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When a soil is subjected to cyclic loading, there are changes in the material's geomechanical behaviour that need to be characterised before safely designing any future projects. In terms of cyclic loading, it is important to characterise not only the failure of the soil but also its behaviour before failure, in particular the yield point and the elastic behaviour of the material. This study examines the effects of the number of loading cycles on the behaviour of a chemically stabilised soft soil with a particular focus on the yield surface. To this end, a series of triaxial tests were performed on specimens, previously or not subjected to a different number of loading cycles (1000–100 000). The results were analysed in terms of the evolution of accumulated permanent axial strain, the yield surface and stress–strain behaviour. It was observed that an increase in the number of loading cycles promoted: an increase in the permanent axial strain, an increase in the undrained resilient modulus, a shrinkage of the yield surface but its shape is maintained, and there is a small increase in the peak strength of the stabilised soil explained by the strain-hardening effect induced by the cyclic loading. [ABSTRACT FROM AUTHOR]

The present study aims to indirectly evaluate the occurrence of suction and its effects in laboratory tests of a chemically stabilized soft soil. To achieve these goals, a series of unconfined compressive strength (UCS) and triaxial tests were performed, with and without the application of cyclic loading and with and without membrane during the cyclic loading stage, to evaluate the occurrence of suction and its effect on the mechanical behavior of a chemically stabilized soft soil. The results show that during the cyclic loading stage there is an occurrence of suction which influences both the permanent axial strain during the cyclic loading and the maximum strength of the stabilized soil. During the cyclic loading stage, the occurrence of suction promoted the increase of the plastic deformation. In terms of strength, it is observed an occurrence of suction in the stabilized soil which may be related with the increase of the strength. It is observed that suction can be avoided by saturation of the sample, verified in triaxial tests, or by using a membrane during the cyclic UCS test.

Synthetic analogues of marine sponge guanidine alkaloids showed in vitro antiparasitic activity against Leishmania (L.) infantum and Trypanosoma cruzi. Guanidines 10 and 11 presented the highest selectivity index when tested against Leishmania. The antiparasitic activity of 10 and 11 was investigated in host cells and in parasites. Both compounds induced depolarization of mitochondrial membrane potential, upregulation of reactive oxygen species levels, and increased plasma membrane permeability in Leishmania parasites. Immunomodulatory assays suggested an NO-independent effect of guanidines 10 and 11 on macrophages. The same compounds also promoted anti-inflammatory activity in L. (L.) infantum-infected macrophages cocultived with splenocytes, reducing the production of cytokines MCP-1 and IFN-γ. Guanidines 10 and 11 affect the bioenergetic metabolism of Leishmania, with selective elimination of parasites via a host-independent mechanism.

When a material is subjected to cyclic loading, there are changes in the material's geomechanical behaviour that need to be characterized for a safe design. For unbounded granular materials, the shakedown theory is used to explain the soil's behaviour under cyclic loading. However, it is not clear yet if such theory is extendable to unreinforced and fibre-reinforced stabilized soils. To this end, a series of unconfined compression cycling loading tests were performed, to study the effect of the number of cycles and initial deviatoric stress level on the behaviour of an unreinforced and reinforced stabilized soil. The results were analysed in terms of shakedown theory, elastic and plastic deformation energy and damping ratio. It was observed that shakedown theory seems to represent the behaviour of the stabilized unreinforced and fibre-reinforced soils under cyclic loading, with threshold between the plastic shakedown and the plastic creep shakedown behaviour at around an absolute axial strain 1 × 10–3. The effect of increasing binder content (from 12 to 39%), comparable to reducing the initial deviatoric stress level (from 85 to 15%), promoted a reduction in plastic deformation (from 2.09 to 0.19% without fibres, and 2.21 to 0.24% with fibres) and damping ratio (from 25.17 to 10.01% without fibres, and 29.18 to 15.95% with fibres) due to the lower degradation of the solid matrix. It also promoted an increase in the difference between elastic and plastic energy (from − 1.04 to 13.92 kJ/m3 without fibres, and − 1.68 to 10.19 kJ/m3 for the first cycle). [ABSTRACT FROM AUTHOR]

When a material is subjected to cyclic loading, there are changes in the material's geomechanical behavior that need to be known and characterized for a safe design. To this end, a series of unconfined compressive strength (UCS) tests was performed, with and without the application of cyclic loading, to study the effect of the number of loading cycles on the behavior of a soft soil stabilized with different binder contents, unreinforced and reinforced with polypropylene fibers. The results were analyzed in terms of the evolution of elastic and plastic deformation energy, and it was observed that plastic energy prevailed in the first cycles, but decreased with the increase in the number of loading cycles. The accumulated plastic deformation occurring during the cyclic loading induced a strain-hardening effect that was responsible for the increase in the undrained resilient modulus and in the postcyclic unconfined compressive strength, regardless of the binder content and fiber reinforcement. The addition of polypropylene fibers led to a reduction in the elastic deformation energy, which was more noticeable in the first cycles, leading to an increase in the accumulated plastic axial strains and to a reduction in the undrained resilient modulus during the cyclic loading. These facts are explained by the high compressibility of the fibers and by the weakening of the stabilized matrix as a result of the physical presence of the fibers which may prevent the development of some cementitious bonds. However, the addition of fibers led to an increase in the energy absorption capacity, explained by the fact that the deformations occurring during the cyclic loading allow an earlier mobilization of the fibers as the UCS test proceeds. [ABSTRACT FROM AUTHOR]

Myxococcus xanthus is a soil bacterium that undergoes a unique life cycle among the prokaryotes upon starvation, which includes the formation of macroscopic structures, the fruiting bodies, and the differentiation of vegetative rods into coccoid myxospores. This peculiarity offers the opportunity to study the copper response in this bacterium in two different stages. In fact, M. xanthus vegetative rods exhibit 15-fold-greater resistance against copper than developing cells. However, cells preadapted to this metal reach the same levels of resistance during both stages. Analysis of the M. xanthus genome reveals that many of the genes involved in copper resistance are redundant, three of which encode proteins of the multicopper oxidase family (MCO). Each MCO gene exhibits a different expression profile in response to external copper addition. Promoters of cuoA and cuoB respond to Cu(II) ions during growth and development; however, they show a 10-fold-increased copper sensitivity during development. The promoter of cuoC shows copper-independent induction upon starvation, but it is copper up-regulated during growth. Phenotypic analyses of deletion mutants reveal that CuoB is involved in the primary copper-adaptive response; CuoA and CuoC are necessary for the maintenance of copper tolerance; and CuoC is required for normal development. These roles seem to be carried out through cuprous oxidase activity.