Academic literature on the topic 'Clay peds'

To study role of gypsum and corn cobs in linkage of fractions in cracking soils. Three soils (Al-Diwaniya , Al-Wihda and college of Agriculture / Abu Ghraib) were chosen for this study . They were treated with two levels of gypsum (0.5 and 1) % with one level (4%) of corncobs . In this experiment , 2 kg of each studied soil were treated with same levels of corn cobs and gypsum above and incubated at 30 + 2 °C for 90 days and 80% relative moisture content at 33 kpa. And then the soils were sieved with 1 mm sieve to measured the x-ray diffractions . The results showed : The intensity of clay minerals peaks which treated with gypsum and corn cobs were decreased comparing with control sample. We believed that the gypsum should be facculated on clay minerals surfaces and mask them to appear clearly , and suggested that the gypsum was played an important role in conjugated of soil particles. Results of X-ray diffractions showed that there was no evidence of interaction between organic matter (corn cobs) and clay mineral inter layers.

Detailed soil profile descriptions were made to assess the residual effect of compaction and tillage treatments applied 10 yr ago on a Ste-Rosalie clay. The treatments applied consisted of five passes at a contact pressure of 61.8 kPa with no tillage, 15 passes of 61.8 kPa with chiselling, moldboard plowing, no tillage, subsoiling, and a control. The results were analyzed using nonparametric statistics. The untilled plots that received 15 wheel passes showed mottling that was more abundant and closer to the surface than the other plots while the subsoiled plots had a finer, less abundant and deeper mottling than the other plots. Peds in the Ae horizon were finer in the subsoiled and chiselled plots and coarser in the untilled plots and conventionally tilled plots that received 15 vehicle passes. It appears from this work that the effect of compaction is very persistent in clay soil and that subsoiling followed by reduced traffic can have a long-term effect on soil structure. Key words: Compaction, tillage, profile descriptions, clay soil

Subcutaneous fat necrosis of the newborn is an uncommon disorder that occurs during the first few weeks of life as firm subcutaneous nodules on the cheeks, buttocks, back, arms, and thighs. This disorder, which initially was described by Harrison and McNee in 1926,1 typically affects full-term newborns who have experienced perinatal distress. Subcutaneous fat necrosis of the newborn usually resolves over a period of months, but may result in death due to its association with hypercalcemia. The association between subcutaneous fat necrosis of the newborn and hypercalcemia was first reported by Clay in 19562; however, the mechanism that results in hypercalcemia remains incompletely understood.3-7

The paper focuses on the hydromechanical behaviour of an unsaturated compacted clayey silt, accounting for fabric changes induced by drying–wetting cycles occurring at low stress levels. The response along isotropic compression and triaxial compression (shear) at constant water content was investigated by laboratory tests on both as-compacted and dried–wetted samples. Compaction induces a microstructural porosity pertinent to clay peds and a macrostructural porosity external to the peds. Drying–wetting cycles decrease the microporosity and increase the macroporosity, which reduces the water retention capacity, increases the compressibility, and promotes higher peak strengths with more brittle behaviour during triaxial compression. A coupled double-porosity elastic–plastic model was formulated to simulate the experimental results. A nonassociated flow rule was defined for the macrostructure, modifying a stress–dilatancy relationship for saturated granular soils to account for the increase in dilatancy with suction observed in the experiments. The average skeleton stress and suction were adopted as stress variables. As correctly predicted by the model, the shear strength at critical state is not significantly influenced by the degree of saturation or by the hydraulic history. On the contrary, the higher peak strength, brittleness, and dilatancy of the dried–wetted samples are mostly explained by their reduced water-retention capacity.

