THE Hanis are an ethnic farming group living in the mountainous area between the Honghe and Lancangjiang rivers in the south of Yunnan Province. Their language had no characters of its own until the Chinese Government...THE Hanis are an ethnic farming group living in the mountainous area between the Honghe and Lancangjiang rivers in the south of Yunnan Province. Their language had no characters of its own until the Chinese Government helped to create a set of characters based on Latin in the 1950s.展开更多
Uzbek〉Region：Around the 16th century,Uzbek businessmen traveled along the Silk Road to sell their goods in China.Some of them settled down in northwest China and formed the Uzbek ethnic minority of China.Today,they ...Uzbek〉Region：Around the 16th century,Uzbek businessmen traveled along the Silk Road to sell their goods in China.Some of them settled down in northwest China and formed the Uzbek ethnic minority of China.Today,they mainly live in the Xinjiang Uygur Autonomous Region.〉Population：Around 14,000〉Language：The Uzbek language belongs to the Turkic branch of the Altaic family.展开更多
DongTHE Dong people live mainly in Guizhou and Hunan provinces though they can also be found in the Guangxi Zhuang Autonomous Region, as well as Jiangsu, Guangdong and Zhejiang provinces. In addition to agriculture, t...DongTHE Dong people live mainly in Guizhou and Hunan provinces though they can also be found in the Guangxi Zhuang Autonomous Region, as well as Jiangsu, Guangdong and Zhejiang provinces. In addition to agriculture, they make their living by growing timber trees, which are then logged and sold. Trees are so important in their lives that they have a unique custom of planting 18 fir trees when a child is born. When the child reaches the age of 18 and gets married, the matured fir trees are felled and used to build houses for the bride and groom展开更多
Bouyei ）） MOST of the Bouyei people live in south Guizhou Province in southwest China, with the rest living scattered in Yunnan and Sichuan provinces and Guangxi Zhuang Autonomous Region. As valley dwellers blessed ...Bouyei ）） MOST of the Bouyei people live in south Guizhou Province in southwest China, with the rest living scattered in Yunnan and Sichuan provinces and Guangxi Zhuang Autonomous Region. As valley dwellers blessed with rivers, they enjoy a fertile land and mild climate, mak- ing their living from agriculture.展开更多
Korean THE Korean people mainly reside in northeast China, Their largest concentration is in the Yanbian Ko- rean Autonomous Prefecture in Jilin Province. They can also be found in Heilongjiang and Liaoning provinces ...Korean THE Korean people mainly reside in northeast China, Their largest concentration is in the Yanbian Ko- rean Autonomous Prefecture in Jilin Province. They can also be found in Heilongjiang and Liaoning provinces and the Inner Mongolia Autonomous Region, They have their own spoken and written language, Korean. which is also the official language of South and North Korea. The ancestors of the Korean ethnic group - mostly peasants fleeing their oppressive feudal landlords - migrated from the Korean Peninsula around the late 17th century. When they settled down in China they gradually formed unique customs, Today.展开更多
Mongolian AN ethnic group known for ＂growing up on horsebacks,＂ the Mongolians live mostly in the In- ner Mongolia Autonomous Region in the northern part of China, which includes vast tracts of excel- lent natural...Mongolian AN ethnic group known for ＂growing up on horsebacks,＂ the Mongolians live mostly in the In- ner Mongolia Autonomous Region in the northern part of China, which includes vast tracts of excel- lent natural pastureland with numerous herds of cattle, sheep, horses and camels. The rest are also distributed in Liaoning Jilin. Heilongjiang. Qinghai and Gansu provinces. Living on grasslands and relying on raising stock as their economic mainstay, the Mongolians have kept their nomadic living style for hundreds of years. Mongolian herdsmen used to live in yurts,which were usually seven to eight feet high and 10 feet in diameter, with an opening in the top of the umbrella-shaped roof. The structure can offer ideal ventilation and good protection against wind and cold. After the mid-20th century, as more and more herdsmen ended their nomadic life and settled down, they began to build yurt-like houses made of mud and wood.展开更多
Tibetan THE Tibetan ethnic minority mostly lives in the Tibet Autonomous Region,but there are also Tibetan communities in Qinghai,Gansu,Sichuan and Yunnan provinces.The places they live are mostly highlands and mounta...Tibetan THE Tibetan ethnic minority mostly lives in the Tibet Autonomous Region,but there are also Tibetan communities in Qinghai,Gansu,Sichuan and Yunnan provinces.The places they live are mostly highlands and mountainous areas studded with snow-capped peaks.展开更多
MAINLY distributed over Yunnan. Sichuan. Guizhou provinces and the Guangxi Zhuang Autonomous Region, the Yi is an ethnic minority with a long history and splendid culture within southwest China.
