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High Porosity (high + porosity)
Selected AbstractsElectrospun Composite Mats of Poly[(D,L -lactide) -co- glycolide] and Collagen with High Porosity as Potential Scaffolds for Skin Tissue EngineeringMACROMOLECULAR MATERIALS & ENGINEERING, Issue 9 2009Ye Yang Abstract Electrospun composite mats of poly[(D,L -lactide) -co- glycolide] and collagen with high porosities of 85,90% and extended pore sizes of 90,130,µm were prepared to mimic the ECM morphologically and chemically. The existence of collagen molecules on the fiber surface was confirmed, enabling the cells to find enhanced binding sites for their integrin receptors. The mechanical data for the blended fibrous mats indicated that they were sufficiently durable for dermal tissue engineering. Fibroblasts derived from GFP transgenic C57BL/6 mice were used to directly observe cell proliferation, and the inoculation of collagen enhanced cell attachment, proliferation and extracellular matrix secretion, which were found to be dependent on the amount of collagen in the composite scaffold. [source] MAPPING AND CLASSIFYING FLOW UNITS IN THE UPPER PART OF THE MID-CRETACEOUS SARVAK FORMATION (WESTERN DEZFUL EMBAYMENT, SW IRAN) BASED ON A DETEMINATION OF RESERVOIR ROCK TYPESJOURNAL OF PETROLEUM GEOLOGY, Issue 4 2007B. Beiranvand The mid-Cretaceous Sarvak Formation, the second-most important reservoir unit in Iran, is composed mainly of grain-supported carbonates. For the purposes of this study, flow units in the upper part of the formation were identified, mapped and classified as part of an integrated reservoir characterization study at a giant oilfield in SW Iran. Pore types and geometries, pore-scale diagenetic history and core-scale depositional attributes were logged using conventional petrographic and lithological methods. The resulting data were combined with core descriptions, mercury-injection capillary pressure data, and wireline log and geophysical data to identify five reservoir rock types: (i) highly oil-stained, grain-supported carbonates, including patch reef and barrier complex deposits with high porosities and permeabilities; (ii) leeward and seaward shoal deposits including grain-supported packstones and skeletal wackestones with high porosities and permeabilities; (iii) dominantly mud-supported lagoonal and open-marine facies with fair porosity and permeability; (iv) grain-supported but highly cemented facies which had poor reservoir characteristics; and (v) calcareous shales and shaly limestones with no reservoir quality. Based on the reservoir rock types, eight flow units were recognised. Subsequently, four reservoir zones were defined based on these flow units at a field scale. This study has contributed to our understanding of flow units in this complex carbonate reservoir, and has improved our ability to characterize and model the architecture of the reservoir from pore to core to field scale. [source] Electrospun Composite Mats of Poly[(D,L -lactide) -co- glycolide] and Collagen with High Porosity as Potential Scaffolds for Skin Tissue EngineeringMACROMOLECULAR MATERIALS & ENGINEERING, Issue 9 2009Ye Yang Abstract Electrospun composite mats of poly[(D,L -lactide) -co- glycolide] and collagen with high porosities of 85,90% and extended pore sizes of 90,130,µm were prepared to mimic the ECM morphologically and chemically. The existence of collagen molecules on the fiber surface was confirmed, enabling the cells to find enhanced binding sites for their integrin receptors. The mechanical data for the blended fibrous mats indicated that they were sufficiently durable for dermal tissue engineering. Fibroblasts derived from GFP transgenic C57BL/6 mice were used to directly observe cell proliferation, and the inoculation of collagen enhanced cell attachment, proliferation and extracellular matrix secretion, which were found to be dependent on the amount of collagen in the composite scaffold. [source] An international and multidisciplinary drilling project into a young complex impact structure: The 2004 ICDP Bosumtwi Crater Drilling Project,An overviewMETEORITICS & PLANETARY SCIENCE, Issue 4-5 2007Christian KOEBERL It is the source crater of the Ivory Coast tektites. The structure was excavated in 2.1,2.2 Gyr old metasediments and metavolcanics of the Birimian Supergroup. A drilling project was conceived that would combine two major scientific interests in this crater: 1) to obtain a complete paleoenvironmental record from the time of crater formation about one million years ago, at a near-equatorial location in Africa for which very few data are available so far, and 2) to obtain a complete record of impactites at the central uplift and in the crater moat, for ground truthing and comparison with other structures. Within the framework of an international and multidisciplinary drilling project led by the International Continental Scientific Drilling Program (ICDP), 16 drill cores were obtained from June to October 2004 at six locations within Lake Bosumtwi, which is 8.5 km in diameter. The 14 sediment cores are currently being investigated for paleoenvironmental indicators. The two impactite cores LB-07A and LB-08A were drilled into the deepest section of the annular moat (540 m) and the flank of the central uplift (450 m), respectively. They are the main subject of this special issue of Meteoritics & Planetary Science, which represents the first detailed presentations of results from the deep drilling into the Bosumtwi impactite sequence. Drilling progressed in both cases through the impact breccia layer into fractured bedrock. LB-07A comprises lithic (in the uppermost part) and suevitic impact breccias with appreciable amounts of impact melt fragments. The lithic clast content is dominated by graywacke, besides various metapelites, quartzite, and a carbonate target component. Shock deformation in the form of quartz grains with planar microdeformations is abundant. First chemical results indicate a number of suevite samples that are strongly enriched in siderophile elements and Mg, but the presence of a definite