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Copyright of Journal of Railway Science & Engineering is the property of Journal of Railway Science & Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of New Building Materials / Xinxing Jianzhu Cailiao is the property of New Building Materials Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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Guilin is a famous karst area, and currently the view that the disintegration of red clay will cause soil cave collapse is increasingly recognized. In order to study the influence of the coupling effect of moisture content and void ratio on the disintegration of red clay, different moisture contents and void ratios of Guilin red clay were placed on a self-made disintegration apparatus to record the real-time disintegration amount and observe the disintegration phenomenon. Images of the structural characteristics of soil were obtained by a scanning electron microscope (SEM). Additionally, nuclear magnetic resonance (NMR) was applied to analyze the distribution of water in both natural and saturated states. The results show that the disintegration rate of red clay decreases as the initial moisture content increases, but increases with the increase of void ratio. Both moisture content and void ratio affect the structural characteristics of red clay. When the moisture content remains constant, the soil changes from a three-peak to a two-peak structure as the void ratio increases. The total area and secondary peak area of the T2 spectrum increase, while the starting T2 value of the main peak shifts to the right and the area decreases. Meanwhile, the starting T2 value of the secondary peak shifts to the right and the area increases. When the void ratio remains constant, the starting T2 value of the main peak gradually shifts to the left and the area decreases as the moisture content increases. However, the starting T2 value of the secondary peak shifts to the right and the area decreases or first decreases and then increases. The disintegration rate does not exhibit a significant relationship with either pore volume or macropore volume. The combined water saturation shows a bilinear relationship with both the moisture content and void ratio, where it increases as the initial moisture content increases, but decreases as the void ratio increases, with a correlation coefficient of 0.9929. The disintegration rate has an exponential relationship with the combined water saturation, and it decreases as the combined water saturation increases, with a correlation coefficient of 0.9934.

Under the background of climate warming in the Qinghai-Tibetan Plateau (QTP), frequent freeze–thaw cycling (FTC) brings about great geological disasters such as subgrade failure, landslides, and mudslides, which is closely related to the strength reduction caused by the structural damage of soils. In this study, to explore the association between macro shear strength and microstructure evolution of soils subjected to FTC, the red clay distributed widely in the QTP was chosen and used to conduct a series of triaxial shear and nuclear magnetic resonance (NMR) tests in the range of 1 to 7 FTCs. Triaxial shear test results reveal that the shear strength reduction of specimens mainly occurs within five FTCs, and the trend of peak deviator stress with increasing FTCs can be described in three stages: rapid descent (FTCs less than three), slow descent (FTCs between three and five), and stabilization (FTCs greater than five). NMR tests show that the T2 spectrum curves exhibit a distinct bimodal distribution characteristic, corresponding to macropores and micropores. Part of the micropores gradually develop into macropores with increasing FTCs, especially within five FTCs. The increase in macropores proportion leads to a loose soil structure, which is consistent with the deterioration of the shear strength of specimens. Finally, based on the experimental results and classical Mohr–Coulomb theory, a new shear strength model with structural damage for red clay has been proposed by introducing a damage factor expressed by T2 spectral area.

Constructing a microstructure of red clay is an important part of studying the physical and mechanical properties of red clay. The study of red clay microstructure is generalized. The red clay matrix and pores are regarded as two types of randomly moving particles, and the microstructure model of three-dimensional red clay random porous media is established from the Langevin equation of the phase separation process in stochastic dynamics, using the separation and aggregation of the two particles. The model controls the evolution process of the porous medium by artificially controlling the particle placement. Here, the trends of porosity, average pore length, Euler’s number, and the fractal dimension of the porous medium during the evolution process under different parameter conditions (smooth length Δ and rise and fall term η) are calculated, and a feasible method for surviving the microstructure of red clay is summarized. Due to the consideration of the interaction forces between the solid- and void-phase particles, the porous media generated by this model are more similar to the real porous media in nature, with connected and unconnected pore structures and tortuous pore channels. Finally, the red clay of Bijie, Guizhou, is modeled as an example to prove the feasibility of the method.

In this paper, mixtures with different proportions of lime, phosphogypsum, and red clay were prepared, and the road properties and micromechanisms of lime–phosphogypsum-stabilized red clay were investigated by unconfined compressive strength test, water stability test, swelling test, shrinkage test, XRD quantitative analysis, and scanning electron microscope analysis. The results showed that the unconfined compressive strength of the mix increased and then decreased with the increase of phosphogypsum content. With the increase of age, the growth was faster in the first 14 days and basically stabilized in the last 14 days. The mixture has poor water stability, large absolute swelling rate, and low linear shrinkage. The reason for the increase of strength is that the reaction of lime, phosphogypsum, and red clay produces ettringite, and the cementing substance gels form a three-dimensional mesh skeleton structure; the excess of ettringite will cause the skeleton to expand and break, and the strength decreases. [ABSTRACT FROM AUTHOR]

Red clay is susceptible to cracking in desiccating environments, with resulting crisscrossing cracks that compromise the soil structure and increase the likelihood of geological hazards. To investigate the dynamic mechanism of the initiation and propagation of soil desiccation cracks under natural hygrothermal conditions, a desiccation test was conducted on a red clay slurry using three-dimensional digital image correlation (3D DIC) technology. The evolution behaviour of desiccation cracks was analysed, and the dynamic relationships between moisture content, displacement field, strain field, and soil desiccation cracking were explored. The test results showed that the Atterberg limits of red clay are correlated with desiccation cracking. Cracks tend to initiate in areas where tensile strain is concentrated or significant displacement differences exist. Following crack initiation, the surrounding strain and displacement fields redistribute, influencing the propagation direction, development rate, and morphology of subsequent cracks nearby. Additionally, the relative displacement and strain at the edges of cracks are related to the crack propagation direction. Earlier crack initiation usually corresponds to a larger relative displacement and strain at the crack edges, while the displacement and strain at the soil clod centre are typically smaller than those at the crack edges. DIC technology can quickly and accurately obtain dynamic information about displacement and strain fields, providing feasible technical support for analysing the dynamic mechanism behind soil desiccation cracking. It has potential value in engineering hazard prevention and sustainable development. [ABSTRACT FROM AUTHOR]

