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Sample records for pore size distributions

  1. Size dependent pore size distribution of shales by gas physisorption

    NASA Astrophysics Data System (ADS)

    Roshan, Hamid; Andersen, Martin S.; Yu, Lu; Masoumi, Hossein; Arandian, Hamid

    2017-04-01

    Gas physisorption, in particular nitrogen adsorption-desorption, is a traditional technique for characterization of geomaterials including the organic rich shales. The low pressure nitrogen is used together with adsorption-desorption physical models to study the pore size distribution (PSD) and porosity of the porous samples. The samples are usually crushed to a certain fragment size to measure these properties however there is not yet a consistent standard size proposed for sample crushing. Crushing significantly increases the surface area of the fragments e.g. the created surface area is differentiated from that of pores using BET technique. In this study, we show that the smaller fragment sizes lead to higher cumulative pore volume and smaller pore diameters. It is also shown that some of the micro-pores are left unaccounted because of the correction of the external surface area. In order to illustrate this, the nitrogen physisorption is first conducted on the identical organic rich shale samples with different sizes: 20-25, 45-50 and 63-71 µm. We then show that such effects are not only a function of pore structure changes induced by crushing, but is linked to the inability of the physical models in differentiating between the external surface area (BET) and micro-pores for different crushing sizes at relatively low nitrogen pressure. We also discuss models currently used in nano-technology such as t-method to address this issue and their advantages and shortcoming for shale rock characterization.

  2. Pore-size-distribution of cationic polyacrylamide hydrogels. Progress report

    SciTech Connect

    Kremer, M.; Prausnitz, J.M.

    1992-06-01

    The pore size distribution of a AAm/MAPTAC (acrylamide copolymerized with (3-methacrylamidopropyl)trimethylammonium chloride) hydrogel was investigated using Kuga`s mixed-solute-exclusion method, taking into account the wall effect. A Brownian-motion model is also used. Results show the feasibility of determining pore-size distribution of porous materials using the mixed-solute-exclusion method in conjunction with solution of the Fredholm equation; good agreement was obtained with experiment, even for bimodal pore structures. However, different pore size distributions were calculated for the two different probe-solutes (Dextran and poly(ethylene glycol/oxide)). Future work is outlined. 32 figs, 25 refs.

  3. Pore-size-distribution of cationic polyacrylamide hydrogels

    SciTech Connect

    Kremer, M.; Prausnitz, J.M.

    1992-06-01

    The pore size distribution of a AAm/MAPTAC (acrylamide copolymerized with (3-methacrylamidopropyl)trimethylammonium chloride) hydrogel was investigated using Kuga's mixed-solute-exclusion method, taking into account the wall effect. A Brownian-motion model is also used. Results show the feasibility of determining pore-size distribution of porous materials using the mixed-solute-exclusion method in conjunction with solution of the Fredholm equation; good agreement was obtained with experiment, even for bimodal pore structures. However, different pore size distributions were calculated for the two different probe-solutes (Dextran and poly(ethylene glycol/oxide)). Future work is outlined. 32 figs, 25 refs.

  4. Mechanical properties, pore size distribution, and pore solution of fly ash-belite cement mortars

    SciTech Connect

    Guerrero, A.; Goni, S.; Macias, A.; Luxan, M.P.

    1999-11-01

    The mechanical properties, pore size distribution, and extracted pore solution of fly ash-belite cement (FABC) mortars were studied for a period of 200 days. The influence of the calcination temperature, which ranged from 700 to 900 C, of the fly ash-belite cement was discussed. The evolution with hydration time of the pore size distribution was followed by mercury intrusion porosimetry, and the results correlated with those of flexural and compressive strength. The pore solution was expressed and analyzed at different times of hydration.

  5. Pore-size distributions of N-isopropylacrylamide (NIPA) hydrogels

    SciTech Connect

    Walther, D.H.; Blanch, H.W.; Prausnitz, J.M. |

    1993-11-01

    Pore-size distributions have been measured for N-isopropylacrylamide (NIPA) hydrogels at 25 and 32{degrees}C with swelling capacities 11.3 and 6.0 g swollen gel per g dry gel. The mixed-solute-exclusion method (introduced by Kuga) was used to obtain the experimental solute-exclusion curve which represents the amount of imbibed liquid inside the gel inaccessible for a solute of radius r. The pore-size distributions were obtained by using Casassa`s Brownian-motion model and numerically solving the Fredholm integral equation. The pore-size distributions of temperature-sensitive NIPA hydrogels are strongly dependent on temperature which determines swelling capacity. With increasing swelling capacity (from 6.0 to 11.3), the pore-size distribution shifts to higher mode values (27.3 to 50.6 {angstrom}) and to higher variance (1.07{center_dot}10{sup 3} to 3.58{center_dot}10{sup 3} {angstrom}{sup 2}).

  6. Pore size distribution in an uncompacted equilibrated ordinary chondrite

    SciTech Connect

    Friedrich, J.M.; Macke, R.J.; Wignarajah, D.P.; Rivers, M.L.; Britt, D.T.; Ebel, D.S.

    2008-05-30

    The extraordinarily uncompacted nature of the ordinary L chondrite fall Baszkowka gives a unique opportunity to investigate the potentially pre-compaction pore size distribution in an equilibrated ordinary chondrite. Using X-ray microtomography and helium pycnometry on two samples of Baszkowka, we have found that on average, two-thirds of the 19.0% porosity resides in inter- and intra-granular voids with volumes between {approx}3 x10{sup 05} and 3 mm{sup 3}. We show the cumulative number density of pore volumes observable by X-ray microtomography obeys a power law distribution function in this equilibrated ordinary chondrite. We foresee these data adding to our understanding of the impact processing of chondrites and their parent asteroids, where porosity and pore size play significant roles in the parameterization of impact events.

  7. Multifractal Characteristics of Bimodal Mercury Pore Size Distribution Curves

    NASA Astrophysics Data System (ADS)

    dos Santos Bonini, C.; Alves, M. C.; Paz González, A.

    2012-04-01

    Characterization of Hg pore size distribution (PSDs) curves by monofractal or multifractal analysis has been demonstrated to be an useful tool, which allows a better understanding of the organization of the soil pore space. There are also evidences that multiscale analysis of different segments found in bimodal pore size distributions measured by Hg intrusion can provide further valuable information. In this study we selected bimodal PSDs from samples taken from an experimental area in São Paulo state, Brazil, where a revegetation trial was set up over saprolitic material. The saprolite was left abandoned after decapitation of an Oxisol for building purposes. The field trial consisted of various treatments with different grass species and amendments. Pore size distribution of the sampled aggregates was measured in the equivalent diameter range from 0.005 to about 50 μm and it was characterized by a bimodal pattern, so that two compartments, i.e. 0.005 to 0.2 μm and 0.2 to 50 μm, could be distinguished. The multifractal theory was used to analyse both segments. The scaling properties of these two segments could be fitted reasonably well with multifractal models. Multifractal parameters obtained for equivalent diameters for the segments > 0.2 and < 0.2 μm showed great differences. For example, entropy dimension, D1, values from the segment 0.005-0.2 μm were always lower than those for the segment 0.2-50 μm form NDI , whereas the Hólder exponent of order zero, α0, were higher for the former segment. These results indicate the probability different degrees of heterogeneity within the Hg pore size distributions studied.

  8. Polyester scaffolds with bimodal pore size distribution for tissue engineering.

    PubMed

    Sosnowski, Stanislaw; Woźniak, Piotr; Lewandowska-Szumieł, Małgorzata

    2006-06-16

    This paper presents a method for the preparation of porous poly(L-lactide)/poly[(L-lactide)-co-glycolide] scaffolds for tissue engineering. Scaffolds were prepared by a mold pressing-salt leaching technique from structured microparticles. The total porosity was in the range 70-85%. The pore size distribution was bimodal. Large pores, susceptible for osteoblasts growth and proliferation had the dimensions 50-400 microm. Small pores, dedicated to the diffusion of nutrients or/and metabolites of bone forming cells, as well as the products of hydrolysis of polyesters from the walls of the scaffold, had sizes in the range 2 nm-5 microm. The scaffolds had good mechanical strength (compressive modulus equal to 41 MPa and a strength of 1.64 MPa for 74% porosity). Scaffolds were tested in vitro with human osteoblast-like cells (MG-63). It was found that the viability of cells seeded within the scaffolds obtained using the mold pressing-salt leaching technique from structured microparticles was better when compared to cells cultured in scaffolds obtained by traditional methods. After 34 d of culture, cells within the tested scaffolds were organized in a tissue-like structure. Photos of section of macro- and mesoporous PLLA/PLGA scaffold containing 50 wt.-% of PLGA microspheres after 34 d of culture. Dark spots mark MG-63 cells, white areas belong to the scaffold. The specimen was stained with haematoxylin/eosin. Bar = 100 microm.

  9. Catalytic reforming catalyst with modified pore size distribution

    SciTech Connect

    Unmuth, E.E.; Fleming, B.A.

    1987-10-27

    In a naphtha reforming catalyst having at least one catalytic metal deposited on a porous solid catalyst support, an improvement is described which comprises the catalyst having the following in combination: (A) a surface area above about 250M/sup 2//gram of catalyst; (B) A pore volume above about 0.4 cc/gram of catalyst in pores having diameters of from about 30 angstroms to about 38,000 angstroms; and (C) A pore volume distribution wherein about 70 percent or less of the pore volume is in pores having diameters of from about 30 angstroms to about 400 angstroms, and 30 percent or more of the pore volume is in pores having diameters of from about 400 angstroms to about 38,000 angstroms.

  10. Molecular theory of size exclusion chromatography for wide pore size distributions.

    PubMed

    Sepsey, Annamária; Bacskay, Ivett; Felinger, Attila

    2014-02-28

    Chromatographic processes can conveniently be modeled at a microscopic level using the molecular theory of chromatography. This molecular or microscopic theory is completely general; therefore it can be used for any chromatographic process such as adsorption, partition, ion-exchange or size exclusion chromatography. The molecular theory of chromatography allows taking into account the kinetics of the pore ingress and egress processes, the heterogeneity of the pore sizes and polymer polydispersion. In this work, we assume that the pore size in the stationary phase of chromatographic columns is governed by a wide lognormal distribution. This property is integrated into the molecular model of size exclusion chromatography and the moments of the elution profiles were calculated for several kinds of pore structure. Our results demonstrate that wide pore size distributions have strong influence on the retention properties (retention time, peak width, and peak shape) of macromolecules. The novel model allows us to estimate the real pore size distribution of commonly used HPLC stationary phases, and the effect of this distribution on the size exclusion process. Copyright © 2014 Elsevier B.V. All rights reserved.

  11. A theoretical analysis and prediction of pore size and pore size distribution in electrospun multilayer nanofibrous materials.

    PubMed

    Bagherzadeh, Roohollah; Najar, Saeed Shaikhzadeh; Latifi, Masoud; Tehran, Mohammad Amani; Kong, Lingxue

    2013-07-01

    Electrospinning process can fabricate nanomaterials with unique nanostructures for potential biomedical and environmental applications. However, the prediction and, consequently, the control of the porous structure of these materials has been impractical due to the complexity of the electrospinning process. In this research, a theoretical model for characterizing the porous structure of the electrospun nanofibrous network has been developed by combining the stochastic and stereological probability approaches. From consideration of number of fiber-to-fiber contacts in an electrospun nanofibrous assembly, geometrical and statistical theory relating morphological and structural parameters of the network to the characteristic dimensions of interfibers pores is provided. It has been shown that these properties are strongly influenced by the fiber diameter, porosity, and thickness of assembly. It is also demonstrated that at a given network porosity, increasing fiber diameter and thickness of the network reduces the characteristic dimensions of pores. It is also discussed that the role of fiber diameter and number of the layer in the assembly is dominant in controlling the pore size distribution of the networks. The theory has been validated experimentally and results compared with the existing theory to predict the pore size distribution of nanofiber mats. It is believed that the presented theory for estimation of pore size distribution is more realistic and useful for further studies of multilayer random nanofibrous assemblies. Copyright © 2013 Wiley Periodicals, Inc.

  12. Using radial NMR profiles to characterize pore size distributions

    NASA Astrophysics Data System (ADS)

    Deriche, Rachid; Treilhard, John

    2012-02-01

    Extracting information about axon diameter distributions in the brain is a challenging task which provides useful information for medical purposes; for example, the ability to characterize and monitor axon diameters would be useful in diagnosing and investigating diseases like amyotrophic lateral sclerosis (ALS)1 or autism.2 Three families of operators are defined by Ozarslan,3 whose action upon an NMR attenuation signal extracts the moments of the pore size distribution of the ensemble under consideration; also a numerical method is proposed to continuously reconstruct a discretely sampled attenuation profile using the eigenfunctions of the simple harmonic oscillator Hamiltonian: the SHORE basis. The work presented here extends Ozarlan's method to other bases that can offer a better description of attenuation signal behaviour; in particular, we propose the use of the radial Spherical Polar Fourier (SPF) basis. Testing is performed to contrast the efficacy of the radial SPF basis and SHORE basis in practical attenuation signal reconstruction. The robustness of the method to additive noise is tested and analysed. We demonstrate that a low-order attenuation signal reconstruction outperforms a higher-order reconstruction in subsequent moment estimation under noisy conditions. We propose the simulated annealing algorithm for basis function scale parameter estimation. Finally, analytic expressions are derived and presented for the action of the operators on the radial SPF basis (obviating the need for numerical integration, thus avoiding a spectrum of possible sources of error).

  13. Effect of pore size distribution on enzyme immobilization in porous supports

    SciTech Connect

    Wang, Y.J.; Wu, T.C. ); Chiang, C.L. )

    1989-09-01

    The objective of this study is to improve Clark's model by incorporating a pore size distribution into the pore central core restricted diffusion model. By using a refined equation for the void cross-sectional area of pore, the authors recalculate the amount of enzyme immobilized vs. time on stream. In addition, a real pore size distribution of silica supports is measured to investigate the deviation of the loaded amount of enzyme predicted by Clark's model.

  14. Determination of the pore size distribution and porosity of aerobic granules using size-exclusion chromatography.

    PubMed

    Zheng, Yu-Ming; Yu, Han-Qing

    2007-01-01

    The pore size distribution and porosity of aerobic granules with different diameters were evaluated using size-exclusion chromatography, in which polyethylene glycols and distilled water were, respectively, used as solute and mobile phase. The porosity of the aerobic granules varied from 68% to 93% and the exclusion limit, expressed as molecular mass, showed a significant difference. For the small-size granules with a diameter of 0.2-0.6mm, molecules greater than 137,000Da could not penetrate the pores, while the exclusion limits of the middle-size granules with a diameter of 0.6-0.9mm and large-size ones with a diameter of 0.9-1.5mm were 76,000 and 29,000Da, respectively. The extracellular polymeric substances of the granules might clog the pores and might be responsible for the reduced porosity. A correlation between the bioactivity and available porosity of the aerobic granules was found. The experimental results show that the size-exclusion chromatography was appropriate for elucidating the pore size distribution and porosity of the aerobic granules.

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

    USDA-ARS?s Scientific Manuscript database

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

  16. Influence of stress-path on pore size distribution in granular materials

    NASA Astrophysics Data System (ADS)

    Das, Arghya; Kumar, Abhinav

    2017-06-01

    Pore size distribution is an important feature of granular materials in the context of filtration and erosion in soil hydraulic structures. Present study focuses on the evolution characteristics of pore size distribution for numerically simulated granular assemblies while subjected to various compression boundary constrain, namely, conventional drained triaxial compression, one-dimensional or oedometric compression and isotropic compression. We consider the effects initial packing of the granular assembly, loose or dense state. A simplified algorithm based on Delaunay tessellation is used for the estimation of pore size distribution for the deforming granular assemblies at various stress states. The analyses show that, the evolution of pore size is predominantly governed by the current porosity of the granular assembly while the stress path or loading process has minimal influence. Further it has also been observed that pore volume distribution reaches towards a critical distribution at the critical porosity during shear enhanced loading process irrespective of the deformation mechanism either compaction or dilation.

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

    PubMed

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

    2015-02-03

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

  18. Water and Solute Transport Governed by Tunable Pore Size Distributions in Nanoporous Graphene Membranes.

    PubMed

    Jang, Doojoon; Idrobo, Juan-Carlos; Laoui, Tahar; Karnik, Rohit

    2017-10-10

    Nanoporous graphene has the potential to advance membrane separations by offering high selectivity with minimal resistance to flow, but how mass transport depends on the structure of pores in this atomically thin membrane is poorly understood. Here, we investigate the relationship between tunable pore creation using ion bombardment and oxygen plasma etching, the resulting pore size distributions, and the consequent water and solute transport. Through tuning of the pore creation process, we demonstrate nanofiltration membranes that reject small molecules but offer high permeance to water or monovalent ions. Theoretical multiscale modeling of transport across the membranes reveals a disproportionate contribution of large pores to osmotic water flux and diffusive solute transport and captures the observed trends in transport measurements except for the smallest pores. This work provides insights into the effects of graphene pore size distribution and support layer on transport and presents a framework for designing atomically thin membranes.

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

    NASA Astrophysics Data System (ADS)

    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

  20. Pore-size distribution in loamy soils: A comparison between microtomographic and capillarimetric determination methods

    NASA Astrophysics Data System (ADS)

    Shein, E. V.; Skvortsova, E. B.; Dembovetskii, A. V.; Abrosimov, K. N.; Il'in, L. I.; Shnyrev, N. A.

    2016-03-01

    Pore-size distribution in a soddy-podzolic silt loamy soil developing from mantle loesslike loam (Eutric Albic Retisol (Loamic, Cutanic)) was calculated from the water retention curve according to Jurin's equation and directly determined in microtomographic experiments. Rounded macropores with the diameter of their sections from 75 to 1000 μm predominate in horizontal sections if the studied soil samples. A larger part of the soil pores (>30-35%) belongs to micro- and nanopores, and they cannot be quantitatively determined by the tomographic method, because their sizes are smaller than the detection limit of the applied X-ray microtomography (8.75 μm per pixel). This leads to a significantly larger pore volume determined from the water retention curve in comparison with the "tomographic" pore volume. A comparative analysis of pore-size distribution curves obtained by these methods shows that the major regularities of the pore-size distribution in the range from 30 to 5000 μm are similar in both cases. Fine macropores and, partly, mesopores predominate. Common characteristics of the pore-size distribution curves obtained by these methods, including the coincidence of the peaks, attest to the validity of classical approaches, according to which the hydrology of soil pore space can be perceived as a physical model of cylindrical capillaries of different sizes with capillary-sorbed water.

  1. Changes in pore size distribution inside sludge under various ultrasonic conditions.

    PubMed

    Zhao, Fang; Cheng, Daolai

    2017-09-01

    The pore size distribution is quite significant for determining the transport capacity of heat and moisture in sludge during the drying process. It is crucial to investigate the transformation of the pore size in sludge under sonication. In this paper, the microstructures of pores inside sludge before and after ultrasonic treatment with various ultrasonic conditions were observed using a microscope. Fractal geometry and image analysis were combined to quantitatively identify the evolution of pore size in sludge undergoing various acoustic energy densities and treatment times. The surface fractal dimension (df) was applied to characterize the pore size distribution of sludge. The results confirmed that sonication has a positive influence on the characteristics of pore structure inside the sludge and that the average pore size increases with increasing ultrasonic energy level, as determined by both acoustic energy density and treatment time. The df appropriately characterizes and quantifies the evolution of the pore size distribution of sludge under various ultrasonic conditions. This work is quite valuable for further investigating and evaluating moisture removal in the sludge drying process assisted by ultrasonic treatment. Copyright © 2017 Elsevier B.V. All rights reserved.

  2. Porosity and pore size distribution in a sedimentary rock: Implications for the distribution of chlorinated solvents

    NASA Astrophysics Data System (ADS)

    Shapiro, Allen M.; Evans, Christopher E.; Hayes, Erin C.

    2017-08-01

    Characterizing properties of the rock matrix that control retention and release of chlorinated solvents is essential in evaluating the extent of contamination and the application of remediation technologies in fractured rock. Core samples from seven closely spaced boreholes in a mudstone subject to trichloroethene (TCE) contamination were analyzed using Mercury Intrusion Porosimetry to investigate porosity and pore size distribution as a function of mudstone characteristics, and depth and lateral extent in the aquifer; organic carbon content was also evaluated to identify the potential for adsorption. Porosity and retardation factor varied over two orders of magnitude, with the largest porosities and largest retardation factors associated with carbon-rich mudstone layers. Larger porosities were also measured in the shallow rock that has been subject to enhanced groundwater flow. Porosity also varied over more than an order of magnitude in spatially continuous mudstone layers. The analyses of the rock cores indicated that the largest pore diameters may be accessible to entry of the nonaqueous form of TCE. Although the porosity associated with the largest pore diameters is small ( 0.1%), that volume of TCE can significantly affect the total TCE that is retained in the rock matrix. The dimensions of the largest pore diameters may also be accessible to microbes responsible for reductive dechlorination; however, the small percentage of the pore space that can accommodate microbes may limit the extent of reductive dechlorination in the rock matrix.

  3. Porosity and pore size distribution in a sedimentary rock: Implications for the distribution of chlorinated solvents

    USGS Publications Warehouse

    Shapiro, Allen M.; Evans, Chrsitopher E.; Hayes, Erin C.

    2017-01-01

    Characterizing properties of the rock matrix that control retention and release of chlorinated solvents is essential in evaluating the extent of contamination and the application of remediation technologies in fractured rock. Core samples from seven closely spaced boreholes in a mudstone subject to trichloroethene (TCE) contamination were analyzed using Mercury Intrusion Porosimetry to investigate porosity and pore size distribution as a function of mudstone characteristics, and depth and lateral extent in the aquifer; organic carbon content was also evaluated to identify the potential for adsorption. Porosity and retardation factor varied over two orders of magnitude, with the largest porosities and largest retardation factors associated with carbon-rich mudstone layers. Larger porosities were also measured in the shallow rock that has been subject to enhanced groundwater flow. Porosity also varied over more than an order of magnitude in spatially continuous mudstone layers. The analyses of the rock cores indicated that the largest pore diameters may be accessible to entry of the nonaqueous form of TCE. Although the porosity associated with the largest pore diameters is small (~ 0.1%), that volume of TCE can significantly affect the total TCE that is retained in the rock matrix. The dimensions of the largest pore diameters may also be accessible to microbes responsible for reductive dechlorination; however, the small percentage of the pore space that can accommodate microbes may limit the extent of reductive dechlorination in the rock matrix.

  4. Porosity and pore size distribution in a sedimentary rock: Implications for the distribution of chlorinated solvents.

    PubMed

    Shapiro, Allen M; Evans, Christopher E; Hayes, Erin C

    2017-08-01

    Characterizing properties of the rock matrix that control retention and release of chlorinated solvents is essential in evaluating the extent of contamination and the application of remediation technologies in fractured rock. Core samples from seven closely spaced boreholes in a mudstone subject to trichloroethene (TCE) contamination were analyzed using Mercury Intrusion Porosimetry to investigate porosity and pore size distribution as a function of mudstone characteristics, and depth and lateral extent in the aquifer; organic carbon content was also evaluated to identify the potential for adsorption. Porosity and retardation factor varied over two orders of magnitude, with the largest porosities and largest retardation factors associated with carbon-rich mudstone layers. Larger porosities were also measured in the shallow rock that has been subject to enhanced groundwater flow. Porosity also varied over more than an order of magnitude in spatially continuous mudstone layers. The analyses of the rock cores indicated that the largest pore diameters may be accessible to entry of the nonaqueous form of TCE. Although the porosity associated with the largest pore diameters is small (~0.1%), that volume of TCE can significantly affect the total TCE that is retained in the rock matrix. The dimensions of the largest pore diameters may also be accessible to microbes responsible for reductive dechlorination; however, the small percentage of the pore space that can accommodate microbes may limit the extent of reductive dechlorination in the rock matrix. Published by Elsevier B.V.

  5. Pore invasion dynamics during fluid front displacement in porous media determine functional pore size distribution and phase entrapment

    NASA Astrophysics Data System (ADS)

    Moebius, F.; Or, D.

    2012-12-01

    Dynamics of fluid fronts in porous media shape transport properties of the unsaturated zone and affect management of petroleum reservoirs and their storage properties. What appears macroscopically as smooth and continuous motion of a displacement fluid front may involve numerous rapid interfacial jumps often resembling avalanches of invasion events. Direct observations using high-speed camera and pressure sensors in sintered glass micro-models provide new insights on the influence of flow rates, pore size, and gravity on invasion events and on burst size distribution. Fundamental differences emerge between geometrically-defined pores and "functional" pores invaded during a single burst (invasion event). The waiting times distribution of individual invasion events and decay times of inertial oscillations (following a rapid interfacial jump) are characteristics of different displacement regimes. An invasion percolation model with gradients and including the role of inertia provide a framework for linking flow regimes with invasion sequences and phase entrapment. Model results were compared with measurements and with early studies on invasion burst sizes and waiting times distribution during slow drainage processes by Måløy et al. [1992]. The study provides new insights into the discrete invasion events and their weak links with geometrically-deduced pore geometry. Results highlight factors controlling pore invasion events that exert strong influence on macroscopic phenomena such as front morphology and residual phase entrapment shaping hydraulic properties after the passage of a fluid front.

  6. Pore size distribution, strength, and microstructure of portland cement paste containing metal hydroxide waste

    SciTech Connect

    Majid, Z.A.; Mahmud, H.; Shaaban, M.G.

    1996-12-31

    Stabilization/solidification of hazardous wastes is used to convert hazardous metal hydroxide waste sludge into a solid mass with better handling properties. This study investigated the pore size development of ordinary portland cement pastes containing metal hydroxide waste sludge and rice husk ash using mercury intrusion porosimetry. The effects of acre and the addition of rice husk ash on pore size development and strength were studied. It was found that the pore structures of mixes changed significantly with curing acre. The pore size shifted from 1,204 to 324 {angstrom} for 3-day old cement paste, and from 956 to 263 {angstrom} for a 7-day old sample. A reduction in pore size distribution for different curing ages was also observed in the other mixtures. From this limited study, no conclusion could be made as to any correlation between strength development and porosity. 10 refs., 6 figs., 3 tabs.

  7. Direct correlation of internal gradients and pore size distributions with low field NMR

    NASA Astrophysics Data System (ADS)

    Zhang, Yan; Xiao, Lizhi; Liao, Guangzhi; Blümich, Bernhard

    2016-06-01

    Internal magnetic field gradients Gint, which arise from the magnetic susceptibility difference Δχ between solid matrix and fluid in porous media relate to the pore geometry. However, this relationship is complex and not well understood. Here we correlate internal-gradient distributions to pore-size distributions directly to examine internal gradients in detail at low field NMR. The pore-size distributions were obtained by the method of Decay due to Diffusion in the Internal Field (DDIF), and the internal-gradient distributions were measured with the Carr-Purcell-Meiboom-Gill (CPMG) method. The internal-gradient-pore-size distributions correlation maps were obtained for water in packs of glass beads with different diameter and in a sandstone sample. The relationship between internal gradients and pore structure is analyzed in detail by considering the restricted diffusion of fluids in porous samples. For each case diffusion regimes are assigned by plotting normalized CPMG data and comparing the diffusion lengths, the dephasing lengths and pore diameters. In the free-diffusion limit, the correlation maps reveal the true relationship between pore structure and internal gradients so that Δχ can be approximated from the correlation maps. This limit is met most easily at low field. It provides information about porous media, which is expected to benefit the oil industry, in particular NMR well logging.

  8. Direct correlation of internal gradients and pore size distributions with low field NMR.

    PubMed

    Zhang, Yan; Xiao, Lizhi; Liao, Guangzhi; Blümich, Bernhard

    2016-06-01

    Internal magnetic field gradients Gint, which arise from the magnetic susceptibility difference Δχ between solid matrix and fluid in porous media relate to the pore geometry. However, this relationship is complex and not well understood. Here we correlate internal-gradient distributions to pore-size distributions directly to examine internal gradients in detail at low field NMR. The pore-size distributions were obtained by the method of Decay due to Diffusion in the Internal Field (DDIF), and the internal-gradient distributions were measured with the Carr-Purcell-Meiboom-Gill (CPMG) method. The internal-gradient-pore-size distributions correlation maps were obtained for water in packs of glass beads with different diameter and in a sandstone sample. The relationship between internal gradients and pore structure is analyzed in detail by considering the restricted diffusion of fluids in porous samples. For each case diffusion regimes are assigned by plotting normalized CPMG data and comparing the diffusion lengths, the dephasing lengths and pore diameters. In the free-diffusion limit, the correlation maps reveal the true relationship between pore structure and internal gradients so that Δχ can be approximated from the correlation maps. This limit is met most easily at low field. It provides information about porous media, which is expected to benefit the oil industry, in particular NMR well logging. Copyright © 2016 Elsevier Inc. All rights reserved.

  9. Effect of pore size distribution on the rate of enzymatic hydrolysis of cellulosic substrates

    SciTech Connect

    Grethlein, H.E.

    1985-02-01

    Hard and softwoods were pretreated by mild acid hydrolysis and their pore size distribution determined. Regardless of the substrate, the initial rate of hydrolysis using cellulase from Trichoderma reesei is linearly correlated with the pore volume of the substrate accessible to a nominal diameter of 51 Angstroms representative of the size of the cellulase. In contrast, crystallinity index has no relationship to the rate of hydrolysis. 21 references.

  10. Pore size distribution, survival probability, and relaxation time in random and ordered arrays of fibers

    NASA Astrophysics Data System (ADS)

    Tomadakis, Manolis M.; Robertson, Teri J.

    2003-07-01

    We present a random walk based investigation of the pore size probability distribution and its moments, the survival probability and mean survival time, and the principal relaxation time, for random and ordered arrays of cylindrical fibers of various orientation distributions. The dimensionless mean survival time, principal relaxation time, mean pore size, and mean square pore size are found to increase with porosity, remain practically independent of the directionality of random fiber beds, and attain lower values for ordered arrays. Wide pore size distributions are obtained for random fiber structures and relatively narrow for ordered square arrays, all in very good agreement with theoretically predicted limiting values. Analytical results derived for the pore size probability and its lower moments for square arrays of fibers practically coincide with the corresponding simulation results. Earlier variational bounds on the mean survival time and principal relaxation time are obeyed by our numerical results in all cases, and are found to be quite sharp up to very high porosities. Dimensionless groups representing the deviation of such bounds from our simulation results vary in practically the same range as the corresponding values reported earlier for beds of spherical particles. A universal scaling expression of the literature relating the mean survival time to the mean pore size [S. Torquato and C. L. Y. Yeong, J. Chem. Phys. 106, 8814 (1997)] agrees very well with our results for all types of fiber structures, thus validated for the first time for anisotropic porous media.

  11. Estimating the 3D Pore Size Distribution of Biopolymer Networks from Directionally Biased Data

    PubMed Central

    Lang, Nadine R.; Münster, Stefan; Metzner, Claus; Krauss, Patrick; Schürmann, Sebastian; Lange, Janina; Aifantis, Katerina E.; Friedrich, Oliver; Fabry, Ben

    2013-01-01

    The pore size of biopolymer networks governs their mechanical properties and strongly impacts the behavior of embedded cells. Confocal reflection microscopy and second harmonic generation microscopy are widely used to image biopolymer networks; however, both techniques fail to resolve vertically oriented fibers. Here, we describe how such directionally biased data can be used to estimate the network pore size. We first determine the distribution of distances from random points in the fluid phase to the nearest fiber. This distribution follows a Rayleigh distribution, regardless of isotropy and data bias, and is fully described by a single parameter—the characteristic pore size of the network. The bias of the pore size estimate due to the missing fibers can be corrected by multiplication with the square root of the visible network fraction. We experimentally verify the validity of this approach by comparing our estimates with data obtained using confocal fluorescence microscopy, which represents the full structure of the network. As an important application, we investigate the pore size dependence of collagen and fibrin networks on protein concentration. We find that the pore size decreases with the square root of the concentration, consistent with a total fiber length that scales linearly with concentration. PMID:24209841

  12. Flow rate through microfilters: Influence of the pore size distribution, hydrodynamic interactions, wall slip, and inertia

    NASA Astrophysics Data System (ADS)

    Jensen, Kaare H.; Valente, André X. C. N.; Stone, Howard A.

    2014-05-01

    We examine the fluid mechanics of viscous flow through filters consisting of perforated thin plates. We classify the effects that contribute to the hydraulic resistance of the filter. Classical analyses assume a single pore size and account only for filter thickness. We extend these results to obtain an analytical formula for the pressure drop across the microfilter versus the flow rate that accounts for the non-uniform distribution of pore sizes, the hydrodynamic interactions between the pores given their layout pattern, and wall slip. Further, we discuss inertial effects and their order of scaling.

  13. Synthesis and characterization of mesoporous ZnS with narrow size distribution of small pores

    NASA Astrophysics Data System (ADS)

    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.

  14. A thermal porosimetry method to estimate pore size distribution in highly porous insulating materials

    SciTech Connect

    Felix, V.; Jannot, Y.; Degiovanni, A.

    2012-05-15

    Standard pore size determination methods such as mercury porosimetry, nitrogen sorption, microscopy, or x-ray tomography are not always applicable to highly porous, low density, and thus very fragile materials. For this kind of materials, a method based on thermal characterization is proposed. Indeed, the thermal conductivity of a highly porous and insulating medium is significantly dependent on the thermal conductivity of the interstitial gas that depends on both gas pressure and size of the considered pore (Knudsen effect). It is also possible to link the pore size with the thermal conductivity of the medium. Thermal conductivity measurements are realized on specimens placed in an enclosure where the air pressure is successively set to different values varying from 10{sup -1} to 10{sup 5} Pa. Knowing the global porosity ratio, an effective thermal conductivity model for a two-phase air-solid material based on a combined serial-parallel model is established. Pore size distribution can be identified by minimizing the sum of the quadratic differences between measured values and modeled ones. The results of the estimation process are the volume fractions of the chosen ranges of pore size. In order to validate the method, measurements done on insulating materials are presented. The results are discussed and show that pore size distribution estimated by the proposed method is coherent.

  15. New general pore size distribution model by classical thermodynamics application: Activated carbon

    USGS Publications Warehouse

    Lordgooei, M.; Rood, M.J.; Rostam-Abadi, M.

    2001-01-01

    A model is developed using classical thermodynamics to characterize pore size distributions (PSDs) of materials containing micropores and mesopores. The thermal equation of equilibrium adsorption (TEEA) is used to provide thermodynamic properties and relate the relative pore filling pressure of vapors to the characteristic pore energies of the adsorbent/adsorbate system for micropore sizes. Pore characteristic energies are calculated by averaging of interaction energies between adsorbate molecules and adsorbent pore walls as well as considering adsorbate-adsorbate interactions. A modified Kelvin equation is used to characterize mesopore sizes by considering variation of the adsorbate surface tension and by excluding the adsorbed film layer for the pore size. The modified-Kelvin equation provides similar pore filling pressures as predicted by density functional theory. Combination of these models provides a complete PSD of the adsorbent for the micropores and mesopores. The resulting PSD is compared with the PSDs from Jaroniec and Choma and Horvath and Kawazoe models as well as a first-order approximation model using Polanyi theory. The major importance of this model is its basis on classical thermodynamic properties, less simplifying assumptions in its derivation compared to other methods, and ease of use.

  16. The effect of magnetic particles on pore size distribution in soft polyurethane foams

    NASA Astrophysics Data System (ADS)

    Schümann, M.; Günther, S.; Odenbach, S.

    2014-07-01

    The combination of elastomeric matrices with magnetic particles to obtain magnetically controllable hybrid materials is an actual field of intense research. An important aspect in this context is the stiffness of the matrix, which determines the effectiveness of the magnetically driven changes in the material properties. In this paper an approach has been undertaken to use soft polyurethane foams as matrix material. By means of x-ray computed microtomography and digital image processing the pore size distribution has been determined to get information on how this distribution is affected by the introduction of magnetic microparticles. To do so, 20 000 to 40 000 pores per foam sample were evaluated. As a result, it could be proven that the pore sizes of the analysed foams clearly obey the Weibull distribution. Increasing the carbonyl iron particle concentrations leads to a decrement of the shape parameter of the distribution. Based on known particle stabilization mechanisms, an approach to explain the experimental results is proposed.

  17. Direct correlation of diffusion and pore size distributions with low field NMR

    NASA Astrophysics Data System (ADS)

    Zhang, Yan; Xiao, Lizhi; Liao, Guangzhi; Song, Yi-Qiao

    2016-08-01

    The time-dependent diffusion coefficient (D) is a powerful tool to probe microstructure in porous media, and can be obtained by the NMR method. In a real porous sample, molecular diffusion is very complex. Here we present a new method which directly measures the relationship between effective diffusion coefficients and pore size distributions without knowing surface relaxivity. This method is used to extract structural information and explore the relationship between D and a in porous media having broad pore size distributions. The diffusion information is encoded by the Pulsed Field Gradient (PFG) method and the pore size distributions are acquired by the Decay due to Diffusion in the Internal Field (DDIF) method. Two model samples were measured to verify this method. Restricted diffusion was analyzed, and shows that most fluid molecules experience pore wall. The D(a) curves obtained from correlation maps were fitted to the Padé approximant equation and a good agreement was found between the fitting lines and the measured data. Then a sandstone sample with unknown structure was measured. The state of confined fluids was analyzed and structural information, such as pore size distributions, were extracted. The D - T1 correlation maps were also obtained using the same method, which yielded surface relaxivities for different samples. All the experiments were conducted on 2 MHz NMR equipment to obtain accurate diffusion information, where internal gradients can be neglected. This method is expected to have useful applications in the oil industry, particularly for NMR logging in the future.

  18. Strategies for Tailoring the Pore-Size Distribution of Virus Retention Filter Papers.

    PubMed

    Gustafsson, Simon; Mihranyan, Albert

    2016-06-08

    The goal of this work is to demonstrate how the pore-size distribution of the nanocellulose-based virus-retentive filter can be tailored. The filter paper was produced using cellulose nanofibers derived from Cladophora sp. green algae using the hot-press drying at varying drying temperatures. The produced filters were characterized using scanning electron microscopy, atomic force microscopy, and N2 gas sorption analysis. Further, hydraulic permeability and retention efficiency toward surrogate 20 nm model particles (fluorescent carboxylate-modified polystyrene spheres) were assessed. It was shown that by controlling the rate of water evaporation during hot-press drying the pore-size distribution can be precisely tailored in the region between 10 and 25 nm. The mechanism of pore formation and critical parameters are discussed in detail. The results are highly valuable for development of advanced separation media, especially for virus-retentive size-exclusion filtration.

  19. Investigation of pore size and energy distributions by statistical physics formalism applied to agriculture products

    NASA Astrophysics Data System (ADS)

    Aouaini, Fatma; Knani, Salah; Yahia, Manel Ben; Bahloul, Neila; Ben Lamine, Abdelmottaleb; Kechaou, Nabil

    2015-12-01

    In this paper, we present a new investigation that allows determining the pore size distribution (PSD) in a porous medium. This PSD is achieved by using the desorption isotherms of four varieties of olive leaves. This is by the means of statistical physics formalism and Kelvin's law. The results are compared with those obtained with scanning electron microscopy. The effect of temperature on the distribution function of pores has been studied. The influence of each parameter on the PSD is interpreted. A similar function of adsorption energy distribution, AED, is deduced from the PSD.

  20. Pore size distribution and supercritical hydrogen adsorption in activated carbon fibers

    NASA Astrophysics Data System (ADS)

    Purewal, J. J.; Kabbour, H.; Vajo, J. J.; Ahn, C. C.; Fultz, B.

    2009-05-01

    Pore size distributions (PSD) and supercritical H2 isotherms have been measured for two activated carbon fiber (ACF) samples. The surface area and the PSD both depend on the degree of activation to which the ACF has been exposed. The low-surface-area ACF has a narrow PSD centered at 0.5 nm, while the high-surface-area ACF has a broad distribution of pore widths between 0.5 and 2 nm. The H2 adsorption enthalpy in the zero-coverage limit depends on the relative abundance of the smallest pores relative to the larger pores. Measurements of the H2 isosteric adsorption enthalpy indicate the presence of energy heterogeneity in both ACF samples. Additional measurements on a microporous, coconut-derived activated carbon are presented for reference.

  1. Investigations of surface acidities and pore size distributions of selected pillared layered materials

    SciTech Connect

    Odom, M.A.; Wade, K.L.; Morgan, D.M.; White, J.L.; Schroeder, N.C.

    1996-10-01

    Pillared Layered Materials (PLMs) are being designed for a variety of applications. Currently, PLMs are being prepared in this laboratory for the selective sorption of radionuclides from liquid-nuclear wastes. It is important to have a good understanding of characteristics, such as pore size distributions and surface acidities, in order to tailor there sizes and environments are manipulated by varying the layered materials and pillaring species used for preparing the PLM. A variety of techniques have been employed to study these characteristics. For this study the pore size distributions were derived by determining the sorption of hydrocarbons of various sizes and shapes into the PLMs. The surface acidities were probed by sorbing basic species, such as ammonia and pyridine, and assessing the interactions with the acid sites using FTIR spectroscopy.

  2. Pore size distributions in polyelectrolyte multilayers determined by nuclear magnetic resonance cryoporometry

    NASA Astrophysics Data System (ADS)

    Vaca Chávez, Fabián; Schönhoff, Monika

    2007-03-01

    Polyelectrolyte multilayers (PEMs) are thin films, which are assembled one molecular layer at a time, by alternatingly adsorbing polycations and polyanions making use of their attractive electrostatic interaction. Since the porosity of PEMs is one of the properties of major interest, in the current work the first pore size distribution of PEMs in samples consisting of silica particles coated with poly(allylamine hydrochloride) and poly(sodium 4-styrenesulfonate) is presented. To this end, the nuclear magnetic resonance (NMR) cryoporometry technique was applied. The proton NMR signal of liquid water is analyzed assuming a log normal distribution of motional correlation times. From the results, it is possible to determine the size of water sites in the layers to around 1nm. In addition, a slight variation with the number of layers is found. The average pore size agrees with cutoff sizes found in permeation experiments.

  3. Survival and relaxation time, pore size distribution moments, and viscous permeability in random unidirectional fiber structures

    NASA Astrophysics Data System (ADS)

    Tomadakis, Manolis M.; Robertson, Teri J.

    2005-03-01

    Computer simulation results are presented for the mean survival time, principal relaxation time, mean pore size, and mean square pore size, for random porous structures consisting of parallel nonoverlapping or partially overlapping fibers. The numerical procedure is based on a discrete step-by-step random walk mechanism simulating the Brownian diffusion trajectories of molecules in the porous media. Numerical results on the viscous permeability of these structures are computed with a method based on electrical conduction principles and compared to a variational bound derived from the mean survival time. The results show that nonoverlapping fiber structures exhibit lower values of the dimensionless mean survival time, principal relaxation time, mean pore size, and mean square pore size than randomly overlapping fiber structures of the same porosity, while partially overlapping fiber structures show behavior intermediate to those of the two extreme cases. The mean square pore size (second moment of the pore size distribution) is found to be a very good predictor of the mean survival time for non-, partially, and randomly overlapping fiber structures. Dimensionless groups representing the deviation of variational bounds from our simulation results vary in practically the same range as the corresponding values reported earlier for beds of spherical particles. A universal scaling expression of the literature relating the mean survival time to structural properties [S. Torquato and C. L. Y. Yeong, J. Chem. Phys. 106, 8814 (1997)] agrees very well with our results for all examined fiber structures, thus validated for the first time for porous media formed by partially overlapping particles. The permeability behavior of partially overlapping fiber structures resembles that of nonoverlapping fiber structures for flow parallel to the fibers, but not for transverse flow, where percolation phenomena prevail. The permeability results for beds of unidirectional partially

  4. Survival and relaxation time, pore size distribution moments, and viscous permeability in random unidirectional fiber structures.

    PubMed

    Tomadakis, Manolis M; Robertson, Teri J

    2005-03-01

    Computer simulation results are presented for the mean survival time, principal relaxation time, mean pore size, and mean square pore size, for random porous structures consisting of parallel nonoverlapping or partially overlapping fibers. The numerical procedure is based on a discrete step-by-step random walk mechanism simulating the Brownian diffusion trajectories of molecules in the porous media. Numerical results on the viscous permeability of these structures are computed with a method based on electrical conduction principles and compared to a variational bound derived from the mean survival time. The results show that nonoverlapping fiber structures exhibit lower values of the dimensionless mean survival time, principal relaxation time, mean pore size, and mean square pore size than randomly overlapping fiber structures of the same porosity, while partially overlapping fiber structures show behavior intermediate to those of the two extreme cases. The mean square pore size (second moment of the pore size distribution) is found to be a very good predictor of the mean survival time for non-, partially, and randomly overlapping fiber structures. Dimensionless groups representing the deviation of variational bounds from our simulation results vary in practically the same range as the corresponding values reported earlier for beds of spherical particles. A universal scaling expression of the literature relating the mean survival time to structural properties [S. Torquato and C. L. Y. Yeong, J. Chem. Phys. 106, 8814 (1997)] agrees very well with our results for all examined fiber structures, thus validated for the first time for porous media formed by partially overlapping particles. The permeability behavior of partially overlapping fiber structures resembles that of nonoverlapping fiber structures for flow parallel to the fibers, but not for transverse flow, where percolation phenomena prevail. The permeability results for beds of unidirectional partially

  5. A facile method to determine pore size distribution in porous scaffold by using image processing.

    PubMed

    Lo Re, G; Lopresti, F; Petrucci, G; Scaffaro, R

    2015-09-01

    Image processing permits scientists to investigate morphological properties of three-dimensional structures starting from their bi-dimensional gray-scale representation. In many cases porous structure with complex architecture has to be designed in order to attempt specific properties such in the case of scaffold for tissue engineering. Traditional morphological characterization, like scanning electron microscopy, should be coupled with quantitative information such as pore size distribution (PSD) in order to get a deeper understanding of the influence of the porous structure on tissue regeneration processes and on other related applications, it is remarkable to study a quantitative analysis of porosity and of pores dimension. In this work it was developed as a software able to accomplish the segmentation of images containing pores of any geometry in a semi-automatic way with the aim to measure the PSD. Case study constituted by PLA porous scaffolds with different pore size was adopted. Results indicate that image processing methods well fit the pore size features of PLA scaffolds, overcoming the limits of the more invasive porosimetry techniques.

  6. A solid with a hierarchical tetramodal micro-meso-macro pore size distribution

    PubMed Central

    Ren, Yu; Ma, Zhen; Morris, Russell E.; Liu, Zheng; Jiao, Feng; Dai, Sheng; Bruce, Peter G.

    2013-01-01

    Porous solids have an important role in addressing some of the major energy-related problems facing society. Here we describe a porous solid, α-MnO2, with a hierarchical tetramodal pore size distribution spanning the micro-, meso- and macro pore range, centred at 0.48, 4.0, 18 and 70 nm. The hierarchical tetramodal structure is generated by the presence of potassium ions in the precursor solution within the channels of the porous silica template; the size of the potassium ion templates the microporosity of α-MnO2, whereas their reactivity with silica leads to larger mesopores and macroporosity, without destroying the mesostructure of the template. The hierarchical tetramodal pore size distribution influences the properties of α-MnO2 as a cathode in lithium batteries and as a catalyst, changing the behaviour, compared with its counterparts with only micropores or bimodal micro/mesopores. The approach has been extended to the preparation of LiMn2O4 with a hierarchical pore structure. PMID:23764887

  7. Nanofiltration Membranes with Narrow Pore Size Distribution via Contra-Diffusion-Induced Mussel-Inspired Chemistry.

    PubMed

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

    2016-11-02

    Nanofiltration membranes (NFMs) are widely used in saline water desalination, wastewater treatment, and chemical product purification. However, conventional NFMs suffer from broad pore size distribution, which limits their applications for fine separation, especially in complete separation of molecules with slight differences in molecular size. Herein, defect-free composite NFMs with narrow pore size distribution are fabricated using a contra-diffusion method, with dopamine/polyethylenimine solution on the skin side and ammonium persulfate solution on the other side of the ultrafiltration substrate. Persulfate ions can diffuse through the ultrafiltration substrate into the other side and in situ trigger dopamine to form a codeposited coating with polyethylenimine. The codeposition is hindered on those sites completely covered by the polydopamine/polyethylenimine coating, although it is promoted at the defects or highly permeable regions because it is induced by the diffused persulfate ions. Such a "self-completion" process results in NFMs with highly uniform structures and narrow pore size distribution, as determined by their rejection of neutral solutes. These near electrically neutral NFMs show a high rejection of divalent ions with a low rejection of monovalent ions (MgCl2 rejection = 96%, NaCl rejection = 23%), majorly based on a steric hindrance effect. The as-prepared NFMs can be applied in molecular separation such as isolating cellulose hydrogenation products.

  8. Permeability-Selectivity Analysis of Microfiltration and Ultrafiltration Membranes: Effect of Pore Size and Shape Distribution and Membrane Stretching

    PubMed Central

    Siddiqui, Muhammad Usama; Arif, Abul Fazal Muhammad; Bashmal, Salem

    2016-01-01

    We present a modeling approach to determine the permeability-selectivity tradeoff for microfiltration and ultrafiltration membranes with a distribution of pore sizes and pore shapes. Using the formulated permeability-selectivity model, the effect of pore aspect ratio and pore size distribution on the permeability-selectivity tradeoff of the membrane is analyzed. A finite element model is developed to study the effect of membrane stretching on the distribution of pore sizes and shapes in the stretched membrane. The effect of membrane stretching on the permeability-selectivity tradeoff of membranes is also analyzed. The results show that increasing pore aspect ratio improves membrane performance while increasing the width of pore size distribution deteriorates the performance. It was also found that the effect of membrane stretching on the permeability-selectivity tradeoff is greatly affected by the uniformity of pore distribution in the membrane. Stretching showed a positive shift in the permeability-selectivity tradeoff curve of membranes with well-dispersed pores while in the case of pore clustering, a negative shift in the permeability-selectivity tradeoff curve was observed. PMID:27509528

  9. Permeability-Selectivity Analysis of Microfiltration and Ultrafiltration Membranes: Effect of Pore Size and Shape Distribution and Membrane Stretching.

    PubMed

    Siddiqui, Muhammad Usama; Arif, Abul Fazal Muhammad; Bashmal, Salem

    2016-08-06

    We present a modeling approach to determine the permeability-selectivity tradeoff for microfiltration and ultrafiltration membranes with a distribution of pore sizes and pore shapes. Using the formulated permeability-selectivity model, the effect of pore aspect ratio and pore size distribution on the permeability-selectivity tradeoff of the membrane is analyzed. A finite element model is developed to study the effect of membrane stretching on the distribution of pore sizes and shapes in the stretched membrane. The effect of membrane stretching on the permeability-selectivity tradeoff of membranes is also analyzed. The results show that increasing pore aspect ratio improves membrane performance while increasing the width of pore size distribution deteriorates the performance. It was also found that the effect of membrane stretching on the permeability-selectivity tradeoff is greatly affected by the uniformity of pore distribution in the membrane. Stretching showed a positive shift in the permeability-selectivity tradeoff curve of membranes with well-dispersed pores while in the case of pore clustering, a negative shift in the permeability-selectivity tradeoff curve was observed.

  10. Importance of Pore Size Distribution of Fine-grained Sediments on Gas Hydrate Equilibrium

    NASA Astrophysics Data System (ADS)

    Kwon, T. H.; Kim, H. S.; Cho, G. C.; Park, T. H.

    2015-12-01

    Gas hydrates have been considered as a new source of natural gases. For the gas hydrate production, the gas hydrate reservoir should be depressurized below the equilibrium pressure of gas hydrates. Therefore, it is important to predict the equilibrium of gas hydrates in the reservoir conditions because it can be affected by the pore size of the host sediments due to the capillary effect. In this study, gas hydrates were synthesized in fine-grained sediment samples including a pure silt sample and a natural clayey silt sample cored from a hydrate occurrence region in Ulleung Basin, East Sea, offshore Korea. Pore size distributions of the samples were obtained by the nitrogen adsorption and desorption test and the mercury intrusion porosimetry. The equilibrium curve of gas hydrates in the fine-grained sediments were found to be significantly influenced by the clay fraction and the corresponding small pores (>50 nm in diameter). For the clayey silt sample, the equilibrium pressure was higher by ~1.4 MPa than the bulk equilibrium pressure. In most cases of oceanic gas hydrate reservoirs, sandy layers are found interbedded with fine-grained sediment layers while gas hydrates are intensively accumulated in the sandy layers. Our experiment results reveal the inhibition effect of fine-grained sediments against gas hydrate formation, in which greater driving forces (e.g., higher pressure or lower temperature) are required during natural gas migration. Therefore, gas hydrate distribution in interbedded layers of sandy and fine-grained sediments can be explained by such capillary effect induced by the pore size distribution of host sediments.

  11. Multiscale characterization of pore size distributions using mercury porosimetry and nitrogen adsorption

    NASA Astrophysics Data System (ADS)

    Paz-Ferreiro, J.; Tarquis, A. M.; Miranda, J. G. V.; Vidal Vázquez, E.

    2009-04-01

    The soil pore space is a continuum extremely variable in size, including structures smaller than nanometres and as large as macropores or cracks with millimetres or even centimetres size. Pore size distributions (PSDs) affects important soil functions, such as those related with transmission and storage of water, and root growth. Direct and indirect measurements of PSDs are becoming increasingly used to characterize soil structure. Mercury injection porosimetry and nitrogen adsorption isotherms are techniques commonly employed for assessing equivalent pore size diameters in the range from about 50 nm to 100 m and 2 to 500 nm, respectively. The multifractal formalism was used to describe Hg injection curves and N2 adsorption isotherms from two series of a Mollisol cultivated under no tillage and minimum tillage. Soil samples were taken from 0-10, 10-20 and 20-30 cm depths in two experimental fields located in the north of Buenos Aires and South of Santa Fe provinces, Argentina. All the data sets analyzed from the two studied soil attributes showed remarkably good scaling trends as assessed by singularity spectrum and generalized dimension spectrum. Both, experimental Hg injection curves and N2 adsorption isotherms could be fitted reasonably well with multifractal models. A wide variety of singularity and generalized dimension spectra was found for the variables. The capacity dimensions, D0, for both Hg injection and N2 adsorption data were not significantly different from the Euclidean dimension. However, the entropy dimension, D1, and correlation dimension, D2, obtained from mercury injection and nitrogen adsorption data showed significant differences. So, D1 values were on average 0.868 and varied from 0.787 to 0.925 for Hg intrusion curves. Entropy dimension, D1, values for N2 adsorption isotherms were on average 0.582 significantly lower than those obtained when using the former technique. Twenty-three out of twenty-four N2 isotherms had D1 values in a

  12. Pore-size distributions of cationic polyacrylamide hydrogels varying in initial monomer concentration and cross-linker/monomer ratio

    SciTech Connect

    Kremer, M.; Pothmann, E.; Roessler, T.; Baker, J.; Yee, A.; Blanch, H.; Prausnitz, J.M. )

    1994-05-23

    Pore-size distributions have been measured for cationic acrylamide-based hydrogels. The authors use the experimental mixed-solute-exclusion method, MSE (introduced by Kuga), to obtain the solute-exclusion curve representing the amount of imbibed liquid inside the gel inaccessible for a solute of radius r. The authors use the Brownian motion model (developed by Cassasa) to convert the size-exclusion curve into the pore-size distribution, which gives the frequency of pore radius R as a function of R. This theoretically-based interpretation of MSE data leads to the Fredholm integral equation that they solve numerically. Results are reported for a series of hydrogels containing acrylamide and 3% MAPTAC; the hydrogels differed in extent of cross-linking and/or initial concentration of monomer. Pore-size distributions shift to lower pore sizes with rising initial monomer concentration and with rising cross-linker-to-monomer ratio.

  13. Pore Size Distributions Inferred from Modified Inversion Percolation Modeling of Drainage Curves

    NASA Astrophysics Data System (ADS)

    Dralus, D. E.; Wang, H. F.; Strand, T. E.; Glass, R. J.; Detwiler, R. L.

    2005-12-01

    Experiments have been conducted of drainage in sand packs. At equilibrium, the interface between the fluids forms a saturation transition fringe where the saturation decreases monotonically with height. This behavior was observed in a 1-inch thick pack of 20-30 sand contained front and back within two thin, 12-inch-by-24-inch glass plates. The translucent chamber was illuminated from behind by a bank of fluorescent bulbs. Acquired data were in the form of images captured by a CCD camera with resolution on the grain scale. The measured intensity of the transmitted light was used to calculate the average saturation at each point in the chamber. This study used a modified invasion percolation (MIP) model to simulate the drainage experiments to evaluate the relationship between the saturation-versus-height curve at equilibrium and the pore size distribution associated with the granular medium. The simplest interpretation of a drainage curve is in terms of a distribution of capillary tubes whose radii reproduce the the observed distribution of rise heights. However, this apparent radius distribution obtained from direct inversion of the saturation profile did not yield the assumed radius distribution. Further investigation demonstrated that the equilibrium height distribution is controlled primarily by the Bond number (ratio of gravity to capillary forces) with some influence from the width of the pore radius distribution. The width of the equilibrium fringe is quantified in terms of the ratio of Bond number to the standard deviation of the pore throat distribution. The normalized saturation-vs-height curves exhibit a power-law scaling behavior consistent with both Brooks-Corey and Van Genuchten type curves. Fundamental tenets of percolation theory were used to quantify the relationship between the apparent and actual radius distributions as a function of the mean coordination number and of the ratio of Bond number to standard deviation, which was supported by both MIP

  14. Jointly deriving NMR surface relaxivity and pore size distributions by NMR relaxation experiments on partially desaturated rocks

    NASA Astrophysics Data System (ADS)

    Mohnke, O.; Hughes, B.

    2014-06-01

    Nuclear magnetic resonance (NMR) relaxometry is a geophysical method widely used in borehole and laboratory applications to nondestructively infer transport and storage properties of rocks and soils as it is directly sensitive to the water/oil content and pore sizes. However, for inferring pore sizes, NMR relaxometry data need to be calibrated with respect to a surface interaction parameter, surface relaxivity, which depends on the type and mineral constituents of the investigated rock. This study introduces an inexpensive and quick alternative to the classical calibration methods, e.g., mercury injection, pulsed field gradient (PFG) NMR, or grain size analysis, which allows for jointly estimating NMR surface relaxivity and pore size distributions using NMR relaxometry data from partially desaturated rocks. Hereby, NMR relaxation experiments are performed on the fully saturated sample and on a sample partially drained at a known differential pressure. Based on these data, the (capillary) pore radius distribution and surface relaxivity are derived by joint optimization of the Brownstein-Tarr and the Young-Laplace equation assuming parallel capillaries. Moreover, the resulting pore size distributions can be used to predict water retention curves. This inverse modeling approach—tested and validated using NMR relaxometry data measured on synthetic porous borosilicate samples with known petrophysical properties (i.e., permeability, porosity, inner surfaces, pore size distributions)—yields consistent and reproducible estimates of surface relaxivity and pore radii distributions. Also, subsequently calculated water retention curves generally correlate well with measured water retention curves.

  15. Pore Size Distribution and Methane Equilibrium Conditions at Walker Ridge Block 313, Northern Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Bihani, A. D.; Daigle, H.; Cook, A.; Glosser, D.; Shushtarian, A.

    2015-12-01

    Coexistence of three methane phases (liquid (L), gas (G), hydrate (H)) in marine gas hydrate systems may occur according to in-situ pressure, temperature, salinity and pore size. In sediments with salinity close to seawater, a discrete zone of three-phase (3P) equilibrium may occur near the base of the regional hydrate stability zone (RHSZ) due to capillary effects. The existence of a 3P zone influences the location of the bottom-simulating reflection (BSR) and has implications for methane fluxes at the base of the RHSZ. We studied hydrate stability conditions in two wells, WR313-G and WR313-H, at Walker Ridge Block 313 in the northern Gulf of Mexico. We determined pore size distributions (PSD) by constructing a synthetic nuclear magnetic resonance (NMR) relaxation time distribution. Correlations were obtained by non-linear regression on NMR, gamma ray, and bulk density logs from well KC-151 at Keathley Canyon. The correlations enabled construction of relaxation time distributions for WR313-G and WR313-H, which were used to predict PSD through comparison with mercury injection capillary pressure measurements. With the computed PSD, L+H and L+G methane solubility was determined from in-situ pressure and temperature. The intersection of the L+G and L+H curves for various pore sizes allowed calculation of the depth range of the 3P equilibrium zone. As in previous studies at Blake Ridge and Hydrate Ridge, the top of the 3P zone moves upwards with increasing water depth and overlies the bulk 3P equilibrium depth. In clays at Walker Ridge, the predicted thickness of the 3P zone is approximately 35 m, but in coarse sands it is only a few meters due to the difference in absolute pore sizes and the width of the PSD. The thick 3P zone in the clays may explain in part why the BSR is only observed in the sand layers at Walker Ridge, although other factors may influence the presence or absence of a BSR.

  16. Pore size distribution and methane equilibrium conditions at Walker Ridge Block 313, northern Gulf of Mexico

    SciTech Connect

    Bihani, Abhishek; Daigle, Hugh; Cook, Ann; Glosser, Deborah; Shushtarian, Arash

    2015-12-15

    Coexistence of three methane phases (liquid (L), gas (G), hydrate (H)) in marine gas hydrate systems may occur according to in-situ pressure, temperature, salinity and pore size. In sediments with salinity close to seawater, a discrete zone of three-phase (3P) equilibrium may occur near the base of the regional hydrate stability zone (RHSZ) due to capillary effects. The existence of a 3P zone influences the location of the bottom-simulating reflection (BSR) and has implications for methane fluxes at the base of the RHSZ. We studied hydrate stability conditions in two wells, WR313-G and WR313-H, at Walker Ridge Block 313 in the northern Gulf of Mexico. We determined pore size distributions (PSD) by constructing a synthetic nuclear magnetic resonance (NMR) relaxation time distribution. Correlations were obtained by non-linear regression on NMR, gamma ray, and bulk density logs from well KC-151 at Keathley Canyon. The correlations enabled construction of relaxation time distributions for WR313-G and WR313-H, which were used to predict PSD through comparison with mercury injection capillary pressure measurements. With the computed PSD, L+H and L+G methane solubility was determined from in-situ pressure and temperature. The intersection of the L+G and L+H curves for various pore sizes allowed calculation of the depth range of the 3P equilibrium zone. As in previous studies at Blake Ridge and Hydrate Ridge, the top of the 3P zone moves upwards with increasing water depth and overlies the bulk 3P equilibrium depth. In clays at Walker Ridge, the predicted thickness of the 3P zone is approximately 35 m, but in coarse sands it is only a few meters due to the difference in absolute pore sizes and the width of the PSD. The thick 3P zone in the clays may explain in part why the BSR is only observed in the sand layers at Walker Ridge, although other factors may influence the presence or absence of a BSR.

  17. Catalytic reforming catalyst with modified pore size distribution and a process using the same

    SciTech Connect

    Unmuth, E.E.; Fleming, B.A.

    1987-05-12

    This patent describes a catalytic reforming process for conversion of a naptha hydrocarbon at reforming conditions using a catalyst comprising at least one catalytic metal and alumina. The improvement comprises using a catalyst having the following properties in combination: a surface area above about 250 M/sup 2//gram of catalyst; a pore volume above about 0.44 cc/gram of catalyst in pores having diameters of from about 30 angstroms to about 38,000 angstroms; and a pore volume distribution wherein about 70 percent or less of the pore volume is in pores having diameters of from about 30 angstroms to about 400 angstroms. About 30 percent or more pore volume is in pores having diameters of from about 400 angstroms to about 38,000 angstroms.

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

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

  19. Pore size distribution analysis of activated carbons prepared from coconut shell using methane adsorption data

    NASA Astrophysics Data System (ADS)

    Ahmadpour, A.; Okhovat, A.; Darabi Mahboub, M. J.

    2013-06-01

    The application of Stoeckli theory to determine pore size distribution (PSD) of activated carbons using high pressure methane adsorption data is explored. Coconut shell was used as a raw material for the preparation of 16 different activated carbon samples. Four samples with higher methane adsorption were selected and nitrogen adsorption on these adsorbents was also investigated. Some differences are found between the PSD obtained from the analysis of nitrogen adsorption isotherms and their PSD resulting from the same analysis using methane adsorption data. It is suggested that these differences may arise from the specific interactions between nitrogen molecules and activated carbon surfaces; therefore caution is required in the interpretation of PSD obtained from the nitrogen isotherm data.

  20. Effect of mica content on pore-size distribution and porosity of sandy sediment using proton nuclear magnetic resonance measurement

    NASA Astrophysics Data System (ADS)

    Kimura, S.

    2015-12-01

    As a part of a Japanese National hydrate research program (MH21, funded by METI), we performed a study on effect of mica content on pore size distribution and porosity of sandy sediment. This study used proton nuclear magnetic resonance (NMR) to measure the pore-size distribution and porosity of specimen to investigate mica content effect in sandy sediment. A mixture of silica sand No. 7 and mica (mica of 0 wt. %, 5 wt. % and 20 wt. %) was used in this study. The median D50 by laser diffraction method was obtained as 215.7 μm of silica sand No. 7 and 278.9 μm of mica. Pore-size distributions of specimens by the distribution of transverse magnetic relaxation time (T2) measurement by NMR were performed for the water-saturated sample under effective confining pressure of 1.0 MPa. The peaks of pore-size distribution curves decreased and showed finer shifts with increasing of mica content. The porosity of silica sand No. 7 specimen was 46.3%, and that of mica 5% and 20 % were 45.9% and 42.2%m, respectively. A change in pore-size distribution and porosity were observed with an increasing ratio of mica.

