Aviation turbine engine oils require excellent thermal-oxidative stability because of their high-temperature environments.High-temperature bearing deposit testing is a mandatory method for measuring the thermal-oxidat...Aviation turbine engine oils require excellent thermal-oxidative stability because of their high-temperature environments.High-temperature bearing deposit testing is a mandatory method for measuring the thermal-oxidative performance of aviation lubricant oils,and the relevant apparatus was improved in the present study.Two different commercial aviation turbine engine oils were tested,one with standard performance(known as the SL oil)and the other with high thermal stability,and their thermal-oxidative stability characteristics were evaluated.After 100 h of high-temperature bearing testing,the SL oil was analyzed by using various analytical techniques to investigate its thermal-oxidative process in the bearing test,with its thermal-oxidative degradation mechanism also being discussed.The results indicate that the developed high-temperature bearing apparatus easily meets the test requirements of method 3410.1 in standard FED-STD-791D.The viscosity and total acid number(TAN)of the SL oil increased with the bearing test time,and various deposits were produced in the bearing test,with the micro-particles of the carbon deposits being sphere-like,rod-like,and sheet-like in appearance.The antioxidant additives in the oil were consumed very rapidly in the first 30 h of the bearing test,with N-phenyl-1-naphthylamine being consumed faster than dioctyldiphenylamine.Overall,the oil thermal-oxidative process involves very complex physical and chemical mechanisms.展开更多
目的:分析并探讨南京市4所小学学生近视流行现状和与屈光相关的眼部生物学参数兼关系,为近视防控提供参考依据。方法:采用随机整群抽样调查方法,抽取南京市4所小学217名一年级学生,开展连续6年的随访研究。结果:随访6年后,小学生近视检...目的:分析并探讨南京市4所小学学生近视流行现状和与屈光相关的眼部生物学参数兼关系,为近视防控提供参考依据。方法:采用随机整群抽样调查方法,抽取南京市4所小学217名一年级学生,开展连续6年的随访研究。结果:随访6年后,小学生近视检出率由基线值6.70%增长至72.63%;中度近视人数在随访期间逐年增多,中度近视构成比由基线值8.33%增长至52.31%;随访初期167名非近视屈光群体中,有124名在随访期间发展为近视,其中3~4、5~6年级为近视高发期;随访期间,轴率比(axial length/corneal radius of curvature,AL/CRC)由基线数值2.89±0.08增至3.13±0.14(P值<0.05);等效球镜度(spherical equivalent refraction,SER)与最小分辨角对数(logarithm of the minimum angle of resolution,logMAR)视力、AL和AL/CRC(1年级除外)具有明显相关性(P值均<0.05)。结论:南京市4所小学学生的近视检出率随年级逐渐升高,其中中度近视构成比增加最为显著;3~4、5~6年级为近视发病高峰阶段;SER与logMAR视力、AL和AL/CRC均存在相关性,其中AL/CRC可考虑作为近视筛查的评估指标。展开更多
基金supported by the National Key Research and Development Program of China(2022YFB3809005)by SINOPEC(120060-6,121027,and 122042).
文摘Aviation turbine engine oils require excellent thermal-oxidative stability because of their high-temperature environments.High-temperature bearing deposit testing is a mandatory method for measuring the thermal-oxidative performance of aviation lubricant oils,and the relevant apparatus was improved in the present study.Two different commercial aviation turbine engine oils were tested,one with standard performance(known as the SL oil)and the other with high thermal stability,and their thermal-oxidative stability characteristics were evaluated.After 100 h of high-temperature bearing testing,the SL oil was analyzed by using various analytical techniques to investigate its thermal-oxidative process in the bearing test,with its thermal-oxidative degradation mechanism also being discussed.The results indicate that the developed high-temperature bearing apparatus easily meets the test requirements of method 3410.1 in standard FED-STD-791D.The viscosity and total acid number(TAN)of the SL oil increased with the bearing test time,and various deposits were produced in the bearing test,with the micro-particles of the carbon deposits being sphere-like,rod-like,and sheet-like in appearance.The antioxidant additives in the oil were consumed very rapidly in the first 30 h of the bearing test,with N-phenyl-1-naphthylamine being consumed faster than dioctyldiphenylamine.Overall,the oil thermal-oxidative process involves very complex physical and chemical mechanisms.
