A coordination polymer based on iron（II） carboxylate helical chains [Fe（bpdc）（H2O）2]n 1 has been constructed hydrothermally using H2bpdc （H2bpdc = 2,2＇-bipyridine-4,4＇-dicarboxylic acid）, pyridine and FeSO4&...A coordination polymer based on iron（II） carboxylate helical chains [Fe（bpdc）（H2O）2]n 1 has been constructed hydrothermally using H2bpdc （H2bpdc = 2,2＇-bipyridine-4,4＇-dicarboxylic acid）, pyridine and FeSO4·7H2O. Its crystal structure reveals that the Fe（Ⅱ） ion adopts a slightly distorted octahedron. The carboxylates of bpdc ligands alternately bridge the Fe（Ⅱ） cations to form 1D infinite helical chains. The Fe···Fe intrachain distance is 4.8246（6） . The adjacent chains are further interlinked by the coordination of bpdc ligands and hydrogen bonding to form a 3D framework. Magnetic studies for complex 1 show weak antiferromagnetic coupling between the Fe（Ⅱ） ions. The best-fit for χM T vs. T with a Hamiltonian∑∑==iBiiHJSi SigHS11 leadsto g = 2.314（4） and J = –0.68（1） cm-1.展开更多
A comparative study on the phenotypic and genetic characteristics among Acidithiobacillus ferrooxidans （AF2）, a typic strain ATCC23270 and a previously isolated strain AF3 was performed. AF2 can use ferrous ion （F...A comparative study on the phenotypic and genetic characteristics among Acidithiobacillus ferrooxidans （AF2）, a typic strain ATCC23270 and a previously isolated strain AF3 was performed. AF2 can use ferrous ion （Fe^2＋） or elemental sulfur （S^0） as sole energy source, but oxidizes So more effectively than Fe^2＋, which is different from ATCC23270 and AF3. The G＋C content of AF2 is 51.8% （molar fraction）, however, ATCC23270 and AF3 strains have G＋C content of 63.7% and 64.8% （molar fraction）, respectively. The DNA-DNA hybridization results show that AF2 has 41.53% and 52.38% genome similarity to ATCC 23270 and AF3, respectively, but AF3 has a high genome similarity of 89.86% to ATCC 23270 strain. Rusticyanin （rus） and subunit III of aa3-type cytochrome oxidase （coxC） genes are not detected in AF2, but Fe^2＋ oxidase （iro） gene can be detected. To understand the genomic organization of iro gene, a cosmid library of AF2 genome was constructed and iro gene-containing clone was screened. The sequencing result shows that although the nucleotide sequence of iro gene in AF2 is completely identical to that of ATCC 23270 strain, its genomic organization is different from that of ATCC 23270. In AF2, iro is located at downstream ofpurA gene, while it is located at downstream ofpetC-2 gene in ATCC 23270 strain. These results indicate that AF2 is a novel strain ofA. ferrooxidans, and that phenotypic differences among the strains ofA. ferrooxidans are closely correlated with their genetic polymorphisms.展开更多
This study examines the structural characteristics and technical principles of the hybrid framing cantilever bridges along the Longchuan River in Tengchong, Yunnan, China, taking the Yezhuqing Bridge as a case example...This study examines the structural characteristics and technical principles of the hybrid framing cantilever bridges along the Longchuan River in Tengchong, Yunnan, China, taking the Yezhuqing Bridge as a case example. Such bridges integrate diverse construction techniques-including inclined cantilevers, iron chains, three-sided arches, and strut frames-showcasing the craftsmanship characteristic of a region shaped by cultural blending.This paper first analyzes the structural design and mechanical principles based on the bridge's form, and then examines construction details to understand material selection, reconstruct fabrication methods, and explore craftsmanship thinking. The findings reveal that in the structural design, iron chains, strut frames, and three-sided arches each take on distinct loadbearing roles in a cantilever bridge, enabling it to achieve a large span. By coordinating structural components, this bridge type does not require scaffolding during construction, instead relying on the components themselves for mutual support throughout the building process.In terms of construction details, skillful arrangement of elements like wooden pegs enhances convenience and precision during construction, while ensuring overall integrity and stability.Additionally, this study examines existing structural vulnerabilities and past restoration issues,providing insights for future conservation efforts.展开更多
基金Supported by Open Project of Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education, Lanzhou University (MMM 200822)
文摘A coordination polymer based on iron（II） carboxylate helical chains [Fe（bpdc）（H2O）2]n 1 has been constructed hydrothermally using H2bpdc （H2bpdc = 2,2＇-bipyridine-4,4＇-dicarboxylic acid）, pyridine and FeSO4·7H2O. Its crystal structure reveals that the Fe（Ⅱ） ion adopts a slightly distorted octahedron. The carboxylates of bpdc ligands alternately bridge the Fe（Ⅱ） cations to form 1D infinite helical chains. The Fe···Fe intrachain distance is 4.8246（6） . The adjacent chains are further interlinked by the coordination of bpdc ligands and hydrogen bonding to form a 3D framework. Magnetic studies for complex 1 show weak antiferromagnetic coupling between the Fe（Ⅱ） ions. The best-fit for χM T vs. T with a Hamiltonian∑∑==iBiiHJSi SigHS11 leadsto g = 2.314（4） and J = –0.68（1） cm-1.
