高分辨质谱直接分析食用油中脂肪酸甘油酯

食用油中不饱和脂肪酸甘油酯的含量与人体健康密切相关,针对其建立快速有效的检测方法具有重要意义。本研究建立了一种可直接分析食用油中脂肪酸甘油酯的方法,采用大气压化学电离-高分辨质谱技术（APCI-HRMS）对食用油中脂肪酸甘油三酯及脂肪酸甘油二酯分子直接进样分析,在指纹区高分辨质谱数据的基础上,采用分解系数和平均不饱和度（DBE）对不同油品进行比较分析。结果表明,食用油与餐厨回收油及动物油具有明显差别,当分解系数大于10时,或DBE小于3时,可判断样品为餐厨回收油或动物油,利用这两个特征参数可成功地区分食用油与餐厨回收油样品。通过偏最小二乘法的分组验证,以及添加不同比例餐厨回收油的食用植物油样品分解系数和平均不饱和度的比较验证,表明该方法可便捷、准确地分析油品中脂肪酸甘油酯的含量变化,有望成为监测食用油品质的快速、有效的新型分析方法。     

蠕墨铸铁切削机理的探讨研究

为了推广蠕墨铸铁的应用领域和降低企业生产成本,改善蠕墨铸铁的切削加工具有重要意义。针对蠕墨铸铁难以切削加工的材料特性和目前改善蠕墨铸铁切削加工方法的局限性,提出改变蠕墨铸铁的化学成分以改善其切削加工的研究方法。通过往蠕墨铸铁中添加3个不同量的氮化硼化合物,用单因素实验方法测出氮化硼对蠕墨铸铁抗拉强度、硬度及耐磨特性的影响。实验结果表明,蠕墨铸铁中的氮化硼含量为0.0144%、0.0223%和0.0288%时,其抗拉强度和硬度没有改变;当氮化硼含量为0.0144%时,蠕墨铸铁与实验钢球组成的摩擦副的摩擦系数最小,为0.188。在不改变蠕墨铸铁的力学性能的前提下,往蠕墨铸铁中添加适量的氮化硼以改善其切削加工性能的研究方法具有可行性。     

WLD-4C型光电直读光谱仪在含镁铸铁分析中的应用

本文论述了影响铸铁分析的各种因素以及解决的办法,用国产含镁铸铁标准样品在光源的激发下建立各元素的工作曲线,将待测样品经过磨样机磨制后用建立的工作曲线进行测定其合金中的主要元素C、Si、Mn、P、S、Mg、Cr、Ni、Mo、Al等的含量,与精确化学分析法得出的分析结果进行对比, 结果令人满意。     

高碳铸铁焊条冷焊铸铁

铸铁焊补在修复铸件中起到一定作用。由于铸铁的可焊性差,焊后易产生白口和裂纹,因此多采用热焊法焊补。但是劳动条件差,生产率低、成本高、操作不便,因此近年来各单位对铸铁的冷焊十分重视。铸铁冷焊中应用了镍基铸铁焊条,铜铁、铜不锈钢铸铁焊条,高钒铸铁焊条等。这些焊条由于资源等方面问题影响大量采用。本期和下期向大家推荐两种冷焊铸铁的焊条,可供推广采用。     

不同碳含量高硬度共晶高铬铸铁的微观组织与力学性能

通过控制不同元素含量制备出含有2.9%碳和3.1%碳(质量百分比)的两种共晶高铬铸铁，并讨论了碳元素对共晶高铬铸铁微观组织与力学性能的影响。研究结果表明，两种高铬铸铁微观组织和力学性能存在显著差异。Ni、Mo、Mn、Cu和稀土元素的复合合金化以及优化热处理工艺可以控制碳化物的分布和数量，从而进一步提高样品硬度。此外通过弯曲和冲击测试，证实了两种不同碳含量的共晶高铬铸铁合金都具有优秀的硬度(65HRC)、抗弯强度(≥1160 MPa)和冲击韧性(≥2.88 J)。3.1%的较高碳含量导致铸态样品具有更高硬度，但抗弯强度明显降低。     

