Debates regarding the specific effects of general anesthesia on developing brains have persisted for over 30 years.A consensus has been reached that prolonged,repeated,high-dose exposure to anesthetics is associated w...Debates regarding the specific effects of general anesthesia on developing brains have persisted for over 30 years.A consensus has been reached that prolonged,repeated,high-dose exposure to anesthetics is associated with a higher incidence of deficits in behavior and executive function,while single exposure has a relatively minor effect on long-term neurological function.In this review,we summarize the dose-dependent neuroprotective or neurotoxic effects of gamma-aminobutyric acid type A receptor agonists,a representative group of sedatives,on developing brains or central nervous system diseases.Most preclinical research indicates that anesthetics have neurotoxic effects on the developing brain through various signal pathways.However,recent studies on low-dose anesthetics suggest that they may promote neurodevelopment during this critical period.These findings are incomprehensible for the general“dose-effect”principles of pharmacological research,which has attracted researchers'interest and led to the following questions:What is the threshold for the dual effects exerted by anesthetics such as propofol and sevoflurane on the developing brain?To what extent can their protective effects be maximized?What are the underlying mechanisms involved in these effects?Consequently,this issue has essentially become a“mathematical problem.”After summarizing the dose-dependent effects of gamma-aminobutyric acid type A receptor agonist sedatives in both the developing brain and the brains of patients with central nervous system diseases,we believe that all such anesthetics exhibit specific threshold effects unique to each drug.These effects range from neuroprotection to neurotoxicity,depending on different brain functional states.However,the exact values of the specific thresholds for different drugs in various brain states,as well as the underlying mechanisms explaining why these thresholds exist,remain unclear.Further in-depth exploration of these issues could significantly enhance the therapeutic translational value of these anesthetics.展开更多
The objective of this research was to acquire a raindrop size distribution(DSDs)retrieved from C-band polarimetric radar observations scheme for the first time in south China.An observation period of the precipitation...The objective of this research was to acquire a raindrop size distribution(DSDs)retrieved from C-band polarimetric radar observations scheme for the first time in south China.An observation period of the precipitation process was selected,and the shape-slope(μ-Λ)relationship of this region was statistically analyzed using the raindrop sample observations from the two-dimensional video disdrometer(2DVD)at Xinfeng Station,Guangdong Province.Simulated data of the C-band polarimetric radar reflectivity ZHHand differential reflectivity ZDRwere obtained through scattering simulation.The simulation data were combined with DSD fitting to determine the ZDR-Λand log10(ZHH/N0)-Λrelationships.Using Xinfeng C-band polarimetric radar observations ZDRand ZHH,the raindrop Gamma size distribution parametersμ,Λ,and N0were retrieved.A scheme for using C-band polarimetric radar to retrieve the DSDs was developed.This research revealed that during precipitation process,the DSDs obtained using the C-band polarimetric radar retrieval scheme are similar to the 2DVD observations,the precipitation characteristics of rainfall intensity(R),mass-weighted mean diameter(Dm)and intercept parameter(Nw)with time obtained by radar retrieval are basically consistent with the observational results of the 2DVD.This scheme establishes the relationship between the observations of the C-band polarimetric radar and the physical quantities of the numerical model.This method not only can test the prediction of the model data assimilation system on the convective scale and determine error sources,but also can improve the microphysical precipitation processes analysis and radar quantitative precipitation estimation.The present research will facilitate radar data assimilation in the future.展开更多
