We report the extraordinary performance of carbon‐coated sodium super ion conductor (NASICON)‐type LiTi2(PO4)3 as an ideal host matrix for reversible insertion of both Li and Na ions. The NASICON‐type compound was prepared by means of a Pechini‐type polymerizable complex method and was subsequently carbon coated. Several characterization techniques such as XRD, thermogravimetric analysis (TGA), field‐emission (FE) SEM, TEM, and Raman analysis were used to study the physicochemical properties. Both guest species underwent a two‐phase insertion mechanism during the charge/discharge process that was clearly evidenced from galvanostatic and cyclic voltammetric studies. Unlike that of Li (≈1.5 moles of Li), Na insertion exhibits better reversibility (≈1.59 moles of Na) while experiencing a slightly higher capacity fade (≈8 % higher than Li) and polarization (780 mV) than Li. However, excellent rate capability profiles were noted for Na insertion relative to its counterpart Li. Overall, the Na insertion properties were found to be superior relative to Li insertion, which makes carbon‐coated NASICON‐type LiTi2(PO4)3 hosts attractive for the development of next‐generation batteries. 相似文献
A new rapid method has been developed for the determination of Th, Pu, Np, U, Am and Cm isotopes in water samples of about 1 L. Actinides are pre-concentrated by co-precipitation with Ca phosphate, sequentially separated on stacked TEVA and TK221 cartridges and measured by alpha spectrometry. The TK221 extraction chromatographic resin contains i.e. CMPO and DGA extractants. It has been characterized by measuring the weight distribution ratios (Dw) of actinides which are higher than 1000 for all actinides in 3 M HNO3. The method has been optimized, applied for the analysis of tap and seawater samples and validated by participating in an IAEA proficiency test. Chemical recoveries for all actinides are better than 50%. The method can be performed within one day.
We present the first experimental demonstration of lensless diffractive imaging using coherent soft x rays generated by a tabletop soft-x-ray source. A 29 nm high harmonic beam illuminates an object, and the subsequent diffraction is collected on an x-ray CCD camera. High dynamic range diffraction patterns are obtained by taking multiple exposures while blocking small-angle diffraction using beam blocks of varying size. These patterns reconstruct to images with 214 nm resolution. This work demonstrates a practical tabletop lensless microscope that promises to find applications in materials science, nanoscience, and biology. 相似文献
The structure and properties of optimal networks depend on the cost functional being minimized and on constraints to which the minimization is subject. We show here two different formulations that lead to identical results: minimizing the dissipation rate of an electrical network under a global constraint is equivalent to the minimization of a power-law cost function introduced by Banavar et al. [Phys. Rev. Lett. 84, 4745 (2000)10.1103/PhysRevLett.84.4745]. An explicit scaling relation between the currents and the corresponding conductances is derived, proving the potential flow nature of the latter. Varying a unique parameter, the topology of the optimized networks shows a transition from a tree topology to a very redundant structure with loops; the transition corresponds to a discontinuity in the slope of the power dissipation. 相似文献
Capillary sieving electrophoresis utilizing SDS (CE(SDS)) is one of the most applied methods for the analysis of antibody (mAb) size heterogeneity in the biopharmaceutical industry. Inadequate peak identification of observed protein fragments is still a major issue. In a recent publication, we introduced an electrophoretic 2D system, enabling online mass spectrometric detection of generic CE(SDS) separated peaks and identification of several mAb fragments. However, an improvement regarding system stability and handling of the approach was desired. Here, we introduce a novel 8-port valve in conjunction with an optimized decomplexation strategy. The valve contains four sample loops with increased distances between the separation dimensions. Thus, successively coinjection of solvent and cationic surfactant without any additional detector in the second dimension is enabled, simplifying the decomplexation strategy. Removal efficiency was optimized by testing different volumes of solvents as presample and cationic surfactant as postsample zone. 2D measurements of the light and heavy chain of the reduced NIST mAb with the 8-port valve and the optimized decomplexation strategy demonstrates the increased robustness of the system. The presented novel set-up is a step toward routine application of CE(SDS)-CZE-MS for impurity characterization of proteins in the biopharmaceutical field. 相似文献
Mild transition-metal catalysed cross-couplings enable direct functionalisation of biocatalytically halogenated tryptophans with alkyl iodides, representing a new alternative for late-stage derivatisations of halogenated aromatic amino acids. Moreover, this strategy enables preparation of (homo)tryptophan regioisomers in a simple two-step synthesis using a Pd-catalysed Negishi cross coupling. This method provides access to non-canonical constitutional surrogates of tryptophan, ready for use in peptide synthesis. 相似文献
Let G be a bridgeless cubic graph. Consider a list of k 1‐factors of G. Let be the set of edges contained in precisely i members of the k 1‐factors. Let be the smallest over all lists of k 1‐factors of G. Any list of three 1‐factors induces a core of a cubic graph. We use results on the structure of cores to prove sufficient conditions for Berge‐covers and for the existence of three 1‐factors with empty intersection. Furthermore, if , then is an upper bound for the girth of G. We also prove some new upper bounds for the length of shortest cycle covers of bridgeless cubic graphs. Cubic graphs with have a 4‐cycle cover of length and a 5‐cycle double cover. These graphs also satisfy two conjectures of Zhang 18 . We also give a negative answer to a problem stated in 18 . 相似文献
In view of increasing demands for efficient photosensitizers for photodynamic therapy (PDT), we herein report the synthesis and photophysical characterizations of new chlorin e6 trimethyl ester and protoporphyrin IX dimethyl ester dyads as free bases and ZnII complexes. The synthesis of these molecules linked at the β‐pyrrolic positions to pyrano[3,2‐c]coumarin, pyrano[3,2‐c]quinolinone, and pyrano[3,2‐c]naphthoquinone moieties was performed by using the domino Knoevenagel hetero Diels–Alder reaction. The α‐methylenechromanes, α‐methylenequinoline, and ortho‐quinone methides were generated in situ from a Knoevenagel reaction of 4‐hydroxycoumarin, 4‐hydroxy‐6‐methylcoumarin, 4‐hydroxy‐N‐methylquinolinone, and 2‐hydroxy‐1,4‐naphthoquinone, respectively, with paraformaldehyde in dioxane. All the dyads as free bases and as ZnII complexes were obtained in high yields. All new compounds were fully characterized by 1D and 2D NMR techniques, UV/Vis spectroscopy, and HRMS. Their photophysical properties were evaluated by measuring the fluorescence quantum yield, the singlet oxygen quantum yield by luminescence detection, and also the triplet lifetimes were correlated by flash photolysis and intersystem crossing (ISC) rates. The fluorescence lifetimes were measured by a time‐correlated single photon count (TCSPC) method, fluorescence decay associated spectra (FDAS), and anisotropy measurements. Magnetic circular dichroism (MCD) and circular dichroism (CD) spectra were recorded for one ZnII complex in order to obtain information, respectively, on the electronic and conformational states, and interpretation of these spectra was enhanced by molecular orbital (MO) calculations. Electrochemical studies of the ZnII complexes were also carried out to gain insights into their behavior for such applications. 相似文献