A lead（II） coordination polymer,{[Pb2（butca）（H2O）2]（H2O）2}n （1）,has been synthe-sized by the hydrothermal reaction of Pb（OH）2 and 1,2,3,4-butanetetracarboxylic acid （H4butca） at 160 °C.Single-crysta...A lead（II） coordination polymer,{[Pb2（butca）（H2O）2]（H2O）2}n （1）,has been synthe-sized by the hydrothermal reaction of Pb（OH）2 and 1,2,3,4-butanetetracarboxylic acid （H4butca） at 160 °C.Single-crystal X-ray analyses reveal that it crystallizes in monoclinic,space group P21/c with a=7.616（5）,b=7.584（4）,c=12.314（7）,β=105.595（12）o,V=685.0（7）3,Z=4,C8H14O12Pb2,Mr=716.57,Dc=3.474 g/cm3,μ=24.610 mm-1,F（000）=644,the final R=0.0381 and wR=0.1176 for 1465 observed reflections with I 〉 2σ（I）.The complex presents a 2D-layered structure featuring two different types of rings,and has a （4,36）topology based on Pb and butca4-nodes.In solid state,complex 1 shows photoluminescence with the maximum emission intensity at 468 nm under 286 nm excitation.展开更多
Two definitions are given that Definitionl： an induced subgraph by a vertex vie G and its neighbors in G is defined as a vertex adjacent closed subgraph, and denoted by Qi （=G[V（Nvi）]）, with the vertex vi called ...Two definitions are given that Definitionl： an induced subgraph by a vertex vie G and its neighbors in G is defined as a vertex adjacent closed subgraph, and denoted by Qi （=G[V（Nvi）]）, with the vertex vi called the hub; and Definition2： A r（k,I）-I vertices graph is called the （k,l）-Ramsey graph, denoted by RG（k,1）, if RG（k,1） only contains cliques Kk.1 and the intersect QiNQj of any two nonadjacent vertices vi and vj of RG（k,I） contains only Kk-2. Meanwhile, the RG（k,l）＇s complement RG（I,k） contains only cliques Kl.l, and the intersect QiNQj of any two nonadjacent vertices vi and vj of RG（I,k） contains only Ki.2. On the basis of those definitions, two theorems are put forward and proved in this paper. They are Theoreml： the biggest clique in G is contained in some Qi of G, and Theorem 2： r（k,1） = [V（RG（k,I））I ＋ 1. With those definitions and theorems as well as analysis of chord property, a method for quick inspection and building RG（k,1） is proposed. Accordingly, RG（4,6） is built, it is a strongly 14-regular graph on order 35. We have tested RG（4,6） and its complement, as a result, they meet the defintion2, so we proclaim that r（4,6）=36.展开更多
Environmental concerns have highlighted the need of cleaner technologies. A cleaner, convenient and selective technology has been developed for the preparation of 3-(4,6-dimethoxy-pyrimidin-2-yloxy)-2-methyl-phenol (...Environmental concerns have highlighted the need of cleaner technologies. A cleaner, convenient and selective technology has been developed for the preparation of 3-(4,6-dimethoxy-pyrimidin-2-yloxy)-2-methyl-phenol (DPMP) from 2-methyl-benzene-1,3-diol in water as solvent. The isolated yield of DPMP is up to 86% in good selectivity. The product structure was characterized by conventional methods, H-NMR and MS. This technology belongs to the modern concept of 1 environmentally friendly low wastes or non-wastes technology (LWNWT).展开更多
The Total Coloring Conjecture (TCC) proposes that every simple graph G is (Δ + 2)-totally-colorable, where Δ is the maximum degree of G. For planar graph, TCC is open only in case Δ = 6. In this paper, we prove tha...The Total Coloring Conjecture (TCC) proposes that every simple graph G is (Δ + 2)-totally-colorable, where Δ is the maximum degree of G. For planar graph, TCC is open only in case Δ = 6. In this paper, we prove that TCC holds for planar graph with Δ = 6 and every 7-cycle contains at most two chords.展开更多
A novel composite material(TD)composed of TS-1 microcrystalline and dendritic mesoporous silica nanospheres(DMSNs)was successfully prepared.The TD composite material had open pore structure and large specific surface ...A novel composite material(TD)composed of TS-1 microcrystalline and dendritic mesoporous silica nanospheres(DMSNs)was successfully prepared.The TD composite material had open pore structure and large specific surface area,which was conducive to the mass transfer of reactants and products.The Ti element in TS-1 could be used as an electron assistant,and the spillover d-electrons were conducive to the improvement of the sulfidation and dispersion of MoS_(2),thereby forming more type II MoS_(2) active phases.The incorporation of Ti could bring more Brønsted(B)and Lewis(L)acid,which was conducive to the hydrogenation pathway(HYD)selectivity(41.2%)of dibenzothiophene(DBT)hydrodesulfurization(HDS)and isomerization(ISO)route selectivity(21.9%)of 4,6-dimethyldibenzothiophene(4,6-DMDBT)HDS,thus improve the HDS activity of DBT and 4,6-DMDBT.NiMo/TD-70(Aging temperature=70℃)had the best HDS activities of DBT(99.0%)and 4,6-DMDBT(93.7%)due to its large open pore structure,good acidity,suitable metal-support interaction(MSI)and perfect dispersion of the metallic active sites.展开更多
In this paper we consider the problem of finding the smallest number such that any graph G of order n admits a decomposition into edge disjoint copies of C4 and single edges with at most elements. We solve this proble...In this paper we consider the problem of finding the smallest number such that any graph G of order n admits a decomposition into edge disjoint copies of C4 and single edges with at most elements. We solve this problem for n sufficiently large.展开更多
基金Supported by the Education Department of Jiangxi Province (No. 2007-125)the Initial Fund for Doctors from Jiangxi Normal University
文摘A lead（II） coordination polymer,{[Pb2（butca）（H2O）2]（H2O）2}n （1）,has been synthe-sized by the hydrothermal reaction of Pb（OH）2 and 1,2,3,4-butanetetracarboxylic acid （H4butca） at 160 °C.Single-crystal X-ray analyses reveal that it crystallizes in monoclinic,space group P21/c with a=7.616（5）,b=7.584（4）,c=12.314（7）,β=105.595（12）o,V=685.0（7）3,Z=4,C8H14O12Pb2,Mr=716.57,Dc=3.474 g/cm3,μ=24.610 mm-1,F（000）=644,the final R=0.0381 and wR=0.1176 for 1465 observed reflections with I 〉 2σ（I）.The complex presents a 2D-layered structure featuring two different types of rings,and has a （4,36）topology based on Pb and butca4-nodes.In solid state,complex 1 shows photoluminescence with the maximum emission intensity at 468 nm under 286 nm excitation.
