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141.
Phoresis, a classic example of particle transport driven by thermodynamic gradients, is enjoying a resurgent research interest motivated both by technological developments and by its relevance to the motility of chemically active particles. Here we succinctly review, using the case of chemophoresis (also called diffusiophoresis), the general framework of phoresis and self-phoresis formulated as a Stokes-flow problem for a liquid solution (solvent and solute) maintained out of thermodynamic equilibrium by solute gradients. Within the constraints of local equilibrium, we discuss the simplest extension of the theory in order to account for correlations in the fluid. We show that this leads to a shift from the paradigm based on the ideal case, in that self-phoresis can no longer be represented as phoresis in a self-generated composition gradient. Our review concludes with a concise overview of a few directions which we think hold the potential to reveal a rich behavior in future investigations. 相似文献
142.
探讨DCE-MRI参数及IFIT1基因对腰椎间盘突出症(LDH)患者椎间盘退变(IDD)程度的评估价值。随机选取确诊的66例LDH患者作为研究对象,根据改良Pfirrmann分级法将患者分为2组:轻中度IDD(Ⅰ~Ⅲ级)组(46例)和重度IDD(Ⅳ~Ⅴ级)组20例。通过DCE-MRI检查考察患者的K-trans值,采用日本骨科学会评分(JOA)评估腰椎功能,采用视觉模拟评分法(VAS)评估腰部疼痛,采用RT-PCR检测外周血单个核细胞(PBMC)中IFIT1的mRNA表达。轻中度IDD组的K-trans值显著低于重度IDD组。轻中度IDD组患者PBMC中的IFIT1 mRNA相对表达量显著低于重度IDD组。K-trans值与PBMC中的IFIT1 mRNA水平和VAS评分正相关,与JOA评分负相关(P<0.05)。PBMC中的IFIT1 mRNA水平与VAS评分正相关,与JOA评分负相关(P<0.05)。K-trans值和PBMC中的IFIT1 mRNA水平联合诊断重度IDD的AUC值、敏感性和特异性分别为0.991、91.3%和100.0%,AUC值和特异性均高于单独诊断。DCE-MRI检查中的K-trans值联合PBMC中的IFIT1 mRNA水平可用于LDH患者IDD程度的诊断。 相似文献
143.
Karuppasamy Kohila Rani Rajkumar Devasenathipathy Jia-Zheng Wang Xiao-Yuan Hui Jian-De Lin Yi-Miao Zhang Liu-Bin Zhao Jian-Zhang Zhou De-Yin Wu Zhong-Qun Tian 《Current Opinion in Electrochemistry》2022
Plasmonic noble metal nanostructures have been targeted due to their strong surface plasmon resonance at photoelectrochemical interfaces. Recently, it has been concluded that, the plasmonic noble metal nanostructures on photoexcitation permit the transfer of effective hot carriers (hot electron/hole pair) to nearby adsorbed molecules where, the transformed hot carriers can efficiently decrease the activation barrier of a reaction. In this review, our recent achievements in the plasmon-mediated chemical reactions of organic molecules such as para-aminothiophenol, substituted para-aminothiophenol and para-nitrothiophenol at nanostructures modified noble metal electrodes using surface enhanced Raman spectroscopy, electrochemical methods, and theoretical calculations will be discussed. 相似文献
144.
The electrochemical CO2 reduction (CO2RR) is a sustainable approach to mitigate the increased CO2 emissions and simultaneously produce value-added chemicals and fuels. Metal-nitrogen-carbon (M-N-C) based single-atom catalysts (SACs) have emerged as promising electrocatalysts for CO2RR with high activity, selectivity, and stability. To design efficient SACs for CO2RR, the key influence factors need to be understood. Here, we summarize recent achievements on M-N-C SACs for CO2RR and highlight the significance of the key constituting factors, metal sites, the coordination environment, and the substrates, for achieving high CO2RR performance. The perspective views and guidelines are provided for the future direction of developing M-N-C SACs as CO2RR catalysts. 相似文献
145.
Mahitha Udayakumar Bilal El Mrabate Tamás Koós Katalin Szemmelveisz Ferenc Kristály Máté Leskó Ádám Filep Róbert Géber Mateusz Schabikowski Péter Baumli János Lakatos Pál Tóth Zoltán Németh 《Arabian Journal of Chemistry》2021,14(7):103214
Carbon foams have gained significant attention due to their tuneable properties that enable a wide range of applications including catalysis, energy storage and wastewater treatment. Novel synthesis pathways enable novel applications via yielding complex, hierarchical material structure. In this work, activated carbon foams (ACFs) were produced from waste polyurethane elastomer templates using different synthesis pathways, including a novel one-step method. Uniquely, the produced foams exhibited complex structure and contained carbon microspheres. The ACFs were synthesized by impregnating the elastomers in an acidified sucrose solution followed by direct activation using CO2 at 1000 ℃. Different pyrolysis and activation conditions were investigated. The ACFs were characterized by a high specific surface area (SBET) of 2172 m2/g and an enhanced pore volume of 1.08 cm3/g. Computer tomography and morphological studies revealed an inhomogeneous porous structure and the presence of numerous carbon spheres of varying sizes embedded in the porous network of the three-dimensional carbon foam. X-ray diffraction (XRD) and Raman spectroscopy indicated that the obtained carbon foam was amorphous and of turbostratic structure. Moreover, the activation process enhanced the surface of the carbon foam, making it more hydrophilic via altering pore size distribution and introducing oxygen functional groups. In equilibrium, the adsorption of methylene blue on ACF followed the Langmuir isotherm model with a maximum adsorption capacity of 592 mg/g. Based on these results, the produced ACFs have potential applications as adsorbents, catalyst support and electrode material in energy storage systems. 相似文献
146.