文摘目的探讨经皮椎体成形术(percutaneous vertebroplasty,PVP)治疗骨质疏松性椎体压缩骨折(osteoporotic vertebral compression fractures,OVCF)中骨水泥渗漏的危险因素。方法回顾性分析2020年10月至2022年6月于我院行PVP手术治疗的160例(167个椎体)OVCF病人的临床资料,其中男39例,女121例,年龄为(72.8±7.9)岁(58~93岁)。根据术后是否发生骨水泥渗漏分为渗漏组(42例,42个椎体)和无渗漏组(118例,125个椎体),采用单因素分析两组性别、年龄、身体质量指数(body mass index,BMI)、骨密度、骨折部位、伤椎皮质缺损情况、椎内裂隙征、椎基静脉孔、伤椎体积、椎体压缩率、骨水泥注入量、骨水泥注入量/伤椎体积比、骨水泥注入量/伤椎丢失体积比之间的差异,将与骨水泥渗漏有关的因素纳入Logistic回归分析,明确PVP术后骨水泥渗漏的独立危险因素。绘制ROC曲线,根据曲线下面积(area under curve,AUC)来评估模型的诊断价值。结果单因素分析结果显示,皮质缺损、椎内裂隙征、椎基静脉孔、骨水泥注入量及骨水泥注入量/伤椎丢失体积比与术后骨水泥渗漏有关(P<0.05),多因素Logistic回归分析显示椎内裂隙征[OR=5.215,95%CI(2.006,13.159),P<0.001]、椎基静脉孔[OR=3.357,95%CI(1.205,9.356),P=0.021]、骨水泥注入量[OR=2.519,95%CI(1.148,4.477),P=0.002]及骨水泥注入量/伤椎丢失体积比[OR=12.305,95%CI(1.875,80.756),P=0.009]为PVP术后骨水泥渗漏的独立危险因素。ROC曲线图显示骨水泥注入量/伤椎丢失体积比预测骨水泥渗漏的受试者工作特征AUC为0.641,且P<0.01,具有一定的预测价值。骨水泥注入量/伤椎丢失体积比预测骨水泥渗漏的Cut⁃off值为61.82%,敏感度为69.00%,特异性为38.4%。结论椎内裂隙征、椎基静脉孔、骨水泥注入量和骨水泥注入量/伤椎丢失体积比为术中骨水泥渗漏的独立危险因素,治疗时应保持骨水泥注入量/伤椎丢失体积比在61.82%以下,以降低发生骨水泥渗漏的风险。
文摘目的:分析并探讨南京市4所小学学生近视流行现状和与屈光相关的眼部生物学参数兼关系,为近视防控提供参考依据。方法:采用随机整群抽样调查方法,抽取南京市4所小学217名一年级学生,开展连续6年的随访研究。结果:随访6年后,小学生近视检出率由基线值6.70%增长至72.63%;中度近视人数在随访期间逐年增多,中度近视构成比由基线值8.33%增长至52.31%;随访初期167名非近视屈光群体中,有124名在随访期间发展为近视,其中3~4、5~6年级为近视高发期;随访期间,轴率比(axial length/corneal radius of curvature,AL/CRC)由基线数值2.89±0.08增至3.13±0.14(P值<0.05);等效球镜度(spherical equivalent refraction,SER)与最小分辨角对数(logarithm of the minimum angle of resolution,logMAR)视力、AL和AL/CRC(1年级除外)具有明显相关性(P值均<0.05)。结论:南京市4所小学学生的近视检出率随年级逐渐升高,其中中度近视构成比增加最为显著;3~4、5~6年级为近视发病高峰阶段;SER与logMAR视力、AL和AL/CRC均存在相关性,其中AL/CRC可考虑作为近视筛查的评估指标。
