提前肝素化和超选择冠状动脉内注入替罗非班对STEMI患者PCI的影响

目的评价提前肝素化和超选择冠状动脉内注入替罗非班对急性ST段抬高心肌梗死(STEMI)患者经皮冠脉介入术(PCI)的影响。方法选取2016年1月—2018年12月中山大学附属第三医院粤东医院STEMI患者行急诊PCI共120例,随机将其分为对照组和观察组各60例。对照组采用常规PCI程序,观察组采用提前肝素化、直接用指引导管造影和超选择冠状动脉内注入替罗非班。比较两组靶血管TIMI血流3级的校正帧数,术后90 min的心电图ST段回落率,入院后30 min、6、12、24、36和48 h的心肌型酸酶同工酶(CK-MB)和血清心肌肌钙蛋白I(cTn I)值和到达峰值时间,住院期间主要心脏不良事件(MACE)和严重出血事件。结果观察组与对照组比较,TIMI校正帧数减小,ST段回落率增加,CK-MB和c Tn I的峰值降低,峰值时间提前,MACE发生率降低,差异有统计学意义(P <0.05)。两组严重出血事件比较差异无统计学意义(P>0.05)。结论提前肝素化和超选择冠状动脉内注入替罗非班对STEMI患者急诊PCI可缩短缺血心肌再灌注时间,增加心肌存活,改善近期预后。

Effects of Crystal Orientations on the Low-Cycle Fatigue of a Single-Crystal Nickel-Based Superalloy at 980 °C

The influence of crystal orientations on the low-cycle fatigue(LCF) behavior of a 3Re-bearing Ni-based single-crystal superalloy at 980 °C has been investigated. It is found that the orientation dependence of the fatigue life not only depends on the elastic modulus, but also the number of active slip planes and the plasticity of materials determine the LCF life,especially for the [011] and [111] specimens. The [011] and [111] specimens with better plasticity withstand relatively concentrated inelastic deformation caused by fewer active slip planes, compared to the [001] specimens resisting widespread deformation caused by a higher number of active slip planes. Additionally, fatigue fracture is also influenced by cyclic plastic deformation mechanisms of the alloy with crystal orientations, and the [001] specimens are plastically deformed by wave slip mechanism and fracture along the non-crystallographic plane, while the [011] and [111] specimens are plastically deformed by planar slip mechanism and fracture along the crystallographic planes. Moreover, casting pores,eutectics, inclusions and surface oxide layers not only initiate the crack, but also reduce the stress concentration around crack tips. Our results throw light upon the effect of inelastic strain on the LCF life and analyze the cyclic plastic deformation for the alloy with different orientations.

Role of Ru on the Microstructural Evolution During Long-Term Aging of Ni-Based Single Crystal Superalloys

Two experimental alloys containing diff erent contents of Ru were investigated to study the eff ect of Ru on the microstructural evolution during long-term thermal exposure.The increase in Ru promoted the formation of cubical,tiny,and evenγ′phase after full heat treatment.Moreover,the samples after full heat treatment were exposed at 1100℃ for diff erent time.Based on the classical model by Lifshitz,Slyozov,and Wagner,the coarsening ofγ′phase of the alloy containing 2.5 and3.5 wt.%Ru during the long-term aging was controlled by the interface reaction and diff usion,respectively.Theγ/γ′lattice misfi t was more negative with the increment of Ru addition,which induced the formation of stable raftedγ′phase in the alloy containing 3.5 wt.%Ru at the initiation of long-term aging.Besides,the increase in Ru reduced the diff usion coeffi cient,which could restrain theγ′phase coarsening.The lowerγ/γ′lattice misfi t of the alloy containing 2.5 wt.%Ru promoted the interface reaction,which induced the rapid coarsening ofγ′phase.Therefore,the increase in Ru improved the microstructural stability of the alloys.On the other hand,the raise of Ru induced"reverse partitioning"behavior,which was eff ective in suppressing the emergence of the topologically close-packed phase(TCP phase).The TCP phase occasionally occurred in the alloy containing 2.5 wt.%Ru,which was attributed to the high temperature and the supersaturation of theγmatrix.Moreover,the TCP phase was determined asμphase,which had a high concentration of Co,Re,Mo,and W.A sketch map describing the evolution of the TCP phase was also constructed.

Effect of Orientation on Stress-Rupture Property and Related Deformation Microstructure of a Ni-Base Re-containing Single-Crystal Superalloy at 900℃

Stress-rupture properties of a Ni-base Re-containing single-crystal superalloy with three orientations have been tested under 900℃/445 MPa.An obvious anisotropy of stress-rupture property is attributed to orientation reliant deformation microstructure.The good strength in[001]orientation is attributed to the rapid multiplication of dislocations active in horizontal channels and laterγ'cutting via dislocations pair coupled with anti-phase boundary.The microtwin formation largely limits the strength and plasticity as a result of the continuous shearing acrossγ/γ'microstructure by{111}112 slip activated in[011]orientation.The property in[111]orientation results mainly from the lateral cross-slip movements of the screw dislocations within connected matrix channels as well as the precipitate shearing by coplanar dislocations.Microcracks all initially originate from the interdendritic micropores in three orientations.The critical temperature of stress-rupture anisotropy could be increased by a high level of refractory solutes especially Re.

Effect of Interactions Among Elements on Diffusion Process Associated with γ′ Coarsening in a Ni-Based Single-Crystal Superalloy

Coarsening of cuboidal γ’ precipitates and relevant diffusion process in Ni-based single-crystal superalloy CMSX-4 were investigated at 1000,1020 and 1040℃ for specific times.The y’ coarsening kinetics followed a cubic rate law with time and was presumably controlled by bulk diffusion of elements in y matrix.The associated diffusion activation energy was experimentally determined to be about 300 kJ/mol when it is considered the temperature-dependent thermo-physical parameters in modified Lifshitz-Slyozov-Wagner theory.The influence of temperature on γ/γ’ microstructure is briefly discussed based on pseudo-binary [Ni]-[Al] phase diagram.Interactions among elements can effectively raise the local vacancy formation and vacancy-atom exchange barriers close to γ-and γ’-partitioning elements,respectively.Thus,it can significantly reduce the inter-coupling migrations of atoms during the macroscopic cross-diffusion process associated with γ’ coarsening of Ni-based superalloys.