  1. Critical assessment of the pore size distribution in the rim region of high burnup UO2 fuels

    NASA Astrophysics Data System (ADS)

    Cappia, F.; Pizzocri, D.; Schubert, A.; Van Uffelen, P.; Paperini, G.; Pellottiero, D.; Macián-Juan, R.; Rondinella, V. V.

    2016-11-01

    A new methodology is introduced to analyse porosity data in the high burnup structure. Image analysis is coupled with the adaptive kernel density estimator to obtain a detailed characterisation of the pore size distribution, without a-priori assumption on the functional form of the distribution. Subsequently, stereological analysis is carried out. The method shows advantages compared to the classical approach based on the histogram in terms of detail in the description and accuracy within the experimental limits. Results are compared to the approximation of a log-normal distribution. In the investigated local burnup range (80-200 GWd/tHM), the agreement of the two approaches is satisfactory. From the obtained total pore density and mean pore diameter as a function of local burnup, pore coarsening is observed starting from ≈100 GWd/tHM, in agreement with a previous investigation.

  2. Application of SAXS and SANS in evaluation of porosity, pore size distribution and surface area of coal

    USGS Publications Warehouse

    Radlinski, A.P.; Mastalerz, Maria; Hinde, A.L.; Hainbuchner, M.; Rauch, H.; Baron, M.; Lin, J.S.; Fan, L.; Thiyagarajan, P.

    2004-01-01

    This paper discusses the applicability of small angle X-ray scattering (SAXS) and small angle neutron scattering (SANS) techniques for determining the porosity, pore size distribution and internal specific surface area in coals. The method is noninvasive, fast, inexpensive and does not require complex sample preparation. It uses coal grains of about 0.8 mm size mounted in standard pellets as used for petrographic studies. Assuming spherical pore geometry, the scattering data are converted into the pore size distribution in the size range 1 nm (10 A??) to 20 ??m (200,000 A??) in diameter, accounting for both open and closed pores. FTIR as well as SAXS and SANS data for seven samples of oriented whole coals and corresponding pellets with vitrinite reflectance (Ro) values in the range 0.55% to 5.15% are presented and analyzed. Our results demonstrate that pellets adequately represent the average microstructure of coal samples. The scattering data have been used to calculate the maximum surface area available for methane adsorption. Total porosity as percentage of sample volume is calculated and compared with worldwide trends. By demonstrating the applicability of SAXS and SANS techniques to determine the porosity, pore size distribution and surface area in coals, we provide a new and efficient tool, which can be used for any type of coal sample, from a thin slice to a representative sample of a thick seam. ?? 2004 Elsevier B.V. All rights reserved.

  3. Unsaturated hydraulic properties of Sphagnum moss and peat reveal trimodal pore-size distributions

    NASA Astrophysics Data System (ADS)

    Weber, Tobias K. D.; Iden, Sascha C.; Durner, Wolfgang

    2017-01-01

    In ombrotrophic peatlands, the moisture content of the vadose zone (acrotelm) controls oxygen diffusion rates, redox state, and the turnover of organic matter. Whether peatlands act as sinks or sources of atmospheric carbon thus relies on variably saturated flow processes. The Richards equation is the standard model for water flow in soils, but it is not clear whether it can be applied to simulate water flow in live Sphagnum moss. Transient laboratory evaporation experiments were conducted to observe evaporative water fluxes in the acrotelm, containing living Sphagnum moss, and a deeper layer containing decomposed moss peat. The experimental data were evaluated by inverse modeling using the Richards equation as process model for variably-saturated flow. It was tested whether water fluxes and time series of measured pressure heads during evaporation could be simulated. The results showed that the measurements could be matched very well providing the hydraulic properties are represented by a suitable model. For this, a trimodal parametrization of the underlying pore-size distribution was necessary which reflects three distinct pore systems of the Sphagnum constituted by inter-, intra-, and inner-plant water. While the traditional van Genuchten-Mualem model led to great discrepancies, the physically more comprehensive Peters-Durner-Iden model which accounts for capillary and noncapillary flow, led to a more consistent description of the observations. We conclude that the Richards equation is a valid process description for variably saturated moisture fluxes over a wide pressure range in peatlands supporting the conceptualization of the live moss as part of the vadose zone.

  4. Statistical physics studies of multilayer adsorption isotherm in food materials and pore size distribution

    NASA Astrophysics Data System (ADS)

    Aouaini, F.; Knani, S.; Ben Yahia, M.; Ben Lamine, A.

    2015-08-01

    Water sorption isotherms of foodstuffs are very important in different areas of food science engineering such as for design, modeling and optimization of many processes. The equilibrium moisture content is an important parameter in models used to predict changes in the moisture content of a product during storage. A formulation of multilayer model with two energy levels was based on statistical physics and theoretical considerations. Thanks to the grand canonical ensemble in statistical physics. Some physicochemical parameters related to the adsorption process were introduced in the analytical model expression. The data tabulated in literature of water adsorption at different temperatures on: chickpea seeds, lentil seeds, potato and on green peppers were described applying the most popular models applied in food science. We also extend the study to the newest proposed model. It is concluded that among studied models the proposed model seems to be the best for description of data in the whole range of relative humidity. By using our model, we were able to determine the thermodynamic functions. The measurement of desorption isotherms, in particular a gas over a solid porous, allows access to the distribution of pore size PSD.

  5. In-situ method for determining pore size distribution, capillary pressure and permeability

    SciTech Connect

    Vinegar, H.J.; Waxman, M.H.

    1987-02-17

    A method is described for determining the pore sizes entered by the oil phase in an oil-bearing formation, comprising: logging the formation of interest with an induced polarization logging tool having at least one source electrode; computing from the induced polarization measurements obtained by the logging tool a normalized induced polarization response function; obtaining core material from the formation of interest; extracting the water and hydrocarbons from the core material; resaturating the core material with formation brine; measuring the normalized induced polarization response function for the core material; and determining the pore sizes containing oil in the formation by comparing the normalized induced polarization response function from the formation with the normalized induced polarization response function of the core.

  6. Estimating the surface relaxivity as a function of pore size from NMR T2 distributions and micro-tomographic images

    NASA Astrophysics Data System (ADS)

    Benavides, Francisco; Leiderman, Ricardo; Souza, Andre; Carneiro, Giovanna; Bagueira, Rodrigo

    2017-09-01

    In the present work, we formulate and solve an inverse problem to recover the surface relaxivity as a function of pore size. The input data for our technique are the T2 distribution measurement and the micro-tomographic image of the rock sample under investigation. We simulate the NMR relaxation signal for a given surface relaxivity function using the random walk method and rank different surface relaxivity functions according to the correlation of the resulting simulated T2 distributions with the measured T2 distribution. The optimization is performed using genetic algorithms and determines the surface relaxivity function whose corresponding simulated T2 distribution best matches the measured T2 distribution. In the proposed methodology, pore size is associated with a number of collisions in the random walk simulations. We illustrate the application of the proposed method by performing inversions from synthetic and laboratory input data and compare the obtained results with those obtained using the uniform relaxivity assumption.

  7. A pore-hindered diffusion and reaction model can help explain the importance of pore size distribution in enzymatic hydrolysis of biomass.

    PubMed

    Luterbacher, Jeremy S; Parlange, Jean-Yves; Walker, Larry P

    2013-01-01

    Until now, most efforts to improve monosaccharide production from biomass through pretreatment and enzymatic hydrolysis have used empirical optimization rather than employing a rational design process guided by a theory-based modeling framework. For such an approach to be successful a modeling framework that captures the key mechanisms governing the relationship between pretreatment and enzymatic hydrolysis must be developed. In this study, we propose a pore-hindered diffusion and kinetic model for enzymatic hydrolysis of biomass. When compared to data available in the literature, this model accurately predicts the well-known dependence of initial cellulose hydrolysis rates on surface area available to a cellulase-size molecule. Modeling results suggest that, for particles smaller than 5 × 10(-3) cm, a key rate-limiting step is the exposure of previously unexposed cellulose occurring after cellulose on the surface has hydrolyzed, rather than binding or diffusion. However, for larger particles, according to the model, diffusion plays a more significant role. Therefore, the proposed model can be used to design experiments that produce results that are either affected or unaffected by diffusion. Finally, by using pore size distribution data to predict the biomass fraction that is accessible to degradation, this model can be used to predict cellulose hydrolysis with time using only pore size distribution and initial composition data.

  8. Impact of matric potential and pore size distribution on growth dynamics of filamentous and non-filamentous soil bacteria.

    PubMed

    Wolf, Alexandra B; Vos, Michiel; de Boer, Wietse; Kowalchuk, George A

    2013-01-01

    The filamentous growth form is an important strategy for soil microbes to bridge air-filled pores in unsaturated soils. In particular, fungi perform better than bacteria in soils during drought, a property that has been ascribed to the hyphal growth form of fungi. However, it is unknown if, and to what extent, filamentous bacteria may also display similar advantages over non-filamentous bacteria in soils with low hydraulic connectivity. In addition to allowing for microbial interactions and competition across connected micro-sites, water films also facilitate the motility of non-filamentous bacteria. To examine these issues, we constructed and characterized a series of quartz sand microcosms differing in matric potential and pore size distribution and, consequently, in connection of micro-habitats via water films. Our sand microcosms were used to examine the individual and competitive responses of a filamentous bacterium (Streptomyces atratus) and a motile rod-shaped bacterium (Bacillus weihenstephanensis) to differences in pore sizes and matric potential. The Bacillus strain had an initial advantage in all sand microcosms, which could be attributed to its faster growth rate. At later stages of the incubation, Streptomyces became dominant in microcosms with low connectivity (coarse pores and dry conditions). These data, combined with information on bacterial motility (expansion potential) across a range of pore-size and moisture conditions, suggest that, like their much larger fungal counterparts, filamentous bacteria also use this growth form to facilitate growth and expansion under conditions of low hydraulic conductivity. The sand microcosm system developed and used in this study allowed for precise manipulation of hydraulic properties and pore size distribution, thereby providing a useful approach for future examinations of how these properties influence the composition, diversity and function of soil-borne microbial communities.

  9. Determination of pore size distributions in capillary-channeled polymer fiber stationary phases by inverse size-exclusion chromatography and implications for fast protein separations.

    PubMed

    Wang, Zhengxin; Marcus, R Kenneth

    2014-07-18

    Capillary-channeled polymer (C-CP) fibers have been utilized as liquid chromatography stationary phases, primarily for biomacromolecule separations on the analytical and preparative scales. The collinear packing of the eight-channeled C-CP fibers provides for very efficient flow, allowing operation at high linear velocity (u>100mm s(-1)) and low backpressure (<2000psi) in analytical-scale separations. To take advantage of these fluid transport properties, there must not be mass transfer limitations as would be imposed by having an appreciably porous phase, wherein solute diffusion limits the overall mass transport rates. To better understand the physical nano-/micro- structure of C-CP fibers, inverse size exclusion chromatography (iSEC) has been employed to determine the pore size distribution (PSD) within C-CP fibers. A diversity of test species (from metal ions to large proteins) was used as probes under non-retaining conditions to obtain a response curve reflecting the apparent partition coefficient (Kd) versus hydrodynamic radii (rm). A mean pore radius (rp) of 4.2nm with standard deviation (sp) of ±1.1nm was calculated by fitting the Kd versus rm data to model equations with a Gaussian pore size distribution, and a pore radius of 4.0±0.1nm was calculated based on a log-normal distribution. The derived mean pore radius is much smaller than traditional support materials, with the standard deviation showing a relatively uniform pore distribution. van Deemter plots were analyzed to provide practical confirmation of the structural implications. Large molecules (e.g., proteins) that are fully excluded from pores have no significant C-terms in the van Deemter plots whereas small molecules that can access the pore volumes display appreciable C-terms, as expected. Fitting of retention data to the Knox equation suggests that the columns operate with a characteristic particle diameter (dp) of ∼53μm.

  10. Isolating the effect of pore size distribution on electrochemical double-layer capacitance using activated fluid coke

    NASA Astrophysics Data System (ADS)

    Zuliani, Jocelyn E.; Tong, Shitang; Kirk, Donald W.; Jia, Charles Q.

    2015-12-01

    Electrochemical double-layer capacitors (EDLCs) use physical ion adsorption in the capacitive electrical double layer of high specific surface area (SSA) materials to store electrical energy. Previous work shows that the SSA-normalized capacitance increases when pore diameters are less than 1 nm. However, there still remains uncertainty about the charge storage mechanism since the enhanced SSA-normalized capacitance is not observed in all microporous materials. In previous studies, the total specific surface area and the chemical composition of the electrode materials were not controlled. The current work is the first reported study that systematically compares the performance of activated carbon prepared from the same raw material, with similar chemical composition and specific surface area, but different pore size distributions. Preparing samples with similar SSAs, but different pores sizes is not straightforward since increasing pore diameters results in decreasing the SSA. This study observes that the microporous activated carbon has a higher SSA-normalized capacitance, 14.1 μF cm-2, compared to the mesoporous material, 12.4 μF cm-2. However, this enhanced SSA-normalized capacitance is only observed above a threshold operating voltage. Therefore, it can be concluded that a minimum applied voltage is required to induce ion adsorption in these sub-nanometer micropores, which increases the capacitance.

  11. Pore size distribution of soil near saturation as affected by soil type, land use, and soil amendments

    NASA Astrophysics Data System (ADS)

    Mamedov, A. I.; Wagner, L. E.; Levy, G. J.

    2008-12-01

    Storage and flow of water in soil voids, which are related to the size and geometry of the voids and flow rate are usually controlled by the void of the smallest size. Another reason for the complexity of water flow in soils is the intricate nature and change of the soil pores due to the modification of soil structure under different agricultural management and climatic conditions. Shrinking and swelling stresses enhance breakdown of aggregates and to subsequent collapse of pores, thus adversely affecting the movement of water and solutes in the soil. Our objective was to study the role of soil type, nature of cultivation, waste and soil stabilizers application, and soil condition on disturbed soil pore-size distribution, drainable porosity and water holding capacity at near saturation (infiltration porosity) using the high energy moisture characteristic method. In this method, the wetting process of the aggregates is accurately controlled, and the energy of hydration and entrapped air are the main forces responsible for aggregate breakdown. We studied a large number (> 300) of soil samples from different climatic regions varying (i) in their inherent properties (clay mineralogy, dispersion potential, texture, organic matter, Fe and Al oxides content), and; (ii) the conditions prevailing in the soil (water quality, salinity, sodicity, redox potential, type of tillage); and finally that were subjected to the addition of different soil amendments (polymers, gypsum, manure, sludge). The results showed that structural stability and pore size distribution strongly depended on soil type, conditions prevailing in the soil and the type of amendment used. Detailed analyses of the results provided valuable information on inter- and intra- aggregate porosities that may have vital bearing on the understanding of (i) solution transport processes in different soil types under different treatments or with different solute concentration, and (ii) down-profile transport of soil

  12. Phase-field simulations of the impact of bimodal pore size distributions on solid-state densification

    NASA Astrophysics Data System (ADS)

    Berry, Bruce E.; Millett, Paul C.

    2017-08-01

    The densification behavior of a porous body subjected to elevated temperature is relevant to many nuclear fuel performance metrics. The diffusional processes that govern such densification occur on microscopic length scales, and depend on the type of material and the nature of the porosity. In this study, we explore how bimodal pore size distributions impact diffusion-based densification relative to monomodal pore sizes for a given overall value of porosity. We utilize a Cahn-Hilliard phase-field model implemented with the MOOSE framework to simulate densification evolution with a range of overall porosities and a variety of porosity distributions between small and large pores. The results demonstrate that bimodal porosity can resist densification to a much greater extent than monomodal porosity. These findings have implications for the microstructural design of metallic nuclear fuels, in which an initial, bimodal porosity may resist early-stage densification and therefore provide collection sites for fission gases, thus reducing in-pile fission gas swelling.

  13. Quantification of pore size distribution in reservoir rocks using MRI logging: A case study of South Pars Gas Field.

    PubMed

    Ghojogh, Jalal Neshat; Esmaili, Mohammad; Noruzi-Masir, Behrooz; Bakhshi, Puyan

    2017-09-23

    Pore size distribution (PSD) is an important factor for controlling fluid transport through porous media. The study of PSD can be applicable in areas such as hydrocarbon storage, contaminant transport, prediction of multiphase flow, and analysis of the formation damage by mud infiltration. Nitrogen adsorption, centrifugation method, mercury injection, and X-ray computed tomography are commonly used to measure the distribution of pores. A core sample is occasionally not available because of the unconsolidated nature of reservoirs, high cost of coring operation, and program limitations. Magnetic resonance imaging logging (MRIL) is a proper logging technique that allows the direct measurement of the relaxation time of protons in pore fluids and correlating T2 distribution to PSD using proper mathematical equations. It is nondestructive and fast and does not require core samples. In this paper, 8 core samples collected from the Dalan reservoir in South Pars Gas Field were studied by processing MRIL data and comparing them by PSD determined in the laboratory. By using the MRIL method, variation in PSD corresponding to the depth for the entire logged interval was determined. Moreover, a detailed mineralogical composition of the reservoir samples related to T2 distribution was obtained. A good correlation between MRIL and mercury injection data was observed. High degree of similarity was also observed between T2 distribution and PSD (R(2) = 0.85 to 0.91). Based on the findings from the MRIL method, the obtained values for clay bond water varied between 1E-6 and 1E-3µm, a range that is comprehended from an extra peak on the PSD curve. The frequent pore radius was determined to be 1µm. Copyright © 2017 Elsevier Ltd. All rights reserved.

  14. Pore size distribution of OPC and SRPC mortars in presence of chlorides

    SciTech Connect

    Suryavanshi, A.K.; Scantlebury, J.D.; Lyon, S.B.

    1995-07-01

    The pore structure of chloride-free ordinary portland cement (OPC) and sulphate resistant portland cement (SRPC) mortars are compared with the corresponding mortars with NaCl and CaCl{sub 2} added during mixing. In both OPC and SRPC mortars the addition of chlorides reduced the total accessible pore volumes compared to the corresponding chloride-free mortars. Also, in the presence of chlorides, the number of coarse pores were increased. These changes in the pore structure are believed to be due to dense calcium silicate hydrate (C-S-H) gel morphology formed in the presence of chlorides. The SRPC showed greater changes in pore structures than the OPC with equivalent amounts of chlorides added. This may be due to the lower chloride binding capacity of the SRPC and hence the higher availability of free chlorides to modify the gel morphology.

  15. Control of pore size in epoxy systems.

    SciTech Connect

    Sawyer, Patricia Sue; Lenhart, Joseph Ludlow; Lee, Elizabeth; Kallam, Alekhya; Majumdar, Partha; Dirk, Shawn M.; Gubbins, Nathan; Chisholm, Bret J.; Celina, Mathias C.; Bahr, James; Klein, Robert J.

    2009-01-01

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

  16. Dynamic adsorption of diarrhetic shellfish poisoning (DSP) toxins in passive sampling relates to pore size distribution of aromatic adsorbent.

    PubMed

    Li, Aifeng; Ma, Feifei; Song, Xiuli; Yu, Rencheng

    2011-03-18

    Solid-phase adsorption toxin tracking (SPATT) technology was developed as an effective passive sampling method for dissolved diarrhetic shellfish poisoning (DSP) toxins in seawater. HP20 and SP700 resins have been reported as preferred adsorption substrates for lipophilic algal toxins and are recommended for use in SPATT testing. However, information on the mechanism of passive adsorption by these polymeric resins is still limited. Described herein is a study on the adsorption of OA and DTX1 toxins extracted from Prorocentrum lima algae by HP20 and SP700 resins. The pore size distribution of the adsorbents was characterized by a nitrogen adsorption method to determine the relationship between adsorption and resin porosity. The Freundlich equation constant showed that the difference in adsorption capacity for OA and DTX1 toxins was not determined by specific surface area, but by the pore size distribution in particular, with micropores playing an especially important role. Additionally, it was found that differences in affinity between OA and DTX1 for aromatic resins were as a result of polarity discrepancies due to DTX1 having an additional methyl moiety.

  17. Experimental Study of Porosity Changes in Shale Caprocks Exposed to CO2-Saturated Brines I: Evolution of Mineralogy, Pore Connectivity, Pore Size Distribution, and Surface Area

    DOE PAGES

    Mouzakis, Katherine M.; Navarre-Sitchler, Alexis K.; Rother, Gernot; ...

    2016-07-18

    Carbon capture, utilization, and storage, one proposed method of reducing anthropogenic emissions of CO2, relies on low permeability formations, such as shales, above injection formations to prevent upward migration of the injected CO2. Porosity in caprocks evaluated for sealing capacity before injection can be altered by geochemical reactions induced by dissolution of injected CO2 into pore fluids, impacting long-term sealing capacity. Therefore, long-term performance of CO2 sequestration sites may be dependent on both initial distribution and connectivity of pores in caprocks, and on changes induced by geochemical reaction after injection of CO2, which are currently poorly understood. This paper presentsmore » results from an experimental study of changes to caprock porosity and pore network geometry in two caprock formations under conditions relevant to CO2 sequestration. Pore connectivity and total porosity increased in the Gothic Shale; while total porosity increased but pore connectivity decreased in the Marine Tuscaloosa. Gothic Shale is a carbonate mudstone that contains volumetrically more carbonate minerals than Marine Tuscaloosa. Carbonate minerals dissolved to a greater extent than silicate minerals in Gothic Shale under high CO2 conditions, leading to increased porosity at length scales <~200 nm that contributed to increased pore connectivity. In contrast, silicate minerals dissolved to a greater extent than carbonate minerals in Marine Tuscaloosa leading to increased porosity at all length scales, and specifically an increase in the number of pores >~1 μm. Mineral reactions also contributed to a decrease in pore connectivity, possibly as a result of precipitation in pore throats or hydration of the high percentage of clays. Finally, this study highlights the role that mineralogy of the caprock can play in geochemical response to CO2 injection and resulting changes in sealing capacity in long-term CO2 storage projects.« less

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

    NASA Astrophysics Data System (ADS)

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

    2013-05-01

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

  19. Non-linear behaviour of electrical parameters in porous, water-saturated rocks: a model to predict pore size distribution

    NASA Astrophysics Data System (ADS)

    Hallbauer-Zadorozhnaya, Valeriya; Santarato, Giovanni; Abu Zeid, Nasser

    2015-08-01

    In this paper, two separate but related goals are tackled. The first one is to demonstrate that in some saturated rock textures the non-linear behaviour of induced polarization (IP) and the violation of Ohm's law not only are real phenomena, but they can also be satisfactorily predicted by a suitable physical-mathematical model, which is our second goal. This model is based on Fick's second law. As the model links the specific dependence of resistivity and chargeability of a laboratory sample to the injected current and this in turn to its pore size distribution, it is able to predict pore size distribution from laboratory measurements, in good agreement with mercury injection capillary pressure test results. This fact opens up the possibility for hydrogeophysical applications on a macro scale. Mathematical modelling shows that the chargeability acquired in the field under normal conditions, that is at low current, will always be very small and approximately proportional to the applied current. A suitable field test site for demonstrating the possible reliance of both resistivity and chargeability on current was selected and a specific measuring strategy was established. Two data sets were acquired using different injected current strengths, while keeping the charging time constant. Observed variations of resistivity and chargeability are in agreement with those predicted by the mathematical model. These field test data should however be considered preliminary. If confirmed by further evidence, these facts may lead to changing the procedure of acquiring field measurements in future, and perhaps may encourage the design and building of a new specific geo-resistivity meter. This paper also shows that the well-known Marshall and Madden's equations based on Fick's law cannot be solved without specific boundary conditions.

  20. Pore size distribution of soil near saturation as affected by soil type, land use, and soil amendments

    USDA-ARS?s Scientific Manuscript database

    Storage and flow of water in soil voids, which are related to the size and geometry of the voids and flow rate are usually controlled by the void of the smallest size. Another reason for the complexity of water flow in soils is the intricate nature and change of the soil pores due to the modificatio...

  1. Effect of rock composition and texture on pore size distributions in shales: Applications in low field nuclear magnetic resonance

    NASA Astrophysics Data System (ADS)

    Saidian, Milad

    There are various methods to assess the pore size distribution (PSD) of porous materials; amongst all, NMR is the only technique that can be utilized for subsurface applications. The key parameter to transform NMR time domain response to PSD size domain data is surface relaxivity. The common practice is to consider a constant surface relaxivity throughout a well, formation or rock type regardless of the variations in rock compositions; this results in inaccurate PSD estimation using NMR log data. In this thesis I established a methodology to calculate the surface relaxivity in shales considering the rock composition and texture. I present the steps to achieve this goal in three steps: (a) Understanding the challenges of NMR acquisition, analysis and interpretation in shales, (b) Measuring the porosity, PSD and surface area and providing a practice to check the reliability of these measurements in shales, (c) Developing a methodology to calculate the surface relaxivity honoring the variations paramagnetic mineral content, susceptibility, distribution and texture. Application of NMR in unconventional rocks requires adjustment of NMR data acquisition and analysis to the unique properties of these rocks such as high level of heterogeneity, complex pore structure, fine grains, and presence of nano-scale pores. Identifying these challenges improves our understanding of NMR response in shales and increases the quality of the acquired and analyzed data. Calculation of surface relaxivity, as a measure of how fluids and rock surfaces react, requires reliable measurement of different petrophysical properties of the rock such as porosity, total specific surface area, and PSD using other techniques. I studied the reliability of different techniques to measure these petrophysical properties for shales by performing a thorough comparative study of porosity and PSD for different shale formations. The result of my study showed that clay type and content, total organic carbon (TOC

  2. Nonparametric pore size distribution using d-PFG: Comparison to s-PFG and migration to MRI

    NASA Astrophysics Data System (ADS)

    Benjamini, Dan; Komlosh, Michal E.; Basser, Peter J.; Nevo, Uri

    2014-09-01

    Here we present the successful translation of a pore size distribution (PSD) estimation method from NMR to MRI. This approach is validated using a well-characterized MRI phantom consisting of stacked glass capillary arrays (GCA) having different diameters. By employing a double pulsed-field gradient (d-PFG) MRI sequence, this method overcomes several important theoretical and experimental limitations of previous single-PFG (s-PFG) based MRI methods by allowing the relative diffusion gradients’ direction to vary. This feature adds an essential second dimension in the parameters space, which can potentially improve the reliability and stability of the PSD estimation. To infer PSDs from the MRI data in each voxel an inverse linear problem is solved in conjunction with the multiple correlation function (MCF) framework, which can account for arbitrary experimental parameters (e.g., long diffusion pulses). This scheme makes no a priori assumptions about the functional form of the underlying PSD. Creative use of region of interest (ROI) analysis allows us to create different underlying PSDs using the same GCA MRI phantom. We show that an s-PFG experiment on the GCA phantom fails to accurately reconstruct the size distribution, thus demonstrating the superiority of the d-PFG experiment. In addition, signal simulations corrupted by different noise levels were used to generate continuous and complex PSDs, which were then successfully reconstructed. Finally, owing to the reduced q- or b- values required to measure microscopic PSDs via d-PFG MRI, this method will be better suited to biomedical and clinical applications, in which gradient strength of scanners is limited.

  3. Nonlinear Effect of Moisture Content on Effective Thermal Conductivity of Building Materials with Different Pore Size Distributions

    NASA Astrophysics Data System (ADS)

    Liu, Yanfeng; Ma, Chao; Wang, Dengjia; Wang, Yingying; Liu, Jiaping

    2016-06-01

    Understanding the quantitative relationship between the effective thermal conductivity and the moisture content of a material is required to accurately calculate the envelope heat and mass transfer and, subsequently, the building energy consumption. We experimentally analyzed the pore size distributions and porosities of common building materials and the influence of the moisture content on the effective thermal conductivity of building materials. We determined the quantitative relationship between the effective thermal conductivity and moisture content of building materials. The results showed that a larger porosity led to a more significant effect of the moisture content on the effective thermal conductivity. When the volumetric moisture content reached 10 %, the thermal conductivities of foam concrete and aerated concrete increased by approximately 200 % and 100 %, respectively. The effective thermal conductivity increased rapidly in the low moisture content range and increased slowly in the high moisture content range. The effective thermal conductivity is related to the moisture content of the materials through an approximate power function. As the moisture content in the walls of a new building stabilizes, the effective thermal conductivity of normal concrete varies only slightly, whereas that of aerated concrete varies more significantly. The effective thermal conductivity of the material is proportional to the relative humidity of the environment. This trend is most noticeable when the wall material is aerated concrete.

  4. Relationship between Pore-size Distribution and Flexibility of Adsorbent Materials: Statistical Mechanics and Future Material Characterization Techniques.

    PubMed

    Siderius, Daniel W; Mahynski, Nathan A; Shen, Vincent K

    2017-05-01

    Measurement of the pore-size distribution (PSD) via gas adsorption and the so-called "kernel method" is a widely used characterization technique for rigid adsorbents. Yet, standard techniques and analytical equipment are not appropriate to characterize the emerging class of flexible adsorbents that deform in response to the stress imparted by an adsorbate gas, as the PSD is a characteristic of the material that varies with the gas pressure and any other external stresses. Here, we derive the PSD for a flexible adsorbent using statistical mechanics in the osmotic ensemble to draw analogy to the kernel method for rigid materials. The resultant PSD is a function of the ensemble constraints including all imposed stresses and, most importantly, the deformation free energy of the adsorbent material. Consequently, a pressure-dependent PSD is a descriptor of the deformation characteristics of an adsorbent and may be the basis of future material characterization techniques. We discuss how, given a technique for resolving pressure-dependent PSDs, the present statistical mechanical theory could enable a new generation of analytical tools that measure and characterize certain intrinsic material properties of flexible adsorbents via otherwise simple adsorption experiments.

  5. Size of seismic events during borehole injections: the effects of source mechanisms, stress and pore pressure distribution

    NASA Astrophysics Data System (ADS)

    Fischer, T.; Ondovcin, T.; Zhao, P.

    2012-12-01

    and space-time distributions, source mechanisms and stress analyses on the available data to shed light on these questions. Our inversion for moment tensors of the Basel injection-induced seismicity shows that the microearthquakes had higher non-DC components during injection than after shut-in. This could be related to the higher stress drops found during injection. We model the pore pressure distribution and out-flow from the well the numerically solving the diffusion equation for the shut-in and open-well conditions. We compare the results of seismicity analysis with the models of pore pressure distribution during and after the injection to test the relevancy of several hypotheses of the occurrence of large events. We find that their anomalous occurrence during the shut-in phase is most-likely caused by the transient effects during the stop of injection. The anomalous space occurrence of large events is probably also related to the unequal distribution of faults in the vicinity of the injection well.

  6. Ovariectomized rats' femur treated with fibrates and statins. Assessment of pore-size distribution by ¹H-NMR relaxometry.

    PubMed

    Şipoş, Remus Sebastian; Fechete, Radu; Chelcea, Ramona Ioana; Moldovan, Dumitriţa; Pap, Zsuzsánna; Pávai, Zoltán; Demco, Dan Eugen

    2015-01-01

    The effects of two wonder drugs, simvastatins and fenofibrates on the proximal part of the femoris of a series of ovariectomized and non-ovariectomized Wistar albino rats was estimated qualitatively and semi-quantitatively by the modern method of 1D 1H-NMR T2-distribution. The 72 rats subjected to this study were divided in six groups and were sacrificed at two, four, six and eight weeks after ovariectomy and the proximal part of femoris was harvested. The CPMG (Carr-Purcell-Meiboom-Gill) echoes train curves were measured for the bones fully saturated with water during two months after two months of natural drying. These decays were analyzed by Laplace inversion and an average of normalized T2-distributions was considered for all rat's groups. The 1D averaged T2-distributions present four peaks, which were associated with protons in four major environments, from which the free water protons are used as spy molecules to explore the boundaries of cavities. In the approximation of spherical pores, the averaged T2-distributions were transformed in distributions of pores diameters. These were found in the range from 2 μm up to 2 mm. The relative amplitudes, widths and position of deconvoluted distributions of small, medium and large cavities are used for a qualitatively analysis of the effect of our lipid-lowering drugs. For a semi-quantitatively analysis, we chose the diameter d of proximal part of femoris' trabecular cavities. We show that the positive or negative effects of treatments with simvastatins and fenofibrates are strongly dependent on the duration of treatment. Moreover, the treatment of healthy bone is generally counter-indicated.

  7. Effect of Pore Size Distribution on Humidity Sensing Properties of MgO doped ZrO2-TiO2 Ceramic

    NASA Astrophysics Data System (ADS)

    Jain, M. K.; Bhatnagar, M. C.; Sharma, G. L.

    2000-01-01

    The MgO doped ZrO2-TiO2 composite is studied for its humidity sensing characteristics. Though dc electrical properties show very high sensitivity to humidity, it is not useful for practical applications because of the charging effect. The ac conductivity vs relative humidity characteristics of the pellet becomes linear with an increase in sintering temperature. The post treatment at high temperature and high humidity is found to accelerate initial ageing of the pellet and therefore, stabilizes the characteristics more quickly. A physical model has been proposed to correlate initial ageing, effect of sintering temperature and response time with pore size distribution. Pores below 300 Å radii are present in abundance near the ZrTiO4 phase formation temperature. These pores are responsible for higher sensitivity in low humidity region and linear characteristics.

  8. Pore size engineering applied to starved electrochemical cells and batteries

    NASA Technical Reports Server (NTRS)

    Abbey, K. M.; Thaller, L. H.

    1982-01-01

    To maximize performance in starved, multiplate cells, the cell design should rely on techniques which widen the volume tolerance characteristics. These involve engineering capillary pressure differences between the components of an electrochemical cell and using these forces to promote redistribution of electrolyte to the desired optimum values. This can be implemented in practice by prescribing pore size distributions for porous back-up plates, reservoirs, and electrodes. In addition, electrolyte volume management can be controlled by incorporating different pore size distributions into the separator. In a nickel/hydrogen cell, the separator must contain pores similar in size to the small pores of both the nickel and hydrogen electrodes in order to maintain an optimum conductive path for the electrolyte. The pore size distributions of all components should overlap in such a way as to prevent drying of the separator and/or flooding of the hydrogen electrode.

  9. Effects of coarse grain size distribution and fine particle content on pore fluid pressure and shear behavior in experimental debris flows

    NASA Astrophysics Data System (ADS)

    Kaitna, Roland; Palucis, Marisa C.; Yohannes, Bereket; Hill, Kimberly M.; Dietrich, William E.

    2016-02-01

    Debris flows are typically a saturated mixture of poorly sorted particles and interstitial fluid, whose density and flow properties depend strongly on the presence of suspended fine sediment. Recent research suggests that grain size distribution (GSD) influences excess pore pressures (i.e., pressure in excess of predicted hydrostatic pressure), which in turn plays a governing role in debris flow behaviors. We report a series of controlled laboratory experiments in a 4 m diameter vertically rotating drum where the coarse particle size distribution and the content of fine particles were varied independently. We measured basal pore fluid pressures, pore fluid pressure profiles (using novel sensor probes), velocity profiles, and longitudinal profiles of the flow height. Excess pore fluid pressure was significant for mixtures with high fines fraction. Such flows exhibited lower values for their bulk flow resistance (as measured by surface slope of the flow), had damped fluctuations of normalized fluid pressure and normal stress, and had velocity profiles where the shear was concentrated at the base of the flow. These effects were most pronounced in flows with a wide coarse GSD distribution. Sustained excess fluid pressure occurred during flow and after cessation of motion. Various mechanisms may cause dilation and contraction of the flows, and we propose that the sustained excess fluid pressures during flow and once the flow has stopped may arise from hindered particle settling and yield strength of the fluid, resulting in transfer of particle weight to the fluid. Thus, debris flow behavior may be strongly influenced by sustained excess fluid pressures controlled by particle settling rates.

  10. The role of fine material and grain size distribution on excess pore pressure dissipation and particle support mechanisms in granular deposits based in large-scale physical experiments

    NASA Astrophysics Data System (ADS)

    Palucis, M. C.; Kaitna, R.; Tewoldebrhan, B.; Hill, K. M.; Dietrich, W. E.

    2011-12-01

    The dominant mechanisms behind sustained mobilization in granular debris flows are poorly understood, and experiments are needed to determine the conditions under which the fluid can fully support the coarse fraction. However, field-scale studies are difficult to instrument and constrain and laboratory studies suffer from scaling issues. A 4-m rotating drum located at UC Berkeley's Richmond Field Station allowed us to perform reproducible experiments with materials similar to those in the field to explore mechanisms relevant to slow pore fluid pressure dissipation. Specifically, we performed a series of experiments to assess the role of fines and grain size distribution on the rate of pore fluid pressure dissipation upon deposition of a granular mass. For each experiment we kept the total mass of the gravel particles constant and varied the amount of fines (from no fines to amounts found in an actual debris flow deposit) and the gravel particle size distribution (from a single grain size to a range found in natural flows). We first rotated each mixture in the drum, during which we monitored fluid pressures at the base of the flows (near the wall of the drum and at the center). Then we stopped the drum and continued to monitor the fluid pressures. Immediately upon stopping, the pore fluid pressure was nearly hydrostatic for the gravel-water flows, and any elevated pore pressure quickly dissipated. On the other hand, the mixtures with fines contents close to those found in actual debris flows had elevated pore pressures indicating they were almost fully liquefied. Furthermore, the rate of pore pressure dissipation was an order of magnitude slower than when no fines were present; the grain size distribution of the coarse fraction did not strongly influence the dissipation rates in either case. We also placed a cobble upon a fines-rich mixture after cessation of motion above the center pressure sensor, and observed that the pore fluid pressure rose instantly, bearing

  11. Comparative DNA isolation behaviours of silica and polymer based sorbents in batch fashion: monodisperse silica microspheres with bimodal pore size distribution as a new sorbent for DNA isolation.

    PubMed

    Günal, Gülçin; Kip, Çiğdem; Eda Öğüt, S; İlhan, Hasan; Kibar, Güneş; Tuncel, Ali

    2017-03-22

    Monodisperse silica microspheres with bimodal pore-size distribution were proposed as a high performance sorbent for DNA isolation in batch fashion under equilibrium conditions. The proposed sorbent including both macroporous and mesoporous compartments was synthesized 5.1 μm in-size, by a "staged shape templated hydrolysis and condensation method". Hydrophilic polymer based sorbents were also obtained in the form of monodisperse-macroporous microspheres ca 5.5 μm in size, with different functionalities, by a developed "multi-stage microsuspension copolymerization" technique. The batch DNA isolation performance of proposed material was comparatively investigated using polymer based sorbents with similar morphologies. Among all sorbents tried, the best DNA isolation performance was achieved with the monodisperse silica microspheres with bimodal pore size distribution. The collocation of interconnected mesoporous and macroporous compartments within the monodisperse silica microspheres provided a high surface area and reduced the intraparticular mass transfer resistance and made easier both the adsorption and desorption of DNA. Among the polymer based sorbents, higher DNA isolation yields were achieved with the monodisperse-macroporous polymer microspheres carrying trimethoxysilyl and quaternary ammonium functionalities. However, batch DNA isolation performances of polymer based sorbents were significantly lower with respect to the silica microspheres.

  12. Metal oxide porous ceramic membranes with small pore sizes

    DOEpatents

    Anderson, Marc A.; Xu, Qunyin

    1991-01-01

    A method is disclosed for the production of metal oxide ceramic membranes of very small pore size. The process is particularly useful in the creation of titanium and other transition metal oxide membranes. The method utilizes a sol-gel process in which the rate of particle formation is controlled by substituting a relatively large alcohol in the metal alkoxide and by limiting the available water. Stable, transparent metal oxide ceramic membranes are created having a narrow distribution of pore size, with the pore diameter being manipulable in the range of 5 to 40 Angstroms.

  13. Metal oxide porous ceramic membranes with small pore sizes

    DOEpatents

    Anderson, Marc A.; Xu, Qunyin

    1992-01-01

    A method is disclosed for the production of metal oxide ceramic membranes of very small pore size. The process is particularly useful in the creation of titanium and other transition metal oxide membranes. The method utilizes a sol-gel process in which the rate of particle formation is controlled by substituting a relatively large alcohol in the metal alkoxide and by limiting the available water. Stable, transparent metal oxide ceramic membranes are created having a narrow distribution of pore size, with the pore diameter being manipulable in the range of 5 to 40 Angstroms.

  14. Effect of seawater salinity on pore-size distribution on a poly(styrene)-based HP20 resin and its adsorption of diarrhetic shellfish toxins.

    PubMed

    Fan, Lin; Sun, Geng; Qiu, Jiangbing; Ma, Qimin; Hess, Philipp; Li, Aifeng

    2014-12-19

    In the present study, okadaic acid (OA) and dinophysistoxin-1 (DTX1) were spiked into artificial seawater at low, medium and high estuarine salinities (9‰, 13.5‰ and 27‰). Passive samplers (HP20 resin) used for solid phase adsorption toxin tracking (SPATT) technology were exposed in these seawaters for 12-h periods. Adsorption curves well fitted a pseudo-secondary kinetics model. The highest initial sorption rates of both toxins occurred in the seawater of medium salinity, followed by seawater of low and high estuarine salinity. Pore volumes of micropores (<2 nm) and small mesopores (2 nmsize) in seawaters of high and low salinity. More toxin or other matrix agglomerates were displayed on the surface of resin deployed in the seawater of medium salinity. Taking into consideration the pore-size distribution and surface images, it appears that intra-particle diffusion governs toxin adsorption in seawater at high salinity while film diffusion mainly controls the adsorption process in seawater at medium salinity. This is the first study to confirm that molecules of OA and DTX1 are able to enter into micropores (<2nm) and small mesopores (2-10nm) of HP20 resin in estuarine seawater with high salinity (∼27‰).

  15. Tailoring the pore size of hypercrosslinked polymer foams

    SciTech Connect

    Steckle, W.P. Jr.; Mitchell, M.A.; Apen, P.G.

    1996-12-31

    Organic analogues to inorganic zeolites would be a significant step forward in engineered porous materials and would provide advantages in range, selectivity, tailorability and processing. Rigid molecular foams or organic zeolites would not be crystalline materials and could be tailored over a broader range of pore sizes and volumes. A novel process for preparing hypercrosslinked polymeric foams has been developed via a Friedel-Crafts polycondensation reaction. A series of rigid hypercrosslinked foams have been prepared using simple rigid polyaromatic hydrocarbons including benzene, biphenyl, m-terphenyl, diphenylmethane, and polystyrene, with p-dichloroxylene (DCX) or divinylbenzene (DVB) as the crosslinking agent. Transparent gels are formed suggesting a very small pore size. After drying the foams are robust and rigid. Densities of the resulting foams can range from 0.15 g/cc to 0.75 g/cc. Nitrogen adsorption studies have shown that by judiciously selecting monomers and crosslinking agent along with the level of crosslinking and the cure time of the resulting gel, the pore size, pore size distribution, and the total surface area of the foam can be tailored. Surface areas range from 160 to 1,200 m{sup 2}/g with pore sizes ranging from 6{angstrom} to 2,000{angstrom}. Further evidence of the uniformity of the foams and their pore sizes has been confirmed by high resolution TEM.

  16. Predicting the adsorption of organic pollutants from water onto activated carbons based on the pore size distribution and molecular connectivity index.

    PubMed

    Bunmahotama, Warisa; Hung, Wei-Nung; Lin, Tsair-Fuh

    2015-11-15

    A new model approach is developed to predict the adsorption isotherms of low-molecular-weight nonpolar organic compounds (LMWNPOCs) onto activated carbons (ACs). The model is based on the Polanyi-Dubinin (PD) equation, with the limiting pore volume of adsorbent estimated from the pore size distribution (PSD) data, and the adsorption affinity of adsorbate described by the molecular connectivity index (MCI). To obtain the MCI parameters, the model was first tested for the adsorption of 34 LMWNPOCs primarily on F400 AC from 3 reports. The models fit the experimental data well, with only 39.2% of errors. The approach was further employed to predict the adsorption capacity of 40 LMWNPOCs on F400 AC, 12 LMWNPOCs onto 9 other ACs, and 8 LMWNPOCs onto 5 ACs with unknown PSD, with the errors of 41.9%, showing the model being reasonable. The model approach may provide a simple means for predicting adsorption capacities of LMWNPOCs onto different ACs. Copyright © 2015 Elsevier Ltd. All rights reserved.

  17. Development of an automated gas adsorption apparatus for the characterization of the surface area, pore size distribution, and density of powdered materials

    NASA Astrophysics Data System (ADS)

    Badalyan, Alexander; Pendleton, Phillip; Wu, Hua

    2001-07-01

    An automated apparatus for the characterization of the surface area, pore size distribution, and density of powdered materials is described. A newly developed liquid nitrogen level control system maintains the nitrogen level around the tube containing the sample within ±0.2 mm of the initial predefined level. The dosing volume and pneumatically operated control valves are maintained at 25.00±0.05 °C. Equilibrium pressure is measured with the accuracy of ±0.05% of reading. The apparatus may be operated either in a manual or an automatic mode. The control software developed, using the VISIDAQ Version 3.11 software package, operates involving equilibrium and barometric pressure measurements, opening and closing pneumatically operated valves, and transferring experimental data to MS EXCEL spreadsheets. The subroutines developed within the spreadsheet program plot the adsorption and desorption isotherms, calculate the sample specific surface area and density, and provide αs- and t-plots and mesopore and micropore size distributions. Specific surface areas were defined using the Brunauer-Emmett-Teller method of analysis. The apparatus accuracy was tested via surface reference materials. These included garnet, kaolinite, and carbon black with quoted multiple-point surface areas of 3.00±0.30, 16.45±0.8, and 113±5 m2/g. Our values were 2.84±0.28, 16.02±0.8, and 110±5 m2/g. Specific surface areas as low as 0.2 m2/g have been reproducibly measured using this apparatus. Results of nitrogen adsorption on activated carbon B1 together with specific surface area determination, evaluation of α-plot, and micro-, and mesopore size distributions are reported. Automatic pressure and flow controllers allow adsorption and desorption isotherm definition either in continuous or in conventional static flow volumetric modes.

  18. Experimental Study of Porosity Changes in Shale Caprocks Exposed to CO2-Saturated Brines I: Evolution of Mineralogy, Pore Connectivity, Pore Size Distribution, and Surface Area

    SciTech Connect

    Mouzakis, Katherine M.; Navarre-Sitchler, Alexis K.; Rother, Gernot; Bañuelos, José Leobardo; Wang, Xiuyu; Kaszuba, John P.; Heath, Jason E.; Miller, Quin R. S.; Alvarado, Vladimir; McCray, John E.

    2016-07-18

    Carbon capture, utilization, and storage, one proposed method of reducing anthropogenic emissions of CO2, relies on low permeability formations, such as shales, above injection formations to prevent upward migration of the injected CO2. Porosity in caprocks evaluated for sealing capacity before injection can be altered by geochemical reactions induced by dissolution of injected CO2 into pore fluids, impacting long-term sealing capacity. Therefore, long-term performance of CO2 sequestration sites may be dependent on both initial distribution and connectivity of pores in caprocks, and on changes induced by geochemical reaction after injection of CO2, which are currently poorly understood. This paper presents results from an experimental study of changes to caprock porosity and pore network geometry in two caprock formations under conditions relevant to CO2 sequestration. Pore connectivity and total porosity increased in the Gothic Shale; while total porosity increased but pore connectivity decreased in the Marine Tuscaloosa. Gothic Shale is a carbonate mudstone that contains volumetrically more carbonate minerals than Marine Tuscaloosa. Carbonate minerals dissolved to a greater extent than silicate minerals in Gothic Shale under high CO2 conditions, leading to increased porosity at length scales <~200 nm that contributed to increased pore connectivity. In contrast, silicate minerals dissolved to a greater extent than carbonate minerals in Marine Tuscaloosa leading to increased porosity at all length scales, and specifically an increase in the number of pores >~1 μm. Mineral reactions also contributed to a decrease in pore connectivity, possibly as a result of precipitation in pore throats or hydration of the high percentage of clays. Finally, this study highlights the role that mineralogy of the caprock can play in geochemical response to CO2 injection and resulting changes in

  19. Experimental Study of Porosity Changes in Shale Caprocks Exposed to CO2-Saturated Brines I: Evolution of Mineralogy, Pore Connectivity, Pore Size Distribution, and Surface Area

    SciTech Connect

    Mouzakis, Katherine M.; Navarre-Sitchler, Alexis K.; Rother, Gernot; Bañuelos, José Leobardo; Wang, Xiuyu; Kaszuba, John P.; Heath, Jason E.; Miller, Quin R. S.; Alvarado, Vladimir; McCray, John E.

    2016-07-18

    Carbon capture, utilization, and storage, one proposed method of reducing anthropogenic emissions of CO2, relies on low permeability formations, such as shales, above injection formations to prevent upward migration of the injected CO2. Porosity in caprocks evaluated for sealing capacity before injection can be altered by geochemical reactions induced by dissolution of injected CO2 into pore fluids, impacting long-term sealing capacity. Therefore, long-term performance of CO2 sequestration sites may be dependent on both initial distribution and connectivity of pores in caprocks, and on changes induced by geochemical reaction after injection of CO2, which are currently poorly understood. This paper presents results from an experimental study of changes to caprock porosity and pore network geometry in two caprock formations under conditions relevant to CO2 sequestration. Pore connectivity and total porosity increased in the Gothic Shale; while total porosity increased but pore connectivity decreased in the Marine Tuscaloosa. Gothic Shale is a carbonate mudstone that contains volumetrically more carbonate minerals than Marine Tuscaloosa. Carbonate minerals dissolved to a greater extent than silicate minerals in Gothic Shale under high CO2 conditions, leading to increased porosity at length scales <~200 nm that contributed to increased pore connectivity. In contrast, silicate minerals dissolved to a greater extent than carbonate minerals in Marine Tuscaloosa leading to increased porosity at all length scales, and specifically an increase in the number of pores >~1 μm. Mineral reactions also contributed to a decrease in pore connectivity, possibly as a result of precipitation in pore throats or hydration of the high percentage of clays. Finally, this study highlights the role that mineralogy of the caprock can play in geochemical response to CO2 injection and resulting changes in

  20. Pore size of agarose gels by atomic force microscopy.

    PubMed

    Pernodet, N; Maaloum, M; Tinland, B

    1997-01-01

    The pore size of agarose gel in water at different concentrations was directly measured using atomic force microscopy (AFM). The experiment was specially designed to work under aqueous conditions and allows direct observation of the "unperturbed" gel without invasive treatment. The pore size a as a function of gel concentration C shows a power law dependence a approximately C-gamma, where gamma lies between the prediction of the Ogston model for a random array of straight chains, 0.5, and the value predicted by De Gennes for a network of flexible chains, 0.75. We confirm that gels present a wide pore size distribution and show that it narrows as the concentration increases.

  1. Differences in soluble organic carbon chemistry in pore waters sampled from different pore size domains

    DOE PAGES

    Bailey, Vanessa L.; Smith, A. P.; Tfaily, Malak; ...

    2017-01-11

    Spatial isolation of soil organic carbon (SOC) in different sized pores may be a mechanism by which otherwise labile carbon (C) could be protected in soils. When soil water content increases, the hydrologic connectivity of soil pores also increases, allowing greater transport of SOC and other resources from protected locations, to microbially colonized locations more favorable to decomposition. The heterogeneous distribution of specialized decomposers, C, and other resources throughout the soil indicates that the metabolism or persistence of soil C compounds is highly dependent on short-distance transport processes. The objective of this research was to characterize the complexity of Cmore » in pore waters held at weak and strong water tensions (effectively soil solution held behind coarse- and fine-pore throats, respectively) and evaluate the microbial decomposability of these pore waters. We saturated intact soil cores and extracted pore waters with increasing suction pressures to sequentially sample pore waters from increasingly fine pore domains. Ultrahigh resolution mass spectrometry of the SOC was used to profile the major biochemical classes (i.e., lipids, proteins, lignin, carbohydrates, and condensed aromatics) of compounds present in the pore waters; some of these samples were then used as substrates for growth of Cellvibrio japonicus (DSMZ 16018), Streptomyces cellulosae (ATCC® 25439™), and Trichoderma reseei (QM6a) in 7 day incubations. The soluble C in finer pores was more complex than the soluble C in coarser pores, and the incubations revealed that the more complex C in these fine pores is not recalcitrant. The decomposition of this complex C led to greater losses of C through respiration than the simpler C from coarser pore waters. Our research suggests that soils that experience repeated cycles of drying and wetting may be accompanied by repeated cycles of increased CO2 fluxes that are driven by i) the transport of C from protected pools into

  2. Differences in soluble organic carbon chemistry in pore waters sampled from different pore size domains

    DOE PAGES

    Bailey, V. L.; Smith, A. P.; Tfaily, M.; ...

    2017-04-01

    Spatial isolation of soil organic carbon (SOC) in different sized pores may be a mechanism by which otherwise labile carbon (C) could be protected in soils. When soil water content increases, the hydrologic connectivity of soil pores also increases, allowing greater transport of SOC and other resources from protected locations, to microbially colonized locations more favorable to decomposition. The heterogeneous distribution of specialized decomposers, C, and other resources throughout the soil indicates that the metabolism or persistence of soil C compounds is highly dependent on short-distance transport processes. The objective of this research was to characterize the complexity of Cmore » in pore waters held at weak and strong water tensions (effectively soil solution held behind coarse- and fine-pore throats, respectively) and evaluate the microbial decomposability of these pore waters. We saturated intact soil cores and extracted pore waters with increasing suction pressures to sequentially sample pore waters from increasingly fine pore domains. Ultrahigh resolution mass spectrometry of the SOC was used to profile the major biochemical classes (i.e., lipids, proteins, lignin, carbohydrates, and condensed aromatics) of compounds present in the pore waters; some of these samples were then used as substrates for growth of Cellvibrio japonicus (DSMZ 16018), Streptomyces cellulosae (ATCC® 25439™), and Trichoderma reseei (QM6a) in 7 day incubations. The soluble C in finer pores was more complex than the soluble C in coarser pores, and the incubations revealed that the more complex C in these fine pores is not recalcitrant. The decomposition of this complex C led to greater losses of C through respiration than the simpler C from coarser pore waters. Our research suggests that soils that experience repeated cycles of drying and wetting may result in patterns of CO2 fluxes that are driven by i) the transport of C from protected pools into active, ii) the chemical

  3. Sulfur-infiltrated porous carbon microspheres with controllable multi-modal pore size distribution for high energy lithium-sulfur batteries.

    PubMed

    Zhao, Cunyu; Liu, Lianjun; Zhao, Huilei; Krall, Andy; Wen, Zhenhai; Chen, Junhong; Hurley, Patrick; Jiang, Junwei; Li, Ying

    2014-01-21

    Sulfur has received increasing attention as a cathode material for lithium-sulfur (Li-S) batteries due to its high theoretical specific capacity. However, the commercialization of Li-S batteries is limited by the challenges of poor electrical conductivity of sulfur, dissolution of the polysulfide intermediates into the electrolyte, and volume expansion of sulfur during cycling. Herein, we report the fabrication of novel-structured porous carbon microspheres with a controllable multi-modal pore size distribution, i.e., a combination of interconnected micropores, mesopores and macropores. Cathodes made of sulfur infiltrated in such a hierarchical carbon framework provide several advantages: (1) a continuous and high surface area carbon network for enhanced electrical conductivity and high sulfur loading; (2) macropores and large mesopores bridged by small mesopores to provide good electrolyte accessibility and fast Li ion transport and to accommodate volume expansion of sulfur; and (3) small mesopores and micropores to improve carbon/sulfur interaction and to help trap polysulfides. An initial discharge capacity at 1278 mA h g(-1) and capacity retention at 70.7% (904 mA h g(-1)) after 100 cycles at a high rate (1 C) were achieved. The material fabrication process is relatively simple and easily scalable.

  4. Nanoporous carbide-derived carbon with tunable pore size

    NASA Astrophysics Data System (ADS)

    Gogotsi, Yury; Nikitin, Alexei; Ye, Haihui; Zhou, Wei; Fischer, John E.; Yi, Bo; Foley, Henry C.; Barsoum, Michel W.

    2003-09-01

    Porous solids are of great technological importance due to their ability to interact with gases and liquids not only at the surface, but throughout their bulk. Although large pores can be produced and well controlled in a variety of materials, nanopores in the range of 2 nm and below (micropores, according to IUPAC classification) are usually achieved only in carbons or zeolites. To date, major efforts in the field of porous materials have been directed towards control of the size, shape and uniformity of the pores. Here we demonstrate that porosity of carbide-derived carbons (CDCs) can be tuned with subångström accuracy in a wide range by controlling the chlorination temperature. CDC produced from Ti3SiC2 has a narrower pore-size distribution than single-wall carbon nanotubes or activated carbons; its pore-size distribution is comparable to that of zeolites. CDCs are produced at temperatures from 200-1,200 °C as a powder, a coating, a membrane or parts with near-final shapes, with or without mesopores. They can find applications in molecular sieves, gas storage, catalysts, adsorbents, battery electrodes, supercapacitors, water/air filters and medical devices.

  5. Nanoporous carbide-derived carbon with tunable pore size.

    PubMed

    Gogotsi, Yury; Nikitin, Alexei; Ye, Haihui; Zhou, Wei; Fischer, John E; Yi, Bo; Foley, Henry C; Barsoum, Michel W

    2003-09-01

    Porous solids are of great technological importance due to their ability to interact with gases and liquids not only at the surface, but throughout their bulk. Although large pores can be produced and well controlled in a variety of materials, nanopores in the range of 2 nm and below (micropores, according to IUPAC classification) are usually achieved only in carbons or zeolites. To date, major efforts in the field of porous materials have been directed towards control of the size, shape and uniformity of the pores. Here we demonstrate that porosity of carbide-derived carbons (CDCs) can be tuned with subångström accuracy in a wide range by controlling the chlorination temperature. CDC produced from Ti3SiC2 has a narrower pore-size distribution than single-wall carbon nanotubes or activated carbons; its pore-size distribution is comparable to that of zeolites. CDCs are produced at temperatures from 200-1,200 degrees C as a powder, a coating, a membrane or parts with near-final shapes, with or without mesopores. They can find applications in molecular sieves, gas storage, catalysts, adsorbents, battery electrodes, supercapacitors, water/air filters and medical devices.

  6. Relation between the ion size and pore size for an electric double-layer capacitor.

    PubMed

    Largeot, Celine; Portet, Cristelle; Chmiola, John; Taberna, Pierre-Louis; Gogotsi, Yury; Simon, Patrice

    2008-03-05

    The research on electrochemical double layer capacitors (EDLC), also known as supercapacitors or ultracapacitors, is quickly expanding because their power delivery performance fills the gap between dielectric capacitors and traditional batteries. However, many fundamental questions, such as the relations between the pore size of carbon electrodes, ion size of the electrolyte, and the capacitance have not yet been fully answered. We show that the pore size leading to the maximum double-layer capacitance of a TiC-derived carbon electrode in a solvent-free ethyl-methylimmidazolium-bis(trifluoro-methane-sulfonyl)imide (EMI-TFSI) ionic liquid is roughly equal to the ion size (approximately 0.7 nm). The capacitance values of TiC-CDC produced at 500 degrees C are more than 160 F/g and 85 F/cm(3) at 60 degrees C, while standard activated carbons with larger pores and a broader pore size distribution present capacitance values lower than 100 F/g and 50 F/cm(3) in ionic liquids. A significant drop in capacitance has been observed in pores that were larger or smaller than the ion size by just an angstrom, suggesting that the pore size must be tuned with sub-angstrom accuracy when selecting a carbon/ion couple. This work suggests a general approach to EDLC design leading to the maximum energy density, which has been now proved for both solvated organic salts and solvent-free liquid electrolytes.

  7. Study on pore characteristics and microstructure of sandstones with different grain sizes

    NASA Astrophysics Data System (ADS)

    Li, Huigui; Li, Huamin; Gao, Baobin; Wang, Wen; Liu, Chuang

    2017-01-01

    The grain sizes have a pronounced influence on the pore characteristics and microstructure of sandstone. This work examined the pore structure and characteristics of three kinds of sandstones with different grain sizes using the scanning electron microscopy (SEM) and nuclear magnetic resonance (NMR) methods and analyzed their grain size distributions, pore size distributions, T2-distributions, and porosity variations. The experimental results showed that sandstones with different grain sizes have significant differences in the microstructures grain size distribution, pore size distribution, T2-distribution, and porosity variation. The results show that coarse, medium and fine sandstones have two peaks in T2-distributions, mean grain size of 398.5, 145.1 and 25.1 μm, respectively, mean pore size of 46.3, 25.9, and 8.4 μm, respectively, porosity of 7.52%, 5.88% and 1.55%, respectively, indicating that both coarse and medium sandstones contain big pores, while fine sandstone contains small pores. This study is of significance for understanding of water migration characteristics in aquifers and gas in coal seams after the working face exploitation.

  8. Preparation of mesoporous cadmium sulfide nanoparticles with moderate pore size

    SciTech Connect

    Han Zhaohui Zhu, Huaiyong; Shi, Jeffrey; Parkinson, Gordon; Lu, G.Q.

    2007-03-15

    The preparation of cadmium sulfide nanoparticles that have a moderate pore size is reported. This preparation method involves a hydrothermal process that produces a precursor mixture and a following acid treatment of the precursor to get the porous material. The majority of the particles have a pore size close to 20nm, which complements and fills in the gap between the existing cadmium sulfide materials, which usually have a pore size either less than 10nm or are well above 100nm.

  9. Distributed pore model for bio-molecule chromatography.

    PubMed

    Coquebert de Neuville, Bertrand; Tarafder, Abhijit; Morbidelli, Massimo

    2013-07-12

    One of the main peculiarities in protein chromatography is that the adsorbing proteins and the adsorbent pores have comparable sizes. This has the consequence that the pore accessibility depends not only on the solute size but also on the loading conditions of the adsorbent because protein adsorption significantly reduces the size of the pores. A model that accounts for the pore size distribution of the stationary phase and for the pore shrinkage due to protein adsorption has been developed to describe mass transport and adsorption in the porous particles. This model has been shown to be equivalent to the general rate model (GRM) in the case of processes under highly diluted conditions with little adsorption. This implies that the model parameters determination follows the same procedure as for the classical GRM. The new pore model has been applied and compared to the GRM for the simulation of lysozyme breakthrough experiments and for the prediction of 5% dynamic binding capacity values solely based on static capacity measurements.

  10. Decreasing transmembrane segment length greatly decreases perfringolysin O pore size

    SciTech Connect

    Lin, Qingqing; Li, Huilin; Wang, Tong; London, Erwin

    2015-04-08

    Perfringolysin O (PFO) is a transmembrane (TM) β-barrel protein that inserts into mammalian cell membranes. Once inserted into membranes, PFO assembles into pore-forming oligomers containing 30–50 PFO monomers. These form a pore of up to 300 Å, far exceeding the size of most other proteinaceous pores. In this study, we found that altering PFO TM segment length can alter the size of PFO pores. A PFO mutant with lengthened TM segments oligomerized to a similar extent as wild-type PFO, and exhibited pore-forming activity and a pore size very similar to wild-type PFO as measured by electron microscopy and a leakage assay. In contrast, PFO with shortened TM segments exhibited a large reduction in pore-forming activity and pore size. This suggests that the interaction between TM segments can greatly affect the size of pores formed by TM β-barrel proteins. PFO may be a promising candidate for engineering pore size for various applications.

  11. Decreasing transmembrane segment length greatly decreases perfringolysin O pore size

    DOE PAGES

    Lin, Qingqing; Li, Huilin; Wang, Tong; ...

    2015-04-08

    Perfringolysin O (PFO) is a transmembrane (TM) β-barrel protein that inserts into mammalian cell membranes. Once inserted into membranes, PFO assembles into pore-forming oligomers containing 30–50 PFO monomers. These form a pore of up to 300 Å, far exceeding the size of most other proteinaceous pores. In this study, we found that altering PFO TM segment length can alter the size of PFO pores. A PFO mutant with lengthened TM segments oligomerized to a similar extent as wild-type PFO, and exhibited pore-forming activity and a pore size very similar to wild-type PFO as measured by electron microscopy and a leakagemore » assay. In contrast, PFO with shortened TM segments exhibited a large reduction in pore-forming activity and pore size. This suggests that the interaction between TM segments can greatly affect the size of pores formed by TM β-barrel proteins. PFO may be a promising candidate for engineering pore size for various applications.« less

  12. Effect of pore size on the performance of immobilised enzymes.

    PubMed

    Bayne, Lauren; Ulijn, Rein V; Halling, Peter J

    2013-12-07

    Porous materials are widely employed as supports in the immobilisation of enzymes. Traditionally macroporous materials with pore diameters >50 nm were believed to be the most suitable support material, ensuring no spatial restrictions upon enzyme molecules entering such large pores. In recent years however, there has been growing emphasis in the use of mesoporous supports with pore diameters ranging between 2 and 50 nm. It is thought this smaller pore range may offer enhanced conformational stability to immobilised enzymes while not being so small as to restrict enzyme access. Despite their increasing popularity, many argue that mesoporous materials have not yet proven superior to traditional macroporous supports for enzyme immobilisation. Through the design and application of a unique confidence rating system we were able to accurately compare data and establish trends between pore characteristics and protein loading. By analysing published data (182 experiments in total) and extracting pore characteristics and protein loading values, we have described three categories of pore diameters in which correlations between pore characteristics and protein loading are noted. With pore diameters less than 10 nm we see a general decrease in protein loading as the enzymes find physical restrictions in accessing the high surface offered in this pore diameter range. At pore sizes greater than 100 nm, protein loading generally decreases due to a concomitant reduction in available surface area. In the pore range of 10-100 nm there it is expected to see a decrease in protein loading level with increasing pore diameter. In fact protein loading in this range remains largely constant, suggesting some degree of protein-protein interaction blocking pores and restricting access to the increasing surface area available at decreasing pore diameters. No trends were established between pore characteristics and retention of activity.

  13. Measurement of variation in soil solute tracer concentration across a range of effective pore sizes

    USGS Publications Warehouse

    Harvey, Judson W.

