Finite element-based micromechanical modeling of the influence of phase properties on the elastic response of cementitious mortars

This study reports the influence of inclusion stiffness and its distribution on the stress distributions in the microstructural phases of different cementitious mortars using microstructure-guided finite element simulations. Randomly generated periodic microstructures with single/multiple inclusion sizes and random spatial distribution, subjected to periodic boundary conditions and a strain-controlled virtual testing regime are chosen for final analysis. Numerical simulations reveal: (i) the differences in locations/magnitudes of stress concentrations as a function of inclusion stiffness and size distribution, and (ii) the sometimes detrimental influence of matrix and interface stiffening/strengthening on the overall composite response, leading to material design strategies when non-conventional inclusions are used in cementitious systems for special properties. The constitutive behavior in the linear elastic regime is extracted based on the predicted dominant principal stresses and strains in the representative area element. Thus, in addition to the microstructural phase stresses, this methodology also provides predictions of the composite elastic modulus, which are observed to be more reliable than those obtained from analytical prediction models

Presence of integrase core domain in mutant type black pepper Piper nigrum L. ‘Thekken’ with altered inflorescence architecture

770-773Black pepper (Piper nigrum L.), referred as the ‘King of Spices’, is native to India and has shown declined productivity over the years. It exhibits diverse quantitative and qualitative traits, particularly in spike length, floral composition, floral arrangement, fruit size and number. The novel mutant variety of black pepper (Piper nigrum L.) ‘Thekken’ shows a remarkable branching character in the spikes. In the present study, we analyzed RAMOSA3 (RA3) gene at the molecular level in this variety for yield improvement. Screening using degenerate primers designed for RA3 was carried out in ‘Thekken’ and a non-branching variety ‘Karimunda’ at the genomic level and at different stages of spike development at the transcriptome level. Sequence analysis of the amplicons generated in RT-PCR revealed the presence of an integrase core domain in the mutant type of black pepper, suggesting a possibility of mutation at this locus in the branched variety due to retrotransposon integration. The study suggests a possibility for introgression of the genes responsible for branching trait from the mutant variety of black pepper type ‘Thekken’ to other conventional cultivated varieties of black pepper that show single unbranched spike thereby increasing the productivity of black pepper which has very high economic value and export potential

Porous inclusions as hosts for phase change materials in cementitious composites: Characterization, thermal performance, and analytical models

This paper examines the influence of four different porous hosts (lightweight aggregates (LWA)) having different pore structure features, as hosts for phase change materials (PCM). The porosity and absorption capacity of the LWAs significantly influence the composite thermal conductivity. The incorporation of 5% of PCMs by total volume of the cementitious system reduces the composite thermal conductivity by ⩾10%. The fact that the inclusions (LWAs) in these composites are by themselves heterogeneous, and contain multiple components (solid phase, PCM, water, and air) necessitate careful application of predictive models. Multi-step Mori-Tanaka mean-field homogenization methods, either based on known microstructural arrangement in the composite, or property contrast between the constituents, are applied to predict the composite thermal conductivity. A microstructural contrast factor is used to account for both the thermal conductivities and the volume fractions of the phases with the highest property contrast. Smaller contrast factors result in improved agreement of the models with the experiments, thereby aiding in the selection of suitable predictive schemes for effective properties of such multi-phase composites