Supercritical anti-solvent micronization of chromatography purified marigold lutein using hexane and ethyl acetate solvent mixture

This work aims to study supercritical anti-solvent micronization of marigold derived purified lutein that was dissolved in the mixture of hexane and ethyl acetate (70:30 v/v), the solvent used as the mobile phase for chromatographic purification. The results show significant effect of pressure on the morphology of micronized lutein particles. The increase in lutein initial concentration from 1.5 mg/ml to 3.2 mg/ml and the increase in SC-CO₂ flow rate from 15 ml/min to 25 ml/min show no significant effects on the morphology of lutein particles. However, the reduction of mean particle size from about 2 μm to 0.8 μm was observed by increasing SC-CO₂ flow rate. The X-ray diffraction patterns of the micronized lutein particles show apparent amorphous nature, while the Fourier transform infrared spectroscopy results show that no chemical structural changes occurred. Moreover, the solubility of the micronized lutein particles in aqueous solution was found to increase significantly from being almost insoluble to having approximately 20% solubility     

Alcoholic fermentation effects on malt spiked with trichothecenes

Malt contaminated with DON and T-2 toxin at levels of between 0 and 1000 ng/g was used for fermentation on a laboratorial scale in order to evaluate the decontamination caused by alcoholic fermentation using Saccharomyces cerevisiae. Fermentation was carried out over a period of 120 h at 14 °C and a reduction in the levels of contamination was detected by GC. Forty one percent of the initial quantity of DON and T-2 toxin contamination was passed on to the final liquid portion. Six percent of the initial contamination was detected in the wort, which signifies a total decontamination of 53% of DON and T-2 toxin, taking into account both the wort and the filtered sample.     

Protein interactions in milk protein concentrate powders

Solutions (5%, w/w, pH 6.9), made from six different pilot-plant milk protein concentrate (MPC) powders, were centrifuged (700 g for 10 min at 20 °C) to isolate the insoluble material. The sediment (insoluble material) was characterized using one-dimensional (1D) and two-dimensional (2D) sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and transmission electron microscopy (TEM). The levels of solubility in MPC powders varied between 32% and 98%. The TEM results showed that the insoluble material consisted of large particles (∼100 μm) where the casein micelles are fused together by some form of protein–protein interactions. The 1D PAGE results showed that the amounts of insoluble material in MPC powders increased with storage time at elevated temperatures. This material consisted predominantly of α- and β-caseins. This material was formed largely by weak non-covalent (hydrophobic) protein–protein interactions that were dissociable under SDS-PAGE conditions. The 2D PAGE results demonstrated that the disulphide-linked protein aggregates present in MPC powders consisted of κ-casein, β-lactoglobulin and some α_s2-casein, and not all of this material was sedimented. These aggregates were not considered to play a major role in the formation of the insoluble material.     

磁性拓扑绝缘体中的量子反常霍尔效应

量子反常霍尔效应是一种不需要外磁场、具有手性边缘态的量子化霍尔效应,可以用于构建其他新奇量子态和发展未来低功耗电子学器件等.该全新的量子效应于2012年首先由中国科学家在五层Cr掺杂的(Bi,Sb)₂Te₃拓扑绝缘体薄膜中实现.在过去七年间,经过大家的努力,其观测温度从最初的30 mK已经提高到2 K左右,进一步提高量子反常霍尔效应的观测温度是目前该领域主要的研究方向之一,是许多拓扑量子效应走向应用的关键因素.本文主要总结了量子反常霍尔效应研究的实验进展,特别在提高其观测温度方面的研究进展.文章包括四个部分:前两个部分分别介绍磁性掺杂和磁性近邻拓扑绝缘体体系中量子反常霍尔效应研究,第三部分介绍最新发现的内禀磁性拓扑绝缘体体系,最后一部分对设计和构造高温量子反常霍尔效应系统的原理和路线图给出一些建议和展望.     

The lethal giant larvae Gene in Tribolium castaneum: Molecular Properties and Roles in Larval and Pupal Development as Revealed by RNA Interference

We identified and characterized the TcLgl gene putatively encoding lethal giant larvae (Lgl) protein from the red flour beetle (Tribolium castaneum). Analyses of developmental stage and tissue-specific expression patterns revealed that TcLgl was constitutively expressed. To examine the role of TcLgl in insect development, RNA interference was performed in early (1-day) larvae, late (20-day) larvae, and early (1-day) pupae. The early larvae injected with double-stranded RNA of TcLgl (dsTcLgl) at 100, 200, and 400 ng/larva failed to pupate, and 100% mortality was achieved within 20 days after the injection or before the pupation. The late larvae injected with dsTcLgl at these doses reduced the pupation rates to only 50.3%, 36.0%, and 18.2%, respectively. The un-pupated larvae gradually died after one week, and visually unaffected pupae failed to emerge into adults and died during the pupal stage. Similarly, when early pupae were injected with dsTcLgl at these doses, the normal eclosion rates were reduced to only 22.5%, 18.0%, and 11.2%, respectively, on day 7 after the injection, and all the adults with abnormal eclosion died in two days after the eclosion. These results indicate that TcLgl plays an essential role in insect development, especially during their metamorphosis.     

