements agree with previous results using small-angle X-ray scattering results but that USANS may also be used to investigate the meso porosity. Findings from small-angle scattering are confirmed using electron microscopy. We also show evidence from electron diffraction that thermal conditions within the brown coals during the upgrade procedure may be far more extreme than previously thought.

  11. The pore structure in processed Victorian brown coal

    Energy Technology Data Exchange (ETDEWEB)

    McMahon, P.J.; Snook, I.K.; Treimer, W. [University of Melbourne, Melbourne, Vic. (Australia). School of Physics

    2002-07-01

    Changes in the pore structure of Victorian Brown coal when upgraded with heated gases under pressure are investigated. It is shown that the results obtained from ultra-small-angle neutron scattering (USANS) measurements agree with previous results using small-angle X-ray scattering results but that USANS may also be used to investigate the meso porosity. Findings from small-angle scattering are confirmed using electron microscopy. Evidence is given from electron diffraction that thermal conditions within the brown coals during the upgrade procedure may be far more extreme than previously thought.

  12. NMDA receptor structures reveal subunit arrangement and pore architecture.

    Science.gov (United States)

    Lee, Chia-Hsueh; Lü, Wei; Michel, Jennifer Carlisle; Goehring, April; Du, Juan; Song, Xianqiang; Gouaux, Eric

    2014-07-10

    N-methyl-d-aspartate (NMDA) receptors are Hebbian-like coincidence detectors, requiring binding of glycine and glutamate in combination with the relief of voltage-dependent magnesium block to open an ion conductive pore across the membrane bilayer. Despite the importance of the NMDA receptor in the development and function of the brain, a molecular structure of an intact receptor has remained elusive. Here we present X-ray crystal structures of the Xenopus laevis GluN1-GluN2B NMDA receptor with the allosteric inhibitor, Ro25-6981, partial agonists and the ion channel blocker, MK-801. Receptor subunits are arranged in a 1-2-1-2 fashion, demonstrating extensive interactions between the amino-terminal and ligand-binding domains. The transmembrane domains harbour a closed-blocked ion channel, a pyramidal central vestibule lined by residues implicated in binding ion channel blockers and magnesium, and a ∼twofold symmetric arrangement of ion channel pore loops. These structures provide new insights into the architecture, allosteric coupling and ion channel function of NMDA receptors.

  13. NMDA receptor structures reveal subunit arrangement and pore architecture

    Science.gov (United States)

    Lee, Chia-Hsueh; Lü, Wei; Michel, Jennifer Carlisle; Goehring, April; Du, Juan; Song, Xianqiang; Gouaux, Eric

    2014-01-01

    Summary N-methyl-d-aspartate (NMDA) receptors are Hebbian-like coincidence detectors, requiring binding of glycine and glutamate in combination with the relief of voltage-dependent magnesium block to open an ion conductive pore across the membrane bilayer. Despite the importance of the NMDA receptor in the development and function of the brain, a molecular structure of an intact receptor has remained elusive. Here we present x-ray crystal structures of the GluN1/GluN2B NMDA receptor with the allosteric inhibitor, Ro25-6981, partial agonists and the ion channel blocker, MK-801. Receptor subunits are arranged in a 1-2-1-2 fashion, demonstrating extensive interactions between the amino terminal and ligand binding domains. The transmembrane domains harbor a closed-blocked ion channel, a pyramidal central vestibule lined by residues implicated in binding ion channel blockers and magnesium, and a ~2-fold symmetric arrangement of ion channel pore loops. These structures provide new insights into the architecture, allosteric coupling and ion channel function of NMDA receptors. PMID:25008524

  14. The pore wall structure of porous semi-crystalline anatase TiO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Man-Ho; Doh, Jeong-Mann; Han, Seong Chul; Chae, Keun Hwa; Yu, Byung-Yong; Hong, Kyung Tae [Korea Institute of Science and Technology, Seoul (Korea, Republic of); Jackson, Andrew [NIST National Institute of Standards and Technology, Gaithersburg, MD (United States). Center for Neutron Research; Maryland Univ., College Park, MD (United States). Dept. of Materials Science and Engineering; Anovitz, Lawrence M. [Oak Ridge National Laboratory, Oak Ridge, TN (United States). Chemical Sciences Div.

    2011-12-15

    The structure of porous TiO{sub 2} prepared by electrochemical anodization in a fluoride-containing ethylene glycol electrolyte solution was quantitatively studied using small-angle neutron scattering (SANS) and ultra-small-angle neutron scattering (USANS). The cylindrical pores along the coaxial direction were somewhat irregular in shape, were widely distributed in diameter, and seemed to have a broadly pseudo-hexagonal arrangement. The scattering from the pore wall showed a negative deviation from Porod scattering, indicating that the interface between TiO2 and the pore was not sharp. A density gradient of around 40-60 A at the pore wall (i.e. the interface between the pore and the TiO{sub 2} matrix) was estimated using both constant and semi-sigmoidal interface models. This gradient may be due to the presence of fluorine and carbon partially absorbed by the pore wall from the fluoride-containing electrolyte or to sorbed water molecules on the wall. The neutron contrast-matching point between the TiO{sub 2} matrix and the pores filled with liquid H{sub 2}O/D{sub 2}O mixtures was 51/49%(v/v) H{sub 2}O/D{sub 2}O, yielding an estimated mass density of 3.32 g cm{sup -3}. The specific surface area of the sample derived from the (U)SANS data was around 939-1003 m{sup 2} cm{sup -3} (283-302 m{sup 2} g{sup -1}). (orig.)

  15. The pore-load modulus of ordered nanoporous materials with surface effects

    Science.gov (United States)

    Liu, Mingchao; Wu, Jian; Gan, Yixiang; Chen, C. Q.

    2016-03-01

    Gas and liquid adsorption-induced deformation of ordered porous materials is an important physical phenomenon with a wide range of applications. In general, the deformation can be characterized by the pore-load modulus and, when the pore size reduces to nanoscale, it is affected by surface effects and shows prominent size-dependent features. In this Letter, the influence of surface effects on the elastic properties of ordered nanoporous materials with internal pressure is accounted for in a single pore model. A porosity and surface elastic constants dependent closed form solution for the size dependent pore-load modulus is obtained and verified by finite element simulations and available experimental results. In addition, it is found to depend on the geometrical arrangement of pores. This study provides an efficient tool to analyze the surface effects on the elastic response of ordered nanoporous materials.

  16. Do Surface Porosity and Pore Size Influence Mechanical Properties and Cellular Response to PEEK?

    Science.gov (United States)

    Torstrick, F Brennan; Evans, Nathan T; Stevens, Hazel Y; Gall, Ken; Guldberg, Robert E

    2016-11-01

    Despite its widespread use in orthopaedic implants such as soft tissue fasteners and spinal intervertebral implants, polyetheretherketone (PEEK) often suffers from poor osseointegration. Introducing porosity can overcome this limitation by encouraging bone ingrowth; however, the corresponding decrease in implant strength can potentially reduce the implant's ability to bear physiologic loads. We have previously shown, using a single pore size, that limiting porosity to the surface of PEEK implants preserves strength while supporting in vivo osseointegration. However, additional work is needed to investigate the effect of pore size on both the mechanical properties and cellular response to PEEK. (1) Can surface porous PEEK (PEEK-SP) microstructure be reliably controlled? (2) What is the effect of pore size on the mechanical properties of PEEK-SP? (3) Do surface porosity and pore size influence the cellular response to PEEK? PEEK-SP was created by extruding PEEK through NaCl crystals of three controlled ranges: 200 to 312, 312 to 425, and 425 to 508 µm. Micro-CT was used to characterize the microstructure of PEEK-SP. Tensile, fatigue, and interfacial shear tests were performed to compare the mechanical properties of PEEK-SP with injection-molded PEEK (PEEK-IM). The cellular response to PEEK-SP, assessed by proliferation, alkaline phosphatase activity, vascular endothelial growth factor production, and calcium content of osteoblast, mesenchymal stem cell, and preosteoblast (MC3T3-E1) cultures, was compared with that of machined smooth PEEK and Ti6Al4V. Micro-CT analysis showed that PEEK-SP layers possessed pores that were 284 ± 35 µm, 341 ± 49 µm, and 416 ± 54 µm for each pore size group. Porosity and pore layer depth ranged from 61% to 69% and 303 to 391 µm, respectively. Mechanical testing revealed tensile strengths > 67 MPa and interfacial shear strengths > 20 MPa for all three pore size groups. All PEEK-SP groups exhibited > 50% decrease

  17. Pore structure modification of diatomite as sulfuric acid catalyst support by high energy electron beam irradiation and hydrothermal treatment

    Energy Technology Data Exchange (ETDEWEB)

    Li, Chong [Research Center of the Ministry of Education for High Gravity Engineering and Technology, Beijing University of Chemical Technology, Beijing 100029 (China); Zhang, Guilong; Wang, Min [Key Laboratory of Ion Beam Bioengineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031 (China); Chen, Jianfeng [Research Center of the Ministry of Education for High Gravity Engineering and Technology, Beijing University of Chemical Technology, Beijing 100029 (China); Cai, Dongqing, E-mail: dqcai@ipp.ac.cn [Key Laboratory of Ion Beam Bioengineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031 (China); Wu, Zhengyan, E-mail: zywu@ipp.ac.cn [Key Laboratory of Ion Beam Bioengineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei 230031 (China)

    2014-08-15

    Highlights: • High energy electron beam (HEEB) irradiation and hydrothermal treatment were used. • HEEB irradiation could make the impurities in the pores of diatomite loose. • Hydrothermal treatment (HT) could remove these impurities from the pores. • They could effectively improve pore size distribution and decrease the bulk density. • Catalytic performance of the corresponding catalyst was significantly improved. - Abstract: High energy electron beam (HEEB) irradiation and hydrothermal treatment (HT), were applied in order to remove the impurities and enlarge the pore size of diatomite, making diatomite more suitable to be a catalyst support. The results demonstrated that, through thermal, charge, impact and etching effects, HEEB irradiation could make the impurities in the pores of diatomite loose and remove some of them. Then HT could remove rest of them from the pores and contribute significantly to the modification of the pore size distribution of diatomite due to thermal expansion, water swelling and thermolysis effects. Moreover, the pore structure modification improved the properties (BET (Brunauer–Emmett–Teller) specific surface area, bulk density and pore volume) of diatomite and the catalytic efficiency of the catalyst prepared from the treated diatomite.

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

    Science.gov (United States)

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

    2014-09-16

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

  19. Three-dimensional pore structure and ion conductivity of porous ceramic diaphragms

    OpenAIRE

    Wiedenmann, Daniel; Keller, Lukas; Holzer, Lorenz; Stojadinović, Jelena; Münch, Beat; Suarez, Laura; Fumey, Benjamin; Hagendorfer, Harald; Brönnimann, Rolf; Modregger, Peter; Gorbar, Michal; Vogt, Ulrich F.; Züttel, Andreas; Mantia, Fabio La; Wepf, Roger

    2013-01-01

    The ion conductivity of two series of porous ceramic diaphragms impregnated with caustic potash was investigated by electrochemical impedance spectroscopy. To understand the impact of the pore structure on ion conductivity, the three-dimensional (3-D) pore geometry of the diaphragms was characterized with synchrotron x-ray absorption tomography. Ion migration was calculated based on an extended pore structure model, which includes the electrolyte conductivity and geometric pore parameters, fo...

  20. Structure and gating of the nuclear pore complex

    Science.gov (United States)

    Eibauer, Matthias; Pellanda, Mauro; Turgay, Yagmur; Dubrovsky, Anna; Wild, Annik; Medalia, Ohad

    2015-06-01

    Nuclear pore complexes (NPCs) perforate the nuclear envelope and allow the exchange of macromolecules between the nucleus and the cytoplasm. To acquire a deeper understanding of this transport mechanism, we analyse the structure of the NPC scaffold and permeability barrier, by reconstructing the Xenopus laevis oocyte NPC from native nuclear envelopes up to 20 Å resolution by cryo-electron tomography in conjunction with subtomogram averaging. In addition to resolving individual protein domains of the NPC constituents, we propose a model for the architecture of the molecular gate at its central channel. Furthermore, we compare and contrast this native NPC structure to one that exhibits reduced transport activity and unveil the spatial properties of the NPC gate.

  1. Tailor-Made Pore Surface Engineering in Covalent Organic Frameworks: Systematic Functionalization for Performance Screening

    NARCIS (Netherlands)

    Huang, N.; Krishna, R.; Jiang, D.

    2015-01-01

    Imine-linked covalent organic frameworks (COFs) were synthesized to bear content-tunable, accessible, and reactive ethynyl groups on the walls of one-dimensional pores. These COFs offer an ideal platform for pore-wall surface engineering aimed at anchoring diverse functional groups ranging from

  2. 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.

  3. Pore- and micro-structural characterization of a novel structural binder based on iron carbonation

    Energy Technology Data Exchange (ETDEWEB)

    Das, Sumanta, E-mail: Sumanta.Das@asu.edu [School of Sustainable Engineering and the Built Environment, Arizona State University, Tempe, AZ (United States); Stone, David, E-mail: dajstone@gmail.com [Iron Shell LLC, Tucson, AZ (United States); Convey, Diana, E-mail: Diana.Convey@asu.edu [LeRoy Eyring Center for Solid State Science, Arizona State University, Tempe, AZ (United States); Neithalath, Narayanan, E-mail: Narayanan.Neithalath@asu.edu [School of Sustainable Engineering and the Built Environment, Arizona State University, Tempe, AZ (United States)

    2014-12-15

    The pore- and micro-structural features of a novel binding material based on the carbonation of waste metallic iron powder are reported in this paper. The binder contains metallic iron powder as the major ingredient, followed by additives containing silica and alumina to facilitate favorable reaction product formation. Compressive strengths sufficient for a majority of concrete applications are attained. The material pore structure is investigated primarily through mercury intrusion porosimetry whereas electron microscopy is used for microstructural characterization. Reduction in the overall porosity and the average pore size with an increase in carbonation duration from 1 day to 4 days is noticed. The pore structure features are used in predictive models for gas and moisture transport (water vapor diffusivity and moisture permeability) through the porous medium which dictates its long-term durability when used in structural applications. Comparisons of the pore structure with those of a Portland cement paste are also provided. The morphology of the reaction products in the iron-based binder, and the distribution of constituent elements in the microstructure are also reported. - Highlights: • Carbonation of iron produces a dense microstructure. • Pore volume in iron carbonate lower, critical size higher than those in OPC pastes • Reaction product contains iron, carbon, silicon, aluminum and calcium. • Power-law for porosity-moisture permeability relationship was established.

  4. Particle Size and Pore Structure Characterization of Silver Nanoparticles Prepared by Confined Arc Plasma

    Directory of Open Access Journals (Sweden)

    Mingru Zhou

    2009-01-01

    Full Text Available In the protecting inert gas, silver nanoparticles were successfully prepared by confined arc plasma method. The particle size, microstructure, and morphology of the particles by this process were characterized via X-ray powder diffraction (XRD, transmission electron microscopy (TEM and the corresponding selected area electron diffraction (SAED. The N2 absorption-desorption isotherms of the samples were measured by using the static volumetric absorption analyzer, the pore structure of the sample was calculated by Barrett-Joyner-Halenda (BJH academic model, and the specific surface area was calculated from Brunauer-Emmett-Teller (BET adsorption equation. The experiment results indicate that the crystal structure of the samples is face-centered cubic (FCC structure the same as the bulk materials, the particle size distribution ranging from 5 to 65 nm, with an average particle size about 26 nm obtained by TEM and confirmed by XRD and BET results. The specific surface area is 23.81 m2/g, pore volumes are 0.09 cm3/g, and average pore diameter is 18.7 nm.

  5. Pore-Structure-Optimized CNT-Carbon Nanofibers from Starch for Rechargeable Lithium Batteries

    Directory of Open Access Journals (Sweden)

    Yongjin Jeong

    2016-12-01

    Full Text Available Porous carbon materials are used for many electrochemical applications due to their outstanding properties. However, research on controlling the pore structure and analyzing the carbon structures is still necessary to achieve enhanced electrochemical properties. In this study, mesoporous carbon nanotube (CNT-carbon nanofiber electrodes were developed by heat-treatment of electrospun starch with carbon nanotubes, and then applied as a binder-free electrochemical electrode for a lithium-ion battery. Using the unique lamellar structure of starch, mesoporous CNT-carbon nanofibers were prepared and their pore structures were controlled by manipulating the heat-treatment conditions. The activation process greatly increased the volume of micropores and mesopores of carbon nanofibers by etching carbons with CO2 gas, and the Brunauer-Emmett-Teller (BET specific area increased to about 982.4 m2·g−1. The activated CNT-carbon nanofibers exhibited a high specific capacity (743 mAh·g−1 and good cycle performance (510 mAh·g−1 after 30 cycles due to their larger specific surface area. This condition presents many adsorption sites of lithium ions, and higher electrical conductivity, compared with carbon nanofibers without CNT. The research suggests that by controlling the heat-treatment conditions and activation process, the pore structure of the carbon nanofibers made from starch could be tuned to provide the conditions needed for various applications.

  6. MASS TRANSFER IN PORE STRUCTURES OF SUPPORTED CATALYSTS

    Directory of Open Access Journals (Sweden)

    F.R.C. Silva

    1997-09-01

    Full Text Available The effects of gas-solid interaction and mass transfer in fixed-bed systems of supported catalysts were analyzed for g -Al2O3 (support and Cu/g -Al2O3 (catalyst systems. Evaluations of the mass transfer coefficients in the macropores and of the diffusivity in the micropores, as formed by the crystallite agglomerates of the metallic phases, were obtained. Dynamic experiments with gaseous tracers permitted the quantification of the parameters based on models for these two pore structures. With a flow in a range of 18 cm3 s-1 to 39.98 cm3 s-1 at 45oC, 65oC and 100oC, mass transfer coefficients km =4.33x10-4 m s-1 to 7.38x10-4 m s-1 for macropore structures and diffusivities Dm =1.29x10-11 m2 s-1 to 5.35x10-11 m2 s-1 for micropore structures were estimated

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

    Science.gov (United States)

    Ellis, Jonathan S; Bazylak, Aimy

    2012-06-21

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

  8. Different size biomolecules anchoring on porous silicon surface: fluorescence and reflectivity pores infiltration comparative studies

    Energy Technology Data Exchange (ETDEWEB)

    Giovannozzi, Andrea M.; Rossi, Andrea M. [National Institute for Metrological Research, Thermodynamic Division, Strada delle Cacce 91, 10135 Torino (Italy); Renacco, Chiara; Farano, Alessandro [Ribes Ricecrhe Srl, Via Lavoratori Vittime del Col du Mont 24, 11100 Aosta (Italy); Derosas, Manuela [Biodiversity Srl, Via Corfu 71, 25124 Brescia (Italy); Enrico, Emanuele [National Institute for Metrological Research, Electromagnetism Division, Strada delle Cacce 91, 10135 Torino (Italy)

    2011-06-15

    The performance of porous silicon optical based biosensors strongly depends on material nanomorphology, on biomolecules distribution inside the pores and on the ability to link sensing species to the pore walls. In this paper we studied the immobilization of biomolecules with different size, such as antibody anti aflatoxin (anti Aflatox Ab, {proportional_to}150 KDa), malate dehydrogenase (MDH, {proportional_to}36KDa) and metallothionein (MT, {proportional_to}6KDa) at different concentrations on mesoporous silicon samples ({proportional_to}15 nm pores diameter). Fluorescence measurements using FITC- labeled biomolecules and refractive index analysis based on reflectivity spectra have been employed together to detect the amount of proteins bound to the surface and to evaluate their diffusion inside the pores. Here we suggest that these two techniques should be used together to have a better understanding of what happens at the porous silicon surface. In fact, when pores dimensions are not perfectly tuned to the protein size a higher fluorescence signal doesn't often correspond to a higher biomolecules distribution inside the pores. When a too much higher concentration of biomolecule is anchored on the surface, steric crowd effects and repulsive interactions probably take over and hinder pores infiltration, inducing a small or absent shift in the fringe pattern even if a higher fluorescence signal is registered. (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  9. Pore structure, mechanical properties and polymer characteristics of porous materials impregnated with methylmethacrylate

    International Nuclear Information System (INIS)

    Hastrup, K.

    1976-05-01

    The pore structure of porous materials plays a decisive role with regard to many properties of the materials. One therefore expects property improvement due to impregnation to be mostly brought about as a result of pore structure modification. This supposition formed the basis for the project here presented, which had the main aim of investigating polymer impregnation in relation to pore structure. Objectives were: 1) to examine the pore structure of hardened cement paste, beech wood and porous glass before and after gas-phase impregnation with methyl-methacrylate monomer and in situ polymerization, 2) to investigate the influence of the pore structure on the molecular weight of the polymer, 3) to investigate the influence of the degree of pore filling on the elastic modulus, damping coefficient and bending strength. (author)

  10. Optimizing the Pore Structure of Bio-Based ACFs through a Simple KOH–Steam Reactivation

    Directory of Open Access Journals (Sweden)

    Yuxiang Huang

    2016-05-01

    Full Text Available Highly microporous bio-based activated carbon fibers (ACFs were prepared through a simple reactivation method. Sawdust, as the starting material, was liquefied and melt-spun to produce the precursor fibers. Then, the precursor fibers were activated by KOH and reactivated by steam. By varying the conditions of the two activation processes, the formation mechanism of the pore structure was studied, and the result showed that steam reactivation has a positive effect on the development of microporosity. The sample with the optimal condition exhibited the highest specific surface area of 2578 m2·g−1 as well as the largest pore volume of 1.425 cm3·g−1, where micropores contributed 70.3%. Due to its excellent texture properties, the ACF exhibited a high adsorption capacity of 1934 mg/g for iodine.

  11. MD simulation analysis of resin filling into nano-sized pore formed on metal surface

    Science.gov (United States)

    Mori, Hodaka; Matubayasi, Nobuyuki

    2018-01-01

    All-atom MD simulation was conducted for the filling of epoxy resin into a nano-sized pore formed on aluminum surface. The resin species examined were polyphenol mixed with polyglycidylether of o-cresol formaldehyde novolac and their oligomers formed through ring-opening reactions. The degree of oligomerization was varied from 0.5 to 2.5 nm in terms of the radius of gyration, and the radius of the cylindrical pore was fixed at 2.5 nm. It was observed that a small resin penetrates into the pore along the wall, while larger resins move rather uniformly in the pore. The maximum density in the pore achieved with pushing was then seen to be larger when the resin is smaller. It was found that when the radius of gyration of resin is larger than half the pore radius, the resin density in the pore does not reach half the bulk density of the resin. This implies that the resin-resin interaction inhibits the filling of the nano-sized pore.

  12. The effects of diatom pore-size on the structures and extensibilities of single mucilage molecules.

    Science.gov (United States)

    Sanka, Immanuel; Suyono, Eko Agus; Alam, Parvez

    2017-08-07

    Diatoms secrete extracellular polymeric substances (EPS), or mucilage, around the cell wall that may serve to aid in motility and form a discrete layer that may help maintain thicker layers of EPS that have a greater role in adhesion. Mucilage molecules adhere to the diatom frustules, which are biosilica skeletons that develop from the diatom cell walls. Here, molecular dynamics methods were used to determine the characteristics of mucilage molecules as a function of pore size; notably 1,4-α-D-galacturonic acid, 1,4-β-glucuronic acid and 1,4-β-D-mannuronic acid. These uronic acids differ from each other in structure and extensibility as a function of their folding characteristics. Here, we find that when overlain upon a pore, mucilage molecules try to return to their native folded states but are restrained by their interactions with the silica surfaces. Furthermore, the extensibility of mucilage molecules over pore spaces affects the extent of mechanical energy required to straighten them. As such, different EPS molecules will affect sliding, friction and adhesion to subsequent layers of EPS in different ways. We conclude that higher EPS extensibility is homonymous with higher adhesive or frictive resistance since the molecules will be able to strain more before they reach the most extended (and thus rigid) conformation. The research herein is applicable to modern engineering as it yields insight into the biomimetic design of molecules and surfaces for improved adhesion or motility. Copyright © 2017 Elsevier Ltd. All rights reserved.

  13. Effects of pore structure and distribution on strength of porous Cu-Sn-Ti alumina composites

    Directory of Open Access Journals (Sweden)

    Biao ZHAO

    2017-12-01

    Full Text Available Porous Cu-Sn-Ti alumina composites were fabricated by sintering Cu-Sn-Ti alloy powders, graphite particles, and alumina hollow particles agent. The effects of the pore structure and distribution on the composites strength were evaluated. Different pore distributions were modeled by using finite element analysis to investigate the tensile strength of the composites. Furthermore, a fractal analysis-based box-covering algorithm was used on the Cu-Sn-Ti alumina composites topology graphs to better investigate the pore structure and distribution. Results obtained show that different sizes and concentrations of alumina hollow particles could result in different porosities from 20% to 50%. A larger pore size and a higher pore concentration reduce the strength, but provide more space for chip formation as a bonding material of a grinding wheel. The body-centered pore structure of the composites shows the highest stress under a tension load. The original composites topology graphs have been transformed to ordered distributed pore graphs based on the total pore area conservation. The information dimension magnitude difference between the original topology graphs and the ordered distributed circulars graphs is found to be linear with the Cu-Sn-Ti alumina composites strength. A larger difference renders a lower flexural strength, which indicates that uniform ordered distributed pores could benefit the composites strength. Keywords: Finite element analysis (FEA, Metal-matrix composites (MMCs, Microstructural analysis, Pore structure, Strength

  14. 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...

  15. Analysis of the pore structure of activated carbons produced from paper mill sludge using small angle neutron scattering data

    Energy Technology Data Exchange (ETDEWEB)

    Sandi, G.; Khalil, N. R.; Littrell, K.; Thiyagarajan, P.

    1999-12-13

    A novel, cost-effective, and environmentally benign process was developed to produce highly efficient carbon-based adsorbents (CBAs) from paper mill sludge. The production process required chemical activation of sludge using zinc chloride and pyrolysis at 750 C in N{sub 2} gas. The produced CBAs were characterized according to their surface area and pore size distribution using N{sub 2}-BET adsorption isotherm data. Further characterization of the surface and pore structure was conducted using a unified exponential/power law approach applied to small angle neutron scattering (SANS) data. The structural features analyzed by SANS revealed the dependence of porosity with zinc chloride concentration. The presence of inaccessible pores was also determined by contrast-match experiments.

  16. The lamellar structure of reactive mixtures in porous media: Pore scale experimental imaging and upscaling

    Science.gov (United States)

    Le Borgne, T.; De Anna, P.; Turuban, R.; Jimenez-Martinez, J.; Tabuteau, H.; Meheust, Y.; Ginn, T. R.; Dentz, M.

    2014-12-01

    Effective reaction rates in porous media are controlled by the spatial organization of chemical species concentrations at the pore scale. From high resolution millifluidic pore scale imaging of reactive tracers we report experimental evidence of the formation of well-developed lamellar structures in reactive mixtures transported through porous media (de Anna et al., Environ. Sci. Technol., 2014). The latter are highlighted by a chemioluminescent reaction producing photons that localize along spatially coherent lines, representing hotspots of mixing and reaction at pore scale. These elongated spatial structures are naturally created by the stretching action of the pore scale velocity field, which induces a dynamic deformation of the material elements carrying solutes (Le Borgne et al., Phys. Rev. Lett., 2013). This particular spatial organization is shown to have a major impact on global reactivity by increasing the surface available for reactive mixing and by enhancing local chemical gradients (de Anna et al., Geophys. Res. Lett. 2014). We quantify this phenomenon for different flow topologies using a reactive lamella representation, which links fluid deformation, diffusion and reaction at the elementary scale. The upscaled reaction rates, estimated by integrating the distribution of local deformation rates, are shown to follow different temporal behavior depending on the distribution of local velocity gradients. This approach allows for the systematic evaluation of the temporal evolution of upscaled reaction rates, and establishes a direct link between the global reaction efficiency and the spatial characteristics of the underlying pore scale flow field.References:[1] P. de Anna, J. Jimenez-Martinez, H. Tabuteau, R. Turuban, T. Le Borgne, M. Derrien,and Yves Méheust, Mixing and reaction kinetics in porous media : an experimental pore scale quantification, Environ. Sci. Technol.48, 508-516, 2014. [2] de Anna, P., Dentz, M., Tartakovsky A. and Le Borgne, T., The

  17. Calcitonin Forms Oligomeric Pore-Like Structures in Lipid Membranes

    Science.gov (United States)

    Diociaiuti, Marco; Polzi, Laura Zanetti; Valvo, Luisa; Malchiodi-Albedi, Fiorella; Bombelli, Cecilia; Gaudiano, Maria Cristina

    2006-01-01

    Calcitonin is a polypeptidic hormone involved in calcium metabolism in the bone. It belongs to the amyloid protein family, which is characterized by the common propensity to aggregate acquiring a β-sheet conformation and include proteins associated with important neurodegenerative diseases. Here we show for the first time, to our knowledge, by transmission electron microscopy (TEM) that salmon-calcitonin (sCT) forms annular oligomers similar to those observed for β-amyloid and α-sinuclein (Alzheimer's and Parkinson's diseases). We also investigated the interaction between sCT and model membranes, such as liposomes, with particular attention to the effect induced by lipid “rafts” made of cholesterol and GM1. We observed, by TEM immunogold labeling of sCT, that protein binding is favored by the presence of rafts. In addition, we found by TEM that sCT oligomers inserted in the membrane have the characteristic pore-like morphology of the amyloid proteins. Circular dichroism experiments revealed an increase in β-content in sCT secondary structure when the protein was reconstituted in rafts mimicking liposomes. Finally, we showed, by spectrofluorimetry experiments, that the presence of sCT allowed Ca2+ entry in rafts mimicking liposomes loaded with the Ca2+-specific fluorophore Fluo-4. This demonstrates that sCT oligomers have ion-channel activity. Our results are in good agreement with recent electrophysiological studies reporting that sCT forms Ca2+-permeable ion channels in planar model membranes. It has been proposed that, beyond the well-known interaction of the monomer with the specific receptor, the formation of Ca2+ channels due to sCT oligomers could represent an extra source of Ca2+ entry in osteoblasts. Structural and functional data reported here support this hypothesis. PMID:16940475

  18. The Effect of Membrane Material and Surface Pore Size on the Fouling Properties of Submerged Membranes

    Directory of Open Access Journals (Sweden)

    Sungil Jeon

    2016-12-01

    Full Text Available We aimed to investigate the relationship between membrane material and the development of membrane fouling in a membrane bioreactor (MBR using membranes with different pore sizes and hydrophilicities. Batch filtration tests were performed using submerged single hollow fiber membrane ultrafiltration (UF modules with different polymeric membrane materials including cellulose acetate (CA, polyethersulfone (PES, and polyvinylidene fluoride (PVDF with activated sludge taken from a municipal wastewater treatment plant. The three UF hollow fiber membranes were prepared by a non-solvent-induced phase separation method and had similar water permeabilities and pore sizes. The results revealed that transmembrane pressure (TMP increased more sharply for the hydrophobic PVDF membrane than for the hydrophilic CA membrane in batch filtration tests, even when membranes with similar permeabilities and pore sizes were used. PVDF hollow fiber membranes with smaller pores had greater fouling propensity than those with larger pores. In contrast, CA hollow fiber membranes showed good mitigation of membrane fouling regardless of pore size. The results obtained in this study suggest that the surface hydrophilicity and pore size of UF membranes clearly affect the fouling properties in MBR operation when using activated sludge.

  19. Hydrothermal and postsynthesis surface modification of cubic, MCM-48, and ultralarge pore SBA-15 mesoporous silica with titanium

    Energy Technology Data Exchange (ETDEWEB)

    Morey, M.S.; O' Brien, S.; Schwarz, S.; Stucky, G.D.

    2000-04-01

    The authors describe the introduction of titanium centers to cubic MCM-48 was hydrothermally prepared with a gemini surfactant that favors the cubic phase and leads to a high degree of long-range pore ordering. This phase was chosen due to its high surface area (1100--1300 m{sup 2}/g) and its three-dimensional, bicontinuous pore array. SBA-15, synthesized with a block copolymer template under acidic conditions, has a surface area from 600 to 900 m{sup 2}/g and an average pore diameter of 69 {angstrom}, compared to 24--27 {angstrom} for MCM-48. Alkoxide precursors of titanium were used to prepare samples of Ti-MCM-48 and Ti-SBA-15. The authors have detailed the bulk and molecular structure of both the silica framework and the local bonding environment of the titanium ions within each matrix. X-ray powder diffraction and nitrogen adsorption shows the pore structure is maintained despite some shrinkage of the pore diameter at high Ti loadings by grafting methods. UV-visible and Raman spectroscopy indicate that grafting produces the least amount of Ti-O-Ti bonds and instead favors isolated tetrahedral and octahedral titanium centers. High-resolution photoacoustic FTIR spectra demonstrated the presence of intermediate range order within the silicate walls of MCM-48, established the consumption of surface silanols to form Si-O-Ti bonds by grafting, and resolved the characteristic IR absorbance at 960 cm{sup {minus}1}, occurring in titanium silicates, into two components. All three spectroscopic techniques, including in situ Raman, reveal the reactive intermediates formed when the materials are contacted with hydrogen peroxide.

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

    Science.gov (United States)

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

    2013-12-01

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

  1. Influence of pore structure on solute transport in degraded and undegraded fen peat soils

    Directory of Open Access Journals (Sweden)

    C. Kleimeier

    2017-10-01

    Full Text Available In peat soils, decomposition and degradation reduce the proportion of large pores by breaking down plant debris into smaller fragments and infilling inter-particle pore spaces. This affects water flow and solute migration which, in turn, influence reactive transport processes and biogeochemical functions. In this study we conducted flow-through reactor experiments to investigate the interplay between pore structure and solute transport in samples of undegraded and degraded peat collected in Canada and Germany, respectively. The pore size distributions and transport parameters were characterised using the breakthrough curve and two-region non-equilibrium transport model analyses for a non-reactive solute. The results of transport characterisation showed a higher fraction of immobile pores in the degraded peat with higher diffusive exchanges of solutes between the mobile and immobile pores associated with the dual-porosity structure. The rates of steady-state potential nitrate reduction were compared with pore fractions and exchange coefficients to investigate the influence of pore structure on the rates of nitrate reduction. The results indicated that the degraded peat has potential to provide the necessary boundary conditions to support nitrate removal and serves as a favourable substrate for denitrification, due to the nature of its pore structure and its lower organic carbon content compared to undegraded peat.

  2. Mechanical, Thermal and Acoustic Properties of Open-pore Phenolic Multi-structured Cryogel

    Science.gov (United States)

    Yao, Rui; Yao, Zhengjun; Zhou, Jintang; Liu, Peijiang; Lei, Yiming

    2017-09-01

    Open-pore phenolic cryogel acoustic multi-structured plates (OCMPs) were prepared via modified sol gel polymerization and freeze-dried methods. The pore morphology, mechanical, thermal and acoustic properties of the cryogels were investigated. From the experimental results, the cryogels exhibited a porous sandwich microstructure: A nano-micron double-pore structure was observed in the core layer of the plates, and nanosized pores were observed in the inner part of the micron pores. In addtion, compared with cryogel plates with uniform-pore (OCPs), the OCMPs had lower thermal conductivities. What’s more, the compressive and tensile strength of the OCMPs were much higher than those of OCPs. Finally, the OCMPs exhibited superior acoustic performances (20% solid content OCMPs performed the best) as compared with those of OCPs. Moreover, the sound insulation value and sound absorption bandwidth of OCMPs exhibited an improvement of approximately 3 and 2 times as compared with those of OCPs, respectively.

  3. Structure of the nuclear pore complex in mammalian cells. Two annular components.

    NARCIS (Netherlands)

    J.H.J. Hoeijmakers (Jan); J.H.N. Schel; F. Wanka

    1974-01-01

    textabstractThe ultrastructure of the nuclear pore complex has been investigated in isolated nuclei of an in vitro cultured bovine liver cell line. In shadow-cast replicas of the surface of nuclei isolated in Tris buffer containing low K+ and Mg2+ concentrations (RSB) the rims of the pores appeared

  4. New insights into the pore structure of poly(d,l-lactide-co-glycolide) microspheres.

    Science.gov (United States)

    Vay, Kerstin; Scheler, Stefan; Friess, Wolfgang

    2010-12-15

    The objective of this work was to develop a fast and significant method for the determination of the intraparticulate pore size distribution of microspheres. Poly(lactide-co-glycolide) (PLGA) microspheres prepared with a solvent extraction/evaporation process were studied. From the envelope and the skeletal volume of the microspheres the porosity was calculated. The skeletal volume was determined with nitrogen and helium pycnometry and mercury intrusion porosimetry. Based on single particle optical sensing (SPOS) a novel method was developed by which the envelope volume is calculated from the particle size distribution (PSD), provided that all particles have a spherical shape. The penetration capacity of the applied intrusion media is limited by their atomic or molecular diameter or by the surface tension and the pressure in case of mercury. A classification of the pore structure was obtained by comparing these different skeletal values with the values for the envelope volume. Two well separated pore fractions were found, a nanoporous fraction smaller than 0.36nm and a macroporous fraction larger than 3.9μm. The total porosity and the ratio between both fractions is controlled by the preparation process and was shown to depend on the solvent extraction temperature. Copyright © 2010 Elsevier B.V. All rights reserved.

  5. Pore scale heterogeneity in the mineral distribution and reactive surface area of rocks

    Science.gov (United States)

    Lai, P. E.; Krevor, S. C.

    2013-12-01

    There are long-standing challenges in characterizing reactive transport in porous media at scales larger than individual pores. This hampers the prediction of the field-scale impact of geochemical processes on fluid flow [1]. This is a source of uncertainty for CO2 injection, which results in a reactive fluid-rock system, particularly in carbonate rock reservoirs. A potential cause is the inability of the continuum approach to incorporate the impact of heterogeneity in pore-scale reaction rates. This results in part from pore-scale heterogeneities in surface area of reactive minerals [2,3]. In this study we have created μm resolution 3D images of 3 sandstone and 4 carbonate rocks using x-ray microtomography. Using in-house image processing techniques and auxiliary characterisation with thin section, electron microscope and spectroscopic techniques we quantified the surface area of each mineral phase in the x-ray CT images. This quantification was validated against N2 BET surface area and He porosity measurements of the imaged samples. Distributions in reactive surface area for each mineral phase were constructed by calculating surface areas in thousands of randomly selected subvolume images of the total sample, each normalized to the pore volume in that image. In all samples, there is little correlation between the reactive surface area fraction and the volumetric fraction of a mineral in a bulk rock. Berea sandstone was far less heterogeneous and has a characteristic pore size at which a surface area distribution may be used to quantify heterogeneity. In carbonates, heterogeneity is more complex and surface area must be characterized at multiple length scales for an accurate description of reactive transport. [1] Maher, Steefel, Depaolo and Vianni (2006) Geochimica et Cosmochimica Acta, 70, 337-363 [2] Landrot, Ajo-Franklin, Yang, Cabrini and Steefel (2012) Chemical Geology 318-319, 113-125 [3] Li, Peters and Celia (2007) American Journal of Science 307, 1146

  6. Investigation on pore structure and small-scale agglomeration ...

    Indian Academy of Sciences (India)

    The increase in the additives results in the modification in the pore size distribution and to some extent the total porosity. SANS revealed a mass fractal nature of the agglomerated matrix microstructure. The fractal dimension of the matrix does not change appreciably with the additives although the upper cut-off value of the ...

  7. Cross-Sectional Information on Pore Structure and Element Distribution of Sediment Particles by SEM and EDS

    Directory of Open Access Journals (Sweden)

    Minghong Chen

    2017-01-01

    Full Text Available The interaction between pollutants and sediment particles often occurs on the particle surface, so surface properties directly affect surface reaction. The physical and chemical processes occurring on sediment particle surfaces are microscopic processes and as such need to be studied from a microscopic perspective. In this study, field emission scanning electron microscopy (SEM and energy dispersive X-ray spectrometer (EDS were adopted to observe and analyze the pore structure and element distribution of sediment particles. In particular, a special method of sample preparation was used to achieve the corresponding cross-sectional information of sediment particles. Clear images of a particle profile and pore microstructure were obtained by high-resolution SEM, while element distribution maps of sediment particles were obtained by EDS. The results provide an intuitive understanding of the internal microenvironment and external behavior of sediment particles, in addition to revealing a significant role of pore microstructure in the adsorption and desorption of pollutants. Thus, a combination of different experimental instruments and observation methods can provide real images and information on microscopic pore structure and element distribution of sediment particles. These results should help to improve our understanding of sediment dynamics and its environmental effects.

  8. Influence of Carbon Dioxide Bubble on Pore in Fibrous Structure of Direct Methanol Fuel Cell

    Science.gov (United States)

    Sugimura, Masahiko; Fujimoto, Kozo

    Direct methanol fuel cell (DMFC) is promising as new portable power source in various electronics devises. However, the performance of DMFC decreases by many problems which the factor of the structure and material effects each species concentration in the electrode catalyst layer. The anode reaction in DMFC products carbon dioxide, and CO2 bubbles generate in anode electrode. Diffusion layer in DMFC electrode is made carbon paper. The CO2 bubbles resulted in gas slugs blocking the pores in carbon paper. The CO2 bubble is affected by structure and surface characteristics in the diffusion layer. The behavior of bubble is analyzed some structure. We showed the relationship between bubble effect and contact angle of carbon fiber. And also, the model results indicate that the contact angle can improve the cell performance.

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

    DEFF Research Database (Denmark)

    Arthur, Emmanuel; Møldrup, Per; Schjønning, Per

    2013-01-01

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

  10. Effect of heat treatment on pore structure in nanocrystalline NiO: A ...

    Indian Academy of Sciences (India)

    heat treatment temperature. The pore structures at various heat treatment temperatures do not scale. This has been attributed to the grain boundary diffusion leading to an asymmetric shrinkage of the pores. Keywords. Nanoceramics; small angle neutron scattering; sintering; NiO. PACS Nos 61.10; 61.12. 1. Introduction.

  11. 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.

  12. 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.

  13. 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.

  14. Role of uniform pore structure and high positive charges in the arsenate adsorption performance of Al13-modified montmorillonite

    International Nuclear Information System (INIS)

    Zhao, Shou; Feng, Chenghong; Huang, Xiangning; Li, Baohua; Niu, Junfeng; Shen, Zhenyao

    2012-01-01

    Highlights: ► Al 13 modification changes As(V) sorption mechanism of montmorillonites. ► Intercalated ion charges mainly affects As(V) adsorption kinetics. ► Uniform pore structure exhibit more excellent As(V) adsorption performance. - Abstract: Four modified montmorillonite adsorbents with varied Al 13 contents (i.e., Na-Mont, AC-Mont, PAC 20 -Mont, and Al 13 -Mont) were synthesized and characterized by N 2 adsorption/desorption, X-ray diffraction, and Fourier-transform infrared analyses. The arsenate adsorption performance of the four adsorbents were also investigated to determine the role of intercalated Al 13 , especially its high purity, high positive charge (+7), and special Keggin structure. With increased Al 13 content, the physicochemical properties (e.g., surface area, structural uniformity, basal spacing, and pore volume) and adsorption performance of the modified montmorillonites were significantly but disproportionately improved. The adsorption data well fitted the Freundlich and Redlich–Peterson isotherm model, whereas the kinetic data better correlated with the pseudo-second-order kinetic model. The arsenate sorption mechanism of the montmorillonites changed from physical to chemisorption after intercalation with Al 13 . Increasing charges of the intercalated ions enhanced the arsenate adsorption kinetics, but had minimal effect on the structural changes of the montmorillonites. The uniform pore structure formed by intercalation with high-purity Al 13 greatly enhanced the pore diffusion and adsorption rate of arsenate, resulting in the high adsorption performance of Al 13 -Mont.

  15. 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)

  16. Functionalization of MOFs via a mixed-ligand strategy: enhanced CO2 uptake by pore surface modification.

    Science.gov (United States)

    Liu, Bo; Zhou, Hui-Fang; Hou, Lei; Wang, Yao-Yu

    2018-03-26

    A new Zn(ii) metal-organic framework (MOF) [Me2NH2][Zn2(BDPP)(HTZ)]·4DMF (1) (H4BDPP = 3,5-bis(3,5-dicarboxylphenyl)pyridine, HTZ = 1H-tetrazole) has been constructed under solvothermal conditions by using a mixed-ligand strategy. Structural analysis demonstrates that 1 is a 3D framework based on four kinds of secondary building units (SBUs), which presents a rare structure constructed from quaternary SBUs and shows an uncommon (3,3,4,6)-connected topology. In particular, 1 contains two shapes of 1D open channels with suitable pore sizes, high porosity, and a highly polar pore system decorated with uncoordinated N atoms and carboxylic O atoms, providing a good environment for selective adsorption of CO2. Inspired by the structure of 1 and reticular chemistry, 5-amino-1H-tetrazole (ATZ) was used to replace 1H-tetrazole to enhance CO2 sorption capacity by pore surface modification; as a result, an amino-functionalized MOF, [Me2NH2][Zn2(BDPP)(ATZ)]·4DMF (1-NH2) was successfully built. 1-NH2 exhibits multipoint interactions between the CO2 molecules and the framework, resulting in better CO2 uptake and selectivity for CO2 over CH4 than 1.

  17. Integrating SANS and fluid-invasion methods to characterize pore structure of typical American shale oil reservoirs.

    Science.gov (United States)

    Zhao, Jianhua; Jin, Zhijun; Hu, Qinhong; Jin, Zhenkui; Barber, Troy J; Zhang, Yuxiang; Bleuel, Markus

    2017-11-13

    An integration of small-angle neutron scattering (SANS), low-pressure N 2 physisorption (LPNP), and mercury injection capillary pressure (MICP) methods was employed to study the pore structure of four oil shale samples from leading Niobrara, Wolfcamp, Bakken, and Utica Formations in USA. Porosity values obtained from SANS are higher than those from two fluid-invasion methods, due to the ability of neutrons to probe pore spaces inaccessible to N 2 and mercury. However, SANS and LPNP methods exhibit a similar pore-size distribution, and both methods (in measuring total pore volume) show different results of porosity and pore-size distribution obtained from the MICP method (quantifying pore throats). Multi-scale (five pore-diameter intervals) inaccessible porosity to N 2 was determined using SANS and LPNP data. Overall, a large value of inaccessible porosity occurs at pore diameters pores in these shales. While each method probes a unique aspect of complex pore structure of shale, the discrepancy between pore structure results from different methods is explained with respect to their difference in measurable ranges of pore diameter, pore space, pore type, sample size and associated pore connectivity, as well as theoretical base and interpretation.

  18. Pore Structure Evolution and Its Effect on Strength Development of Sulfate-Containing Cemented Paste Backfill

    Directory of Open Access Journals (Sweden)

    Hao Rong

    2017-01-01

    Full Text Available In this study, the effects of the initial sulfate content on the properties of cemented paste backfill (CPB made from coarse tailings has been investigated via mercury intrusion porosimetry. The combined effects of the sulfate content and curing time on the total porosity, pore size distribution, and unconfined compressive strength of the produced material were discussed. It was found that the specimens with an initial sulfate content of 5000 and 35,000 ppm exhibited higher unconfined compressive strength, while the resulting fine porous structures characterized by pore radii of 10–400 and 1–10 μm significantly improved the mechanical properties of the CPB. In addition, an increase in the curing time decreased the overall pore volume in the radius range of 1–400 μm but increased the pore volume at pore radii less than 1 μm.

  19. Pore scale heterogeneity in the mineral distribution and surface area of porous rocks

    Science.gov (United States)

    Lai, Peter; Moulton, Kevin; Krevor, Samuel

    2014-05-01

    There are long-standing challenges in characterizing reactive transport in porous media at scales larger than individual pores. This hampers the prediction of the field-scale impact of geochemical processes on fluid flow [1]. This is a source of uncertainty for carbon dioxide injection, which results in a reactive fluid-rock system, particularly in carbonate rock reservoirs. A potential cause is the inability of the continuum approach to incorporate the impact of heterogeneity in pore-scale reaction rates. This results in part from pore-scale heterogeneities in surface area of reactive minerals [2,3]. The objective of this study was to quantify heterogeneity in reactive surface and observe the extent of its non-normal character. In this study we describe our work in using micron-scale x-ray imaging and other spectroscopic techniques for the purpose of describing the statistical distribution of reactive surface area within a porous medium, and identifying specific mineral phases and their distribution in 3-dimensions. Using in-house image processing techniques and auxilary charactersation with thin section, electron microscope and spectroscopic techniques we quantified the surface area of each mineral phase in the x-ray CT images. This quantification was validated against nitrogen BET surface area and backscattered electron imaging measurements of the CT-imaged samples. Distributions in reactive surface area for each mineral phase were constructed by calculating surface areas in thousands of randomly selected subvolume images of the total sample, each normalized to the pore volume in that image. In all samples, there is little correlation between the reactive surface area fraction and the volumetric fraction of a mineral in a bulk rock. Berea sandstone was far less heterogeneous and has a characteristic pore size at which a surface area distribution may be used to quantify heterogeneity. In carbonates, heterogeneity is more complex and surface area must be

  20. Controlling drug delivery kinetics from mesoporous titania thin films by pore size and surface energy

    Directory of Open Access Journals (Sweden)

    Karlsson J

    2015-07-01

    Full Text Available Johan Karlsson, Saba Atefyekta, Martin Andersson Department of Chemical and Biological Engineering, Chalmers University of Technology, Gothenburg, Sweden Abstract: The osseointegration capacity of bone-anchoring implants can be improved by the use of drugs that are administrated by an inbuilt drug delivery system. However, to attain superior control of drug delivery and to have the ability to administer drugs of varying size, including proteins, further material development of drug carriers is needed. Mesoporous materials have shown great potential in drug delivery applications to provide and maintain a drug concentration within the therapeutic window for the desired period of time. Moreover, drug delivery from coatings consisting of mesoporous titania has shown to be promising to improve healing of bone-anchoring implants. Here we report on how the delivery of an osteoporosis drug, alendronate, can be controlled by altering pore size and surface energy of mesoporous titania thin films. The pore size was varied from 3.4 nm to 7.2 nm by the use of different structure-directing templates and addition of a swelling agent. The surface energy was also altered by grafting dimethylsilane to the pore walls. The drug uptake and release profiles were monitored in situ using quartz crystal microbalance with dissipation (QCM-D and it was shown that both pore size and surface energy had a profound effect on both the adsorption and release kinetics of alendronate. The QCM-D data provided evidence that the drug delivery from mesoporous titania films is controlled by a binding–diffusion mechanism. The yielded knowledge of release kinetics is crucial in order to improve the in vivo tissue response associated to therapeutic treatments. Keywords: mesoporous titania, controlled drug delivery, release kinetics, alendronate, QCM-D

  1. Porous coordination polymer with flexibility imparted by coordinatively changeable lithium ions on the pore surface.

    Science.gov (United States)

    Xie, Lin-Hua; Lin, Jian-Bin; Liu, Xiao-Min; Wang, Yu; Zhang, Wei-Xiong; Zhang, Jie-Peng; Chen, Xiao-Ming

    2010-02-01

    Solvothermal reactions of equimolar zinc acetate, lithium acetate, and 1,3,5-benzenetricarboxylic acid (H(3)btc) in different mixed solvents yielded isostructural three-dimensional frameworks [LiZn(btc)(cG)].lG [cG and lG denote coordinated and lattice guests, respectively; cG = (nmp)(0.5)(H(2)O)(0.5), lG = (EtOH)(0.5) (1a); cG = H(2)O, lG = EtOH (1b); nmp = N-methyl-2-pyrrolidone] with one-dimensional channels occupied by guest molecules and solvent-coordinated, extrusive Li(+) ions. Thermogravimetry analyses and powder X-ray diffraction measurements revealed that both 1a and 1b can lose all lattice and coordinated guests to form a desolvated phase [LiZn(btc)] (MCF-27, 1) and almost retains the original framework structure. Gas adsorption measurements on 1 confirmed its permanent porosity but suggested a structural transformation from 1a/1b to 1. It is noteworthy that only 1a can undergo a single-crystal to single-crystal (SCSC) transformation into 1 upon desolvation. The crystal structure of 1 revealed that the Li(+) ions were retracted into the channel walls via complementary coordination to the carboxylate oxygen atoms in the framework rather than being exposed on the pore surface. Single-crystal X-ray diffraction analyses were also performed for N(2)- and CO(2)-loaded samples of 1, revealing that the framework remained unchanged when the gases were adsorbed. Although the gas molecules could not be modeled, the residue electrons inside the channels demonstrated that the retracted Li(+) ions still behave as the primary interacting site for CO(2) molecules. Nevertheless, solvent molecules such as H(2)O can readily compete with the framework oxygen atom to retrieve the extrusive Li(+) ions, accompanying the reverse structural transformation, i.e., from 1 to 1a/1b.

  2. Pore structure characteristics after two years biochar application to a sandy loam field

    DEFF Research Database (Denmark)

    Sun, Zhencai; Arthur, Emmanuel; de Jonge, Lis Wollesen

    2015-01-01

    Soil pore structure comprises the size and shape of soil pores and has a major impact on water retention and gas movement. The porous nature of biochar suggests that its application to soil can potentially alter soil pore structure characteristics, and the purpose of this study was to evaluate...... the effects of birch wood biochar (20, 40, and 100 Mg ha−1) applied to a sandy loam on soil total porosity and pore structure indices. Bulk and intact soil samples were collected for physicochemical analyses and water retention and gas diffusivity measurements between pF 1.0 and pF 3.0. Biochar application...... reduced bulk density and increased total porosity especially for soil with 100 Mg ha−1 biochar (16% and 14% reduction in bulk density and total porosity, respectively). Biochar application of more than 20 Mg ha−1 enhanced water retention, and the trend increased with increasing biochar application rate...

  3. Change of Pore-Fracture Structure of Anthracite Modified by Electrochemical Treatment Using Micro-CT

    Directory of Open Access Journals (Sweden)

    Xianfa Kong

    2018-01-01

    Full Text Available The electrochemical method can strengthen gas desorption and seepage from coal. The study on change of the pore-fracture structure of coal after electrochemical modification can help to reveal the mechanism. Anthracite was modified by the electrochemical method using our own self-developed experiment apparatus. The pore-fracture structure of modified samples was measured by micro-CT. Combined with the Matlab software, its characteristics such as pore number, porosity, and average pore diameter were analyzed. The results show that (1 the number of fractures in modified coal samples increases. The shape of new fractures in samples in the anodic and cathodic zones was irregular voids and striola, respectively. The effect of electrochemical treatment on the section of samples close to the electrode is relatively obvious. (2 With increasing pore size, the number of pores in samples changes according to negative exponential rules. After electrochemical modification, the porosity of modified samples in the anodic zone increases from 11.88% to 31.65%, and the porosity of modified samples in the cathodic zone increases from 12.13% to 36.71%. (3 The main reason for the increase in the number of pores of coal samples in the anodic and cathodic zones is the treatment of electrolytic dissolution of minerals and electrophoretic migration of charged particles, respectively.

  4. A variable pressure method for characterizing nanoparticle surface charge using pore sensors.

    Science.gov (United States)

    Vogel, Robert; Anderson, Will; Eldridge, James; Glossop, Ben; Willmott, Geoff

    2012-04-03

    A novel method using resistive pulse sensors for electrokinetic surface charge measurements of nanoparticles is presented. This method involves recording the particle blockade rate while the pressure applied across a pore sensor is varied. This applied pressure acts in a direction which opposes transport due to the combination of electro-osmosis, electrophoresis, and inherent pressure. The blockade rate reaches a minimum when the velocity of nanoparticles in the vicinity of the pore approaches zero, and the forces on typical nanoparticles are in equilibrium. The pressure applied at this minimum rate can be used to calculate the zeta potential of the nanoparticles. The efficacy of this variable pressure method was demonstrated for a range of carboxylated 200 nm polystyrene nanoparticles with different surface charge densities. Results were of the same order as phase analysis light scattering (PALS) measurements. Unlike PALS results, the sequence of increasing zeta potential for different particle types agreed with conductometric titration.