    1993-01-01

    Solute transport concepts in soil are based on speculation that solutes are distributed nonuniformly within large and small pores. Solute concentrations have not previously been measured across a range of pore sizes and examined in relation to soil hydrological properties. For this study, modified pressure cells were used to measure variation in concentration of a solute tracer across a range of pore sizes. Intact cores were removed from the site of a field tracer experiment, and soil water was eluted from 10 or more discrete classes of pore size. Simultaneous changes in water content and unsaturated hydraulic conductivity were determined on cores using standard pressure cell techniques. Bromide tracer concentration varied by as much as 100% across the range of pore sizes sampled. Immediately following application of the bromide tracer on field plots, bromide was most concentrated in the largest pores; concentrations were lower in pores of progressively smaller sizes. After 27 days, bromide was most dilute in the largest pores and concentrations were higher in the smaller pores. A sharp, threefold decrease in specific water capacity during elution indicated separation of two major pore size classes at a pressure of 47 cm H2O and a corresponding effective pore diameter of 70 μm. Variation in tracer concentration, on the other hand, was spread across the entire range of pore sizes investigated in this study. A two-porosity characterization of the transport domain, based on water retention criteria, only broadly characterized the pattern of variation in tracer concentration across pore size classes during transport through a macroporous soil.

  14. Study into the correlation of dominant pore throat size and SIP relaxation frequency

    NASA Astrophysics Data System (ADS)

    Kruschwitz, Sabine; Prinz, Carsten; Zimathies, Annett

    2016-12-01

    There is currently a debate within the SIP community about the characteristic textural length scale controlling relaxation time of consolidated porous media. One idea is that the relaxation time is dominated by the pore throat size distribution or more specifically the modal pore throat size as determined in mercury intrusion capillary pressure tests. Recently new studies on inverting pore size distributions from SIP data were published implying that the relaxation mechanisms and controlling length scale are well understood. In contrast new analytical model studies based on the Marshall-Madden membrane polarization theory suggested that two relaxation processes might compete: the one along the short narrow pore (the throat) with one across the wider pore in case the narrow pores become relatively long. This paper presents a first systematically focused study into the relationship of pore throat sizes and SIP relaxation times. The generality of predicted trends is investigated across a wide range of materials differing considerably in chemical composition, specific surface and pore space characteristics. Three different groups of relaxation behaviors can be clearly distinguished. The different behaviors are related to clay content and type, carbonate content, size of the grains and the wide pores in the samples.

  15. Immobilization of nanobeads on a surface to control the size, shape and distribution of pores in electrochemically generated sol-gel films

    PubMed Central

    Ciabocco, Michela; Berrettoni, Mario; Zamponi, Silvia

    2015-01-01

    Electrochemically assisted deposition of an ormosil film at a potential where hydrogen ion is generated as the catalyst yields insulating films on electrodes. When the base electrode is modified with 20-nm poly(styrene sulfonate), PSS, beads bound to the surface with 3-aminopropyltriethoxysilane (APTES) and using (CH3)3SiOCH3 as the precursor, the resulting film of organically modified silica (ormosil) has cylindrical channels that reflect both the diameter of the PSS and the distribution of the APTES-PSS on the electrode. At an electrode modified by a 20-min immersion in 0.5 mmol dm-3 APTES followed by a 30-s immersion in PSS, a 20-min electrolysis at 1.5 V in acidified (CH3)3SiOCH3 resulted in an ormosil film with 20-nm pores separated by 100 nm. Cyclic voltammetry of Ru(CN)64- at scan rates above 5 mVs-1 yielded currents controlled primarily by linear diffusion. Below 5 mVs-1, convection rather than the expected factor, radial diffusion, apparently limited the current. PMID:26167128

  16. Size of diffusion pore of Alcaligenes faecalis.

    PubMed Central

    Ishii, J; Nakae, T

    1988-01-01

    The diffusion pore of the outer membrane of Alcaligenes faecalis was shown to be substantially smaller than the Escherichia coli porin pore. In experiments with intact cells, pentoses and hexoses penetrated into the NaCl-expanded periplasm, whereas saccharides of Mr greater than 342 did not. Cells treated with 0.5 M saccharides of Mr greater than 342 weighed 33 to 38% less than cells treated with isotonic solution, suggesting that these saccharides do not permeate through the outer membrane. The diffusion rates of various solutes through the liposome membranes reconstituted from the Mr-43,000 outer membrane protein showed the following characteristics. (i) The relative diffusion rates of pentoses, hexoses, and methylhexoses appeared to be about 1.0, 0.6, and negligibly small, respectively. (ii) The diffusion rate of glucose appeared to be about 1/10th that with the E. coli B porin. (iii) The diffusion rate of gluconic acid was five to seven times higher than that of glucose. (iv) The diffusion rates of beta-lactam antibiotics appeared to be 40 to less than 10% of those with the E. coli B porin. Images PMID:2835003

  17. Fabrication of polymeric scaffolds with a controlled distribution of pores.

    PubMed

    Capes, J S; Ando, H Y; Cameron, R E

    2005-12-01

    The design of tissue engineering scaffolds must take into account many factors including successful vascularisation and the growth of cells. Research has looked at refining scaffold architecture to promote more directed growth of tissues through well-defined anisotropy in the pore structure. In many cases it is also desirable to incorporate therapeutic ingredients, such as growth factors, into the scaffold so that their release occurs as the scaffold degrades. Therefore, scaffold fabrication techniques must be found to precisely control, not only the overall porosity of scaffolds, but also the pore size, shape and spatial distribution. This work describes the use of a regularly shaped porogen, sugar spheres, to manufacture polymeric scaffolds. Results show that pre-assembling the spheres created scaffolds with a constant porosity of 60%, but with varying pores sizes from 200-800 microm, leading to a variation in the surface area and likely degradation rate of the scaffolds. Employing different polymer impregnation techniques tailored the number of pores present with a diameter of less than 100 microm to suit different functions, and altering the packing structure of the sugar spheres created scaffolds with novel layered porosity. Replacing sugar spheres with sugar strands formed scaffolds with pores aligned in one direction.

  18. Pore size matters for potassium channel conductance

    PubMed Central

    Moldenhauer, Hans; Pincuntureo, Matías

    2016-01-01

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

  19. Pore size matters for potassium channel conductance.

    PubMed

    Naranjo, David; Moldenhauer, Hans; Pincuntureo, Matías; Díaz-Franulic, Ignacio

    2016-10-01

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

  20. Pore size--a key property for selective toxin removal in blood purification.

    PubMed

    Harm, Stephan; Falkenhagen, Dieter; Hartmann, Jens

    2014-09-01

    Extracorporeal blood purification systems based on combined membrane/adsorption technologies are used in acute liver failure to replace detoxification as well as to remove inflammatory mediators in sepsis patients. In addition to coating and chemical modification of the surface, pore size significantly controls the selectivity of adsorption materials. This study addresses the adsorption of albumin bound liver toxins, cytokines, and representative plasma compounds on three adsorbents which differ only in pore size distribution. All three adsorbents are based on hydrophobic poly(styrene-divinylbenzene) copolymer matrices and have mean pore sizes of 15, 30, and 100 nm. The pores of adsorbents act as molecular sieves and prevent the entry of molecules that are larger than their molecular cut-off. The results of this study reveal that adsorbents based on styrene-divinylbenzene polymers with 15 nm pores are suitable for cytokine removal, and the same adsorbents with 30-40 nm pores are the best choice for the removal of albumin-bound toxins in the case of liver failure. Adsorbents with very large pores lack selectivity which leads to uncontrolled adsorption of all plasma proteins. Therefore, hydrophobic adsorbents with large pores offer inadequate plasma compatibility and do not fulfill the requirements for blood purification. Biocompatibility and efficiency of adsorbents used for blood purification can improved by fine tuning of adsorbent surface pore distributions.

  1. Modelling adipocytes size distribution.

    PubMed

    Soula, H A; Julienne, H; Soulage, C O; Géloën, A

    2013-09-07

    Adipocytes are cells whose task is to store excess energy as lipid droplets in their cytoplasm. Adipocytes can adapt their size according to the lipid amount to be stored. Adipocyte size variation can reach one order of magnitude inside the same organism which is unique among cells. A striking feature in adipocytes size distribution is the lack of characteristic size since typical size distributions are bimodal. Since energy can be stored and retrieved and adipocytes are responsible for these lipid fluxes, we propose a simple model of size-dependent lipid fluxes that is able to predict typical adipocytes size distribution. Copyright © 2013 Elsevier Ltd. All rights reserved.

  2. Porous Boron Nitride with Tunable Pore Size.

    PubMed

    Dai, Jun; Wu, Xiaojun; Yang, Jinlong; Zeng, Xiao Cheng

    2014-01-16

    On the basis of a global structural search and first-principles calculations, we predict two types of porous boron-nitride (BN) networks that can be built up with zigzag BN nanoribbons (BNNRs). The BNNRs are either directly connected with puckered B (N) atoms at the edge (type I) or connected with sp(3)-bonded BN chains (type II). Besides mechanical stability, these materials are predicted to be thermally stable at 1000 K. The porous BN materials entail large surface areas, ranging from 2800 to 4800 m(2)/g. In particular, type-II BN material with relatively large pores is highly favorable for hydrogen storage because the computed hydrogen adsorption energy (-0.18 eV) is very close to the optimal adsorption energy (-0.15 eV) suggested for reversible hydrogen storage at room temperature. Moreover, the type-II materials are semiconductors with width-dependent direct bandgaps, rendering the type-II BN materials promising not only for hydrogen storage but also for optoelectronic and photonic applications.

  3. Facile fabrication of BiVO4 nanofilms with controlled pore size and their photoelectrochemical performances.

    PubMed

    Feng, Chenchen; Jiao, Zhengbo; Li, Shaopeng; Zhang, Yan; Bi, Yingpu

    2015-12-28

    We demonstrate a facile method for the rational fabrication of pore-size controlled nanoporous BiVO(4) photoanodes, and confirmed that the optimum pore-size distributions could effectively absorb visible light through light diffraction and confinement functions. Furthermore, in situ X-ray photoelectron spectroscopy (XPS) reveals more efficient photoexcited electron-hole separation than conventional particle films, induced by light confinement and rapid charge transfer in the inter-crossed worm-like structures.

  4. EFFECT OF PORE SIZE ON TRAPPING ZINC VAPORS

    SciTech Connect

    Korinko, P.

    2010-12-17

    A series of experiments were conducted to determine the effect of pore size on pumping efficiency and zinc vapor trapping efficiency. A simple pumping efficiency test was conducted for all five pore diameters where it was observed that evacuation times were adversely affected by reducing the pore size below 5 {micro}m. Common test conditions for the zinc trapping efficiency experiments were used. These conditions resulted in some variability, to ascribe different efficiencies to the filter media. However, the data suggest that there is no significant difference in trapping efficiency for filter media with pores from 0.2 to 20 {micro}m with a thickness of 0.065-inch. Consequently, the 20 {micro}m pore filter media that is currently used at SRS is a suitable filter material for to utilize for future extractions. There is evidence that smaller pore filter will adversely affect the pumping times for the TEF and little evidence to suggest that a smaller pore diameters have significant impact on the trapping efficiency.

  5. Chitosan scaffolds: interconnective pore size and cartilage engineering.

    PubMed

    Griffon, Dominique J; Sedighi, M Reza; Schaeffer, David V; Eurell, Jo Ann; Johnson, Ann L

    2006-05-01

    This study was designed to determine the effect of interconnective pore size on chondrocyte proliferation and function within chitosan sponges, and compare the potential of chitosan and polyglycolic acid (PGA) matrices for chondrogenesis. Six million porcine chondrocytes were seeded on each of 52 prewetted scaffolds consisting of chitosan sponges with (1) pores 10 microm in diameter (n=10, where n is the number of samples); (2) pores measuring 10-50 microm in diameter (n=10); and (3) pores measuring 70-120 microm in diameter (n=10), versus (4) polyglycolic acid mesh (n=22), as a positive control. Constructs were cultured for 28 days in a rotating bioreactor prior to scanning electron microscopy (SEM), histology, and determination of their water, DNA, glycosaminoglycan (GAG) and collagen II contents. Parametric data was compared (p=0.05) with an ANOVA and Tukey's Studentized range test. PGA constructs consisted essentially of a matrix containing more cells than normal cartilage. Whereas very few remnants of PGA remained, chitosan scaffolds appeared intact. DNA and GAG concentrations were greater in PGA scaffolds than in any of the chitosan groups. However, chitosan sponges with the largest pores contained more chondrocytes, collagen II and GAG than the matrix with the smallest pores. Constructs produced with PGA contained less water and more GAG than all chitosan groups. Chondrocyte proliferation and metabolic activity improved with increasing interconnective pore size of chitosan matrices. In vitro chondrogenesis is possible with chitosan but the composition of constructs produced on PGA more closely approaches that of natural cartilage.

  6. Distributed Pore Chemistry in Porous Organic Polymers

    NASA Technical Reports Server (NTRS)

    Koontz, Steven L. (Inventor)

    1998-01-01

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

  7. Distributed Pore Chemistry in Porous Organic Polymers

    NASA Technical Reports Server (NTRS)

    Koontz, Steven L. (Inventor)

    1999-01-01

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

  8. Method of making metal oxide ceramic membranes with small pore sizes

    DOEpatents

    Anderson, Marc A.; Xu, Qunyin

    1992-01-01

    A method for the production of metal oxide ceramic membranes is composed of very small pore size. The process is particularly useful in the creation of titanium and other transition metal oxide membranes. The method utilizes a sol-gel process in which the rate of particle formation is controlled by substituting a relatively large alcohol in the metal alkoxide and by limiting the available water. Stable, transparent metal oxide ceramic membranes are created having a narrow distribution of pore size, with the pore diameter being manipulable in the range of 5 to 40 Angstroms.

  9. Validity of NMR pore-size analysis of cultural heritage ancient building materials containing magnetic impurities.

    PubMed

    Brai, M; Casieri, C; De Luca, F; Fantazzini, P; Gombia, M; Terenzi, C

    2007-12-01

    NMR relaxation time distributions, obtained with laboratory and portable devices, are utilized to characterize the pore-size distributions of building materials coming from the Roman remains of the Greek-Roman Theatre of Taormina. To validate the interpretation of relaxation data in terms of pore-size distribution, comparison of results from standard and in situ NMR experiments with results of the mercury intrusion porosimetry (MIP) has been made. Although the pore-size distributions can be obtained by NMR in terms of either longitudinal (T(1)) or transverse (T(2)) relaxation times distributions, the shorter duration of the T(2) measurement makes it, in principle, preferable, although the determination of T(2) distributions is not necessarily an easy alternative to finding T(1) distributions. Among other things, the T(1) distribution is almost independent of the inhomogeneity of the magnetic field, while the T(2) distribution is strongly influenced by it. This paper was aimed at answering two questions: what are the validity limits to interpret NMR data in terms of pore-size distributions and whether the portable device can successfully be applied as a non-destructive and non-invasive tool for in situ NMR analysis of building materials, particularly those of Cultural Heritage interest.

  10. Pore-throat sizes in sandstones, tight sandstones, and shales

    USGS Publications Warehouse

    Nelson, Philip H.

    2009-01-01

    Pore-throat sizes in silidclastic rocks form a continuum from the submillimeter to the nanometer scale. That continuum is documented in this article using previously published data on the pore and pore-throat sizes of conventional reservoir rocks, tight-gas sandstones, and shales. For measures of central tendency (mean, mode, median), pore-throat sizes (diameters) are generally greater than 2 μm in conventional reservoir rocks, range from about 2 to 0.03 μm in tight-gas sandstones, and range from 0.1 to 0.005 μm in shales. Hydrocarbon molecules, asphaltenes, ring structures, paraffins, and methane, form another continuum, ranging from 100 Å (0.01 μm for asphaltenes to 3.8 A (0.00038 μm) for methane. The pore-throat size continuum provides a useful perspective for considering (1) the emplacement of petroleum in consolidated siliciclastics and (2) fluid flow through fine-grained source rocks now being exploited as reservoirs.

  11. Flux theory for Poisson distributed pores with Gaussian permeability.

    PubMed

    Salinas, Dino G

    2016-01-01

    The mean of the solute flux through membrane pores depends on the random distribution and permeability of the pores. Mathematical models including such randomness factors make it possible to obtain statistical parameters for pore characterization. Here, assuming that pores follow a Poisson distribution in the lipid phase and that their permeabilities follow a Gaussian distribution, a mathematical model for solute dynamics is obtained by applying a general result from a previous work regarding any number of different kinds of randomly distributed pores. The new proposed theory is studied using experimental parameters obtained elsewhere, and a method for finding the mean single pore flux rate from liposome flux assays is suggested. This method is useful for pores without requiring studies by patch-clamp in single cells or single-channel recordings. However, it does not apply in the case of ion-selective channels, in which a more complex flux law combining the concentration and electrical gradient is required.

  12. Neutrons measure phase behavior in pores at Angstrom size

    SciTech Connect

    Bardoel, Agatha A; Melnichenko, Yuri B

    2012-01-01

    Researchers have measured the phase behavior of green house gases in pores at the Angstrom-level, using small angle neutron scattering (SANS) at the Oak Ridge National Laboratory's High Flux Isotope Reactor. Yuri Melnichenko, an instrument scientist on the General Purpose Small Angle Neutron Scattering (GP SANS) Diffractometer at ORNL's High Flux Isotope Reactor, his postdoctoral associate Lilin He and collaborators Nidia Gallego and Cristian Contescu from the Material Sciences Division (ORNL) were engaged in the work. They were studying nanoporous carbons to assess their attractiveness as storage media for hydrogen, with a view to potential use for on-board hydrogen storage for transportation applications. Nanoporous carbons can also serve as electrode material for supercapacitors and batteries. The researchers successfully determined that the most efficiently condensing pore size in a carbon nanoporous material for hydrogen storage is less than one nanometer. In a paper recently published by the Journal of the American Chemical Society, the collaborators used small angle neutron scattering to study how hydrogen condenses in small pores at ambient temperature. They discovered that the surface-molecule interactions create internal pressures in pores that may exceed the external gas pressure by a factor of up to 50. 'This is an exciting result,' Melnichenko said, 'as you achieve extreme densification in pores 'for free', i.e. without spending any energy. These results can be used to guide the development of new carbon adsorbents tailored to maximize hydrogen storage capacities.' Another important factor that defines the adsorption capacity of sub-nanometer pores is their shape. In order to get accurate structural information and maximize sorption capacity, it is important that pores are small and of approximately uniform size. In collaboration with Drexel University's Yury Gogotsi who supplied the samples, Melnichenko and his collaborators used the GP SANS

  13. Size effects of pore density and solute size on water osmosis through nanoporous membrane.

    PubMed

    Zhao, Kuiwen; Wu, Huiying

    2012-11-15

    Understanding the behavior of osmotic transport across nanoporous membranes at molecular level is critical to their design and applications, and it is also beneficial to the comprehension of the mechanism of biological transmembrane transport processes. Pore density is an important parameter for nanoporous membranes. To better understand the influence of pore density on osmotic transport, we have performed systematic molecular dynamics simulations on water osmosis across nanoporous membranes with different pore densities (i.e., number of pores per unit area of membrane). The simulation results reveal that significant size effects occur when the pore density is so high that the center-to-center distance between neighboring nanopores is comparable to the solute size. The size effects are independent of the pore diameter and solute concentration. A simple quantitative correlation between pore density, solute size, and osmotic flux has been established. The results are excellently consistent with the theoretical predictions. It is also shown that solute hydration plays an important role in real osmotic processes. Solute hydration strengthens the size effects of pore density on osmotic processes due to the enlarged effective solute size induced by hydration. The influence of pore density, solute size, and solute hydration on water osmosis through nanoporous membranes can be introduced to eliminate the deviations of real osmotic processes from ideal behavior.

  14. Influence of the pore size of reversed phase materials on peptide purification processes.

    PubMed

    Gétaz, David; Dogan, Nihan; Forrer, Nicola; Morbidelli, Massimo

    2011-05-20

    The influence of the pore size of a chromatographic reversed phase material on the adsorption equilibria and diffusion of two industrially relevant peptides (i.e. a small synthetic peptide and insulin) has been studied using seven different reversed phase HPLC materials having pore sizes ranging from 90 Å to 300 Å. The stationary phase pore size distribution was obtained by inverse size exclusion measurement (iSEC). The effect of the pore size on the mass transfer properties of the materials was evaluated from Van Deemter experiments. It has been shown that the lumped mass transfer coefficient increases linearly with the average pore size. The Henry coefficient and the impurity selectivity were determined in diluted conditions. The saturation capacity of the main peptides was determined in overloaded conditions using the inverse method (i.e. peak fitting). It was shown that the adsorption equilibria of the peptides on the seven materials is well described by a surface-specific adsorption isotherm. Based on this a lumped kinetic model has been developed to model the elution profile of the two peptides in overloaded conditions and to simulate the purification of the peptide from its crude mixture. It has been found that the separation of insulin from its main impurity (i.e. desamido-insulin) was not affected by the pore size. On the other hand, in the case of the synthetic peptide, it was found that the adsorption of the most significant impurity decreases with the pore size. This decrease is probably due to an increase in silanol activity with decreasing pore size.

  15. Aromatization of Ethanol Over Desilicated ZSM-5 Zeolites: Effect of Pore Size in the Mesoporous Region.

    PubMed

    Jun, Jong Won; Hasan, Zubair; Kim, Chul-Ung; Jeong, Soon-Yong; Jhung, Sung Hwa

    2016-05-01

    Mesoporous ZSM-5 zeolites were obtained from microporous ZSM-5 by desilication using aqueous NaOH solutions, and their catalytic activity in the aromatization of ethanol was investigated in order to understand the effects of pore size, in the mesoporous region, on the product distribution and stability of the catalysts. Mesopores generally enhanced the selectivities towards aromatics and stability for aromatization. Mesopores with a maximum pore diameter of around 13 nm were the most effective in the aromatization process (especially for benzene and toluene), suggesting that pore-diameter optimization is necessary for efficient catalysis such as aromatization.

  16. Pore distributions in nanocrystalline metals from small-angle neutron scattering

    SciTech Connect

    Sanders, P.G.; Weertman, J.R.; Eastman, J.A.

    1998-07-24

    Recent upgrades in inert-gas condensation processing equipment have produced nanocrystalline metal samples with high densities and low-impurity levels. Typical Cu and Pd samples have densities {ge}98% of theoretical and oxygen and hydrogen impurity concentrations {le}0.5 at. %. Lower porosity and impurity levels may make it difficult to produce and maintain samples with the smallest nanocrystalline grain sizes. These improved samples were studied by small-angle neutron scattering (SANS) to determine the volume fraction and size distribution of pores. Excellent correlation was obtained between the total volume fraction of pores and the Archimedes density for Pd, signifying that most of the pores were relatively small and in the detectability range of SANS ({approx}1--100 nm). Nanocrystalline Cu is shown to exhibit a wider pore size distribution. For Pd, the average pore sizes were slightly smaller than the average grain size, while for Cu the pore size and grain size were about the same. Both materials exhibited a trend of increasing pore size with increasing grain size. In terms of processing prerequisites, the principal condition for the production of high-density nanocrystalline Cu is an exceptionally clean synthesis environment, while nanocrystalline Pd requires compaction at elevated temperatures. These differences are the result of Cu having both a lower melting point and a greater susceptibility to contamination by gaseous impurities such as oxygen.

  17. Magnification of the pore size in biodegradable collagen sponges.

    PubMed

    Kuberka, M; von Heimburg, D; Schoof, H; Heschel, I; Rau, G

    2002-01-01

    In tissue engineering cells are often combined with a carrying structure with collagen being a suitable material to form a 3D-scaffold. A process to manufacture collagen sponges with an adjustable and homogeneous structure has been developed at the Helmholtz-Institute. Using this process, collagen suspensions are frozen directionally and subsequently vacuum-dried. One clinical application in which these scaffolds can be used is soft tissue reconstruction. Various soft tissue defects require an adequate replacement, e.g. in the case of severe burn wounds, or after tumour resections. Collagen (type I) sponges, which are cultured with preadipocytes, may be used to regenerate such defects. In this case, pore sizes of approximately 100 microm are desired to allow a complete differentiation of preadipocytes into adipocytes. Based on known technology to manufacture collagen sponges with an adjustable and homogeneous pore structure, research on the increase of pore size beyond the previous limit of 40 microm was necessary in order to enable soft tissue replacement. A scaffold with an average pore size of 100 microm was obtained.

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

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

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

  19. Simulation of porosity decrease with protein adsorption using the distributed pore model.

    PubMed

    Coquebert de Neuville, Bertrand; Thomas, Helen; Morbidelli, Massimo

    2013-11-01

    Chromatographic stationary phases such as Fractogel EMD SO3 (M) have a pore size distribution that is close to the size of proteins. The accessible porosity and the mass transfer inside the particles are therefore strongly affected by the pore to solute size ratio. This effect was simulated using the distributed pore model for three media: Base Fractogel SO3, Fractogel EMD SO3 (M) and (S). This model was extended so as to be able to account for the effect of pore shrinkage due to protein loading on the chromatographic behavior of other proteins. Pulse chromatographic experiments using dextrans of various sizes on column pre-loaded with antibodies have been conducted to test the model reliability.

  20. Business size distributions

    NASA Astrophysics Data System (ADS)

    D'Hulst, R.; Rodgers, G. J.

    2001-10-01

    In a recent work, we introduced two models for the dynamics of customers trying to find the business that best corresponds to their expectation for the price of a commodity. In agreement with the empirical data, a power-law distribution for the business sizes was obtained, taking the number of customers of a business as a proxy for its size. Here, we extend one of our previous models in two different ways. First, we introduce a business aggregation rate that is fitness dependent, which allows us to reproduce a spread in empirical data from one country to another. Second, we allow the bankruptcy rate to take a different functional form, to be able to obtain a log-normal distribution with power-law tails for the size of the businesses.

  1. Effect of pore size and surface area of carbide derived carbons on specific capacitance

    NASA Astrophysics Data System (ADS)

    Chmiola, J.; Yushin, G.; Dash, R.; Gogotsi, Y.

    This work presents a systematic study on how pore size and specific surface area (SSA) of carbon effect specific capacitance and frequency response behavior. Carbide derived carbons (CDC) produced by leaching metals from TiC and ZrC at temperatures from 600 to 1200 °C have highly tailorable microstructure and porosity, allowing them to serve as excellent model systems for porous carbons in general. BET SSA and average pore size increased with synthesis temperature and was 600-2000 m 2 g -1 and 0.7-1.85 nm, respectively. Maximum specific capacitance in 1 M H 2SO 4 was found to occur at an intermediate synthesis temperature, 800 °C, for both ZrC and TiC derived carbons and was 190 and 150 F g -1, respectively. Volumetric capacitance for TiC and ZrC derived carbons was maximum at 140 and 110 F cm -3. These results contradict an oft-reported axiom that increasing pore size and SSA, all other things being held constant, increases specific capacitance. A correlation between specific capacitance and SSA of micropores (less than 2 nm in diameter) has been shown. As expected, increasing pore size was found to improve the frequency response. However, CDCs with similar pore size distributions but obtained from different starting materials showed noticeable differences in impedance behavior. This highlights the importance of not only the pore size and specific surface area measured using gas sorption techniques, but also the pore shape or tortuousity, which is non-trivial to characterize, on energy storage.

  2. Time-Dependent Model for Fluid Flow in Porous Materials with Multiple Pore Sizes.

    PubMed

    Cummins, Brian M; Chinthapatla, Rukesh; Ligler, Frances S; Walker, Glenn M

    2017-04-18

    An understanding of fluid transport through porous materials is critical for the development of lateral flow assays and analytical devices based on paper microfluidics. Models of fluid transport within porous materials often assume a single capillary pressure and permeability value for the material, implying that the material comprises a single pore size and that the porous material is fully saturated behind the visible wetted front. As a result, current models can lead to inaccuracies when modeling transport over long distances and/or times. A new transport model is presented that incorporates a range of pore sizes to more accurately predict the capillary transport of fluid in porous materials. The model effectively predicts the time-dependent saturation of rectangular strips of Whatman filter no. 1 paper using the manufacturer's data, published pore-size distribution measurements, and the fluid's properties.

  3. Effects of Pore Distributions on Ductility of Thin-Walled High Pressure Die-Cast Magnesium

    SciTech Connect

    Choi, Kyoo Sil; Li, Dongsheng; Sun, Xin; Li, Mei; Allison, John

    2013-06-01

    In this paper, a microstructure-based three-dimensional (3D) finite element modeling method is adopted to investigate the effects of porosity in thin-walled high pressure die-cast (HPDC) Magnesium alloys on their ductility. For this purpose, the cross-sections of AM60 casting samples are first examined using optical microscope and X-ray tomography to obtain the general information on the pore distribution features. The experimentally observed pore distribution features are then used to generate a series of synthetic microstructure-based 3D finite element models with different pore volume fractions and pore distribution features. Shear and ductile damage models are adopted in the finite element analyses to induce the fracture by element removal, leading to the prediction of ductility. The results in this study show that the ductility monotonically decreases as the pore volume fraction increases and that the effect of ‘skin region’ on the ductility is noticeable under the condition of same local pore volume fraction in the center region of the sample and its existence can be beneficial for the improvement of ductility. The further synthetic microstructure-based 3D finite element analyses are planned to investigate the effects of pore size and pore size distribution.

  4. Induced polarization of volcanic rocks. 2. Influence of pore size and permeability

    NASA Astrophysics Data System (ADS)

    Revil, A.; Breton, M. Le; Niu, Q.; Wallin, E.; Haskins, E.; Thomas, D. M.

    2016-12-01

    We investigate the relationship between complex conductivity spectra and both permeability and pore mean size and distribution of 22 core samples (21 volcanic rocks and one clayey sandstone). The volcanic core samples were extracted from a wellbore drilled for the Humu´ula Groundwater Research Project in the Humu´ula saddle region between Mauna Kea and Mauna Loa volcanoes (Hawaii). The quadrature conductivity spectra of volcanic rocks exhibit a subtle, but generally detectable, relaxation frequency in the range 0.3 Hz to 45 kHz similar to the relaxation frequency observed for clayey sandstones. We find a fair relationship between this relaxation frequency and the pore size determined by mercury porosimetry. Combined with the intrinsic formation factor of the core samples, the relaxation frequency can be used as an indicator of the permeability of the material. The predicted values of the permeability are grossly consistent with the permeability values to air (in the range 0.001-100 mD) within two orders of magnitude. The measured permeability values are highly correlated to the peak of the pore size distribution determined from mercury porosimetry divided by the intrinsic formation factor. By fitting the complex conductivity spectra with the pore size distribution, we obtain the normalized chargeability of the core samples, which is, in turn, highly correlated to the measured cation exchange capacity (CEC).

  5. Induced polarization of volcanic rocks. 2. Influence of pore size and permeability

    NASA Astrophysics Data System (ADS)

    Revil, A.; Breton, M. Le; Niu, Q.; Wallin, E.; Haskins, E.; Thomas, D. M.

    2017-02-01

    We investigate the relationship between complex conductivity spectra and both permeability and pore mean size and distribution of 22 core samples (21 volcanic rocks and 1 clayey sandstone). The volcanic core samples were extracted from a wellbore drilled for the Humu`ula Groundwater Research Project in the Humu`ula saddle region between Mauna Kea and Mauna Loa volcanoes (Hawaii). The quadrature conductivity spectra of volcanic rocks exhibit a subtle, but generally detectable, relaxation frequency in the range 0.3 Hz to 45 kHz similar to the relaxation frequency observed for clayey sandstones. We find a fair relationship between this relaxation frequency and the pore size determined by mercury porosimetry. Combined with the intrinsic formation factor of the core samples, the relaxation frequency can be used as an indicator of the permeability of the material. The predicted values of the permeability are grossly consistent with the permeability values to air (in the range 0.001-100 mD) within two orders of magnitude. The measured permeability values are highly correlated to the peak of the pore size distribution determined from mercury porosimetry divided by the intrinsic formation factor. By fitting the complex conductivity spectra with the pore size distribution, we obtain the normalized chargeability of the core samples, which is, in turn, highly correlated to the measured cation exchange capacity.

  6. Silica mesostructures: control of pore size and surface area using a surfactant-templated hydrothermal process.

    PubMed

    Ganguly, Aparna; Ahmad, Tokeer; Ganguli, Ashok K

    2010-09-21

    The cooperative self-assembly of the silica precursor, tetraethyl ortho silicate (TEOS), with the surfactant molecule followed by the basic hydrolysis led to the formation of mesoporous silica with varying pore sizes. The pores are formed by the removal of the intermediate assemblies of the charged surfactant molecules. In the absence of formation of such assemblies of surfactants (example in the case of nonionic surfactants), the resulting mesostructures have very small pores, giving low surface area mesostructures. This study outlines the precise control of pore size in a wide size distribution (3.4-22 nm) by the systematic variation of the surfactant. The addition of polyethylene glycol (in situ) while carrying out the hydrolysis of TEOS results in the formation of large-sized cavities (∼40 nm). Uniform spherical particles with pores (different from the cavities) as large as 22 nm and surface areas of ∼1100 m(2)/g have been obtained by the combined effect of the hydrothermal conditions on the cetyl trimethyl ammonium bromide-templated synthesis.

  7. Pore Size Determination Using Frequency-Dependent Electro-Osmosis

    NASA Astrophysics Data System (ADS)

    Reppert, P. M.; Morgan, F. D.

    2001-12-01

    Frequency-dependent electro-osmosis has the potential for use as an alternative method for determining the average pore size of porous media. It has been previously shown for the frequency-dependent streaming potential case that the frequency response of the streaming potential coupling coefficient is directly related to the pore size of the rock. However, a drawback to using frequency-dependent streaming potentials is that it is difficult to generate sufficient pressures at intermediate frequencies where both mechanical and piezoelectric devices are not efficient. Frequency-dependent electro-osmosis does not have this problem since the driving electric field can efficiently be applied in the frequency range of interest. Although the underlying physics of both the frequency-dependent electro-osmosis and frequency-dependent streaming potential cases are similar, there are differences in their frequency responses. Similar to the frequency-dependent streaming potential case, it is shown that the electro-osmosis frequency-dependent coupling coefficient is constant with increasing frequency until the critical frequency is reached, at which time the coupling coefficient starts to decrease with increasing frequency. The frequency response of the electro-osmosis coupling coefficient is dependent on the capillary radius. As the capillary radius decreases, the rollover frequency increases. The theory is developed that demonstrates the rollover frequency for the electro-osmosis frequency response is higher than that for the related streaming potential frequency response for the same size capillary. It is shown that this higher rollover frequency is due to the presence of velocity zeros within the bulk fluid of the capillary which serve to reduce the effective radius of the capillary. Data is presented for a 0.127 mm capillary that supports the theoretical findings. Frequency-dependent electro-osmosis can be used for the laboratory determination of average pore sizes of rocks

  8. Pore Distribution Characteristics of the Igneous Reservoirs in the Eastern Sag of the Liaohe Depression

    NASA Astrophysics Data System (ADS)

    Zongli, Liu; Zhuwen, Wang; Dapeng, Zhou; Shuqin, Zhao; Min, Xiang

    2017-05-01

    In the Es3 formation (third section of the Shahejie) of the Eastern sag section of the Liaohe Depression, basalt and trachyte are predominant in the igneous rock. The reservoir consists of complex reservoir space types. Based on the porosity bins of nuclear magnetic logging and the porosity distribution of electric imaging logging, the pores' sizes and distribution, as well as the mutual connectivity of the reservoir, were analyzed. Also, the characteristics of the different reservoirs were summarized. In regards to the oil reservoirs, large pores (PS>10) were found to account for the majority of the reservoir spaces, and the pore distribution was concentrated and well connected. However, for the poor oil reservoirs, the large and small pores were found to alternate, and the pore distribution was scattered and poorly connected. Within the dry layers, the smaller pores (PS<10) were predominant. The pore distributions were found to be influenced by lithology, facies, and tectonism. The reservoirs of the pyroclastic flow of the explosive facies had good connectivity, and the interlayer heterogeneity was relatively weak. This reservoir's pore distributions were found to be mainly dominated by the larger pores (PS10-PS13), which displayed a concentrated distribution mainly in one porosity bin. Therefore, it was taken as a favorable facie belt in the eastern sag of the Liaohe Depression. The examination of the pore distribution characteristics of the igneous rock was the key to the evaluation of the properties and effectiveness of the igneous reservoirs in this study, which potentially has great significance to the future exploration and development of igneous rock.

  9. Facile fabrication of BiVO4 nanofilms with controlled pore size and their photoelectrochemical performances

    NASA Astrophysics Data System (ADS)

    Feng, Chenchen; Jiao, Zhengbo; Li, Shaopeng; Zhang, Yan; Bi, Yingpu

    2015-12-01

    We demonstrate a facile method for the rational fabrication of pore-size controlled nanoporous BiVO4 photoanodes, and confirmed that the optimum pore-size distributions could effectively absorb visible light through light diffraction and confinement functions. Furthermore, in situ X-ray photoelectron spectroscopy (XPS) reveals more efficient photoexcited electron-hole separation than conventional particle films, induced by light confinement and rapid charge transfer in the inter-crossed worm-like structures.We demonstrate a facile method for the rational fabrication of pore-size controlled nanoporous BiVO4 photoanodes, and confirmed that the optimum pore-size distributions could effectively absorb visible light through light diffraction and confinement functions. Furthermore, in situ X-ray photoelectron spectroscopy (XPS) reveals more efficient photoexcited electron-hole separation than conventional particle films, induced by light confinement and rapid charge transfer in the inter-crossed worm-like structures. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr06584d

  10. An undulation theory for condensation in open end slit pores: critical hysteresis temperature & critical hysteresis pore size.

    PubMed

    Fan, Chunyan; Zeng, Yonghong; Do, D D; Nicholson, D

    2014-06-28

    A new theory of condensation in an open end slit pore, based on the concept of temperature dependent undulation, at the interface separating the adsorbed phase and the gas-like region, is presented. The theory, describes, for the first time, the microscopic origin of the critical hysteresis temperature and the critical hysteresis pore size, properties which are not accessible to any classical theories.

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

    SciTech Connect

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

    2007-08-01

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

  12. Pore size engineering applied to the design of separators for nickel-hydrogen cells and batteries

    NASA Technical Reports Server (NTRS)

    Abbey, K. M.; Britton, D. L.

    1983-01-01

    Pore size engineering in starved alkaline multiplate cells involves adopting techniques to widen the volume tolerance of individual cells. Separators with appropriate pore size distributions and wettability characteristics (capillary pressure considerations) to have wider volume tolerances and an ability to resist dimensional changes in the electrodes were designed. The separators studied for potential use in nickel-hydrogen cells consist of polymeric membranes as well as inorganic microporous mats. In addition to standard measurements, the resistance and distribution of electrolyte as a function of total cell electrolyte content were determined. New composite separators consisting of fibers, particles and/or binders deposited on Zircar cloth were developed in order to engineer the proper capillary pressure characteristics in the separator. These asymmetric separators were prepared from a variety of fibers, particles and binders.

  13. Pore size engineering applied to the design of separators for nickel-hydrogen cells and batteries

    NASA Technical Reports Server (NTRS)

    Abbey, K. M.; Britton, D. L.

    1983-01-01

    Pore size engineering in starved alkaline multiplate cells involves adopting techniques to widen the volume tolerance of individual cells. Separators with appropriate pore size distributions and wettability characteristics (capillary pressure considerations) to have wider volume tolerances and an ability to resist dimensional changes in the electrodes were designed. The separators studied for potential use in nickel-hydrogen cells consist of polymeric membranes as well as inorganic microporous mats. In addition to standard measurements, the resistance and distribution of electrolyte as a function of total cell electrolyte content were determined. New composite separators consisting of fibers, particles and/or binders deposited on Zircar cloth were developed in order to engineer the proper capillary pressure characteristics in the separator. These asymmetric separators were prepared from a variety of fibers, particles and binders. Previously announced in STAR as N83-24571

  14. Hail Size Distribution Mapping

    NASA Technical Reports Server (NTRS)

    2008-01-01

    A 3-D weather radar visualization software program was developed and implemented as part of an experimental Launch Pad 39 Hail Monitor System. 3DRadPlot, a radar plotting program, is one of several software modules that form building blocks of the hail data processing and analysis system (the complete software processing system under development). The spatial and temporal mapping algorithms were originally developed through research at the University of Central Florida, funded by NASA s Tropical Rainfall Measurement Mission (TRMM), where the goal was to merge National Weather Service (NWS) Next-Generation Weather Radar (NEXRAD) volume reflectivity data with drop size distribution data acquired from a cluster of raindrop disdrometers. In this current work, we adapted these algorithms to process data from a cluster of hail disdrometers positioned around Launch Pads 39A or 39B, along with the corresponding NWS radar data. Radar data from all NWS NEXRAD sites is archived at the National Climatic Data Center (NCDC). That data can be readily accessed at . 3DRadPlot plots Level III reflectivity data at four scan elevations (this software is available at Open Channel Software, ). By using spatial and temporal interpolation/extrapolation based on hydrometeor fall dynamics, we can merge the hail disdrometer array data coupled with local Weather Surveillance Radar-1988, Doppler (WSR-88D) radial velocity and reflectivity data into a 4-D (3-D space and time) picture of hail size distributions. Hail flux maps can then be generated and used for damage prediction and assessment over specific surfaces corresponding to structures within the disdrometer array volume. Immediately following a hail storm, specific damage areas and degree of damage can be identified for inspection crews.

  15. Sebum output as a factor contributing to the size of facial pores.

    PubMed

    Roh, M; Han, M; Kim, D; Chung, K

    2006-11-01

    Many endogenous and exogenous factors are known to cause enlarged pilosebaceous pores. Such factors include sex, genetic predisposition, ageing, chronic ultraviolet light exposure, comedogenic xenobiotics, acne and seborrhoea. This study was an attempt to determine the factors related to enlarged pores. To assess the relationship of sebum output, age, sex, hormonal factors and severity of acne with pore size. A prospective, randomized, controlled study was designed. A total of 60 volunteers, 30 males and 30 females, were recruited for this study. Magnified images of pores were taken using a dermoscopic video camera and measured using an image analysis program. The sebum output level was measured with a Sebumeter. Using multiple linear regression analysis, increased pore size was significantly associated with increased sebum output level, sex and age. Among the variables, sebum output level correlated most with the pore size followed by male sex. In comparing male and female participants, males had higher correlation between the sebum output level and the pore size (male: r = 0.47, female: r = 0.38). Thus, additional factors seem to influence pore size in females. Pore size was significantly increased during the ovulation phase (P = 0.008), but severity of acne was not significantly associated with the pore size. Enlarged pore sizes are associated with increased sebum output level, age and male sex. In female patients, additional hormonal factors, such as those of the menstrual cycle, affect the pore size.

  16. Experimental evidence of the role of pores on movement and distribution of bacteria in soil

    NASA Astrophysics Data System (ADS)

    Kravchenko, Alexandra N.; Rose, Joan B.; Marsh, Terence L.; Guber, Andrey K.

    2014-05-01

    It has been generally recognized that micro-scale heterogeneity in soil environments can have a substantial effect on movement, fate, and survival of soil microorganisms. However, only recently the development of tools for micro-scale soil analyses, including X-ray computed micro-tomography (μ-CT), enabled quantitative analyses of these effects. The long-term goal of our work is to explore how differences in micro-scale characteristics of pore structures influence movement, spatial distribution patterns, and activities of soil microorganisms. Using X-ray μ-CT we found that differences in land use and management practices lead to development of contrasting patterns in pore size-distributions within intact soil aggregates. Then our experiments with Escherichia coli added to intact soil aggregates demonstrated that the differences in pore structures can lead to substantial differences in bacteria redistribution and movement within the aggregates. Specifically, we observed more uniform E.coli redistribution in aggregates with homogeneously spread pores, while heterogeneous pore structures resulted in heterogeneous E.coli patterns. Water flow driven by capillary forces through intact aggregate pores appeared to be the main contributor to the movement patterns of the introduced bacteria. Influence of pore structure on E.coli distribution within the aggregates further continued after the aggregates were subjected to saturated water flow. E. coli's resumed movement with saturated water flow and subsequent redistribution within the soil matrix was influenced by porosity, abundance of medium and large pores, pore tortuosity, and flow rates, indicating that greater flow accompanied by less convoluted pores facilitated E. coli transport within the intra-aggregate space. We also found that intra-aggregate heterogeneity of pore structures can have an effect on spatial distribution patterns of indigenous microbial populations. Preliminary analysis showed that in aggregates from

  17. First Synthesis of Continuous Mesoporous Copper Films with Uniformly Sized Pores by Electrochemical Soft Templating.

    PubMed

    Li, Cuiling; Jiang, Bo; Wang, Zhongli; Li, Yunqi; Hossain, Md Shahriar A; Kim, Jung Ho; Takei, Toshiaki; Henzie, Joel; Dag, Ömer; Bando, Yoshio; Yamauchi, Yusuke

    2016-10-04

    Although mesoporous metals have been synthesized by electrochemical methods, the possible compositions have been limited to noble metals (e.g., palladium, platinum, gold) and their alloys. Herein we describe the first fabrication of continuously mesoporous Cu films using polymeric micelles as soft templates to control the growth of Cu under sophisticated electrochemical conditions. Uniformly sized mesopores are evenly distributed over the entire film, and the pore walls are composed of highly crystalized Cu.

  18. Pore-throat sizes in sandstones, siltstones, and shales: Reply

    USGS Publications Warehouse

    Nelson, Philip H.

    2011-01-01

    In his discussion of my article (Nelson, 2009), W. K. Camp takes issue with the concept that buoyancy is not the dominant force in forming and maintaining the distribution of gas in tight-gas accumulations (Camp, 2011). I will restrict my response to the issues he raised regarding buoyant versus nonbuoyant drive and to a few comments regarding water saturation and production. I claim that the pressure generated in petroleum source rocks (Pg), instead of the buoyancy pressure (Pb), provides the energy to charge most tight sandstones with gas. The arguments are fourfold: (1) buoyant columns of sufficient height seldom exist in low-permeability sand-shale sequences, (2) tight-gas systems display a pressure profile that declines instead of increases upward, (3) gas is pervasive in overpressured systems, and (4) source rocks can generate pore pressures sufficiently high to charge tight sandstones.

  19. Pore distribution effect of activated carbon in adsorbing organic micropollutants from natural water.

    PubMed

    Ebie, K; Li, F; Azuma, Y; Yuasa, A; Hagishita, T

    2001-01-01

    Adsorption isotherms of organic micropollutants in coexistence with natural organic matter (NOM) were analyzed to evaluate the impacts of pore size distribution of activated carbon (AC) on the competition effects of the NOM. Single solute adsorption experiments and simultaneous adsorption experiments with NOM contained in a coagulation-pretreated surface water were performed for four agricultural chemicals and three coal-based activated carbons (ACs) having different pore distributions. The results showed that, for all the carbons used, the adsorption capacity of the chemicals was reduced distinctly in the presence of NOM. Such a reduction was more apparent for AC with a larger portion of small pores suitable for the adsorption of small organic molecules and for the agricultural chemicals with a more hydrophilic nature. Ideal adsorbed solution theory (IAST) incorporated with the Freundlich isotherm expression (IAST-Freundlich model) could not interpret the impact of NOM on the adsorption capacity of the chemicals unless a pore blockage effect caused by the adsorption of NOM was also considered. By taking into account this effect, the adsorption isotherm of the chemicals in the presence of NOM was well described, and the capacity reduction caused by the NOM was quantitatively assessed from the viewpoints of the site competition and the pore blockage. Analytical results clearly indicated that pore blockage was an important competition mechanism that contributed to 10-99% of the total capacity reductions of the chemicals, the level depended greatly on the ACs, the chemicals and the equilibrium concentrations, and could possibly be alleviated by broadening the pore size distributions of the ACs to provide a large volume percentage for pores with sizes above 30 A.

  20. Size distributions in urban aerosols

    SciTech Connect

    Lippmann, M.

    1980-01-01

    Data on the size distributions of urban aerosols are reviewed with emphasis on the physical characteristics of the particles. Types of size distributions, the reliability of size distribution data, and factors affecting urban aerosol size distributions are considered. As examples, the grand average number aerosol distribution from the 1969 Los Angeles smog experiment is compared with a Junge power law distribution calculated with the constants of Clark and Whitby. The computer-prepared volume size distribution measured during the General Motors Sulfate Study in Milford, Mich. is presented, the median size distribution by number for the New York Summer Aerosol Study is considered, and volume concentration distributions for Denver-area aerosols are presented.

  1. Pore size and pore throat types in a heterogeneous dolostone reservoir, Devonian Grosmont formation, western Canada sedimentary basin

    SciTech Connect

    Luo, P.; Machel, H. G.

    1995-11-01

    The Devonian Grosmont Formation in northeastern Alberta, Canada, is a giant heavy-oil reservoir. The main reservoir rocks are dolomitized and karstified platform and ramp carbonates, and the best reservoir facies occur in the upper Grosmont (UGM) units 3 and 2. In these units, reservoir properties are highly heterogeneous. Hand specimen, thin section, UV, and SEM petrography, as well as grading scales, mercury capillary pressure curve analysis, and statistics, have been used to characterize reservoir heterogeneity. Our investigation led to a new pore size classification for carbonate reservoirs; this new classification has four pore sizes: microporosity (pore diameters <1 {mu}m), mesoporosity (pore diameters 1-1000 {mu}m), macroporosity (pore diameters 1-256 mm), and megaporosity (pore diameters >256 mm). A combination of microscopic observations and capillary pressure curve characteristics led to the recognition of four pore throat texture types on the microporosity scale, and to five types on the mesoporosity scale. Microporosity pore types include (1) intracrystal dissolution porosity, (2) pervasive intercrystal and intracrystal dissolution porosity, (3) intergranular and/or intercrystal porosity in grainstones, and (4) primary or solution microporosity in mud matrix (only in limestones). Mesoporosity pore types include (1) intercrystal porosity, (2) solution-enhanced intercrystal porosity, (3) oversized porosity, (4) intragranular solution porosity, and (5) intergranular solution porosity. Some of these types are homogeneous (e.g., non-fabric selective dissolution porosity and intercrystal primary porosity), whereas others are heterogeneous. Generally, hydrocarbon recovery efficiency is good in the homogeneous pore throat types, but poor in the heterogeneous types.

  2. Determining the dynamic range of MCPs based on pore size and strip current

    NASA Astrophysics Data System (ADS)

    Hunt, C.; Adrian, M. L.; Herrero, F.; James, P.; Jones, H. H.; Rodriguez, M.; Roman, P.; Shappirio, M.

    2010-12-01

    Micro-Channel Plates (MCPs) are used as detectors for almost all detectors measuring particles (both ions, electrons and neutrals) below 30 keV. Recent advances in the manufacturing technology of the MCPs have increased the number of options one has when selecting plates for an instrument. But it is not clear how many of these options affect the performance of the MCPs. In particular the dynamic range is not a clear cut calculation to make from the strip current. There is also some evidence that pore size and coating play a role. We measured the dynamic range and pulse height distribution of MCPs detector chevron stacks with a wide variety of strip currents from the low “normal” range in the EDR range. We also looked at the effects of varying the pore size from 25 microns to 10 microns, partial plating of the MCP surface and coating one surface on each MCP with gold rather than the standard zinc chromium. We will show how the dynamic range and pulse height distributions vary vs. strip current, pore size, and surface plating configurations.

  3. Pore space analysis of NAPL distribution in sand-clay media

    USGS Publications Warehouse

    Matmon, D.; Hayden, N.J.

    2003-01-01

    This paper introduces a conceptual model of clays and non-aqueous phase liquids (NAPLs) at the pore scale that has been developed from a mathematical unit cell model, and direct micromodel observation and measurement of clay-containing porous media. The mathematical model uses a unit cell concept with uniform spherical grains for simulating the sand in the sand-clay matrix (???10% clay). Micromodels made with glass slides and including different clay-containing porous media were used to investigate the two clays (kaolinite and montmorillonite) and NAPL distribution within the pore space. The results were used to understand the distribution of NAPL advancing into initially saturated sand and sand-clay media, and provided a detailed analysis of the pore-scale geometry, pore size distribution, NAPL entry pressures, and the effect of clay on this geometry. Interesting NAPL saturation profiles were observed as a result of the complexity of the pore space geometry with the different packing angles and the presence of clays. The unit cell approach has applications for enhancing the mechanistic understanding and conceptualization, both visually and mathematically, of pore-scale processes such as NAPL and clay distribution. ?? 2003 Elsevier Science Ltd. All rights reserved.

  4. 3D Scaffold of Electrosprayed Fibers with Large Pore Size for Tissue Regeneration

    PubMed Central

    Hong, Jong Kyu; Madihally, Sundararajan V.

    2010-01-01

    Regeneration of tissues using biodegradable porous scaffolds has been an intensely investigated area. Since electrospinning can produce scaffolds mimicking nanofibrous architecture found in the body, it recently has gained widespread attention. However, a major problem is the lack of pore size necessary for infiltration of cells into the layers below the surface, restricting cell colonization to the surfaces only. This study describes a novel twist to the traditional electrospinning technology. In particular, collector plates are designed which allows forming very thin layers with pore sizes suitable for cell infiltration. Thin samples can be handled without mechanically damaging the structure and can be transferred into cell culture. These thin layers were stacked by layer-by-layer assembly to develop thick structures. Thirty day cultures of fibroblasts show attachment and spreading of cells in every layer. This concept is useful in regenerating thick tissues with uniformly distributed cells and others in vitro cell culture. PMID:20620245

  5. Nuclear magnetic resonance pore size determination for unconsolidated sediments with strong internal gradients

    NASA Astrophysics Data System (ADS)

    Duschl, M.; Pohlmeier, A. J.; Galvosas, P.; Vereecken, H.

    2014-12-01

    Water distribution and flow within porous media are mainly controlled by the pore space structure. Well established methods for the determination of pore sizes like multistep outflow and gas adsorption isotherms (BET) are often time consuming, expensive, or produce toxic waste. As an alternative fast and non-destructive technique, nuclear magnetic resonance (NMR) is used because it probes hydrogen and therefore the dynamics and interactions of water. Pore space is most easily characterized by NMR relaxometry where the total relaxation rate is controlled by the surface relaxivity ρ of the porous medium in combination with the surface-to-volume ratio (S/V) [1]. Furthermore, there are contributions of molecular diffusion through local magnetic field gradients which are created by susceptibility differences between solid and liquid phases [2] as well as by paramagnetic impurities [3]. Hence, surface to volume ratios and surface relaxivities of porous media cannot be measured individually with NMR relaxometry. Therefore, NMR diffusion measurements are applied to probe the S/V of pores without other contributions. In this study, we demonstrate that NMR diffusion measurements are feasible to determine the S/V ratio of the pore space of quartz sand coated with goethite (α-FeOOH) as paramagnetic impurity. Our findings were compared to BET measurements and we found no dependence of the S/V on the coating density with NMR diffusion and a clear dependence between coating density and S/V with krypton BET measurements. Possible explanations are the different characteristic length scales on which the pore space is probed, and the intrinsic fractal nature of porous media [4] together with the roughness of the pore surface on a nm-scale due to the coating process. After isolating the additional contribution of the paramagnetic impurities to the NMR relaxation and the calibration of the NMR relaxation signal for each coating density it was possible to use fast relaxometry

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

    PubMed

    Morishige, Kunimitsu; Tateishi, Masayoshi

    2006-04-25

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

  7. Modelling the influence of pore size on the response of materials to infrared lasers An application to human enamel

    NASA Astrophysics Data System (ADS)

    Vila Verde, A.; Ramos, Marta M. D.

    2005-07-01

    We present an analytical model for a ceramic material (hydroxyapatite, HA) containing nanometre-scale water pores, and use it to estimate the pressure at the pore as a function of temperature at the end of a single 0.35 μs laser pulse by Er:YAG (2.94 μm) and CO 2 (10.6 μm) lasers. Our results suggest that the pressure at the pore is directly related to pore temperature, and that very high pressures can be generated simply by the thermal expansion of liquid water. Since the temperature reached in the pores at the end of the laser pulse is a strong function of pore size for Er:YAG lasers, but is independent of pore size for CO 2 lasers, our present results provide a possible explanation for the fact that human dental enamel threshold ablation fluences vary more for Er:YAG lasers than for CO 2 lasers. This suggests that experimentalists should analyse their results accounting for factors, like age or type of tooth, that may change the pore size distribution in their samples.

  8. Modeling of Microporosity Size Distribution in Aluminum Alloy A356

    NASA Astrophysics Data System (ADS)

    Yao, Lu; Cockcroft, Steve; Zhu, Jindong; Reilly, Carl

    2011-12-01

    Porosity is one of the most common defects to degrade the mechanical properties of aluminum alloys. Prediction of pore size, therefore, is critical to optimize the quality of castings. Moreover, to the design engineer, knowledge of the inherent pore population in a casting is essential to avoid potential fatigue failure of the component. In this work, the size distribution of the porosity was modeled based on the assumptions that the hydrogen pores are nucleated heterogeneously and that the nucleation site distribution is a Gaussian function of hydrogen supersaturation in the melt. The pore growth is simulated as a hydrogen-diffusion-controlled process, which is driven by the hydrogen concentration gradient at the pore liquid interface. Directionally solidified A356 (Al-7Si-0.3Mg) alloy castings were used to evaluate the predictive capability of the proposed model. The cast pore volume fraction and size distributions were measured using X-ray microtomography (XMT). Comparison of the experimental and simulation results showed that good agreement could be obtained in terms of both porosity fraction and size distribution. The model can effectively evaluate the effect of hydrogen content, heterogeneous pore nucleation population, cooling conditions, and degassing time on microporosity formation.

  9. Comprehensive pore structure characterization of silica monoliths with controlled mesopore size and macropore size by nitrogen sorption, mercury porosimetry, transmission electron microscopy and inverse size exclusion chromatography.

    PubMed

    Lubda, Dieter; Lindner, Wolfgang; Quaglia, Milene; du Fresne von Hohenesche, Cedric; Unger, Klaus K

    2005-08-12

    The porosity of monolithic silica columns is measured by using different analytical methods. Two sets of monoliths were prepared with a given mesopore diameter of 10 and 25 nm, respectively and with gradated macropore diameters between 1.8 and 7.5 microm. After preparing the two sets of monolithic silica columns with different macro- and mesopores the internal, external and total porosity of these columns are determined by inverse size-exclusion chromatography (ISEC) using polystyrene samples of narrow molecular size distribution and known average molecular weight. The ISEC data from the 4.6 mm analytical monolithic silica columns are used to determine the structural properties of monolithic silica capillaries (100 microm I.D.) prepared as a third set of samples. The ISEC results illustrate a multimodal mesopore structure (mesopores are pores with stagnant zones) of the monoliths. It is found by ISEC that the ratio of the different types of pores is dependent on the change in diameter of the macropores (serve as flow-through pores). The porosity data achieved from the mercury penetration measurement and nitrogen adsorption as well of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) pictures are correlated with the results we calculated from the ISEC measurements. The ISEC results, namely the multimodal pore structure of the monoliths, reported in several publications, are not confirmed analyzing the pore structures of the different silica monoliths using all other analytical methods.

  10. Characterization of pore scale NAPL morphology in homogeneous sands as a function of grain size and NAPL dissolution.

    PubMed

    Cho, Jaehyun; Annable, Michael D

    2005-11-01

    In this study, we investigate pore scale morphology of nonaqueous phase liquids (NAPLs) trapped in different pore sizes using tracer techniques. Specific interfacial area and saturation of NAPL trapped in homogeneous sands were measured using the interfacial and partitioning tracer techniques. The observed NAPL-water interfacial areas increased in a log-linear fashion with decreasing sand grain size, but showed no clear trend with residual NAPL saturation formed in the various grain sizes. The measured values were used to calculate the NAPL morphology index, which characterizes the spatial NAPL distribution within the pore space. The NAPL morphology indices, increased exponentially with decreasing grain size, indicating that the NAPL becomes smaller, but more blobs. For a fixed grain size, the specific interfacial area and saturation of the NAPL were measured following changes caused by dissolution using alcohol. The observed interfacial areas showed a decrease linearly as a function of the NAPL saturation.

  11. Laser scanning confocal microscopy characterization of water repellent distribution in a sandstone pore network.

    PubMed

    Zoghlami, Karima; Gómez-Gras, David; Corbella, Mercè; Darragi, Fadila

    2008-11-01

    In the present work, we propose the use of the Laser Scanning Confocal Microscopy (LSCM) to determine the effect of water repellents on rock's pore-network configuration and interconnection. The rocks studied are sandstones of Miocene age, a building material that is commonly found in the architectural heritage of Tunisia. The porosity quantitative data of treated and untreated samples, obtained by mercury porosimetry tests, were compared. The results show a slight decrease in total porosity with the water repellent treatment, which reduced both microporosity and macroporosity. This reduction produced a modification in pore size distribution and a shift of the pore access size mode interval toward smaller pore diameters (from the 30-40 microm to the 20-30 microm intervals). The water repellent was observed in SEM images as a continuous film coating grain surfaces; moreover, it was easily visualized in LSCM, by staining the water repellent with Epodye fluorochrome, and the coating thickness was straightforwardly measured (1.5-2 microm). In fact, the combination of mercury intrusion porosimetry data and LSCM observations suggests that the porosity reduction and the shift of the pore diameter mode were mainly due to the general reduction of pore diameters, but also to the plugging of the smallest pores (less than 3-4 microm in diameter) by the water repellent film. Finally, the LSCM technique enabled the reconstruction of 3D views of the water repellent coating film in the pore network, indicating that its distribution was uniform and continuous over the 100 microm thick sample. The LSCM imaging facilitates the integration and interpretation of mercury porosimetry and SEM data.

  12. Direct Measurement of the Critical Pore Size in a Model Membrane.

    PubMed

    Ilton, Mark; DiMaria, Christian; Dalnoki-Veress, Kari

    2016-12-16

    We study pore nucleation in a model membrane system, a freestanding polymer film. Nucleated pores smaller than a critical size close, while pores larger than the critical size grow. Holes of varying size were purposefully prepared in liquid polymer films, and their evolution in time was monitored using optical and atomic force microscopy to extract a critical radius. The critical radius scales linearly with film thickness for a homopolymer film. The results agree with a simple model which takes into account the energy cost due to surface area at the edge of the pore. The energy cost at the edge of the pore is experimentally varied by using a lamellar-forming diblock copolymer membrane. The underlying molecular architecture causes increased frustration at the pore edge resulting in an enhanced cost of pore formation.

  13. Direct Measurement of the Critical Pore Size in a Model Membrane

    NASA Astrophysics Data System (ADS)

    Ilton, Mark; DiMaria, Christian; Dalnoki-Veress, Kari

    2016-12-01

    We study pore nucleation in a model membrane system, a freestanding polymer film. Nucleated pores smaller than a critical size close, while pores larger than the critical size grow. Holes of varying size were purposefully prepared in liquid polymer films, and their evolution in time was monitored using optical and atomic force microscopy to extract a critical radius. The critical radius scales linearly with film thickness for a homopolymer film. The results agree with a simple model which takes into account the energy cost due to surface area at the edge of the pore. The energy cost at the edge of the pore is experimentally varied by using a lamellar-forming diblock copolymer membrane. The underlying molecular architecture causes increased frustration at the pore edge resulting in an enhanced cost of pore formation.

  14. Two micron pore size MCP-based image intensifiers

    NASA Astrophysics Data System (ADS)

    Glesener, John; Estrera, Joseph

    2010-02-01

    Image intensifiers (I2) have many advantages as detectors. They offer single photon sensitivity in an imaging format, they're light in weight and analog I2 systems can operate for hours on a single AA battery. Their light output is such as to exploit the peak in color sensitivity of the human eye. Until recent developments in CMOS sensors, they also were one of the highest resolution sensors available. The closest all solid state solution, the Texas Instruments Impactron chip, comes in a 1 megapixel format. Depending on the level of integration, an Impactron based system can consume 20 to 40 watts in a system configuration. In further investing in I2 technology, L-3 EOS determined that increasing I2 resolution merited a high priority. Increased I2 resolution offers the system user two desirable options: 1) increased detection and identification ranges while maintaining field-of-view (FOV) or 2) increasing FOV while maintaining the original system resolution. One of the areas where an investment in resolution is being made is in the microchannel plate (MCP). Incorporation of a 2 micron MCP into an image tube has the potential of increasing the system resolution of currently fielded systems. Both inverting and non-inverting configurations are being evaluated. Inverting tubes are being characterized in night vision goggle (NVG) and sights. The non-inverting 2 micron tube is being characterized for high resolution I2CMOS camera applications. Preliminary measurements show an increase in the MTF over a standard 5 micron pore size, 6 micron pitch plate. Current results will be presented.

  15. Discontinuous pore fluid distribution under microgravity--KC-135 flight investigations.

    PubMed

    Reddi, Lakshmi N; Xiao, Ming; Steinberg, Susan L

    2005-01-01

    Designing a reliable plant growth system for crop production in space requires the understanding of pore fluid distribution in porous media under microgravity. The objective of this experimental investigation, which was conducted aboard NASA KC-135 reduced gravity flight, is to study possible particle separation and the distribution of discontinuous wetting fluid in porous media under microgravity. KC-135 aircraft provided gravity conditions of 1, 1.8, and 10(-2) g. Glass beads of a known size distribution were used as porous media; and Hexadecane, a petroleum compound immiscible with and lighter than water, was used as wetting fluid at residual saturation. Nitrogen freezer was used to solidify the discontinuous Hexadecane ganglia in glass beads to preserve the ganglia size changes during different gravity conditions, so that the blob-size distributions (BSDs) could be measured after flight. It was concluded from this study that microgravity has little effect on the size distribution of pore fluid blobs corresponding to residual saturation of wetting fluids in porous media. The blobs showed no noticeable breakup or coalescence during microgravity. However, based on the increase in bulk volume of samples due to particle separation under microgravity, groups of particles, within which pore fluid blobs were encapsulated, appeared to have rearranged themselves under microgravity.

