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Highlights • A 2-D high-efficiency micro-mixer was designed by inducing shear- & extension-induced elastic instabilities. • The mixing enhancement by elastic instabilities was the first time realized by DNSs. • The irregularly motions by flexibility of polymers is mainly responsible the superior mixing. • The biocompatible working fluids makes the efficient mixing potential for bioengineering and chemical engineering. Abstract Efficient mixing is one of the keen interest of many bioengineering and chemical engineering processes. In this work, we designed an efficient micro-mixer with viscoelastic fluid which can induce both strong shear and strong extension by being embedded several rhombic blocks to destabilize the viscoelastic fluid flow and can be also easily integrated. Experimental visualization and direct numerical simulation (DNS) of mixing process were conducted to evaluate the mixing performance. By adding green fluorescent particles into the fluids, apparent mixing enhancement was observed for viscoelastic fluid flow when the flow rate exceeded a threshold. The efficient micro mixing progress also shows great potential for bioengineering application with the biocompatible working fluids. Through DNS, we discussed the flow patterns and the role of polymers playing in viscoelastic fluid flow to respectively figure out the underlying mechanism of efficient mixing and the occurrence of unstable flow motions. The results show that when the elasticity is strong enough, the viscoelastic fluid flow is irregularly twisting and swinging in the channel, and as a result enhances the mixing by increasing the intersecting frequency of fluids of different concentrations. Moreover, owing to the special designed geometry, the polymers act as the energy supplier of unstable flow motions, which keeps the fluctuations from decaying towards the laminar regime. [ABSTRACT FROM AUTHOR]

Cotton (Gossypium spp.) is a vital global source of renewable fiber and ranks among the world's most important cash crops. While extensive nuclear genomic data of Gossypium has been explored, the organellar genomic resources of allotetraploid cotton, remain largely untapped at the population level. The plastid genome (plastome) is well suited for studying plant species relationships and diversity due to its nonrecombinant uniparental inheritance. Here, we conducted de novo assembly of 336 Gossypium plastomes, mainly from domesticated cultivars, and generated a pan‐plastome level resource for population structure and genetic diversity analyses. The assembled plastomes exhibited a typical quadripartite structure and varied in length from 160 103 to 160 597 bp. At the species level, seven allotetraploid species were resolved into three clades, where Gossypium tomentosum and Gossypium mustelinum formed an early diverging clade rooted by diploids, followed by splitting two sister clades of Gossypium darwinii–Gossypium barbadense and Gossypium hirsutum–Gossypium ekmanianum–Gossypium stephensii. Within the G. hirsutum clade the resolution of cultivated accessions was less polyphyletic with landrace and wild accessions than in G. barbadense suggesting some selection on plastome in the domestication of this adaptable species of cotton. The nucleotide diversity of G. hirsutum was higher than that of G. barbadense. We specifically compared the plastomes of G. hirsutum and G. barbadense to find mutational hotspots within each species as potential molecular markers. These findings contribute a valuable resource for exploring cotton evolution as well as in the breeding of new cotton cultivars and the preservation of wild and cultivated germplasm. [ABSTRACT FROM AUTHOR]

We study exponential stability of superstable systems in Hilbert spaces under perturbations. Formulas to calculate or to estimate the exponential growth bound of the perturbed systems are derived via which sufficient conditions on exponential stability are established. The obtained results are applied to a partial differential equation governing the vibration of a smart beam made of self-straining material. Several numerical simulations are given. [ABSTRACT FROM AUTHOR]

We investigate the nonlinear modes in a rotating double well potential with 풫풯 symmetry. Focus on the existence and stability of the nonlinear PT modes in this system, we found that five types of PT modes can stably exist by given certain parameter settings. The multistable area between these modes are studied numerically and the bistable and tristable areas are delimited. With different input trial wavefunctions, five types of solitary wave modes are identified. We found that the rotating of the potential can significantly affect the power flow of the fundamental harmonic mode, whose effect is absent for the other modes. [ABSTRACT FROM AUTHOR]