KazakTHE Kazak people, mainly living in the Xin- jiang Uygur Autonomous Region in northwest China, can also be found in Gansu and Qinghai provinces, where they live in small groups. The Kazak language is a fnember of...KazakTHE Kazak people, mainly living in the Xin- jiang Uygur Autonomous Region in northwest China, can also be found in Gansu and Qinghai provinces, where they live in small groups. The Kazak language is a fnember of the Turkic branch of the Altaic language family. The written language originally used the Arabic al- phabet. It is still in use but a new Latinized form was developed in 1954.展开更多
Photosynthesis of H_(2)O_(2)via sustainable biomass-derived carbon catalysts facilitate the conversion of renewable resources into valuable chemicals.However,the regulatory function of surface functional groups over r...Photosynthesis of H_(2)O_(2)via sustainable biomass-derived carbon catalysts facilitate the conversion of renewable resources into valuable chemicals.However,the regulatory function of surface functional groups over reaction kinetics has not been sufficiently investigated.Herein,hydrothermal carbon spheres(CS)rich in oxygencontaining functional groups demonstrated a remarkably high H_(2)O_(2)production rate(653μmol/(g·h))in both pure water and actual seawater,even in the absence of any sacrificial agent.Meanwhile,the catalyst demonstrates outstanding activity(92%conversion and>99%selectivity)in the visible-light-driven photocatalytic oxidation of benzylamine to imines.Comprehensive analysis reveals that CS was rich in surface oxygen-containing functional groups,a feature strongly associated with its high photocatalytic efficiency.The observed positive Zeta potential of CS in seawater likely diminished the electrostatic repulsion against the positively charged intermediates,thereby facilitating their accumulation at the liquid-solid interface.This work proposes a strategic framework for developing metal-free photocatalysts from biomass,offering a sustainable pathway for photocatalytic applications.展开更多
Let T_(n) and S_(n) be the full transformation semigroup and the symmetric group on X_(n)={1,2,...,n},respectively.Let G be a transitiveimprimitive subgroupof S_(n) with nontrivial blocksΔand letαbe a transformation...Let T_(n) and S_(n) be the full transformation semigroup and the symmetric group on X_(n)={1,2,...,n},respectively.Let G be a transitiveimprimitive subgroupof S_(n) with nontrivial blocksΔand letαbe a transformation in T_(n)\S_(n).The kernel ofαis the partition of X_(n) induced by the equivalence relation{(x,y)|xα=yα};the kernel type ofαis the partition of n given by the sizes of the parts of the kernel.A transformation semigroup is called synchronizing if it contains a constant map.Then a group G synchronizes a transformationαif the semigroup(G,α)contains a constant map.In this paper,we study a transitive imprimitive permutation group G together with a non-invertible transformationαthat generate a synchronizing semigroup.We mainly discuss 7 cases where G synchronizes a special transformationαwith each kernel class A_(i)(A_(1)j)satisfying|A_(i)∩Δ|=1(|A_(1)j∩Δ|=1)for all blocksΔofG,that is,the kernel type ofαis(|A_(1)|,1,...,1),(|A_(1)1|,...,|A_(1m)|,|A_(2)|,...,|Ar|),or(|A_(1)|,...,|A_(t)|,1,...,1),or the rank is 2,3,4,or n-2.展开更多
This paper investigates the in uence of local SS-quasinormal maximal subgroups of Sylow subgroups on the structure of nite groups.We present several new criteria on p-nilpotency of nite groups by utilizing a small qua...This paper investigates the in uence of local SS-quasinormal maximal subgroups of Sylow subgroups on the structure of nite groups.We present several new criteria on p-nilpotency of nite groups by utilizing a small quantity of local SS-quasinormal maximal subgroups of Sylow p-subgroups.As applications,we obtain some sucient conditions for a nite group to be in a saturated formation containing the class of supersolvable groups.展开更多
Let G be a finite group and H a subgroup of G.The normal index of H in G is defined as the order of K/H_(G),where K is a normal supplement of H in G such that|K|is minimal and H_(G)≤K■G.Let p be a prime which divide...Let G be a finite group and H a subgroup of G.The normal index of H in G is defined as the order of K/H_(G),where K is a normal supplement of H in G such that|K|is minimal and H_(G)≤K■G.Let p be a prime which divides the order of a group G.In this paper,some characterizations of G being p-solvable or p-supersolvable were obtained by analyzing the normal index of certain subgroups of G.These results can be viewed as local version of recent results in the literature.展开更多
