Fatigue Performance Evaluation of AZ31B Magnesium Alloy Based on Statistical Analysis of Self-Heating.

AZ31B magnesium alloy is the experimental material in this study. Considering its anisotropy, fatigue assessment based on self-heating is carried out for both the extrusion direction and the transverse direction. The self-heating behavior in the two orientations is compared. Similar to steels, an obvious inflection point that corresponds to the fatigue limit can be found in the self-heating vs. load curve for AZ31B. A new fatigue limit assessment method is proposed based on a statistical analysis of self-heating data. This method can provide a satisfactory assessment of the fatigue limit for AZ31B in the both orientations.

Thermographic Study of AZ31B Magnesium Alloy under Cyclic Loading: Temperature Evolution Analysis and Fatigue Limit Estimation.

In this paper, infrared thermography was employed to study the fatigue process of AZ31B magnesium alloy. In order to eliminate the interference caused by the temperature rise of the fixture, a data processing method was proposed, which is based on a special model to describe the temperature change of the specimen. Based on the temperature data after processing, the temperature evolution indicates that AZ31B magnesium alloy has undergone cyclic hardening during fatigue. Three different temperature indicators were selected to evaluate the fatigue limit based on the evolution curve after processing. In addition, the experimental results showed that the temperature data processed by the proposed method can be used to estimate the fatigue limit of AZ31B magnesium alloy. Experiments were performed for both extrusion and transverse directions in consideration of the anisotropy of the AZ31B.

[Determination of higenamine in Chinese herbal medicine, condiments, and topical medicine by QuEChERS combined with liquid chromatography-tandem mass spectrometry].

A method combining QuEChERS with liquid chromatography-tandem mass spectrometry (LC-MS/MS) was developed for the determination of higenamine in Chinese herbal medicine, condiments, and topical medicine. The sample was subjected to extraction using a formic acid-ethanol mixture, followed by purification of the QuEChERS sorbents; then, the extraction solution was introduced into the LC-MS/MS system for detection in multiple reaction monitoring (MRM) mode. Under the optimal conditions, the detection limit of the developed method was 0.03 ng/g, and the linear range was 0.10-100 ng/g with a relative standard deviation (RSD) of 4.33% (0.5 ng/g, n=7). The method was then applied to the determination of higenamine in 13 kinds of Chinese herbal medicine, four kinds of condiments, and a topical medicine. Higenamine was detected in dried lotus leaf, dried lotus seed, Chinese yam, Yuzhu, Yam, Sichuan pepper, Cassia, and the topical medicine at 9667.6, 1183.8, 21.5, 8.2, 8.5, 148.6, 21.3, and 173.3 µg/kg, respectively. The recoveries of higenamine in Sichuan pepper and cassia was 92.6%-109.8%. In conclusion, the method is fast, simple, reliable, and suitable for use in batch operation.

Preparation of Molecularly Imprinted Composites Initiated by Hemin/Graphene Hybrid Nanosheets and Its Application in Detection of Sulfamethoxazole.

Molecularly imprinted polymers (MIPs) exhibit high selectivity resulting from imprinted cavities and superior performance from functional materials, which have attracted much attention in many fields. However, the combination of MIPs film and functional materials is a great challenge. In this study, hemin/graphene hybrid nanosheets (H-GNs) were used to initiate the imprinted polymerization by catalyzing the generation of free radicals. Thus, MIPs using sulfamethoxazole as the template was directly prepared on the surface of H-GNs without any film modification. Most importantly, the template could be absorbed on the H-GNs to enhance the number of imprinted sites per unit surface area, which could improve the selectivity of MIPs film. Thus, the composites could exhibit high adsorption capacity (29.4 mg/g), imprinting factor (4.2) and excellent conductivity, which were modified on the surface of electrode for rapid, selective and sensitive detection of sulfamethoxazole in food and serum samples. The linear range was changed from 5 µg/kg to 1 mg/g and the limit of detection was 1.2 µg/kg. This sensor was free from interference caused by analogues of sulfamethoxazole, which provides a novel insight for the preparation of MIPs-based sensor and its application in food safety monitoring and human exposure study.

Magnetic Solid-Phase Extraction Based on ß-Cyclodextrins/Acrylic Acid Modified Magnetic Gelatin for Determination of Moxidectin in Milk Samples.

ß-Cyclodextrins/acrylic acid modified magnetic gelatin was prepared and then employed as the magnetic solid-phase extraction (MSPE) sorbent for extraction of moxidectin in milk samples. Due to the rigidity of hydrophobic cavity of ß-cyclodextrins and carboxyl groups of acrylic acid, magnetic composites are prepared to form a complex with target molecules through various kinds of chemical reactions and then showed excellent extraction performance. This method exhibits the advantages of simplicity of implementation, short extraction time (5 min), low solvent consumption, and high extraction efficiency. A rapid, simple, and effective method for the analysis of moxidectin in milk samples was established by MSPE coupled with liquid chromatography-fluorescence detection. The limit of detection was 0.1 ng·mL(-1) and the recoveries from milk samples were in the range of 93.8%-112.5%. The relative standard deviation was not higher than 6.4%. In conclusion, magnetic solid-phase extraction is a simple and robust preconcentration technique that can be coupled to other analytical methods for the quantitative determination of target molecules in complex samples.

[Determination of Sudan Red dyes in eggs using liquid chromatography-tandem mass spectrometry and matrix solid-phase dispersion technique].

A new method was established for determining Sudan Red I - IV dyes in eggs using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The target analytes in eggs such as hen eggs, duck eggs and preserved eggs, were extracted by solid-phase dispersion technique with a mixture of chloroform-acetonitrile (9: 1, v/v). The chromatographic separation was achieved on a ZORBAX SB-C18 column. The identification and quantification were performed using MS/MS with multiple-reaction monitoring (MRM) and electrospray ionizatio in positive mode. The linearity ranges of Sudan Red I - IV dyes were 0.5 - 100 ng/g, 5.0 - 100 ng/g, 1.0 - 100 ng/g and 2.0 - 100 ng/g, respectively, and all linear correlation coefficient were higher than 0.99. The recoveries of Sudan Red dyes in eggs were between 87.3% and 113% with the relative standard deviations less than 9.1%. The detection limits of this method were 0.1 microg/kg for Sudan Red I, 2.0 microg/kg for Sudan Red II , 0.2 microg/kg for Sudan Red III and 0.4 microg/kg for Sudan Red IV, which could meet the monitoring requirements of the Suda Red dyes both abroad and home.