meteoritic component in these samples cannot be confirmed due to high indigenous values. Core LB-08A comprises suevitic breccia in the uppermost part, followed with depth by a thick sequence of graywacke-dominated metasediment with suevite and a few granitoid dike intercalations. It is assumed that the metasediment package represents bedrock intersected in the flank of the central uplift. Both 7A and 8A suevite intersections differ from suevites outside of the northern crater rim. Deep drilling results confirmed the gross structure of the crater as imaged by the pre-drilling seismic surveys. Borehole geophysical studies conducted in the two boreholes confirmed the low seismic velocities for the post-impact sediments (less than 1800 m/s) and the impactites (2600,3300 m/s). The impactites exhibit very high porosities (up to 30 vol%), which has important implications for mechanical rock stability. The statistical analysis of the velocities and densities reveals a seismically transparent impactite sequence (free of prominent internal reflections). Petrophysical core analyses provide no support for the presence of a homogeneous magnetic unit (= melt breccia) within the center of the structure. Borehole vector magnetic data point to a patchy distribution of highly magnetic rocks within the impactite sequence. The lack of a coherent melt sheet, or indeed of any significant amounts of melt rock in the crater fill, is in contrast to expectations from modeling and pre-drilling geophysics, and presents an interesting problem for comparative studies and requires re-evaluation of existing data from other terrestrial impact craters, as well as modeling parameters. [source] Biological control of beech and hornbeam affects species richness via changes in the organic layer, pH and soil moisture characteristicsFUNCTIONAL ECOLOGY, Issue 2 2010Anne Mieke Kooijman Summary 1. ,Litter quality is an important ecosystem factor, which may affect undergrowth species richness via decomposition and organic layers directly, but also via longer-term changes in soil pH and moisture. The impact of beech trees with low-degradable and hornbeam trees with high-degradable litter on biodiversity and soil characteristics was studied in ancient forests on decalcified marl, a parent material sensitive to changes in pH and clay content, and characteristic of large parts of western Europe. 2. ,Vegetation analysis clearly separated beech and hornbeam plots, and showed that species richness was consistently lower under beech. Low species richness under beech was associated with low pH, high mass of the organic layer and low soil moisture, which were all interrelated. 3. ,Development of the organic layer was affected by, not only litter quality, but also by pH levels and soil moisture. Under hornbeam, older organic matter increased from almost zero to 1 kg m,2 in drier and more acid soil. Under beech tree litter decay was generally slow, but slowed further in acid soils, where older organic matter amounted to 4 kg m,2. 4. ,Soil moisture and pH levels were strongly related, possibly due to long-term soil development. Under hornbeam, which is more palatable to soil organisms, moisture, bulk density, clay content and pH were high. Acidification and clay eluviation may be counteracted by earthworms, which bring base cations and clay particles back to the surface, and stimulate erosion, so that the impermeable, clay-rich subsoil remains close to the surface. Soils remain base-rich and moist, which further stimulates litter decay and species richness. 5. ,The unpalatable beech showed low pH and clay content, and high porosity, air-filled pore space and depth to the impermeable subsoil. Acidification and clay eluviation may proceed uninhibited, because earthworm activity is low, and erosion limited by protective litter covers. This may lead to drier and more acid soils, which reduce litter decay and species richness even further. 6. ,Trees with low and high litter quality may thus act as an ecosystem engineer, and not only affect ecosystem functioning via mass of the organic layer, but also via longer-term changes in soil characteristics, which in turn affect species richness of the understorey. [source] Determining the dilation factor in 4D monitoring of compacting reservoirs by rock-physics modelsGEOPHYSICAL PROSPECTING, Issue 6 2007José M. Carcione ABSTRACT Hydrocarbon depletion and fluid injection cause compaction and stretching of the reservoir and overburden layers. 4D prestack seismic data can be used to detect these changes because compaction/stretching causes changes in traveltimes and seismic velocities. We show that, by using two different petro-elastic models at varying effective pressures, a good approximation is to assume that the fractional changes in layer thickness, ,L/L, and seismic velocity, ,v/v, are related by a linear function of ,L/L. The slope of this function (the dilation factor, ,= (,v/v)/(,L/L)) is negative and its absolute value generally decreases (shale, low porosity) or increases (sandstone, high porosity) with increasing layer thickness and decreasing effective pressure. The analysis is mainly performed for isotropic deformations. The dilation factor for uniaxial deformations is smaller in absolute value. The dilation factor, which can be calculated from time-lapse data, can be used to predict reservoir compaction/stretching as a function of depth and surface subsidence. [source] Pure-Phase Transport and Dissolution of TCE in Sedimentary Rock SaproliteGROUND WATER, Issue 3 2006M. Lenczewski The objective of this study was to experimentally determine the influence of pore structure on the transport and dissolution of trichloroethylene (TCE) in clay-rich saprolite. In order to simulate a "spill," pure-phase TCE containing a water-insoluble fluorescent dye was injected into two heterogeneous 24-cm-diameter by 37-cm-long undisturbed columns of water-saturated saprolite. TCE entry occurred at capillary pressures of 2.7 and 4.0 kPa. Ten or 28 d after injection, the column was sliced horizontally into three sections and visually examined. The