Chemical transesterification of flaxseed oil and medium-chain triacylglycerols: MLCT yield,DAG content,physicochemical properties,minor compounds and oxidation stability

A type of medium- and long-chain triacylglycerols (MLCT) rich in α-linolenic acid (ALA) was produced by chemical transesterification of medium-chain triacylglycerols (MCT) and flaxseed oils. Under the optimal substrate conditions of 60%, catalyst loading of 0.3% at 60 °C for 15 min, the product contained MLCT (74.06%), ALA (37.26%) and diacylglycerol (DAG) (11.25%). After that, changes in fatty acid (FA) composition, physicochemical properties and minor compounds after chemical transesterification (CTE) were investigated. The correlations analysis results of these factors on oxidative stability showed these factors could be divided into positive and negative groups. Although DAG appears to be beneficial in slowing down oil oxidation, it is critical to avoid its mass production because it would decrease MLCT.     

Very low voltage sputter coating

Very low voltage sputter coating, in the range 175–300 V, has been used to produce finely structured thin films of noble and refractory metals for use in high resolution scanning electron microscopy. There is a marked diminution in the particle size with a decrease in cathode voltage. Although the sputtering times are longer than with conventional diode sputter coating, such times are shorter than those required to produce similar films by Penning or ion-beam sputtering. The refractory metals produce films which are fine grained and suitable for high resolution studies. The method has been used to sputter coat thin layers of aluminium. All attempts at sputtering carbon have failed; the reasons for this are discussed in some detail.     

中小企业网络化动态联盟服务与管理平台研究

网络化制造作为新世纪的企业生产和管理模式，已经成为世界制造业发展的趋势。我国制造业企业如何因应人世的机遇和挑战，如何采取这一新的生产组织方式，成为现阶段国内企业尤其是中小企业所关注的焦点。本文提出了中小企业网络化动态联盟服务与管理平台，正是试图找到以上海地区中小企业为应用对象的动态联盟解决方案。     

熔融制样-X射线荧光光谱法测定深海沉积物中20种主次组分

深海沉积物中含有多种矿产资源,准确测定深海沉积物主次组分,对深海沉积物中矿产资源的开发利用有重要意义。实验采用熔融制样-X射线荧光光谱法(XRF)准确测定了深海沉积物样品中Na₂O、MgO、Al₂O₃、SiO₂、P₂O₅、SO₃、Cl、K₂O、CaO、TiO₂、MnO、Fe₂O₃、Ba、Cu、Ni、Sr、V、Y、Zn和Zr等20种主次组分。由于深海沉积物样品中SO₃和Cl含量(0.10%~3.00%)较高及微量元素Cu、Ni、Sr、V、Y、Zn和Zr一般在5~600μg/g之间,为了准确测定这些组分,对熔融制样条件进行了详细探讨。由于SO₃及Cl在熔融时易挥发损失,实验分别在600℃和700℃进行两次预氧化,有效防止了SO₃及Cl在熔融时挥发损失。经试验,熔融温度选为1100℃,样品和混合熔剂(m(Li₂B₄O₇)∶m(LiBO₂)=67∶33)的质量分别是0.7000g和7.000g,熔片质量较好。为了使制备的各元素校准曲线既有一定的含量范围,又有适当含量梯度,除选用深海沉积物标准样品GBW07313~GBW07316外,还选用海洋沉积物标准样品GBW07333~GBW07336,并将它们按1∶1质量比混合制备校准样品,同时还用深海沉积物标样GBW07316与硫酸钠、氯化钠高纯试剂按一定的比例混合,制备成SO₃质量分数为1.00%和Cl质量分数为5.00%合成校准样品。用经验系数法校正谱线重叠效应,理论α系数校正基体效应。在选定的实验条件下,利用GBW07316标准样品制备12个熔片进行精密度考察,各组分测定结果的相对标准偏差(RSD)在0.10%~4.6%;采用实验方法分别对标样及实际样品进行测定,主次组分的测定结果与标样的认定值及实际样品的电感耦合等离子体原子发射光谱法(ICP-AES)结果基本一致。     

