Reconstructive treatment of symptomatic vertebral artery dissecting aneurysms with Willis covered stent: Initial experience

Background:Symptomatic vertebral artery dissecting aneurysm(VADA)is a challenging disease with controversy on treatment strategy due to anatomic configuration and their nature.Moreover,the outcomes of reconstructive treatment have not been well established.Objective:To evaluate the safety and efficacy of reconstructive endovascular treatment(EVT)for symptomatic VADAs with Willis covered stent.Methods:We evaluated retrospectively 13 patients with symptomatic VADAs who treated with Willis covered stent,compared with stent-assisted coiling(SAC)on the characteristics,posttreatment course,angiographic and clinical follow-up outcomes at an average of 14.4 months(range,3-48 months).Results:A total of 33 patients with symptomatic VADAs were reviewed,23 of these patients with ruptured VADAs.The technical successful rate is 100%respectively in Willis covered stent(Group A)and SAC(Group B,n=20).The initial complete occlusion rate was significant higher in group A(100%)than group B(30%)(p<0.01).Major procedure-related complications were not significant different in the two groups.Serial follow-up angiograms revealed 5 recurrent VADAs in group B and no recurrence in group A(p>0.05).No obvious in-stent stenosis and no re-hemorrhage and delayed ischemic symptoms during the follow-up period.The final angiograms of all survived patients demonstrated the complete occlusion rate was higher in group A(100%)than group B(80%),but no significant statistical difference(p>0.05).Clinical outcomes were favorable in 31(93.9%),severe disability occurred in one in group B,and only one death in group A.The final clinical outcomes were also not significant difference in the two groups(p>0.05).Conclusions:Our initial result demonstrated reconstructive EVT with Willis covered stent provides a viable approach for selected symptomatic VADAs involving the intracranial and extracranial segments,which is similar to favorable results with SAC.However,an expanded clinical experiences and larger cohort studies are needed.

Influence of rare earth oxides on microstructure and mechanical properties of nickel-based superalloys fabricated by high energy beam processing:A review

In this paper,the effects of rare earth oxides on the micro structure and mechanical properties of nickelbased superalloys prepared by high-energy beam processing technology were critically studied.The focus is on the optimal amount of rare earth oxides that can produce ideal results.Special attention was paid to their main strengthening mechanisms,including solid solution strengthening mainly in the form of solid solution dissolved in the nickel-based alloy and improving the microstructure of the alloy by grain refinement or fine grain strengthening produced by homogenizing the distribution phase.Y_(2)O_(3),La_(2)O_(3) and CeO_(2) rare earth oxides can also improve the fluidity of the alloy molten pool and reduce the segregation of alloying elements.These advantages can significantly improve the mechanical properties of the alloy.Thereafter,this paper outlines the future research directions of rare earth oxides,aiming to expand their application potential.

钛合金表面激光熔覆Ti-Ni+TiN+MoS_2/TiS自润滑复合涂层

以NiCrBSi、TiN和Ni包MoS_2为熔覆材料,采用激光熔覆技术在Ti-6Al-4V合金表面制备了以TiN、Ti Mo和Ti-Ni金属间化合物为增强相,以MoS_2、TiS为润滑相的自润滑复合涂层。采用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、能谱仪(EDS)、显微硬度仪和多功能摩擦磨损实验机等手段分析涂层的物相、显微组织结构、显微硬度和摩擦学性能,研究了复合涂层的磨损机理。结果表明:复合涂层的平均显微硬度为1060～1140HV0.3,约为基体硬度(约为370HV0.3)的3倍。由于涂层中硬质增强相TiN、TiMo、Ti-Ni和润滑相MoS_2、Ti S的综合作用,Ti N含量为25%的复合涂层其摩擦系数(0.3199)和磨损量(2.2 mg)均比基体的(0.3535和11.8 mg)低,具有良好的自润滑耐磨性能。