Photocatalysis has demonstrated considerable potential as a highly efficient approach to the valorization of biomass under mild conditions,while the selectivity control is a long-standing challenge,notably when the ta...Photocatalysis has demonstrated considerable potential as a highly efficient approach to the valorization of biomass under mild conditions,while the selectivity control is a long-standing challenge,notably when the targets are complex and reactive biopolyols.In this study,we have successfully achieved selectivity control of photocatalytic biopolyols reforming to formic acid(FA)or CO by modulating the surface hydroxyl groups on TiO_(2) semiconductor.Photogenerated holes typically localize at bridging oxygen atoms(O2c)on the TiO_(2) surface,while shifting to terminal hydroxyl groups upon their introduction.The state of holes strongly affects the hole transfer process,which in turn influences the course of the reaction and thus controls the selectivity.By modulating the surface hydroxyl groups,the model substrate glycerol was selectively converted to CO(49%yield)and FA(50%yield).A range of other biopolyols,exemplified by erythritol,have demonstrated the same reaction selectivity.This work provides an effective strategy to manipulate reaction pathways by means of regulating the catalyst surface structure itself.展开更多
There are limitations to using hard carbon(HC)in K^(+)storage due to its insufficient high-current reversible capacity and plateau potential,which result from the lack of effective active sites and low intercalation c...There are limitations to using hard carbon(HC)in K^(+)storage due to its insufficient high-current reversible capacity and plateau potential,which result from the lack of effective active sites and low intercalation capabilities.The construction of HC cathodes with more available functional groups and ordered carbon nanocrystal structures is essential for improving K^(+)storage efficiency.Herein,a new perspective is proposed for synthesizing hard carbon nanosheets(HCNS)with abundant hydroxyl groups(O-H)/carboxylic groups(O-C=O)and rational carbon nanocrystals by interfacial assembly and carbonization.Systematic in ex-situ observations,dynamic analysis and theory calculations elucidate that the superior electrochemical capability of HCNS is ascribed to the synergistic effect of abundant available functional groups and ordered graphitic microcrystalline.Consequently,the HCNS exhibits outstanding K^(+)storage capabilities in terms of superb energy density(146.2 Wh/kg),high power density(1,7800 Wh/kg),and ultralong lifespan(102.9%capacity retention after 10,000 cycles).It was also found that the HC structure correlates with the discharge/charge plateau,confirming the'adsorption-insertion'charge storage mechanism.Furthermore,the proposed work provides a theoretical basis for making high-performance HC anodes by understanding the effect of their microstructure on K^(+)storage.展开更多
The fluorination strategy has been proven effective in significantly enhancing the photovoltaic performance of organic solar cells(OSCs) based on non-fused ring electron acceptors(NFREAs).However,research on the impac...The fluorination strategy has been proven effective in significantly enhancing the photovoltaic performance of organic solar cells(OSCs) based on non-fused ring electron acceptors(NFREAs).However,research on the impact of fluorination positions at side chains on NFREAs device performance remains scant.In this study,we introduce two isomeric NFREAs,designated as GA-2F-E and GA-2F,distinguished by their fluorination positions at the side chains.Both NFREAs share a thiophene[3,2-b]thiophene core,but their side chains differ:GA-2F-E features two(4-butylphenyl)-N-(4-fluorophenyl) amino groups,whereas GA-2F's side chains consist of bis(4-fluorophenyl)amino and bis(4-butylphenyl)amino groups attached to opposite sides of the core.To delve into the influence of fluorination positions on the optoelectronic properties,aggregation behavior,and overall efficiency of the acceptor molecules,a comprehensive investigation was conducted.The findings reveal that,despite similar photophysical properties and comparable absorption bandwidths,GA-2F-E,with fluorine atoms positioned on both sides of the molecular framework,demonstrates more compact π-π stacking,reduced bimolecular recombination,superior exciton transport,and a more balanced,higher mobility.As a result of these advantages,OSCs optimized with D18:GA-2F-E achieve a remarkable power conversion efficiency(PCE) of 16.45 %,surpassing the 15.83 %PCE of devices utilizing D18:GA-2F.This research underscores the potential of NFREAs in future applications and highlights the significance of fluorination positions in enhancing OSC performance,paving the way for the development of more efficient NFREAs.展开更多
