It is urgent to develop catalysts with application potential for oxidative coupling of methane(OCM)at relatively lower temperature.Herein,three-dimensional ordered macro porous(3 DOM)La_(2-x)Sr_(x)Ce_(2-y)CayO_(7-δ)(...It is urgent to develop catalysts with application potential for oxidative coupling of methane(OCM)at relatively lower temperature.Herein,three-dimensional ordered macro porous(3 DOM)La_(2-x)Sr_(x)Ce_(2-y)CayO_(7-δ)(A_(2)B_(2)O_(7)-type)catalysts with disordered defective cubic fluorite phased structure were successfully prepared by a colloidal crystal template method.3DOM structure promotes the accessibility of the gaseous reactants(O2and CH4)to the active sites.The co-doping of Ca and Sr ions in La_(2-x)Sr_(x)Ce_(2-y)CayO_(7-δ)catalysts improved the formation of oxygen vacancies,thereby leading to increased density of surface-active oxygen species(O_(2)^(-))for the activation of CH4and the formation of C2products(C2H6and C2H4).3DOM La_(2-x)Sr_(x)Ce_(2-y)CayO_(7-δ)catalysts exhibit high catalytic activity for OCM at low temperature.3DOM La1.7Sr0.3Ce1.7Ca0.3O7-δcatalyst with the highest density of O_(2)^(-)species exhibited the highest catalytic activity for low-temperature OCM,i.e.,its CH4conversion,selectivity and yield of C2products at 650℃are 32.2%,66.1%and 21.3%,respectively.The mechanism was proposed that the increase in surface oxygen vacancies induced by the co-doping of Ca and Sr ions boosts the key step of C-H bond breaking and C-C bond coupling in catalyzing low-temperature OCM.It is meaningful for the development of the low-temperature and high-efficient catalysts for OCM reaction in practical application.展开更多
AIM： To study an inherent effect of insulin on small intestinal transit and to explore involvement of various systems/mechanisms in normal mice. METHODS： Insulin at the doses of 2 μU/kg, 2 mU/kg, 2 U/kg or vehicle ...AIM： To study an inherent effect of insulin on small intestinal transit and to explore involvement of various systems/mechanisms in normal mice. METHODS： Insulin at the doses of 2 μU/kg, 2 mU/kg, 2 U/kg or vehicle was subcutaneously administered to four groups of overnight fasted normal male mice. Blood glucose （BG） levels were measured 2 min before insulin administration and 2 min before sacrificing the animals for the measurement of small intestinal transit （SIT）. Charcoal meal was administered （0.3 mL） intragastrically 20 min after insulin administration and animals were sacrificed after 20 min and SIT was determined. For exploration of the various mechanisms involved in insulin-induced effect on SIT, the dose of insulin which can produce a significant acceleration of SIT without altering BG levels was determined. The following drugs, atropine （1 mg/kg）, clonidine （0.1 mg/kg）, ondansetron （1 mg/kg）, naloxone （5 mg/kg）, verapamil （8 mg/kg） and glibenclamide （10 mg/kg）, were administered intravenously 10 min prior to the administration of insulin （2 μU/kg）. RESULTS： The lower doses of insulin （2 μU/kg and 2 mU/kg） produced a significant acceleration of SIT from 52.0% to 70.7% and 73.5% without lowering blood glucose levels （P〈0.01）, while the highest dose of insulin （2 U/kg） produced a fall in blood glucose levels which was also associated with significant acceleration of SIT （P〈0.01）. After pretreatment of insulin （2 μU/kg） group with atropine, insulin could reverse 50% of the inhibition produced by atropine. In clonidine-pretreated