distribution of fluorescent dye indicated that pure-phase TCE migrated mainly through fractures in the shale saprolite and through fine root holes or other macropores in the limestone saprolite residuum. Analysis of saprolite subsamples indicated that TCE was present throughout much of the saprolite column but usually at concentrations less than the solubility of TCE. This spreading was caused by diffusion, which also contributed to the rapid dissolution of TCE in the fractures and macropores. Modeling was carried out using previously published dissolution and diffusion equations. The calculations confirm that rapid disappearance of immiscible TCE can occur in this type of material because of the small size of fracture or macropore openings and the high porosity of the fine-grained material. This study indicates that industrial solvents can readily enter fractures and macropores in otherwise very fine-grained subsoils and then rapidly dissolve and diffuse into the fine-pore structure, fromc which they may be very difficult to remove. [source] Snow, frozen soils and permafrost hydrology in Canada, 1999,2002HYDROLOGICAL PROCESSES, Issue 1 2005Ming-Ko Woo Abstract An overview is provided of Canadian research on snow, frozen soils and permafrost hydrology for 1999,2002, the period between the 1999 IUGG meeting in Birmingham and the 2003 IUGG in Sapporo. Snow research during this period emphasized the blowing snow and sublimation processes, the role of trees in snow distribution, and melt and the effect of heat advection on snowmelt, from patch to regional scales. Regional-scale studies, largely in connection with the Mackenzie GEWEX study, examined the snow conditions of the lower Mackenzie basin and developed a coupled land surface scheme,hydrological model that incorporates snow processes. In frost hydrology, the effects of organic soils on runoff generation and flow delivery were given much attention. Field investigations ranged from plot to hillslope scales, and the results indicate that organic layers of high porosity permit the production of quick flow, even when frozen. Highly fractured bedrock in the Canadian Shield has likewise the effect of permitting snowmelt infiltration at below-freezing temperatures. Finally, changes in snow-covered areas and in snow equivalent over periods from a decade to a century were examined. The responses of snow and ground ice to the warm year of 1998 were also studied as an indication of hydrological responses to climatic warming. Copyright © 2005 Crown in the right of Canada. Published by John Wiley & Sons, Ltd. [source] Random porosity fields and their influence on the stability of granular mediaINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 10 2008José E. Andrade Abstract It is well established that the mechanical behavior of granular media is strongly influenced by the media's microstructure. In this work, the influence of the microstructure is studied by integrating advances in the areas of geostatistics and computational plasticity, by spatially varying the porosity on samples of sand. In particular, geostatistical tools are used to characterize and simulate random porosity fields that are then fed into a nonlinear finite element model. The underlying effective mechanical response of the granular medium is governed by a newly developed elastoplastic model for sands, which readily incorporates spatial variability in the porosity field at the meso-scale. The objective of this study is to assess the influence of heterogeneities in the porosity field on the stability of sand samples. One hundred and fifty isotropic and anisotropic samples of dense sand are failed under plane-strain compression tests using Monte Carlo techniques. Results from parametric studies indicate that the axial strength of a specimen is affected by both the degree and orientation of anisotropy in heterogeneous porosity values with anisotropy orientation having a dominant effect, especially when the bands of high porosity are aligned with the natural orientation of shear banding in the specimen. Copyright © 2007 John Wiley & Sons, Ltd. [source] The Electrophoretic Deposition of Lanthanum Manganite Powders for a Cathode-Supported Solid Oxide Fuel Cell in Planar and Tubular ConfigurationsINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 6 2008Ivana Krklju The purpose of this research was to obtain porous, high-quality cathodes for solid oxide fuel cells in both planar and tubular shapes. To accomplish this, cathodic electrophoretic deposition of the LaMnO3 powder (synthesized by the modified sol,gel method proposed by Pechini) was performed. The optimal sintering temperatures were 1200°C and 1300°C for the tubular and planar configurations, respectively. Single-phase deposits with about 40% porosity were obtained in both configurations. The cathode quality was confirmed by depositing an electrolyte layer of YSZ. After the cosintering of both layers, an extremely dense electrolyte layer was obtained, and the cathode layer retained its high porosity. [source] Comparison of performance of heat regenerators: Relation between heat transfer efficiency and pressure dropINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 4 2001Françoise Duprat Abstract Heat regenerators transfer heat from one gas to another, with an intermediate storage in solids. The heat transfer surface for gas flow application should provide at the same time high surface area and low friction factor. Three geometries of heat transfer surface, monolith, stack of woven screens and bed of spheres, have been compared. Their performance was evaluated from the pressure drop of the heat regenerator working at a given heat transfer efficiency. The comparison was performed using numerical simulation and published measurements of heat transfer and flow friction characteristics. By adjusting the length and the period of the exchanger, it is possible to obtain the same heat transfer efficiency with the three geometries. Beds of spheres give very short and compact heat regenerators, working at high pressure drop. At the opposite, monoliths