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Multiphase flow in porous matrix with embedded free-flowing regions has wide application in industry, environment and biological systems. Due to its permo-porosity characteristics, the free-flow regions, represented by fractures and vugs embedded within the porous matrix, make multiphase flow modeling challenging. This study compares different approaches that can be used to describe two-phase flow through vugular porous media. Brinkman equation is used to describe physical phenomena considering both flow through the porous matrix and through free-flow regions. The predictions obtained with Brinkman model are compared with two different Darcy models: heterogeneous and homogeneous. In the heterogeneous Darcy model, the vugular region is characterized as a porous medium with high porosity and permeability. In the homogeneous Darcy model, the complex two-phase flow through the vugular domain is represented by an equivalent absolute permeability and relative permeability curves. The accuracy of the homogenization procedure is evaluated as a function of vug configuration. [ABSTRACT FROM AUTHOR]

During casting, two kinds of porosities are generally found, viz., macroporosity and microporosity. Macroporosity or shrinkage cavity is a major casting defect affecting the yield and quality of the product. The evolution of macroporosity during solidification is governed by complex physics. Apart from the transport of momentum, energy, and species, it is affected by the thermodynamics and kinetics of solidification. It has been an active area of research for quite some time now, despite which, our understanding of macroporosity is far from satisfactory. The possibility of the formation of many patterns of macropores from the same casting system makes the task of analysis difficult. In the present study, a combined numerical and experimental analysis of the evolution of shrinkage cavity in aluminum alloys is carried out. An Al-4.5% Cu alloy slab was solidified under laboratory conditions, and the formation of the shrinkage cavity was observed and quantified. A 3-dimensional full-scale conjugate CFD model of the experimental setup was developed and simulated using a commercial finite-volume-based solver. The model was validated by comparing it with the experimental results. Further, a reduced-order 2D CFD model was developed by applying reasonable assumptions but maintaining the model accuracy as compared to the full-scale 3D model. The 2D model developed in such a way shows a close correspondence with the actual experimental results in terms of depth and shape of shrinkage cavity. The model has a potential to predict shrinkage cavity formation in an industrial setting with low computational efforts. [ABSTRACT FROM AUTHOR]

In the Brazilian Amazon, logging is primarily restricted to the driest months of the year by law. Even so, the dry season in the humid tropics is susceptible to considerable rain events, with rain occurring monthly. Therefore, an experiment was established in unentered Central Amazonian old-growth forest to compare skid trail use in the wet season, when logging operations are not permitted, as well as in the dry season. This was done to investigate the differences in soil compaction for the season closed to logging versus the season open to logging. A randomized complete block design (RCBD) was utilized with three blocks composed of seven sub-blocks each, which contained a control, 1, 3 and 12 tractor cycles in both the wet and dry seasons. A Caterpillar track-type tractor model D6D was used for experimental skid trail establishment. Regardless of season the initial machine cycle caused the greatest increase in soil bulk density (BD) and penetration resistance (PR), as well as the greatest decrease in macroporosity. In fact, the initial dry season cycle caused more severe compaction than the wet season. Nevertheless, after 3 cycles, increases to BD and PR were similar for both seasons, with the end result after 12 cycles nearly identical. To the contrary, macroporosity was substantially reduced in the dry season versus the wet season. Overall, the site impacts were similar in both seasons. Thus, skidding operations could be permissible during the wet season with similar impacts caused in the dry season. [ABSTRACT FROM AUTHOR]

The behavior of primarily isolated human stromal cells including dermal fibroblasts and mesenchymal stem/stromal cells (MSCs) upon interaction with ceramic materials based on tricalcium phosphate (TCP) with different pore sizes is studied. The effect of the emulsifier on the rheological characteristics of photosensitive emulsions based on calcium phosphate is investigated. The dependence of the conditions of preparation of photosensitive emulsions on the pore size in ceramic materials based on Ca3(PO4)2 is demonstrated. Studies of the biocompatibility of macroporous bioceramics upon cultivation of human stromal cells and effect of the samples of the material with different pore sizes on the in vitro transcriptional activity of MSCs are carried out. [ABSTRACT FROM AUTHOR]