Let M be a compact n-manifold of positive sectional curvature.We will review classical results on the fundamental group of M,a motivation on the c(n)-cyclic conjecture that the fundamental group of M contains a cyclic...Let M be a compact n-manifold of positive sectional curvature.We will review classical results on the fundamental group of M,a motivation on the c(n)-cyclic conjecture that the fundamental group of M contains a cyclic subgroup of index bounded above by c(n),a constant depending only on n,and we will survey partial results(up to date)on the c(n)-cyclic conjecture.展开更多
Let G be a group and H;K be subgroups of G.H is called a TI-subgroup of G if H∩H^(g)=1 or H for every g∈G.K is called P-subnormal in G if there is a chain of subgroups K=K_(0)≤K_(1)≤K_(2)≤…≤K_(n-1)≤K_(n)=G suc...Let G be a group and H;K be subgroups of G.H is called a TI-subgroup of G if H∩H^(g)=1 or H for every g∈G.K is called P-subnormal in G if there is a chain of subgroups K=K_(0)≤K_(1)≤K_(2)≤…≤K_(n-1)≤K_(n)=G such that|K_(i):K_(i-1)|∈P for i∈{1;2;…;n}.Furthermore,K is called K-P-subnormal in G if there is a chain of subgroups K=K_(0)≤K_(1)≤K_(2)≤…≤K_(n-1)≤K_(n)=G such that either K_(i-1)is normal in Ki or|K_(i):K_(i-1)|∈P for i∈{1;2;…;n}.In this paper,some properties of a nite group in which some particular subgroups are TI-subgroups or P-subnormal subgroups or K-P-subnormal subgroups are given.展开更多
International trade serves as a crucial pathway for enhancing global food security and equality amid severe food crises worldwide.Under globalization,economic development has profoundly influenced food trade,while dis...International trade serves as a crucial pathway for enhancing global food security and equality amid severe food crises worldwide.Under globalization,economic development has profoundly influenced food trade,while disparities in food purchasing power among different economic development groups have led to uneven food security outcomes.However,the varying contributions of international trade to food security across these groups remain to be quantitatively elucidated.This study categorized countries into four economic development groups—high,high-medium,medium-low,and low—and examined changes in their food security scores from 2010 to 2019.The cross-group contributions of international trade to food security across these groups were compared.The results revealed that the food security score of the high economic development group was 9.22 times higher than that of the low economic development group.From 2010 to 2019,the high economic development group exhibited a significant upward trend in food security scores,whereas the low economic development group showed a significant decline.Moreover,international trade contributed significantly to both cross-group and within-group food security in the high economic development group,while its contribution to the low economic development group remained negligible.These findings demonstrated that international trade has further widened the food security gap between the high and low economic development groups,and its limited contribution to the low economic development group has failed to reverse the declining trend in their food security scores.This study quantified the divergent impacts of international trade on food security across economic development groups,providing valuable insights for optimizing global food trade policies—particularly in addressing the food security challenges faced by low econominc development group.展开更多