It has been demonstrated that the high bulk densities of clayey subsoils of Sodosols can result from a process involving shrink/swell cycles and the development of ped coatings containing topsoil material. Our objective was to study this process according to land use and to compute the amount of organic carbon introduced into the subsoil as a consequence of ped coating in the subsoil. In an area located east of Katanning, we carried out an intensive soil survey and selected 2 closely adjacent sites with similar soils but differing in their land use: a cultivated soil and a never cultivated soil in an undisturbed strip of land. Pit faces and horizontal planes of the top of the subsoil were studied. The polygonal network corresponding to the cross-section of the prismatic peds was described. The clay content and bulk density of the prisms was determined. The carbon contents of the coatings and of the sandy material rich in organic carbon that corresponded to remnants of native vegetation was measured. Results showed that the coating process has occurred under native vegetation but is more active when the land has been used for agricultural and pastoral activities, as indicated by thicker sandy-clay coatings on the vertical faces of prisms and the higher bulk densities in the subsoil. The mean bulk density was 1.71 g/cm3 at 20-25 cm depth at the undisturbed site and was 1.86 and 1.82 g/cm3 at 20-25 and 25-30 cm depth, respectively, at the cultivated site. The total soil organic carbon stock was estimated to be close to 68.9 and 61.0 Mg/ha at the undisturbed and cultivated sites, respectively. The organic carbon stock in the subsoil was 38.5 and 23.3% of the respective total stocks. One fourth of the carbon stock in the subsoil corresponded to materials rich in organic carbon that originated from roots of native vegetation. The organic carbon stock in the ped coatings was <1% of the total stock at the 2 sites. Finally, our results support the adoption of zero-till agricultural system for the soil studied to restrict subsoil densification.

In this work, the polymeric electrolyte composites (PECs) based on poly(ethylene oxide) (PEO), ethylene carbonate (EC) as a plasticizer, and lithium montmorillonite (Li-MMT) clay were fabricated, and investigated for understanding the effects of Li-MMT/EC in the polymer matrix on the ionic conductivity. For a lithium battery application, the native sodium cations in MMT were exchanged for lithium cations. As a result, the lithium ion was intercalated into the layer of the MMT clay, and thus PEO entered the galleries of MMT clay. The ionic conductivity was enhanced with increasing MMT contents due to the immobile MMT clay serving as the anion species and the decreased crystallinity of PEO.

The proper delineation of site-specific management zones is very important in the agricultural land management of potentially degraded areas. There is a necessity for the development of prospective tools in management plans to correctly understand the land degradation processes. In order to accomplish this, we present a pedo-geomorphological approach using soil texture, land elevation and flow vector aspects to distinguish different management zones and to discretize soil micronutrients. To achieve this goal, we conducted the study in the Neyshabur plain, Northeast Iran. For data collection, grid sampling (500 × 500 m) was used with 70 specific points. Soil samples were collected in triplicates from various sites as composite samples (0–30 cm) to analyse clay, Zn, Mn, Cu and Fe. Using the altitude information (obtained with GPS at each sampling point), flow vectors were also modelled for all selected points. Based on the values of altitude, flow vectors and clay, management zones were delimited using geographic information systems. The best data organization was obtained from the combination of clay + elevation + flow vector attributes, generating two different management zones. In this circumstance, the lowest fuzzy performance index (FPI) and modified partition entropy (MPE) values were generated. It can be observed that the management zone 1 (MZ1) is located in the areas with a lower elevation and higher content of clay. On the other hand, the MZ2 was characterized by areas with a higher elevation and lower clay content. This study concluded that the design of management zones, using pedo-geomorphological information could reduce the time and cost of sampling necessary to assess potentially degraded areas of land.

