Monte Carlo Simulation for the Morphology and Kinetics of Spherulites and Shish-Kebabs in Isothermal Polymer Crystallization

Monte Carlo method is used to capture the evolution of spherulites and shish-kebabs and to predict the crystallization kinetics in isothermal polymer crystallization. Effects of nucleation density and growth rate of spherulites, nucleation density, and length growth rate of shish-kebabs, respectively, on crystallization are investigated. Results show that nucleation densities of both spherulites and shish-kebabs strongly affect crystallization rate as well as morphology. An increase in nucleation density of either spherulites or shish-kebabs leads to a quicker crystallization rate and a smaller average spherulite size. It is also shown that nucleation density of shish-kebabs has a stronger impact on crystallization rate. Growth rate of spherulites and length growth rate of shish-kebabs also have significant effect on crystallization rate and morphology. An increase in growth rate of spherulites or length growth rate of shish-kebabs also speeds up the crystallization rate; additionally, a decrease in growth rate of spherulites or an increase in length growth rate of shish-kebabs results in a more highly anisotropic shish-kebab structure and a smaller average size of spherulites. Results also show that the effect of growth rate of spherulites is more important than the effect of length growth rate of shish-kebabs on crystallization

A class of self-affine tiles in Rd\mathbb{R}^d that are dd-dimensional tame balls

We study a family of self-affine tiles in $\mathbb{R}^d$ ($d\ge2$) with noncollinear digit sets, which naturally generalizes a class studied originally by Deng and Lau in $\mathbb{R}^2$ and its extension to \mathbb{R}^3} by the authors. By using Brouwer's invariance of domain theorem, along with a tool which we call horizontal distance, we obtain necessary and sufficient conditions for the tiles to be $d$-dimensional tame balls. This answers positively the conjecture in an earlier paper by the authors stating that a member in a certain class of self-affine tiles is homeomorphic to a $d$-dimensional ball if and only if its interior is connected.Comment: 56 pages, 17 figure

Expression analysis of OsbZIP transcription factors in resistance response by the rice blast resistance gene Pi36-mediated

Plant basic leucine zipper (bZIP) proteins play an essential role in the genes expression and regulation in higher plants. They have been shown to regulate diverse plant specific phenomena, including germination, floral induction and development, seed maturation, photomorphogenesis, biotic and abiotic stresses. Resistance response mediated by the rice blast resistance gene Pi36 is a typical signal transduction, in which 12 OsbZIP genes were differentially expressed by microarray analyses. To understand the potential function of OsbZIP genes during the defense responses against rice blast, the expression analysis of these OsbZIP genes, in response to the blast fungus inoculation and the related defense signal molecules induction, were further conducted using real-time fluorescent quantitative polymerase chain reaction (PCR) technique. Our data indicates that among the 12 OsbZIP genes, the expression level eight tested genes were differentially regulated and maintained to 96 h points post inoculation in rice resistant and susceptible cultivars during Magnaporthe oryzae infection, and all of them were also significantly up-regulated by one or several kinds of exogenous plant hormones stresses. Although, these genes were induced only at early time points (1 to 24 h); it is evident that the OsbZIP genes may be involved in different signaling pathway, and play potential important functions in the defense response to rice blast.Keywords: OsbZIP transcription factors, rice blast, resistance response, plant hormones stresses.African Journal of Biotechnology Vol. 12(34), pp. 5294-530

Lightweight conductive graphene/thermoplastic polyurethane foams with ultrahigh compressibility for piezoresistive sensing

Lightweight conductive porous graphene/thermoplastic polyurethane (TPU) foams with ultrahigh compressibility were successfully fabricated by using the thermal induced phase separation (TISP) technique. The density and porosity of the foams were calculated to be about 0.11 g cm−3 and 90% owing to the porous structure. Compared with pure TPU foams, the addition of graphene could effectively increase the thickness of the cell wall and hinder the formation of small holes, leading to a robust porous structure with excellent compression property. Meanwhile, the cell walls with small holes and a dendritic structure were observed due to the flexibility of graphene, endowing the foam with special positive piezoresistive behaviors and peculiar response patterns with a deflection point during the cyclic compression. This could effectively enhance the identifiability of external compression strain when used as piezoresistive sensors. In addition, larger compression sensitivity was achieved at a higher compression rate. Due to high porosity and good elasticity of TPU, the conductive foams demonstrated good compressibility and stable piezoresistive sensing signals at a strain of up to 90%. During the cyclic piezoresistive sensing test under different compression strains, the conductive foam exhibited good recoverability and reproducibility after the stabilization of cyclic loading. All these suggest that the fabricated conductive foam possesses great potential to be used as lightweight, flexible, highly sensitive, and stable piezoresistive sensors

Structural Reliability Based Dynamic Positioning of Turret-Moored FPSOs in Extreme Seas

