A High Performance Plasmonic Sensor Based on Metal-Insulator-Metal Waveguide Coupled with a Double-Cavity Structure

A high performance plasmonic sensor based on a metal-insulator-metal (MIM) waveguide coupled with a double-cavity structure consisting of a side-coupled rectangular cavity and a disk cavity is proposed. The transmission characteristics of the rectangular cavity and disk cavity are analyzed theoretically and the improvements of performance for the double-cavity structure compared with a single cavity are studied. The influence of structural parameters on the transmission spectra and sensing performance are investigated in detail. A sensitivity of 1136 nm/RIU with a high figure of merit of 51,275 can be achieved at the resonant wavelength of 1148.5 nm. Due to the high performance and easy fabrication, the proposed structure may be applied in integrated optical circuits and on-chip nanosensors.     

Soil nutrient patchiness affects nutrient use efficiency,though not photosynthesis and growth of parental Glechoma longituba ramets: both patch contrast and direction matter

Aims Most plants are clonal in nature. Clonal ramets can share water, nutrients and photosynthate, especially when they experience patchy resources. Patch contrast (i.e. a difference in resources among patches) and patch direction (i.e. source–sink relations) are among the basic attributes of spatial patchiness. Here, I hypothesize that young established ramets in nutrient-rich patches support old ramets in nutrient-poor patches when ramets are subjected to different patch contrasts and patch directions.Methods In a greenhouse experiment, old and young ramets of Glechoma longituba were grown in four combinations consisting of patch contrast and patch direction. Minus patch direction refers to a patch combination in which parent ramets grow in nutrient-rich patches while connected daughter ramets grow in nutrient-poor ones and plus patch direction is the opposite direction. I measured photosynthesis and fluorescence traits, harvested all ramets, took morphological measures, weighed their dry mass and determined their nutrient uptake and use.Important findings For parental ramets of G. longituba, patch contrast and patch direction and their interactions had no significant effects on net photosynthetic rate, maximal fluorescence yield, photochemical quenching (quenching refers to any process which decreases the fluorescence intensity of a given substance), non-photochemical quenching, nutrient uptake, biomass and stolon weight ratio. Patch direction alone significantly affected root weight ratio. Large patch contrast enhanced N use efficiency (NUE) and P use efficiency (PUE); plus patch direction decreased NUE, but increased PUE; the patch contrast by patch direction interaction affected PUE and K use efficiency (KUE). There were significant interactions between patch direction and patch contrast on PUE and KUE. It is concluded that soil nutrient patchiness may influence nutrient use strategies, but not nutrient uptake, photosynthesis and growth of parent ramets of G. longituba connected to daughter ramets, and that patch contrast and patch direction jointly affect PUE and KUE.     

盐度对秋茄凋落叶分解过程中物质与能量动态的影响

在室内人工模拟潮汐, 研究了4种盐度(0、10‰、25‰和35‰, 分别代表淡水、低盐、中盐和高盐)下秋茄(Kandelia candel)凋落叶分解过程中物质与能量动态的差异。结果表明, 高盐处理下的失重率和平均分解速率显著低于淡水和低盐处理, 而高盐下的半分解理论值则高于其他处理; 盐度对分解过程中的残叶氮磷变化动态有显著影响, 其中, 残叶氮的释放速率在实验后期会随着盐度的升高而上升, 高盐度下残叶总氮含量显著低于低盐或淡水处理; 而在分解第1周, 淡水或低盐处理能加速磷的释放, 但中高盐度残叶中总磷含量最终会低于淡水和低盐处理; 盐度同样能对残叶热值产生显著影响, 淡水和低盐处理下的碎屑热值要显著高于高盐处理下的残叶热值, 但不同盐度下分解的能量损失差异不显著。     

AhDMT1, a Fe<Superscript>2+</Superscript> transporter,is involved in improving iron nutrition and N<Subscript>2</Subscript> fixation in nodules of peanut intercropped with maize in calcareous soils

Peanut (Arachis hypogaea L.) is an important legume providing edible proteins and N₂ fixation. However, iron deficiency severely reduces peanut growth in calcareous soils. The maize/peanut intercropping effectively improves iron nutrition and N₂ fixation of peanut under pot and field conditions on calcareous soils. However, little was known of how intercropping regulates iron transporters in peanut. We identified AhDMT1 as a Fe²⁺ transporter which was highly expressed in mature nodules with stronger N₂ fixation capacity. Promoter expression analysis indicated that AhDMT1 was localized in the vascular tissues of both roots and nodules in peanut. Short-term Fe-deficiency temporarily induced an AhDmt1 expression in mature nodules in contrast to roots. However, analysis of the correlation between the complex regulation pattern of AhDmt1 expression and iron nutrition status indicated that sufficient iron supply for long term was a prerequisite for keeping AhDmt1 at a high expression level in both, peanut roots and mature nodules. The AhDmt1 expression in peanut intercropped with maize under 3 years greenhouse experiments was similar to that of peanut supplied with sufficient iron in laboratory experiments. Thus, the positive interspecific effect of intercropping may supply sufficient iron to enhance the expression of AhDmt1 in peanut roots and mature nodules to improve the iron nutrition and N₂ fixation in nodules. This study may also serve as a paradigm in which functionally important genes and their ecological significance in intercropping were characterized using a candidate gene approach.     