Abstract Orchid gynostemium, the fused organ of the androecium and gynoecium, and ovule development are unique developmental processes. Two DROOPING LEAF/CRABS CLAW (DL/CRC) genes, PeDL1 and PeDL2, were identified from the Phalaenopsis orchid genome and functionally characterized. Phylogenetic analysis indicated that the most recent common ancestor of orchids contained the duplicated DL/CRC-like genes. Temporal and spatial expression analysis indicated that PeDL genes are specifically expressed in the gynostemium and at the early stages of ovule development. Both PeDLs could partially complement an Arabidopsis crc-1 mutant. Virus-induced gene silencing (VIGS) of PeDL1 and PeDL2 affected the number of protuberant ovule initials differentiated from the placenta. Transient overexpression of PeDL1 in Phalaenopsis orchids caused abnormal development of ovule and stigmatic cavity of gynostemium. PeDL1, but not PeDL2, could form a heterodimer with Phalaenopsis equestris CINCINNATA 8 (PeCIN8). Paralogous retention and subsequent divergence of the gene sequences of PeDL1 and PeDL2 in P. equestris might result in the differentiation of function and protein behaviors. These results reveal that the ancestral duplicated DL/CRC-like genes play important roles in orchid reproductive organ innovation.

Under field conditions in the Amazon forest, soil bulk density is difficult to measure. Rigorous methodological criteria must be applied to obtain reliable inventories of C stocks and soil nutrients, making this process expensive and sometimes unfeasible. This study aimed to generate models to estimate soil bulk density based on parameters that can be easily and reliably measured in the field and that are available in many soil-related inventories. Stepwise regression models to predict bulk density were developed using data on soil C content, clay content and pH in water from 140 permanent plots in terra firme (upland) forests near Manaus, Amazonas State, Brazil. The model results were interpreted according to the coefficient of determination (R2) and Akaike information criterion (AIC) and were validated with a dataset consisting of 125 plots different from those used to generate the models. The model with best performance in estimating soil bulk density under the conditions of this study included clay content and pH in water as independent variables and had R2 = 0.73 and AIC = -250.29. The performance of this model for predicting soil density was compared with that of models from the literature. The results showed that the locally calibrated equation was the most accurate for estimating soil bulk density for upland forests in the Manaus region.

Abstract Given the increasing exploitation of clay in Morocco for ceramic industry and for the purpose of the benefit reuse of this resource, a study is conducted in order to carry out the identification and characterization of Miocene clay after doping with pozzolan. The objective of this work is to improve the physicalchemical characteristics of Miocene clay of Fez region, by doping it pozzolan at different contents: 5, 10, 15 and 20%. Physical and chemical characterization of this clay was carried out before and after doping with pozzolan following various analytical technics, such as the X- ray fluorescence and geotechnical investigation. The result of geochemical analysis showed a higher rate of aluminum oxide (Al2O3), iron oxide (Fe2O3) and titanium oxide (TiO2). Further characterization of Atterberg limits have shown that the plasticity of doped materials increases. Similarly the mechanical behaviour of marls doped with pozzolan have significantly improved, providing a mechanical strength of obtained materials up to 670N when firing at 1000 °C, compared to the raw marls.