group, insulin administration could reverse only 37% of the inhibition produced by clonidine and inhibition of SIT was significant compared with vehicle ＋ insulintreated group, i.e. from 74.7% to 27.7% （P〈0.01）. In ondansetron-pretreated group, insulin administration could produce only mild acceleration of SIT （23.5%）. In naloxone-pretreated group, insulin administration could significantly reverse the inhibition of SIT produced by naloxone when compared with naloxoneperse group, i.e. from 32.3% to 53.9% （P〈0.01）. In verapamil-pretreated group, insulin administration could only partially reverse the inhibition （65%）. In glibenclamide-pretreated group, insulin administration produced further acceleration of SIT （12.2%）. CONCLUSION： Insulin inherently possesses an acceleratory effect on SIT in normal mice. Adrenergic and cholinergic systems can play a significant role. Calcium channels and opioidergic system can play a supportive role; in addition, enhancement of endogenous insulin release can augment the effect of exogenously administered insulin on SIT.展开更多
为满足41Ca生物示踪样品测量的需要,在北京HI-13串列加速器质谱(Accelerator Mass Spec- trometry,AMS)系统上建立了以CaF2为靶样的41Ca AMS分析方法.生物样品和41Ca标准样品经过化学分离和纯化,制备成CaF2作为靶物质,AMS测量41Ca时,离...为满足41Ca生物示踪样品测量的需要,在北京HI-13串列加速器质谱(Accelerator Mass Spec- trometry,AMS)系统上建立了以CaF2为靶样的41Ca AMS分析方法.生物样品和41Ca标准样品经过化学分离和纯化,制备成CaF2作为靶物质,AMS测量41Ca时,离子源引出CaF3-负离子,膜剥离后的电荷态选择为7+态,加速器端电压选定为8.5MV,用充有140mbarP10气体的多阳极电离室探测41Ca.结果显示探测器可实现对41Ca与同量异位素干扰41K的分辨,粒子谱中41K的计数率很低,对41Ca不形成干扰.对制备的4个标准样品(41Ca/40Ca在1.785×10-8-1.750×10-10范围)的测量结果显示41Ca/40Ca绝对测量值与标称值之间的线性关系良好(r2=0.997),经41Ca/40Ca为1.785×10-8的标准样品归一化后,S2,S4两个标样的测量值与标称值吻合较好,但标样S3的测量值与标称值有较大偏离.估计生物样品的41Ca/40Ca本底值低于8.2×10-13.展开更多
基金supported by the National Key Research and Development Program of China(Nos.2022YFB3504100,2022YFB3506200)the National Natural Science Foundation of China(Nos.22208373,22376217)+1 种基金the Beijing Nova Program(No.20220484215)the Science Foundation of China University of Petroleum,Beijing(No.2462023YJRC030)。
文摘It is urgent to develop catalysts with application potential for oxidative coupling of methane(OCM)at relatively lower temperature.Herein,three-dimensional ordered macro porous(3 DOM)La_(2-x)Sr_(x)Ce_(2-y)CayO_(7-δ)(A_(2)B_(2)O_(7)-type)catalysts with disordered defective cubic fluorite phased structure were successfully prepared by a colloidal crystal template method.3DOM structure promotes the accessibility of the gaseous reactants(O2and CH4)to the active sites.The co-doping of Ca and Sr ions in La_(2-x)Sr_(x)Ce_(2-y)CayO_(7-δ)catalysts improved the formation of oxygen vacancies,thereby leading to increased density of surface-active oxygen species(O_(2)^(-))for the activation of CH4and the formation of C2products(C2H6and C2H4).3DOM La_(2-x)Sr_(x)Ce_(2-y)CayO_(7-δ)catalysts exhibit high catalytic activity for OCM at low temperature.3DOM La1.7Sr0.3Ce1.7Ca0.3O7-δcatalyst with the highest density of O_(2)^(-)species exhibited the highest catalytic activity for low-temperature OCM,i.e.,its CH4conversion,selectivity and yield of C2products at 650℃are 32.2%,66.1%and 21.3%,respectively.The mechanism was proposed that the increase in surface oxygen vacancies induced by the co-doping of Ca and Sr ions boosts the key step of C-H bond breaking and C-C bond coupling in catalyzing low-temperature OCM.It is meaningful for the development of the low-temperature and high-efficient catalysts for OCM reaction in practical application.
