Microstructure, mechanical, and corrosion properties of extruded low-alloyed Mg–xZn–0.2Ca alloys

The microstructure, mechanical, and corrosion properties of extruded low-alloyed Mg xZn 0.2Ca (x=0, 1.0, 2.0, 3.0) alloys were investigated in this study. Findings from scanning electron microscope, X-ray diffraction and transmission electron microscopy results indicate that the amount of ternary Ca2Mg6Zn3 phase, as the only secondary phase in 1.0Zn, 2.0Zn, and 3.0Zn alloys, gradually increases with the addition of Zn, while the Mg2Ca phase was observed in the Mg 0.2Ca alloy only. Zn has a strong effect on the orientation and intensity of textures, which also influence mechanical behaviors, as revealed by electron back-scatter diffraction. Among all the alloys, the Mg 2.0Zn 0.2Ca alloy obtains the maximum tensile strength (278 MPa) and yield strength (230 MPa). Moreover, Zn addition has an evident influence on the corrosion properties of Mg xZn 0.2Ca alloy, and Mg 1.0Zn 0.2Ca alloy exhibits the minimum corrosion rate. This paper provides a novel low-alloyed magnesium alloy as a potential biodegradable material.

Microstructure,mechanical properties and corrosion behavior of quaternary Mg−1Zn−0.2Ca−xAg alloy wires applied as degradable anastomotic nails

The microstructure,mechanical properties and corrosion behavior of quaternary degradable Mg−1Zn−0.2Ca−xAg(x=1,2,4 wt.%)alloy wires,intended as anastomotic nails,were investigated.It was found that these Ag-containing alloy wires mainly consist of Mg matrix and Ag17Mg54 phase,characterized by SEM,EDS,XRD and TEM.Tensile and knotting tests results demonstrate the superior mechanical properties of these alloy wires.Especially,Mg−1Zn−0.2Ca−4Ag alloy exhibits the highest mechanical properties,i.e.an ultimate tensile strength of 334 MPa and an elongation of 8.6%.Moreover,with increasing Ag content,the corrosion rates of these alloy wires remarkably increase due to the formation of more micro-galvanic coupling between Mg matrix and Ag17Mg54 phase,shown by mass loss and scanning Kelvin probe force microscopy(SKPFM)results.The present alloy can be completely degraded within 28 d,satisfying the property requirements of anastomotic nails.

Interfacial microstructure and mechanical behavior of Mg/Cu bimetal composites fabricated by compound casting process

Mg/Cu bimetal composites were prepared by compound casting method, and the microstructure evolution, phase constitution and bonding strength at the interface were investigated.It is found that a good metallurgical bonding can be achieved at the interface of Mg and Cu,which consists of two sub-layers,i.e.,layer I with 30μm on the copper side composed of Mg2Cu matrix phase, on which a small amount of dendritic MgCu2 phase was randomly distributed;layerⅡ with 140μm on the magnesium side made up of the lamellar nano-eutectic network Mg2Cu+(Mg) and a small amount of detached Mg2Cu phase. The average interfacial shear strength of the bimetal composite is measured to be 13 MPa.This study provides a new fabrication process for the application of Mg/Cu bimetal composites as the hydrogen storage materials.

Influence of Ca addition on microstructure,mechanical properties and corrosion behavior of Mg-2Zn alloy

The microstructure,mechanical properties and corrosion behaviors of as-cast ternary Mg-2Zn-x Ca(x=0,0.2,0.4,0.8)alloys have been investigated in this study.Results indicate that the microstructure of Mg-Zn-Ca alloys can be significantly refined with increasing Ca concentration.Moreover,the alloys with different contents of Ca exhibit the different phases formation behaviors,i.e.α-Mg+Ca_2Mg_6Zn_3 phases for Mg-2Zn-0.2Ca and Mg-2Zn-0.4Ca alloys,andα-Mg+Ca_2Mg_6Zn_3+Mg_2Ca phases for Mg-2Zn-0.8Ca alloy,respectively.Among all the alloys,the maximum ultimate tensile strength and elongation(161 MPa and 9.1%)can be attained for the Mg-2Zn-0.2Ca alloy.Corrosion tests in Hanks’balanced salt solution indicated that Ca addition is detrimental to corrosion resistance of Mg-2Zn alloy.The relationship between as-cast microstructure and properties for different Ca-containing alloys is also discussed in detail.