form long regenerators working at low pressure drop. Stacks of woven screens cover a wide range of performance: low porosity woven screens give high heat transfer efficiency and high pressure drop, while high porosity woven screens offer performance similar to that of the monoliths. Copyright © 2001 John Wiley & Sons, Ltd. [source] Nonwoven as heat barrier: Modeling of the efficiency of Carbtex fibersJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2008Serge Bourbigot Abstract In this work, we examine the use of nonwoven (NW) as heat barrier to protect a metallic substrate. Carbtex fibers consisting in a thermoplastic core inside an oxidized outer shell (polyacrylonitrile or PAN fibers) are selected to make the NW. Measuring temperature profiles in a heat radiator test; it is revealed that Carbtex NW is an efficient heat barrier. A macroscopic model is then developed to simulate heat transfer in NW (considered as a porous medium) used as a protective heat barrier on aluminum plate. The model is validated comparing experimental results obtained by the heat radiator test and predicted values. The efficiency of NW layer is simulated varying different parameters characteristic of the NW (porosity and heat conductivity) and of the design (thickness of the layer). It is revealed to get good efficiency of the NW heat barrier that heat conductivity of the fibers is crucial to get superior performance as well as high porosity (higher than 0.5) associated with a reasonable thickness of NW (5,7 mm). © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] An innovative method to obtain porous PLLA scaffolds with highly spherical and interconnected poresJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 1 2008Cédryck Vaquette Abstract Scaffolding is an essential issue in tissue engineering and scaffolds should answer certain essential criteria: biocompatibility, high porosity, and important pore interconnectivity to facilitate cell migration and fluid diffusion. In this work, a modified solvent casting-particulate leaching out method is presented to produce scaffolds with spherical and interconnected pores. Sugar particles (200,300 ,m and 300,500 ,m) were poured through a horizontal Meker burner flame and collected below the flame. While crossing the high temperature zone, the particles melted and adopted a spherical shape. Spherical particles were compressed in plastic mold. Then, poly- L -lactic acid solution was cast in the sugar assembly. After solvent evaporation, the sugar was removed by immersing the structure into distilled water for 3 days. The obtained scaffolds presented highly spherical interconnected pores, with interconnection pathways from 10 to 100 ,m. Pore interconnection was obtained without any additional step. Compression tests were carried out to evaluate the scaffold mechanical performances. Moreover, rabbit bone marrow mesenchymal stem cells were found to adhere and to proliferate in vitro in the scaffold over 21 days. This technique produced scaffold with highly spherical and interconnected pores without the use of additional organic solvents to leach out the porogen. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2008 [source] AN AEOLIANITE IN THE UPPER DALAN MEMBER (KHUFF FORMATION), SOUTH PARS FIELD, IRANJOURNAL OF PETROLEUM GEOLOGY, Issue 2 2010G. Frébourg A laterally continuous, 3m thick oolitic grainstone has been studied in cores from two wells from the South Pars field (offshore Iran). This high porosity but low permeability interval occurs at the top of the gas-bearing succession in the Permian Upper Dalan Member, and is equivalent to the informally-defined K4 unit of the Khuff Formation. This interval can easily be traced between the wells and overlies high-energy marine deposits. It is composed of oomouldic, fine-grained azooic grainstones with cm-thick coarser-grained layers. Horizontal to oblique lamination or steep foresets were observed together with pinstripe lamination. Petrographic observations indicate a clean oomouldic grainstone with very thin chitonic rims associated with pedogenetic imprints as first-generation cements. Later cements include early vadose meniscus and pendant cements in coarser-grained layers and pseudophreatic cements in the finer-grained material with a tighter pore network, prior to ooid dissolution. Rhizoliths were observed in cores and thin-sections. The pedogenic imprints and the early vadose cementation, both related to emergence, as well as the presence of pinstripe lamination, suggest an aeolian depositional setting. This interval is the first aeolianite recorded within the Khuff Formation or equivalent units, and the first hydrocarbon-bearing carbonate aeolianite described in a hydrocarbon-producing unit. The discovery of aeolianites has important implications for regional sequence-stratigraphic interpretations and reservoir volume calculations. These deposits do not conform to classic subaqueous sequence stratigraphy and do not record eustatic variations in the associated marine basin. Their recognition is crucial for well-to-well correlations. [source] Synthesis of macroporous polymer rods based on an acrylamide derivative monomerJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 22 2006Ruben Dario Arrua Abstract New macroporous polymer rods were prepared by free-radical crosslinking copolymerization from N -acryloyl-tris(hydroxymethyl)aminomethane and N,N,-methylenebisacrylamide as a crosslinking agent with different porogenic mixtures and with azobisisobutyronitrile as an initiator. The porous properties of these materials were controlled through changes in the proportions of the porogenic mixture, the polymerization temperature, or the concentration of the crosslinking agent. Pore size distribution profiles that shifted toward a larger pore size were obtained in the following cases: when the percentage of the coporogen was increased, when the copolymerization reactions were carried out at a low temperature (55 °C), and when the crosslinking concentration was reduced. Alternatively, a porogenic mixture formed from dimethyl sulfoxide and a 1:1 combination of tetradecanol and poly(ethylene glycol) 6000 as coporogens yielded a polymer rod with a high porosity and pore size. These hydrophilic materials are promising as base supports for different chromatographic processes and as throughput bioreactors. