为了克服现有Internet架构存在的众所周知的缺点,未来网络的研究成为热点.ICN(information-centricnetworking)在众多新架构中正逐渐被公认为最有前途的方案.它把传输的内容缓存到沿途的节点.高效的缓存机制是它的一个重要研究方面.为此...为了克服现有Internet架构存在的众所周知的缺点,未来网络的研究成为热点.ICN(information-centricnetworking)在众多新架构中正逐渐被公认为最有前途的方案.它把传输的内容缓存到沿途的节点.高效的缓存机制是它的一个重要研究方面.为此,提出了一种在分布式缓存机制中嵌入中心式缓存决策的机制(content-awareplacement,discovery and replacement,简称APDR),它把内容的放置、发现、替换统一起来考虑,实现内容的有序缓存,提高网络的性能.APDR的主要思想是:Interest报文除了携带对内容的请求以外,还收集沿途各节点对该内容的潜在需求、空闲缓存等信息,使得Interest的汇聚点和目的地节点可以据此计算出一个缓存方案,并把该方案附加在Data报文上,通知返程途中的某些节点缓存该内容并设置指定的缓存时间.在多种实验条件下对APDR进行了仿真验证,结果表明,APDR可以改善网络性能,包括缓存命中率、接入代价、替换数量、转发效率以及缓存鲁棒性等;而且APDR的额外开销也不大.展开更多
Background:The aortic arch replacement and cardiopulmonary bypass(CPB)are both associated with the early mortality after cardiothoracic surgery.This study aimed to investigate the relationship between CPB time and 90-...Background:The aortic arch replacement and cardiopulmonary bypass(CPB)are both associated with the early mortality after cardiothoracic surgery.This study aimed to investigate the relationship between CPB time and 90-day post-operative mortality in patients undergoing aortic arch surgery using the frozen elephant trunk(FET)technique with selective ante-grade cerebral perfusion(SACP).Methods:We retrospectively reviewed data of 377 adult patients undergoing aortic arch surgery via FET with SACP from July 1,2017 to December 31,2018 at Beijing Anzhen Hospital.The baseline characteristics,intra-operative data,and post-operative data were collected.Univariate and multivariate Cox regression analyses were used to determine independent predictors of 90-day postoperative mortality.Results:The 90-day post-operative mortality was 13.53%.The 78.51%of patients were men.There were 318(84.35%)type A aortic dissections and 28(7.43%)aortic aneurysms.Among those,264(70.03%)were emergency operations.Median CPB time was 202.0(176.0,227.0)min.Multivariate Cox regression analysis revealed that CPB time was independently associated with 90-day post-operative mortality after adjusting confounding factors(hazard ratio:1.21/10 min increase in CPB time,95%confidence interval:1.15–1.27,P<0.001).Kaplan-Meier analysis based on CPB time tertiles revealed that the top tertile(median 236.0 min)was associated with reduced survival rate compared with middle and bottom tertiles(P<0.001).Each sub-group analysis based on the complexity of the underlying disease process showed similar associations between CPB time and 90-day post-operative mortality.Conclusions:CPB time remains a significant factor in determining 90-day post-operative mortality in patients undergoing aortic arch surgery using FET with SACP.Surgeons should be aware of the relationship between CPB time and 90-day post-operative mortality during operative procedures and avoid extended CPB time as far as possible.展开更多
文摘为了克服现有Internet架构存在的众所周知的缺点,未来网络的研究成为热点.ICN(information-centricnetworking)在众多新架构中正逐渐被公认为最有前途的方案.它把传输的内容缓存到沿途的节点.高效的缓存机制是它的一个重要研究方面.为此,提出了一种在分布式缓存机制中嵌入中心式缓存决策的机制(content-awareplacement,discovery and replacement,简称APDR),它把内容的放置、发现、替换统一起来考虑,实现内容的有序缓存,提高网络的性能.APDR的主要思想是:Interest报文除了携带对内容的请求以外,还收集沿途各节点对该内容的潜在需求、空闲缓存等信息,使得Interest的汇聚点和目的地节点可以据此计算出一个缓存方案,并把该方案附加在Data报文上,通知返程途中的某些节点缓存该内容并设置指定的缓存时间.在多种实验条件下对APDR进行了仿真验证,结果表明,APDR可以改善网络性能,包括缓存命中率、接入代价、替换数量、转发效率以及缓存鲁棒性等;而且APDR的额外开销也不大.
文摘Background:The aortic arch replacement and cardiopulmonary bypass(CPB)are both associated with the early mortality after cardiothoracic surgery.This study aimed to investigate the relationship between CPB time and 90-day post-operative mortality in patients undergoing aortic arch surgery using the frozen elephant trunk(FET)technique with selective ante-grade cerebral perfusion(SACP).Methods:We retrospectively reviewed data of 377 adult patients undergoing aortic arch surgery via FET with SACP from July 1,2017 to December 31,2018 at Beijing Anzhen Hospital.The baseline characteristics,intra-operative data,and post-operative data were collected.Univariate and multivariate Cox regression analyses were used to determine independent predictors of 90-day postoperative mortality.Results:The 90-day post-operative mortality was 13.53%.The 78.51%of patients were men.There were 318(84.35%)type A aortic dissections and 28(7.43%)aortic aneurysms.Among those,264(70.03%)were emergency operations.Median CPB time was 202.0(176.0,227.0)min.Multivariate Cox regression analysis revealed that CPB time was independently associated with 90-day post-operative mortality after adjusting confounding factors(hazard ratio:1.21/10 min increase in CPB time,95%confidence interval:1.15–1.27,P<0.001).Kaplan-Meier analysis based on CPB time tertiles revealed that the top tertile(median 236.0 min)was associated with reduced survival rate compared with middle and bottom tertiles(P<0.001).Each sub-group analysis based on the complexity of the underlying disease process showed similar associations between CPB time and 90-day post-operative mortality.Conclusions:CPB time remains a significant factor in determining 90-day post-operative mortality in patients undergoing aortic arch surgery using FET with SACP.Surgeons should be aware of the relationship between CPB time and 90-day post-operative mortality during operative procedures and avoid extended CPB time as far as possible.