Acyclovir (ACV) is a promising candidate for drug repurposing because of its potential to provide an effective treatment for viral infections and non-viral diseases, such as cancer, for which limited treatment options exist. However, its poor physicochemical properties limit its application. This study aimed to formulate and evaluate an ACV-loaded red clay nanodrug delivery system exhibiting an effective cytotoxicity. The study focused on the preparation of a complex between ACV and red clay (RC) using sucrose stearate (SS) (nanocomplex F1) as an immediate-release drug-delivery system for melanoma treatment. The synthesized nanocomplex, which had nanosized dimensions, a negative zeta potential and the drug release of approximately 85% after 3 h, was found to be promising. Characterization techniques, including FT-IR, XRD and DSC-TGA, confirmed the effective encapsulation of ACV within the nanocomplex and its stability due to intercalation. Cytotoxicity experiments conducted on melanoma cancer cell lines SK-MEL-3 revealed that the ACV release from the nanocomplex formulation F1 effectively inhibited the growth of melanoma cancer cells, with an IC50 of 25 ± 0.09 µg/mL. Additionally, ACV demonstrated a significant cytotoxicity at approximately 20 µg/mL in the melanoma cancer cell line, indicating its potential repurposing for skin cancer treatment. Based on these findings, it can be suggested that the RC-SS complex could be an effective drug delivery carrier for localized cancer therapy. Furthermore, the results of an in silico study suggested the addition of chitosan to the formulation for a more effective drug delivery. Energy and interaction analyses using various modules in a material studio demonstrated the high stability of the composite comprising red clay, sucrose stearate, chitosan and ACV. Thus, it could be concluded that the utilization of the red clay-based drug delivery system is a promising strategy to improve the effectiveness of targeted cancer therapy. [ABSTRACT FROM AUTHOR]

In this study, we investigated the impact of micro- and nano-sized barium oxide addition on the radiation-shielding properties of red clay tiles mixed with waste marble and different sizes of BaO (micro- or nanoparticles) for comparative analysis. The linear attenuation coefficients (LAC) of the prepared samples were measured using an HPGe detector between 0.060 and 1.333 MeV. Moreover, a comparison was made between the experimental micro-composites and values obtained by Phy-X software. The results revealed that the red clay/waste marble tile composites doped with nano-sized BaO demonstrated superior radiation-shielding properties compared to those doped with micro-sized BaO. At 1.33 MeV, WR-20mBaO (containing 20 wt % micro-sized BaO) and WR-20nBaO (containing 20 wt % nano-sized BaO) exhibited HVL values of 4.75 cm and 4.25 cm, respectively. The lower HVL value of WR-20nBaO indicates superior radiation-shielding performance, highlighting the potential benefits of using nano-sized BaO as a radiation-shielding additive. Our findings also demonstrated that increasing the amount of BaO deposited onto red clay mixed-waste marble resulted in improved radiation-shielding properties. Our study demonstrates that adjusting the concentration of BaO is a viable strategy for enhancing the radiation attenuation properties of red clay tiles. In addition, the addition of waste marble to the tiles enhances its mechanical properties, and it is also positively recycled in community service. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Central South University is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to study the improvement effect of cement-basalt fiber on the dynamic properties of red clay in Kunming area, based on the existing laboratory experiments, the unmodified red clay and the modified red clay with 12% cement and 0. 5% basalt fiber were respectively tested. Indoor dynamic triaxial tests were carried out under certain confining pressure and loading frequency, and the effects of confining pressure, frequency and wet-dry cycle on dynamic deformation properties and dynamic strength properties were emphatically analyzed. The test results show that the dynamic characteristics of the red clay before and after the improvement are different. The dynamic stress amplitude and dynamic strain amplitude before the improvement conform to the hyperbolic model, while the dynamic deformation of the improved red clay shows linear elasticity as a whole, which is in line with the linear regression model and the Logistic regression model. The maximum dynamic elastic modulus of the improved red clay increases significantly, the damping ratio decreases significantly, the dynamic failure mode changes, and the dynamic strength increases significantly. The influence of confining pressure, frequency, and dry wet cycles on the dynamic characteristics of the improved red clay was analyzed, and the relevant parameters were proposed. [ABSTRACT FROM AUTHOR]

In order to study the disintegration characteristics of red clay under different moisture content and temperature, red clay taken from Guilin was prepared into samples with different moisture content, and the disintegration test of red clay was carried out by self-made test equipment. Considering the influence of water absorption and weight gain in red clay, a parallel water absorption test was carried out for each disintegration test, and the disintegration amount–time relationship curve was corrected with the results of the water absorption test so as to propose a new disintegration amount calculation formula. In this experiment, the disintegration characteristics of red clay under different moisture content and temperature were investigated. The experimental results show that the disintegration amount decreases with the increase in moisture content, the moisture content exceeds 25%, and the red clay basically does not disintegrate within 2 h. The amount of disintegration increases with increasing temperature, but the disintegration of red clay in natural environments is not sensitive to temperature. The comprehensive analysis of moisture content and temperature shows that in the natural climate range, moisture content is the main influencing factor of soil disintegration. [ABSTRACT FROM AUTHOR]

In the construction of artificial freezing methods, the strength and deformation characteristics of frozen soil are crucial to the stability of frozen walls. To investigate the effect of different water contents on the strength and creep of the soil under freezing action after specimen preparation, the specimen was kept in an incubator for 24 hours, and the influence of moisture content on the strength and creep characteristics of Jiangxi red clay was studied by freezing triaxial tests at -10℃. The results show that the compressive strength of frozen red clay first increases and then decreases with increasing water content in the range of 16%-32%. In the range of 16%-28% water content, the cohesion increases and the internal friction angle decreases with increasing water content.The creep curves under confining pressures of 0.2 MPa and 0.5 MPa show that the red clay with a low water content only has a decay creep stage and stable creep.The results can be used as a reference for the artificial freezing method in the construction of subway tunnels in the red clay stratum in Jiangxi Province.