Sandy soils have low water and nutrient holding capacity which limit crop growth. In the short-term, these constraints can be overcome by increased fertiliser application or irrigation. However, long-term solutions are needed to improve farm productivity and sustainability. Clay added to sandy soils may be such a solution. Compared to sandy soils, clay soils have smaller pores and higher cation exchange capacity and therefore greater water and nutrient holding capacity. Clay can also bind organic matter via cation bridges and thereby reduce its accessibility to decomposing microbes. In sandy soils with clay subsoil, the clay can be mixed into the sandy top soil by delving or spading. However, the clay subsoil is not uniformly distributed in the sandy top soil. It forms clay peds of varying size which creates a highly non-uniform soil environment with patches of sandy soil with clay peds next to sandy soil with little or no clay. The clay-rich patches can hold more water and nutrients compared to the surrounding sandy soil that could influence nutrient availability and organic C binding. Little is known about the influence of ped size and rate of clay added to sandy soil on nutrient availability and organic C binding after residue addition. The aims of the study were i) to determine the effect of clay addition rate and ped size in residue amended sandy soil on soil respiration, nutrient availability and organic C retention ii) to assess the effect of clay soil particle size and clay soil properties on nutrient availability and organic C binding after addition of residues with low or high C/N ratio iii) to determine the effect of clay addition rate and ped size on nutrient leaching after mineral fertilizer addition. A series of incubation experiments were carried out to assess the effect of clay addition rate and ped size on nutrient availability and organic C retention on < 53 μm fraction after mixing with low and high C/N ratio residue. In the first study, clay peds of 1, 2 or 3 mm size derived from a clay-rich Vertosol (73% clay) were added to a sandy soil (3% clay) at clay addition rates of 10% and 20% w/w. After addition of ground mature faba bean residue (C/N 37) at 10 g kg-1, the soils were incubated for 45 days at 80% of water holding capacity. Clay addition to sandy soil influenced nutrient availability after plant residue addition, particularly when small peds are added at higher rates. Sandy soil with clay peds had a greater maximum NH4 and P sorption capacity than sandy soil alone, sorption capacity was higher at 20% compared to 10% clay addition and greater with 1 mm than 3 mm peds. Retrieval of clay peds at the end of the experiment showed ped breakdown during the experiment but also formation of larger peds. Compared to the < 53 μm fraction added at the start of the experiment, total organic carbon (TOC) content of the < 53 μm fraction was up to two-fold higher, particularly in the smaller peds (1 and 2 mm). The study confirmed that claying can increase organic C sequestration, but also showed that organic C sequestration is likely to be greatest when the added clay peds are small. The capacity to bind organic C and nutrients may depend on clay soil properties such as mineralogy, clay concentration and exchangeable Fe and Al. A 45-day experiment was carried out to investigate the effect of clay type on nutrient availability and organic carbon retention with residues differing in C/N ratio (20 or 47). Two clay soils with smectite as a dominant mineral were used. They differed in smectite percentage [high (40%) or low (5-10%)], clay content (73 or 42%) and exchangeable Fe and Al concentration (low or high). The clay soils were added to sandy soil at rate of 20% w/w either finely ground or as 2 mm peds. Over 45 days, available N and P, microbial biomass N and P concentrations and cumulative respiration were greater with low C/N than high C/N residue. With low C/N residue, compared to sandy soil alone clay addition increased available N concentration and initial microbial biomass C and N, but decreased cumulative respiration and P availability. This study showed that addition of clay soil to sandy soil influences nutrient availability, but there were no clear differences between clay soils or sizes. The lack of differences between high and low smectite clay soil suggests that a high concentration of Fe and Al oxides can compensate for a lower clay concentration and proportion of smectite with respect to binding of organic matter and nutrients. In the previous studies, we found that clay addition had no consistent effect on cumulative respiration and ped size effect was variable. Secondly, low C/N ratio residue had stronger effect on nutrient availability due to its high decomposition rate and nutrient release compared to high C/N ratio residue. The third experiment was conducted to investigate that if clay addition has a different effect on respiration and nutrient availability when added as peds with a greater range of sizes (1, 3 and 5 mm) in presence of plant residue with lower C/N ratio. The aims of this experiment were to (i) determine the effect of clay addition rate and ped size in residue amended sandy soil on nutrient availability, and (ii) assess breakdown of peds during the experiment and organic C retention by the < 53 μm fraction of the peds. Clay soil addition to sandy soil amended with plant residue reduced respiration rate and available P concentration. Ped size had little effect on respiration and nutrient availability. Clay soil addition increased soil organic carbon retention compared to sandy soil alone. With respect to ped size, the experiment showed substantial ped breakdown and but also formation of larger peds over 45 days. The first three experiments were conducted over 45 days. But longer term studies are needed to better evaluate the effect of claying in the field. To investigate the effect of repeated addition of residue (finely ground wheat mature shoots added every 2 months) in clay amended sandy soil, a longer term (8 months) study was conducted with clay soil added as finely ground soil, 1 and 3 mm peds. The organic C content of the whole soil increased during the experiment with a greater increase in clay amended soils. The organic C content of the > 53 μm fraction was very low and changed little over time. With finely ground clay soil and 1 mm peds, the organic C content of the < 53 μm fraction increased mainly in the first 2 months while in 3 mm peds it increased over 6 months to reach similar concentrations as with finely ground clay soil and 1 mm peds. Excessive use of fertilizer in sandy soils can cause leaching of nutrient elements N and P into water ways and cause eutrophication. In the fifth experiment, clay soil was added in sandy soil at 10% or 20% clay soil w/w finely ground or as 2 and 5 mm peds with and without N and P fertiliser (27 mg N kg-1 and 7 mg P kg-1). The clay sand mixture (30 g) was placed in cores with nylon mesh at the bottom. The soils were incubated at 80% water holding capacity and leachate was collected weekly for 50 days. Clay addition significantly reduced leaching of N and P as compared to sandy soil alone. In sandy soil alone, the highest N (68%) leaching occurred after the first week whereas the highest amount (41%) of P was leached after two weeks. It can be concluded that clay addition to sandy soil can reduce the risk of nutrient leaching and enhance carbon sequestration in sandy soils by decreasing C loss via respiration and leaching. This effect will be greatest with finely ground clay soil or small peds.
Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food & Wine, 2017

