The low-energy electronic states and energy gaps of carbon nanocones in an electric field are studied using a single-?-band tight-binding model. The analysis considers five perfect carbon nanocones with disclination a...The low-energy electronic states and energy gaps of carbon nanocones in an electric field are studied using a single-?-band tight-binding model. The analysis considers five perfect carbon nanocones with disclination angles of 60°, 120°, 180°, 240° and 300°, respectively. The numerical results reveal that the low-energy electronic states and energy gaps of a carbon nanocones are highly sensitive to its geometric shape(i.e. the disclination angle and height), and to the direction and magnitude of an electric field. The electric field causes a strong modulation of the state energies and energy gaps of the nanocones, changes their Fermi levels, and induces zero-gap transitions. The energy-gap modulation effect becomes particularly pronounced at higher strength of the applied electric field, and is strongly related to the geometric structure of the nanocone.展开更多
Identifying the species composition of a microbial ecosystem is often hampered by difficulties in culturing the organisms and in the low sequencing depth of traditional DNA barcoding.Metagenomic analysis,a huge-scale ...Identifying the species composition of a microbial ecosystem is often hampered by difficulties in culturing the organisms and in the low sequencing depth of traditional DNA barcoding.Metagenomic analysis,a huge-scale nucleotide-sequence-based tool,can overcome such difficulties.In this study,Sanger sequencing of 500 nrITS clones uncovered 29 taxa of 19 fungal genera,whereas metagenomics with next-generation sequencing identified 512 operational taxonomic units(OTUs)for ITS1/2 and 364 for ITS3/4.Nevertheless,high throughput sequencing of PCR amplicons of ITS1/2,ITS3/4,nrLSU-LR,nrLSU-U,mtLSU,and mtATP6,all with at least 1,300×coverage and about 21 million reads in total,yielded a very diverse fungal composition.The fact that 74%of the OTUs were exclusively uncovered with single barcodes indicated that each marker provided its own insights into the fungal flora.To deal with the high heterogeneity in the data and to integrate the information on species composition across barcodes,a rank-scoring strategy was developed.Accordingly,205 genera among 64 orders of fungi were identified in healthy Phalaenopsis roots.Of the barcodes utilized,ITS1/2,ITS3/4,and nrLSU-U were the most competent in uncovering the fungal diversity.These barcodes,though detecting different compositions likely due to primer preference,provided complementary and comprehensive power in deciphering the microbial diversity,especially in revealing rare species.展开更多
基金supported in part by the National Science Council of Taiwan under Grant Nos.NSC 96-2221-E-492-007-MY3 and NSC 98-2221-E-006-131-MY3National Center for Theoretical Science(NCTS)in Taiwan
文摘The low-energy electronic states and energy gaps of carbon nanocones in an electric field are studied using a single-?-band tight-binding model. The analysis considers five perfect carbon nanocones with disclination angles of 60°, 120°, 180°, 240° and 300°, respectively. The numerical results reveal that the low-energy electronic states and energy gaps of a carbon nanocones are highly sensitive to its geometric shape(i.e. the disclination angle and height), and to the direction and magnitude of an electric field. The electric field causes a strong modulation of the state energies and energy gaps of the nanocones, changes their Fermi levels, and induces zero-gap transitions. The energy-gap modulation effect becomes particularly pronounced at higher strength of the applied electric field, and is strongly related to the geometric structure of the nanocone.
基金This study was financially supported by the National Cheng Kung University and the National Science Council,Taiwan.
文摘Identifying the species composition of a microbial ecosystem is often hampered by difficulties in culturing the organisms and in the low sequencing depth of traditional DNA barcoding.Metagenomic analysis,a huge-scale nucleotide-sequence-based tool,can overcome such difficulties.In this study,Sanger sequencing of 500 nrITS clones uncovered 29 taxa of 19 fungal genera,whereas metagenomics with next-generation sequencing identified 512 operational taxonomic units(OTUs)for ITS1/2 and 364 for ITS3/4.Nevertheless,high throughput sequencing of PCR amplicons of ITS1/2,ITS3/4,nrLSU-LR,nrLSU-U,mtLSU,and mtATP6,all with at least 1,300×coverage and about 21 million reads in total,yielded a very diverse fungal composition.The fact that 74%of the OTUs were exclusively uncovered with single barcodes indicated that each marker provided its own insights into the fungal flora.To deal with the high heterogeneity in the data and to integrate the information on species composition across barcodes,a rank-scoring strategy was developed.Accordingly,205 genera among 64 orders of fungi were identified in healthy Phalaenopsis roots.Of the barcodes utilized,ITS1/2,ITS3/4,and nrLSU-U were the most competent in uncovering the fungal diversity.These barcodes,though detecting different compositions likely due to primer preference,provided complementary and comprehensive power in deciphering the microbial diversity,especially in revealing rare species.