Surface silanol structures, acid properties, and tungsten dispersion of the sol-gel-derived 7W/SiO2–xAl2O3 (x = 0.2–23 wt%) were investigated by means of 29Si, 27Al, and 1H MAS NMR, NH3-TPD, in-situ NH3-IR spectroscopy, XRD, and Raman spectroscopy. The surface silanol structure changed upon Al and tungsten loadings; however, loading of 1 wt% Al2O3 appeared to be the threshold for preserving the Si(OH)Al with isolated bridge after impregnation of 7 wt% W. The 7W/SiO2–1Al2O3 (1 wt% Al2O3) was also found to exhibit the lowest ratio of Bronsted to Lewis acid with the highest amount of Lewis acid sites and the best catalyst performances in propene self-metathesis at 550 °C in terms of both propene conversion and ethylene/butene selectivity. Despite its low tungsten dispersion, the metathesis activity was correlated well with the higher amount of tungsten carbene species, which were formed on the catalysts containing higher isolated bridge silanol and the presence of higher Lewis acid sites. 相似文献
147.
We tested the hypothesis that partial volume effects due to poor in-plane resolution and/or low temporal resolution used in clinical dynamic contrast-enhanced magnetic resonance imaging results in erroneous diagnostic information based on inaccurate estimates of tumor contrast agent extravasation and tested whether reduced encoding techniques can correct for dynamic data volume averaging. Image spatial resolution was reduced from 469 x 469 microm2 to those reported below by selecting a subset of k-space data. We then compared the top five K(trans)/V(T) "hot spots" obtained from the original data set, 469 x 469-microm in-plane spatial resolution and an 18-s temporal resolution processed by fast Fourier transform (FFT), with values obtained from data sets having in-plane spatial resolutions of 938 x 938, 1875 x 1875 and 2500 x 2500 microm2 and a temporal resolution of 18 s, or data sets with temporal resolutions of 36, 54 and 72 and a spatial resolution of 469 x 469 microm2, and found them to statistically differ from the parent data sets. We then tested four different post processing methods for improving the spatial resolution without sacrificing temporal resolution: zero-filled FFT, keyhole, reduced-encoding imaging by generalized-series reconstruction (RIGR) and two-reference RIGR (TRIGR). The top five values of K(trans)/V(T) obtained from data sets, the in-plane spatial resolutions of which were improved to 469 x 469 microm2 by zero-filling FFT, Keyhole and RIGR, statistically differed from those obtained from the original 469 x 469 microm2 FFT parent image data set. Only the 938 x 938 and 1875 x 1875 microm2 data sets reconstructed to 469 x 469 microm2 with TRIGR reconstruction method yielded values of the top five K(trans)/V(T) hot spots statistically the same as the original parent data set, 469 x 469 microm2 in-plane spatial and 18-s temporal-resolution FFT. That is, partial volume effects from data sets of different in-plane spatial resolution resulted in statistically different values of the top five K(trans)/V(T) hot spots relative to a high spatial and temporal resolution data set, and TRIGR reconstruction of these low resolution data sets to high resolution images provided statistically similar values with a savings in temporal resolution of 2 to 4 times. 相似文献
148.
In this short letter, we describe the effects of low temperature on the Metal-Enhanced Fluorescence (MEF) phenomenon. Fluorophores
close to Silver Island Films (SiFs) show on average two- to ten-fold enhancements in their fluorescence signatures at room
temperature. However, at 77 K, we have observed that MEF is even more pronounced as compared to an identical glass control
sample. We also demonstrate that the further enhancements in MEF occur at low temperature over a range of visible wavelengths
for different fluorophores, for both SiFs and 20 nm surface deposited gold colloids. 相似文献
149.
以抗坏血酸为还原剂,柠檬酸为结构导向剂,一步还原硝酸银,合成了尺寸和形状可调的花状银颗粒。纳米粒子的粒径可在600~1 200 nm范围内调整,表面突起可达到10~25 nm。柠檬酸的化学性质在银纳米粒子合成多级花状银结构的过程中起着至关重要的作用。通过改变柠檬酸或抗坏血酸溶液的用量,银结构的各向异性形貌可以很容易地调节。以制备的多级花状银颗粒作为表面增强拉曼散射(SERS)基底,对浓度为10~(-10)mol·L~(-1)的罗丹明6G(R6G)仍具有较高的检测灵敏度。 相似文献
150.
We give a complete classification of Lagrangian immersions of homogeneous 3-manifolds (the Berger spheres, the Heisenberg group , the universal covering of the Lie group and the Lie group ) in 3-dimensional complex space forms. As a corollary, we get a new characterization of the Berger sphere in complex projective space. 相似文献