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The transformation of tert-butylhydroquinone (TBHQ) added in lard, soybean and palm oil was investigated during storage. The results showed that when the storage time was extended, the sum of the remaining amount of TBHQ and the production of 2-tert-butyl-1,4-benzoquinone (TBBQ) in oil samples was less than the initial amount of TBHQ added. The same chromatographic peaks except for TBHQ and TBBQ were found in the gas chromatograms of the methanol extracts from different oil samples. The unknown chromatographic peaks were isolated and purified by preparative liquid chromatography (Prep-LC), and their structures were identified and characterized by ultra-high performance liquid chromatography-quadrupole-time of flight-mass spectrometry (UPLC-Q-TOF-MS), nuclear magnetic resonance (NMR), ultraviolet (UV) spectroscopy, and Fourier transform infrared (FTIR) spectroscopy. These results showed that the conversion products of added TBHQ were the same in different oils and fats, including TBBQ and 2-methylallyl-hydroquinone (MAHQ).

Abstract Background Nursing students are one of the most vulnerable groups suffering from workplace violence. This study aimed to investigate the workplace violence incidence of Chinese nursing students during clinical practice, to describe the characteristics of violence and students’ responses and to analyse the relationship between the experience of workplace violence and professional identity. Methods A cross-sectional study was conducted among 954 nursing students in ten universities in China through convenience sampling. Workplace violence was surveyed through Hospital Workplace Violence Questionnaire for Nursing Students. Students’ professional identity was measured by Professional Identity Questionnaire for Nursing Students. Statistical methods included descriptive statistics, chi-square test, independent-samples t-test, analysis of variance and linear regression analysis. Results It was found that the incidence of workplace violence among nursing students was 42.98%. The violent incidents ranking from high to low were: verbal abuse, threat, physical attack, sexual harassment, and gathering disturbance. The majority of the nursing students chose to avoid the conflict during the incident. 86.34% of the students didn’t report the incidents. More than half of the victims developed post-traumatic stress disorder after the incidents. Regression analysis results showed that workplace violence experience (β = − 0.076, P

为优化Novozym 40086酶在无溶剂体系下催化油酸与棕榈硬脂酯交换制备OPO工艺条件，以OPO含量、PPP含量以及sn-2位棕榈酸占所有棕榈酸含量作为指标，通过单因素实验考察加酶量、底物摩尔比、反应时间和反应温度对反应效果的影响，在考察加酶量时对脂肪酶重复利用次数进行了研究，并通过对酶成本的核算确定了加酶量。在单因素实验的基础上，采用响应面实验对OPO制备工艺条件进行了优化。结果表明：单因素实验确定最佳加酶量为6%（以总底物质量计），酶可重复利用6次；响应面实验得到制备OPO的最佳工艺条件为加酶量6.3%、油酸与棕榈硬脂摩尔比5.7∶ 1、反应时间5.2 h、反应温度60 ℃，在此条件下，制备的产品中OPO含量为43.13%，PPP含量为7.65%，sn-2位棕榈酸占所有棕榈酸含量为61.28%，产品符合GB 30604—2015要求。为优化Novozym 40086酶在无溶剂体系下催化油酸与棕榈硬脂酯交换制备OPO工艺条件，以OPO含量、PPP含量以及sn-2位棕榈酸占所有棕榈酸含量作为指标，通过单因素实验考察加酶量、底物摩尔比、反应时间和反应温度对反应效果的影响，在考察加酶量时对脂肪酶重复利用次数进行了研究，并通过对酶成本的核算确定了加酶量。在单因素实验的基础上，采用响应面实验对OPO制备工艺条件进行了优化。结果表明：单因素实验确定最佳加酶量为6%（以总底物质量计），酶可重复利用6次；响应面实验得到制备OPO的最佳工艺条件为加酶量6.3%、油酸与棕榈硬脂摩尔比5.7∶ 1、反应时间5.2 h、反应温度60 ℃，在此条件下，制备的产品中OPO含量为43.13%，PPP含量为7.65%，sn-2位棕榈酸占所有棕榈酸含量为61.28%，产品符合GB 30604—2015要求。The aim was to optimize the technological conditions of preparing OPO by transesterification of oleic acid and palm stearate catalyzed by Novozym 40086 enzyme in solvent-free system. Taking OPO content, PPP content and the content of palmitic acid at sn-2 position in all palmitic acid as indicators, the effects of enzyme dosage, substrate molar ratio, reaction time and reaction temperature on the transesterification were investigated by single factor experiment. The reuse times of lipase was studied, and the lipase dosage was determined by calculating the cost of the enzyme. Based on the single factor experiment, the OPO preparation conditions were optimized using response surface methodology. The results showed that the optimal lipase dosage determined by single factor experiment was 6%(on the basis of total substrate mass), which could be reused for 6 times. The optimal OPO preparation conditions were obtained by response surface methodology as follows: dosage of enzyme 6.3%, molar ratio of oleic acid to palm stearate 5.7∶ 1, reaction time 5.2 h, reaction temperature 60 ℃. Under the optimal conditions, the content of OPO, PPP and palmitic acid at sn-2 position in all palmitic acid were 43.13%, 7.65% and 61.28%, respectively, which matched the requirements of GB 30604-2015.