  5. Experimental Investigation on Pore Structure Characterization of Concrete Exposed to Water and Chlorides.

    Science.gov (United States)

    Liu, Jun; Tang, Kaifeng; Qiu, Qiwen; Pan, Dong; Lei, Zongru; Xing, Feng

    2014-09-16

    In this paper, the pore structure characterization of concrete exposed to deionised water and 5% NaCl solution was evaluated using mercury intrusion porosity (MIP), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The effects of calcium leaching, fly ash incorporation, and chloride ions on the evolution of pore structure characteristics were investigated. The results demonstrate that: (i) in ordinary concrete without any fly ash, the leaching effect of the cement products is more evident than the cement hydration effect. From the experimental data, Ca(OH)₂ is leached considerably with the increase in immersion time. The pore structure of concrete can also be affected by the formation of an oriented structure of water in concrete materials; (ii) incorporation of fly ash makes a difference for the performance of concrete submersed in solutions as the total porosity and the pore connectivity can be lower. Especially when the dosage of fly ash is up to 30%, the pores with the diameter of larger than 100 nm show significant decrease. It demonstrates that the pore properties are improved by fly ash, which enhances the resistance against the calcium leaching; (iii) chlorides have a significant impact on microstructure of concrete materials because of the chemical interactions between the chlorides and cement hydrates.

  6. Soil pore space arrangement as a geometric indicator of soil structure

    Science.gov (United States)

    Skvortsova, E. B.; Utkaeva, V. F.

    2008-11-01

    Modern concepts of the morphology and geometry of soil structure are discussed. It is shown that the geometry of soil pores can serve as an indispensable indicator of the structural state of soils. The structural-functional significance of the shape and orientation of soil pores in addition to the total soil porosity is demonstrated by the example of agrogray and alluvial soils of the forest-steppe zone. Theoretical concepts and factual materials discussed in this paper can be considered the first stage of formalization of existing notions about the geometrical aspects of soil structure in the context of the systems arrangement of soils.

  7. Influence of lyophilization factors and gelatin concentration on pore structures of atelocollagen/gelatin sponge biomaterial.

    Science.gov (United States)

    Yang, Longqiang; Tanabe, Koji; Miura, Tadashi; Yoshinari, Masao; Takemoto, Shinji; Shintani, Seikou; Kasahara, Masataka

    2017-07-26

    This study aimed to investigate influences of lyophilization factors and gelatin concentration on pore structures of ACG sponge. ACG sponges of different freezing temperatures (-30, -80 and -196 o C), freezing times (1, 2 and 24 h), gelatin concentrations (0.6%AC+0.15%G, 0.6%AC+0.6%G and 0.6%AC+2.4%G), and with 500 μM fluvastatin were fabricated. Pore structures including porosity and pore size were analyzed by scanning electron microscopy and ImageJ. The cytotoxic effects of ACG sponges were evaluated in vitro. Freezing temperature did not affect porosity while high freezing temperature (-30 o C) increased pore size. The high gelatin concentration group (0.6%AC+2.4%G) had decreased porosity and pore size. Freezing time and 500 μM fluvastatin did not affect pore structures. The cytotoxicity and cell proliferation assays revealed that ACG sponges had no cytotoxic effects on human mesenchymal stromal cell growth and proliferation. These results indicate that ACG sponge may be a good biomaterial scaffold for bone regeneration.

  8. 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

    Formations in the Horonobe research area of Japan, where the Japan Atomic Energy Agency (JAEA) has been operating an Underground Research Laboratory. The rock samples are of cylindrical shape with 50 mm in diameter and 10 mm in length. The rock samples were immersed in 0.1 M NaCl solutions before experiments. The densities, specific surface area and cation exchange capacity were measured for the remains of drill cores from which the samples were taken. Pore radius distribution, average pore radius and porosity were also evaluated for each drill cores by mercury porosimetry. The permeability and chemical-osmosis experiments were performed in sequence on each rock sample under the confining pressures simulating in-situ effective stress condition. 0.1 M NaCl solution was used as permeant fluid in the permeability experiment, and the same solution was used as initial solution in the subsequent chemical-osmosis experiment. In the permeability experiment, a constant pressure was applied to the upper surface of rock sample. In the chemical-osmosis experiment, the bottom reservoir solution was replaced with 0.6 M NaCl solution. Both experiments were performed with the bottom reservoir isolated from the pressure buffer tank, and the progress of each experiment was monitored by measuring the bottom reservoir pressure. Figure 2 shows the chemico-osmotic, diffusion and hydraulic parameters determined for the Koetoi and Wakkanai mud-stone samples as functions of porosity. The diffusion and hydraulic parameters of these samples generally decrease with the decrease of porosity, while the osmotic efficiency is not a simple function of porosity. A relatively large osmotic efficiency was obtained only from a Wakkanai mud-stone sample with porosity of 0.33. The Wakkanai mud-stone samples have similar average pore radius, ranging from 6.8 to 7.6 nm; however, the Wakkanai mud-stone samples without large osmotic efficiency have bimodal pore structures. These suggest that even if small size pores

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

    Science.gov (United States)

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

    2014-11-01

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

  10. The role of graphite foam pore structure on saturated pool boiling enhancement

    International Nuclear Information System (INIS)

    Pranoto, I.; Leong, K.C.; Jin, L.W.

    2012-01-01

    This paper presents an experimental study of the pool boiling phenomena and performance of porous graphite foam evaporators of different structures and thermophysical properties. Two dielectric liquids viz. FC-72 and HFE-7000 were used as working fluids. Block and fin evaporators of different fin-to-block-surface-area ratios (AR) were designed to study the role of the internal pore structure of graphite foams in a compact air-cooled thermosyphon under saturated pool boiling condition for high heat flux electronics cooling applications. The wall temperatures were measured and the boiling heat transfer coefficients were calculated to analyze the boiling performance. It was found that both fin structures with AR = 3.70 and 2.73 result in reduced boiling heat transfer performances and higher wall temperatures. The experimental results show that the boiling heat transfer coefficients of the block structures are about 1.2–1.6 times higher than those of the fin structures. The total internal surface area to volume ratio (β) and the total exposed areas (A T ) of the graphite foams were calculated in this study. The results show that the values of β and A T of the block structures are much higher than the fin structures for both tested “Pocofoam” 61% porosity and “Kfoam” 78% porosity evaporators which resulted in higher boiling heat transfer coefficient and lower wall temperature of the block structures. A visualization study shows that more bubbles were generated from the block structures compared to the fin structures due to the larger number of nucleation sites from the block structures. It was also found that use of FC-72 resulted in better boiling heat transfer performance compared to HFE-7000. - Highlights: ► We studied the pool boiling performance of a thermosyphon with graphite foam evaporators of block and fin structures. ► FC-72 and HFE-7000 were used as the working fluids. ► The boiling heat transfer coefficients of the block structures are 1.2

  11. Probing the intrinsically oil-wet surfaces of pores in North Sea chalk at subpore resolution

    DEFF Research Database (Denmark)

    Hassenkam, Tue; Skovbjerg, Lone Lindbæk; Stipp, Susan Louise Svane

    2009-01-01

    atomic force microscopy-mediated adhesion and elasticity mapping derived from maps of force curves, to examine 5 x 5 µm2 areas of internal pore surfaces, using a tip functionalised to make it hydrophobic.  We investigated chalk samples from inside a drill core sample from the Danish North Sea that had...... been drilled in a water-bearing formation. At this site, the chalk has never seen oil, though at other locations, the same stratigraphic horizon with the same rock properties is known to be a productive oil reservoir. Thus the properties of the investigated particle surfaces are inherent to the chalk...

  12. Pore Scale Heterogeneity in the Mineral Distribution, Surface Area and Adsorption in Porous Rocks

    Science.gov (United States)

    Lai, P. E. P.; Krevor, S. C.

    2014-12-01

    The impact of heterogeneity in chemical transport and reaction is not understood in continuum (Darcy/Fickian) models of reactive transport. This is manifested in well-known problems such as scale dependent dispersion and discrepancies in reaction rate observations made at laboratory and field scales [1]. Additionally, this is a source of uncertainty for carbon dioxide injection, which produces a reactive fluid-rock system particularly in carbonate rock reservoirs. A potential cause is the inability of the continuum approach to incorporate the impact of heterogeneity in pore-scale reaction rates. This results in part from pore-scale heterogeneities in surface area of reactive minerals [2, 3]. We use x-ray micro tomography to describe the non-normal 3-dimensional distribution of reactive surface area within a porous medium according to distinct mineral groups. Using in-house image processing techniques, thin sections, nitrogen BET surface area, backscattered electron imaging and energy dispersive spectroscopy, we compare the surface area of each mineral phase to those obtained from x-ray CT imagery. In all samples, there is little correlation between the reactive surface area fraction and the volumetric fraction of a mineral in a bulk rock. Berea sandstone was far less heterogeneous and has a characteristic pore size at which a surface area distribution may be used to quantify heterogeneity. In carbonates, heterogeneity is more complex and surface area must be characterized at multiple length scales for an accurate description of reactive transport. We combine the mineral specific surface area characterisation to dynamic tomography, imaging the flow of water and solutes, to observe flow dependent and mineral specific adsorption. The observations may contribute to the incorporation of experimentally based statistical descriptions of pore scale heterogeneity in reactive transport into upscaled models, moving it closer to predictive capabilities for field scale

  13. New approach to increase the gas throughput through mica track microfilters by changing their pore structure

    International Nuclear Information System (INIS)

    Shi-lun Guo; Tress, G.; Vater, P.; Khan, E.U.; Dersch, R.; Plachky, M.; Brandt, R.; Khan, H.A.

    1986-01-01

    A new approach has been developed to increase the gas throughput of nuclear track microfilters by changing the structure of the etched channels. This can be achieved by reducing the pore length of the filters and by changing the etched channel to two open funnels with a short neck in-between. The mica track microfilters are etched with hot concentrated NaOH solution only. The bulk etch rate is found to be 100 A h -1 . The structure of the mica pores has been studied in detail with optical and scanning electron microscopes. We find that the etching behavior of mica is anisotropic in several directions. A ''funnel-neck-funnel'' structure has been formed in mica by etching in NaOH. The gas throughput increase has been calculated from the modified structure of the mica pore. (author)

  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. Structure and dynamics of confined flexible and unentangled polymer melts in highly adsorbing cylindrical pores

    International Nuclear Information System (INIS)

    Carrillo, Jan-Michael Y.; Sumpter, Bobby G.

    2014-01-01

    Coarse-grained molecular dynamics simulations are used to probe the dynamic phenomena of polymer melts confined in nanopores. The simulation results show excellent agreement in the values obtained for the normalized coherent single chain dynamic structure factor, (S(Q,Δt))/(S(Q,0)) . In the bulk configuration, both simulations and experiments confirm that the polymer chains follow Rouse dynamics. However, under confinement, the Rouse modes are suppressed. The mean-square radius of gyration 〈R g 2 〉 and the average relative shape anisotropy 〈κ 2 〉 of the conformation of the polymer chains indicate a pancake-like conformation near the surface and a bulk-like conformation near the center of the confining cylinder. This was confirmed by direct visualization of the polymer chains. Despite the presence of these different conformations, the average form factor of the confined chains still follows the Debye function which describes linear ideal chains, which is in agreement with small angle neutron scattering experiments (SANS). The experimentally inaccessible mean-square displacement (MSD) of the confined monomers, calculated as a function of radial distance from the pore surface, was obtained in the simulations. The simulations show a gradual increase of the MSD from the adsorbed, but mobile layer, to that similar to the bulk far away from the surface

  16. Asymmetric block copolymer membranes with ultrahigh porosity and hierarchical pore structure by plain solvent evaporation

    KAUST Repository

    Yu, H.

    2016-09-14

    Membranes with a hierarchical porous structure could be manufactured from a block copolymer blend by pure solvent evaporation. Uniform pores in a 30 nm thin skin layer supported by a macroporous structure were formed. This new process is attractive for membrane production because of its simplicity and the lack of liquid waste.

  17. Pore Structure of Macroporous Polymers Using Polystyrene/Silica Composite Particles as Pickering Stabilizers.

    Science.gov (United States)

    Tu, Shuhua; Zhu, Chenxu; Zhang, Lingyun; Wang, Haitao; Du, Qiangguo

    2016-12-13

    A novel approach for the preparation of interconnected macroporous polymers with a controllable pore structure was reported. The method was based on the polymerization of water-in-oil Pickering high internal phase emulsion (HIPE) stabilized by polystyrene (PS)/silica composite particles. The composite Pickering stabilizers were facilely obtained by mixing positively charged PS microspheres and negatively charged silica nanoparticles, and their amphiphilicity could be delicately tailored by varying the ratio of PS and silica. The droplet size of Pickering HIPEs was characterized using an optical microscope. The pore structure of polymer foams was observed using a scanning electron microscope. The interconnectivity of macroporous polymers was evaluated upon their gas permeability, which was greatly improved after etching PS microspheres included in the Pickering stabilizers with tetrahydrofuran. As a result, fine tailoring of the pore structure of polymer foams could be realized by simply tuning the ratio of PS to silica particles in the composite stabilizer.

  18. Pore structure and mechanical properties of directionally solidified porous aluminum alloys

    Directory of Open Access Journals (Sweden)

    Komissarchuk Olga

    2014-01-01

    Full Text Available Porous aluminum alloys produced by the metal-gas eutectic method or GASAR process need to be performed under a certain pressure of hydrogen, and to carry over melt to a tailor-made apparatus that ensures directional solidification. Hydrogen is driven out of the melt, and then the quasi-cylindrical pores normal to the solidification front are usually formed. In the research, the effects of processing parameters (saturation pressure, solidification pressure, temperature, and holding time on the pore structure and porosity of porous aluminum alloys were analyzed. The mechanical properties of Al-Mg alloys were studied by the compressive tests, and the advantages of the porous structure were indicated. By using the GASAR method, pure aluminum, Al-3wt.%Mg, Al-6wt.%Mg and Al-35wt.%Mg alloys with oriented pores have been successfully produced under processing conditions of varying gas pressure, and the relationship between the final pore structure and the solidification pressure, as well as the influences of Mg quantity on the pore size, porosity and mechanical properties of Al-Mg alloy were investigated. The results show that a higher pressure of solidification tends to yield smaller pores in aluminum and its alloys. In the case of Al-Mg alloys, it was proved that with the increasing of Mg amount, the mechanical properties of the alloys sharply deteriorate. However, since Al-3%Mg and Al-6wt.%Mg alloys are ductile metals, their porous samples have greater compressive strength than that of the dense samples due to the existence of pores. It gives the opportunity to use them in industry at the same conditions as dense alloys with savings in weight and material consumption.

  19. Structural basis for pore-forming mechanism of staphylococcal α-hemolysin.

    Science.gov (United States)

    Sugawara, Takaki; Yamashita, Daichi; Kato, Koji; Peng, Zhao; Ueda, Junki; Kaneko, Jun; Kamio, Yoshiyuki; Tanaka, Yoshikazu; Yao, Min

    2015-12-15

    Staphylococcal α-hemolysin (α-HL) is a β-barrel pore-forming toxin (PFT) expressed by Staphylococcus aureus. α-HL is secreted as a water-soluble monomeric protein, which binds to target membranes and forms membrane-inserted heptameric pores. To explore the pore-forming mechanism of α-HL in detail, we determined the crystal structure of the α-HL monomer and prepore using H35A mutant and W179A/R200A mutant, respectively. Although the overall structure of the monomer was similar to that of other staphylococcal PFTs, a marked difference was observed in the N-terminal amino latch, which bent toward the prestem. Moreover, the prestem was fastened by the cap domain with a key hydrogen bond between Asp45 and Tyr118. Prepore structure showed that the transmembrane region is roughly formed with flexibility, although the upper half of the β-barrel is formed appropriately. Structure comparison among monomer, prepore and pore revealed a series of motions, in which the N-terminal amino latch released upon oligomerization destroys its own key hydrogen bond between Asp45-Tyr118. This action initiated the protrusion of the prestem. Y118F mutant and the N-terminal truncated mutant markedly decreased in the hemolytic activity, indicating the importance of the key hydrogen bond and the N-terminal amino latch on the pore formation. Based on these observations, we proposed a dynamic molecular mechanism of pore formation for α-HL. Copyright © 2015 Elsevier Ltd. All rights reserved.

  20. Role of low flow and backward flow zones on colloid transport in pore structures derived from real porous media.

    Science.gov (United States)

    Li, Xiqing; Li, Zhelong; Zhang, Dongxiao

    2010-07-01

    To examine the relevance of low flow zones and flow vortices to colloid transport in real porous media, lattice-Boltzmann (LB) simulations were combined with X-ray microtomography (XMT) to simulate flow fields in glass beads and quartz sand. Backward flow zones were demonstrated to be widely present in both porous media, with a greater volume fraction in the former relative to the latter porous media. Glass beads in the XMT images were approximated as spheres and their coordinates and radii were extracted to allow reconstruction of pore structures. LB simulations were again performed and the simulated flow fields in the reconstructed pore structures were coupled to a three-dimensional particle tracking algorithm. Particle tracking simulations demonstrated that significant amounts of colloids stayed in the simulated domains for long periods (up to 50 pore volumes). The percentages of colloids with long residence time increased as the depth of the secondary energy minimum increased. The majority of the colloids with long residence time were translated to low flow zones while being associated with grain surfaces via secondary minima. A small fraction of colloids entered low flow zones without being associated with the grains surfaces. Backward flow zones were also found to trap a small fraction of colloids for significantly long time (up to 10 pore volumes). In overall, however, backward flow zones trapped fewer colloids for shorter durations than low flow zones. In summary, this work demonstrates the importance of temporary trapping of colloids by the low flow and backward flow zones in real porous media. This trapping process can explain a number of intriguing experimental observations.

  1. 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.”

  2. Proton Conduction in Sulfonated Organic-Inorganic Hybrid Monoliths with Hierarchical Pore Structure.

    Science.gov (United States)

    von der Lehr, Martin; Seidler, Christopher F; Taffa, Dereje H; Wark, Michael; Smarsly, Bernd M; Marschall, Roland

    2016-09-28

    Porous organic-inorganic hybrid monoliths with hierarchical porosity exhibiting macro- and mesopores are prepared via sol-gel process under variation of the mesopore size. Organic moieties in the pore walls are incorporated by substituting up to 10% of the silicon precursor tetramethylorthosilicate with bisilylated benzene molecules. After functionalization with sulfonic acid groups, the resulting sulfonated hybrid monoliths featuring a bimodal pore structure are investigated regarding proton conduction depending on temperature and relative humidity. The hierarchical pore system and controlled mesopore design turn out to be crucial for sulfonation and proton conduction. These sulfonated hybrid hierarchical monoliths containing only 10% organic precursor exhibit higher proton conduction at different relative humidities than sulfonated periodic mesoporous organosilica made of 100% bisilylated precursors exhibiting solely mesopores, even with a lower concentration of sulfonic acid groups.

  3. Surface Energy Anisotropy Effects on Pore-Channel Stability:Rayleigh Instabilities in m-Plane Sapphire

    Energy Technology Data Exchange (ETDEWEB)

    Santala, Melissa K.; Glaeser, Andreas M.

    2005-09-07

    Internal, high-aspect-ratio pore channels with their long axes parallel to the m(10{bar 1}0) plane of sapphire were generated through sequential application of photolithography, ion-beam etching and solid-state diffusion bonding. The axial orientation of channels within the m plane was systematically varied to sample a range of bounding-surface crystallographies. The morphologic evolution of these pore channels during anneals at 1700 C was recorded by postanneal optical microscopy. The development and growth of periodic axial variations in the pore channel radius was observed, and ultimately led to the formation of discrete pores. The wavelength and average pore spacing, assumed to reflect the kinetically dominant perturbation wavelength, varied with the in-plane pore channel orientation, as did the time for complete channel breakup. Results are compared to those previously obtained when pore channels were etched into c(0001)-plane sapphire and annealed under similar conditions. The results indicate a strong effect of surface stability on the evolution behavior.

  4. A DSC investigation on the changes in pore structure of skin during leather processing

    International Nuclear Information System (INIS)

    Fathima, N. Nishad; Kumar, M. Pradeep; Rao, J. Raghava; Nair, B.U.

    2010-01-01

    Leather processing involves many unit operations that modify the physical, chemical and biological properties of the raw skin/hide of an animal. One such major variation is brought to pore structure and size, which determines the breathing property of skin. Understanding this property is essential to improve the end use of the leather matrix. Thermoporometric technique has been used in this study to bring out the influence of various process steps on the pore size distribution of skin. Marked changes in the depression of freezing point are observed for each process. Scanning electron microscopy study reveals the morphological changes in the grain and cross-section of the skin during leather processing. Understanding and predictions of pore structure changes at various stages of leather processing would benefit: (a) in process control, (b) analysis of cost benefit ratio and (c) strategic planning and transport. Thus, this study aids in better understanding of the pore structure of skin to improve the functional properties of the leather.

  5. Structure and Thermodynamics of Carbon Dioxide Sorption in Silica Pores from Experiments and Computer Models

    Science.gov (United States)

    Vlcek, L.; Rother, G.; Chialvo, A.; Cole, D. R.

    2011-12-01

    Injection of CO2 into geologic formations has been proposed as a key element to reduce the impact of greenhouse gases emissions. Quantitative understanding of CO2 adsorption in porous mineral environments at thermodynamic conditions relevant to proposed sequestration sites is thus a prerequisite for the assessment of their viability. In this study we use a combination of neutron scattering, adsorption experiments, and computer modeling to investigate the thermodynamics of near-critical carbon dioxide in the pores of SiO2 aerogel, which serves as a model of a high-porosity reservoir rock. Small angle neutron scattering (SANS) experiments provide input for the optimization of the computer model of the aerogel matrix, and also serve as a sensitive probe of local density changes of confined CO2 as a function of external pressure. Additional details of the aerogel basic building blocks and SiO2 surface are derived from TEM images. An independent source of global adsorption data is obtained from gravimetric experiments. The structural and thermodynamic aspects of CO2 sorption are linked using computer simulations, which include the application of the optimized diffusion limited cluster-cluster aggregation algorithm (DLCA), classical density functional theory (DFT) modeling of large-scale CO2 density profiles, and molecular dynamics simulations of the details of interactions between CO2 molecules and the amorphous silica surfaces. This integrated approach allows us to span scales ranging from 1Å to 1μm, as well as to infer the detailed structure of silica threads forming the framework of the silica matrix.

  6. Changes in the geometric structure of pores and aggregates as indicators of the structural degradation of cultivated soils

    Science.gov (United States)

    Skvortsova, E. B.

    2009-11-01

    As shown by the example of loamy soils of the European territory of Russia, the geometric parameters of soil structure, along with the agrophysical soil parameters, should be taken into account for the comprehensive assessment of the physical degradation of cultivated soils. Different variants of the geometric transformation of soil structure in the plow horizons are analyzed. The shape and orientation of soil pores in thin sections prepared from undisturbed oriented soil samples are considered to be the main diagnostic indices. A computer-aided analysis of soil pores in thin sections made it possible to distinguish and characterize different levels of the geometric transformation of soil structure upon soil compaction: (a) without the disturbance of the shape and orientation of the aggregates, (b) with the transformation of soil aggregates from the crumb (granular) to the angular blocky shape, (c) with the development of a platy structure characterized by the predominantly horizontal orientation of the pores and aggregates, and (d) the complete disappearance of separate aggregates with the formation of a massive soil structure. The validity of the assessments of the geometric transformation of the soil pore space against the background of a considerable spatial variability in the geometric properties of soil structure in the plow horizon is discussed. The structural-functional specificity of the distinguished levels of the geometric transformation of soil structure is outlined.

  7. Nitrogen-mediated effects of elevated CO2 on intra-aggregate soil pore structure.

    Science.gov (United States)

    Caplan, Joshua S; Giménez, Daniel; Subroy, Vandana; Heck, Richard J; Prior, Stephen A; Runion, G Brett; Torbert, H Allen

    2017-04-01

    Soil pore structure has a strong influence on water retention, and is itself influenced by plant and microbial dynamics such as root proliferation and microbial exudation. Although increased nitrogen (N) availability and elevated atmospheric CO 2 concentrations (eCO 2 ) often have interacting effects on root and microbial dynamics, it is unclear whether these biotic effects can translate into altered soil pore structure and water retention. This study was based on a long-term experiment (7 yr at the time of sampling) in which a C 4 pasture grass (Paspalum notatum) was grown on a sandy loam soil while provided factorial additions of N and CO 2 . Through an analysis of soil aggregate fractal properties supported by 3D microtomographic imagery, we found that N fertilization induced an increase in intra-aggregate porosity and a simultaneous shift toward greater accumulation of pore space in larger aggregates. These effects were enhanced by eCO 2 and yielded an increase in water retention at pressure potentials near the wilting point of plants. However, eCO 2 alone induced changes in the opposite direction, with larger aggregates containing less pore space than under control conditions, and water retention decreasing accordingly. Results on biotic factors further suggested that organic matter gains or losses induced the observed structural changes. Based on our results, we postulate that the pore structure of many mineral soils could undergo N-dependent changes as atmospheric CO 2 concentrations rise, having global-scale implications for water balance, carbon storage, and related rhizosphere functions. © 2016 John Wiley & Sons Ltd.

  8. Reconstruction of 3D Micro Pore Structure of Coal and Simulation of Its Mechanical Properties

    Directory of Open Access Journals (Sweden)

    Guang-zhe Deng

    2017-01-01

    Full Text Available This article takes the low permeability coal seam in the coalfield of South Judger Basin in Xinjiang, as a research object. The pore structure characteristics of coal rock mass in low permeability coal seam were analyzed quantitatively using scanning electron microscopy (SEM through the methods of statistics and digital image analysis. Based on the pore structure parameters and the distribution function of the coal rock mass, a three-dimensional porous cylinder model with different porosity was reconstructed by FLAC3D. The numerical simulation study of reconstructed pore model shows that (1 the porosity and the compressive strength have obvious nonlinear relation and satisfy the negative exponential relation; (2 the porosity significantly affects the stress distribution; with the increase of micro porosity, the stress distribution becomes nonuniform; (3 the compressive failures of different models are mainly shear failures, and the shape of fracture section is related to porosity; (4 the variation of seepage coefficient of the pore reconstruction model is consistent with the development of micro cracks. The micro mechanism of the deformation and failure of coal and the interaction of multiphase flow with porosity are revealed, which provides a theoretical reference for the clean development of the low permeability coal seam.

  9. Full Field X-Ray Fluorescence Imaging Using Micro Pore Optics for Planetary Surface Exploration

    Science.gov (United States)

    Sarrazin, P.; Blake, D. F.; Gailhanou, M.; Walter, P.; Schyns, E.; Marchis, F.; Thompson, K.; Bristow, T.

    2016-01-01

    Many planetary surface processes leave evidence as small features in the sub-millimetre scale. Current planetary X-ray fluorescence spectrometers lack the spatial resolution to analyse such small features as they only provide global analyses of areas greater than 100 mm(exp 2). A micro-XRF spectrometer will be deployed on the NASA Mars 2020 rover to analyse spots as small as 120m. When using its line-scanning capacity combined to perpendicular scanning by the rover arm, elemental maps can be generated. We present a new instrument that provides full-field XRF imaging, alleviating the need for precise positioning and scanning mechanisms. The Mapping X-ray Fluorescence Spectrometer - "Map-X" - will allow elemental imaging with approximately 100µm spatial resolution and simultaneously provide elemental chemistry at the scale where many relict physical, chemical and biological features can be imaged in ancient rocks. The arm-mounted Map-X instrument is placed directly on the surface of an object and held in a fixed position during measurements. A 25x25 mm(exp 2) surface area is uniformly illuminated with X-rays or alpha-particles and gamma-rays. A novel Micro Pore Optic focusses a fraction of the emitted X-ray fluorescence onto a CCD operated at a few frames per second. On board processing allows measuring the energy and coordinates of each X-ray photon collected. Large sets of frames are reduced into 2d histograms used to compute higher level data products such as elemental maps and XRF spectra from selected regions of interest. XRF spectra are processed on the ground to further determine quantitative elemental compositions. The instrument development will be presented with an emphasis on the characterization and modelling of the X-ray focussing Micro Pore Optic. An outlook on possible alternative XRF imaging applications will be discussed.

  10. Adsorption of 4,6-dimethyldibenzothiophene and collidine over MoO(3)/γ-Al(2)subO(3) catalysts with different pore structures.

    Science.gov (United States)

    Zhang, Di; Xue, Lijun; Xu, Yongqiang; Song, Lijuan; Liu, Xinmei

    2017-05-01

    Mesoporous γ-Al 2 O 3 supports with different pore structures were prepared by the cation-anion double hydrolysis method. Based on these samples, MoO 3 /γ-Al 2 O 3 catalysts were made via impregnation. The adsorptions of 4,6-dimethyldibenzothiophene (4,6-DMDBT) and collidine over the supports and catalysts were studied by FT-IR. The supports or catalysts with larger pores can adsorb more 4,6-DMDBT. The methyl groups on adsorbate molecules are very close to the sulfur atom, resulting in apparent steric hindrance. Increasing the pore size can promote the interaction between the adsorbates and supports or catalysts, enhancing the CC bond and weakening the CS bond of 4,6-DMDBT. 4,6-DMDBT molecules were coordinated with the unsaturated Mo atoms over the catalysts to form π-complexation adsorption. There was much difference between thiophene and 4,6-DMDBT adsorption. The adsorption of collidine over the catalysts also illustrated that there existed steric hindrance. Significantly, the catalyst with hierarchical mesopores was beneficial for the adsorbates with larger molecular dynamics diameter. Compared with the pore size, the specific surface area was not the key factor to affect the adsorptions of 4,6-DMDBT and collidine. The hydrodesulfurization reaction of 4,6-DMDBT illustrated that the catalysts with larger pore size or hierarchical pore structure presented higher desulfurization efficiency (above than 80%). Copyright © 2017 Elsevier Inc. All rights reserved.

  11. Surprising transformation of a block copolymer into a high performance polystyrene ultrafiltration membrane with a hierarchically organized pore structure

    KAUST Repository

    Shevate, Rahul

    2018-02-08

    We describe the preparation of hierarchical polystyrene nanoporous membranes with a very narrow pore size distribution and an extremely high porosity. The nanoporous structure is formed as a result of unusual degradation of the poly(4-vinyl pyridine) block from self-assembled poly(styrene)-b-poly(4-vinyl pyridine) (PS-b-P4VP) membranes through the formation of an unstable pyridinium intermediate in an alkaline medium. During this process, the confined swelling and controlled degradation produced a tunable pore size. We unequivocally confirmed the successful elimination of the P4VP block from a PS-b-P4VPVP membrane using 1D/2D NMR spectroscopy and other characterization techniques. Surprisingly, the long range ordered surface porosity was preserved even after degradation of the P4VP block from the main chain of the diblock copolymer, as revealed by SEM. Aside from a drastically improved water flux (∼67% increase) compared to the PS-b-P4VP membrane, the hydraulic permeability measurements validated pH independent behaviour of the isoporous PS membrane over a wide pH range from 3 to 10. The effect of the pore size on protein transport rate and selectivity (a) was investigated for lysozyme (Lys), bovine serum albumin (BSA) and globulin-γ (IgG). A high selectivity of 42 (Lys/IgG) and 30 (BSA/IgG) was attained, making the membranes attractive for size selective separation of biomolecules from their synthetic model mixture solutions.

  12. Research of forming of the system of transport pores in the structure of carbon composites by their gasification

    Directory of Open Access Journals (Sweden)

    Віктор Олексійович Скачков

    2016-12-01

    Full Text Available The structure of pores for carbonized carbon plastics is considered. Description of porous structure by the parabolic law of distribution on four local maximums is offered. Mechanism of forming for the system of transport pores are researched in the structure of carbonized carbon plastics taking into account oxidization of its lateral face and real distribution of porous structure on the size of radiuses at gasification in the medium of carbon dioxide. The task of carbon dioxide transfer on length of carbonizing carbon plastic pores, providing the given profiling of its structure in the process of gasification, is considered

  13. The anisotropy of the structure and the microspatial pattern of the pores at the aggregate level of texturally differentiated soils

    Science.gov (United States)

    Skvortsova, E. B.; Rozhkov, V. A.

    2011-07-01

    The anisotropy of the soil pores in texturally differentiated soils is an important soil-genetic index. The morphological study of thin soil sections with vertical and horizontal orientation showed that the pore space of a texturally differentiated light gray forest soil at the aggregate level of organization has isotropic, anisotropic, and partially anisotropic structures in the different horizons. In the horizons with a platy structure, the anisotropy of the pore space is largely determined by the anisometry of the structural units. In the horizons with a massive structure not separated into aggregates, the anisotropic indices can be related to the structural features of the recent and relic biogenic pores. To reveal the total anisotropy of the soil pore space, the most informative and genetically determined indices should be studied: the shape, area, and orientation of the pores. In the soil studied, the variation of the pore sizes in the vertical thin sections was higher than in the horizontal thin sections, which agreed with the concept of the anisotropy of the entire soil profile. The fixed vertical and horizontal orientation of the soil thin sections allowed the obtained results to be integrated into the full-profile anisotropy of the soil properties. The vertical thin sections were found to be of greater information value for the profile-genetic analysis of the structure and variability of the soil pore space than their horizontal analogues.

  14. Fast and non-destructive pore structure analysis using terahertz time-domain spectroscopy.

    Science.gov (United States)

    Markl, Daniel; Bawuah, Prince; Ridgway, Cathy; van den Ban, Sander; Goodwin, Daniel J; Ketolainen, Jarkko; Gane, Patrick; Peiponen, Kai-Erik; Zeitler, J Axel

    2018-02-15

    Pharmaceutical tablets are typically manufactured by the uni-axial compaction of powder that is confined radially by a rigid die. The directional nature of the compaction process yields not only anisotropic mechanical properties (e.g. tensile strength) but also directional properties of the pore structure in the porous compact. This study derives a new quantitative parameter, S a , to describe the anisotropy in pore structure of pharmaceutical tablets based on terahertz time-domain spectroscopy measurements. The S a parameter analysis was applied to three different data sets including tablets with only one excipient (functionalised calcium carbonate), samples with one excipient (microcrystalline cellulose) and one drug (indomethacin), and a complex formulation (granulated product comprising several excipients and one drug). The overall porosity, tablet thickness, initial particle size distribution as well as the granule density were all found to affect the significant structural anisotropies that were observed in all investigated tablets. The S a parameter provides new insights into the microstructure of a tablet and its potential was particularly demonstrated for the analysis of formulations comprising several components. The results clearly indicate that material attributes, such as particle size and granule density, cause a change of the pore structure, which, therefore, directly impacts the liquid imbibition that is part of the disintegration process. We show, for the first time, how the granule density impacts the pore structure, which will also affect the performance of the tablet. It is thus of great importance to gain a better understanding of the relationship of the physical properties of material attributes (e.g. intragranular porosity, particle shape), the compaction process and the microstructure of the finished product. Copyright © 2017 Elsevier B.V. All rights reserved.

  15. Macroporous Polymers with Hierarchical Pore Structure from Emulsion Templates Stabilised by Both Particles and Surfactants.

    Science.gov (United States)

    Wong, Ling L Ching; Ikem, Vivian O; Menner, Angelika; Bismarck, Alexander

    2011-10-04

    Inspired by natural porous materials, such as wood, bamboo and spongy bone consisting of individual structural units that are hierarchically arranged to optimise mechanical properties such as strength and toughness, synthetic macroporous polymers with enhanced physical properties were created by emulsion templating. Hierarchical poly(merised) high internal phase emulsions (HIPE) were created from HIPEs stabilised simultaneously by particles and a surfactant. In these HIPEs, surfactant stabilised and particle stabilised water droplets coexist, which upon polymerisation of the minority oil phase gives rise to macroporous polymers with a hierarchical pore structure. An improvement of the mechanical properties of our hierarchically structured macroporous polymers at equal porosity was observed, due to a more efficient packing of pores in a configuration that improves mechanical strength despite the presence of interconnecting pore throats. Moreover, the permeability of the hierarchically structured polyHIPEs are exceeding those measured for conventional polyHIPEs made from surfactant only stabilised HIPEs. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Pore structures and mechanical properties of porous titanium scaffolds by bidirectional freeze casting.

    Science.gov (United States)

    Yan, Leiming; Wu, Jisi; Zhang, Lei; Liu, Xinli; Zhou, Kechao; Su, Bo

    2017-06-01

    Porous titanium scaffolds with long-range lamellar structure were fabricated using a novel bidirectional freeze casting method. Compared with the ordinarily porous titanium materials made by traditional freeze casting, the titanium walls can offer the structure of ordered arrays with parallel to each other in the transverse cross-sections. And titanium scaffolds with different pore width, wall size and porosity can be synthesized in terms of adjusting the fabrication parameters. As the titanium content was increased from 15vol.% to 25vol.%, the porosity and pore width decreased from 67±3% to 50±2% and 80±10μm to 67±7μm, respectively. On the contrary, as the wall size was increased from 18±2μm to 30±3μm, the compressive strength and stiffness were increased from 58±8MPa to 162±10MPa and from 2.5±0.7GPa to 6.5±0.9GPa, respectively. The porous titanium scaffolds with long-range lamellar structure and controllable pore structure produced in present work will be capable of having potential application as bone tissue scaffold materials. Copyright © 2016 Elsevier B.V. All rights reserved.

  17. New bimodal pore catalysts for Fischer-Tropsch synthesis

    Energy Technology Data Exchange (ETDEWEB)

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

    2004-11-15

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

  18. Numerical and Experimental Study of the Structural Color by Widening the Pore Size of Nanoporous Anodic Alumina

    OpenAIRE

    Jiawen Li; Zhiqiang Zhu; Yanlei Hu; Jinjin Zheng; Jiaru Chu; Wenhao Huang

    2014-01-01

    The structural color originated from the nanoporous anodic alumina (NAA) film is related to the structural characteristics. This paper aimed to obtain different structural colors which can cover the whole visible range by widening the pore size of metal-coated NAA. First, we used the Finite Difference Time Domain (FDTD) method to analyze the relationship between the physical structure and optical properties. Then, we fabricated different colors and expected color pattern by widening the pore...

  19. An improvement of the fractal theory and its application in pore structure evaluation and permeability estimation

    Science.gov (United States)

    Ge, Xinmin; Fan, Yiren; Deng, Shaogui; Han, Yujiao; Liu, Jiaxiong

    2016-09-01

    We present an improved fractal model for pore structure evaluation and permeability estimation based on the high pressure mercury porosimetry data. An accumulative fractal equation is introduced to characterize the piecewise nature of the capillary pressure and the mercury saturation. The iterative truncated singular value decomposition algorithm is developed to solve the accumulative fractal equation and obtain the fractal dimension distributions. Furthermore, the fractal dimension distributions and relevant parameters are used to characterize the pore structure and permeability. The results demonstrate that the proposed model provides better characterization of the mercury injection capillary pressure than conventional monofractal theory. In addition, there is a direct relationship between the pore structure types and the fractal dimension spectrums. What is more, the permeability is strongly correlated with the geometric and the arithmetic mean values of fractal dimensions, and the permeability estimated using these new fractal dimension parameters achieve excellent result. The improved model and solution give a fresh perspective of the conventional monofractal theory, which may be applied in many geological and geophysical fields.

  20. Adsorption performance of salicylic acid on a novel resin with distinctive double pore structure.

    Science.gov (United States)

    Xiao, Guqing; Wen, Ruiming; Liu, Aijiao; He, Guowen; Wu, Dan

    2017-05-05

    Two approaches were used to synthesize two resins with different pore structures. In one way, the CH 2 Cl groups in macroporous chloromethylated polystyrene resin were transformed to methylene bridges, and achieved a hypercrosslinked resin with plentiful micropores (denoted GQ-06). In the other way, 50% of the CH 2 Cl groups in chloromethylated polystyrene resin was used to produce micropores, while the residual 50% of the CH 2 Cl groups was reacted with 2-aminopyridine, and prepared another resin with double pore structure of hypercrosslinked resin and macroporous resin (denoted GQ-11). The adsorption of salicylic acid (SA) on GQ-11 was investigated using GQ-06 as the reference adsorbent. The effect of pH on the adsorption of SA on GQ-06 was consistent with the dissociation curve of SA. The maximum adsorption capacity of SA on GQ-11 was observed at the solution pH of 2.64. The greater adsorption rate of SA on GQ-11 than that of GQ-06 was attributed to its double pore structure. The multifunctional adsorption mechanism of anion exchange and hydrophobic interaction resulted in the larger equilibrium capacity of SA on GQ-11 than that of GQ-06. GQ-06 and GQ-11 could be regenerated by absolute alcohol and 80% of alcohol -0.5mol/L of sodium hydroxide aqueous solution, respectively. Copyright © 2017 Elsevier B.V. All rights reserved.

  1. Characterization of the intragranular water regime within subsurface sediments: pore volume, surface area, and mass transfer limitations

    Science.gov (United States)

    Hay, Michael B.; Stoliker, Deborah L.; Davis, James A.; Zachara, John M.

    2011-01-01

    Although "intragranular" pore space within grain aggregates, grain fractures, and mineral surface coatings may contain a relatively small fraction of the total porosity within a porous medium, it often contains a significant fraction of the reactive surface area, and can thus strongly affect the transport of sorbing solutes. In this work, we demonstrate a batch experiment procedure using tritiated water as a high-resolution diffusive tracer to characterize the intragranular pore space. The method was tested using uranium-contaminated sediments from the vadose and capillary fringe zones beneath the former 300A process ponds at the Hanford site (Washington). Sediments were contacted with tracers in artificial groundwater, followed by a replacement of bulk solution with tracer-free groundwater and the monitoring of tracer release. From these data, intragranular pore volumes were calculated and mass transfer rates were quantified using a multirate first-order mass transfer model. Tritium-hydrogen exchange on surface hydroxyls was accounted for by conducting additional tracer experiments on sediment that was vacuum dried after reaction. The complementary ("wet" and "dry") techniques allowed for the simultaneous determination of intragranular porosity and surface area using tritium. The Hanford 300A samples exhibited intragranular pore volumes of ~1% of the solid volume and intragranular surface areas of ~20%–35% of the total surface area. Analogous experiments using bromide ion as a tracer yielded very different results, suggesting very little penetration of bromide into the intragranular porosity.

  2. Description and Reconstruction of Soil Structure Using Correlation Functions: Morphological and Pore-Scale Modeling Study

    Science.gov (United States)

    Karsanina, M.; Gerke, K.; Vasilyev, R.; Skvortsova, E. B.; Korost, D. V.; Mallants, D.

    2013-12-01

    It is now well-established that structure of porous or composite media (i.e., distribution of different materials or phases) defines all physical properties, including multi-phase flow and solute transport. To characterize soil structure conventional soil science uses such metrics as grain size distribution, morphology or numerous classifications. However, all these descriptors provide only limited and often qualitative information about structural properties, cannot be used to reconstruct real structure or predict physical properties. With the progress of modern non-destructive analysis tools we can obtain detailed 3D structure information and use it for calculation of any physical property. Such 3D data is a valuable verification dataset to check the usefulness of soil structure description using stochastic measures such as correlation functions. Any potential soil structure descriptor should possess two main features: 1) represent structure in some mathematical way, 2) reconstruction based on this mathematical function alone should be statistically equal to the original structure (e.g., have similar pore size distributions, physical properties, etc.). To check the applicability to soil science, we choose different 2D and 3D segmented soil images and calculated their correlation function. The modified Yeong-Torquato procedure was then used to reconstruct images based on calculated correlation functions. This method was applied to three different soil datasets: 1) a set of 2D thin-sections, 2) 3D images of soils with known hydraulic properties (Ksat and WRC), 3) 3D images of soils and aggregates from the same soil profile, but different genetic horizons. In the first case, we use conventional morphological descriptors in 2D original and reconstructed images (pore size, shapes and orientations) to quantify reconstructions quality. In the second case, we use pore-network models extracted from original and reconstructed 3D images to calculate Ksat, WRC and relative

  3. Structural Changes Fundamental to Gating of the Cystic Fibrosis Transmembrane Conductance Regulator Anion Channel Pore.

    Science.gov (United States)

    Linsdell, Paul

    2017-01-01

    Cystic fibrosis is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR), an epithelial cell anion channel. Potentiator drugs used in the treatment of cystic fibrosis act on the channel to increase overall channel function, by increasing the stability of its open state and/or decreasing the stability of its closed state. The structure of the channel in either the open state or the closed state is not currently known. However, changes in the conformation of the protein as it transitions between these two states have been studied using functional investigation and molecular modeling techniques. This review summarizes our current understanding of the architecture of the transmembrane channel pore that controls the movement of chloride and other small anions, both in the open state and in the closed state. Evidence for different kinds of changes in the conformation of the pore as it transitions between open and closed states is described, as well as the mechanisms by which these conformational changes might be controlled to regulate normal channel gating. The ways that key conformational changes might be targeted by small compounds to influence overall CFTR activity are also discussed. Understanding the changes in pore structure that might be manipulated by such small compounds is key to the development of novel therapeutic strategies for the treatment of cystic fibrosis.

  4. 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.

  5. Synthesis of silica aerogel monoliths with controlled specific surface areas and pore sizes

    Science.gov (United States)

    Gao, Bingying; Lu, Shaoxiang; Kalulu, Mulenga; Oderinde, Olayinka; Ren, Lili

    2017-07-01

    To replace traditional preparation methods of silica aerogels, a small-molecule 1,2-epoxypropane (PO) has been introduced into the preparation process instead of using ammonia as the cross-linking agent, thus generating a lightweight, high porosity, and large surface area silica aerogel monolithic. We put forward a simple solution route for the chemical synthesis of silica aerogels, which was characterized by scanning electron microscopy (SEM), TEM, XRD, FTIR, thermogravimetric analysis (TGA) and the Brunauer-Emmett-Teller (BET) method In this paper, the effect of the amount of PO on the microstructure of silica aerogels is discussed. The BET surface areas and pore sizes of the resulting silica aerogels can be freely adjusted by changing the amount of PO, which will be helpful in promoting the development of silica aerogels to fabricate other porous materials with similar requirements. We also adopted a new organic solvent sublimation drying (OSSD) method to replace traditional expensive and dangerous drying methods such as critical point drying and freeze drying. This simple approach is easy to operate and has good repeatability, which will further facilitate actual applications of silica aerogels.

  6. Cytolytic pore-forming protein associated with the surface membrane of Naegleria fowleri

    Energy Technology Data Exchange (ETDEWEB)

    Lowrey, D.M.

    1985-01-01

    Whole cell homogenates of Naegleria fowleri were examined by hemolytic and /sup 51/Cr-release assays for the presence of cytolytic molecules which may participate in the cytopathogenic action of this amoeba. Two distinct cytolytic activities were found. A surface membrane cytolysin was identified which was found to be avidly associated with membranes possessing an equilibrium density of 1.135 g/cm/sup 3/ in isopycnic sucrose gradients. The activity of the surface membrane cytolysin was not affected by heating at 75/sup 0/C for 30 min. The second cytolytic activity was found in putative lysosomes possessing an equilibrium density of 1.162 g/cm/sup 3/ and was completely inactivated by heating at 75/sup 0/C for 30 min. Cytolysis produced in the presence of both cytolysins was consistently synergistic with respect to the activity of either cytolysin alone. The lesions produced on erythrocytes by this cooperative process were characterized by electron microscopy as transmembrane pores resembling a number of other cytolytic effector molecules including the ninth component of complement, perforins of cytolytic T lymphocytes, and the alphatoxin of Staphylococcus aureus.

  7. Evaporation-based method for preparing gelatin foams with aligned tubular pore structures

    Energy Technology Data Exchange (ETDEWEB)

    Frazier, Shane D.; Srubar, Wil V., E-mail: wsrubar@colorado.edu

    2016-05-01

    Gelatin-based foams with aligned tubular pore structures were prepared via liquid-to-gas vaporization of tightly bound water in dehydrated gelatin hydrogels. This study elucidates the mechanism of the foaming process by investigating the secondary (i.e., helical) structure, molecular interactions, and water content of gelatin films before and after foaming using X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry and thermogravimetric analysis (TGA), respectively. Experimental data from gelatin samples prepared at various gelatin-to-water concentrations (5–30 wt.%) substantiate that resulting foam structures are similar in pore diameter (approximately 350 μm), shape, and density (0.05–0.22 g/cm{sup 3}) to those fabricated using conventional methods (e.g., freeze-drying). Helical structures were identified in the films but were not evident in the foamed samples after vaporization (~ 150 °C), suggesting that the primary foaming mechanism is governed by the vaporization of water that is tightly bound in secondary structures (i.e., helices, β-turns, β-sheets) that are present in dehydrated gelatin films. FTIR and TGA data show that the foaming process leads to more disorder and reduced hydrogen bonding to hydroxyl groups in gelatin and that no thermal degradation of gelatin occurs before or after foaming. - Highlights: • A new method is presented for fabricating gelatin foams with aligned, tubular pores. • Gelatin hydrogels were dehydrated then heated to 150 °C to induce foaming. • Vaporization of tightly (vs. loosely) bound water is the primary foaming mechanism • Foaming induced no thermal degradation but caused disorder in secondary structures • Foam microstructures are similar to those prepared using conventional methods.

  8. Characterization of pore structure in cement-based materials using pressurization-depressurization cycling mercury intrusion porosimetry (PDC-MIP)

    International Nuclear Information System (INIS)

    Zhou Jian; Ye Guang; Breugel, Klaas van

    2010-01-01

    Numerous mercury intrusion porosimetry (MIP) studies have been carried out to investigate the pore structure in cement-based materials. However, the standard MIP often results in an underestimation of large pores and an overestimation of small pores because of its intrinsic limitation. In this paper, an innovative MIP method is developed in order to provide a more accurate estimation of pore size distribution. The new MIP measurements are conducted following a unique mercury intrusion procedure, in which the applied pressure is increased from the minimum to the maximum by repeating pressurization-depressurization cycles instead of a continuous pressurization followed by a continuous depressurization. Accordingly, this method is called pressurization-depressurization cycling MIP (PDC-MIP). By following the PDC-MIP testing sequence, the volumes of the throat pores and the corresponding ink-bottle pores can be determined at every pore size. These values are used to calculate pore size distribution by using the newly developed analysis method. This paper presents an application of PDC-MIP on the investigation of the pore size distribution in cement-based materials. The experimental results of PDC-MIP are compared with those measured by standard MIP. The PDC-MIP is further validated with the other experimental methods and numerical tool, including nitrogen sorption, backscanning electron (BSE) image analysis, Wood's metal intrusion porosimetry (WMIP) and the numerical simulation by the cement hydration model HYMOSTRUC3D.

  9. Evaluation of Surface and Transport Limitations to the Rate of Calcite Dissolution Using Pore Scale Modeling of a Capillary Tube Experiment at pCO2 4 bar

    Science.gov (United States)

    Molins, S.; Trebotich, D.; Yang, L.; Ajo Franklin, J. B.; Ligocki, T.; Shen, C.; Steefel, C. I.

    2013-12-01

    Mineral trapping is generally considered to account for most of the long-term trapping of CO2 in the subsurface. Prediction of mineral trapping at the reservoir scale requires knowledge of continuum-scale mineral dissolution and precipitation rates. However, processes that take place at the pore scale (e.g., transport limitation to reactive surfaces) affect rates applicable at the continuum scale. To explore the pore scale processes that result in the discrepancy between rates measured in laboratory experiments and those calibrated from continuum-scale models, we have developed a high-resolution pore scale model of a capillary tube experiment. The capillary tube (L=0.7-cm, D=500-μm) is packed with crushed calcite (Iceland spar) and the resulting 3D pore structure is imaged by X-ray computed microtomography (XCMT) at Berkeley Lab's Advanced Light Source at a 0.899-μm resolution. A solution in equilibrium with a partial pressure of CO2 of 4 bars is injected at a rate of 5 microliter/min and the effluent concentrations of calcium are measured to ensure steady state conditions are achieved. A simulation domain is constructed from the XCMT image using implicit functions to represent the mineral surface locally on a grid. The pore-scale reactive transport model is comprised of high performance simulation tools and algorithms for incompressible Navier-Stokes flow, advective-diffusive transport and multicomponent geochemical reactions. Simulations are performed using 6,144 processors on NERSC's Cray XE6 Hopper to achieve a grid resolution of 2.32 μm. Equivalent continuum scale simulations are also performed to evaluate the effect of pore scale processes. Comparison of results is performed based on flux-averaged effluent calcium concentrations, which are used as indicator of effective rates in the capillary tube. Results from both pore- and continuum-scale simulations overestimate the calcium effluent concentrations, suggesting that the TST rate expression parameters

  10. Connecting membrane fluidity and surface charge to pore-forming antimicrobial peptides resistance by an ANN-based predictive model.

    Science.gov (United States)

    Mehla, Jitender; Sood, S K

    2013-05-01

    Efficiency of antibacterial chemotherapy is gradually more challenged by the emergence of pathogenic strains exhibiting high levels of antibiotic resistance. Pore-forming antimicrobial peptides (PF-AMPs) such as alamethicin (Alm) are therefore in the focus of extensive research efforts. In the present study, an artificial neural network (ANN)-based quantitative structure-activity relationship (SAR) modeling of membrane phospholipids vs. PF-AMPs, in context to membrane fluidity and surface charge, was carried out. We observed that the potency of PF-AMPs depends on the fatty acyl chain and polar head group of phospholipids. Alm showed surface interactions with zwitterionic phospholipids however could penetrate deeper inside the hydrophobic core of anionic membranes. Here, the resistance developed in bacterial cells was coupled to membrane fluidity and surface charge, and simultaneously, these principles could be applied for combating resistance against PF-AMPs. The correlation coefficient between observed CR and predicted CR using ANN was found to be 0.757. Thus, ANN could be used as a reliable modeling method for predicting CR, given the structure of the biomimetic membrane in terms of membrane fluidity and surface charge. Fully explored mechanisms of resistance, a forward modeling step in the design cycle of AMPs, can be cross-linked to the inward modeling using ANN to complete the peptide design cycle. The SAR between membrane phospholipids and PF-AMPs could furnish valuable information regarding their design to provide us efficacious peptides against premier pathogens. So far, this is the only report available to predict and quantify interactions of PF-AMPs with membrane phospholipids.

  11. Diffusion behavior of anion in hardened low-heat portland cement paste containing fly ash. Dependence of effective diffusion coefficient on pore structure

    International Nuclear Information System (INIS)

    Chida, Taiji; Yoshida, Takahiro

    2012-01-01

    In the sub-surface disposal system, the closely packed concrete layer is expected the low diffusivity to retard the migration of radionuclides. Low-heat portland cement containing 30 wt% fly ash (FAC) is a candidate cement material for the construction of sub-surface repository because of its high dense structure and its resistance to cracking. Previously, we reported that FAC has lower diffusivity than Ordinary Portland Cement (OPC) for acetic acid and iodine. However, the mechanism for low diffusivity of FAC was not clear. In this study, the diffusion of multiple trace ions (chlorine, bromine and iodine) in hardened cement pastes was examined by through-diffusion experiments. The effective diffusion coefficients, D e , of the trace ions for hardened OPC cement pastes were on the order of 10 -12 m 2 s -1 for trace ions, and D e for hardened FAC cement pastes were on the order of 10 -13 m 2 s -1 for chlorine, 10 -14 m 2 s -1 for bromine and 10 -15 m 2 s -1 for iodine. Additionally, the pore size distribution and porosity of FAC changed to more closely packed structure for 13 months by the pozzolanic reaction, and the pore size distribution of FAC (mainly 3-10 nm) were an order of magnitude smaller than that of OPC. These results suggest that the low diffusivity of FAC is based on the continuous change in the pore structure and the nano-scale pore size retarding the migration of trace ions. (author)

  12. Surface effects on ionic Coulomb blockade in nanometer-size pores

    Science.gov (United States)

    Tanaka, Hiroya; Iizuka, Hideo; Pershin, Yuriy V.; Di Ventra, Massimiliano

    2018-01-01

    Ionic Coulomb blockade in nanopores is a phenomenon that shares some similarities but also differences with its electronic counterpart. Here, we investigate this phenomenon extensively using all-atom molecular dynamics of ionic transport through nanopores of about one nanometer in diameter and up to several nanometers in length. Our goal is to better understand the role of atomic roughness and structure of the pore walls in the ionic Coulomb blockade. Our numerical results reveal the following general trends. First, the nanopore selectivity changes with its diameter, and the nanopore position in the membrane influences the current strength. Second, the ionic transport through the nanopore takes place in a hopping-like fashion over a set of discretized states caused by local electric fields due to membrane atoms. In some cases, this creates a slow-varying ‘crystal-like’ structure of ions inside the nanopore. Third, while at a given voltage, the resistance of the nanopore depends on its length, the slope of this dependence appears to be independent of the molarity of ions. An effective kinetic model that captures the ionic Coulomb blockade behavior observed in MD simulations is formulated.