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6616,6623, 2006 [source] Effects of Oxidation Curing and Sintering Additives on the Formation of Polymer-Derived Near-Stoichiometric Silicon Carbide FibersJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2008Lifu Chen The effects of oxygen pick-up and sintering additives on the formation of silicon carbide (SiC) fibers from polyaluminocarbosilane are studied. It has been found that the strict control of oxygen pick up during the oxidation curing is essential to produce near-stoichiometric SiC fibers. When the molar ratio of oxygen to excess carbon in the pyrolyzed fibers (SiCxOy) is slightly over 1 (O/CExcess=y/(x,1)>1), the excess carbon is eliminated during the subsequent sintering as CO and CO2 as a result of the decomposition of SiCxOy; the remaining oxygen is removed as SiO and CO vapor, leaving near-stoichiometric SiC as the residue. However, with still increasing oxygen pick up, the final ceramic fibers become more porous and rich in silicon. The evolution of CO, CO2, and SiO generates high porosity in the absence of a sintering additive, leading to low fiber density. The inter-connected and open porosity favors the formation of CO. In contrast, for the fibers containing aluminum (Al) or Al/B sintering additives, the pores are much smaller and essentially closed, favoring the formation of CO2. Therefore, after sintering at 1800°C, the fibers without sintering additives contain excess silicon, while those with sintering additives are near stoichiometric. Al is beneficial to the densification but it alone cannot produce fibers of high density. When B is added in addition to Al, the fibers can be sintered to nearly full density. [source] Fabrication of a Porous Bioactive Glass,Ceramic Using Room-Temperature Freeze CastingJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2006Ju-Ha Song The room-temperature freeze-casting method was used to fabricate porous bioactive glass,ceramics. In this method, a glass/camphene slurry prepared at 60°C was cast into a mold at 20°C, resulting in the production of a rigid green body that was comprised of three-dimensional dendritic camphene networks surrounded by highly concentrated glass powder walls. After the sublimation of camphene, the samples were sintered for 3 h at elevated temperatures ranging from 700° to 1100°C. As the sintering temperature was increased to 1000°C, the densification of the glass,ceramic wall was remarkably enhanced, while its highly porous structure was preserved. The sample sintered at 1000°C showed a high porosity of 53% and pore channels with a size of several tens of micrometers, as well as dense glass,ceramic walls. In addition, the fabricated samples effectively induced the deposition of apatite on their surfaces when immersed in simulated body fluid, implying that they are very bioactive. [source] Preparation and Properties of Porous Aluminum Nitride,Silicon Carbide Composite CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2004Eirik Hagen Microporous two-phase AlN,SiC composites were prepared using Al4C3 and either Si (N2 atmosphere) or Si3N4 (Ar atmosphere) as precursors. The reaction mechanisms of the two synthesis routes and the effect of processing conditions on reaction rate and the material microstructures were demonstrated. The exothermic reaction between Si and Al4C3 under N2 atmosphere was shown to be a simple processing route for the preparation of porous two-phase AlN,SiC materials. The homogeneous two-phase AlN,SiC composites had a grain size in the range of 1,5 ,m, and the porosity varied in the range of 36%,45%. The bending strength was 50,60 MPa, in accordance with the high porosity. [source] Synthesis of Porous Silicon Nitride with Unidirectionally Aligned Channels Using Freeze-Drying ProcessJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2002Takayuki Fukasawa Porous silicon nitride with macroscopically aligned channels was synthesized using a freeze-drying process. Freezing of a water-based slurry of silicon nitride was done while unidirectionally controlling the growth direction of the ice. Pores were generated subsequently by sublimation of the columnar ice during freeze-drying. By sintering this green body, a porous silicon nitride with high porosity (over 50%) was obtained and its porosity was controllable by the slurry concentration. The porous Si3N4 had a unique microstructure, where macroscopically aligned open pores contained fibrous grains protruding from the internal walls of the Si3N4 matrix. It is hypothesized that vapor/solid phase reactions were important to the formation mechanism of the fibrous grains. [source] Limiting factors for reforestation of mine spoils from Galicia (Spain)LAND DEGRADATION AND DEVELOPMENT, Issue 1 2005F. A. Vega Abstract Mined areas are a continuing source of heavy metals and acidity that move off site in response to erosion. Revegetation of the mine tailings could limit the spread of these heavy metals and acidity. This study was conducted to evaluate, at four tailings on opencast mines of Galicia (Touro: copper mine; and Meirama: lignite mine, NW Spain), the chemical and physical soil quality indicators and limiting edaphic factors concerning forest production. Selected zones were: (1) The tailings formed by the waste materials from the depleted Touro mine; (2) the decantation site of deposited sludge coming from the copper extraction in the flotation stage; (3) and (4) tailings of 3 and 10 years old of the Meirama lignite mine. The main physical limitations of the mine soils are the low effective depth (<50,cm), high stoniness (>30,per,cent) and high porosity (>60,per,cent); which make them vulnerable to soil erosion and seriously interferes with the forest production. Soils coming from the decantation site of copper mine do not have physical limitations. The