文摘AIM： To study an inherent effect of insulin on small intestinal transit and to explore involvement of various systems/mechanisms in normal mice. METHODS： Insulin at the doses of 2 μU/kg, 2 mU/kg, 2 U/kg or vehicle was subcutaneously administered to four groups of overnight fasted normal male mice. Blood glucose （BG） levels were measured 2 min before insulin administration and 2 min before sacrificing the animals for the measurement of small intestinal transit （SIT）. Charcoal meal was administered （0.3 mL） intragastrically 20 min after insulin administration and animals were sacrificed after 20 min and SIT was determined. For exploration of the various mechanisms involved in insulin-induced effect on SIT, the dose of insulin which can produce a significant acceleration of SIT without altering BG levels was determined. The following drugs, atropine （1 mg/kg）, clonidine （0.1 mg/kg）, ondansetron （1 mg/kg）, naloxone （5 mg/kg）, verapamil （8 mg/kg） and glibenclamide （10 mg/kg）, were administered intravenously 10 min prior to the administration of insulin （2 μU/kg）. RESULTS： The lower doses of insulin （2 μU/kg and 2 mU/kg） produced a significant acceleration of SIT from 52.0% to 70.7% and 73.5% without lowering blood glucose levels （P〈0.01）, while the highest dose of insulin （2 U/kg） produced a fall in blood glucose levels which was also associated with significant acceleration of SIT （P〈0.01）. After pretreatment of insulin （2 μU/kg） group with atropine, insulin could reverse 50% of the inhibition produced by atropine. In clonidine-pretreated group, insulin administration could reverse only 37% of the inhibition produced by clonidine and inhibition of SIT was significant compared with vehicle ＋ insulintreated group, i.e. from 74.7% to 27.7% （P〈0.01）. In ondansetron-pretreated group, insulin administration could produce only mild acceleration of SIT （23.5%）. In naloxone-pretreated group, insulin administration could significantly reverse the inhibition of SIT produced by naloxone when compared with naloxoneperse group, i.e. from 32.3% to 53.9% （P〈0.01）. In verapamil-pretreated group, insulin administration could only partially reverse the inhibition （65%）. In glibenclamide-pretreated group, insulin administration produced further acceleration of SIT （12.2%）. CONCLUSION： Insulin inherently possesses an acceleratory effect on SIT in normal mice. Adrenergic and cholinergic systems can play a significant role. Calcium channels and opioidergic system can play a supportive role; in addition, enhancement of endogenous insulin release can augment the effect of exogenously administered insulin on SIT.
文摘为满足41Ca生物示踪样品测量的需要,在北京HI-13串列加速器质谱(Accelerator Mass Spec- trometry,AMS)系统上建立了以CaF2为靶样的41Ca AMS分析方法.生物样品和41Ca标准样品经过化学分离和纯化,制备成CaF2作为靶物质,AMS测量41Ca时,离子源引出CaF3-负离子,膜剥离后的电荷态选择为7+态,加速器端电压选定为8.5MV,用充有140mbarP10气体的多阳极电离室探测41Ca.结果显示探测器可实现对41Ca与同量异位素干扰41K的分辨,粒子谱中41K的计数率很低,对41Ca不形成干扰.对制备的4个标准样品(41Ca/40Ca在1.785×10-8-1.750×10-10范围)的测量结果显示41Ca/40Ca绝对测量值与标称值之间的线性关系良好(r2=0.997),经41Ca/40Ca为1.785×10-8的标准样品归一化后,S2,S4两个标样的测量值与标称值吻合较好,但标样S3的测量值与标称值有较大偏离.估计生物样品的41Ca/40Ca本底值低于8.2×10-13.
