PpNAC187 Enhances Lignin Synthesis in ‘Whangkeumbae’ Pear (Pyrus pyrifolia) ‘Hard-End’ Fruit

A disorder in pears that is known as ‘hard-end’ fruit affects the appearance, edible quality, and market value of pear fruit. RNA-Seq was carried out on the calyx end of ‘Whangkeumbae’ pear fruit with and without the hard-end symptom to explore the mechanism underlying the formation of hard-end. The results indicated that the genes in the phenylpropanoid pathway affecting lignification were up-regulated in hard-end fruit. An analysis of differentially expressed genes (DEGs) identified three NAC transcription factors, and RT-qPCR analysis of PpNAC138, PpNAC186, and PpNAC187 confirmed that PpNAC187 gene expression was correlated with the hard-end disorder in pear fruit. A transient increase in PpNAC187 was observed in the calyx end of ‘Whangkeumbae’ fruit when they began to exhibit hard-end symptom. Concomitantly, the higher level of PpCCR and PpCOMT transcripts was observed, which are the key genes in lignin biosynthesis. Notably, lignin content in the stem and leaf tissues of transgenic tobacco overexpressing PpNAC187 was significantly higher than in the control plants that were transformed with an empty vector. Furthermore, transgenic tobacco overexpressing PpNAC187 had a larger number of xylem vessel elements. The results of this study confirmed that PpNAC187 functions in inducing lignification in pear fruit during the development of the hard-end disorder. View Full-Tex

Virtual Inertia Adaptive Control of a Doubly Fed Induction Generator (DFIG) Wind Power System with Hydrogen Energy Storage

This paper presents a doubly fed induction generator (DFIG) wind power system with hydrogen energy storage, with a focus on its virtual inertia adaptive control. Conventionally, a synchronous generator has a large inertia from its rotating rotor, and thus its kinetic energy can be used to damp out fluctuations from the grid. However, DFIGs do not provide such a mechanism as their rotor is disconnected with the power grid, owing to the use of back-to-back power converters between the two. In this paper, a hydrogen energy storage system is utilized to provide a virtual inertia so as to dampen the disturbances and support the grid’s stability. An analytical model is developed based on experimental data and test results show that: (1) the proposed method is effective in supporting the grid frequency; (2) the maximum power point tracking is achieved by implementing this proposed system; and, (3) the DFIG efficiency is improved. The developed system is technically viable and can be applied to medium and large wind power systems. The hydrogen energy storage is a clean and environmental-friendly technology, and can increase the renewable energy penetration in the power network

In Situ Characterization of 17-4PH Stainless Steel by Small-Angle Neutron Scattering

17-4PH martensitic steel is usually used as valve stems in nuclear power plants and it suffers from thermal aging embrittlement due to long-time service in a high-temperature and high-pressure environment. Here, we characterized the evolution of microstructures at the nano-scale in 17-4PH steel by in situ small-angle neutron scattering (SANS) with a thermo-mechanically coupled loading device. The device could set different temperatures and tensile so that an in situ SANS experiment could dynamically characterize the process of nanoscale structural changes. The results showed that with increasing thermal aging time, the ε-Cu phase precipitates and grows as the temperature is 475 °C and 590 °C, and the ε-Cu phase is spherical at 475 °C but became elongated cylinders at 590 °C. Moreover, the loading stress could aid in the growth of the ε-Cu phase at 475 °C

Effect of carbon-coated Al2O3 powder on structure and properties of low-carbon MgO-C refractory composites

In this study, low-carbon MgO-C refractory composites with addition of uncoated (UA) and carbon-coated Al2O3 (CCA) powders were prepared. The effect of heat-treatment temperature on apparent porosity, cold modulus of rupture and thermal expansion was investigated. The results indicated that the CCA was present in the form of porous agglomerates of 400–800 µm in diameter in MgO-C matrix. The formation of spinel started at 1100 °C and 1250 °C in UA-MgO-C and CCA-MgO-C specimens, respectively. In the specimen CCA-MgOC, cyclic spinel was formed on the outer layer of CCA agglomerates, and the dense spinel layer hindered the diffusion of Mg(g) to the interior of the agglomerates, resulting in alumina residues at 1550 °C. The specimen CCA-MgO-C showed better mechanical properties and reduced porosity. Additionally, the average coefficient of thermal expansion of CCA-MgO-C was significantly lower than that of UA-MgO-C. Thus, CCA powder could improve the volume stability of the low-carbon MgO-C refractory composites

Singular Solutions Of Parabolic P-Laplacian With Absorption

We consider, for p ∈ (1, 2) and q \u3e 1, the p-Laplacian evolution equation with absorption ut = div(|∇u|p-2∇u)- uq in ℝn × (0,∞). We are interested in those solutions, which we call singular solutions, that are non-negative, non-trivial, continuous in ℝn × [0,∞) \ {(0, 0)}, and satisfy u(x, 0) = 0 for all x ≠ 0. We prove the following: (i) When q ≥ p-1 + p/n, there does not exist any such singular solution. (ii) When q \u3c p-1+p/n, there exists, for every c \u3e 0, a unique singular solution u = uc that satisfies ∫ℝn u(·, t) → c as t ↘ 0. Also, uc ↗ u∞ as c ↗ ∞, where u∞ is a singular solution that satisfies ∫ℝn u∞(·, t)→∞ as t ↘ 0. Furthermore, any singular solution is either u∞ or u c for some finite positive c. © 2007 American Mathematical Society

Classification Of Singular Solutions Of Porous Media Equations With Absorption

We consider, for m ∈ (0, 1) and q \u3e 1, the porous media equation with absorption ut = Δum - uq in ℝn × (0, ∞). We are interested in those solutions, which we call singular solutions, that are non-negative, non-trivial, continuous in ℝn × (0, ∞)\{(0,0)}, and satisfy u(x,0) = 0 for all x ≠ 0. We prove the following results. When q ≥ m + 2/n, there does not exist any such singular solution. When q \u3c m + 2/n, there exists, for every c \u3e 0, a unique singular solution u = u(c), called the fundamental solution with initial mass c, which satisfies ∫ ℝnu(.,t) → c as t ↘ 0. Also, there exists a unique singular solution u = u∞, called the very singular solution, which satisfies ∫ℝn u∞(.,t) → ∞ as ↘ 0. In addition, any singular solution is either u∞ or u(c) for some finite positive c, u(c1) \u3c u (c2) when c1 \u3c c2, and u(c) ↗ u∞ as c↗ ∞. Furthermore, u ∞ is self-similar in the sense that u∞(x,t) = t-αw(|x|t-αβ) for α = 1/(q - 1), β= 1/2(q - m), and some smooth function w defined on [0, ∞), so that ∫ℝn unβ∞(.,t) is a finite positive constant independent of t \u3e 0. © 2005 The Royal Society of Edinburgh

A Strongly Coupled Predator-Prey System With Non-Monotonic Functional Response

The predator-prey system with non-monotonic functional response is an interesting field of theoretical study. In this paper we consider a strongly coupled partial differential equation model with a non-monotonic functional response-a Holling type-IV function in a bounded domain with no flux boundary condition. We prove a number of existence and non-existence results concerning non-constant steady states (patterns) of the underlying system. In particular, we demonstrate that cross-diffusion can create patterns when the corresponding model without cross-diffusion fails. © 2006 Elsevier Ltd. All rights reserved