  16. Discontinuous pore fluid distribution under microgravity--KC-135 flight investigations

    NASA Technical Reports Server (NTRS)

    Reddi, Lakshmi N.; Xiao, Ming; Steinberg, Susan L.

    2005-01-01

    Designing a reliable plant growth system for crop production in space requires the understanding of pore fluid distribution in porous media under microgravity. The objective of this experimental investigation, which was conducted aboard NASA KC-135 reduced gravity flight, is to study possible particle separation and the distribution of discontinuous wetting fluid in porous media under microgravity. KC-135 aircraft provided gravity conditions of 1, 1.8, and 10(-2) g. Glass beads of a known size distribution were used as porous media; and Hexadecane, a petroleum compound immiscible with and lighter than water, was used as wetting fluid at residual saturation. Nitrogen freezer was used to solidify the discontinuous Hexadecane ganglia in glass beads to preserve the ganglia size changes during different gravity conditions, so that the blob-size distributions (BSDs) could be measured after flight. It was concluded from this study that microgravity has little effect on the size distribution of pore fluid blobs corresponding to residual saturation of wetting fluids in porous media. The blobs showed no noticeable breakup or coalescence during microgravity. However, based on the increase in bulk volume of samples due to particle separation under microgravity, groups of particles, within which pore fluid blobs were encapsulated, appeared to have rearranged themselves under microgravity.

  17. A general diagram for estimating pore size of ultrafiltration and reverse osmosis membranes

    NASA Technical Reports Server (NTRS)

    Sarbolouki, M. N.

    1982-01-01

    A slit sieve model has been used to develop a general correlation between the average pore size of the upstream surface of a membrane and the molecular weight of the solute which it retains by better than 80%. The pore size is determined by means of the correlation using the high retention data from an ultrafiltration (UF) or a reverse osmosis (RO) experiment. The pore population density can also be calculated from the flux data via appropriate equations.

  18. A general diagram for estimating pore size of ultrafiltration and reverse osmosis membranes

    NASA Technical Reports Server (NTRS)

    Sarbolouki, M. N.

    1982-01-01

    A slit sieve model has been used to develop a general correlation between the average pore size of the upstream surface of a membrane and the molecular weight of the solute which it retains by better than 80%. The pore size is determined by means of the correlation using the high retention data from an ultrafiltration (UF) or a reverse osmosis (RO) experiment. The pore population density can also be calculated from the flux data via appropriate equations.

  19. Processing and Characterization of Porous Ti2AlC with Controlled Porosity and Pore Size

    DTIC Science & Technology

    2012-09-11

    fabricated by spark plasma sintering , were also characterized. The effects of porosity and/or pore size on the room temperature elastic moduli...pressureless- sintered without NaCl pore former, or fabricated by spark plasma sintering , were also characterized. The effects of porosity and/or pore size...as well as several samples sintered using spark plasma sintering (SPS). Furthermore, we demon- strate that the developed methodology can be implemented

  20. Determination of the pore size of woven structures through image analysis

    NASA Astrophysics Data System (ADS)

    Angelova, R. A.

    2012-03-01

    The paper presents an experimental procedure developed for determination of the pore size, shape and distribution in a single layer woven fabric, for the construction of a virtual model to be incorporated in a future CFD software package. The procedure is based on non-destructive observation and analysis of woven samples. 14 different samples of gray fabrics of 100 % cotton in plain and twill weaves are investigated. The results obtained allow the creation of reality more realistic virtual model of the woven structure, and theoretical investigation of its porosity and permeability through computer simulation.

  1. Microporous polyphenylenes with tunable pore size for hydrogen storage.

    PubMed

    Yuan, Shengwen; Dorney, Brian; White, Desiree; Kirklin, Scott; Zapol, Peter; Yu, Luping; Liu, Di-Jia

    2010-07-07

    A series of highly porous polymers with similar BET surface areas of higher than 1000 m(2) g(-1) but tunable pore ranging from 0.7 nm to 0.9 nm were synthesized through facile ethynyl trimerization reaction to demonstrate the surface property-hydrogen adsorption relationship.

  2. Microporous polyphenylenes with tunable pore size for hydrogen storage.

    SciTech Connect

    Yuan, S.; Dorney, B.; White, D.; Kirklin, S.; Zapol, P.; Yu, L.; Liu, D. J.; Univ. of Chicago

    2010-01-01

    A series of highly porous polymers with similar BET surface areas of higher than 1000 m2 g-1 but tunable pore ranging from 0.7 nm to 0.9 nm were synthesized through facile ethynyl trimerization reaction to demonstrate the surface property-hydrogen adsorption relationship.

  3. Slow Desorption of Phenanthrene from Silica Particles: Influence of Pore Size, Pore Water, and Aging Time

    SciTech Connect

    Huesemann, Michael H.; Fortman, Timothy J.; Riley, Robert G.; Thompson, Christopher J.; Wang, Zheming; Truex, Michael J.; Peyton, Brent M.

    2006-01-16

    When micro-porous and meso-porous silica particles were exposed to aqueous phenanthrene solutions for various durations it was observed that sorbed-phase phenanthrene concentrations increased with aging time only for meso-porous but not micro-porous silicas. Desorption equilibrium was reached almost instantaneously for the micro-porous particles while both the rate and extent of desorption decreased with increasing aging time for the meso-porous silicas. These findings indicate that phenanthrene can be sequestered within the internal pore-space of meso-porous silicas while the internal surfaces of micro-porous silicas are not accessible to phenanthrene sorption, possibly due to the presence of physi- or chemi-sorbed water that may sterically hinder the diffusion of phenanthrene inside water-filled micro-pores. By contrast, the internal surfaces of these micro-porous silicas are accessible to phenanthrene when aging methods are employed which assure that pores are devoid of physi-sorbed water. Consequently, when phenanthrene was incorporated into these particles using either supercritical CO2 or via solvent soaking, the aqueous desorption kinetics were extremely slow indicating effective sequestration of phenanthrene inside micro-porous particles. Finally, a two-compartment conceptual model is used to interpret the experimental findings.

  4. A direct and quantitative three-dimensional reconstruction of the internal structure of disordered mesoporous carbon with tailored pore size.

    PubMed

    Balach, Juan; Soldera, Flavio; Acevedo, Diego F; Mücklich, Frank; Barbero, César A

    2013-06-01

    A new technique that allows direct three-dimensional (3D) investigations of mesopores in carbon materials and quantitative characterization of their physical properties is reported. Focused ion beam nanotomography (FIB-nt) is performed by a serial sectioning procedure with a dual beam FIB-scanning electron microscopy instrument. Mesoporous carbons (MPCs) with tailored mesopore size are produced by carbonization of resorcinol-formaldehyde gels in the presence of a cationic surfactant as a pore stabilizer. A visual 3D morphology representation of disordered porous carbon is shown. Pore size distribution of MPCs is determined by the FIB-nt technique and nitrogen sorption isotherm methods to compare both results. The obtained MPCs exhibit pore sizes of 4.7, 7.2, and 18.3 nm, and a specific surface area of ca. 560 m(2)/g.

  5. Effect on the Pore-Size Dependence of an Organic Electrolyte Supercapacitor

    SciTech Connect

    Jiang, Deen; Jin, Zhehui; Henderson, Douglous; Wu, Jianzhong

    2012-01-01

    Organic electrolytes such as tetraethylammonium tetrafluoroborate dissolved in acetonitrile (TEA-BF{sub 4}/ACN) are widely used in commercial supercapacitors and academic research, but conflicting experimental results have been reported regarding the dependence of surface-area-normalized capacitance on the pore size. Here we show from a classical density functional theory the dependence of capacitance on the pore size from 0.5 to 3.0 nm for a model TEA-BF{sub 4}/ACN electrolyte. We find that the capacitance-pore size curve becomes roughly flat after the first peak around the ion diameter, and the peak capacitance is not significantly higher than the large-pore average. We attribute the invariance of capacitance with the pore size to the formation of an electric double-layer structure that consists of counterions and highly organized solvent molecules. This work highlights the role of the solvent molecules in modulating the capacitance and reconciles apparently conflicting experimental reports.

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

    NASA Astrophysics Data System (ADS)

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

    2016-11-01

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

  7. Pore-size-dependent calcium carbonate precipitation controlled by surface chemistry.

    PubMed

    Stack, Andrew G; Fernandez-Martinez, Alejandro; Allard, Lawrence F; Bañuelos, José L; Rother, Gernot; Anovitz, Lawrence M; Cole, David R; Waychunas, Glenn A

    2014-06-03

    Induced mineral precipitation is potentially important for the remediation of contaminants, such as during mineral trapping during carbon or toxic metal sequestration. The prediction of precipitation reactions is complicated by the porous nature of rocks and soils and their interaction with the precipitate, introducing transport and confinement effects. Here X-ray scattering measurements, modeling, and electron microscopies were used to measure the kinetics of calcium carbonate precipitation in a porous amorphous silica (CPG) that contained two discrete distributions of pore sizes: nanopores and macropores. To examine the role of the favorability of interaction between the substrate and precipitate, some of the CPG was functionalized with a self-assembled monolayer (SAM) similar to those known to enhance nucleation densities on planar substrates. Precipitation was found to occur exclusively in macropores in the native CPG, while simultaneous precipitation in nanopores and macropores was observed in the functionalized CPG. The rate of precipitation in the nanopores estimated from the model of the X-ray scattering matched that measured on calcite single crystals. These results suggest that the pore-size distribution in which a precipitation reaction preferentially occurs depends on the favorability of interaction between substrate and precipitate, something not considered in most studies of precipitation in porous media.

  8. Magnetic relaxation - coal swelling, extraction, pore size. Final technical report

    SciTech Connect

    Doetschman, D.C.

    1994-10-26

    The aim of the contract was to employ electron and nuclear magnetic relaxation techniques to investigate solvent swelling of coals, solvent extraction of coals and molecular interaction with solvent coal pores. Many of these investigations have appeared in four major publications and a conference proceedings. Another manuscript has been submitted for publication. The set of Argonne Premium Coals was chosen as extensively characterized and representative samples for this project.

  9. Tailoring Pore Size and Chemical Interior of near 1 nm Sized Pores in a Nanoporous Polymer Based on a Discotic Liquid Crystal

    PubMed Central

    2017-01-01

    A triazine based disc shaped molecule with two hydrolyzable units, imine and ester groups, was polymerized via acyclic diene metathesis in the columnar hexagonal (Colhex) LC phase. Fabrication of a cationic nanoporous polymer (pore diameter ∼1.3 nm) lined with ammonium groups at the pore surface was achieved by hydrolysis of the imine linkage. Size selective aldehyde uptake by the cationic porous polymer was demonstrated. The anilinium groups in the pores were converted to azide as well as phenyl groups by further chemical treatment, leading to porous polymers with neutral functional groups in the pores. The pores were enlarged by further hydrolysis of the ester groups to create ∼2.6 nm pores lined with −COONa surface groups. The same pores could be obtained in a single step without first hydrolyzing the imine linkage. XRD studies demonstrated that the Colhex order of the monomer was preserved after polymerization as well as in both the nanoporous polymers. The porous anionic polymer lined with −COOH groups was further converted to the −COOLi, −COONa, −COOK, −COOCs, and −COONH4 salts. The porous polymer lined with −COONa groups selectively adsorbs a cationic dye, methylene blue, over an anionic dye. PMID:28416888

  10. Hydrogen Storage Properties of Rigid Three-Dimensional Hofmann Clathrate Derivatives: The Effects of Pore Size

    SciTech Connect

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

    2008-05-01

    The effects of pore size on the hydrogen storage properties of a series of pillared layered solids based on the M(L)[M'(CN)4] structural motif, where M ) Co or Ni, L ) pyrazine (pyz), 4,4'-bipyridine (bpy), or 4,4'-dipyridylacetylene (dpac), and M' ) Ni, Pd, or Pt, has been investigated. The compounds all possess slitlike pores with constant in-plane dimensions and similar organic functionality. The pore heights vary as a function of L and provide a means for a systematic investigation of the effects of pore dimension on hydrogen storage properties in porous materials. Hydrogen isotherms were measured at 77 and 87 K up to a pressure of 1 atm. The pyz pillared materials with the smallest pore dimensions store hydrogen at a pore density similar to that of liquid hydrogen. The adsorbed hydrogen density drops by a factor of 2 as the relative pore size is tripled in the dpac material. The decreased storage efficiency diminishes the expected gravimetric gain in capacity for the larger pore materials. The heats of adsorption were found to range from 6 to 8 kJ/mol in the series and weakly correlate with pore size.

  11. Quantifying pore size and density for membranes in the Knudsen and transitional-flow regimes

    NASA Astrophysics Data System (ADS)

    Castellano, Richard; Purri, Matthew; Hernandez, Erick; Shan, Jerry; Bui, Ngoc; Chen, Chiati; Meshot, Eric; Fornasiero, Francesco

    2016-11-01

    Membranes with well-controlled nanoscale pores have interest for applications as diverse as chemical separations, water purification, and "green" power generation. For instance, membranes incorporating carbon nanotubes (CNTs) as through-pores have been shown to pass fluids orders-of-magnitude faster than predicted by theory. However, the efficient characterization of the pore size and density of membranes is an important area of focus, particularly for membranes fabricated from bulk nanotubes. Here, we report on a new technique to identify the pore size (d) and number of open pores (N) in membranes. A nanoporous membrane is characterized with a combination of pressure-driven gas flow, and electrical-conductance measurements in aqueous solution. For the conductance measurements, the electrical current passing through the membrane scales as d2 N . For pressurized gas flow, the scaling with molecular weight (M) and gas viscosity (μ) identifies the flow as either Poiseuille or Knudsen, scaling as either d4N/ μ or d3 N /M 1 / 2 , respectively. With this combination of measurements, the pore size and number of pores in the membrane can be calculated. We validate this technique using track-etched polycarbonate membranes and CNT membranes with known pores, and show that it can be used to count open pores and identify defects in CNT membranes. We would like to acknowledge DTRA for their funding and support of our research.

  12. Hydrogen Storage Properties of Rigid Three-Dimensional Hofmann Clathrate Derivatives: The Effects of Pore Size

    SciTech Connect

    Culp, Jeffery T.; Natesakhawat, Sittichai; Smith, Milton R.; Bittner, Edward; Matranga, Christopher; Bockrath, Bradley

    2008-05-01

    The effects of pore size on the hydrogen storage properties of a series of pillared layered solids based on the M(L)[M'(CN)(4)] structural motif, where M = Co or Ni, L = pyrazine (pyz), 4,4'-bipyridine (bpy), or 4,4'-dipyridylacetylene (dpac), and M' = Ni, Pd, or Pt, has been investigated. The compounds all possess slitlike pores with constant in-plane dimensions and similar organic functionality. The pore heights vary as a function of L and provide a means for a systematic investigation of the effects of pore dimension on hydrogen storage properties in porous materials. Hydrogen isotherms were measured at 77 and 87 K up to a pressure of 1 atm. The pyz pillared materials with the smallest pore dimensions store hydrogen at a pore density similar to that of liquid hydrogen. The adsorbed hydrogen density drops by a factor of 2 as the relative pore size is tripled in the dpac material. The decreased storage efficiency diminishes the expected gravimetric gain in capacity for the larger pore materials. The heats of adsorption were found to range from 6 to 8 kJ/mol in the series and weakly correlate with pore size.

  13. Estimation of pore size in a microstructure phantom using the optimised gradient waveform diffusion weighted NMR sequence.

    PubMed

    Siow, Bernard; Drobnjak, Ivana; Chatterjee, Aritrick; Lythgoe, Mark F; Alexander, Daniel C

    2012-01-01

    There has been increasing interest in nuclear magnetic resonance (NMR) techniques that are sensitive to diffusion of molecules containing NMR visible nuclei for the estimation of microstructure parameters. A microstructure parameter of particular interest is pore radius distribution. A recent in silico study optimised the shape of the gradient waveform in diffusion weighted spin-echo experiments for estimating pore size. The study demonstrated that optimised gradient waveform (GEN) protocols improve pore radius estimates compared to optimised pulse gradient spin-echo (PGSE) protocols, particularly at shorter length scales. This study assesses the feasibility of implementing GEN protocols on a small bore 9.4 T scanner and verifies their additional sensitivity to pore radius. We implement GEN and PGSE protocols optimised for pore radii of 1, 2.5, 5, 7.5, 10 μm and constrained to maximum gradient strengths of 40, 80, 200 mT m(-1). We construct microstructure phantoms, which have a single pore radius for each phantom, using microcapillary fibres. The measured signal shows good agreement with simulated signal, strongly indicating that the GEN waveforms can be implemented on a 9.4 T system. We also demonstrate that GEN protocols provide improved sensitivity to the smaller pore radii when compared to optimised PGSE protocols, particularly at the lower gradient amplitudes investigated in this study. Our results suggest that this improved sensitivity of GEN protocols would be reflected in clinical scenarios.

  14. Use of intradermal botulinum toxin to reduce sebum production and facial pore size.

    PubMed

    Shah, Anil R

    2008-09-01

    Review the safety profile and subjective efficacy of intradermal botulinum toxin type A in facial pore size and sebum production. Retrospective analysis of 20 patients. Twenty consecutive patients with a single application of intradermal botulinum toxin type A were examined: Patients (17/20) noted an improvement in sebum production and a decrease in pores size at 1 month after injection. No complications were observed, and 17/20 patients were satisfied with the procedure. Preliminary data suggests that intradermal botulinum toxin may play a role in decreasing sebum production. Further quantitive study may be necessary to determine effects of intradermal botulinum toxin on pore size.

  15. Pore Distribution and Water Uptake in a Cenosphere-Cement Paste Composite Material

    NASA Astrophysics Data System (ADS)

    Baronins, J.; Setina, J.; Sahmenko, G.; Lagzdina, S.; Shishkin, A.

    2015-11-01

    Alumina silicate cenospheres (CS) is a significant waste material from power plants that use a coal. Use CS as Portland cement replacement material gives opportunity to control physical and mechanical properties and makes a product lighter and more cost-effective. In the frame of this study, Portland cement paste samples were produced by adding CS in the concentration range from 0 to 40 volume %. Water uptake of hardened samples was checked and pore size distribution by using the mercury porosimetry was determined. In a cold climate where the temperature often falls below 0 °C, it is important to avoid the amount of micrometer sized pores in the final structure and to decrease water absorption capacity of material. In winter conditions, water fills such pores and causes additional stresses to their walls by expansion while freezing. It was found that generally water uptake capacity for cement paste samples decreased up to 20% by increasing the concentration of CS up to 40 volume %, at the same time, the volume of micrometer sized opened pores increases.

  16. Improving prediction of hydraulic conductivity by constraining capillary bundle models to a maximum pore size

    NASA Astrophysics Data System (ADS)

    Iden, Sascha; Peters, Andre; Durner, Wolfgang

    2017-04-01

    Soil hydraulic properties are required to solve the Richards equation, the most widely applied model for variably-saturated flow. While the experimental determination of the water retention curve does not pose significant challenges, the measurement of unsaturated hydraulic conductivity is time consuming and costly. The prediction of the unsaturated hydraulic conductivity curve from the soil water retention curve by pore-bundle models is a cost-effective and widely applied technique. A well-known problem of conductivity prediction for retention functions with wide pore-size distributions is the sharp drop in conductivity close to water saturation. This problematic behavior is well known for the van Genuchten model if the shape parameter n assumes values smaller than about 1.3. So far, the workaround for this artefact has been to introduce an explicit air-entry value into the capillary saturation function. However, this correction leads to a retention function which is not continuously differentiable and thus a discontinuous water capacity function. We present an improved parametrization of the hydraulic properties which uses the original capillary saturation function and introduces a maximum pore radius only in the pore-bundle model. Closed-form equations for the hydraulic conductivity function were derived for the unimodal and multimodal retention functions of van Genuchten and have been tested by sensitivity analysis and applied in curve fitting and inverse modeling of multistep outflow experiments. The resulting hydraulic conductivity function is smooth, increases monotonically close to saturation, and eliminates the sharp drop in conductivity close to saturation. Furthermore, the new model retains the smoothness and continuous differentiability of the water retention curve. We conclude that the resulting soil hydraulic functions are physically more reasonable than the ones predicted by previous approaches, and are thus ideally suited for numerical simulations

  17. Controlling the pore sizes and related properties of inverse opal scaffolds for tissue engineering applications.

    PubMed

    Zhang, Yu Shrike; Regan, Kevin P; Xia, Younan

    2013-03-25

    Inverse opal scaffolds are finding widespread use in tissue engineering and regenerative medicine. Herein, the way in which the pore sizes and related physical properties of poly(D,L-lactide-co-glycolide) inverse opal scaffolds are affected by the fabrication conditions is systematically investigated. It is found that the window size of an inverse opal scaffold is mainly determined by the annealing temperature rather than the duration of time, and the surface pore size is largely determined by the concentration of the infiltration solution. Although scaffolds with larger pore or window sizes facilitate faster migration of cells, they show slightly lower compressive moduli than scaffolds with smaller pore or window sizes. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Analysis and Visualization of 2D and 3D Grain and Pore Size ofFontainebleau Sandstone Using Digital Rock Physics

    NASA Astrophysics Data System (ADS)

    Latief, FDE

    2016-08-01

    Fontainebleau sandstone is sandstone found in one of the cities in France. This sandstone has unique characteristics, which is a clean-fme sandstone, composed of 99% quartz, virtually devoid of clay, with the grain size of about 200 μm. Fontainebleau sandstone is widely used as a reference in the study of rock microstructure analysis and modelling. In this work analysis regarding the grain and pore size of Fontainebleau is presented. Calculation of 2D pore size and grain size distribution were done on the 299 slice of digital image of the Fontainebleau sandstone using Feret's diameters, equivalent diameters (d = 4A/P), and by means of local thickness/separation using plate model. For the 3D grain and pore size distribution, calculation of local thickness and local separation of the structure were used. Two dimensional analysis by means of Feret's diameter and equivalent diameter reveal that both grain and pore size distributions are in the form of reverse-J shaped (right skewed) while the local thickness/separation approach produces almost similar to symmetric Gaussian distribution. Three dimensional analysis produces fairly symmetric Gaussian distribution for both the grain and pore size. Further image processing were conducted and were succeed in producing three dimensional visual of the colour coded structure thickness (grain related) and structure separation (pore related).

  19. Modulation of Asymmetric Flux in Heterotypic Gap Junctions by Pore Shape, Particle Size and Charge.

    PubMed

    Mondal, Abhijit; Sachse, Frank B; Moreno, Alonso P

    2017-01-01

    Gap junction channels play a vital role in intercellular communication by connecting cytoplasm of adjoined cells through arrays of channel-pores formed at the common membrane junction. Their structure and properties vary depending on the connexin isoform(s) involved in forming the full gap junction channel. Lack of information on the molecular structure of gap junction channels has limited the development of computational tools for single channel studies. Currently, we rely on cumbersome experimental techniques that have limited capabilities. We have earlier reported a simplified Brownian dynamics gap junction pore model and demonstrated that variations in pore shape at the single channel level can explain some of the differences in permeability of heterotypic channels observed in in vitro experiments. Based on this computational model, we designed simulations to study the influence of pore shape, particle size and charge in homotypic and heterotypic pores. We simulated dye diffusion under whole cell voltage clamping. Our simulation studies with pore shape variations revealed a pore shape with maximal flux asymmetry in a heterotypic pore. We identified pore shape profiles that match the in silico flux asymmetry results to the in vitro results of homotypic and heterotypic gap junction formed out of Cx43 and Cx45. Our simulation results indicate that the channel's pore-shape established flux asymmetry and that flux asymmetry is primarily regulated by the sizes of the conical and/or cylindrical mouths at each end of the pore. Within the set range of particle size and charge, flux asymmetry was found to be independent of particle size and directly proportional to charge magnitude. While particle charge was vital to creating flux asymmetry, charge magnitude only scaled the observed flux asymmetry. Our studies identified the key factors that help predict asymmetry. Finally, we suggest the role of such flux asymmetry in creating concentration imbalances of messenger

  20. Nuclear size, nuclear pore number and cell cycle.

    PubMed

    Maeshima, Kazuhiro; Iino, Haruki; Hihara, Saera; Imamoto, Naoko

    2011-01-01

    In eukaryotic cells, the nucleus is a complex and sophisticated organelle containing genomic DNA and supports essential cellular activities. Its surface contains many nuclear pore complexes (NPCs), channels for macromolecular transport between the cytoplasm and nucleus. It has been observed that the nuclear volume and the number of NPCs almost doubles during interphase in dividing cells, but the coordination of these events with the cell cycle was poorly understood, particularly in mammalian cells. Recently, we demonstrated that cyclin-dependent protein kinases (Cdks) control interphase NPC formation in dividing human cells. Cdks drive the very early step of NPC formation because Cdk inhibition suppressed the generation of "nascent pores," which are considered to be immature NPCs, and disturbed expression and localization of some nucleoporins. Cdk inhibition did not affect nuclear volume, suggesting that these two processes have distinct regulatory mechanisms in the cell cycle. The details of our experimental systems and finding are discussed in more depth. With new findings recently reported, we also discuss possible molecular mechanisms of interphase NPC formation.

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

    NASA Astrophysics Data System (ADS)

    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

  2. Pore-size dependent effects on structure and vibrations of 1-ethyl-3-methylimidazolium tetrafluoroborate in nanoporous carbon

    NASA Astrophysics Data System (ADS)

    Thürmer, Stephan; Kobayashi, Yoshikazu; Ohba, Tomonori; Kanoh, Hirofumi

    2015-09-01

    We report XRD and IR measurements of 1-ethyl-3-methylimidazolium tetrafluoroborate (EMI-BF4) adsorbed in activated carbons, molecular sieving carbon, and single wall carbon nanohorn, where we specifically chose a wide range of pore sizes from 0.5 nm to 2.5 nm. Electron radial distribution function analysis reveals denser packing upon adsorption in two steps, for pore widths larger and comparable to the ion size. Average ion-distance was decreased by 0.05 nm in the latter case. With support of DFT calculations we identify a suppression of specific vibrational modes, which are interpreted as constrainment by the pore walls. Possible consequences for supercapacitor application are discussed.

  3. Role of Pore Size Location in Determining Bacterial Activity during Predation by Protozoa in Soil.

    PubMed

    Wright, D A; Killham, K; Glover, L A; Prosser, J I

    1995-10-01

    The predation of a luminescence-marked strain of Pseudomonas fluorescens by the soil ciliate Colpoda steinii was studied in soil microcosms. Bacterial cells were introduced in either small (neck diameter, <6 (mu)m) or intermediate-sized (neck diameter, 6 to 30 (mu)m) pores in the soil by inoculation at appropriate matric potentials, and ciliates were introduced into large pores (neck diameter, 30 to 60 (mu)m). Viable cell concentrations of bacteria introduced into intermediate-sized pores decreased at a greater rate than those in small pores, with reductions in bacterial populations being accompanied by an increase in viable cell numbers of the ciliate. The data indicate that the location of bacteria in small pores provides significant protection from predation. In the absence of C. steinii, the level of metabolic activity of the bacterial population, measured by luminometry, decreased at a greater rate than cell number, and the level of luminescence cell(sup-1) consequently decreased. The decrease in levels of luminescence indicates a loss of activity due to starvation. During predation by C. steinii, the level of the activity of cells introduced into small pores fell in a similar manner. The level of cell activity was, however, significantly greater for cells introduced into intermediate-sized pores, despite their greater susceptibility to predation. The data suggest that increased activity arises from a release of nutrients by the predator and the greater accessibility of bacteria to nutrients in larger pores. Nutrient amendment of microcosms resulted in increases in bacterial populations to sustained, higher levels, while levels of luminescence increased transiently. The predation of cells introduced into intermediate-sized pores was greater, and there was also evidence that the level of activity of surviving bacteria was greater for bacteria in intermediate-sized but not small pores.

  4. Centaur size distribution with DECam

    NASA Astrophysics Data System (ADS)

    Fuentes, Cesar; Trilling, David E.; Schlichting, Hilke

    2014-11-01

    We present the results of the 2014 centaur search campaign on the Dark Energy Camera (DECam) in Tololo, Chile. This is the largest debiased Centaur survey to date, measuring for the first time the size distribution of small Centaurs (1-10km) and the first time the sizes of planetesimals from which the entire Solar System formed are directly detected.The theoretical model for the coagulation and collisional evolution of the outer solar system proposed in Schlichting et al. 2013 predicts a steep rise in the size distribution of TNOs smaller than 10km. These objects are below the detection limit of current TNO surveys but feasible for the Centaur population. By constraining the number of Centaurs and this feature in their size distribution we can confirm the collisional evolution of the Solar System and estimate the rate at which material is being transferred from the outer to the inner Solar System. If the shallow power law behavior from the TNO size distribution at ~40km can be extrapolated to 1km, the size of the Jupiter Family of Comets (JFC), there would not be enough small TNOs to supply the JFC population (Volk & Malhotra, 2008), debunking the link between TNOs and JFCs.We also obtain the colors of small Centaurs and TNOs, providing a signature of collisional evolution by measuring if there is in fact a relationship between color and size. If objects smaller than the break in the TNO size distribution are being ground down by collisions then their surfaces should be fresh, and then appear bluer in the optical than larger TNOs that are not experiencing collisions.

  5. Pore distribution and material properties of bone cement cured at different temperatures.

    PubMed

    Pelletier, Matthew H; Lau, Abe C B; Smitham, Peter J; Nielsen, Gary; Walsh, William R

    2010-03-01

    Implant heating has been advocated as a means to alter the porosity of the bone cement/implant interface; however, little is known about the influence on cement properties. This study investigates the mechanical properties and pore distribution of 10 commercially available cements cured in molds at 20, 37, 40 and 50 degrees Celsius. Although each cement reacted differently to the curing environments, the most prevalent trend was increased mechanical properties when cured at 50 degrees Celsius vs. room temperature. Pores were shown to gather near the surface of cooler molds and near the center in warmer molds for all cement brands. Pore size was also influenced. Small pores were more often present in cements cured at cooler temperatures, with higher-temperature molds producing more large pores. The mechanical properties of all cements were above the minimum regulatory standards. This work shows the influence of curing temperature on cement properties and porosity characteristics, and supports the practice of heating cemented implants to influence interfacial porosity.

  6. Detection, 3-D positioning, and sizing of small pore defects using digital radiography and tracking

    NASA Astrophysics Data System (ADS)

    Lindgren, Erik

    2014-12-01

    This article presents an algorithm that handles the detection, positioning, and sizing of submillimeter-sized pores in welds using radiographic inspection and tracking. The possibility to detect, position, and size pores which have a low contrast-to-noise ratio increases the value of the nondestructive evaluation of welds by facilitating fatigue life predictions with lower uncertainty. In this article, a multiple hypothesis tracker with an extended Kalman filter is used to track an unknown number of pore indications in a sequence of radiographs as an object is rotated. Each pore is not required to be detected in all radiographs. In addition, in the tracking step, three-dimensional (3-D) positions of pore defects are calculated. To optimize, set up, and pre-evaluate the algorithm, the article explores a design of experimental approach in combination with synthetic radiographs of titanium laser welds containing pore defects. The pre-evaluation on synthetic radiographs at industrially reasonable contrast-to-noise ratios indicate less than 1% false detection rates at high detection rates and less than 0.1 mm of positioning errors for more than 90% of the pores. A comparison between experimental results of the presented algorithm and a computerized tomography reference measurement shows qualitatively good agreement in the 3-D positions of approximately 0.1-mm diameter pores in 5-mm-thick Ti-6242.

  7. Fabrication of Aluminum Foams with Small Pore Size by Melt Foaming Method

    NASA Astrophysics Data System (ADS)

    Cheng, Ying; Li, Yanxiang; Chen, Xiang; Shi, Tong; Liu, Zhiyong; Wang, Ningzhen

    2017-01-01

    This article introduces an improvement to the fabrication of aluminum foams with small pore size by melt foaming method. Before added to the melt, the foaming agent (titanium hydride) was pretreated in two steps. It firstly went through the traditional pre-oxidation treatment, which delayed the decomposition of titanium hydride and made sure the dispersion stage was controllable. Then such pre-oxidized titanium hydride powder was mixed with copper powder in a planetary ball mill. This treatment can not only increase the number of foaming agent particles and make them easier to disperse in the melt, which helps to increase the number of pores, but also reduce the amount of hydrogen released in the foaming stage. Therefore, the pore size could be decreased. Using such a ball-milled foaming agent in melt foaming method, aluminum foams with small pore size (average size of 1.6 mm) were successfully fabricated.

  8. Fabrication of Aluminum Foams with Small Pore Size by Melt Foaming Method

    NASA Astrophysics Data System (ADS)

    Cheng, Ying; Li, Yanxiang; Chen, Xiang; Shi, Tong; Liu, Zhiyong; Wang, Ningzhen

    2017-04-01

    This article introduces an improvement to the fabrication of aluminum foams with small pore size by melt foaming method. Before added to the melt, the foaming agent (titanium hydride) was pretreated in two steps. It firstly went through the traditional pre-oxidation treatment, which delayed the decomposition of titanium hydride and made sure the dispersion stage was controllable. Then such pre-oxidized titanium hydride powder was mixed with copper powder in a planetary ball mill. This treatment can not only increase the number of foaming agent particles and make them easier to disperse in the melt, which helps to increase the number of pores, but also reduce the amount of hydrogen released in the foaming stage. Therefore, the pore size could be decreased. Using such a ball-milled foaming agent in melt foaming method, aluminum foams with small pore size (average size of 1.6 mm) were successfully fabricated.

  9. Effects of calcination temperature on the pore size and wall crystalline structure of mesoporous alumina.

    PubMed

    Sun, Zhong-Xi; Zheng, Ting-Ting; Bo, Qi-Bing; Du, Miao; Forsling, Willis

    2008-03-01

    In this paper, mesoporous alumina with different pore sizes and wall crystalline structures was synthesized at calcination temperatures over 550 degrees C. The characterization of the samples calcined at 550, 800, 1100, and 1300 degrees C, respectively, was performed using TEM, XRD, FTIR, TG/DTA, and N2 adsorption/desorption techniques. The correlation between pore size and wall crystalline structure on calcination temperature was systematically investigated.

  10. IMPACT OF COMPOSITION AND HEAT TREATMENT ON PORE SIZE IN POROUS WALLED HOLLOW GLASS MICROSPHERES

    SciTech Connect

    Raszewski, F; Erich Hansen, E; Ray Schumacher, R; David Peeler, D

    2007-12-04

    The Savannah River National Laboratory (SRNL) developed a new geometric form: hollow glass microspheres (HGMs), with unique porous walls. The new geometric form combines the existing technology of HGMs with basic glass science knowledge in the realm of glass-in-glass phase separation. Conceptually, the development of a HGM with porous walls (referred to as a PWHGM) provides a unique system in which various media or filling agents can be incorporated into the PWHGM (via transport through the porous walls) and ultimately has the capacity to serve as a functional delivery system in various industrial applications. Applications of these types of systems could range from hydrogen storage, molecular sieves, drug and bioactive delivery systems, to environmental, chemical and biological indicators, relevant to Energy, Environmental Processing and Homeland Security fields. As a specific example, previous studies at SRNL have introduced materials capable of hydrogen storage (as well as other materials) into the interior of the PWHGMs. The goal of this project was to determine if the microstructure (i.e., pore size and pore size distribution) of a PWHGM could be altered or tailored by varying composition and/or heat treatment (time and/or temperature) conditions. The ability to tailor the microstructure through composition or heat treatments could provide the opportunity to design the PWHGM system to accommodate different additives or fill agents. To meet this objective, HGMs of various alkali borosilicate compositions were fabricated using a flame forming apparatus installed at the Aiken County Technical Laboratory (ACTL). HGMs were treated under various heat treatment conditions to induce and/or enhance glass in glass phase separation. Heat treatment temperatures ranged from 580 C to 620 C, while heat treatment times were either 8 or 24 hours. Of the two primary variables assessed in this study, heat treatment temperature was determined to be most effective in changing the

  11. Pore-scale distribution of mucilage affecting water repellency in the rhizosphere

    NASA Astrophysics Data System (ADS)

    Benard, Pascal; Zarebanadkouki, Mohsen; Hedwig, Clemens; Holz, Maire; Ahmed, Mutez; Carminati, Andrea

    2017-04-01

    The hydraulic properties of the rhizosphere are altered by plants, fungi and microorganism. Plant roots release different compounds into the soil. One of these substances is mucilage, a gel which turns water repellent upon drying. We introduce a conceptual model of mucilage deposition during soil drying and its impact on the soil wettability. As the soil dries, water menisci recede and draw mucilage towards the contact region between particles where it is deposited. At high mucilage content, mucilage deposits expand into the open pore space and finally block water infiltration when a critical fraction of the pore space is blocked. To test this hypothesis, we mixed mucilage and particles of different grain size, we let them dry and measured the contact angle using the sessile drop method. Mucilage deposition was visualized by light microscopy imaging. Contact angle measurements showed a distinct threshold-like behavior with a sudden increase in apparent contact angle at high mucilage concentrations. Particle roughness induced a more uniform distribution of mucilage. The observed threshold corresponds to the concentration when mucilage deposition occupies a critical fraction of the pore space, as visualized with the microscope images. In conclusion, water repellency is critically affected by the distribution of mucilage on the pore-scale. This microscopic heterogeneity has to be taken into account in the description of macroscopic processes, like water infiltration or rewetting of water repellent soil.

  12. The distribution and mechanism of pore formation in copper foams fabricated by Lost Carbonate Sintering method

    SciTech Connect

    Shahzeydi, Mohammad Hosein; Parvanian, Amir Masoud; Panjepour, Masoud

    2016-01-15

    In this research, utilizing X-ray computed tomography (XCT), geometrical characterization, and pore formation mechanisms of highly porous copper foams manufactured by powder metallurgical (PM) process are investigated. Open-cell copper foams with porosity percentages of 60% and 80% and with a pore size within the range of 300–600 μm were manufactured by using potassium carbonate as a space holder agent via the Lost Carbonate Sintering (LCS) technique. XCT and SEM were also employed to investigate the three-dimensional structure of foams and to find the effect of the parameters of the space holders on the structural properties of copper foams. The result showed an excellent correlation between the structural properties of the foams including the size and shape of the pores, porosity percentage, volume percentage, particle size, and the shape of the sacrificial agent used. Also, the advanced image analysis of XCT images indicated fluctuations up to ± 10% in porosity distribution across different cross-sections of the foams. Simultaneous thermal analysis (STA: DTA–TG) was also used to study the thermal history of the powders used during the manufacturing process of the foams. The results indicated that the melting and thermal decomposition of the potassium carbonate occurred simultaneously at 920 °C and created the porous structure of the foams. By combining the STA result with the result of the tension analysis of cell walls, the mechanisms of open-pore formation were suggested. In fact, most open pores in the samples were formed due to the direct contact of potassium carbonate particles with each other in green compact. Also, it was found that the thermal decomposition of potassium carbonate particles into gaseous CO{sub 2} led to the production of gas pressure inside the closed pores, which eventually caused the creation of cracks on the cell walls and the opening of the pores in foam's structure. - Highlights: • Structural characterization of copper foam

  13. Determination of an equivalent pore size from acoustic flow measurements

    NASA Astrophysics Data System (ADS)

    Clark, Linde; Liu, Jin; Garrett, Steven

    2005-09-01

    The hydraulic radius, rh, is defined as the ratio of a channel's cross-sectional area to its perimeter. This parameter is important for specification of the performance of a porous medium that can be used as a regenerator in a Stirling engine or refrigerator. It is easy to calculate rh for pores of regular geometry, but difficult in more complex media. Two techniques which use oscillating flow to determine this parameter will be presented and compared. One technique extracts rh by finding the low velocity limit of the standard expression for viscous pressure drop in the Poiseuille flow regime. The other involves a plot of the nondimensional viscous flow resistance, Δpvis/Δxωρu, versus the reciprocal of the viscous penetration depth, 1/δν, in the laminar flow regime. When rh<δν, the flow behavior is frequency independent and the dynamics is characterized by rh only. When rh>δν, the flow resistance is frequency dependent and the dynamics is characterized by both rh and δν. It is possible to identify an effective hydraulic radius by equating it to the value of δν where that transition occurs. [Work supported by ONR.

  14. Relation between pore size and the compressibility of a confined fluid

    SciTech Connect

    Gor, Gennady Y.; Siderius, Daniel W.; Krekelberg, William P.; Shen, Vincent K.; Rasmussen, Christopher J.; Bernstein, Noam

    2015-11-21

    When a fluid is confined to a nanopore, its thermodynamic properties differ from the properties of a bulk fluid, so measuring such properties of the confined fluid can provide information about the pore sizes. Here, we report a simple relation between the pore size and isothermal compressibility of argon confined in such pores. Compressibility is calculated from the fluctuations of the number of particles in the grand canonical ensemble using two different simulation techniques: conventional grand-canonical Monte Carlo and grand-canonical ensemble transition-matrix Monte Carlo. Our results provide a theoretical framework for extracting the information on the pore sizes of fluid-saturated samples by measuring the compressibility from ultrasonic experiments.

  15. Relation Between Pore Size and the Compressibility of a Confined Fluid

    PubMed Central

    Gor, Gennady Y.; Siderius, Daniel W.; Rasmussen, Christopher J.; Krekelberg, William P.; Shen, Vincent K.; Bernstein, Noam

    2015-01-01

    When a fluid is confined to a nanopore, its thermodynamic properties differ from the properties of a bulk fluid, so measuring such properties of the confined fluid can provide information about the pore sizes. Here we report a simple relation between the pore size and isothermal compressibility of argon confined in these pores. Compressibility is calculated from the fluctuations of the number of particles in the grand canonical ensemble using two different simulation techniques: conventional grand-canonical Monte Carlo and grand-canonical ensemble transition-matrix Monte Carlo. Our results provide a theoretical framework for extracting the information on the pore sizes of fluid-saturated samples by measuring the compressibility from ultrasonic experiments. PMID:26590541

  16. Relation between pore size and the compressibility of a confined fluid.

    PubMed

    Gor, Gennady Y; Siderius, Daniel W; Rasmussen, Christopher J; Krekelberg, William P; Shen, Vincent K; Bernstein, Noam

    2015-11-21

    When a fluid is confined to a nanopore, its thermodynamic properties differ from the properties of a bulk fluid, so measuring such properties of the confined fluid can provide information about the pore sizes. Here, we report a simple relation between the pore size and isothermal compressibility of argon confined in such pores. Compressibility is calculated from the fluctuations of the number of particles in the grand canonical ensemble using two different simulation techniques: conventional grand-canonical Monte Carlo and grand-canonical ensemble transition-matrix Monte Carlo. Our results provide a theoretical framework for extracting the information on the pore sizes of fluid-saturated samples by measuring the compressibility from ultrasonic experiments.

  17. Origin and heterogeneity of pore sizes in the Mount Simon Sandstone and Eau Claire Formation: Implications for multiphase fluid flow

    SciTech Connect

    Mozley, Peter S.; Heath, Jason E.; Dewers, Thomas A.; Bauer, Stephen J.

    2016-01-01

    The Mount Simon Sandstone and Eau Claire Formation represent a principal reservoir - caprock system for wastewater disposal, geologic CO2 storage, and compressed air energy storage (CAES) in the Midwestern United States. Of primary concern to site performance is heterogeneity in flow properties that could lead to non-ideal injectivity and distribution of injected fluids (e.g., poor sweep efficiency). Using core samples from the Dallas Center Structure, Iowa, we investigate pore structure that governs flow properties of major lithofacies of these formations. Methods include gas porosimetry and permeametry, mercury intrusion porosimetry, thin section petrography, and X-ray diffraction. The lithofacies exhibit highly variable intra- and inter-informational distributions of pore throat and body sizes. Based on pore-throat size, samples fall into four distinct groups. Micropore-throat dominated samples are from the Eau Claire Formation, whereas the macropore-, mesopore-, and uniform-dominated samples are from the Mount Simon Sandstone. Complex paragenesis governs the high degree of pore and pore-throat size heterogeneity, due to an interplay of precipitation, non-uniform compaction, and later dissolution of cements. Furthermore, the cement dissolution event probably accounts for much of the current porosity in the unit. The unusually heterogeneous nature of the pore networks in the Mount Simon Sandstone indicates that there is a greater-than-normal opportunity for reservoir capillary trapping of non-wetting fluids — as quantified by CO2 and air column heights — which should be taken into account when assessing the potential of the reservoir-caprock system for CO2 storage and CAES.

  18. Origin and heterogeneity of pore sizes in the Mount Simon Sandstone and Eau Claire Formation: Implications for multiphase fluid flow

    DOE PAGES

    Mozley, Peter S.; Heath, Jason E.; Dewers, Thomas A.; ...

    2016-01-01

    The Mount Simon Sandstone and Eau Claire Formation represent a principal reservoir - caprock system for wastewater disposal, geologic CO2 storage, and compressed air energy storage (CAES) in the Midwestern United States. Of primary concern to site performance is heterogeneity in flow properties that could lead to non-ideal injectivity and distribution of injected fluids (e.g., poor sweep efficiency). Using core samples from the Dallas Center Structure, Iowa, we investigate pore structure that governs flow properties of major lithofacies of these formations. Methods include gas porosimetry and permeametry, mercury intrusion porosimetry, thin section petrography, and X-ray diffraction. The lithofacies exhibit highlymore » variable intra- and inter-informational distributions of pore throat and body sizes. Based on pore-throat size, samples fall into four distinct groups. Micropore-throat dominated samples are from the Eau Claire Formation, whereas the macropore-, mesopore-, and uniform-dominated samples are from the Mount Simon Sandstone. Complex paragenesis governs the high degree of pore and pore-throat size heterogeneity, due to an interplay of precipitation, non-uniform compaction, and later dissolution of cements. Furthermore, the cement dissolution event probably accounts for much of the current porosity in the unit. The unusually heterogeneous nature of the pore networks in the Mount Simon Sandstone indicates that there is a greater-than-normal opportunity for reservoir capillary trapping of non-wetting fluids — as quantified by CO2 and air column heights — which should be taken into account when assessing the potential of the reservoir-caprock system for CO2 storage and CAES.« less

  19. Protein adsorption on DEAE ion-exchange resins with different ligand densities and pore sizes.

    PubMed

    Lu, Hui-Li; Lin, Dong-Qiang; Zhu, Mi-Mi; Yao, Shan-Jing

    2012-11-01

    Ion exchange chromatography (IEC) is a common and powerful technique for the purification of proteins. The ligand density and pore properties of ion-exchange resins have significant effects on the separation behaviors of protein, however, the understandings are quite limited. In the present work, the adsorption isotherms of bovine serum albumin (BSA) and human serum albumin (HSA) were investigated systematically with series of diethylaminoethyl (DEAE) ion-exchange resins, which have different ligand densities and pore sizes. The Langmuir equation was used to fit the experimental data and the influences of ligand density and pore size on the saturated adsorption capacity and the dissociation constant were discussed. The zeta potentials and hydrodynamic diameters of proteins at different pHs were also measured, and the surface charge characteristics of proteins and the adsorption mechanism were discussed. The results demonstrated that the ligand density, pore size, and protein properties affect the protein adsorption capacities in an integrative way. An integrative parameter was introduced to describe the complicated effects of ligand density and pore size on the protein adsorption. For a given protein, the ligand density and pore size should be optimized for improving the protein adsorption.

  20. Computationally-Guided Synthetic Control over Pore Size in Isostructural Porous Organic Cages

    PubMed Central

    2017-01-01

    The physical properties of 3-D porous solids are defined by their molecular geometry. Hence, precise control of pore size, pore shape, and pore connectivity are needed to tailor them for specific applications. However, for porous molecular crystals, the modification of pore size by adding pore-blocking groups can also affect crystal packing in an unpredictable way. This precludes strategies adopted for isoreticular metal–organic frameworks, where addition of a small group, such as a methyl group, does not affect the basic framework topology. Here, we narrow the pore size of a cage molecule, CC3, in a systematic way by introducing methyl groups into the cage windows. Computational crystal structure prediction was used to anticipate the packing preferences of two homochiral methylated cages, CC14-R and CC15-R, and to assess the structure–energy landscape of a CC15-R/CC3-S cocrystal, designed such that both component cages could be directed to pack with a 3-D, interconnected pore structure. The experimental gas sorption properties of these three cage systems agree well with physical properties predicted by computational energy–structure–function maps. PMID:28776015

  1. Role of pore size and morphology in musculo-skeletal tissue regeneration.

    PubMed

    Perez, Roman A; Mestres, Gemma

    2016-04-01

    Biomaterials in the form of scaffolds hold great promise in the regeneration of diseased tissues. The scaffolds stimulate cellular adhesion, proliferation and differentiation. While the scaffold composition will dictate their biocompatibility, their porosity plays a key role in allowing proper cell penetration, nutrient diffusion as well as bone ingrowth. Porous scaffolds are processed with the help of a wide variety of techniques. Designing scaffolds with the appropriate porosity is a complex issue since this may jeopardize other physico-chemical properties. From a macroscopic point of view, parameters such as the overall architecture, pore morphology, interconnectivity and pore size distribution, have unique roles in allowing bone ingrowth to take place. From a microscopic perspective, the adsorption and retention of proteins in the microporosities of the material will dictate the subsequent cell adhesion. Therefore, the microstructure of the substrate can determine cell proliferation as well as the expression of specific osteogenic genes. This review aims at discussing the effect of micro- and macroporosity on the physico-chemical and biological properties of scaffolds for musculo-skeletal tissue regeneration. Copyright © 2016 Elsevier B.V. All rights reserved.

  2. Size-selective biocatalysis of myoglobin immobilized into a mesoporous metal-organic framework with hierarchical pore sizes.

    PubMed

    Chen, Yao; Lykourinou, Vasiliki; Hoang, Tran; Ming, Li-June; Ma, Shengqian

    2012-09-03

    The protein myoglobin has been successfully immobilized into a mesoporous metal-organic framework with hierarchical pore sizes, which demonstrates interesting size-selective biocatalysis as well as superior catalytic activities toward small substrate oxidation compared to its mesoporous silica material counterpart.

  3. New and conventional pore size tests in virus-removing membranes.

    PubMed

    Duek, Aviv; Arkhangelsky, Elizabeth; Krush, Ronit; Brenner, Asher; Gitis, Vitaly

    2012-05-15

    Microorganisms are retained by ultrafiltration (UF) membranes mainly due to size exclusion. The sizes of viruses and membrane pores are close to each other and retention of viruses can be guaranteed only if the precise pore diameter is known. Unfortunately and rather surprisingly, there is no direct method to determine the membrane pore size. As a result, the UF membranes are not trusted to remove the viruses, and the treatment plants are required to enhance viral disinfection. Here we propose a new, simple and effective method for UF pore size determination using aquasols of gold and silver nanoparticles. We synthesized highly monodispersed suspensions ranging in diameter from 3 to 50 nm, which were later transferred through polymer and ceramic UF membranes. The retention percentage was plotted against the particle diameter to determine the pore size for which a membrane has a retention capability of 50, 90 and 100%. The d(50), d(90) and d(100) values were compared with data obtained from conventional transmembrane flux, polyethylene glycol, and dextran tests, and with the retention of phi X 174 and MS2 bacteriophages. The absolute pore size, d(100), for the majority of tested UF membranes is within 40-50 nm, and can only be detected with the new tests. The average 1.2 log retention of hydrophilic phi X 174 was predicted accurately by models based on the virus hydrodynamic radii and d(100) pore size. The 2.5 log MS2 retention suggests hydrophobic interactions in addition to simple ball-through-cylinder geometry.

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

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

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

  5. Passive permeability and effective pore size of HeLa cell nuclear membranes.

    PubMed

    Samudram, Arunkarthick; Mangalassery, Bijeesh M; Kowshik, Meenal; Patincharath, Nandakumar; Varier, Geetha K

    2016-09-01

    Nuclear pore complexes in the nuclear membrane act as the sole gateway of transport of molecules from the cytoplasm to the nucleus and vice versa. Studies on biomolecular transport through nuclear membranes provide vital data on the nuclear pore complexes. In this work, we use fluorescein isothiocyanate-labeled dextran molecules as a model system and study the passive nuclear import of biomolecules through nuclear pore complexes in digitonin-permeabilized HeLa cells. Experiments are carried out under transient conditions in the time lapse imaging scheme using an in-house constructed confocal laser scanning microscope. Transport rates of dextran molecules having molecular weights of 4-70 kDa corresponding to Stokes radius of 1.4-6 nm are determined. Analyzing the permeability of the nuclear membrane for different sizes the effective pore radius of HeLa cell nuclear membrane is determined to be 5.3 nm, much larger than the value reported earlier using proteins as probe molecules. The range of values reported for the nuclear pore radius suggest that they may not be rigid structures and it is quite probable that the effective pore size of nuclear pore complexes is critically dependent on the probe molecules and on the environmental factors.

  6. Probing the SecYEG translocation pore size with preproteins conjugated with sizable rigid spherical molecules.

    PubMed

    Bonardi, Francesco; Halza, Erik; Walko, Martin; Du Plessis, François; Nouwen, Nico; Feringa, Ben L; Driessen, Arnold J M

    2011-05-10

    Protein translocation in Escherichia coli is mediated by the translocase that in its minimal form consists of the protein-conducting channel SecYEG, and the motor protein, SecA. SecYEG forms a narrow pore in the membrane that allows passage of unfolded proteins only. Molecular dynamics simulations suggest that the maximal width of the central pore of SecYEG is limited to . To access the functional size of the SecYEG pore, the precursor of outer membrane protein A was modified with rigid spherical tetraarylmethane derivatives of different diameters at a unique cysteine residue. SecYEG allowed the unrestricted passage of the precursor of outer membrane protein A conjugates carrying tetraarylmethanes with diameters up to , whereas a sized molecule blocked the translocation pore. Translocation of the protein-organic molecule hybrids was strictly proton motive force-dependent and occurred at a single pore. With an average diameter of an unfolded polypeptide chain of , the pore accommodates structures of at least , which is vastly larger than the predicted maximal width of a single pore by molecular dynamics simulations.

  7. Synaptotagmin IV Modulation of Vesicle Size and Fusion Pores in PC12 Cells

    PubMed Central

    Zhang, Zhenjie; Zhang, Zhen; Jackson, Meyer B.

    2010-01-01

    Many synaptotagmins are Ca2+-binding membrane proteins with functions in Ca2+-triggered exocytosis. Synaptotagmin IV (syt IV) has no Ca2+ binding activity, but nevertheless modulates exocytosis. Here, cell-attached capacitance recording was used to study single vesicle fusion and fission in control and syt IV overexpressing PC12 cells. Unitary capacitance steps varied widely in size, indicating that both microvesicles (MVs) and dense-core vesicles (DCVs) undergo fusion. Syt IV overexpression reduced the size of DCVs and endocytotic vesicles but not MVs. Syt IV also reduced the basal rate of Ca2+-induced fusion. During kiss-and-run, syt IV increased the conductance and duration of DCV fusion pores but not MV fusion pores. During full-fusion of DCVs syt IV increased the fusion pore conductance but not the duration. Syt IV overexpression increased the duration but not the conductance of fission pores during endocytosis. The effects of syt IV on fusion pores in PC12 cells resembled the effects on fusion pores in peptidergic nerve terminals. However, differences between these and results obtained with amperometry may indicate that amperometry and capacitance detect the fusion of different populations of vesicles. The effects of syt IV on fusion pores are discussed in terms of structural models and kinetic mechanisms. PMID:20303854

  8. Proapoptotic Bax and Bak Proteins Form Stable Protein-permeable Pores of Tunable Size

    PubMed Central

    Bleicken, Stephanie; Landeta, Olatz; Landajuela, Ane; Basañez, Gorka; García-Sáez, Ana J.

    2013-01-01

    The Bcl-2 proapoptotic proteins Bax and Bak mediate the permeabilization of the mitochondrial outer membrane during apoptosis. Current models consider that Bax and Bak form pores at the mitochondrial outer membrane that are responsible for the release of cytochrome c and other larger mitochondrial apoptotic factors (i.e. Smac/DIABLO, AIF, and endoglycosidase G). However, the properties and nature of Bax/Bak apoptotic pores remain enigmatic. Here, we performed a detailed analysis of the membrane permeabilizing activity of Bax and Bak at the single vesicle level. We directly visualized that cBid-activated Bax and BakΔC21 can form membrane pores large enough to release not only cytochrome c, but also allophycocyanine, a protein of 104 kDa. Interestingly, the size of Bax and BakΔC21 pores is not constant, as typically observed in purely proteinaceous channels, but evolves with time and depends on protein concentration. We found that Bax and BakΔC21 formed long-lived pores, whose areas changed with the amount of Bax/BakΔC21 but not with cardiolipin concentration. Altogether, our results demonstrate that Bax and BakΔC21 follow similar mechanisms of membrane permeabilization characterized by the formation of protein-permeable pores of dynamic size, in agreement with the proteolipidic nature of these apoptotic pores. PMID:24100034

  9. Physiologic upper limits of pore size of different blood capillary types and another perspective on the dual pore theory of microvascular permeability

    PubMed Central

    2010-01-01

    Background Much of our current understanding of microvascular permeability is based on the findings of classic experimental studies of blood capillary permeability to various-sized lipid-insoluble endogenous and non-endogenous macromolecules. According to the classic small pore theory of microvascular permeability, which was formulated on the basis of the findings of studies on the transcapillary flow rates of various-sized systemically or regionally perfused endogenous macromolecules, transcapillary exchange across the capillary wall takes place through a single population of small pores that are approximately 6 nm in diameter; whereas, according to the dual pore theory of microvascular permeability, which was formulated on the basis of the findings of studies on the accumulation of various-sized systemically or regionally perfused non-endogenous macromolecules in the locoregional tissue lymphatic drainages, transcapillary exchange across the capillary wall also takes place through a separate population of large pores, or capillary leaks, that are between 24 and 60 nm in diameter. The classification of blood capillary types on the basis of differences in the physiologic upper limits of pore size to transvascular flow highlights the differences in the transcapillary exchange routes for the transvascular transport of endogenous and non-endogenous macromolecules across the capillary walls of different blood capillary types. Methods The findings and published data of studies on capillary wall ultrastructure and capillary microvascular permeability to lipid-insoluble endogenous and non-endogenous molecules from the 1950s to date were reviewed. In this study, the blood capillary types in different tissues and organs were classified on the basis of the physiologic upper limits of pore size to the transvascular flow of lipid-insoluble molecules. Blood capillaries were classified as non-sinusoidal or sinusoidal on the basis of capillary wall basement membrane layer

  10. Large pore size nanoporous materials from the self-assembly of asymmetric bottlebrush block copolymers.

    PubMed

    Bolton, Justin; Bailey, Travis S; Rzayev, Javid

    2011-03-09

    Asymmetric polystyrene-polylactide (PS-PLA) bottlebrush block copolymers have been shown to self-assemble into a cylindrical morphology with large domain spacings. PLA cylinders can be selectively etched out of the shear-aligned polymer monoliths to generate nanoporous materials with an average cylindrical pore diameter of 55 nm. The remaining bottlebrush backbone provides a functional, hydrophilic coating inside the nanopores. This methodology significantly expands the range of pore sizes attainable in block copolymer based nanoporous materials.

  11. Controlling the Pore Size of Mesoporous Carbon Thin Films through Thermal and Solvent Annealing.

    PubMed

    Zhou, Zhengping; Liu, Guoliang

    2017-02-02

    Herein an approach to controlling the pore size of mesoporous carbon thin films from metal-free polyacrylonitrile-containing block copolymers is described. A high-molecular-weight poly(acrylonitrile-block-methyl methacrylate) (PAN-b-PMMA) is synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization. The authors systematically investigate the self-assembly behavior of PAN-b-PMMA thin films during thermal and solvent annealing, as well as the pore size of mesoporous carbon thin films after pyrolysis. The as-spin-coated PAN-b-PMMA is microphase-separated into uniformly spaced globular nanostructures, and these globular nanostructures evolve into various morphologies after thermal or solvent annealing. Surprisingly, through thermal annealing and subsequent pyrolysis of PAN-b-PMMA into mesoporous carbon thin films, the pore size and center-to-center spacing increase significantly with thermal annealing temperature, different from most block copolymers. In addition, the choice of solvent in solvent annealing strongly influences the block copolymer nanostructure and the pore size of mesoporous carbon thin films. The discoveries herein provide a simple strategy to control the pore size of mesoporous carbon thin films by tuning thermal or solvent annealing conditions, instead of synthesizing a series of block copolymers of various molecular weights and compositions.

  12. Relating pore size variation of poly (ɛ-caprolactone) scaffolds to molecular weight of porogen and evaluation of scaffold properties after degradation.

    PubMed

    Columbus, Soumya; Krishnan, Lissy K; Kalliyana Krishnan, V

    2014-05-01

    The major challenge in designing a scaffold for fabricating tissue engineered blood vessels is optimization of its microstructure for supporting uniform cellular in-growth with good mechanical integrity and degradation kinetics suitable for long-term implantation. In this study, we have investigated the feasibility of varying the pore size of poly(ɛ-caprolactone) (PCL) scaffold by altering the molecular weight of porogen and studied the effect of degradation on morphological characteristics and mechanical properties of scaffolds by correlating to the extent of degradation. Scaffolds with two different pore sizes were prepared by solvent casting and particulate leaching where poly(ethylene glycol) (PEG) porogens having two molecular weights (3400 and 8000) were used and subjected to in vitro degradation in phosphate buffered saline (PBS) upto six months. Microcomputed tomography studies of scaffolds revealed narrower pore size distribution when PEG-3400 was used as porogen and had 78% pores in the 12-24 µ range, whereas incorporation of PEG-8000 resulted in broader distribution with only 65% pores in the same range. Degradation resulted in scaffolds with narrower pore size distribution to have better retention of morphological and mechanical characteristics compared to scaffolds with broader distribution. Gravimetric and molecular weight studies also showed that scaffold degradation in both cases was only in initial stages after 6 months and PCL scaffolds had potential to be recommended for vascular tissue engineering applications. Copyright © 2013 Wiley Periodicals, Inc.

  13. Modulation of Asymmetric Flux in Heterotypic Gap Junctions by Pore Shape, Particle Size and Charge

    PubMed Central

    Mondal, Abhijit; Sachse, Frank B.; Moreno, Alonso P.

    2017-01-01

    Gap junction channels play a vital role in intercellular communication by connecting cytoplasm of adjoined cells through arrays of channel-pores formed at the common membrane junction. Their structure and properties vary depending on the connexin isoform(s) involved in forming the full gap junction channel. Lack of information on the molecular structure of gap junction channels has limited the development of computational tools for single channel studies. Currently, we rely on cumbersome experimental techniques that have limited capabilities. We have earlier reported a simplified Brownian dynamics gap junction pore model and demonstrated that variations in pore shape at the single channel level can explain some of the differences in permeability of heterotypic channels observed in in vitro experiments. Based on this computational model, we designed simulations to study the influence of pore shape, particle size and charge in homotypic and heterotypic pores. We simulated dye diffusion under whole cell voltage clamping. Our simulation studies with pore shape variations revealed a pore shape with maximal flux asymmetry in a heterotypic pore. We identified pore shape profiles that match the in silico flux asymmetry results to the in vitro results of homotypic and heterotypic gap junction formed out of Cx43 and Cx45. Our simulation results indicate that the channel's pore-shape established flux asymmetry and that flux asymmetry is primarily regulated by the sizes of the conical and/or cylindrical mouths at each end of the pore. Within the set range of particle size and charge, flux asymmetry was found to be independent of particle size and directly proportional to charge magnitude. While particle charge was vital to creating flux asymmetry, charge magnitude only scaled the observed flux asymmetry. Our studies identified the key factors that help predict asymmetry. Finally, we suggest the role of such flux asymmetry in creating concentration imbalances of messenger

  14. Pore size assessment during corneal endothelial cells permeabilization by femtosecond laser activated carbon nanoparticles

    NASA Astrophysics Data System (ADS)

    Jumelle, C.; Mauclair, C.; Houzet, J.; Bernard, A.; He, Z.; Piselli, S.; Perrache, C.; Egaud, G.; Baubeau, E.; Gain, P.; Thuret, G.

    2015-07-01

    Corneal therapeutic molecules delivery represents a promising solution to maintain human corneal endothelial cells (HCECs) viability, but the difficulty is transport across cell membrane. A new delivery method published recently consists in ephemerally permeabilizing cell membranes using a photo-acoustic reaction produced by carbon nanoparticles (CNPs) and femtosecond laser (FsL). The aim of this work is to investigate the size of pores formed at cell membrane by this technique. To induce cell permeabilization, HCECs were put in contact with CNPs and irradiated with a 500 μm diameter Ti:Sa FsL focalized spot. Four sizes of marker molecules were delivered into HCECs to investigate pore sizes: calcein (1.2 nm), FITC-Dextran 4kDa (2.8 nm) and FITC-Dextran 70kDa (12 nm) and FITC-Dextran 2MDa (50 nm). Delivery of each molecule was assessed by flow cytometry, a technique able to measure their presence into cells. We showed that the delivery rate was dependent of their size. Calcein was delivered in 56.1±8.2% of HCECs, FITC-Dextran 4kDa in 42.2±3.5%, FITC-Dextran 70 kDa in 21.5±2.7% and finally FITC-Dextran 2MDa in 12.9±2.0%. It means that a large number of pores in the size ranging from 1.2 to 2.8 nm were formed. However, 12 nm and larger pores were almost half more infrequent. Pore sizes formed at cell membrane by the technique of cell permeabilization by FsL activated CNPs was investigated. The results indicated that the pore sizes are large enough for the efficient delivery of small, medium and big therapeutics molecules on HCECs by this technique.