  13. Numerical study of viscoelastic polymer flow in simplified pore structures using stabilised finite element model

    Energy Technology Data Exchange (ETDEWEB)

    Qi, M.; Wegner, J.; Ganzer, L. [Technische Univ. Clausthal, Clausthal-Zellerfeld (Germany). ITE

    2013-08-01

    Polymer flooding, as an EOR method, has become one of the most important driving forces after water flooding. The conventional believe is that polymer flooding can only improve sweep efficiency, but it has no contribution to residual oil saturation reduction. However, experimental studies indicated that polymer solution can also improve displacement efficiency and decrease residual oil saturation. To get a better understanding of the mechanism to increase the microscopic sweep efficiency and the displacement efficiency, theoretical studies are required. In this paper, we studied the viscoelasticity effect of polymer by using a numerical simulator, which is based on Finite Element Analysis. Since it is showed experimentally that the first normal stress difference of viscoelastic polymer solution is higher than the second stress difference, the Oldroyd-B model was selected as the constitutive equation in the simulation. Numerical modelling of Oldroyd-B viscoelastic fluids is notoriously difficult. Standard Galerkin finite element methods are prone to numerical oscillations, and there is no convergence as the elasticity of fluid increases. Therefore, we use a stabilised finite element model. In order to verify our model, we first built up a model with the same geometry and fluid properties as presented in literature and compared the results. Then, with the tested model we simulated the effect of viscoelastic polymer fluid on dead pores in three simplified pore structures, which are contraction structure, expansion structure and expansion-contraction structure. Correspondingly, the streamlines and velocity contours of polymer solution, with different Reynolds numbers (Re) and Weissenberg numbers (We), flowing in these three structures are showed. The simulation results indicate that the viscoelasticity of polymer solution is the main contribution to increase the micro-scale sweep efficiency. With higher elasticity, the velocity of polymer solution is getting bigger at

  14. Influence of nickel–phosphorus surface roughness on wettability and pores formation in solder joints for high power electronic applications

    Energy Technology Data Exchange (ETDEWEB)

    Vivet, L., E-mail: laurent.vivet@valeo.com [Valeo, Group Electronic Expertise and Development Services, 2 rue André Boulle, 94046 Créteil (France); Joudrier, A.-L. [Institut Lavoisier de Versailles, UMR CNRS 8180, 45 Avenue des Etats-Unis, 78035 Versailles (France); Tan, K.-L.; Morelle, J.-M. [Valeo, Group Electronic Expertise and Development Services, 2 rue André Boulle, 94046 Créteil (France); Etcheberry, A. [Institut Lavoisier de Versailles, UMR CNRS 8180, 45 Avenue des Etats-Unis, 78035 Versailles (France); Chalumeau, L. [Egide, Site industriel du Sactar, 85500 Bollène (France)

    2013-12-15

    Electroless nickel-high-phosphorus Ni–P plating is used as substrate coating in the electronic component technology. The ability to minimize pores formation in solder joints and the wettability of the Ni–P layer remain points of investigation. The qualities and the control of the physical and chemical properties of the deposits are essential for the reliability of the products. In this contribution it has been measured how a controlled change of one property of the Ni–P surface, its average roughness, changes the wettability of this surface before soldering completion, at ambient temperature and under ambient air, and how it contribute to change the amount and size of pores inside solder joints, after soldering completion. Before all, observations of the Ni–P surfaces using scanning electron microscopy have been achieved. Then the wettability has been measured through the determination of both the disperse and the polar fractions of the substrate surface tension, based on the measurements of the wetting angle for droplets of four different liquids, under ambient air and at room temperature (classical sessile drop technique). Finally the X-ray micro-radiography measurements of both the area fraction of pores and the size of the largest pore inside the solder joint of dice laser soldered on the studied substrate, using high melting temperature solder (300 °C, PbSnAg) have been achieved. This study clearly demonstrates that both the ability to minimize pores formation in solder joints and the wettability under ambient conditions of the Ni–P substrate decrease and become more variable when its average roughness increases. These effects can be explained considering the Cassie–Baxter model for rough surface wetting behaviour, completed by the model of heterogeneous nucleation and growth for gas bubbles inside a liquid.

  15. Confocal laser microscopic imaging of conspicuous facial pores in vivo: relation between the appearance and the internal structure of skin.

    Science.gov (United States)

    Sugata, Keiichi; Nishijima, Takafumi; Kitahara, Takashi; Takema, Yoshinori

    2008-05-01

    Conspicuous facial pores are one of the more serious esthetic defects of most concern to women. Previous microscopic observations of the skin surface around conspicuous pores have discovered large hollows and uneven skin tone. In this study, the observation area was extended from the skin surface to deeper skin to find the characteristic features of conspicuous pores in a wider spectrum. First, a magnified surface image of the cheek skin was obtained using a video microscope. Second, replicas were collected from the same area. Third, the horizontal cross-sectioned images of the epidermis and papillary dermis in different depths were non-invasively obtained using in vivo confocal laser scanning microscopy. These images were compared with each other to find a correlation between features of the skin surface and those of deeper layers. In cross-sectioned images of conspicuous pores, a strongly undulated epidermal-dermal junction was commonly observed around a pore's opening. Areas with this feature correlated well to the areas with larger hollows and an uneven skin tone. Our results indicate that there is a positive correlation between the incidence of the characteristic feature at the epidermal-dermal junction and the visual appearance of a pore.

  16. Effects of pressure and temperature on pore structure of ceramic synthesized from rice husk: A small angle neutron scattering investigation

    International Nuclear Information System (INIS)

    Raut Dessai, R.; Desa, J.A.E.; Sen, D.; Mazumder, S.

    2013-01-01

    Highlights: ► A porous ceramic has been prepared from silica obtained from rice husk. ► The ceramic has a hierarchical pore structure from micrometric to nano-metric. ► Small Angle Neutron Scattering data indicate nano-pore connectivity to micro-pores. ► Pore morphology can be tuned by compaction pressure and sintering temperature. -- Abstract: Ceramic powder has been synthesized from rice husk as the source of silica. In order to probe the evolution of its hierarchical mesoscopic and microscopic porous structure, the ceramic powder was compacted at different pressures and was sintered at different temperatures. A glassy ceramic to crystalline transition under thermal treatment (up to 1000 °C) was revealed by X-ray diffraction. Existence of pores in two widely separated length scales was indicated by small angle neutron scattering with the smaller ones having mass fractal arrangement. Although no significant change in small pore structure under thermal effect was indicated, a significant modification of the same has been revealed by small angle neutron scattering at different compaction pressures. Connectivity between the pores was ascertained from scattering experiments on the ceramic compact impregnated with heavy water. Scanning electron microscopy shows the microstructure to undergo appreciable coalescence of micrometric ceramic particles for sintering temperature and pressure changes

  17. Irreversible Change of the Pore Structure of ZIF-8 in Carbon Dioxide Capture with Water Coexistence

    DEFF Research Database (Denmark)

    Liu, Huang; Guo, Ping; Regueira Muñiz, Teresa

    2016-01-01

    showed an irreversible change of its framework, which occurs during the CO2 capture process. It was found that there is an irreversible chemical reaction among ZIF-8, water, and CO2, which creates both zinc carbonate (or zinc carbonate hydroxides) and single 2-methylimidazole crystals, and therefore...... the pore structure of ZIF-8 collapses. It is suggested therefore that care must be taken when using ZIF-8 or products containing ZIF-8 for gas capture, gas separation, or other applications where both water and acid gases coexist....

  18. A pore-scale approach to colloid-surface interaction in liquid using lattice Boltzmann models.

    Science.gov (United States)

    Larsen, J. D.; Schaap, M. G.

    2016-12-01

    Knowledge of colloid transport and collection efficiency is important for understanding the transport of some contaminants of emerging concern (CEC) and for developing environmental remediation systems such as geologic filters. The interaction forces between colloids and soil materials are central to colloid transport and retention or immobilization. In this study a physical modeling approach to represent colloidal transport through porous media has been developed, using the lattice Boltzmann methodology. Lattice Boltzmann models have the uncanny ability to represent pore scale fluid flow through complex structures such as geological material. A cellular approach to computing colloid forces is applied for computational efficiency, and colloids are tracked continuously through the model. Grid refinement effects are quantified to balance computational efficiency with discretization effects. Representation of physical forces including DLVO create a natural fluid solid boundary condition for colloid transport. Collector efficiencies of geologic materials and colloid distribution curves can be produced. The present work focuses on simple porous media with a single wetting fluid phase, but the approach can be extended to heterogeneous geologic materials and multiphase systems.

  19. 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.

  20. Protein translocation in narrow pores: Inferring bottlenecks from native structure topology

    Science.gov (United States)

    Bacci, Marco; Chinappi, Mauro; Casciola, Carlo Massimo; Cecconi, Fabio

    2013-08-01

    Coarse-grained simulations of protein translocation across narrow pores suggest that the transport is characterized by long stall events. The translocation bottlenecks and the associated free-energy barriers are found to be strictly related to the structural properties of the protein native structure. The ascending ramps of the free-energy profile systematically correspond to regions of the chain denser in long range native contacts formed with the untranslocated portion of the protein. These very regions are responsible for the stalls occurring during the protein transport along the nanopore. The decomposition of the free energy in internal energyand entropic terms shows that the dominant energetic contribution can be estimated on the base of the protein native structure only. Interestingly, the essential features of the dynamics are retained in a reduced phenomenological model of the process describing the evolution of a suitable collective variable in the associated free-energy landscape.

  1. Effect of pore structure on anomalous behaviour of the lithium intercalation into porous V2O5 film electrode using fractal geometry concept

    International Nuclear Information System (INIS)

    Jung, Kyu-Nam; Pyun, Su-Il

    2006-01-01

    The effect of pore structure on anomalous behaviour of the lithium intercalation into porous V 2 O 5 film electrode has been investigated in terms of fractal geometry by employing ac-impedance spectroscopy combined with N 2 gas adsorption method and atomic force microscopy (AFM). For this purpose, porous V 2 O 5 film electrodes with different pore structures were prepared by the polymer surfactant templating method. From the analysis of N 2 gas adsorption isotherms and the triangulation analysis of AFM images, it was found that porous V 2 O 5 surfaces exhibited self-similar scaling properties with different fractal dimensions depending upon amount of the polymer surfactant in solution and the spatial cut-off ranges. All the ac-impedance spectra measured on porous V 2 O 5 film electrodes showed the non-ideal behaviour of the charge-transfer reaction and the diffusion reaction, which resulted from the interfacial capacitance dispersion and the frequency dispersion of the diffusion impedance, respectively. From the comparison between the surface fractal dimensions by using N 2 gas adsorption method and AFM, and the analysis of ac-impedance spectra by employing a constant phase element (CPE), it is experimentally confirmed that the lithium intercalation into porous V 2 O 5 film electrode is crucially influenced by the pore surface irregularity and the film surface irregularity

  2. Effect of Pore Structure on Soot Deposition in Diesel Particulate Filter

    Directory of Open Access Journals (Sweden)

    Kazuhiro Yamamoto

    2016-12-01

    Full Text Available Nowadays, in the after-treatment of diesel exhaust gas, a diesel particulate filter (DPF has been used to trap nano-particles of the diesel soot. However, as there are more particles inside the filter, the pressure which corresponds to the filter backpressure increases, which worsens the fuel consumption rate, together with the abatement of the available torque. Thus, a filter with lower backpressure would be needed. To achieve this, it is necessary to utilize the information on the phenomena including both the soot transport and its removal inside the DPF, and optimize the filter substrate structure. In this paper, to obtain useful information for optimization of the filter structure, we tested seven filters with different porosities and pore sizes. The porosity and pore size were changed systematically. To consider the soot filtration, the particle-laden flow was simulated by a lattice Boltzmann method (LBM. Then, the flow field and the pressure change were discussed during the filtration process.

  3. Properties of soil pore space regulate pathways of plant residue decomposition and community structure of associated bacteria.

    Science.gov (United States)

    Negassa, Wakene C; Guber, Andrey K; Kravchenko, Alexandra N; Marsh, Terence L; Hildebrandt, Britton; Rivers, Mark L

    2015-01-01

    Physical protection of soil carbon (C) is one of the important components of C storage. However, its exact mechanisms are still not sufficiently lucid. The goal of this study was to explore the influence of soil structure, that is, soil pore spatial arrangements, with and without presence of plant residue on (i) decomposition of added plant residue, (ii) CO2 emission from soil, and (iii) structure of soil bacterial communities. The study consisted of several soil incubation experiments with samples of contrasting pore characteristics with/without plant residue, accompanied by X-ray micro-tomographic analyses of soil pores and by microbial community analysis of amplified 16S-18S rRNA genes via pyrosequencing. We observed that in the samples with substantial presence of air-filled well-connected large (>30 µm) pores, 75-80% of the added plant residue was decomposed, cumulative CO2 emission constituted 1,200 µm C g(-1) soil, and movement of C from decomposing plant residue into adjacent soil was insignificant. In the samples with greater abundance of water-filled small pores, 60% of the added plant residue was decomposed, cumulative CO2 emission constituted 2,000 µm C g(-1) soil, and the movement of residue C into adjacent soil was substantial. In the absence of plant residue the influence of pore characteristics on CO2 emission, that is on decomposition of the native soil organic C, was negligible. The microbial communities on the plant residue in the samples with large pores had more microbial groups known to be cellulose decomposers, that is, Bacteroidetes, Proteobacteria, Actinobacteria, and Firmicutes, while a number of oligotrophic Acidobacteria groups were more abundant on the plant residue from the samples with small pores. This study provides the first experimental evidence that characteristics of soil pores and their air/water flow status determine the phylogenetic composition of the local microbial community and directions and magnitudes of soil C

  4. Properties of soil pore space regulate pathways of plant residue decomposition and community structure of associated bacteria.

    Directory of Open Access Journals (Sweden)

    Wakene C Negassa

    Full Text Available Physical protection of soil carbon (C is one of the important components of C storage. However, its exact mechanisms are still not sufficiently lucid. The goal of this study was to explore the influence of soil structure, that is, soil pore spatial arrangements, with and without presence of plant residue on (i decomposition of added plant residue, (ii CO2 emission from soil, and (iii structure of soil bacterial communities. The study consisted of several soil incubation experiments with samples of contrasting pore characteristics with/without plant residue, accompanied by X-ray micro-tomographic analyses of soil pores and by microbial community analysis of amplified 16S-18S rRNA genes via pyrosequencing. We observed that in the samples with substantial presence of air-filled well-connected large (>30 µm pores, 75-80% of the added plant residue was decomposed, cumulative CO2 emission constituted 1,200 µm C g(-1 soil, and movement of C from decomposing plant residue into adjacent soil was insignificant. In the samples with greater abundance of water-filled small pores, 60% of the added plant residue was decomposed, cumulative CO2 emission constituted 2,000 µm C g(-1 soil, and the movement of residue C into adjacent soil was substantial. In the absence of plant residue the influence of pore characteristics on CO2 emission, that is on decomposition of the native soil organic C, was negligible. The microbial communities on the plant residue in the samples with large pores had more microbial groups known to be cellulose decomposers, that is, Bacteroidetes, Proteobacteria, Actinobacteria, and Firmicutes, while a number of oligotrophic Acidobacteria groups were more abundant on the plant residue from the samples with small pores. This study provides the first experimental evidence that characteristics of soil pores and their air/water flow status determine the phylogenetic composition of the local microbial community and directions and magnitudes of

  5. Properties of Soil Pore Space Regulate Pathways of Plant Residue Decomposition and Community Structure of Associated Bacteria

    Science.gov (United States)

    Negassa, Wakene C.; Guber, Andrey K.; Kravchenko, Alexandra N.; Marsh, Terence L.; Hildebrandt, Britton; Rivers, Mark L.

    2015-01-01

    Physical protection of soil carbon (C) is one of the important components of C storage. However, its exact mechanisms are still not sufficiently lucid. The goal of this study was to explore the influence of soil structure, that is, soil pore spatial arrangements, with and without presence of plant residue on (i) decomposition of added plant residue, (ii) CO2 emission from soil, and (iii) structure of soil bacterial communities. The study consisted of several soil incubation experiments with samples of contrasting pore characteristics with/without plant residue, accompanied by X-ray micro-tomographic analyses of soil pores and by microbial community analysis of amplified 16S–18S rRNA genes via pyrosequencing. We observed that in the samples with substantial presence of air-filled well-connected large (>30 µm) pores, 75–80% of the added plant residue was decomposed, cumulative CO2 emission constituted 1,200 µm C g-1 soil, and movement of C from decomposing plant residue into adjacent soil was insignificant. In the samples with greater abundance of water-filled small pores, 60% of the added plant residue was decomposed, cumulative CO2 emission constituted 2,000 µm C g-1 soil, and the movement of residue C into adjacent soil was substantial. In the absence of plant residue the influence of pore characteristics on CO2 emission, that is on decomposition of the native soil organic C, was negligible. The microbial communities on the plant residue in the samples with large pores had more microbial groups known to be cellulose decomposers, that is, Bacteroidetes, Proteobacteria, Actinobacteria, and Firmicutes, while a number of oligotrophic Acidobacteria groups were more abundant on the plant residue from the samples with small pores. This study provides the first experimental evidence that characteristics of soil pores and their air/water flow status determine the phylogenetic composition of the local microbial community and directions and magnitudes of soil C

  6. Using Neutron Scattering and Mercury Intrusion Techniques to Characterize Micro- and Nano-Pore Structure of Shale

    Science.gov (United States)

    Zhang, Y.; Barber, T.; Hu, Q.; Bleuel, M.

    2017-12-01

    The micro- and nano-pore structure of oil shale plays a critical role in hydrocarbon storage and migration. This study aims to characterize the pore structure of three Bakken members (i.e., upper organic-rich shale, middle silty/sandy dolomites, and lower organic-rich shale), through small and ultra-small angle neutron scattering (SANS and USANS) techniques, as well as mercury injection capillary pressure (MICP) analyses. SANS/USANS have the capabilities of measuring total porosity (connected and closed porosity) across nm-mm spectrum, not measurable than other fluid-invasion approaches, such as MICP which obtains connected porosity and pore-throat size distribution. Results from both techniques exhibit different features of upper/lower Bakken and middle Bakken, as a result of various mineral composition and organic matter contents. Middle Bakken is primarily dominated by the mineral pores, while in the upper and lower Bakken, organic pores contribute a significant portion of total porosity. A combination of USANS/SANS and MICP techniques gives a comprehensive picture of shale micro- and nano-pore structure.

  7. A titanium surface with nano-ordered spikes and pores enhances human dermal fibroblastic extracellular matrix production and integration of collagen fibers

    International Nuclear Information System (INIS)

    Yamada, Masahiro; Kato, Eiji; Sakurai, Kaoru; Yamamoto, Akiko

    2016-01-01

    The acquisition of substantial dermal sealing determines the prognosis of percutaneous titanium-based medical devices or prostheses. A nano-topographic titanium surface with ordered nano-spikes and pores has been shown to induce periodontal-like connective tissue attachment and activate gingival fibroblastic functions. This in vitro study aimed to determine whether an alkali-heat (AH) treatment-created nano-topographic titanium surface could enhance human dermal fibroblastic functions and binding strength to the deposited collagen on the titanium surface. The surface topographies of commercially pure titanium machined discs exposed to two different AH treatments were evaluated. Human dermal fibroblastic cultures grown on the discs were evaluated in terms of cellular morphology, proliferation, extracellular matrix (ECM) and proinflammatory cytokine synthesis, and physicochemical binding strength of surface-deposited collagen. An isotropically-patterned, shaggy nano-topography with a sponge-like inner network and numerous well-organized, anisotropically-patterned fine nano-spikes and pores were observed on each nano-topographic surface type via scanning electron microscopy. In contrast to the typical spindle-shaped cells on the machined surfaces, the isotropically- and anisotropically-patterned nano-topographic titanium surfaces had small circular/angular cells containing contractile ring-like structures and elongated, multi-shaped cells with a developed cytoskeletal network and multiple filopodia and lamellipodia, respectively. These nano-topographic surfaces enhanced dermal-related ECM synthesis at both the protein and gene levels, without proinflammatory cytokine synthesis or reduced proliferative activity. Deposited collagen fibers were included in these surfaces and sufficiently bound to the nano-topographies to resist the physical, enzymatic and chemical detachment treatments, in contrast to machined surfaces. Well-organized, isotropically

  8. Surface roughness from highlight structure

    NARCIS (Netherlands)

    Lu, Rong; Koenderink, Jan J.; Kappers, Astrid M L

    1999-01-01

    Highlights are due to specular reflection and cause the lustrous or mirrorlike appearance of many material surfaces. We investigated in detail the structure of highlight patterns that are due to material surface roughness. We interpret results in terms of a simple model of a random Gaussian surface.

  9. Effects of pore size, implantation time and nano-surface properties on rat skin ingrowth into percutaneous porous titanium implants

    OpenAIRE

    Farrell, Brad J.; Prilutsky, Boris I.; Ritter, Jana M.; Kelley, Sean; Popat, Ketul; Pitkin, Mark

    2013-01-01

    The main problem of percutaneous osseointegrated implants is poor skin-implant integration, which may cause infection. This study investigated the effects of pore size (Small, 40–100 microns and Large, 100–160 microns), nanotubular surface treatment (Nano), and duration of implantation (3 and 6 weeks) on skin ingrowth into porous titanium. Each implant type was percutaneously inserted in the back of 35 rats randomly assigned to 7 groups. Implant extrusion rate was measured w...

  10. Bioinspired structured surfaces.

    Science.gov (United States)

    Bhushan, Bharat

    2012-01-24

    Nature has evolved objects with desired functionality using commonly found materials. Nature capitalizes on hierarchical structures to achieve functionality. The understanding of the functions provided by objects and processes found in nature can guide us to produce nanomaterials, nanodevices, and processes with desirable functionality. Various natural objects which provide functionality of commercial interest have been characterized to understand how a natural object provides functionality. We have modeled and fabricated structures in the lab using nature's route and developed optimum structures. Once it is understood how nature does it, optimum structures have been fabricated using smart materials and fabrication techniques. This feature article provides an overview of four topics: Lotus effect, rose petal effect, gecko feet, and shark skin.

  11. Effects of engineered nano-titanium dioxide on pore surface properties and phosphorus adsorption of sediment: its environmental implications.

    Science.gov (United States)

    Luo, Zhuanxi; Wang, Zhenhong; Wei, Qunshan; Yan, Changzhou; Liu, Feng

    2011-09-15

    Understanding the environmental safety and human health implications of engineered nanoparticles (ENPs) is of worldwide importance. As an important ENPs, engineered nano-TiO(2) (Enano-TiO(2)) may have been substantially deposited in aquatic sediments because of its widely uses. Sediment pore surface properties would be thus significantly influenced due to the large surface area of Enano-TiO(2). In this study, Enano-TiO(2) was found to greatly impact on sediment pore surface properties. The attachment of Enano-TiO(2) particles to sediment surfaces enhanced markedly BET specific surface area and t-Plot external specific surface area, and thereby increased sediment phosphorus (P) adsorption maximum (S(max)). Contrarily, the fill of Enano-TiO(2) particles into the micropores of sediments could significantly reduce t-Plot micropore specific surface area, and cause slight decrease in sediment P binding energy (K). Clearly, P sorbed in sediment would be easily released because of the decreasing P binding energy of the sediment with elevated Enano-TiO(2). Enano-TiO(2) would thus cause aggravated endogenous pollution in water if such sediment was re-suspended on disturbance. The results obtained in this study contribute to our increasing knowledge of how to regulate physicochemical behavior of pollutants in sediments under the influences of Enano-TiO(2) and/or similar ENPs. Copyright © 2011 Elsevier B.V. All rights reserved.

  12. Synchrotron-based micro and nanotomographic investigations of soil aggregate microbial and pore structure

    Science.gov (United States)

    Kemner, K. M.; O'Brien, S.; Whiteside, M. D.; Sholto-Douglas, D.; Antipova, O.; Bailey, V.; Boyanov, M.; Dohnalkova, A.; Gursoy, D.; Kovarik, L.; Lai, B.; Roehrig, C.; Vogt, S.

    2017-12-01

    Soil is a highly complex network of pore spaces, minerals, and organic matter (e.g., roots, fungi, and bacteria), making it physically heterogeneous over nano- to macro-scales. Such complexity arises from feedbacks between physical processes and biological activity that generate a dynamic, self-organizing 3D complex. Since we first demonstrated the utility of synchrotron-based transmission tomography to image internal soil aggregate structure [Kemner et al., 1998], we and many other researchers have made use of and have advanced the application of this technique. However, our understanding of how microbes and microbial metabolism are distributed throughout soil aggregates is limited, because no technique is available to image the soil pore network and the life that inhabits it. X-ray transmission microtomography can provide highly detailed 3D renderings of soil structure but cannot distinguish cells from other electron-light material such as air or water. However, the use of CdSe quantum dots (QDs) as a reporter of bacterial presence enables us to overcome this constraint, instilling bacterial cells with enough contrast to detect them and their metabolic functions in their opaque soil habitat, with hard x-rays capable of penetrating 3D soil structures at high resolution. Previous transmission tomographic imaging of soil aggregates with high energy synchrotron x-rays has demonstrated 700 nm3 voxel spatial resolution. These and recent results from nanotomographic x-ray transmission imaging of soil aggregates with 30 nm3 voxel resolution will be presented. In addition, results of submicron voxel-sized x-ray fluorescence 3D imaging to determine microbial distributions within soil aggregates and the critical role to be played by the upgrade of the Advanced Photon Source for 100-1000X increases in hard x-ray brilliance will also be presented. *Kemner, et al., SPIE 3449, 45-53, 1998

  13. Numerical and Experimental Study of the Structural Color by Widening the Pore Size of Nanoporous Anodic Alumina

    Directory of Open Access Journals (Sweden)

    Jiawen Li

    2014-01-01

    Full Text Available The structural color originated from the nanoporous anodic alumina (NAA film is related to the structural characteristics. This paper aimed to obtain different structural colors which can cover the whole visible range by widening the pore size of metal-coated NAA. First, we used the Finite Difference Time Domain (FDTD method to analyze the relationship between the physical structure and optical properties. Then, we fabricated different colors and expected color pattern by widening the pore diameter of NAA. Numerical and experimental study shows that the colors can cover the whole visible range by widening the pore diameter. This work can not only lead to better understanding of the mechanism of tuning color on NAA film, but also help us to fabricate expected color in the whole light range.

  14. Using low temperature calorimetry and moisture fixation method to study the pore structure of cement based materials

    DEFF Research Database (Denmark)

    Wu, Min

    consideration of including the model material in this investigation was to validate the applicability of the chosen methods in the context of pore size determination. In addition, data from literature were used. LTC investigations conducted in this PhD study include the ice content determination from measured...... attention was devoted to investigating important factors influencing the analysis of measured LTC data and using LTC to characterize the pore structure of cement based materials. Besides, the moisture fixation method was selected as a comparison and complementary method to the LTC. Attempts have been made...... data, the impact of sample saturation on the detected porosity, the effect of frost damage on the pore size distribution determination by LTC, the effect of preconditioning the cement paste samples on the freezing and melting behavior of the pore solution, the impact of sample crushing...

  15. Porous polymer adsorbent media constructed by molecular dynamics modeling and simulations: the immobilization of charged ligands and their effect on pore structure and local nonelectroneutrality.

    Science.gov (United States)

    Riccardi, E; Wang, J-C; Liapis, A I

    2009-02-26

    A molecular dynamics modeling and simulation approach is presented and employed to construct porous dextran polymer ion-exchange adsorbent media. Both the activation step of the surface of the pores of the dextran polymer layer grafted on an agarose surface and the immobilization of charged ligands on the activated surface of the porous dextran polymer layer are considered. For the systems studied in this work, the activation step modifies slightly the pore structure of the base, nonactivated porous dextran polymer, while the immobilization of the ligands on the activated pore surface of the dextran layer changes significantly the pore structure of the activated dextran layer. The density distributions of the counterions and immobilized charged ligands along the direction of net transport in the adsorbent media constructed in this study are found to be nonuniform. The variables that affect the shape and magnitude of the density distributions of the counterions and immobilized charged ligands as well as the total number of charged ligands that can be immobilized on the activated porous dextran layer are identified and presented in this work. Furthermore, the data clearly show that there is local nonelectroneutrality in the porous dextran polymer ion-exchange adsorbent media, and this result has very important practical implications for the operation and performance of separation systems involving ion-exchange adsorbent media (e.g., ion-exchange chromatography systems). Also, the results of this work suggest approaches for (1) controlling the immobilization process of charged ligands and (2) constructing and studying the behavior of chromatographic polymeric monoliths and packed bed columns having a gradient of density of functionalities along the axis of the chromatographic polymeric monolith or packed bed column.

  16. Structural and functional analysis of an essential nucleoporin heterotrimer on the cytoplasmic face of the nuclear pore complex

    Energy Technology Data Exchange (ETDEWEB)

    Yoshida, Kimihisa; Seo, Hyuk-Soo; Debler, Erik W.; Blobel, Günter; Hoelz, André (Rockefeller)

    2012-07-25

    So far, only a few of the interactions between the {approx}30 nucleoporins comprising the modular structure of the nuclear pore complex have been defined at atomic resolution. Here we report the crystal structure, at 2.6 {angstrom} resolution, of a heterotrimeric complex, composed of fragments of three cytoplasmically oriented nucleoporins of yeast: Nup82, Nup116, and Nup159. Our data show that the Nup82 fragment, representing more than the N-terminal half of the molecule, folds into an extensively decorated, seven-bladed {beta}-propeller that forms the centerpiece of this heterotrimeric complex and anchors both a C-terminal fragment of Nup116 and the C-terminal tail of Nup159. Binding between Nup116 and Nup82 is mutually reinforced via two loops, one emanating from the Nup82 {beta}-propeller and the other one from the {beta}-sandwich fold of Nup116, each contacting binding pockets in their counterparts. The Nup82-Nup159 interaction occurs through an amphipathic {alpha}-helix of Nup159, which is cradled in a large hydrophobic groove that is generated from several large surface decorations of the Nup82 {beta}-propeller. Although Nup159 and Nup116 fragments bind to the Nup82 {beta}-propeller in close vicinity, there are no direct contacts between them, consistent with the noncooperative binding that was detected biochemically. Extensive mutagenesis delineated hot-spot residues for these interactions. We also showed that the Nup82 {beta}-propeller binds to other yeast Nup116 family members, Nup145N, Nup100 and to the mammalian homolog, Nup98. Notably, each of the three nucleoporins contains additional nuclear pore complex binding sites, distinct from those that were defined here in the heterotrimeric Nup82 {center_dot} Nup159 {center_dot} Nup116 complex.

  17. Effects of engineered nano-titanium dioxide on pore surface properties and phosphorus adsorption of sediment: Its environmental implications

    International Nuclear Information System (INIS)

    Luo, Zhuanxi; Wang, Zhenhong; Wei, QunShan; Yan, Changzhou; Liu, Feng

    2011-01-01

    Highlights: → The attachment of Enano-TiO 2 to surface enhanced markedly sediment BET surface area and t-Plot external surface area. → The fill of Enano-TiO 2 into the micropores reduced significantly the sediment t-Plot micropore surface area. → Enano-TiO 2 could increase sediment phosphorus (P) adsorption maximum and decrease in sediment P binding energy. → P would be easily released because of the decreasing P binding energy of the sediment with elevated Enano-TiO 2 . - Abstract: Understanding the environmental safety and human health implications of engineered nanoparticles (ENPs) is of worldwide importance. As an important ENPs, engineered nano-TiO 2 (Enano-TiO 2 ) may have been substantially deposited in aquatic sediments because of its widely uses. Sediment pore surface properties would be thus significantly influenced due to the large surface area of Enano-TiO 2 . In this study, Enano-TiO 2 was found to greatly impact on sediment pore surface properties. The attachment of Enano-TiO 2 particles to sediment surfaces enhanced markedly BET specific surface area and t-Plot external specific surface area, and thereby increased sediment phosphorus (P) adsorption maximum (S max ). Contrarily, the fill of Enano-TiO 2 particles into the micropores of sediments could significantly reduce t-Plot micropore specific surface area, and cause slight decrease in sediment P binding energy (K). Clearly, P sorbed in sediment would be easily released because of the decreasing P binding energy of the sediment with elevated Enano-TiO 2 . Enano-TiO 2 would thus cause aggravated endogenous pollution in water if such sediment was re-suspended on disturbance. The results obtained in this study contribute to our increasing knowledge of how to regulate physicochemical behavior of pollutants in sediments under the influences of Enano-TiO 2 and/or similar ENPs.

  18. Space-confined preparation of high surface area tungsten oxide and tungsten nitride inside the pores of mesoporous silica SBA-15

    DEFF Research Database (Denmark)

    Meyer, Simon; Beyer, Hans; Köhler, Klaus

    2015-01-01

    For the direct preparation of high surface area nitride materials, a lack of suitable precursors exists. Indirect preparation by gas phase nitridation (e.g. by ammonia) requires high temperatures and often results in sintering. The present work demonstrates that the space-confined preparation of W2......N inside the pores of ordered mesoporous silica SBA-15 offers a possibility to reduce sintering phenomena and thus to obtain smaller particles, porous structures and a higher surface area material. The preparation was pursued in a two-step approach. First, WO3 was introduced into the channels of SBA......-15 and second, ammonolysis was conducted for its conversion to W2N. When performed in the presence of the exo-template, SBA-15 acts as a stabilizer and small W2N particles (6-7 nm) with a high specific surface area (40 m(2) g(-1)) are obtained after template removal. When the template is, however...

  19. A modified Lattice Boltzmann model for pore-scale simulation of desorption process at surface water-groundwater interface

    Science.gov (United States)

    Zhang, Pei; Galindo Torres, Sergio; Tang, Hongwu; Scheuermann, Alexander; Jin, Guangqiu; Li, Ling

    2017-04-01

    A pore-scale numerical model is introduced to simulate the desorption process at surface water-groundwater interface. The Navier-Stokes equations for fluid and Advection-Diffusion equation for scalar transport are solved by Lattice Boltzmann Method (LBM). In previous studies, the macroscopic desorption kinetic equations are usually applied as a boundary condition. However, it may be problematic for pore-scale simulation since most desorption kinetic equations are fitted from macroscopic global variables. We avoid this problem by discretizing the particle surface into a large number of adsorption sites to mimic the microscopic desorption process. The state of each adsorption site follows the Langmuir's theory. Furthermore, benefiting from the mesoscopic inherent of the LBM, the total number of adsorbate which really contacted with the particle surface can be calculated rather than the local concentration. The predicted desorption Isotherm and concentration profile match well with theoretical solutions and experimental data. By using presented model, we find that the desorption process at surface water-groundwater interface shows a complex response to surface water flow.

  20. Effect of support structure on CO2 adsorption properties of pore-expanded hyperbranched aminosilicas

    KAUST Repository

    Drese, Jeffrey H.

    2012-03-01

    Hyperbranched aminosilica (HAS) CO 2 adsorbents are prepared by the ring-opening polymerization of aziridine from SBA-15 mesoporous silica, as in the original synthesis of HAS materials, as well as over an array of new support materials with substantially larger average pore diameters to elucidate the effect of support porosity on final adsorbent properties. Pore-expanded hyperbranched aminosilica (PEHAS) CO 2 adsorbents are prepared from several different pore-expanded, ordered mesoporous silicas including pore-expanded SBA-15, mesocellular foam, and a large-pore commercial silica. The effect of the nature of the silica support is determined by examining the degree of aziridine polymerization and the CO 2 adsorption kinetics and capacities of the resulting organic/inorganic hybrid materials. Comparisons are made to non-pore-expanded SBA-15 based HAS adsorbents, reported previously, where pores become blocked at higher amine loadings. The PEHAS materials unexpectedly possess lower amine loadings than the previously reported HAS materials and do not exhibit pore blocking. The use of acetic acid as a catalyst during PEHAS synthesis only marginally increases amine loading. The adsorption kinetics of PEHAS adsorbents are similar to HAS adsorbents with low amine loadings and do not show the detrimental effects of pore-blocking. However, the inability to synthesize PEHAS adsorbents with high amine loadings via this approach limits the total amount of CO 2 captured per gram of material, compared to HAS adsorbents with high amine loadings. © 2011 Elsevier Inc. All rights reserved.

  1. Concentration and temperature effect on controlling pore size and surface area of mesoporous titania by using template of F-68 and F-127 co-polymer in the sol-gel process.

    Science.gov (United States)

    Jadhav, Nitin A; Kim, Chang Woo; Pal, Umapada; Kim, Jinheung; Kang, Young Soo

    2012-07-01

    Mesoporous titania with crystalline pore walls and controlled pore sizes was fabricated through triblock copolymer (pluronic series) templated sol-gel process by changing the copolymer concentration and by adjusting their calcination temperature. Compared with mesoprous silicate, the synthetic condition of mesoporous titania would be sensitive to calcination temperature. Their pore arrangement and pore size depend strongly on the concentration of copolymer used as a template. Their arrangement of pores and specific surface area increases with the increase of calcination temperature up to critical limit, 320 degrees C. Beyond the critical temperature, the orderness of pores and specific surface area decreases due to the collapse of the pore walls. The specific surface area, pore size and pore orderness can be controlled by optimizing calcination temperature as well as polymer concentration. We demonstrate the mechanism of pore formation and their collapse in the sol-gel synthesis of mesoporous titania.

  2. Facile one-pot approach to the synthesis of spherical mesoporous silica nanoflowers with hierarchical pore structure

    Science.gov (United States)

    Yang, Hui; Liao, Shijun; Huang, Chao; Du, Li; Chen, Peng; Huang, Peiyan; Fu, Zhiyong; Li, Yingwei

    2014-09-01

    Hierarchically structured spherical mesoporous nanoflowers (HSMNF) with well-defined morphology and uniform size were synthesized by a hydrothermal method, in which a mixture of cyclohexane and water was used as the solvent, with cetylpyridinium bromide (CPB) as the template, tetraethyl orthosilicate as the source of inorganic silica, and urea as the hydrolysis additive. The flower size ranged from 200 nm to 500 nm, and the thickness of a "petal" was about 10 nm. We investigated the effects of solvent composition (Vcyclohexane/Vwater), hydrothermal temperature, and molar ratio of Si to CPB on morphology and structure. The presence of cyclohexane was found to be crucial for the nanoflowers to form, and a solvent with high cyclohexane content was beneficial for the formation of smaller and more uniform nanoflowers, whereas low cyclohexane content resulted in the collapse of the nanoflower structure. The optimal ratio of cyclohexane to water was 1:1 by volume. The hydrothermal temperature and molar ratio of Si to CPB strongly affected nanoflower size and structure, as well as petal thickness. The optimal hydrothermal temperature was 120 °C, and the optimal molar ratio of Si to CPB was 4.37. The sample synthesized under optimal conditions exhibited well-defined morphology and uniform flower size. Its BET surface area reached 502 m2/g. The nanoflowers were under 200 nm in diameter, and their average mesopore size was ca. 4 nm, as measured by N2 adsorption-desorption. Using synthesized nanoflowers as the support, we prepared a supported PdAu bimetallic catalyst for the hydrogenation of phenol. This catalyst exhibited high activity (with a conversion rate of up to 90%) and high selectivity for cyclohexanone (up to 92%). This nanoflower's morphology, high surface area, and large pore size may make it a valuable and promising material for applications in the catalysis, adsorption and controlled release of drugs fields.

  3. Simulations of the Pore Structures for a M2GlyR Derived Channel Forming Peptide in Different Membrane Environments

    Science.gov (United States)

    Al-Rawi, A.; Herrera, A.; Tomich, J.; Rahman, T.

    2007-03-01

    As part of an effort to develop a peptide-based compound suitable for clinical use as a channel replacement therapeutic for treating channelopathies such as cystic fibrosis, we present a reductionist model that appears to grasp the characteristics of ion channeling peptides. In particular we present the observed changes in the functional characteristics of NK4-M2GlyR p22 (KKKKPARVGLGITTVLTMTTQS), a M2 GlyR derived channel forming peptide. Starting with a structure determined by multidimensional NMR (800 MHz) in SDS, a potential from CHARMM force-field was used to relax the structure of NK4-M2GlyR p22. Following the relaxation, numerous pore structures were generated for the symmetric five-helix assembly with geometries varying from cylindrical to conical. As it is difficult a priori to assign accurately the orientation of the hydrophilic portion of M2GlyR derived amphipath towards the inside of the pore, we tilted and rotated the helical structure by five different angles about the backbone axis before forming the pore. Energy minimization of the channel was performed in vacuum, in phosphotidylcholine (POPC) membrane, and 60% POPC 30% phosphotidylethanolamine (POPE) in order to determine the effect of the environment surrounding on the structure on its energy minimization. We will present the various pore assemblies, in the different membrane environments, used to predict the most probably membrane bound structure.

  4. Well log and seismic data analysis for complex pore-structure carbonate reservoir using 3D rock physics templates

    Science.gov (United States)

    Li, Hongbing; Zhang, Jiajia

    2018-04-01

    The pore structure in heterogeneous carbonate rock is usually very complex. This complex pore system makes the relationship between the velocity and porosity of the rock highly scattered, so that for the classical two-dimensional rock physics template (2D RPT) it is not enough to accurately describe the quantitative relationship between the rock elastic parameters of this kind of reservoir and its porosity and water saturation. Therefore it is possible to attribute the effect of pore type to that of the porosity or water saturation, and leads to great deviations when applying such a 2D RPT to predict the porosity and water saturation in seismic reservoir prediction and hydrocarbon detection. This paper first presents a method to establish a new three-dimensional rock physics template (3D RPT) by integrating the Gassmann equations and the porous rock physics model, and use it to characterize the quantitative relation between rock elastic properties and the reservoir parameters including the pore aspect ratio, porosity and water saturation, and to predict these parameters from the known elastic properties. The test results on the real logging and seismic inversion data show that the 3D RPT can accurately describe the variations of elastic properties with the porosity, water saturation and pore-structure parameters, and effectively improve the accuracy of reservoir parameters prediction.

  5. Phase separation of borosilicate glass with molybdenum oxide addition and pore structure of porous glass

    International Nuclear Information System (INIS)

    Tanaka, Hiroshi; Yazawa, Tetsuo; Eguchi, Kiyohisa

    1985-01-01

    Porous glass prepared by acid leaching of phase-separated soda borosilicate glass usually contains colloidal silica which originates from the silica component in the borate phase. Molybdenum trioxide was added to the starting borosilicate glass to prevent the formation of colloidal silica. It promoted the opacification of the starting glass. Opaque glasses in as-cast state showed a spherical phase-separated structure and were amorphous by X-ray doffraction. The phase separation was related to the solubility of molybdenum oxide in the glass. The phase separation occurs at a high temperature and proceeds rapidly in the cooling process of the cast glass. Another type of phase separation, which was assigned to the phase separation in the ternary soda borosilicate glass, took place during the heat treatment of the opaque glasses. When the phase-separated structure of the heat-treated glasses is interconnected, the porous glasses composed of silica skeleton are obtained by the acid leaching of the phase-separated glasses. The colloidal silica in the porous glass increased with increasing silica content of the starting glass and at the same time the volume of the pores of skeleton decreased markedly. (author)

  6. Natively Unfolded FG Repeats Stabilize the Structure of the Nuclear Pore Complex.

    Science.gov (United States)

    Onischenko, Evgeny; Tang, Jeffrey H; Andersen, Kasper R; Knockenhauer, Kevin E; Vallotton, Pascal; Derrer, Carina P; Kralt, Annemarie; Mugler, Christopher F; Chan, Leon Y; Schwartz, Thomas U; Weis, Karsten

    2017-11-02

    Nuclear pore complexes (NPCs) are ∼100 MDa transport channels assembled from multiple copies of ∼30 nucleoporins (Nups). One-third of these Nups contain phenylalanine-glycine (FG)-rich repeats, forming a diffusion barrier, which is selectively permeable for nuclear transport receptors that interact with these repeats. Here, we identify an additional function of FG repeats in the structure and biogenesis of the yeast NPC. We demonstrate that GLFG-containing FG repeats directly bind to multiple scaffold Nups in vitro and act as NPC-targeting determinants in vivo. Furthermore, we show that the GLFG repeats of Nup116 function in a redundant manner with Nup188, a nonessential scaffold Nup, to stabilize critical interactions within the NPC scaffold needed for late steps of NPC assembly. Our results reveal a previously unanticipated structural role for natively unfolded GLFG repeats as Velcro to link NPC subcomplexes and thus add a new layer of connections to current models of the NPC architecture. Copyright © 2017 Elsevier Inc. All rights reserved.

  7. Pore structure modified diatomite-supported PEG composites for thermal energy storage.

    Science.gov (United States)

    Qian, Tingting; Li, Jinhong; Deng, Yong

    2016-09-01

    A series of novel composite phase change materials (PCMs) were tailored by blending PEG and five kinds of diatomite via a vacuum impregnation method. To enlarge its pore size and specific surface area, different modification approaches including calcination, acid treatment, alkali leaching and nano-silica decoration on the microstructure of diatomite were outlined. Among them, 8 min of 5 wt% NaOH dissolution at 70 °C has been proven to be the most effective and facile. While PEG melted during phase transformation, the maximum load of PEG could reach 70 wt.%, which was 46% higher than that of the raw diatomite. The apparent activation energy of PEG in the composite was 1031.85 kJ·mol(-1), which was twice higher than that of the pristine PEG. Moreover, using the nano-silica decorated diatomite as carrier, the maximum PEG load was 66 wt%. The composite PCM was stable in terms of thermal and chemical manners even after 200 cycles of melting and freezing. All results indicated that the obtained composite PCMs were promising candidate materials for building applications due to its large latent heat, suitable phase change temperature, excellent chemical compatibility, improved supercooling extent, high thermal stability and long-term reliability.

  8. Pore structure modified diatomite-supported PEG composites for thermal energy storage

    Science.gov (United States)

    Qian, Tingting; Li, Jinhong; Deng, Yong

    2016-09-01

    A series of novel composite phase change materials (PCMs) were tailored by blending PEG and five kinds of diatomite via a vacuum impregnation method. To enlarge its pore size and specific surface area, different modification approaches including calcination, acid treatment, alkali leaching and nano-silica decoration on the microstructure of diatomite were outlined. Among them, 8 min of 5 wt% NaOH dissolution at 70 °C has been proven to be the most effective and facile. While PEG melted during phase transformation, the maximum load of PEG could reach 70 wt.%, which was 46% higher than that of the raw diatomite. The apparent activation energy of PEG in the composite was 1031.85 kJ·mol-1, which was twice higher than that of the pristine PEG. Moreover, using the nano-silica decorated diatomite as carrier, the maximum PEG load was 66 wt%. The composite PCM was stable in terms of thermal and chemical manners even after 200 cycles of melting and freezing. All results indicated that the obtained composite PCMs were promising candidate materials for building applications due to its large latent heat, suitable phase change temperature, excellent chemical compatibility, improved supercooling extent, high thermal stability and long-term reliability.

  9. A new boundary scheme for simulation of gas flow in kerogen pores with considering surface diffusion effect

    Science.gov (United States)

    Wang, Lingquan; Zeng, Zhong; Zhang, Liangqi; Qiao, Long; Zhang, Yi; Lu, Yiyu

    2018-04-01

    Navier-Stokes (NS) equations with no-slip boundary conditions fail to realistically describe micro-flows with considering nanoscale phenomena. Particularly, in kerogen pores, slip-flow and surface diffusion are important. In this study, we propose a new slip boundary scheme for the lattice Boltzmann (LB) method through the non-equilibrium extrapolation scheme to simulate the slip-flow considering surface diffusion effect. Meanwhile, the second-order slip velocity can be taken into account. The predicted characteristics in a two-dimensional micro-flow, including slip-velocity, velocity distribution along the flow direction with/without surface diffusion are present. The results in this study are compared with available analytical and reference results, and good agreements are achieved.

  10. Insight into structure and assembly of the nuclear pore complex by utilizing the genome of a eukaryotic thermophile

    DEFF Research Database (Denmark)

    Amlacher, Stefan; Sarges, Phillip; Flemming, Dirk

    2011-01-01

    Despite decades of research, the structure and assembly of the nuclear pore complex (NPC), which is composed of ~30 nucleoporins (Nups), remain elusive. Here, we report the genome of the thermophilic fungus Chaetomium thermophilum (ct) and identify the complete repertoire of Nups therein. The the...... of a thermophilic eukaryote for studying complex molecular machines....

  11. Bentonite pore structure based on SAXS, chloride exclusion and NMR studies

    International Nuclear Information System (INIS)

    Muurinen, A.; Carlsson, T.

    2013-11-01

    Water-saturated bentonite is planned to be used in many countries as an important barrier component in high-level nuclear waste (HLW) repositories. Knowledge about the microstructure of the bentonite and the distribution of water between interlayer and non-interlayer pores is important for modelling of long-term processes. In this work the microstructure of water-saturated samples prepared from Na montmorillonite, Ca-montmorillonite, sodium bentonite MX-80 and calcium bentonite Deponit CaN were studied with nuclear magnetic resonance (NMR) and small-angle xray scattering spectroscopy (SAXS). The sample dry densities ranged between 0.3 and 1.6 g/cm 3 . The NMR technique was used to get information about the volumes of different water types in the bentonite samples. The results were obtained using 1H NMR spin-lattice T 1ρ relaxation time measurements using the short inter-pulse method. The interpretation of the NMR results was made by fitting distributions of exponentials to observed decay curves. The SAXS measurements were used to get information about the size distribution of the interlayer distance of montmorillonite. The chloride porosity measurements and Donnan exclusion calculations were used together with the SAXS results for evaluation of the bentonite microstructure. The NMR studies and SAXS studies coupled with Cl porosity measurements provided very similar pictures of how the porewater is divided in interlayer and non-interlayer water in MX-80 bentonite. In the case where MX-80 of a dry density 1.6 g/cm 3 was equilibrated with 0.1 M NaCl solution, the results indicated an interlayer porosity of 30 % and non-interlayer porosity of 12 %. The interlayer space mainly contained two water layers but also spaces with more water layers were present. The average size of the non-interlayer pores was evaluated to be 120 - 150 A. From the montmorillonite surface area 98 % was interlayer and 2 % non-interlayer. Evaluation of the interlayer and non

  12. Influence of Fault on the Anisotropy of Pore Structure and Permeability in Granite, Tono Area, Central Japan

    Science.gov (United States)

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

    2002-12-01

    Change in physical properties of granite is strongly affected by brittle deformation. Fractures are the main flow paths for the migration of contaminant materials and change in hydraulic properties of rock mass. Anisotropy of pore structure and permeability were studied using drill core of Toki Granite affected by a reverse fault -Tsukiyoshi Fault Zone (TFZ). The effect of deformation due to faulting is primarily observed on the micro-crack development.Based on fracture frequency distributions logged in the borehole, representative samples of variably deformed granite were selected to show the change in deformation and the control of structures on porosity, pore structure and permeability with depth toward the TFZ. Two fault zones were recognized in the borehole by examination of core and detailed structural analysis using BTV data. Movement indicators (mineral lineations) along fault planes and overall fracture orientations are consistent with regional structures. XRD analysis indicates hydrothermal activities along fault zones. Porosity of granite range from 0.54% to over 5.42%. The pore structure was visualized by a method assisted by a Laser Scanning Confocal Microscope where 3D images of pore structure were reconstructed from impregnated coupons. Micro-cracks were mainly observed at grain boundaries, cutting feldspars and biotite crystals in fresh granite and fracture zone. In the fault zone where the deformation is characterized by grain size reduction, the resin is seen to fill the fault matrix in a diffuse pattern. Crack density increases toward the fault zone where the cracks are highly oriented parallel to the TFZ.Permeability measurements were performed by a High Pressure-Temperature gas apparatus. In this method pore oscillation is applied with nitrogen gas as a pore fluid. Confining pressure was increased and then decreased in the range of 10-200MPa.The pore pressure was kept constant at 20MPa during oscillation method for Pc higher than 30MPa

  13. Variations of Polymer Porous Surface Structures via the Time-Sequenced Dosing of Mixed Solvents.

    Science.gov (United States)

    Wrzecionko, Erik; Minařík, Antonín; Smolka, Petr; Minařík, Martin; Humpolíček, Petr; Rejmontová, Petra; Mráček, Aleš; Minaříková, Magda; Gřundělová, Lenka

    2017-02-22

    A new approach to polystyrene surface treatment via the time-sequenced dispensing of good and poor solvent mixtures on the rotating surface of treated substrate is presented in this study. It is demonstrated that the variation of the sequencing together with other variables (e.g., temperature and solvent concentration) affects the size and depth of pores evolving on the polystyrene surface. A model of the surface pore creation, associated with the viscoelastic phase separation, surface tension, and secondary flows caused by temperature variations and the rapid evaporation of the good solvent is proposed. Experimental results of profilometric, goniometric, and optical measurements show that this approach enables the simple and quick preparation of surfaces with various numbers, diameters, and depths of individual pores, which ultimately affects not only the wetting characteristics of the surfaces but also the fate of cells cultivated there. The presented method allows the easy preparation of a large number of structured substrates for effective cell cultivation and proliferation.

  14. Pore Structure and Limit Pressure of Gas Slippage Effect in Tight Sandstone

    Directory of Open Access Journals (Sweden)

    Lijun You

    2013-01-01

    Full Text Available Gas slip effect is an important mechanism that the gas flow is different from liquid flow in porous media. It is generally considered that the lower the permeability in porous media is, the more severe slip effect of gas flow will be. We design and then carry out experiments with the increase of backpressure at the outlet of the core samples based on the definition of gas slip effect and in view of different levels of permeability of tight sandstone reservoir. This study inspects a limit pressure of the gas slip effect in tight sandstones and analyzes the characteristic parameter of capillary pressure curves. The experimental results indicate that gas slip effect can be eliminated when the backpressure reaches a limit pressure. When the backpressure exceeds the limit pressure, the measured gas permeability is a relatively stable value whose range is less than 3% for a given core sample. It is also found that the limit pressure increases with the decreasing in permeability and has close relation with pore structure of the core samples. The results have an important influence on correlation study on gas flow in porous medium, and are beneficial to reduce the workload of laboratory experiment.

  15. Pore structure and limit pressure of gas slippage effect in tight sandstone.

    Science.gov (United States)

    You, Lijun; Xue, Kunlin; Kang, Yili; Liao, Yi; Kong, Lie

    2013-01-01

    Gas slip effect is an important mechanism that the gas flow is different from liquid flow in porous media. It is generally considered that the lower the permeability in porous media is, the more severe slip effect of gas flow will be. We design and then carry out experiments with the increase of backpressure at the outlet of the core samples based on the definition of gas slip effect and in view of different levels of permeability of tight sandstone reservoir. This study inspects a limit pressure of the gas slip effect in tight sandstones and analyzes the characteristic parameter of capillary pressure curves. The experimental results indicate that gas slip effect can be eliminated when the backpressure reaches a limit pressure. When the backpressure exceeds the limit pressure, the measured gas permeability is a relatively stable value whose range is less than 3% for a given core sample. It is also found that the limit pressure increases with the decreasing in permeability and has close relation with pore structure of the core samples. The results have an important influence on correlation study on gas flow in porous medium, and are beneficial to reduce the workload of laboratory experiment.