This paper reports the mechanical properties of graded macroporous β-Ca3(PO4)2-based ceramic materials produced by stereolithographic 3D printing. We demonstrate the feasibility of using photocurable emulsions for the preparation of ceramic materials with porosity above 80% and controlling the pore size distribution. Graded-porosity ceramic materials with tailored pore size are produced using 3D printing of photocurable tricalcium phosphate-based emulsions. We examine the effect of emulsifier content on the average pore size in ceramic scaffolds with tailored architecture and the effects of porosity, average pore size, and 3D architecture on the strength characteristics of the macroporous ceramic materials. [ABSTRACT FROM AUTHOR]

Iron mining tailings raise several concerns regarding their deposition and the decommissioning of storage dams, particularly regarding the limitations of this substrate for plant establishment, including poor substrate aggregation and limited availability of nutrients. The objective of this study was to evaluate the effect of the interaction of pelleting and fertilization on the physical and chemical conditioning of the root environment for the growth and development of plants in technosol formed by the deposition of iron mining tailings. Three experimental trials were carried out using indicator plants (Urochloa brizantha Hochst. ex A. Rich., Eucalyptus grandis W. Hill ex Maiden, and Phaseolus vulgaris L.), in a randomized block design, and the treatments distributed in a factorial arrangement (5 × 2): five levels of technosol pelleting (0, 25, 50, 75, and 100% m/m), with and without fertilization, with five replications. Fertilization promoted the growth of all plants and demonstrated that the supply of nutrients is fundamental for plant growth in this technosol, mainly by promoting root development, which in turn favored substrate porosity. Pelleting mainly increased the technosol macroporosity in all tests. However, it was only effective in providing better growth conditions and enhancing the supply of nutrients for Eucalyptus grandis. While pelleting improves the physical conditions of the root environment, the availability of nutrients was found to be the main limiting factor for plant growth in the technosol formed by iron mining tailings. With adequate fertilization, the plants had less difficulty developing in this substrate under vase conditions. [ABSTRACT FROM AUTHOR]

The influence of a disperse medium (paraffin oil) on the pore size distribution in Ca3(PO4)2-based ceramic materials designed for bioresorbable implants is studied. The pore size is found to affect the mechanical properties of such materials. The use of photocurable emulsions for the preparation of ceramic materials with a porosity higher than 50% is shown to be promising. The possibility of controlling the pore size distribution is demonstrated. The pore size decreases from 275 to 100 μm as the emulsifier content in the emulsion increases from 0.035 to 0.25 wt %. The uniaxial ultimate compressive strength of the ceramics with a relative density of 52% and an average pore size of 250 μm is 2.87 MPa. [ABSTRACT FROM AUTHOR]

This paper investigates the metallurgical factors that contributed to the failure of several cast U-clamps made of HK40 steel U-clamps during the installation of a pre-startup heater in a petrochemical plant. The presence of extensive macro/micro-shrinkage porosity is identified as the root cause of the failure. The severe shrinkage-related porosity in the material, confirmed by metallographic examination and non-destructive X-ray radiography testing and evidenced by a severe loss in tensile ductility, resulted in a unique fully dendritic fracture surface characteristic. It was found that the loss of structural integrity associated with macro-shrinkage voids and loss of toughness associated with microporosity led to premature failure of U-clamps when subjected to bending forces during installation. The casting process should be designed to guarantee a higher Niyama criterion value, defined as the local thermal gradient divided by the square root of the local cooling rate, in the casting to produce a sound U-clamp. [ABSTRACT FROM AUTHOR]

Based on carbonate-substituted hydroxyapatite (HAP) containing vancomycin, a method is developed for the preparation of macroporous matrices that combine bioresorbability, osteoconductivity, and the possibility for the volumetric impregnation of antibiotics without loss of their activity and their prolonged release. The technology includes treatment with supercritical CO2 as the final stage in the preparation of a matrix, which makes it possible to completely remove the organic solvent that serves as an extractant for the pore formation additive, i.e., polyethylene glycol (PEG) granules, and to increase the biocompatibility of the matrix, as confirmed by the results of histological tests during subcutaneous implantation. The activity of vancomycin after its volumetric incorporation into the calcium phosphate matrix is demonstrated in the regions of inhibiting the growth of bacterial cultures. As proven in in vivo experiments on the implantation of bones, the matrix is a therapeutically effective carrier of antibacterial substances in the treatment of septic purulent inflammations of bone tissues. [ABSTRACT FROM AUTHOR]