等离子发射光谱测定西藏土壤矿质元素前处理方法研究

使用电感耦合等离子体发射光谱法(ICP-AES)同时测定西藏土壤中铝(Al)、镁(Mg)、铁(Fe)、钙(Ca)、锰(Mn)、钛(Ti)等多种矿质元素。对湿法消解与干灰化法处理样品进行比较,通过对标准物质西藏土壤GBW08302样品分解,表明选择HNO3-HClO4体系消解样品优于干灰化法。检测数据证明西藏土壤中矿质元素含量丰富。     

羟基硅酸铝润滑油添加剂对钢/铸铁摩擦副磨损性能的影响

采用球盘试验和销盘试验相结合的方法,研究了钢/铸铁摩擦副在不同油润滑条件下磨损性能的变化,考察了不同含量羟基硅酸铝添加剂的作用效果,采用扫描电镜、X射线衍射仪以及纳米压痕仪对试验样品进行了分析测试。结果表明,该金属陶瓷添加剂表现出显著的抗磨性能,提高了钢/铸铁摩擦副承载能力和使用寿命;随着添加剂含量的增加,抗磨作用更加明显,负磨损现象开始出现;该添加剂可以抑制凹坑和裂纹的扩展,从而使摩擦表面形貌得到改善,并通过改变摩擦表面层的结构使摩擦副的磨损性能得到显著提高。     

PCBN复合片合成与切削离心铸铁性能研究

为了提高PCBN刀具加工离心铸铁的耐磨性和韧性,在PCBN合成过程中添加了具有增韧效果的ZrO_2及具有较高耐磨性能的Al_2O_3进行试验,合成了20wt%～80wt%的PCBN复合片。试验采用共沉淀法制备了ZrO_2-Al_2O_3复合粉体,再将复合粉体与CBN微粉混合均匀后,在六面顶压机上进行高温高压烧结成块,研究了合成温度、CBN含量、氧化铝含量对PCBN复合片切削离心铸铁性能的影响。试验结果显示:添加ZrO_2-Al_2O_3复合粉体合成的低含量PCBN复合片具有较高的韧性和耐磨性能,能有效地对离心铸铁进行加工,刀具具有较长的使用寿命。     

高速钢P6AM5硫氮碳共渗过程的特点

<正> 碳钢与铸铁在尿素与硫磺高温分解产物中进行气体硫氮碳三元共渗的过程在有关文献中已有阐述。其中特别指出:这种扩渗气氛能保证渗氮层的浓度稍低于人HBT-12型高氰盐浴中的硫氮碳共渗.因此在研究高速钢硫氮碳共渗的特点时,采用尿素(NH_2)_2CO和硫脲(NH_2)_2CS分解而得的高温分解气氛,其氮势     

硅酸盐化学分析法(六、七)——含硅量高的材料铝的直接测定、碱金属的测定

含硅量高的材料中铝的直接测定Ａ．δ羟基喹啉重量法１方法原理样品用氢氟酸和硫酸分解，所用的质量取决于铝的含量。在用较多的硫酸重复蒸发至干后，痕量的氟化物和硫酸根，借灼烧到１０００℃来除去。残渣在碳酸钠－硼酸中熔融，并且熔融物用水分解。不溶性材料滤掉，...     