  16. Copper Nanowire-Based Aerogel with Tunable Pore Structure and Its Application as Flexible Pressure Sensor.

    Science.gov (United States)

    Xu, Xiaojuan; Wang, Ranran; Nie, Pu; Cheng, Yin; Lu, Xiaoyu; Shi, Liangjing; Sun, Jing

    2017-04-26

    Aerogel is a kind of material with high porosity and low density. However, the research on metal-based aerogel with good conductivity is quite limited, which hinders its usage in electronic devices, such as flexible pressure sensors. In this work, we successfully fabricate copper nanowire (CuNW) based aerogel through a one-pot method, and the dynamics for the assembly of CuNWs into hydrogel is intensively investigated. The "bubble controlled assembly" mechanism is put forward for the first time, according to which tunable pore structures and densities (4.3-7.5 mg cm -3 ) of the nanowire aerogel is achieved. Subsequently, ultralight flexible pressure sensors with tunable sensitivities (0.02 kPa -1 to 0.7 kPa -1 ) are fabricated from the Cu NWs aerogels, and the negative correlation behavior of the sensitivity to the density of the aerogel sensors is disclosed systematically. This work provides a versatile strategy for the fabrication of nanowire-based aerogels, which greatly broadens their application potential.

  17. Voronoi-Based DEM Simulation Approach for Sandstone Considering Grain Structure and Pore Size

    Science.gov (United States)

    Li, Jun; Konietzky, Heinz; Frühwirt, Thomas

    2017-10-01

    This paper presents a new procedure to create numerical models considering grain shape and size as well as pore size in an explicit and stochastic equivalent manner. Four shape factors are introduced to reproduce shape and size of grains and pores. Thin sections are used to analyze grain shape and pore size of rock specimen. First, a particle-based numerical model is set up by best fitted clumps from a shape library according to thin sections. Finally, an equivalent Voronoi-based discrete element model is set up based on the superimposed particle model. Uniaxial compression and tensile tests are simulated for validation. Both tests indicate that grain boundaries and pores provide preferred paths of weakness for crack propagation, but they also reveal significant differences in terms of intra- and inter-granular fracturing.

  18. Influence of pore structure parameters on thermal properties of corundum based castables

    International Nuclear Information System (INIS)

    Zhu, B Q; Fang, B X; Li, X C; Jiang, X; Zhao, F; Gao, X

    2011-01-01

    A series of corundum based castables bonded by ρ-Al 2 O 3 were prepared and fired at different temperature. Influences of apparent porosity and pore size distribution on thermal properties of the samples at different temperature were studied. The relationship between different pore size intervals and thermal conductivity of the samples was also discussed based on grey relational theory. The results show that thermal properties including thermal conductivity, thermal diffusivity and specific heat decline as apparent porosity of the samples increases. When apparent porosity of the samples keeps stable with little fluctuation, thermal conductivity increases as median pore size of the samples increases. It is found that thermal conductivity of the samples at a certain temperature presents the largest grey relational degree with the pore size interval that takes up the dominant volume ratio.

  19. A combinatorial variation in surface chemistry and pore size of three-dimensional porous poly(ε-caprolactone) scaffolds modulates the behaviors of mesenchymal stem cells

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Yingdi; Tan, Ke; Zhou, Yan; Ye, Zhaoyang, E-mail: zhaoyangye@ecust.edu.cn; Tan, Wen-Song

    2016-02-01

    Biomaterial properties play significant roles in controlling cellular behaviors. The objective of the present study was to investigate how pore size and surface chemistry of three-dimensional (3D) porous scaffolds regulate the fate of mesenchymal stem cells (MSCs) in vitro in combination. First, on poly(ε-caprolactone) (PCL) films, the hydrolytic treatment was found to stimulate the adhesion, spreading and proliferation of human MSCs (hMSCs) in comparison with pristine films, while the aminolysis showed mixed effects. Then, 3D porous PCL scaffolds with varying pore sizes (100–200 μm, 200–300 μm and 300–450 μm) were fabricated and subjected to either hydrolysis or aminolysis. It was found that a pore size of 200–300 μm with hydrolysis in 3D scaffolds was the most favorable condition for growth of hMSCs. Importantly, while a pore size of 200–300 μm with hydrolysis for 1 h supported the best osteogenic differentiation of hMSCs, the chondrogenic differentiation was greatest in scaffolds with a pore size of 300–450 μm and treated with aminolysis for 1 h. Taken together, these results suggest that surface chemistry and pore size of 3D porous scaffolds may potentially have a synergistic impact on the behaviors of MSCs. - Highlights: • Surface chemistry of poly(ε-caprolactone) films actively modulates MSC behaviors. • Varying surface chemistry and pore size in combination is enabled in 3D scaffolds. • Surface chemistry and pore size potentially dictate MSC fates in synergy.

  20. Dissolved organic matter (DOM) in pore water of Arctic Ocean sediments: linking DOM molecular composition with microbial community structure

    Science.gov (United States)

    Rossel, P. E.; Bienhold, C.; Boetius, A.; Dittmar, T.

    2016-02-01

    Marine organic matter (OM) that sinks from surface waters to the seafloor is the energy and carbon source for benthic communities. These communities produce dissolved organic matter (DOM) in the process of remineralization, enriching the sediment porewater with fresh DOM compounds. In the Arctic Ocean, primary production is limited by nutrients and light and is thus strongly influenced by sea ice cover. Ice cover is expected to further decrease due to global warming, which may have important consequences for primary production and the quantity and quality of OM exported to the seafloor. This study focused on: 1) the molecular composition of the DOM in sediment pore waters of the deep Eurasian Arctic basins, 2) whether there is any relation between Arctic Ocean ice cover and DOM composition and 3) whether the DOM composition correlates with microbial community structure. Molecular data, obtained via 15 Tesla Fourier transform ion cyclotron resonance mass spectrometry, were statistically correlated with environmental parameters. The productive ice margin stations showed higher abundances of molecular formulae of peptides, unsaturated aliphatics and saturated fatty acids. This molecular trend is indicative of fresh OM and phytodetritus deposition, compared to the northernmost, ice-covered stations which had stronger aromatic signals. Benthic bacterial community structure, as assessed with the fingerprinting method ARISA, was significantly correlated with DOM molecular composition. Further analyses using Illumina next-generation sequencing will enable the taxonomic identification of specific bacterial groups and their interdependence with DOM compounds. This study contributes to the understanding of the coupling between Arctic Ocean productivity and its depositional regime, and provides first insights into potential links between microbial community structure and DOM molecular composition in Arctic sediments

  1. The structure of stepped surfaces

    International Nuclear Information System (INIS)

    Algra, A.J.

    1981-01-01

    The state-of-the-art of Low Energy Ion Scattering (LEIS) as far as multiple scattering effects are concerned, is discussed. The ion fractions of lithium, sodium and potassium scattered from a copper (100) surface have been measured as a function of several experimental parameters. The ratio of the intensities of the single and double scattering peaks observed in ion scattering spectroscopy has been determined and ion scattering spectroscopy applied in the multiple scattering mode is used to determine the structure of a stepped Cu(410) surface. The average relaxation of the (100) terraces of this surface appears to be very small. The adsorption of oxygen on this surface has been studied with LEIS and it is indicated that oxygen absorbs dissociatively. (C.F.)

  2. Vitamin A transport and the transmembrane pore in the cell-surface receptor for plasma retinol binding protein.

    Directory of Open Access Journals (Sweden)

    Ming Zhong

    Full Text Available Vitamin A and its derivatives (retinoids play diverse and crucial functions from embryogenesis to adulthood and are used as therapeutic agents in human medicine for eye and skin diseases, infections and cancer. Plasma retinol binding protein (RBP is the principal and specific vitamin A carrier in the blood and binds vitamin A at 1:1 ratio. STRA6 is the high-affinity membrane receptor for RBP and mediates cellular vitamin A uptake. STRA6 null mice have severely depleted vitamin A reserves for vision and consequently have vision loss, even under vitamin A sufficient conditions. STRA6 null humans have a wide range of severe pathological phenotypes in many organs including the eye, brain, heart and lung. Known membrane transport mechanisms involve transmembrane pores that regulate the transport of the substrate (e.g., the gating of ion channels. STRA6 represents a new type of membrane receptor. How this receptor interacts with its transport substrate vitamin A and the functions of its nine transmembrane domains are still completely unknown. These questions are critical to understanding the molecular basis of STRA6's activities and its regulation. We employ acute chemical modification to introduce chemical side chains to STRA6 in a site-specific manner. We found that modifications with specific chemicals at specific positions in or near the transmembrane domains of this receptor can almost completely suppress its vitamin A transport activity. These experiments provide the first evidence for the existence of a transmembrane pore, analogous to the pore of ion channels, for this new type of cell-surface receptor.

  3. Probing the intrinsically oil-wet surfaces of pores in North Sea chalk at subpore resolution

    DEFF Research Database (Denmark)

    Hassenkam, Tue; Skovbjerg, Lone Lindbæk; Stipp, Susan Louise Svane

    2009-01-01

    Ultimate Oil recovery from chalk reservoirs is limited by many factors - including the grain size and the surface properties of the small mainly biogenic calcite particles that chalk is made off . Wettability, the tendency for water or oil to spread over a surface, of the particle surfaces is one......, not a product of later migration of oil into the reservoir, which is known to alter the wettability of the surfaces. The data indicated distinct patches, with diameters ranging from 500 to 50 nm, which appears to have different wettability The size of the patches is significantly less than the size of the chalk...

  4. Structure of the moon's surface

    CERN Document Server

    Fielder, Gilbert

    1961-01-01

    Structure of the Moon's Surface aims to assemble and marshal relevant matter, and to produce a largely unprejudiced text which brings lunar studies up to date and stresses the importance of certain features of the Moon which have frequently been disregarded in the past, largely because of lack of knowledge about them. The book contains 14 chapters organized into two parts. Part I reviews and summarizes important physical problems. These include the liberations of the moon; height determinations of points of the moon's surface; the figure of the moon; and the moon's temperature and atmosphere.

  5. Multiscale pore structure and constitutive models of fine-grained rocks

    Science.gov (United States)

    Heath, J. E.; Dewers, T. A.; Shields, E. A.; Yoon, H.; Milliken, K. L.

    2017-12-01

    A foundational concept of continuum poromechanics is the representative elementary volume or REV: an amount of material large enough that pore- or grain-scale fluctuations in relevant properties are dissipated to a definable mean, but smaller than length scales of heterogeneity. We determine 2D-equivalent representative elementary areas (REAs) of pore areal fraction of three major types of mudrocks by applying multi-beam scanning electron microscopy (mSEM) to obtain terapixel image mosaics. Image analysis obtains pore areal fraction and pore size and shape as a function of progressively larger measurement areas. Using backscattering imaging and mSEM data, pores are identified by the components within which they occur, such as in organics or the clastic matrix. We correlate pore areal fraction with nano-indentation, micropillar compression, and axysimmetic testing at multiple length scales on a terrigenous-argillaceous mudrock sample. The combined data set is used to: investigate representative elementary volumes (and areas for the 2D images); determine if scale separation occurs; and determine if transport and mechanical properties at a given length scale can be statistically defined. Clear scale separation occurs between REAs and observable heterogeneity in two of the samples. A highly-laminated sample exhibits fine-scale heterogeneity and an overlapping in scales, in which case typical continuum assumptions on statistical variability may break down. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia LLC, a wholly owned subsidiary of Honeywell International Inc. for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA0003525.

  6. Pore solution in alkali-activated slag cement pastes. Relation to the composition and structure of calcium silicate hydrate

    International Nuclear Information System (INIS)

    Puertas, F.; Fernandez-Jimenez, A.; Blanco-Varela, M.T.

    2004-01-01

    In this work, the relationship between the composition of pore solution in alkali-activated slag cement (AAS) pastes activated with different alkaline activator, and the composition and structure of the main reaction products, has been studied. Pore solution was extracted from hardened AAS pastes. The analysis of the liquids was performed through different techniques: Na, Mg and Al by atomic absorption (AA), Ca ions by ionic chromatography (IC) and Si by colorimetry; pH was also determined. The solid phases were analysed by XRD, FTIR, solid-state 29 Si and 27 Al NMR and BSE/EDX. The most significant changes in the ionic composition of the pore solution of the AAS pastes activated with waterglass take place between 3 and 24 h of reaction. These changes are due to the decrease of the Na content and mainly to the Si content. Results of 29 Si MAS NMR and FTIR confirm that the activation process takes place with more intensity after 3 h (although at this age, Q 2 units already exist). The pore solution of the AAS pastes activated with NaOH shows a different evolution to this of pastes activated with waterglass. The decrease of Na and Si contents progresses with time. The nature of the alkaline activator influences the structure and composition of the calcium silicate hydrate formed as a consequence of the alkaline activation of the slag. The characteristic of calcium silicate hydrate in AAS pastes activated with waterglass is characterised by a low structural order with a low Ca/Si ratio. Besides, in this paste, Q 3 units are detected. The calcium silicate hydrate formed in the pastes activated with NaOH has a higher structural order (higher crystallinity) and contains more Al in its structure and a higher Ca/Si ratio than those obtained with waterglass

  7. Structures of the autoproteolytic domain from the Saccharomyces cerevisiae nuclear pore complex component, Nup145

    Energy Technology Data Exchange (ETDEWEB)

    Sampathkumar, Parthasarathy; Ozyurt, Sinem A.; Do, Johnny; Bain, Kevin T.; Dickey, Mark; Rodgers, Logan A.; Gheyi, Tarun; Sali, Andrej; Kim, Seung Joong; Phillips, Jeremy; Pieper, Ursula; Fernandez-Martinez, Javier; Franke, Josef D.; Martel, Anne; Tsuruta, Hiro; Atwell, Shane; Thompson, Devon A.; Emtage, J. Spencer; Wasserman, Stephen R.; Rout, Michael P.; Sauder, J. Michael; Burley, Stephen K. (SLAC); (Rockefeller); (UCSF); (Lilly)

    2012-04-30

    Nuclear pore complexes (NPCs) are large, octagonally symmetric dynamic macromolecular assemblies responsible for exchange of proteins and RNAs between the nucleus and cytoplasm. NPCs are made up of at least 456 polypeptides from {approx}30 distinct nucleoporins. Several of these components, sharing similar structural motifs, form stable subcomplexes that form a coaxial structure containing two outer rings (the nuclear and cytoplasmic rings), two inner rings, and a membrane ring. The yeast (Saccharomyces cerevisiae) Nup145 and its human counterpart are unique among the nucleoporins, in that they undergo autoproteolysis to generate functionally distinct proteins. The human counterpart of Nup145 is expressed as two alternatively spliced mRNA transcripts. The larger 190 kDa precursor undergoes post-translational autoproteolysis at the Phe863-Ser864 peptide bond yielding the 92 kDa Nup98 and the 96 kDa Nup96. The smaller 98 kDa precursor is also autoproteolysed at an analogous site giving 92 kDa Nup98-N and a 6 kDa C-terminal fragment, which may form a noncovalent complex. The yeast Nup145 precursor [Fig. 1(A)] contains twelve repeats of a 'GLFG' peptide motif (FG repeats) at its N-terminus, an internal autoproteolytic domain (a region of high conservation with the homologous yeast nucleoporins Nup110 and Nup116, neither of which undergo autoproteolysis), followed by the C-terminal domain. Various forms of the FG repeats are present in nearly half of all nucleoporins; they form intrinsically disordered regions implicated in gating mechanisms that control passage of macromolecules through NPCs. Nup145 undergoes autoproteolysis at the Phe605-Ser606 peptide bond to generate two functionally distinct proteins, Nup145N and Nup145C. Subsequently, Nup145C associates with six other proteins to form the heptameric Y-complex, a component of the outer rings of the NPC. Nup145N, on the other hand, can shuttle between the NPC and the nuclear interior. It has been suggested

  8. Manipulation of fluids in three-dimensional porous photonic structures with patterned surface properties

    Energy Technology Data Exchange (ETDEWEB)

    Aizenberg, Joanna; Burgess, Ian; Mishchenko, Lidiya; Hatton, Benjamin; Loncar, Marko

    2017-12-26

    A three-dimensional porous photonic structure, whose internal pore surfaces can be provided with desired surface properties in a spatially selective manner with arbitrary patterns, and methods for making the same are described. When exposed to a fluid (e.g., via immersion or wicking), the fluid can selectively penetrate the regions of the structure with compatible surface properties. Broad applications, for example in security, encryption and document authentication, as well as in areas such as simple microfluidics and diagnostics, are anticipated.

  9. Effects of pore size, implantation time, and nano-surface properties on rat skin ingrowth into percutaneous porous titanium implants.

    Science.gov (United States)

    Farrell, Brad J; Prilutsky, Boris I; Ritter, Jana M; Kelley, Sean; Popat, Ketul; Pitkin, Mark

    2014-05-01

    The main problem of percutaneous osseointegrated implants is poor skin-implant integration, which may cause infection. This study investigated the effects of pore size (Small, 40-100 μm and Large, 100-160 μm), nanotubular surface treatment (Nano), and duration of implantation (3 and 6 weeks) on skin ingrowth into porous titanium. Each implant type was percutaneously inserted in the back of 35 rats randomly assigned to seven groups. Implant extrusion rate was measured weekly and skin ingrowth into implants was determined histologically after harvesting implants. It was found that all three types of implants demonstrated skin tissue ingrowth of over 30% (at week 3) and 50% (at weeks 4-6) of total implant porous area under the skin; longer implantation resulted in greater skin ingrowth (p skin integration with the potential for a safe seal. Copyright © 2013 Wiley Periodicals, Inc.

  10. Pore structure development of in-situ pyrolyzed coals for pollution prevention in iron foundries

    Energy Technology Data Exchange (ETDEWEB)

    Huang, He; Cannon, Fred S. [Department of Civil and Environmental Engineering, The Pennsylvania State University, 212 Sackett Building, University Park, PA 16802 (United States); Wang, Yujue [Department of Environmental Science and Engineering, Tsinghua University, Bejing, 100084 (China)

    2009-09-15

    A protocol was devised for preparing pyrolyzed coals that could be made in-situ at foundries to capture volatile organic compound (VOC) emission. This pyrolysis created extensive micropore volume in lignite over a broad range of temperature and time; and could use waste heat from cupola exhaust gases by a heat-exchange tube. For foundry application, moderate porous carbon with relatively uniform pores over wide ranges of temperature and time would be more practical than highly porous activated carbon (AC) that requires narrowly-controlled operations. This pyrolysis protocol was developed in a thermogravimetric analyzer (TGA) and in a small tube furnace, while using lignite, bituminous coal, and anthracite. The lignite yielded the most pore volume; and this was relatively uniform (0.1-0.13 mL/g of pores) while temperatures were 600-900 C, and times were 0-60 min. Smaller grain sizes yielded improved porosity; and this corresponded to more release of phenols and naphthalenes from smaller grains, as discerned by TGA-mass spectroscopy (MS). TGA-MS also revealed that improved pore development between 600-800 C corresponded to the release of CO{sub 2} and H{sub 2}O; and concurrently higher slurry pH linked to less oxygenated functionality. Adsorption of benzene was compared between the in-situ porous carbon and a commercial AC. (author)

  11. Solution structure of the pore-forming protein of Entamoeba histolytica

    NARCIS (Netherlands)

    Hecht, O.; van Nuland, N.A.J.; Schleinkofer, K.; Dingley, A.J.; Bruhn, H.; Leippe, M.; Grötzinger, J.

    2004-01-01

    Amoebapore A is a 77-residue protein from the protozoan parasite and human pathogen Entamoeba histolytica. Amoebapores lyse both bacteria and eukaryotic cells by pore formation and play a pivotal role in the destruction of host tissues during amoebiasis, one of the most life-threatening parasitic

  12. Structure and function of a unique pore-forming protein from a pathogenic acanthamoeba

    NARCIS (Netherlands)

    Michalek, M.; Sönnichsen, F.D.; Wechselberger, R.W.; Wienk, H.L.J.; Leippe, M.; et al., [No Value

    2013-01-01

    Human pathogens often produce soluble protein toxins that generate pores inside membranes, resulting in the death of target cells and tissue damage. In pathogenic amoebae, this has been exemplified with amoebapores of the enteric protozoan parasite Entamoeba histolytica. Here we characterize

  13. Zinc isotope investigation of surface and pore waters in a mountain watershed impacted by acid rock drainage

    International Nuclear Information System (INIS)

    Aranda, Suzan; Borrok, David M.; Wanty, Richard B.; Balistrieri, Laurie S.

    2012-01-01

    The pollution of natural waters with metals derived from the oxidation of sulfide minerals like pyrite is a global environmental problem. However, the metal loading pathways and transport mechanisms associated with acid rock drainage reactions are often difficult to characterize using bulk chemical data alone. In this study, we evaluated the use of zinc (Zn) isotopes to complement traditional geochemical tools in the investigation of contaminated waters at the former Waldorf mining site in the Rocky Mountains, Colorado, U.S.A. Geochemical signatures and statistical analysis helped in identifying two primary metal loading pathways at the Waldorf site. The first was characterized by a circumneutral pH, high alkalinity, and high Zn/Cd ratios. The second was characterized by acidic pHs and low Zn/Cd ratios. Zinc isotope signatures in surface water samples collected across the site were remarkably similar (the δ 66 Zn, relative to JMC 3-0749-L, for most samples ranged from 0.20 to 0.30‰ ± 0.09‰ 2σ). This probably suggests that the ultimate source of Zn is consistent across the Waldorf site, regardless of the metal loading pathway. The δ 66 Zn of pore water samples collected within a nearby metal-impacted wetland area, however, were more variable, ranging from 0.20 to 0.80‰ ± 0.09‰ 2σ. Here the Zn isotopes seemed to reflect differences in groundwater flow pathways. However, a host of secondary processes might also have impacted Zn isotopes, including adsorption of Zn onto soil components, complexation of Zn with dissolved organic matter, uptake of Zn into plants, and the precipitation of Zn during the formation of reduced sulfur species. Zinc isotope analysis proved useful in this study; however, the utility of this isotopic tool would improve considerably with the addition of a comprehensive experimental foundation for interpreting the complex isotopic relationships found in soil pore waters. - Highlights: ► Zinc isotopes of water were measured in

  14. Zinc isotope investigation of surface and pore waters in a mountain watershed impacted by acid rock drainage

    Energy Technology Data Exchange (ETDEWEB)

    Aranda, Suzan [Department of Geological Sciences, University of Texas at El Paso, El Paso, TX 79968 (United States); Borrok, David M., E-mail: dborrok@utep.edu [Department of Geological Sciences, University of Texas at El Paso, El Paso, TX 79968 (United States); Wanty, Richard B. [US Geological Survey, MS 964d, Denver Federal Center, Denver, CO 80225 (United States); Balistrieri, Laurie S. [U.S. Geological Survey, University of Washington, School of Oceanography, Seattle, WA 98195 (United States)

    2012-03-15

    The pollution of natural waters with metals derived from the oxidation of sulfide minerals like pyrite is a global environmental problem. However, the metal loading pathways and transport mechanisms associated with acid rock drainage reactions are often difficult to characterize using bulk chemical data alone. In this study, we evaluated the use of zinc (Zn) isotopes to complement traditional geochemical tools in the investigation of contaminated waters at the former Waldorf mining site in the Rocky Mountains, Colorado, U.S.A. Geochemical signatures and statistical analysis helped in identifying two primary metal loading pathways at the Waldorf site. The first was characterized by a circumneutral pH, high alkalinity, and high Zn/Cd ratios. The second was characterized by acidic pHs and low Zn/Cd ratios. Zinc isotope signatures in surface water samples collected across the site were remarkably similar (the {delta}{sup 66}Zn, relative to JMC 3-0749-L, for most samples ranged from 0.20 to 0.30 Per-Mille-Sign {+-} 0.09 Per-Mille-Sign 2{sigma}). This probably suggests that the ultimate source of Zn is consistent across the Waldorf site, regardless of the metal loading pathway. The {delta}{sup 66}Zn of pore water samples collected within a nearby metal-impacted wetland area, however, were more variable, ranging from 0.20 to 0.80 Per-Mille-Sign {+-} 0.09 Per-Mille-Sign 2{sigma}. Here the Zn isotopes seemed to reflect differences in groundwater flow pathways. However, a host of secondary processes might also have impacted Zn isotopes, including adsorption of Zn onto soil components, complexation of Zn with dissolved organic matter, uptake of Zn into plants, and the precipitation of Zn during the formation of reduced sulfur species. Zinc isotope analysis proved useful in this study; however, the utility of this isotopic tool would improve considerably with the addition of a comprehensive experimental foundation for interpreting the complex isotopic relationships found in

  15. Free-Molecular Gas Flow in Channels (Pores) with Physico-Chemical Transformation on the Surface

    Czech Academy of Sciences Publication Activity Database

    Levdansky, V.V.; Smolík, Jiří; Moravec, Pavel

    2006-01-01

    Roč. 49, 13-14 (2006), s. 2356-2365 ISSN 0017-9310 Institutional research plan: CEZ:AV0Z40720504 Keywords : free-molecular flow * surface * spatial distribution Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.482, year: 2006

  16. Dynamic reservoir-condition microtomography of reactive transport in complex carbonates: Effect of initial pore structure and initial brine pH

    Science.gov (United States)

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

    2017-05-01

    We study the impact of brine acidity and initial pore structure on the dynamics of fluid/solid reaction at high Péclet numbers and low Damköhler numbers. A laboratory μ-CT scanner was used to image the dissolution of Ketton, Estaillades, and Portland limestones in the presence of CO2-acidified brine at reservoir conditions (10 MPa and 50 °C) at two injected acid strengths for a period of 4 h. Each sample was scanned between 6 and 10 times at ∼4 μm resolution and multiple effluent samples were extracted. The images were used as inputs into flow simulations, and analysed for dynamic changes in porosity, permeability, and reaction rate. Additionally, the effluent samples were used to verify the image-measured porosity changes. We find that initial brine acidity and pore structure determine the type of dissolution. Dissolution is either uniform where the porosity increases evenly both spatially and temporally, or occurs as channelling where the porosity increase is concentrated in preferential flow paths. Ketton, which has a relatively homogeneous pore structure, dissolved uniformly at pH = 3.6 but showed more channelized flow at pH = 3.1. In Estaillades and Portland, increasingly complex carbonates, channelized flow was observed at both acidities with the channel forming faster at lower pH. It was found that the effluent pH, which is higher than that injected, is a reasonably good indicator of effective reaction rate during uniform dissolution, but a poor indicator during channelling. The overall effective reaction rate was up to 18 times lower than the batch reaction rate measured on a flat surface at the effluent pH, with the lowest reaction rates in the samples with the most channelized flow, confirming that transport limitations are the dominant mechanism in determining reaction dynamics at the fluid/solid boundary.

  17. Wetting of geometrically structured surfaces

    CERN Document Server

    Bruschi, L; Mistura, G

    2003-01-01

    We review recent experiments on the growth of cryogenic fluids adsorbed on various substrates structured in different ways. On a very well defined array of microscopic linear wedges sculpted on thin Si wafers, the film mass is found to diverge as a power law in the chemical potential difference from saturation with an exponent x=-1.96+-0.10, in very good agreement with recent scaling analysis results. For the other, more irregular patterns, the observed exponents range from -0.95 to -2. In any case, they are always much smaller than those found for flat or rough surfaces.

  18. Wood decay by brown-rot fungi : changes in pore structure and cell wall volume

    Science.gov (United States)

    Douglas S. Flournoy; T. Kent Kirk; T.L. Highley

    1991-01-01

    Sweetgum (Liquidambar styraciflua L.) wood blocks were decayed by Postia (= Poria) placenta in soilblock cultures. Decay was terminated at various weight losses, and the pore volumes available to four low molecular weight molecules, (water, 4 Å,; glucose, 8 Å,; maltose, 10 Å; and raffinose, 128,) and three dextrans (Mr 6,000, 38 Å; 11,200, 51 Å; nd 17,500, 61 Å) were...

  19. Pore structure and mechanical properties of directionally solidified porous aluminum alloys

    OpenAIRE

    Komissarchuk Olga; Xu Zhengbin; Hao Hai

    2014-01-01

    Porous aluminum alloys produced by the metal-gas eutectic method or GASAR process need to be performed under a certain pressure of hydrogen, and to carry over melt to a tailor-made apparatus that ensures directional solidification. Hydrogen is driven out of the melt, and then the quasi-cylindrical pores normal to the solidification front are usually formed. In the research, the effects of processing parameters (saturation pressure, solidification pressure, temperature, and holding time) on th...

  20. Factors Determining the Pore Shape in Polycarbonate Track Membranes

    CERN Document Server

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

    2004-01-01

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

  1. Active Sampling Device for Determining Pollutants in Surface and Pore Water - the In Situ Sampler for Biphasic Water Monitoring

    Science.gov (United States)

    Supowit, Samuel D.; Roll, Isaac B.; Dang, Viet D.; Kroll, Kevin J.; Denslow, Nancy D.; Halden, Rolf U.

    2016-02-01

    We designed and evaluated an active sampling device, using as analytical targets a family of pesticides purported to contribute to honeybee colony collapse disorder. Simultaneous sampling of bulk water and pore water was accomplished using a low-flow, multi-channel pump to deliver water to an array of solid-phase extraction cartridges. Analytes were separated using either liquid or gas chromatography, and analysis was performed using tandem mass spectrometry (MS/MS). Achieved recoveries of fipronil and degradates in water spiked to nominal concentrations of 0.1, 1, and 10 ng/L ranged from 77 ± 12 to 110 ± 18%. Method detection limits (MDLs) were as low as 0.040-0.8 ng/L. Extraction and quantitation of total fiproles at a wastewater-receiving wetland yielded concentrations in surface water and pore water ranging from 9.9 ± 4.6 to 18.1 ± 4.6 ng/L and 9.1 ± 3.0 to 12.6 ± 2.1 ng/L, respectively. Detected concentrations were statistically indistinguishable from those determined by conventional, more laborious techniques (p > 0.2 for the three most abundant fiproles). Aside from offering time-averaged sampling capabilities for two phases simultaneously with picogram-per-liter MDLs, the novel methodology eliminates the need for water and sediment transport via in situ solid phase extraction.

  2. Structure, thermodynamic properties, and phase diagrams of few colloids confined in a spherical pore

    Science.gov (United States)

    Paganini, Iván E.; Pastorino, Claudio; Urrutia, Ignacio

    2015-06-01

    We study a system of few colloids confined in a small spherical cavity with event driven molecular dynamics simulations in the canonical ensemble. The colloidal particles interact through a short range square-well potential that takes into account the basic elements of attraction and excluded-volume repulsion of the interaction among colloids. We analyze the structural and thermodynamic properties of this few-body confined system in the framework of inhomogeneous fluids theory. Pair correlation function and density profile are used to determine the structure and the spatial characteristics of the system. Pressure on the walls, internal energy, and surface quantities such as surface tension and adsorption are also analyzed for a wide range of densities and temperatures. We have characterized systems from 2 to 6 confined particles, identifying distinctive qualitative behavior over the thermodynamic plane T - ρ, in a few-particle equivalent to phase diagrams of macroscopic systems. Applying the extended law of corresponding states, the square well interaction is mapped to the Asakura-Oosawa model for colloid-polymer mixtures. We link explicitly the temperature of the confined square-well fluid to the equivalent packing fraction of polymers in the Asakura-Oosawa model. Using this approach, we study the confined system of few colloids in a colloid-polymer mixture.

  3. Structure, thermodynamic properties, and phase diagrams of few colloids confined in a spherical pore.

    Science.gov (United States)

    Paganini, Iván E; Pastorino, Claudio; Urrutia, Ignacio

    2015-06-28

    We study a system of few colloids confined in a small spherical cavity with event driven molecular dynamics simulations in the canonical ensemble. The colloidal particles interact through a short range square-well potential that takes into account the basic elements of attraction and excluded-volume repulsion of the interaction among colloids. We analyze the structural and thermodynamic properties of this few-body confined system in the framework of inhomogeneous fluids theory. Pair correlation function and density profile are used to determine the structure and the spatial characteristics of the system. Pressure on the walls, internal energy, and surface quantities such as surface tension and adsorption are also analyzed for a wide range of densities and temperatures. We have characterized systems from 2 to 6 confined particles, identifying distinctive qualitative behavior over the thermodynamic plane T - ρ, in a few-particle equivalent to phase diagrams of macroscopic systems. Applying the extended law of corresponding states, the square well interaction is mapped to the Asakura-Oosawa model for colloid-polymer mixtures. We link explicitly the temperature of the confined square-well fluid to the equivalent packing fraction of polymers in the Asakura-Oosawa model. Using this approach, we study the confined system of few colloids in a colloid-polymer mixture.

  4. Precise small-angle X-ray scattering evaluation of the pore structures in track-etched membranes: Comparison with other convenient evaluation methods

    Energy Technology Data Exchange (ETDEWEB)

    Miyazaki, Tsukasa, E-mail: t_miyazaki@cross.or.jp [Neutron Science and Technology Center, Comprehensive Research Organization for Science and Society, 162-1, Shirakata, Tokai-mura, Naka-gun, Ibaraki 319-1106 (Japan); Takenaka, Mikihito [Department of Polymer Chemistry, Gradual School of Engineering, Kyoto University, Kyotodaigaku-katsura, Kyoto 615-8510 (Japan)

    2017-03-01

    Poly(ethylene terephthalate) (PET)-based track-etched membranes (TMs) with pore sizes ranging from few nanometers to approximately 1 μm are used in various applications in the biological field, and their pore structures are determined by small-angle X-ray scattering (SAXS). These TMs with the nanometer-sized cylindrical pores aligned parallel to the film thickness direction are produced by chemical etching of the track in the PET films irradiated by heavy ions with the sodium hydroxide aqueous solution. It is well known that SAXS allows us to precisely and statistically estimate the pore size and the pore size distribution in the TMs by using the form factor of a cylinder with the extremely long pore length relative to the pore diameter. The results obtained were compared with those estimated with scanning electron microscopy and gas permeability measurements. The result showed that the gas permeability measurement is convenient to evaluate the pore size of TMs within a wide length scale, and the SEM observation is also suited to estimate the pore size, although SEM observation is usually limited above approximately 30 nm.

  5. Ionic Conductivity of Mesostructured Yttria-Stabilized Zirconia Thin Films with Cubic Pore Symmetry—On the Influence of Water on the Surface Oxygen Ion Transport.

    Science.gov (United States)

    Elm, Matthias T; Hofmann, Jonas D; Suchomski, Christian; Janek, Jürgen; Brezesinski, Torsten

    2015-06-10

    Thermally stable, ordered mesoporous thin films of 8 mol % yttria-stabilized zirconia (YSZ) were prepared by solution-phase coassembly of chloride salt precursors with an amphiphilic diblock copolymer using an evaporation-induced self-assembly process. The resulting material is of high quality and exhibits a well-defined three-dimensional network of pores averaging 24 nm in diameter after annealing at 600 °C for several hours. The wall structure is polycrystalline, with grains in the size range of 7 to 10 nm. Using impedance spectroscopy, the total electrical conductivity was measured between 200 and 500 °C under ambient atmosphere as well as in dry atmosphere for oxygen partial pressures ranging from 1 to 10(-4) bar. Similar to bulk YSZ, a constant ionic conductivity is observed over the whole oxygen partial pressure range investigated. In dry atmosphere, the sol-gel derived films have a much higher conductivity, with different activation energies for low and high temperatures. Overall, the results indicate a strong influence of the surface on the transport properties in cubic fluorite-type YSZ with high surface-to-volume ratio. A qualitative defect model which includes surface effects (annihilation of oxygen vacancies as a result of water adsorption) is proposed to explain the behavior and sensitivity of the conductivity to variations in the surrounding atmosphere.

  6. Selective Permeability of Uranyl Peroxide Nanocages to Different Alkali Ions: Influences from Surface Pores and Hydration Shells

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Yunyi; Haso, Fadi; Szymanowski, Jennifer E. S.; Zhou, Jing; Hu, Lang; Burns, Peter C.; Liu, Tianbo

    2015-11-16

    The precise guidance to different ions across the biological channels is essential for many biological processes. An artificial nanopore system will facilitate the study of the ion-transport mechanism through nanosized channels and offer new views for designing nanodevices. Herein we reveal that a 2.5 nm-sized, fullerene-shaped molecular cluster Li48+mK12(OH)m[UO2(O2)(OH)]60-(H2O)n (m≈20 and n≈310) (U60) shows selective permeability to different alkali ions. The subnanometer pores on the water–ligand-rich surface of U60 are able to block Rb+ and Cs+ ions from passing through, while allowing Na+ and K+ ions, which possess larger hydrated sizes, to enter the interior space of U60. An interestingly high entropy gain during the binding process between U60 and alkali ions suggests that the hydration shells of Na+/K+ and U60 are damaged during the interaction. The ion selectivity of U60 is greatly influenced by both the morphologies of the surface nanopores and the dynamics of the hydration shells.

  7. Selective permeability of uranyl peroxide nanocages to different alkali ions: influences from surface pores and hydration shells

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Yunyi; Haso, Fadi; Zhou, Jing; Hu, Lang; Liu, Tianbo [Department of Polymer Science, University of Akron, OH (United States); Szymanowski, Jennifer E.S.; Burns, Peter C. [Department of Civil Engineering and Geological Sciences, University of Notre Dame, IN (United States)

    2015-12-14

    The precise guidance to different ions across the biological channels is essential for many biological processes. An artificial nanopore system will facilitate the study of the ion-transport mechanism through nanosized channels and offer new views for designing nanodevices. Herein we reveal that a 2.5 nm-sized, fullerene-shaped molecular cluster Li{sub 48+m}K{sub 12}(OH){sub m}[UO{sub 2}(O{sub 2})(OH)]{sub 60-}(H{sub 2}O){sub n} (m∼20 and n∼310) (U{sub 60}) shows selective permeability to different alkali ions. The subnanometer pores on the water-ligand-rich surface of U{sub 60} are able to block Rb{sup +} and Cs{sup +} ions from passing through, while allowing Na{sup +} and K{sup +} ions, which possess larger hydrated sizes, to enter the interior space of U{sub 60}. An interestingly high entropy gain during the binding process between U{sub 60} and alkali ions suggests that the hydration shells of Na{sup +}/K{sup +} and U{sub 60} are damaged during the interaction. The ion selectivity of U{sub 60} is greatly influenced by both the morphologies of the surface nanopores and the dynamics of the hydration shells. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  8. Surface structure of AU3Cu(001)

    DEFF Research Database (Denmark)

    Eckstein, G.A.; Maupai, S.; Dakkouri, A.S.

    1999-01-01

    The surface morphology, composition, and structure of Au3Cu(001) as determined by scanning tunneling microscopy and surface x-ray diffraction are presented. Atomic resolution STM images reveal distinctive geometric features. The analysis of the surface x-ray diffraction data provides clear evidence...... for the surface structure. [S0163-1829(99)04535-X]....

  9. High surface area Au-SBA-15 and Au-MCM-41 materials synthesis: tryptophan amino acid mediated confinement of gold nanostructures within the mesoporous silica pore walls.

    Science.gov (United States)

    Selvakannan, Pr; Mantri, Kshudiram; Tardio, James; Bhargava, Suresh K

    2013-03-15

    Advantages of confining the gold nanostructures formation within the mesoporous silica pore walls during its silica condensation and consequent improvement in the textural properties such as specific surface area, pore volume, pore diameter have been demonstrated, while retaining gold nanostructures within the silica walls. This has been achieved by tryptophan mediated confinement of gold nanoparticles formation within the condensing silica framework, to obtain Au-SBA-15 (SSA 1247 m(2)/g, V(t)~1.37 cm(3)/g) and Au-MCM-41 (SSA 1287 m(2)/g, V(t)~1.1 cm(3)/g), mesoporous silica materials having the combination of very high surface area from the porous support as well as gold nanoparticles infiltrated silica walls. Choice of tryptophan for this purpose is that it has an indole group, which was known to reduce gold ions to form gold nanoparticles and its amine and carboxylic acid groups, catalyze the hydrolysis of silica precursors in a wide range of pH. These properties have been utilized in restricting the gold nanostructures formation inside the condensing silica phase without affecting the self assembly between the silica precursors and the triblock copolymer (for SBA-15) or cetyltrimethylammonium bromide template (for MCM-41). The polytryptophan and the gold nanostructures, which were encapsulated within the silica framework and upon removal of the template by calcination resulting in the formation mesoporous materials wherein the silica walls become microporous due to the removal of occluded polytryptophan and the resulting microchannels contain very small gold nanostructures. Hence, the resulting materials have very high surface area, high pore volume and narrow pore size distribution as compared to their parent SBA-15, MCM-41 and SBA-15, MCM-41 post functionalized with gold nanoparticles inside the pores. Copyright © 2012 Elsevier Inc. All rights reserved.

  10. Small-Pore Molecular Sieves SAPO-34 with Chabazite Structure: Theoretical Study of Silicon Incorporation and Interrelated Catalytic Activity

    Science.gov (United States)

    Wang, Hong; Lewis, James; Liu, Zhongmin

    2011-03-01

    The catalytic conversion of methonal to olefin (MTO) has attracted attention both in industrial and academic fields. Strong evidence shows that small-pore molecular sieves with certain amount silicon incorporated (SAPO) present promising high catalytic activity in MTO conversion. Using DFT, we study the structural and electronic properties of chabazite SAPO-34. Although there are extensively experimental results show that silicon incorporation does not change the overall structure as the original AlPO structure, local structural changes are still created by silicon substitution, which probably accounted for the high catalytic activity. It is noted that the catalytic activity of SAPO-34 presents increasing trend along with the silicon incorporation amount increasing and maintain a flat peak even with more silicon incorporated. Hence, there is an optimal silicon incorporation amount which possibly yields the highest catalytic MTO conversion.

  11. NMR Pore Structure and Dynamic Characteristics of Sandstone Caused by Ambient Freeze-Thaw Action

    Directory of Open Access Journals (Sweden)

    Bo Ke

    2017-01-01

    Full Text Available For a deeper understanding of the freeze-thaw weathering effects on the microstructure evolution and deterioration of dynamic mechanical properties of rock, the present paper conducted the nuclear magnetic resonance (NMR tests and impact loading experiments on sandstone under different freeze-thaw cycles. The results of NMR test show that, with the increase of freeze-thaw cycles, the pores expand and pores size tends to be uniform. The experimental results show that the stress-strain curves all go through four stages, namely, densification, elasticity, yielding, and failure. The densification curve is shorter, and the slope of elasticity curve decreases as the freeze-thaw cycles increase. With increasing freeze-thaw cycles, the dynamic peak stress decreases and energy absorption of sandstone increases. The dynamic failure form is an axial splitting failure, and the fragments increase and the size diminishes with increasing freeze-thaw cycles. The higher the porosity is, the more severe the degradation of dynamic characteristics is. An increase model for the relationships between the porosity or energy absorption and freeze-thaw cycles number was built to reveal the increasing trend with the freeze-thaw cycles increase; meanwhile, a decay model was built to predict the dynamic compressive strength degradation of rock after repeated freeze-thaw cycles.

  12. The effect of external magnetic fields on the pore structure of polyurethane foams loaded with magnetic microparticles

    International Nuclear Information System (INIS)

    Schümann, M; Seelig, N; Odenbach, S

    2015-01-01

    Elastic matrices loaded with magnetic microparticles are a new kind of magnetic hybrid material gaining a lot of scientific interest during the last few years. The central advantage of those materials is given by the possibility to control the mechanical properties by external stimuli, in this case external magnetic fields. Due to their extraordinary elastic properties, polyurethane foams are a promising matrix material for a new approach to synthesize such magnetic hybrid materials. A key to a deeper understanding of this new material is the investigation on how the inner structure of the hybrid material is controllable by the application of an external magnetic field during the polymerization. This paper presents a convenient method for analysis of structural changes of magnetically influenced particle loaded polyurethane foams. The geometry and size of up to 40 000 individual pores was evaluated by means of x-ray microtomography and digital image processing. A modest impact of the magnetic field on the pore structure was found with the utilized foam material, proving the convenient applicability of this method for future investigation with magnetic hybrid foams. (paper)

  13. Simulations of the pore structures for a M2G1yR derived channel forming peptide in membrane

    Science.gov (United States)

    Al-Rawi, Ahlam N.; Al-Rawi, Asma; Chen, Jianhan; Herrera, Alvaro; Tomich, John; Rahman, Talat S.

    2008-03-01

    In an effort to develop a peptide-based compound suitable for clinical use as a channel replacement therapeutic for treating channelopathies such as cystic fibrosis, we present a reductionist model that appears to capture many of the biophysical properties of an intact ion channel using short channel-forming peptides. We have developed two anion selective channel-forming peptides with near native and altered properties from the peptides derived from the glycine receptor: NK4-M2GlyR-p22 WT (KKKKPAR-VGLGITTVLTMTTQS) and NK4-M2GlyR-p22 S22W (KKKKPARVGLGITTVLTMTTQW), respectively. Starting with the two structures determined by solution multidimensional NMR (800 MHz) in SDS, we used CHARMM and NAMD to perform molecular dynamics simulations on the monomers. Using the existing experimental data, we then built an initial 5- helix assembly by altering the tilted angle, rotational angle and pore radius. We investigated the impact of the single mutation at position 22 on the structure and dynamics of the pore formed in a membrane build in a hydrated POPC lipid bilayer. Probable structures for both assemblies are presented.

  14. Membrane pore architecture of the CslF6 protein controls (1-3,1-4)-β-glucan structure.

    Science.gov (United States)

    Jobling, Stephen A

    2015-06-01

    The cereal cell wall polysaccharide (1-3,1-4)-β-glucan is a linear polymer of glucose containing both β1-3 and β1-4 bonds. The structure of (1-3,1-4)-β-glucan varies between different cereals and during plant growth and development, but little is known about how this is controlled. The cellulose synthase-like CslF6 protein is an integral membrane protein and a major component of the (1-3,1-4)-β-glucan synthase. I show that a single amino acid within the predicted transmembrane pore domain of CslF6 controls (1-3,1-4)-β-glucan structure. A new mechanism for the control of the polysaccharide structure is proposed where membrane pore architecture and the translocation of the growing polysaccharide across the membrane control how the acceptor glucan is coordinated at the active site and thus the proportion of β1-3 and β1-4 bonds within the polysaccharide.

  15. Effect of non-solvent additives on the morphology, pore structure, and direct contact membrane distillation performance of PVDF-CTFE hydrophobic membranes.

    Science.gov (United States)

    Zheng, Libing; Wu, Zhenjun; Zhang, Yong; Wei, Yuansong; Wang, Jun

    2016-07-01

    Four common types of additives for polymer membrane preparation including organic macromolecule and micromolecule additives, inorganic salts and acids, and the strong non-solvent H2O were used to prepare poly (vinylidene fluoride-co-chlorotrifluoroethylene) (PVDF-CTFE) hydrophobic flat-sheet membranes. Membrane properties including morphology, porosity, hydrophobicity, pore size and pore distribution were investigated, and the permeability was evaluated via direct contact membrane distillation (DCMD) of 3.5g/L NaCl solution in a DCMD configuration. Both inorganic and organic micromolecule additives were found to slightly influence membrane hydrophobicity. Polyethylene glycol (PEG), organic acids, LiCl, MgCl2, and LiCl/H2O mixtures were proved to be effective additives to PVDF-CTFE membranes due to their pore-controlling effects and the capacity to improve the properties and performance of the resultant membranes. The occurrence of a pre-gelation process showed that when organic and inorganic micromolecules were added to PVDF-CTFE solution, the resultant membranes presented a high interconnectivity structure. The membrane prepared with dibutyl phthalate (DBP) showed a nonporous surface and symmetrical cross-section. When H2O and LiCl/H2O mixtures were also used as additives, they were beneficial for solid-liquid demixing, especially when LiCl/H2O mixed additives were used. The membrane prepared with 5% LiCl+2% H2O achieved a flux of 24.53kg/(m(2)·hr) with 99.98% salt rejection. This study is expected to offer a reference not only for PVDF-CTFE membrane preparation but also for other polymer membranes. Copyright © 2016. Published by Elsevier B.V.

  16. Zinc isotope investigation of surface and pore waters in a mountain watershed impacted by acid rock drainage.

    Science.gov (United States)

    Aranda, Suzan; Borrok, David M; Wanty, Richard B; Balistrieri, Laurie S

    2012-03-15

    The pollution of natural waters with metals derived from the oxidation of sulfide minerals like pyrite is a global environmental problem. However, the metal loading pathways and transport mechanisms associated with acid rock drainage reactions are often difficult to characterize using bulk chemical data alone. In this study, we evaluated the use of zinc (Zn) isotopes to complement traditional geochemical tools in the investigation of contaminated waters at the former Waldorf mining site in the Rocky Mountains, Colorado, U.S.A. Geochemical signatures and statistical analysis helped in identifying two primary metal loading pathways at the Waldorf site. The first was characterized by a circumneutral pH, high alkalinity, and high Zn/Cd ratios. The second was characterized by acidic pHs and low Zn/Cd ratios. Zinc isotope signatures in surface water samples collected across the site were remarkably similar (the δ(66)Zn, relative to JMC 3-0749-L, for most samples ranged from 0.20 to 0.30‰±0.09‰ 2σ). This probably suggests that the ultimate source of Zn is consistent across the Waldorf site, regardless of the metal loading pathway. The δ(66)Zn of pore water samples collected within a nearby metal-impacted wetland area, however, were more variable, ranging from 0.20 to 0.80‰±0.09‰ 2σ. Here the Zn isotopes seemed to reflect differences in groundwater flow pathways. However, a host of secondary processes might also have impacted Zn isotopes, including adsorption of Zn onto soil components, complexation of Zn with dissolved organic matter, uptake of Zn into plants, and the precipitation of Zn during the formation of reduced sulfur species. Zinc isotope analysis proved useful in this study; however, the utility of this isotopic tool would improve considerably with the addition of a comprehensive experimental foundation for interpreting the complex isotopic relationships found in soil pore waters. Copyright © 2012 Elsevier B.V. All rights reserved.

  17. Combined Effects of Surface Charge and Pore Size on Co-enhanced Permeability and Ion Selectivity through RGO-OCNT Nanofiltration Membranes.

    Science.gov (United States)

    Zhang, Haiguang; Quan, Xie; Chen, Shuo; Fan, Xinfei; Wei, Gaoliang; Yu, Hongtao

    2018-04-04

    Nanofiltration (NF) has received much attention for wastewater treatment and desalination. However, NF membranes generally suffer from the trade-off between permeability and selectivity. In this work, the co-enhancement of permeability and ion selectivity was achieved through tuning the surface charge and pore size of oxidized carbon nanotube (OCNT) intercalated reduced graphene oxide (RGO) membranes. With the increase of OCNT content from 0 to 83%, the surface charge and the pore size are increased. The permeability increased to 10.6 L m-2 h-1 bar-1 and rejection rate reached 78.1% for Na2SO4 filtration at a transmembrane pressure of 2 bar, which were 11.8 and 1.3 times higher than those of pristine RGO membrane. The composite membrane also showed 11.1 times higher permeability (11.1 L m-2 h-1 bar-1) and 2.9 times higher rejection rate (35.3%) for NaCl filtration. The analyses based on Donnan steric pore model suggest that the increased permeability is attributed to the combined effects of enlarged pore size and increased surface charge, while the enhanced ion selectivity is mainly dependent on the electrostatic interaction between the membrane and target ions. This finding provides a new insight for the development of high-performance NF membranes in water treatment and desalination.

  18. Microarc Oxidation Coating Combined with Surface Pore-Sealing Treatment Enhances Corrosion Fatigue Performance of 7075-T7351 Al Alloy in Different Media.

    Science.gov (United States)

    Yang, Hui-Hui; Wang, Xi-Shu; Wang, Ya-Ming; Wang, Yan-Ling; Zhang, Zhi-Hao

    2017-06-02

    Rotating bending fatigue tests have been performed to evaluate the corrosion fatigue performance and its influence factors of 7075-T7351 Al alloy in different media, namely air and a 5.0 wt % NaCl aqueous solution. All samples were coated by microarc oxidation (MAO) coating technology; some samples were followed by an epoxy resin pore-sealing treatment. Microscopic analyses of the surfaces and fracture cross-sections of samples were carried out. The results reveal that the sample with a MAO coating of 10 μm thickness and pore-sealing treatment by epoxy resin possesses optimal corrosion fatigue performance in the different media. The MAO coating with a pore-sealing treatment significantly improves the corrosion fatigue limit of 7075-T7351 Al alloy.

  19. Soil water retention, air flow and pore structure characteristics after corn cob biochar application to a tropical sandy loam

    DEFF Research Database (Denmark)

    Amoakwah, Emmanuel; Frimpong, Kwame Agyei; Okae-Anti, D

    2017-01-01

    Soil structure is a key soil physical property that affects soil water balance, gas transport, plant growth and development, and ultimately plant yield. Biochar has received global recognition as a soil amendment with the potential to ameliorate the structure of degraded soils. We investigated how...... corn cob biochar contributed to changes in soil water retention, air flow by convection and diffusion, and derived soil structure indices in a tropical sandy loam. Intact soil cores were taken from a field experiment that had plots without biochar (CT), and plots each with 10 t ha− 1 (BC-10), 20 t ha...... to significant increase in soil water retention compared to the CT and BC-10 as a result of increased microporosity (pores biochar had minimal impact. No significant influence of biochar was observed for ka and Dp/D0 for the BC treatments compared to the CT despite...

  20. Appraisal of a cementitious material for waste disposal: Neutron imaging studies of pore structure and sorptivity

    International Nuclear Information System (INIS)

    McGlinn, Peter J.; Beer, Frikkie C. de; Aldridge, Laurence P.; Radebe, Mabuti J.; Nshimirimana, Robert; Brew, Daniel R.M.; Payne, Timothy E.; Olufson, Kylie P.

    2010-01-01

    Cementitious materials are conventionally used in conditioning intermediate and low level radioactive waste. In this study a candidate cement-based wasteform has been investigated using neutron imaging to characterise the wasteform for disposal in a repository for radioactive materials. Imaging showed both the pore size distribution and the extent of the cracking that had occurred in the samples. The rate of the water penetration measured both by conventional sorptivity measurements and neutron imaging was greater than in pastes made from Ordinary Portland Cement. The ability of the cracks to distribute the water through the sample in a very short time was also evident. The study highlights the significant potential of neutron imaging in the investigation of cementitious materials. The technique has the advantage of visualising and measuring, non-destructively, material distribution within macroscopic samples and is particularly useful in defining movement of water through the cementitious materials.

  1. The effect of firing temperature on the irreversible expansion, water absorption and pore structure of a brick body during freeze-thaw cycles

    Directory of Open Access Journals (Sweden)

    Mikuláš ŠVEDA

    2013-12-01

    Full Text Available The paper deals with the monitoring of brick body in the process of volumetric freezing and thawing. The samples were fired at temperatures of 900, 1000 and 1060 °C. Attention is focused on monitoring of the irreversible expansion, water absorption and pore structure of a brick body. We found that in all cases the endpoints take place continuously, where the amount firing temperature plays a crucial role. The greatest influence of freeze/thaw cycles on the change of the pore structure was also observed at the lowest temperature. The change of the pore system during the freeze-thaw cycles occurs in such a way, that the pore volume of small pores further decreases and conversely, the pore volume of large pores increases. The knowledge gained can be used not only in the production of new but also in predicting the remaining durability of older clay roofing tiles. DOI: http://dx.doi.org/10.5755/j01.ms.19.4.2741

  2. 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)

  3. Surface Observation and Pore Size Analyses of Polypropylene/Low-Melting Point Polyester Filter Materials: Influences of Heat Treatment

    Directory of Open Access Journals (Sweden)

    Lin Jia-Horng

    2016-01-01

    Full Text Available This study proposes making filter materials with polypropylene (PP and low-melting point (LPET fibers. The influences of temperatures and times of heat treatment on the morphology of thermal bonding points and average pore size of the PP/LPET filter materials. The test results indicate that the morphology of thermal bonding points is highly correlated with the average pore size. When the temperature of heat treatment is increased, the fibers are joined first with the thermal bonding points, and then with the large thermal bonding areas, thereby decreasing the average pore size of the PP/LPET filter materials. A heat treatment of 110 °C for 60 seconds can decrease the pore size from 39.6 μm to 12.0 μm.

