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Moringa oleifera is a rich source of antioxidants and a promising feed for livestock, due to significant amounts of protein, vitamins, carotenoids and polyphenols, and negligible amounts of anti-nutritional factors. The current study tested whether ensiling would preserve the antioxidant capacity of M. oleifera plants, and assessed whether Moringa silage, fed as a substitute for maize silage, would confer health-promoting traits and affect milk production in dairy cows. To this end, hand-harvested M. oleifera plants were ensiled, with or without molasses and inoculants, in anaerobic jars at room temperature (25 °C) for 37 days. At the end of the storage period the silages were analysed for pH, lactic acid and acetic acid concentrations, aerobic stability, antioxidant capacity, polyphenols and protein content, and tocopherols and carotenoids concentrations. Moringa silages exhibited higher antioxidant capacity compared with fresh and dried Moringa plants, not related to polyphenol content but presumably attributed to accumulation of amino acids and low molecular weight peptides. Based on these findings, a large-scale ensiling protocol was implemented, followed by a feeding trial for dairy cows, in which Moringa silage replaced 263 g maize silage/kg in the diet. Cows fed Moringa silage had higher milk yield and antioxidant capacity and lower milk somatic cell counts compared with controls, during some stages of lactation. These findings imply that ensiling M. oleifera is an appropriate practice by which health and production of dairy cows can be improved.
A direct comparison is made between the dynamics obtained by weakly nonlinear theory and full numerical simulations for Langmuir circulations in a density-stratified layer having finite depth and infinite horizontal extent. In one limit, the mathematical formulation employed is analogous to that of double-diffusion phenonema with the flux of one diffusing quantity fixed at the boundaries of the layer. These problems have multiple bifurcation points, but their amplitude equations have no intrinsic (nonlinear) degeneracies, in contrast to ‘standard’ double-diffusion problems. The symmetry of the physical problem implies invariance with respect to translations and reflections in the horizontal direction normal to the applied wind stress (so-called O(2) symmetry). A multiple bifurcation at a double-zero point serves as an organizing centre for dynamics over a wide range of parameter values. This double zero, or Takens–Bogdanov, bifurcation leads to doubly periodic motions manifested as modulated travelling waves. Other multiple bifurcation points appear as double-Hopf bifurcations. It is believed that this paper gives the first quantitative comparison of dynamics of double-diffusive type predicted by rationally derived amplitude equations and by full nonlinear partial differential equations. The implications for physically observable natural phenomena are discussed. This problem has been treated previously, but the earlier numerical treatment is in error, and is corrected here. When the Stokes drift gradient due to surface waves is not constant, the analogy with the common formulations of double-diffusion problems is compromised. Our bifurcation analyses are extended here to include the case of exponentially decaying Stokes drift gradient.
Two-dimensional Langmuir circulation in a layer of stably stratified water and the mathematically analogous problem of double-diffusive convection are studied with mixed boundary conditions. When the Biot numbers that occur in the mechanical boundary conditions are small and the destabilizing factors are large enough, the system will be unstable to perturbations of large horizontal length. The instability may be either direct or oscillatory depending on the control parameters. Evolution equations are derived here to account for both cases and for the transition between them. These evolution equations are not limited to small disturbances of the nonconvective basic velocity and temperature fields, provided the spatial variations in the horizontal remain small. The direct bifurcation may be supercritical or subcritical, while in the case of oscillatory motions, stable finite-amplitude travelling waves emerge. At the transition, travelling waves, standing waves, and modulated travelling waves all are stable in sub-regimes.
Two-dimensional motions generated by Langmuir circulation instability of stratified layers of water of finite depth are studied under a simplifying assumption making it mathematically analogous to double-diffusive thermosolutal convection with constant solute concentration and constant heat flux at the boundaries. The nature of possible motions is mapped over a significant region in (S, R) parameter space, where S and R are parameters measuring, respectively, the stabilizing and destabilizing agencies in the problem. In the Langmuir circulation problem R measures the effects of wind and surface wave action, and S measures the stabilizing effect of buoyancy: in the thermosolutal problem, R measures the destabilizing effects of heating, while S measures the stabilizing effect of solute concentration. Effects of lateral boundary or symmetry conditions are found to be crucial in determining the qualitative behaviour. Complex temporal behaviour, including intermittently chaotic flows, are found under suitably constrained (no flux) lateral conditions but are unstable and not realized when these constraints are relaxed and replaced by periodic lateral conditions. Multiple steady states also arise, with those found under constrained lateral conditions losing stability either to travelling waves, or to other steady states when the lateral boundary conditions are relaxed. In some regions of the parameter space, multiple stable nonlinear motions have been found under periodic boundary conditions. The multiple stable states may either be coexisting travelling waves and steady states (different from those found under the constrained lateral conditions). The existence of robust travelling waves may explain some field observations of laterally drifting windrows associated with Langmuir circulations.
The stability of forward and rearward slug flows due to the motion of a body through a perfectly conducting liquid with an embedded magnetic field aligned to the direction of motion is studied. It is found that, for sub-Alfvénic flows, the forward and rearward slug flows predicted by Stewartson, Leibovich and Ludford are stable. For super-Alfvénic flows, if at all meaningful, both the forward and the rearward slug flows are stable also.
We consider the spatio-temporal evolution of patterns in the marginally unstable Ekman layer driven by an applied shear stress. Both the normal and tangential components of the Earth's angular velocity are included in a tangent plane approximation of the oceanic boundary layer at latitude $\lambda$. The fluid motion in a layer of finite depth as well as one of infinite depth is considered. The linear instability in the infinite depth case is known to depend on the direction of the applied stress for $\lambda \ne 90\dg$, but this dependence is weak for the stress-driven Ekman layer. By contrast, the weakly nonlinear motion exhibits for finite and infinite depths qualitatively different dynamics for different stress directions.
The problem is treated by the method of multiple scales. In the case of finite depth, this leads to the Davey–Hocking–Stewartson equation, an amplitude equation of complex Ginzburg–Landau type coupled to a Poisson equation. In the case of infinite depth, it leads to the anisotropic complex Ginzburg–Landau equation for the amplitude of the roll motion. Motions in both finite and infinite depth basins are explored by numerical simulation, and are shown to lead to chaotic dynamics for the modulation envelope in most cases. The statistics and the nature of the patterns produced in this motion are discussed.
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