Bifurcated Polarization Rotation in Bismuth‐Based Piezoelectrics

ABO₃ perovskite‐type solid solutions display a large variety of structural and physical properties, which can be tuned by chemical composition or external parameters such as temperature, pressure, strain, electric, or magnetic fields. Some solid solutions show remarkably enhanced physical properties including colossal magnetoresistance or giant piezoelectricity. It has been recognized that structural distortions, competing on the local level, are key to understanding and tuning these remarkable properties, yet, it remains a challenge to experimentally observe such local structural details. Here, from neutron pair‐distribution analysis, a temperature‐dependent 3D atomic‐level model of the lead‐free piezoelectric perovskite Na_0.5Bi_0.5TiO₃ (NBT) is reported. The statistical analysis of this model shows how local distortions compete, how this competition develops with temperature, and, in particular, how different polar displacements of Bi³⁺ cations coexist as a bifurcated polarization, highlighting the interest of Bi‐based materials in the search for new lead‐free piezoelectrics.     

Facile synthesis of reduced graphene oxide/MWNTs nanocomposite supercapacitor materials tested as electrophoretically deposited films on glassy carbon electrodes

This paper reports on a facile synthesis method for reduced graphene oxide (rGO)/multi-walled carbon nanotubes (MWNTs) nanocomposites. The initial step involves the use of graphene oxide to disperse the MWNTs, with subsequent reduction of the resultant graphene oxide/MWNTs composites using l-ascorbic acid (LAA) as a mild reductant. Reduction by LAA preserves the interaction between the rGO sheets and MWNTs. The dispersion-containing rGO/MWNTs composites was characterized and electrophoretically deposited anodically onto glassy carbon electrodes to form high surface area films for capacitance testing. Pseudo capacitance peaks were observed in the rGO/MWNTs composite electrodes, resulting in superior performance with capacitance values up to 134.3 F g^?1 recorded. This capacitance value is higher than those observed for LAA-reduced GO (LAA-rGO) (63.5 F g^?1), electrochemically reduced GO (EC-rGO) (27.6 F g^?1), or electrochemically reduced GO/MWNTs (EC-rGO/MWNTs) (98.4 F g^?1)-based electrodes.     

Obtaining the kinetic function of depolymerization from evolving molecular weight distribution data–an inverse problem

Depolymerization of macromolecules is generally regarded as a first order process with a kinetic function that depends on the molecular weights of the fragmenting molecule and fragmentation products. This article describes a computation scheme for obtaining the kinetic function from observed molecular weight distribution (MWD) data. The integro‐differential equation used by most investigators to compute MWD with some assumed kinetic function is reformulated as an inverse problem in which the kinetic function is treated as the unknown to be extracted from evolving MWD data. A numerical procedure based on two consecutive applications of Tikhonov regularization is developed to solve this inverse problem. It gives the kinetic function as the solution of a set of linear algebraic equations. Implementation of this procedure is described in full and its performance is assessed by applying it to simulated MWD data. A number of issues associated with discretization and regularization are discussed. © 2012 American Institute of Chemical Engineers AIChE J, 59: 912–922, 2013     

Study of Binary Interactions Involving Polyethylene and Hydrocarbons by the Melting Point Depression Method

The thermodynamic interaction parameter, χ_φ, for a low-density polyethylene in p-xylene, ethylbenzene, and n-octane has been determined over a range of segment fraction, φ₂, from 0.2 to 0.7 using the melting point depression method. Taking advantage of a unique feature of polyethylene, a new procedure has been proposed for evaluating the equilibrium melting points from data obtained by differential scanning calorimetry. The experimental χ_φ-φ₂ relations conform well to the recent equation-of-state theory of polymer solutions. The exchange parameters of the model X ₁₂ and Q ₁₂ are accessible by a nonlinear leastsquares algorithm. Apparently, the observed small values of χ_φ for the foregoing dispersion force interactions are originated from the negative contribution of the effective interaction energy as concluded by the present findings.     

Mechanical,Water Absorption and Dimensional Stability Studies of Kenaf Bast Fibre-Filled Poly(butylene succinate) Composites

The effects of fibre loadings (10?40 wt.%) on mechanical properties, water absorption and dimensional stability of poly(butylene succinate)-filled kenaf bast fibre composites were investigated. The flexural strength and modulus of the composites increased with increasing fibre loading, while the impact strength of the composites decreased with increasing fibre loading. The higher the KBF loading was the higher absorption rate, equilibrium moisture content and the poorer dimensional stability of the composites. The poor retention and recovery of the composites from effect of water absorption were reflected by the poor flexural properties of the wet and re-dried composites after exposed to 90 days' water immersion.     

