In Europe, eggs of the Common Cuckoo (Cuculus canorus) have been found in more than 125 different host species. However, very few species are frequently parasitized. The Cuckoo is divided into several distinct races t...In Europe, eggs of the Common Cuckoo (Cuculus canorus) have been found in more than 125 different host species. However, very few species are frequently parasitized. The Cuckoo is divided into several distinct races termed gentes. Females of each gens specialize in parasitizing a particular host species. More than 20 such gentes are recognized in Europe. Each female Cuckoo lays eggs of constant appearance. Most gentes can be separated based on their distinct egg types, which in many cases mimic those of their hosts. Different gentes may occur in sympatry or may be separated geographically. Some gentes may occur in restricted parts of the host’s distribution area. These patterns raise some fundamental questions like: Why are some passerine species preferred as hosts while others are not? Why does a host population consist of individuals either accepting or rejecting Cuckoo eggs? Why is there marked variation in egg rejection behavior between various host populations? How distinct and host-specialized are Cuckoo gentes? These questions are discussed in relation to existing knowledge and future perspectives.展开更多
The development and application of several flot ation reagents of rare earth minerals in China since 1960s and their performance were described. Furthermore, the development trends of flotation reagents of ra re eart...The development and application of several flot ation reagents of rare earth minerals in China since 1960s and their performance were described. Furthermore, the development trends of flotation reagents of ra re earth minerals were discussed.展开更多
By NdFeB magnetic powders treated with the silicon cou-pling agents, mechanical properties of the magnetic composite are remark-ably improved, and its magnetic properties are not affected. The experi-ments show that t...By NdFeB magnetic powders treated with the silicon cou-pling agents, mechanical properties of the magnetic composite are remark-ably improved, and its magnetic properties are not affected. The experi-ments show that the silicon coupling agents react with the oxidates in the surface of NdFeB magnetic powders so that a good adhesiveness can be formed between epoxy resin and NdFeB powders. The results still indicate that the silk or wavy morphological structures in the fracture surface of the magnetic composite are more advantageous to its mechanical properties.展开更多
Objective To identify a new peptide deformylase (PDF) gene (Genebank Accession AY238515) from Enterococcus faecium and to establish a new screening model targeted on PDF. Methods A new PDF gene was identified by BL...Objective To identify a new peptide deformylase (PDF) gene (Genebank Accession AY238515) from Enterococcus faecium and to establish a new screening model targeted on PDF. Methods A new PDF gene was identified by BLAST analysis and PCR and was subsequently over-expressed in the prokaryotic expression host E.coli Bl21(DE3). Over-expressed protein was purified for enzymatic assay by metal affinity chromatography and a new screening model was established for novel antibiotics. Result A new PDF gene of Enterococcus faecium was identified successfully. Ten positive samples were picked up from 8000 compound library and the microbial fermentation broth samples. Conclusion A new PDF of gene Enterococcus faecium was first identified and the model had a high efficacy. Positive samples screened may be antibacterial agents of broad spectrum.展开更多
GENTING Highlands, one of Malaysia＇s bestdeveloped hilI resorts, lies just 58 kilometers from the national capitalof Kuala Lumpur. Embraced by beautiful hills, the resort attracts tourists from around the world who c...GENTING Highlands, one of Malaysia＇s bestdeveloped hilI resorts, lies just 58 kilometers from the national capitalof Kuala Lumpur. Embraced by beautiful hills, the resort attracts tourists from around the world who come for top line entertainment and a broad choice of recreational facilities. Its pleasant climate, enchanting scenery and wide range of services make the 20 million tourists who visit the resort annually reluctant to go home.展开更多
文摘In Europe, eggs of the Common Cuckoo (Cuculus canorus) have been found in more than 125 different host species. However, very few species are frequently parasitized. The Cuckoo is divided into several distinct races termed gentes. Females of each gens specialize in parasitizing a particular host species. More than 20 such gentes are recognized in Europe. Each female Cuckoo lays eggs of constant appearance. Most gentes can be separated based on their distinct egg types, which in many cases mimic those of their hosts. Different gentes may occur in sympatry or may be separated geographically. Some gentes may occur in restricted parts of the host’s distribution area. These patterns raise some fundamental questions like: Why are some passerine species preferred as hosts while others are not? Why does a host population consist of individuals either accepting or rejecting Cuckoo eggs? Why is there marked variation in egg rejection behavior between various host populations? How distinct and host-specialized are Cuckoo gentes? These questions are discussed in relation to existing knowledge and future perspectives.
基金Supported by the National Natural Science Foundation for Young Scientists of China(61903344)the National Natural Science Foundation of China(61733006)。
文摘The development and application of several flot ation reagents of rare earth minerals in China since 1960s and their performance were described. Furthermore, the development trends of flotation reagents of ra re earth minerals were discussed.
文摘By NdFeB magnetic powders treated with the silicon cou-pling agents, mechanical properties of the magnetic composite are remark-ably improved, and its magnetic properties are not affected. The experi-ments show that the silicon coupling agents react with the oxidates in the surface of NdFeB magnetic powders so that a good adhesiveness can be formed between epoxy resin and NdFeB powders. The results still indicate that the silk or wavy morphological structures in the fracture surface of the magnetic composite are more advantageous to its mechanical properties.
基金This work was supported by National Natural Science Foundation of China (grant 30270042) and Technology Platform of New Drugs Screen from Ministry of Science and Technology of China (2002AA22343D).
文摘Objective To identify a new peptide deformylase (PDF) gene (Genebank Accession AY238515) from Enterococcus faecium and to establish a new screening model targeted on PDF. Methods A new PDF gene was identified by BLAST analysis and PCR and was subsequently over-expressed in the prokaryotic expression host E.coli Bl21(DE3). Over-expressed protein was purified for enzymatic assay by metal affinity chromatography and a new screening model was established for novel antibiotics. Result A new PDF gene of Enterococcus faecium was identified successfully. Ten positive samples were picked up from 8000 compound library and the microbial fermentation broth samples. Conclusion A new PDF of gene Enterococcus faecium was first identified and the model had a high efficacy. Positive samples screened may be antibacterial agents of broad spectrum.
文摘GENTING Highlands, one of Malaysia＇s bestdeveloped hilI resorts, lies just 58 kilometers from the national capitalof Kuala Lumpur. Embraced by beautiful hills, the resort attracts tourists from around the world who come for top line entertainment and a broad choice of recreational facilities. Its pleasant climate, enchanting scenery and wide range of services make the 20 million tourists who visit the resort annually reluctant to go home.
