角膜移植术后干眼的研究进展

由于角膜移植手术对眼表结构的破坏和长期滴眼液的应用,使得干眼成为较为常见的移植术后并发症,长期干眼会导致角膜上皮缺损,影响植片的存活。为提高对于角膜移植术后干眼的认识,本文通过查阅国内外相关文献,对于角膜移植术后干眼的发病机制、临床表现、治疗和预防进行综述,为临床应用提供参考。

基于SEER数据库的胰腺癌患者自杀风险因素分析

目的 探讨胰腺癌患者自杀的风险因素。方法 利用SEER(Surveillance,Epidemiology,and End Results)Research Plus数据库筛选1975—2018年胰腺癌患者,描述自杀死亡者、非自杀死亡者和存活者的分布特征,计算人年自杀率、标准化死亡比并分析相应群体特点。使用回归分析探索胰腺癌患者自杀的风险因素,并进一步分析男性患者的自杀风险因素。结果 153 612例胰腺癌患者中,白色人种(80.68%)、65岁及以上(65.02%)、不建议手术(70.57%)、肿瘤远处转移(57.28%)、已婚(56.06%)、家庭年收入中位数在50 000~74 999美元(47.17%)、未采取化疗(52.48%)的患者群体占比较高,且与138名胰腺癌自杀患者的群体特征分布相似。回归分析结果显示,男性[aRR=12.81,95%CI (6.85,23.96),P <0.001]、白色人种[aRR=3.56,95%CI(1.43,8.85),P=0.006]、诊断年龄为65岁及以上[aRR=1.55,95%CI(1.07,2.26),P=0.022]、不建议手术[aRR=2.06,95%CI(1.23,3.44),P=0.006]、建议但未采取手术[aRR=2.86,95%CI(1.37,5.98),P=0.005]的患者具有更高的自杀风险,而肿瘤区域转移[aRR=0.56,95%CI(0.37,0.85),P=0.006]和局部转移[aRR=0.44,95%CI(0.23,0.86),P=0.015]、已婚[aRR=0.57,95%CI(0.40,0.82),P=0.002]、化疗[aRR=0.34,95%CI(0.23,0.51),P <0.001]的患者自杀风险相对较低。男性胰腺癌患者的自杀风险显著高于女性患者,不同种族、手术选择、婚姻状态及化疗选择的男性胰腺癌患者,自杀风险具有显著差异。结论 性别、种族、诊断年龄、是否采取手术治疗、SEER阶段、婚姻状态及化疗选择是胰腺癌患者自杀的重要风险因素。对于男性、白色人种、诊断年龄为65岁及以上、不建议手术或建议但未采取手术治疗、肿瘤处于远处转移阶段、单身、未采取化疗的胰腺癌患者需加强识别、干预和护理。

Mechanical and corrosion properties of low-carbon steel prepared by friction stir processing

Low-carbon steel plates were successfully subjected to normal friction stir processing(NFSP) in air and submerged friction stir processing(SFSP) under water, and the microstructure, mechanical properties, and corrosion behavior of the NFSP and SFSP samples were investigated. Phase transformation and dynamic recrystallization resulted in fine-grained ferrite and martensite in the processed zone. The SFSP samples had smaller ferrites(5.1 μm), finer martensite laths(557 nm), and more uniform distribution of martensite compared to the NFSP samples. Compared to the base material(BM), the microhardness of the NFSP and SFSP samples increased by 19.8% and 27.1%, respectively because of the combined strengthening effects of grain refinement, phase transformation, and dislocation. The ultimate tensile strengths(UTSs) of the NFSP and SFSP samples increased by 27.1% and 38.7%, respectively. Grain refinement and martensite transformation also improved the electrochemical corrosion properties of the low-carbon steel. Overall, the SFSP samples had better mechanical properties and electrochemical corrosion resistance than the NFSP samples.