  4. The Structures of Coiled-Coil Domains from Type III Secretion System Translocators Reveal Homology to Pore-Forming Toxins

    Energy Technology Data Exchange (ETDEWEB)

    Barta, Michael L.; Dickenson, Nicholas E.; Patil, Mrinalini; Keightley, Andrew; Wyckoff, Gerald J.; Picking, William D.; Picking, Wendy L.; Geisbrecht, Brian V. (UMKC); (OKLU)

    2012-03-26

    Many pathogenic Gram-negative bacteria utilize type III secretion systems (T3SSs) to alter the normal functions of target cells. Shigella flexneri uses its T3SS to invade human intestinal cells to cause bacillary dysentery (shigellosis) that is responsible for over one million deaths per year. The Shigella type III secretion apparatus is composed of a basal body spanning both bacterial membranes and an exposed oligomeric needle. Host altering effectors are secreted through this energized unidirectional conduit to promote bacterial invasion. The active needle tip complex of S. flexneri is composed of a tip protein, IpaD, and two pore-forming translocators, IpaB and IpaC. While the atomic structure of IpaD has been elucidated and studied, structural data on the hydrophobic translocators from the T3SS family remain elusive. We present here the crystal structures of a protease-stable fragment identified within the N-terminal regions of IpaB from S. flexneri and SipB from Salmonella enterica serovar Typhimurium determined at 2.1 {angstrom} and 2.8 {angstrom} limiting resolution, respectively. These newly identified domains are composed of extended-length (114 {angstrom} in IpaB and 71 {angstrom} in SipB) coiled-coil motifs that display a high degree of structural homology to one another despite the fact that they share only 21% sequence identity. Further structural comparisons also reveal substantial similarity to the coiled-coil regions of pore-forming proteins from other Gram-negative pathogens, notably, colicin Ia. This suggests that these mechanistically separate and functionally distinct membrane-targeting proteins may have diverged from a common ancestor during the course of pathogen-specific evolutionary events.

  5. Reconstituted Fusion Pore

    OpenAIRE

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

    2003-01-01

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

  6. Closed Pore Structured NiCo2O4-Coated Nickel Foams for Stable and Effective Oil/Water Separation.

    Science.gov (United States)

    Li, Yan; Zheng, Xi; Yan, Zhanheng; Tian, Dongliang; Ma, Jianmin; Zhang, Xiaofang; Jiang, Lei

    2017-08-30

    To solve the serious problem caused by oily wastewater pollution, unique interface designs, for example, membranes with superwetting properties such as superhydrophobicity/superoleophilicity and superhydrophilicity/underwater superoleophobicity, provide a good way to achieve oil/water separation. Here, inspired by the liquid storage property of the honeycomb structure, we propose a strategy to fabricate NiCo 2 O 4 -coated nickel foams for stable and efficient oil/water separation. NiCo 2 O 4 with a closed-pore structure was formed by assembling nanoflakes with a micro/nanoscale hierarchical structure. Compared with nickel foam coated by NiCo 2 O 4 with an open-pore structure (NiCo 2 O 4 nanowires), the enclosed nanostructure of NiCo 2 O 4 nanoflakes can firmly hold water for a more stable superhydrophilic/underwater superoleophobic interface. As a consequence, the NiCo 2 O 4 -nanoflake-coated nickel foam has a larger oil breakthrough pressure than the NiCo 2 O 4 -nanowire-coated nickel foam because of a slightly larger oil advancing angle and a lower underwater oil adhesion force, which makes it more stable and efficient for oil/water separation. Moreover, the NiCo 2 O 4 -coated nickel foams have excellent chemical and mechanical stability, and they are reusable for oil-water separation. This work will be beneficial for the design and development of stable underwater superoleophobic self-cleaning materials and related device applications, such as oil/water separation.

  7. Probing numerical Laplace inversion methods for two and three-site molecular exchange between interconnected pore structures

    Science.gov (United States)

    Silletta, Emilia V.; Franzoni, María B.; Monti, Gustavo A.; Acosta, Rodolfo H.

    2018-01-01

    Two-dimension (2D) Nuclear Magnetic Resonance relaxometry experiments are a powerful tool extensively used to probe the interaction among different pore structures, mostly in inorganic systems. The analysis of the collected experimental data generally consists of a 2D numerical inversion of time-domain data where T2-T2 maps are generated. Through the years, different algorithms for the numerical inversion have been proposed. In this paper, two different algorithms for numerical inversion are tested and compared under different conditions of exchange dynamics; the method based on Butler-Reeds-Dawson (BRD) algorithm and the fast-iterative shrinkage-thresholding algorithm (FISTA) method. By constructing a theoretical model, the algorithms were tested for a two- and three-site porous media, varying the exchange rates parameters, the pore sizes and the signal to noise ratio. In order to test the methods under realistic experimental conditions, a challenging organic system was chosen. The molecular exchange rates of water confined in hierarchical porous polymeric networks were obtained, for a two- and three-site porous media. Data processed with the BRD method was found to be accurate only under certain conditions of the exchange parameters, while data processed with the FISTA method is precise for all the studied parameters, except when SNR conditions are extreme.

  8. Probing numerical Laplace inversion methods for two and three-site molecular exchange between interconnected pore structures.

    Science.gov (United States)

    Silletta, Emilia V; Franzoni, María B; Monti, Gustavo A; Acosta, Rodolfo H

    2018-01-01

    Two-dimension (2D) Nuclear Magnetic Resonance relaxometry experiments are a powerful tool extensively used to probe the interaction among different pore structures, mostly in inorganic systems. The analysis of the collected experimental data generally consists of a 2D numerical inversion of time-domain data where T 2 -T 2 maps are generated. Through the years, different algorithms for the numerical inversion have been proposed. In this paper, two different algorithms for numerical inversion are tested and compared under different conditions of exchange dynamics; the method based on Butler-Reeds-Dawson (BRD) algorithm and the fast-iterative shrinkage-thresholding algorithm (FISTA) method. By constructing a theoretical model, the algorithms were tested for a two- and three-site porous media, varying the exchange rates parameters, the pore sizes and the signal to noise ratio. In order to test the methods under realistic experimental conditions, a challenging organic system was chosen. The molecular exchange rates of water confined in hierarchical porous polymeric networks were obtained, for a two- and three-site porous media. Data processed with the BRD method was found to be accurate only under certain conditions of the exchange parameters, while data processed with the FISTA method is precise for all the studied parameters, except when SNR conditions are extreme. Copyright © 2017 Elsevier Inc. All rights reserved.

  9. Surface magnetic structures in amorphous ferromagnetic microwires

    International Nuclear Information System (INIS)

    Usov, N.A.; Serebryakova, O.N.; Gudoshnikov, S.A.; Tarasov, V.P.

    2017-01-01

    The spatial period of magnetization perturbations that occur near the surface of magnetic nanotube or nanowire under the influence of surface magnetic anisotropy is determined by means of numerical simulation as a function of the sample geometry and material parameters. The surface magnetization distribution obtained is then used to estimate the period of the surface magnetic texture in amorphous microwire of several micrometers in diameter by means of appropriate variational procedure. The period of the surface magnetic texture in amorphous microwire is found to be significantly smaller than the wire diameter. - Highlights: • Magnetic structure may arise near the magnetic nanotube surface under the influence of surface magnetic anisotropy. • The period of the surface magnetization pattern is calculated as a function of the sample geometry. • Similar magnetic structure may exist in amorphous microwire of several micrometers in diameter. • The period of the surface magnetic structure in amorphous wire is found to be significantly smaller than the wire diameter.

  10. Surface magnetic structures in amorphous ferromagnetic microwires

    Energy Technology Data Exchange (ETDEWEB)

    Usov, N.A., E-mail: usov@obninsk.ru [National University of Science and Technology «MISIS», 119049 Moscow (Russian Federation); Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation, Russian Academy of Sciences, IZMIRAN, 108840 Troitsk, Moscow (Russian Federation); Serebryakova, O.N.; Gudoshnikov, S.A. [National University of Science and Technology «MISIS», 119049 Moscow (Russian Federation); Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation, Russian Academy of Sciences, IZMIRAN, 108840 Troitsk, Moscow (Russian Federation); Tarasov, V.P. [National University of Science and Technology «MISIS», 119049 Moscow (Russian Federation)

    2017-05-01

    The spatial period of magnetization perturbations that occur near the surface of magnetic nanotube or nanowire under the influence of surface magnetic anisotropy is determined by means of numerical simulation as a function of the sample geometry and material parameters. The surface magnetization distribution obtained is then used to estimate the period of the surface magnetic texture in amorphous microwire of several micrometers in diameter by means of appropriate variational procedure. The period of the surface magnetic texture in amorphous microwire is found to be significantly smaller than the wire diameter. - Highlights: • Magnetic structure may arise near the magnetic nanotube surface under the influence of surface magnetic anisotropy. • The period of the surface magnetization pattern is calculated as a function of the sample geometry. • Similar magnetic structure may exist in amorphous microwire of several micrometers in diameter. • The period of the surface magnetic structure in amorphous wire is found to be significantly smaller than the wire diameter.

  11. Effect of membrane polymeric materials on relationship between surface pore size and membrane fouling in membrane bioreactors

    Science.gov (United States)

    Miyoshi, Taro; Yuasa, Kotaku; Ishigami, Toru; Rajabzadeh, Saeid; Kamio, Eiji; Ohmukai, Yoshikage; Saeki, Daisuke; Ni, Jinren; Matsuyama, Hideto

    2015-03-01

    We investigated the effect of different membrane polymeric materials on the relationship between membrane pore size and development of membrane fouling in a membrane bioreactor (MBR). Membranes with different pore sizes were prepared using three different polymeric materials, cellulose acetate butyrate (CAB), polyvinyl butyral (PVB), and polyvinylidene fluoride (PVDF), and the development of membrane fouling in each membrane was evaluated by batch filtration tests using a mixed liquor suspension obtained from a laboratory-scale MBR. The results revealed that the optimal membrane pore size to mitigate membrane fouling differed depending on membrane polymeric material. For PVDF membranes, the degree of membrane fouling decreased as membrane pore size increased. In contrast, CAB membranes with smaller pores had less fouling propensity than those with larger ones. Such difference can be attributed to the difference in major membrane foulants in each membrane; in PVDF, they were small colloids or dissolved organics in which proteins are abundant, and in CAB, microbial flocs. The results obtained in this study strongly suggested that optimum operating conditions of MBRs differ depending on the characteristics of the used membrane.

  12. Effect of hydrogel particle additives on water-accessible pore structure of sandy soils: a custom pressure plate apparatus and capillary bundle model.

    Science.gov (United States)

    Wei, Y; Durian, D J

    2013-05-01

    To probe the effects of hydrogel particle additives on the water-accessible pore structure of sandy soils, we introduce a custom pressure plate method in which the volume of water expelled from a wet granular packing is measured as a function of applied pressure. Using a capillary bundle model, we show that the differential change in retained water per pressure increment is directly related to the cumulative cross-sectional area distribution f(r) of the water-accessible pores with radii less than r. This is validated by measurements of water expelled from a model sandy soil composed of 2-mm-diameter glass beads. In particular, it is found that the expelled water is dramatically dependent on sample height and that analysis using the capillary bundle model gives the same pore size distribution for all samples. The distribution is found to be approximately log normal, and the total cross-sectional area fraction of the accessible pore space is found to be f(0)=0.34. We then report on how the pore distribution and total water-accessible area fraction are affected by superabsorbent hydrogel particle additives, uniformly mixed into a fixed-height sample at varying concentrations. Under both fixed volume and free swelling conditions, the total area fraction of water-accessible pore space in a packing decreases exponentially as the gel concentration increases. The size distribution of the pores is significantly modified by the swollen hydrogel particles, such that large pores are clogged while small pores are formed.

  13. A pore structure model for the gas transport property changes, initial oxidation rates and cumulative weight loss of AGR moderator graphite

    International Nuclear Information System (INIS)

    Johnson, P.A.V.

    1985-09-01

    A quantitative model has been developed for the gas transport property variation, cumulative weight loss and initial oxidation rates of AGR moderator graphite. The model utilises the theory of dynamic moments of the pore structure to calculate the changes in physical properties brought about by radiolytic corrosion taking place within the graphite porosity. In order to account for the behaviour of the initial rate curves, and the weight loss data obtained it is necessary to invoke the presence of a group of cylindrical pore and a group of small slab-shaped pores. The latter are methane depleted. This is in addition to the pore group involved in gas transport which is best represented by cylinders of mean radius 2.13 μm. The model satisfactorily predicts the experimental weight loss data obtained from experiments in the DIDO 6V3 and BFB loops. (author)

  14. Polar organic compounds in pore waters of the Chesapeake Bay impact structure, Eyreville core hole: Character of the dissolved organic carbon and comparison with drilling fluids

    Science.gov (United States)

    Rostad, C.E.; Sanford, W.E.

    2009-01-01

    Pore waters from the Chesapeake Bay impact structure cores recovered at Eyreville Farm, Northampton County, Virginia, were analyzed to characterize the dissolved organic carbon. After squeezing or centrifuging, a small volume of pore water, 100 ??L, was taken for analysis by electrospray ionization-mass spectrometry. Porewater samples were analyzed directly without filtration or fractionation, in positive and negative mode, for polar organic compounds. Spectra in both modes were dominated by low-molecular-weight ions. Negative mode had clusters of ions differing by -60 daltons, possibly due to increasing concentrations of inorganic salts. The numberaverage molecular weight and weight-average molecular weight values for the pore waters from the Chesapeake Bay impact structure are higher than those reported for other aquatic sources of natural dissolved organic carbon as determined by electrospray ionization-mass spectrometry. In order to address the question of whether drilling mud fluids may have contaminated the pore waters during sample collection, spectra from the pore waters were compared to spectra from drilling mud fluids. Ions indicative of drilling mud fluids were not found in spectra from the pore waters, indicating there was no detectable contamination, and highlighting the usefulness of this analytical technique for detecting potential contamination during sample collection. ?? 2009 The Geological Society of America.

  15. Atomic structure of the nuclear pore complex targeting domain of a Nup116 homologue from the yeast, Candida glabrata

    Energy Technology Data Exchange (ETDEWEB)

    Sampathkumar, Parthasarathy; Kim, Seung Joong; Manglicmot, Danalyn; Bain, Kevin T.; Gilmore, Jeremiah; Gheyi, Tarun; Phillips, Jeremy; Pieper, Ursula; Fernandez-Martinez, Javier; Franke, Josef D.; Matsui, Tsutomu; Tsuruta, Hiro; Atwell, Shane; Thompson, Devon A.; Emtage, J. Spencer; Wasserman, Stephen R.; Rout, Michael P.; Sali, Andrej; Sauder, J. Michael; Almo, Steven C.; Burley, Stephen K. (Einstein); (SLAC); (Rockefeller); (UCSF); (Lilly)

    2012-10-23

    The nuclear pore complex (NPC), embedded in the nuclear envelope, is a large, dynamic molecular assembly that facilitates exchange of macromolecules between the nucleus and the cytoplasm. The yeast NPC is an eightfold symmetric annular structure composed of {approx}456 polypeptide chains contributed by {approx}30 distinct proteins termed nucleoporins. Nup116, identified only in fungi, plays a central role in both protein import and mRNA export through the NPC. Nup116 is a modular protein with N-terminal 'FG' repeats containing a Gle2p-binding sequence motif and a NPC targeting domain at its C-terminus. We report the crystal structure of the NPC targeting domain of Candida glabrata Nup116, consisting of residues 882-1034 [CgNup116(882-1034)], at 1.94 {angstrom} resolution. The X-ray structure of CgNup116(882-1034) is consistent with the molecular envelope determined in solution by small-angle X-ray scattering. Structural similarities of CgNup116(882-1034) with homologous domains from Saccharomyces cerevisiae Nup116, S. cerevisiae Nup145N, and human Nup98 are discussed.

  16. Moulding of Sub-micrometer Surface Structures

    DEFF Research Database (Denmark)

    Pranov, Henrik; Rasmussen, Henrik K.; Larsen, Niels Bent

    2006-01-01

    The experiments strongly suggest that the possibility to injection mould sub-micrometer surface structures in polymers mainly relates to the forces originating from the adhesive energy between polymer and shim.......The experiments strongly suggest that the possibility to injection mould sub-micrometer surface structures in polymers mainly relates to the forces originating from the adhesive energy between polymer and shim....

  17. Photoelectric effect in surface-barrier structures

    International Nuclear Information System (INIS)

    Kononenko, V.K.; Tupenevich, P.A.

    1985-08-01

    Deviations from the Fowler law were observed when investigating photoelectric emission in p-type ZnTe surface-barrier structures. The revealed peculiarities of the structure photosensitivity spectrum are explained by the electron transitions involving surface states at the metal-semiconductor interface. (author)

  18. Contact area measurements on structured surfaces

    DEFF Research Database (Denmark)

    Kücükyildiz, Ömer Can; Jensen, Sebastian Hoppe Nesgaard; De Chiffre, Leonardo

    In connection with the use of brass specimens featuring structured surfaces in a tribology test, an algorithm was developed for automatic measurement of the contact area by optical means.......In connection with the use of brass specimens featuring structured surfaces in a tribology test, an algorithm was developed for automatic measurement of the contact area by optical means....

  19. Controlling molecular deposition and layer structure with supramolecular surface assemblies

    Science.gov (United States)

    Theobald, James A.; Oxtoby, Neil S.; Phillips, Michael A.; Champness, Neil R.; Beton, Peter H.

    2003-08-01

    Selective non-covalent interactions have been widely exploited in solution-based chemistry to direct the assembly of molecules into nanometre-sized functional structures such as capsules, switches and prototype machines. More recently, the concepts of supramolecular organization have also been applied to two-dimensional assemblies on surfaces stabilized by hydrogen bonding, dipolar coupling or metal co-ordination. Structures realized to date include isolated rows, clusters and extended networks, as well as more complex multi-component arrangements. Another approach to controlling surface structures uses adsorbed molecular monolayers to create preferential binding sites that accommodate individual target molecules. Here we combine these approaches, by using hydrogen bonding to guide the assembly of two types of molecules into a two-dimensional open honeycomb network that then controls and templates new surface phases formed by subsequently deposited fullerene molecules. We find that the open network acts as a two-dimensional array of large pores of sufficient capacity to accommodate several large guest molecules, with the network itself also serving as a template for the formation of a fullerene layer.

  20. Synthesis and Structure Determination of Large-Pore Zeolite SCM-14.

    Science.gov (United States)

    Luo, Yi; Smeets, Stef; Peng, Fei; Etman, Ahmed S; Wang, Zhendong; Sun, Junliang; Yang, Weimin

    2017-11-27

    SCM-14 (Sinopec Composite Material No. 14), a new stable germanosilicate zeolite with a 12×8×8-ring channel system, was synthesized using commercially available 4-pyrrolidinopyridine as organic structure-directing agents (OSDAs) in fluoride medium. The framework structure of SCM-14 was determined using rotation electron diffraction (RED), and refined against synchrotron X-ray powder diffraction (SXPD) data for both as-made and calcined materials. The framework structure of SCM-14 is closely related to that of three known zeolites: mordenite (MOR), GUS-1 (GON), and IM-16 (UOS). SCM-14 has the same projection as that of mordenite and GUS-1 when viewed along the 12-ring channels, and possesses two more straight 8-ring channels running perpendicular to the 12-ring channels. The structure of SCM-14 can be constructed by either the same layers as that of GUS-1 or the same columns as that of IM-16. Based on their structural relationship, three topologically reasonable hypothetical zeolites were predicted. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Dynamic Behavior of Hybrid APM (Advanced Pore Morphology Foam and Aluminum Foam Filled Structures

    Directory of Open Access Journals (Sweden)

    Joerg Weise

    2012-06-01

    Full Text Available The aim of this work is to evaluate the effect of different densities of hybrid aluminum polymer foam on the frequency behavior of a foam filled steel structure with different ratios between steel and foam masses. The foam filled structure is composed of three steel tubes with a welded flange at both ends bolted together to form a portal grounded by its free ends. Structure, internal and ground constraints have been designed and manufactured in order to minimize nonlinear effects and to guarantee optimal constraint conditions. Mode shapes and frequencies were verified with finite elements models (FEM to be in the range of experimental modal analysis, considering the frequency measurement range limits for instrumented hammer and accelerometer. Selected modes have been identified with suitable modal parameters extraction techniques. Each structure has been tested before and after filling, in order to compute the percentage variation of modal parameters. Two different densities of hybrid aluminum polymer foam have been tested and compared with structures filled with aluminum foams produced using the powder compact melting technique. All the foam fillings were able to suppress high frequency membrane modes which results in a reduction of environmental noise and an increase in performance of the components. Low frequency modes show an increase in damping ratio only when small thickness steel frames are filled with either Hybrid APM or Alulight foam.

  2. The structural and surface properties of natural and modified coal gangue.

    Science.gov (United States)

    Jabłońska, Beata; Kityk, Andriy V; Busch, Mark; Huber, Patrick

    2017-04-01

    A novel application of coal gangue as inexpensive adsorbents is considered in this study. The structural and surface properties of natural and modified gangue were studied via nitrogen adsorption. Four types of samples were studied: natural, modified with H 2 NO 3 and H 2 O 2 and calcined at 250 °C and 600 °C. The specific surface area and porosity of the samples were determined using various methods. The raw material is mainly mesoporous with relatively small specific surface area. The chemical modification enlarged the total pore volume and the specific surface area. The calcination at 250 °C enlarged slightly the pore volume and lowered the specific surface area, but did not cause significant changes in the structural properties. The calcination at 600 °C resulted in a significant increase in pore volume and a decrease in specific surface area. These results suggest that the coal gangue studied here could be used as inexpensive adsorbent in industrial wastewater pretreatment. Copyright © 2016 Elsevier Ltd. All rights reserved.

  3. A study of the water vapor sorption isotherms of hardened cement pastes: Possible pore structure changes at low relative humidity and the impact of temperature on isotherms

    DEFF Research Database (Denmark)

    Wu, Min; Johannesson, Björn; Geiker, Mette Rica

    2014-01-01

    Using water vapor sorption isotherms measured by the “dynamic vapor sorption” (DVS) method, a resaturation study was conducted to investigate possible pore structure changes of hardened cement paste samples caused by the drying at low relative humidity during desorption measurements. The results...... indicate that either the relatively short term drying does not cause any microstructure changes or the pore structure of the hardened cement paste samples can be restored during the absorption process. Additionally, the temperature dependency of sorption isotherms was investigated using both hardened...

  4. Atomic and electronic structures of novel silicon surface structures

    Energy Technology Data Exchange (ETDEWEB)

    Terry, J.H. Jr.

    1997-03-01

    The modification of silicon surfaces is presently of great interest to the semiconductor device community. Three distinct areas are the subject of inquiry: first, modification of the silicon electronic structure; second, passivation of the silicon surface; and third, functionalization of the silicon surface. It is believed that surface modification of these types will lead to useful electronic devices by pairing these modified surfaces with traditional silicon device technology. Therefore, silicon wafers with modified electronic structure (light-emitting porous silicon), passivated surfaces (H-Si(111), Cl-Si(111), Alkyl-Si(111)), and functionalized surfaces (Alkyl-Si(111)) have been studied in order to determine the fundamental properties of surface geometry and electronic structure using synchrotron radiation-based techniques.

  5. Synthesis of Silicalite Membrane with an Aluminum-Containing Surface for Controlled Modification of Zeolitic Pore Entries for Enhanced Gas Separation

    Directory of Open Access Journals (Sweden)

    Shaowei Yang

    2018-02-01

    Full Text Available The separation of small molecule gases by membrane technologies can help performance enhancement and process intensification for emerging advanced fossil energy systems with CO2 capture capacity. This paper reports the demonstration of controlled modification of zeolitic channel size for the MFI-type zeolite membranes to enhance the separation of small molecule gases such as O2 and N2. Pure-silica MFI-type zeolite membranes were synthesized on porous α-alumina disc substrates with and without an aluminum-containing thin skin on the outer surface of zeolite membrane. The membranes were subsequently modified by on-stream catalytic cracking deposition (CCD of molecular silica to reduce the effective openings of the zeolitic channels. Such a pore modification caused the transition of gas permeation from the N2-selective gaseous diffusion mechanism in the pristine membrane to the O2-selective activated diffusion mechanism in the modified membrane. The experimental results indicated that the pore modification could be effectively limited within the aluminum-containing surface of the MFI zeolite membrane to minimize the mass transport resistance for O2 permeation while maintaining its selectivity. The implications of pore modification on the size-exclusion-enabled gas selectivity were discussed based on the kinetic molecular theory. In light of the theoretical analysis, experimental investigation was performed to further enhance the membrane separation selectivity by chemical liquid deposition of silica into the undesirable intercrystalline spaces.

  6. Photonic band structures of periodic arrays of pores in a metallic host: tight-binding beyond the quasistatic approximation

    Science.gov (United States)

    Kim, Kwangmoo; Stroud, David

    2014-03-01

    We have calculated the photonic band structures of metallic inverse opals and of periodic linear chains of spherical pores in a metallic host, below a plasma frequency ωp. In both cases, we use a tight-binding approximation, assuming a Drude dielectric function for the metallic component, but without making the quasistatic approximation. The tight-binding modes are linear combinations of the single-cavity transverse magnetic (TM) modes. For the inverse-opal structures, the lowest modes are analogous to those constructed from the three degenerate atomic p-states in fcc crystals. For the linear chains, in the limit of small spheres compared to a wavelength, the results bear some qualitative resemblance to the dispersion relation for metal spheres in an insulating host, as calculated by Brongersma et al. [Phys. Rev. B 62, R16356 (2000)]. Because the electromagnetic fields of these modes decay exponentially in the metal, there are no radiative losses, in contrast to the case of arrays of metallic spheres in air. We suggest that this tight-binding approach to photonic band structures of such metallic inverse materials may be a useful approach for studying photonic crystals containing metallic components. This work was supported by KIAS, by NSF-MRSEC at OSU (DMR-0820414), and by DOE Grant No. DE-FG02-07ER46424. Computing resources were provided by OSC and by Abacus at KIAS.

  7. Impact of ground water - surface water interactions on pore-water and solid sediment phase composition of an acidic mining lake

    Science.gov (United States)

    Beer, J.; Neumann, C.; Fleckenstein, J.; Peiffer, S.; Blodau, C.

    2009-04-01

    Biogeochemical processes in lake sediments are influenced by diffusive and advective supply of solutes from lake and ground water. It has been demonstrated that the pore-water pH in lake sediments characterized by low pH and high concentrations of iron and sulfur (e.g. acidic mining lakes) are significantly affected by exchange flows with moderately acidic or near-neutral ground water (Blodau 20041). The resulting pore-water pH is a master variable which controls many biogeochemical processes such as mineral transformations, the reduction of iron and sulfate, etc. The aim of this study was to investigate whether inflow of ground water into an acidic mining lake leads to a shift from acidic, iron-reducing to near-neutral, sulfate-reducing and pyrite-precipitating conditions within the lake sediment. Therefore, we investigated ground-water advection rates among different sites and related them to concentration-depth profiles of relevant chemical species, and the composition of the solid sediment phase. We observed a heterogeneous pattern of ground water - surface water exchange within the lake. In shallow areas, ground water inflow occurred in the northern part (up to 7 L m-2 d-1) of the lake and outflow (up to 3 L m-2 d-1) in the southern part. In deeper areas, ground water generally infiltrated into the lake with rates of up to 6 L m-2 d-1except one site (> 200 L m-2 d-1). Advective transport affected pore-water concentrations of ferrous iron and sulfate which both ranged from 5 to 30 mmol L-1. Additionally, concentration-depth profiles of these dissolved species were altered by other processes such as schwertmannite transformation, and iron and sulfate reduction. Ground water - surface water exchange flows caused apparent differences in the pore-water pH: under outflow or low inflow conditions the pore water was more acidic (below pH 3.5) compared to the other sites (pH up to 6). Since sulfate reduction is pH-controlled the observed differences in the pore-water p

  8. Structure-function of proteins interacting with the α1 pore-forming subunit of high-voltage-activated calcium channels

    Science.gov (United States)

    Neely, Alan; Hidalgo, Patricia

    2014-01-01

    Openings of high-voltage-activated (HVA) calcium channels lead to a transient increase in calcium concentration that in turn activate a plethora of cellular functions, including muscle contraction, secretion and gene transcription. To coordinate all these responses calcium channels form supramolecular assemblies containing effectors and regulatory proteins that couple calcium influx to the downstream signal cascades and to feedback elements. According to the original biochemical characterization of skeletal muscle Dihydropyridine receptors, HVA calcium channels are multi-subunit protein complexes consisting of a pore-forming subunit (α1) associated with four additional polypeptide chains β, α2, δ, and γ, often referred to as accessory subunits. Twenty-five years after the first purification of a high-voltage calcium channel, the concept of a flexible stoichiometry to expand the repertoire of mechanisms that regulate calcium channel influx has emerged. Several other proteins have been identified that associate directly with the α1-subunit, including calmodulin and multiple members of the small and large GTPase family. Some of these proteins only interact with a subset of α1-subunits and during specific stages of biogenesis. More strikingly, most of the α1-subunit interacting proteins, such as the β-subunit and small GTPases, regulate both gating and trafficking through a variety of mechanisms. Modulation of channel activity covers almost all biophysical properties of the channel. Likewise, regulation of the number of channels in the plasma membrane is performed by altering the release of the α1-subunit from the endoplasmic reticulum, by reducing its degradation or enhancing its recycling back to the cell surface. In this review, we discuss the structural basis, interplay and functional role of selected proteins that interact with the central pore-forming subunit of HVA calcium channels. PMID:24917826

  9. Structure-function of proteins interacting with the alpha1 pore-forming subunit of high voltage-activated calcium channel

    Directory of Open Access Journals (Sweden)

    Alan eNeely

    2014-06-01

    Full Text Available Openings of high-voltage-activated calcium channels lead to a transient increase in calcium concentration that in turn activate a plethora of cellular functions, including muscle contraction, secretion and gene transcription. To coordinate all these responses calcium channels form supramolecular assemblies containing effectors and regulatory proteins that couple calcium influx to the downstream signal cascades and to feedback elements. According to the original biochemical characterization of skeletal muscle Dihydropyridine receptors, high-voltage-activated calcium channels are multi-subunit protein complexes consisting of a pore-forming subunit (α1 associated with four additional polypeptide chains β, α2, δ and γ, often referred to as accessory subunits. Twenty-five years after the first purification of a high-voltage calcium channel, the concept of a flexible stoichiometry to expand the repertoire of mechanisms that regulate calcium channel influx has emerged. Several other proteins have been identified that associate directly with the α1-subunit, including calmodulin and multiple members of the small and large GTPase family. Some of these proteins only interact with a subset of α1-subunits and during specific stages of biogenesis. More strikingly, most of the α1-subunit interacting proteins, such as the β-subunit and small GTPases, regulate both gating and trafficking through a variety of mechanisms. Modulation of channel activity covers almost all biophysical properties of the channel. Likewise, regulation of the number of channels in the plasma membrane is performed by altering the release of the α1-subunit from the endoplasmic reticulum, by reducing its degradation or enhancing its recycling back to the cell surface. In this review, we discuss the structural basis, interplay and functional role of selected proteins that interact with the central pore-forming subunit of high-voltage-activated calcium channels.

  10. Silicon/Carbon Anodes with One-Dimensional Pore Structure for Lithium-Ion Batteries

    Science.gov (United States)

    2013-08-31

    The removal of ethanol , polymerization of furfuryl alcohol, and carbonization of the polymer were carried out in sequence to generate a dense layer...September 1 31, 2012 to August 31, 2013 Submitted to Dr. Robert Mantz Program Manager, Electrochemistry and Catalysis Army Research Office...situ polymer coating.  Synthesis and characterization of mesoporous Fe2O3 and nano-structured carbon-coated CuO hollow spheres by aerosol

  11. The Controls of Pore-Throat Structure on Fluid Performance in Tight Clastic Rock Reservoir: A Case from the Upper Triassic of Chang 7 Member, Ordos Basin, China

    Directory of Open Access Journals (Sweden)

    Yunlong Zhang

    2018-01-01

    Full Text Available The characteristics of porosity and permeability in tight clastic rock reservoir have significant difference from those in conventional reservoir. The increased exploitation of tight gas and oil requests further understanding of fluid performance in the nanoscale pore-throat network of the tight reservoir. Typical tight sandstone and siltstone samples from Ordos Basin were investigated, and rate-controlled mercury injection capillary pressure (RMICP and nuclear magnetic resonance (NMR were employed in this paper, combined with helium porosity and air permeability data, to analyze the impact of pore-throat structure on the storage and seepage capacity of these tight oil reservoirs, revealing the control factors of economic petroleum production. The researches indicate that, in the tight clastic rock reservoir, largest throat is the key control on the permeability and potentially dominates the movable water saturation in the reservoir. The storage capacity of the reservoir consists of effective throat and pore space. Although it has a relatively steady and significant proportion that resulted from the throats, its variation is still dominated by the effective pores. A combination parameter (ε that was established to be as an integrated characteristic of pore-throat structure shows effectively prediction of physical capability for hydrocarbon resource of the tight clastic rock reservoir.

  12. Pore - to - Core Modeling of Soil Organic Matter Decomposition in 3D Soil Structures

    Science.gov (United States)

    Falconer, R. E.; Battaia, G.; Baveye, P.; Otten, W.

    2013-12-01

    There is a growing body of literature supporting the need for microbial contributions to be considered explicitly in carbon-climate models. There is also overwhelming evidence that physical protection within aggregates can play a significant role in organic matter dynamics. Yet current models of soil organic matter dynamics divide soil organic matter into conceptual pools with distinct turnover times, assuming that a combination of biochemical and physical properties control decay without explicit description. Albeit robust in their application, such models are not capable to account for changes in soil structure or microbial populations, or accurately predict the effect of wetness or priming. A spatially explicit model is presented that accounts for microbial dynamics and physical processes, permitting consideration of the heterogeneity of the physical and chemical microenvironments at scales relevant for microbes. Exemplified for fungi, we investigate how micro-scale processes manifest at the core scale with particular emphasis on evolution of CO2 and biomass distribution. The microbial model is based upon previous (Falconer et al, 2012) and includes the following processes: uptake, translocation, recycling, enzyme production, growth, spread and respiration. The model is parameterised through a combination of literature data and parameter estimation (Cazelles et al., 2012).The Carbon model comprises two pools, particulate organic matter which through enzymatic activity is converted into dissolved organic matter. The microbial and carbon dynamics occur within a 3D soil structure obtained by X-ray CT. We show that CO2 is affected not only by the amount of Carbon in the soil but also by microbial dynamics, soil structure and the spatial distribution of OM. The same amount of OM can result in substantially different respiration rates, with surprisingly more CO2 with increased clustering of OM. We can explain this from the colony dynamics, production of enzymes and

  13. Use of activated carbon as a support medium for H2S biofiltration and effect of bacterial immobilization on available pore surface.

    Science.gov (United States)

    Ng, Y L; Yan, R; Chen, X G; Geng, A L; Gould, W D; Liang, D T; Koe, L C C

    2004-12-01

    The use of support media for the immobilization of microorganisms is widely known to provide a surface for microbial growth and a shelter that protects the microorganisms from inhibitory compounds. In this study, activated carbon is used as a support medium for the immobilization of microorganisms enriched from municipal sewage activated sludge to remove gas-phase hydrogen sulfide (H2S), a major odorous component of waste gas from sewage treatment plants. A series of designed experiments is used to examine the effect on bacteria-immobilized activated carbon (termed "biocarbon") due to physical adsorption, chemical reaction, and microbial degradation in the overall removal of H2S. H2S breakthrough tests are conducted with various samples, including microbe-immobilized carbon and Teflon discs, salts-medium-washed carbon, and ultra-pure water-washed carbon. The results show a higher removal capacity for the microbe-immobilized activated carbon compared with the activated carbon control in a batch biofilter column. The increase in removal capacity is attributed to the role played by the immobilized microorganisms in metabolizing adsorbed sulfur and sulfur compounds on the biocarbon, hence releasing the adsorption sites for further H2S uptake. The advantage for activated carbon serving as the support medium is to adsorb a high initial concentration of substrate and progressively release this for microbial degradation, hence acting as a buffer for the microorganisms. Results obtained from surface area and pore size distribution analyses of the biocarbon show a correlation between the available surface area and pore volume with the extent of microbial immobilization and H2S uptake. The depletion of surface area and pore volume is seen as one of the factors which cause the onset of column breakthrough. Microbial growth retardation is due to the accumulation of metabolic products (i.e., sulfuric acid); and a lack of water and nutrient salts in the batch biofilter are other

  14. Unoccupied surface electronic structure of Gd(0001)

    International Nuclear Information System (INIS)

    Li, D.; Dowben, P.A.; Ortega, J.E.; Himpsel, F.J.

    1994-01-01

    The unoccupied surface electronic structure of Gd(0001) was investigated with high-resolution inverse-photoemission spectroscopy. An empty surface state near E F is observed at bar Γ. Two other surface-sensitive features are also revealed at 1.2 and 3.1 eV above the Fermi level. Hydrogen adsorption on Gd surfaces was used to distinguish the surface-sensitive features from the bulk features. The unoccupied bulk-band critical points are determined to be Γ 3 + at 1.9 eV and A 1 at 0.8 eV

  15. A novel layer-structured scaffold with large pore sizes suitable for 3D cell culture prepared by near-field electrospinning.

    Science.gov (United States)

    He, Feng-Li; Li, Da-Wei; He, Jin; Liu, Yang-Yang; Ahmad, Fiaz; Liu, Ya-Li; Deng, Xudong; Ye, Ya-Jing; Yin, Da-Chuan

    2018-05-01

    Electrospinning is a powerful method for preparing porous materials that can be applied as biomedical materials for implantation or tissue engineering or as scaffolds for 3D cell culture experiments. However, this technique is limited in practical applications because the pore size of 3D scaffolds directly prepared by conventional electrospinning is usually less than several tens of micrometres, which may not be suitable for 3D cell culture and tissue growth. To allow for satisfactory 3D cell culture and tissue engineering, the pore size of the scaffold should be controllable according to the requirement of the specific cells to be cultured. Here, we show that layer-structured scaffolds with pore sizes larger than 100μm can be obtained by stacking meshes prepared by direct-writing using the near-field electrospinning (NFES) technique. In the study, we prepared composite scaffolds made of polycaprolactone (PCL) and hydroxyapatite (HAp) via the above-mentioned method and tested the effectiveness of the novel scaffold in cell culture using mouse pre-osteoblast cells (MC3T3-E1). The pore size and the degradability of the PCL/HAp scaffolds were characterized. The results showed that the average pore size of the scaffolds was 167μm, which was controllable based on the required application; the degradation rate was controllable depending on the ratio of PCL to HAp. The biocompatibility of the scaffolds in vitro was studied, and it was found that the scaffolds showed no toxicity and that the cells could effectively attach, proliferate, and differentiate in the 3D skeleton of the scaffolds. Our studies showed that a simple modification of the preparation procedure can lead to a new way to fabricate novel layer-structured 3D scaffolds with controllable structures and pore sizes suitable for practical applications in implantation, tissue engineering and 3D cell culture. Copyright © 2017. Published by Elsevier B.V.

  16. Restricted primitive model for electrolyte solutions in slit-like pores with grafted chains: microscopic structure, thermodynamics of adsorption, and electric properties from a density functional approach.

    Science.gov (United States)

    Pizio, Orest; Sokołowski, Stefan

    2013-05-28

    We apply a density functional theory to describe properties of a restricted primitive model of an ionic fluid in slit-like pores. The pore walls are modified by grafted chains. The chains are built of uncharged or charged segments. We study the influence of modification of the pore walls on the structure, adsorption, ion selectivity, and the electric double layer capacitance of ionic fluid under confinement. The brush built of uncharged segments acts as a collection of obstacles in the walls vicinity. Consequently, separation of charges requires higher voltages, in comparison to the models without brushes. At high grafting densities the formation of crowding-type structure is inhibited. The double layer structure becomes more complex in various aspects, if the brushes are built of charged segments. In particular, the evolution of the brush height with the bulk fluid density and with the charge on the walls depends on the length of the blocks of charged spheres as well as on the distribution of charged species along chains. We also investigated how the dependence of the double layer capacitance on the electrostatic potential (or on the charge on the walls) changes with grafting density, the chain length, distribution of charges along the chain, the bulk fluid density, and, finally, with the pore width. The shape of the electric double layer capacitance vs. voltage changes from a camel-like to bell-like shape, if the bulk fluid density changes from low to moderate and high. If the bulk density is appropriately chosen, it is possible to alter the shape of this curve from the double hump to single hump by changing the grafting density. Moreover, in narrow pores one can observe the capacitance curve with even three humps for a certain set of parameters describing brush. This behavior illustrates how strong the influence of brushes on the electric double layer properties can be, particularly for ionic fluids in narrow pores.

  17. Characterization of the Pore Structure of Functionalized Calcium Carbonate Tablets by Terahertz Time-Domain Spectroscopy and X-Ray Computed Microtomography.

    Science.gov (United States)

    Markl, Daniel; Wang, Parry; Ridgway, Cathy; Karttunen, Anssi-Pekka; Chakraborty, Mousumi; Bawuah, Prince; Pääkkönen, Pertti; Gane, Patrick; Ketolainen, Jarkko; Peiponen, Kai-Erik; Zeitler, J Axel

    2017-06-01

    Novel excipients are entering the market to enhance the bioavailability of drug particles by having a high porosity and, thus, providing a rapid liquid uptake and disintegration to accelerate subsequent drug dissolution. One example of such a novel excipient is functionalized calcium carbonate, which enables the manufacture of compacts with a bimodal pore size distribution consisting of larger interparticle and fine intraparticle pores. Five sets of functionalized calcium carbonate tablets with a target porosity of 45%-65% were prepared in 5% steps and characterized using terahertz time-domain spectroscopy and X-ray computed microtomography. Terahertz time-domain spectroscopy was used to derive the porosity using effective medium approximations, that is, the traditional and an anisotropic Bruggeman model. The anisotropic Bruggeman model yields the better correlation with the nominal porosity (R 2  = 0.995) and it provided additional information about the shape and orientation of the pores within the powder compact. The spheroidal (ellipsoids of revolution) shaped pores have a preferred orientation perpendicular to the compaction direction causing an anisotropic behavior of the dielectric porous medium. The results from X-ray computed microtomography confirmed the nonspherical shape and the orientation of the pores, and it further revealed that the anisotropic behavior is mainly caused by the interparticle pores. The information from both techniques provides a detailed insight into the pore structure of pharmaceutical tablets. This is of great interest to study the impact of tablet microstructure on the disintegration and dissolution performance. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

  18. Effect of natural carbonation on the pore structure and elastic modulus of the alkali-activated fly ash and slag pastes

    NARCIS (Netherlands)

    Nedeljkovic, M.; Šavija, B.; Zuo, Y.; Lukovic, M.; Ye, G.

    2018-01-01

    The aim of this paper was to investigate the effect of natural carbonation on the pore structure, and elastic modulus (E-m) of alkali-activated fly ash (FA) and ground granulated blast furnace slag (GBFS) pastes after one year of exposure in the natural laboratory conditions. The chemical changes

  19. Effect of natural carbonation on the pore structure and elastic modulus of the alkali-activated fly ash and slag pastes

    NARCIS (Netherlands)

    Nedeljkovic, M.; Šavija, B.; Zuo, Y.; Lukovic, M.; Ye, G.

    2018-01-01

    The aim of this paper was to investigate the effect of natural carbonation on the pore structure, and elastic modulus (Em) of alkali-activated fly ash (FA) and ground granulated blast furnace slag (GBFS) pastes after one year of exposure in the natural laboratory conditions. The

  20. Sub-µ structured Lotus Surfaces Manufacturing

    DEFF Research Database (Denmark)

    Worgull, Matthias; Heckele, Mathias; Mappes, Timo

    2008-01-01

    Sub-micro structured surfaces allow modifying the behavior of polymer films or components. Especially in micro fluidics a lotus-like characteristic is requested for many applications. Structure details with a high aspect ratio are necessary to decouple the bottom and the top of the functional layer....... Unlike to stochastic methods, patternin¬g with a LIGA-mold insert it is possible to structure surfaces very uniformly or even with controlled variations (e.g. with gradients). In this paper we present the process chain to realize polymer sub-micro structures with minimum lateral feature size of 400 nm...

  1. Designing visual appearance using a structured surface

    DEFF Research Database (Denmark)

    Johansen, Villads Egede; Thamdrup, Lasse Højlund; Smitrup, Christian

    2015-01-01

    followed by numerical and experimental verification. The approach comprises verifying all design and fabrication steps required to produce a desired appearance. We expect that the procedure in the future will yield structurally colored surfaces with appealing prescribed visual appearances....

  2. Effect of pore structure on the seepage characteristics of tight sandstone reservoirs: A case study of Upper Jurassic Penglaizhen Fm reservoirs in the western Sichuan Basin

    Directory of Open Access Journals (Sweden)

    Liqiang Sima

    2017-01-01

    Full Text Available Tight sandstone reservoirs are characterized by complex pore structures and strong heterogeneity, and their seepage characteristics are much different from those of conventional sandstone reservoirs. In this paper, the tight sandstone reservoirs of Upper Jurassic Penglaizhen Fm in western Sichuan Basin were analyzed in terms of their pore structures by using the data about physical property, mercury injection and nuclear magnetic resonance (NMR tests. Then, the seepage characteristics and the gas–water two-phase migration mechanisms and distribution of tight sandstone reservoirs with different types of pore structures in the process of hydrocarbon accumulation and development were simulated by combining the relative permeability experiment with the visual microscopic displacement model. It is shown that crotch-like viscous fingering occurs in the process of gas front advancing in reservoirs with different pore structures. The better the pore structure is, the lower the irreducible water saturation is; the higher the gas-phase relative permeability of irreducible water is, the more easily the gas reservoir can be developed. At the late stage of development, the residual gas is sealed in reservoirs in the forms of bypass, cutoff and dead end. In various reservoirs, the interference between gas and water is stronger, so gas and water tends to be produced simultaneously. The sealed gas may reduce the production rate of gas wells significantly, and the existence of water phase may reduce the gas permeability greatly; consequently, the water-bearing low-permeability tight sandstone gas reservoirs reveal serious water production, highly-difficult development and low-recovery percentage at the late stage, which have adverse impacts on the effective production and development of gas wells.

  3. The structure of reconstructed chalcopyrite surfaces

    Science.gov (United States)

    Thinius, Sascha; Islam, Mazharul M.; Bredow, Thomas

    2018-03-01

    Chalcopyrite (CuFeS2) surfaces are of major interest for copper exploitation in aqueous solution, called leaching. Since leaching is a surface process knowledge of the surface structure, bonding pattern and oxidation states is important for improving the efficiency. At present such information is not available from experimental studies. Therefore a detailed computational study of chalcopyrite surfaces is performed. The structures of low-index stoichiometric chalcopyrite surfaces {hkl} h, k, l ∈ {0, 1, 2} have been studied with density functional theory (DFT) and global optimization strategies. We have applied ab initio molecular dynamics (MD) in combination with simulated annealing (SA) in order to explore possible reconstructions via a minima hopping (MH) algorithm. In almost all cases reconstruction involving substantial rearrangement has occurred accompanied by reduction of the surface energy. The analysis of the change in the coordination sphere and migration during reconstruction reveals that S-S dimers are formed on the surface. Further it was observed that metal atoms near the surface move toward the bulk forming metal alloys passivated by sulfur. The obtained surface energies of reconstructed surfaces are in the range of 0.53-0.95 J/m2.

  4. Structured nanoporous surfaces from hybrid block copolymer micelle films with metal ions.

    Science.gov (United States)

    Kim, Minsoo P; Kim, Hyeong Jun; Kim, Bumjoon J; Yi, Gi-Ra

    2015-03-06

    We present a novel method for producing structured nanoporous thin films using block copolymer (BCP) micelles loaded with metallic ions. The BCP micellar thin films containing gold (Au) ions were prepared by spin-coating poly(styrene-block-4-vinylpyridine) (PS-b-P4VP) micelle solutions in which Au precursors (AuCl4(-)) were selectively loaded onto the P4VP core. When the micellar films were exposed to cetyltrimethylammonium bromide (CTAB) solutions, the Au precursors were selectively extracted from the P4VP domains due to their strong electrostatic interaction with CTAB, leading to the formation of pores in the micelles. Consequently, regularly patterned nanoporous surfaces were formed. By controlling the molecular weight (Mn) of PS-b-P4VP and the amount of Au precursors (λ) that were loaded in the P4VP domains, the pore size and depth could be tuned precisely. In particular, when a sufficient amount of Au precursors was loaded (λ  ≥ 0.3), the porous surface nanostructure was well developed. In addition, the pore size and depth of the nanostructure increased as the λ value increased. For instance, when the λ value increased from 0.3 to 1.0, the pore size increased from 22.8 nm to 28.8 nm, and the pore depth increased from 2.1 nm to 3.2 nm. Interestingly, the transition from the nonporous structures to the porous structures in the micellar film could be reversibly controlled by adding and removing the Au precursors in the film. Moreover, our method for the preparation of nanoporous films can be extended to micellar film by incorporating other metal ions such as silver (Ag) and iron (Fe).

  5. Nano pores evolution in hydroxyapatite microsphere during spark plasma sintering

    Directory of Open Access Journals (Sweden)

    Lin C.

    2011-01-01

    Full Text Available Micron-spherical granules of hydroxyapatite (HAp nanoparticles were prepared by powder granulation methods. Through subsequent sintering, porous HAp microspheres with tailored pore and grain framework structures were obtained. Detailed microstructure investigation by SEM and TEM revealed the correlation of the pore structure and the necking strength with the sintering profiles that determine the coalescence features of the nanoparticles. The partially sintered porous HAp microspheres containing more than 50% porosity consisting of pores and grains both in nano-scale are active in inducing the precipitation of HAp in simulated body fluid. The nano-porous HAp microspheres with an extensive surface and interconnecting pores thus demonstrate the potential of stimulating the formation of collagen and bone and the integration with the newly formed bones during physiological bone remodeling.

  6. Applying a modified Donnan model to describe the surface complexation of chromate to iron oxyhydroxide agglomerates with heteromorphous pores.

    Science.gov (United States)

    Wei, Zongsu; Semiat, Raphael

    2017-11-15

    In this study, a modified Donnan model (mDM) is incorporated into surface complexation model (SCM) to better understand the physicochemical processes for adsorption of hexavalent chromium, Cr(VI), on porous iron oxyhydroxide agglomerates (IOAs). The mDM includes a chemical potential term μ att to account for ionic transport and electrostatic interaction in micropores (d mi 2nm) demonstrating high Cr(VI) adsorption in a broad range of ionic strengths. The batch data was then fitted with Donnan model in PHREEQC to obtain Stern (ψ S ) and Donnan (ψ D ) potentials used for μ att calculation. The decreasing μ att values with ionic strength indicated obstructing effect of electrolyte ions on Cr(VI) uptake in micropores. Finally, the ionic activity coefficients and reaction constants were corrected using Pitzer model due to the high level electrolytes accumulated in the Donnan layer through osmotic and electrostatic attraction. Results of this study have captured the effects of inner structure of IOAs on Cr(VI) uptake and quantitatively discerned the contribution of micropores and macropores for adsorption reactions at different ionic strengths. Copyright © 2017 Elsevier Inc. All rights reserved.

  7. Effect of variation of average pore size and specific surface area of ZnO electrode (WE) on efficiency of dye-sensitized solar cells.

    Science.gov (United States)

    Jadhav, Nitin A; Singh, Pramod K; Rhee, Hee Woo; Bhattacharya, Bhaskar

    2014-01-01

    Mesoporous ZnO nanoparticles have been synthesized with tremendous increase in specific surface area of up to 578 m(2)/g which was 5.54 m(2)/g in previous reports (J. Phys. Chem. C 113:14676-14680, 2009). Different mesoporous ZnO nanoparticles with average pore sizes ranging from 7.22 to 13.43 nm and specific surface area ranging from 50.41 to 578 m(2)/g were prepared through the sol-gel method via a simple evaporation-induced self-assembly process. The hydrolysis rate of zinc acetate was varied using different concentrations of sodium hydroxide. Morphology, crystallinity, porosity, and J-V characteristics of the materials have been studied using transmission electron microscopy (TEM), X-ray diffraction (XRD), BET nitrogen adsorption/desorption, and Keithley instruments.

  8. Effect of Pore Structure and Chemistry on the Performance of Activated Oil Sands Petroleum Coke Electrodes for use in Electrochemical Double-Layer Capacitors

    Science.gov (United States)

    Zuliani, Jocelyn Ellen

    (surface area, pore size, chemistry) were maintained constant. Through this systematic approach, this thesis investigates and quantifies the relationship between EDLC performance and important characteristic parameters through isolation of each individual parameter. By understanding the key structural and chemical features that improve EDLC performance, focus can be placed on engineering a sustainable and economic porous carbon material that has these desired features.

  9. Facile preparation of raisin-bread sandwich-structured magnetic graphene/mesoporous silica composites with C18-modified pore-walls for efficient enrichment of phthalates in environmental water.

    Science.gov (United States)

    Huang, Danni; Wang, Xianying; Deng, Chunhui; Song, Guoxin; Cheng, Hefa; Zhang, Xiangmin

    2014-01-17

    In this study, novel raisin-bread sandwich-structured magnetic graphene/mesoporous silica composites with C18-modified interior pore-walls (mag-graphene@mSiO2-C18) were synthesized by coating mesoporous silica layers onto each side of magnetic graphene through a surfactant-mediated co-condensation sol-gel process. The prepared functionalized nanocomposites possessed marvelous properties of extended plate-like morphology, fine water dispersibility, high magnetic response, large surface area (315.4cm(2)g(-1)), uniform pore size (3.3nm) and C18-modified interior pore-walls. Several kinds of phthalates were selected as model analytes to systematically evaluate the performance of adsorbents in extracting hydrophobic molecules followed by gas chromatography-mass spectrometry analyses. Various extraction parameters, including pH value of sample solution, amounts of adsorbents, adsorption time, species and volume of eluting solvent, and desorption time were optimized. The anti-interference ability to macromolecular proteins was also investigated. Method validations such as linearity, recovery, reproducibility, and limit of detection were also studied. Finally, mag-graphene@mSiO2-C18 composites were successfully applied to analyzing phthalates in environmental water samples. The results indicated that this novel approach offered an attractive alternative for rapid, convenient, efficient and selective magnetic solid-phase extraction for targeted hydrophobic compounds. Copyright © 2013 Elsevier B.V. All rights reserved.

  10. Projective and superconformal structures on surfaces

    International Nuclear Information System (INIS)

    Harvey, W.J.

    1990-01-01

    Much attention has recently been given to the study of super Riemann surfaces. Detailed accounts of these objects and their infinitesimal deformation theory are referenced where they are fitted into the framework of complex supermanifolds, superconformal structures and graded sheaves. One difficulty, which seems even more of a barrier than in the case of classical deformations of Riemann surface structure, is the lack of a good global description of super-moduli spaces. In this note, we outline an approach which places the theory in the classical setting of projective structures on variable Riemann surfaces. We explain how to construct a distribution (family of vector subspaces) inside the holomorphic cotangent space to the moduli space M g of Riemann surfaces with genus g and furnished with a level-4 homology structure, such that the corresponding rank-(2g-2) complex vector bundle models the soul deformations of a family of super-Riemann surfaces. The keystone in this construction is the existence of holomorphic sections for the space of non-singular odd theta characteristics on C g the universal curve over M g . (author)

  11. Surface band structures on Nb(001)

    International Nuclear Information System (INIS)

    Fang, B.; Lo, W.; Chien, T.; Leung, T.C.; Lue, C.Y.; Chan, C.T.; Ho, K.M.