基于大肠杆菌表达的重组九价人乳头瘤病毒(HPV 6/11/16/18/31/33/45/52/58型)疫苗免疫原性和安全性的Ⅱ期临床试验

人乳头瘤病毒(HPV)16/18型双价疫苗(大肠埃希菌)已上市并通过世界卫生组织预认证.本研究通过一项随机双盲Ⅱ期临床试验评估其第二代HPV6/11/16/18/31/33/45/52/58型九价疫苗在18~45岁健康女性中的免疫原性和安全性.来自江苏省东台市的627名女性志愿者1:1随机分配至九价疫苗组(313人)或对照组(314人),并按照0、1、6月接种程序分别接种三剂1.0 mL(270μg)九价疫苗或空白佐剂,主要终点为第7月时血清抗体阳转率和抗体水平.结果显示,几乎所有疫苗组符合方案人群在第7月时出现针对9种HPV型别的血清中和抗体阳转,仅2人未发生HPV11型阳转,1人未发生HPV52型阳转.九价疫苗组和对照组的总体不良事件发生率分别为80.8%和72.9%,绝大多数不良事件症状轻微并很快恢复,未发生疫苗相关严重不良事件.该研究证明候选九价疫苗具有良好的安全性和免疫原性,支持在更大人群中进一步进行效力研究.

Impact of metabolic syndrome on short-term outcome of carotid revascularization: a large sample size study in Chinese population

Background:Metabolic syndrome(MetS)is relatively common worldwide and an important risk factor for cardiovascular diseases.It is closely linked to arterial stiffness of the carotid artery.However,the association of MetS with the safety of carotid revascularization has been rarely studied.The aim of this study was to observe the current status of MetS and its components in Chinese carotid revascularized patients,and investigate the impact on major adverse clinical events(MACEs)after carotid endarterectomy(CEA)or carotid artery stenting(CAS).Methods:From January 2013 to December 2017,patients undergoing CEA or CAS in the Neurosurgery Department of Xuanwu Hospital were retrospectively recruited.The changes in prevalence of MetS and each component with time were investigated.The primary outcome was 30-day post-operative MACEs.Univariable and multivariable analyses were performed to identify the impact of MetS on CEA or CAS.Results:A total of 2068 patients who underwent CEA(766 cases)or CAS(1302 cases)were included.The rate of MetS was 17.9%;the prevalence rate of MetS increased with time.The occurrence rate of MACEs in CEA was 3.4%(26 cases)and in CAS,3.1%(40 cases).There was no statistical difference between the two groups(3.4%vs.3.1%,P=0.600).For CEA patients,univariate analysis showed that the MACE(+)group had increased diabetes history(53.8%vs.30.9%,P=0.014)and MetS(34.6%vs.15.8%,P=0.023).For CAS patients,univariate analysis showed that the MACE(+)group had increased coronary artery disease history(40.0%vs.21.6%,P=0.006)and internal carotid artery tortuosity(67.5%%vs.37.6%,P<0.001).Furthermore,the MACE(+)group had higher systolic blood pressure(143.38±22.74 vs.135.42±17.17 mmHg,P=0.004).Multivariable analysis showed that the influencing factors for MACEs in CEA included history of diabetes(odds ratio[OR]=2.345;95%confidence interval[CI]=1.057-5.205;P=0.036)and MetS(OR=2.476;95%CI=1.065-5.757;P=0.035).The influencing factors for MACEs in CAS included systolic blood pressure(OR=1.023;95%CI=1.005-1.040;P=0.010),coronary artery disease(OR=2.382;95%CI=1.237-4.587;P=0.009)and internal carotid artery tortuosity(OR=3.221;95%CI=1.637-6.337;P=0.001).Conclusions:The prevalence rate of MetS increased with time in carotid revascularized patients.MetS is a risk for short-term MACEs after CEA,but not CAS.