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Escherichia coli MLB (MG1655 ΔpflB ΔldhA), which can hardly grow on glucose with little succinate accumulation under anaerobic conditions. Two-stage fermentation is a fermentation in which the first stage is used for cell growth and the second stage is used for product production. The ability of glucose consumption and succinate production of MLB under anaerobic conditions can be improved significantly by using acetate as the solo carbon source under aerobic condition during the two-stage fermentation. Then, the adaptive laboratory evolution (ALE) of growing on acetate was applied here. We assumed that the activities of succinate production related enzymes might be further improved in this study. E. coli MLB46-05 evolved from MLB and it had an improved growth phenotype on acetate. Interestingly, in MLB46-05, the yield and tolerance of succinic acid in the anaerobic condition of two-stage fermentation were improved significantly. According to transcriptome analysis, upregulation of the glyoxylate cycle and the activity of stress regulatory factors are the possible reasons for the elevated yield. And the increased tolerance to acetate made it more tolerant to high concentrations of glucose and succinate. Finally, strain MLB46-05 produced 111 g/L of succinic acid with a product yield of 0.74 g/g glucose. Synopsis: [ABSTRACT FROM AUTHOR]

The focus of this paper is on the optimal error bounds of two finite difference schemes for solving the d-dimensional (d = 2, 3) nonlinear Klein-Gordon-Schrödinger (KGS) equations. The proposed finite difference schemes not only conserve the mass and energy in the discrete level but also are efficient in practical computation because only two linear systems need to be solved at each time step. Besides the standard energy method, an induction argument as well as a ‘lifting’ technique are introduced to establish rigorously the optimal H2-error estimates without any restrictions on the grid ratios, while the previous works either are not rigorous enough or often require certain restriction on the grid ratios. The convergence rates of the proposed schemes are proved to be at O(h2 + τ2) with mesh-size h and time step τ in the discrete H2-norm. The analysis method can be directly extended to other linear finite difference schemes for solving the KGS equations in high dimensions. Numerical results are reported to confirm the theoretical analysis for the proposed finite difference schemes. [ABSTRACT FROM AUTHOR]

The effects of isotropic strains on the magnetic properties in ZnO and GaN induced by cation vacancies are comparatively investigated by density functional theory calculations. The magnetic moments and the couplings between vacancies in different charged states are calculated as a function of strains. The modulation of strain on the magnetic properties relies on the materials and the charge states of cation vacancies in them. As the occurrence of charge transfer in ZnO: V under compression, the coupling between $$V_{\rm{Zn}}^{0} $$ is antiferromagnetic (AFM) and it could be stabilized by strains. Tensions can strengthen the ferromagnetic (FM) coupling between $$V_{\rm{Zn}}^{0} $$ but weaken that of $$V_{\rm{Ga}}^{ - } $$ . The neutral V are always AFM coupling under strains from −6 to +6% and could be stabilized by compressions. The interactions between $$V_{\rm{Ga}}^{ - } $$ are always FM with ignorable variations under strains; however, the FM couplings between $$V_{\rm{Ga}}^{2 - } $$ could be strengthened by compressions. These varying trends of magnetic coupling under strains are interpreted by the band coupling models. Therefore, strain-engineering provides a route to manipulate and design high Curie temperature ferromagnetism derived and mediated by intrinsic defect for spintronic applications. [ABSTRACT FROM AUTHOR]