The possibility of obtaining highly porous hydrogel composite materials for biomedical applications based on tricalcium phosphate in a polyethylene glycol diacrylate matrix, aimed at repairing bone defects, has been studied. The effect of different content of inorganic filler particles exerted on the mechanical characteristics of highly porous hydrogel composites β-Ca3(PO4)2/polyethylene glycol diacrylate has been studied. It is demonstrated that the preparation of highly porous composite materials with specified elastic properties is quite possible. The viscoelastic properties of the obtained materials are shown to depend on the preset pore size. Varying the tricalcium phosphate fraction in the highly porous hydrogel material makes it possible to control the relative stiffness of the composite. [ABSTRACT FROM AUTHOR]

Al-Fe-Cu base metallic foams were produced without the need of blowing agents or space holders (“In-Situ” route). The porosity formation mechanism and the effect of the icosahedral phase in the Al80Cu17Fe3 and Al58Cu27Fe15 alloy compositions are presented and discussed. These alloys were melted in an induction furnace under an argon atmosphere. Subsequently, the alloys were slowly solidified inside the furnace crucible, i.e., 0.12 °C/s. Several heat treatments were carried out to obtain the highest percentage of porosity and thus to find out the mechanism associated with the porosity formation. To obtain the heat treatment temperatures, a DTA study was performed. The crystallographic phases were identified by means of X-ray diffraction and scanning electron microscopy. The selected temperatures for the heat treatments were 705 °C and 850 °C for the Al79Cu15Fe6 and Al62Cu28Fe10 alloys, respectively. The XRD showed that the Al79Cu15Fe6 alloy was mainly constituted by Al, ω-Al7Cu2Fe, and θ-Al2Cu phases, generating a porosity of 0.54%. The highest percentage of porosity (60%) was obtained for the Al62Cu28Fe10 alloy, heat-treated at 850 °C for 3 h. SEM images showed that the microstructure was mainly constituted of ι-Al6Cu2Fe and β-AlFe phases. Inside the pores, the ι-Al6Cu2Fe phase was also found as clusters of fivefold symmetry quasicrystals. According to the microstructural analysis, it was found that the porosity formation mechanism could be related to a reaction that involves the interaction between the Liquid, λ-Al13Fe4, and ω-Al7Cu2Fe phases resulting in the formation of ι-Al6Cu2Fe phase (ternary peritectic reaction) and a highly porous structure. [ABSTRACT FROM AUTHOR]

The effect of the pore size of macroporous ceramic materials based on β-Ca3(PO4)2 on their biological activity was studied. The formation conditions of macroporous ceramics with a porosity of >50% and a specified pore size were determined. The effect of components of the light-curing emulsion on the pore size in the final macroporous ceramics was studied. The biocompatibility of β-Ca3(PO4)2-based macroporous ceramics was demonstrated in in vitro biomedical assays. The effect of pore size of macroporous ceramic materials on mesenchymal stromal cell proliferation and viability was established. [ABSTRACT FROM AUTHOR]

