Size-controlled synthesis of nano α-alumina particles through the sol–gel method

Nano α-alumina particles were synthesized by a sol–gel method using aqueous solutions of aluminum isopropoxide and 0.5 M aluminum nitrate. 1/3-benzened disoulfonic acid disodium salt (SDBS) and sodium bis-2-ethylhexyl sulfosuccinate (Na(AOT)) were used as surfactant stabilizing agents. Solution was stirred for different periods (24, 36, 48 and 60 h) at 60 °C. The samples were then analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Introduction of surfactant stabilizing agents and different stirring times will affect the size and shape of particle formed and also the degree of aggregation. SDBS, however, produced better dispersion, finer particles and spherical shape nanoparticles, compared to Na(AOT). The finest particle size (20–30 nm) was obtained at 48 h stirring time with SDBS surfactant.     

Electrical Insulation Characteristics of Silicone and EPDM Polymeric Blends. I

The typical parts of a polymeric insulator are core, metal end fittings and polymeric housing material. The housing is intended to protect the fibre glass rod from the environment and electrical surface discharges. Since the housing materials are made of organic polymeric material, its insulation characteristics need to be studied. Amongst the many different polymers available, this work focuses on silicone rubber and ethylene propylene diene monomer (EPDM). Blends of EPDM and silicone rubber are prepared in a two roll mixing mill. Dicumyl peroxide is used as vulcanizing agent. The blends consisting of various proportions of component polymers are prepared, compression moulded into sheets, and post cured. The blends are tested for their insulation characteristics as per IEC and ASTM standards. Volume and surface resistivity, dielectric strength, dielectric constant, tan delta, tracking resistance, arc resistance, comparative tracking index, tensile strength, and percentage elongation at break of the blends are studied and discussed. The test results show that the increasing proportion of silicone enhances the electrical insulation properties whereas increasing weight percentage of EPDM improves the mechanical strength of the blends.     

TRANSPORT PROPERTIES OF CELLULAR FOOD MATERIALS UNDERGOING FREEZE-DRYING

The samples of sliced and mashed apples were freeze-dried by controlling their surface temperatures over the usual pressure range of commercial operations. The surface of sliced samples could not be maintained at above 10°C in order to prevent the frozen layer from melting, while that of mashed samples was allowed to heat up to 70°C.

Thermal conductivities and permeabilities were determined by applying the uniformly-retreating-ice front model to the dried layer of the samples undergoing freeze-drying. The values of permeability for the mashed samples were found to depend on the ice-crystallization time during freezing. The results indicated that the drying rate of sliced samples was limited by the transfer rate of water vapor flowing through the dried layer. A cellular structural model is proposed for predicting the permeability of the dried layer, based on the resistance of the cell membrane to molecular transfer of water vapor.     

二苯乙烯化合物的提取工艺优化及其酪氨酸酶抑制活性

该研究探讨了桑根来源的三种二苯乙烯化合物(氧化白藜芦醇,白藜芦醇和白藜芦醇苷)的富集提取工艺,并对提取物的抗氧化活性和酪氨酸酶抑制作用进行了研究。结果表明,通过单因素试验和响应面试验确定富集二苯乙烯化合物的最佳条件为：提取时间1h,料液比1:20,乙醇浓度90%,在此条件下,桑根中氧化白藜芦醇,白藜芦醇和白藜芦醇苷的含量分别为2923.59μg/g,32.45μg/g和3.15μg/g,富含三种二苯乙烯化合物提取物的得率为10.23%。并且,提取物表现出极强的DPPH自由基清除能力(IC₅₀=0.063 mg/mL)和ABTS自由基清除能力(IC₅₀=0.008 mg/mL)。此外,提取物比熊果苷表现出更强的酪氨酸酶抑制活性,其酪氨酸酶抑制率IC₅₀(2.514μg/m L)仅约为熊果苷(IC₅₀=15.551μg/m L)的16%。综上,高活性的二苯乙烯化合物提取物具有天然抗氧化剂和美白剂的潜力,在食品、美容与医药领域有很大的应用价值。桑根可作为二苯乙烯化合物的重要天然来源,是值得被开发利用的抗氧...     

Minimizing total costs of forest roads with computer-aided design model

Advances in personal computers (PCs) have increased interest in computer-based road-design systems to provide rapid evaluation of alternative alignments. Optimization techniques can provide road managers with a powerful tool that searches for large numbers of alternative alignments in short spans of time. A forest road optimization model, integrated with two optimization techniques, was developed to help a forest road engineer in evaluating alternative alignments in a faster and more systematic manner. The model aims at designing a path with minimum total road costs, while conforming to design specifications, environmental requirements, and driver safety. To monitor the sediment production of the alternative alignments, the average sediment delivered to a stream from a road section was estimated by using a road erosion/delivery model. The results indicated that this model has the potential to initiate a new procedure that will improve the forest road-design process by employing the advanced hardware and software capabilities of PCs and modern optimization techniques.     

Facile green synthesis, optical and photocatalytic properties of zinc oxide nanosheets via microwave assisted hydrothermal technique

Novel hexagonal two dimensional ZnO nanosheets were successfully and economically synthesized using zinc acetate and urea based on a facile microwave hydrothermal method. The structure, morphology and size of the ZnO nanosheets were investigated by X-ray diffraction (X-ray), field emission scanning electron microscopy (FESEM), energy dispersive analysis of x-ray (EDS), transmission electron microscopy (TEM), selected area electron diffraction (SAED) and Fourier transform infrared spectroscopy (FTIR). X-ray analysis showed that the obtained ZnO nanosheets are crystalline corresponding to the pure ZnO phase with an average particle size of 12 nm. Optical properties of ZnO nanosheets were investigated by UV-Vis absorption and photoluminescence (PL) techniques. The band gap energy of ZnO nanosheets was found to be 3.29 eV. The photoluminescence (PL) measurement shows a strong UV emission, blue emission and blue-green emission bands. ZnO nano sheets possess a higher photocatalytic activity leading to the degradation of methylene blue (MB). The ZnO nanosheets are expected to have new opportunities in vast research areas and for application in catalysts and optoelectronic devices.     

Growth characteristics of agrowaste‐immobilised lactobacilli in soymilk during refrigerated storage

We aimed at evaluating agricultural wastes as solid supports for the immobilisation of lactobacilli in a liquid media, namely soymilk. Lactobacillus acidophilus FTDC 1331, L. acidophilus FTDC 2631, L. acidophilus FTDC 2333, L. acidophilus FTDC 1733 and L. bulgaricus FTCC 0411 were immobilised on solid supports produced from durian (Durio zibethinus), cempedak (Artocarpus champeden) and mangosteen (Garcinia mangostana). The immobilised cells were inoculated into soymilk and stored at 4 °C over 168 h. Soymilk inoculated with non‐immobilised cells was used as the control. Immobilised cells showed higher survivability over 168 h compared to the control, accompanied by higher reduction of simple sugars and oligosaccharides in soymilk. Higher growth and higher utilisation of substrates also led to the higher production of lactic and acetic acids, which lowered the pH in soymilk compared to the control. Our results illustrated that agrowastes could be used as immobilisers to enhance the growth of lactobacilli in a liquid medium.