FPSO is widely used during the deep-sea oil and gas exploration operations, for which it is an effective way to keep their position by means of positioning mooring (PM) technology to ensure the long-term reliability of operations, even in extreme seas. Here, a kind of dynamic positioning (DP) controller in terms of structural reliability is presented for the single-point turret-moored FPSOs. Firstly, the mathematical model of the moored FPSO in terms of kinematics and dynamics is established. Secondly, the catenary method is applied to analyze the mooring line dynamics, and mathematical model of one single mooring line is set up based on the catenary equation. Thereafter, mathematical model for the whole turret mooring system is established. Thirdly, a structural reliability index is defined to evaluate the breaking strength of each mooring line. At the same time, control constraints are also considered to design a state feedback controller using the backstepping technique. Finally, a series of simulation tests are carried out for a certain turret-moored FPSO with eight mooring lines. It is shown in the simulation results that the moored FPSO can keep its position well in extreme seas. Besides, the FPSO mooring line tension is reduced effectively to ensure mooring lines safety to a large extent in harsh sea environment

Present and future of functionalized Cu current collectors for stabilizing lithium metal anodes

Li metal has been recognized as the most promising anode materials for next-generation high-energy-density batteries, however, the inherent issues of dendrite growth and huge volume fluctuations upon Li plating/stripping normally result in fast capacity fading and safety concerns. Functionalized Cu current collectors have so far exhibited significant regulatory effects on stabilizing Li metal anodes (LMAs), and hold a great practical potential owing to their easy fabrication, low-cost and good compatibility with the existing battery technology. In this review, a comprehensive overview of Cu-based current collectors, including planar modified Cu foil, 3D architectured Cu foil and nanostructured 3D Cu substrates, for Li metal batteries is provided. Particularly, the design principles and strategies of functionalized Cu current collectors associated with their functionalities in optimizing Li plating/stripping behaviors are discussed. Finally, the critical issues where there is incomplete understanding and the future research directions of Cu current collectors in practical LMAs are also prospected. This review may shed light on the critical understanding of current collector engineering for high-energy-density Li metal batteries

Cobalt-based electrode materials for sodium-ion batteries

The demand for grid-scale energy storage systems has rapidly grown over recent years, to meet the requirements of structural innovation within the energy industry. Due to their inexpensive manufacturing and operating costs, and the similar electrochemical mechanism with the well-established lithium-ion batteries (LIBs), sodium ion batteries (SIBs) have been considered as an attractive candidate for grid-scale energy storage systems. A variety of cobalt-based cathode and anode materials, including cobalt oxides, cobalt chalcogenides and layered sodium cobaltates, have been synthesized and evaluated for sodium storage within the academic literature. In this article, we present a comprehensive review of the recent progress with cobalt-based electrodes (both as an anode and cathode material) used in SIBs. In detail, the electrochemical mechanisms, advantages and disadvantages, the relationship between crystalline structure and electrochemical performance and strategies to enhance the overall electrochemical performance of cobalt-based cathode and anode materials are discussed. Up to now, some cathode materials have already reached a high energy density, which is comparable to commercial LIBs. Furthermore, some cobalt-based materials can maintain a high Coulombic efficiency of over 99% with high reversible capacity during long cycling life. These encouraging results, allow such cobalt-based electrode materials to be a potential solution for grid-scale SIB systems

Vertically Aligned Silicon Carbide Nanowires/Boron Nitride Cellulose Aerogel Networks Enhanced Thermal Conductivity and Electromagnetic Absorbing of Epoxy Composites

With the innovation of microelectronics technology, the heat dissipation problem inside the device will face a severe test. In this work, cellulose aerogel (CA) with highly enhanced thermal conductivity (TC) in vertical planes were successfully obtained by constructing a vertically aligned silicon carbide nanowires (SiC NWs)/boron nitride (BN) network via the ice template assisted strategy. The unique network structure of SiC NWs connected to BN ensures that the TC of the composite in the vertical direction reaches 2.21 W/(m·K) at a low hybrid filler loading of 16.69 wt, which was increased by 890 compared to pure epoxy (EP). In addition, relying on unique porous network structure of CA, EP based composite also showed higher TC than other comparative samples in the horizontal direction. Meanwhile, the composite exhibits good electrically insulating with a volume electrical resistivity about 2.35×1011 Ω·cm, and displays excellent electromagnetic wave absorption performance with a minimum reflection loss of -21.5 dB and a wide effective absorption bandwidth (< -10 dB) from 8.8 to 11.6 GHz. Therefore, this work provides a new strategy for manufacturing polymer-based composites with excellent multifunctional performances in microelectronic packaging applications

Topological Properties of a Class of Self-Affine Tiles in \u3cem\u3eR\u3c/em\u3e\u3csup\u3e3\u3c/sup\u3e

We construct a class of connected self-affine tiles in R3 and prove that it contains a subclass of tiles that are homeomorphic to a unit ball in R3. Our construction is obtained by generalizing a two-dimensional one by Deng and Lau. The proof of ball-likeness is inspired by the construction of a homeomorphism from Alexander\u27s horned ball to a 3-ball