Effect of hysteresis on the critical state behavior of an unsaturated silty soil

This is the author accepted manuscript. The final version is available from the publisher via the DOI in this recordSome or all data, models, or code generated or used during the study are available from the corresponding author by request.In this paper the effect of hysteresis on the critical state behavior of unsaturated soils is investigated through conducting a number of controlled suction triaxial tests on samples of an unsaturated silty soil. The slurry method was used for preparing the samples for the main tests. The tests were carried out in a double-walled triaxial cell. In the experiments the samples were consolidated isotropically to virgin state at suctions of 0, 100, 200, 250, and 300 kPa on drying and wetting paths of soil water characteristic curve. Then they were sheared under constant suction at various constant cell pressures. The results of the drained triaxial tests were used to determine the effect of the hysteresis phenomenon on the characteristics of the critical state framework. The obtained data were examined in terms of mean net Bishop's stress (p) (by including degree of saturation) or p¯ (i.e., the mean total stress in excess of pore-air pressure), deviator stress (q), suction (s), and specific volume (v) as state variables. The results show that the critical state lines (CSLs) for the dry and wet paths are not parallel for different suctions in the q:p∗ or q:p¯ space. The slopes and intercepts of the CSLs in this space are functions of suction. In addition, the critical state lines in the v:Ln p or v:Ln p¯ plane are not parallel for drying and wetting paths and the slope and intercept of them are also functions of suction. The results also indicated that two frameworks showed similar trends of critical state parameters but the framework based on p is more reliable than the one based on the p¯

Research Paper Silicon alleviates salt stress, decreases malondialdehyde content and affects petal color of saltstressed cut rose (Rosa xhybrida L.) ‘Hot Lady’

A greenhouse experiment was conducted to investigate the effects of different levels of silicon (Si) application on cut rose (Rosa xhybrida L.) ‘Hot Lady’ under two levels of salt stress. Four Si concentrations (0, 50, 100 and 150 ppm) as Si were combined with a 25 mM NaCl (EC 3.8) level in the nutrient solution supplied to the plants. Addition of Si partially maintained membrane permeability but only fully restored it to control levels in the Si50 and Si100 treatments. 150 ppm Si with or without NaCl could not alleviate or decrease cell wall damages. Inclusion of Si significantly reduced malondialdehyde content and chlorophyll content of salt-stressed plants in all treatments except that of 150 ppm. Maximum chlorophyll content was noticed when 50 ppm Si was supplied. Addition of 50 ppm Si increased the flower number in both plants grown under salinity and unstressed conditions. However,no significant difference was observed between 100 and 50 ppm Si accompanying with NaCl. Plants treated with NaCl alone showed a reduction in plant leaf area, while the reduction in plants treated withNaCl plus 50 and 100 ppm Si were like control and other unstressed plants

Impacts of heating and surfactant treatments on the geotechnical properties of a cohesive soil

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this recordAn experimental investigation was performed to assess the effect of heating and surfactant on treatment of a soil contaminated with gasoline. Contaminated soil samples were prepared by adding 5, 10 and 15% weight of gasoline to a cohesive soil. The contaminated soil samples were treated by applying heating at 50, 100 and 150 °C. In addition, treatment of the contaminated samples was done by using two different types of surfactant, namely SDS (Sodium Dodecyl Sulfate) and Tween 80. The physical and mechanical properties of the natural soil, contaminated soil and treated soil were determined through experimental tests including Atterberg limit, grain size distribution, compaction and unconfined compression tests. Comparison of the results showed that adding gasoline to soil changes its behavior and the amount of change was function of percent of gasoline. The results also indicated that heating can be used for treatment of the contaminated soil. Comparison of the results showed that using surfactant was more effective in treating the contaminated soil than thermal treatment and the properties of surfactant-treated soil were closer to the original condition. The results also showed that SDS surfactant was more effective in treating the contaminated soil than Tween 80

Effect of two organic chemical fluids on the mechanical properties of an expansive clay soil

This is the author accepted manuscript. The final version is available from ASTM International via the DOI in this recordAn experimental study was conducted to investigate the effect of two organic chemical fluids (glycerol and acetone) on the mechanical behavior of an expansive clay soil. A number of experimental tests, including Atterberg limits, compaction, free swelling, unconfined compressive strength, California Bearing Ratio (CBR), and one-dimensional consolidation (loading and unloading) tests, were conducted on specimens of natural soil and soil contaminated with pure glycerol and acetone fluids at different percentages (10 %, 15 %, and 20 %) by weight. The results showed that the effect of pure glycerol on the behavior of the contaminated soil is different from acetone. Glycerol caused a reduction of Atterberg limits, free swelling, unconfined compressive strength, CBR, and optimum water content and an increase in maximum dry unit weight, while acetone showed the opposite effects. These variations of mechanical and physical behavior are a function of the percentage of glycerol or acetone. Furthermore, the results of the loading and unloading tests showed that the compression and swelling indexes are independent of the type of organic chemical fluids used. Results from scanning electron microscopy tests confirmed that the effect of glycerol on the behavior of soil is not the same as acetone

Using jasmonates and salicylates to reduce losses within the fruit supply chain

The fresh produce industry is constantly growing, due to increasing consumer demand. The shelf-life of some fruit, however, is relatively short, limited by microbial contamination or visual, textural and nutritional quality loss. Thus, techniques for reducing undesired microbial contamination, spoilage and decay, as well as maintaining product’s visual, textural and nutritional quality are in high demand at all steps within the supply chain. The postharvest use of signalling molecules, i.e. jasmonates and salicylates seems to have unexplored potential. The focus of this review is on the effects of treatment with jasmonates and salicylates on the fresh produce quality, defined by decay incidence and severity, chilling injury, maintenance of texture, visual quality, taste and aroma, and nutritional content. Postharvest treatments with jasmonates and salicylates have the ability to reduce decay by increasing fruit resistance to diseases and reducing chilling injury in numerous products. These treatments also possess the ability to improve other quality characteristics, i.e. appearance, texture maintenance and nutritional content. Furthermore, they can easily be combined with other treatments, e.g. heat treatment, ultrasound treatment. A good understanding of all the benefits and limitations related to the postharvest use of jasmonates and salicylates is needed, and relevant information has been reviewed in this paper

Heat shock and salicylic acid on postharvest preservation of organic strawberries

Heat shock and salicylic acid have been studied on shelf-life extension of fruits. The benefits of these techniques have been related to their effect on inducing physiological defense responses against the oxidative stress and pathogen development. The objective of this study was to evaluate the effect of heat shock and salicylic acid on the postharvest preservation and contents of total phenolics, anthocyanins, ascorbic acid, fresh weight loss and microbiological quality of organic strawberries cv. Dover. Strawberries produced organically and stored at 5 ºC were subjected to heat shock (45 ºC ± 3 ºC for 3 h), application of salicylic acid (soaking in 2.0 mmol L-1 solution), heat shock in combination with salicylic acid and control. After treatment, the fruits were packed and stored in a climatic chamber at 5 ºC ± 2 ºC. At 1, 7 and 14 days, the experimental units were removed from refrigeration and kept at room temperature of approximately 20 ºC for two days. There was no effect of treatments on fresh weight loss, incidence of pathogens or chemical variations in strawberry fruits during the storage period. In natural conditions, organically grown strawberries remained in good condition for sale up to seven days of storage in all treatments