  15. Polystyrene-block-poly(ethylene oxide) copolymers as templates for stacked, spherical large-mesopore silica coatings: dependence of silica pore size on the PS/PEO ratio

    PubMed Central

    Magnacca, Giuliana; Jadhav, Sushilkumar A; Scalarone, Dominique

    2016-01-01

    Summary Large-mesopore silica films with a narrow pore size distribution and high porosity have been obtained by a sol–gel reaction of a silicon oxide precursor (TEOS) and using polystyrene-block-poly(ethylene oxide) (PS-b-PEO) copolymers as templates in an acidic environment. PS-b-PEO copolymers with different molecular weight and composition have been studied in order to assess the effects of the block length on the pore size of the templated silica films. The changes in the morphology of the porous systems have been investigated by transmission electron microscopy and a systematic analysis has been carried out, evidencing the dependence between the hydrophilic/hydrophobic ratio of the two polymer blocks and the size of the final silica pores. The obtained results prove that by tuning the PS/PEO ratio, the pore size of the templated silica films can be easily and finely predicted. PMID:27826520

  16. Size distribution of ring polymers

    PubMed Central

    Medalion, Shlomi; Aghion, Erez; Meirovitch, Hagai; Barkai, Eli; Kessler, David A.

    2016-01-01

    We present an exact solution for the distribution of sample averaged monomer to monomer distance of ring polymers. For non-interacting and local-interaction models these distributions correspond to the distribution of the area under the reflected Bessel bridge and the Bessel excursion respectively, and are shown to be identical in dimension d ≥ 2, albeit with pronounced finite size effects at the critical dimension, d = 2. A symmetry of the problem reveals that dimension d and 4 − d are equivalent, thus the celebrated Airy distribution describing the areal distribution of the d = 1 Brownian excursion describes also a polymer in three dimensions. For a self-avoiding polymer in dimension d we find numerically that the fluctuations of the scaled averaged distance are nearly identical in dimension d = 2, 3 and are well described to a first approximation by the non-interacting excursion model in dimension 5. PMID:27302596

  17. Tricontinuous Cubic Nanostructure and Pore Size Patterning in Mesostructured Silica Films Templated with Glycerol Monooleate.

    PubMed

    Dunphy, Darren R; Garcia, Fred L; Kaehr, Bryan; Khripin, Constantine Y; Collord, Andrew D; Baca, Helen K; Tate, Michael P; Hillhouse, Hugh W; Strzalka, Joseph W; Jiang, Zhang; Wang, Jin; Brinker, C Jeffrey

    2011-04-26

    The fabrication of nanostructured films possessing tricontinuous minimal surface mesophases with well-defined framework and pore connectivity remains a difficult task. As a new route to these structures, we introduce glycerol monooleate (GMO) as a template for evaporation-induced self-assembly. As deposited, a nanostructured double gyroid phase is formed, as indicated by analysis of grazing-incidence small-angle x-ray scattering data. Removal of GMO by UV/O(3) treatment or acid extraction induces a phase change to a nanoporous body-centered structure which we tentatively identify as based on the IW-P surface. To improve film quality, we add a co-surfactant to the GMO in a mass ratio of 1:10; when this co-surfactant is cetyltrimethylammonium bromide, we find an unusually large pore size (8-12 nm) in acid extracted films, while UV/O(3) treated films yield pores of only ca. 4 nm. Using this pore size dependence on film processing procedure, we create a simple method for patterning pore size in nanoporous films, demonstrating spatially-defined size-selective molecular adsorption.

  18. Tricontinuous Cubic Nanostructure and Pore Size Patterning in Mesostructured Silica Films Templated with Glycerol Monooleate

    PubMed Central

    Dunphy, Darren R.; Garcia, Fred L.; Kaehr, Bryan; Khripin, Constantine Y.; Collord, Andrew D.; Baca, Helen K.; Tate, Michael P.; Hillhouse, Hugh W.; Strzalka, Joseph W.; Jiang, Zhang; Wang, Jin; Brinker, C. Jeffrey

    2011-01-01

    The fabrication of nanostructured films possessing tricontinuous minimal surface mesophases with well-defined framework and pore connectivity remains a difficult task. As a new route to these structures, we introduce glycerol monooleate (GMO) as a template for evaporation-induced self-assembly. As deposited, a nanostructured double gyroid phase is formed, as indicated by analysis of grazing-incidence small-angle x-ray scattering data. Removal of GMO by UV/O3 treatment or acid extraction induces a phase change to a nanoporous body-centered structure which we tentatively identify as based on the IW-P surface. To improve film quality, we add a co-surfactant to the GMO in a mass ratio of 1:10; when this co-surfactant is cetyltrimethylammonium bromide, we find an unusually large pore size (8-12 nm) in acid extracted films, while UV/O3 treated films yield pores of only ca. 4 nm. Using this pore size dependence on film processing procedure, we create a simple method for patterning pore size in nanoporous films, demonstrating spatially-defined size-selective molecular adsorption. PMID:21572556

  19. Strong pore-size dependence of the optical properties in porous alumina membranes

    NASA Astrophysics Data System (ADS)

    Jeon, C. H.; Kim, D. H.; Lee, Y. S.; Han, J. K.; Choi, Y. C.; Bu, S. D.; Shin, H. Y.; Yoon, S.

    2013-11-01

    We report on the strong pore-size-dependent optical properties of porous alumina membranes (PAMs) by using the photoluminescence and the optical spectroscopic techniques. The pore diameters of our PAMs varied from 60 to 420 nm. All samples showed a sizable violet/blue emission with a strong temperature dependence. We found that the peak position of the emission shifted to higher energies with increasing pore diameter, which was in accord with the smaller binding energy extracted from the temperature dependence of the emission intensity. From the transmission spectra, we found that the effective bandgap of the PAMs shifted significantly to lower energies with increasing pore diameter, which indicated that the impurity states within the bandgap was affected strongly by the geometry of the PAM.

  20. Characterizing pore sizes and water structure in stimuli-responsive hydrogels

    SciTech Connect

    Hoffman, A.S.; Antonsen, K.P.; Ashida, T.; Bohnert, J.L.; Dong, L.C.; Nabeshima, Y.; Nagamatsu, S.; Park, T.G.; Sheu, M.S.; Wu, X.S.; Yan, Q.

    1993-12-31

    Hydrogels have been extensively investigated as potential matrices for drug delivery. In particular, hydrogels responsive to pH and temperature changes have been of greatest interest most recently. Proteins and peptide drugs are especially relevant for delivery from such hydrogel matrices due to the relatively {open_quotes}passive{close_quotes} and biocompatible microenvironment which should exist within the hydrogel aqueous pores. The large molecular size of many proteins requires an interconnected large pore structure. Furthermore, the gel pore {open_quotes}walls{close_quotes} should not provide hydrophobic sites for strong interactions with proteins. In the special case of ion exchange release the protein would be attracted by opposite charges on the polymer backbones. Therefore, it is important both to control and to characterize the pore structure and the water character within a hydrogel to be used or protein or peptide drug delivery. This talk will critically review techniques for estimating these two key parameters in hydrogels.

  1. Pore-size dependent THz absorption of nano-confined water.

    PubMed

    Sun, Chi-Kuang; You, Borwen; Huang, Yu-Ru; Liu, Kao-Hsiang; Sato, Shusaku; Irisawa, Akiyoshi; Imamura, Motoki; Mou, Chung-Yuan

    2015-06-15

    We performed a THz absorption spectroscopy study on liquid water confined in mesoporous silica materials, MCM-41-S-18 and MCM-41-S-21, of two different pore sizes at room temperatures. We found that stronger confinement with a smaller pore size causes reduced THz absorption, indicating reduced water mobility due to confinement. Combined with recent theoretical studies showing that the microscopic structure of water inside the nanopores can be separated into a core water region and an interfacial water region, our spectroscopy analysis further reveals a bulk-water-like THz absorption behavior in the core water region and a solid-like THz absorption behavior in the interfacial water region.

  2. Pore Size Control of Ultra-thin Silicon Membranes by Rapid Thermal Carbonization

    PubMed Central

    Fang, David Z.; Striemer, Christopher C.; Gaborski, Thomas R.; McGrath, James L.; Fauchet, Philippe M.

    2010-01-01

    Rapid thermal carbonization in a dilute acetylene (C2H2) atmosphere has been used to chemically modify and precisely tune the pore size of ultrathin porous nanocrystalline silicon (pnc-Si). The magnitude of size reduction was controlled by varying the process temperature and time. Under certain conditions, the carbon coating displayed atomic ordering indicative of graphene layer formation conformal to the pore walls. Initial experiments show that carbonized membranes follow theoretical predictions for hydraulic permeability and retain the precise separation capabilities of untreated membranes. PMID:20839831

  3. Synthesis of hollow mesoporous silica nanoparticles with tunable shell thickness and pore size using amphiphilic block copolymers as core templates.

    PubMed

    Zhou, Xiaojun; Cheng, Xiao; Feng, Wei; Qiu, Kexin; Chen, Liang; Nie, Wei; Yin, Zhiqi; Mo, Xiumei; Wang, Hongsheng; He, Chuanglong

    2014-08-21

    This paper presents a facile method for the fabrication of uniform hollow mesoporous silica nanoparticles (HMSNs) with tunable shell thickness and pore size. In this method, a series of amphiphilic block copolymers of polystyrene-b-poly (acrylic acid) (PS-b-PAA) with different hydrophobic block (PS) lengths were first synthesized via atom transfer radical polymerization (ATRP). The as-synthesized PS-b-PAA and cetyltrimethylammonium bromide (CTAB) were subsequently used as co-templates to fabricate HMSNs. This approach allows the control of shell thickness and pore size distribution of the synthesized HMSNs simply by changing the amounts of PS-b-PAA and CTAB, respectively. In vitro cytotoxicity and hemolysis assays demonstrated that the synthesized HMSNs had a low and shell thickness-dependent cytotoxicity and hemolytic activity. Therefore, these HMSNs have great potential for biomedical applications due to their good biocompatibility and ease of synthesis.

  4. Simple thermal treatment for the size control of pore arrays in a polystyrene colloidal crystal films

    NASA Astrophysics Data System (ADS)

    Jamiolkowski, Ryan M.; Fiorenza, Shane A.; Chen, Kevin; Tate, Alyssa M.; Pfeil, Shawn H.; Goldman, Yale E.

    Nanosphere Lithography (NSL) offers an attractive route to fabricating periodic structures with nanoscale features, without e-beam or deep UV lithography. In particular, it is uniquely suited to the low cost fabrication of large repeated arrays pores or pillars created by taking advantage of the interstitial spaces in close-packed monolayers of nano to micro-scale beads. However pore size, shape, and spacing cannot be controlled independently. We present both a robust method for producing large, approximately 1 cm2, hexagonally close packed monolayer films of 1 micron diameter polystyrene beads on glass substrates, and thermal treatment of these films near the glass temperature, Tg, of polystyrene to modify the pore size. This builds on earlier work showing that pore size can be modified for colloidal crystals formed at a liquid gas interface [2]. These processes promise a simple, reproducible, and low cost route to periodic pore arrays for nano-photonic applications such as zero mode waveguides (ZMWs) Funding: F30 AI114187 (RMJ), R01-GM080376 (YEG).

  5. Pore-size dependence and characteristics of water diffusion in slitlike micropores

    SciTech Connect

    Diallo, S. O.

    2015-07-16

    The temperature dependence of the dynamics of water inside microporous activated carbon fibers (ACF) is investigated by means of incoherent elastic and quasielastic neutron-scattering techniques. The aim is to evaluate the effect of increasing pore size on the water dynamics in these primarily hydrophobic slit-shaped channels. Using two different micropore sizes (similar to 12 and 18 angstrom, denoted, respectively, ACF-10 and ACF-20), a clear suppression of the mobility of the water molecules is observed as the pore gap or temperature decreases. Suppression, we found, is accompanied by a systematic dependence of the average translational diffusion coefficient D-r and relaxation time [tau(0)] of the restricted water on pore size and temperature. We observed D-r values and tested against a proposed scaling law, in which the translational diffusion coefficient D-r of water within a porous matrix was found to depend solely on two single parameters, a temperature-independent translational diffusion coefficient D-c associated with the water bound to the pore walls and the ratio theta of this strictly confined water to the total water inside the pore, yielding unique characteristic parameters for water transport in these carbon channels across the investigated temperature range.

  6. Pore-size dependence and characteristics of water diffusion in slitlike micropores

    NASA Astrophysics Data System (ADS)

    Diallo, S. O.

    2015-07-01

    The temperature dependence of the dynamics of water inside microporous activated carbon fibers (ACF) is investigated by means of incoherent elastic and quasielastic neutron-scattering techniques. The aim is to evaluate the effect of increasing pore size on the water dynamics in these primarily hydrophobic slit-shaped channels. Using two different micropore sizes (˜12 and 18 Å, denoted, respectively, ACF-10 and ACF-20), a clear suppression of the mobility of the water molecules is observed as the pore gap or temperature decreases. This suppression is accompanied by a systematic dependence of the average translational diffusion coefficient Dr and relaxation time <τ0> of the restricted water on pore size and temperature. The observed Dr values are tested against a proposed scaling law, in which the translational diffusion coefficient Dr of water within a porous matrix was found to depend solely on two single parameters, a temperature-independent translational diffusion coefficient Dc associated with the water bound to the pore walls and the ratio θ of this strictly confined water to the total water inside the pore, yielding unique characteristic parameters for water transport in these carbon channels across the investigated temperature range.

  7. Pore-size dependence and characteristics of water diffusion in slitlike micropores

    DOE PAGES

    Diallo, S. O.

    2015-07-16

    The temperature dependence of the dynamics of water inside microporous activated carbon fibers (ACF) is investigated by means of incoherent elastic and quasielastic neutron-scattering techniques. The aim is to evaluate the effect of increasing pore size on the water dynamics in these primarily hydrophobic slit-shaped channels. Using two different micropore sizes (similar to 12 and 18 angstrom, denoted, respectively, ACF-10 and ACF-20), a clear suppression of the mobility of the water molecules is observed as the pore gap or temperature decreases. Suppression, we found, is accompanied by a systematic dependence of the average translational diffusion coefficient D-r and relaxation timemore » [tau(0)] of the restricted water on pore size and temperature. We observed D-r values and tested against a proposed scaling law, in which the translational diffusion coefficient D-r of water within a porous matrix was found to depend solely on two single parameters, a temperature-independent translational diffusion coefficient D-c associated with the water bound to the pore walls and the ratio theta of this strictly confined water to the total water inside the pore, yielding unique characteristic parameters for water transport in these carbon channels across the investigated temperature range.« less

  8. Pore-size dependence and characteristics of water diffusion in slitlike micropores.

    PubMed

    Diallo, S O

    2015-07-01

    The temperature dependence of the dynamics of water inside microporous activated carbon fibers (ACF) is investigated by means of incoherent elastic and quasielastic neutron-scattering techniques. The aim is to evaluate the effect of increasing pore size on the water dynamics in these primarily hydrophobic slit-shaped channels. Using two different micropore sizes (∼12 and 18 Å, denoted, respectively, ACF-10 and ACF-20), a clear suppression of the mobility of the water molecules is observed as the pore gap or temperature decreases. This suppression is accompanied by a systematic dependence of the average translational diffusion coefficient D(r) and relaxation time 〈τ(0)〉 of the restricted water on pore size and temperature. The observed D(r) values are tested against a proposed scaling law, in which the translational diffusion coefficient D(r) of water within a porous matrix was found to depend solely on two single parameters, a temperature-independent translational diffusion coefficient D(c) associated with the water bound to the pore walls and the ratio θ of this strictly confined water to the total water inside the pore, yielding unique characteristic parameters for water transport in these carbon channels across the investigated temperature range.

  9. Self-supporting nanopore membranes with controlled pore size and shape.

    PubMed

    Lu, Zhe-Xue; Namboodiri, Arya; Collinson, Maryanne M

    2008-05-01

    Self-supporting membranes containing either isolated or organized arrays of nanosized pores have been prepared using a nonlithographic approach by coupling sol-gel processing, thin film preparation, and templating. Specifically, polystyrene latex spheres were doped into a hybrid sol prepared from tetraethoxysilane and dimethyldiethoxysilane and the resultant sol spin cast on a sacrificial support. Upon removal of the template and the sacrificial support, the self-supporting nanopore membranes were transferred to glass for characterization by atomic force microscopy and scanning electron microscopy. Through variations in the thickness of the membranes and the size of the polystyrene latex spheres, the geometry (cylinder-like to asymmetric-like) and the dimensions of the nanopores were altered. Pores with diameters that range from 35 to 2100 nm, aspect ratios (defined as the top pore diameter divided by the bottom pore diameter) from 1-4, and depths (effective film thickness) from 50 to 1500 nms have been prepared using templates that range in diameter from 100 to 3100 nm. The method described employs "wet-chemistry", is highly versatile, and is easily amenable to modification by utilizing templates of different sizes and geometries to create stable membranes with different pore geometries and sizes that can be used as platforms for nanofiltration and/or chemical sensors.

  10. Development of gelatin-chitosan-hydroxyapatite based bioactive bone scaffold with controlled pore size and mechanical strength.

    PubMed

    Maji, Kanchan; Dasgupta, Sudip; Kundu, Biswanath; Bissoyi, Akalabya

    2015-01-01

    Hydroxyapatite-chitosan/gelatin (HA:Chi:Gel) nanocomposite scaffold has potential to serve as a template matrix to regenerate extra cellular matrix of human bone. Scaffolds with varying composition of hydroxyapatite, chitosan, and gelatin were prepared using lyophilization technique where glutaraldehyde (GTA) acted as a cross-linking agent for biopolymers. First, phase pure hydroxyapatite-chitosan nanocrystals were in situ synthesized by coprecipitation method using a solution of 2% acetic acid dissolved chitosan and aqueous solution of calcium nitrate tetrahydrate [Ca(NO3)2,4H2O] and diammonium hydrogen phosphate [(NH4)2H PO4]. Keeping solid loading constant at 30 wt% and changing the composition of the original slurry of gelatin, HA-chitosan allowed control of the pore size, its distribution, and mechanical properties of the scaffolds. Microstructural investigation by scanning electron microscopy revealed the formation of a well interconnected porous scaffold with a pore size in the range of 35-150 μm. The HA granules were uniformly dispersed in the gelatin-chitosan network. An optimal composition in terms of pore size and mechanical properties was obtained from the scaffold with an HA:Chi:Gel ratio of 21:49:30. The composite scaffold having 70% porosity with pore size distribution of 35-150 μm exhibited a compressive strength of 3.3-3.5 MPa, which is within the range of that exhibited by cancellous bone. The bioactivity of the scaffold was evaluated after conducting mesenchymal stem cell (MSC) - materials interaction and MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) assay using MSCs. The scaffold found to be conducive to MSC's adhesion as evident from lamellipodia, filopodia extensions from cell cytoskeleton, proliferation, and differentiation up to 14 days of cell culture.

  11. Pore size regulates operating stomatal conductance, while stomatal densities drive the partitioning of conductance between leaf sides

    PubMed Central

    Fanourakis, Dimitrios; Giday, Habtamu; Milla, Rubén; Pieruschka, Roland; Kjaer, Katrine H.; Bolger, Marie; Vasilevski, Aleksandar; Nunes-Nesi, Adriano; Fiorani, Fabio; Ottosen, Carl-Otto

    2015-01-01

    Background and Aims Leaf gas exchange is influenced by stomatal size, density, distribution between the leaf adaxial and abaxial sides, as well as by pore dimensions. This study aims to quantify which of these traits mainly underlie genetic differences in operating stomatal conductance (gs) and addresses possible links between anatomical traits and regulation of pore width. Methods Stomatal responsiveness to desiccation, gs-related anatomical traits of each leaf side and estimated gs (based on these traits) were determined for 54 introgression lines (ILs) generated by introgressing segments of Solanum pennelli into the S. lycopersicum ‘M82’. A quantitative trait locus (QTL) analysis for stomatal traits was also performed. Key Results A wide genetic variation in stomatal responsiveness to desiccation was observed, a large part of which was explained by stomatal length. Operating gs ranged over a factor of five between ILs. The pore area per stomatal area varied 8-fold among ILs (2–16 %), and was the main determinant of differences in operating gs between ILs. Operating gs was primarily positioned on the abaxial surface (60–83 %), due to higher abaxial stomatal density and, secondarily, to larger abaxial pore area. An analysis revealed 64 QTLs for stomatal traits in the ILs, most of which were in the direction of S. pennellii. Conclusions The data indicate that operating and maximum gs of non-stressed leaves maintained under stable conditions deviate considerably (by 45–91 %), because stomatal size inadequately reflects operating pore area (R2 = 0·46). Furthermore, it was found that variation between ILs in both stomatal sensitivity to desiccation and operating gs is associated with features of individual stoma. In contrast, genotypic variation in gs partitioning depends on the distribution of stomata between the leaf adaxial and abaxial epidermis. PMID:25538116

  12. Development of hierarchical, tunable pore size polymer foams for ICF targets

    SciTech Connect

    Hamilton, Christopher E.; Lee, Matthew Nicholson; Parra-Vasquez, A. Nicholas Gerardo

    2016-08-01

    In this study, one of the great challenges of inertial confinement fusion experiments is poor understanding of the effects of reactant heterogeneity on fusion reactions. The Marble campaign, conceived at Los Alamos National Laboratory, aims to gather new insights into this issue by utilizing target capsules containing polymer foams of variable pore sizes, tunable over an order of magnitude. Here, we describe recent and ongoing progress in the development of CH and CH/CD polymer foams in support of Marble. Hierarchical and tunable pore sizes have been achieved by utilizing a sacrificial porogen template within an open-celled poly(divinylbenzene) or poly(divinylbenzene-co-styrene) aerogel matrix, resulting in low-density foams (~30 mg/ml) with continuous multimodal pore networks.

  13. Effect of hydrofluoric acid (HF) concentration to pores size diameter of silicon membrane.

    PubMed

    Burham, Norhafizah; Hamzah, Azrul Azlan; Majlis, Burhanuddin Yeop

    2014-01-01

    This paper studies parameters which affect the pore size diameter of a silicon membrane. Electrochemical etching is performed in characterise the parameter involved in this process. The parameter has been studied is volume ratio of hydrofluoric acid (HF) and ethanol as an electrolyte aqueous for electrochemical etch. This electrolyte aqueous solution has been mixed between HF and ethanol with volume ratio 3:7, 5:5, 7:3 and 9:1. As a result, the higher volume of HF in this electrolyte gives the smallest pore size diameter compared to the lower volume of HF. These samples have been dipped into HF and ethanol electrolyte aqueous with supplied 25 mA/cm2 current density for 20, 30, 40, and 50 minutes. The samples will inspect under Scanning Electron Microscope (SEM) to execute the pore formations on silicon membrane surface.

  14. Development of hierarchical, tunable pore size polymer foams for ICF targets

    SciTech Connect

    Hamilton, Christopher E.; Lee, Matthew Nicholson; Parra-Vasquez, A. Nicholas Gerardo

    2016-08-01

    In this study, one of the great challenges of inertial confinement fusion experiments is poor understanding of the effects of reactant heterogeneity on fusion reactions. The Marble campaign, conceived at Los Alamos National Laboratory, aims to gather new insights into this issue by utilizing target capsules containing polymer foams of variable pore sizes, tunable over an order of magnitude. Here, we describe recent and ongoing progress in the development of CH and CH/CD polymer foams in support of Marble. Hierarchical and tunable pore sizes have been achieved by utilizing a sacrificial porogen template within an open-celled poly(divinylbenzene) or poly(divinylbenzene-co-styrene) aerogel matrix, resulting in low-density foams (~30 mg/ml) with continuous multimodal pore networks.

  15. Development of hierarchical, tunable pore size polymer foams for ICF targets

    DOE PAGES

    Hamilton, Christopher E.; Lee, Matthew Nicholson; Parra-Vasquez, A. Nicholas Gerardo

    2016-08-01

    In this study, one of the great challenges of inertial confinement fusion experiments is poor understanding of the effects of reactant heterogeneity on fusion reactions. The Marble campaign, conceived at Los Alamos National Laboratory, aims to gather new insights into this issue by utilizing target capsules containing polymer foams of variable pore sizes, tunable over an order of magnitude. Here, we describe recent and ongoing progress in the development of CH and CH/CD polymer foams in support of Marble. Hierarchical and tunable pore sizes have been achieved by utilizing a sacrificial porogen template within an open-celled poly(divinylbenzene) or poly(divinylbenzene-co-styrene) aerogelmore » matrix, resulting in low-density foams (~30 mg/ml) with continuous multimodal pore networks.« less

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

    PubMed

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

    2017-08-01

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

  17. Metal electrode integration on macroporous silicon: pore distribution and morphology

    PubMed Central

    2012-01-01

    In this work, a new approach for the one-step integration of interdigitated electrodes on macroporous silicon substrates is presented. Titanium/gold interdigitated electrodes are used to pattern p-type silicon substrates prior the anodization in an organic electrolyte. The electrolyte characteristics, conductivity, and pH have been found to affect the adherence of the metal layer on the silicon surface during the electrochemical etching. The impact of the metal pattern on size distribution and morphology of the resulting macroporous silicon layer is analyzed. A formation mechanism supported by finite element simulation is proposed. PMID:22799456

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

    NASA Astrophysics Data System (ADS)

    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

  19. Effects of pore size and dissolved organic matters on diffusion of arsenate in aqueous solution.

    PubMed

    Wang, Yulong; Wang, Shaofeng; Wang, Xin; Jia, Yongfeng

    2017-02-01

    Presented here is the influence of membrane pore size and dissolved organic matters on the diffusion coefficient (D) of aqueous arsenate, investigated by the diffusion cell method for the first time. The pH-dependent diffusion coefficient of arsenate was determined and compared with values from previous studies; the coefficient was found to decrease with increasing pH, showing the validity of our novel diffusion cell method. The D value increased dramatically as a function of membrane pore size at small pore sizes, and then increased slowly at pore sizes larger than 2.0μm. Using the ExpAssoc model, the maximum D value was determined to be 11.2565×10(-6)cm(2)/sec. The presence of dissolved organic matters led to a dramatic increase of the D of arsenate, which could be attributed to electrostatic effects and ionic effects of salts. These results improve the understanding of the diffusion behavior of arsenate, especially the important role of various environmental parameters in the study and prediction of the migration of arsenate in aquatic water systems.

  20. Amine-modified ordered mesoporous silica: The effect of pore size on CO2 capture performance

    NASA Astrophysics Data System (ADS)

    Wang, Lin; Yao, Manli; Hu, Xin; Hu, Gengshen; Lu, Jiqing; Luo, Mengfei; Fan, Maohong

    2015-01-01

    The objective of current research is to investigate the effect of pore size of mesoporous silica supports on the CO2 capture performance of solid amine sorbents. Two ordered mesoporous silicas (OMS) with different pore sizes (5.6 nm and 7.6 nm) were synthesized as tetraethylenepentamine (TEPA) supports. A serious of techniques, such as physical adsorption, infrared spectroscopy and thermal gravimetric analysis were used to characterize the solid amine sorbents. The CO2 capture performances of the sorbents were evaluated using breakthrough method with a fixed-bed reactor equipped with an online mass spectrometer. The experimental results indicate that the pore size has significant influence on CO2 capture performance. Larger pore size could decrease the mass transfer resistance and increase the interaction between CO2 and TEPA. Therefore, OMS-7.6 is better than OMS-5.6 as amine support. The highest CO2 sorption capacities achieved with OMS-7.6 with 50 wt% TEPA loading (OMS-7.6-50) in the absence and presence of moisture are 3.45 mmol/g and 4.28 mmol/g, respectively, under the conditions of 10.0% CO2/N2 mixture at 75 °C. Cyclic CO2 adsorption-desorption experiments indicate that the solid amine sorbents are fairly stable and regenerable.

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

    PubMed

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

    2016-02-02

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

  2. Estimation of the pore size of the large-conductance mechanosensitive ion channel of Escherichia coli.

    PubMed Central

    Cruickshank, C C; Minchin, R F; Le Dain, A C; Martinac, B

    1997-01-01

    The open channel diameter of Escherichia coli recombinant large-conductance mechanosensitive ion channels (MscL) was estimated using the model of Hille (Hille, B. 1968. Pharmacological modifications of the sodium channels of frog nerve. J. Gen. Physiol. 51:199-219) that relates the pore size to conductance. Based on the MscL conductance of 3.8 nS, and assumed pore lengths, a channel diameter of 34 to 46 A was calculated. To estimate the pore size experimentally, the effect of large organic ions on the conductance of MscL was examined. Poly-L-lysines (PLLs) with a diameter of 37 A or larger significantly reduced channel conductance, whereas spermine (approximately 15 A), PLL19 (approximately 25 A) and 1,1'-bis-(3-(1'-methyl-(4,4'-bipyridinium)-1-yl)-propyl)-4,4'-b ipyridinium (approximately 30 A) had no effect. The smaller organic ions putrescine, cadaverine, spermine, and succinate all permeated the channel. We conclude that the open pore diameter of the MscL is approximately 40 A, indicating that the MscL has one of the largest channel pores yet described. This channel diameter is consistent with the proposed homohexameric model of the MscL. PMID:9336188

  3. Mouthpart conduit sizes of fluid-feeding insects determine the ability to feed from pores

    DOE PAGES

    Lehnert, Matthew S.; Bennett, Andrew; Reiter, Kristen E.; ...

    2017-01-04

    Fluid-feeding insects, such as butterflies, moths, and flies (20% of all animal species), are faced with the common selection pressure of having to remove and feed on trace amounts of fluids from porous surfaces. Insects able to acquire fluids that are confined to pores during drought conditions would have an adaptive advantage and increased fitness over other individuals. Here we performed feeding trials using solutions with magnetic nanoparticles to show that butterflies and flies have mouthparts adapted to pull liquids from porous surfaces using capillary action as the governing principle. In addition, the ability to feed on the liquids collectedmore » from pores depends on a relationship between the diameter of the mouthpart conduits and substrate pore size diameter; insects with mouthpart conduit diameters larger than the pores cannot successfully feed, thus there is a limiting substrate pore size from which each species can acquire liquids for fluid uptake. In conclusion, given that natural selection independently favored mouthpart architectures that support these methods of fluid uptake (Diptera and Lepidoptera share a common ancestor 280 mya that had chewing mouthparts), we suggest that the convergence of this mechanism advocates this as an optimal strategy for pulling trace amounts of fluids from porous surfaces.« less

  4. Imaging calcium carbonate distribution in human sweat pore in vivo using nonlinear microscopy

    NASA Astrophysics Data System (ADS)

    Chen, Xueqin; Gasecka, Alicja; Formanek, Florian; Galey, Jean-Baptiste; Rigneault, Hervé

    2015-03-01

    Nonlinear microscopies, including two-photon excited autofluorescence (TPEF) and coherent anti-Stokes Raman scattering (CARS), were used to study individual human sweat pore morphology and topically applied antiperspirant salt penetration inside sweat pore, in vivo on human palms. Sweat pore inner morphology in vivo was imaged up to the depth of 100 μm by TPEF microscopy. The 3D penetration and distribution of "in situ calcium carbonate" (isCC), an antiperspirant salt model, was investigated using CARS microscopy.

  5. Three-Dimensional Scaffolds for Tissue Engineering Applications: Role of Porosity and Pore Size

    PubMed Central

    Loh, Qiu Li

    2013-01-01

    Tissue engineering applications commonly encompass the use of three-dimensional (3D) scaffolds to provide a suitable microenvironment for the incorporation of cells or growth factors to regenerate damaged tissues or organs. These scaffolds serve to mimic the actual in vivo microenvironment where cells interact and behave according to the mechanical cues obtained from the surrounding 3D environment. Hence, the material properties of the scaffolds are vital in determining cellular response and fate. These 3D scaffolds are generally highly porous with interconnected pore networks to facilitate nutrient and oxygen diffusion and waste removal. This review focuses on the various fabrication techniques (e.g., conventional and rapid prototyping methods) that have been employed to fabricate 3D scaffolds of different pore sizes and porosity. The different pore size and porosity measurement methods will also be discussed. Scaffolds with graded porosity have also been studied for their ability to better represent the actual in vivo situation where cells are exposed to layers of different tissues with varying properties. In addition, the ability of pore size and porosity of scaffolds to direct cellular responses and alter the mechanical properties of scaffolds will be reviewed, followed by a look at nature's own scaffold, the extracellular matrix. Overall, the limitations of current scaffold fabrication approaches for tissue engineering applications and some novel and promising alternatives will be highlighted. PMID:23672709

  6. Organic-inorganic hybrid mesoporous silicas: functionalization, pore size, and morphology control.

    PubMed

    Park, Sung Soo; Ha, Chang-Sik

    2006-01-01

    Topological design of mesoporous silica materials, pore architecture, pore size, and morphology are currently major issues in areas such as catalytic conversion of bulky molecules, adsorption, host-guest chemistry, etc. In this sense, we discuss the pore size-controlled mesostructure, framework functionalization, and morphology control of organic-inorganic hybrid mesoporous silicas by which we can improve the applicability of mesoporous materials. First, we explain that the sizes of hexagonal- and cubic-type pores in organic-inorganic hybrid mesoporous silicas are well controlled from 24.3 to 98.0 A by the direct micelle-control method using an organosilica precursor and surfactants with different alkyl chain lengths or triblock copolymers as templates and swelling agents incorporated in the formed micelles. Second, we describe that organic-inorganic hybrid mesoporous materials with various functional groups form various external morphologies such as rod, cauliflower, film, rope, spheroid, monolith, and fiber shapes. Third, we discuss that transition metals (Ti and Ru) and rare-earth ions (Eu(3+) and Tb(3+)) are used to modify organic-inorganic hybrid mesoporous silica materials. Such hybrid mesoporous silica materials are expected to be applied as excellent catalysts for organic reactions, photocatalysis, optical devices, etc. c) 2006 The Japan Chemical Journal Forum and Wiley Periodicals, Inc.

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

    PubMed

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

    2014-08-01

    A mathematical model is developed to simulate the transport and deposition of virus-sized colloids in a cylindrical pore throat considering various processes such as advection, diffusion, colloid-collector surface interactions and hydrodynamic wall effects. The pore space is divided into three different regions, namely, bulk, diffusion and potential regions, based on the dominant processes acting in each of these regions. In the bulk region, colloid transport is governed by advection and diffusion whereas in the diffusion region, colloid mobility due to diffusion is retarded by hydrodynamic wall effects. Colloid-collector interaction forces dominate the transport in the potential region where colloid deposition occurs. The governing equations are non-dimensionalized and solved numerically. A sensitivity analysis indicates that the virus-sized colloid transport and deposition is significantly affected by various pore-scale parameters such as the surface potentials on colloid and collector, ionic strength of the solution, flow velocity, pore size and colloid size. The adsorbed concentration and hence, the favorability of the surface for adsorption increases with: (i) decreasing magnitude and ratio of surface potentials on colloid and collector, (ii) increasing ionic strength and (iii) increasing pore radius. The adsorbed concentration increases with increasing Pe, reaching a maximum value at Pe=0.1 and then decreases thereafter. Also, the colloid size significantly affects particle deposition with the adsorbed concentration increasing with increasing particle radius, reaching a maximum value at a particle radius of 100nm and then decreasing with increasing radius. System hydrodynamics is found to have a greater effect on larger particles than on smaller ones. The secondary minimum contribution to particle deposition has been found to increase as the favorability of the surface for adsorption decreases. The sensitivity of the model to a given parameter will be high if

  8. Virus-sized colloid transport in a single pore: Model development and sensitivity analysis

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

    A mathematical model is developed to simulate the transport and deposition of virus-sized colloids in a cylindrical pore throat considering various processes such as advection, diffusion, colloid-collector surface interactions and hydrodynamic wall effects. The pore space is divided into three different regions, namely, bulk, diffusion and potential regions, based on the dominant processes acting in each of these regions. In the bulk region, colloid transport is governed by advection and diffusion whereas in the diffusion region, colloid mobility due to diffusion is retarded by hydrodynamic wall effects. Colloid-collector interaction forces dominate the transport in the potential region where colloid deposition occurs. The governing equations are non-dimensionalized and solved numerically. A sensitivity analysis indicates that the virus-sized colloid transport and deposition is significantly affected by various pore-scale parameters such as the surface potentials on colloid and collector, ionic strength of the solution, flow velocity, pore size and colloid size. The adsorbed concentration and hence, the favorability of the surface for adsorption increases with: (i) decreasing magnitude and ratio of surface potentials on colloid and collector, (ii) increasing ionic strength and (iii) increasing pore radius. The adsorbed concentration increases with increasing Pe, reaching a maximum value at Pe = 0.1 and then decreases thereafter. Also, the colloid size significantly affects particle deposition with the adsorbed concentration increasing with increasing particle radius, reaching a maximum value at a particle radius of 100 nm and then decreasing with increasing radius. System hydrodynamics is found to have a greater effect on larger particles than on smaller ones. The secondary minimum contribution to particle deposition has been found to increase as the favorability of the surface for adsorption decreases. The sensitivity of the model to a given parameter will be high

  9. Effective porosity and pore-throat sizes of Conasauga Group mudrock: Application, test and evaluation of petrophysical techniques

    SciTech Connect

    Dorsch, J.; Katsube, T.J.; Sanford, W.E. |; Dugan, B.E.; Tourkow, L.M.

    1996-04-01

    Effective porosity (specifically referring to the interconnected pore space) was recently recognized as being essential in determining the effectiveness and extent of matrix diffusion as a transport mechanism within fractured low-permeability rock formations. The research presented in this report was performed to test the applicability of several petrophysical techniques for the determination of effective porosity of fine-grained siliciclastic rocks. In addition, the aim was to gather quantitative data on the effective porosity of Conasauga Group mudrock from the Oak Ridge Reservation (ORR). The quantitative data reported here include not only effective porosities based on diverse measurement techniques, but also data on the sizes of pore throats and their distribution, and specimen bulk and grain densities. The petrophysical techniques employed include the immersion-saturation method, mercury and helium porosimetry, and the radial diffusion-cell method.

  10. Fabrication of Cell-Laden Macroporous Biodegradable Hydrogels with Tunable Porosities and Pore Sizes

    PubMed Central

    Wang, Limin; Lu, Steven; Lam, Johnny; Kasper, F. Kurtis

    2015-01-01

    In this work, we investigated a cytocompatible particulate leaching method for the fabrication of cell-laden macroporous hydrogels. We used dehydrated and uncrosslinked gelatin microspheres as leachable porogens to create macroporous oligo(poly(ethylene glycol) fumarate) hydrogels. Varying gelatin content and size resulted in a wide range of porosities and pore sizes, respectively. Encapsulated mesenchymal stem cells (MSCs) exhibited high viability immediately following the fabrication process, and culture of cell-laden hydrogels revealed improved cell viability with increasing porosity. Additionally, the osteogenic potential of the encapsulated MSCs was evaluated over 16 days. Overall, this study presents a robust method for the preparation of cell-laden macroporous hydrogels with desired porosity and pore size for tissue engineering applications. PMID:25156274

  11. A general approach to crystalline and monomodal pore size mesoporous materials.

    PubMed

    Poyraz, Altug S; Kuo, Chung-Hao; Biswas, Sourav; King'ondu, Cecil K; Suib, Steven L

    2013-01-01

    Mesoporous oxides attract a great deal of interest in many fields, including energy, catalysis and separation, because of their tunable structural properties such as surface area, pore volume and size, and nanocrystalline walls. Here we report thermally stable, crystalline, thermally controlled monomodal pore size mesoporous materials. Generation of such materials involves the use of inverse micelles, elimination of solvent effects, minimizing the effect of water content and controlling the condensation of inorganic frameworks by NO(x) decomposition. Nanosize particles are formed in inverse micelles and are randomly packed to a mesoporous structure. The mesopores are created by interconnected intraparticle voids and can be tuned from 1.2 to 25 nm by controlling the nanoparticle size. Such phenomena allow the preparation of multiple phases of the same metal oxide and syntheses of materials having compositions throughout much of the periodic table, with different structures and thermal stabilities as high as 800 °C.

  12. Isoreticular Expansion of Metal-Organic Frameworks with Multiple Functionalities and Controlled Pore Sizes

    NASA Astrophysics Data System (ADS)

    Deng, Hexiang

    Metal-Organic Frameworks (MOFs) are made by linking organic and inorganic molecular building blocks into extended structures through strong bonds. With a judicious choice of inorganic joints and various functional groups available in organic links, a large number of MOFs have been synthesized in the past decade. Along with the fast expansion of the family of MOFs, important applications emerge including hydrogen storage and carbon dioxide capture, both of which address the most pressing societal demand for clean and sustainable energy resources. Although numerous MOFs are now known and they have found widespread applications, the introduction of more than one kind of building block into their crystal structures remains challenging. One of the main objectives of this study is to demonstrate the successful incorporating of multiple functional groups into MOFs. Here, a new strategy has been developed to achieve the synthesis of a series of eighteen multivariate MOFs (MTV-MOFs) containing up to eight distinct functional groups, while their parent topologies were fully preserved. The backbone of these MTV-MOFs was found to be ordered, while the orientation, number, relative position and ratio of the functionalities along the backbone could be controlled by virtue of the unchanged length of the link and its unaltered connectivity. This strategy allows us to endow the pores of these MOFs with a new level of complexity which far exceeds any held by that of the original mono-functional MOFs---an aspect that makes it possible to fine-tune the pore environment of a porous crystal with favorable implications. Indeed, one member of these MTV-MOFs has already shown an 87% improvement of the hydrogen uptake while another member demonstrated a 400% increase in CO2 selectivity comparing to their mono-functional counterparts. Another goal of this study has been to maximize MOF porosity and pore size. There were three major obstacles against expanding the pore size of porous crystals

  13. Ion-track membranes of fluoropolymers: Toward controlling the pore size and shape

    NASA Astrophysics Data System (ADS)

    Yamaki, T.; Nuryanthi, N.; Koshikawa, H.; Asano, M.; Sawada, S.; Hakoda, T.; Maekawa, Y.; Voss, K.-O.; Severin, D.; Seidl, T.; Trautmann, C.; Neumann, R.

    2013-11-01

    The possibility of varying the beam parameters and applying the effect of a pre-etching treatment for poly(vinylidene fluoride) (PVDF) ion-track membranes was investigated with the goal of achieving enhanced track etching for effective control of the pore size and shape. Commercially available 25 μm-thick PVDF films were irradiated at room temperature with swift heavy ions from the JAEA's TIARA cyclotron and GSI's UNILAC linear accelerator. Irradiation with a higher linear energy transfer (LET) beam gave faster track etching and larger pores, suggesting that the LET could be the most crucial factor determining the pore size. In-situ infra-red absorption and residual gas analyses shed light on the detailed chemistry of not only the ion-induced degradation, but also post-irradiation reactions. The pre-etching treatment effect involved oxidation of the unsaturated bonds within the latent track, which accelerated the chemical dissolution for efficient pore evolution. In other words, exposure to a gaseous oxidant, i.e., ozone, shortened the breakthrough time.

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  15. Fast two-dimensional bubble analysis of biopolymer filamentous networks pore size from confocal microscopy thin data stacks.

    PubMed

    Molteni, Matteo; Magatti, Davide; Cardinali, Barbara; Rocco, Mattia; Ferri, Fabio

    2013-03-05

    The average pore size ξ0 of filamentous networks assembled from biological macromolecules is one of the most important physical parameters affecting their biological functions. Modern optical methods, such as confocal microscopy, can noninvasively image such networks, but extracting a quantitative estimate of ξ0 is a nontrivial task. We present here a fast and simple method based on a two-dimensional bubble approach, which works by analyzing one by one the (thresholded) images of a series of three-dimensional thin data stacks. No skeletonization or reconstruction of the full geometry of the entire network is required. The method was validated by using many isotropic in silico generated networks of different structures, morphologies, and concentrations. For each type of network, the method provides accurate estimates (a few percent) of the average and the standard deviation of the three-dimensional distribution of the pore sizes, defined as the diameters of the largest spheres that can be fit into the pore zones of the entire gel volume. When applied to the analysis of real confocal microscopy images taken on fibrin gels, the method provides an estimate of ξ0 consistent with results from elastic light scattering data.

  16. Control of both particle and pore size in nanoporous palladium alloy powders

    SciTech Connect

    Jones, Christopher G.; Cappillino, Patrick J.; Stavila, Vitalie; Robinson, David B.

    2014-07-15

    Energy storage materials often involve chemical reactions with bulk solids. Porosity within the solids can enhance reaction rates. The porosity can be either within or between individual particles of the material. Greater control of the size and uniformity of both types of pore should lead to enhancements of charging and discharging rates in energy storage systems. Furthermore, to control both particle and pore size in nanoporous palladium (Pd)-based hydrogen storage materials, first we created uniformly sized copper particles of about 1 μm diameter by the reduction of copper sulfate with ascorbic acid. In turn, these were used as reducing agents for tetrachloropalladate in the presence of a block copolymer surfactant. The copper reductant particles are geometrically self-limiting, so the resulting Pd particles are of similar size. The surfactant induces formation of 10 nm-scale pores within the particles. Some residual copper is alloyed with the Pd, reducing hydrogen storage capacity; use of a more reactive Pd salt can mitigate this. The reaction is conveniently performed in gram-scale batches.

  17. Control of both particle and pore size in nanoporous palladium alloy powders

    DOE PAGES

    Jones, Christopher G.; Cappillino, Patrick J.; Stavila, Vitalie; ...

    2014-07-15

    Energy storage materials often involve chemical reactions with bulk solids. Porosity within the solids can enhance reaction rates. The porosity can be either within or between individual particles of the material. Greater control of the size and uniformity of both types of pore should lead to enhancements of charging and discharging rates in energy storage systems. Furthermore, to control both particle and pore size in nanoporous palladium (Pd)-based hydrogen storage materials, first we created uniformly sized copper particles of about 1 μm diameter by the reduction of copper sulfate with ascorbic acid. In turn, these were used as reducing agentsmore » for tetrachloropalladate in the presence of a block copolymer surfactant. The copper reductant particles are geometrically self-limiting, so the resulting Pd particles are of similar size. The surfactant induces formation of 10 nm-scale pores within the particles. Some residual copper is alloyed with the Pd, reducing hydrogen storage capacity; use of a more reactive Pd salt can mitigate this. The reaction is conveniently performed in gram-scale batches.« less

  18. Improvement of the Kruk-Jaroniec-Sayari method for pore size analysis of ordered silicas with cylindrical mesopores.

    PubMed

    Jaroniec, Mietek; Solovyov, Leonid A

    2006-08-01

    In this work, the X-ray diffraction structure modeling was employed for analysis of hexagonally ordered large-pore silicas, SBA-15, to determine their pore width independently of adsorption measurements. Nitrogen adsorption isotherms were used to evaluate the relative pressure of capillary condensation in cylindrical mesopores of these materials. This approach allowed us to extend the original Kruk-Jaroniec-Sayari (KJS) relation (Langmuir 1997, 13, 6267) between the pore width and capillary condensation pressure up to 10 nm instead of previously established range from 2 to 6.5 nm for a series of MCM-41 and to improve the KJS pore size analysis of large pore silicas.

  19. Water Desalination Using Nanoporous Single-Layer Graphene with Tunable Pore Size

    DOE PAGES

    Surwade, Sumedh P.; Smirnov, Sergei N.; Vlassiouk, Ivan V.; ...

    2015-03-23

    Graphene has great potential to serve as a separation membrane due to its unique properties such as chemical and mechanical stability, flexibility and most importantly its one-atom thickness. In this study, we demonstrate first experimental evidence of the use of single-layer porous graphene as a desalination membrane. Nanometer-sized pores are introduced into single layer graphene using a convenient oxygen plasma etching process that permits tuning of the pore size. The resulting porous graphene membrane exhibited high rejection of salt ions and rapid water transport, thus functioning as an efficient water desalination membrane. Salt rejection selectivity of nearly 100% and exceptionallymore » high water fluxes exceeding 105 g m-2 s-1 at 40 C were measured using saturated water vapor as a driving force.« less

  20. Porous silicon structures with high surface area/specific pore size

    DOEpatents

    Northrup, M.A.; Yu, C.M.; Raley, N.F.

    1999-03-16

    Fabrication and use of porous silicon structures to increase surface area of heated reaction chambers, electrophoresis devices, and thermopneumatic sensor-actuators, chemical preconcentrates, and filtering or control flow devices. In particular, such high surface area or specific pore size porous silicon structures will be useful in significantly augmenting the adsorption, vaporization, desorption, condensation and flow of liquids and gases in applications that use such processes on a miniature scale. Examples that will benefit from a high surface area, porous silicon structure include sample preconcentrators that are designed to adsorb and subsequently desorb specific chemical species from a sample background; chemical reaction chambers with enhanced surface reaction rates; and sensor-actuator chamber devices with increased pressure for thermopneumatic actuation of integrated membranes. Examples that benefit from specific pore sized porous silicon are chemical/biological filters and thermally-activated flow devices with active or adjacent surfaces such as electrodes or heaters. 9 figs.

  1. Porous silicon structures with high surface area/specific pore size

    DOEpatents

    Northrup, M. Allen; Yu, Conrad M.; Raley, Norman F.

    1999-01-01

    Fabrication and use of porous silicon structures to increase surface area of heated reaction chambers, electrophoresis devices, and thermopneumatic sensor-actuators, chemical preconcentrates, and filtering or control flow devices. In particular, such high surface area or specific pore size porous silicon structures will be useful in significantly augmenting the adsorption, vaporization, desorption, condensation and flow of liquids and gasses in applications that use such processes on a miniature scale. Examples that will benefit from a high surface area, porous silicon structure include sample preconcentrators that are designed to adsorb and subsequently desorb specific chemical species from a sample background; chemical reaction chambers with enhanced surface reaction rates; and sensor-actuator chamber devices with increased pressure for thermopneumatic actuation of integrated membranes. Examples that benefit from specific pore sized porous silicon are chemical/biological filters and thermally-activated flow devices with active or adjacent surfaces such as electrodes or heaters.

  2. Water Desalination Using Nanoporous Single-Layer Graphene with Tunable Pore Size

    SciTech Connect

    Surwade, Sumedh P.; Smirnov, Sergei N.; Vlassiouk, Ivan V.; Unocic, Raymond R.; Veith, Gabriel M.; Dai, Sheng; Mahurin, Shannon Mark

    2015-03-23

    Graphene has great potential to serve as a separation membrane due to its unique properties such as chemical and mechanical stability, flexibility and most importantly its one-atom thickness. In this study, we demonstrate first experimental evidence of the use of single-layer porous graphene as a desalination membrane. Nanometer-sized pores are introduced into single layer graphene using a convenient oxygen plasma etching process that permits tuning of the pore size. The resulting porous graphene membrane exhibited high rejection of salt ions and rapid water transport, thus functioning as an efficient water desalination membrane. Salt rejection selectivity of nearly 100% and exceptionally high water fluxes exceeding 105 g m-2 s-1 at 40 C were measured using saturated water vapor as a driving force.

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

    PubMed

    Karlsson, Johan; Atefyekta, Saba; Andersson, Martin

    2015-01-01

    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.

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

    PubMed Central

    Karlsson, Johan; Atefyekta, Saba; Andersson, Martin

    2015-01-01

    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. PMID:26185444

  5. Numerical simulation of pore size dependent anhydrite precipitation in geothermal reservoirs

    NASA Astrophysics Data System (ADS)

    Mürmann, Mario; Kühn, Michael; Pape, Hansgeorg; Clauser, Christoph

    2013-04-01

    Porosity and permeability of reservoirs are key parameters for an economical use of hot water from geothermal installations and can be significantly reduced by precipitation of minerals, such as anhydrite. The borehole Allermöhe 1 near Hamburg (Germany) represents a failed attempt of geothermal heat mining due to anhydrite precipitation (Baermann et al. 2000). For a risk assessment of future boreholes it is essential to understand how and when anhydrite cementation occurred under reservoir conditions. From core samples of the Allermöhe borehole it was determined that anhydrite precipitation took place in regions of relatively high porosity while regions of low porosity remained uncemented (Wagner et al. 2005). These findings correspond to the fact that e.g. halite precipitation in porous media is found only in relatively large pores (Putnis and Mauthe 2001). This study and others underline that pore size controls crystallization and that it is therefore necessary to establish a relation between pore size and nucleation. The work presented here is based on investigations of Emmanuel and Berkowitz (2007) who present such a relation by applying a thermodynamic approach. However this approach cannot explain the heterogeneous precipitation observed in the Allermöhe core samples. We chose an advanced approach by considering electric system properties resulting in another relation between pore size and crystallization. It is well known that a high fluid supersaturation can be maintained in porous rocks (Putnis and Mauthe 2001). This clearly indicates that a supersaturation threshold exists exceeding thermodynamic equilibrium considerably. In order to quantify spatially heterogeneous anhydrite cementation a theoretical approach was chosen which considered the electric interaction between surface charges of the matrix and calcium and sulphate ions in the fluid. This approach was implemented into the numerical code SHEMAT (Clauser 2003) and used to simulate anhydrite

  6. Impact of pore size on the sorption of uranyl under seawater conditions

    SciTech Connect

    Mayes, Richard T.; Gorka, Joanna; Dai, Sheng

    2016-04-05

    The extraction of uranium from seawater has received significant interest recently, because of the possibility of a near-limitless supply of uranium to fuel the nuclear power industry. While sorbent development has focused primarily on polymeric sorbents, nanomaterials represent a new area that has the potential to surpass the current polymeric sorbents, because of the high surface areas that are possible. Mesoporous carbon materials are a stable, high-surface-area material capable of extracting various chemical species from a variety of environments. Herein, we report the use of a dual templating process to understand the effect of pore size on the adsorption of uranyl ions from a uranyl brine consisting of seawater-relevant sodium, chloride, and bicarbonate ions. It was found that pore size played a more significant role in the effective use of the grafted polymer, leading to higher uranium capacities than the surface area. Furthermore, the pore size must be tailored to meet the demands of the extraction medium and analyte metal to achieve efficacy as an adsorbent.

  7. Impact of pore size on the sorption of uranyl under seawater conditions

    DOE PAGES

    Mayes, Richard T.; Gorka, Joanna; Dai, Sheng

    2016-04-05

    The extraction of uranium from seawater has received significant interest recently, because of the possibility of a near-limitless supply of uranium to fuel the nuclear power industry. While sorbent development has focused primarily on polymeric sorbents, nanomaterials represent a new area that has the potential to surpass the current polymeric sorbents, because of the high surface areas that are possible. Mesoporous carbon materials are a stable, high-surface-area material capable of extracting various chemical species from a variety of environments. Herein, we report the use of a dual templating process to understand the effect of pore size on the adsorption ofmore » uranyl ions from a uranyl brine consisting of seawater-relevant sodium, chloride, and bicarbonate ions. It was found that pore size played a more significant role in the effective use of the grafted polymer, leading to higher uranium capacities than the surface area. Furthermore, the pore size must be tailored to meet the demands of the extraction medium and analyte metal to achieve efficacy as an adsorbent.« less

  8. Pore size dependent molecular adsorption of cationic dye in biomass derived hierarchically porous carbon.

    PubMed

    Chen, Long; Ji, Tuo; Mu, Liwen; Shi, Yijun; Wang, Huaiyuan; Zhu, Jiahua

    2017-03-08

    Hierarchically porous carbon adsorbents were successfully fabricated from different biomass resources (softwood, hardwood, bamboo and cotton) by a facile two-step process, i.e. carbonization in nitrogen and thermal oxidation in air. Without involving any toxic/corrosive chemicals, large surface area of up to 890 m(2)/g was achieved, which is comparable to commercial activated carbon. The porous carbons with various surface area and pore size were used as adsorbents to investigate the pore size dependent adsorption phenomenon. Based on the density functional theory, effective (E-SSA) and ineffective surface area (InE-SSA) was calculated considering the geometry of used probing adsorbate. It was demonstrated that the adsorption capacity strongly depends on E-SSA instead of total surface area. Moreover, a regression model was developed to quantify the adsorption capacities contributed from E-SSA and InE-SSA, respectively. The applicability of this model has been verified by satisfactory prediction results on porous carbons prepared in this work as well as commercial activated carbon. Revealing the pore size dependent adsorption behavior in these biomass derived porous carbon adsorbents will help to design more effective materials (either from biomass or other carbon resources) targeting to specific adsorption applications.

  9. Control of porosity and pore size of metal reinforced carbon nanotube membranes.

    PubMed

    Dumee, Ludovic; Velleman, Leonora; Sears, Kallista; Hill, Matthew; Schutz, Jurg; Finn, Niall; Duke, Mikel; Gray, Stephen

    2010-12-21

    Membranes are crucial in modern industry and both new technologies and materials need to be designed to achieve higher selectivity and performance. Exotic materials such as nanoparticles offer promising perspectives, and combining both their very high specific surface area and the possibility to incorporate them into macrostructures have already shown to substantially increase the membrane performance. In this paper we report on the fabrication and engineering of metal-reinforced carbon nanotube (CNT) Bucky-Paper (BP) composites with tuneable porosity and surface pore size. A BP is an entangled mesh non-woven like structure of nanotubes. Pure CNT BPs present both very high porosity (>90%) and specific surface area (>400 m2/g). Furthermore, their pore size is generally between 20-50 nm making them promising candidates for various membrane and separation applications. Both electro-plating and electroless plating techniques were used to plate different series of BPs and offered various degrees of success. Here we will report mainly on electroless plated gold/CNT composites. The benefit of this method resides in the versatility of the plating and the opportunity to tune both average pore size and porosity of the structure with a high degree of reproducibility. The CNT BPs were first oxidized by short UV/O3 treatment, followed by successive immersion in different plating solutions. The morphology and properties of these samples has been investigated and their performance in air permeation and gas adsorption will be reported.

  10. Control of Porosity and Pore Size of Metal Reinforced Carbon Nanotube Membranes

    PubMed Central

    Dumee, Ludovic; Velleman, Leonora; Sears, Kallista; Hill, Matthew; Schutz, Jurg; Finn, Niall; Duke, Mikel; Gray, Stephen

    2011-01-01

    Membranes are crucial in modern industry and both new technologies and materials need to be designed to achieve higher selectivity and performance. Exotic materials such as nanoparticles offer promising perspectives, and combining both their very high specific surface area and the possibility to incorporate them into macrostructures have already shown to substantially increase the membrane performance. In this paper we report on the fabrication and engineering of metal-reinforced carbon nanotube (CNT) Bucky-Paper (BP) composites with tuneable porosity and surface pore size. A BP is an entangled mesh non-woven like structure of nanotubes. Pure CNT BPs present both very high porosity (>90%) and specific surface area (>400 m2/g). Furthermore, their pore size is generally between 20–50 nm making them promising candidates for various membrane and separation applications. Both electro-plating and electroless plating techniques were used to plate different series of BPs and offered various degrees of success. Here we will report mainly on electroless plated gold/CNT composites. The benefit of this method resides in the versatility of the plating and the opportunity to tune both average pore size and porosity of the structure with a high degree of reproducibility. The CNT BPs were first oxidized by short UV/O3 treatment, followed by successive immersion in different plating solutions. The morphology and properties of these samples has been investigated and their performance in air permeation and gas adsorption will be reported. PMID:24957493

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

    SciTech Connect

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

    2010-10-19

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

  12. On dependence of mechanical properties of brittle material on partial concentrations of different sized pores in its structure in a wide range of porosity

    NASA Astrophysics Data System (ADS)

    Konovalenko, Igor S.; Smolin, Alexey Yu.; Psakhie, Sergey G.

    2015-10-01

    2D and 3D models of mechanical behavior of brittle porous material under uniaxial compression loading were developed in the framework of the movable cellular automaton method. The considered material was characterized by pore size distribution function having two maxima. On the basis of simulation results the dependence of the strength properties of brittle porous material on its total porosity and partial porosities corresponding to pores with different size was revealed. The change in internal structure of material in a wide range of mentioned parameters was analyzed. The main structural factors influencing compression strength of the material at various combinations of values of porosity parameters were identified.

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

    NASA Astrophysics Data System (ADS)

    Zhu, Shenmin; Zhang, Di; Yang, Na

    2009-04-01

    Mesostructure cellular foam (MCF) materials were modified with hydrophobic polyisoprene (PI) through free radical polymerization in the pores network, and the resulting materials (MCF-PI) were investigated as matrices for drug storage. The successful synthesis of PI inside MCF was characterized by Fourier transform infrared (FT-IR), hydrogen nuclear magnetic resonance (1H NMR), X-ray diffraction patterns (XRD) and nitrogen adsorption/desorption measurements. It was interesting to find the resultant system held a relatively large pore size (19.5 nm) and pore volume (1.02 cm3 g-1), which would benefit for drug storage. Ibuprofen (IBU) and vancomycin were selected as model drugs and loaded onto unmodified MCF and modified MCF (MCF-PI). The adsorption capacities of these model drugs on MCF-PI were observed increase as compared to that of on pure MCF, due to the trap effects induced by polyisoprene chains inside the pores. The delivery system of MCF-PI was found to be more favorable for the adsorption of IBU (31 wt%, IBU/silica), possibly attributing to the hydrophobic interaction between IBU and PI formed on the internal surface of MCF matrix. The release of drug through the porous network was investigated by measuring uptake and release of IBU.

  14. Quantitative sizing of nano/microparticles with a tunable elastomeric pore sensor.

    PubMed

    Vogel, Robert; Willmott, Geoff; Kozak, Darby; Roberts, G Seth; Anderson, Will; Groenewegen, Linda; Glossop, Ben; Barnett, Anne; Turner, Ali; Trau, Matt

    2011-05-01

    The use of a "size-tunable" polyurethane resistive pulse sensor for quantitative sizing of nano- and microparticles is presented. A linear relationship, as first suggested by Maxwell, between particle volume and change in electric resistance across the pore was observed. Particle sizes were quantified for a given size-tunable membrane, by first creating a linear calibration curve to a series of monodisperse carboxylated polystyrene particles of various diameters and then applying this curve to calculate the size of "unknown" nanoparticles. The diameters of a selection of synthetic and biological particles, being PMMA and nonfunctionalized polystyrene particles, along with biological nanoparticles (adenovirus) were calculated using this methodology. Calculated particle diameters and coefficients of variation were shown to be in good agreement with both transmission electron microscopy and dynamic light scattering results.

  15. Control of pore size and structure of tissue engineering scaffolds produced by supercritical fluid processing.

    PubMed

    Tai, Hongyun; Mather, Melissa L; Howard, Daniel; Wang, Wenxin; White, Lisa J; Crowe, John A; Morgan, Steve P; Chandra, Amit; Williams, David J; Howdle, Steven M; Shakesheff, Kevin M

    2007-12-17

    Tissue engineering scaffolds require a controlled pore size and structure to host tissue formation. Supercritical carbon dioxide (scCO2) processing may be used to form foamed scaffolds in which the escape of CO2 from a plasticized polymer melt generates gas bubbles that shape the developing pores. The process of forming these scaffolds involves a simultaneous change in phase in the CO2 and the polymer, resulting in rapid expansion of a surface area and changes in polymer rheological properties. Hence, the process is difficult to control with respect to the desired final pore size and structure. In this paper, we describe a detailed study of the effect of polymer chemical composition, molecular weight and processing parameters on final scaffold characteristics. The study focuses on poly(DL-lactic acid) (PDLLA) and poly(DL-lactic acid-co-glycolic acid) (PLGA) as polymer classes with potential application as controlled release scaffolds for growth factor delivery. Processing parameters under investigation were temperature (from 5 to 55 degrees C) and pressure (from 60 to 230 bar). A series of amorphous PDLLA and PLGA polymers with various molecular weights (from 13 KD to 96 KD) and/or chemical compositions (the mole percentage of glycolic acid in the polymers was 0, 15, 25, 35 and 50 respectively) were employed. The resulting scaffolds were characterised by optical microscopy, scanning electron microscopy (SEM), and micro X-ray computed tomography (microCT). This is the first detailed study on using these series polymers for scaffold formation by supercritical technique. This study has demonstrated that the pore size and structure of the supercritical PDLLA and PLGA scaffolds can be tailored by careful control of processing conditions.

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

    NASA Astrophysics Data System (ADS)

    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

  17. Reversible control of pore size and surface chemistry of mesoporous silica through dynamic covalent chemistry: philicity mediated catalysis.

    PubMed

    Singh, Dheeraj Kumar; Pavan Kumar, B V V S; Eswaramoorthy, M

    2015-08-28

    Here, we report the synthesis of adaptive hybrid mesoporous silica having the ability to reconfigure its pore properties such as pore size and philicity in response to the external environment. Decyl chains were reversibly appended to the pore walls of silica through imine motifs as dynamic covalent modules to switch the pore size and philicity in response to pH. This switching of pore properties was used to gate the access of reactants to the gold nanoparticles immobilized inside the nanopores, thus enabling us to turn-on/turn-off the catalytic reaction. The use of such dynamic covalent modules to govern pore properties would enable the realization of intelligent hybrids capable of controlling many such chemical processes in response to stimuli.