The ABAB-type 1,4,15,18-tetrapentyloxy-8,11,22,25-tetrachlorophthalocyaninato magnesium compound Mg(trans-TPTCPc)(1)was successfully isolated from the mixed cyclic tetramerization of 4,7-bis(pentyloxy)-1,3-diiminoisoi...The ABAB-type 1,4,15,18-tetrapentyloxy-8,11,22,25-tetrachlorophthalocyaninato magnesium compound Mg(trans-TPTCPc)(1)was successfully isolated from the mixed cyclic tetramerization of 4,7-bis(pentyloxy)-1,3-diiminoisoindoline as precursor A,actually the 1,3-diiminoisoindoline form of 3,6-bis(pentyloxy)-1,2-benzenedinitrile,and 4,5-dichlorophthalonitrile as precursor B in refluxing pentanol in the presence of magnesium pentoxide in a relatively good yield of 6.2%.Its molecular structure was clearly revealed on the basis of single crystal X-ray diffraction analysis,representing the first structurally characterized ABAB-type phthalocyanine compound,simultaneously bearing electron-donating pentyloxy groups and electron-accepting chloro substituents.Nevertheless,with 1 as the starting material,the corresponding sandwich-type bis(phthalocyaninato)lutetium double-decker complex Lu^(Ⅲ)(trans-TPTCPc)_(2)(2)was also prepared and structurally characterized,showing a high hyperpolarizability of 1240×10^(-30) esu as determined by harmonic light scattering(HLS),indicating the great potential of these kinds of phthalocyanine compounds in the field of second-order NLO materials.展开更多
文摘THE Hanis are an ethnic farming group living in the mountainous area between the Honghe and Lancangjiang rivers in the south of Yunnan Province. Their language had no characters of its own until the Chinese Government helped to create a set of characters based on Latin in the 1950s.
文摘Uzbek〉Region：Around the 16th century,Uzbek businessmen traveled along the Silk Road to sell their goods in China.Some of them settled down in northwest China and formed the Uzbek ethnic minority of China.Today,they mainly live in the Xinjiang Uygur Autonomous Region.〉Population：Around 14,000〉Language：The Uzbek language belongs to the Turkic branch of the Altaic family.
文摘DongTHE Dong people live mainly in Guizhou and Hunan provinces though they can also be found in the Guangxi Zhuang Autonomous Region, as well as Jiangsu, Guangdong and Zhejiang provinces. In addition to agriculture, they make their living by growing timber trees, which are then logged and sold. Trees are so important in their lives that they have a unique custom of planting 18 fir trees when a child is born. When the child reaches the age of 18 and gets married, the matured fir trees are felled and used to build houses for the bride and groom
文摘Bouyei ）） MOST of the Bouyei people live in south Guizhou Province in southwest China, with the rest living scattered in Yunnan and Sichuan provinces and Guangxi Zhuang Autonomous Region. As valley dwellers blessed with rivers, they enjoy a fertile land and mild climate, mak- ing their living from agriculture.
文摘Korean THE Korean people mainly reside in northeast China, Their largest concentration is in the Yanbian Ko- rean Autonomous Prefecture in Jilin Province. They can also be found in Heilongjiang and Liaoning provinces and the Inner Mongolia Autonomous Region, They have their own spoken and written language, Korean. which is also the official language of South and North Korea. The ancestors of the Korean ethnic group - mostly peasants fleeing their oppressive feudal landlords - migrated from the Korean Peninsula around the late 17th century. When they settled down in China they gradually formed unique customs, Today.
文摘Mongolian AN ethnic group known for ＂growing up on horsebacks,＂ the Mongolians live mostly in the In- ner Mongolia Autonomous Region in the northern part of China, which includes vast tracts of excel- lent natural pastureland with numerous herds of cattle, sheep, horses and camels. The rest are also distributed in Liaoning Jilin. Heilongjiang. Qinghai and Gansu provinces. Living on grasslands and relying on raising stock as their economic mainstay, the Mongolians have kept their nomadic living style for hundreds of years. Mongolian herdsmen used to live in yurts,which were usually seven to eight feet high and 10 feet in diameter, with an opening in the top of the umbrella-shaped roof. The structure can offer ideal ventilation and good protection against wind and cold. After the mid-20th century, as more and more herdsmen ended their nomadic life and settled down, they began to build yurt-like houses made of mud and wood.
文摘Tibetan THE Tibetan ethnic minority mostly lives in the Tibet Autonomous Region,but there are also Tibetan communities in Qinghai,Gansu,Sichuan and Yunnan provinces.The places they live are mostly highlands and mountainous areas studded with snow-capped peaks.