Preservation conditions are key to enriching shallow shale gas.Therefore,the veins of two typical wells in the Shixi syncline in northern Guizhou as research objects.Based on core observation,vein thin-section observa...Preservation conditions are key to enriching shallow shale gas.Therefore,the veins of two typical wells in the Shixi syncline in northern Guizhou as research objects.Based on core observation,vein thin-section observation,cathodoluminescence,calcite in situ U-Pb dating,fluid inclusion microthermometry,Raman spectrum shift,single well basin simulation,and C-O isotope geochemical analysis,the researchers clarified the characteristics of the veins and the differences in paleofluid activity,as well as their significance for shale gas preservation.The results showed that:1)a small number of high-angle fractures had developed mainly in the Shixi syncline in northern Guizhou.The width of viens is small and filled primarily with early calcite-quartz and late calcite.The inclusions were mainly methane and brine.The proportion of brine inclusions in the SD1 well was greater than that in the SX1 well.The SD1 well has experienced more intense second-stage uplift and denudation,and the consequent gas loss is serious.2)The results of the C-O isotope analysis showed that most of the vein-forming fluids were derived from marine carbonate rocks.The O_(3)b had obvious negative deviations ofδ^(13)C andδ^(18)O,which were modified by exogenous or deep hydrothermal fluid.The C-O isotope difference between the vein bodies and the surrounding rock of the SX1 well was small,and the preservation conditions were better.3)The difference in gas content in the Shixi syncline depends on the degree of damage to gas reservoir preservation conditions caused by burial depth and other factors.Shixi syncline is a wide and gentle syncline with central retention enrichment mode.Therefore,clarifying the development of shale veins,the characteristics of paleofluid activity,and their significance for shale gas preservation can lay a foundation for studying the enrichment mechanism of shallow shale gas and thus guide further exploration and development.展开更多
铸造耐热Al-Si-Cu-Ni-Mg合金是制备高功率密度发动机活塞等耐热轻量化部件的重要基础材料,通过添加高熔点、低热扩散系数的Sc元素来调控合金的相结构和形貌是提升此类合金耐温性的重要思路。因此,探究了Sc元素添加及其含量对铸造耐热Al-...铸造耐热Al-Si-Cu-Ni-Mg合金是制备高功率密度发动机活塞等耐热轻量化部件的重要基础材料,通过添加高熔点、低热扩散系数的Sc元素来调控合金的相结构和形貌是提升此类合金耐温性的重要思路。因此,探究了Sc元素添加及其含量对铸造耐热Al-Si-Cu-Ni-Mg活塞合金凝固组织和热暴露过程中富铜镍相组织演变的影响。结果表明,随Sc含量增加,活塞合金中形成Al Si CuNiSc新相,并且Al Si CuNiSc相的数量和尺寸随Sc含量的增加而增加;此外,随着Al Si CuNiSc相的形成,δ-Al_(3)CuNi相发生由典型共晶层片向棒杆状组织的转变。热暴露过程中,δ-Al_(3)CuNi相中的Cu和Ni原子向α-Al基体中扩散,并在δ-Al_(3)CuNi的相界面处形成纳米尺度的γ-Al_(7)Cu_(4)Ni相;而富Sc的Al Si CuNiSc相在热暴露前后形貌和成分几乎不发生变化,表现出极高的热稳定性;分析认为,高熔点、低热扩散系数的Si和Sc等原子在富铜镍相中的存在极大提高了富铜镍相的热稳定性。展开更多
基于中国气象局龙门云物理野外科学试验基地2DVD(Two-Dimensional Video Disdrometer)雨滴谱观测资料,分析广东地区2017年5月4日(槽前型飑线)和2017年8月22日(东风型飑线)两次不同飑线系统不同降水类型的雨滴谱特征。根据雨强和雷达反...基于中国气象局龙门云物理野外科学试验基地2DVD(Two-Dimensional Video Disdrometer)雨滴谱观测资料,分析广东地区2017年5月4日(槽前型飑线)和2017年8月22日(东风型飑线)两次不同飑线系统不同降水类型的雨滴谱特征。根据雨强和雷达反射率随时间变化将降水分成对流降水和层云降水,同时以20 mm/h为阈值将对流降水划分为对流前沿、对流中心和对流后沿。结果表明,两次飑线系统在不同降水时期的微物理特征参数变化有所差异。槽前型飑线过程中,对流降水的粒子分布较为分散,中等粒径的粒子比重较高,且对流区前半部分粒子尺寸大于“大陆性”对流特征,后半部分粒子尺寸小于“海洋性”对流特征;层云降水的粒子分布较为集中,小粒径粒子居多。而东风型飑线整个降水时期基本上是由高浓度中小粒径粒子组成,降水粒子粒径分布较为集中,对流降水粒子介于“海洋性”和“大陆性”对流区之间。展开更多