Amorphous solid water produced by cryosectioning of crystalline ice at 113 K

Amorphous solid (vitreous) water can be obtained by a number of methods, including quick freezing of a very small volume of pure water, low pressure condensation of water vapour on a cold substrate or transformation of hexagonal ice (the ice which is naturally formed) under very high pressure at liquid nitrogen temperature. Larger volumes can be vitrified if cryoprotectant is added or when samples are frozen under high pressure. We show that a sample of 17.5% dextran solution or mouse brain tissue, respectively, frozen under high pressure (200 MPa) into cubic or hexagonal ice can be transformed into vitreous water by the very process of cryosectioning. The vitreous sections obtained by this procedure differ from cryosections obtained from vitreous samples by the irregular aspect of the sections and by small but significant differences in the electron diffraction patterns. For the growing community of cryo‐ultramicrotomists it is important to know that vitrification can occur at the knife edge. A vitreous sample is considered to show the best possible structural preservation. The sort of vitrification described here, however, can lead to bad structural preservation and is therefore considered to be a pitfall. Furthermore, we compare these sections with other forms of amorphous solid water and find it similar to high density amorphous water produced at very high pressures (about 1 GPa) from hexagonal ice and annealed close to its transformation temperature at 117 K.     

An electrical conductivity translator for carbons

The variety of methodologies used to determine the electrical conductivity of carbons makes it very difficult to compare samples and establish reference values. In this study, the electrical conductivity of a wide range of carbons was determined using two different methods: four-point probe and compression. Although the methodologies and the operating conditions are very different, linear correlations between the values measured by these two methods can be established for some of the materials studied. Only materials with a very high conductivity (graphite and carbon black) could not be correlated.     

串联质谱技术在食品安全分析中的应用

食品安全分析的污染物主要以痕量或超痕量的浓度水平存在于被测样品之中。样品制备方法要求较高，对分析仪器的检测能力要求更为苛刻。串联质谱技术以其强的抗背景干扰能力、极高的检测更敏度和准确、丰富的检测信息正在被得到广泛的认同。而使其成为了一种常规的检测手段，进入到食品安全分析领域。     

Observation of the ion-mirror effect during microscopy of insulating materials

Utilizing the ion beam of a focused ion beam (FIB)/scanning electron microscope (SEM) microscope to investigate non‐conductive samples, we observe a mirror image very much similar to the one that is commonly obtained with the electron beam and the same samples. To our knowledge this is the first observation of what can be called ‘Ion‐Mirror Effect’. This effect is produced by a positive charging of the sample obtained by rastering with high‐energy ions (30 kV) and a subsequent imaging with low energy ones (5 kV). The proposed explanation is that first a positive charge is trapped within the sample and eventually the lower energy ions are deflected back by the latter, and hit the surface of the microscope chamber very similar to what happens in the ‘Electron‐Mirror Effect’. The mirror image is produced after detection of the electrons produced by the interaction between ions and the chamber materials.     

Unconventional immuno double labelling by energy filtered transmission electron microscopy

A new method of immuno double labelling of biological specimens with a very high spatial resolution is presented. The advantage over conventional techniques is the possibility of using two very small labels leading to higher labelling efficiency, better penetration into the specimen and reduced steric hindrance between labels at closely spaced sites. The two labels are distinguished by their electron energy loss spectra using principal component analysis and then identified by comparison with an external standard using discriminant function analysis. The method is tested on samples of insect flight muscle labelled with 8 nm colloidal gold and silver and the statistical reliability of the classification is assessed. Extensions of the method are suggested and its potential for biological research is discussed.     

Innovative methods for the selection of bandpass sampling rate in cost-effective RF measurement instruments

The modern instruments involved in the measurement on the telecommunication systems are generally based on suitable digital signal processing methods which provide the desired quantities by elaborating the acquired samples. To warrant suitable accuracy and repeatability as well as the alias-free sampling (Nyquist–Shannon theorem), the measurement instruments are usually forced to operate with high sampling frequencies, long observation periods and very fast measurement algorithms. However, if bandpass signals are involved, as it happens in modern telecommunication systems, the bandpass sampling theory could be employed to significantly reduce the sampling rate, without any replica overlapping. This opportunity is very attractive for both instrument designers and users, since it allows optimizing the hardware resources through a more efficient employment.     

Preservation and visualization of molecular structure in detergent-extracted whole mounts of cultured cells.