Divergent Responses of Soil Fungi Functional Groups to Short-term Warming

Soil fungi fill pivotal ecological roles in biogeochemical processes, particularly dominating decomposition of lignin. Little is known, however, about the responses of different fungal groups to climate warming with respect to bacteria. In this study, using barcode pyrosequencing, we showed that short-term (15 months) of field exposure of an alpine meadow to warming (elevated 1 and 2 °C) did not markedly alter the overall soil fungal community structures and α-diversity on Tibetan Plateau, but the average β-diversity dramatically decreased in response to warming. However, soil respiration rates were stimulated in the growing season, which significantly (P?Ascomycota and rare taxa (relative abundance?Basidiomycota-affiliated members significantly increased, while Ascomycota showed a range of responses to warming. Collectively, we conclude that the fungal communities are resistant to short-term warming, though variations are observed in certain species and rare taxa. This report indicates that changes in a relatively small subset of the soil fungal community are sufficient to produce substantial changes in function, such as CO₂ efflux rates.     

Site-specific solvent exposure analysis of a membrane protein using unnatural amino acids and 19F nuclear magnetic resonance

Membrane proteins play an essential role in cellular metabolism, transportation and signal transduction across cell membranes. The scarcity of membrane protein structures has thus far prevented a full understanding of their molecular mechanisms. Preliminary topology studies and residue solvent exposure analysis have the potential to provide valuable information on membrane proteins of unknown structure. Here, a (19)F-containing unnatural amino acid (trimethylfluoro-phenylalanine, tfmF) was applied to accomplish site-specific (19)F spin incorporation at different sites in diacylglycerol kinase (DAGK, an Escherichia coli membrane protein) for site-specific solvent exposure analysis. Due to isotope effect on (19)F spins, a standard curve for (19)F-tfmF chemical shifts was drawn for varying solvent H(2)O/D(2)O ratios. Further site-specific (19)F solvent isotope shift analysis was conducted for DAGK to distinguish residues in water-soluble loops, interfacial areas or hydrophobic membrane regions. This site-specific solvent exposure analysis method could be applied for further topological analysis of other membrane proteins.     

Genetic analysis of IREB2, FAM13A and XRCC5 variants in Chinese Han patients with chronic obstructive pulmonary disease

Recently, variants (rs2568494, rs2869967 and rs3821104) in the IREB2, FAM13A and XRCC5 genes were found to be associated with chronic obstructive pulmonary disease (COPD) in non-Asian populations by genome-wide association study (GWAS) analysis. To evaluate whether variants in these genes are related to COPD in Chinese Han population, we investigated COPD patients of Chinese Han ethnicity from Mainland China. Significant differences in genotypic distributions (χ² = 6.319, p = 0.042 for rs2869967; χ² = 6.062, p = 0.048 for rs3821104) and allele distributions (χ² = 4.014, p = 0.045 for rs2869967; χ² = 5.607, p = 0.018 for rs3821104) were observed between patients and control subjects for variants rs2869967 and rs3821104, whereas no statistically significant associations for genotypic and allelic distribution between IREB2 rs2568494 and COPD phenotype (p > 0.05) were identified. Our results support that FAM13A rs2869967 and XRCC5 rs3821104 are associated with COPD in Chinese Han population.     

Molecular Characterization of High Plant Species Using PCR with Primers Designed from Consensus Branch Point Signal Sequences

A novel method is introduced for producing molecular markers in plants using single 15- to 18-mer PCR primers designed from the short conserved consensus branch point signal sequences and standard agarose gel electrophoresis. This method was tested on cultivated peanut and verified to give good fingerprinting results in other plant species (mango, banana, and longan). These single primers, designed from relatively conserved branch point signal sequences within gene introns, should be universal across other plant species. The method is rapid, simple, and efficient, and it requires no sequence information of the plant genome of interest. It could be used in conjunction with, or as a substitute for, conventional RAPD or ISSR techniques for applications including genetic diversity analysis, phylogenetic tree construction, and quantitative trait locus mapping. This technique provides a new way to develop molecular markers for assessing genetic diversity of germplasm in diverse species based on conserved branch point signal sequences.