The impact of copper contamination on the quality of the second wire bonding process using X-ray photoelectron spectroscopy method

A lot of wedge bonding failures were observed on the leadframe (LF) type A due to non-stick on lead (NSOL) during the second wire bonding process of TQFP package. The copper ion contamination from the plating process was identified as one of the key factors that attributed to the NSOL failures. Surface analyses were performed in terms of X-ray photoelectron spectroscopy on the surface of LF type A. It was found that as received silver-plated surface of the copper LF type A was contaminated by the copper. After the copper contamination was solved in the plating process, the design of experiment was implemented for the verification of the influence of copper contamination on the quality of the second bonding process. It was confirmed that copper contamination dramatically reduced the strength of wedge bonding. The wedge pull test showed that NSOL failures were not observed after the copper ion contamination in the plating process was well controlled.     

Study on property variation due to the interface between PZT and electrode

Abstract

The ferroelectric capacitors are fabricated using RuO₂/Pt electrode to examine the electrode effect on ferroelectric properties. PZT films are prepared by metalorganic decomposition (MOD) on sputter deposited electrodes. In particular, inductively coupled plasma(ICP) etcher is used to minimize the etching damage. In addition, TiO₂ reaction barrier layer is also employed to retard the degradation of ferroelectric properties due to the reaction between a passivation layer and PZT film. The better hysteretic properties were obtained from Pt/RuO₂/PZT/RuO₂/Pt ferroelectric capacitors. The enhancement of ferroelectric properties is likely attributed to the modification in the microstructure of PZT film. The interfacial modification would be affected by the factors such as surface roughness, stress, and porosity of RuO₂ film. The result implies RuO₂/Pt would be a good electrode for a nonvolatile memory application.     

Fungi and mycotoxins in vineyards and grape products

Many fungi may occur on grapes during growth in the vineyard, but the main concern from the viewpoint of mycotoxin contamination is the black Aspergilli, Aspergillus carbonarius and A. niger. These fungi are capable of producing ochratoxin A (OA) which may contaminate grapes and grape products such as wine, grape juice and dried vine fruit. Understanding the ecology and physiology of the black Aspergilli can provide tools for management of OA at all stages of grape production and processing. In the vineyard, careful management of cultivation, irrigation and pruning can assist in minimising the levels of black Aspergilli in the soil, which in turn, can minimise contamination of grapes by these fungi. Minimising damage to grapes on the vine by the use of open vine canopies, grape varieties with resistance to rain damage and by the management of insect pests and fungal diseases (e.g., mildew, Botrytis bunch rot) can reduce the incidence of Aspergillus rot in mature berries. The risk of OA in table grapes can be minimised by careful visual inspection to avoid damaged and discoloured berries. In wine, harvesting grapes with minimal damage, rapid processing and good sanitation practices in the winery assist in minimising OA. During vinification, pressing of grapes, and clarification steps which remove grape solids, grape proteins and spent yeast can also remove a significant proportion of OA. For dried vine fruit production, avoiding berry damage, rapid drying, and final cleaning and sorting to remove dark berries can reduce overall OA levels in finished products.     

Site-Specific and Multiple Fluorogenic Metabolic Glycan Labeling and Glycoproteomic Profiling in Live Cells

Multicolor labeling for monitoring the intracellular localization of the same target type in the native environment using chemical fluorescent dyes is a challenging task. This approach requires both bioorthogonal and biocompatible ligations with an excellent fluorescence signal-to-noise ratio. Here, we present a metabolic glycan labeling technique that uses homemade fluorogenic dyes to investigate glycosylation patterns in live cells. These dyes allowed us to demonstrate rapid and efficient simultaneous multilabeling of glycoconjugates with minimum fluorescence noise. Our results demonstrate that this approach is capable of not only probing sialylation and GlcNAcylation in cells but also specifically labeling the cell-surface and intracellular sialylated glycoconjugates in live cells. In particular, we performed site-specific dual-channel fluorescence imaging of extra and intracellular sialylated glycans in HeLa and PC9 cancer cells as well as identified fluorescently labeled sialylated glycoproteins and glycans by a direct enrichment approach combined with an MS-based proteomic analysis in the same experiment. In conclusion, this study provides multilabeling tools in cellular systems for simultaneous site-specific glycan imaging and glycoproteomic analysis to study potential cancer- and disease-associated glycoconjugates.     

Investigation of failure mechanisms in GFRP sandwich structures with face sheet wrinkle defects used for wind turbine blades

Wrinkle defects can be formed during the production of wind turbine blades consisting of composite monolithic and sandwich laminates. Earlier studies have shown that the in-plane compressive strength of a sandwich panel with wrinkle defects may decrease dramatically. This study focuses on the failure modes of sandwich specimens consisting of thick GFRP face sheets with a wrinkle defect and a balsa wood core subjected to in-plane compression loading. Three distinct modes of failure were found, and the strain distributions leading up to these failures were established by use of digital image correlation (DIC). Finite element analyses were subsequently conducted to model the response of the test specimens prior to failure, and generally a very good agreement was found with the DIC measurements, although slight differences between the predicted and measured strain fields were observed in the local strain values around the wrinkle defect. The Northwestern University (NU) failure criterion was applied to predict failure initiation, and a good correlation with the experimental observations was achieved.