文摘MAINLY distributed over Yunnan. Sichuan. Guizhou provinces and the Guangxi Zhuang Autonomous Region, the Yi is an ethnic minority with a long history and splendid culture within southwest China.
文摘KazakTHE Kazak people, mainly living in the Xin- jiang Uygur Autonomous Region in northwest China, can also be found in Gansu and Qinghai provinces, where they live in small groups. The Kazak language is a fnember of the Turkic branch of the Altaic language family. The written language originally used the Arabic al- phabet. It is still in use but a new Latinized form was developed in 1954.
基金Supported by the Natural Science Foundation of Shanxi Province(202203021222233,202203021212398,202203021212403)。
文摘Photosynthesis of H_(2)O_(2)via sustainable biomass-derived carbon catalysts facilitate the conversion of renewable resources into valuable chemicals.However,the regulatory function of surface functional groups over reaction kinetics has not been sufficiently investigated.Herein,hydrothermal carbon spheres(CS)rich in oxygencontaining functional groups demonstrated a remarkably high H_(2)O_(2)production rate(653μmol/(g·h))in both pure water and actual seawater,even in the absence of any sacrificial agent.Meanwhile,the catalyst demonstrates outstanding activity(92%conversion and>99%selectivity)in the visible-light-driven photocatalytic oxidation of benzylamine to imines.Comprehensive analysis reveals that CS was rich in surface oxygen-containing functional groups,a feature strongly associated with its high photocatalytic efficiency.The observed positive Zeta potential of CS in seawater likely diminished the electrostatic repulsion against the positively charged intermediates,thereby facilitating their accumulation at the liquid-solid interface.This work proposes a strategic framework for developing metal-free photocatalysts from biomass,offering a sustainable pathway for photocatalytic applications.
基金Supported by NSFC (No.12401024)the Scientific Research Innovation Project of Lingnan Normal University (Nos.LT2401,LT2410)。
文摘Let T_(n) and S_(n) be the full transformation semigroup and the symmetric group on X_(n)={1,2,...,n},respectively.Let G be a transitiveimprimitive subgroupof S_(n) with nontrivial blocksΔand letαbe a transformation in T_(n)\S_(n).The kernel ofαis the partition of X_(n) induced by the equivalence relation{(x,y)|xα=yα};the kernel type ofαis the partition of n given by the sizes of the parts of the kernel.A transformation semigroup is called synchronizing if it contains a constant map.Then a group G synchronizes a transformationαif the semigroup(G,α)contains a constant map.In this paper,we study a transitive imprimitive permutation group G together with a non-invertible transformationαthat generate a synchronizing semigroup.We mainly discuss 7 cases where G synchronizes a special transformationαwith each kernel class A_(i)(A_(1)j)satisfying|A_(i)∩Δ|=1(|A_(1)j∩Δ|=1)for all blocksΔofG,that is,the kernel type ofαis(|A_(1)|,1,...,1),(|A_(1)1|,...,|A_(1m)|,|A_(2)|,...,|Ar|),or(|A_(1)|,...,|A_(t)|,1,...,1),or the rank is 2,3,4,or n-2.
基金Supported by NSF of China(12061011)NSF of Guangxi(2023GXN-SFAA026333)。
文摘This paper investigates the in uence of local SS-quasinormal maximal subgroups of Sylow subgroups on the structure of nite groups.We present several new criteria on p-nilpotency of nite groups by utilizing a small quantity of local SS-quasinormal maximal subgroups of Sylow p-subgroups.As applications,we obtain some sucient conditions for a nite group to be in a saturated formation containing the class of supersolvable groups.
基金Supported by the National Natural Science Foundation of China(Grant No.12071092)Guangdong Basic and Applied Basic Research Foundation(Grant No.2025A1515012072)+1 种基金the Natural Science Research Project of Anhui Educational Committee(Grant No.2024AH051298)the Scientific Research Foundation of Bozhou University(Grant No.BYKQ202419).
文摘Let G be a finite group and H a subgroup of G.The normal index of H in G is defined as the order of K/H_(G),where K is a normal supplement of H in G such that|K|is minimal and H_(G)≤K■G.Let p be a prime which divides the order of a group G.In this paper,some characterizations of G being p-solvable or p-supersolvable were obtained by analyzing the normal index of certain subgroups of G.These results can be viewed as local version of recent results in the literature.