  18. Influence of the pore size in multi-walled carbon nanotubes on the hydrogen storage behaviors

    SciTech Connect

    Lee, Seul-Yi; Park, Soo-Jin

    2012-10-15

    Activated multi-walled carbon nanotubes (A-MWCNTs) were prepared using a chemical activation method to obtain well-developed pore structures for use as hydrogen storage materials. The microstructure and crystallinity of the A-MWCNTs were evaluated by X-ray diffraction and Fourier transform Raman spectroscopy. The textural properties of the A-MWCNTs were investigated by nitrogen gas sorption analysis at 77 K. The hydrogen storage capacity of the A-MWCNTs was evaluated at 77 K and 1 bar. The results showed that the specific surface area of the MWCNTs increased from 327 to 495 m{sup 2}/g as the activation temperature was increased. The highest hydrogen storage capacity was observed in the A-MWCNTs sample activated at 900 Degree-Sign C (0.54 wt%). This was attributed to it having the narrowest microporosity, which is a factor closely related to the hydrogen storage capacity. This shows that the hydrogen storage behaviors depend on the pore volume. Although a high pore volume is desirable for hydrogen storage, it is also severely affected if the pore size in the A-MWCNTs for the hydrogen molecules is suitable for creating the activation process. Highlights: Black-Right-Pointing-Pointer The AT-800 and AT-900 samples were prepared by a chemical activation method at activation temperature of 800 and 900 Degree-Sign C, respectively. Black-Right-Pointing-Pointer The AT-900 sample has the narrowest peak in comparison with the AT-800 sample, resulting from the overlap of the two peaks (Peak I and Peak II). Black-Right-Pointing-Pointer This overlapping effect is due to the newly created micropores or shrinkages of pores in Peak II. So, these determining characteristics are essential for designing materials that are suitable for molecular hydrogen storage.

  19. Flare Size Distributions and Active Region Types

    NASA Astrophysics Data System (ADS)

    Bai, Taeil

    2007-05-01

    Size distributions of solar flares measured by various size indicators follow a power law with a negative index of about 1.8. On the basis of general appearance of power-law distributions, Lu and his collegues proposed an avalenche model. According to this model, the power-law index should be independent of active region size, but the cutoff size above which the size distribution steepens rapidly is expected to depend on the active region size. I have analyzed the size distribution of flares, using GOES soft X-ray observations for 2004 and 2005. For flares observed by GOES during these years, their locations are almost completely identified even for C-class flares. This enable us to study the dependence of size distribution on active region type. Comparing the power-law portion of size distributions below the high-end cutoff, I have found that the size distribution index depends on active region type. Flares from prolific active regions exhibit a flatter distribution, while flares from non-prolific active regions exhibit a steeper distribution. I plan to discuss a plausible mechanism for such behavior.

  20. Porous carbon with defined pore size as anode of microbial fuel cell.

    PubMed

    Chen, Xiaofen; Cui, Dan; Wang, Xiaojun; Wang, Xianshu; Li, Weishan

    2015-07-15

    This paper reported a novel anode material, porous carbon with a defined pore size (DPC) matching bacteria, for microbial fuel cell (MFC). The DPC was prepared by using silica spheres as templates and sucrose as carbon precursor. The structure and morphology of the as-prepared DPC were characterized with X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), and its performance as anode of MFC based on Escherichia coli (E. coli) was evaluated with chronoamperometry, cyclic voltammetry (CV) and polarization curve measurement. The result from SEM demonstrates that pores in the as-prepared DPC are well defined with an average diameter of 400nm, which is a little larger than that of E. coli, and the polarization curve measurement shows that the as-prepared DPC exhibits superior performance as anode material loaded on carbon felt, delivering a power output of 1606mWm(-2), compared to the 402mWm(-2) of naked carbon felt anode, in the solution containing 2g/L glucose. The excellent performance of the as-prepared DPC is attributed to its suitable pore size for accommodating E. coli strain, which facilitates the formation of bacterial biofilm and the electron transfer between bacteria and anode. Copyright © 2015 Elsevier B.V. All rights reserved.

  1. Systematic Design of Pore Size and Functionality in Isoreticular MOFs and Their Application in Methane Storage

    NASA Astrophysics Data System (ADS)

    Eddaoudi, Mohamed; Kim, Jaheon; Rosi, Nathaniel; Vodak, David; Wachter, Joseph; O'Keeffe, Michael; Yaghi, Omar M.

    2002-01-01

    A strategy based on reticulating metal ions and organic carboxylate links into extended networks has been advanced to a point that allowed the design of porous structures in which pore size and functionality could be varied systematically. Metal-organic framework (MOF-5), a prototype of a new class of porous materials and one that is constructed from octahedral Zn-O-C clusters and benzene links, was used to demonstrate that its three-dimensional porous system can be functionalized with the organic groups -Br, -NH2, -OC3H7, -OC5H11, -C2H4, and -C4H4 and that its pore size can be expanded with the long molecular struts biphenyl, tetrahydropyrene, pyrene, and terphenyl. We synthesized an isoreticular series (one that has the same framework topology) of 16 highly crystalline materials whose open space represented up to 91.1% of the crystal volume, as well as homogeneous periodic pores that can be incrementally varied from 3.8 to 28.8 angstroms. One member of this series exhibited a high capacity for methane storage (240 cubic centimeters at standard temperature and pressure per gram at 36 atmospheres and ambient temperature), and others the lowest densities (0.41 to 0.21 gram per cubic centimeter) for a crystalline material at room temperature.

  2. Estimating the number and size of phloem sieve plate pores using longitudinal views and geometric reconstruction.

    PubMed

    Bussières, Philippe

    2014-05-12

    Because it is difficult to obtain transverse views of the plant phloem sieve plate pores, which are short tubes, to estimate their number and diameters, a method based on longitudinal views is proposed. This method uses recent methods to estimate the number and the sizes of approximately circular objects from their images, given by slices perpendicular to the objects. Moreover, because such longitudinal views are obtained from slices that are rather close to the plate centres whereas the pore size may vary with the pore distance from the plate edge, a sieve plate reconstruction model was developed and incorporated in the method to consider this bias. The method was successfully tested with published longitudinal views of phloem of Soybean and an exceptional entire transverse view from the same tissue. The method was also validated with simulated slices in two sieve plates from Cucurbita and Phaseolus. This method will likely be useful to estimate and to model the hydraulic conductivity and the architecture of the plant phloem, and it could have applications for other materials with approximately cylindrical structures.

  3. Estimating the number and size of phloem sieve plate pores using longitudinal views and geometric reconstruction

    PubMed Central

    Bussières, Philippe

    2014-01-01

    Because it is difficult to obtain transverse views of the plant phloem sieve plate pores, which are short tubes, to estimate their number and diameters, a method based on longitudinal views is proposed. This method uses recent methods to estimate the number and the sizes of approximately circular objects from their images, given by slices perpendicular to the objects. Moreover, because such longitudinal views are obtained from slices that are rather close to the plate centres whereas the pore size may vary with the pore distance from the plate edge, a sieve plate reconstruction model was developed and incorporated in the method to consider this bias. The method was successfully tested with published longitudinal views of phloem of Soybean and an exceptional entire transverse view from the same tissue. The method was also validated with simulated slices in two sieve plates from Cucurbita and Phaseolus. This method will likely be useful to estimate and to model the hydraulic conductivity and the architecture of the plant phloem, and it could have applications for other materials with approximately cylindrical structures. PMID:24816291

  4. Reversible control of pore size and surface chemistry of mesoporous silica through dynamic covalent chemistry: philicity mediated catalysis

    NASA Astrophysics Data System (ADS)

    Singh, Dheeraj Kumar; Pavan Kumar, B. V. V. S.; Eswaramoorthy, M.

    2015-08-01

    Here, we report the synthesis of adaptive hybrid mesoporous silica having the ability to reconfigure its pore properties such as pore size and philicity in response to the external environment. Decyl chains were reversibly appended to the pore walls of silica through imine motifs as dynamic covalent modules to switch the pore size and philicity in response to pH. This switching of pore properties was used to gate the access of reactants to the gold nanoparticles immobilized inside the nanopores, thus enabling us to turn-on/turn-off the catalytic reaction. The use of such dynamic covalent modules to govern pore properties would enable the realization of intelligent hybrids capable of controlling many such chemical processes in response to stimuli.Here, we report the synthesis of adaptive hybrid mesoporous silica having the ability to reconfigure its pore properties such as pore size and philicity in response to the external environment. Decyl chains were reversibly appended to the pore walls of silica through imine motifs as dynamic covalent modules to switch the pore size and philicity in response to pH. This switching of pore properties was used to gate the access of reactants to the gold nanoparticles immobilized inside the nanopores, thus enabling us to turn-on/turn-off the catalytic reaction. The use of such dynamic covalent modules to govern pore properties would enable the realization of intelligent hybrids capable of controlling many such chemical processes in response to stimuli. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr02959g

  5. Porosity, Pore Size, and Permeability of Sediments from Site C0002, IODP Expedition 338

    NASA Astrophysics Data System (ADS)

    Dugan, B.; Huepers, A.; Song, I.; Kitajima, H.; Esteban, L.

    2013-12-01

    Mercury injection capillary pressure (MICP) measurements were made on cuttings and core samples from Integrated Ocean Drilling Program (IODP) Site C0002 to evaluate porosity, pore throat size, and permeability of mud(stone) at the centerpiece drill site of the Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE). Core samples from 221-464 meters below sea floor (mbsf) in the Kumano forearc basin have MICP-determined porosities from 40-56%, median pore radii from 0.077-0.205 microns, and permeability from 3.3x10-10 - 2.0x10-9 m2. The porosity of these core samples is similar to shipboard porosity determined from moisture and density (MAD) analyses. During IODP Expedition 338 cuttings samples were recovered from ~865-2005 mbsf during riser drilling at Site C0002F. MICP analyses of cuttings samples, greater than 4 mm size fraction, from 928-1980 mbsf in the inner wedge of the accretionary prism constrain porosities from 21-44%, median pore radii from 0.021-0.032 microns, and permeability from 1.2x10-11 - 1.6x10-10 m2. The porosity of these cuttings samples is consistently lower than the MAD-determined porosity on cuttings from the >4mm size fraction, however the values are consistent with core-based, MAD-derived porosity from Hole C0002B above 1057 mbsf and with cuttings-based, MAD-derived porosity on select samples from 1700-2000 mbsf that were determined to be intact formation and not influenced by drilling disturbance. These results suggest that select formation cuttings or MICP-analyses can help define in situ porosity. Additional post-expedition research will be used to better understand the ability of MICP data to define mudstone permeability and to constrain permeability-porosity and permeability-grain size-pore throat relations for sediments at Site C0002. A detailed model of permeability and porosity behavior will inform modeling studies of pore pressure generation and fluid and heat transport.

  6. Laboratory air bubble generation of various size distributions

    SciTech Connect

    Puleo, Jack A.; Johnson, Rex V.; Kooney, Tim N.

    2004-11-01

    Air bubble size in aqueous environments is an important factor governing natural processes ranging from fluid/atmosphere gas transfer to noise production. Bubbles are also known to affect various scientific instruments. In this study we investigate the production capability of eight inexpensive bubble generators using optical imaging techniques. Specific emphasis is directed towards determining bubble size and distribution for a given device, flow conditions, and type of water used (fresh vs salt). In almost all cases tested here, bubbles produced in salt water were more numerous, and smaller than for the same bubbler and conditions in fresh water. For porous media, the finer the pore size, the smaller the bubble produced with some variation depending on thickness of material containing the pore and water type. While no single generator tested was capable of spanning all the bubble sizes observed (100 to 6000 microns), the data contained herein will enable proper choice of bubbler or combinations thereof for future studies depending on the size and distribution of bubbles required.

  7. An integrated approach for determination of pore-type distribution in carbonate-siliciclastic Asmari Reservoir, Cheshmeh-Khosh Oilfield, SW Iran

    NASA Astrophysics Data System (ADS)

    Gharechelou, Sajjad; Amini, Abdolhossein; Kadkhodaie-Ilkhchi, Ali; Moradi, Babak

    2015-10-01

    This paper presents an integrated pore type study at microscopic (core data), mesoscopic (well logs) and megascopic scales (3D seismic data) in the mixed carbonate-siliciclastic Asmari Reservoir of the Cheshmeh-Khosh Oilfield, SW Iran. Firstly, pore types are determined in a microscopic scale based on petrographic studies of thin sections. Well logs and nuclear magnetic resonance (NMR) log data are employed for pore type determination based on a velocity deviation log (mesoscopic scale). For each pore type subclass, a suite of physical rock properties including average poroperm values, T2 distribution, capillary pressure, pore size distribution and depositional texture are calculated. For this purpose, the NMR log, mercury injection capillary pressure data and core descriptions are interpreted in an integrated approach. Capillary pressure and pore size distribution in each pore type class are determined by mercury injection capillary pressure tests and synthesis of a continuous capillary pressure log from the NMR log (pseudo Pc curves). For dynamic behavior examination of the reservoir, the pore types are analysed in the framework of hydraulic flow units. Finally, 3D post-stacked seismic data are converted to a cube of pore types based on acoustic impedance inversion and seismic attributes. The methodology of this study is accomplished by using core and log data from three key wells and a 3D post-stack seismic data from the studied field. Lastly, a map of pore type distribution is established to provide a clue on the high and low permeable zones of the field. The presented methodology signifies reservoir anatomy on micro to mega scales.

  8. Variations of sediment size and size distribution along a river

    NASA Astrophysics Data System (ADS)

    Jan, C. D.; Tsai, Y. C.; Yang, S. Y.

    2015-12-01

    Sediment material of a river bed is an important factor for river morphodynamics. Typically, alluvial rivers construct their own geometries based on the sediment size and its distribution that affect the sediment transport capacity in river channel networks, involving the issues of watershed sediment yield, flood controls and the evolution of flood plain, habitats, deltas and adjacent coastline. Hence, investigating grain size and size distribution of sediment materials on riverbeds is important for practical river management and assessment of landscape evolution. In this study, we collected total 43 sediment samplings along the Koaping River in southern Taiwan to analyze the grain size and its distribution along the river. Spatial distributions of different representative grain sizes, such as D50 and D90, and the size corresponding Manning's n values are analyzed and discussed in this paper. An exponential grain size distribution (GSD) formula is used to explore the relation between the frequency and size of riverbed sediment. Results show that the grain size has a wide range distribution in the river upstream but displays a narrow-range variation in the river downstream. For example, the sediment medium size D50 ranges from 1.25 mm to 391.27 mm with an average of 49.36 mm in the upstream while it ranges from 0.135 mm to 0.625 mm with an average of 0.338 mm in the downstream. The best fitting curves of GSD with exponential scaling are analyzed with an empirical parameter Dc that is used to normalize the sediment grain size. This study finds that the empirical parameter Dc could be replaced by the sediment resentative size D65 (65% of sediment smaller than it). The results obtained herein could be useful not only in analyzing sediment transport of a river but also in river management.

  9. Fabricating tubular scaffolds with a radial pore size gradient by a spinning technique.

    PubMed

    Harley, Brendan A; Hastings, Abel Z; Yannas, Ioannis V; Sannino, Alessandro

    2006-02-01

    A novel fabrication process has been developed to produce collagen-based, porous tubular scaffolds to facilitate the study of myofibroblast migration during peripheral nerve regeneration; however, this fabrication technique offers broader appeal for the production of a variety of tubular structures without the use of a complicated mold system. A collagen-glycosaminoglycan (CG) suspension in acetic acid was spun in a cylindrical copper mold about its longitudinal axis at variable angular velocities and for different times, resulting in variable relative sedimentation of the CG content towards the mold outer edge; after the specified spinning time, the spinning mold was placed into a bath of liquid nitrogen where the CG suspension was rapidly frozen. Due to the rapid solidification, the CG content remained sedimented while an interconnected network of ice crystals formed throughout. Sublimation of the frozen mass removed the solvent (acetic acid) content, producing a porous, tubular structure defined by sedimentation and ice crystal nucleation processes. A porous, tubular scaffold with a sharply defined inner tube wall can be produced; further, increasing the spinning time and/or spinning velocity increases the sedimentation effect leading to the production of a hollow tube with a larger inner diameter. The tube walls display a radially aligned pore structure, even in cases where sedimentation was not sufficient to produce a hollow tube. A gradient of porosity along the tube radius was also observed in cases of extreme sedimentation: the pore structure of the external portion of the tube wall had a larger solid volume fraction and a smaller mean pore size compared to the internal portion of the tube. This tubular structure may allow preferential cell migration from the inner tube lumen towards the outer tube edge while blocking cell entrance into the tube through its outer surface due to increased scaffold relative density and decreased pore size.

  10. Novel magnetic Fe onion-like fullerene micrometer-sized particles of narrow size distribution

    NASA Astrophysics Data System (ADS)

    Snovski, Ron; Grinblat, Judith; Margel, Shlomo

    2012-01-01

    Magnetic polydivinylbenzene (PDVB)/magnetite micrometer-sized particles of narrow size distribution were prepared by entrapping Fe(CO)5 within the pores of uniform porous PDVB particles, followed by the thermal decomposition of the encapsulated Fe(CO)5 at 300 °C in a sealed cell under inert atmosphere. Magnetic Fe onion-like fullerene micrometer-sized particles of narrow size distribution have been prepared by the thermal decomposition of the PDVB/magnetite magnetic microspheres at 1100 °C under inert atmosphere. The graphitic coating protects the elemental iron particles from oxidation and thereby preserves their very high magnetic moment for at least a year. Characterization of these unique magnetic carbon graphitic particles was also performed.

  11. City-size distribution and the size of urban systems.

    PubMed

    Thomas, I

    1985-07-01

    "This paper is an analysis of the city-size distribution for thirty-five countries of the world in 1975; the purpose is to explain statistically the regularity of the rank-size distribution by the number of cities included in the urban systems. The rank-size parameters have been computed for each country and also for four large urban systems in which several population thresholds have been defined. These thresholds seem to have more influence than the number of cities included in the urban system on the regularity of the distribution." The data are from the U.N. Demographic Yearbook. excerpt

  12. Cumulative frequency fit for particle size distribution.

    PubMed

    Xu, Zhuyun; Gautam, Mridul; Mehta, Sandeep

    2002-08-01

    A cumulative frequency distribution fit method is presented for analyzing particle size distributions by minimizing the summation of the square of cumulative frequency errors. Compared to the frequency fit method, the cumulative frequency fit method yields a more accurate solution. Based upon this, a spreadsheet was developed for analyzing multi-modal particle size distribution. The motivation for the work presented in this article was the current interest in ultra-fine and nano-sized particle exhaust emissions from heavy-duty diesel engines. The new spreadsheet provides a quick and convenient way to conduct particle size distribution analysis.

  13. Gel-impregnated pore membranes with mesh-size asymmetry for biohybrid artificial organs.

    PubMed

    Dai, W S; Barbari, T A

    2000-07-01

    Membranes based on mechanically supported poly(vinyl alcohol) (PVA) hydrogels with mesh-size asymmetry were developed for potential application in biohybrid artificial organs. The pores of cellulose ester microfiltration membranes were impregnated with a PVA solution, which was lightly crosslinked with glutaraldehyde and then modified under a glutaraldehyde gradient to produce mesh-size asymmetry. Permeation experiments were performed with the resulting homogeneous and asymmetric gel-impregnated pore membranes (GIPMs). Creatinine (MW: 113), goat Fab (MW: 50 kD) and human IgG (MW: 150 kD) were used to simulate the molecular size of nutrients, therapeutic proteins, and immunological molecules, respectively. The transport properties of the GIPMs were compared to those of conventional ultrafiltration (UF) and dialysis membranes. Experimental results indicate that GIPMs with mesh-size asymmetry have thickness-normalized creatinine permeabilities that are slightly higher than those in cellulosic UF membranes but as much as 100% greater than those in polysulfone UF or cellulosic dialysis membranes. IgG permeabilities in the GIPMs are from 5 to 50 times lower than those in the UF membranes. Fab permeabilities are 6 to 40 times higher in the UF membranes than those in the GIPMs, but the required permeability for a therapeutic protein is application specific. GIPMs may also be suitable as an alternative for hemodialysis.

  14. Effect of pore sizes of PLGA scaffolds on mechanical properties and cell behaviour for nucleus pulposus regeneration in vivo.

    PubMed

    Kim, Hye Yun; Kim, Ha Neul; Lee, So Jin; Song, Jeong Eun; Kwon, Soon Yong; Chung, Jin Wha; Lee, Dongwon; Khang, Gilson

    2017-01-01

    This study investigated the influence of pore sizes of poly(lactic-co-glycolic acid) (PLGA) scaffolds on the compressive strength of tissue-engineered biodiscs and selection of the best suitable pore size for cells to grow in vivo. PLGA scaffolds were fabricated by solvent casting/salt-leaching with pore sizes of 90-180, 180-250, 250-355 and 355-425 µm. Nucleus pulposus (NP) cells were seeded on PLGA scaffolds with various pore sizes. Each sample was harvested at each time point, after retrieval of PLGA scaffolds seeded with NP cells, which were implanted into subcutaneous spaces in nude mice at 4 and 6 weeks. MTT assay, glycosaminoglycan (GAG) assay, haematoxylin and eosin (H&E) staining, safranin O staining and immunohistochemistry (for collagen type II) were performed at each time point. As the pores became smaller, the value of the compressive strength of the scaffold was increased. The group of scaffolds with pore sizes of 90-250 µm showed better cell proliferation and ECM production. These results demonstrated that the compressive strength of the scaffold was improved while the scaffold had pore sizes in the range 90-250 µm and good cell interconnectivity. Suitable space in the scaffold for cell viability is a key factor for cell metabolism. Copyright © 2014 John Wiley & Sons, Ltd. Copyright © 2014 John Wiley & Sons, Ltd.

  15. The Influence of Pore Size on the Indentation Behavior of Metallic Nanoporous Materials: A Molecular Dynamics Study.

    PubMed

    Esqué-de Los Ojos, Daniel; Pellicer, Eva; Sort, Jordi

    2016-05-11

    In general, the influence of pore size is not considered when determining the Young's modulus of nanoporous materials. Here, we demonstrate that the pore size needs to be taken into account to properly assess the mechanical properties of these materials. Molecular dynamics simulations of spherical indentation experiments on single crystalline nanoporous Cu have been undertaken in systems with: (i) a constant degree of porosity and variable pore diameter; and (ii) a constant pore diameter and variable porosity degree. The classical Gibson and Ashby expression relating Young's modulus with the relative density of the nanoporous metal is modified to include the influence of the pore size. The simulations reveal that, for a fixed porosity degree, the mechanical behavior of materials with smaller pores differs more significantly from the behavior of the bulk, fully dense counterpart. This effect is ascribed to the increase of the overall surface area as the pore size is reduced, together with the reduced coordination number of the atoms located at the pores edges.

  16. Pore-size effect on photovoltaic performance of dye-sensitized solar cells composed of mesoporous anatase-titania

    NASA Astrophysics Data System (ADS)

    Yun, Tae Kwan; Park, Sung Soo; Kim, Duckhyun; Hwang, Yong-Kyung; Huh, Seong; Bae, Jae Young; Won, Yong Sun

    The effect of the pore size of mesoporous anatase-TiO 2 on the photovoltaic performance of dye-sensitized solar cells (DSSCs) is investigated. The mesoporous TiO 2 particles are synthesized by two different methods using a soft template of tri-block copolymer and a hard template of mesoporous ZnO/Zn(OH) 2-composite. These methods produce the same high surface area (S BET ∼ 210 m 2 g -1) but different pore sizes of 6.8 and 3.0 nm, respectively. With the mesoporous TiO 2 having larger pores, the photo-conversion efficiency (η) is increased significantly to 6.71%, compared with 5.62% that is typically achieved using P25 TiO 2 nanopowders. By comparison, only half the performance (3.05%) has been observed with mesoporous TiO 2 that has small pores. Mesoporous TiO 2 with suitable pore sizes (∼6.8 nm) makes the most of its high surface area and thereby allows a high uptake of dye to enhance the current density. In contrast, the low efficiency of mesoporous TiO 2 with small pores is attributed to the low uptake of dye due to the smaller pore size (∼3.0 nm), which blocks the diffusion and adsorption of dye molecules through the pores.

  17. The Influence of Pore Size on the Indentation Behavior of Metallic Nanoporous Materials: A Molecular Dynamics Study

    PubMed Central

    Esqué-de los Ojos, Daniel; Pellicer, Eva; Sort, Jordi

    2016-01-01

    In general, the influence of pore size is not considered when determining the Young’s modulus of nanoporous materials. Here, we demonstrate that the pore size needs to be taken into account to properly assess the mechanical properties of these materials. Molecular dynamics simulations of spherical indentation experiments on single crystalline nanoporous Cu have been undertaken in systems with: (i) a constant degree of porosity and variable pore diameter; and (ii) a constant pore diameter and variable porosity degree. The classical Gibson and Ashby expression relating Young’s modulus with the relative density of the nanoporous metal is modified to include the influence of the pore size. The simulations reveal that, for a fixed porosity degree, the mechanical behavior of materials with smaller pores differs more significantly from the behavior of the bulk, fully dense counterpart. This effect is ascribed to the increase of the overall surface area as the pore size is reduced, together with the reduced coordination number of the atoms located at the pores edges. PMID:28773476

  18. Inversion of Seismic Velocities to obtain the Crack and Pore Aspect Ratio Distribution

    NASA Astrophysics Data System (ADS)

    Zimmerman, R. W.; David, E. C.

    2010-12-01

    During a hydrostatic experiment, in the elastic regime, P and S elastic wave velocities measured on rock samples generally increase with pressure and reach asymptotic values at high pressures. This increase of seismic velocities with confining pressure is known to be caused by the closure of compliant pores, such as flat “cracks”, and therefore the high-pressure values of the velocities must reflect only the influence of stiff, “equant” pores. If the pores are assumed to be spheroids, the use of an effective medium theory, combined with a crack closure model, gives a model to relate the elastic properties to the microstructure at each pressure. Therefore, the pressure dependence of elastic velocities can be inverted to obtain the pore aspect ratio distribution. This is done more easily using data obtained in dry experiments, since pore fluids have a strong effect on velocities and to some extent mask the effect of the pore geometry. However, thus far most models have used restrictive assumptions, such as assuming that the stiff pores are spherical, or the interactions between inclusions can be neglected (such as Morlier’s method), which is unfortunately not realistic in most cases. Others methods, such as the one developed by Cheng and Toksoz (1979), assume that the rock contains a discrete distribution of crack aspect ratios, and are complicated to implement numerically. Moreover, in most work only the dry data have been inverted, or jointly the dry and wet data, but it seems that few works have tried to look in detail at a consistent pore model, that remains simple and is able to predict the dependence of Vp and Vs under saturated conditions, based on data collected on dry rocks. We assume that the rock contains a distribution of cracks with different aspect ratios, and two families of stiff pores, each with their own finite aspect ratio. We use this model to invert the wavespeeds to obtain aspect ratio distributions of some isotropic sandstones (Berea

  19. Biotemplating pores with size and shape diversity for Li-oxygen Battery Cathodes

    PubMed Central

    Oh, Dahyun; Ozgit-Akgun, Çagla; Akca, Esin; Thompson, Leslie E.; Tadesse, Loza F.; Kim, Ho-Cheol; Demirci, Gökhan; Miller, Robert D.; Maune, Hareem

    2017-01-01

    Synthetic porogens provide an easy way to create porous structures, but their usage is limited due to synthetic difficulties, process complexities and prohibitive costs. Here we investigate the use of bacteria, sustainable and naturally abundant materials, as a pore template. The bacteria require no chemical synthesis, come in variable sizes and shapes, degrade easier and are approximately a million times cheaper than conventional porogens. We fabricate free standing porous multiwalled carbon nanotube (MWCNT) films using cultured, harmless bacteria as porogens, and demonstrate substantial Li-oxygen battery performance improvement by porosity control. Pore volume as well as shape in the cathodes were easily tuned to improve oxygen evolution efficiency by 30% and double the full discharge capacity in repeated cycles compared to the compact MWCNT electrode films. The interconnected pores produced by the templates greatly improve the accessibility of reactants allowing the achievement of 4,942 W/kg (8,649 Wh/kg) at 2 A/ge (1.7 mA/cm2). PMID:28374862

  20. Biotemplating pores with size and shape diversity for Li-oxygen Battery Cathodes

    NASA Astrophysics Data System (ADS)

    Oh, Dahyun; Ozgit-Akgun, Çagla; Akca, Esin; Thompson, Leslie E.; Tadesse, Loza F.; Kim, Ho-Cheol; Demirci, Gökhan; Miller, Robert D.; Maune, Hareem

    2017-04-01

    Synthetic porogens provide an easy way to create porous structures, but their usage is limited due to synthetic difficulties, process complexities and prohibitive costs. Here we investigate the use of bacteria, sustainable and naturally abundant materials, as a pore template. The bacteria require no chemical synthesis, come in variable sizes and shapes, degrade easier and are approximately a million times cheaper than conventional porogens. We fabricate free standing porous multiwalled carbon nanotube (MWCNT) films using cultured, harmless bacteria as porogens, and demonstrate substantial Li-oxygen battery performance improvement by porosity control. Pore volume as well as shape in the cathodes were easily tuned to improve oxygen evolution efficiency by 30% and double the full discharge capacity in repeated cycles compared to the compact MWCNT electrode films. The interconnected pores produced by the templates greatly improve the accessibility of reactants allowing the achievement of 4,942 W/kg (8,649 Wh/kg) at 2 A/ge (1.7 mA/cm2).

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

    PubMed

    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.

  2. Optimization of protein fractionation by skim milk microfiltration: Choice of ceramic membrane pore size and filtration temperature.

    PubMed

    Jørgensen, Camilla Elise; Abrahamsen, Roger K; Rukke, Elling-Olav; Johansen, Anne-Grethe; Schüller, Reidar B; Skeie, Siv B

    2016-08-01

    The objective of this study was to investigate how ceramic membrane pore size and filtration temperature influence the protein fractionation of skim milk by cross flow microfiltration (MF). Microfiltration was performed at a uniform transmembrane pressure with constant permeate flux to a volume concentration factor of 2.5. Three different membrane pore sizes, 0.05, 0.10, and 0.20µm, were used at a filtration temperature of 50°C. Furthermore, at pore size 0.10µm, 2 different filtration temperatures were investigated: 50 and 60°C. The transmission of proteins increased with increasing pore size, giving the permeate from MF with the 0.20-µm membrane a significantly higher concentration of native whey proteins compared with the permeates from the 0.05- and 0.10-µm membranes (0.50, 0.24, and 0.39%, respectively). Significant amounts of caseins permeated the 0.20-µm membrane (1.4%), giving a permeate with a whitish appearance and a casein distribution (αS2-CN: αS1-CN: κ-CN: β-CN) similar to that of skim milk. The 0.05- and 0.10-µm membranes were able to retain all caseins (only negligible amounts were detected). A permeate free from casein is beneficial in the production of native whey protein concentrates and in applications where transparency is an important functional characteristic. Microfiltration of skim milk at 50°C with the 0.10-µm membrane resulted in a permeate containing significantly more native whey proteins than the permeate from MF at 60°C. The more rapid increase in transmembrane pressure and the significantly lower concentration of caseins in the retentate at 60°C indicated that a higher concentration of caseins deposited on the membrane, and consequently reduced the native whey protein transmission. Optimal protein fractionation of skim milk into a casein-rich retentate and a permeate with native whey proteins were obtained by 0.10-µm MF at 50°C.

  3. Micro and nano-size pores of clay minerals in shale reservoirs: Implication for the accumulation of shale gas

    NASA Astrophysics Data System (ADS)

    Chen, Shangbin; Han, Yufu; Fu, Changqin; Zhang, han; Zhu, Yanming; Zuo, Zhaoxi

    2016-08-01

    A pore is an essential component of shale gas reservoirs. Clay minerals are the adsorption carrier second only to organic matter. This paper uses the organic maturity test, Field-Emission Scanning Electron Microscopy (FE-SEM), and X-ray Diffraction (XRD) to study the structure and effect of clay minerals on storing gas in shales. Results show the depositional environment and organic maturity influence the content and types of clay minerals as well as their structure in the three types of sedimentary facies in China. Clay minerals develop multi-size pores which shrink to micro- and nano-size by close compaction during diagenesis. Micro- and nano-pores can be divided into six types: 1) interlayer, 2) intergranular, 3) pore and fracture in contact with organic matter, 4) pore and fracture in contact with other types of minerals, 5) dissolved and, 6) micro-cracks. The contribution of clay minerals to the presence of pores in shale is evident and the clay plane porosity can even reach 16%, close to the contribution of organic matter. The amount of clay minerals and pores displays a positive correlation. Clay minerals possess a strong adsorption which is affected by moisture and reservoir maturity. Different pore levels of clay minerals are mutually arranged, thus essentially producing distinct reservoir adsorption effects. Understanding the structural characteristics of micro- and nano-pores in clay minerals can provide a tool for the exploration and development of shale gas reservoirs.

  4. Body size distribution of the dinosaurs.

    PubMed

    O'Gorman, Eoin J; Hone, David W E

    2012-01-01

    The distribution of species body size is critically important for determining resource use within a group or clade. It is widely known that non-avian dinosaurs were the largest creatures to roam the Earth. There is, however, little understanding of how maximum species body size was distributed among the dinosaurs. Do they share a similar distribution to modern day vertebrate groups in spite of their large size, or did they exhibit fundamentally different distributions due to unique evolutionary pressures and adaptations? Here, we address this question by comparing the distribution of maximum species body size for dinosaurs to an extensive set of extant and extinct vertebrate groups. We also examine the body size distribution of dinosaurs by various sub-groups, time periods and formations. We find that dinosaurs exhibit a strong skew towards larger species, in direct contrast to modern day vertebrates. This pattern is not solely an artefact of bias in the fossil record, as demonstrated by contrasting distributions in two major extinct groups and supports the hypothesis that dinosaurs exhibited a fundamentally different life history strategy to other terrestrial vertebrates. A disparity in the size distribution of the herbivorous Ornithischia and Sauropodomorpha and the largely carnivorous Theropoda suggests that this pattern may have been a product of a divergence in evolutionary strategies: herbivorous dinosaurs rapidly evolved large size to escape predation by carnivores and maximise digestive efficiency; carnivores had sufficient resources among juvenile dinosaurs and non-dinosaurian prey to achieve optimal success at smaller body size.

  5. Body Size Distribution of the Dinosaurs

    PubMed Central

    O’Gorman, Eoin J.; Hone, David W. E.

    2012-01-01

    The distribution of species body size is critically important for determining resource use within a group or clade. It is widely known that non-avian dinosaurs were the largest creatures to roam the Earth. There is, however, little understanding of how maximum species body size was distributed among the dinosaurs. Do they share a similar distribution to modern day vertebrate groups in spite of their large size, or did they exhibit fundamentally different distributions due to unique evolutionary pressures and adaptations? Here, we address this question by comparing the distribution of maximum species body size for dinosaurs to an extensive set of extant and extinct vertebrate groups. We also examine the body size distribution of dinosaurs by various sub-groups, time periods and formations. We find that dinosaurs exhibit a strong skew towards larger species, in direct contrast to modern day vertebrates. This pattern is not solely an artefact of bias in the fossil record, as demonstrated by contrasting distributions in two major extinct groups and supports the hypothesis that dinosaurs exhibited a fundamentally different life history strategy to other terrestrial vertebrates. A disparity in the size distribution of the herbivorous Ornithischia and Sauropodomorpha and the largely carnivorous Theropoda suggests that this pattern may have been a product of a divergence in evolutionary strategies: herbivorous dinosaurs rapidly evolved large size to escape predation by carnivores and maximise digestive efficiency; carnivores had sufficient resources among juvenile dinosaurs and non-dinosaurian prey to achieve optimal success at smaller body size. PMID:23284818

  6. Scaling in animal group-size distributions

    PubMed Central

    Bonabeau, Eric; Dagorn, Laurent; Fréon, Pierre

    1999-01-01

    An elementary model of animal aggregation is presented. The group-size distributions resulting from this model are truncated power laws. The predictions of the model are found to be consistent with data that describe the group-size distributions of tuna fish, sardinellas, and African buffaloes. PMID:10200286

  7. Effective pore size and radius of capture for K+ ions in K-channels

    PubMed Central

    Moldenhauer, Hans; Díaz-Franulic, Ignacio; González-Nilo, Fernando; Naranjo, David

    2016-01-01

    Reconciling protein functional data with crystal structure is arduous because rare conformations or crystallization artifacts occur. Here we present a tool to validate the dimensions of open pore structures of potassium-selective ion channels. We used freely available algorithms to calculate the molecular contour of the pore to determine the effective internal pore radius (rE) in several K-channel crystal structures. rE was operationally defined as the radius of the biggest sphere able to enter the pore from the cytosolic side. We obtained consistent rE estimates for MthK and Kv1.2/2.1 structures, with rE = 5.3–5.9 Å and rE = 4.5–5.2 Å, respectively. We compared these structural estimates with functional assessments of the internal mouth radii of capture (rC) for two electrophysiological counterparts, the large conductance calcium activated K-channel (rC = 2.2 Å) and the Shaker Kv-channel (rC = 0.8 Å), for MthK and Kv1.2/2.1 structures, respectively. Calculating the difference between rE and rC, produced consistent size radii of 3.1–3.7 Å and 3.6–4.4 Å for hydrated K+ ions. These hydrated K+ estimates harmonize with others obtained with diverse experimental and theoretical methods. Thus, these findings validate MthK and the Kv1.2/2.1 structures as templates for open BK and Kv-channels, respectively. PMID:26831782

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

    PubMed

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

    2016-08-22

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

  9. City size distributions and spatial economic change.

    PubMed

    Sheppard, E

    1982-10-01

    "The concept of the city size distribution is criticized for its lack of consideration of the effects of interurban interdependencies on the growth of cities. Theoretical justifications for the rank-size relationship have the same shortcomings, and an empirical study reveals that there is little correlation between deviations from rank-size distributions and national economic and social characteristics. Thus arguments suggesting a close correspondence between city size distributions and the level of development of a country, irrespective of intranational variations in city location and socioeconomic characteristics, seem to have little foundation." (summary in FRE, ITA, JPN, ) excerpt

  10. Particles size distribution in diluted magnetic fluids

    NASA Astrophysics Data System (ADS)

    Yerin, Constantine V.

    2017-06-01

    Changes in particles and aggregates size distribution in diluted kerosene based magnetic fluids is studied by dynamic light scattering method. It has been found that immediately after dilution in magnetic fluids the system of aggregates with sizes ranging from 100 to 250-1000 nm is formed. In 50-100 h after dilution large aggregates are peptized and in the sample stationary particles and aggregates size distribution is fixed.

  11. Size distributions of solar energetic particle events

    NASA Technical Reports Server (NTRS)

    Cliver, E.; Reames, D.; Kahler, S.; Cane, H.

    1991-01-01

    NASA particle detectors on the IMP-8 are employed to determine the size distributions of the peak fluxes of events related to solar-energetic particles including protons and electrons. The energetic proton events show a flatter size distribution which suggests that not all flares are proton flares. Both the electron and proton events are classified as either 'impulsive' or 'gradual', and the impulsive events tend to have a steeper power-law distribution.

  12. Experimental determination of size distributions: analyzing proper sample sizes

    NASA Astrophysics Data System (ADS)

    Buffo, A.; Alopaeus, V.

    2016-04-01

    The measurement of various particle size distributions is a crucial aspect for many applications in the process industry. Size distribution is often related to the final product quality, as in crystallization or polymerization. In other cases it is related to the correct evaluation of heat and mass transfer, as well as reaction rates, depending on the interfacial area between the different phases or to the assessment of yield stresses of polycrystalline metals/alloys samples. The experimental determination of such distributions often involves laborious sampling procedures and the statistical significance of the outcome is rarely investigated. In this work, we propose a novel rigorous tool, based on inferential statistics, to determine the number of samples needed to obtain reliable measurements of size distribution, according to specific requirements defined a priori. Such methodology can be adopted regardless of the measurement technique used.

  13. Asteroid Size-Frequency Distribution

    NASA Technical Reports Server (NTRS)

    Tedesco, Edward F.

    2001-01-01

    A total of six deep exposures (using AOT CAM01 with a 6 inch PFOV) through the ISOCAM LW10 filter (IRAS Band 1, i.e. 12 micron) were obtained on an approximately 15 arcminute square field centered on the ecliptic plane. Point sources were extracted using the technique described. Two known asteroids appear in these frames and 20 sources moving with velocities appropriate for main belt asteroids are present. Most of the asteroids detected have flux densities less than 1 mJy, i,e., between 150 and 350 times fainter than any of the asteroids observed by IRAS. These data provide the first direct measurement of the 12 pm sky-plane density for asteroids on the ecliptic equator. The median zodiacal foreground, as measured by ISOCAM during this survey, is found to be 22.1 +/- 1.5 mJy per pixel, i.e., 26.2 +/- 1.7 MJy/sr. The results presented here imply that the actual number of kilometer-sized asteroids is significantly greater than previously believed and in reasonable agreement with the Statistical Asteroid Model.

  14. Anodic aluminum oxide with fine pore size control for selective and effective particulate matter filtering

    NASA Astrophysics Data System (ADS)

    Zhang, Su; Wang, Yang; Tan, Yingling; Zhu, Jianfeng; Liu, Kai; Zhu, Jia

    2016-07-01

    Air pollution is widely considered as one of the most pressing environmental health issues. Particularly, atmospheric particulate matters (PM), a complex mixture of solid or liquid matter suspended in the atmosphere, are a harmful form of air pollution due to its ability to penetrate deep into the lungs and blood streams, causing permanent damages such as DNA mutations and premature death. Therefore, porous materials which can effectively filter out particulate matters are highly desirable. Here, for the first time, we demonstrate that anodic aluminum oxide with fine pore size control fabricated through a scalable process can serve as effective and selective filtering materials for different types of particulate matters (such as PM2.5, PM10). Combining selective and dramatic filtering effect, fine pore size control and a scalable process, this type of anodic aluminum oxide templates can potentially serve as a novel selective filter for different kinds of particulate matters, and a promising and complementary solution to tackle this serious environmental issue.

  15. Prediction of velocity distribution from pore structure in 3D porous media

    NASA Astrophysics Data System (ADS)

    AlAdwani, M. S. K. F. S.; De Anna, P.; Juanes, R.

    2016-12-01

    Fluid flow and particle transport through porous media are determined by the geometry of the host medium itself. Despite the fundamental importance of the velocity distribution in controlling early-time and late-time transport properties (e.g., early breakthrough and superdiffusive spreading), direct relations linking velocity distribution with the statistics of pore structure in 3D porous media have not been established yet. High velocities are controlled by the formation of channels, while low velocities are dominated by stagnation zones. Recent studies have proposed phenomenological models for the distribution of high velocities including stretched exponential and power-exponential distributions but without an underlying mechanistic or statistical physics theory. Here, we investigate the relationship between the structure of the host medium and the resulting fluid flow and particle transport properties. We extend recent work on simple 2D media consisting of circular nonoverlapping disks, and consider 3D random packs of spheres. This disordered spherical-pack arrangement can be characterized geometrically by constructing a Delaunay triangulation of the disk centers: each tetrahedron defines a pore body and each triangular face defines a pore throat. We simulate flow in the exact pore geometry at low Reynolds numbers by solving the Stokes equations and imposing a no-slip boundary condition at the boundary of each sphere. We develop a theoretical model to explain the observed distribution of the low velocities. We understand flow through the porous medium as being controlled by the pore throats, and we conceptualize flow through each pore throat as a Hagen-Poiseuille flow through a pipe of irregular shape controlled by its area and its shape factor. Despite its simplicity, the analytical predictions from the model agree well with high-resolution simulations, both in terms of velocity distribution and ensuing anomalous particle spreading.

  16. Stable Covalently Photo-Crosslinked Poly(Ionic Liquid) Membrane with Gradient Pore Size.

    PubMed

    Dani, Alessandro; Täuber, Karoline; Zhang, Weiyi; Schlaad, Helmut; Yuan, Jiayin

    2017-08-01

    Porous polyelectrolyte membranes stable in a highly ionic environment are obtained by covalent crosslinking of an imidazolium-based poly(ionic liquid). The crosslinking reaction involves the UV light-induced thiol-ene (click) chemistry, and the phase separation, occurring during the crosslinking step, generates a fully interconnected porous structure in the membrane. The porosity is on the order of the micrometer scale and the membrane shows a gradient of pore size across the membrane cross-section. The membrane can separate polystyrene latex particles of different size and undergoes actuation in contact with acetone due to the asymmetric porous structure. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Size and ability do matter! Influence of acidity and pore size on the synthesis of hindered halogenated meso-phenyl porphyrins catalysed by porous solid oxides.

    PubMed

    Silva, Mónica; Fernandes, Auguste; Bebiano, Suse S; Calvete, Mário J F; Ribeiro, M Filipa; Burrows, Hugh D; Pereira, Mariette M

    2014-06-25

    The rationalisation of the influence of acidity and pore size of several solid oxides so that they selectively act as supports for preparation of encapsulated porphyrin hybrid materials or as catalysts for synthesis of porphyrins in solution is discussed. Encapsulated porphyrin yields are dependent on both the acidity and the material pore size, Al-MCM-41 being the best fitting solid, with Lewis acidity of 120 μmol Py per g and a pore size 30 Å. On the other hand, when the goal is the synthesis of hindered mesoarylporphyrins in solution, the best solid porous catalyst is NaY, with Lewis acidity of 510 μmol Py per g and a pore size 14 Å. This method provides an appealing efficient, reusable and scalable catalyst alternative for one-pot synthesis of meso-arylporphyrins in high yields.

  18. The effect of pore size on tissue ingrowth and neovascularization in porous bioceramics of controlled architecture in vivo.

    PubMed

    Feng, Bai; Jinkang, Zhang; Zhen, Wang; Jianxi, Lu; Jiang, Chang; Jian, Liu; Guolin, Meng; Xin, Dong

    2011-02-01

    The purpose of this study was to investigate the role of pore size on tissue ingrowth and neovascularization in porous bioceramics under the accurate control of the pore parameters. For that purpose, β-tricalcium phosphate (β-TCP) cylinders with four different macropore sizes (300-400, 400-500, 500-600 and 600-700 µm) but the same interconnection size (120 µm) and unchangeable porosity were implanted into fascia lumbodorsalis in rabbits. The fibrous tissues and blood vessels formed in scaffolds were observed histologically and histomorphometrically. The vascularization of the porous bioceramics was analyzed by single-photon emission computed tomography (SPECT). It is found that pore size as an important parameter of a porous structure plays an important role in tissue infiltration into porous biomaterial scaffolds. The amount of fibrous tissue ingrowth increases with the decrease of the pore size. In four kinds of scaffolds with different macropore sizes (300-400, 400-500, 500-600 and 600-700 µm) and a constant interconnection size of 120 µm, the areas of fibrous tissue (%) were 60.5%, 52.2%, 41.3% and 37.3%, respectively, representing a significant decrease at 4 weeks (P < 0.01). The pore size of a scaffold is closely related to neovascularization of macroporous biomaterials implanted in vivo. A large pore size is beneficial for the growth of blood vessels, and the diameter of a pore smaller than 400 µm limits the growth of blood vessels and results in a smaller blood vessel diameter.

  19. Pore size controls on the base of the methane hydrate stability zone in the Kumano Basin, offshore Japan

    NASA Astrophysics Data System (ADS)

    Daigle, Hugh; Dugan, Brandon

    2014-11-01

    The base of the methane hydrate stability zone (MHSZ) in the Kumano Basin, offshore Japan, is marked by a bottom-simulating reflection (BSR) on seismic data. At Integrated Ocean Drilling Program Site C0002, which penetrates this BSR, the in situ temperature profile combined with bulk seawater methane equilibrium conditions suggest that the base of the MHSZ is 428 m below seafloor (bsf), which is 28 m deeper than the observed BSR (400 m bsf). We found that submicron pore sizes determined by mercury injection capillary pressure are sufficiently small to cause 64% of the observed uplift of the base of the MHSZ by the Gibbs-Thomson effect. This is the most thorough characterization of pore sizes within the MHSZ performed to date and illustrates the extent to which pore size can influence MHSZ thickness. Our results demonstrate the importance of considering lithology and pore structure when assessing methane hydrate stability conditions in marine sediments.

  20. Understanding Animal Group-Size Distributions

    PubMed Central

    Griesser, Michael; Ma, Qi; Webber, Simone; Bowgen, Katharine; Sumpter, David J. T.

    2011-01-01

    One of the most striking aspects of animal groups is their remarkable variation in size, both within and between species. While a number of mechanistic models have been proposed to explain this variation, there are few comprehensive datasets against which these models have been tested. In particular, we only vaguely understand how environmental factors and behavioral activities affect group-size distributions. Here we use observations of House sparrows (Passer domesticus) to investigate the factors determining group-size distribution. Over a wide range of conditions, we observed that animal group sizes followed a single parameter distribution known as the logarithmic distribution. This single parameter is the mean group size experienced by a randomly chosen individual (including the individual itself). For sparrows, the experienced mean group size, and hence the distribution, was affected by four factors: morning temperature, place, behavior and the degree of food spillage. Our results further indicate that the sparrows regulate the mean group size they experience, either by groups splitting more or merging less when local densities are high. We suggest that the mean experienced group size provides a simple but general tool for assessing the ecology and evolution of grouping. PMID:21912596

  1. Predicting Stress vs. Strain Behaviors of Thin-Walled High Pressure Die Cast Magnesium Alloy with Actual Pore Distribution

    SciTech Connect

    Choi, Kyoo Sil; Barker, Erin; Cheng, Guang; Sun, Xin; Forsmark, Joy; Li, Mei

    2016-01-06

    In this paper, a three-dimensional (3D) microstructure-based finite element modeling method (i.e., extrinsic modeling method) is developed, which can be used in examining the effects of porosity on the ductility/fracture of Mg castings. For this purpose, AM60 Mg tensile samples were generated under high-pressure die-casting in a specially-designed mold. Before the tensile test, the samples were CT-scanned to obtain the pore distributions within the samples. 3D microstructure-based finite element models were then developed based on the obtained actual pore distributions of the gauge area. The input properties for the matrix material were determined by fitting the simulation result to the experimental result of a selected sample, and then used for all the other samples’ simulation. The results show that the ductility and fracture locations predicted from simulations agree well with the experimental results. This indicates that the developed 3D extrinsic modeling method may be used to examine the influence of various aspects of pore sizes/distributions as well as intrinsic properties (i.e., matrix properties) on the ductility/fracture of Mg castings.

  2. Quantitative multi-scale analysis of mineral distributions and fractal pore structures for a heterogeneous Junger Basin shale

    NASA Astrophysics Data System (ADS)

    Wang, Y. D.; Liu, K. Y.; Yang, Y. S.; Ren, Y. Q.; Hu, T.; Deng, B.; Xiao, T. Q.

    2016-04-01

    Three dimensional (3D) characterization of shales has recently attracted wide attentions in relation to the growing importance of shale oil and gas. Obtaining a complete 3D compositional distribution of shale has proven to be challenging due to its multi-scale characteristics. A combined multi-energy X-ray micro-CT technique and data-constrained modelling (DCM) approach has been used to quantitatively investigate the multi-scale mineral and porosity distributions of a heterogeneous shale from the Junger Basin, northwestern China by sub-sampling. The 3D sub-resolution structures of minerals and pores in the samples are quantitatively obtained as the partial volume fraction distributions, with colours representing compositions. The shale sub-samples from two areas have different physical structures for minerals and pores, with the dominant minerals being feldspar and dolomite, respectively. Significant heterogeneities have been observed in the analysis. The sub-voxel sized pores form large interconnected clusters with fractal structures. The fractal dimensions of the largest clusters for both sub-samples were quantitatively calculated and found to be 2.34 and 2.86, respectively. The results are relevant in quantitative modelling of gas transport in shale reservoirs.

  3. Micron-pore-sized metallic filter tube membranes for filtration of particulates and water purification

    SciTech Connect

    Phelps, Tommy Joe; Palumbo, Anthony Vito; Fagan, Lisa Anne; Bischoff, Brian L; Miller, Curtis Jack; Drake, Meghan M; Judkins, Roddie Reagan

    2008-01-01

    Robust filtering techniques capable of efficiently removing particulates and biological agents from water or air suffer from plugging, poor rejuvenation, low permeance, and high backpressure. Operational characteristics of pressure-driven separations are in part controlled by the membrane pore size, charge of particulates, transmembrane pressure and the requirement for sufficient water flux to overcome fouling. With long term use filters decline in permeance due to filter-cake plugging of pores, fouling, or filter deterioration. Though metallic filter tube development at ORNL has focused almost exclusively on gas separations, a small study examined the applicability of these membranes for tangential filtering of aqueous suspensions of bacterial-sized particles. A mixture of fluorescent polystyrene microspheres ranging in size from 0.5 to 6 {micro}m in diameter simulated microorganisms in filtration studies. Compared to a commercial filter, the ORNL 0.6 {micro}m filter averaged approximately 10-fold greater filtration efficiency of the small particles, several-fold greater permeance after considerable use and it returned to approximately 85% of the initial flow upon backflushing versus 30% for the commercial filter. After filtering several liters of the particle-containing suspension, the ORNL composite filter still exhibited greater than 50% of its initial permeance while the commercial filter had decreased to less than 20%. When considering a greater filtration efficiency, greater permeance per unit mass, greater percentage of rejuvenation upon backflushing (up to 3-fold), and likely greater performance with extended use, the ORNL 0.6 {micro}m filters can potentially outperform the commercial filter by factors of 100-1000 fold.

  4. Micron-pore-sized metallic filter tube membranes for filtration of particulates and water purification.

    PubMed

    Phelps, T J; Palumbo, A V; Bischoff, B L; Miller, C J; Fagan, L A; McNeilly, M S; Judkins, R R

    2008-07-01

    Robust filtering techniques capable of efficiently removing particulates and biological agents from water or air suffer from plugging, poor rejuvenation, low permeance, and high backpressure. Operational characteristics of pressure-driven separations are in part controlled by the membrane pore size, charge of particulates, transmembrane pressure and the requirement for sufficient water flux to overcome fouling. With long term use filters decline in permeance due to filter-cake plugging of pores, fouling, or filter deterioration. Though metallic filter tube development at ORNL has focused almost exclusively on gas separations, a small study examined the applicability of these membranes for tangential filtering of aqueous suspensions of bacterial-sized particles. A mixture of fluorescent polystyrene microspheres ranging in size from 0.5 to 6 microm in diameter simulated microorganisms in filtration studies. Compared to a commercial filter, the ORNL 0.6 microm filter averaged approximately 10-fold greater filtration efficiency of the small particles, several-fold greater permeance after considerable use and it returned to approximately 85% of the initial flow upon backflushing versus 30% for the commercial filter. After filtering several liters of the particle-containing suspension, the ORNL composite filter still exhibited greater than 50% of its initial permeance while the commercial filter had decreased to less than 20%. When considering a greater filtration efficiency, greater permeance per unit mass, greater percentage of rejuvenation upon backflushing (up to 3-fold), and likely greater performance with extended use, the ORNL 0.6 microm filters can potentially outperform the commercial filter by factors of 100-1,000 fold.

  5. Seismic velocity deviation log: An effective method for evaluating spatial distribution of reservoir pore types

    NASA Astrophysics Data System (ADS)

    Shirmohamadi, Mohamad; Kadkhodaie, Ali; Rahimpour-Bonab, Hossain; Faraji, Mohammad Ali

    2017-04-01

    Velocity deviation log (VDL) is a synthetic log used to determine pore types in reservoir rocks based on a combination of the sonic log with neutron-density logs. The current study proposes a two step approach to create a map of porosity and pore types by integrating the results of petrographic studies, well logs and seismic data. In the first step, velocity deviation log was created from the combination of the sonic log with the neutron-density log. The results allowed identifying negative, zero and positive deviations based on the created synthetic velocity log. Negative velocity deviations (below - 500 m/s) indicate connected or interconnected pores and fractures, while positive deviations (above + 500 m/s) are related to isolated pores. Zero deviations in the range of [- 500 m/s, + 500 m/s] are in good agreement with intercrystalline and microporosities. The results of petrographic studies were used to validate the main pore type derived from velocity deviation log. In the next step, velocity deviation log was estimated from seismic data by using a probabilistic neural network model. For this purpose, the inverted acoustic impedance along with the amplitude based seismic attributes were formulated to VDL. The methodology is illustrated by performing a case study from the Hendijan oilfield, northwestern Persian Gulf. The results of this study show that integration of petrographic, well logs and seismic attributes is an instrumental way for understanding the spatial distribution of main reservoir pore types.

  6. Analytic modeling of aerosol size distributions

    NASA Technical Reports Server (NTRS)

    Deepack, A.; Box, G. P.

    1979-01-01

    Mathematical functions commonly used for representing aerosol size distributions are studied parametrically. Methods for obtaining best fit estimates of the parameters are described. A catalog of graphical plots depicting the parametric behavior of the functions is presented along with procedures for obtaining analytical representations of size distribution data by visual matching of the data with one of the plots. Examples of fitting the same data with equal accuracy by more than one analytic model are also given.

  7. Soil signature simulation of complex mixtures and particle size distributions

    NASA Astrophysics Data System (ADS)

    Carson, Tyler; Bachmann, Charles M.; Salvaggio, Carl

    2015-09-01

    Soil reflectance signatures were modeled using the digital imaging and remote sensing image generation model and Blender three-dimensional (3-D) graphic design software. Using these tools, the geometry, radiometry, and chemistry of quartz and magnetite were exploited to model the presence of particle size and porosity effects in the visible and the shortwave infrared spectrum. Using the physics engines within the Blender 3-D graphic design software, physical representations of granular soil scenes were created. Each scene characterized a specific particle distribution and density. Chemical and optical properties of pure quartz and magnetite were assigned to particles in the scene based on particle size. This work presents a model to describe an observed phase-angle dependence of beach sand density. Bidirectional reflectance signatures were simulated for targets of varying size distribution and density. This model provides validation for a phenomenological trade space between density and particle size distribution in complex, heterogeneous soil mixtures. It also confirms the suggestion that directional reflectance signatures can be defined by intimate mixtures that depend on pore spacing. The study demonstrated that by combining realistic target geometry and spectral measurements of pure quartz and magnetite, effects of soil particle size and density could be modeled without functional data fitting or rigorous analysis of material dynamics. This research does not use traditional function-based models for simulation. The combination of realistic geometry, physically viable particle structure, and first-principles ray-tracing enables the ability to represent signature changes that have been observed in experimental observations.

  8. A family of zeolites with controlled pore size prepared using a top-down method

    NASA Astrophysics Data System (ADS)

    Roth, Wieslaw J.; Nachtigall, Petr; Morris, Russell E.; Wheatley, Paul S.; Seymour, Valerie R.; Ashbrook, Sharon E.; Chlubná, Pavla; Grajciar, Lukáš; Položij, Miroslav; Zukal, Arnošt; Shvets, Oleksiy; Čejka, Jiří

    2013-07-01

    The properties of zeolites, and thus their suitability for different applications, are intimately connected with their structures. Synthesizing specific architectures is therefore important, but has remained challenging. Here we report a top-down strategy that involves the disassembly of a parent zeolite, UTL, and its reassembly into two zeolites with targeted topologies, IPC-2 and IPC-4. The three zeolites are closely related as they adopt the same layered structure, and they differ only in how the layers are connected. Choosing different linkers gives rise to different pore sizes, enabling the synthesis of materials with predetermined pore architectures. The structures of the resulting zeolites were characterized by interpreting the X-ray powder-diffraction patterns through models using computational methods; IPC-2 exhibits orthogonal 12- and ten-ring channels, and IPC-4 is a more complex zeolite that comprises orthogonal ten- and eight-ring channels. We describe how this method enables the preparation of functional materials and discuss its potential for targeting other new zeolites.

  9. A family of zeolites with controlled pore size prepared using a top-down method.

    PubMed

    Roth, Wieslaw J; Nachtigall, Petr; Morris, Russell E; Wheatley, Paul S; Seymour, Valerie R; Ashbrook, Sharon E; Chlubná, Pavla; Grajciar, Lukáš; Položij, Miroslav; Zukal, Arnošt; Shvets, Oleksiy; Cejka, Jiří

    2013-07-01

    The properties of zeolites, and thus their suitability for different applications, are intimately connected with their structures. Synthesizing specific architectures is therefore important, but has remained challenging. Here we report a top-down strategy that involves the disassembly of a parent zeolite, UTL, and its reassembly into two zeolites with targeted topologies, IPC-2 and IPC-4. The three zeolites are closely related as they adopt the same layered structure, and they differ only in how the layers are connected. Choosing different linkers gives rise to different pore sizes, enabling the synthesis of materials with predetermined pore architectures. The structures of the resulting zeolites were characterized by interpreting the X-ray powder-diffraction patterns through models using computational methods; IPC-2 exhibits orthogonal 12- and ten-ring channels, and IPC-4 is a more complex zeolite that comprises orthogonal ten- and eight-ring channels. We describe how this method enables the preparation of functional materials and discuss its potential for targeting other new zeolites.

  10. Evaluation of borate bioactive glass scaffolds with different pore sizes in a rat subcutaneous implantation model.

    PubMed

    Deliormanli, Aylin M; Liu, Xin; Rahaman, Mohamed N

    2014-01-01

    Borate bioactive glass has been shown to convert faster and more completely to hydroxyapatite and enhance new bone formation in vivo when compared to silicate bioactive glass (such as 45S5 and 13-93 bioactive glass). In this work, the effects of the borate glass microstructure on its conversion to hydroxyapatite (HA) in vitro and its ability to support tissue ingrowth in a rat subcutaneous implantation model were investigated. Bioactive borate glass scaffolds, designated 13-93B3, with a grid-like microstructure and pore widths of 300, 600, and 900 µm were prepared by a robocasting technique. The scaffolds were implanted subcutaneously for 4 weeks in Sprague Dawley rats. Silicate 13-93 glass scaffolds with the same microstructure were used as the control. The conversion of the scaffolds to HA was studied as a function of immersion time in a simulated body fluid. Histology and scanning electron microscopy were used to evaluate conversion of the bioactive glass implants to hydroxyapatite, as well as tissue ingrowth and blood vessel formation in the implants. The pore size of the scaffolds was found to have little effect on tissue infiltration and angiogenesis after the 4-week implantation.

  11. Single molecule FRET reveals pore size and opening mechanism of a mechano-sensitive ion channel

    PubMed Central

    Wang, Yong; Liu, Yanxin; DeBerg, Hannah A; Nomura, Takeshi; Hoffman, Melinda Tonks; Rohde, Paul R; Schulten, Klaus; Martinac, Boris; Selvin, Paul R

    2014-01-01

    The mechanosensitive channel of large conductance, which serves as a model system for mechanosensitive channels, has previously been crystallized in the closed form, but not in the open form. Ensemble measurements and electrophysiological sieving experiments show that the open-diameter of the channel pore is >25 Å, but the exact size and whether the conformational change follows a helix-tilt or barrel-stave model are unclear. Here we report measurements of the distance changes on liposome-reconstituted MscL transmembrane α-helices, using a ‘virtual sorting’ single-molecule fluorescence energy transfer. We observed directly that the channel opens via the helix-tilt model and the open pore reaches 2.8 nm in diameter. In addition, based on the measurements, we developed a molecular dynamics model of the channel structure in the open state which confirms our direct observations. DOI: http://dx.doi.org/10.7554/eLife.01834.001 PMID:24550255

  12. Adjustable virtual pore-size filter for automated sample preparation using acoustic radiation force

    SciTech Connect

    Jung, B; Fisher, K; Ness, K; Rose, K; Mariella, R

    2008-05-22

    We present a rapid and robust size-based separation method for high throughput microfluidic devices using acoustic radiation force. We developed a finite element modeling tool to predict the two-dimensional acoustic radiation force field perpendicular to the flow direction in microfluidic devices. Here we compare the results from this model with experimental parametric studies including variations of the PZT driving frequencies and voltages as well as various particle sizes and compressidensities. These experimental parametric studies also provide insight into the development of an adjustable 'virtual' pore-size filter as well as optimal operating conditions for various microparticle sizes. We demonstrated the separation of Saccharomyces cerevisiae and MS2 bacteriophage using acoustic focusing. The acoustic radiation force did not affect the MS2 viruses, and their concentration profile remained unchanged. With optimized design of our microfluidic flow system we were able to achieve yields of > 90% for the MS2 with > 80% of the S. cerevisiae being removed in this continuous-flow sample preparation device.

  13. Pore size dependent behavior of hydrated Ag+ ions confined in mesoporous MCM-41 materials under synchrotron X-ray irradiation.

    PubMed

    Ito, Kanae; Yoshida, Koji; Kittaka, Shigeharu; Yamaguchi, Toshio

    2012-01-01

    The behavior of hydrated Ag+ ions in a 1.5 mol dm(-3) AgNO3 aqueous solution confined in mesoporous silica MCM-41 with different pore sizes was characterized by synchrotron X-ray absorption spectroscopy. The hydrated Ag+ ions are stabilized in 4-fold coordination down to 195 K in the pores (21 Å in diameter), whereas in the larger pores (28 Å) the hydrated Ag+ ions are reduced to Ag0 to form nano clusters with the Ag-Ag interactions of 2.80 Å.

  14. Particle Size Distributions in Atmospheric Clouds

    NASA Technical Reports Server (NTRS)

    Paoli, Roberto; Shariff, Karim

    2003-01-01

    In this note, we derive a transport equation for a spatially integrated distribution function of particles size that is suitable for sparse particle systems, such as in atmospheric clouds. This is done by integrating a Boltzmann equation for a (local) distribution function over an arbitrary but finite volume. A methodology for evolving the moments of the integrated distribution is presented. These moments can be either tracked for a finite number of discrete populations ('clusters') or treated as continuum variables.

  15. Effect of pore size on the condensation/evaporation transition of confined water in equilibrium with saturated bulk water.

