Search

Understanding the photoluminescence mechanism of carbon dots (C‐dots) is both of fundamental and technical significance. However, it has remained an extreme challenge due to C‐dots' indeterminate constitution and complicated composition/structure. Herein, a combined processing system, namely extraction and subsequent preparative thin layer chromatography for C‐dots separation is presented. Benefiting from its powerful separation performances, two minimalistic C‐dots with almost identical structure and optical properties (named as "twin" C‐dots) are well separated. Then, by contrastive analysis, a photophysical picture for the C‐dots' photoluminescence is presented: The C‐dots' photoluminescence comes from uniform surface polycyclic aromatic hydrocarbon units instead of the whole particles, which is both size‐ and oxygen‐independent. The products not only are highly bright and stable against photobleaching, but possess repeatable photoluminescence with molecular level accuracy. So, the C‐dots favorably integrate the advantages from small molecule dyes to photoluminescent nanomaterials, which is unprecedented and desirable for property exploration and application expansion. [ABSTRACT FROM AUTHOR]

Ferula diversifolia W.Jun Li & Lei Yang, is described and illustrated from Xinjiang Province, China. The new species is morphologically similar to F. foetidissima Regel & Schmalh. in terms of its garlic‐like odor, robust stem, and characetristic branching pattern with a paniculate inflorescence. However, it is distinctly different from F. foetidissima in its ternate‐2‐pinnate compound leaves with much broader and shorter leaflets that are incised‐elliptical to rhombic in shape, and significantly smaller fruits. The diagnosis of the new species is supported by a comprehensive investigation including a molecular phylogeny, detailed description, conservation status, photographs, and comparison with morphologically similar species. [ABSTRACT FROM AUTHOR]

The generalized aggregation ∑i=1nWiϕ(Xi,ai) arises in many research fields including applied probability, actuarial science, and reliability theory, where ϕ is a bivariate kernel function and a is a parameter vector. One of its remarkable features is that both X and W are dependent in many practical situations. Therefore, studying the stochastic properties of generalized aggregations under various dependence structures is an interesting and meaningful problem. In this paper, by using left tail weakly stochastic arrangement increasing, right tail weakly stochastic arrangement increasing, and comonotonicity to characterize the dependent structures among X or W, we establish the increasing convex ordering and the expectation ordering of generalized aggregations to investigate the effects of the arrangement and heterogeneity among ai's. Numerical examples and three practical applications are presented to illustrate our results as well. [ABSTRACT FROM AUTHOR]

Systematic evolution of ligands by exponential enrichment is a traditional approach to select aptamer, which has a great potential in biosensing field. However, chemical modifications of DNA library or targets before selection might block the real recognition and binding sites between aptamers and their targets. In this study, a label‐ and modification‐free‐based in situ selection strategy was developed to overcome this limitation. The strategy is an attempt to screen bovine serum albumin aptamers according to the principle of electrophoretic mobility shift assay, and allowed single‐stranded DNA sequence to be fully exposed to interact with bovine serum albumin which was mixed with the agarose gel beforehand. After eight rounds of selection, specific aptamer with low dissociation constant (Kd) value of 69.44 ± 7.60 nM was selected and used for subsequent establishment of fluorescence biosensor. After optimization, the optimal aptasensor exhibited a high sensitivity toward bovine serum albumin with a limit of detection of 0.24 ng/mL (linear range from 1 to 120 ng/mL). These results indicated that the label‐ and modification‐free‐based in situ selection strategy proposed in this work could effectively select specific aptamer to develop aptasensor for sensitive detection of bovine serum albumin or other targets in actual complicated samples. [ABSTRACT FROM AUTHOR]

Summary: By using a complete set of poroelastodynamic spherical wave potentials (SWPs) representing a fast compressional wave PI, a slow compressional wave PII, and a shear wave S with 3 vectorial potentials (not all are independent), a solution scheme based on the method of fundamental solution (MFS) is devised to solve 3‐D wave scattering and dynamic stress concentration problems due to inhomogeneous inclusions and cavities embedded in an infinite poroelastic domain. The method is verified by comparing the result with the elastic analytical solution, which is a degenerated case, as well as with poroelastic solution obtained using other numerical methods. The accuracy and stability of the SWP‐MFS are also demonstrated. The displacement, hoop stress, and fluid pore pressure around spherical cavity and poroelastic inclusion with permeable and impermeable boundary are investigated for incident plane PI and SV waves. The scattering characteristics are examined for a range of material properties, such as porosity and shear modulus contrast, over a range of frequency. Compared with other boundary‐based numerical strategy, such as the boundary element method and the indirect boundary integral equation method, the current SWP‐MFS is a meshless method that does not need elements to approximate the geometry and is free from the treatment of singularities. The SWP‐MFS is a highly accurate and efficient solution methodology for wave scattering problems of arbitrary geometry, particularly when a part of the domain extends to infinity. [ABSTRACT FROM AUTHOR]

Abundant, exquisitely preserved specimens of the enigmatic tubular microfossil Megathrix longus are reported from the early Cambrian Yanjiahe Formation in the Yangtze Gorges area. Studies of their morphology and taphonomy reveal that the inner cross-wall of Megathrix longus is topographically flat, the trichome terminus is blunt and closed, and incomplete cross-walls are regularly intercalated between complete ones. The deformation of trichomes, as well as the corrugation of their cross-walls, are postmortem features caused by compaction, rather than biological features as previously interpreted. Statistical analysis indicates that chamber division is accomplished by the closure of incomplete cross-walls. This process, which contributed to trichome growth, is extremely similar to that of modern Oscillatoriaceae. Trichome fragmentation was also observed in a series of specimens, which closely resembles that of cyanobacteria, particularly the Oscillatoriaceae. The termini of Megathrix longus suggest that it was planktonic. In general, Megathrix longus bears a close affinity to the extant Oscillatoriaceae (Cyanophyta). [ABSTRACT FROM AUTHOR]

Applications of conventional localized nuclear magnetic resonance correlated spectroscopy are restrained by long acquisition times and poor performance under inhomogeneous magnetic fields. Here, a method that combines the spatiotemporal encoding technique with the localization technique and implements the encoding and decoding in unison with suitable asymmetrical gradients is proposed to obtain high-resolution localized correlated spectra under inhomogeneous fields in greatly reduced times. Experiments on phantom solutions prove its insensitivity to linear field inhomogeneities along three orthogonal axes. Moreover, this method is applied to adipose study of marrow tissue with resolution improvements. The proposed method may offer promising perspectives for fast analyses of biological tissues. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]