Background: Fires are a natural occurrence in African savannas yet little is known about how fires affect soil hydrological properties over time. This study aimed to determine the short-term (1–9 months post fire) and long-term (> seven decades fire exclusion) impact of experimental fires on soil hydrology in a fire-prone African savanna. This study also investigated how soil hydrological properties may vary under different vegetation physiognomies.Saturated hydraulic conductivity (K) was determined using a modified falling head method through macropores (KMacro) while unsaturated K was measured using a tension disc infiltrometer (Ψ = 30 mm) to reflect the meso- and micro-pore conductivity (KMeso+Micro). Soil hydrophobicity was measured using the water droplet penetration time (WDPT) test.For the finer soil pores, fires significantly reduce KMeso+Micro in the short-term one month post-burn but returns to Pre-burn KMeso+Micro rates nine months later. After decades of fire suppression, KMacro is significantly faster compared to burned soils while KMeso+Micro was significantly slower through smaller pores compared to soils burned annually. KMeso+Micro is slowest under shrubs in fire suppression plots compared to other vegetation physiognomies. Fires did not induce hydrophobicity in the short-term nor the long-term.Whilst fire reduces KMeso+Micro in the short-term, soils recovered nine months later, indicating that prescribed burning does not lead to lasting detrimental impacts on soil hydrological properties. Interestingly, decades of active fire suppression had either a positive or negative effect on the soil’s ability to allow water to infiltrate through the soil surface depending on the pore size and possible susceptibility to bioclogging and biocrusts.Methods: Fires are a natural occurrence in African savannas yet little is known about how fires affect soil hydrological properties over time. This study aimed to determine the short-term (1–9 months post fire) and long-term (> seven decades fire exclusion) impact of experimental fires on soil hydrology in a fire-prone African savanna. This study also investigated how soil hydrological properties may vary under different vegetation physiognomies.Saturated hydraulic conductivity (K) was determined using a modified falling head method through macropores (KMacro) while unsaturated K was measured using a tension disc infiltrometer (Ψ = 30 mm) to reflect the meso- and micro-pore conductivity (KMeso+Micro). Soil hydrophobicity was measured using the water droplet penetration time (WDPT) test.For the finer soil pores, fires significantly reduce KMeso+Micro in the short-term one month post-burn but returns to Pre-burn KMeso+Micro rates nine months later. After decades of fire suppression, KMacro is significantly faster compared to burned soils while KMeso+Micro was significantly slower through smaller pores compared to soils burned annually. KMeso+Micro is slowest under shrubs in fire suppression plots compared to other vegetation physiognomies. Fires did not induce hydrophobicity in the short-term nor the long-term.Whilst fire reduces KMeso+Micro in the short-term, soils recovered nine months later, indicating that prescribed burning does not lead to lasting detrimental impacts on soil hydrological properties. Interestingly, decades of active fire suppression had either a positive or negative effect on the soil’s ability to allow water to infiltrate through the soil surface depending on the pore size and possible susceptibility to bioclogging and biocrusts.Results: Fires are a natural occurrence in African savannas yet little is known about how fires affect soil hydrological properties over time. This study aimed to determine the short-term (1–9 months post fire) and long-term (> seven decades fire exclusion) impact of experimental fires on soil hydrology in a fire-prone African savanna. This study also investigated how soil hydrological properties may vary under different vegetation physiognomies.Saturated hydraulic conductivity (K) was determined using a modified falling head method through macropores (KMacro) while unsaturated K was measured using a tension disc infiltrometer (Ψ = 30 mm) to reflect the meso- and micro-pore conductivity (KMeso+Micro). Soil hydrophobicity was measured using the water droplet penetration time (WDPT) test.For the finer soil pores, fires significantly reduce KMeso+Micro in the short-term one month post-burn but returns to Pre-burn KMeso+Micro rates nine months later. After decades of fire suppression, KMacro is significantly faster compared to burned soils while KMeso+Micro was significantly slower through smaller pores compared to soils burned annually. KMeso+Micro is slowest under shrubs in fire suppression plots compared to other vegetation physiognomies. Fires did not induce hydrophobicity in the short-term nor the long-term.Whilst fire reduces KMeso+Micro in the short-term, soils recovered nine months later, indicating that prescribed burning does not lead to lasting detrimental impacts on soil hydrological properties. Interestingly, decades of active fire suppression had either a positive or negative effect on the soil’s ability to allow water to infiltrate through the soil surface depending on the pore size and possible susceptibility to bioclogging and biocrusts.Conclusion: Fires are a natural occurrence in African savannas yet little is known about how fires affect soil hydrological properties over time. This study aimed to determine the short-term (1–9 months post fire) and long-term (> seven decades fire exclusion) impact of experimental fires on soil hydrology in a fire-prone African savanna. This study also investigated how soil hydrological properties may vary under different vegetation physiognomies.Saturated hydraulic conductivity (K) was determined using a modified falling head method through macropores (KMacro) while unsaturated K was measured using a tension disc infiltrometer (Ψ = 30 mm) to reflect the meso- and micro-pore conductivity (KMeso+Micro). Soil hydrophobicity was measured using the water droplet penetration time (WDPT) test.For the finer soil pores, fires significantly reduce KMeso+Micro in the short-term one month post-burn but returns to Pre-burn KMeso+Micro rates nine months later. After decades of fire suppression, KMacro is significantly faster compared to burned soils while KMeso+Micro was significantly slower through smaller pores compared to soils burned annually. KMeso+Micro is slowest under shrubs in fire suppression plots compared to other vegetation physiognomies. Fires did not induce hydrophobicity in the short-term nor the long-term.Whilst fire reduces KMeso+Micro in the short-term, soils recovered nine months later, indicating that prescribed burning does not lead to lasting detrimental impacts on soil hydrological properties. Interestingly, decades of active fire suppression had either a positive or negative effect on the soil’s ability to allow water to infiltrate through the soil surface depending on the pore size and possible susceptibility to bioclogging and biocrusts. [ABSTRACT FROM AUTHOR]