Because of the particularity and complexity of Jinan spring area, the quaternary sedimentary layer is mainly composed of clay and silty clay, which has the characteristics of a strong permeability. In the construction of excavation, a series of problems such as the precipitation abnormal difficulties and the serious structural water seepage would occur. In order to reveal the causes of the strong permeability of Jinan red clay, a study from the perspective of micropore structure of Jinan red clay was conducted. First, the basic physical properties of the undisturbed red clay were tested, and the micro particle arrangement of the red clay was obtained by the scanning electron microscope (SEM). Then, a soil seepage device based on computed tomography (CT) was developed. The three-dimensional pore structure and the water flow visualization of the red clay in different seepage stages were obtained through CT scanning. Finally, a pore network model (PNM) was established to quantitatively analyze the number and the volume proportion of the pores and throats in the soil during the seepage process. The results show that the overlapping of particles in the horizontal section of Jinan red clay is more loose, and the pore structure is mainly developed vertically, with the existence of large connected channels. Water flows preferentially along the existing connected pore channel of the red clay, which leads to the expansion of the seepage channel. The connected channel with a large pore diameter is the main factor affecting the permeability of the soil.

Today, industrial and sanitation wastewater production and their penetration into water resources have caused numerous challenges. Moreover, limitations on water resources used in industry, agriculture, drinking water, and wastewater have led human societies to make optimal use of available resources and treat the polluted water. This study investigated the effect of the acid and alkaline activation methods on dye adsorption by red clay. Each activated soil was used to remove methylene blue paint by adsorption method to determine the activated soil with the highest efficiency. The influential factors on adsorption, including the effects of solution pH (5-11), dye concentration (100-100 mg/L), and the amount of adsorbent (0.3-0.2 g) in adsorption of methylene blue dye, were examined on the optimal adsorbent, and the optimal conditions were investigated and determined. Then, X-Ray diffraction, measurement of porosity and effective surfaces, and Fourier transform infrared analysis were used to study the physical, chemical, and morphological properties. The results of chemical analysis showed that the soil activated with 3 M acid has the highest adsorption capacity among other activation methods. According to the detection analyses, the surface area of the clay increased after the acid activation operation due to some of the bonds in the structure of the clay breaking (results of Fourier transform infrared) and the opening of the plates (scanning electron microscope images). These factors increased the uptake of activated soil significantly (27 to 81%) compared to raw soil. The adsorption behavior of the adsorbent showed that the adsorption isotherm is consistent with the Langmuir equation model. The results of the reusability study showed that the adsorbent is reusable. Results also showed that the modified soil is an effective adsorbent to remove methylene blue from aqueous solutions.

Red clay slopes are easy to produce cracks under cyclic drying and wetting, and the development of cracks will adversely affect the hydraulic properties and strength of the soil, thus reducing the slope stability. Taking Changsha red clay as the research object, red clay specimens with different numbers of cracks were prepared, and then permeability tests, soil water retention tests and direct shear tests were performed. The evolution of saturated permeability coefficient, soil water characteristic curve, and shear strength parameters of red clay with the crack number and dry density were revealed, and the corresponding mathematical expressions were established. The results show that the order of magnitude of the soil permeability coefficient is 10-5 ~ 10-7 m/ s. The saturated permeability coefficient drops with an increase in dry density and grows exponentially with an increase in crack number. When the crack number increases by 5, the saturated permeability coefficient increases by 66. 4 times. The specimen with a lower dry density or a larger crack number has a higher saturated volumetric water content, and the volumetric water content drops faster with the matric suction in the drying process. As a result, the residual water content is lower, and the water retention capacity is worse. The shear strength parameters of red clay are directly proportional to dry density and inversely proportional to crack number. Particularly, when the dry density increases by 0. 28 g / cm³, the cohesion and internal friction angle increase by 2. 35 times and 0. 94 times, respectively. When the crack number increases by 5, the cohesion and internal friction angle decrease by 57. 09% and 49. 59%, respectively. [ABSTRACT FROM AUTHOR]

Due to the peculiarity of the spring domain strata in Jinan, the phenomenon of serious water seepage appears in the process of excavation. The macro permeability of soil is closely correlated with its microstructure. In this study, using the X-ray micro-tomography (micro-CT) system and a self-designed soil seepage device, the internal pore structure of Jinan red clay and the water flow inside the sample under different seepage stages were observed. The microstructure of water phase and air phase in the sample was segmented by the watershed algorithm. Calculation and comparison of pore and throat size distributions and coordination number (CN) at different seepage stages were conducted by establishing pore network model (PNM). Meanwhile, the seepage experiment simulations were conducted based on the 3D pore structure of red clay. The results show that the preferentially flow of Jinan red clay is obvious due to the existence of the vertically developed macropore channel. The fine particles (mainly silt particles) are washed away during seepage, thereby expanding the pore channels. The maximum pore radius and pore connectivity have important influence on seepage characteristics of Jinan red clay, but the correlation between porosity is small. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Architecture & Civil Engineering is the property of Chang'an Daxue Zazhishe and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The effects of basalt fiber incorporation on the mechanical properties of red clay soils were investigated. Through the direct shear test, unconfined compressive strength test, and microstructure test, the shear strength curves and stress–strain curves of basalt fiber-modified red clay soils were obtained under different basalt fiber incorporation rates and different soil dry density conditions. The results showed that: (1) the shear strength and compressive strength of the soil were significantly increased after the incorporation of basalt fiber; (2) the strength increase was greatest at 0.3% of basalt fiber incorporation, which was the optimum incorporation level; (3) the damage form of the soil changed, and the red clay soil incorporated with basalt fiber changed from brittle damage to ductile damage; and (4) the microscopic electron microscope pictures showed that, at the appropriate amount of fiber incorporation conditions, the fiber bond with the soil particles and form a fiber‒soil column. When subjected to external forces, the discrete fiber‒soil columns interact with each other to form an approximate three-dimensional fiber‒soil network, which acts to restrain the displacement and deformation of the soil particles, which is the main reason for the improved mechanical properties of the improved soil. The experimental research on the improvement of red clay soil with basalt fiber can provide a theoretical basis for engineering practice and help provide an environmentally friendly and efficient method of road base treatment in engineering. [ABSTRACT FROM AUTHOR]