基金supported by the National Natural Science Foundation of China,China(22372023)the Liaoning Revitalization Talents Program,China(XLYC2403019)。
文摘Photocatalysis has demonstrated considerable potential as a highly efficient approach to the valorization of biomass under mild conditions,while the selectivity control is a long-standing challenge,notably when the targets are complex and reactive biopolyols.In this study,we have successfully achieved selectivity control of photocatalytic biopolyols reforming to formic acid(FA)or CO by modulating the surface hydroxyl groups on TiO_(2) semiconductor.Photogenerated holes typically localize at bridging oxygen atoms(O2c)on the TiO_(2) surface,while shifting to terminal hydroxyl groups upon their introduction.The state of holes strongly affects the hole transfer process,which in turn influences the course of the reaction and thus controls the selectivity.By modulating the surface hydroxyl groups,the model substrate glycerol was selectively converted to CO(49%yield)and FA(50%yield).A range of other biopolyols,exemplified by erythritol,have demonstrated the same reaction selectivity.This work provides an effective strategy to manipulate reaction pathways by means of regulating the catalyst surface structure itself.
基金supported by the National Natural Science Foundation of China(Nos.22269020,42167068,U23A20582)Gansu Province Higher Education Industry Support Plan Project(No.2023CYZC-17)2024 Major Cultivation Projectfor University Research and Innovation Platforms(No.2024CXPT-10).
文摘There are limitations to using hard carbon(HC)in K^(+)storage due to its insufficient high-current reversible capacity and plateau potential,which result from the lack of effective active sites and low intercalation capabilities.The construction of HC cathodes with more available functional groups and ordered carbon nanocrystal structures is essential for improving K^(+)storage efficiency.Herein,a new perspective is proposed for synthesizing hard carbon nanosheets(HCNS)with abundant hydroxyl groups(O-H)/carboxylic groups(O-C=O)and rational carbon nanocrystals by interfacial assembly and carbonization.Systematic in ex-situ observations,dynamic analysis and theory calculations elucidate that the superior electrochemical capability of HCNS is ascribed to the synergistic effect of abundant available functional groups and ordered graphitic microcrystalline.Consequently,the HCNS exhibits outstanding K^(+)storage capabilities in terms of superb energy density(146.2 Wh/kg),high power density(1,7800 Wh/kg),and ultralong lifespan(102.9%capacity retention after 10,000 cycles).It was also found that the HC structure correlates with the discharge/charge plateau,confirming the'adsorption-insertion'charge storage mechanism.Furthermore,the proposed work provides a theoretical basis for making high-performance HC anodes by understanding the effect of their microstructure on K^(+)storage.
基金financially supported by the National Natural Science Foundation of China (Nos.22375024,21975031,51933001,and 21734009)。
文摘The fluorination strategy has been proven effective in significantly enhancing the photovoltaic performance of organic solar cells(OSCs) based on non-fused ring electron acceptors(NFREAs).However,research on the impact of fluorination positions at side chains on NFREAs device performance remains scant.In this study,we introduce two isomeric NFREAs,designated as GA-2F-E and GA-2F,distinguished by their fluorination positions at the side chains.Both NFREAs share a thiophene[3,2-b]thiophene core,but their side chains differ:GA-2F-E features two(4-butylphenyl)-N-(4-fluorophenyl) amino groups,whereas GA-2F's side chains consist of bis(4-fluorophenyl)amino and bis(4-butylphenyl)amino groups attached to opposite sides of the core.To delve into the influence of fluorination positions on the optoelectronic properties,aggregation behavior,and overall efficiency of the acceptor molecules,a comprehensive investigation was conducted.The findings reveal that,despite similar photophysical properties and comparable absorption bandwidths,GA-2F-E,with fluorine atoms positioned on both sides of the molecular framework,demonstrates more compact π-π stacking,reduced bimolecular recombination,superior exciton transport,and a more balanced,higher mobility.As a result of these advantages,OSCs optimized with D18:GA-2F-E achieve a remarkable power conversion efficiency(PCE) of 16.45 %,surpassing the 15.83 %PCE of devices utilizing D18:GA-2F.This research underscores the potential of NFREAs in future applications and highlights the significance of fluorination positions in enhancing OSC performance,paving the way for the development of more efficient NFREAs.