    PubMed

    Brovchenko, Ivan; Oleinikova, Alla

    2011-08-25

    The effect of pore size on the condensation/evaporation transition of confined water upon varying the strength of the water-surface interaction is studied under conditions of equilibrium with saturated bulk. Monte Carlo simulations in the grand canonical ensemble were used to determine water density in spherical pores of radius R(p) = 9, 12, 15, 20, and 25 Å in the temperature range from T = 270 K to the bulk critical temperature. The critical values of the well depth of the water-surface interaction potential, which mark the limits of the metastability of vapor and liquid phases in pores (U(0)(cond) and U(0)(evap), respectively), were determined. U(0)(cond) strongly depends on temperature, practically does not depend on the pore size, and corresponds to some particular density of water vapor near a surface. In contrast, U(0)(evap) only slightly depends on temperature, depends strongly on pore size, and corresponds to the density in the pore interior by about 2% below the bulk value. The critical water-pore interaction U(0)(c), which separates regimes of capillary condensation and capillary evaporation, is found to be changed from -1.75 to -0.94 kcal/mol when the pore radius R(p) increases from 9 to 25 Å. The size dependence of U(0)(c) is attributed to the change of the contact angle due to the line tension effect. Extrapolation of the dependence U(0)(c)(R(p)) to the flat surface gives the critical value U(0)(c)(∞) ≈ -0.61 kcal/mol. © 2011 American Chemical Society

  16. Single-Crystalline, Nanoporous Gallium Nitride Films With Fine Tuning of Pore Size for Stem Cell Engineering.

    PubMed

    Han, Lin; Zhou, Jing; Sun, Yubing; Zhang, Yu; Han, Jung; Fu, Jianping; Fan, Rong

    2014-11-01

    Single-crystalline nanoporous gallium nitride (GaN) thin films were fabricated with the pore size readily tunable in 20-100 nm. Uniform adhesion and spreading of human mesenchymal stem cells (hMSCs) seeded on these thin films peak on the surface with pore size of 30 nm. Substantial cell elongation emerges as pore size increases to ∼80 nm. The osteogenic differentiation of hMSCs occurs preferentially on the films with 30 nm sized nanopores, which is correlated with the optimum condition for cell spreading, which suggests that adhesion, spreading, and stem cell differentiation are interlinked and might be coregulated by nanotopography.

  17. Exponential Size Distribution of von Willebrand Factor

    PubMed Central

    Lippok, Svenja; Obser, Tobias; Müller, Jochen P.; Stierle, Valentin K.; Benoit, Martin; Budde, Ulrich; Schneppenheim, Reinhard; Rädler, Joachim O.

    2013-01-01

    Von Willebrand Factor (VWF) is a multimeric protein crucial for hemostasis. Under shear flow, it acts as a mechanosensor responding with a size-dependent globule-stretch transition to increasing shear rates. Here, we quantify for the first time, to our knowledge, the size distribution of recombinant VWF and VWF-eGFP using a multilateral approach that involves quantitative gel analysis, fluorescence correlation spectroscopy, and total internal reflection fluorescence microscopy. We find an exponentially decaying size distribution of multimers for recombinant VWF as well as for VWF derived from blood samples in accordance with the notion of a step-growth polymerization process during VWF biosynthesis. The distribution is solely described by the extent of polymerization, which was found to be reduced in the case of the pathologically relevant mutant VWF-IIC. The VWF-specific protease ADAMTS13 systematically shifts the VWF size distribution toward smaller sizes. This dynamic evolution is monitored using fluorescence correlation spectroscopy and compared to a computer simulation of a random cleavage process relating ADAMTS13 concentration to the degree of VWF breakdown. Quantitative assessment of VWF size distribution in terms of an exponential might prove to be useful both as a valuable biophysical characterization and as a possible disease indicator for clinical applications. PMID:24010664

  18. Quasi-elastic light scattering determination of the size distribution of extruded vesicles.

    PubMed

    Kölchens, S; Ramaswami, V; Birgenheier, J; Nett, L; O'Brien, D F

    1993-04-01

    The size distribution of phospholipid vesicles prepared by the freeze thaw-extrusion method were determined by the non-perturbing technique of quasi-elastic light scattering (QELS) and compared to latex particles of known size. Multiangle QELS experiments were performed to avoid errors due to the angular dependence of the scattering function of the particles. The experimentally determined autocorrelation function was analyzed by multiple mathematical procedures, i.e. single exponential, CUMULANT, exponential sampling, non-negatively constrained least square and CONTIN, in order to select suitable models for vesicle characterization. The most consistent results were obtained with CUMULANT, non-negatively constrained least square and CONTIN. In many instances single exponential analysis gave comparable results to these procedures, which indicates the vesicles have a narrow distribution of sizes. The influence of filter pore size, extrusion pressure and lipid concentration on the size and size distribution of extruded vesicles was determined. Extrusion through 100-, 200- and 400-nm pore size filters produced a unimodal distribution of vesicles, with somewhat smaller diameters as the extrusion pressure increased. The larger the filter pore size, the more dependent the vesicle size was on applied pressure. The observed vesicle size was independent of the lipid concentration between 0.1 and 10 mg ml-1.

  19. Temperature and pore pressure distribution in a concrete slab during the microwave decontamination process

    SciTech Connect

    Li, W.; Ebadian, M.A.; White, T.L.; Grubb, R.G.; Foster, D. Jr.

    1994-10-01

    As an application of microwave engineering, the new technology of concrete decontamination and decommissioning using microwave energy has been recently developed. The temperature and pore pressure within the concrete are studied theoretically in this paper. The heat and mass transfer within the porous concrete, coupled with temperature dependent dielectric property are investigated. The effects of microwave frequency (f), microwave power intensity (Q{sub 0,ave}), concrete porosity ({phi}) on the temperature and pore pressure distributions and their variations are fully discussed. The effects of the variation of complex dielectric permittivity ({epsilon}) and presentation of different steel reinforcements are also illustrated.

  20. Acoustic particle filter with adjustable effective pore size for automated sample preparation.

    PubMed

    Jung, Byoungsok; Fisher, Karl; Ness, Kevin D; Rose, Klint A; Mariella, Raymond P

    2008-11-15

    This article presents analysis and optimization of a microfluidic particle filter that uses acoustic radiation forces to remove particles larger than a selected size by adjusting the driving conditions of the piezoelectric transducer (PZT). Operationally, the acoustic filter concentrates microparticles to the center of the microchannel, minimizing undesirable particle adsorption to the microchannel walls. Finite element models predict the complex two-dimensional acoustic radiation force field perpendicular to the flow direction in microfluidic devices. We compare these results with experimental parametric studies including variations of the PZT driving frequencies and voltages as well as various particle sizes (0.5-5.0 microm in diameter). These results provide insight into the optimal operating conditions and show the efficacy of our device as a filter with an adjustable effective pore size. We demonstrate the separation of Saccharomyces cerevisiae from MS2 bacteriophage using our acoustic device. With optimized design of our microfluidic flow system, we achieved yields of greater than 90% for the MS2 with greater than 80% removal of the S. cerevisiae in this continuous-flow sample preparation device.

  1. Formation factor and the microscopic distribution of wetting phase in pore space of Berea sandstone

    SciTech Connect

    Schlueter, E.M.; Myer, L.R.; Cook, N.G.W.; Witherspoon, P.A.

    1992-11-01

    Experimental studies have been accomplished aimed at studying the formation factor of a partially saturated rock. The effective formation factors to an electrolyte solution of the pore spaces not occupied by a wetting raid (paraffin wax) have been measured at various saturations, after solidifying the wetting fluid in place. The experimental data is studied in light of the role of the pore structure on the wetting fluid invasion process with the aid of fluid distributions at each saturation regime, a complete rock pore cast, and its associated rock section. The effect of clay minerals on formation factor is studied. The surface conductance contribution of day minerals to overall electrical conductivity is assessed. The effect of partial hydrocarbon saturation on overall rock conductivity and on the Archei saturation exponent is discussed.

  2. Acoustical properties of air-saturated porous material with periodically distributed dead-end pores.

    PubMed

    Leclaire, P; Umnova, O; Dupont, T; Panneton, R

    2015-04-01

    A theoretical and numerical study of the sound propagation in air-saturated porous media with straight main pores bearing lateral cavities (dead-ends) is presented. The lateral cavities are located at "nodes" periodically spaced along each main pore. The effect of periodicity in the distribution of the lateral cavities is studied, and the low frequency limit valid for the closely spaced dead-ends is considered separately. It is shown that the absorption coefficient and transmission loss are influenced by the viscous and thermal losses in the main pores as well as their perforation rate. The presence of long or short dead-ends significantly alters the acoustical properties of the material and can increase significantly the absorption at low frequencies (a few hundred hertz). These depend strongly on the geometry (diameter and length) of the dead-ends, on their number per node, and on the periodicity along the propagation axis. These effects are primarily due to low sound speed in the main pores and to thermal losses in the dead-end pores. The model predictions are compared with experimental results. Possible designs of materials of a few cm thicknesses displaying enhanced low frequency absorption at a few hundred hertz are proposed.

  3. Particle size and surface area distributions of pharmaceutical powders by microcomputerized mercury porosimetry.

    PubMed

    Carli, F; Motta, A

    1984-02-01

    The Mayer-Stowe theory was applied to derive the particle size distribution of powders of pharmaceutical interest using mercury porosimetry. Particle size data obtained by this approach are fairly comparable with data derived by other, more popular, techniques such as the electrical sensing zone or the air jet sieving methods provided that the experimental value of the mercury-powder contact angle and the state of aggregation of the powder are carefully studied. Furthermore, by applying the Rootare-Prenzlow method a surface area distribution can also be derived from the same porosimetry data used to obtain the particle size distribution. All experiments were carried out with a microcomputerized mercury porosimeter, which allows storage of data during the analysis and a subsequent fast elaboration at the end of the run, with fully printed data on pore size, pore volume, surface area, and particle size of the powder sample.

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

    NASA Astrophysics Data System (ADS)

    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.

  5. A macromolecular crowding study of RNA folding and activity: polymer pore size matters! (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Börner, Richard; Fiorini, Erica; Paudel, Bishnu; Rueda, David; Sigel, Roland K. O.

    2016-03-01

    Catalytic RNAs, like the group IIB intron ribozyme of S. cerevesiae, require a high magnesium(II) concentration to show folding and function in vitro [1]. In contrast, in vivo conditions are characterized by a highly crowded cellular environment and much lower ion concentration. Molecular crowding agents are a widespread tool to mimic cellular crowding [2]. However, particular physical/chemical properties explaining the crowders influence are mostly not understood. In this study, we gain new insights on how polymer properties like viscosity, pore size etc. influence the activity and folding of a large RNA. We combined bulk activity assays and single-molecule Förster Resonance Energy Transfer experiments, screening the PEG volume fraction (%) and molecular weight (MW). Our results revealed that upon the influence of crowding agents, a compaction of the underlying structure depends on the PEG % and the presence of different PEG MW and % unveiled an optimal pore size in terms of catalytic activity. In summary, an increasing density of the crowding environment shifts the RNA towards the most compact state, but the ribozyme is only active if the crowders network matches its size [4]. We interpret the most compact state as necessary, but not sufficient, to keep the ribozyme active. Financial support from the European Research Council (MIRNA N° 259092, to RKOS), the Swiss National Fund (SNF), and the Forschungskredit Grant of the University of Zürich (FK-14-096 and 15-092 to RB) are gratefully acknowledged. [1] Swisher J.F., Su L.J., Brenowitz M., Anderson V.E., Pyle A.M., J. Mol. Bio., 315, 297-310 (2002). [2] Kilburn D., Roh J.H., Guo L., Briber R.M., Woodson S.A., JACS, 132, 8690-6 (2010). [3] Steiner M., Karunatilaka K.S., Sigel R.K.O., Rueda D., Proc. Natl. Acad. Sci. U.S.A.,105, 13853-8 (2008). [4] aBörner R, Fiorini E, Sigel R.K.O., Chimia, 69, 207-212 (2015).; bFiorini E., Paudel B., Börner R., Rueda D., Sigel R.K.O., submitted. [5] König S.L.B., Hadzic M

  6. Substantial Expansion of Detectable Size Range in Ionic Current Sensing through Pores by Using a Microfluidic Bridge Circuit.

    PubMed

    Yasaki, Hirotoshi; Yasui, Takao; Yanagida, Takeshi; Kaji, Noritada; Kanai, Masaki; Nagashima, Kazuki; Kawai, Tomoji; Baba, Yoshinobu

    2017-09-07

    Measuring ionic currents passing through nano- or micro-pores has shown great promise for the electrical discrimination of various biomolecules, cells, bacteria, and viruses. However, conventional measurements have shown there is an inherent limitation to the detectable particle volume (1% of the pore volume), which critically hinders applications to real mixtures of biomolecule samples with a wide size range of suspended particles. Here we propose a rational methodology which can detect samples with the detectable particle volume of 0.01% of the pore volume by measuring a transient current generated from the potential differences in a microfluidic bridge circuit. Our method substantially suppresses the background ionic current from the µA level to the pA level, which essentially lowers the detectable particle volume limit even for relatively large pore structures. Indeed, utilizing a microscale long pore structure (volume of 5.6 × 10(4) aL; height and width of 2.0 × 2.0 µm; length of 14 µm), we successfully detected various samples including polystyrene nanoparticles (volume: 4 aL), bacteria, cancer cells, and DNA molecules. Our method will expand the applicability of ionic current sensing systems for various mixed biomolecule samples with a wide size range, which have been difficult to measure by previously existing pore technologies.

  7. Activity size distribution of some natural radionuclides.

    PubMed

    Mohery, M; Abdallah, A M; Al-Amoudi, Z M; Baz, S S

    2014-03-01

    In this study, the results concerning the activity size distribution of the long-lived ((210)Pb) radon decay product aerosols and the thoron decay product aerosols ((212)Pb) and ((7)Be) of the outdoor atmosphere are presented. Also, the mass size distribution of the aerosol particles is determined. The low-pressure Berner cascade impactor Model 20/0.015 was used as a sampling device. The activity size distribution of these radionuclides was determined by one log-normal distribution (accumulation mode) whereas the mass size distribution was by two log-normal distributions (accumulation and coarse mode). The activity median aerodynamic diameter (AMAD) of (212)Pb was found to be 305 nm with a geometric standard deviation (σg) of 2.41. The specific air activity concentration of (212)Pb was found to be 0.14 ± 0.012 Bq m(-3). An AMAD of (210)Pb of 610 nm with σg of 1.8 was determined, whereas that of 550 nm with σg of 1.97 was determined for (7)Be. The specific air activity concentration of (210)Pb and (7)Be was found to be 0.0016±2.5×10(-4) and 0.00348 ± 4×10(-4) Bq m(-3), respectively. Using a dosimetric model, the total deposition fraction as well as the total equivalent dose has been evaluated considering the observed parameters of the activity size distribution of (212)Pb. At a total deposition fraction of ∼21 %, the total equivalent dose was found to be 0.41 µSv.

  8. Martian crater size distributions and terrain age

    NASA Technical Reports Server (NTRS)

    Barlow, N. G.; Strom, R. G.

    1984-01-01

    The crater size/frequency distributions of large ( 8 km) craters on the Moon and terrestrial planets display two very different curves representing two crater populations. The heavily cratered regions of the Moon, Mercury, and Mars show the same highly structured curve which cannot be represented by a single slope distribution function. In contrast, the lunar post mare crater population has a size/frequency distribution which differs significantly from that in the highlands over the same diameter range, and can be represented by a single-slope distribution function of -2.8 differential. On areas of martian lightly cratered northern plains, the crater population is essentially identical to that of the post mare population. This indicates that the same two families of impacting objects were responsible for the cratering records on both Moon and Mars. The thickness of mantling material varies among the various plains units, and can be calculated from the depth/diameter scaling relations for martian craters.

  9. Aerosol and air pollution size distribution

    NASA Astrophysics Data System (ADS)

    Shani, Gad; Haccoun, A.; Kushelevsky, A.

    The size distribution of aerosols was measured in a moderately industrial city, in a semi-arid zone on the Negev desert border. The aerosols in the city of Beer Sheva are from two sources: the dust coming from the desert and urban pollution. The size measurements were done with a cascade impactor. The elemental content of the aerosols was investigated by neutron activation analysis and X-ray fluorescence. The main elements of the dust are: Ca, Si, Fe, Na and the trace elements are: Sc, Se, La, Sm, Hf and others. The main elements of the urban pollution are S, Br, Pb, Cl, Hg and others. It was found that the elements belonging to each group can easily be classified by the size distribution. The analytical consideration of the aerosol size distribution of each group are discussed and two corresponding analytical expressions are suggested. It is shown that aerosols originating in the dust have a hump shape distribution around ~ 4μm, and those originating in urban pollution have a distribution decreasing with increasing aerosol diameter. Many examples are given to prove the conclusions.

  10. Comparison of drop size distributions from two droplet sizing systems

    NASA Technical Reports Server (NTRS)

    Oldenburg, John R.; Ide, Robert F.

    1990-01-01

    A comparison between the Phase Doppler Particle Analyzer and the combined measurements from Particle Measuring Systems' Forward Scattering Spectrometer Probe and the Optical Array Probe was conducted in an icing wind tunnel using NASA Icing Research Tunnel spray nozzles to produce the supercooled water droplet cloud. Clouds having a range of volume median diameters from 10 to greater than 50 microns were used for the instrument comparisons. A volume median diameter was calculated from combining the droplet distributions of the Optical Array Probe and the Forward Scattering Spectrometer Probe. A comparison of the combined volume median diameters and the Phase Doppler Particle Analyzer volume median diameters showed agreement from 10 microns up to 30 microns. Typical drop size distributions from the Phase Doppler Particle Analyzer, the Forward Scattering Spectrometer Probe, and Optical Array Probe are presented for several median volume diameters. A comparison of the distributions illustrates regions of the distributions where there is good agreement and other regions where there are discrepancies between the Phase Doppler Particle Analyzer and the Particle Measuring Systems' droplet size instruments.

  11. Distribution of carbon nanotube sizes from adsorption measurements and computer simulation.

    PubMed

    Kowalczyk, Piotr; Hołyst, Robert; Tanaka, Hideki; Kaneko, Katsumi

    2005-08-04

    The method for the evaluation of the distribution of carbon nanotube sizes from the static adsorption measurements and computer simulation of nitrogen at 77 K is developed. We obtain the condensation/evaporation pressure as a function of pore size of a cylindrical carbon tube using Gauge Cell Monte Carlo Simulation (Gauge Cell MC). To obtain the analytical form of the relationships mentioned above we use Derjaguin-Broekhoff-deBoer theory. Finally, the pore size distribution (PSD) of the single-walled carbon nanohorns (SWNHs) is determined from a single nitrogen adsorption isotherm measured at 77 K. We neglect the conical part of an isolated SWNH tube and assume a structureless wall of a carbon nanotube. We find that the distribution of SWNH sizes is broad (internal pore radii varied in the range 1.0-3.6 nm with the maximum at 1.3 nm). Our method can be used for the determination of the pore size distribution of the other tubular carbon materials, like, for example, multiwalled or double-walled carbon nanotubes. Besides the applicable aspect of the current work the deep insight into the problem of capillary condensation/evaporation in confined carbon cylindrical geometry is presented. As a result, the critical pore radius in structureless single-walled carbon tubes is determined as being equal to three nitrogen collision diameters. Below that size the adsorption-desorption isotherm is reversible (i.e., supercritical in nature). We show that the classical static adsorption measurements combined with the proper modeling of the capillary condensation/evaporation phenomena is a powerful method that can be applied for the determination of the distribution of nanotube sizes.

  12. Size distributions in two porous chondritic micrometeorites

    NASA Astrophysics Data System (ADS)

    Rietmeijer, F. J. M.

    1993-06-01

    Quantitative size measurements of granular units (GUs), and nm-sized minerals in these units, in two porous chondritic micrometeorites are investigated. The matrix of these micrometeorites consist of loosely packed, 0.1 micron-sized, GUs. These objects were a major component of the solar nebula dust that accreted into protoplanets. The matrix in micrometeorite W7010*A2 has a fractal dimension with a small coefficient that supports efficient sticking of carbon-rich GUs during accretion. The fractal nature of the matrix provides a way to calculate the density using the aggregate size. The resulting very low density for porous chondritic micrometeorites is 0.08-0.14 g/cu cm, which supports the view that they are the solid debris from unconsolidated solar system bodies. Chondritic GUs contain ultrafine olivines, pyroxenes, and sulfides, embedded in hydrocarbons and amorphous carbons. Nanocrystals in the micrometeorites W7010*A2 and U2015*B show log normal size distributions. The high incidence of disk-shaped grains, a changeover from disk-shaped to euhedral grains, the unevolved nature of the size distributions, and multiple populations for grains less than 127 nm in size, are consistent with continuous postaccretion nucleation and growth in amorphous GUs, including coarsening via Ostwald ripening.

  13. Bimodal spatial distribution of pores in anodically oxidized aluminum thin films

    NASA Astrophysics Data System (ADS)

    Behnke, J. F.; Sands, T.

    2000-12-01

    Though porous anodic aluminum oxide has been the subject of considerable research since the 1950s, little attention has been devoted to the characterization of the self-organization of the pore structures, and fewer of these studies have focused on anodization of thin films. The degree to which these structures self-organize, however, could play a vital role in future applications of porous anodic aluminum oxide. In this study a model is developed to describe pore ordering in thin anodized aluminum films. The model is based on a radial distribution function approach to describe the interpore spacings. Idealized one-dimensional and two-dimensional (2D) radial distribution functions are combined by linear superposition to approximate experimental radial distribution functions. Using these radial distribution functions, an order parameter is developed and an improved definition of pore spacing is constructed. This method confirms that the oxide initially forms with a highly frustrated porous structure and reorganizes toward greater 2D order as the oxide grows into the film.

  14. Pore size is a critical parameter for obtaining sustained protein release from electrochemically synthesized mesoporous silicon microparticles

    PubMed Central

    Pastor, Ester L.; Reguera-Nuñez, Elaine; Matveeva, Eugenia

    2015-01-01

    Mesoporous silicon has become a material of high interest for drug delivery due to its outstanding internal surface area and inherent biodegradability. We have previously reported the preparation of mesoporous silicon microparticles (MS-MPs) synthesized by an advantageous electrochemical method, and showed that due to their inner structure they can adsorb proteins in amounts exceeding the mass of the carrier itself. Protein release from these MS-MPs showed low burst effect and fast delivery kinetics with complete release in a few hours. In this work, we explored if tailoring the size of the inner pores of the particles would retard the protein release process. To address this hypothesis, three new MS-MPs prototypes were prepared by electrochemical synthesis, and the resulting carriers were characterized for morphology, particle size, and pore structure. All MS-MP prototypes had 90 µm mean particle size, but depending on the current density applied for synthesis, pore size changed between 5 and 13 nm. The model protein α-chymotrypsinogen was loaded into MS-MPs by adsorption and solvent evaporation. In the subsequent release experiments, no burst release of the protein was detected for any prototype. However, prototypes with larger pores (>10 nm) reached 100% release in 24–48 h, whereas prototypes with small mesopores (<6 nm) still retained most of their cargo after 96 h. MS-MPs with ∼6 nm pores were loaded with the osteogenic factor BMP7, and sustained release of this protein for up to two weeks was achieved. In conclusion, our results confirm that tailoring pore size can modify protein release from MS-MPs, and that prototypes with potential therapeutic utility for regional delivery of osteogenic factors can be prepared by convenient techniques. PMID:26557423

  15. PARTICLE SIZE DISTRIBUTIONS FOR AN OFFICE AEROSOL

    EPA Science Inventory

    The article discusses an evaluation of the effect of percent outdoor air supplied and occupation level on the particle size distributions and mass concentrations for a typical office building. (NOTE: As attention has become focused on indoor air pollution control, it has become i...

  16. PARTICLE SIZE DISTRIBUTIONS FOR AN OFFICE AEROSOL

    EPA Science Inventory

    The article discusses an evaluation of the effect of percent outdoor air supplied and occupation level on the particle size distributions and mass concentrations for a typical office building. (NOTE: As attention has become focused on indoor air pollution control, it has become i...

  17. Furthering Chemical and Geophysical Computations: Analysis of SACROC SEM and CT images to obtain pore percentage, size, and connectivity data

    NASA Astrophysics Data System (ADS)

    Mur, A. J.; Purcell, C. C.; Harbert, W. P.; Soong, Y.; Kutchko, B. G.; Kennedy, S.; McIntryre, D.

    2009-12-01

    methods to calculate porosity giving us a large range (13% - 45%). The high average can be attributed to a percentage of small lighter colored calcite crystals and polygons that share sides yet are connected pores. This increases the average pore perimeter. The lower estimate was formulated by using the maximum pore perimeter as the average pore size. By using the 13% porosity model and assuming spherical pores, we calculated that a 1cm3 sample of SACROC limestone would have a surface area of 6.7838 cm2. Along with the permeability measurements found through CT imagery, this new method of SEM analysis with ArcMap will be helpful in formulating a rate of reaction estimate for a planned experiment that will emulate underground time exposure of CO2 to limestone. As more images are analyzed and compared to lab measurements of porosity, this method could potentially be used as a faster, cheaper way to obtain pore information from SEM images.

  18. Raindrop Size Distribution Measurements in Tropical Cyclones

    NASA Technical Reports Server (NTRS)

    Tokay, Ali; Bashor, Paul G.; Habib, Emad; Kasparis, Takis

    2008-01-01

    Characteristics of the raindrop size distribution in seven tropical cyclones have been studied through impact-type disdrometer measurements at three different sites during the 2004-06 Atlantic hurricane seasons. One of the cyclones has been observed at two different sites. High concentrations of small and/or midsize drops were observed in the presence or absence of large drops. Even in the presence of large drops, the maximum drop diameter rarely exceeded 4 mm. These characteristics of raindrop size distribution were observed in all stages of tropical cyclones, unless the storm was in the extratropical stage where the tropical cyclone and a midlatitude frontal system had merged. The presence of relatively high concentrations of large drops in extratropical cyclones resembled the size distribution in continental thunderstorms. The integral rain parameters of drop concentration, liquid water content, and rain rate at fixed reflectivity were therefore lower in extratropical cyclones than in tropical cyclones. In tropical cyclones, at a disdrometercalculated reflectivity of 40 dBZ, the number concentration was 700 plus or minus 100 drops m(sup -3), while the liquid water content and rain rate were 0.90 plus or minus 0.05 g m(sup -3) and 18.5 plus or minus 0.5 mm h(sup -1), respectively. The mean mass diameter, on the other hand, was 1.67 plus or minus 0.3 mm. The comparison of raindrop size distributions between Atlantic tropical cyclones and storms that occurred in the central tropical Pacific island of Roi-Namur revealed that the number density is slightly shifted toward smaller drops, resulting in higher-integral rain parameters and lower mean mass and maximum drop diameters at the latter site. Considering parameterization of the raindrop size distribution in tropical cyclones, characteristics of the normalized gamma distribution parameters were examined with respect to reflectivity. The mean mass diameter increased rapidly with reflectivity, while the normalized

  19. Raindrop Size Distribution Measurements in Tropical Cyclones

    NASA Technical Reports Server (NTRS)

    Tokay, Ali; Bashor, Paul G.; Habib, Emad; Kasparis, Takis

    2008-01-01

    Characteristics of the raindrop size distribution in seven tropical cyclones have been studied through impact-type disdrometer measurements at three different sites during the 2004-06 Atlantic hurricane seasons. One of the cyclones has been observed at two different sites. High concentrations of small and/or midsize drops were observed in the presence or absence of large drops. Even in the presence of large drops, the maximum drop diameter rarely exceeded 4 mm. These characteristics of raindrop size distribution were observed in all stages of tropical cyclones, unless the storm was in the extratropical stage where the tropical cyclone and a midlatitude frontal system had merged. The presence of relatively high concentrations of large drops in extratropical cyclones resembled the size distribution in continental thunderstorms. The integral rain parameters of drop concentration, liquid water content, and rain rate at fixed reflectivity were therefore lower in extratropical cyclones than in tropical cyclones. In tropical cyclones, at a disdrometercalculated reflectivity of 40 dBZ, the number concentration was 700 plus or minus 100 drops m(sup -3), while the liquid water content and rain rate were 0.90 plus or minus 0.05 g m(sup -3) and 18.5 plus or minus 0.5 mm h(sup -1), respectively. The mean mass diameter, on the other hand, was 1.67 plus or minus 0.3 mm. The comparison of raindrop size distributions between Atlantic tropical cyclones and storms that occurred in the central tropical Pacific island of Roi-Namur revealed that the number density is slightly shifted toward smaller drops, resulting in higher-integral rain parameters and lower mean mass and maximum drop diameters at the latter site. Considering parameterization of the raindrop size distribution in tropical cyclones, characteristics of the normalized gamma distribution parameters were examined with respect to reflectivity. The mean mass diameter increased rapidly with reflectivity, while the normalized

  20. Pore-scale dynamics of salt transport and distribution in drying porous media

    SciTech Connect

    Shokri, Nima

    2014-01-15

    Understanding the physics of water evaporation from saline porous media is important in many natural and engineering applications such as durability of building materials and preservation of monuments, water quality, and mineral-fluid interactions. We applied synchrotron x-ray micro-tomography to investigate the pore-scale dynamics of dissolved salt distribution in a three dimensional drying saline porous media using a cylindrical plastic column (15 mm in height and 8 mm in diameter) packed with sand particles saturated with CaI{sub 2} solution (5% concentration by mass) with a spatial and temporal resolution of 12 μm and 30 min, respectively. Every time the drying sand column was set to be imaged, two different images were recorded using distinct synchrotron x-rays energies immediately above and below the K-edge value of Iodine. Taking the difference between pixel gray values enabled us to delineate the spatial and temporal distribution of CaI{sub 2} concentration at pore scale. Results indicate that during early stages of evaporation, air preferentially invades large pores at the surface while finer pores remain saturated and connected to the wet zone at bottom via capillary-induced liquid flow acting as evaporating spots. Consequently, the salt concentration increases preferentially in finer pores where evaporation occurs. Higher salt concentration was observed close to the evaporating surface indicating a convection-driven process. The obtained salt profiles were used to evaluate the numerical solution of the convection-diffusion equation (CDE). Results show that the macro-scale CDE could capture the overall trend of the measured salt profiles but fail to produce the exact slope of the profiles. Our results shed new insight on the physics of salt transport and its complex dynamics in drying porous media and establish synchrotron x-ray tomography as an effective tool to investigate the dynamics of salt transport in porous media at high spatial and temporal

  1. Pore-scale dynamics of salt transport and distribution in drying porous media

    NASA Astrophysics Data System (ADS)

    Shokri, Nima

    2014-01-01

    Understanding the physics of water evaporation from saline porous media is important in many natural and engineering applications such as durability of building materials and preservation of monuments, water quality, and mineral-fluid interactions. We applied synchrotron x-ray micro-tomography to investigate the pore-scale dynamics of dissolved salt distribution in a three dimensional drying saline porous media using a cylindrical plastic column (15 mm in height and 8 mm in diameter) packed with sand particles saturated with CaI2 solution (5% concentration by mass) with a spatial and temporal resolution of 12 μm and 30 min, respectively. Every time the drying sand column was set to be imaged, two different images were recorded using distinct synchrotron x-rays energies immediately above and below the K-edge value of Iodine. Taking the difference between pixel gray values enabled us to delineate the spatial and temporal distribution of CaI2 concentration at pore scale. Results indicate that during early stages of evaporation, air preferentially invades large pores at the surface while finer pores remain saturated and connected to the wet zone at bottom via capillary-induced liquid flow acting as evaporating spots. Consequently, the salt concentration increases preferentially in finer pores where evaporation occurs. Higher salt concentration was observed close to the evaporating surface indicating a convection-driven process. The obtained salt profiles were used to evaluate the numerical solution of the convection-diffusion equation (CDE). Results show that the macro-scale CDE could capture the overall trend of the measured salt profiles but fail to produce the exact slope of the profiles. Our results shed new insight on the physics of salt transport and its complex dynamics in drying porous media and establish synchrotron x-ray tomography as an effective tool to investigate the dynamics of salt transport in porous media at high spatial and temporal resolution.

  2. Ångstrom-size exocytotic fusion pore: Implications for pituitary hormone secretion.

    PubMed

    Kreft, Marko; Jorgačevski, Jernej; Stenovec, Matjaž; Zorec, Robert

    2017-04-27

    In the past, vesicle content release was thought to occur immediately and completely after triggering of exocytosis. However, vesicles may merge with the plasma membrane to form an Ångstrom diameter fusion pore that prevents the exit of secretions from the vesicle lumen. The advantage of such a narrow pore is to minimize the delay between the trigger and the release. Instead of stimulating a sequence of processes, leading to vesicle merger with the plasma membrane and a formation of a fusion pore, the stimulus only widens the pre-established fusion pore. The fusion pore may be stable and may exhibit repetitive opening of the vesicle lumen to the cell exterior accompanied by a content discharge. Such release of vesicle content is partial (subquantal), and depends on fusion pore open time, diameter and the diffusibility of the cargo. Such transient mode of fusion pore opening was not confirmed until the development of the membrane capacitance patch-clamp technique, which enables high-resolution measurement of changes in membrane surface area. It allows millisecond dwell-time measurements of fusion pores with subnanometer diameters. Currently, the soluble N-ethylmaleimide-sensitive factor-attachment protein receptor (SNARE) proteins are considered to be key entities in end-stage exocytosis, and the SNARE complex assembly/disassembly may regulate the fusion pore. Moreover, lipids or other membrane constituents with anisotropic (non-axisymmetric) geometry may also favour the establishment of stable narrow fusion pores, if positioned in the neck of the fusion pore. Copyright © 2017 Elsevier B.V. All rights reserved.

  3. Phase behavior and molecular mobility of n-octylcyanobiphenyl confined to molecular sieves: dependence on the pore size.

    PubMed

    Frunza, Ligia; Frunza, Stefan; Kosslick, Hendrik; Schönhals, Andreas

    2008-11-01

    The molecular dynamics of 4-n-octyl-4'-cyanobiphenyl (8CB) confined inside the pores of a series of AlMCM-41 samples with the same structure, constant composition (SiAl=14.7) but different pore sizes (diameter between 2.3 and 4.6 nm) was investigated by broadband dielectric spectroscopy (10(-2)-10(9) Hz) in a large temperature interval. Two relaxation processes are observed: one has a bulklike behavior and is assigned to the 8CB in the pore center. The relaxation time of the second relaxation process is essentially slower than that of the former one and this process is related to the dynamics of molecules in a surface layer with a paranematic order. Both relaxation processes are specifically influenced by the interaction of the molecules with the surface and by the confinement. Above the clearing temperature the temperature dependence of the relaxation rate of the bulklike process obeys the Vogel-Fulcher-Tammann (VFT) law. The Vogel temperature increases with decreasing pore size. This is explained by increasing influence of paranematic potential of the surface layer with decreasing pore size. The temperature dependence of the relaxation rate of the surface layer follows also the VFT formula and the Vogel temperature decreases with decreasing pore size. This temperature dependence is controlled by both the interaction of the 8CB molecules with the surface via hydrogen bonding and by spatial confinement effects. To discriminate between both effects the data for the surface layer of 8CB confined to the molecular sieves are compared with results concerning 8CB adsorbed as a quasimonolayer on the surface of silica spheres of aerosil. On this basis a confinement parameter is defined and discussed.

  4. Effect of pore size on bone ingrowth into porous titanium implants fabricated by additive manufacturing: An in vivo experiment.

    PubMed

    Taniguchi, Naoya; Fujibayashi, Shunsuke; Takemoto, Mitsuru; Sasaki, Kiyoyuki; Otsuki, Bungo; Nakamura, Takashi; Matsushita, Tomiharu; Kokubo, Tadashi; Matsuda, Shuichi

    2016-02-01

    Selective laser melting (SLM) is an additive manufacturing technique with the ability to produce metallic scaffolds with accurately controlled pore size, porosity, and interconnectivity for orthopedic applications. However, the optimal pore structure of porous titanium manufactured by SLM remains unclear. In this study, we evaluated the effect of pore size with constant porosity on in vivo bone ingrowth in rabbits into porous titanium implants manufactured by SLM. Three porous titanium implants (with an intended porosity of 65% and pore sizes of 300, 600, and 900μm, designated the P300, P600, and P900 implants, respectively) were manufactured by SLM. A diamond lattice was adapted as the basic structure. Their porous structures were evaluated and verified using microfocus X-ray computed tomography. Their bone-implant fixation ability was evaluated by their implantation as porous-surfaced titanium plates into the cortical bone of the rabbit tibia. Bone ingrowth was evaluated by their implantation as cylindrical porous titanium implants into the cancellous bone of the rabbit femur for 2, 4, and 8weeks. The average pore sizes of the P300, P600, and P900 implants were 309, 632, and 956μm, respectively. The P600 implant demonstrated a significantly higher fixation ability at 2weeks than the other implants. After 4weeks, all models had sufficiently high fixation ability in a detaching test. Bone ingrowth into the P300 implant was lower than into the other implants at 4weeks. Because of its appropriate mechanical strength, high fixation ability, and rapid bone ingrowth, our results indicate that the pore structure of the P600 implant is a suitable porous structure for orthopedic implants manufactured by SLM.

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

    NASA Astrophysics Data System (ADS)

    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. Determination of filter pore size for use in HB line phase II production of plutonium oxide

    SciTech Connect

    Shehee, T.; Crowder, M.; Rudisill, T.

    2014-08-01

    H-Canyon and HB-Line are tasked with the production of plutonium oxide (PuO2) from a feed of plutonium (Pu) metal. The PuO2 will provide feed material for the Mixed Oxide (MOX) Fuel Fabrication Facility. After dissolution of the Pu metal in H-Canyon, plans are to transfer the solution to HB-Line for purification by anion exchange. Anion exchange will be followed by plutonium(IV) oxalate precipitation, filtration, and calcination to form PuO2. The filtrate solutions, remaining after precipitation, contain low levels of Pu ions, oxalate ions, and may include solids. These solutions are transferred to H-Canyon for disposition. To mitigate the criticality concern of Pu solids in a Canyon tank, past processes have used oxalate destruction or have pre-filled the Canyon tank with a neutron poison. The installation of a filter on the process lines from the HB-Line filtrate tanks to H-Canyon Tank 9.6 is proposed to remove plutonium oxalate solids. This report describes SRNL’s efforts to determine the appropriate pore size for the filters needed to perform this function. Information provided in this report aids in developing the control strategies for solids in the process.

  7. Facile synthesis of diverse graphene nanomeshes based on simultaneous regulation of pore size and surface structure

    NASA Astrophysics Data System (ADS)

    Zhang, Jia; Song, Huaibing; Zeng, Dawen; Wang, Hao; Qin, Ziyu; Xu, Keng; Pang, Aimin; Xie, Changsheng

    2016-08-01

    Recently, graphene nanomesh (GNM) has attracted great attentions due to its unique porous structure, abundant active sites, finite band gap and possesses potential applications in the fields of electronics, gas sensor/storage, catalysis, etc. Therefore, diverse GNMs with different physical and chemical properties are required urgently to meet different applications. Herein we demonstrate a facile synthetic method based on the famous Fenton reaction to prepare GNM, by using economically fabricated graphene oxide (GO) as a starting material. By precisely controlling the reaction time, simultaneous regulation of pore size from 2.9 to 11.1 nm and surface structure can be realized. Ultimately, diverse GNMs with tunable band gap and work function can be obtained. Specially, the band gap decreases from 4.5–2.3 eV for GO, which is an insulator, to 3.9–1.24 eV for GNM-5 h, which approaches to a semiconductor. The dual nature of electrophilic addition and oxidizability of HO• is responsible for this controllable synthesis. This efficient, low-cost, inherently scalable synthetic method is suitable for provide diverse and optional GNMs, and may be generalized to a universal technique.

  8. Tailoring the porosity and pore size of electrospun synthetic human elastin scaffolds for dermal tissue engineering.

    PubMed

    Rnjak-Kovacina, Jelena; Wise, Steven G; Li, Zhe; Maitz, Peter K M; Young, Cara J; Wang, Yiwei; Weiss, Anthony S

    2011-10-01

    We obtained low and high porosity synthetic human elastin scaffolds by adapting low (1 mL/h) and high (3 mL/h) flow rates respectively during electrospinning. Physical, mechanical and biological properties of these scaffolds were screened to identify the best candidates for the bioengineering of dermal tissue. SHE scaffolds that were electrospun at the higher flow rate presented increased fiber diameter and greater average pore size and over doubling of overall scaffold porosity. Both types of scaffold displayed Young's moduli comparable to that of native elastin, but the high porosity scaffolds possessed higher tensile strength. Low and high porosity scaffolds supported early attachment, spreading and proliferation of primary dermal fibroblasts, but only high porosity scaffolds supported active cell migration and infiltration into the scaffold. High porosity SHE scaffolds promoted cell persistence and scaffold remodeling in vitro with only moderate scaffold contraction. The scaffolds persisted for at least 6 weeks in a mouse subcutaneous implantation study with fibroblasts on the exterior and infiltrating, evidence of scaffold remodeling including de novo collagen synthesis and early stage angiogenesis. Copyright © 2011 Elsevier Ltd. All rights reserved.

  9. Improvement of Methane-Framework Interaction by Controlling Pore Size and Functionality of Pillared MOFs.

    PubMed

    Razavi, Sayed Ali Akbar; Masoomi, Mohammad Yaser; Islamoglu, Timur; Morsali, Ali; Xu, Yan; Hupp, Joseph T; Farha, Omar K; Wang, Jun; Junk, Peter C

    2017-03-06

    The rational design of functionalized porous metal-organic frameworks (MOFs) for gas adsorption applications has been applied using three spacer ligands H2DPT (3,6-di(pyridin-4-yl)-1,4-dihydro-1,2,4,5-tetrazine), DPT (3,6-di(pyridin-4-yl)-1,2,4,5-tetrazine), and BPDH (2,5-bis(4-pyridyl)-3,4-diaza-2,4-hexadiene) to synthesize TMU-34, [Zn(OBA)(H2DPT)0.5]n·DMF, TMU-34(-2H), [Zn(OBA)(DPT)0.5]n·DMF, and TMU-5, [Zn(OBA)(BPDH)0.5]n·1.5DMF, respectively. By controlling the pore size and chemical functionality of these three MOFs, we can improve the interactions between CO2 and especially CH4 with the frameworks. Calculated Qst(CH4) for TMU-5, TMU-34, and TMU-34(-2H) are 27, 23, and 22 kJ mol(-1), respectively. These Qst values are among the highest for CH4-framework interactions. For systematic comparison, two reported frameworks, TMU-4 and TMU-5, have been compared with TMU-34 and TMU-34(-2H) in CO2 adsorption.

  10. Facile synthesis of diverse graphene nanomeshes based on simultaneous regulation of pore size and surface structure

    PubMed Central

    Zhang, Jia; Song, Huaibing; Zeng, Dawen; Wang, Hao; Qin, Ziyu; Xu, Keng; Pang, Aimin; Xie, Changsheng

    2016-01-01

    Recently, graphene nanomesh (GNM) has attracted great attentions due to its unique porous structure, abundant active sites, finite band gap and possesses potential applications in the fields of electronics, gas sensor/storage, catalysis, etc. Therefore, diverse GNMs with different physical and chemical properties are required urgently to meet different applications. Herein we demonstrate a facile synthetic method based on the famous Fenton reaction to prepare GNM, by using economically fabricated graphene oxide (GO) as a starting material. By precisely controlling the reaction time, simultaneous regulation of pore size from 2.9 to 11.1 nm and surface structure can be realized. Ultimately, diverse GNMs with tunable band gap and work function can be obtained. Specially, the band gap decreases from 4.5–2.3 eV for GO, which is an insulator, to 3.9–1.24 eV for GNM-5 h, which approaches to a semiconductor. The dual nature of electrophilic addition and oxidizability of HO• is responsible for this controllable synthesis. This efficient, low-cost, inherently scalable synthetic method is suitable for provide diverse and optional GNMs, and may be generalized to a universal technique. PMID:27561350

  11. Size Dependent Pore Formation in Germanium Nanowires Undergoing Reversible Delithiation Observed by In Situ TEM

    SciTech Connect

    Lu, Xiaotang; He, Yang; Mao, Scott X.; Wang, Chong-min; Korgel, Brian A.

    2016-12-22

    Germanium (Ge) nanowires coated with an amorphous silicon (Si) shell undergoing lithiation and delithiation were studied using in situ transmission electron microscopy (TEM). Delithiation creates pores in nanowires with diameters larger than ~25 nm, but not in smaller diameter nanowires. The formation of pores in Ge nanowires undergoing delithiation has been observed before in in situ TEM experiments, but there has been no indication that a critical diameter exists below which pores do not form. Pore formation occurs as a result of fast lithium diffusion compared to vacancy migration. We propose that a short diffusion path for vacancies to the nanowire surface plays a role in limiting pore formation even when lithium diffusion is fast.

  12. Comparison of polytetrafluoroethylene flat-sheet membranes with different pore sizes in application to submerged membrane bioreactor.

    PubMed

    Nittami, Tadashi; Hitomi, Tetsuo; Matsumoto, Kanji; Nakamura, Kazuho; Ikeda, Takaharu; Setoguchi, Yoshihiro; Motoori, Manabu

    2012-06-01

    This study focused on phase separation of activated sludge mixed liquor by flat-sheet membranes of polytetrafluoroethylene (PTFE). A 20 liter working volume lab-scale MBR incorporating immersed PTFE flat-sheet membrane modules with different pore sizes (0.3, 0.5 and 1.0 μm) was operated for 19 days treating a synthetic wastewater. The experiment was interrupted twice at days 5 and 13 when the modules were removed and cleaned physically and chemically in sequence. The pure water permeate flux of each membrane module was measured before and after each cleaning step to calculate membrane resistances. Results showed that fouling of membrane modules with 0.3 μm pore size was more rapid than other membrane modules with different pore sizes (0.5 and 1.0 μm). On the other hand, it was not clear whether fouling of the 0.5 μm membrane module was more severe than that of the 1.0 μm membrane module. This was partly because of the membrane condition after chemical cleaning, which seemed to determine the fouling of those modules over the next period. When irreversible resistance (Ri) i.e., differences in membrane resistance before use and after chemical cleaning was high, the transmembrane pressure increased quickly during the next period irrespective of membrane pore size.

  13. Tailoring Pore Size of Nitrogen-Doped Hollow Carbon Nanospheres for Confi ning Sulfur in Lithium–Sulfur Batteries

    SciTech Connect

    Zhou, Weidong; Wang, Chong M.; Zhang, Quiglin; Abruna, Hector D.; He, Yang; Wang, Jiangwei; Mao, Scott X.; Xiao, Xingcheng

    2015-08-19

    Three types of nitrogen-doped hollow carbon spheres with different pore sized porous shells are prepared to investigate the performance of sulfur confinement. The reason that why no sulfur is observed in previous research is determined and it is successfully demonstrated that the sulfur/polysulfide will overflow the porous carbon during the lithiation process.

  14. Size distributions of submicrometer aerosols from cooking

    SciTech Connect

    Li, C.S.; Lin, W.H.; Jeng, F.T. )

    1993-01-01

    Although gas stove usage varies from country to country, it is still one of the major indoor combustion sources. In order to assess the health effects of using gas stoves, the physical characteristics of the particle emissions from cooking were conducted in a first-floor apartment in the Taipei area. The particle size distributions from scrambling eggs, frying chicken, and cooking soup were measured in the kitchen by a high resolution particle sizer, which could measure the particles in the size range of 0.01 [mu]m to 1 [mu]m. The concentrations of the submicrometer particles increased significantly from 15,000 cm[sup [minus]3] to 150,000 cm[sup [minus]3] during cooking. Additionally, the ultrafine particles constituted 60%--70% of the total submicron aerosols. The changes in the size distributions and the concentrations of the submicrometer aerosols before, during, and after the aerosol generations were compared. On the average, the median diameters of scrambling eggs, frying chicken, cooking soup, and of the background conditions were 40 nm, 50 nm, 30 nm, and 70 nm, respectively. Regarding the surface area-weighted size distributions, the surface median diameters of the four situations were 180 nm, 300 nm, 150 nm, and 220 nm, respectively. Furthermore, the volume median diameters in the conditions mentioned above were almost similar, namely 300--350 nm. 10 refs., 6 figs., 2 tabs.

  15. Oriented bioactive glass (13-93) scaffolds with controllable pore size by unidirectional freezing of camphene-based suspensions: microstructure and mechanical response

    PubMed Central

    Liu, Xin; Rahaman, Mohamed N.; Fu, Qiang

    2010-01-01

    Scaffolds of 13-93 bioactive glass (composition 6Na2O, 8K2O, 8MgO, 22CaO, 2P2O5, 54SiO2; mol %), containing oriented pores with controllable diameter, were prepared by unidirectional freezing of camphene-based suspensions (10 vol% particles) on a cold substrate (−196°C or 3°C). By varying the annealing time (0–72 h) to coarsen the camphene phase, constructs with the same porosity (86 ± 1%) but with controllable pore diameters (15–160 μm) were obtained after sublimation of the camphene. The pore diameters had a self-similar distribution that could be fitted by a diffusion-controlled coalescence model. Sintering (1 h at 690°C) was accompanied by a decrease in the porosity and pore diameter, the magnitude of which depended on the pore size of the green constructs, giving scaffolds with a porosity of 20–60% and average pore diameter of 6–120 μm. The compressive stress vs. deformation response of the sintered scaffolds in the orientation direction was linear, followed by failure. The compressive strength and elastic modulus in the orientation direction varied from 180 MPa and 25 GPa, respectively, (porosity = 20%) to 16 MPa and 4 GPa, respectively, (porosity = 60%), which were 2–3 times larger than the values in the direction perpendicular to the orientation. The potential use of these 13-93 bioactive glass scaffolds for the repair of large defects in load-bearing bones, such as segmental defects in long bones, is discussed. PMID:20807594

  16. The phenotype of cancer cell invasion controlled by fibril diameter and pore size of 3D collagen networks.

    PubMed

    Sapudom, Jiranuwat; Rubner, Stefan; Martin, Steve; Kurth, Tony; Riedel, Stefanie; Mierke, Claudia T; Pompe, Tilo

    2015-06-01

    The behavior of cancer cells is strongly influenced by the properties of extracellular microenvironments, including topology, mechanics and composition. As topological and mechanical properties of the extracellular matrix are hard to access and control for in-depth studies of underlying mechanisms in vivo, defined biomimetic in vitro models are needed. Herein we show, how pore size and fibril diameter of collagen I networks distinctively regulate cancer cell morphology and invasion. Three-dimensional collagen I matrices with a tight control of pore size, fibril diameter and stiffness were reconstituted by adjustment of concentration and pH value during matrix reconstitution. At first, a detailed analysis of topology and mechanics of matrices using confocal laser scanning microscopy, image analysis tools and force spectroscopy indicate pore size and not fibril diameter as the major determinant of matrix elasticity. Secondly, by using two different breast cancer cell lines (MDA-MB-231 and MCF-7), we demonstrate collagen fibril diameter--and not pore size--to primarily regulate cell morphology, cluster formation and invasion. Invasiveness increased and clustering decreased with increasing fibril diameter for both, the highly invasive MDA-MB-231 cells with mesenchymal migratory phenotype and the MCF-7 cells with amoeboid migratory phenotype. As this behavior was independent of overall pore size, matrix elasticity is shown to be not the major determinant of the cell characteristics. Our work emphasizes the complex relationship between structural-mechanical properties of the extracellular matrix and invasive behavior of cancer cells. It suggests a correlation of migratory and invasive phenotype of cancer cells in dependence on topological and mechanical features of the length scale of single fibrils and not on coarse-grained network properties.

  17. Company size distribution in different countries

    NASA Astrophysics Data System (ADS)

    Ramsden, J. J.; Kiss-Haypál, Gy.

    2000-03-01

    The distribution of companies in a country, ranked in order of size (annual net revenue) s, follows the simplified canonical law s r∼(r+ρ) -1/θ remarkably well, where r is the rank, and θ and ρ are the parameters of the distribution. These parameters have been determined for 20 countries in America, Asia and Europe. Significant differences between countries are found. Neither θ nor ρ appears to correlate well with traditional economic indicators; indeed some countries often thought to be economically and politically, but not necessarily socially, similar show surprising differences, suggesting that wealth and prosperity are influenced by hidden layers hitherto inaccessible through standard economic theory.

  18. Particle Size Distributions in Atmospheric Clouds

    DTIC Science & Technology

    2003-12-01

    UNCLASSIFIED Center for Turbulence Research 39 Annual Research Briefs 2003 Particle size distributions in atmospheric clouds By Roberto Paoli & Karim...atmospheric turbulence is an important, though complex, problem in cloud physics ( Shaw 2003). From a computational point of view, two major factors...contribute to this complexity. First is the very high turbulence Reynolds number and the large range of spatial scales (Vaillancourt & Yau 2000; Shaw 2003

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

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

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

  20. Genome Sizes and the Benford Distribution

    PubMed Central

    Friar, James L.; Goldman, Terrance; Pérez–Mercader, Juan

    2012-01-01

    Background Data on the number of Open Reading Frames (ORFs) coded by genomes from the 3 domains of Life show the presence of some notable general features. These include essential differences between the Prokaryotes and Eukaryotes, with the number of ORFs growing linearly with total genome size for the former, but only logarithmically for the latter. Results Simply by assuming that the (protein) coding and non-coding fractions of the genome must have different dynamics and that the non-coding fraction must be particularly versatile and therefore be controlled by a variety of (unspecified) probability distribution functions (pdf’s), we are able to predict that the number of ORFs for Eukaryotes follows a Benford distribution and must therefore have a specific logarithmic form. Using the data for the 1000+ genomes available to us in early 2010, we find that the Benford distribution provides excellent fits to the data over several orders of magnitude. Conclusions In its linear regime the Benford distribution produces excellent fits to the Prokaryote data, while the full non-linear form of the distribution similarly provides an excellent fit to the Eukaryote data. Furthermore, in their region of overlap the salient features are statistically congruent. This allows us to interpret the difference between Prokaryotes and Eukaryotes as the manifestation of the increased demand in the biological functions required for the larger Eukaryotes, to estimate some minimal genome sizes, and to predict a maximal Prokaryote genome size on the order of 8–12 megabasepairs.These results naturally allow a mathematical interpretation in terms of maximal entropy and, therefore, most efficient information transmission. PMID:22629319

  1. Size distribution of ions in atmospheric aerosols

    NASA Astrophysics Data System (ADS)

    Krivácsy, Z.; Molnár, Á.

    The aim of this paper is to present data about the concentration and size distribution of ions in atmospheric aerosol under slightly polluted urban conditions in Hungary. Concentration of inorganic cations (ammonium, sodium, potassium, calcium, magnesium), inorganic anions (sulfate, nitrate, chloride, carbonate) and organic acids (oxalic, malonic, succinic, formic and acetic acid) for 8 particle size range between 0.0625 and 16 μm were determined. As was the case for ammonium, sulfate and nitrate, the organic acids were mostly found in the fine particle size range. Potassium and chloride were rather uniformly distributed between fine and coarse particles. Sodium, calcium, magnesium and carbonate were practically observed in the coarse mode. The results obtained for the summer and the winter half-year were also compared. The mass concentrations were recalculated in equivalents, and the ion balance was found to be reasonable in most cases. Measurement of the pH of the aerosol extracts indicates that the aerosol is acidic in the fine mode, but alkaline in the coarse particle size range.

  2. Atomic-Sized Pores Enhanced Electrocatalysis of TaS2 Nanosheets for Hydrogen Evolution.

    PubMed

    Li, Hui; Tan, Yongwen; Liu, Pan; Guo, Chenguang; Luo, Min; Han, Jiuhui; Lin, Tianquan; Huang, Fuqiang; Chen, Mingwei

    2016-10-01

    A plasma oxidation method is developed to fabricate atomic-scale pores in the basal planes of electrochemically inert TaS2 nanosheets to functionalize the 2D crystals with high electrocatalysis for hydrogen evolution reaction. Quantitative measurements of under-coordinated atoms at edges of the pores by aberration-corrected transmission electron microscopy reveal the intrinsic correlation between the defective atomic sites and electrocatalytic activities of 2D TaS2 .

  3. Beer Clarification by Novel Ceramic Hollow-Fiber Membranes: Effect of Pore Size on Product Quality.

    PubMed

    Cimini, Alessio; Moresi, Mauro

    2016-10-01

    In this work, the crossflow microfiltration performance of rough beer samples was assessed using ceramic hollow-fiber (HF) membrane modules with a nominal pore size ranging from 0.2 to 1.4 μm. Under constant operating conditions (that is, transmembrane pressure difference, TMP = 2.35 bar; feed superficial velocity, vS = 2.5 m/s; temperature, T = 10 °C), quite small steady-state permeation fluxes (J(*) ) of 32 or 37 L/m(2) /h were achieved using the 0.2- or 0.5-μm symmetric membrane modules. Both permeates exhibited turbidity <1 EBC unit, but a significant reduction in density, viscosity, color, extract, and foam half-life with respect to their corresponding retentates. The 0.8-μm asymmetric membrane module might be selected, its corresponding permeate having quite a good turbidity and medium reduction in the aforementioned beer quality parameters. Moreover, it exhibited J(*) values of the same order of magnitude of those claimed for the polyethersulfone HF membrane modules currently commercialized. The 1.4-μm asymmetric membrane module yielded quite a high steady-state permeation flux (196 ± 38 L/m(2) /h), and a minimum decline in permeate quality parameters, except for the high levels of turbidity at room temperature and chill haze. In the circumstances, such a membrane module might be regarded as a real valid alternative to conventional powder filters on condition that the resulting permeate were submitted to a final finishing step using 0.45- or 0.65-μm microbially rated membrane cartridges prior to aseptic bottling. A novel combined beer clarification process was thus outlined.

  4. Pore-scale simulations of drainage in granular materials: Finite size effects and the representative elementary volume

    NASA Astrophysics Data System (ADS)

    Yuan, Chao; Chareyre, Bruno; Darve, Félix

    2016-09-01

    A pore-scale model is introduced for two-phase flow in dense packings of polydisperse spheres. The model is developed as a component of a more general hydromechanical coupling framework based on the discrete element method, which will be elaborated in future papers and will apply to various processes of interest in soil science, in geomechanics and in oil and gas production. Here the emphasis is on the generation of a network of pores mapping the void space between spherical grains, and the definition of local criteria governing the primary drainage process. The pore space is decomposed by Regular Triangulation, from which a set of pores connected by throats are identified. A local entry capillary pressure is evaluated for each throat, based on the balance of capillary pressure and surface tension at equilibrium. The model reflects the possible entrapment of disconnected patches of the receding wetting phase. It is validated by a comparison with drainage experiments. In the last part of the paper, a series of simulations are reported to illustrate size and boundary effects, key questions when studying small samples made of spherical particles be it in simulations or experiments. Repeated tests on samples of different sizes give evolution of water content which are not only scattered but also strongly biased for small sample sizes. More than 20,000 spheres are needed to reduce the bias on saturation below 0.02. Additional statistics are generated by subsampling a large sample of 64,000 spheres. They suggest that the minimal sampling volume for evaluating saturation is one hundred times greater that the sampling volume needed for measuring porosity with the same accuracy. This requirement in terms of sample size induces a need for efficient computer codes. The method described herein has a low algorithmic complexity in order to satisfy this requirement. It will be well suited to further developments toward coupled flow-deformation problems in which evolution of the

  5. The invariances of power law size distributions.

    PubMed

    Frank, Steven A

    2016-01-01

    Size varies. Small things are typically more frequent than large things. The logarithm of frequency often declines linearly with the logarithm of size. That power law relation forms one of the common patterns of nature. Why does the complexity of nature reduce to such a simple pattern? Why do things as different as tree size and enzyme rate follow similarly simple patterns? Here I analyze such patterns by their invariant properties. For example, a common pattern should not change when adding a constant value to all observations. That shift is essentially the renumbering of the points on a ruler without changing the metric information provided by the ruler. A ruler is shift invariant only when its scale is properly calibrated to the pattern being measured. Stretch invariance corresponds to the conservation of the total amount of something, such as the total biomass and consequently the average size. Rotational invariance corresponds to pattern that does not depend on the order in which underlying processes occur, for example, a scale that additively combines the component processes leading to observed values. I use tree size as an example to illustrate how the key invariances shape pattern. A simple interpretation of common pattern follows. That simple interpretation connects the normal distribution to a wide variety of other common patterns through the transformations of scale set by the fundamental invariances.

  6. The invariances of power law size distributions

    PubMed Central

    Frank, Steven A.

    2016-01-01

    Size varies. Small things are typically more frequent than large things. The logarithm of frequency often declines linearly with the logarithm of size. That power law relation forms one of the common patterns of nature. Why does the complexity of nature reduce to such a simple pattern? Why do things as different as tree size and enzyme rate follow similarly simple patterns? Here I analyze such patterns by their invariant properties. For example, a common pattern should not change when adding a constant value to all observations. That shift is essentially the renumbering of the points on a ruler without changing the metric information provided by the ruler. A ruler is shift invariant only when its scale is properly calibrated to the pattern being measured. Stretch invariance corresponds to the conservation of the total amount of something, such as the total biomass and consequently the average size. Rotational invariance corresponds to pattern that does not depend on the order in which underlying processes occur, for example, a scale that additively combines the component processes leading to observed values. I use tree size as an example to illustrate how the key invariances shape pattern. A simple interpretation of common pattern follows. That simple interpretation connects the normal distribution to a wide variety of other common patterns through the transformations of scale set by the fundamental invariances. PMID:27928497

  7. Remote Laser Diffraction Particle Size Distribution Analyzer

    SciTech Connect

    Batcheller, Thomas Aquinas; Huestis, Gary Michael; Bolton, Steven Michael

    2001-03-01

    In support of a radioactive slurry sampling and physical characterization task, an “off-the-shelf” laser diffraction (classical light scattering) particle size analyzer was utilized for remote particle size distribution (PSD) analysis. Spent nuclear fuel was previously reprocessed at the Idaho Nuclear Technology and Engineering Center (INTEC—formerly recognized as the Idaho Chemical Processing Plant) which is on DOE’s INEEL site. The acidic, radioactive aqueous raffinate streams from these processes were transferred to 300,000 gallon stainless steel storage vessels located in the INTEC Tank Farm area. Due to the transfer piping configuration in these vessels, complete removal of the liquid can not be achieved. Consequently, a “heel” slurry remains at the bottom of an “emptied” vessel. Particle size distribution characterization of the settled solids in this remaining heel slurry, as well as suspended solids in the tank liquid, is the goal of this remote PSD analyzer task. A Horiba Instruments Inc. Model LA-300 PSD analyzer, which has a 0.1 to 600 micron measurement range, was modified for remote application in a “hot cell” (gamma radiation) environment. This technology provides rapid and simple PSD analysis, especially down in the fine and microscopic particle size regime. Particle size analysis of these radioactive slurries down in this smaller range was not previously achievable—making this technology far superior than the traditional methods used. Successful acquisition of this data, in conjunction with other characterization analyses, provides important information that can be used in the myriad of potential radioactive waste management alternatives.

  8. Raindrop Size Distribution Measurements in Tropical Cyclones

    NASA Astrophysics Data System (ADS)

    Tokay, A.; Bashor, P. G.; Habib, E.; Kasparis, T. C.

    2006-12-01

    Measurements of the raindrop size distribution (RSD) have been collected in tropical cyclones and hurricanes with an impact type disdrometer during the past three Atlantic hurricane seasons. The measurements were taken at Wallops Island, Virginia, Lafayette, Louisiana, and Orlando, Florida. The RSDs from the remnants of tropical cyclones or hurricanes at 40 dBZ agreed well with each other where the mean mass diameter was 1.65-1.7 mm, and the total concentration had a range of 600 to 800 drops/m3. Assuming the normalized gamma size distribution, the shape parameter will be 5-8 to satisfy the observed rain rate of 18-20 mm/hr. If the observations were taken during the extratropical phase of the storm where the tropical cyclone merges with a frontal system, the composite spectra at 40 dBZ include more large drops and less small to mid-size drops, typical for continental thunderstorms. Thus, the mean mass diameter was larger, while total concentration, and rain rate was less in extratropical cyclones than in tropical cyclones.

  9. Preparation, characterization, and silanization of 3D microporous PDMS structure with properly sized pores for endothelial cell culture.

    PubMed

    Zargar, Reyhaneh; Nourmohammadi, Jhamak; Amoabediny, Ghassem

    2016-01-01

    Nowadays, application of porous polydimethylsiloxane (PDMS) structure in biomedical is becoming widespread, and many methods have been established to create such structure. Although the pores created through these methods are mostly developed on the outer surface of PDMS membrane, this study offers a simple and cost-efficient technique for creating three-dimensional (3D) microporous PDMS structure with appropriate pore size for endothelial cell culture. In this study, combination of gas foaming and particulate leaching methods, with NaHCO3 as effervescent salt and NaCl as progen are used to form a 3D PDMS sponge. The in situ chemical reaction between NaHCO3 and HCl resulted in the formation of small pores and channels. Moreover, soaking the samples in HCl solution temporarily improved the hydrophilicity of PDMS, which then facilitated the penetration of water for further leaching of NaCl. The surface chemical modification process was performed by (3-aminopropyl)triethoxysilane to culture endothelial cells on porous PDMS matrix. The results are an indication of positive response of endothelial cells to the fabricated PDMS sponge. Because of simplicity and practicality of this method for preparing PDMS sponge with appropriate pore size and biological properties, the fabricated matrix can perfectly be applied to future studies in blood-contacting devices. © 2015 International Union of Biochemistry and Molecular Biology, Inc.

  10. Particle size distribution of indoor aerosol sources

    SciTech Connect

    Shah, K.B.

    1990-10-24

    As concern about Indoor Air Quality (IAQ) has grown in recent years, it has become necessary to determine the nature of particles produced by different indoor aerosol sources and the typical concentration that these sources tend to produce. These data are important in predicting the dose of particles to people exposed to these sources and it will also enable us to take effective mitigation procedures. Further, it will also help in designing appropriate air cleaners. A new state of the art technique, DMPS (Differential Mobility Particle Sizer) System is used to determine the particle size distributions of a number of sources. This system employs the electrical mobility characteristics of these particles and is very effective in the 0.01--1.0 {mu}m size range. A modified system that can measure particle sizes in the lower size range down to 3 nm was also used. Experimental results for various aerosol sources is presented in the ensuing chapters. 37 refs., 20 figs., 2 tabs.