Red clay with features of high liquid (plastic) limit, low permeability, medium-low compressibility and high strength is widely used in anti-seepage projects including roadbed, earth dam, tailings and landfill cover. This study investigates the hydraulic conductivity and propagation of desiccation cracks of compacted red clay in Dalian, China, considering the effect of freeze-thaw (F-T) cycles and saline intrusion. A series of compacted specimens were subjected to different F-T cycles at various controlled salt concentration of 0.2% and 4%. The surface cracking initiation and propagation process of compacted specimens under wetting-drying (W-D) cycles were monitored by Digital Image Correlation technique. The results indicated that permeability coefficient of compacted specimens increased significantly after the first F-T cycle regardless of specimens with variable dry density and salt concentration. The relationship between the number of F-D cycles and permeability coefficient can be expressed as the exponential function for Dalin red clay. Dry density and Saline inhibits the desiccation cracks of compacted specimens under W-D cycles. However, the F-T cycles have a modest promoting effect on crack propagation on the surface of saturated red clay. This study analyzes the underlying formation mechanisms of desiccation cracking-inducing geohazards and provides some guidance for the long-term performance of infrastructures upon saline intrusion and F-T cycles for red clay. [ABSTRACT FROM AUTHOR]

Thermal conductivity is an important parameter in the study of temperature field. Based on the evolution of acid-base mutual loss between lime and red clay over time, the influence of water content, dry density and age on thermal conductivity of limemodified red clay was studied by using transient hot-wire thermal conductivity instrument, and the empirical model and back propagation( BP) neural network prediction model were established. The results show that the thermal conductivity of lime-modified red clay increases exponentially with the increase of water content and linearly with the increase of dry density. In the range of 15% ~ 27% moisture content, its thermal conductivity increases by 53. 87% on average. In the dry density range of 1. 25 ~1. 65 g/ cm3, the thermal conductivity increases by 87. 06% on average. The thermal conductivity of improved soil decreases exponentially with the increase of age, and the decreasing rate gradually decreases and finally tends to be stable. Within 90 days of age, the thermal conductivity decreases by 16. 6% on average. Empirical analysis shows that the overall errors of the two models are less than 10%. The thermal conductivity of lime modified red clay can be well described with the change of influence factors. The law and model can provide reference for lime improvement of the same soil samples. [ABSTRACT FROM AUTHOR]

The southern island of the Philippines is abundant in silicate minerals, including the province of Lanao del Norte. However, some of these resources in the region are untapped for use as raw materials in the production of various ceramic products for industrial, pharmaceutical, and nanotechnology applications. These could include tiles, sanitary ware, dinnerware, insulating bricks, porcelain, membranes and coatings. Some of the explored minerals are the red clay in the municipality of Linamon, diatomaceous earth in Kapatagan and black cinder in Salvador. It is the aim of this study that these minerals are evaluated in terms of their physical and chemical properties so that these will be used for optimum application. The properties that were determined were their specific gravities, raw and fired surface colors, Atterberg limits, particle size distribution, thermal properties, morphologies and mineralogical compositions. Pellets were formed for each raw material and fired at two temperature levels 1000 °C and 1200 °C to evaluate their physical properties. Linamon red clay has a 38.88% cumulative passing size of 150 µm, and the black cinder of Salvador and diatomaceous earth of Kapatagan have cumulative passing sizes of 96.53% and 60.12% at 150-micron sieve, respectively. The common mineral contents of the three samples are montmorillonite, quartz and andesine. Black cinder fired at 1200 °C has the darkest shade of red with a greasy quasi-submetallic luster. It attained the highest fusion coverage on the platform among the three materials, which makes it a potential supplement or replacement for feldspar in clay-based triaxial materials for ceramic production. The diatomaceous earth has the potential to be a secondary clay content source and a good source of flux for a certain temperature range. Both the red clay and diatomaceous earth were classified as plastic materials that are suitable for brick production, and the red clay is also feasible for pottery production. These are a few of the features of the clay minerals in the region that present suitable properties for application as raw materials in the production of ceramic tiles and hollow ceramic products. [ABSTRACT FROM AUTHOR]

Copyright of Bulletin of the Chinese Ceramic Society is the property of Bulletin of the Chinese Ceramic Society Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Bleaching of red clay is carried out by reacting iron-containing clay with the system of two reducing agents Na2S2O4, and NaBH4, in an acidic environment. The treatment process is performed with the help of ultrasonic equipment, as well as mixing operations performed at high temperature. Several physical-chemical methods such as XRF, XRD, and FTIR were used to evaluate clay samples before and after treatment. The results showed effective iron-removal in red clay. Comparison of whiteness between the processed sample and the original sample is performed by measuring parameters in the CIE L*a*b* color-system. The analysis shows that the whiteness of the treated sample reached 78.72%, showing that the treated clay has clearly improved its whiteness, and can be applied in making high-end ceramic products that require the clay with high whiteness.

To investigate the influencing factors and mechanisms of shear strength of red clay with a high liquid limit, which was selected at different milepost locations based on the Nanning Bobai Nabu Section Project of the Nanning Zhanjiang Expressway, the basic physical properties of red clay were determined using a liquid plastic limit test, compaction test, inductively coupled plasma optical emission spectrometer (ICP-OES), and X-ray fully automatic diffractometer (XRD). Red clay with a high liquid limit was selected. Furthermore, the direct shear test was used to study the effect of different water contents and compaction degrees on the shear strength. The experimental results demonstrate that under the same compaction degree, the shear stress of the soil sample increases significantly with an increase in normal stress, and the greater the water content, the smaller the shear stress of the soil sample. At 200 kPa, the shear strength of soil samples with 24% water content is 57%, 46%, and 35% of the shear strength of soil samples with 15% water content under different compaction degrees(K) of 86%, 90%, and 93%, respectively. Under the same moisture content, the shear stress of the soil sample shows an increasing trend with an increase in the degree of compaction, and the greater the compaction degrees, the greater the shear stress of the soil sample. The cohesion c and internal friction angle φ of soil samples increase with an increase in the compaction degree, but the increase in cohesion c is also affected by the water content. Under the condition of low water content, the cohesion c of soil samples can be increased by 1.06 times when the water content is 15% and by 0.47 times when the water content is 18%. Under the condition of high water content, the cohesion c of soil samples with 21% water content only increases by 0.3 times, and that with 24% water content only increases by 0.35 times.