文摘Debates regarding the specific effects of general anesthesia on developing brains have persisted for over 30 years.A consensus has been reached that prolonged,repeated,high-dose exposure to anesthetics is associated with a higher incidence of deficits in behavior and executive function,while single exposure has a relatively minor effect on long-term neurological function.In this review,we summarize the dose-dependent neuroprotective or neurotoxic effects of gamma-aminobutyric acid type A receptor agonists,a representative group of sedatives,on developing brains or central nervous system diseases.Most preclinical research indicates that anesthetics have neurotoxic effects on the developing brain through various signal pathways.However,recent studies on low-dose anesthetics suggest that they may promote neurodevelopment during this critical period.These findings are incomprehensible for the general“dose-effect”principles of pharmacological research,which has attracted researchers'interest and led to the following questions:What is the threshold for the dual effects exerted by anesthetics such as propofol and sevoflurane on the developing brain?To what extent can their protective effects be maximized?What are the underlying mechanisms involved in these effects?Consequently,this issue has essentially become a“mathematical problem.”After summarizing the dose-dependent effects of gamma-aminobutyric acid type A receptor agonist sedatives in both the developing brain and the brains of patients with central nervous system diseases,we believe that all such anesthetics exhibit specific threshold effects unique to each drug.These effects range from neuroprotection to neurotoxicity,depending on different brain functional states.However,the exact values of the specific thresholds for different drugs in various brain states,as well as the underlying mechanisms explaining why these thresholds exist,remain unclear.Further in-depth exploration of these issues could significantly enhance the therapeutic translational value of these anesthetics.
基金National Key R&D Program of China(2018YFC1507401)Science and Technology Planning Project of Guangdong Province(2017B020244002)+1 种基金National Natural Science Foundation of China(41975138,41705020)Natural Science Foundation of Guangdong Province(2019A1515010814)。
文摘The objective of this research was to acquire a raindrop size distribution(DSDs)retrieved from C-band polarimetric radar observations scheme for the first time in south China.An observation period of the precipitation process was selected,and the shape-slope(μ-Λ)relationship of this region was statistically analyzed using the raindrop sample observations from the two-dimensional video disdrometer(2DVD)at Xinfeng Station,Guangdong Province.Simulated data of the C-band polarimetric radar reflectivity ZHHand differential reflectivity ZDRwere obtained through scattering simulation.The simulation data were combined with DSD fitting to determine the ZDR-Λand log10(ZHH/N0)-Λrelationships.Using Xinfeng C-band polarimetric radar observations ZDRand ZHH,the raindrop Gamma size distribution parametersμ,Λ,and N0were retrieved.A scheme for using C-band polarimetric radar to retrieve the DSDs was developed.This research revealed that during precipitation process,the DSDs obtained using the C-band polarimetric radar retrieval scheme are similar to the 2DVD observations,the precipitation characteristics of rainfall intensity(R),mass-weighted mean diameter(Dm)and intercept parameter(Nw)with time obtained by radar retrieval are basically consistent with the observational results of the 2DVD.This scheme establishes the relationship between the observations of the C-band polarimetric radar and the physical quantities of the numerical model.This method not only can test the prediction of the model data assimilation system on the convective scale and determine error sources,but also can improve the microphysical precipitation processes analysis and radar quantitative precipitation estimation.The present research will facilitate radar data assimilation in the future.