  11. Model of the radial distribution function of pores in a layer of porous aluminum oxide

    NASA Astrophysics Data System (ADS)

    Cherkas, N. L.; Cherkas, S. L.

    2016-03-01

    An empirical formula is derived to describe the quasi-periodic structure of a layer of porous aluminum oxide obtained by anodization. The formula accounts for two mechanisms of the transition from the ordered state (2D crystal) to the amorphous state. The first mechanism infers that vacancy-type defects arise, but the crystal lattice remains undestroyed. The second mechanism describes the lattice destruction. The radial distribution function of the pores in porous aluminum oxide is obtained using the Bessel transform. Comparison with a real sample is performed.

  12. Particle Size Distribution in Aluminum Manufacturing Facilities

    PubMed Central

    Liu, Sa; Noth, Elizabeth M.; Dixon-Ernst, Christine; Eisen, Ellen A.; Cullen, Mark R.; Hammond, S. Katharine

    2015-01-01

    As part of exposure assessment for an ongoing epidemiologic study of heart disease and fine particle exposures in aluminum industry, area particle samples were collected in production facilities to assess instrument reliability and particle size distribution at different process areas. Personal modular impactors (PMI) and Minimicro-orifice uniform deposition impactors (MiniMOUDI) were used. The coefficient of variation (CV) of co-located samples was used to evaluate the reproducibility of the samplers. PM2.5 measured by PMI was compared to PM2.5 calculated from MiniMOUDI data. Mass median aerodynamic diameter (MMAD) and concentrations of sub-micrometer (PM1.0) and quasi-ultrafine (PM0.56) particles were evaluated to characterize particle size distribution. Most of CVs were less than 30%. The slope of the linear regression of PMI_PM2.5 versus MiniMOUDI_PM2.5 was 1.03 mg/m3 per mg/m3 (± 0.05), with correlation coefficient of 0.97 (± 0.01). Particle size distribution varied substantively in smelters, whereas it was less variable in fabrication units with significantly smaller MMADs (arithmetic mean of MMADs: 2.59 μm in smelters vs. 1.31 μm in fabrication units, p = 0.001). Although the total particle concentration was more than two times higher in the smelters than in the fabrication units, the fraction of PM10 which was PM1.0 or PM0.56 was significantly lower in the smelters than in the fabrication units (p < 0.001). Consequently, the concentrations of sub-micrometer and quasi-ultrafine particles were similar in these two types of facilities. It would appear, studies evaluating ultrafine particle exposure in aluminum industry should focus on not only the smelters, but also the fabrication facilities. PMID:26478760

  13. Particle Size Distribution in Aluminum Manufacturing Facilities.

    PubMed

    Liu, Sa; Noth, Elizabeth M; Dixon-Ernst, Christine; Eisen, Ellen A; Cullen, Mark R; Hammond, S Katharine

    2014-10-01

    As part of exposure assessment for an ongoing epidemiologic study of heart disease and fine particle exposures in aluminum industry, area particle samples were collected in production facilities to assess instrument reliability and particle size distribution at different process areas. Personal modular impactors (PMI) and Minimicro-orifice uniform deposition impactors (MiniMOUDI) were used. The coefficient of variation (CV) of co-located samples was used to evaluate the reproducibility of the samplers. PM2.5 measured by PMI was compared to PM2.5 calculated from MiniMOUDI data. Mass median aerodynamic diameter (MMAD) and concentrations of sub-micrometer (PM1.0) and quasi-ultrafine (PM0.56) particles were evaluated to characterize particle size distribution. Most of CVs were less than 30%. The slope of the linear regression of PMI_PM2.5 versus MiniMOUDI_PM2.5 was 1.03 mg/m(3) per mg/m(3) (± 0.05), with correlation coefficient of 0.97 (± 0.01). Particle size distribution varied substantively in smelters, whereas it was less variable in fabrication units with significantly smaller MMADs (arithmetic mean of MMADs: 2.59 μm in smelters vs. 1.31 μm in fabrication units, p = 0.001). Although the total particle concentration was more than two times higher in the smelters than in the fabrication units, the fraction of PM10 which was PM1.0 or PM0.56 was significantly lower in the smelters than in the fabrication units (p < 0.001). Consequently, the concentrations of sub-micrometer and quasi-ultrafine particles were similar in these two types of facilities. It would appear, studies evaluating ultrafine particle exposure in aluminum industry should focus on not only the smelters, but also the fabrication facilities.

  14. Electronic cigarette aerosol particle size distribution measurements.

    PubMed

    Ingebrethsen, Bradley J; Cole, Stephen K; Alderman, Steven L

    2012-12-01

    The particle size distribution of aerosols produced by electronic cigarettes was measured in an undiluted state by a spectral transmission procedure and after high dilution with an electrical mobility analyzer. The undiluted e-cigarette aerosols were found to have particle diameters of average mass in the 250-450 nm range and particle number concentrations in the 10(9) particles/cm(3) range. These measurements are comparable to those observed for tobacco burning cigarette smoke in prior studies and also measured in the current study with the spectral transmission method and with the electrical mobility procedure. Total particulate mass for the e-cigarettes calculated from the size distribution parameters measured by spectral transmission were in good agreement with replicate determinations of total particulate mass by gravimetric filter collection. In contrast, average particle diameters determined for e-cigarettes by the electrical mobility method are in the 50 nm range and total particulate masses calculated based on the suggested diameters are orders of magnitude smaller than those determined gravimetrically. This latter discrepancy, and the very small particle diameters observed, are believed to result from almost complete e-cigarette aerosol particle evaporation at the dilution levels and conditions of the electrical mobility analysis. A much smaller degree, ~20% by mass, of apparent particle evaporation was observed for tobacco burning cigarette smoke. The spectral transmission method is validated in the current study against measurements on tobacco burning cigarette smoke, which has been well characterized in prior studies, and is supported as yielding an accurate characterization of the e-cigarette aerosol particle size distribution.

  15. Measurement of nonvolatile particle number size distribution

    NASA Astrophysics Data System (ADS)

    Gkatzelis, G. I.; Papanastasiou, D. K.; Florou, K.; Kaltsonoudis, C.; Louvaris, E.; Pandis, S. N.

    2016-01-01

    An experimental methodology was developed to measure the nonvolatile particle number concentration using a thermodenuder (TD). The TD was coupled with a high-resolution time-of-flight aerosol mass spectrometer, measuring the chemical composition and mass size distribution of the submicrometer aerosol and a scanning mobility particle sizer (SMPS) that provided the number size distribution of the aerosol in the range from 10 to 500 nm. The method was evaluated with a set of smog chamber experiments and achieved almost complete evaporation (> 98 %) of secondary organic as well as freshly nucleated particles, using a TD temperature of 400 °C and a centerline residence time of 15 s. This experimental approach was applied in a winter field campaign in Athens and provided a direct measurement of number concentration and size distribution for particles emitted from major pollution sources. During periods in which the contribution of biomass burning sources was dominant, more than 80 % of particle number concentration remained after passing through the thermodenuder, suggesting that nearly all biomass burning particles had a nonvolatile core. These remaining particles consisted mostly of black carbon (60 % mass contribution) and organic aerosol (OA; 40 %). Organics that had not evaporated through the TD were mostly biomass burning OA (BBOA) and oxygenated OA (OOA) as determined from AMS source apportionment analysis. For periods during which traffic contribution was dominant 50-60 % of the particles had a nonvolatile core while the rest evaporated at 400 °C. The remaining particle mass consisted mostly of black carbon with an 80 % contribution, while OA was responsible for another 15-20 %. Organics were mostly hydrocarbon-like OA (HOA) and OOA. These results suggest that even at 400 °C some fraction of the OA does not evaporate from particles emitted from common combustion processes, such as biomass burning and car engines, indicating that a fraction of this type of OA

  16. Daptomycin forms cation- and size-selective pores in model membranes.

    PubMed

    Zhang, TianHua; Muraih, Jawad K; MacCormick, Ben; Silverman, Jared; Palmer, Michael

    2014-10-01

    Daptomycin is a lipopeptide antibiotic that is used clinically to treat severe infections caused by Gram-positive bacteria. Its bactericidal action involves the calcium-dependent binding to membranes containing phosphatidylglycerol, followed by the formation of membrane-associated oligomers. Bacterial cells exposed to daptomycin undergo membrane depolarization, suggesting the formation of channels or pores in the target membranes. We here used a liposome model to detect and characterize the permeability properties of the daptomycin pores. The pores are selective for cations, with permeabilities being highest for Na(+), K(+), and other alkali metal ions. The permeability is approximately twice lower for Mg(++), and lower again for the organic cations choline and hexamethonium. Anions are excluded, as is the zwitterion cysteine. These observations account for the observed depolarization of bacterial cells by daptomycin and suggest that under typical in vivo conditions depolarization is mainly due to sodium influx.

  17. Landslide size distribution in seismic areas

    NASA Astrophysics Data System (ADS)

    Valagussa, Andrea; Frattini, Paolo; Crosta, Giovanni B.

    2015-04-01

    In seismic areas, the analysis of the landslides size distribution with the distance from the seismic source is very important for hazard zoning and land planning. From numerical modelling (Bourdeau et al., 2004), it has been observed that the area of the sliding mass tends to increase with the ground-motion amplitude up to a certain threshold input acceleration. This has been also observed empirically for the 1989 Loma Prieta earthquake (Keefer and Manson, 1998) and 1999 Chi Chi earthquake (Khazai and Sitar, 2003). Based on this, it possible to assume that the landslide size decreases with the increase of the distance from the seismic source. In this research, we analysed six earthquakes-induced landslides inventories (Papua New Guinea Earthquake, 1993; Northridge Earthquake, 1994; Niigata-Chuetsu Earthquake 2004; Iwate-Miyagi Nairiku Earthquake, 2008; Wenchuan Earthquake, 2008; Tohoku Earthquake, 2011) with a magnitude ranging between 6.6 and 9.0 Mw. For each earthquake, we first analysed the size of landslides as a function of different factors such as the lithology, the PGA, the relief, the distance from the seismic sources (both fault and epicentre). Then, we analysed the magnitude frequency curves for different distances from the source area and for each lithology. We found that a clear relationship between the size distribution and the distance from the seismic source is not evident, probably due to the combined effect of the different influencing factors and to the non-linear relationship between the ground-motion intensity and the distance from the seismic source.

  18. Aerosol Size Distribution in the marine regions

    NASA Astrophysics Data System (ADS)

    Markuszewski, Piotr; Petelski, Tomasz; Zielinski, Tymon; Pakszys, Paulina; Strzalkowska, Agata; Makuch, Przemyslaw; Kowalczyk, Jakub

    2014-05-01

    We would like to present the data obtained during the regular research cruises of the S/Y Oceania over a period of time between 2009 - 2012. The Baltic Sea is a very interesting polygon for aerosol measurements, however, also difficult due to the fact that mostly cases of a mixture of continental and marine aerosols are observed. It is possible to measure clear marine aerosol, but also advections of dust from southern Europe or even Africa. This variability of data allows to compare different conditions. The data is also compared with our measurements from the Arctic Seas, which have been made during the ARctic EXperiment (AREX). The Arctic Seas are very suitable for marine aerosol investigations since continental advections of aerosols are far less frequent than in other European sea regions. The aerosol size distribution was measured using the TSI Laser Aerosol Spectrometer model 3340 (99 channels, measurement range 0.09 μm to 7 μm), condensation particle counter (range 0.01 μm to 3 μm) and laser particle counter PMS CSASP-100-HV-SP (range 0.5 μm to 47 μm in 45 channels). Studies of marine aerosol production and transport are important for many Earth sciences such as cloud physics, atmospheric optics, environmental pollution studies and interaction between ocean and atmosphere. All equipment was placed on one of the masts of S/Y Oceania. Measurements using the laser aerosol spectrometer and condensation particle counter were made on one level (8 meters above sea level). Measurements with the laser particle counter were performed at five different levels above the sea level (8, 11, 14, 17 and 20 m). Based on aerosol size distribution the parameterizations with a Log-Normal and a Power-Law distributions were made. The aerosol source functions, characteristic for the region were also determined. Additionally, poor precision of the sea spray emission determination was confirmed while using only the aerosol concentration data. The emission of sea spray depends

  19. Measurement of the aerosol size distribution with NRL's mobility analyzer

    NASA Technical Reports Server (NTRS)

    Hoppel, W. A.

    1981-01-01

    The size distribution was measured in the size range between 0.0057 and 0.57 micrometer radius. A description of the instrumentation and data analysis is given, together with the measured size distributions calculated for 23 experiments.

  20. Detection and identification of groundwater bacteria capable of escaping entrapment on 0.45-micron-pore-size membrane filters.

    PubMed

    Shirey, J J; Bissonnette, G K

    1991-08-01

    Rural drinking water systems supplied by untreated groundwater were examined to determine whether coliform or heterotrophic plate count bacteria are capable of escaping entrapment on standard porosity (0.45-micron-pore-size) membrane filters. Filterable bacteria were present in 42% of the 24 groundwater sources examined by using nonselective media (R2A, full strength m-HPC, and 0.1x m-HPC agars). Pseudomonads were the most frequently identified group of filterable bacteria detected. Flavobacterium, Alcaligenes, Acinetobacter, and Achromobacter isolates were also identified. Total coliforms were not recovered from any of the 24 groundwater samples following filtration through 0.45-micron-pore-size membrane filters by using selective M-Endo LES agar or mT7 agar. In addition, none of the isolates identified from nonselective media were coliforms. Similarly, neither total coliforms nor specifically Escherichia coli were detected in these filtrates when Colilert P/A medium was used.

  1. Contribution of peat soil structure to biogeochemical processes: A physical understanding of pore distribution and solute transport characteristics

    NASA Astrophysics Data System (ADS)

    Rezanezhad, Fereidoun; Kleimeier, Christian; Milojevic, Tatjana; Liu, Haojie; Van Cappellen, Philippe; Lennartz, Bernd

    2017-04-01

    Peatlands are a valuable but environmentally vulnerable resource. They represent a globally-significant carbon and energy reservoir and play major roles in water and biogeochemical cycles. Peat soils are highly complex porous media with unique physical and hydraulic properties. In peat soils, the unique complex dual-porosity structure with mobile-immobile pore fractions controls water flow and solute migration, which, in turn, affect reactive transport processes and biogeochemical functions. In this presentation, we start with an introduction of key physical and hydraulic properties related to the structure of peat soils and discuss their implications for water storage, flow and the migration of solutes. Then, we present the results of two experiments to understand the effect of pore fractions on the denitrification process in a peat depth profile, with the main objective to show how this process is controlled by pore-scale mass transfer and exchange of nitrate between mobile and immobile pores. In these experiments, bromide and nitrate breakthrough curves were used to constrain transport parameters and steady-state nitrate reduction rates in the depth profile. The vertical distribution of potential denitrification rates were compared with depth distributions of partitioning mobile-immobile pores and the exchange coefficient between the pores. The results showed that an increase of immobile pore fractions with depth increases the common interface surface area between mobile and immobile pores which leads to a more pronounced exchange between the two transport domains and enhances the denitrification activities. Furthermore, the physical non-equilibrium approaches were linked to reactive geochemical transformation processes by comparing the different transport characteristics using the pore distribution analyses between degraded and un-degraded peats and their effects on denitrification activities. The conclusion was that in addition to a reducing condition

  2. Particle size distribution from a GTL engine.

    PubMed

    Li, Xinling; Huang, Zhen; Wang, Jiasong; Zhang, Wugao

    2007-09-01

    Measurements of exhaust particle number concentration and size distribution from an engine fueled with GTL at different engine loads and speeds were carried out by using a two-stage dilution system. The results for GTL were compared with those from the original engine fueled with diesel. The fuel composition and engine operation condition had significant effects on the exhaust particle size distribution, the total exhaust particle number and volume concentrations. For both fuels, the load had no significant influence on the total exhaust particle number concentration at middle speed, while the total exhaust particle number concentration increased with the increase of the load at high speed. At 1400 rpm and 2200 rpm, the total exhaust particle volume concentration increased as the load increased for both fuels. GTL was found to be a "cleaner" fuel. Compared with diesel, under the same operation conditions, the total exhaust particle number concentrations decreased 18-92%, and the total exhaust particle volume concentrations for GTL decreased 21-59%.

  3. Effect of Pore Size and Porosity on the Biomechanical Properties and Cytocompatibility of Porous NiTi Alloys.

    PubMed

    Jian, Yu-Tao; Yang, Yue; Tian, Tian; Stanford, Clark; Zhang, Xin-Ping; Zhao, Ke

    2015-01-01

    Five types of porous Nickel-Titanium (NiTi) alloy samples of different porosities and pore sizes were fabricated. According to compressive and fracture strengths, three groups of porous NiTi alloy samples underwent further cytocompatibility experiments. Porous NiTi alloys exhibited a lower Young's modulus (2.0 GPa ~ 0.8 GPa). Both compressive strength (108.8 MPa ~ 56.2 MPa) and fracture strength (64.6 MPa ~ 41.6 MPa) decreased gradually with increasing mean pore size (MPS). Cells grew and spread well on all porous NiTi alloy samples. Cells attached more strongly on control group and blank group than on all porous NiTi alloy samples (p < 0.05). Cell adhesion on porous NiTi alloys was correlated negatively to MPS (277.2 μm ~ 566.5 μm; p < 0.05). More cells proliferated on control group and blank group than on all porous NiTi alloy samples (p < 0.05). Cellular ALP activity on all porous NiTi alloy samples was higher than on control group and blank group (p < 0.05). The porous NiTi alloys with optimized pore size could be a potential orthopedic material.

  4. A simple semi-quantitative approach studying the in vivo degradation of regenerated silk fibroin scaffolds with different pore sizes.

    PubMed

    Guo, Yongwei; Chen, Zhongchun; Wen, Jianchuan; Jia, Minghui; Shao, Zhengzhong; Zhao, Xia

    2017-10-01

    The biocompatibility and in vivo degradation rate of biomaterials represent critical control points in the long-term success of scaffolds for tissue restoration. In this study, new three-dimensional (3D) regenerated silk fibroin scaffolds (RSFs) were prepared by the freezing-defrosting procedure, and then were implanted beneath the dorsal skin of rats. This study aims to develop a kinetic semi-quantitative approach to assess in vivo degradation rate and biocompatibility of this kind of RSFs with different pore sizes for the first time, and to evaluate the relationship between the biodegradation and tissue responses by measuring the thickness of residual scaffolds, fibrous capsules and infiltrated tissues through integrated techniques of histology, optical imaging and image analysis. Our results showed that scaffolds with both pore sizes (74.35±10.84μm and 139.23±44.93μm, respectively) were well tolerated by host animals and pore size was found to be the rate limiting factor to the biodegradation in the subcutaneous implantation model. In addition, the biodegradation of RSFs was inflammation-mediated to a certain degree and fibroblasts may play a critical role in this process. Overall, such semi-quantitative approach was demonstrated to be a simple and effective method to assess the in vivo degradation rate, and the prepared RSFs were presented to have promising potential in tissue engineering applications. Copyright © 2017 Elsevier B.V. All rights reserved.

  5. Modeling The Size Distribution Of Saturn's Rings

    NASA Astrophysics Data System (ADS)

    Albers, Nicole; Esposito, L. W.

    2007-10-01

    Spatial structures such as density and bending waves, self-gravity and moonlet wakes are among the better known pieces in the puzzle of the formation and evolution of Saturn's main rings. But also the actual sizes of ring particles are very important to understand the long-term behavior or the system. The Cassini mission is continuing to provide a wealth of new observations. Among those are the transient features, bright clumps, and brightness fluctuations in the rather mysterious F ring that are partially attributed to a population of moonlets hidden well within the bright core of the structure. Detections of opaque features during stellar occultations of the UVIS and VIMS instruments strongly support this idea. Further, the discovery of embedded moonlets in Saturn's A ring raises questions about the origin of these objects; not to forget about the km-sized moons, Pan and Daphnis, orbiting within the A ring. Are they remnants of a shattered moon or is it possible to accrete these objects from the surrounding ring material? Currently, the theory still lags behind the observations. Here, we employ a generalized kinetic approach aiming at the long-term evolution of the size distribution that cannot be achieved by current N-body simulations and discuss its implications for the evolution and origin of Saturn's rings.

  6. Estimation of the pore pressure distribution from three dimensional groundwater flow model at mine sites in Korea

    NASA Astrophysics Data System (ADS)

    Kang, Sangsoo; Jang, Myounghwan; Kim, Gyoungman; Kim, Donghui; Kim, Daehoon; Baek, Hwanjo

    2016-04-01

    Mining activities continually change the groundwater flow and associated pore pressure distributions within the rockmass around the mine openings or the open-pit bench during the operational periods. As the pore pressure distributions may substantially affect the mechanical behaviour or stability of the rockmass, it is important to monitor the variation of pore pressure incurred by mining operation. The pore pressure distributions within the rockmass can be derived using a two- or three-dimensional finite element groundwater flow model, adopted to simulate the groundwater flow. While the groundwater inflow at mines has generally been dealt with respect to the working environment, detailed case studies on the distribution of pore water pressure related to the stability analysis of mine openings have been relatively rare in Korea. Recently, however, as the health and safety problems are emerged for sustainable mining practice, these issues are of the major concerns for the mining industries. This study aims to establish a three dimensional groundwater flow model to estimate the pore pressure distributions in order to employ as an input parameter for numerical codes such as the FLAC 3D. Also, the groundwater flow simulated can be used for de-watering design at a mine site. The MINEDW code, a groundwater flow model code specifically developed to simulate the complicated hydro-geologic conditions related to mining, has mainly been used in this study. Based on the data collected from field surveys and literature reviews, a conceptual model was established and sensitivity analysis was performed.

  7. Exploitation of 3D face-centered cubic mesoporous silica as a carrier for a poorly water soluble drug: influence of pore size on release rate.

    PubMed

    Zhu, Wenquan; Wan, Long; Zhang, Chen; Gao, Yikun; Zheng, Xin; Jiang, Tongying; Wang, Siling

    2014-01-01

    The purposes of the present work were to explore the potential application of 3D face-centered cubic mesoporous silica (FMS) with pore size of 16.0nm as a delivery system for poorly soluble drugs and investigate the effect of pore size on the dissolution rate. FMS with different pore sizes (16.0, 6.9 and 3.7nm) was successfully synthesized by using Pluronic block co-polymer F127 as a template and adjusting the reaction temperatures. Celecoxib (CEL), which is a BCS class II drug, was used as a model drug and loaded into FMS with different pore sizes by the solvent deposition method at a drug-silica ratio of 1:4. Characterization using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transformation infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), nitrogen adsorption, X-ray diffraction (XRD), and differential scanning calorimetry (DSC) was used to systematically investigate the drug loading process. The results obtained showed that CEL was in a non-crystalline state after incorporation of CEL into the pores of FMS-15 with pore size of 16.0nm. In vitro dissolution was carried out to demonstrate the effects of FMS with different pore sizes on the release of CEL. The results obtained indicated that the dissolution rate of CEL from FMS-15 was significantly enhanced compared with pure CEL. This could be explained by supposing that CEL encountered less diffusion resistance and its crystallinity decreased due to the large pore size of 16.0nm and the nanopore channels of FMS-15. Moreover, drug loading and pore size both play an important role in enhancing the dissolution properties for the poorly water-soluble drugs. As the pore size between 3.7 and 16.0nm increased, the dissolution rate of CEL from FMS gradually increased. © 2013.

  8. Pore-scale investigation on stress-dependent characteristics of granular packs and the impact of pore deformation on fluid distribution

    SciTech Connect

    Yoon, Hongkyu; Klise, Katherine A.; Torrealba, Victor A.; Karpyn, Zuleima T.; Crandall, D.

    2015-05-25

    Understanding the effect of changing stress conditions on multiphase flow in porous media is of fundamental importance for many subsurface activities including enhanced oil recovery, water drawdown from aquifers, soil confinement, and geologic carbon storage. Geomechanical properties of complex porous systems are dynamically linked to flow conditions, but their feedback relationship is often oversimplified due to the difficulty of representing pore-scale stress deformation and multiphase flow characteristics in high fidelity. In this work, we performed pore-scale experiments of single- and multiphase flow through bead packs at different confining pressure conditions to elucidate compaction-dependent characteristics of granular packs and their impact on fluid flow. A series of drainage and imbibition cycles were conducted on a water-wet, soda-lime glass bead pack under varying confining stress conditions. Simultaneously, X-ray micro-CT was used to visualize and quantify the degree of deformation and fluid distribution corresponding with each stress condition and injection cycle. Micro-CT images were segmented using a gradient-based method to identify fluids (e.g., oil and water), and solid phase redistribution throughout the different experimental stages. Changes in porosity, tortuosity, and specific surface area were quantified as a function of applied confining pressure. Results demonstrate varying degrees of sensitivity of these properties to confining pressure, which suggests that caution must be taken when considering scalability of these properties for practical modeling purposes. Changes in capillary number with confining pressure are attributed to the increase in pore velocity as a result of pore contraction. Furthermore, this increase in pore velocity was found to have a marginal impact on average phase trapping at different confining pressures.

  9. Pore-scale investigation on stress-dependent characteristics of granular packs and the impact of pore deformation on fluid distribution

    DOE PAGES

    Yoon, Hongkyu; Klise, Katherine A.; Torrealba, Victor A.; ...

    2015-05-25

    Understanding the effect of changing stress conditions on multiphase flow in porous media is of fundamental importance for many subsurface activities including enhanced oil recovery, water drawdown from aquifers, soil confinement, and geologic carbon storage. Geomechanical properties of complex porous systems are dynamically linked to flow conditions, but their feedback relationship is often oversimplified due to the difficulty of representing pore-scale stress deformation and multiphase flow characteristics in high fidelity. In this work, we performed pore-scale experiments of single- and multiphase flow through bead packs at different confining pressure conditions to elucidate compaction-dependent characteristics of granular packs and their impactmore » on fluid flow. A series of drainage and imbibition cycles were conducted on a water-wet, soda-lime glass bead pack under varying confining stress conditions. Simultaneously, X-ray micro-CT was used to visualize and quantify the degree of deformation and fluid distribution corresponding with each stress condition and injection cycle. Micro-CT images were segmented using a gradient-based method to identify fluids (e.g., oil and water), and solid phase redistribution throughout the different experimental stages. Changes in porosity, tortuosity, and specific surface area were quantified as a function of applied confining pressure. Results demonstrate varying degrees of sensitivity of these properties to confining pressure, which suggests that caution must be taken when considering scalability of these properties for practical modeling purposes. Changes in capillary number with confining pressure are attributed to the increase in pore velocity as a result of pore contraction. Furthermore, this increase in pore velocity was found to have a marginal impact on average phase trapping at different confining pressures.« less

  10. The Size Distribution of Cometary Nuclei

    NASA Astrophysics Data System (ADS)

    Weissman, P. R.; Lowry, S. C.

    2001-11-01

    We are conducting a program of ground-based CCD photometry of distant cometary nuclei, in order to estimate their sizes, shapes, rotation periods and axial ratios. We have combined our data with that reported in the literature by other observers to obtain an estimate of the size distribution of observed Jupiter-family and Halley-type comets. The catalog consists of 79 measurements of 52 JF and HT comets using a variety of techniques, including CCD photometry, IR photometry, and HST imaging. The data has been normalized to an assumed albedo of 0.04 except in cases where the albedo was directly measured. We find that the cumulative number of comets at or larger than a given radius can be described by a power law function with a slope of --1.40 +/- 0.03. This corresponds to a slope of --0.28 +/- 0.01 for the cumulative luminosity function, close to the slope of --0.32 +/- 0.02 found by Lowry (2001), derived from a homogeneously reduced CCD survey of distant JF comets. Both values are considerably less than the slope of --0.53 +/- 0.05 found by Fernández et al. (1999). This inconsistency is most likely attributed to the inhomogeneous nature of the Fernández et al. dataset, and the inclusion of active comets within their sample. Typical values of the CLF slope for Kuiper belt objects are --0.64 to --0.69 (Gladman et al. 2001; Trujillo et al. 2001). The shallower slope of the JF and HT comets, which are considerably smaller than the measured Kuiper belt objects, may be due to intrinsic differences in the KBO size distribution at the different size ranges (Weissman & Levison 1998) or to the physical evolution of JF and HT comets as they lose mass through sublimation and fragmentation (Lowry 2001). This work was supported by the NASA Planetary Astronomy and Planetary Geology & Geophysics Programs. Support from the National Research Council is also gratefully acknowledged.

  11. Metals in sediment/pore water in Chaohu Lake: distribution, trends and flux.

    PubMed

    Wen, Shengfang; Shan, Baoqing; Zhang, Hong

    2012-01-01

    Nine metals, Cd, Cu, Ni, Pb, As, Cr, Zn, Fe, and Mn in sediment and pore water from 57 sampling sites in Chaohu Lake (Anhui Province, China) were analyzed for spatial distribution, temporal trends and diffuse flux in 2010. Metals in the surface sediment were generally the highest in the western lake center and Nanfei-Dianbu River estuary, with another higher area of As, Fe, and Mn occurring in the Qiyang River estuary. Metal contamination assessment using the New York sediment screening criteria showed that the sediment was severely contaminated in 44% of the area with Mn, 20% with Zn, 16% with Fe, 14% with As, and 6% with Cr and Ni. An increasing trend of toxic metals (Cd, Cu, Ni, Pb, As, Cr, Zn) and Mn with depth was shown in the western lake. Compared with metal content data from the sediment survey conducted in 1980s, the metal content of surface sediment in 2010 was 2.0 times that in the 1980s for Cr, Cu, Zn, and As in the western lake, and less than 1.5 times higher for most of the metals in the eastern lake. Among the metals, only Mn and As had a widespread positive diffuse flux from the pore water to overlying water across the whole lake. The estimated flux in the whole lake was on average 3.36 mg/(m2 x day) for Mn and 0.08 mg/(m2 x day) for As, which indicated a daily increase of 0.93 microg/L for Mn and 0.02 microg/L for As in surface water. The increasing concentration of metals in the sediment and the flux of metals from pore water to overlying water by diffusion and other physical processes should not be ignored for drinking-water sources.

  12. [Vegetation influence on nutrients distribution in pore water of salt marsh sediment].

    PubMed

    Wang, Wei-Wei; Li, Dao-Ji; Gao, Lei

    2009-11-01

    The variations of nutrients in pore water of salt marsh sediment were surveyed in the middle intertidal zone of Chongming Dongtan during August 2007 to May 2008 to identify plant impact on nutrients distribution. The results show that NH4(+) -N and PO4(3-) -P concentrations are lower in pore water of Spartina alterniflora and Phragmites australis zones than in bare flat, and specially, NH4(+) -N concentrations in summer and autumn decrease by one more orders of magnitude. Compared to winter, nutrients concentrations are obviously higher during the period of plant growth, and plant biomass is clearly correlative to nitrogen and phosphorus. Vegetation growth influences nitrogen content intensively. NH4(-) -N concentrations in Spartina alterniflora and Phragmites australis zones are 44.21 and 74.38 micromol x L(-1) respectively, distinctly lower than that in bare flat and Scirpus mariquete zone (340.14 and 291.87 micromol x L(-1) respectively). Moreover, NO(x)(-) -N concentration is one to two order(s) of magnitude lower than NH4(+) -N, and its highest value exists in Phragmites australis zone (5.94 micromol x L(-1)). The results of molecule diffusive flux of nutrients in the surface sediment-overlying water interface indicate that marsh sediment is the source for SiO3(2-) -Si, NH4(+) -N and PO4(3-) -P, and the rank for NO(x)(-) -N (NO3(-) -N + NO2(-) -N), and NO(x)(-) -N flux from overlying water to sediment [16.23 micromol x (m2 x h)(-1)] is higher than NH4(+) -N flux from sediment to overlying water [15.53 micromol x (m2 x h)(-1)]. Vegetation growth accommodates nutrient structure of the estuarine ecosystem by affecting sediment-water interface mass flux and nutrient ratios in pore water and overlying water.

  13. Aggregate size distribution of the soil loss

    NASA Astrophysics Data System (ADS)

    Szabó, Judit Alexandra; Jakab, Gergely; Szabó, Boglárka; Józsa, Sándor; Szalai, Zoltán; Centeri, Csaba

    2016-04-01

    aggregate size distribution which is led to nutrient and organic matter redistribution is one of a key questions to improve erosion estimation. G. Jakab was supported by the János Bolyai fellowship of the HAS.

  14. Size-Dependent Filling Behavior of UV-Curable Di(meth)acrylate Resins into Carbon-Coated Anodic Aluminum Oxide Pores of around 20 nm.

    PubMed

    Nakagawa, Masaru; Nakaya, Akifumi; Hoshikawa, Yasuto; Ito, Shunya; Hiroshiba, Nobuya; Kyotani, Takashi

    2016-11-09

    Ultraviolet (UV) nanoimprint lithography is a promising nanofabrication technology with cost efficiency and high throughput for sub-20 nm size semiconductor, data storage, and optical devices. To test formability of organic resist mask patterns, we investigated whether the type of polymerizable di(meth)acrylate monomer affected the fabrication of cured resin nanopillars by UV nanoimprinting using molds with pores of around 20 nm. We used carbon-coated, porous, anodic aluminum oxide (AAO) films prepared by electrochemical oxidation and thermal chemical vapor deposition as molds, because the pore diameter distribution in the range of 10-40 nm was suitable for combinatorial testing to investigate whether UV-curable resins comprising each monomer were filled into the mold recesses in UV nanoimprinting. Although the UV-curable resins, except for a bisphenol A-based one, detached from the molds without pull-out defects after radical photopolymerization under UV light, the number of cured resin nanopillars was independent of the viscosity of the monomer(s) in each resin. The number of resin nanopillars increased and their diameter decreased as the number of hydroxy groups in the aliphatic diacrylate monomers increased. It was concluded that the filling of the carbon-coated pores having diameters of around 20 nm with UV-curable resins was promoted by the presence of hydroxy groups in the aliphatic di(meth)acrylate monomers.

  15. Förster Resonance Energy Transfer (FRET) between Heterogeneously Distributed Probes: Application to Lipid Nanodomains and Pores

    PubMed Central

    Šachl, Radek; Johansson, Lennart B.-Å.; Hof, Martin

    2012-01-01

    The formation of membrane heterogeneities, e.g., lipid domains and pores, leads to a redistribution of donor (D) and acceptor (A) molecules according to their affinity to the structures formed and the remaining bilayer. If such changes sufficiently influence the Förster resonance energy transfer (FRET) efficiency, these changes can be further analyzed in terms of nanodomain/pore size. This paper is a continuation of previous work on this theme. In particular, it is demonstrated how FRET experiments should be planned and how data should be analyzed in order to achieve the best possible resolution. The limiting resolution of domains and pores are discussed simultaneously, in order to enable direct comparison. It appears that choice of suitable donor/acceptor pairs is the most crucial step in the design of experiments. For instance, it is recommended to use DA pairs, which exhibit an increased affinity to pores (i.e., partition coefficients KD,A > 10) for the determination of pore sizes with radii comparable to the Förster radius R0. On the other hand, donors and acceptors exhibiting a high affinity to different phases are better suited for the determination of domain sizes. The experimental setup where donors and acceptors are excluded from the domains/pores should be avoided. PMID:23203189

  16. Filter-extruded liposomes revisited: a study into size distributions and morphologies in relation to lipid-composition and process parameters.

    PubMed

    Hinna, Askell; Steiniger, Frank; Hupfeld, Stefan; Stein, Paul; Kuntsche, Judith; Brandl, Martin

    2016-01-01

    Filter-extrusion is a widely used technique for down-sizing of phospholipid vesicles. In order to gain a detailed insight into size and size distributions of filter-extruded vesicles composed of egg phosphatidyl-choline (with varying fractions of cholesterol)--in relation to extrusion-parameters (pore-size, number of filter passages, and flow-rate), flow field-flow fractionation in conjunction with multi-angle laser light scattering (AF4-MALLS, Wyatt Technology Corp., Santa Barbara, CA) was employed. Liposome size-distributions determined by AF4-MALLS were compared with those of dynamic light scattering and correlated with cryo-transmission electron microscopy and (31)P-NMR-analysis of lamellarity. Both the mean size of liposome and the width of size distribution were found to decrease with sequential extrusion through smaller pore size filters, starting at a size range of ≈70-415 nm upon repeated extrusion through 400 nm pore-filters, eventually ending with a size range from ≈30 to 85 nm upon extrusion through 30 nm pore size filters. While for small pores sizes (50 nm), increased flow rates resulted in smaller vesicles, no significant influence of flow rate on mean vesicle size was seen with larger pores. Cholesterol at increasing mol fractions up to 0.45 yielded bigger vesicles (at identical process conditions). For a cholesterol mol fraction of 0.5 in combination with small filter pore size, a bimodal size distribution was seen indicating cholesterol micro-crystallites. Finally, a protocol is suggested to prepare large (∼ 300 nm) liposomes with rather narrow size distribution, based on the filter extrusion at defined flow-rates in combination with freeze-/thaw-cycling and bench-top centrifugation.

  17. The effect of particle shape and size distribution on the acoustical properties of mixtures of hemp particles.

    PubMed

    Glé, Philippe; Gourdon, Emmanuel; Arnaud, Laurent; Horoshenkov, Kirill-V; Khan, Amir

    2013-12-01

    Hemp concrete is an attractive alternative to traditional materials used in building construction. It has a very low environmental impact, and it is characterized by high thermal insulation. Hemp aggregate particles are parallelepiped in shape and can be organized in a plurality of ways to create a considerable proportion of open pores with a complex connectivity pattern, the acoustical properties of which have never been examined systematically. Therefore this paper is focused on the fundamental understanding of the relations between the particle shape and size distribution, pore size distribution, and the acoustical properties of the resultant porous material mixture. The sound absorption and the transmission loss of various hemp aggregates is characterized using laboratory experiments and three theoretical models. These models are used to relate the particle size distribution to the pore size distribution. It is shown that the shape of particles and particle size control the pore size distribution and tortuosity in shiv. These properties in turn relate directly to the observed acoustical behavior.

  18. Power laws, discontinuities and regional city size distributions

    USGS Publications Warehouse

    Garmestani, A.S.; Allen, C.R.; Gallagher, C.M.

    2008-01-01

    Urban systems are manifestations of human adaptation to the natural environment. City size distributions are the expression of hierarchical processes acting upon urban systems. In this paper, we test the entire city size distributions for the southeastern and southwestern United States (1990), as well as the size classes in these regions for power law behavior. We interpret the differences in the size of the regional city size distributions as the manifestation of variable growth dynamics dependent upon city size. Size classes in the city size distributions are snapshots of stable states within urban systems in flux. ?? 2008.

  19. Parameterizing Size Distribution in Ice Clouds

    SciTech Connect

    DeSlover, Daniel; Mitchell, David L.

    2009-09-25

    PARAMETERIZING SIZE DISTRIBUTIONS IN ICE CLOUDS David L. Mitchell and Daniel H. DeSlover ABSTRACT An outstanding problem that contributes considerable uncertainty to Global Climate Model (GCM) predictions of future climate is the characterization of ice particle sizes in cirrus clouds. Recent parameterizations of ice cloud effective diameter differ by a factor of three, which, for overcast conditions, often translate to changes in outgoing longwave radiation (OLR) of 55 W m-2 or more. Much of this uncertainty in cirrus particle sizes is related to the problem of ice particle shattering during in situ sampling of the ice particle size distribution (PSD). Ice particles often shatter into many smaller ice fragments upon collision with the rim of the probe inlet tube. These small ice artifacts are counted as real ice crystals, resulting in anomalously high concentrations of small ice crystals (D < 100 µm) and underestimates of the mean and effective size of the PSD. Half of the cirrus cloud optical depth calculated from these in situ measurements can be due to this shattering phenomenon. Another challenge is the determination of ice and liquid water amounts in mixed phase clouds. Mixed phase clouds in the Arctic contain mostly liquid water, and the presence of ice is important for determining their lifecycle. Colder high clouds between -20 and -36 oC may also be mixed phase but in this case their condensate is mostly ice with low levels of liquid water. Rather than affecting their lifecycle, the presence of liquid dramatically affects the cloud optical properties, which affects cloud-climate feedback processes in GCMs. This project has made advancements in solving both of these problems. Regarding the first problem, PSD in ice clouds are uncertain due to the inability to reliably measure the concentrations of the smallest crystals (D < 100 µm), known as the “small mode”. Rather than using in situ probe measurements aboard aircraft, we employed a treatment of ice

  20. Preparation of Porous Stainless Steel Hollow-Fibers through Multi-Modal Particle Size Sintering towards Pore Engineering.

    PubMed

    Allioux, Francois-Marie; David, Oana; Etxeberria Benavides, Miren; Kong, Lingxue; Pacheco Tanaka, David Alfredo; Dumée, Ludovic F

    2017-08-04

    The sintering of metal powders is an efficient and versatile technique to fabricate porous metal elements such as filters, diffusers, and membranes. Neck formation between particles is, however, critical to tune the porosity and optimize mass transfer in order to minimize the densification process. In this work, macro-porous stainless steel (SS) hollow-fibers (HFs) were fabricated by the extrusion and sintering of a dope comprised, for the first time, of a bimodal mixture of SS powders. The SS particles of different sizes and shapes were mixed to increase the neck formation between the particles and control the densification process of the structure during sintering. The sintered HFs from particles of two different sizes were shown to be more mechanically stable at lower sintering temperature due to the increased neck area of the small particles sintered to the large ones. In addition, the sintered HFs made from particles of 10 and 44 μm showed a smaller average pore size (<1 μm) as compared to the micron-size pores of sintered HFs made from particles of 10 μm only and those of 10 and 20 μm. The novel HFs could be used in a range of applications, from filtration modules to electrochemical membrane reactors.

  1. Distributed Pore Chemistry in Porous Organic Polymers in Tissue Culture Flasks

    NASA Technical Reports Server (NTRS)

    Koontz, Steven L. (Inventor)

    1999-01-01

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

  2. Impact of the carbon pore size and topology on the equilibrium quantum sieving of hydrogen isotopes at zero coverage and finite pressures.

    PubMed

    Kowalczyk, Piotr; Gauden, Piotr A; Terzyk, Artur P; Furmaniak, Sylwester

    2009-04-08

    Carbonaceous slit-shaped and square-shaped pores efficiently differentiate adsorbed hydrogen isotopes at 77 and 33 K. Extensive path integral Monte Carlo simulations revealed that the square-shaped carbon pores enhanced the selectivity of deuterium over hydrogen in comparison to equivalent slit-shaped carbon pores at zero coverage as well as at finite pressures (i.e. quantum sieving of hydrogen isotopes is pore-topology-dependent). We show that this enhancement of the D(2)/H(2) equilibrium selectivity results from larger localization of hydrogen isotopes in square-shaped pores. The operating pressures for efficient quantum sieving of hydrogen isotopes are strongly dependent on the topology as well as on the size of the carbon pores. However, for both considered carbon pore topologies the highest D(2)/H(2) separation factor is observed at zero-coverage limit. Depending on carbon pore size and topology we predicted monotonic decreasing and non-monotonic shape of the D(2)/H(2) equilibrium selectivity at finite pressures. For both kinds of carbonaceous pores of molecular sizes we predict high compression of hydrogen isotopes at 77 and 33 K (for example, the pore density of compressed hydrogen isotopes at 77 K and 0.25 MPa in a square-shaped carbon pore of size 2.6 Å exceeds 60 mmol cm(-3); for comparison, the liquid density of para-H(2) at 30 K and 30 MPa is 42 mmol cm(-3)). Finally, by direct comparison of simulation results with experimental data it is explained why 'ordinary' carbonaceous materials are not efficient quantum sieves.

  3. Antimicrobial performance of mesoporous titania thin films: role of pore size, hydrophobicity, and antibiotic release.

    PubMed

    Atefyekta, Saba; Ercan, Batur; Karlsson, Johan; Taylor, Erik; Chung, Stanley; Webster, Thomas J; Andersson, Martin

    2016-01-01

    Implant-associated infections are undesirable complications that might arise after implant surgery. If the infection is not prevented, it can lead to tremendous cost, trauma, and even life threatening conditions for the patient. Development of an implant coating loaded with antimicrobial substances would be an effective way to improve the success rate of implants. In this study, the in vitro efficacy of mesoporous titania thin films used as a novel antimicrobial release coating was evaluated. Mesoporous titania thin films with pore diameters of 4, 6, and 7 nm were synthesized using the evaporation-induced self-assembly method. The films were characterized and loaded with antimicrobial agents, including vancomycin, gentamicin, and daptomycin. Staphylococcus aureus and Pseudomonas aeruginosa were used to evaluate their effectiveness toward inhibiting bacterial colonization. Drug loading and delivery were studied using a quartz crystal microbalance with dissipation monitoring, which showed successful loading and release of the antibiotics from the surfaces. Results from counting bacterial colony-forming units showed reduced bacterial adhesion on the drug-loaded films. Interestingly, the presence of the pores alone had a desired effect on bacterial colonization, which can be attributed to the documented nanotopographical effect. In summary, this study provides significant promise for the use of mesoporous titania thin films for reducing implant infections.

  4. Antimicrobial performance of mesoporous titania thin films: role of pore size, hydrophobicity, and antibiotic release

    PubMed Central

    Atefyekta, Saba; Ercan, Batur; Karlsson, Johan; Taylor, Erik; Chung, Stanley; Webster, Thomas J; Andersson, Martin

    2016-01-01

    Implant-associated infections are undesirable complications that might arise after implant surgery. If the infection is not prevented, it can lead to tremendous cost, trauma, and even life threatening conditions for the patient. Development of an implant coating loaded with antimicrobial substances would be an effective way to improve the success rate of implants. In this study, the in vitro efficacy of mesoporous titania thin films used as a novel antimicrobial release coating was evaluated. Mesoporous titania thin films with pore diameters of 4, 6, and 7 nm were synthesized using the evaporation-induced self-assembly method. The films were characterized and loaded with antimicrobial agents, including vancomycin, gentamicin, and daptomycin. Staphylococcus aureus and Pseudomonas aeruginosa were used to evaluate their effectiveness toward inhibiting bacterial colonization. Drug loading and delivery were studied using a quartz crystal microbalance with dissipation monitoring, which showed successful loading and release of the antibiotics from the surfaces. Results from counting bacterial colony-forming units showed reduced bacterial adhesion on the drug-loaded films. Interestingly, the presence of the pores alone had a desired effect on bacterial colonization, which can be attributed to the documented nanotopographical effect. In summary, this study provides significant promise for the use of mesoporous titania thin films for reducing implant infections. PMID:27022263

  5. Gradients in pore size enhance the osteogenic differentiation of human mesenchymal stromal cells in three-dimensional scaffolds

    NASA Astrophysics Data System (ADS)

    di Luca, Andrea; Ostrowska, Barbara; Lorenzo-Moldero, Ivan; Lepedda, Antonio; Swieszkowski, Wojcech; van Blitterswijk, Clemens; Moroni, Lorenzo

    2016-03-01

    Small fractures in bone tissue can heal by themselves, but in case of larger defects current therapies are not completely successful due to several drawbacks. A possible strategy relies on the combination of additive manufactured polymeric scaffolds and human mesenchymal stromal cells (hMSCs). The architecture of bone tissue is characterized by a structural gradient. Long bones display a structural gradient in the radial direction, while flat bones in the axial direction. Such gradient presents a variation in bone density from the cancellous bone to the cortical bone. Therefore, scaffolds presenting a gradient in porosity could be ideal candidates to improve bone tissue regeneration. In this study, we present a construct with a discrete gradient in pore size and characterize its ability to further support the osteogenic differentiation of hMSCs. Furthermore, we studied the behaviour of hMSCs within the different compartments of the gradient scaffolds, showing a correlation between osteogenic differentiation and ECM mineralization, and pore dimensions. Alkaline phosphatase activity and calcium content increased with increasing pore dimensions. Our results indicate that designing structural porosity gradients may be an appealing strategy to support gradual osteogenic differentiation of adult stem cells.

  6. Thermal Investigations of Periodically Nanoporous Si Films -- The Impact of Structure Sizes and Pore-Edge Amorphization

    NASA Astrophysics Data System (ADS)

    Xu, Dongchao; Zhao, Hongbo; Hao, Qing

    In recent years, nanoporous Si films have been intensively studied as promising thermoelectric materials, which mainly benefits from their dramatically reduced lattice thermal conductivity kL and bulk-like electrical properties.1,2 Despite many encouraging results, challenges still exist in the theoretical explanation of the observed low kL.3 Existing studies mainly attribute the low kL to 1) phonon bandstructure modification by coherent phonon processes in a periodic structure (phononic effects), and/or 2) pore-edge defects. In this work, temperature-dependent kL is measured for nanoporous Si films with different pore sizes and spacing to compare with model predictions. For systematic studies, two fabrication techniques are used to drill the nanopores: 1) reactive ion etching, and 2) a focus ion beam to introduce more pore-edge defects. The results from this work will provide guidance for phonon engineering in general materials with periodic interfaces or boundaries. References: 1. Tang et al., Nano Letters 10, 4279-4283 (2010). 2. Yu et al., Nature Nanotechnology 5, 718-721 (2010). 3. Cahill et al., Applied Physics Reviews 1, 011305/1-45 (2014) Nanoscale thermal transport. II. 2003-2012.

  7. Impact of electrospun conduit fiber diameter and enclosing pouch pore size on vascular constructs grown within rat peritoneal cavities.

    PubMed

    Bashur, Chris A; Eagleton, Matthew J; Ramamurthi, Anand

    2013-04-01

    The generation of vascular grafts by recruiting autologous cells within the peritoneal cavity has shown promise. However, the microenvironment affects cell differentiation and elastic matrix production. Therefore, this study determined the impact of systematic changes in the average fiber diameter of electrospun poly(ɛ-caprolactone) conduits, and the pore size of pouches used to enclose the conduits, on recruited cells. After 2 weeks in the peritoneal cavity, fibrous capsules formed containing macrophages, α-smooth muscle actin (α-SMA)(+) and SM22α(+) myofibroblastic or smooth muscle like-cells, and what appeared to be mesothelial cells on the outer surfaces. These cells infiltrated and deposited matrix (e.g., collagen, hyaluoronan, and limited elastin) within conduit walls. Constructs enclosed within the largest pore pouches exhibited significantly better tissue generation responses (e.g., better cell infiltration, elongation, and matrix deposition). Additionally, the healing response was impacted by the conduit average fiber diameter, and consequently, the effective pore diameter, with the largest diameter fibers promoting the most positive healing response (e.g., greater total cellularity, extracellular matrix deposition, and α-SMA(+) cells). Six weeks post-intra-aortal grafting, constructs were occluded, but significant remodeling also occurred in the arterial microenvironment. Overall, these results demonstrate the importance of microenvironmental cues on recruited peritoneal cells and the necessity of developing strategies to further improve elastic matrix synthesis.

  8. Gradients in pore size enhance the osteogenic differentiation of human mesenchymal stromal cells in three-dimensional scaffolds

    PubMed Central

    Di Luca, Andrea; Ostrowska, Barbara; Lorenzo-Moldero, Ivan; Lepedda, Antonio; Swieszkowski, Wojcech; Van Blitterswijk, Clemens; Moroni, Lorenzo

    2016-01-01

    Small fractures in bone tissue can heal by themselves, but in case of larger defects current therapies are not completely successful due to several drawbacks. A possible strategy relies on the combination of additive manufactured polymeric scaffolds and human mesenchymal stromal cells (hMSCs). The architecture of bone tissue is characterized by a structural gradient. Long bones display a structural gradient in the radial direction, while flat bones in the axial direction. Such gradient presents a variation in bone density from the cancellous bone to the cortical bone. Therefore, scaffolds presenting a gradient in porosity could be ideal candidates to improve bone tissue regeneration. In this study, we present a construct with a discrete gradient in pore size and characterize its ability to further support the osteogenic differentiation of hMSCs. Furthermore, we studied the behaviour of hMSCs within the different compartments of the gradient scaffolds, showing a correlation between osteogenic differentiation and ECM mineralization, and pore dimensions. Alkaline phosphatase activity and calcium content increased with increasing pore dimensions. Our results indicate that designing structural porosity gradients may be an appealing strategy to support gradual osteogenic differentiation of adult stem cells. PMID:26961859

  9. Effects of particle size and forming pressure on pore properties of Fe-Cr-Al porous metal by pressureless sintering

    NASA Astrophysics Data System (ADS)

    Koo, Bon-Uk; Yi, Yujeong; Lee, Minjeong; Kim, Byoung-Kee

    2017-03-01

    With increased hydrogen consumption in ammonia production, refining and synthesis, fuel cells and vehicle industries, development of the material components related to hydrogen production is becoming an important factor in industry growth. Porous metals for fabrication of hydrogen are commonly known for their relative excellence in terms of large area, lightness, lower heat capacity, high toughness, and permeability. Fe-Cr-Al alloys not only have high corrosion resistance, heat resistance, and chemical stability but also ductility, excellent mechanical properties. In order to control powder size and sintering temperature effects of Fe-Cr-Al porous metal fabrication, Fe-Cr-Al powder was classified into 25-35 μm, 35-45 μm, 45-75 μm using an auto shaking sieve machine and then classified Fe-Cr-Al powders were pressed into disk shapes using a uniaxial press machine and CIP. The pelletized Fe-Cr-Al specimens were sintered at various temperatures in high vacuum. Properties such as pore size, porosity, and air permeability were evaluated using perm-porosimetry. Microstructure and phase changes were observed with SEM and XRD. Porosity and relative density were proportionated to increasing sintering temperature. With sufficient sintering at increasing temperatures, the pore size is expected to be gradually reduced. Porosity decreased with increasing sintering temperature and gradually increased necking of the powder.

  10. Nanometer scale pores similar in size to the entrance of the ribosomal exit cavity are a common feature of large RNAs

    PubMed Central

    Rivas, Mario; Tran, Quyen; Fox, George E.

    2013-01-01

    The highly conserved peptidyl transferase center (PTC) of the ribosome contains an RNA pore that serves as the entrance to the exit tunnel. Analysis of available ribosome crystal structures has revealed the presence of multiple additional well-defined pores of comparable size in the ribosomal (rRNA) RNAs. These typically have dimensions of 1–2 nm, with a total area of ∼100 Å2 or more, and most are associated with one or more ribosomal proteins. The PTC example and the other rRNA pores result from the packing of helices. However, in the non-PTC cases the nitrogenous bases do not protrude into the pore, thereby limiting the potential for hydrogen bonding within the pore. Instead, it is the RNA backbone that largely defines the pore likely resulting in a negatively charged environment. In many but not all cases, ribosomal proteins are associated with the pores to a greater or lesser extent. With the exception of the PTC case, the large subunit pores are not found in what are thought to be the evolutionarily oldest regions of the 23S rRNA. The unusual nature of the PTC pore may reflect a history of being created by hybridization between two or more RNAs early in evolution rather than simple folding of a single RNA. An initial survey of nonribosomal RNA crystal structures revealed additional pores, thereby showing that they are likely a general feature of RNA tertiary structure. PMID:23940386

  11. Metal(loid) speciation and size fractionation in sediment pore water depth profiles examined with a new meso profiling system.

    PubMed

    Schroeder, Henning; Fabricius, Anne-Lena; Ecker, Dennis; Ternes, Thomas A; Duester, Lars

    2017-03-23

    In an exemplary incubation study with an anaerobic sediment sampled at an oxbow of the river Lahn in Germany (50°18'56.87″N; 7°37'41.25″E) and contaminated by former mining activity, a novel meso profiling and sampling system (messy) is presented. Messy enables a low invasive, automated sampling of pore water profiles across the sediment water interface (SWI), down to ∼20 cm depth with a spacial resolution of 1 cm. In parallel to the pore water sampling it measures physicochemical sediment parameters such as redox potential and pH value. In an incubation experiment of 151 days the ability of the setup was proven to address several different aspects relevant for fresh water and marine sediment studies: (i) The influence of mechanical disturbance and oxygen induced acidification on the mobility of 13 metals and metalloids (Cd, Co, Cu, Fe, Mn, Mo, Ni, Sb, U, V, Zn) was quantified based on 11 profiles. The analytes were quantified by inductively coupled plasma-mass spectrometry. Three groups of elements were identified with respect to the release into the pore water and the overlying water under different experimental conditions. (ii) The capability to investigate the impacts of changing physicochemical sediment properties on arsenic and antimony (III/V) speciation is shown. (iii) An approach to obtain information on size fractionation effects and to address the colloidal pore water fractions (0.45 μm-16 μm) was successfully conducted for the elements Ag, As, Cu, Fe and Mn.

  12. A fractal-based approach to lake size-distributions

    NASA Astrophysics Data System (ADS)

    Seekell, David A.; Pace, Michael L.; Tranvik, Lars J.; Verpoorter, Charles

    2013-02-01

    The abundance and size distribution of lakes is critical to assessing the role of lakes in regional and global biogeochemical processes. Lakes are fractal but do not always conform to the power law size-distribution typically associated with fractal geographical features. Here, we evaluate the fractal geometry of lakes with the goal of explaining apparently inconsistent observations of power law and non-power law lake size-distributions. The power law size-distribution is a special case for lakes near the mean elevation. Lakes in flat regions are power law distributed, while lakes in mountainous regions deviate from power law distributions. Empirical analyses of lake size data sets from the Adirondack Mountains in New York and the flat island of Gotland in Sweden support this finding. Our approach provides a unifying framework for lake size-distributions, indicates that small lakes cannot dominate total lake surface area, and underscores the importance of regional hypsometry in influencing lake size-distributions.

  13. Relationships between specific surface area and pore size in electrospun polymer fibre networks.

    PubMed

    Eichhorn, S J; Sampson, W W

    2010-04-06

    From consideration of the extent of contact between fibres in electrospun polymer networks, we provide theory relating the specific surface area of the network to the characteristic dimensions of interfibre voids. We show that these properties are strongly influenced by the cross-sectional morphologies of fibres. Whereas porosity has a strong influence on pore dimensions, in the range of porosities typically obtained in real networks, its influence on specific surface area is weak. By considering reference geometries of collapsed ribbons and fibres with circular cross sections, we demonstrate that at a given network porosity, fibre parameters that increase the specific surface area reduce the characteristic dimensions of voids. The implications of the theory, mainly in the context of cell proliferation on electrospun polymer scaffolds, are discussed; the theory has relevance also to future applications of these materials in composites.

  14. Determination of pore sizes and relative porosity in porous nanoshell architectures using dextran retention with single monomer resolution and proton permeation.

    PubMed

    Muhandiramlage, Thusitha P; Cheng, Zhiliang; Roberts, David L; Keogh, John P; Hall, Henry K; Aspinwall, Craig A

    2012-11-20

    Unilamellar phospholipid vesicles prepared using the polymerizable lipid bis-sorbylphosphatidylcholine (bis-SorbPC) yield three-dimensional nanoarchitectures that are highly permeable to small molecules. The resulting porous phospholipid nanoshells (PPNs) are potentially useful for a range of biomedical applications including nanosensors and nanodelivery vehicles for cellular assays and manipulations. The uniformity and size distribution of the pores, key properties for sensor design and utilization, have not previously been reported. Fluorophore-assisted carbohydrate electrophoresis (FACE) was utilized to assess the nominal molecular weight cutoff limit (NMCL) of the PPN via analysis of retained dextran with single monomer resolution. The NMCL of PPNs prepared from pure bis-SorbPC was equivalent to a 1800 Da linear dextran, corresponding to a maximum pore diameter of 2.6 nm. Further investigation of PPNs prepared using binary mixtures of bis-SorbPC and dioleoylphosphatidylcholine (DOPC) revealed a similar NMCL when the bis-SorbPC content exceeded 30 mol %, whereas different size-dependent permeation was observed below this composition. Below 30 mol % bis-SorbPC, dextran retention provided insufficient mass resolution (162 Da) to observe porosity on the experimental time scale; however, proton permeability showed a marked enhancement for bis-SorbPC ≥ 10 mol %. Combined, these data suggest that the NMCL for native pores in bis-SorbPC PPNs results from an inherent property within the lipid assembly that can be partially disrupted by dilution of bis-SorbPC below a critical value for domain formation. Additionally, the analytical method described herein should prove useful for the challenging task of elucidating porosity in a range of three-dimensional nanomaterials.

  15. Atmospheric Ion Clusters: Properties and Size Distributions

    NASA Astrophysics Data System (ADS)

    D'Auria, R.; Turco, R. P.

    2002-12-01

    Ions are continuously generated in the atmosphere by the action of galactic cosmic radiation. Measured charge concentrations are of the order of 103 ~ {cm-3} throughout the troposphere, increasing to about 5 x 103 ~ {cm-3} in the lower stratosphere [Cole and Pierce, 1965; Paltridge, 1965, 1966]. The lifetimes of these ions are sufficient to allow substantial clustering with common trace constituents in air, including water, nitric and sulfuric acids, ammonia, and a variety of organic compounds [e.g., D'Auria and Turco, 2001 and references cited therein]. The populations of the resulting charged molecular clusters represent a pre-nucleation phase of particle formation, and in this regard comprise a key segment of the over-all nucleation size spectrum [e.g., Castleman and Tang, 1972]. It has been suggested that these clusters may catalyze certain heterogeneous reactions, and given their characteristic crystal-like structures may act as freezing nuclei for supercooled droplets. To investigate these possibilities, basic information on cluster thermodynamic properties and chemical kinetics is needed. Here, we present new results for several relevant atmospheric ion cluster families. In particular, predictions based on quantum mechanical simulations of cluster structure, and related thermodynamic parameters, are compared against laboratory data. We also describe a hybrid approach for modeling cluster sequences that combines laboratory measurements and quantum predictions with the classical liquid droplet (Thomson) model to treat a wider range of cluster sizes. Calculations of cluster mass distributions based on this hybrid model are illustrated, and the advantages and limitations of such an analysis are summarized. References: Castelman, A. W., Jr., and I. N. Tang, Role of small clusters in nucleation about ions, J. Chem. Phys., 57, 3629-3638, 1972. Cole, R. K., and E. T. Pierce, Electrification in the Earth's atmosphere for altitudes between 0 and 100 kilometers, J

  16. Uranium distribution in the coastal waters and pore waters of Tampa Bay, Florida

    USGS Publications Warehouse

    Swarzenski, P.W.; Baskaran, M.

    2006-01-01

    The geochemical reactivity of uranium (238U) and dissolved organic carbon (DOC), Fe, Mn, Ba, and V was investigated in the water column, pore waters, and across a river/estuarine mixing zone in Tampa Bay, Florida. This large estuary is impacted both by diverse anthropogenic activity and by extensive U-rich phosphatic deposits. Thus, the estuarine behavior of uranium may be examined relative to such known U enrichments and anthropogenic perturbations. Dissolved (< 0.45??m) uranium exhibited both removal and enrichment processes across the Alafia River/estuarine mixing zone relative to conservative mixing. Such non-conservative U behavior may be attributed to: i) physical mixing processes within the river; ii) U carrier phase reactivity; and/or iii) fluid exchange processes across sediment/water interface. In the bay proper, U concentrations were ?????2 to 3 times greater than those reported for other estuarine systems and are likely a result of erosional inputs from the extensive, underlying U-rich phosphatic deposits. Whereas dissolved U concentrations generally did not approach seawater values (13.6??nM) along the Alafia River salinity transect, water column U concentrations exceeded 16??nM in select regions of the bay. Within the hydrogeological framework of the bay, such enriched U may also be derived from advective fluid transport processes across the sediment/water interface, such as submarine groundwater discharge (SGD) or hyporheic exchange within coastal rivers. Pore water profiles of U in Tampa Bay show both a flux into and out of bottom sediments, and average, diffusive U pore water fluxes (Jdiff) ranged from - 82.0 to 116.6??mol d- 1. It is likely that negative U fluxes imply seawater entrainment or infiltration (i.e., submarine groundwater recharge), which may contribute to the removal of water column uranium. For comparison, a bay-wide, Ra-derived submarine groundwater discharge estimate for Tampa Bay (8??L m- 2 d- 1) yielded an average, advective

  17. Evaluation of Factors Affecting Size and Size Distribution of Chitosan-Electrosprayed Nanoparticles.

    PubMed

    Abyadeh, Morteza; Karimi Zarchi, Ali Akbar; Faramarzi, Mohammad Ali; Amani, Amir

    2017-01-01

    Size and size distribution of polymeric nanoparticles have important effect on their properties for pharmaceutical application. In this study, Chitosan nanoparticles were prepared by electrospray method (electrohydrodynamic atomization) and parameters that simultaneously affect size and/or size distribution of chitosan nanoparticles were optimized. Effect of formulation/processing three independent formulation/processing parameters, namely concentration, flow rate and applied voltage was investigated on particle size and size distribution of generated nanoparticles using a Box-Behnken experimental design. All the studied factors showed important effects on average size and size distribution of nanoparticles. A decrease in size and size distribution was obtainable with decreasing flow rate and concentration and increasing applied voltage. Eventually, a sample with minimum size and polydispersity was obtained with polymer concentration, flow rate and applied voltage values of 0.5 %w/v, 0.05 ml/hr and 15 kV, respectively. The experimentally prepared nanoparticles, expected having lowest size and size distribution values had a size of 105 nm, size distribution of 36 and Zeta potential of 59.3 mV. Results showed that optimum condition for production of chitosan nanoparticles with the minimum size and narrow size distribution was a minimum value for flow rate and highest value for applied voltage along with an optimum chitosan concentration.

  18. Linking basin-scale and pore-scale gas hydrate distribution patterns in diffusion-dominated marine hydrate systems

    NASA Astrophysics Data System (ADS)

    Nole, Michael; Daigle, Hugh; Cook, Ann E.; Hillman, Jess I. T.; Malinverno, Alberto

    2017-02-01

    The goal of this study is to computationally determine the potential distribution patterns of diffusion-driven methane hydrate accumulations in coarse-grained marine sediments. Diffusion of dissolved methane in marine gas hydrate systems has been proposed as a potential transport mechanism thro