文摘Two definitions are given that Definitionl： an induced subgraph by a vertex vie G and its neighbors in G is defined as a vertex adjacent closed subgraph, and denoted by Qi （=G[V（Nvi）]）, with the vertex vi called the hub; and Definition2： A r（k,I）-I vertices graph is called the （k,l）-Ramsey graph, denoted by RG（k,1）, if RG（k,1） only contains cliques Kk.1 and the intersect QiNQj of any two nonadjacent vertices vi and vj of RG（k,I） contains only Kk-2. Meanwhile, the RG（k,l）＇s complement RG（I,k） contains only cliques Kl.l, and the intersect QiNQj of any two nonadjacent vertices vi and vj of RG（I,k） contains only Ki.2. On the basis of those definitions, two theorems are put forward and proved in this paper. They are Theoreml： the biggest clique in G is contained in some Qi of G, and Theorem 2： r（k,1） = [V（RG（k,I））I ＋ 1. With those definitions and theorems as well as analysis of chord property, a method for quick inspection and building RG（k,1） is proposed. Accordingly, RG（4,6） is built, it is a strongly 14-regular graph on order 35. We have tested RG（4,6） and its complement, as a result, they meet the defintion2, so we proclaim that r（4,6）=36.
文摘Environmental concerns have highlighted the need of cleaner technologies. A cleaner, convenient and selective technology has been developed for the preparation of 3-(4,6-dimethoxy-pyrimidin-2-yloxy)-2-methyl-phenol (DPMP) from 2-methyl-benzene-1,3-diol in water as solvent. The isolated yield of DPMP is up to 86% in good selectivity. The product structure was characterized by conventional methods, H-NMR and MS. This technology belongs to the modern concept of 1 environmentally friendly low wastes or non-wastes technology (LWNWT).
文摘The Total Coloring Conjecture (TCC) proposes that every simple graph G is (Δ + 2)-totally-colorable, where Δ is the maximum degree of G. For planar graph, TCC is open only in case Δ = 6. In this paper, we prove that TCC holds for planar graph with Δ = 6 and every 7-cycle contains at most two chords.
基金This research was supported by the Science Foundation of China University of Petroleum-Beijing(No.2462023QNXZ002)the National Key R&D Program of China(2021YFA1501201)+2 种基金the National Natural Science Foundation of China(No.22278174)Independent research project of State Key Laboratory of heavy oil(2021–01)Shandong Excellent Young Scientists Fund Program(Overseas,2022HWYQ-082).
文摘A novel composite material(TD)composed of TS-1 microcrystalline and dendritic mesoporous silica nanospheres(DMSNs)was successfully prepared.The TD composite material had open pore structure and large specific surface area,which was conducive to the mass transfer of reactants and products.The Ti element in TS-1 could be used as an electron assistant,and the spillover d-electrons were conducive to the improvement of the sulfidation and dispersion of MoS_(2),thereby forming more type II MoS_(2) active phases.The incorporation of Ti could bring more Brønsted(B)and Lewis(L)acid,which was conducive to the hydrogenation pathway(HYD)selectivity(41.2%)of dibenzothiophene(DBT)hydrodesulfurization(HDS)and isomerization(ISO)route selectivity(21.9%)of 4,6-dimethyldibenzothiophene(4,6-DMDBT)HDS,thus improve the HDS activity of DBT and 4,6-DMDBT.NiMo/TD-70(Aging temperature=70℃)had the best HDS activities of DBT(99.0%)and 4,6-DMDBT(93.7%)due to its large open pore structure,good acidity,suitable metal-support interaction(MSI)and perfect dispersion of the metallic active sites.
基金support from FCT—Fundacao para a Ciencia e a Tecnologia(Portugal),through Projects PTDC/MAT/113207/2009PEst-OE/MAT/UI0297/2011(CMA).
文摘In this paper we consider the problem of finding the smallest number such that any graph G of order n admits a decomposition into edge disjoint copies of C4 and single edges with at most elements. We solve this problem for n sufficiently large.