碩士
國立中興大學
材料工程學研究所
93
Polymer substrate has considered to be used in the flat panel display, where the demand for remote information access is driving the development of rugged, flexible, lightweight, power efficient displays. However, there are some technological difficulties for the realization of a display on polymer substrate, such as lower thermal stability and higher oxygen and water molecules permeation. Polyethersulfone（PES） is an amorphous polymer containing excellent thermostability and transparency, high glass transition temperature, lower birefringence and outstanding chemical resistance which is considered to be a candidate for polymer substrate used in the flat panel display. In this research we have successfully been prepared PES/clay nanocomposites through the mixing of PES with organically-modified clay in solution to reduce the water/oxygen permeation. The addition of clay into PES increase the physical and mechanical properties of PES, and the water and oxygen permeation can be reduced by 29% and 24%. Further surface treatment by plasma and multi-layer organic/inorganic barrier layer has also been developed. The inorganic material SiO2 prepared by sol-gel process with various diameters, such as 30 nm, 40 nm and 45 nm, can be coated on the surface of PES/clay nanocomposites. The water and oxygen permeation of nanocomposites can further reduce by 29% and 49%.

This chapter discusses the role of the skull in forming the face and in identifying individuality, particularly in reconstructing ancient faces that bear semblance to the dead. Skulls serve as the armature of the face, where tissue, muscles and the skin are attached to form a distinct face. Whereas a surgeon removes layers of skin and tissue to reveal the skull, a medical artist builds each muscle in the skull by using well-established statistics for the flesh thickness and adds layers of clay for the skin. In general, the reconstruction of the face involves the use of a plaster cast replica of the skull. In such replicas, pegs are inserted to the cast to mark the thickness of the skull. In the whole process of face reconstruction, the skull, the medical and the pathological evidence provided by the skull and the post cranial skeleton dictate the formation of the face. In instances when the skull is absent or inaccessible, portraits found on the coffins are vital for reconstruction. While face reconstruction may seem simple, the process of reconstructing faces is a difficult task. Reconstruction of the face requires painstaking work, and knowledge of pathology, anatomy, dentistry and much more to build a case for history. Nevertheless, the painstaking work of face reconstruction is important in the field of forensics and in medical applications. Some of the cases of face reconstruction described in this chapter include the face reconstruction of Phillip II of Macedon, the face reconstruction of the Great Harwood case, the recreation of the faces of the Grave Gamma and the Seianti.