The problem of producing biodegradable implants based on calcium phosphate porous ceramics is being solved. Highly porous ceramics with a uniform distribution of pores of a specified size is fabricated by slip casting from a suspension containing tricalcium phosphate Ca3(PO4)2 and polymeric granules 50–100 μm in size in amounts of 20 and 50 vol %, respectively, followed by heat treatment. For the chosen sintering parameters, the porosity of the ceramics is not lower than 40% and its tensile strength and biocompatibility satisfy the corrsponding requirements. [ABSTRACT FROM AUTHOR]

This study presents a new route for the synthesis of carbon gels with a structure that includes aligned fibers of the same material. A modification of the heating process during polymerization of resorcinol and formaldehyde produces a combination of the classical polymeric nodules in carbon gels with arrays of totally aligned fibers. This new morphology, produced through a very simple process, opens up new application possibilities to the already numerous existing ones for carbon gels. Highlights: Combination of polymeric nodules and aligned fibers are produced by one-pot sol-gel process. Formation of fiber arrays is favoured at late polymerization point under acid catalysis. The fiber arrays lead to materials with very good combination of porosity and surface area. [ABSTRACT FROM AUTHOR]

We have developed a method for the preparation of macroporous carbonate hydroxyapatite-based matrices with the use of the technology of self-setting cements for surgical osteology. Macroporosity of osteoconductive calcium phosphate matrices was produced by adding paraffin granules to a dry cement mixture, followed by organic solvent extraction of the granules from matrices hydrated in an aqueous solution. In vivo tests of the resultant materials demonstrated high biocompatibility with pronounced angiogenesis, which was achieved via additional treatment with supercritical carbon dioxide. [ABSTRACT FROM AUTHOR]

Alternating degradation and restoration phases of soil quality, as is common in crop-fallow systems, can be avoided if the restorative elements of trees and forests can be integrated into productive agroforestry systems. However, evidence for the hypothesis of 'internal restoration' in agroforestry is patchy and the effectiveness may depend on local context. We investigated to what extent cocoa (Theobroma cacao, L.) agroforestry can recover soil structure and infiltration in comparison to monoculture systems across the Konaweha Watershed, Southeast Sulawesi. We compared soil organic carbon, fine root length and weight, soil aggregate stability, macroporosity and infiltration from three soil layers at five land use systems: i.e. degraded forests, 9–14 years old of complex-cocoa agroforestry, simple-cocoa agroforestry, monoculture cocoa and 1–4 years old annual food crops, all with three replications. In general, roots were concentrated in the upper 40 cm of soil depth, contained of 70% and 86% of total fine root length and weight. Compared to simple agroforestry and cocoa monoculture, complex agroforestry had greater root length and weight in the topsoil, even though it attained only half the values found in degraded forests. Higher root density was positively correlated to soil organic carbon. In upper soil layers, complex agroforestry had slightly higher soil aggregate stability compared to other agricultural systems. However, no significant difference was found in deeper layers. Complex agroforestry had higher soil macroporosity than other agricultural systems, but not sufficient to mimic forests. Degraded forests had two times faster steady-state soil infiltration than agricultural systems tested (13.2 cm h−1 and 6 cm h−1, respectively), relevant during peak rainfall events. Compared to other agricultural systems, complex agroforestry improves soil structure of degraded soil resulting from forest conversion. However, a considerable gap remains with forest soil conditions. [ABSTRACT FROM AUTHOR]

