BACKGROUND Cardiac resynchronization therapy(CRT)has been a major therapeutic advancement for patients with heart failure and electrical dyssynchrony.While CRT improves symptoms,reduces hospitalizations,and enhances s...BACKGROUND Cardiac resynchronization therapy(CRT)has been a major therapeutic advancement for patients with heart failure and electrical dyssynchrony.While CRT improves symptoms,reduces hospitalizations,and enhances survival,the role of implantable cardioverter-defibrillators(ICDs)alongside CRT in patients with non-ischemic cardiomyopathy(NICM)remains controversial.To evaluate and compare the outcomes of CRT with ICD(CRT-D)versus CRT with pacemaker-only(CRT-P)in individuals diagnosed with NICM,with a specific focus on the elderly.METHODS A comprehensive search of PubMed,Embase,and the Cochrane Central Register of Controlled Trials was conducted in January 2024.Studies comparing CRT-D and CRT-P in patients with NICM were included,with subgroup analyses focusing on patients aged 75 years and older.RESULTS Twelve studies,including two randomized clinical trials,with a total of 62,145 patients and 16,754 pooled death events(9,171 in CRT-D and 7,583 in CRT-P),were analyzed.CRT-D was associated with a significantly lower risk of all-cause mortality compared to CRT-P(pooled OR=0.72;95%CI:0.61-0.85;P<0.01),with significant heterogeneity(I2=83%).RCT subgroup analysis,was not statistically significant(pooled OR=0.82;95%CI:0.64-1.06;P=0.41;I2=0%).In patients older than 75 years,no significant difference in mortality risk was observed(pooled OR 0.96;95%CI:0.81-1.15;I2=39%).CONCLUSION Our meta-analysis suggests that the addition of ICD therapy to CRT in patients with NICM significantly reduces all-cause mortality.However,this benefit does not extend to cardiovascular mortality,likely due to the primary role of ICDs in preventing sudden cardiac death rather than other causes such as progressive heart failure.The survival advantage of CRT-D is most pronounced in younger patients,with those over 75 years of age deriving less benefit.This highlights the importance of careful patient selection,considering age and comorbidities,when deciding on ICD implantation in NICM patients.展开更多
This study focuses on the distribution of high-resistance media(pores and spinels)within ZnO varistors and explores the mechanical and electrical failure mechanisms of varistors under different pulse actions.Micro-CT ...This study focuses on the distribution of high-resistance media(pores and spinels)within ZnO varistors and explores the mechanical and electrical failure mechanisms of varistors under different pulse actions.Micro-CT technology revealed that the proportion of high-resistance media in the edge area is much higher than in the internal area.Simulation results indicated that a high porosity significantly increased temperature rise and thermal stress concentration,while a high spinel proportion exacerbated current concentration but had a relatively minor impact on the distribution of temperature rise and thermal stress.Under an electric field of 1000-1250 V/mm,pores transition from an insulating state to a conductive state,especially in the edge area,leading to concentrated temperature rise and thermal stress.Once the thermal stress exceeded the critical value of the mechanical strength of the pores,cracking failure occurred.The high spinel proportion in the edge area further intensified current concentration under high electric fields,working together with the conductivity of the pores to produce a significant local temperature rise,melting grain structure,and ultimately leading to puncture failure.This study provides a new perspective for understanding the failure mechanism of ZnO varistors and lays a theoretical foundation for the development of varistor materials with high energy absorption capacity.展开更多
Controversies still exist over the necessity of equipping with an emergency water supply system in the supercritical circulating fluidized bed/CFB unit.To resolve the dispute,research on the safety of the heating surf...Controversies still exist over the necessity of equipping with an emergency water supply system in the supercritical circulating fluidized bed/CFB unit.To resolve the dispute,research on the safety of the heating surfaces in the supercritical CFB boiler during the electricity failure accident under the assumption of not putting the emergency water supply system into use must be conducted.However,due to the low incidence rate of this accident,no relevant data have been reported yet.To provide useful data for the related research,a breakdown accident of the main feed water pump that happened in a 350 MW supercritical CFB boiler was introduced in this work.The analysis of the physical processes in both the furnace and water side of the boiler during this accident was performed.Then the discussion on the similarities and discrepancies between the two accidents was carried out.It was found out that with appropriate handling,the data collected in two periods of the breakdown accident of the main feed water pump can provide a reference for the verification of the prediction model of the electricity failure accident.Finally,a preliminary prediction model was established as the first step of the verification work.展开更多