Today's electron microscopes have a resolution sufficient to resolve supramolecular structures. However, the methods used to prepare biological samples for electron microscopy often limit our ability to achieve the resolution that is theoretically possible. We use whole mounts of detergent-extracted cells grown on Formvar-coated gold grids as a model system to evaluate various steps in the preparation of biological samples for high resolution scanning electron microscopy (SEM). Factors that are important in determining the structure and composition of detergent-extracted cells include the nature of the detergent and the composition of the extraction vehicle. Chelation of calcium is extremely important to stabilize and preserve the cytoskeletal filaments. We have also demonstrated both morphologically and by gel electrophoresis that treatment of cells with bifunctional protein crosslinkers before or during extraction with detergent can significantly enhance the preservation of both proteins and supramolecular structures. The methods used to dry samples are a major determinant of the quality of structural preservation. For cytoskeletons freeze-drying (FD) is superior to critical point-drying (CPD), one reason being that CPD samples have to be dehydrated, thereby causing more shrinkage as compared to FD samples. The high pressures to which samples are exposed during CPD may also cause increased shrinkage, and water contamination during CPD causes severe structural damage. We have obtained the best structural preservation of detergent-extracted and fixed cells by manually plunging them into liquid propane and drying over night in a freeze-dryer. The factor that most limits achievement of high resolution in SEM is the metal coat, which has to be very thin, uniform, and free of grain in order not to hide structures or to create artifactual ones. We have found that sputter-coating with 1-3 nm of tungsten (W) or niobium (Nb) gives extremely fine-grained films as well as satisfactory emission of secondary electrons. These samples can also be examined at high resolution by transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM). The best preservation and visualization of supramolecular structures have been obtained using cryosputtering, in which the samples are freeze-dried and then sputter-coated within the freeze-dryer while still frozen.     

Stiffness determination of angular-contact ball bearings by using neural network

All angular-contact ball bearings have similar features regarding geometry, mechanism, and structure. The stiffness of this type of bearings can be related to geometry, dimension, and operating conditions by a very complex function. This function involves high order and coupled variables. This study presents this stiffness function for all angular-contact ball bearings by a back-propagation neural network method (BPNN), which is trained by using several (not all) samples. The utility of the BPNN is demonstrated for actual cases. Each are catalogued SKF series angular-contact ball bearings.     

A novel intelligent gear fault diagnosis model based on EMD and multi-class TSVM

In the condition monitoring of gear reducer, the labeled fault samples are sparse and expensive, while the unlabeled samples are plentiful and cheap. How to diagnose the faults occurring in complex and special gear reducer effectively becomes a troublesome problem in case of insufficient labeled samples or excess unlabeled samples. This paper presents a novel model for fault diagnosis based on empirical mode decomposition (EMD) and multi-class transductive support vector machine (TSVM), which is applied to diagnose the faults of the gear reducer. The experimental results obtain a very high diagnosis accuracy. Even though the number of unlabeled samples is 50 times as that of labeled samples, the mean of testing accuracy of the proposed novel method can reach at 91.62%, which distinctly precedes the testing success rates of the other similar models in the same experimental condition.     

一种新的液液萃取模式-分散液液微萃取

分散液-液微萃取是2006年才问世的一种新型微萃取技术。它基于使用微量注射器将微升级萃取剂快速注入样液内,在分散剂-水相内形成萃取剂微珠,很大地扩展了有机萃取剂和水样之间相接触面,大大加快了萃取平衡的速度,使目标化合物迅速萃入萃取剂微珠内,提高了萃取效率和富集倍数。萃取富集操作与后续检测方法有很好的相容性,萃取相可直接进样气相色谱、高效液相色谱、薄层色谱、气相色谱-质谱、分光光度、火焰原子吸收光谱和电热原子吸收光谱,对目标化合物进行测定。它不仅适用于痕量有机物的分离富集,也适用于痕量无机金属离子的分离富集,已成功地应用于各种坏境水样(包括高含盐量水样)、多种饮料、生物样品、煤和矿物样品中痕量组分的分离富集,是一种有发展前途的环境友好的分离富集技术。