In order to explore the creep characteristics of red clay under different pressures, the stress–strain curve and stress–strain–time curve of red clay under different pressures were obtained, and the triaxial shear and creep characteristics of red clay under different pressures were analysed. A triaxial shear test and creep test were carried out on red clay from Guilin as the research object under different pressures. The results show that: ➀ the cohesion and the angle of internal friction of red clay from Guilin, obtained from a triaxial shear test, are 57.20 kPa and 22.47°, respectively; ➁ according to the physical meaning of the parameters of the Burgers creep model, a simple and practical parameter inversion method is proposed, which can be used to obtain the parameters of the Burgers model for red clay under different perimeter pressures and differing deviatoric stress; and ➂ when comparing the calculation results with the test results, the correlation coefficients R2 of the two are above 0.9, with a good fitting effect, so the model can accurately describe the creep characteristics of red clay from Guilin. This study can provide a theoretical basis and technical support for engineering construction in the red clay area of Guilin.

Abstract The red clay is widely distributed in Guizhou province, which is characterized by high natural moisture content, difficult compaction and serious shrinkage and crackingin, and phosphogypsum is discharged for 5 million tons every year in Guizhou province. For the sake of effectively reducing the accumulation of phosphogypsum, mixtures were prepared with cement as a curing agent and mass ratios of cement to phosphogypsum of 1:1, 1:2 and 1:3 (low content phosphogypsum group) and phosphogypsum to red clay of 1:1, 1:2 and 1:3 (high content phosphogypsum group). Unconfined compressive strength, expansion, shrinkage and dynamic characteristic tests were conducted to analyze the behavior and mechanical properties of the mixtures. The modification mechanism of the mixtures by phosphogypsum was further explored by XRD (X-ray diffraction) and SEM (scanning electron microscopy). which provided a theoretical basis for the application of phosphogypsum in highway engineering and improved the engineering properties of red clay. The results show that the unconfined compressive strength of the phosphogypsum stabilized soil in the low content phosphogypsum group is greater than that in the high content phosphogypsum group. When cement:phosphogypsum = 1:2.2–1:3, the unconfined compressive strength of the mixture is maximum. When cement:phosphogypsum = 1:3, the maximum dynamic shear modulus of phosphogypsum stabilized soil is the largest. The absolute expansion rate and linear shrinkage rate of phosphogypsum stabilized soil in the low content phosphogypsum group are greater than those in the high content phosphogypsum group. When cement: phosphogypsum = 1:1–1:3, the absolute expansion rate is 6.5–12.3%, and the linear shrinkage rate is 1.3–2%. When red clay:Phosphogypsum = 1:1–1:3, the absolute expansion rate is 0.2–4%, and the linear shrinkage rate is 1–1.5%. The more phosphogypsum content, the smaller the expansion deformation and shrinkage deformation of the mixture. It is suggested that mass ratios of phosphogypsum to red clay is 1:1, and the cement content is 5%. Which can not only make full use of phosphogypsum solid waste, but also improve the engineering properties of red clay. Article Highlights The unconfined compressive strength of the phosphogypsum stabilized soil in the low content phosphogypsum group is greater than that in the high content phosphogypsum group. The absolute expansion rate and linear shrinkage rate of phosphogypsum stabilized soil in the low content phosphogypsum group are greater than those in the high content phosphogypsum group. The strength of phosphogypsum stabilized soil is derived from the comprehensive effect of cement and phosphogypsum. Due to the increment of the phosphogypsum and the decline of proportion of red clay, leading to the decrease in the content of hydrophilic minerals, the expansion deformation and shrinkage deformation characteristics are changed. Considering strength and deformation characteristics, it is recommended that mixtures with 5% cement content, and phosphogypsum to red clay of 1:1 as subgrade filler, which can not only make full use of phosphogypsum solid waste, but also improve the engineering properties of red clay.

The bearing capacity of the phyllite soil subgrade can be greatly improved by red clay, but the water stability of the modified soil is still poor. Hence, the blended soil has been found to be unsuitable for the construction of high-speed railways. This paper proposes an innovative scheme, by adding appropriate amounts of cement and red clay concurrently, to improve phyllite soil, which achieves a higher bearing capacity of the subgrade immediately after compaction, while also solving the problem of insufficient water stability. Laboratory tests of the permeability and disintegration characteristics of phyllite soils improved by cement, red clay, and both were carried out. The test results show that the permeability coefficient and maximum disintegration rate of soil can be improved effectively by using both red clay and cement. It was found that the optimal combination scheme is to add 3% cement and 40% red clay to phyllite soil by mass. Under the optimal scheme, the permeability coefficient, maximum disintegration rate, and disintegration rate of the improved soil decreased by 90.02%, 90.30%, and 99.02%, respectively, compared with the phyllite soil. The microscopic study shows that the mechanism of red clay blending with phyllite is that the finer particles of red clay infill the pores among the phyllite particles, thus reducing its permeability coefficient. The mechanism of adding cement to the blending soil mainly results from the production of hard-setting new materials and the formation of a cementation network among the soil particles, which not only increases the shear strength of the soil, but also reduces the permeability coefficient and the maximum disintegration ratio of the soil. This work makes full use of the complementary characteristics of red clay and phyllite soil and the advantages of hard-setting new materials, which will provide a new idea for soil improvement of the phyllite soil in the future. [ABSTRACT FROM AUTHOR]

The colour of soil is one of its most striking features, and records the palaeoenvironment conditions when the soil is formed; however, the controlling factors and palaeoclimatic significance of colour reflectance in the Late Tertiary red clay are poorly understood. In this study, the Jiaxian section, on the northern edge of the Chinese Loess Plateau, was selected to explore the aforementioned issue using colour reflectance, diffuse reflectance spectroscopy (DRS), geochemical, and magnetic approaches. In the red clay sequence, (1) the concentration of iron oxides (mainly haematite and goethite) and the intensity of pedogenesis were significantly positively correlated with redness (a*) and yellowness (b*). (2) a*, b*, and a*/b* can be used as proxy indicators of haematite concentration, goethite concentration, and temperature, respectively. (3) The parameters derived from colour reflectance and DRS measurements were proven to be better than magnetic susceptibility (χ) in recording palaeoclimatic evolution, and Ca*b* was better than the chemical weathering index in recording soil development. [ABSTRACT FROM AUTHOR]