Purpose: Grassland exclosure is a widely-used option to prevent from grazing in degraded grasslands for restoration. However, the influence of exclosure on soil macropore of grassland remain scarce. The objective of this study was to quantify the pore architecture of grassland soils under exclosure.Materials and methods: Two treatments, 9E (grassland enclosed for 9 years) and 5E (grassland enclosed for 5 years), were designed, with grazing as a control in the experiment. Nine soil columns (0–50 cm deep) were taken at the three sites with three replicates. At each site, three soil columns were from the grassland, and cores were scanned with a Philips Brilliance ICT Medical Scanner. Numbers of macropores, macroporosity, network density, length density, and node density within the 50-cm soil profile were interpreted from X-ray computed tomography to analyze soil pore architecture.Results and discussion: The results indicated that exclosure significantly influenced CT-measured soil macroporosity in the Inner Mongolia grassland of northern China. Soils under enclosed grassland had greater macroporosity, length density, total volume, and node density than that of under freely grazed grassland. Macroporosity increased as the enclosure age increased. For soils under enclosed grassland, macropores were concentrated at 0–300-mm soil layers, and macropores were mainly present at 0–100-mm soil depth under freely grazed grassland. The large number of macropores found in soil under enclosed grassland can be attributed to greater root development.Conclusions: Exclosure increases soil macroporosity and improve soil structure. [ABSTRACT FROM AUTHOR]

Influence of more than 20 years (1988-2010) of reduced tillage (RT) practices on water and pesticide balances and dynamics is analyzed and compared to results from a conventional tillage plot (CT). The field study soils are described as silty clay stagnic luvisol, developed on a low permeable schist layer. A drainage network was set up according to French criteria (0.9 m deep, 10 m space) to avoid soil winter waterlogging. Climate is temperate oceanic and drainage generally occurs from November to March. Data were analyzed at yearly, weekly (pesticides) and hourly (water) time steps. Over the long term, cumulated drainage decreases significantly on RT (3999 mm) compared to CT (5100 mm). This differentiation becomes significant from 1999, 10 years after plowing was stopped. Strikingly, hourly drainage peak flows are higher under RT, especially during the second period (2000-2010), associated with low or no base flow. These results suggest a strong influence of the macropore network under RT practice. In particular, drainage peaks are higher at the beginning of the drainage season (mid-October to December). Consistently, pesticides applied in late autumn, which are the most quantified on this site, are often significantly more exported under RT. For atrazine, applied in spring, fluxes are linked to cumulative flow and are de facto higher under CT. For others pesticides, losses appear to be heterogeneous, with generally low or null export rates for spring application. Generally speaking, higher concentrations are measured on RT plot and explain observed exportation rate differences. Finally, there is no clear evidence of correlation between pesticide losses and long-term impacts of RT on hydrodynamics, pointing the importance of studying the short-term effect of tillage on water and especially solute flow. [ABSTRACT FROM AUTHOR]

Information on the root system of fully mature apricot ( Prunus armeniaca L.) orchards is scarce. This paper deals with the root system of apricot trees in a semi-arid region of Romania. The 15-year old orchard was established with Hungarian Best variety grafted on Constanta 14 generative rootstock. Sprinkler irrigation was applied under a mild water stress regime. The purpose of this paper was to: (1) test the hypothesis that the roots of trees planted within a certain layout occupy the whole soil space, (2) describe the spatial distribution of root density using the trench technique, and (3) emphasize the rootedness of apricot in this soil type. Soil samples were taken from both in row (IR) and inter-row (ITR) positions to determine soil properties. Some physical properties were deteriorated in ITR versus IR, mainly due to soil compaction induced by the technological traffic. The root density was almost similar in ITR and IR, decreasing with both soil depth and distance from the tree trunk, and stronger correlations were obtained with soil depth. The roots of apricot trees are mainly concentrated within 0.5 m depth and occupy the entire soil space between trees, showing the highest density at about 1 m from the tree trunk. No root avoidance for neighboring trees was found. The horizontal decrease in root density can be used in optimizing tree arrangement in orchards. Canopy shape, light penetration and groundcover management system are also important in this decision. The results could be used in countries with similar environments. [ABSTRACT FROM AUTHOR]