Shale-caprock integrity is critical in ensuring that subsurface injection and storage of anthropogenic carbon dioxide (CO2) is permanent. The interaction of clay-rich rock with aqueous CO2 under dynamic conditions requires characterization at the nano-scale due to the low-reactivity of clay minerals. Geochemical mineral-fluid interaction can impact properties of shale rocks primarily through changes in pore geometry/connectivity. Several simulation results had predicted that influx-triggered mineral dissolution/precipitation reactions within clay-rich rock can continuously diminish micro-fracture networks, while pressure and effective-stress evolution initially increase then gradually constrict them. However, most of these studies have not investigated changes under experimental conditions and applying experimental techniques capable of detecting changes at nano-scale, which are ultimately representing pathways for molecular diffusion of fluids through porous media. The experimental work reported in this paper applied specific analytical techniques in investigating changes in surface/near-surface properties of crushed shale rocks after exposure (by flooding) to CO2-brine for a time frame ranging between 30 days to 92 days at elevated pressure and fractional flow rate. Initial capillary entry parameters for the shale were estimated from digitally acquired pressure data evolution. Flooding of the shale samples with CO2-brine was followed by Nano-scale measurement of changes in internal specific surface area, pore volume and linear/cumulative pore size distribution. The BET Technique showed that changes in the shale caprock occurred due to geochemical interaction with aqueous CO2 will impact petrophysical properties of the rock. The intrinsically low permeability in shale may be altered by changes in surface properties as the effective permeability of any porous medium is largely a function of its global pore geometry. Diffusive transport of CO2 as well as carbon accounting could be significantly affected over the long term. The estimation of dimensionless quantities such as Peclet (Pe) and Peclet-Damkohler (PeDa) Numbers that are associated with geochemical reactivity of rocks and acidic fluid transport through porous media gave insight into the impact of diffusion and reaction rate on shale caprock.

The evolution of the engineered barrier system (EBS) of geological repositories for radioactive waste has been the subject of many research programmes during the last decade. The emphasis of the research activities was on the elaboration of a detailed understanding of the complex thermo-hydro-mechanical-chemical processes, which are expected to evolve in the early post closure period in the near field. It is important to understand the coupled THM-C processes and their evolution occurring in the EBS during the early post-closure phase so it can be confirmed that the safety functions will be fulfilled. Especially, it needs to be ensured that interactions during the resaturation phase (heat pulse, gas generation, non-uniform water uptake from the host rock) do not affect the performance of the EBS in terms of its safety-relevant parameters (e.g. swelling pressure, hydraulic conductivity, diffusivity). The 7th Framework PEBS project (Long Term Performance of Engineered Barrier Systems) aims at providing in depth process understanding for constraining the conceptual and parametric uncertainties in the context of long-term safety assessment. As part of the PEBS project a series of laboratory and URL experiments are envisaged to describe the EBS behaviour after repository closure when resaturation is taking place. In this paper the very early post-closure period is targeted when the EBS is subjected to high temperatures and unsaturated conditions with a low but increasing moisture content. So far the detailed thermo-hydraulic behaviour of a bentonite EBS in a clay host rock has not been evaluated at a large scale in response to temperatures of up to 140°C at the canister surface, produced by HLW (and spent fuel), as anticipated in some of the designs considered. Furthermore, earlier THM experiments have shown that upscaling of thermal conductivity and its dependency on water content and/or humidity from the laboratory scale to a field scale needs further attention. This early post-closure thermal behaviour will be elucidated by the HE-E experiment, a 1:2 scale heating experiment setup at the Mont Terri rock laboratory, that started in June 2011. It will characterise in detail the thermal conductivity at a large scale in both pure bentonite as well as a bentonite-sand mixture, and in the Opalinus Clay host rock. The HE-E experiment is especially designed as a model validation experiment at the large scale and a modelling programme was launched in parallel to the different experimental steps. Scoping calculations were run to help the experimental design and prediction exercises taking the final design into account are foreseen. Calibration and prediction/validation will follow making use of the obtained THM dataset. This benchmarking of THM process models and codes should enhance confidence in the predictive capability of the recently developed numerical tools. It is the ultimate aim to be able to extrapolate the key parameters that might influence the fulfilment of the safety functions defined for the long term steady state.