    1994-01-01

    We report the joint studies of experimental and theoretical surface band structures of Nb(001). Angle-resolved photoelectron spectroscopy was used to determine surface-state dispersions along three high-symmetry axes bar Γ bar M, bar Γ bar X, and bar M bar X in the surface Brillouin zone. Ten surface bands have been identified. The experimental data are compared to self-consistent pseudopotential calculations for the 11-layer Nb(001) slabs that are either bulk terminated or fully relaxed (with a 12% contraction for the first interlayer spacing). The band calculations for a 12% surface-contracted slab are in better agreement with the experimental results than those for a bulk-terminated slab, except for a surface resonance near the Fermi level, which is related to the spin-orbit interaction. The charge profiles for all surface states or resonances have been calculated. Surface contraction effects on the charge-density distribution and the energy position of surface states and resonances will also be discussed

  12. Surface modification of nanoporous alumina layers by deposition of Ag nanoparticles. Effect of alumina pore diameter on the morphology of silver deposit and its influence on SERS activity

    Energy Technology Data Exchange (ETDEWEB)

    Pisarek, Marcin, E-mail: mpisarek@ichf.edu.pl [Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, Warsaw, 01-224 (Poland); Nowakowski, Robert [Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, Warsaw, 01-224 (Poland); Kudelski, Andrzej [Faculty of Chemistry, University of Warsaw, Pasteur 1, Warsaw, 02-093 (Poland); Holdynski, Marcin; Roguska, Agata; Janik-Czachor, Maria [Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, Warsaw, 01-224 (Poland); Kurowska-Tabor, Elżbieta; Sulka, Grzegorz D. [Department of Physical Chemistry and Electrochemistry, Jagiellonian University, Ingardena 3, Cracow, 30-060 (Poland)

    2015-12-01

    Graphical abstract: - Highlights: • Magnetron sputtering of Ag is a suitable method of producing a SERS-active substrate. • Morphology of nanoporous substrate is crucial in the resulting of SERS activity. • Free Ag-NPs act as surface nanoresonators for pyridine molecules. - Abstract: Self-organized Al{sub 2}O{sub 3} nanoporous/nanotubular (Al{sub 2}O{sub 3}-NP) oxide layers decorated with silver nanoparticles (Ag-NPs) exhibiting specific properties may serve as attractive SERS substrates for investigating the interactions between an adsorbate and adsorbent, or as stable platforms for detecting various organic compounds. This article presents the influence of the size of the alumina nanopores with a deposit of silver nanoparticles obtained by the magnetron sputtering technique on the morphology of silver film. Moreover, the effect of pore diameter on the intensity of SERS spectra in Ag-NPs/Al{sub 2}O{sub 3}-NP/Al composites has also been estimated. For such investigations we used pyridine as a probe molecule, since it has a large cross-section for Raman scattering. To characterize the morphology of the composite oxide layer Ag-NPs/Al{sub 2}O{sub 3}-NP/Al, before and after deposition of Ag-NPs by PVD methods (Physical Vapor Deposition), we used scanning electron microscopy (SEM) and atomic force microscopy (AFM). The surface analytical technique of surface-enhanced Raman spectroscopy (SERS) was used to investigate the surface activity of the composite. The results obtained show that, for a carefully controlled amount of Ag (0.020 mg/cm{sup 2} - deposited on the top of alumina nanopores whose average size varies from ∼86 nm up to ∼320 nm) in the composites investigated, pore size significantly affects SERS enhancement. We obtained distinctly higher intensities of SERS spectra for substrates with an Ag-NPs deposit having a larger diameter of the alumina nanopores. AFM results suggest that both the lateral and perpendicular distribution of Ag-NPs within and on

  13. Use of activated carbon as a support medium for H{sub 2}S biofiltration and effect of bacterial immobilization on available pore surface

    Energy Technology Data Exchange (ETDEWEB)

    Ng, Y.L.; Yan, R.; Chen, X.G.; Geng, A.L.; Liang, D.T.; Koe, L.C.C. [Institute of Environmental Science and Engineering, Nanyang Technological Univ., Singapore (Singapore); Gould, W.D. [Environmental Lab., CANMET, Natural Resources Canada, Ottawa, ON (Canada)

    2004-12-01

    The use of support media for the immobilization of micro-organisms widely known to provide a surface for microbial growth and a shelter that protects the microorganisms from inhibitory compounds. In this study, activated carbon is used as a support medium for the immobilization of microorganisms enriched from municipal sewage activated sludge to remove gas-phase hydrogen sulfide (H{sub 2}S), a major odorous component of waste gas from sewage treatment plants. A series of designed experiments is used to examine the effect on bacteria-immobilized activated carbon (termed ''biocarbon'') due to physical adsorption, chemical reaction and microbial degradation in the overall removal of H{sub 2}S. H{sub 2}S breakthrough tests are conducted with various samples, including micro-immobilized carbon and Teflon discs, salts-medium-washed carbon, and ultra-pure water-washed carbon. The results show a higher removal capacity for the microbe-immobilized activated carbon compared with the activated carbon control in a batch biofilter column. The increase in removal capacity is attributed to the role played by the immobilized micro-organisms in metabolizing adsorbed sulfur and sulfur compounds on the biocarbon, hence releasing the adsorption sites for further H{sub 2}S uptake. The advantage for activated carbon serving as the support medium is to adsorb a high initial concentration of substrate and progressively release this for microbial degradation, hence acting as a buffer for the microorganisms. Results obtained from surface area and pore size distribution analyses of the biocarbon show a correlation between the available surface area and pore volume with the extent of microbial immobilization and H{sub 2}S uptake. The depletion of surface area and pore volume is seen as one of the factors which cause the onset of column breakthrough. Microbial growth retardation is due to the accumulation of metabolic products (i.e., sulfuric acid); and a lack of water and

  14. Influence of pore structure and architecture of photo-grafted functional layers on separation performance of cellulose-based macroporous membrane adsorbers.

    Science.gov (United States)

    Wang, Jun; Faber, Rene; Ulbricht, Mathias

    2009-09-11

    New weak cation-exchange membrane adsorbers were prepared via UV-initiated heterogeneous graft copolymerization on Hydrosart macroporous regenerated cellulose membranes. The dynamic performance was investigated in detail with respect to the pore size and pore size distribution of the base membranes, ion-exchange capacity and architecture of the grafted functional layers as well as binding of target proteins. Main characterization methods were pore analysis (BET and permporometry), titration, analysis of protein binding under static conditions including visualization by confocal laser scanning microscopy and chromatographic analysis of dynamic protein binding and system dispersion. The trade-off between static binding capacity of the membrane adsorber and its permeability has partially been overcome by adapted architecture of the grafted functional layer achieved via the introduction of uncharged moieties as spacers and via stabilization of the binding layer by chemical cross-linking. The resulting membranes show only negligible effects of flow rate on dynamic binding capacity. There is no considerable size exclusion effect for large proteins due to mesh size of functional cross-linked layers. Investigation of system dispersion based on breakthrough curves confirms that the adapted grafted layer architecture has drastically reduced the contribution of the membrane to total system dispersion. The optimum pore structure of base membranes in combination with the best suited architecture of functional layers was identified in this study.

  15. Description and reconstruction of the soil pore space using correlation functions

    Science.gov (United States)

    Gerke, K. M.; Karsanina, M. V.; Skvortsova, E. B.

    2012-09-01

    In this paper a method for the description and reconstruction of the soil pore space using correlation functions has been examined. The reconstruction procedure employed here is the best way of verification of the potential descriptor of the soil pore space. Thin sections representing eight major types of pore space in zonal loamy soils and parent materials of the Russian Plain with pores of different shapes and orientations have been chosen for this study. Comparison based on the morphological analysis of the original pore space images and their correlation function reconstructions obtained using simulated annealing technique indicates that this method of reconstruction adequately describes the isometric soil pore space with isometric dissected, isometric slightly dissected, and rounded pores. The two-point correlation functions calculated with the use of the orthogonal method proved to be different for the examined types of soil pore space; they reflect the soil porosity, specific surface, and pore structure correlations at different lengths. The results of this study allow us to conclude that the description of the soil pore space with the help of correlation functions is a promising approach, but requires more development. Further directions of the development of this method for describing the soil pore space and determining the soil physical processes are outlined.

  16. Surface and mineral structure of ferrihydrite

    NARCIS (Netherlands)

    Hiemstra, T.

    2013-01-01

    Ferrihydrite (Fh) is an yet enigmatic nano Fe(III)-oxide material, omnipresent in nature that can bind ions in large quantities, regulating bioavailability and ion mobility. Although extensively studied, to date no proper view exists on the surface structure and composition, while it is of vital

  17. Melamine structures on the Au(111) surface

    NARCIS (Netherlands)

    Silly, Fabien; Shaw, Adam Q.; Castell, Martin R.; Briggs, G. A. D.; Mura, Manuela; Martsinovich, Natalia; Kantorovich, Lev

    2008-01-01

    We report on a joint experimental and theoretical study of the ordered structures of melamine molecules formed on the Au(111)-(22 x root 3) surface. Scanning tunneling microscopy (STM) images taken under UHV conditions reveal two distinct monolayers one of which has never been reported before on

  18. Single crystal surface structure by bragg scattering

    DEFF Research Database (Denmark)

    Nielsen, Mogens

    1985-01-01

    X-ray diffraction is becoming an important tool in the measurements of surface structures. Single crystalline samples are used as in Low Energy Electron Diffraction (LEED)-studies. The X-ray technique is somewhat more involved due to the need of bright, collimated photon sources, in general...

  19. Surface characterisation and photocatalytic performance of N-doped TiO2 thin films deposited onto 200 nm pore size alumina membranes by sol–gel methods

    International Nuclear Information System (INIS)

    Grilli, R.; Di Camillo, D.; Lozzi, L.; Horovitz, I.; Mamane, H.; Avisar, D.; Baker, M.A.

    2015-01-01

    Membrane filtration is employed for water treatment and wastewater reclamation purposes, but membranes alone are unable to remove pollutant molecules and certain pathogens. Photocatalytically active N-doped TiO 2 coatings have been deposited by sol–gel onto 200 nm pore size alumina membranes for water treatment applications using two different methods, via pipette droplets or spiral bar applicator. The uncoated and coated membranes were characterised by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive X-ray spectrometry (EDX). Both coatings showed the presence of N-doped anatase, with a surface coverage between 84 and 92%, and nitrogen concentration (predominantly interstitial) of 0.9 at.%. The spiral bar applicator deposited coatings exhibit a thicker mud-cracked surface layer with limited penetration of the porous membrane, whilst the pipette deposited coatings have mostly penetrated into the bulk of the membrane and a thinner layer is present at the surface. The photocatalytic activity (PCA), measured through the degradation of carbamazepine (CBZ), under irradiation of a solar simulator was 58.6% for the pipette coating and 63.3% for the spiral bar coating. These photocatalytically active N-doped sol–gel coated membranes offer strong potential in forming the fundamental basis of a sunlight based water treatment system. - Highlights: • Sol gel N-doped TiO 2 thin films were deposited on 200 nm pore size Al 2 O 3 membranes. • Two sol–gel methods have been compared – pipette drop and spiral bar deposition. • The coatings showed a similar microstructure and composition but different morphology. • The PCA (degradation of carbamazepine) was ∼60% for both sol–gel coatings. • The coated membranes are promising for use in a membrane based water treatment system

  20. The interior structure of Ceres as revealed by surface topography

    Science.gov (United States)

    Fu, Roger R.; Ermakov, Anton; Marchi, Simone; Castillo-Rogez, Julie C.; Raymond, Carol A.; Hager, Bradford; Zuber, Maria; King, Scott D.; Bland, Michael T.; De Sanctis, Maria Cristina; Preusker, Frank; Park, Ryan S.; Russell, Christopher T.

    2017-01-01

    Ceres, the largest body in the asteroid belt (940 km diameter), provides a unique opportunity to study the interior structure of a volatile-rich dwarf planet. Variations in a planetary body's subsurface rheology and density affect the rate of topographic relaxation. Preferential attenuation of long wavelength topography (≥150 km) on Ceres suggests that the viscosity of its crust decreases with increasing depth. We present finite element (FE) geodynamical simulations of Ceres to identify the internal structures and compositions that best reproduce its topography as observed by the NASA Dawn mission. We infer that Ceres has a mechanically strong crust with maximum effective viscosity ∼1025 Pa s. Combined with density constraints, this rheology suggests a crustal composition of carbonates or phyllosilicates, water ice, and at least 30 volume percent (vol.%) low-density, high-strength phases most consistent with salt and/or clathrate hydrates. The inference of these crustal materials supports the past existence of a global ocean, consistent with the observed surface composition. Meanwhile, we infer that the uppermost ≥60 km of the silicate-rich mantle is mechanically weak with viscosity <1021 Pa s, suggesting the presence of liquid pore fluids in this region and a low temperature history that avoided igneous differentiation due to late accretion or efficient heat loss through hydrothermal processes.

  1. Ion and water transport in a Nafion{reg_sign} membrane pore: A statistical mechanical model with molecular structure

    Energy Technology Data Exchange (ETDEWEB)

    Paddison, S.J.; Zawodzinski, T.A. Jr. [Los Alamos National Lab., NM (United States). Electronic and Electrochemical Materials and Devices Group; Paul, R. [Univ. of Calgary, Alberta (Canada). Dept. of Chemistry

    1998-12-31

    With the well established importance of the coupling of water and protons through electroosmotic drag in operating PEFCs the authors present here a derivation of a mathematical model that focuses on the computation of the mobility of an hydronium ion through an arbitrary cylindrical pore of a PEM with a non-uniform charge distribution on the walls of the pore. The total Hamiltonian is derived for the hydronium ion as it moves through the hydrated pore and is effected by the net potential due to interaction with the solvent molecules and the pendant side chains. The corresponding probability density is derived through solution of the Liouville equation. This probability density is then used to compute the friction tensor for the hydronium ion. The authors find two types of contributions: (a) due to the solvent-ion interactions for which they adopt the conventional continuum model; (b) due to the interaction between the pendant charges and the hydronium ion. The latter is a new result and displays the role of the non-uniform nature of the charge distribution on the pore wall.

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

    Science.gov (United States)

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

    2017-12-01

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

  3. 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.

  4. Surface structure of oriented PET films

    CERN Document Server

    Kirov, K

    2001-01-01

    crystallinity and the level of molecular orientation of the polymer are highest at the film surface and gradually decrease away from it. The same trend for an increase in structural order nearer the film surface was observed in a series of PET films drawn uniaxially in laboratory conditions. The observed strong dependence of stratification in the oriented films on drawing ratio, lead to the conclusion, that the structural gradients arise as a result of viscous flow. The molecular mechanism of stratification is discussed and leads to the idea of enhanced chain mobility at the PET film surface. The idea is in line with recent studies showing a depression of the glass transition temperature of free polymer surfaces. In addition, the results on structure formation in PET films during drawing, give support to the existing view that polymer crystallisation is assisted by a spinodal-decomposition nucleation process. Polymer films are widely used as substrates in nano-composite materials and therefore have to possess...

  5. Engineering a Zirconium MOF through Tandem "Click" Reactions: A General Strategy for Quantitative Loading of Bifunctional Groups on the Pore Surface.

    Science.gov (United States)

    Zhang, Yingfan; Gui, Bo; Chen, Rufan; Hu, Guiping; Meng, Yi; Yuan, Daqiang; Zeller, Matthias; Wang, Cheng

    2018-02-19

    Metal-organic frameworks (MOFs) assembled from linkers of identical length but with different functional groups have gained increasing interests recently. However, it is very challenging for precise control of the ratios of different functionalities. Herein, we reported a stable azide- and alkyne-appended Zr-MOF that can undergo quantitative tandem click reactions on the different functional sites, thus providing a unique platform for quantitative loading of bifunctional moieties. As an added advantage, the same MOF product can be obtained via two independent routes. The method is versatile and can tolerate a wide variety of functional groups, and furthermore, a heterogeneous acid-base MOF organocatalyst was synthesized by tandemly introducing both acidic and basic groups onto the predesigned pore surface. The presented strategy provides a general way toward the construction of bifunctional MOFs with a precise control of ratio of different functionalities for desirable applications in future.

  6. Structurally tuned iridescent surfaces inspired by nature

    International Nuclear Information System (INIS)

    Deparis, Olivier; Rassart, Marie; Vandenbem, Cedric; Welch, Victoria; Vigneron, Jean Pol; Lucas, Stephane

    2008-01-01

    Iridescent surfaces exhibit vivid colours which change with the angle of incidence or viewing due to optical wave interference in the multilayer structure present at the wavelength scale underneath the surface. In nature, one can find examples of iridescent Coleoptera for which the hue changes either greatly or slightly with the angle. Because these species typically make these structures from a single biological material (usually chitin) and air or water as the low refractive index component, they have evolved by adjusting the layer thicknesses in order to display quite different iridescent aspects. Taking inspiration from this proven strategy, we have designed and fabricated periodic TiO 2 /SiO 2 multilayer films in order to demonstrate the concept of structurally tuned iridescent surfaces. Titanium or silicon oxide layers were deposited on a glass substrate using dc reactive or RF magnetron sputtering techniques, respectively. Two structures were designed for which the period and the TiO 2 /SiO 2 layer thickness ratio were varied in such a way that the films displayed radically different iridescent aspects: a reddish-to-greenish changing hue and a stable bluish hue. The fabricated samples were characterized through specular reflectance/transmittance measurements. Modelling of transmittance spectra using standard multilayer film theory confirmed the high quality of the twelve-period Bragg reflectors. The chromaticity coordinates, which were calculated from measured reflectance spectra taken at different angles, were in accordance with theoretical predictions

  7. Deconstructing three-dimensional (3D) structure of absorptive glass mat (AGM) separator to tailor pore dimensions and amplify electrolyte uptake

    Science.gov (United States)

    Rawal, Amit; Rao, P. V. Kameswara; Kumar, Vijay

    2018-04-01

    Absorptive glass mat (AGM) separator is a vital technical component in valve regulated lead acid (VRLA) batteries that can be tailored for a desired application. To selectively design and tailor the AGM separator, the intricate three-dimensional (3D) structure needs to be unraveled. Herein, a toolkit of 3D analytical models of pore size distribution and electrolyte uptake expressed via wicking characteristics of AGM separators under unconfined and confined states is presented. 3D data of fiber orientation distributions obtained previously through X-ray micro-computed tomography (microCT) analysis are used as key set of input parameters. The predictive ability of pore size distribution model is assessed through the commonly used experimental set-up that usually apply high level of compressive stresses. Further, the existing analytical model of wicking characteristics of AGM separators has been extended to account for 3D characteristics, and subsequently, compared with the experimental results. A good agreement between the theory and experiments pave the way to simulate the realistic charge-discharge modes of the battery by applying cyclic loading condition. A threshold criterion describing the invariant behavior of pore size and wicking characteristics in terms of maximum permissible limit of key structural parameters during charge-discharge mode of the battery has also been proposed.

  8. The dependence of phase change enthalpy on the pore structure and interfacial groups in hydrated salts/silica composites via sol-gel.

    Science.gov (United States)

    Wu, Yuping; Wang, Tao

    2015-06-15

    It was found that the procedures for incorporating hydrated salts into silica, including mixing with sol in an instant (S1 procedure), mixing with sol via drop by drop (S2 procedure) and mixing until the sol forming the gel (S3 procedure), had pronounced effects on the phase change enthalpy of hydrated salts/silica composite via sol-gel process. The discrepancy of phase change enthalpies of the composites with the same content of hydrated salts can be as high as 40 kJ/kg. To unveil the mechanism behind, the pore structure of silica matrix and interfacial functional groups were investigated extensively. It was revealed that different incorporation procedures resulted in distinct pore structure of silica matrix and different intensities of interfacial Si-OH groups. The S3 procedure was beneficial to induce the silica matrix with bigger pore size and fewer Si-OH groups. Consequently, the phase change enthalpy of the hydrated salts/silica composite prepared by this procedure was the highest because of its lower size confinement effects and weaker adsorption by Si-OH groups. This study will provide insight into the preparation of shape-stabilized phase change materials for thermal energy storage applications. Copyright © 2015 Elsevier Inc. All rights reserved.

  9. A structural, functional, and computational analysis suggests pore flexibility as the base for the poor selectivity of CNG channels.

    Science.gov (United States)

    Napolitano, Luisa Maria Rosaria; Bisha, Ina; De March, Matteo; Marchesi, Arin; Arcangeletti, Manuel; Demitri, Nicola; Mazzolini, Monica; Rodriguez, Alex; Magistrato, Alessandra; Onesti, Silvia; Laio, Alessandro; Torre, Vincent

    2015-07-07

    Cyclic nucleotide-gated (CNG) ion channels, despite a significant homology with the highly selective K(+) channels, do not discriminate among monovalent alkali cations and are permeable also to several organic cations. We combined electrophysiology, molecular dynamics (MD) simulations, and X-ray crystallography to demonstrate that the pore of CNG channels is highly flexible. When a CNG mimic is crystallized in the presence of a variety of monovalent cations, including Na(+), Cs(+), and dimethylammonium (DMA(+)), the side chain of Glu66 in the selectivity filter shows multiple conformations and the diameter of the pore changes significantly. MD simulations indicate that Glu66 and the prolines in the outer vestibule undergo large fluctuations, which are modulated by the ionic species and the voltage. This flexibility underlies the coupling between gating and permeation and the poor ionic selectivity of CNG channels.

  10. 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

  11. The influence of the pore structure on the moisture transport in lime plaster-brick systems as studied by NMR

    Czech Academy of Sciences Publication Activity Database

    Nunes, Cristiana Lara; Pel, L.; Kunecký, Jiří; Slížková, Zuzana

    2017-01-01

    Roč. 142, July (2017), s. 395-409 ISSN 0950-0618 R&D Projects: GA MŠk(CZ) LO1219 Keywords : drying * moisture transport * NMR * pore water distribution * plaster * brick * lime * metakaolin * water-repellent * linseed oil Subject RIV: AL - Art, Architecture, Cultural Heritage OBOR OECD: Materials engineering Impact factor: 3.169, year: 2016 http://www.sciencedirect.com/science/article/pii/S0950061817304543

  12. Structure Interlacing and Pore Engineering of Zn2GeO4 Nanofibers for Achieving High Capacity and Rate Capability as an Anode Material of Lithium Ion Batteries.

    Science.gov (United States)

    Wang, Wei; Qin, Jinwen; Cao, Minhua

    2016-01-20

    An interlaced Zn2GeO4 nanofiber network with continuous and interpenetrated mesoporous structure was prepared using a facile electrospinning method followed by a thermal treatment. The mesoporous structure in Zn2GeO4 nanofibers is directly in situ constructed by the decomposition of polyvinylpyrolidone (PVP), while the interlaced nanofiber network is achieved by the mutual fusion of the junctions between nanofibers in higher calcination temperatures. When used as an anode material in lithium ion batteries (LIBs), it exhibits superior lithium storage performance in terms of specific capacity, cycling stability, and rate capability. The pore engineering and the interlaced network structure are believed to be responsible for the excellent lithium storage performance. The pore structure allows for easy diffusion of electrolyte, shortens the pathway of Li(+) transport, and alleviates large volume variation during repeated Li(+) extraction/insertion. Moreover, the interlaced network structure can provide continuous electron/ion pathways and effectively accommodate the strain induced by the volume change during the electrochemical reaction, thus maintaining structural stability and mechanical integrity of electrode materials during lithiation/delithiation process. This strategy in current work offers a new perspective in designing high-performance electrodes for LIBs.

  13. 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

  14. Bacterial attachment and biofilm formation on surfaces are reduced by small-diameter nanoscale pores: how small is small enough?

    OpenAIRE

    Feng, Guoping; Cheng, Yifan; Wang, Shu-Yi; Borca-Tasciuc, Diana A; Worobo, Randy W; Moraru, Carmen I

    2015-01-01

    Background/Objectives: Prevention of biofilm formation by bacteria is of critical importance to areas that directly affect human health and life including medicine, dentistry, food processing and water treatment. This work showcases an effective and affordable solution for reducing attachment and biofilm formation by several pathogenic bacteria commonly associated with foodborne illnesses and medical infections. Methods: Our approach exploits anodisation to create alumina surfaces with cylind...

  15. Fabrication of Nano-Micro Hybrid Structures by Replication and Surface Treatment of Nanowires

    Directory of Open Access Journals (Sweden)

    Yeonho Jeong

    2017-07-01

    Full Text Available Nanowire structures have attracted attention in various fields, since new characteristics could be acquired in minute regions. Especially, Anodic Aluminum Oxide (AAO is widely used in the fabrication of nanostructures, which has many nanosized pores and well-organized nano pattern. Using AAO as a template for replication, nanowires with a very high aspect ratio can be fabricated. Herein, we propose a facile method to fabricate a nano-micro hybrid structure using nanowires replicated from AAO, and surface treatment. A polymer resin was coated between Polyethylene terephthalate (PET and the AAO filter, roller pressed, and UV-cured. After the removal of aluminum by using NaOH solution, the nanowires aggregated to form a micropattern. The resulting structure was subjected to various surface treatments to investigate the surface behavior and wettability. As opposed to reported data, UV-ozone treatment can enhance surface hydrophobicity because the UV energy affects the nanowire surface, thus altering the shape of the aggregated nanowires. The hydrophobicity of the surface could be further improved by octadecyltrichlorosilane (OTS coating immediately after UV-ozone treatment. We thus demonstrated that the nano-micro hybrid structure could be formed in the middle of nanowire replication, and then, the shape and surface characteristics could be controlled by surface treatment.

  16. Multifractal Characterization of Soil Pore Shapes

    Science.gov (United States)

    Gimenez, Daniel; Posadas, Adolfo; Cooper, Miguel

    2010-05-01

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

  17. Nanoscale surface topographies for structural colors

    DEFF Research Database (Denmark)

    Clausen, Jeppe Sandvik

    The thesis describes and demonstrates the possibilities for utilization of structural colors in mass fabricated plastic products as replacement for or in combination with pigments and inks. The motivation is the possible advantages related to re-cycling and re-use of plastic by limiting the number......-polymer interface is suppressed. This improves the ability to see through a clear plastic in the presence of specular reflection. The tapered nanostructures are also utilized to enhance the chroma of pigmented polymers. Larger tapered structures fabricated in a similar manor are shown to work as color filters....... Through an experimental study is the color of the transmitted light linked directly to the random topography of the surface by use of diffraction theory. The color effects from periodic structures and how these might be employed to create bright colors are investigated. This is done both for opaque...

  18. Influence of Sintering Temperature on Pore Structure and Electrical properties of Technologically Modified MgO-Al2O3 Ceramics

    Directory of Open Access Journals (Sweden)

    Halyna Klym

    2015-03-01

    Full Text Available Technologically modified spinel ceramics are prepared from Al2O3 and 4MgCO3×Mg(OH2×5H2O powders at 1200, 1300 and 1400 oC. The influence of sintering temperature on porous structure and exploitation properties of obtained humidity-sensitive MgO-Al2O3 ceramics are studied. It is shown that increasing of preparing temperature from 1200 to 1400 oC result in transformation of pore size distribution in ceramics from tri- to bi-modal including the open macro- and mesopores with sizes from tem to hundreds nm and nanopores until to a few nm. The studied ceramic elements with electrical resistances ~ 10-2-102 MОhm are high humidity sensitive in the region of 30-95 % with minimal hysteresis in adsorption-desorption cycles. It is established that increasing of humidity sensitivity in ceramics are related to achievement near to optimum pore size distribution and quantity of pores in the all regions. Prolonged degradation transformation in ceramics at higher temperature and relative humidity result in lose sensitivity up to 40-50 %.DOI: http://dx.doi.org/10.5755/j01.ms.21.1.5189

  19. Influence of porosity and pore shape on structural, mechanical and biological properties of poly ϵ-caprolactone electro-spun fibrous scaffolds.

    Science.gov (United States)

    Fuller, Kieran P; Gaspar, Diana; Delgado, Luis M; Pandit, Abhay; Zeugolis, Dimitrios I

    2016-05-01

    Electro-spun scaffolds are utilized in a diverse spectrum of clinical targets, with an ever-increasing quantity of work progressing to clinical studies and commercialization. The limited number of conformations in which the scaffolds can be fabricated hampers their wide acceptance in clinical practice. Herein, we assessed a single-strep fabrication process for predesigned electro-spun scaffold preparation and the ramifications of the introduction of porosity (0, 30, 50, 70%) and pore shape (circle, rhomboid, square) on structural, mechanical (tensile and ball burst) and biological (dermal fibroblast and THP-1) properties. The collector design did not affect the fibrous nature of the scaffold. Modulation of the porosity and pore shape offered control over the mechanical properties of the scaffolds. Neither the porosity nor the pore shape affected cellular (dermal fibroblast and THP-1) response. Overall, herein we provide evidence that electro-spun scaffolds of controlled architecture can be fabricated with fibrous fidelity, adequate mechanical properties and acceptable cytocompatibility for a diverse range of clinical targets.

  20. 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.

  1. Architectural Surfaces and Structures from Circular Arcs

    KAUST Repository

    Shi, Ling

    2013-12-01

    In recent decades, the popularity of freeform shapes in contemporary architecture poses new challenges to digital design. One of them is the process of rationalization, i.e. to make freeform skins or structures affordable to manufacture, which draws the most attention from geometry researchers. In this thesis, we aim to realize this process with simple geometric primitives, circular arcs. We investigate architectural surfaces and structures consisting of circular arcs. Our focus is lying on how to employ them nicely and repetitively in architectural design, in order to decrease the cost in manufacturing. Firstly, we study Darboux cyclides, which are algebraic surfaces of order ≤ 4. We provide a computational tool to identify all families of circles on a given cyclide based on the spherical model of M ̈obius geometry. Practical ways to design cyclide patches that pass through certain inputs are presented. In particular, certain triples of circle families on Darboux cyclides may be suitably arranged as 3-webs. We provide a complete classification of all possible 3-webs of circles on Darboux cyclides. We then investigate the circular arc snakes, which are smooth sequences of circu- lar arcs. We evolve the snakes such that their curvature, as a function of arc length, remains unchanged. The evolution of snakes is utilized to approximate given surfaces by circular arcs or to generated freeform shapes, and it is realized by a 2-step pro- cess. More interestingly, certain 6-arc snake with boundary constraints can produce a smooth self motion, which can be employed to build flexible structures. Another challenging topic is approximating smooth freeform skins with simple panels. We contribute to this problem area by approximating a negatively-curved 5 surface with a smooth union of rational bilinear patches. We provide a proof for vertex consistency of hyperbolic nets using the CAGD approach of the rational B ́ezier form. Moreover, we use Darboux transformations for the

  2. Bioinspired, dynamic, structured surfaces for biofilm prevention

    Science.gov (United States)

    Epstein, Alexander K.

    Bacteria primarily exist in robust, surface-associated communities known as biofilms, ubiquitous in both natural and anthropogenic environments. Mature biofilms resist a wide range of biocidal treatments and pose persistent pathogenic threats. Treatment of adherent biofilm is difficult, costly, and, in medical systems such as catheters, frequently impossible. Adding to the challenge, we have discovered that biofilm can be both impenetrable to vapors and extremely nonwetting, repelling even low surface tension commercial antimicrobials. Our study shows multiple contributing factors, including biochemical components and multiscale reentrant topography. Reliant on surface chemistry, conventional strategies for preventing biofilm only transiently affect attachment and/or are environmentally toxic. In this work, we look to Nature's antifouling solutions, such as the dynamic spiny skin of the echinoderm, and we develop a versatile surface nanofabrication platform. Our benchtop approach unites soft lithography, electrodeposition, mold deformation, and material selection to enable many degrees of freedom—material, geometric, mechanical, dynamic—that can be programmed starting from a single master structure. The mechanical properties of the bio-inspired nanostructures, verified by AFM, are precisely and rationally tunable. We examine how synthetic dynamic nanostructured surfaces control the attachment of pathogenic biofilms. The parameters governing long-range patterning of bacteria on high-aspect-ratio (HAR) nanoarrays are combinatorially elucidated, and we discover that sufficiently low effective stiffness of these HAR arrays mechanoselectively inhibits ˜40% of Pseudomonas aeruginosa biofilm attachment. Inspired by the active echinoderm skin, we design and fabricate externally actuated dynamic elastomer surfaces with active surface microtopography. We extract from a large parameter space the critical topographic length scales and actuation time scales for achieving

  3. Enhancement of cell growth on honeycomb-structured polylactide surface using atmospheric-pressure plasma jet modification

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, Kuang-Yao; Chang, Chia-Hsing; Yang, Yi-Wei; Liao, Guo-Chun; Liu, Chih-Tung; Wu, Jong-Shinn, E-mail: chongsin@faculty.nctu.edu.tw

    2017-02-01

    Graphical abstract: Atmospheric-pressure plasma enhances cell growth on two different pore sizes of honeycomb pattern on polylactide surface. - Highlights: • Different pore sizes of honeycomb pattern on PLA film are created. • The two-step plasma treatment provided the oxygen- and nitrogen-containing functional groups that had a major impact on cell cultivation. • The plasma treatment had a significant effect for cell proliferation. • The surface structures are the main influence on cell cultivation, while plasma treatment can indeed improve the growth environment. - Abstract: In this paper, we compare the cell growth results of NIH-3T3 and Neuro-2A cells over 72 h on flat and honeycomb structured PLA films without and with a two-step atmospheric-pressure nitrogen-based plasma jet treatment. We developed a fabrication system used for forming of a uniform honeycomb structure on PLA surface, which can produce two different pore sizes, 3–4 μm and 7–8 μm, of honeycomb pattern. We applied a previously developed nitrogen-based atmospheric-pressure dielectric barrier discharge (DBD) jet system to treat the PLA film without and with honeycomb structure. NIH-3T3 and a much smaller Neuro-2A cells were cultivated on the films under various surface conditions. The results show that the two-step plasma treatment in combination with a honeycomb structure can enhance cell growth on PLA film, should the cell size be not too smaller than the pore size of honeycomb structure, e.g., NIH-3T3. Otherwise, cell growth would be better on flat PLA film, e.g., Neuro-2A.

  4. The surface electronic structure of Y(0001)

    International Nuclear Information System (INIS)

    Searle, C.

    1998-12-01

    Yttrium has been grown epitaxially on W(110). The growth was monitored by using photoemission spectroscopy with a synchrotron radiation source. The film thickness has been gauged by the attenuation of the W 4f 7/2 bulk component. The films have been grown reproducibly and show a prominent surface state which is indicative of good order and low contamination. Angle-Resolved Ultra-Violet Photoemission Spectroscopy has been used to examine the valence band of these ultra-thin films. The films show a very different structure to the valence band of a bulk crystal of yttrium. The differences have been investigated by a series of model calculations using the LMASA-46 tight-binding LMTO program. The calculations suggest that the ultra-thin film surface state may be hybridised with a tungsten orbital having (x 2 - y 2 ) character. (author)

  5. Frequency Selective Surface for Structural Health Monitoring

    Science.gov (United States)

    Norlyana Azemi, Saidatul; Mustaffa, Farzana Hazira Wan; Faizal Jamlos, Mohd; Abdullah Al-Hadi, Azremi; Soh, Ping Jack

    2018-03-01

    Structural health monitoring (SHM) technologies have attained attention to monitor civil structures. SHM sensor systems have been used in various civil structures such as bridges, buildings, tunnels and so on. However the previous sensor for SHM is wired and encounter with problem to cover large areas. Therefore, wireless sensor was introduced for SHM to reduce network connecting problem. Wireless sensors for Structural Health monitoring are new technology and have many advantages to overcome the drawback of conventional and wired sensor. This project proposed passive wireless SHM sensor using frequency selective surface (FSS) as an alternative to conventional sensors. The electromagnetic wave characteristic of FSS will change by geometrical changes of FSS due to mechanical strain or structural failure. The changes feature is used as a sensing function without any connecting wires. Two type of design which are circular ring and square loop along with the transmission and reflection characteristics of SHM using FSS were discussed in this project. A simulation process has shown that incident angle characteristics can be use as a data for SHM application.

  6. Structure and thermodynamics of surface recognition

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, G.

    1998-11-01

    This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). Interactions of the surface glycoprotein, gp120, with the receptors of host cells define the pathogenesis of HIV-1, the virus that causes AIDS. gp120 is made of several disulfide-bridged loops--the amino acid sequences of some of these loops are fairly conserved whereas the rest are variable. The third variable (V3) loop has been the target of vaccine design for quite some time since this loop is involved in various steps of viral pathogenesis. However, this loop also happens to be the most variable one. The authors have carried out structural and immunological studies to determine the sequence-structure-antigenicity correlations of the HIV-1 V3 loops. This resulted in the identification of a secondary structure at the tip of the V3 loop that remains invariant in spite of the sequence variation. The authors designed a multi-valent V3-based antigen that presents multiple copies of the same tip element several times in the same structure. During the course of this project, they realized that the protective epitopes of gp120 should be judged in the context of the native structure. Therefore, the authors developed a method to obtain a model of gp120 that is consistent with all the immunology and virology data. This model is useful in choosing or designing gp120 subdomains for vaccine development.

  7. Sulfur-nitrogen co-doped three-dimensional carbon foams with hierarchical pore structures as efficient metal-free electrocatalysts for oxygen reduction reactions

    Science.gov (United States)

    Liu, Zheng; Nie, Huagui; Yang, Zhi; Zhang, Jing; Jin, Zhiping; Lu, Yanqi; Xiao, Zhubing; Huang, Shaoming

    2013-03-01

    Despite the good progress in developing doped carbon catalysts for oxygen-reduction reaction (ORR), the current metal-free carbon catalysts are still far from satisfactory for large-scale applications of fuel cell. Developing new metal free doped carbon materials with abundance active sites as well as excellent electron transfer and reactant transport rate towards ORR may be a potential solution. Herein, we develop a novel three-dimensional (3D) sulfur-nitrogen co-doped carbon foams (S-N-CF) with hierarchical pore structures, using a convenient, economical, and scalable method. The experimental results have demonstrated that the obtained 3D S-N-CF exhibited better catalytic activity, longer-term stability and higher methanol tolerance than a commercial Pt/C catalyst. Such excellent performances may be attributed to the synergistic effect, which includes high catalytic sites for ORR provided by high S-N heteroatom loading, excellent reactant transport caused by hierarchical pore structures and high electron transfer rate provided by 3D continuous networks. Our results not only develop a new type of catalysts with excellent electrocatalytic performance by a commercially valid route, but also provide useful information for further clarification of the relationship between the microstructures of metal-free carbon materials and catalyst properties for ORR. More importantly, the idea to design hierarchical pore structures could be applied to other catalytic materials and serve as a general strategy for improving the activity of various ORR catalysts.Despite the good progress in developing doped carbon catalysts for oxygen-reduction reaction (ORR), the current metal-free carbon catalysts are still far from satisfactory for large-scale applications of fuel cell. Developing new metal free doped carbon materials with abundance active sites as well as excellent electron transfer and reactant transport rate towards ORR may be a potential solution. Herein, we develop a novel

  8. The pore space scramble

    Science.gov (United States)

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

    2015-04-01

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

  9. The Surface Structure of Ground Metal Crystals

    Science.gov (United States)

    Boas, W.; Schmid, E.

    1944-01-01

    The changes produced on metallic surfaces as a result of grinding and polishing are not as yet fully understood. Undoubtedly there is some more or less marked change in the crystal structure, at least, in the top layer. Hereby a diffusion of separated crystal particles may be involved, or, on plastic material, the formation of a layer in greatly deformed state, with possible recrystallization in certain conditions. Czochralski verified the existence of such a layer on tin micro-sections by successive observations of the texture after repeated etching; while Thomassen established, roentgenographically by means of the Debye-Scherrer method, the existence of diffused crystal fractions on the surface of ground and polished tin bars, which he had already observed after turning (on the lathe). (Thickness of this layer - 0.07 mm). Whether this layer borders direct on the undamaged base material or whether deformed intermediate layers form the transition, nothing is known. One observation ty Sachs and Shoji simply states that after the turning of an alpha-brass crystal the disturbance starting from the surface, penetrates fairly deep (approx. 1 mm) into the crystal (proof by recrystallization at 750 C).

  10. Hybrid Titanium/Biodegradable Polymer Implants with an Hierarchical Pore Structure as a Means to Control Selective Cell Movement

    Science.gov (United States)

    Vrana, Nihal Engin; Dupret, Agnès; Coraux, Christelle; Vautier, Dominique; Debry, Christian; Lavalle, Philippe

    2011-01-01

    In order to improve implant success rate, it is important to enhance their responsiveness to the prevailing conditions following implantation. Uncontrolled movement of inflammatory cells and fibroblasts is one of these in vivo problems and the porosity properties of the implant have a strong effect on these. Here, we describe a hybrid system composed of a macroporous titanium structure filled with a microporous biodegradable polymer. This polymer matrix has a distinct porosity gradient to accommodate different cell types (fibroblasts and epithelial cells). The main clinical application of this system will be the prevention of restenosis due to excessive fibroblast migration and proliferation in the case of tracheal implants. Methodology/Principal Findings A microbead-based titanium template was filled with a porous Poly (L-lactic acid) (PLLA) body by freeze-extraction method. A distinct porosity difference was obtained between the inner and outer surfaces of the implant as characterized by image analysis and Mercury porosimetry (9.8±2.2 µm vs. 36.7±11.4 µm, p≤0.05). On top, a thin PLLA film was added to optimize the growth of epithelial cells, which was confirmed by using human respiratory epithelial cells. To check the control of fibroblast movement, PKH26 labeled fibroblasts were seeded onto Titanium and Titanium/PLLA implants. The cell movement was quantified by confocal microscopy: in one week cells moved deeper in Ti samples compared to Ti/PLLA. Conclusions In vitro experiments showed that this new implant is effective for guiding different kind of cells it will contact upon implantation. Overall, this system would enable spatial and temporal control over cell migration by a gradient ranging from macroporosity to nanoporosity within a tracheal implant. Moreover, mechanical properties will be dependent mainly on the titanium frame. This will make it possible to create a polymeric environment which is suitable for cells without the need to meet mechanical

  11. Optimization of the Pore Structure of Biomass-Based Carbons in Relation to Their Use for CO2Capture under Low- and High-Pressure Regimes.

    Science.gov (United States)

    Sevilla, Marta; Al-Jumialy, Abdul Salam M; Fuertes, Antonio B; Mokaya, Robert

    2018-01-17

    A versatile chemical activation approach for the fabrication of sustainable porous carbons with a pore network tunable from micro- to hierarchical micro-/mesoporous is hereby presented. It is based on the use of a less corrosive and less toxic chemical, i.e., potassium oxalate, rather than the widely used KOH. The fabrication procedure is exemplified for glucose as precursor, although it can be extended to other biomass derivatives (saccharides) with similar results. When potassium oxalate alone is used as activating agent, highly microporous carbons are obtained (S BET ≈ 1300-1700 m 2 g -1 ). When a melamine-mediated activation process is used, hierarchical micro-/mesoporous carbons with surface areas as large as 3500 m 2 g -1 are obtained. The microporous carbons are excellent adsorbents for CO 2 capture at low pressure and room temperature, able to adsorb 4.2-4.5 mmol CO 2 g -1 at 1 bar and 1.1-1.4 mmol CO 2 g -1 at 0.15 bar. However, the micro-/mesoporous carbons provide record-high room temperature CO 2 uptakes at 30 bar of 32-33 mmol g -1 CO 2 and 44-49 mmol g -1 CO 2 at 50 bar. The findings demonstrate the key relevance of pore size in CO 2 capture, with narrow micropores having the leading role at pressures pressures. In this regard, the fabrication strategy presented here allows fine-tuning of the pore network to maximize both the overall CO 2 uptake and the working capacity at any target pressure.

  12. Fabrication of scalable tissue engineering scaffolds with dual-pore microarchitecture by combining 3D printing and particle leaching.

    Science.gov (United States)

    Mohanty, Soumyaranjan; Sanger, Kuldeep; Heiskanen, Arto; Trifol, Jon; Szabo, Peter; Dufva, Marin; Emnéus, Jenny; Wolff, Anders

    2016-04-01

    Limitations in controlling scaffold architecture using traditional fabrication techniques are a problem when constructing engineered tissues/organs. Recently, integration of two pore architectures to generate dual-pore scaffolds with tailored physical properties has attracted wide attention in tissue engineering community. Such scaffolds features primary structured pores which can efficiently enhance nutrient/oxygen supply to the surrounding, in combination with secondary random pores, which give high surface area for cell adhesion and proliferation. Here, we present a new technique to fabricate dual-pore scaffolds for various tissue engineering applications where 3D printing of poly(vinyl alcohol) (PVA) mould is combined with salt leaching process. In this technique the sacrificial PVA mould, determining the structured pore architecture, was filled with salt crystals to define the random pore regions of the scaffold. After crosslinking the casted polymer the combined PVA-salt mould was dissolved in water. The technique has advantages over previously reported ones, such as automated assembly of the sacrificial mould, and precise control over pore architecture/dimensions by 3D printing parameters. In this study, polydimethylsiloxane and biodegradable poly(ϵ-caprolactone) were used for fabrication. However, we show that this technique is also suitable for other biocompatible/biodegradable polymers. Various physical and mechanical properties of the dual-pore scaffolds were compared with control scaffolds with either only structured or only random pores, fabricated using previously reported methods. The fabricated dual-pore scaffolds supported high cell density, due to the random pores, in combination with uniform cell distribution throughout the scaffold, and higher cell proliferation and viability due to efficient nutrient/oxygen transport through the structured pores. In conclusion, the described fabrication technique is rapid, inexpensive, scalable, and compatible

  13. Effect of Wood Flour Addition on the Pore Volume and BET Surface Area Properties of the Prepared Gamma Alumina (ɤ-Al2O3 Extrudates Used in Catalyst Carriers

    Directory of Open Access Journals (Sweden)

    Alaa D. Jawad Al-Bayati

    2015-11-01

    Full Text Available The effect of Wood Flour addition to the gamma alumina powder used in the preparation of gamma alumina (ɤ-Al2O3 catalyst carrier extrudates on the pore volume and BET surface area physical properties was investigated. Two parameters which are size of wood flour particles and its quantity were studied. The sizes of wood flour particles used are 150 µm, 212 µm and 500 µm and the weight percentage added to the gamma alumina powder during the preparation of the extrudates are (1%, 3%, 5% and 10%. The results showed that the addition of wood flour to the gamma alumina powder in order to get gamma alumina extrudates used as catalyst carrier is one of the successful methods to improve the pore volume and BET surface area of the alumina extrudates. The size of wood flour particles and its quantity have main effect on the above texture properties. The smaller the size of wood flour leaded to higher BET surface area, where maximum BET surface area of 127.3 m2/g was got with addition 10% by weight wood flour of 150µm particle size. BET surface area for the same addition percentage of 10% resulted to 114.5m2/g and 105.2m2/g when adding wood flour of 212 µm and 500 µm particle sizes respectively. The weight percentage of wood flour addition has an effect on the BET surface area, where the 3% addition gives maximum BET surface area when the size of the wood flour particles is 500 µm. Regarding the pore volume property for the gamma alumina prepared extrudates, the results showed that the pore volume of the extrudates increased to 0.83 cm3/g and 1.0 cm3/g when 10% wood flour of 150 µm and 500 µm particle sizes were added respectively. The maximum BET surface area was reached when 10% wood flour of 150 µm particle size was added, and the maximum pore volume was reached when 10% wood flour of 500 µm particle size was added, the increase percentage for the BET surface area and pore volume is more than 40% and 400% respectively.

  14. Influence of zeolite pore structure on product selectivities for protolysis and hydride transfer reactions in the cracking of n-pentane.

    Science.gov (United States)

    Miyaji, Akimitsu; Iwase, Yasuyoshi; Nishitoba, Toshiki; Long, Nguyen Quang; Motokura, Ken; Baba, Toshihide

    2015-02-21

    The conversion of n-pentane was carried out to examine the effects of reaction conditions on changes in product selectivities at 823 K, using zeolites with 10- and 12-membered rings. We also investigated the influence of the pore structure of these zeolites on their catalytic activities for both protolysis and hydride transfer reactions. In the first half of this work, we examined the influence of acidic proton concentration and n-pentane pressure on the reaction rates for protolysis and hydride transfer reactions using ZSM-5 zeolites. The rates of hydride transfer reactions were more influenced by pentane pressure compared to protolysis reactions, and were proportional to the square of n-pentane pressure and the concentration of acidic protons. In the second half of this work, the influence of the zeolite pore structure on changes in product selectivities with n-pentane conversion and that on the rates of protolysis and the hydride transfer reactions were revealed using various zeolites with 10- and 12-membered rings. The catalytic activities of zeolites for the protolysis and hydride transfer reactions were influenced more by the spatial volume of the zeolite cavity than the acid strength of protons on the zeolite.

  15. Adherence of human oral keratinocytes and gingival fibroblasts to nano-structured titanium surfaces.

    Science.gov (United States)

    Dorkhan, Marjan; Yücel-Lindberg, Tülay; Hall, Jan; Svensäter, Gunnel; Davies, Julia R

    2014-06-21

    A key element for long-term success of dental implants is integration of the implant surface with the surrounding host tissues. Modification of titanium implant surfaces can enhance osteoblast activity but their effects on soft-tissue cells are unclear. Adherence of human keratinocytes and gingival fibroblasts to control commercially pure titanium (CpTi) and two surfaces prepared by anodic oxidation was therefore investigated. Since implant abutments are exposed to a bacteria-rich environment in vivo, the effect of oral bacteria on keratinocyte adhesion was also evaluated. The surfaces were characterized using scanning electron microscopy (SEM). The number of adhered cells and binding strength, as well as vitality of fibroblasts and keratinocytes were evaluated using confocal scanning laser microscopy after staining with Live/Dead Baclight. To evaluate the effect of bacteria on adherence and vitality, keratinocytes were co-cultured with a four-species streptococcal consortium. SEM analysis showed the two anodically oxidized surfaces to be nano-structured with differing degrees of pore-density. Over 24 hours, both fibroblasts and keratinocytes adhered well to the nano-structured surfaces, although to a somewhat lesser degree than to CpTi (range 42-89% of the levels on CpTi). The strength of keratinocyte adhesion was greater than that of the fibroblasts but no differences in adhesion strength could be observed between the two nano-structured surfaces and the CpTi. The consortium of commensal streptococci markedly reduced keratinocyte adherence on all the surfaces as well as compromising membrane integrity of the adhered cells. Both the vitality and level of adherence of soft-tissue cells to the nano-structured surfaces was similar to that on CpTi. Co-culture with streptococci reduced the number of keratinocytes on all the surfaces to approximately the same level and caused cell damage, suggesting that commensal bacteria could affect adherence of soft-tissue cells to

  16. The Dynamics and Structures of Adsorbed Surfaces

    DEFF Research Database (Denmark)

    Nielsen, M; Ellenson, W. D.; McTague, J. P.

    1978-01-01

    Reviews neutron scattering work performed on films of simple gas atoms and molecules adsorbed primarily on graphite surfaces. Exfoliated graphite substrates such as Grafoil were first used in this kind of measurements about five years ago and new results have been reported at an increasing pace....... Elastic neutron diffraction measurements, determining the two-dimensional structural ordering of the adsorbed films, have been performed on layers of N2, Ar, H2, D2, O2, Kr, and He. Measurements on layers of larger molecules such as CD4 and ND3 have also been reported. Inelastic neutron scattering...... of molecules such as NH3 or the internal modes of adsorbed molecules such as C4H10. Neutron scattering measurements where substrates other than graphite products are used as the adsorbents will not be reviewed here. However, the power of the technique will be demonstrated in an example of H2 physisorbed...

  17. Lunar surface structural concepts and construction studies

    Science.gov (United States)

    Mikulas, Martin

    The topics are presented in viewgraph form and include the following: lunar surface structures construction research areas; lunar crane related disciplines; shortcomings of typical mobile crane in lunar base applications; candidate crane cable suspension systems; NIST six-cable suspension crane; numerical example of natural frequency; the incorporation of two new features for improved performance of the counter-balanced actively-controlled lunar crane; lunar crane pendulum mechanics; simulation results; 1/6 scale lunar crane testbed using GE robot for global manipulation; basic deployable truss approaches; bi-pantograph elevator platform; comparison of elevator platforms; perspective of bi-pantograph beam; bi-pantograph synchronously deployable tower/beam; lunar module off-loading concept; module off-loader concept packaged; starburst deployable precision reflector; 3-ring reflector deployment scheme; cross-section of packaged starburst reflector; and focal point and thickness packaging considerations.

  18. Structure, composition and morphology of bioactive titanate layer on porous titanium surfaces

    Science.gov (United States)

    Li, Jinshan; Wang, Xiaohua; Hu, Rui; Kou, Hongchao

    2014-07-01

    A bioactive coating was produced on pore surfaces of porous titanium samples by an amendatory alkali-heat treatment method. Porous titanium was prepared by powder metallurgy and its porosity and average size were 45% and 135 μm, respectively. Coating morphology, coating structure and phase constituents were examined by SEM, XPS and XRD. It was found that a micro-network structure with sizes of bone-like carbonate-hydroxylapatite showing a good biocompatibility was detected on the coating surface. And the redundant Ca advanced the bioactivity of the coating. Thus, the present modification is expected to allow the use of the bioactive porous titanium as artificial bones even under load-bearing conditions.

  19. THERMAL TOMOGRAPHY OF ASTEROID SURFACE STRUCTURE

    Energy Technology Data Exchange (ETDEWEB)

    Harris, Alan W.; Drube, Line, E-mail: alan.harris@dlr.de [German Aerospace Center (DLR) Institute of Planetary Research, Rutherfordstrasse 2, D-12489 Berlin (Germany)

    2016-12-01

    Knowledge of the surface thermal inertia of an asteroid can provide insight into its surface structure: porous material has a lower thermal inertia than rock. We develop a means to estimate thermal inertia values of asteroids and use it to show that thermal inertia appears to increase with spin period in the case of main-belt asteroids (MBAs). Similar behavior is found on the basis of thermophysical modeling for near-Earth objects (NEOs). We interpret our results in terms of rapidly increasing material density and thermal conductivity with depth, and provide evidence that thermal inertia increases by factors of 10 (MBAs) to 20 (NEOs) within a depth of just 10 cm. Our results are consistent with a very general picture of rapidly changing material properties in the topmost regolith layers of asteroids and have important implications for calculations of the Yarkovsky effect, including its perturbation of the orbits of potentially hazardous objects and those of asteroid family members after the break-up event. Evidence of a rapid increase of thermal inertia with depth is also an important result for studies of the ejecta-enhanced momentum transfer of impacting vehicles (“kinetic impactors”) in planetary defense.

  20. Protein-mediated surface structuring in biomembranes

    Directory of Open Access Journals (Sweden)

    Maggio B.

    2005-01-01

    Full Text Available The lipids and proteins of biomembranes exhibit highly dissimilar conformations, geometrical shapes, amphipathicity, and thermodynamic properties which constrain their two-dimensional molecular packing, electrostatics, and interaction preferences. This causes inevitable development of large local tensions that frequently relax into phase or compositional immiscibility along lateral and transverse planes of the membrane. On the other hand, these effects constitute the very codes that mediate molecular and structural changes determining and controlling the possibilities for enzymatic activity, apposition and recombination in biomembranes. The presence of proteins constitutes a major perturbing factor for the membrane sculpturing both in terms of its surface topography and dynamics. We will focus on some results from our group within this context and summarize some recent evidence for the active involvement of extrinsic (myelin basic protein, integral (Folch-Lees proteolipid protein and amphitropic (c-Fos and c-Jun proteins, as well as a membrane-active amphitropic phosphohydrolytic enzyme (neutral sphingomyelinase, in the process of lateral segregation and dynamics of phase domains, sculpturing of the surface topography, and the bi-directional modulation of the membrane biochemical reactivity.

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

    Science.gov (United States)

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

    2008-12-01

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

  2. Photoelectron spectroscopy bulk and surface electronic structures

    CERN Document Server

    Suga, Shigemasa

    2014-01-01

    Photoelectron spectroscopy is now becoming more and more required to investigate electronic structures of various solid materials in the bulk, on surfaces as well as at buried interfaces. The energy resolution was much improved in the last decade down to 1 meV in the low photon energy region. Now this technique is available from a few eV up to 10 keV by use of lasers, electron cyclotron resonance lamps in addition to synchrotron radiation and X-ray tubes. High resolution angle resolved photoelectron spectroscopy (ARPES) is now widely applied to band mapping of materials. It attracts a wide attention from both fundamental science and material engineering. Studies of the dynamics of excited states are feasible by time of flight spectroscopy with fully utilizing the pulse structures of synchrotron radiation as well as lasers including the free electron lasers (FEL). Spin resolved studies also made dramatic progress by using higher efficiency spin detectors and two dimensional spin detectors. Polarization depend...

  3. Surface and interface electronic structure: Three year activity report

    International Nuclear Information System (INIS)

    Kevan, S.D.

