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排序方式: 共有137条查询结果,搜索用时 15 毫秒
61.
Dr. Kunpeng Ruan Prof. Xuetao Shi Dr. Yali Zhang Dr. Yongqiang Guo Dr. Xiao Zhong Prof. Junwei Gu 《Angewandte Chemie (International ed. in English)》2023,62(38):e202309010
The positive liquid crystals, 4′-heptyl-4-biphenylcarbonitrile (7CB), are used to functionalize carbon nanotubes (LC-CNT), which can be aligned in the liquid crystalline polyimide (LC-PI) matrix under an alternating electric field to fabricate the thermally conductive LC-CNT/LC-PI composite films. The efficient establishment of thermal conduction pathways in thermally conductive LC-CNT/LC-PI composite films with a low amount of LC-CNT is achieved through the oriented alignment of LC-CNT within the LC-PI matrix. When the mass fraction of LC-CNT is 15 wt %, the in-plane thermal conductivity coefficient (λ∥) and the through-plane thermal conductivity coefficient (λ⊥) of the LC-CNT/LC-PI composite films reach 4.02 W/(m ⋅ K) and 0.55 W/(m⋅K), which are 90.5 % and 71.9 % higher than those of the intrinsically thermally conductive LC-PI films respectively, also 28.8 % and 5.8 % higher than those of the CNT/LC-PI composite films respectively. Meanwhile, the thermally conductive LC-CNT/LC-PI composite films also possess excellent mechanical and heat resistance properties. The Young's modulus and the heat resistance index are 2.3 GPa and 297.7 °C, respectively, which are higher than the intrinsically thermally conductive LC-PI films and the thermally conductive CNT/LC-PI composite films under the same amount of CNT. 相似文献
62.
63.
K. Magnus Åberg Erik Alm Ralf J. O. Torgrip 《Analytical and bioanalytical chemistry》2009,394(1):151-162
In metabonomics it is difficult to tell which peak is which in datasets with many samples. This is known as the correspondence problem. Data from different samples are not synchronised, i.e., the peak from one metabolite does not appear in exactly the same place in all samples. For datasets with many samples, this problem is nontrivial, because each sample contains hundreds to thousands of peaks that shift and are identified ambiguously. Statistical analysis of the data assumes that peaks from one metabolite are found in one column of a data table. For every error in the data table, the statistical analysis loses power and the risk of missing a biomarker increases. It is therefore important to solve the correspondence problem by synchronising samples and there is no method that solves it once and for all. In this review, we analyse the correspondence problem, discuss current state-of-the-art methods for synchronising samples, and predict the properties of future methods. 相似文献
64.
65.
Aligned functionalized multiwalled carbon nanotubes/polylactic acid (MWNTs-PCL/PLA) composite fibers were successfully prepared by electrospinning processing. The MWNTs bonded with the polycaprolactone chains exhibited excellent uniform dispersion in PLA solution by comparing with the acid-functionalized MWNTs and amino-functionalized MWNTs. Optical microscopy was used to study the aligned degree of the fibers and to investigate the influences of the electrodes distance on the alignment and structure of the fibers, and results showed that the best quality of aligned fibers with dense structure and high aligned degree were obtained at an electrodes distance of 3 cm. Moreover, the MWNTs embedded inside the MWNTs-PCL/PLA fibers displayed well orientation along the axes of the fibers, which was demonstrated by field emission scanning electron microscopy, transmission electron microscopy and Raman spectroscopy. 相似文献
66.
We discuss three different experiments for studying electron-excitation of atoms where lasers have been used in combination. These are stepwise electron–photon excitation, superelastic electron scattering from laser excited atoms and excitation of atoms using spin polarized electrons produced by lasers. We present distorted wave calculations and compare our results with the recently reported such experimental measurements. In particular, the results for the alignment and orientation of the excited n 2P states of K () and Rb () atoms and the spin parameters for the lowest excited 1P1 and 3P0,1,2 states of argon by polarized electrons are presented and discussed. 相似文献
67.
A conceptually new approach for aligning chromatograms is introduced and applied to examples of metabolite identification in human blood plasma by liquid chromatography–mass spectrometry (LC–MS). A square-root representation of the chromatogram's derivative coupled with an extended Fisher–Rao metric enables the computation of relative differences between chromatograms. Minimization of these differences using a common dynamic programming algorithm brings the chromatograms into alignment. Application to a complex sample, National Institute of Standards and Technology (NIST) Standard Reference Material 1950, Metabolites in Human Plasma, analyzed by two different LC–MS methods having significantly different ranges of elution time is described. 相似文献
68.
