In this study the compressive strength and durability of soft clay soil stabilized with halloysite nanotubes are investigated. Halloysite nanotubes are novel 1D natural nanomaterials which are widely used in reinforcing polymer, pollution remediation, and as nanoreactors for biocatalyst. The wide use of halloysite nanotubes is due to their high aspect ratio, appropriate mechanical strength, high thermal stability, nature-friendly and cost-effectiveness. However, the use of halloysite nanotubes as a stabilizing agent for improving the durability of soil is not clear. In this research, halloysite nanotubes was used in the amounts of 2%, 5% and 10% by the weight of dried soil. Unconfined compressive strength, wet/dry cycles and freeze/thaw cycles tests were performed to evaluate the strength and durability of stabilized soft clay soil. Experimental results showed that halloysite nanotubes considerably improves the compressive strength and durability of soft clay soil. The optimum amount of halloysite nanotubes for soil stabilizing in terms of compressive strength and durability was 5%. The compressive strength of soft clay increased as much as 129% by applying 5% halloysite nanotubes. Also, the specimen containing 5% halloysite nanotubes showed the least strength loss after wet/dry and freeze/thaw cycles. The soil sample containing 5% halloysite nanotubes lost 20% of its initial compressive strength after 8 cycles of freezing and thawing, while the soil sample without any halloysite content lost 100% of its compressive strength after the same number of freezing and thawing. Based on the obtained results, the use of halloysite nanotubes in order to enhance the strength and durability of soft clay is strongly recommended., Tavakolipour Masoud, Salemi Niloofar., and Obsahuje bibliografické odkazy
The paper is concerned with the graph formulation of forced anisotropic mean curvature flow in the context of the heteroepitaxial growth of quantum dots. The problem is generalized by including anisotropy by means of Finsler metrics. A semi-discrete numerical scheme based on the method of lines is presented. Computational results with various anisotropy settings are shown and discussed.
Photochemical efficiency of PSII of Ctenanthe setosa was investigated to understand the photosynthetic adaptation mechanism under drought stress causing leaf rolling. Stomatal conductance (gs), the levels of photosynthetic pigments and chlorophyll (Chl) fluorescence parameters were determined in leaves that had four different visual leaf rolling scores from 1 to 4, opened after re-watering and mechanically opened at score 4. gs value gradually decreased in adaxial and abaxial surfaces in relation to scores of leaf rolling. Pigment contents decreased until score 3 but approached score 1 level at score 4. No significant variations in effective quantum yield of PSII (ΦPSII), and photochemical quenching (qp) were found until score 3, while they significantly decreased at score 4. Non-photochemical quenching (NPQ) increased at score 2 but then decreased. After re-watering, the Chl fluorescence and other physiological parameters reached to approximately score 1 value, again. As for mechanically opened leaves, gs decreased during drought period. The decrease in adaxial surface was higher than that of the rolled leaves. NPQ was higher than that of the rolled leaves. ΦPSII and qp significantly declined and the decreases were more than those of the rolled leaves. In conclusion, the results indicate that leaf rolling protects PSII functionality from damage induced by drought stress. and H. Nar ... [et al.].
Giant rosettes are ones of the most striking features of the vegetation in the high tropical Andes, with Coespeletia moritziana reaching the highest altitudes up to 4,600 m a.s.l. Different from other giant rosettes, this species grows on rock outcrops with poorly developed soils and where water availability may be limited. Two questions are addressed in this study: How does this species respond in terms of water relations to maintain favorable gas-exchange conditions? Considering that adult plants rely on a water-reserving central pith, how do early stages respond to this environment’s extreme conditions? Water relations and gas-exchange studies were carried out on juveniles, intermediate and adult C. moritziana plants during wet and dry seasons in Páramo de Piedras Blancas at 4,200 m a.s.l. Adult plants maintained higher leaf water potentials (ΨL) during the wet season, however, no differences between stages were found for the dry season. Minimum dry season ΨL were never near the turgor loss point in any of the stages. Juveniles show a more strict stomatal control during the dry season to maintain a favorable water status. Net photosynthesis significantly decreased in intermediate and juvenile stages from wet to dry seasons. Our results suggest that
C. moritziana resists more extreme conditions compared to other Andean giant rosettes., F. Rada, A. Azócar, A. Rojas-Altuve., and Obsahuje bibliografii