We prepared a macro-mesoporous NiMo/alumina catalyst by the introduction of macroporosity to an alumina support, and tested its catalytic performance in the hydrocracking of vacuum residue for the first time. In this reaction, the use of the macro-mesoporous NiMo/alumina catalyst clearly led to a more desirable product distribution-a higher liquid yield and lower gas yield-than a mesoporous NiMo/alumina catalyst. This indicates that the macro-mesoporous catalyst structure facilitated hydrogenation relative to the mesoporous catalyst; for the latter, hydrocracking was relatively dominant. N adsorption/desorption experiments confirmed that NiMo impregnation reduced the pore size and volume, as well as the surface area, implying that the NiMo phases were located inside the mesopores and macropores. Macroporosity in the alumina support played an important role in improving the accessibility of vacuum residue to the NiMo active sites located inside pores, which are responsible for hydrogenation. By promoting hydrogenation, the macro-mesoporous NiMo/alumina catalyst increased the liquid yield of the hydrocracking of vacuum residue. [ABSTRACT FROM AUTHOR]

Decatungstate WO was efficiently intercalated between the layers of three-dimensionally ordered macroporous MgAl-layered double hydroxide. The structural and textural properties of as-prepared intercalated compound were characterized using different solid-state characterization techniques such as X-ray powder diffraction, FTIR and Raman spectroscopies and electronic microscopy. The photocatalytic properties of immobilized WO within MgAl structure were investigated using 2-(1-naphthyl) acetamide (NAD) as a model of pesticide. The influence of different parameters such as amount of catalyst, pH and oxygen concentration were investigated. An optimal NAD degradation was obtained for a photocatalyst concentration of 60 mg l. Under our experimental conditions, this heterogeneous photocatalyst induces photodegradation of 60 % of NAD after 17 h of irradiation at 365 nm and at pH 6.6. Interestingly, pesticide photodegradation leads to the mineralization of substrates to HO and CO and the photocatalyst can be recycled and reused without any loss of activity over four cycles. [ABSTRACT FROM AUTHOR]

Manufacturing a hybrid bone substitute requires a dynamic culture of the cells preliminarily seeded in a scaffold through a flow of physiological fluid. The velocity, pressure, and the distribution of fluid flow in this kind of macroporous medium are the important keys. Because of the difficulties in determining these parameters by experiment, a numerical approach has been chosen. One of the primary step of this study consists in the determination of permeability K. In this article, two types of structure of macroporous bioceramics are concerned. One is the interconnected pore spheres arranged either simple cubic, body-centered cubic or face-centered cubic systems. The other is the interconnected pore spheres randomly arranged. Based on Darcy's law, the permeability K was calculated for many cases (type, porosity) by simulating the fluid flow through a small representative volume. These results are compared with some previous models such as Ergun, Carman-Kozeny, Rumpf-Gupte, and Du Plessis. The limits of Darcy's law and the above-mentioned models have been determined using numerical simulation. The result showed that the porous media with spherical interconnected pores of BCC systems can be used to replace a complex random system in a range of porosity from 0.71 to 0.76 (i.e., porosity of our scaffolds). This assumption is validated for a pressure gradient lower the 1,000 Pa m and a simple polynomial relation linking permeability and porosity (0.71-0.76) has been established. [ABSTRACT FROM AUTHOR]

groforestry and grass buffers have been proposed for improving water quality in watersheds. Soil porosity can be significantly influenced by buffer vegetation which affects water transport and water quality. The objective of the study was to compare differences in computed tomography (CT)-measured macroporosity (>1,000-μm diam.) and coarse mesoporosity (200- to 1,000-μm diam.) parameters for agroforestry and grass buffer systems associated with rotationally grazed and continuously grazed pasture systems. Soils at the site were Menfro silt loam (fine-silty, mixed, superactive, mesic Typic Hapludalf). Six replicate intact soil cores, 76.2 mm diam. by 76.2 mm long, were collected using a core sampler from the four treatments at five soil depths (0–50 cm at 10-cm intervals). Images were acquired using a hospital CT scanner and subsequently soil bulk density and saturated hydraulic conductivity ( K) were measured after scanning the cores. Image-J software was used to analyze five equally spaced images from each core. Bulk density was 5.9% higher and saturated hydraulic conductivity ( K) values were five times lower for pasture treatments relative to buffer treatments. For the 0–10 cm soil depth, CT-measured soil macroporosity (>1,000 μm diam.) was 13 times higher for the buffer treatments compared to the pasture treatments. Buffer treatments had greater macroporosity (0.020 m m) compared to pasture (0.0045 m m) treatments. CT-measured pore parameters were positively correlated with K. The project illustrates benefits of agroforestry and grass buffers for maintaining soil porosity critical for soil water and nutrient transport. [ABSTRACT FROM AUTHOR]

