Background:The ergogenic effects of caffeine intake on exercise performance are well-established,even if differences exist among individuals in response to caffeine intake.The genetic variation of a specific gene,huma...Background:The ergogenic effects of caffeine intake on exercise performance are well-established,even if differences exist among individuals in response to caffeine intake.The genetic variation of a specific gene,human cytochrome P450 enzyme 1A2(CYP1A2)(rs762551),may be one reason for this difference.This systematic review and meta-analysis aimed to comprehensively evaluate the influence of CYP1A2 gene types on athletes’exercise performance after caffeine intake.Methods:A literature search through 4 databases(Web of Science,PubMed,Scopus,and China National Knowledge Infrastructure)was conducted until March 2023.The effect size was expressed as the weighted mean difference(WMD)by calculating fixed effects meta-analysis if heterogeneity was not significant(I^(2)≤50%and p≥0.1).Subgroup analyses were performed based on AA and AC/CC genotype of CYP1A2.Results:The final number of studies meeting the inclusion criteria was 12(n=666 participants).The overall analysis showed that the cycling time trial significantly improved after caffeine intake(WMD=-0.48,95%confidence interval(95%CI):-0.83 to-0.13,p=0.007).In subgroup analyses,acute caffeine intake improved cycling time trial only in individuals with the A allele(WMD=-0.90,95%CI:-1.48 to-0.33,p=0.002),but not the C allele(WMD=-0.08,95%CI:-0.32 to 0.17,p=0.53).Caffeine supplementation did not influence the Wingate(WMD=8.07,95%CI:-22.04 to 38.18,p=0.60)or countermovement jump test(CMJ)performance(WMD=1.17,95%CI:-0.02 to 2.36,p=0.05),and these outcomes were not influenced by CYP1A2 genotype.Conclusion:Participants with the CYP1A2 genotype with A allele improved their cycling time trials after caffeine supplementation.However,compared to placebo,acute caffeine supplementation failed to increase the Wingate or CMJ performance,regardless of CYP1A2 genotype.展开更多
A novel optical instrumentation system for flame characterization was developed and tested. The two-color system is capable of performing on-line measurement of flame and temperature distribution, providing temporal a...A novel optical instrumentation system for flame characterization was developed and tested. The two-color system is capable of performing on-line measurement of flame and temperature distribution, providing temporal and spatial characterization of the combustion process. In addition, the system has the advantage of being non-intrusive. The on-line measurement of temperature distribution on a methane-air combustor revealed some interesting characteristics. When air flow rate was kept constant, an increase in CH4 flow rate would enhance the combustion intensity and elevate the flame temperature. While under constant CH4 flow rate, the increase of air flow rate would lead the measured flame temperature first to increase and then decrease. The drop of temperature might partially be caused by the heat losses due to excessive air. However, with insufficient soot particles in the flame, the temperature could be under-evaluated.展开更多
In recent years,the Middle East region countries have experienced rapid population and economy growth,which has resulted in large increase of energy and power demand.Although the traditional fossil fuels remain the ma...In recent years,the Middle East region countries have experienced rapid population and economy growth,which has resulted in large increase of energy and power demand.Although the traditional fossil fuels remain the majority for supplying the domestic demand,additional generating capacity and fuel supply are necessary according to current situation and future demand forecast.The renewable energy provides an alternative resource for satisfying demand,especially in this region with high potential of solar and wind energy.Besides the development of renewable energy,interconnected electricity networks also enable the cross-border power exchange to fulfil electricity demand.Many Middle East countries have already started developing renewable energy and reforming the national power sector for regional electricityintegration.However,none of them has already implemented their targets and the challenges are still huge.This study reviews current conditions of electricity and energy interconnection development,and analyzes the process of regional electricity network integration and national power sector reforms and provides suggestion for regions’plan.Finally,the technology developments for future power grid interconnection and renewable energy integration are also reviewed.展开更多
文摘Background:The ergogenic effects of caffeine intake on exercise performance are well-established,even if differences exist among individuals in response to caffeine intake.The genetic variation of a specific gene,human cytochrome P450 enzyme 1A2(CYP1A2)(rs762551),may be one reason for this difference.This systematic review and meta-analysis aimed to comprehensively evaluate the influence of CYP1A2 gene types on athletes’exercise performance after caffeine intake.Methods:A literature search through 4 databases(Web of Science,PubMed,Scopus,and China National Knowledge Infrastructure)was conducted until March 2023.The effect size was expressed as the weighted mean difference(WMD)by calculating fixed effects meta-analysis if heterogeneity was not significant(I^(2)≤50%and p≥0.1).Subgroup analyses were performed based on AA and AC/CC genotype of CYP1A2.Results:The final number of studies meeting the inclusion criteria was 12(n=666 participants).The overall analysis showed that the cycling time trial significantly improved after caffeine intake(WMD=-0.48,95%confidence interval(95%CI):-0.83 to-0.13,p=0.007).In subgroup analyses,acute caffeine intake improved cycling time trial only in individuals with the A allele(WMD=-0.90,95%CI:-1.48 to-0.33,p=0.002),but not the C allele(WMD=-0.08,95%CI:-0.32 to 0.17,p=0.53).Caffeine supplementation did not influence the Wingate(WMD=8.07,95%CI:-22.04 to 38.18,p=0.60)or countermovement jump test(CMJ)performance(WMD=1.17,95%CI:-0.02 to 2.36,p=0.05),and these outcomes were not influenced by CYP1A2 genotype.Conclusion:Participants with the CYP1A2 genotype with A allele improved their cycling time trials after caffeine supplementation.However,compared to placebo,acute caffeine supplementation failed to increase the Wingate or CMJ performance,regardless of CYP1A2 genotype.
基金The author gratefully acknowledges the support of K.C.Wang Education Foundation, Hong Kong.
文摘A novel optical instrumentation system for flame characterization was developed and tested. The two-color system is capable of performing on-line measurement of flame and temperature distribution, providing temporal and spatial characterization of the combustion process. In addition, the system has the advantage of being non-intrusive. The on-line measurement of temperature distribution on a methane-air combustor revealed some interesting characteristics. When air flow rate was kept constant, an increase in CH4 flow rate would enhance the combustion intensity and elevate the flame temperature. While under constant CH4 flow rate, the increase of air flow rate would lead the measured flame temperature first to increase and then decrease. The drop of temperature might partially be caused by the heat losses due to excessive air. However, with insufficient soot particles in the flame, the temperature could be under-evaluated.
基金supported by China EPRI under the State Grid Corporation of China Science and Technology Project“Research on the Framework of Cross-Border Electricity Trading Market”(No.5442DZ150052)the University of Birmingham
文摘In recent years,the Middle East region countries have experienced rapid population and economy growth,which has resulted in large increase of energy and power demand.Although the traditional fossil fuels remain the majority for supplying the domestic demand,additional generating capacity and fuel supply are necessary according to current situation and future demand forecast.The renewable energy provides an alternative resource for satisfying demand,especially in this region with high potential of solar and wind energy.Besides the development of renewable energy,interconnected electricity networks also enable the cross-border power exchange to fulfil electricity demand.Many Middle East countries have already started developing renewable energy and reforming the national power sector for regional electricityintegration.However,none of them has already implemented their targets and the challenges are still huge.This study reviews current conditions of electricity and energy interconnection development,and analyzes the process of regional electricity network integration and national power sector reforms and provides suggestion for regions’plan.Finally,the technology developments for future power grid interconnection and renewable energy integration are also reviewed.