Red clay is widespread in southern China, exhibiting undesirable properties of softening upon contact with water and cracking after losing water. Using red clay as roadbed filler frequently results in a series of geotechnical hazards such as foundation settlement and slope instability. Consequently, it is necessary to improve the engineering properties of red clay. Using natural plant fibers offers improved environmental sustainability and greater economic advantages compared to traditional methods involving lime and cement. In this study, palm fibers were used to improve the properties of red clay. The aim was to quantitatively analyze the influence of palm fiber content and length on the unconfined compressive strength (UCS) of red clay, study the capacity of palm fibers to inhibit soil desiccation cracking, and explore the underlying mechanisms by conducting UCS and desiccation tests. The results show that the UCS and residual strength of red clay can be significantly enhanced by palm fiber, and the soil damage form will be changed from brittle damage to ductile damage. Particularly noteworthy, the content of 0.45% palm fiber with a length of 20 mm increased the UCS by 43.4%. Palm fiber also effectively inhibited soil desiccation cracking, the content of 0.3% palm fiber with a length of 20 mm reduced the crack ratio by 54.4%. This study presents a novel approach for improving red clay, offering valuable insights for the use of palm fiber-improved red clay in road construction and slope protection projects. [ABSTRACT FROM AUTHOR]

In the present work, composites with non-toxic metal oxides, such as TiO2 and ZnO, and a natural red clay (taua) reach in hematite were used in the photocatalytic degradation of Fenthion. The composite TiO2/Taua (0.5:1 wt. ratio) and pure TiO2 were prepared by sol-gel method while ZnO/Taua (0.5:1 wt. ratio) and pure ZnO were prepared by Pechini method. The materials were characterized by XRD, SEM, EDX, and DRS. The anatase phase was formed in both pure TiO2 and TiO2/Taua, while the hexagonal phase was formed in pure ZnO and ZnO/Taua. The bandgap energies for the two composites were narrowed compared to the respective pure oxides as consequence of the hematite (α-Fe2O3, Eg = 2.1 eV) in the red clay, reaching 2.1 eV for TiO2/Taua and 2.0 eV for ZnO/Taua, while the bandgap energies for pure TiO2 and ZnO were 3.2 and 3.0 eV, respectively. Fenthion was not degraded in the dark, but the concentration droped 20% after 180 min under visible light irradiation without photocatalyst and 60% after 210 min in the presence of the pure red clay. Both TiO2/Taua and ZnO/Taua composites were also photocatalytic active to degrade Fenthion (λ > 420 nm), with degradation of 78% (in 180 min) and 85% (in 210 min) respectively. In the optimized conditions (pH 2, 100 mg L−1 of H2O2 and 30 mg L−1 of Fenthion), the ZnO/Taua composite was the most efficient, reaching 89% degradation in up to 30 min, with Fenthion sulfoxide as the degradation product. [ABSTRACT FROM AUTHOR]

Due to the long-term effect of cyclic traffic loads, the accumulated deformation of red clay subgrades is increasing, strength is decreasing, and problems such as uneven settlement are occurring. In order to improve the stability and durability of red clay subgrade, this paper analyzes the effects of cyclic stress ratios and compactness on the development of the dynamic elastic modulus of saturated red clay. This is achieved through dynamic triaxial tests on red clay in the Qingyuan County, Zhejiang Province, China. The results show that the saturated red clay has an attenuation threshold cyclic stress ratio under cyclic loading. The attenuation threshold cyclic stress ratio prediction models were constructed based on the confining pressure and compactness, respectively. By introducing the concept of a relative cyclic stress ratio, the prediction model of the dynamic elastic modulus of saturated red clay (as based on cyclic vibration times and close cyclic stress ratio) is constructed. The model realizes the prediction of the dynamic elastic modulus of red clay under arbitrary cyclic vibration times via the initial cyclic stress ratio, compactness, and other parameters. It provides a theoretical basis for rationally evaluating the dynamic stability of red clay subgrade under cyclic loading. [ABSTRACT FROM AUTHOR]

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The primary goal of this research is to determine the mechanical properties of opaque glazed ceramic tiles containing fly ash, tincal waste, and recycled red clay, including to assess if the results meet international requirements. Opaque glaze and tincal waste were the main components of all glaze compositions of four groups, which were named OG (original), FA, RC, and FC (mixture) according to the additive. The ceramic tiles were prepared by dipping the biscuits in the glaze composition and firing them at 1150°C. The water absorption of the FA, RC, and FC tiles was less than that of the OG tiles (< 0.52%) and the scratch hardness values were between 6 and 7. All the experimental groups were also resistant to thermal shock, chemicals, and staining showing high opacity (L* > 92) and having a light yellow–red color. The micro- and crystallographic structure of some selected tiles were determined by scanning electron microscopy and x-ray diffraction techniques. Zircon, diopside and augite phases were recognized. [ABSTRACT FROM AUTHOR]

Taking the red clay from Guilin, China as the object, this paper prepares red clay samples with different initial water contents, extracts the crack parameters from the images on the samples under cyclic drying and wetting through image processing, and analyzes the laws of crack development. In addition, parallel red clay samples were subject to shrinkage tests and direct shear tests under the same cyclic drying and wetting. Based on the test results, the authors discussed the laws of shrinkage deformaiton and strength change for the samples under cyclic drying and wetting, and examined the relationship between cracking, shrinkage properties, and strength detiroation of the red clay. The results show that: (1) With the growing crack rate, the volume shrinkage ratio constantly declined; the area shrinkage ratio was generally decreasing, but the decrement was not obvious in local places (in some places, the area shrinkage ratio even increased); the shrinkage coefficient generally declined, (2) Through the five dry-wet cycles, it was learned that the cohesion and internal friction angle of red clay strength can be quantified using the crack rate. This finding lays the basis for judging soil strength based on crack rate, and solving actual engineering problems with the red clay.