    1992-01-01

    The 3-year activity report covers surface structure and phonon anomalies (surface reconstruction on W(001) and Mo(001), adsorbate lateral ordering, surface Fermi contours and phonon anomalies on Pt(111) and Pd(001)), adsorbate vibrational damping, charge transfer in momentum space: W(011)-K, surface states and resonances (relativistic effects ampersand computations, surface resonances)

  4. Pore-Scale Model for Microbial Growth

    Science.gov (United States)

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

    2011-12-01

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

  5. A stable metal-organic framework with suitable pore sizes and rich uncoordinated nitrogen atoms on the internal surface of micropores for highly efficient CO2 capture

    NARCIS (Netherlands)

    Bao, S.J.; Krishna, R.; He, Y.B.; Qin, J.S.; Su, Z.M.; Li, S.L.; Xie, W.; Du, D.Y.; He, W.W.; Zhang, S.R.; Lan, Y.Q.

    2015-01-01

    An air-stable tetrazolate-containing framework, [ZN(2)L(2)]center dot 2DMF (NENU-520, H2L = 4-(1H-tetrazole-5-yl) biphenyl-4-carboxylic acid), with uncoordinated N atoms on its internal surface was solvothermally synthesized and structurally characterized. This metal-organic framework (MOF)

  6. Observations of flow path interactions with surface structures during initial soil development stage using irrigation experiments

    Science.gov (United States)

    Bartl, Steffen; Biemelt, Detlef; Badorreck, Annika; Gerke, Horst H.

    2010-05-01

    Structures and processes are dynamically linked especially during initial stages of soil and ecosystem development. Here we assume that soil pore structures and micro topography determine the flow paths and water fluxes as well as further structure changes. Reports about flow path developments at the soil surface are still limited because of an insufficient knowledge of the changing micro topography at the surface. The objective of this presentation is to evaluate methods for parameterisation of surface micro topography for analysing interactions between infiltration and surface runoff. Complex irrigation experiments were carried out at an experimental site in the neighbourhood of the artificially created water catchment "Chicken Creek". The irrigation rates between 160 mm/h and 250 mm/h were held constant over a time period of 20 minutes. The incoming intensities were measured as well as the raindrop-velocity and -size distributions. The surface runoff was continuously registered, soil samples were taken, and soil water potential heads were monitored using tensiometers. Surface and subsurface flow paths were identified using different tracers. The soil surface structures were recorded using a high resolution digital camera before, during, and after irrigation. Micro topography was surveyed using close-range photogrammetry. With this experimental design both, flow paths on the surface and in the soil as well as structure and texture changes could be observed simultaneously. In 2D vertical cross-sections, the effect of initial sediment deposition structure on infiltration and runoff was observed. Image analysis of surface pictures allowed identifying structural and soil textural changes during the runoff process. Similar structural changes related to surface flow paths were found with the photogrammetric surface analysis. We found evidence for the importance of the initial structures on the flow paths as well as a significant influence of the system development

  7. On the structure of Si(100) surface

    DEFF Research Database (Denmark)

    Back, Seoin; Schmidt, Johan Albrecht; Ji, Hyunjun

    2013-01-01

    We revisit a dangling theoretical question of whether the surface reconstruction of the Si(100) surface would energetically favor the symmetric or buckled dimers on the intrinsic potential energy surfaces at 0 K. This seemingly simple question is still unanswered definitively since all existing...... of the electron-electron correlation as well as proper multireference wave functions when exploring the extremely delicate potential energy surfaces of the reconstructed Si(100) surface. (C) 2013 AIP Publishing LLC....

  8. Analysis of Lotus japonicus nuclear pore NUP107-160 subcomplex mutants reveals pronounced structural plasticity and functional redundancy

    Directory of Open Access Journals (Sweden)

    Andreas eBinder

    2014-01-01

    Full Text Available Mutations in the Lotus japonicus nucleoporin genes, NUP85, NUP133 and NENA (SEH1, lead to defects in plant-microbe symbiotic signaling. The homologous proteins in yeast and vertebrates are part of the conserved NUP84/NUP107-160 sub-complex, which is an essential component of the nuclear pore scaffold and has a pivotal role in NPC assembly. Loss and down-regulation of NUP84/NUP107-160 members has previously been correlated with a variety of growth and molecular defects, however, in L. japonicus only surprisingly specific phenotypes have been reported. We investigated whether Lotus nup85, nup133 and nena mutants exhibit general defects in NPC composition and distribution. Whole mount immunofluorescence confirmed a typical nucleoporin-like localization for NUP133, which was unchanged in the nup85-1 mutant. Severe NPC clustering and aberrations in the nuclear envelope have been reported for Saccharomyces cerevisiae nup85 and nup133 mutants. However, upon transmission electron microscopy analysis, we did not detect any significant changes in L. japonicus nup85 and nena, and only a slight reduction in the average distances between neighboring NPCs in nup133. Using quantitative immunodetection on protein-blots we observed that loss of individual nucleoporins affected the protein levels of other NUP107-160 complex members. Unlike the single mutants, nup85/nup133 double mutants exhibited severe temperature dependent growth and developmental defects, suggesting that the loss of more than one NUP107-160 member affects basal functions of the NPC.

  9. Three-dimensional cheese-like carbon nanoarchitecture with tremendous surface area and pore construction derived from corn as superior electrode materials for supercapacitors

    Science.gov (United States)

    Gopiraman, Mayakrishnan; Deng, Dian; Kim, Byoung-Suhk; Chung, Ill-Min; Kim, Ick Soo

    2017-07-01

    Highly porous carbon nanoarchitectures (HPCNs) were derived from biomass materials, namely, corn fibers (CF), corn leafs (CL), and corn cobs (CC). We surprisingly found that by a very simple activation process the CF, CL, and CC materials can be transformed into exciting two-dimensional (2D) and three-dimensional (3D) carbon nanoarchitectures with excellent physicochemical properties. FESEM and HRTEM results confirmed a three different carbon forms (such as foams-like carbon, carbon sheets with several holes and cheese-like carbon morphology) of HPCNs. Huge surface area (2394-3475 m2/g) with excellent pore properties of HPCNs was determined by BET analysis. Well condensed graphitic plans of HPCNs were confirmed by XRD, XPS and Raman analyses. As an electrode material, HPCNs demonstrated a maximum specific capacitance (Cs) of 575 F/g in 1.0 M H2SO4 with good stability over 20,000 cycles. The CC-700 °C showed a tremendous Cs of 375 F/g even at 20000th cycles. To the best of our knowledge, this is the highest Cs by the biomass derived activated carbons in aqueous electrolytes. The CC-700 °C exhibited excellent charge-discharge behavior at various current densities (0.5-10 A g-1). Notably, CC-700 °C demonstrated an excellent Cs of 207 F/g at current density of 10 A g-1. An extraordinary change-discharge behavior was noticed at low current density of 0.5 A g-1.

  10. The dynamics and structures of adsorbed surfaces

    International Nuclear Information System (INIS)

    Nielsen, M.; Ellenson, W.D.; McTague, J.P.

    1978-01-01

    This article reviews neutron scattering work performed on films of simple gas atoms and molecules adsorbed primarily on graphite surfaces. Exfoliated graphite substrates such as Grafoil were first used in this kind of measurements about five years ago and new results have been reported at an increasing pace. Elastic neutron diffraction measurements, determining the two-dimensional structural ordering of the adsorbed films, have been performed on layers of N 2 , Ar, H 2 , D 2 , O 2 , Kr, and He. Measurements on layers of larger molecules such as CD 4 and ND 3 have been reported very recently. Inelastic neutron scattering measurements, studying the dynamics of the adsorbed films are only possible in a few especially favourable cases such as 36 Ar and D 2 films, where the coherent phonon scattering cross-sections are very large. In other cases incoherent scattering from hydrogen can give information about e.g. the mobility of molecules such as NH 3 or the internal modes of adsorbed molecules such as C 4 H 10 . Neutron scattering measurements where substrates other than graphite products are used as the adsorbents will not be reviewed here. However, the power of the technique will be demonstrated in an example of H 2 physisorbed to activated alumina and in an example where hydrogen is chemisorbed to Raney nickel. (author)

  11. Application of Neutron imaging in pore structure of hydrated wellbore cement: comparison of hydration of H20 with D2O based Portland cements

    Science.gov (United States)

    Dussenova, D.; Bilheux, H.; Radonjic, M.

    2012-12-01

    Wellbore Cement studies have been ongoing for decades. The studies vary from efforts to reduce permeability and resistance to corrosive environment to issues with gas migration also known as Sustained Casing Pressure (SCP). These practical issues often lead to health and safety problems as well as huge economic loss in oil and gas industry. Several techniques have been employed to reduce the impact of gas leakage. In this study we purely focus on expandable liners, which are introduced as part of oil well reconstruction and work-overs and as well abandonment procedures that help in prevention of SCP. Expandable liner is a tube that after application of a certain tool can increase its diameter. The increase in diameter creates extra force on hydrated cement that results in reducing width of interface fractures and cement-tube de-bonding. Moreover, this also causes cement to change its microstructure and other porous medium properties, primarily hydraulic conductivity. In order to examine changes before and after operations, cement pore structure must be well characterized and correlated to cement slurry design as well as chemical and physical environmental conditions. As modern oil well pipes and tubes contain iron, it is difficult to perform X-ray tomography of a bulk measurement of the cement in its wellbore conditions, which are tube wall-cement-tube wall. Neutron imaging is a complementary technique to x-ray imaging and is well suited for detection of light elements imbedded in metallic containers. Thus, Neutron Imaging (NI) is investigated as a tool for the detection of pore structure of hydrated wellbore cement. Recent measurements were conducted at the Oak Ridge National Laboratory (ORNL) High Flux Isotope Reactor (HFIR) neutron imaging facility. NI is is highly sensitive to light elements such as Hydrogen (H). Oil well cements that have undergone a full hydration contain on average 30%-40% of free water in its pore structure. The unreacted water is the main

  12. Hydrophilicity, pore structure and mechanical performance of CNT/PVDF materials affected by carboxyl contents in multi-walled carbon nanotubes

    Science.gov (United States)

    Zhang, Yanxia; Jiang, Ce; Tian, Run; Li, Guangfen

    2018-01-01

    Poly (vinylidene fluoride) (PVDF) membranes have been prepared by loading different type of MWCNTs-COOH as the dispersed phase via phase inversion method. The chemically functionalized MWCNTs with increasing carboxyl content were chosen for achieving a better dispersion in PVDF and altering the membrane hydrophilicity. The effect of the carboxyl content in MWCNTs on crystal structure, thermal behavior, membrane morphology, hydrophilicity, and water flux of blended membranes were investigated. Due to the addition of carbon nanotubes, various performances of the hybrid membrane had obvious changes. The most prominent was that thermal stability could be enhanced and the pore morphology was more preferable, also that the hydrophilicity were improved, further that water flux could be increased to some extent.

  13. Modeling laser-induced periodic surface structures: an electromagnetic approach

    NARCIS (Netherlands)

    Skolski, J.Z.P.

    2014-01-01

    This thesis presents and discusses laser-induced periodic surface structures (LIPSSs), as well as a model explaining their formation. LIPSSs are regular wavy surface structures with dimensions usually in the submicrometer range, which can develop on the surface of many materials exposed to laser

  14. The structure and properties of fluorite crystal surfaces

    OpenAIRE

    Tasker, P.

    1980-01-01

    The surface energies, tensions and structure of the (111) and (110) surfaces of CaF2, SrF2, BaF2 and UO2, ThO2, PrO2, PuO2, CeO2 have been calculated using an ionic shell model. The surface energies for the natural cleavage plane (111) are compared with the available experimental data and agree well. The surface tensions indicate a compressive stress in both surfaces. The surface structures show increasing relaxation with increasing ion size and the rumpling of the (110) surface indicates a q...

  15. Synthesis and characterization of mesoporous ZnS with narrow size distribution of small pores

    Science.gov (United States)

    Nistor, L. C.; Mateescu, C. D.; Birjega, R.; Nistor, S. V.

    2008-08-01

    Pure, nanocrystalline cubic ZnS forming a stable mesoporous structure was synthesized at room temperature by a non-toxic surfactant-assisted liquid liquid reaction, in the 9.5 10.5 pH range of values. The appearance of an X-ray diffraction (XRD) peak in the region of very small angles (˜ 2°) reveals the presence of a porous material with a narrow pore size distribution, but with an irregular arrangement of the pores, a so-called worm hole or sponge-like material. The analysis of the wide angle XRD diffractograms shows the building blocks to be ZnS nanocrystals with cubic structure and average diameter of 2 nm. Transmission electron microscopy (TEM) investigations confirm the XRD results; ZnS crystallites of 2.5 nm with cubic (blende) structure are the building blocks of the pore walls with pore sizes from 1.9 to 2.5 nm, and a broader size distribution for samples with smaller pores. Textural measurements (N2 adsorption desorption isotherms) confirm the presence of mesoporous ZnS with a narrow range of small pore sizes. The relatively lower surface area of around 100 m2/g is attributed to some remaining organic molecules, which are filling the smallest pores. Their presence, confirmed by IR spectroscopy, seems to be responsible for the high stability of the resulting mesoporous ZnS as well.

  16. 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.

  17. Atomic probes of surface structure and dynamics

    International Nuclear Information System (INIS)

    Heller, E.J.; Jonsson, H.

    1992-01-01

    Progress for the period Sept. 15, 1992 to Sept. 14, 1993 is discussed. Semiclassical methods that will allow much faster and more accurate three-dimensional atom--surface scattering calculations, both elastic and inelastic, are being developed. The scattering of He atoms from buckyballs is being investigated as a test problem. Somewhat more detail is given on studies of He atom scattering from defective Pt surfaces. Molecular dynamics simulations of He + and Ar + ion sputtering of Pt surfaces are also being done. He atom scattering from Xe overlayers on metal surfaces and the thermalized dissociation of H 2 on Cu(110) are being studied. (R.W.R.) 64 refs

  18. Structural analysis of the surface-layer protein of spirillum serpens by high-resolution electron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Wu, W.H.; Glaeser, R.M.

    1983-01-01

    In order to understand the detailed association of the macro-molecules of the structure of the protein, a high resolution structural analysis was performed. Large, single layered arrays of the surface layer protein have been obtained for this purpose by means of extensive heating in high CaCl/sub 2/. The computer processed image reveals a pore of about 10 Angstrom diameter at the 6-fold symmetry center; the handedness of the images is quite evident. The individual molecular envelope of the protein monomers are apparent and details of the protein-protein contact at the three-fold lattice positions emerge.

  19. Mercury capture by selected Bulgarian fly ashes: Influence of coal rank and fly ash carbon pore structure on capture efficiency

    Science.gov (United States)

    Kostova, I.J.; Hower, J.C.; Mastalerz, Maria; Vassilev, S.V.

    2011-01-01

    Mercury capture by fly ash C was investigated at five lignite- and subbituminous-coal-burning Bulgarian power plants (Republika, Bobov Dol, Maritza East 2, Maritza East 3, and Sliven). Although the C content of the ashes is low, never exceeding 1.6%, the Hg capture on a unit C basis demonstrates that the low-rank-coal-derived fly ash carbons are more efficient in capturing Hg than fly ash carbons from bituminous-fired power plants. While some low-C and low-Hg fly ashes do not reveal any trends of Hg versus C, the 2nd and, in particular, the 3rd electrostatic precipitator (ESP) rows at the Republika power plant do have sufficient fly ash C range and experience flue gas sufficiently cool to capture measurable amounts of Hg. The Republika 3rd ESP row exhibits an increase in Hg with increasing C, as observed in other power plants, for example, in Kentucky power plants burning Appalachian-sourced bituminous coals. Mercury/C decreases with an increase in fly ash C, suggesting that some of the C is isolated from the flue gas stream and does not contribute to Hg capture. Mercury capture increases with an increase in Brunauer-Emmett-Teller (BET) surface area and micropore surface area. The differences in Hg capture between the Bulgarian plants burning low-rank coal and high volatile bituminous-fed Kentucky power plants suggests that the variations in C forms resulting from the combustion of the different ranks also influence the efficiency of Hg capture. ?? 2010 Elsevier Ltd.

  20. Formation of multiscale surface structures on nickel via above surface growth and below surface growth mechanisms using femtosecond laser pulses.

    Science.gov (United States)

    Zuhlke, Craig A; Anderson, Troy P; Alexander, Dennis R

    2013-04-08

    The formation of self-organized micro- and nano-structured surfaces on nickel via both above surface growth (ASG) and below surface growth (BSG) mechanisms using femtosecond laser pulse illumination is reported. Detailed stepped growth experiments demonstrate that conical mound-shaped surface structure development is characterized by a balance of growth mechanisms including scattering from surface structures and geometric effects causing preferential ablation of the valleys, flow of the surface melt, and redeposition of ablated material; all of which are influenced by the laser fluence and the number of laser shots on the sample. BSG-mound formation is dominated by scattering, while ASG-mound formation is dominated by material flow and redeposition. This is the first demonstration to our knowledge of the use of femtosecond laser pulses to fabricate metallic surface structures that rise above the original surface. These results are useful in understanding the details of multi-pulse femtosecond laser interaction with metals.

  1. Effect of hierarchical pore structure on ALP expression of MC3T3-E1 cells on bioglass films.

    Science.gov (United States)

    Yu, Cuixia; Zhuang, Junjun; Dong, Lingqing; Cheng, Kui; Weng, Wenjian

    2017-08-01

    Hierarchical porous bioglass films on the tantalum were designed to enhance osteointegration of metallic implants. The films were prepared by a sol-gel method using P123 as the mesopore template and polystyrene microsphere as the nanopore template. The films with 5.4nm mesopores and 100nm nanopores (MBG-100) elicited an obviously elongated morphology of the cultured MC3T3-E1 cells, as a result, a higher alkaline phosphatase level was expressed. It is suggested that the nanopores play an important role in regulating cellular behavior by initial protein adsorption through nanopore curvatures. The mesopores were proven very effective for loading rhBMP-2, and the rhBMP-2 loaded on MBG-100 films showed a better function of enhancing osteogenic differentiation, which is attributed to that the nanopore structure could expedite rhBMP-2 release and provide a microenvironment for intensifying the interaction of rhBMP-2 with the cells. Hence, the cell osteogenic differentiation can be enhanced by hierarchical porous bioglass films through both the porous structure and rhBMP-2 induction. Copyright © 2017 Elsevier B.V. All rights reserved.

  2. Characterizing the effects of elevated temperature on the air void pore structure of advanced gas-cooled reactor pressure vessel concrete using x-ray computed tomography

    Directory of Open Access Journals (Sweden)

    Withers P.J.

    2013-07-01

    Full Text Available X-ray computed tomography (X-ray CT has been applied to nondestructively characterise changes in the microstructure of a concrete used in the pressure vessel structure of Advanced Gas-cooled Reactors (AGR in the UK. Concrete specimens were conditioned at temperatures of 105 °C and 250 °C, to simulate the maximum thermal load expected to occur during a loss of coolant accident (LOCA. Following thermal treatment, these specimens along with an unconditioned control sample were characterised using micro-focus X-ray CT with a spatial resolution of 14.6 microns. The results indicate that the air void pore structure of the specimens experienced significant volume changes as a result of the increasing temperature. The increase in the porous volume was more prevalent at 250 °C. Alterations in air void size distributions were characterized with respect to the unconditioned control specimen. These findings appear to correlate with changes in the uni-axial compressive strength of the conditioned concrete.

  3. Titanium(IV) in the organic-structure-directing-agent-free synthesis of hydrophobic and large-pore molecular sieves as redox catalysts.

    Science.gov (United States)

    Wang, Jingui; Yokoi, Toshiyuki; Kondo, Junko N; Tatsumi, Takashi; Zhao, Yanli

    2015-08-10

    Titanium(IV) incorporated into the framework of molecular sieves can be used as a highly active and sustainable catalyst for the oxidation of industrially important organic molecules. Unfortunately, the current process for the incorporation of titanium(IV) requires a large amount of expensive organic molecules used as organic-structure-directing agents (OSDAs), and this significantly increases the production costs and causes environmental problems owing to the removal of OSDAs by pyrolysis. Herein, an OSDA-free process was developed to incorporate titanium(IV) into BEA-type molecular sieves for the first time. More importantly, the hydrophobic environment and the robust, 3 D, and large pore structure of the titanium(IV)-incorporated molecular sieves fabricated from the OSDA-free process created a catalyst that was extremely active and selective for the epoxidation of bulky cyclooctene in comparison to Ti-incorporated BEA-type molecular sieves synthesized with OSDAs and commercial titanosilicate TS-1. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Hydroxyl migration disorders the surface structure of hydroxyapatite nanoparticles

    Science.gov (United States)

    Cheng, Xiajie; Wu, Hong; Zhang, Li; Ma, Xingtao; Zhang, Xingdong; Yang, Mingli

    2017-09-01

    The surface structure of nano-hydroxyapatite (HAP) was investigated using a combined simulated annealing and molecular dynamics method. The stationary structures of nano-HAP with 4-7 nm in diameter and annealed under different temperatures were analyzed in terms of pair distribution function, structural factor, mean square displacement and atomic coordination number. The particles possess different structures from bulk crystal. A clear radial change in their atomic arrangements was noted. From core to surface the structures change from ordered to disordered. A three-shell model was proposed to describe the structure evolution of nano-HAP. Atoms in the core zone keep their arrangements as in crystal, while atoms in the surface shell are in short-range order and long-range disorder, adopting a typically amorphous structure. Atoms in the middle shell have small displacements and/or deflections but basically retain their original locations as in crystal. The disordered shell is about 1 nm in thickness, in agreement with experimental observations. The disordering mainly stems from hydroxyl migration during which hydroxyls move to the surface and bond with the exposed Ca ions, and their left vacancies bring about a rearrangement of nearby atoms. The disordering is to some extent different for particles unannealed under different temperatures, resulting from fewer number of migrated hydroxyls at lower temperatures. Particles with different sizes have similar surface structures, and their surface energy decreases with increasing size. Moreover, the surface energy is reduced by hydroxyl migration because the exposed Ca ions on the surface are ionically bonded with the migrated hydroxyls. Our calculations proposed a new structure model for nano-HAP, which indicates a surface structure with activities different from those without surface reorganization. This is particularly interesting because most bioactivities of biomaterials are dominated by their surface activity.

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

    OpenAIRE

    Subburaj, Yamunadevi

    2014-01-01

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

  6. The X-37 Hot Structure Control Surface Testing

    Science.gov (United States)

    Hudson, Larry D.; Stephens, Craig A.

    2006-01-01

    Thermal-structural testing of three hot structure control surface subcomponent test articles (STA) designed for the X-37 (Boeing Phantom Works, Huntington Beach, California) Orbital Vehicle (OV) has been completed. The test articles were subcomponents of the X-37 OV bodyflap and flaperon control surfaces.

  7. Synthesis, Structure and Hirshfeld surface analysis, vibrational and ...

    Indian Academy of Sciences (India)

    3

    lead to the formation of a three-dimensional architecture. Hirshfeld surface analysis for visually analyzing intermolecular interactions in crystal structures employing molecular surface contours and 2D fingerprint plots have been used to scrutinize molecular shapes. The vibration properties of this structure were studied by IR ...

  8. Oxidized g-C3N4Nanospheres as Catalytically Photoactive Linkers in MOF/g-C3N4Composite of Hierarchical Pore Structure.

    Science.gov (United States)

    Giannakoudakis, Dimitrios A; Travlou, Nikolina A; Secor, Jeff; Bandosz, Teresa J

    2017-01-01

    A unique composite of the copper-based metal-organic framework (Cu-benzene tricarboxylic acid (BTC)) with oxidized graphitic carbon nitride nanospheres is synthesized. For comparison, a hybrid material consisting of g-C 3 N 4 and Cu-BTC is also obtained. Their surface features are analyzed using Fourier transform infrared spectroscopy, X-ray diffraction, sorption of nitrogen, thermal analysis, scanning electron microscopy, photoluminescence, and diffuse reflectance UV-Vis spectroscopy. The results suggest that the formed nanospheres of oxidized g-C 3 N 4 act as linkers between the copper sites, playing a crucial role in the composite building process. Their incorporation to the Cu-BTC framework causes the development of new mesoporosity. Remarkable alterations in the optical properties, as a result of the coordination of oxygen containing functional groups of the oxidized graphitic carbon nitride to the copper atoms of the framework, suggest an increase in photoreactivity. On the other hand, for the hybrid material consisting of Cu-BTC and g-C 3 N 4 , the unaltered pore volume and optical properties support the formation of a physical mixture rather than of a composite. The tests on reactive adsorption and detoxification of G-series organophosphate nerve agent surrogate show the enhanced performance of the composite as catalysts and photocatalyst in visible light. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Fragmentation pathways of nanofractal structures on surfaces

    DEFF Research Database (Denmark)

    Dick, Veronika V.; Solov'yov, Ilia; Solov'yov, Andrey V.

    2011-01-01

    We present a theoretical analysis of the post-growth processes occurring in nanofractals grown on a surface. For this study we have developed a method that accounts for the internal dynamics of particles in a fractal. We demonstrate that the detachment of particles from the fractal and their diff...

  10. Facile fabrication of superhydrophobic surfaces with hierarchical structures.

    Science.gov (United States)

    Lee, Eunyoung; Lee, Kun-Hong

    2018-03-06

    Hierarchical structures were fabricated on the surfaces of SUS304 plates using a one-step process of direct microwave irradiation under a carbon dioxide atmosphere. The surface nanostructures were composed of chrome-doped hematite single crystals. Superhydrophobic surfaces with a water contact angle up to 169° were obtained by chemical modification of the hierarchical structures. The samples maintained superhydrophobicity under NaCl solution up to 2 weeks.

  11. Quantifying similarity of pore-geometry in nanoporous materials

    Science.gov (United States)

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

    2017-05-01

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

  12. Ultralow contact angle hysteresis and no-aging effects in superhydrophobic tangled nanofiber structures generated by controlling the pore size of a 99.5% aluminum foil

    Science.gov (United States)

    Lee, Sangmin; Hwang, Woonbong

    2009-03-01

    Superhydrophobic surfaces designed to improve hydrophobicity have high advancing contact angles corresponding to the Cassie state, but these surfaces also exhibit high contact angle hysteresis. We report here a simple and inexpensive method for fabricating superhydrophobic tangled nanofiber structures with ultralow contact angle hysteresis and no-aging degradation, based on a widening process. The resulting nanostructures are suitable for diverse applications including microfluidic devices for biological studies and industrial self-cleaning products for automobiles, ships and houses.

  13. The "GEOMODEL" at Kiel University: A Hydrogeophysical full scale model to study pore water, contamination and structure of vadose soils

    Science.gov (United States)

    Hagrey, S. A.; Rabbel, W.; Working Group Of Wateruse

    2003-04-01

    Erecting new improved GeoModel at Kiel University is based on our experiences with the pilot model for studying preferential flow processes and takes into account objectives of the EU - project "wateruse" for developing new high resolving techniques for hydro- and bio-geophysical studies. The GeoModel consists of a soil model (3x5x2m), computer room and monitoring chamber. A special irrigation device is installed above the model to simulate irrigations of different rates, intensities and contaminations (tracers). At the base a filter pebble layer divided into different segments for monitoring lateral distribution of discharge indicating for flowpaths and processes. A self developed vacuum aperture is installed to overcome effects of the hydraulic capillary barrier which is related to the abrupt jump in grain size at the soil sand-filter pebble interface. The concept of the GeoModel is to carry out controlled experiment with predefined boundary conditions (as in laboratory) on a full scale soil model (as in the field, i.e., no scale problems). The GeoModel, currently filled with silty sand is equipped with diverse fine electrode grids, radar hardware, TDR-, Tensiometer probes for measuring electrical resistivity, electromagnetic wave velocity and amplitude, water content and potential, respectively. The (infiltration) experiments aim at developing high resolution integrative spatiotemporal 3D techniques for monitoring flow processes of fluids and contaminants, mapping fine structure as preferential flow paths, root networks and trunk rings (which opens new applications in biogeophysics and geobiology), quantification of soil water content. The GeoModel serve for calibration of new instruments and techniques and is applied for special geotechnical and environmental experiments (e.g. anti-person mines, tracer experiments) as well as for technical courses for specialists. Also laboratory study of petrophysical parameters of soil material is carried out to establish

  14. Structural and electronic properties of hydrosilylated silicon surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Baumer, A.

    2005-11-15

    The structural and electronic properties of alkyl-terminated Si surfaces prepared by thermallyinduced hydrosilylation have been studied in detail in the preceding chapters. Various surfaces have been used for the functionalization ranging from crystalline Si over amorphous hydrogenated Si to nanoscaled materials such as Si nanowires and nanoparticles. In each case, the alkyl-terminated surfaces have been compared to the native oxidized and H-terminated surfaces. (orig.)

  15. Impact load-induced micro-structural damage and micro-structure associated mechanical response of concrete made with different surface roughness and porosity aggregates

    International Nuclear Information System (INIS)

    Erdem, Savaş; Dawson, Andrew Robert; Thom, Nicholas Howard

    2012-01-01

    The relationship between the nature of micro damage under impact loading and changes in mechanical behavior associated with different microstructures is studied for concretes made with two different coarse aggregates having significant differences mainly in roughness and porosity — sintered fly ash and uncrushed gravel. A range of techniques including X-ray diffraction, digital image analysis, mercury porosimetry, X-ray computed tomography, laser surface profilometry and scanning electron microscopy were used to characterize the aggregates and micro-structures. The concrete prepared with lightweight aggregates was stronger in compression than the gravel aggregate concrete due to enhanced hydration as a result of internal curing. In the lightweight concrete, it was deduced that an inhomogeneous micro-structure led to strain incompatibilities and consequent localized stress concentrations in the mix, leading to accelerated failure. The pore structure, compressibility, and surface texture of the aggregates are of paramount importance for the micro-cracking growth.

  16. LASER SURFACE CLADDING FOR STRUCTURAL REPAIR

    OpenAIRE

    SANTANU PAUL

    2018-01-01

    Laser cladding is a powder deposition technique, which is used to deposit layers of clad material on a substrate to improve its surface properties. It has widespread application in the repair of dies and molds used in the automobile industry. These molds and dies are subjected to cyclic thermo-mechanical loading and therefore undergo localized damage and wear. The final clad quality and integrity is influenced by various physical phenomena, namely, melt pool morphology, microst...

  17. Structure of Solids Surfaces in Wear Situations.

    Science.gov (United States)

    1984-10-17

    lactones , respectively. As pointed out by Greenler 12J, the most intense emission bands from a material adsorbed in a thin layer on a metal surface...peroxides are formed instead of hydroper-.,. .," ", oxides. The decomposition of these peroxides then leads to unsaturates , aldehydes, ketones and...around 1100 cm-1 (OH and unsaturation ) and at 730 cm-1 (CH2 rock). weeIt is clear that such analyses are difficult, but can yield a welthof information

  18. Importance of surface structure on dissolution of fluorite

    DEFF Research Database (Denmark)

    Godinho, Jose; Piazolo, Sandra; Balic Zunic, Tonci

    2014-01-01

    Dissolution rates are usually calculated as a function of surface area, which is assumed to remain constant ignoring the changes occurring on the surface during dissolution. Here we present a study of how topography of natural fluorite surfaces with different orientation changes during up to 3200...... by the relative stability of the planes and type of edges that constitute a surface needs to be considered. Significant differences between dissolution rates calculated based on surface area alone, and based on surface reactivity are expected for materials with the fluorite structure....

  19. Particle diffusion in complex nanoscale pore networks

    DEFF Research Database (Denmark)

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

    2015-01-01

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

  20. Compact complex surfaces with geometric structures related to split quaternions

    International Nuclear Information System (INIS)

    Davidov, Johann; Grantcharov, Gueo; Mushkarov, Oleg; Yotov, Miroslav

    2012-01-01

    We study the problem of existence of geometric structures on compact complex surfaces that are related to split quaternions. These structures, called para-hypercomplex, para-hyperhermitian and para-hyperkähler, are analogs of the hypercomplex, hyperhermitian and hyperkähler structures in the definite case. We show that a compact 4-manifold carries a para-hyperkähler structure iff it has a metric of split signature together with two parallel, null, orthogonal, pointwise linearly independent vector fields. Every compact complex surface admitting a para-hyperhermitian structure has vanishing first Chern class and we show that, unlike the definite case, many of these surfaces carry infinite-dimensional families of such structures. We provide also compact examples of complex surfaces with para-hyperhermitian structures which are not locally conformally para-hyperkähler. Finally, we discuss the problem of non-existence of para-hyperhermitian structures on Inoue surfaces of type S 0 and provide a list of compact complex surfaces which could carry para-hypercomplex structures.

  1. Compact complex surfaces with geometric structures related to split quaternions

    Energy Technology Data Exchange (ETDEWEB)

    Davidov, Johann, E-mail: jtd@math.bas.bg [Institute of Mathematics and Informatics, Bulgarian Academy of Sciences, 1113 Sofia (Bulgaria); ' L. Karavelov' Civil Engineering Higher School, 175 Suhodolska Str., 1373 Sofia (Bulgaria); Grantcharov, Gueo, E-mail: grantchg@fiu.edu [Department of Mathematics and Statistics, Florida International University, Miami, FL 33199 (United States); Mushkarov, Oleg, E-mail: muskarov@math.bas.bg [Institute of Mathematics and Informatics, Bulgarian Academy of Sciences, 1113 Sofia (Bulgaria); Yotov, Miroslav, E-mail: yotovm@fiu.edu [Department of Mathematics and Statistics, Florida International University, Miami, FL 33199 (United States)

    2012-12-11

    We study the problem of existence of geometric structures on compact complex surfaces that are related to split quaternions. These structures, called para-hypercomplex, para-hyperhermitian and para-hyperkaehler, are analogs of the hypercomplex, hyperhermitian and hyperkaehler structures in the definite case. We show that a compact 4-manifold carries a para-hyperkaehler structure iff it has a metric of split signature together with two parallel, null, orthogonal, pointwise linearly independent vector fields. Every compact complex surface admitting a para-hyperhermitian structure has vanishing first Chern class and we show that, unlike the definite case, many of these surfaces carry infinite-dimensional families of such structures. We provide also compact examples of complex surfaces with para-hyperhermitian structures which are not locally conformally para-hyperkaehler. Finally, we discuss the problem of non-existence of para-hyperhermitian structures on Inoue surfaces of type S{sup 0} and provide a list of compact complex surfaces which could carry para-hypercomplex structures.

  2. Fabrication of scalable tissue engineering scaffolds with dual-pore microarchitecture by combining 3D printing and particle leaching

    Energy Technology Data Exchange (ETDEWEB)

    Mohanty, Soumyaranjan; Sanger, Kuldeep; Heiskanen, Arto [DTU Nanotech, Department of Micro- and Nanotechnology, Technical University of Denmark, Ørsteds Plads, DK-2800 Kgs. Lyngby (Denmark); Trifol, Jon; Szabo, Peter [Danish Polymer Centre, Department of Chemical and Biochemical Engineering, Søltofts Plads, Building 229, DK-2800 Kgs. Lyngby (Denmark); Dufva, Marin; Emnéus, Jenny [DTU Nanotech, Department of Micro- and Nanotechnology, Technical University of Denmark, Ørsteds Plads, DK-2800 Kgs. Lyngby (Denmark); Wolff, Anders, E-mail: anders.wolff@nanotech.dtu.dk [DTU Nanotech, Department of Micro- and Nanotechnology, Technical University of Denmark, Ørsteds Plads, DK-2800 Kgs. Lyngby (Denmark)

    2016-04-01

    Limitations in controlling scaffold architecture using traditional fabrication techniques are a problem when constructing engineered tissues/organs. Recently, integration of two pore architectures to generate dual-pore scaffolds with tailored physical properties has attracted wide attention in tissue engineering community. Such scaffolds features primary structured pores which can efficiently enhance nutrient/oxygen supply to the surrounding, in combination with secondary random pores, which give high surface area for cell adhesion and proliferation. Here, we present a new technique to fabricate dual-pore scaffolds for various tissue engineering applications where 3D printing of poly(vinyl alcohol) (PVA) mould is combined with salt leaching process. In this technique the sacrificial PVA mould, determining the structured pore architecture, was filled with salt crystals to define the random pore regions of the scaffold. After crosslinking the casted polymer the combined PVA-salt mould was dissolved in water. The technique has advantages over previously reported ones, such as automated assembly of the sacrificial mould, and precise control over pore architecture/dimensions by 3D printing parameters. In this study, polydimethylsiloxane and biodegradable poly(ϵ-caprolactone) were used for fabrication. However, we show that this technique is also suitable for other biocompatible/biodegradable polymers. Various physical and mechanical properties of the dual-pore scaffolds were compared with control scaffolds with either only structured or only random pores, fabricated using previously reported methods. The fabricated dual-pore scaffolds supported high cell density, due to the random pores, in combination with uniform cell distribution throughout the scaffold, and higher cell proliferation and viability due to efficient nutrient/oxygen transport through the structured pores. In conclusion, the described fabrication technique is rapid, inexpensive, scalable, and compatible

  3. Fabrication of scalable tissue engineering scaffolds with dual-pore microarchitecture by combining 3D printing and particle leaching

    International Nuclear Information System (INIS)

    Mohanty, Soumyaranjan; Sanger, Kuldeep; Heiskanen, Arto; Trifol, Jon; Szabo, Peter; Dufva, Marin; Emnéus, Jenny; Wolff, Anders

    2016-01-01

    Limitations in controlling scaffold architecture using traditional fabrication techniques are a problem when constructing engineered tissues/organs. Recently, integration of two pore architectures to generate dual-pore scaffolds with tailored physical properties has attracted wide attention in tissue engineering community. Such scaffolds features primary structured pores which can efficiently enhance nutrient/oxygen supply to the surrounding, in combination with secondary random pores, which give high surface area for cell adhesion and proliferation. Here, we present a new technique to fabricate dual-pore scaffolds for various tissue engineering applications where 3D printing of poly(vinyl alcohol) (PVA) mould is combined with salt leaching process. In this technique the sacrificial PVA mould, determining the structured pore architecture, was filled with salt crystals to define the random pore regions of the scaffold. After crosslinking the casted polymer the combined PVA-salt mould was dissolved in water. The technique has advantages over previously reported ones, such as automated assembly of the sacrificial mould, and precise control over pore architecture/dimensions by 3D printing parameters. In this study, polydimethylsiloxane and biodegradable poly(ϵ-caprolactone) were used for fabrication. However, we show that this technique is also suitable for other biocompatible/biodegradable polymers. Various physical and mechanical properties of the dual-pore scaffolds were compared with control scaffolds with either only structured or only random pores, fabricated using previously reported methods. The fabricated dual-pore scaffolds supported high cell density, due to the random pores, in combination with uniform cell distribution throughout the scaffold, and higher cell proliferation and viability due to efficient nutrient/oxygen transport through the structured pores. In conclusion, the described fabrication technique is rapid, inexpensive, scalable, and compatible

  4. Distinct modulation of inactivation by a residue in the pore domain of voltage-gated Na+channels: mechanistic insights from recent crystal structures.

    Science.gov (United States)

    Cervenka, Rene; Lukacs, Peter; Gawali, Vaibhavkumar S; Ke, Song; Koenig, Xaver; Rubi, Lena; Zarrabi, Touran; Hilber, Karlheinz; Sandtner, Walter; Stary-Weinzinger, Anna; Todt, Hannes

    2018-01-12

    Inactivation of voltage-gated Na + channels (VGSC) is essential for the regulation of cellular excitability. The molecular rearrangement underlying inactivation is thought to involve the intracellular linker between domains III and IV serving as inactivation lid, the receptor for the lid (domain III S4-S5 linker) and the pore-lining S6 segements. To better understand the role of the domain IV S6 segment in inactivation we performed a cysteine scanning mutagenesis of this region in rNav 1.4 channels and screened the constructs for perturbations in the voltage-dependence of steady state inactivation. This screen was performed in the background of wild-type channels and in channels carrying the mutation K1237E, which profoundly alters both permeation and gating-properties. Of all tested constructs the mutation I1581C was unique in that the mutation-induced gating changes were strongly influenced by the mutational background. This suggests that I1581 is involved in specific short-range interactions during inactivation. In recently published crystal structures VGSCs the respective amino acids homologous to I1581 appear to control a bend of the S6 segment which is critical to the gating process. Furthermore, I1581 may be involved in the transmission of the movement of the DIII voltage-sensor to the domain IV S6 segment.

  5. Surface Structures of Model Metal Catalysts in Reactant Gases.

    Science.gov (United States)

    Tao, Franklin Feng; Ralston, Walter T; Liu, Huimin; Somorjai, Gabor A

    2018-01-18

    Atomic scale knowledge of the surface structure of a metal catalyst is essential for fundamentally understanding the catalytic reactions performed on it. A correlation between the true atomic surface structure of a metal catalyst under reaction conditions and the corresponding catalytic performance is the key in pursuing mechanistic insight at a molecular level. Here the surface structures of model, metal catalysts in both ultrahigh vacuum (UHV) and gaseous environments of CO at a wide range of pressures are discussed. The complexity of observed surface structures in CO is illustrated, driving the necessity for visualization of the catalytic metals under realistic reaction conditions. Technical barriers for visualization of metal surfaces in situ at high temperature and high pressure are discussed.

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

    Science.gov (United States)

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

    2015-12-01

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

  7. Transmitted-light microscopy - a new method for surface structure analysis of cleanable non-woven dust filter media.

    Science.gov (United States)

    Rud, Heimo; Mauschitz, Gerd; Höflinger, Wilhelm

    2007-06-18

    With regard to the more stringent legislation in environmental protection strong efforts have been made to reduce fine dust emissions. As a result filter devices equipped with dry operating cleanable textile filter media have become one of the most favoured separation techniques for fine dust. For improvement of cleanable filter media it is necessary to understand the influence of their structure on their filtration behaviour and to develop parameters for characterising their clogging and penetration behaviour. The aim of the research work presented in this paper was to improve the already developed reflected-light method [W. Koschutnig, G. Mauschitz, W. Höflinger, Charakterisierung der Oberflächenbehandlung und des Verstopfungsverhaltens von abreinigbaren Staubfiltermedien mittels Bildanalyse, CIT 76, 2004, 10, 5 pp.] to get a structure parameter of cleanable non-woven dust filter media, which can give information about the particle penetration. To reach this goal transmitted-light is used instead of reflected-light. By that way images with higher contrast will be achieved which enable to define a mean hydraulic diameter for the pores near the outer surface of cleanable non-woven dust filter media. Experimental measurements were carried out which prove that the mean hydraulic pore diameter can be a measure for the particle penetration of a filter medium. The pore volume equivalent, which can be used as a measure of the dust storage capacity of the filter medium can also be detected by the transmitted-light method.

  8. Local structures of mesoporous bioactive glasses and their surface alterations in vitro: inferences from solid-state nuclear magnetic resonance

    Science.gov (United States)

    Gunawidjaja, Philips N.; Mathew, Renny; Lo, Andy Y. H.; Izquierdo-Barba, Isabel; García, Ana; Arcos, Daniel; Mattias Edén, María Vallet-Regí

    2012-01-01

    We review the benefits of using 29Si and 1H magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy for probing the local structures of both bulk and surface portions of mesoporous bioactive glasses (MBGs) of the CaO–SiO2−(P2O5) system. These mesoporous materials exhibit an ordered pore arrangement, and are promising candidates for improved bone and tooth implants. We discuss experimental MAS NMR results from three MBGs displaying different Ca, Si and P contents: the 29Si NMR spectra were recorded either directly by employing radio-frequency pulses to 29Si, or by magnetization transfers from neighbouring protons using cross polarization, thereby providing quantitative information about the silicate speciation present in the pore wall and at the MBG surface, respectively. The surface modifications were monitored for the three MBGs during their immersion in a simulated body fluid (SBF) for intervals between 30 min and one week. The results were formulated as a reaction sequence describing the interconversions between the distinct silicate species. We generally observed a depletion of Ca2+ ions at the MBG surface, and a minor condensation of the silicate-surface network over one week of SBF soaking. PMID:22349247

  9. Surfaces of Microparticles in Colloids: Structure and Molecular Adsorption Kinetics

    Science.gov (United States)

    Dai, Hai-Lung

    2002-03-01

    Surfaces of micron and sub-micron size particles in liquid solution are probed by second harmonic generation (SHG) facilitated with femtosecond laser pulses. The particles probed include inorganic objects such as carbon black and color pigments, polymeric species like polystyrene beads, and biological systems such as blood cells and ecoli. In the experiments, dye molecules are first adsorbed onto the particle surface to allow generation of second harmonics upon light irradiation. Competition for adsorption between these surface dye molecules and the molecules of interest in the solution is then monitored by the SHG signal to reveal the molecular adsorption kinetics and surface structure. Specifically, surfactant adsorption on polymer surfaces, the structure of carbon black surface, and protein adsorption on biological surfaces, monitored by this technique, will be discussed.

  10. Surface forces between rough and topographically structured interfaces

    DEFF Research Database (Denmark)

    Thormann, Esben

    2017-01-01

    and manufactured materials, which possess topographical variations. Further, with technological advances in nanotechnology, fabrication of nano- or micro-structured surfaces has become increasingly important for many applications, which calls for a better understanding of the effect of surface topography...... on the interaction between interfaces. This paper presents a review of the current state of understanding of the effect of surface roughness on DLVO forces, as well as on the interactions between topographically structured hydrophobic surfaces in water. While the first case is a natural choice because it represents...

  11. Structure of stable degeneration of K3 surfaces into pairs of rational elliptic surfaces

    OpenAIRE

    Kimura, Yusuke

    2018-01-01

    F-theory/heterotic duality is formulated in the stable degeneration limit of a K3 fibration on the F-theory side. In this note, we analyze the structure of the stable degeneration limit. We discuss whether stable degeneration exists for pairs of rational elliptic surfaces. We demonstrate that, when two rational elliptic surfaces have an identical complex structure, stable degeneration always exists. We provide an equation that systematically describes the stable degeneration of a K3 surface i...

  12. Characterization of polymer surface structure and surface mechanical behaviour by sum frequency generation surface vibrational spectroscopy and atomic force microscopy

    International Nuclear Information System (INIS)

    Opdahl, Aric; Koffas, Telly S; Amitay-Sadovsky, Ella; Kim, Joonyeong; Somorjai, Gabor A

    2004-01-01

    Sum frequency generation (SFG) vibrational spectroscopy and atomic force microscopy (AFM) have been used to study polymer surface structure and surface mechanical behaviour, specifically to study the relationships between the surface properties of polymers and their bulk compositions and the environment to which the polymer is exposed. The combination of SFG surface vibrational spectroscopy and AFM has been used to study surface segregation behaviour of polyolefin blends at the polymer/air and polymer/solid interfaces. SFG surface vibrational spectroscopy and AFM experiments have also been performed to characterize the properties of polymer/liquid and polymer/polymer interfaces, focusing on hydrogel materials. A method was developed to study the surface properties of hydrogel contact lens materials at various hydration conditions. Finally, the effect of mechanical stretching on the surface composition and surface mechanical behaviour of phase-separated polyurethanes, used in biomedical implant devices, has been studied by both SFG surface vibrational spectroscopy and AFM. (topical review)

  13. Structure of stable degeneration of K3 surfaces into pairs of rational elliptic surfaces

    Science.gov (United States)

    Kimura, Yusuke

    2018-03-01

    F-theory/heterotic duality is formulated in the stable degeneration limit of a K3 fibration on the F-theory side. In this note, we analyze the structure of the stable degeneration limit. We discuss whether stable degeneration exists for pairs of rational elliptic surfaces. We demonstrate that, when two rational elliptic surfaces have an identical complex structure, stable degeneration always exists. We provide an equation that systematically describes the stable degeneration of a K3 surface into a pair of isomorphic rational elliptic surfaces. When two rational elliptic surfaces have different complex structures, whether their sum glued along a smooth fiber admits deformation to a K3 surface can be determined by studying the structure of the K3 lattice. We investigate the lattice theoretic condition to determine whether a deformation to a K3 surface exists for pairs of extremal rational elliptic surfaces. In addition, we discuss the configurations of singular fibers under stable degeneration. The sum of two isomorphic rational elliptic surfaces glued together admits a deformation to a K3 surface, the singular fibers of which are twice that of the rational elliptic surface. For special situations, singular fibers of the resulting K3 surface collide and they are enhanced to a fiber of another type. Some K3 surfaces become attractive in these situations. We determine the complex structures and the Weierstrass forms of these attractive K3 surfaces. We also deduce the gauge groups in F-theory compactifications on these attractive K3 surfaces times a K3. E 6, E 7, E 8, SU(5), and SO(10) gauge groups arise in these compactifications.

  14. Quasilinear ridge structures in water surface waves

    Science.gov (United States)

    Blümel, R.; Davidson, I. H.; Reinhardt, W. P.; Lin, H.; Sharnoff, M.

    1992-02-01

    Nodal patterns of stationary capillary waves formed on the surface of water enclosed in an agitated ripple tank with circular and stadium-shaped cylindrical walls are examined in the low-frequency (ν700 Hz) regimes. In the low-frequency regime, in agreement with predictions of quantum-chaos theory, the shape of the tank's boundaries (integrable or nonintegrable) dictates the type of nodal patterns obtained. In the high-frequency regime we obtain nodal patterns characterized by short-range order (called ``scarlets'' because they are believed to be the precursors of quantum scars), as recently predicted in the quantum-chaos context by P. O'Connor, J. Gehlen, and E. J. Heller [Phys. Rev. Lett. 58, 1296 (1987)].

  15. 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.

  16. Influence of surface structure and chemistry on water droplet splashing.

    Science.gov (United States)

    Koch, Kerstin; Grichnik, Roland

    2016-08-06

    Water droplet splashing and aerosolization play a role in human hygiene and health systems as well as in crop culturing. Prevention or reduction of splashing can prevent transmission of diseases between animals and plants and keep technical systems such as pipe or bottling systems free of contamination. This study demonstrates to what extent the surface chemistry and structures influence the water droplet splashing behaviour. Smooth surfaces and structured replicas of Calathea zebrina (Sims) Lindl. leaves were produced. Modification of their wettability was done by coating with hydrophobizing and hydrophilizing agents. Their wetting was characterized by contact angle measurement and splashing behaviour was observed with a high-speed video camera. Hydrophobic and superhydrophilic surfaces generally showed fewer tendencies to splash than hydrophobic ones. Structuring amplified the underlying behaviour of the surface chemistries, increasing hydrophobic surfaces' tendency to splash and decreasing splash on hydrophilic surfaces by quickly transporting water off the impact point by capillary forces. The non-porous surface structures found in C. zebrina could easily be applied to technical products such as plastic foils or mats and coated with hydrophilizing agents to suppress splash in areas of increased hygiene requirements or wherever pooling of liquids is not desirable.This article is part of the themed issue 'Bioinspired hierarchically structured surfaces for green science'. © 2016 The Author(s).

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

    Science.gov (United States)

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

    2015-12-01

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

  18. Two separate interfaces between the voltage sensor and pore are required for the function of voltage-dependent K(+ channels.

    Directory of Open Access Journals (Sweden)

    Seok-Yong Lee

    2009-03-01

    Full Text Available Voltage-dependent K(+ (Kv channels gate open in response to the membrane voltage. To further our understanding of how cell membrane voltage regulates the opening of a Kv channel, we have studied the protein interfaces that attach the voltage-sensor domains to the pore. In the crystal structure, three physical interfaces exist. Only two of these consist of amino acids that are co-evolved across the interface between voltage sensor and pore according to statistical coupling analysis of 360 Kv channel sequences. A first co-evolved interface is formed by the S4-S5 linkers (one from each of four voltage sensors, which form a cuff surrounding the S6-lined pore opening at the intracellular surface. The crystal structure and published mutational studies support the hypothesis that the S4-S5 linkers convert voltage-sensor motions directly into gate opening and closing. A second co-evolved interface forms a small contact surface between S1 of the voltage sensor and the pore helix near the extracellular surface. We demonstrate through mutagenesis that this interface is necessary for the function and/or structure of two different Kv channels. This second interface is well positioned to act as a second anchor point between the voltage sensor and the pore, thus allowing efficient transmission of conformational changes to the pore's gate.

  19. Imprinted and injection-molded nano-structured optical surfaces

    DEFF Research Database (Denmark)

    Christiansen, Alexander Bruun; Højlund-Nielsen, Emil; Clausen, Jeppe Sandvik

    2013-01-01

    . In this paper, nanostructured polymer surfaces suitable for up-scalable polymer replication methods, such as imprinting/embossing and injection-molding, are discussed. The limiting case of injection-moulding compatible designs is investigated. Anti-reflective polymer surfaces are realized by replication...... of light from polymer surfaces and their implication for creating structural colors is discussed. In the case of injection-moulding compatible designs, the maximum reflection of nano-scale textured surfaces cannot exceed the Fresnel reflection of a corresponding flat polymer surface, which is approx. 4...

  20. Dimers on Surface Graphs and Spin Structures. I

    DEFF Research Database (Denmark)

    Cimasoni, David; Reshetikhin, Nicolai

    2007-01-01

    Partition functions for dimers on closed oriented surfaces are known to be alternating sums of Pfaffians of Kasteleyn matrices. In this paper, we obtain the formula for the coefficients in terms of discrete spin structures....

  1. Synthesis, structure and Hirshfeld surface analysis, vibrational and ...

    Indian Academy of Sciences (India)

    dimensional architecture. Hirshfeld surface analysis for visually analysing intermolecular interactions in crystal structures employing molecular sur- face contours and 2D fingerprint plots has been used to scrutinize molecular shapes. The vibration ...

  2. Domain Structures in Nematic Liquid Crystals on a Polycarbonate Surface

    Directory of Open Access Journals (Sweden)

    Vasily F. Shabanov

    2013-08-01

    Full Text Available Alignment of nematic liquid crystals on polycarbonate films obtained with the use of solvents with different solvations is studied. Domain structures occurring during the growth on the polymer surface against the background of the initial thread-like or schlieren texture are demonstrated. It is established by optical methods that the domains are stable formations visualizing the polymer surface structures. In nematic droplets, the temperature-induced transition from the domain structure with two extinction bands to the structure with four bands is observed. This transition is shown to be caused by reorientation of the nematic director in the liquid crystal volume from the planar alignment to the homeotropic state with the pronounced radial configuration of nematic molecules on the surface. The observed textures are compared with different combinations of the volume LC orientations and the radial distribution of the director field and the disclination lines at the polycarbonate surface.

  3. Electronic structure of disordered alloys, surfaces and interfaces

    CERN Document Server

    Turek, Ilja; Kudrnovský, Josef; Šob, Mojmír; Weinberger, Peter

    1997-01-01

    At present, there is an increasing interest in the prediction of properties of classical and new materials such as substitutional alloys, their surfaces, and metallic or semiconductor multilayers. A detailed understanding based on a thus of the utmost importance for fu­ microscopic, parameter-free approach is ture developments in solid state physics and materials science. The interrela­ tion between electronic and structural properties at surfaces plays a key role for a microscopic understanding of phenomena as diverse as catalysis, corrosion, chemisorption and crystal growth. Remarkable progress has been made in the past 10-15 years in the understand­ ing of behavior of ideal crystals and their surfaces by relating their properties to the underlying electronic structure as determined from the first principles. Similar studies of complex systems like imperfect surfaces, interfaces, and mul­ tilayered structures seem to be accessible by now. Conventional band-structure methods, however, are of limited use ...

  4. Surface structure investigations using noncontact atomic force microscopy

    International Nuclear Information System (INIS)

    Kolodziej, J.J.; Such, B.; Goryl, M.; Krok, F.; Piatkowski, P.; Szymonski, M.

    2006-01-01

    Surfaces of several A III B V compound semiconductors (InSb, GaAs, InP, InAs) of the (0 0 1) orientation have been studied with noncontact atomic force microscopy (NC-AFM). Obtained atomically resolved patterns have been compared with structural models available in the literature. It is shown that NC-AFM is an efficient tool for imaging complex surface structures in real space. It is also demonstrated that the recent structural models of III-V compound surfaces provide a sound base for interpretation of majority of features present in recorded patterns. However, there are also many new findings revealed by the NC-AFM method that is still new experimental technique in the context of surface structure determination

  5. Surface Relaxations, Surface Energies and Electronic Structures of BaSnO3 (001) Surfaces: Ab Initio Calculations

    Science.gov (United States)

    Slassi, A.; Hammi, M.; El Rhazouani, O.