main chemical limitations of mine soils are their acidity (pH from 3·62 to 5·71), and aluminium saturation (>60,per,cent in copper mine soils, and >20,per,cent in lignite mine soils), low CECe (from 5·34 to 9·47,cmol(+),kg,1), organic carbon (from 0·47 to 7·52,mg,kg,1) and Ca2+ and Mg2+ contents, and imbalance between exchange bases. Mine soils coming from the decantation site of copper mine soils are strongly limited by the high Cu content (1218,mg,kg,1). Lime and organic amendments are the most important factors in providing a suitable medium for plant growth. Copyright © 2004 John Wiley & Sons, Ltd. [source] Waterlogging tolerance in the tribe Triticeae: the adventitious roots of Critesion marinum have a relatively high porosity and a barrier to radial oxygen lossPLANT CELL & ENVIRONMENT, Issue 6 2001M. P. Mcdonald Abstract Nine species from the tribe Triticeae , three crop, three pasture and three ,wild' wetland species , were evaluated for tolerance to growth in stagnant deoxygenated nutrient solution and also for traits that enhance longitudinal O2 movement within the roots. Critesion marinum (syn. Hordeum marinum) was the only species evaluated that had a strong barrier to radial O2 loss (ROL) in the basal regions of its adventitious roots. Barriers to ROL have previously been documented in roots of several wetland species, although not in any close relatives of dryland crop species. Moreover, the porosity in adventitious roots of C. marinum was relatively high: 14% and 25% in plants grown in aerated and stagnant solutions, respectively. The porosity of C. marinum roots in the aerated solution was 1·8,5·4-fold greater, and in the stagnant solution 1·2,2·8-fold greater, than in the eight other species when grown under the same conditions. These traits presumably contributed to C. marinum having a 1·4,3 times greater adventitious root length than the other species when grown in deoxygenated stagnant nutrient solution or in waterlogged soil. The length of the adventitious roots and ROL profiles of C. marinum grown in waterlogged soil were comparable to those of the extremely waterlogging-tolerant species Echinochloa crus-galli L. (P. Beauv.). The superior tolerance of C. marinum, as compared to Hordeum vulgare (the closest cultivated relative), was confirmed in pots of soil waterlogged for 21 d; H. vulgare suffered severe reductions in shoot and adventitious root dry mass (81% and 67%, respectively), whereas C. marinum shoot mass was only reduced by 38% and adventitious root mass was not affected. [source] Engineering and Design of Wear and Corrosion Resistant PVD Coatings Regarding the Exceptional Properties of Magnesium SubstratesPLASMA PROCESSES AND POLYMERS, Issue S1 2007Holger Hoche Abstract Although magnesium alloys were popular in the first half of the 20th century, the bad corrosion properties prevented their breakthrough in industrial mass production. Since the technology for the production of high purity alloys was introduced in the 1970s, magnesium alloys became more and more in the focus of industrial attention. Today magnesium alloys are state-of-the-art in construction parts in automotive industry. Despite its outstanding properties like good castability, low density and nearly unlimited availability the negative aspects like weak corrosion and wear behaviour still limit the application of magnesiums in industry, due to the need of sufficient surface protection (E. Aghion, B. Bronfin, Mater. Sci. Forum2000, 350,351, 19). Today, plasma electrolytic anodisations are state-of-the-art (H. Haferkamp, "Magnesiumkorrosion,Prozesse, Schutz von Anode und Kathode", in: Moderne Beschichtungsverfahren, F.-W. Bach, T. Duda, Eds., Wiley-VCH, Weinheim 2000, ISBN 3-527-30117-8, 242; M. Thoma, Metalloberfläche1984, 38, 393; T. W. Jelinek, Galvanotechnik2003, 94, 46; A. Kuhn, Galvanotechnik2003, 94, 1114). They provide acceptable corrosion resistance and protect the magnesium from mechanical damage due to their high hardness. On the other hand, their high porosity limits their use in combination with electrochemically noble materials, leading to galvanic corrosion (J. Senf, "Untersuchung und Beschreibung von Magnesiumdruckgusslegierungen unter tribologischer, korrosiver und mechanisch-korrosiver Beanspruchung, Berichte aus der Werkstofftechnik", Shaker Verlag, Germany 2001, ISBN 3-8265-8428-7). In addition, the high surface roughness of the plasma electrolytic anodisations restricts their use in tribological applications, particularly under sliding conditions (H. Hoche, "Grundlegende Untersuchungen zur Entwicklung von PVD-Beschichtungen auf Magnesiumlegierungen im Hinblick auf die Erhöhung der Verschleißbeständigkeit und unter Berücksichtigung des Korrosionsverhaltens", Dissertation, TU-Darmstadt D17, Shaker Verlag, Germany 2004). In order to achieve smooth surfaces with high quality, the PVD technology moves into the centre of interest. Since the 1980s PVD coatings are well established and widely used for different industrial applications, mainly for steel and tool coatings. The authors were the first who carried out serious studies on the development of PVD coatings for magnesium alloys in 1999 (J. Senf, "Untersuchung und Beschreibung von Magnesiumdruckgusslegierungen unter tribologischer, korrosiver und mechanisch-korrosiver Beanspruchung, Berichte aus der Werkstofftechnik", Shaker Verlag, Germany 2001, ISBN 3-8265-8428-7; H. Hoche, "Grundlegende Untersuchungen zur Entwicklung von PVD-Beschichtungen auf Magnesiumlegierungen im Hinblick auf die Erhöhung der Verschleißbeständigkeit und unter Berücksichtigung des Korrosionsverhaltens", Dissertation, TU-Darmstadt D17, Shaker Verlag, Germany 2004). The extensive research activities lead to the recent development of a coating system, which provides both, good wear properties as well as good corrosion behaviour. [source] Electrospinning functional nanoscale fibers: a perspective for the futurePOLYMER INTERNATIONAL, Issue 3 2008Matthew T Hunley Abstract Over the past decade, electrospinning has grown from a small niche process to a widely used fiber formation technique. Applying a strong electric potential on a polymer solution or melt produces nanoscale fibers. These nanofibers form non-woven textile mats, oriented fibrous bundles and even three-dimensional structured scaffolds, all with large surface areas and high porosity. Major applications of electrospun membranes include tissue engineering, controlled drug delivery, sensing, separations, filtration, catalysis and nanowires. This perspective article highlights many recent advances in electrospun fibers for functional applications, with an emphasis on the advantages and proposed technologies for these non-woven fibrous scaffolds. Copyright © 2007 Society of Chemical Industry [source] Dimensionierung von Vakuumwasserhaltungen im tertiären FeinsandBAUTECHNIK, Issue 7 2004Peter-Michael Mayer Dr.