• Based on morphology analysis, the cracking process of red clay in three stages was proposed. • Based on the sensitivity and crack-tip displacement, crack propagation characteristics were revealed. • The application of cohesive crack model in type I fracture of red clay was verified. Red clay was a special roadbed filling soil that was easy to expand and shrink because of the characteristics of high liquid limit and high porosity, leading to the appearance of a large number of cracks. In order to understand the cracking mechanism and nonlinear fracture failure process of red clay, the fracture toughness and crack sensitivity of red clay with different saturation, compaction and gravel content were analyzed by three-point bending cracking experiment and Image processing technology, and then the cohesive crack model was established to describe the fracture toughness. The results showed that the cracking process of red clay could be divided into three stages: crack incubation period, crack initiation and propagation period and visible cracks appearance stage. There was a conic function relationship between fracture toughness and saturation and a positive correlation between fracture toughness and compactness. The influence of gravel content on the final fracture path of red clay was the most significant, while the effects of saturation and compaction could be ignored. In addition, the fracture toughness converted from the cohesive crack model was basically as the same as the measured. This work provided a basis for theoretical analysis and numerical calculation for the fracture toughness of red clay under three-point bending. [ABSTRACT FROM AUTHOR]

Red clay is prone to softening and disintegration when exposed to water, often triggering severe geological disasters. To enhance its resistance to disintegration, this paper employs a homemade wet-dry cycling disintegration apparatus, combined with XRD, SEM, MIP, and fractal theory, to analyze the effects of different activators on the disintegration characteristics and microscopic mechanisms of SSP-improved soil. Under wet-dry cycling, the disintegration process of SSP-improved soil can be divided into five stages: rapid water absorption, saturation wetting, rapid disintegration, softening and dissolution, and stable non-disintegration. As the activator and SSP content increase, the resistance to disintegration of SSP-improved soil gradually enhances. After the addition of activators, the porosity, pore area, pore length and width, and probability entropy of SSP-improved soil decrease (i.e., 7 % NS < 7 % CSW < 7 % NH < undisturbed soil), while the average shape factor, regional probability distribution index, and fractal dimension increase. This is because activators promote ion exchange, cementation, crystallization, and carbonation reactions in SSP-improved soil, generating a substantial amount of hydration products such as C-S(A)-H, Ca(OH) 2 and CaCO 3 , which fill and encapsulate inter-particle pores, thereby reducing water flow channels within the pores. In contrast, the pore structure between particles in undisturbed soil is simple and well-connected, providing favorable conditions for the migration and dissolution of fine particles and the loss of cementing materials, which accelerates the destruction and disintegration of the soil structure. [Display omitted] • The disintegration process of SSP-improved soil can be divided into five stages. • SSP can significantly enhance the resistance to disintegration of the soil mass. • The content of activator exhibits a negative correlation with the disintegration rate. • The fractal dimension exhibits a positive correlation with the number of wet-dry cycles. [ABSTRACT FROM AUTHOR]

Pb-contaminated soil poses significant environmental and health risks as well as soil stability issues. Research on sandy soils highlights CO 2 -enhanced reactive MgO as a promising solution for improving the solidification of Pb-contaminated soils. However, carbonation effects can differ markedly between soil types owing to varying soil properties. In this study, we evaluated the effects of CO 2 -enhanced reactive MgO on the engineering and environmental characteristics of Pb-contaminated red clay and explored its mechanism of carbonation solidification. The results showed that CO 2 -enhanced reactive MgO increased the strength of Pb-contaminated red clay to over 3 MPa within 1 h, which was approximately 25 times the strength of untreated soil (0.2 MPa) and significantly higher than that of reactive MgO-treated, uncarbonated soil (0.8 MPa). The pH of the carbonated soil (9–10) facilitated Pb2+ immobilization, and the increase over the initial parameter elevated the electrical conductivity value. Moreover, CO 2 -enhanced reactive MgO reduced the Pb2+ leaching concentration to below 0.1 mg/L, even at high Pb concentrations (10,000 mg/kg). Pb2+ transformed into lead carbonates during the carbonation process, with the hydrated magnesium carbonates forming a dense internal structure. This solidification mechanism included chemical precipitation, physical adsorption, and encapsulation. Notably, the carbonation time should be controlled within 1 h to prevent soil expansion. Together, these findings support the potential of CO 2 -enhanced reactive MgO for efficient and low-carbon application in the solidification of Pb-contaminated red clay. [Display omitted] • MgO-CO 2 can rapidly improve strength to over 3MPa and effectively reduce leaching concentration to below 0.1mg/L. • The intrinsic mechanisms of carbonated Pb-contaminated red clay are systematically clarified. • For Pb-contaminated red clay, it is recommended that the carbonation time be set to 1 hour and the MgO dosage be over 10%. • This approach could serve as a potential means of carbonation sequestration. [ABSTRACT FROM AUTHOR]

Phyllite soil and red clay belong to the soils that negatively impact the engineering performance of railway subgrade and may cause subgrade bulges, uneven subgrade settlement, and other subgrade distresses. In order to make full use of these two soils, a collaborative improvement plan was proposed. A series of tests were conducted to analyze the synergistic effects of lime and red clay on the improvement of phyllite soil. The tests included the no loading swelling ratio, swelling pressure, consolidation, and direct shear tests. Additionally, scanning electron microscopy was used to investigate the role of lime and red clay in soil improvement. The test results show that a red clay ratio of 60% + lime content of 3% is the optimal composite improvement scheme. The scheme led to a 93% reduction in the no loading swelling ratio and an 88% reduction in swelling pressure. Additionally, cohesion, the internal friction angle, and the compression modulus increased by 345%, 73%, and 373%. Red clay and lime had weak synergistic improvement effects on the no loading swelling ratio, the swelling pressure, and the internal friction angle of phyllite soil, that is, the synergistic improvement effect of red clay and lime was less than the sum of the single improvement effect but greater than the single improvement effect. Red clay and lime had a strong synergistic improvement effect on the cohesion and the compression modulus of phyllite, that is, the synergistic improvement effect of red clay and lime was greater than the sum of the single improvement effect. The microstructure analysis test results show that red clay can fill the pores of phyllite soil and improve its immediate strength. Through hardening and cementation, lime can enhance the strength of phyllite soil as well as address the issue of the reduced engineering properties of phyllite soil and red clay when exposed to water. Red clay and lime promote each other’s reactions and have a synergistic improvement effect on phyllite soil.