Comparison between multiple logistic regression and machine learning methods in prediction of abnormal thallium scans in type 2 diabetes

BACKGROUND The prevalence of type 2 diabetes(T2D)has been increasing dramatically in recent decades,and 47.5%of T2D patients will die of cardiovascular disease.Thallium-201 myocardial perfusion scan(MPS)is a precise and noninvasive method to detect coronary artery disease(CAD).Most previous studies used traditional logistic regression(LGR)to evaluate the risks for abnormal CAD.Rapidly developing machine learning(Mach-L)techniques could potentially outperform LGR in capturing non-linear relationships.AIM To aims were:(1)Compare the accuracy of Mach-L methods and LGR;and(2)Found the most important factors for abnormal TMPS.METHODS 556 T2D were enrolled in the study(287 men and 269 women).Demographic and biochemistry data were used as independent variables and the sum of stressed score derived from MPS scan was the dependent variable.Subjects with a MPS score≥9 were defined as abnormal.In addition to traditional LGR,classification and regression tree(CART),random forest,Naïve Bayes,and eXtreme gradient boosting were also applied.Sensitivity,specificity,accuracy and area under the receiver operation curve were used to evaluate the respective accuracy of LGR and Mach-L methods.RESULTS Except for CART,the other Mach-L methods outperformed LGR,with gender,body mass index,age,low-density lipoprotein cholesterol,glycated hemoglobin and smoking emerging as the most important factors to predict abnormal MPS.CONCLUSION Four Mach-L methods are found to outperform LGR in predicting abnormal TMPS in Chinese T2D,with the most important risk factors being gender,body mass index,age,low-density lipoprotein cholesterol,glycated hemoglobin and smoking.

Friction Stir Processing of Magnesium Alloys:A Review

Magnesium(Mg)alloys have been extensively used in various fields,such as aerospace,automobile,electronics,and biomedical industries,due to their high specific strength and stiff ness,excellent vibration absorption,electromagnetic shielding eff ect,good machinability,and recyclability.Friction stir processing(FSP)is a severe plastic deformation technique,based on the principle of friction stir welding.In addition to introducing the basic principle and advantages of FSP,this paper reviews the studies of FSP in the modification of the cast structure,superplastic deformation behavior,preparation of finegrained Mg alloys and Mg-based surface composites,and additive manufacturing.FSP not only refines,homogenizes,and densifies the microstructure,but also eliminates the cast microstructure defects,breaks up the brittle and network-like phases,and prepares fine-grained,ultrafine-,and nano-grained Mg alloys.Indeed,FSP significantly improves the comprehensive mechanical properties of the alloys and achieves low-temperature and/or high strain rate superplasticity.Furthermore,FSP can produce particle-and fiber-reinforced Mg-based surface composites.As a promising additive manufacturing technique of light metals,FSP enables the additive manufacturing of Mg alloys.Finally,we prospect the future research direction and application with friction stir processed Mg alloys.

Microstructure and mechanical properties of magnesium–lithium alloy prepared by friction stir processing

In this study, the fine-grained Mg–Li alloy was prepared by friction stir processing(FSP). The microstructure and mechanical properties of the frictionstir-processed(FSPed) Mg–Li alloy were investigated. The result showed that FSP resulted in the grain refinement, and the average grain size of the b-Li phase was about 7.5 lm.Besides the a-Mg and b-Li phases, a small amount of Li_(3)Mg_(7), Li_(2)MgAl and AlLi phases were obtained. Compared with the base metal(BM), the weakening of the crystallographic texture occurred in the FSPed material,and the c-axis of the a-phase and the <001> crystallographic orientation of the b-phase were tilted about 45°with respect to the transverse direction(TD). The average microhardness(HV 67.8) of the stir zone was higher than that of the BM(HV 61.5). The yield strength(YS) and the ultimate tensile strength(UTS) of the FSPed material were higher than those of the BM, while the elongation slightly reduced. Grain refinement had more significant effect on strength improvement compared with the texture variation for the FSPed material. The fracture surfaces of the BM and FSPed materials showed dimple characteristics.