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排序方式: 共有251条查询结果,搜索用时 20 毫秒
91.
Zhangyong Si Hui Wen Lim Moon Y. F. Tay Yu Du Lin Ruan Haofeng Qiu Rubí Zamudio-Vazquez Sheethal Reghu Yahua Chen Wen Shuo Tiong Kalisvar Marimuthu Partha Pratim De Oon Tek Ng Prof. Yabin Zhu Prof. Yunn-Hwen Gan Prof. Yonggui Robin Chi Prof. Hongwei Duan Prof. Guillermo C. Bazan Prof. E. Peter Greenberg Prof. Mary B. Chan-Park Prof. Kevin Pethe 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(17):6886-6893
Carbapenem-resistant Gram-negative bacteria (GNB) are heading the list of pathogens for which antibiotics are the most critically needed. Many antibiotics are either unable to penetrate the outer-membrane or are excluded by efflux mechanisms. Here, we report a cationic block β-peptide (PAS8-b-PDM12) that reverses intrinsic antibiotic resistance in GNB by two distinct mechanisms of action. PAS8-b-PDM12 does not only compromise the integrity of the bacterial outer-membrane, it also deactivates efflux pump systems by dissipating the transmembrane electrochemical potential. As a result, PAS8-b-PDM12 sensitizes carbapenem- and colistin-resistant GNB to multiple antibiotics in vitro and in vivo. The β-peptide allows the perfect alternation of cationic versus hydrophobic side chains, representing a significant improvement over previous antimicrobial α-peptides sensitizing agents. Together, our results indicate that it is technically possible for a single adjuvant to reverse innate antibiotic resistance in all pathogenic GNB of the ESKAPE group, including those resistant to last resort antibiotics. 相似文献
92.
Liu L. Loh N. H. Tay B. Y. Tor S. B. Yin H. Q. Qu X. H. 《Applied Physics A: Materials Science & Processing》2011,103(4):1145-1151
Micro powder injection molding (μPIM) has been developed as a potential technique for mass production of microcomponents in microsystems due to its shaping
complexity at low cost, in which sintering is a crucial step to dictate the final properties of the microcomponents. In this
paper, final-stage sintering behavior of 316L stainless steel microsize structures prepared by μPIM, φ100 μm and φ60 μm, respectively, was studied. The effect of size reduction in the regime of micrometers on the density of various microsize
structures was investigated. Sintering kinetics of the microsize structures of φ100 μm and φ60 μm were studied based on particle level sintering models. It is found that the microsize structures of φ60 μm had higher density than the microsize structures of φ100 μm given the same sintering condition. The results indicate that size reduction in the regime of micrometers facilitated
densification of microsize structures. The grain growth mechanism of microsize structures varied with size. Whereas the grain
growth of the microsize structures of φ100 μm is governed by surface-diffusion-controlled pore drag, the grain growth of the microsize structures of φ60 μm is controlled by boundary diffusion. During densification, the microsize structures, φ100 μm and φ60 μm, are both controlled by lattice diffusion. The corresponding activation energies are reported in the paper. 相似文献
93.
Boon-Ying Tay Ludger P. Stubbs Chacko Jacob Martin van Meurs 《Journal of organometallic chemistry》2011,696(21):3431-3435
A series of alkali metal cyclopentadienides, amides, alkoxides and phenoxides was characterized using NMR spectroscopy in deuterated dimethyl sulfoxide. Deuterated dimethyl sulfoxide showed very good stability and solubility for these compounds. Very nice and well resolved spectra were obtained for most compounds tested. The low cost of the solvent makes it possible to use it for the routine characterization of these alkali salts as the ligands in organometallic synthesis. 相似文献
94.
The dynamics of structure evolution of nanodiamonds ranging from 22 to 318 atoms of various shapes is studied by density functional tight-binding molecular dynamics. The spherical and cubic nanodiamonds can be transformed into fullerene-like structures upon heating. A number of the transformed fullerenes consist of pentagons and hexagons only. Others contain squares, heptagons, and octagons. One simulated fullerene is an isomer of C(60). The temperature of the transformation depends on the size, shape, and orientation of initial cluster. To be transformed into onion-like fullerenes, the spherical nanodiamonds should have 200 atoms or more, while the cubic ones require 302 atoms or more. The time-resolved energy profiles of all the transformations clearly reveal three-stage transformation character. During the first stage, the energy reduces quickly due to converting sp(3) carbon with dangling bond at the surface into sp(2) one, and the formation of partial sp(2) envelope wrapping the cluster. For the second stage, energy decreases slowly. The remaining interior carbon atoms come to the surface through the hole in the sp(2) envelope, and similar amount of sp(3) and sp(2) atoms coexist. The third stage involves the closure of holes, accompanied by the detachment of C(2) molecules and carbon chains from the edges. The energy decreases relatively fast in this stage. The proposed three-stage transformation pathway holds for all the simulations performed in this work, including those with the instant heating. 相似文献
95.