文摘Preservation conditions are key to enriching shallow shale gas.Therefore,the veins of two typical wells in the Shixi syncline in northern Guizhou as research objects.Based on core observation,vein thin-section observation,cathodoluminescence,calcite in situ U-Pb dating,fluid inclusion microthermometry,Raman spectrum shift,single well basin simulation,and C-O isotope geochemical analysis,the researchers clarified the characteristics of the veins and the differences in paleofluid activity,as well as their significance for shale gas preservation.The results showed that:1)a small number of high-angle fractures had developed mainly in the Shixi syncline in northern Guizhou.The width of viens is small and filled primarily with early calcite-quartz and late calcite.The inclusions were mainly methane and brine.The proportion of brine inclusions in the SD1 well was greater than that in the SX1 well.The SD1 well has experienced more intense second-stage uplift and denudation,and the consequent gas loss is serious.2)The results of the C-O isotope analysis showed that most of the vein-forming fluids were derived from marine carbonate rocks.The O_(3)b had obvious negative deviations ofδ^(13)C andδ^(18)O,which were modified by exogenous or deep hydrothermal fluid.The C-O isotope difference between the vein bodies and the surrounding rock of the SX1 well was small,and the preservation conditions were better.3)The difference in gas content in the Shixi syncline depends on the degree of damage to gas reservoir preservation conditions caused by burial depth and other factors.Shixi syncline is a wide and gentle syncline with central retention enrichment mode.Therefore,clarifying the development of shale veins,the characteristics of paleofluid activity,and their significance for shale gas preservation can lay a foundation for studying the enrichment mechanism of shallow shale gas and thus guide further exploration and development.
文摘铸造耐热Al-Si-Cu-Ni-Mg合金是制备高功率密度发动机活塞等耐热轻量化部件的重要基础材料,通过添加高熔点、低热扩散系数的Sc元素来调控合金的相结构和形貌是提升此类合金耐温性的重要思路。因此,探究了Sc元素添加及其含量对铸造耐热Al-Si-Cu-Ni-Mg活塞合金凝固组织和热暴露过程中富铜镍相组织演变的影响。结果表明,随Sc含量增加,活塞合金中形成Al Si CuNiSc新相,并且Al Si CuNiSc相的数量和尺寸随Sc含量的增加而增加;此外,随着Al Si CuNiSc相的形成,δ-Al_(3)CuNi相发生由典型共晶层片向棒杆状组织的转变。热暴露过程中,δ-Al_(3)CuNi相中的Cu和Ni原子向α-Al基体中扩散,并在δ-Al_(3)CuNi的相界面处形成纳米尺度的γ-Al_(7)Cu_(4)Ni相;而富Sc的Al Si CuNiSc相在热暴露前后形貌和成分几乎不发生变化,表现出极高的热稳定性;分析认为,高熔点、低热扩散系数的Si和Sc等原子在富铜镍相中的存在极大提高了富铜镍相的热稳定性。
文摘基于中国气象局龙门云物理野外科学试验基地2DVD(Two-Dimensional Video Disdrometer)雨滴谱观测资料,分析广东地区2017年5月4日(槽前型飑线)和2017年8月22日(东风型飑线)两次不同飑线系统不同降水类型的雨滴谱特征。根据雨强和雷达反射率随时间变化将降水分成对流降水和层云降水,同时以20 mm/h为阈值将对流降水划分为对流前沿、对流中心和对流后沿。结果表明,两次飑线系统在不同降水时期的微物理特征参数变化有所差异。槽前型飑线过程中,对流降水的粒子分布较为分散,中等粒径的粒子比重较高,且对流区前半部分粒子尺寸大于“大陆性”对流特征,后半部分粒子尺寸小于“海洋性”对流特征;层云降水的粒子分布较为集中,小粒径粒子居多。而东风型飑线整个降水时期基本上是由高浓度中小粒径粒子组成,降水粒子粒径分布较为集中,对流降水粒子介于“海洋性”和“大陆性”对流区之间。