    2017-07-01

    The surface relaxations, surface energies and electronic structures of BaO- and SnO2-terminated BaSnO3 (001) surfaces have been studied by employing the first-principles density functional theory. For both terminations, we find that the upper-layer Ba and Sn atoms move inward, whereas upper-layer O atoms move outward from the surface. Moreover, the largest relaxations are occurred on the first-layer atoms of both terminations. The surface rumpling of BaO-terminated BaSnO3 (001) is slightly less than that of the SnO2-terminated BaSnO3 (001) surface. The surface energies show that both terminated surfaces are energetically stable and favorable. Finally, the surface band gap is slightly decreased for the BaO termination, while it is dramatically decreased for the SnO2 termination.

  6. Thermal migration of deuterium implanted in graphite: Influence of free surface proximity and structure

    Energy Technology Data Exchange (ETDEWEB)

    Le Guillou, M. [Institut de Physique Nucléaire de Lyon, CNRS/IN2P3 UMR 5822, Université Claude Bernard Lyon 1, Université de Lyon, F-69622 Villeurbanne cedex (France); Moncoffre, N., E-mail: n.moncoffre@ipnl.in2p3.fr [Institut de Physique Nucléaire de Lyon, CNRS/IN2P3 UMR 5822, Université Claude Bernard Lyon 1, Université de Lyon, F-69622 Villeurbanne cedex (France); Toulhoat, N. [Institut de Physique Nucléaire de Lyon, CNRS/IN2P3 UMR 5822, Université Claude Bernard Lyon 1, Université de Lyon, F-69622 Villeurbanne cedex (France); CEA/DEN – Centre de Saclay, F-91191 Gif-sur-Yvette cedex (France); Pipon, Y. [Institut de Physique Nucléaire de Lyon, CNRS/IN2P3 UMR 5822, Université Claude Bernard Lyon 1, Université de Lyon, F-69622 Villeurbanne cedex (France); Institut Universitaire Technologique, Université Claude Bernard Lyon 1, Université de Lyon, F-69622 Villeurbanne cedex (France); Ammar, M.R. [CNRS, CEMHTI UPR3079, Université Orléans, CS90055, F-45071 Orléans cedex 2 (France); Rouzaud, J.N.; Deldicque, D. [Laboratoire de Géologie de l’Ecole Normale Supérieure, Paris, UMR CNRS ENS 8538, F-75231 Paris cedex 5 (France)

    2016-03-15

    This paper is a contribution to the study of the behavior of activation products produced in irradiated nuclear graphite, graphite being the moderator of the first French generation of CO{sub 2} cooled nuclear fission reactors. This paper is focused on the thermal release of Tritium, a major contributor to the initial activity, taking into account the role of the free surfaces (open pores and graphite surface). Two kinds of graphite were compared. On one hand, Highly Oriented Pyrolitic Graphite (HOPG), a model well graphitized graphite, and on the other hand, SLA2, a porous less graphitized nuclear graphite. Deuterium ion implantation at three different energies 70, 200 and 390 keV allows simulating the presence of Tritium at three different depths, corresponding respectively to projected ranges R{sub p} of 0.75, 1.7 and 3.2 μm. The D isotopic tracing is performed thanks to the D({sup 3}He,p){sup 4}He nuclear reaction. The graphite structure is studied by Raman microspectrometry. Thermal annealing is performed in the temperature range 200–1200 °C up to 300 h annealing time. As observed in a previous study, the results show that the D release occurs according to three kinetic regimes: a rapid permeation through open pores, a transient regime corresponding to detrapping and diffusion of D located at low energy sites correlated to the edges of crystallites and finally a saturation regime attributed to detrapping of interstitial D located at high energy sites inside the crystallites. Below 600 °C, D release is negligible whatever the implantation depth and the graphite type. The present paper clearly puts forward that above 600 °C, the D release decreases at deeper implantation depths and strongly depends on the graphite structure. In HOPG where high energy sites are more abundant, the D release is less dependent on the surface proximity compared to SLA2. In SLA2, in which the low energy sites prevail, the D release curves are clearly shifted towards lower

  7. Thermal migration of deuterium implanted in graphite: Influence of free surface proximity and structure

    Science.gov (United States)

    Le Guillou, M.; Moncoffre, N.; Toulhoat, N.; Pipon, Y.; Ammar, M. R.; Rouzaud, J. N.; Deldicque, D.

    2016-03-01

    This paper is a contribution to the study of the behavior of activation products produced in irradiated nuclear graphite, graphite being the moderator of the first French generation of CO2 cooled nuclear fission reactors. This paper is focused on the thermal release of Tritium, a major contributor to the initial activity, taking into account the role of the free surfaces (open pores and graphite surface). Two kinds of graphite were compared. On one hand, Highly Oriented Pyrolitic Graphite (HOPG), a model well graphitized graphite, and on the other hand, SLA2, a porous less graphitized nuclear graphite. Deuterium ion implantation at three different energies 70, 200 and 390 keV allows simulating the presence of Tritium at three different depths, corresponding respectively to projected ranges Rp of 0.75, 1.7 and 3.2 μm. The D isotopic tracing is performed thanks to the D(3He,p)4He nuclear reaction. The graphite structure is studied by Raman microspectrometry. Thermal annealing is performed in the temperature range 200-1200 °C up to 300 h annealing time. As observed in a previous study, the results show that the D release occurs according to three kinetic regimes: a rapid permeation through open pores, a transient regime corresponding to detrapping and diffusion of D located at low energy sites correlated to the edges of crystallites and finally a saturation regime attributed to detrapping of interstitial D located at high energy sites inside the crystallites. Below 600 °C, D release is negligible whatever the implantation depth and the graphite type. The present paper clearly puts forward that above 600 °C, the D release decreases at deeper implantation depths and strongly depends on the graphite structure. In HOPG where high energy sites are more abundant, the D release is less dependent on the surface proximity compared to SLA2. In SLA2, in which the low energy sites prevail, the D release curves are clearly shifted towards lower temperatures when D is located

  8. Laser-induced nanoscale superhydrophobic structures on metal surfaces

    NARCIS (Netherlands)

    Radhakrishnan, J.; Pathiraj, B.; Karatay, Elif; Römer, Gerardus Richardus, Bernardus, Engelina; Huis in 't Veld, Bert

    2011-01-01

    The combination of a dual-scale (nano and micro) roughness with an inherent low-surface energy coating material is an essential factor for the development of superhydrophobic surfaces. Ultrashort pulse laser (USPL) machining/structuring is a promising technique for obtaining the dual-scale

  9. 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.

  10. On the role of melt flow into the surface structure and porosity development during selective laser melting

    International Nuclear Information System (INIS)

    Qiu, Chunlei; Panwisawas, Chinnapat; Ward, Mark; Basoalto, Hector C.; Brooks, Jeffery W.; Attallah, Moataz M.

    2015-01-01

    In this study, the development of surface structure and porosity of Ti–6Al–4V samples fabricated by selective laser melting under different laser scanning speeds and powder layer thicknesses has been studied and correlated with the melt flow behaviour through both experimental and modelling approaches. The as-fabricated samples were investigated using optical microscopy (OM) and scanning electron microscopy (SEM). The interaction between laser beam and powder particles was studied by both high speed imaging observation and computational fluid dynamics (CFD) calculation. It was found that at a high laser power and a fixed powder layer thickness (20 μm), the samples contain particularly low porosity when the laser scanning speeds are below 2700 mm/s. Further increase of scanning speed led to increase of porosity but not significantly. The porosity is even more sensitive to powder layer thickness with the use of thick powder layers (above 40 μm) leading to significant porosity. The increase of porosity with laser scanning speed and powder layer thickness is not inconsistent with the observed increase in surface roughness complicated by increasingly irregular-shaped laser scanned tracks and an increased number of discontinuity and cave-like pores on the top surfaces. The formation of pores and development of rough surfaces were found by both high speed imaging and modelling, to be strongly associated with unstable melt flow and splashing of molten material

  11. Structures of multidomain proteins adsorbed on hydrophobic interaction chromatography surfaces.

    Science.gov (United States)

    Gospodarek, Adrian M; Sun, Weitong; O'Connell, John P; Fernandez, Erik J

    2014-12-05

    In hydrophobic interaction chromatography (HIC), interactions between buried hydrophobic residues and HIC surfaces can cause conformational changes that interfere with separations and cause yield losses. This paper extends our previous investigations of protein unfolding in HIC chromatography by identifying protein structures on HIC surfaces under denaturing conditions and relating them to solution behavior. The thermal unfolding of three model multidomain proteins on three HIC surfaces of differing hydrophobicities was investigated with hydrogen exchange mass spectrometry (HXMS). The data were analyzed to obtain unfolding rates and Gibbs free energies for unfolding of adsorbed proteins. The melting temperatures of the proteins were lowered, but by different amounts, on the different surfaces. In addition, the structures of the proteins on the chromatographic surfaces were similar to the partially unfolded structures produced in the absence of a surface by temperature as well as by chemical denaturants. Finally, it was found that patterns of residue exposure to solvent on different surfaces at different temperatures can be largely superimposed. These findings suggest that protein unfolding on various HIC surfaces might be quantitatively related to protein unfolding in solution and that details of surface unfolding behavior might be generalized. Copyright © 2014 Elsevier B.V. All rights reserved.

  12. Color effects from scattering on random surface structures in dielectrics

    DEFF Research Database (Denmark)

    Clausen, Jeppe; Christiansen, Alexander B; Garnæs, Jørgen

    2012-01-01

    We show that cheap large area color filters, based on surface scattering, can be fabricated in dielectric materials by replication of random structures in silicon. The specular transmittance of three different types of structures, corresponding to three different colors, have been characterized....... The angle resolved scattering has been measured and compared to predictions based on the measured surface topography and by the use of non-paraxial scalar diffraction theory. From this it is shown that the color of the transmitted light can be predicted from the topography of the randomly textured surfaces....

  13. Formation of highly efficient dye-sensitized solar cells by hierarchical pore generation with nanoporous TiO{sub 2} spheres

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Yong Joo; Lee, Mi Hyeon; Kim, Hark Jin; Lim, Gooil; Choi, Young Sik; Lee, Wan In [Nano Materials and Devices Lab., Department of Chemistry, Inha University Incheon 402-751 (Korea); Park, Nam-Gyu; Kim, Kyungkon [Center for Energy Materials Materials Science and Technology Division, Korea Institute Science and Technology (KIST) Seoul 136-791 (Korea)

    2009-09-25

    Nanoporous TiO{sub 2} structures were successfully applied for the fabrication of DSC electrodes, providing high surface areas and large pore sizes at the same time. High photocurrent was induced in these DSCs by great adsorption of dye molecules and efficient electrolyte diffusion, caused by the generated hierarchical pore structures in the TiO{sub 2} layer. (Abstract Copyright [2009], Wiley Periodicals, Inc.)

  14. Synthesis, structure and Hirshfeld surface analysis, vibrational and ...

    Indian Academy of Sciences (India)

    Hirshfeld surface analysis for visually analysing intermolecular interactions in crystal structures employing molecular surfacecontours and 2D fingerprint plots has been used to scrutinize molecular shapes. The vibration properties of this structure were studied by IR spectroscopy and Raman scattering. Vibration spectra ...

  15. Facile fabrication of dendritic silver structures and their surface ...

    Indian Academy of Sciences (India)

    The dendritic or fractal Ag nanostructures have attracted the attention of scientists recently due to their attractive supramolecular structures, large surface area and excellent connectivity between the different parts of the structures. Significantly, it has been established that dendritic or fractal Ag nanostructures are an excel-.

  16. Characteristics of surface wind structure of tropical cyclones over the ...

    Indian Academy of Sciences (India)

    the effective utilization of above-mentioned multi- platform-based satellite-derived wind product is very essential to minimize the error in intensity and structure monitoring and forecast. So, a study has been undertaken to analyze the mean character- istics of surface wind distribution and hence the structure of TC based on ...

  17. Influence of the atomic structure of crystal surfaces on the surface diffusion in medium temperature range

    International Nuclear Information System (INIS)

    Cousty, J.P.

    1981-12-01

    In this work, we have studied the influence of atomic structure of crystal surface on surface self-diffusion in the medium temperature range. Two ways are followed. First, we have measured, using a radiotracer method, the self-diffusion coefficient at 820 K (0.6 T melting) on copper surfaces both the structure and the cleanliness of which were stable during the experiment. We have shown that the interaction between mobile surface defects and steps can be studied through measurements of the anisotropy of surface self diffusion. Second, the behavior of an adatom and a surface vacancy is simulated via a molecular dynamics method, on several surfaces of a Lennard Jones crystal. An inventory of possible migration mechanisms of these surface defects has been drawn between 0.35 and 0.45 Tsub(m). The results obtained with both the methods point out the influence of the surface atomic structure in surface self-diffusion in the medium temperature range [fr

  18. Near Surface Characterization Of Concrete Structures Using Rayleigh Waves

    Science.gov (United States)

    Al Wardany, R.; Ballivy, G.; Saleh, K.; Rhazi, J.; Gallias, J.

    2004-05-01

    The deterioration of the near surface concrete minimises the structural behaviour, capacity, and working lifespan for civil engineering structures and dams. Repair strategy and maintenance require careful examination and determination of the degraded depth. In this aim, dispersive properties of Rayleigh waves are used to detect concrete stratification and cracks. Current work focuses on an experimental study and application of multichannel Rayleigh wave methods on high concrete volumes. The method considers a wavefield in the frequency-wavenumber domain to separate existing Rayleigh modes and determine the appropriate shear wave velocity profile. The classical phase unwrapping analysis technique is also used to localise near surface cracks and defects. This new way in concrete nondestructive testing lead to a best evaluation of near surface stiffness and properties from the surface of concrete structures.

  19. The physical structure of the oceanic surface-layer

    Energy Technology Data Exchange (ETDEWEB)

    Fedorov, K.N.

    1981-01-01

    A study is presented of the structure of the near-surface layer of the ocean under various hydrometeorological conditions. Such a study allows the isolation of border measures for a four characteristic regime for the top ocean layer: 1) intensive wind-wave mixing; 2) Langmuir circulation; 3) intense solar heating during still and calm weather (with and without internal wave modulations); 4) a pressing-out of surface sediment. It is demonstrated that the spatial temperature change in the ocean surface, the thermal structure, and the heat attainment in the top layer have various characteristics during different regimes and this must be considered during the measuring of the ocean surface temperature with the contact method as well as during the comparison of contact and satallite data on the ocean surface temperature. The necessity for more research in this area is underscored.

  20. The effects of chain length, embedded polar groups, pressure, and pore shape on structure and retention in reversed-phase liquid chromatography: molecular-level insights from Monte Carlo simulations.

    Science.gov (United States)

    Rafferty, Jake L; Siepmann, J Ilja; Schure, Mark R

    2009-03-20

    Particle-based simulations using the configurational-bias and Gibbs ensemble Monte Carlo techniques are carried out to probe the effects of various chromatographic parameters on bonded-phase chain conformation, solvent penetration, and retention in reversed-phase liquid chromatography (RPLC). Specifically, we investigate the effects due to the length of the bonded-phase chains (C(18), C(8), and C(1)), the inclusion of embedded polar groups (amide and ether) near the base of the bonded-phase chains, the column pressure (1, 400, and 1000 atm), and the pore shape (planar slit pore versus cylindrical pore with a 60A diameter). These simulations utilize a bonded-phase coverage of 2.9 micromol/m(2)and a mobile phase containing methanol at a molfraction of 33% (about 50% by volume). The simulations show that chain length, embedded polar groups, and pore shape significantly alter structural and retentive properties of the model RPLC system, whereas the column pressure has a relatively small effect. The simulation results are extensively compared to retention measurements. A molecular view of the RPLC retention mechanism emerges that is more complex than can be inferred from thermodynamic measurements.

  1. A genetic algorithm approach in interface and surface structure optimization

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Jian [Iowa State Univ., Ames, IA (United States)

    2010-01-01

    The thesis is divided into two parts. In the first part a global optimization method is developed for the interface and surface structures optimization. Two prototype systems are chosen to be studied. One is Si[001] symmetric tilted grain boundaries and the other is Ag/Au induced Si(111) surface. It is found that Genetic Algorithm is very efficient in finding lowest energy structures in both cases. Not only existing structures in the experiments can be reproduced, but also many new structures can be predicted using Genetic Algorithm. Thus it is shown that Genetic Algorithm is a extremely powerful tool for the material structures predictions. The second part of the thesis is devoted to the explanation of an experimental observation of thermal radiation from three-dimensional tungsten photonic crystal structures. The experimental results seems astounding and confusing, yet the theoretical models in the paper revealed the physics insight behind the phenomena and can well reproduced the experimental results.

  2. Nano-porous carbide derived carbon with tunable pore size: synthesis and energy-related applications

    International Nuclear Information System (INIS)

    Gleb Yushin; John Chmiola; Ranjan K Dash; Elisabeth Hoffman; Michel Barsoum; Yury Gogotsi; Giovanna Laudisio; John E Fischer

    2005-01-01

    The large surface area and adjustable internal surface chemistry of porous carbons are attractive for a wide range of energy applications, including gas separation and storage, high power super-capacitors and lithium ion batteries. Major efforts in the field have been directed toward control of pore size, shape and uniformity, and total pore volume. Here we demonstrate that pore size can be precisely tuned with sub-Angstroms accuracy over a 0.5-3.0 nm range by preferentially removing metals from metal carbides. This is achieved by 'burning out' the metals (and metalloids) in halogen atmospheres at modest temperatures. The resulting carbide-derived carbon (CDC) retains the original shape of the carbide and shows linear reaction kinetics, allowing conversion of a carbide surface to a CDC layer of any thickness, including the entire monolith, film or particle. CDCs produced from binary and ternary carbides have been investigated, and specific surface areas (SSA) in excess of 2000 m 2 /g have been achieved. Pore size is determined by the structure and chemistry of the precursor, and by process parameters including temperature and composition of the reaction mixture. Most CDCs show smaller and more uniform pores when processed below 400-800 C, while larger and less uniform pores are found at 600-1200 C. Some CDCs (e.g. from B 4 C) have relatively broad pore size distributions, including meso-pores, even when processed at low temperatures. In contrast, other CDCs, e.g from SiC maintain a narrow distribution up to 1200 C. CDC microstructures become more ordered, evolving from amorphous to graphitic, with increasing process temperature. Other carbon forms, e.g. nano-tubes, onions, and nanocrystalline diamonds have also been obtained as CDC. The ability to fine tune the pore size, and independently to control the microstructure and surface termination, offers unique opportunities for parametric studies of gas sorption and desorption phenomena. Our recent studies show that

  3. Nanoscale Structuring of Surfaces by Using Atomic Layer Deposition.

    Science.gov (United States)

    Sobel, Nicolas; Hess, Christian

    2015-12-07

    Controlled structuring of surfaces is interesting for a wide variety of areas, including microelectronic device fabrication, optical devices, bio(sensing), (electro-, photo)catalysis, batteries, solar cells, fuel cells, and sorption. A unique feature of atomic layer deposition (ALD) is the possibility to form conformal uniform coatings on arbitrarily shaped materials with controlled atomic-scale thickness. In this Minireview, we discuss the potential of ALD for the nanoscale structuring of surfaces, highlighting its versatile application to structuring both planar substrates and powder materials. Recent progress in the application of ALD to porous substrates has even made the nanoscale structuring of high-surface-area materials now feasible, thereby enabling novel applications, such as those in the fields of catalysis and alternative energy. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Prediction of Protein Structure Using Surface Accessibility Data.

    Science.gov (United States)

    Hartlmüller, Christoph; Göbl, Christoph; Madl, Tobias

    2016-09-19

    An approach to the de novo structure prediction of proteins is described that relies on surface accessibility data from NMR paramagnetic relaxation enhancements by a soluble paramagnetic compound (sPRE). This method exploits the distance-to-surface information encoded in the sPRE data in the chemical shift-based CS-Rosetta de novo structure prediction framework to generate reliable structural models. For several proteins, it is demonstrated that surface accessibility data is an excellent measure of the correct protein fold in the early stages of the computational folding algorithm and significantly improves accuracy and convergence of the standard Rosetta structure prediction approach. © 2016 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

  5. Scale-adaptive surface modeling of vascular structures

    Directory of Open Access Journals (Sweden)

    Ma Xin

    2010-11-01

    Full Text Available Abstract Background The effective geometric modeling of vascular structures is crucial for diagnosis, therapy planning and medical education. These applications require good balance with respect to surface smoothness, surface accuracy, triangle quality and surface size. Methods Our method first extracts the vascular boundary voxels from the segmentation result, and utilizes these voxels to build a three-dimensional (3D point cloud whose normal vectors are estimated via covariance analysis. Then a 3D implicit indicator function is computed from the oriented 3D point cloud by solving a Poisson equation. Finally the vessel surface is generated by a proposed adaptive polygonization algorithm for explicit 3D visualization. Results Experiments carried out on several typical vascular structures demonstrate that the presented method yields both a smooth morphologically correct and a topologically preserved two-manifold surface, which is scale-adaptive to the local curvature of the surface. Furthermore, the presented method produces fewer and better-shaped triangles with satisfactory surface quality and accuracy. Conclusions Compared to other state-of-the-art approaches, our method reaches good balance in terms of smoothness, accuracy, triangle quality and surface size. The vessel surfaces produced by our method are suitable for applications such as computational fluid dynamics simulations and real-time virtual interventional surgery.

  6. Structure and optical properties of water covered Cu(110) surfaces

    International Nuclear Information System (INIS)

    Baghbanpourasl, A.

    2014-01-01

    In this thesis structural and optical properties of the water covered Cu(110) surface is studied using density functional theory within independent particle approximation. Several stable adsorption structures are studied such as water clusters (monomer, dimer, trimer, tetramer and pentamer), different hexagonal monolayers, partially dissociated water monolayers and three different types of chains among them a chain that consists of pentagon rings. For a copper surface in contact with water vapor, the energetically stable H 2 O/OH adsorbed structures are compared thermodynamically using adsorption free energy (change of free energy due to adsorption). Several phase diagrams with respect to temperature and pressure are calculated. It is found that among the large number of energetically stable structures (i.e. structures with positive adsorption energy ) only limited number of them are thermodynamically stable. These thermodynamically stable structures are the class of almost energetically degenerate hexagonal overlayers, one type of partially dissociated water structure that contains Bjerrum defect in the hydrogen bond network and pentagon chain. Since hydrogen atoms are light weight their vibrational effects can be considerable. Zero point vibration decreases the adsorption energy up to 0.1 eV and free energy of adsorbed molecules arising from vibrational degree of freedom can go up to -0.2 eV per adsorbed molecule at 500 Kelvin. However zero point energy and vibrational free energy of adsorbed molecules do not alter relative stability of the adsorbed structures. To account for the long range van der Waals interactions, a semi-empirical scheme is applied. Reflectance Anisotropy Spectroscopy (RAS) is a fast and non destructive optical method that can be used to prob the surface in different conditions such as vacuum and electro-chemical environment. Elasto-optic coeficients of bulk are calculated from first principles and the change of the RA spectrum of the bare Cu

  7. Importance of surface structure on dissolution of fluorite: Implications for surface dynamics and dissolution rates

    Science.gov (United States)

    Godinho, J. R. A.; Piazolo, S.; Balic-Zunic, T.

    2014-02-01

    Dissolution rates are usually calculated as a function of surface area, which is assumed to remain constant ignoring the changes occurring on the surface during dissolution. Here we present a study of how topography of natural fluorite surfaces with different orientation changes during up to 3200 h of dissolution. Results are analyzed in terms of changes in surface area, surface reactivity and dissolution rates. All surfaces studied present fast changes in topography during the initial 200 h of dissolution. The controlling factors that cause the development of topography are the stability of the step edges forming the initial surface and its inclination to the closest stable planes, which are specific for each surface orientation. During an initial dissolution regime dissolution rates decrease significantly, even though the total surface area increases. During a second dissolution regime, some surfaces continue to present significant changes in topography, while for others the topography tends to remain approximately constant. The observed variation of dissolution rates are attributed to a decrease of the density of step edges on the surface and the continuous increase in exposure of more stable surfaces. Calculations of dissolution rates, which assume that dissolution rates are directly proportional to surface area, are not valid for the type of surfaces studied. Instead, to develop accurate kinetic dissolution models and more realistic stochastic dissolution simulations the surface reactivity, determined by the relative stability of the planes and type of edges that constitute a surface needs to be considered. Significant differences between dissolution rates calculated based on surface area alone, and based on surface reactivity are expected for materials with the fluorite structure.

  8. Porous structure and surface chemistry of phosphoric acid activated carbon from corncob

    International Nuclear Information System (INIS)

    Sych, N.V.; Trofymenko, S.I.; Poddubnaya, O.I.; Tsyba, M.M.; Sapsay, V.I.; Klymchuk, D.O.; Puziy, A.M.

    2012-01-01

    Highlights: ► Phosphoric acid activation results in formation of carbons with acidic surface groups. ► Maximum amount of surface groups is introduced at impregnation ratio 1.25. ► Phosphoric acid activated carbons show high capacity to copper. ► Phosphoric acid activated carbons are predominantly microporous. ► Maximum surface area and pore volume achieved at impregnation ratio 1.0. - Abstract: Active carbons have been prepared from corncob using chemical activation with phosphoric acid at 400 °C using varied ratio of impregnation (RI). Porous structure of carbons was characterized by nitrogen adsorption and scanning electron microscopy. Surface chemistry was studied by IR and potentiometric titration method. It has been shown that porosity development was peaked at RI = 1.0 (S BET = 2081 m 2 /g, V tot = 1.1 cm 3 /g), while maximum amount of acid surface groups was observed at RI = 1.25. Acid surface groups of phosphoric acid activated carbons from corncob includes phosphate and strongly acidic carboxylic (pK = 2.0–2.6), weakly acidic carboxylic (pK = 4.7–5.0), enol/lactone (pK = 6.7–7.4; 8.8–9.4) and phenol (pK = 10.1–10.7). Corncob derived carbons showed high adsorption capacity to copper, especially at low pH. Maximum adsorption of methylene blue and iodine was observed for carbon with most developed porosity (RI = 1.0).

  9. Porous structure and surface chemistry of phosphoric acid activated carbon from corncob

    Energy Technology Data Exchange (ETDEWEB)

    Sych, N.V.; Trofymenko, S.I.; Poddubnaya, O.I.; Tsyba, M.M. [Institute for Sorption and Endoecology Problems, National Academy of Sciences of Ukraine, 13 General Naumov St., 03164 Kyiv (Ukraine); Sapsay, V.I.; Klymchuk, D.O. [M.G. Kholodny Institute of Botany, National Academy of Sciences of Ukraine, 2 Tereshchenkivska St., 01601 Kyiv (Ukraine); Puziy, A.M., E-mail: alexander.puziy@ispe.kiev.ua [Institute for Sorption and Endoecology Problems, National Academy of Sciences of Ukraine, 13 General Naumov St., 03164 Kyiv (Ukraine)

    2012-11-15

    Highlights: Black-Right-Pointing-Pointer Phosphoric acid activation results in formation of carbons with acidic surface groups. Black-Right-Pointing-Pointer Maximum amount of surface groups is introduced at impregnation ratio 1.25. Black-Right-Pointing-Pointer Phosphoric acid activated carbons show high capacity to copper. Black-Right-Pointing-Pointer Phosphoric acid activated carbons are predominantly microporous. Black-Right-Pointing-Pointer Maximum surface area and pore volume achieved at impregnation ratio 1.0. - Abstract: Active carbons have been prepared from corncob using chemical activation with phosphoric acid at 400 Degree-Sign C using varied ratio of impregnation (RI). Porous structure of carbons was characterized by nitrogen adsorption and scanning electron microscopy. Surface chemistry was studied by IR and potentiometric titration method. It has been shown that porosity development was peaked at RI = 1.0 (S{sub BET} = 2081 m{sup 2}/g, V{sub tot} = 1.1 cm{sup 3}/g), while maximum amount of acid surface groups was observed at RI = 1.25. Acid surface groups of phosphoric acid activated carbons from corncob includes phosphate and strongly acidic carboxylic (pK = 2.0-2.6), weakly acidic carboxylic (pK = 4.7-5.0), enol/lactone (pK = 6.7-7.4; 8.8-9.4) and phenol (pK = 10.1-10.7). Corncob derived carbons showed high adsorption capacity to copper, especially at low pH. Maximum adsorption of methylene blue and iodine was observed for carbon with most developed porosity (RI = 1.0).

  10. 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.

  11. Superhydrophobicity of biological and technical surfaces under moisture condensation: stability in relation to surface structure.

    Science.gov (United States)

    Mockenhaupt, Bernd; Ensikat, Hans-Jürgen; Spaeth, Manuel; Barthlott, Wilhelm

    2008-12-02

    The stability of superhydrophobic properties of eight plants and four technical surfaces in respect to water condensation has been compared. Contact and sliding angles were measured after application of water drops of ambient temperature (20 degrees C) onto cooled surfaces. Water evaporating from the drops condensed, due to the temperature difference between the drops and the surface, on the cooled samples, forming "satellite droplets" in the vicinity of the drops. Surface cooling to 15, 10, and 5 degrees C showed a gradual decrease of superhydrophobicity. The decrease was dependent on the specific surface architecture of the sample. The least decrease was found on hierarchically structured surfaces with a combination of a coarse microstructure and submicrometer-sized structures, similar to that of the Lotus leaf. Control experiments with glycerol droplets, which show no evaporation, and thus no condensation, were carried out to verify that the effects with water were caused by condensation from the drop (secondary condensation). Furthermore, the superhydrophobic properties after condensation on cooled surfaces from a humid environment for 10 min were examined. After this period, the surfaces were covered with spherical water droplets, but most samples retained their superhydrophobicity. Again, the best stability of the water-repellent properties was found on hierarchically structured surfaces similar to that of the Lotus leaf.

  12. SurfCut: Surfaces of Minimal Paths From Topological Structures

    KAUST Repository

    Algarni, Marei Saeed Mohammed

    2017-04-30

    We present SurfCut, an algorithm for extracting a smooth, simple surface with an unknown 3D curve boundary from a noisy 3D image and a seed point. Our method is built on the novel observation that certain ridge curves of a function defined on a front propagated using the Fast Marching algorithm lie on the surface. Our method extracts and cuts these ridges to form the surface boundary. Our surface extraction algorithm is built on the novel observation that the surface lies in a valley of the distance from Fast Marching. We show that the resulting surface is a collection of minimal paths. Using the framework of cubical complexes and Morse theory, we design algorithms to extract these critical structures robustly. Experiments on three 3D datasets show the robustness of our method, and that it achieves higher accuracy with lower computational cost than state-of-the-art.

  13. SurfCut: Surfaces of Minimal Paths From Topological Structures

    KAUST Repository

    Algarni, Marei Saeed Mohammed

    2018-03-05

    We present SurfCut, an algorithm for extracting a smooth, simple surface with an unknown 3D curve boundary from a noisy image and a seed point. Our method is built on the novel observation that certain ridge curves of a function defined on a front propagated using the Fast Marching algorithm lie on the surface. Our method extracts and cuts these ridges to form the surface boundary. Our surface extraction algorithm is built on the novel observation that the surface lies in a valley of the distance from Fast Marching. We show that the resulting surface is a collection of minimal paths. Using the framework of cubical complexes and Morse theory, we design algorithms to extract these critical structures robustly. Experiments on three 3D datasets show the robustness of our method, and that it achieves higher accuracy with lower computational cost than state-of-the-art.

  14. Understanding surface structure and chemistry of single crystal lanthanum aluminate

    KAUST Repository

    Pramana, Stevin S.

    2017-03-02

    The surface crystallography and chemistry of a LaAlO3 single crystal, a material mainly used as a substrate to deposit technologically important thin films (e.g. for superconducting and magnetic devices), was analysed using surface X-ray diffraction and low energy ion scattering spectroscopy. The surface was determined to be terminated by Al-O species, and was significantly different from the idealised bulk structure. Termination reversal was not observed at higher temperature (600 °C) and chamber pressure of 10−10 Torr, but rather an increased Al-O occupancy occurred, which was accompanied by a larger outwards relaxation of Al from the bulk positions. Changing the oxygen pressure to 10−6 Torr enriched the Al site occupancy fraction at the outermost surface from 0.245(10) to 0.325(9). In contrast the LaO, which is located at the next sub-surface atomic layer, showed no chemical enrichment and the structural relaxation was lower than for the top AlO2 layer. Knowledge of the surface structure will aid the understanding of how and which type of interface will be formed when LaAlO3 is used as a substrate as a function of temperature and pressure, and so lead to improved design of device structures.

  15. The Production of Nickel-Chromium-Molybdenum Alloy with Open Pore Structure as an Implant and the Investigation of Its Biocompatibility In Vivo

    Directory of Open Access Journals (Sweden)

    Yusuf Er

    2013-01-01

    Full Text Available A dental crown material, Nickel-Chrome-Molybdenum alloy, is manufactured using precision casting method from a polyurethane foam model in a regular and open-pore form, as a hard tissue implant for orthopedic applications. The samples produced have 10, 20, and 30 (±3 pores per inch of pore densities and 0.0008, 0.0017, and 0.0027 g/mm3 densities, respectively. Samples were implanted in six dogs and observed for a period of two, four, and six months for the histopathological examinations. The dogs were examined radiologically in 15-day intervals and clinically in certain intervals. The implants were taken out with surrounding tissue at the end of these periods. Implants and surrounding tissues were examined histopathologically in terms of biocompatibility. As a result, it is seen that new bone tissue was formed, in pores of the porous implant at the head of the tibia in dogs implanted. Any pathology, inflammation, and reaction in old and new tissues were not observed. It was concluded that a dental alloy (Ni-Cr-Mo alloy could also be used as a biocompatible hard tissue implant material for orthopedics.

  16. Condensation and Wetting Dynamics on Micro/Nano-Structured Surfaces

    Science.gov (United States)

    Olceroglu, Emre

    Because of their adjustable wetting characteristics, micro/nanostructured surfaces are attractive for the enhancement of phase-change heat transfer where liquid-solid-vapor interactions are important. Condensation, evaporation, and boiling processes are traditionally used in a variety of applications including water harvesting, desalination, industrial power generation, HVAC, and thermal management systems. Although they have been studied by numerous researchers, there is currently a lack of understanding of the underlying mechanisms by which structured surfaces improve heat transfer during phase-change. This PhD dissertation focuses on condensation onto engineered surfaces including fabrication aspect, the physics of phase-change, and the operational limitations of engineered surfaces. While superhydrophobic condensation has been shown to produce high heat transfer rates, several critical issues remain in the field. These include surface manufacturability, heat transfer coefficient measurement limitations at low heat fluxes, failure due to surface flooding at high supersaturations, insufficient modeling of droplet growth rates, and the inherent issues associated with maintenance of non-wetted surface structures. Each of these issues is investigated in this thesis, leading to several contributions to the field of condensation on engineered surfaces. A variety of engineered surfaces have been fabricated and characterized, including nanostructured and hierarchically-structured superhydrophobic surfaces. The Tobacco mosaic virus (TMV) is used here as a biological template for the fabrication of nickel nanostructures, which are subsequently functionalized to achieve superhydrophobicity. This technique is simple and sustainable, and requires no applied heat or external power, thus making it easily extendable to a variety of common heat transfer materials and complex geometries. To measure heat transfer rates during superhydrophobic condensation in the presence of non

  17. Structural and vibrational studies of clean and chemisorbed metal surfaces

    International Nuclear Information System (INIS)

    Jiang, Qing-Tang.

    1992-01-01

    Using Medium Energy Ion Scattering, we have studied the structural and vibrational properties of a number of clean and chemisorbed metal surfaces. The work presented in this thesis is mainly of a fundamental nature. However, it is believed that an atomistic understanding of the forces that affect surface structural and vibrational properties can have a beneficial impact on a large number of areas of applied nature. We find that the surface structure of Cu(001) follows the common trend for metal surfaces, where a small oscillatory relaxation exists beginning with a slight contraction in the top layer. In addition, the surface vibrational amplitude is enhanced (as s usually the case) by ∼80%. A detailed analysis of our data shows an unexpected anisotropy of the vibrational amplitude, such that the out-of-plane vibrational amplitude is 30% smaller than the in-plane vibrational amplitude. The unexpected results may imply a large tensile stress on Cu(001). Upon adsorption of 1/4 of a monolayer of S, a p(2 x 2)-S/Cu(001) surface is created. This submonolayer amount of S atoms makes the surface bulk-like, in which the anisotropy of the surface vibrations is removed and the first interlayer contraction is lifted. By comparing our model to earlier contradictory results on this controversial system. We find excellent agreement with a recent LEED study. The presence of 0.1 monolayer of Ca atoms on the Au(113) surface induces a drastic atomic rearrangements, in which half of the top layer Au atoms are missing and a (1 x 2) symmetry results. In addition, the first interlayer spacing of Au(113) is significantly reduced. Our results are discussed in terms of the energy balance between competing surface electronic charge densities

  18. Surface and Core Electronic Structure of Oxidized Silicon Nanocrystals

    Directory of Open Access Journals (Sweden)

    Noor A. Nama

    2010-01-01

    Full Text Available Ab initio restricted Hartree-Fock method within the framework of large unit cell formalism is used to simulate silicon nanocrystals between 216 and 1000 atoms (1.6–2.65 nm in diameter that include Bravais and primitive cell multiples. The investigated properties include core and oxidized surface properties. Results revealed that electronic properties converge to some limit as the size of the nanocrystal increases. Increasing the size of the core of a nanocrystal resulted in an increase of the energy gap, valence band width, and cohesive energy. The lattice constant of the core and oxidized surface parts shows a decreasing trend as the nanocrystal increases in a size that converges to 5.28 Ǻ in a good agreement with the experiment. Surface and core convergence to the same lattice constant reflects good adherence of oxide layer at the surface. The core density of states shows highly degenerate states that split at the oxygenated (001-(1×1 surface due to symmetry breaking. The nanocrystal surface shows smaller gap and higher valence and conduction bands when compared to the core part, due to oxygen surface atoms and reduced structural symmetry. The smaller surface energy gap shows that energy gap of the nanocrystal is controlled by the surface part. Unlike the core part, the surface part shows a descending energy gap that proves its obedience to quantum confinement effects. Nanocrystal geometry proved to have some influence on all electronic properties including the energy gap.

  19. Nonlinear Tamm states and surface effects in periodic photonic structures

    International Nuclear Information System (INIS)

    Kivshar, Yu S

    2008-01-01

    We present a brief overview of the basic concepts and important experimental observations of the effect of light localization near the surfaces of truncated periodic photonic structures. In particular, we discuss the formation of nonlinear localized modes and discrete surface solitons near the edges of nonlinear optical waveguide arrays and two-dimensional photonic lattices. We draw an analogy between the nonlinear surface optical modes and the surface Tamm states known in the electronic theory. We discuss the crossover between discrete solitons in the array and surface solitons at the edge of the array by analyzing the families of even and odd nonlinear localized modes located at finite distances from the edge of a waveguide array. We discuss various generalization of this concept including surface solitons in chirped lattices, multi-gap vector surface solitons, polychromatic surface states generated by a supercontinuum source, surface modes in two-dimensional photonic lattices, and spatiotemporal surface solitons. Finally, we discuss briefly several other related concepts including the enhanced beaming of light from subwavelength waveguides in photonic crystals

  20. Crystallography and surface structure an introduction for surface scientists and nanoscientists

    CERN Document Server

    Hermann, Klaus

    2017-01-01

    A valuable learning tool as well as a reference, this book provides students and researchers in surface science and nanoscience with the theoretical crystallographic foundations, which are necessary to understand local structure and symmetry of bulk crystals, including ideal and real single crystal surfaces. The author deals with the subject at an introductory level, providing numerous graphic examples to illustrate the mathematical formalism. The book brings together and logically connects many seemingly disparate structural issues and notations used frequently by surface scientists and nanoscientists. Numerous exercises of varying difficulty, ranging from simple questions to small research projects, are included to stimulate discussions about the different subjects.

  1. Laser Surface Preparation for Adhesive Bonding of Aerospace Structural Composites

    Science.gov (United States)

    Belcher, M. A.; Wohl, C. J.; Hopkins, J. W.; Connell, J. W.

    2010-01-01

    Adhesive bonds are critical to the integrity of built-up structures. Disbonds can often be detected but the strength of adhesion between surfaces in contact is not obtainable without destructive testing. Typically the number one problem in a bonded structure is surface contamination, and by extension, surface preparation. Standard surface preparation techniques, including grit blasting, manual abrasion, and peel ply, are not ideal because of variations in their application. Etching of carbon fiber reinforced plastic (CFRP) panels using a neodymium-doped yttrium aluminum garnet (Nd:YAG) laser appears to be a highly precise and promising way to both clean a composite surface prior to bonding and provide a bond-promoting patterned surface akin to peel ply without the inherent drawbacks from the same (i.e., debris and curvature). CFRP surfaces prepared using laser patterns conducive to adhesive bonding were compared to typical pre-bonding surface treatments through optical microscopy, contact angle goniometry, and post-bonding mechanical testing.

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

    Science.gov (United States)

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

    2017-06-01

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

  3. Sulfur-induced structural motifs on copper and gold surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Walen, Holly [Iowa State Univ., Ames, IA (United States)

    2016-01-01

    The interaction of sulfur with copper and gold surfaces plays a fundamental role in important phenomena that include coarsening of surface nanostructures, and self-assembly of alkanethiols. Here, we identify and analyze unique sulfur-induced structural motifs observed on the low-index surfaces of these two metals. We seek out these structures in an effort to better understand the fundamental interactions between these metals and sulfur that lends to the stability and favorability of metal-sulfur complexes vs. chemisorbed atomic sulfur. The experimental observations presented here—made under identical conditions—together with extensive DFT analyses, allow comparisons and insights into factors that favor the existence of metal-sulfur complexes, vs. chemisorbed atomic sulfur, on metal terraces. We believe this data will be instrumental in better understanding the complex phenomena occurring between the surfaces of coinage metals and sulfur.

  4. Compact surface structures for the efficient excitation of surface plasmon-polaritons

    Energy Technology Data Exchange (ETDEWEB)

    De la Cruz, S.; Mendez, E.R. [Division de Fisica Applicada, Centro de Investigacion Cientifica y de Educacion Superior de Ensenada, Carretera Ensenada-Tijuana No. 3918, Ensenada 22860, BC (Mexico); Macias, D.; Salas-Montiel, R.; Adam, P.M. [Laboratoire de Nanotechnologie et d' Instrumentation Optique, Universite de Technologie de Troyes, 12 rue Marie Curie, BP-2060, 10010 Troyes Cedex (France)

    2012-06-15

    We present calculations of the efficiency of excitation of surface plasmon-polaritons (SPPs) with surface structures illuminated by focussed beams. First, it is shown that the low reflectivity observed with broad highly directional beams and periodic gratings does not necessarily imply an efficient coupling to SPPs. We then consider the coupling through surface features like steps, grooves and angled steps, and calculate efficiency maps for these structures as functions of the parameters that define them. Finally, we explore the possibilities of improving the coupling efficiency using periodic structures consisting of a small number of rectangular grooves. We find that a surface section with a length of about four wavelengths can couple as much as 45% of the incident light into a directional SPP. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  5. Robust biomimetic-structural superhydrophobic surface on aluminum alloy.

    Science.gov (United States)

    Li, Lingjie; Huang, Tao; Lei, Jinglei; He, Jianxin; Qu, Linfeng; Huang, Peiling; Zhou, Wei; Li, Nianbing; Pan, Fusheng

    2015-01-28

    The following facile approach has been developed to prepare a biomimetic-structural superhydrophobic surface with high stabilities and strong resistances on 2024 Al alloy that are robust to harsh environments. First, a simple hydrothermal treatment in a La(NO3)3 aqueous solution was used to fabricate ginkgo-leaf like nanostructures, resulting in a superhydrophilic surface on 2024 Al. Then a low-surface-energy compound, dodecafluoroheptyl-propyl-trimethoxylsilane (Actyflon-G502), was used to modify the superhydrophilic 2024 Al, changing the surface character from superhydrophilicity to superhydrophobicity. The water contact angle (WCA) of such a superhydrophobic surface reaches up to 160°, demonstrating excellent superhydrophobicity. Moreover, the as-prepared superhydrophobic surface shows high stabilities in air-storage, chemical and thermal environments, and has strong resistances to UV irradiation, corrosion, and abrasion. The WCAs of such a surface almost remain unchanged (160°) after storage in air for 80 days, exposure in 250 °C atmosphere for 24 h, and being exposed under UV irradiation for 24 h, are more than 144° whether in acidic or alkali medium, and are more than 150° after 48 h corrosion and after abrasion under 0.98 kPa for 1000 mm length. The remarkable durability of the as-prepared superhydrophobic surface can be attributed to its stable structure and composition, which are due to the existence of lanthanum (hydr)oxides in surface layer. The robustness of the as-prepared superhydrophobic surface to harsh environments will open their much wider applications. The fabricating approach for such robust superhydrophobic surface can be easily extended to other metals and alloys.

  6. Structure and properties of GMA surfaced armour plates

    OpenAIRE

    A. Klimpel; K. Luksa; M. Burda

    2010-01-01

    Purpose: In the combat vehicles many materials can be used for the armour. Application of the monolithic armour plates in light combat vehicles is limited by the high armour weigh. Introduction of the layered armour plates is a way to limit the vehicle weight. In the paper test results of graded and nanostructural GMA surfaced armour plates are presented.Design/methodology/approach: Metallographic structure, chemical composition and hardness of surfaced layers were investigated in order to ex...

  7. Synthesis of anatase mesoporous by using cyclodextrin as a pore forming template via hydrothermal treatment

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Joo Hee; An, So Young; Jang, Soe Hyun; Lee, Jun Woo; Chung, Jae Woo [Dept. of Organic Materials and Fiber Engineering, Soongsil University, Seoul (Korea, Republic of)

    2015-06-15

    Porous titanium dioxide with an average pore diameter of several nanometers and a narrow pore size distribution was prepared by using cyclodextrin (CD) in a sol–gel reaction of titanium precursor. After the reaction, a hydrothermal treatment was performed, and a WAXD analysis shows that the hydrothermal treatment successfully induces an anatase crystalline structure in TiO{sub 2} . The combined results from TGA, FT-IR, N{sub 2} adsorption–desorption isotherm, TEM, and SEM analyses show that the CD act as a pore forming template to form TiO{sub 2} with a wormhole-type pore and a large specific surface area. Furthermore, the ratio of the CD/Ti precursor affects the porosity and the morphology of the mesoporous TiO{sub 2} . In contrast, TiO{sub 2} prepared without CD does not exhibit a porous structure. The formation of these porous structures is a result of the self-assembly of Ti species around the CD molecules, TiO{sub 2} growth, and pore-forming by the removal of CD.

  8. Surface plasmon polariton amplification in semiconductor-graphene-dielectric structure

    Energy Technology Data Exchange (ETDEWEB)

    Dadoenkova, Yuliya S. [Ulyanovsk State University, Ulyanovsk (Russian Federation); Novgorod State University, Veliky Novgorod (Russian Federation); Donetsk Institute for Physics and Technology, Donetsk (Ukraine); Moiseev, Sergey G. [Ulyanovsk State University, Ulyanovsk (Russian Federation); Kotelnikov Institute of Radio Engineering and Electronics, Russian Academy of Sciences, Ulyanovsk (Russian Federation); Abramov, Aleksei S. [Ulyanovsk State University, Ulyanovsk (Russian Federation); Kadochkin, Aleksei S.; Zolotovskii, Igor O. [Ulyanovsk State University, Ulyanovsk (Russian Federation); Institute of Nanotechnologies of Microelectronics of the Russian Academy of Sciences, 32A Leninskiy Prosp., 119991, Moscow (Russian Federation); Fotiadi, Andrei A. [Ulyanovsk State University, Ulyanovsk (Russian Federation); Universite de Mons (Belgium)

    2017-05-15

    A mechanism of amplification of surface plasmon polaritons due to the transfer of electromagnetic energy from a drift current wave into a far-infrared surface wave propagating along a semiconductor-dielectric boundary in waveguide geometry is proposed. A necessary condition of the interaction of these waves is phase matching condition, i. e., when the phase velocity of the surface wave approaches the drift velocity of charge carriers. It is shown that in the spectral region of the surface plasmon polariton slowing-down its amplification coefficient can reach values substantially exceeding the ohmic loss coefficient of the surface wave in the structure. (copyright 2017 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  9. Soil Structure - A Neglected Component of Land-Surface Models

    Science.gov (United States)

    Fatichi, S.; Or, D.; Walko, R. L.; Vereecken, H.; Kollet, S. J.; Young, M.; Ghezzehei, T. A.; Hengl, T.; Agam, N.; Avissar, R.

    2017-12-01

    Soil structure is largely absent in most standard sampling and measurements and in the subsequent parameterization of soil hydraulic properties deduced from soil maps and used in Earth System Models. The apparent omission propagates into the pedotransfer functions that deduce parameters of soil hydraulic properties primarily from soil textural information. Such simple parameterization is an essential ingredient in the practical application of any land surface model. Despite the critical role of soil structure (biopores formed by decaying roots, aggregates, etc.) in defining soil hydraulic functions, only a few studies have attempted to incorporate soil structure into models. They mostly looked at the effects on preferential flow and solute transport pathways at the soil profile scale; yet, the role of soil structure in mediating large-scale fluxes remains understudied. Here, we focus on rectifying this gap and demonstrating potential impacts on surface and subsurface fluxes and system wide eco-hydrologic responses. The study proposes a systematic way for correcting the soil water retention and hydraulic conductivity functions—accounting for soil-structure—with major implications for near saturated hydraulic conductivity. Modification to the basic soil hydraulic parameterization is assumed as a function of biological activity summarized by Gross Primary Production. A land-surface model with dynamic vegetation is used to carry out numerical simulations with and without the role of soil-structure for 20 locations characterized by different climates and biomes across the globe. Including soil structure affects considerably the partition between infiltration and runoff and consequently leakage at the base of the soil profile (recharge). In several locations characterized by wet climates, a few hundreds of mm per year of surface runoff become deep-recharge accounting for soil-structure. Changes in energy fluxes, total evapotranspiration and vegetation productivity

  10. Thermodynamics and structure of liquid surfaces investigated directly with surface analytical tools

    Energy Technology Data Exchange (ETDEWEB)

    Andersson, Gunther [Flinders Univ., Adelaide, SA (Australia). Centre for NanoScale Science and Technology; Morgner, Harald [Leipzig Univ. (Germany). Wilhelm Ostwald Inst. for Physical and Theoretical Chemistry

    2017-06-15

    Measuring directly the composition, the distribution of constituents as function of the depth and the orientation of molecules at liquid surfaces is essential for determining physicochemical properties of liquid surfaces. While the experimental tools that have been developed for analyzing solid surfaces can in principal be applied to liquid surfaces, it turned out that they had to be adjusted to the particular challenges imposed by liquid samples, e.g. by the unavoidable vapor pressure and by the mobility of the constituting atoms/molecules. In the present work it is shown, how electron spectroscopy and ion scattering spectroscopy have been used for analyzing liquid surfaces. The emphasis of this review is on using the structural information gained for determining the physicochemical properties of liquid surfaces. (copyright 2017 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  11. Ion induced millimetre-scale structures growth on metal surfaces

    Science.gov (United States)

    Girka, O.; Bizyukov, O.; Balkova, Y.; Myroshnyk, M.; Bizyukov, I.; Bogatyrenko, S.

    2018-04-01

    Polished polycrystalline Plansee tungsten (W) sample with purity 99.99 wt% and 0.75 mm thickness has been exposed to intense argon (Ar) ion beam with average energy of 2 keV and etched through in the centre. As a result, castle-like structures with strong asymmetry and with the height of >200 μm have been formed. Structures can be observed by naked eyes and with scanning-electron microscopy (SEM). It has been revealed, that the structures have been formed not immediately, but at the later stages of irradiation. Primary factors favouring the formation for the structures are relaxation of the surface stresses and activated surface mobility of atoms.

  12. Studies on electronic structure of GaN(0001) surface

    CERN Document Server

    Xie Chang Kun; Xu Fa Qiang; Deng Rui; Liu Feng; Yibulaxin, K

    2002-01-01

    An electronic structure investigation on GaN(0001) is reported. The authors employ a full-potential linearized augmented plane-wave (FPLAPW) approach to calculate the partial density of state, which is in agreement with previous experimental results. The effects of the Ga3d semi-core levels on the electronic structure of GaN are discussed. The valence-electronic structure of the wurtzite GaN(0001) surface is investigated using synchrotron radiation excited angle-resolved photoemission spectroscopy. The bulk bands dispersion along GAMMA A direction in the Brillouin zones is measured using normal-emission spectra by changing photon-energy. The band structure derived from authors' experimental data is compared well with the results of authors' FPLAPW calculation. Furthermore, off-normal emission spectra are also measured along the GAMMA K and GAMMA M directions. Two surface states are identified, and their dispersions are characterized

  13. Quantitative parameterization of soil surface structure with increasing rainfall volumes

    OpenAIRE

    Edison Aparecido Mome Filho

    2016-01-01

    The study of soil structure allows inferences on soil behavior. Quantitative parameters are oftentimes required to describe soil structure and the multifractal ones are still underused in soil science. Some studies have shown relations between the multifractal spectrum and both soil surface roughness decay by rainfall and porous system heterogeneity, however, a particular multifractal response to a specific soil behavior is not established yet. Therefore, the objectives of this research were:...

  14. Moduli spaces of convex projective structures on surfaces

    DEFF Research Database (Denmark)

    Fock, V. V.; Goncharov, A. B.

    2007-01-01

    We introduce explicit parametrisations of the moduli space of convex projective structures on surfaces, and show that the latter moduli space is identified with the higher Teichmüller space for defined in [V.V. Fock, A.B. Goncharov, Moduli spaces of local systems and higher Teichmüller theory, ma.......AG/0311149]. We investigate the cluster structure of this moduli space, and define its quantum version....

  15. VOPcPhO:P3HT composite micro-structures with nano-porous surface morphology

    Energy Technology Data Exchange (ETDEWEB)

    Azmer, Mohamad Izzat [Low Dimensional Materials Research Centre (LDMRC), Department of Physics, Faculty of Science, University of Malaya, 50603 Kuala Lumpur (Malaysia); Ahmad, Zubair, E-mail: zubairtarar@qu.edu.qa [Center for Advanced Materials (CAM), Qatar University, P. O. Box 2713, Doha (Qatar); Sulaiman, Khaulah, E-mail: khaulah@um.edu.my [Low Dimensional Materials Research Centre (LDMRC), Department of Physics, Faculty of Science, University of Malaya, 50603 Kuala Lumpur (Malaysia); Touati, Farid [Department of Electrical Engineering, College of Engineering, Qatar University, P. O. Box 2713, Doha (Qatar); Bawazeer, Tahani M. [Department of Chemistry, Faculty of Applied Science, Umm Al-Qura University, Makkah (Saudi Arabia); Alsoufi, Mohammad S. [Mechanical Engineering Department, College of Engineering and Islamic Architecture, Umm Al-Qura University, Makkah (Saudi Arabia)

    2017-03-31

    Highlights: • VOPcPhO:P3HT micro-structures with nano-porous surface morphology have been formed. • Multidimensional structures have been formed by electro-spraying technique. • The electro-sprayed films are very promising for the humidity sensors. - Abstract: In this paper, composite micro-structures of Vanadyl 2,9,16,23-tetraphenoxy-29H,31H-phthalocyanine) (VOPcPhO) and Poly (3-hexylthiophene-2,5-diyl) (P3HT) complex with nano-porous surface morphology have been developed by electro-spraying technique. The structural and morphological characteristics of the VOPcPhO:P3HT composite films have been studied by field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). The multidimensional VOPcPhO:P3HT micro-structures formed by electro-spraying with nano-porous surface morphology are very promising for the humidity sensors due to the pore sizes in the range of micro to nano-meters scale. The performance of the VOPcPhO:P3HT electro-sprayed sensor is superior in term of sensitivity, hysteresis and response/recovery times as compared to the spin-coated one. The electro-sprayed humidity sensor exhibits ∼3 times and 0.19 times lower hysteresis in capacitive and resistive mode, respectively, as compared