基金Project(200805032) supported by the Scientific Research Program of Marine Public Welfare Industry of China
文摘A comparative study on the phenotypic and genetic characteristics among Acidithiobacillus ferrooxidans （AF2）, a typic strain ATCC23270 and a previously isolated strain AF3 was performed. AF2 can use ferrous ion （Fe^2＋） or elemental sulfur （S^0） as sole energy source, but oxidizes So more effectively than Fe^2＋, which is different from ATCC23270 and AF3. The G＋C content of AF2 is 51.8% （molar fraction）, however, ATCC23270 and AF3 strains have G＋C content of 63.7% and 64.8% （molar fraction）, respectively. The DNA-DNA hybridization results show that AF2 has 41.53% and 52.38% genome similarity to ATCC 23270 and AF3, respectively, but AF3 has a high genome similarity of 89.86% to ATCC 23270 strain. Rusticyanin （rus） and subunit III of aa3-type cytochrome oxidase （coxC） genes are not detected in AF2, but Fe^2＋ oxidase （iro） gene can be detected. To understand the genomic organization of iro gene, a cosmid library of AF2 genome was constructed and iro gene-containing clone was screened. The sequencing result shows that although the nucleotide sequence of iro gene in AF2 is completely identical to that of ATCC 23270 strain, its genomic organization is different from that of ATCC 23270. In AF2, iro is located at downstream ofpurA gene, while it is located at downstream ofpetC-2 gene in ATCC 23270 strain. These results indicate that AF2 is a novel strain ofA. ferrooxidans, and that phenotypic differences among the strains ofA. ferrooxidans are closely correlated with their genetic polymorphisms.
基金funded by the National Key R&D Program of China,“Key Technologies and Demonstration for Risk Assessment and Hazard Identification of Bridge Cultural Heritage”(Grant No.2023YFF0906100)the National Natural Science Foundation of China,“A Research Paradigm for Traditional Craftsmanship Based on‘Unconventional’Historical Timber Bridges”(Grant No.52378021).
文摘This study examines the structural characteristics and technical principles of the hybrid framing cantilever bridges along the Longchuan River in Tengchong, Yunnan, China, taking the Yezhuqing Bridge as a case example. Such bridges integrate diverse construction techniques-including inclined cantilevers, iron chains, three-sided arches, and strut frames-showcasing the craftsmanship characteristic of a region shaped by cultural blending.This paper first analyzes the structural design and mechanical principles based on the bridge's form, and then examines construction details to understand material selection, reconstruct fabrication methods, and explore craftsmanship thinking. The findings reveal that in the structural design, iron chains, strut frames, and three-sided arches each take on distinct loadbearing roles in a cantilever bridge, enabling it to achieve a large span. By coordinating structural components, this bridge type does not require scaffolding during construction, instead relying on the components themselves for mutual support throughout the building process.In terms of construction details, skillful arrangement of elements like wooden pegs enhances convenience and precision during construction, while ensuring overall integrity and stability.Additionally, this study examines existing structural vulnerabilities and past restoration issues,providing insights for future conservation efforts.