Zhong Li Jia‐Jun Wang Jing Huang Zhi‐Min Zhang Hong‐Mei Lu Yi‐Bao Zheng De‐Jian Zhan Yi‐Zeng Liang 《Journal of separation science》2013,36(9-10):1677-1684
The preprocessing of chromatograms is essential to modern chromatography for further qualitative and quantitative analysis, especially when chromatographic instruments are used for herb products analysis involving large number of samples. To accurately compare and analyze the obtained chromatograms, it is necessary to preprocess, especially align retention time shifts. Here moving window fast Fourier transform (FFT) cross‐correlation is introduced to perform nonlinear alignment of high‐throughput chromatograms. Since elution characteristics of chromatograms will produce local similarity in retention time shifts, moving window procedure seems to be a better substitute of segmentation steps. The retention time shifts can be calculated and accelerated by FFT cross‐correlation. The artifacts can be detected and eliminated from the retention time shifts profile since the continuity of moving window procedure. The proposed method is demonstrated in comparison with recursive alignment by FFT on chromatographic datasets from herb products analysis. It is shown that the proposed method can address nonlinear retention time shift problem in chromatograms with the simple moving window procedure, which will not introduce segments size optimization problem. In additional, the parameters are intuitive and easy to adjust, which makes it off‐the‐shelf toolbox for alignment of chromatograms. 相似文献
69.
Aligned and random fibres of strontium hexaferrite (SrM, SrFe12O19) and barium hexaferrite (BaM, BaFe12O19) were manufactured by blow spinning from an aqueous inorganic sol–gel precursor, which was then fired to give the hexagonal ferrite fibre. Their magnetic properties were studied by VSM, investigating the evolution of these properties with firing and measurement temperature, and in particular the effects of fibre alignment. It has been predicted that aligned ferrite fibres will demonstrate an enhanced magnetisation along the axis of alignment with respect to perpendicular to the axis, and this has been demonstrated here for the first time. The optimum firing temperature was 1000 °C, at which point they still had submicron grains. In BaM random fibres Ms=63.8 emu g−1 and Hc=428.1 kA m−1, and in SrM random fibres Ms=63.3 emu g−1 and Hc=452.8 kA m−1, high values for polycrystalline materials. Fibres aligned parallel to the applied field had saturation magnetisation (Ms) values equal to those of the random fibres, whilst fibres aligned perpendicular to the field had Ms values 62% and 75% lower, for BaM and SrM, respectively. There was no change in coercivity (Hc) between random or aligned fibres of any orientation, and fibres aligned 45° and parallel to H appeared identical. Therefore, properties along the axis of alignment were superior when compared to measurements perpendicular to the axis of alignment, giving a directionality to the magnetisation in an otherwise randomly oriented ferrite material. 相似文献
70.
Keng-Liang Ou Chin-Sung Chen Li-Hsiang Lin Jen-Chieh Lu Yao-Chi Shu Wen-Chin Tseng Jen-Chang Yang Sheng-Yang Lee Chien-Chung Chen 《European Polymer Journal》2011,47(5):882-892
Novel epitaxial-like packed, super aligned, mono-layered hollow fibrous membranes were prepared by co-axial electrospinning technology. PLLA pellets were dissolved in solvent mixture of dichloromethane and dimethyl formamide (DCM/DMF = 9:1) to prepare sheath solution dope with various concentrations (from 8 to 19 wt.%). Aqueous solution of poly-ethylene glycol (PEG) was used as core solution dope. During the electrospinning process, dope concentrations and feed rate ratios were adjusted, separately, to evaluate the formation of resulting membranes. With lower shell solution concentration (from 8 to 15 wt.%), the collected, flattened film showed arrangement of lower order. A stood-up film was clearly seen when concentration increased to 17 wt.% and higher. As the collecting time went longer, these fibers piled up and eventually, stood up as a thin film from the surface of collector. Increasing flow rate ratio (FRR) also resulted similar outcomes and verify the cause of this phenomenon. After washing with water, scanning electron microscopy (SEM) revealed sheets of mono-layered, micron-sized hollow fiber arrays which were well aligned and tightly packed, just like the epitaxial growth of some semiconducting materials. These perfectly aligned and tightly packed hollow fiber arrays can be considered as highly anisotropic scaffolds that mimic tissue structures, such as nerve tissue, vascular structure as well as other application. 相似文献