The paper presents results of a field experiment designed to investigate the potential use of forage legume Stylosanthes hamata (stylo) to ameliorate the structure of a compact layer in sandy soils of Northeast Thailand. Sandy and acidic soils that are common to Northeast Thailand have restricted agronomic potential due to inherent chemical and physical properties. A compact layer at 20–40 cm reduces root elongation for most crops, thereby restricting the quantity of nutrients and water available for the plant growth. Deep ploughing and subsoiling are costly and have not been shown to be effective in overcoming compaction since these soils are unstable and collapse after the first heavy rainfall event. A three-year study was conducted in order to evaluate the effect of continuous stylo on the porosity of the compact layer and its influence on root elongation and yield of a subsequent maize crop. Continuous stylo was grown for two years in experimental plots and compared to a currently used stylo-maize rotation. Root distribution and macropore density were measured under the two cropping systems. After 24 months of continuous stylo, roots were able to penetrate the compact layer, resulting in a significant improvement in the macroporosity of this layer. The subsequent maize crop developed a deeper and more extensive root system using macropores created after 24 months of continuous stylo when compared to the stylo-maize rotation treatment. This study demonstrates the potential role of Stylosanthes hamata in structural amelioration of sandy compact layers. [ABSTRACT FROM AUTHOR]

This paper reviews recent advances in analytical and numerical solution of problems of water flow through rigid soils in the unsaturated zone. The Richards model remains the most widely accepted and fertile framework for water flow analyses. More general formulations are reserved for the analysis of problems involving macroporosity, thermal effects, and air pressure effects. Many exact and approximate solutions have been derived for particular boundary value problems of homogeneous soils using methods such as quasi-linear analysis, Green-Ampt analysis, perturbation, and the kinematic wave approximation. Numerical simulators have become bigger and more accurate due to improvements in the areas of nonlinear solution procedures, mass conservation, computational efficiency, and computer hardware. Problems of natural heterogeneity have been addressed primarily through application of various stochastic methods to the Richards model. The stochastic formulations generally refute the concept of simple 'equivalent' homogeneous properties, but do themselves offer a certain limited potential for a predictive capability. [ABSTRACT FROM AUTHOR]

The potential of Pontoscolex corethrurus to repair the physical degradation of a compacted Oxisol was studied. The Oxisol from Kingaroy, Queensland, Australia was uniformly packed to four treatments of different bulk densities (0.95, 1.15, 1.25, 1.35 Mg m–3) in pots of 0.24 m diameter and 0.22 m deep. Each pot was inoculated with 12 earthworms (equivalent to 300 m–2) and maintained close to field capacity water content for 3 months, after which selected soil physical (dry bulk density, penetration resistance, water infiltration), worm activity (cast production, worm weight) measurements and image analysis were carried out. Results showed that worm numbers were maintained at the initial levels in all the treatments except in the 1.35 Mg m–3 treatment, where there was a 33% decrease. The weight of surface casts per surviving worm was the greatest in the 1.35 Mg m–3 treatment compared to the lower density treatments. Final soil density was lessened in all treatments to a depth of 0.2 m. Surface cast production was positively correlated with the percentage reduction in bulk density. The greatest percentage reduction in bulk density was in the 1.35 Mg m–3 treatment and was equivalent to a doubling of soil aeration (to 18.4%). Penetration resistance to the 0.2-m layer was also reduced and values were less than 2 MPa. Slumping of the surface soil was evident in both the lowest and the highest bulk densities resulting in low rates of water infiltration. Image analysis supported the soil physical properties showing an abundance of both fine pores and worm channels in the three lowest bulk densities, and lesser activity (concentrated in the immediate soil surface) in the 1.35 Mg m–3 treatment. [ABSTRACT FROM AUTHOR]