Ultra-fast synthesis and properties of high dielectric constant calcium copper titanate (CCT) ceramics synthesized by electric discharge assisted mechanical milling in oxygen and argon plasma

Synthesis of high dielectric constant calcium copper titanate (CCT) was carried out using the novel approach of electric discharge assisted mechanical milling (EDAMM) under oxygen and argon atmospheres. X-ray diffraction revealed complex structural changes associated with processing for different periods and under the different atmosphere. Morphology and grain size were investigated by field emission scanning electron microscopy and transmission electron microscopy. CCT was found to form directly by EDAMM processing in oxygen, while EDAMM processing in argon resulted in formation of intermediated nanostructure phases. Both the oxygen and argon EDAMM processed samples were sintered in air at 900 °C, and coarsen to produce CCT microstructures. The oxygen processed samples were found to have the larger grain size. Dielectric properties of the prepared samples were investigated using an LCR meter. The highest reported dielectric constant of CaCu₃Ti₄O₁₂ (CCT) was found for the oxygen EDAMM processed and annealed sample, a dielectric constant of 48,000 measured at room temperature. This is the highest value ever reported for CCT materials which are not in nano-powder form.     

Antioxidative capacity of rhizome extract and rhizome knot extract of edible lotus (Nelumbo nuficera)

Extracts from rhizomes (Lotus roots) knot (LRK) and whole rhizomes (LR) were investigated for their antioxidative capacity in comparison with commonly used antioxidants from plant material. Radical scavenging activity was measured spectrophotometrically using the stable radicals 1-diphenyl-2-picrylhydrazyl and 2,2′-azino(3-ethylbenzothioazolino-6-sulfonate), and measured by electron spin resonance (ESR) trapping of the transient carbon-centered 1-hydroxyethyl radical (generated in a Fenton-type reaction). Efficiencies as chain-breaking antioxidants were evaluated by electrochemical measurement of oxygen consumption rate in a peroxidating methyl linoleate emulsion. LRK exhibited high antioxidative capacity, as measured by each of four different methods. LR, however, only showed a significantly high scavenging activity for small carbon-centered radicals, as measured by the ESR method. Total phenol content in the plant extract correlated with the antioxidant capacity, except for the scavenging of carbon-centered radical. Lotus rhizomes knot, as a waste from food production, will be a potential material for extracting antioxidants.     

蛋白基体系美拉德反应在荔枝皮原花青素作用下的抑制研究

本试验分别研究了在乳清蛋白-葡萄糖和牛血清白蛋白-葡萄糖模拟生理体系中,荔枝果皮原花青素(Litchi pericarp procyanidins,LPPC)对美拉德反应和晚期糖基化终末产物(advanced glycation end products,AGEs)的抑制作用,以荧光性AGEs的强度为表征依据。结果表明,在乳清蛋白-葡萄糖模拟体系中孵育35 d时,LPPC对AGEs的抑制效果最强,达60.21±1.34%。LPPC浓度为1 mg/m L时,相对抑制率最大可达85.33±9.02%(显著高于维生素C(Vc),p0.05)。在牛血清白蛋白-葡萄糖体系中,孵育35 d后LPPC对AGEs的相对抑制率最高达70.01±1.32%,且与LPPC浓度呈现正相关。当LPPC浓度为0.5 mg/m L时,抑制率最大为95.46±10.12%(显著高于氨基胍(AG),p0.05)。不同p H值下蛋白质的稳定性研究表明,乳清蛋白在与LPPC长期孵育后,其热稳定性明显降低,再次提示了LPPC对美拉德反应的抑制作用。LPPC可作为一种天然的食品基质的AGEs抑制剂深度开发。     

Review on the natural co-occurrence of AFB1 and FB1 in maize and the combined toxicity of AFB1 and FB1

Mycotoxins rarely occur individually in foodstuffs and are considered a food safety risk, particularly for highly consumed foods like maize. Aflatoxin B1 (AFB1) and fumonisin B1 (FB1) are two of the toxicologically most relevant mycotoxins occurring in maize. Their co-occurrence in field and stored maize is described in this review, and the highest co-occurrence rate is observed in stored maize. In all reviewed studies, fumonisin B1 levels exceed aflatoxin B1 levels and in some cases even by up to a thousand fold. Co-occurrence and subsequently combined exposure of AFB1 and FB1 is of public health concern given that both in-vivo and in-vitro scientific evidence exists that various toxicological effects caused by combined exposure occur. In the majority of the studies reviewed in this paper the data suggest a modulation of the toxic effects of aflatoxin B1 and fumonisin B1 ranging from increased carcinogenicity, immunotoxicity and decreased growth in various animal species and cell lines. The emerging scientific data indicating the modulatory effects of combined exposure to aflatoxin B1 and fumonisin B1 is a sound basis for further investigation of the effects of combined exposure and the subsequent human health risk.     

Investigation of AlN ceramic anisotropic deformation behavior during scratching

To explore the anisotropic deformation behavior of aluminum nitride ceramic during processing, ramp and constant load scratch experiments were conducted with Vickers indenter. Characteristics of deformation anisotropy were observed in ramp-load scratch with differences found in the directions of pile-ups, slip lines and cracks produced by grains with various orientations. Constant-load scratches were conducted to explore the anisotropic deformation behavior in plastic stage. Obvious differences were found in scratch pile-up height and residual depth of grains with different orientations. As the grain orientation Euler angle changes from the basal to the two prism surfaces, the residual depth of the scratch gradually increases. Molecular dynamics simulation was performed to disclose the mechanisms of anisotropic dislocation and deformation during scratching. The activation of the slip system for different grain orientations was calculated by a scratch Schmid factor model which was verified by the observation of pile-ups and slip lines around the scratches.     

Dopamine-mimetic-coated polyamidoamine-functionalized Fe3O4 nanoparticles for safe and efficient gene delivery

Fe₃O₄ nanoparticles (NPs) are widely used in the construction of drug and gene delivery vectors because of their particular physicochemical properties. Surface modification can not only reduce the cytotoxicity of Fe₃O₄, but also further improve the biocompatibility and delivery efficiency. In this work, firstly, polydopamine (PDA)-coated Fe₃O₄ NPs (named Fe₃O₄@PDA) were prepared by using the self-polymerization characteristics of dopamine in alkaline environment. Then, polyamidoamine (PAMAM) was modified by the Michael addition reaction to prepare water-soluble core‒shell magnetic NPs of Fe₃O₄@PDA@PAMAM, and its potential as gene vector was further evaluated. The results revealed that Fe₃O₄@PDA@PAMAM had the ability to condense and protect DNA, and showed lower cytotoxicity, higher cell uptake and transfection efficiency than those of PAMAM. It has the potential to become a magnetic targeted gene vector for further study.     

Strain rate sensitivity of a high strain rate superplastic TiNp/2014 Al composite

The effects of deformation temperature and strain in hot rolling deformation on strain rate sensitivity of the TiN_p/2014 Al composite were studied by tensile tests conducted out at 773, 798, 818 and 838 K with the strain rates from 1.7 ×10^?3 to 1.7 × 10⁰ s^?1. It is shown that the curves of m value of the TiN_p/2014Al composite deformed at different temperatures can be divided into two stages with the variation of strain rate, and the critical strain rates are 10^?1 s^?1. The optimum deformation temperature of the TiN_p/2014 Al composite is near incipient melting temperature of 816 K and the optimum strain rate is a little higher than the critical strain rate. The effect of deformation temperature on strain rate sensitivity is relative to liquid phase helper accommodation. The effect of strain in hot rolling deformation on strain rate sensitivity attributes to change of microstructure and deformation mechanism.