-Ing. Der Entwurf umfangreicher Vakuumwasserhaltungen ist aufgrund fehlender allgemeingültiger analytischer Berechnungsverfahren bisher auf Abschätzungen und Erfahrungen angewiesen. Vorliegende Untersuchungen zeigen exemplarisch für eine 80 m lange und 37 m breite Spundwandbaugrube im tertiären Feinsand, wie mittels räumlicher Finite-Element-Modelle die erforderliche Anzahl und Tiefe von Vakuumtiefbrunnen zur Grundwasserabsenkung berechnet werden kann. Die Auswirkungen von Schichtanisotropien bzw. lokaler Bereiche mit hoher Durchlässigkeit auf das erreichte Absenkziel und die geförderten Pumpmengen werden aufgezeigt. Darüberhinaus wird auch der Wasserdruck auf die Spundwand analysiert. Die Bedeutung zeitabhängiger Strömungsberechnungen wird durch die Verbindung von Aushub und Wasserhaltung deutlich und kann durch instationäre Betrachtungen erfaßt werden. Der Vergleich von in-situ-Messungen und Berechnungsergebnissen zeigt die Leistungsfähigkeit, aber auch die Grenzen numerischer Strömungsmodelle bei der Abschätzung des Ausführungsrisikos und möglicher wirtschaftlicher Optimierungen. Dimensioning of vacuum dewaterings in tertiary fine sand. Because of outstanding valid analytical solutions, the study of extensive dewatering depends actually only on estimations and experiences. This paper show, for a 80 m long and 37 m large excavation in fine sand, how to calculate the requested number and depth of vacuum deep well for the lowering of the groundwater level by Finite-Element-Models. The effects of anisotropic layer and layer with local ranges with high porosity for the achieved lowering and pumping capacity have been showed. Additionally the water pressure on sheet pile wall was also analyzed. The significance of transient flow calculations becomes clearly by the connection of excavation and dewatering. The comparison of in-situ measurements and results of calculations shows the performance but also the limits of the numerical flow models on the estimation of the execution risks and possible improvement on dewatering process. [source] Synthesis and utilization of E. coli -encapsulated PEG-based microdroplet using a microfluidic chip for biological applicationBIOTECHNOLOGY & BIOENGINEERING, Issue 4 2010Kyoung G. Lee Abstract We report herein an effective strategy for encapsulating Escherichia coli in polyethylene glycol diacrylate (PEGDA) microdroplets using a microfluidic device and chemical polymerization. PEGDA was employed as a reactant due to the biocompatibility, high porosity, and hydrophilic property. The uniform size and shape of microdroplets are obtained in a single-step process using microfluidic device. The size of microdroplets can be controlled through the changing continuous flow rate. The combination of microdroplet generation and chemical polymerization techniques provide unique environment to produce non-toxic ways of fabricating microorganism-encapsulated hydrogel microbeads. Due to these unique properties of micro-sized hydrogel microbeads, the encapsulated E. coli can maintain viability inside of microbeads and green fluorescent protein (GFP) and red fluorescent protein (RFP) genes are efficiently expressed inside of microbeads after isopropyl- , - D -thiogalactopyranoside induction, suggesting that there is no low-molecular weight substrate transfer limitation inside of microbeads. Furthermore, non-toxic, gentle, and outstanding biocompatibility of microbeads, the encapsulated E. coli can be used in various applications including biotransformation, biosensing, bioremediation, and engineering of artificial cells. Biotechnol. Bioeng. 2010;107:747,751. © 2010 Wiley Periodicals, Inc. [source] A rotating bed system bioreactor enables cultivation of primary osteoblasts on well-characterized sponceram® regarding structural and flow propertiesBIOTECHNOLOGY PROGRESS, Issue 3 2010Kirstin Suck Abstract The development of bone tissue engineering depends on the availability of suitable biomaterials, a well-defined and controlled bioreactor system, and on the use of adequate cells. The biomaterial must fulfill chemical, biological, and mechanical requirements. Besides biocompatibility, the structural and flow characteristics of the biomaterial are of utmost importance for a successful dynamic cultivation of osteoblasts, since fluid percolation within the microstructure must be assured to supply to cells nutrients and waste removal. Therefore, the biomaterial must consist of a three-dimensional structure, exhibit high porosity and present an interconnected porous network. Sponceram®, a ZrO2 based porous ceramic, is characterized in the presented work with regard to its microstructural design. Intrinsic permeability is obtained through a standard Darcy's experiment, while Young's modulus is derived from a two plates stress,strain test in the linear range. Furthermore, the material is applied for the dynamic cultivation of primary osteoblasts in a newly developed rotating bed bioreactor. © 2010 American Institute of Chemical Engineers Biotechnol. Prog., 2010 [source] Control of Fades and Potential on Jurassic Hydrocarbon Accumulation and Prediction of Favorable Targets in the Hinterland Region of the Junggar BasinACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 5 2010CHEN Dongxia Abstract: Exploration practices show that the Jurassic