工程管理专业模拟仿真教学问题与对策

工程管理专业的实践教学有利于将相关学科知识和管理技能联系起来,但传统的工地实习、沙盘等实践教学已不能满足社会需求。随着计算机和网络技术的发展,国内外部分高校正逐步利用计算机模拟和仿真教学手段,提升和优化实践教学质量。文章通过分析工程管理专业实践教学存在的问题,研究模拟和仿真教学现实情况,并对该专业模拟仿真教学提出建议。     

紫外分光光度法测定沉香药材中2-(2-苯乙基)色酮类化合物总含量!

建立了测定沉香药材中2-(2-苯乙基)色酮类化合物总含量的紫外分光光度法。结果表明,2-(2-苯乙基)色酮类化合物对照品溶液和沉香药材2-(2-苯乙基)色酮提取液在230nm波长下均有较强吸收,建立的方法重复性好,在5h内稳定性良好,加样回收率为101.24%(RSD=2.25%),具有操作简便、快速、准确度高、用样少的特点,可用于沉香药材中2-(2-苯乙基)色酮类化合物总含量的快速测定,以及对不同沉香药材进行品质评价。     

Supercritical carbon dioxide extraction of 2-acetyl-1-pyrroline from Pandanus amaryllifolius Roxb

A comparative evaluation of the extraction of 2-acetyl pyrroline (2-AP) from Pandanus amaryllifolius Roxb. using either solvent extraction (3:1 chloroform:methanol), Likens–Nickerson apparatus or supercritical fluid extraction (SFE) with carbon dioxide extraction was carried out. SFE at 450 bar pressure for 3 h at 60 °C, at a constant flow rate of 0.1 l min⁻¹ of CO₂, could extract 2-AP from P. amaryllifolius Roxb. in yields greater than those obtained by solvent extraction or Likens–Nickerson extraction. This extract could find novel applications in food flavouring.     

Chemical and quality traits of ‘Olinda’ and ‘Campbell’ oranges after heat treatment at 44 or 46 °C for fruit fly disinfestation

The chemical and quality characteristics of ‘Olinda’ and ‘Campbell’ oranges (nucellar budlines from Valencia late cultivar) were evaluated after exposure to a fruit core temperature of 44 °C and held at 44 °C for 100 min or 46 °C and held at 46 °C for 50 min, subsequent storage at 6 °C for 2 weeks and an additional week of simulated marketing period (SMP) at 20 °C. Exposure to either heat treatment caused neither visible damage nor fruit softening. Fruit weight loss rate in ‘Olinda’ oranges was unaffected by treatment but was higher than control fruit in heat exposed ‘Campbell’ oranges after storage, though at the end of SMP differences between treated and untreated fruit were non-significant. While neither heat treatment affected decay incidence in ‘Olinda’ oranges, significantly less decay was found in heat treated ‘Campbell’ fruit compared to control fruit both during storage and SMP.The chemical analyses of flavedo tissue of ‘Olinda’ oranges revealed that there were no treatment differences in neutral sugars, soluble and insoluble pectins and calcium bound to insoluble pectin fraction. The calcium content bound to soluble pectin fractions increased following heat treatments. At the end of SMP there was a significant decrease of soluble pectin and a significant increase of calcium bound to insoluble pectins in flavedo from oranges of the 46 and 44 °C treatments.Following treatment at 46 °C ‘Olinda’ fruit had a significantly lower content of soluble solids concentration. However, differences in soluble solids concentration between treated and control fruit after storage and SMP were not significant.Post-treatment levels of ethanol in both cultivars were significantly higher than in non-treated fruit. During storage and SMP, significant increases of ethanol were detected in control fruits with respect to their initial levels, whereas a reverse trend occurred in fruit subjected to heat treatment. Upon termination of the heat treatment at 44 or 46 °C, mean taste scores of ‘Olinda’ oranges were lower than those of untreated fruit, while the taste of ‘Campbell’ oranges was adversely affected only by the 46 °C treatment. After storage and SMP, taste differences between treated and control fruit were not significant. Flavour scores were unaffected by the treatment at 44 °C. Following treatment at 46 °C flavour rating in ‘Olinda’ fruit was significantly lower than control fruit while after storage and SMP the differences in flavour scores between treated and untreated fruit were non significant. Heat treatment to a fruit core temperature of 44 °C for 100 min or 46 °C for 50 min can thus have important commercial applications as an alternative to toxic chemical fumigants or to longer and more expensive disinfestation treatments such as cold quarantine.