1,974 research outputs found
Flavonoids and Pectins
Pectins and flavonoids are two related groups of important secondary metabolites derived from plants. The interaction between pectins and flavonoids can affect their shelf-life stability, functionality, bioavailability, and bioaccessibility. In this chapter, we will concentrate on the current opinions on the flavonoids to understand how to classify this group of secondary metabolites, what biological and pharmacological activities they possess, and how to biosynthesize them in plants. We will then discuss the general strategies for the derivation of these small secondary compounds. The strategies comprise traditional plant extraction, chemical synthesis, and biosynthesis. We will also discuss the advantages and disadvantages of these three production strategies in the derivation of flavonoids and the future research directions in generating health-beneficial flavonoids using the biosynthetic strategy
Existence and stability of periodic solutions for a delayed prey–predator model with diffusion effects
Existence and stability of spatially periodic solutions for a delay prey-predator diffusion system are concerned in this work. We obtain that the system can generate the spatially nonhomogeneous periodic solutions when the diffusive rates are suitably small. This result demonstrates that the diffusion plays an important role on deriving the complex spatiotemporal dynamics. Meanwhile, the stability of the spatially periodic solutions is also studied. Finally, in order to verify our theoretical results, some numerical simulations are also included
Physics-Transfer Learning for Material Strength Screening
The strength of materials, like many problems in the natural sciences, spans
multiple length and time scales, and the solution has to balance accuracy and
performance. Peierls stress is one of the central concepts in crystal
plasticity that measures the strength through the resistance of a dislocation
to plastic flow. The determination of Peierls stress involves a multiscale
nature depending on both elastic lattice responses and the energy landscape of
crystal slips. Material screening by strength via the Peierls stress from
first-principles calculations is computationally intractable for the nonlocal
characteristics of dislocations, and not included in the state-of-the-art
computational material databases. In this work, we propose a physics-transfer
framework to learn the physics of crystal plasticity from empirical atomistic
simulations and then predict the Peierls stress from chemically accurate
density functional theory-based calculations of material parameters. Notably,
the strengths of single-crystalline metals can be predicted from a few
single-point calculations for the deformed lattice and on the {\gamma} surface,
allowing efficient, high-throughput screening for material discovery.
Uncertainty quantification is carried out to assess the accuracy of models and
sources of errors, showing reduced physical and system uncertainties in the
predictions by elevating the fidelity of training models. This physics-transfer
framework can be generalized to other problems facing the accuracy-performance
dilemma, by harnessing the hierarchy of physics in the multiscale models of
materials science
Numerical Analysis Methods of Structural Fatigue and Fracture Problems
Fatigue and fracture problems, which lead to 95% of structural failure, have attracted much attention of engineers and researchers all over the world. Compared with experimental method, numerical simulation method based on empirical models shows its remarkable advantages in structure design because of less cost and higher efficiency. However, the application of numerical simulation method in fatigue lifetime prediction is restricted by low accuracy and poor applicability in some circumstances. Most numerical method is based on empirical models. This chapter first reviews various kinds of empirical models of fatigue and fracture problems, including some modifying methods of basic empirical models, which have been widely applied to fatigue lifetime prediction and indicated their advantages and disadvantages. Then, FEM is introduced as an important method to obtain stress intensity factor or crack growth route. At last, this chapter is finished with existing problems and current trends in fatigue lifetime prediction via numerical method
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