The onset of convection in a gravity-modulated viscoelastic fluid-saturated anisotropic porous layer

This study presents a linear stability analysis of thermal convection in a porous layer saturated with viscoelastic fluid subjected to harmonic vertical vibrations so that the gravity varies periodically with time. The fluid obeys an Oldroyd-B constitutive relationship. The porous layer is considered to be densely packed and to possess vertical anisotropy in both mechanical and thermal properties. The onset threshold in terms of correction to a critical Rayleigh number is computed using the regular perturbation method based on small amplitude of modulation. Due to the imposed gravity modulation, there is a shift in the onset criteria. It is found that the low-frequency gravity modulation advances the convection, while for moderate and large frequencies stabilization occurs. The thermal anisotropy, normalized porosity, Darcy-Prandtl number, and relaxation parameter reinforce-while the mechanical anisotropy and retardation parameters suppress-the stabilizing effect of g-jitter. © 2013 by Begell House, Inc

Genomic Approaches to Using Diversity for the Adaptation of Modern Varieties of Wheat and Barley to Climate Change

Plant genetic resources have contributed to the identification and characterization of key loci and genes for important agronomic traits such as flowering time, plant height, root and shoot growth and resistance to abiotic stresses. Key loci for pre-anthesis growth vigor and drought tolerance have been revealed by genome-wide mapping in three diverse barley panels. Recent studies have identified candidate loci for biomass and/or the corresponding growth rates, water use efficiency, root traits, tiller number, plant height under drought or/and well-watered conditions using destructive and non-invasive 48phenotyping. In all three panels, 76 genomic regions were identified in at least two panels in which QTLs for growth and/or drought tolerance cluster, some marker-trait associations were even found for identical SNPs in all panels. The main genomic regions identified in three different mapping panels for trait complexes such as growth vigor, root architecture and pre-anthesis drought tolerance are highly relevant for future research on adaptation to climate change