In the work, an analysis of the phase formation process proceeding in a quaternary red clay-low-melting cullet-iron oxide (Fe2O3)-WAS (waste activated sludge) system in treatment at 1000oC in air has been performed. It has been established that, in sintering of the mixtures, porous ceramics consisting of a glass phase alloyed with iron ions with inclusions of cristobalite, iron-containing silicates of complex composition, α-Fe2O3, and an insignificant amount of Fe3O4 forms. The porous glass ceramics meets the compressive strength requirements imposed on building bricks.

The objective of this research is to improve the strength characteristics of red clay as a subgrade filler and increase the stability of subgrade engineering. During the laboratory tests, different amounts of waste tire rubber powder were added to the red clay. This study aims to identify the optimal amount of rubber powder required to improve the strength characteristics of red clay using a triaxial test and Duncan–Chang model. Using the depth of a field microscope, the apparent morphology of red clay and modified red clay was analyzed, and the pore variation of plain red clay and rubber powder modified red clay was described using a mercury intrusion test(MIP). The experimental results indicate that the asymptotic value of the main stress difference is significantly higher than the other four admixtures at 3%. The 3D surface comparison chart indicates that the addition of rubber powder significantly increases the relatively flat area range while reducing the overall area range. According to the comparison of porosity and contact area ratio, RPA1 is larger than RPA2, and RCA1 is smaller than RCA2. According to the characteristics of BJH pore size distribution, modified red clay has a higher pore fractal dimension than pure red clay.

Uplift of the Tibetan Plateau, expansion/shrinkage of the Paratethys Sea, and global climate are three major forcings for central-east Asian climatic and environmental variations during the Cenozoic. However, knowledge of expansion/shrinkage history of the Paratethys Sea is much less well known in comparison with the other two forcings. Here, we present a first multiple-parameter environmental magnetic and diffuse reflectance spectroscopy study of the Eocene eolian Red Clay deposits (∼51–40 Ma) in the Xorkol Basin of the northeastern Tibetan Plateau, which is near the easternmost maximum boundary of the Eocene Paratethys Sea. The first detailed Eocene expansion/shrinkage history of the Paratethys Sea was reconstructed based on the hematite content of the Eocene Red Clay, which shows remarkable consistency with the previous low-resolution Paratethys Sea paleowater depth record in the southwestern Tarim Basin. These results demonstrate that the Paratethys Sea experienced a three-stage (shrinkage-expansion-shrinkage) evolution between ∼51 and 40 Ma, with boundaries at ∼46.2 and 42 Ma. Superimposed on this framework, the Paratethys Sea experienced four times of rapid shrinkages at the expansion phase (shows 400-kyr cycles) during ∼44–42 Ma modulated by eccentricity forcings. These new results are of great significance to evaluate respective role of Tibetan uplift, global climate, and Paratethys Sea area variations in Asian climate and environmental change over the Eocene.

In order to study the influence of different clay contents on the fractality of red clay, specimens having four different water contents were prepared. The cracking characteristics of the specimens were observed at 20 °C and 60 °C. Image J software was used to measure and calculate the crack area, crack ratio, crack length and width of each sample. The test results showed that the development of cracks in red clay could be divided into three stages: crack generation, crack development and crack stabilization. The clay particle content, temperature and water content have significant effects on crack development, and from the test analyses, it was determined that for construction in the Guilin area, it is necessary to pay attention to drainage protection. [ABSTRACT FROM AUTHOR]

Annual coffee consumption has increased to 10 million tons. Of the coffee consumed, 65% is discarded as spent coffee grounds (SCG). However, most SCG are buried in the ground as organic waste. The more coffee consumption increases, the more land is used for disposing of spent coffee. SCG recycling has gotten considerable attention as a solution involved in these issues. The construction community has studied means and methods to recycle SCG as construction materials, such as bricks, subgrade fillers, thermal insulators, etc. This paper presents a new method, which recycles SCG as a construction material, maximally using its acidity. The SCG were hardened with natural binders (i.e., animal glue (AG) and starch (S)) and red clay (RC). The SCG mixtures were pressed with 2 MPa in a cylindrical mold and cured for 7 days. Then, the strength, durability, and pH tests were measured. The AG- and RC-treated SCG sample, which outputs 1933 kPa of strength and a 4.9 pH value, is identified as the optimal sampling method among the acid materials produced in this study. The optimal sample decreases the pH to approximately 7 of water where 68% weight of Ordinary Portland cement was soaked in. [ABSTRACT FROM AUTHOR]

High-liquid limit red clay has poor engineering characteristics, namely poor water stability, low strength, and large expansion and contraction deformation. The clay may be reinforced with an F1 ionic soil stabilizer. The engineering characteristics of this reinforced clay were studied, specifically concerning its basic physical parameters, shear strength parameters, and micropore structure. The F1 ionic soil stabilizer significantly improved the water sensitivity, compaction characteristics, and shear strength of red clay. We determined that the optimal F1 ionic soil stabilizer mix was 0.5 L/m3, resulting in a reinforced clay with plastic limit increased by 45.74%, optimal moisture content increased by 12.12%, maximum dry density increased by 5.8%, liquid limit reduced by 8.4%, plasticity index reduced by 43.8%, infiltration coefficient reduced by 41.8%, cohesion increased 1.64-fold, and internal friction angle increased 1.30-fold. Freeze-thaw cycles reduced the shear strength parameters of the reinforced red clay, although even after 15 cycles, it still had 18.4% higher cohesion and 57.1% higher internal friction angle than undisturbed red clay. The F1 ionic soil stabilizer significantly reduced the pore size and area of red clay, the complex connected pore structure is adjusted to a more regular structure. The reinforced clay had 56.64% lower pore area ratio, 32.27% lower average Feret diameter, and 2.43% lower fractal dimension. [ABSTRACT FROM AUTHOR]

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Copyright of Industrial Minerals & Processing / Huagong Kuangwu yu Jiagong is the property of Industrial Minerals & Processing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)