文摘Let M be a compact n-manifold of positive sectional curvature.We will review classical results on the fundamental group of M,a motivation on the c(n)-cyclic conjecture that the fundamental group of M contains a cyclic subgroup of index bounded above by c(n),a constant depending only on n,and we will survey partial results(up to date)on the c(n)-cyclic conjecture.
文摘Let G be a group and H;K be subgroups of G.H is called a TI-subgroup of G if H∩H^(g)=1 or H for every g∈G.K is called P-subnormal in G if there is a chain of subgroups K=K_(0)≤K_(1)≤K_(2)≤…≤K_(n-1)≤K_(n)=G such that|K_(i):K_(i-1)|∈P for i∈{1;2;…;n}.Furthermore,K is called K-P-subnormal in G if there is a chain of subgroups K=K_(0)≤K_(1)≤K_(2)≤…≤K_(n-1)≤K_(n)=G such that either K_(i-1)is normal in Ki or|K_(i):K_(i-1)|∈P for i∈{1;2;…;n}.In this paper,some properties of a nite group in which some particular subgroups are TI-subgroups or P-subnormal subgroups or K-P-subnormal subgroups are given.
基金supported by National Natural Science Foundation of China(Grants No.42361144888 and 42401308)National Key Research and Development Program of China(Grant No.2024YFF1309200).
文摘International trade serves as a crucial pathway for enhancing global food security and equality amid severe food crises worldwide.Under globalization,economic development has profoundly influenced food trade,while disparities in food purchasing power among different economic development groups have led to uneven food security outcomes.However,the varying contributions of international trade to food security across these groups remain to be quantitatively elucidated.This study categorized countries into four economic development groups—high,high-medium,medium-low,and low—and examined changes in their food security scores from 2010 to 2019.The cross-group contributions of international trade to food security across these groups were compared.The results revealed that the food security score of the high economic development group was 9.22 times higher than that of the low economic development group.From 2010 to 2019,the high economic development group exhibited a significant upward trend in food security scores,whereas the low economic development group showed a significant decline.Moreover,international trade contributed significantly to both cross-group and within-group food security in the high economic development group,while its contribution to the low economic development group remained negligible.These findings demonstrated that international trade has further widened the food security gap between the high and low economic development groups,and its limited contribution to the low economic development group has failed to reverse the declining trend in their food security scores.This study quantified the divergent impacts of international trade on food security across economic development groups,providing valuable insights for optimizing global food trade policies—particularly in addressing the food security challenges faced by low econominc development group.
基金the National Key Basic Research Program of China(Grant No.2013CB933402)the National Natural Science Foundation of China(Grant No.21290174,21301017,and 21401009)the Beijing Municipal Commission of Education is gratefully acknowledged.
文摘The ABAB-type 1,4,15,18-tetrapentyloxy-8,11,22,25-tetrachlorophthalocyaninato magnesium compound Mg(trans-TPTCPc)(1)was successfully isolated from the mixed cyclic tetramerization of 4,7-bis(pentyloxy)-1,3-diiminoisoindoline as precursor A,actually the 1,3-diiminoisoindoline form of 3,6-bis(pentyloxy)-1,2-benzenedinitrile,and 4,5-dichlorophthalonitrile as precursor B in refluxing pentanol in the presence of magnesium pentoxide in a relatively good yield of 6.2%.Its molecular structure was clearly revealed on the basis of single crystal X-ray diffraction analysis,representing the first structurally characterized ABAB-type phthalocyanine compound,simultaneously bearing electron-donating pentyloxy groups and electron-accepting chloro substituents.Nevertheless,with 1 as the starting material,the corresponding sandwich-type bis(phthalocyaninato)lutetium double-decker complex Lu^(Ⅲ)(trans-TPTCPc)_(2)(2)was also prepared and structurally characterized,showing a high hyperpolarizability of 1240×10^(-30) esu as determined by harmonic light scattering(HLS),indicating the great potential of these kinds of phthalocyanine compounds in the field of second-order NLO materials.