文摘BACKGROUND Cardiac resynchronization therapy(CRT)has been a major therapeutic advancement for patients with heart failure and electrical dyssynchrony.While CRT improves symptoms,reduces hospitalizations,and enhances survival,the role of implantable cardioverter-defibrillators(ICDs)alongside CRT in patients with non-ischemic cardiomyopathy(NICM)remains controversial.To evaluate and compare the outcomes of CRT with ICD(CRT-D)versus CRT with pacemaker-only(CRT-P)in individuals diagnosed with NICM,with a specific focus on the elderly.METHODS A comprehensive search of PubMed,Embase,and the Cochrane Central Register of Controlled Trials was conducted in January 2024.Studies comparing CRT-D and CRT-P in patients with NICM were included,with subgroup analyses focusing on patients aged 75 years and older.RESULTS Twelve studies,including two randomized clinical trials,with a total of 62,145 patients and 16,754 pooled death events(9,171 in CRT-D and 7,583 in CRT-P),were analyzed.CRT-D was associated with a significantly lower risk of all-cause mortality compared to CRT-P(pooled OR=0.72;95%CI:0.61-0.85;P<0.01),with significant heterogeneity(I2=83%).RCT subgroup analysis,was not statistically significant(pooled OR=0.82;95%CI:0.64-1.06;P=0.41;I2=0%).In patients older than 75 years,no significant difference in mortality risk was observed(pooled OR 0.96;95%CI:0.81-1.15;I2=39%).CONCLUSION Our meta-analysis suggests that the addition of ICD therapy to CRT in patients with NICM significantly reduces all-cause mortality.However,this benefit does not extend to cardiovascular mortality,likely due to the primary role of ICDs in preventing sudden cardiac death rather than other causes such as progressive heart failure.The survival advantage of CRT-D is most pronounced in younger patients,with those over 75 years of age deriving less benefit.This highlights the importance of careful patient selection,considering age and comorbidities,when deciding on ICD implantation in NICM patients.
基金National Natural Science Foundation of China(Youth Fund Program),Grant/Award Number:52107158Natural Science Foundation of Sichuan Province,Grant/Award Number:2024NSFSC0116Project of‘Gathering Resources to Prosper Sichuan’,Grant/Award Number:25JYXC0046。
文摘This study focuses on the distribution of high-resistance media(pores and spinels)within ZnO varistors and explores the mechanical and electrical failure mechanisms of varistors under different pulse actions.Micro-CT technology revealed that the proportion of high-resistance media in the edge area is much higher than in the internal area.Simulation results indicated that a high porosity significantly increased temperature rise and thermal stress concentration,while a high spinel proportion exacerbated current concentration but had a relatively minor impact on the distribution of temperature rise and thermal stress.Under an electric field of 1000-1250 V/mm,pores transition from an insulating state to a conductive state,especially in the edge area,leading to concentrated temperature rise and thermal stress.Once the thermal stress exceeded the critical value of the mechanical strength of the pores,cracking failure occurred.The high spinel proportion in the edge area further intensified current concentration under high electric fields,working together with the conductivity of the pores to produce a significant local temperature rise,melting grain structure,and ultimately leading to puncture failure.This study provides a new perspective for understanding the failure mechanism of ZnO varistors and lays a theoretical foundation for the development of varistor materials with high energy absorption capacity.
基金financial supported by the National Key Research Plan(2019YFE0102100)Huaneng Group Science and Technology Research Project(HNKJ20-H50)C9 University Science and Technology Project(201903D421009)。
文摘Controversies still exist over the necessity of equipping with an emergency water supply system in the supercritical circulating fluidized bed/CFB unit.To resolve the dispute,research on the safety of the heating surfaces in the supercritical CFB boiler during the electricity failure accident under the assumption of not putting the emergency water supply system into use must be conducted.However,due to the low incidence rate of this accident,no relevant data have been reported yet.To provide useful data for the related research,a breakdown accident of the main feed water pump that happened in a 350 MW supercritical CFB boiler was introduced in this work.The analysis of the physical processes in both the furnace and water side of the boiler during this accident was performed.Then the discussion on the similarities and discrepancies between the two accidents was carried out.It was found out that with appropriate handling,the data collected in two periods of the breakdown accident of the main feed water pump can provide a reference for the verification of the prediction model of the electricity failure accident.Finally,a preliminary prediction model was established as the first step of the verification work.