On the behaviour of minor active elements during oxidation of selected Ni-base high-temperature alloys

We have examined the distribution of active minor elements in the oxide scales developed by selected Ni-base alloys with commercial grades. Emphasis is placed upon Mn, La and Si in a chromia-forming alloy and Y in an alumina-forming alloy. Initially, La and Y have been segregated at free surfaces and then become constituents of the oxides in contact with the substrates. A continuous layer of MnCr₂O₄ is formed above La- and Si-modified inner chromia layer. Silicon has been homogenously distributed throughout the grain structure, however, some La is present as LaCr₂O₃ particles and most of the remainder has been segregated at grain boundaries. The results indicate that the collective effect of Mn, Si and La is to extend protection by chromia to temperatures in excess of 1000 °C. Yttrium in the alumina- forming alloy is found to predominantly segregate at grain boundaries of nanostructured oxide with improved mechanical strength.     

Low molecular weight polypeptides in virgin and refined olive oils

Twenty-eight virgin olive oils—from different regions of Spain and prepared from olive drupes of different varieties—and six refined olive oils were analyzed to determine the presence of proteins in these oils. All oils studied showed the presence of proteins in the range of 7–51 μ/100 g of oil. There were no significant differences in protein content in oils from different varieties or between virgin or refined oils. In addition, all oils exhibited analogous amino acid patterns, suggesting a similarity among protein fractions obtained from different oils. A polypeptide with an apparent M.W. of 4600 Da was common to the isolated protein fractions. These results suggest that this polypeptide is a previously unknown minor component in olive oils. No clear influence of this component on oil stability was observed when oil stabilities were estimated as a function of phenol, tocopherol, phosphorus, and protein contents of the oils.     

Minor components ofLesquerella fendleri seed oil

Routine analysis of fatty ester fractions ofLesquerella fendleri oil suggested the presence of epoxy compounds and other minor components. By a combination of open silica column and high performance liquid chromatography (HPLC) fractionations of the methyl esters prepared from the oil, these constitutents were isolated and then characterized by thin-layer chromatography-mass spectrometry (GC-MS—electron ionization, EI, and chemical ionization, CI) and nuclear magnetic resonance (NMR—¹H and¹³C). Three epoxy acids, 15,16-epoxy-9,12-octadecadienoic, 9,10-epoxy-12-octadecenoic and 9,10-epoxy-octadecanoic, were found. Hydroxy acids present included a C-22 homologue of lesquerolic acid (16-hydroxy-12-docosenoic acid) and 14,15-dihydroxy-tricosanoic acid. Other minor ocmponents included four sterols, brassicasterol, campesterol, β-sitosterol and stigmasterol, and a series of saturated and unsaturated fatty acids up to C30. Visiting postdoctoral scientist sponsored by the government of India.     

从“6.28”事件透视如何抓好预防青少年违法犯罪工作

对未成年人违法犯罪主要原因从自身、家庭、学校、社会四个因素进行分析,对瓮安县进行预防青少年违法犯罪制度化建设,重点人群教育、管理和服务、依托社区管理实现预防青少年违法犯罪教育全覆盖,聚集社会合力巩固预防青少年违法犯罪成果等方面的措施和效果进行了分析和评价,从而总结出预防青少年违法犯罪工作存在的薄弱环节,从加强领导、提高认识、抓好基层和建立长效机制等方面提出预防青少年违法犯罪工作的对策措施。     

小波变换在电力系统故障暂态信号中的应用解析

小波变换理论在时域和频域的局部化性质,使之能有效地检测信号的奇异性。文章分析了电力系统故障暂态信号的奇异性,得出其奇异的特殊性,即具有不确定的奇异度,从而提出用小波变换进行奇异检测时对所用小波函数的要求,确保奇异性的准确检出,并给出了故障时刻检测的仿真。     

正交矩阵的进一步探究

利用欧氏空间的理论得出了正交矩阵的子式的性质,并从代数余子式、相似形、特征向量等方面刻画正交矩阵,同时,研究正交矩阵的对角化问题。