System in the hinterland region of the Junggar Basin has a low degree of exploration but huge potential, however the oil/gas accumulation rule is very complicated, and it is difficult to predict hydrocarbon-bearing properties. The research indicates that the oil and gas is controlled by structure fades belt and sedimentary system distribution macroscopically, and hydrocarbon-bearing properties of sand bodies are controlled by lithofacies and petrophysical facies microscopically. Controlled by ancient and current tectonic frameworks, most of the discovered oil and gas are distributed in the delta front sedimentary system of a palaeo-tectonic belt and an ancient slope belt. Subaqueous branch channels and estuary dams mainly with medium and fine sandstone are the main reservoirs and oil production layers, and sand bodies of high porosity and high permeability have good hydrocarbon-bearing properties; the facies controlling effect shows a reservoir controlling geologic model of relatively high porosity and permeability. The hydrocarbon distribution is also controlled by relatively low potential energy at the high points of local structure macroscopically, while most of the successful wells are distributed at the high points of local structure, and the hydrocarbon-bearing property is good at the place of relatively low potential energy; the hydrocarbon distribution is in close connection with faults, and the reservoirs near the fault in the region of relatively low pressure have good oil and gas shows; the distribution of lithologic reservoirs at the depression slope is controlled by the distribution of sand bodies at positions of relatively high porosity and permeability. The formation of the reservoir of the Jurassic in the Junggar Basin shows characteristics of favorable facies and low-potential coupling control, and among the currently discovered reservoirs and industrial hydrocarbon production wells, more than 90% are developed within the scope of facies-potential index FPI>0.5, while the FPI and oil saturation of the discovered reservoir and unascertained traps have relatively good linear correlation. By establishing the relation model between hydrocarbon-bearing properties of traps and FPI, totally 43 favorable targets are predicted in four main target series of strata and mainly distributed in the Badaowan Formation and the Sangonghe Formation, and the most favorable targets include the north and east of the Shinan Sag, the middle and south of the Mobei Uplift, Cai-35 well area of the Cainan Oilfield, and North-74 well area of the Zhangbei fault-fold zone. [source] The Genetic Mechanism and Model of Deep-Basin Gas Accumulation and Methods for Predicting the Favorable AreasACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 4 2003WANG Tao Abstract, As a kind of abnormal natural gas formed with special mechanism, the deep-basin gas, accumulated in the lower parts of a basin or syncline and trapped by a tight reservoir, has such characteristics as gas-water inversion, abnormal pressure, continuous distribution and tremendous reserves. Being a geological product of the evolution of petroliferous basins by the end of the middle-late stages, the formation of a deep-basin gas accumulation must meet four conditions, i.e., continuous and sufficient gas supply, tight reservoirs in continuous distribution, good sealing caps and stable structures. The areas, where the expansion force of natural gas is smaller than the sum of the capillary force and the hydrostatic pressure within tight reservoirs, are favorable for forming deep-basin gas pools. The range delineated by the above two forces corresponds to that of the deep-basin gas trap. Within the scope of the deep-basin gas trap, the balance relationship between the amounts of ingoing and overflowing gases determines the gas-bearing area of the deep-basin gas pool. The gas volume in regions with high porosity and high permeability is worth exploring under current technical conditions and it is equivalent to the practical resources (about 10%-20% of the deep-basin gas). Based on studies of deep-basin gas formation conditions, the theory of force balance and the equation of material balance, the favorable areas and gas-containing ranges, as well as possible gas-rich regions are preliminarily predicted in the deep-basin gas pools in the Upper Paleozoic He-8 segment of the Ordos basin. [source] Spontaneous Organization of Uniform CeO2 Nanoflowers by 3D Oriented Attachment in Hot Surfactant Solutions Monitored with an In Situ Electrical Conductance TechniqueCHEMISTRY - A EUROPEAN JOURNAL, Issue 11 2008Huan-Ping Zhou Abstract Uniform CeO2 nanoflowers were synthesized by rapid thermolysis of (NH4)2Ce(NO3)6 in oleic acid (OA)/oleylamine (OM), by a unique 3D oriented-attachment mechanism. CeO2 nanoflowers with controlled shape (cubic, four-petaled, and starlike) and tunable size (10,40,nm) were obtained by adjusting the reaction conditions including solvent composition, precursor concentration, reaction temperature, and reaction time. The nanoflower growth mechanism was investigated by in situ electrical conductance measurements, transmission electron microscopy, and UV/Vis spectroscopy. The CeO2 nanoflowers are likely formed in two major steps, that is, initial formation of ceria cluster particles capped with various ligands (e.g., OA, OM, and NO3,) via hydrolysis of (NH4)2Ce(NO3)6 at temperatures in the range 140,220,°C, and subsequent spontaneous organization of the primary particles into nanoflowers by 3D oriented attachment, due to a rapid decrease in surface ligand coverage caused by sudden decomposition of the precursor at temperatures above 220,°C in a strong redox reaction. After calcination at 400,°C for 4,h the 33.8,nm CeO2 nanoflowers have a specific surface area as large as 156,m2,g,1 with high porosity, and they are highly active for conversion of CO to CO2 in the low temperature range of 200,400,°C. The present approach has also been extended to the preparation of other transition metal oxide (CoO, NiO, and CuOx) nanoflowers. [source] | ||||||||||||||||||||||||||||||||||