Kennedy DC McKay CS Tay LL Rouleau Y Pezacki JP 《Chemical communications (Cambridge, England)》2011,47(11):3156-3158
Silver nanoparticles bonded to terminal alkynes form stable particles in aqueous solution, produce strong SERS signals for molecular imaging that arise from the carbon-metal bond, and expand the scope of molecules that can be used to stably functionalize plasmonic particles for mammalian cell imaging applications. β-Lactams represent a class of biologically important molecules that can be adapted to SERS studies in this manner. 相似文献
96.
Pd and bimetallic PdRu nanoparticles supported on Vulcan XC-72 carbon prepared by the microwave-assisted polyol process are
examined as electrocatalysts for the electrooxidation of formic acid. The catalysts are characterized by transmission electron
microscopy and X-ray diffraction. The Pd and PdRu nanoparticles with sizes of <10 nm display the characteristic diffraction
peaks of a Pd face-centered cubic (fcc) crystal structure. It is found that the addition of Ru to Pd/C can decrease the lattice
parameter of Pd (fcc) crystal. The electrocatalytic activities of the catalysts are evaluated in sulfuric acid solution containing
1 M formic acid using linear sweeping voltammetry and chronoamperometry. The results show that Pd5Ru1/C displays the best electrocatalytic performance among all catalysts for formic acid electrooxidation. 相似文献
97.
Cetin H Tufan-Cetin O Turk AO Tay T Candan M Yanikoglu A Sumbul H 《Natural product research》2012,26(4):350-355
The larvicidal activity of some lichen metabolites, (+)-usnic acid, atranorin, 3-hydroxyphysodic acid and gyrophoric acid, against the second and third instar larvae of the mosquito Culiseta longiareolata were studied. All metabolites caused high larvicidal activities. When metabolites were compared on the basis of their LC(50) values, the order of increasing toxicity was as follows: gyrophoric acid (0.41?ppm)?>?(+)-usnic acid (0.48?ppm)?>?atranorin (0.52?ppm)?>?3-hydroxyphysodic acid (0.97?ppm). However, when LC(90) values were compared, the order of toxicity was (+)-usnic acid (1.54?ppm)?>?gyrophoric acid (1.93?ppm)?>?3-hydroxyphysodic acid (4.33?ppm)?>?atranorin (5.63?ppm). In conclusion, our results found that lichen secondary metabolites may have a promising role as potential larvicides. 相似文献
98.
Chor Yong Tay Wanru Fang Magdiel Inggrid Setyawati Chee Peng Sum Jianping Xie Kee Woei Ng Xiaodong Chen Catherine Hsu Ling Hong David Tai Leong 《Particle & Particle Systems Characterization》2013,30(9):784-793
Silica nanoparticles (SiO2 NPs) are one of the most widely used engineered nanoparticles and can been found in a wide range of consumer products. Despite their massive global production scale, little is known about their potential effects in the context of unintended exposure or ingestion. Using TR146 cells as an in vitro model of the human oral buccal mucosa, the uptake, spatial intracellular distribution, reactive oxygen species (ROS) production, inflammatory response, and cytotoxic effects of commercial SiO2 NPs are examined. SiO2 NPs are shown to dock and cross the cellular membrane barrier in a dose–time‐dependent manner. Confocal sectioning reveals translocation of SiO2 NPs into the cell nucleus after 12 h of exposure. A concentration threshold of more than 500 × 10?6 m is observed, above which SiO2 NPs are shown to exert significant oxidative stress with concomitant upregulation of inflammatory genes IL6 and TNFA. Further analysis of the p53 pathway and a series of apoptotic and cell cycle biomarkers reveals intracellular accumulation of SiO2 NPs exert marginal nanotoxicity. Collectively, this study provides important information regarding the uptake, intracellular distribution, and potential adverse cellular effects of SiO2 NPs commonly found in consumer products in the human oral epithelium. 相似文献
99.
Color-encoded digital fringe projection profilometry (CDFPP) has the advantage of fast speed, non-contact and full-field testing. It is one of the most important dynamic three-dimensional (3D) profile measurement techniques. However, due to factors such as color cross-talk and gamma distortion of electro-optical devices, phase errors arise when conventional phase-shifting algorithms with fixed phase shift values are utilized to retrieve phases. In this paper, a simple and effective blind phase error suppression approach based on isotropic n-dimensional fringe pattern normalization (INFPN) and carrier squeezing interferometry (CSI) is proposed. It does not require pre-calibration for the gamma and color-coupling coefficients or the phase shift values. Simulation and experimental works show that our proposed approach is able to effectively suppress phase errors and achieve accurate measurement results in CDFPP. 相似文献
100.
Quantitative detection and compensation of phase-shifting error in two-step phase-shifting digital holography 总被引:1,自引:0,他引:1
Phase-shifting digital holographic technique is a powerful tool for the measurement of various physical parameters, such as object deformation and liquid or cell’s refractive index change. However, for an accurate measurement, phase-shifting error in the reference wave path is still a major issue. In this paper, three novel and simple algorithms are proposed to quantitatively detect and correct phase-shifting error for a pure phase object in two-step phase-shifting digital holography. Influence of phase-shifting error is illustrated, and the effectiveness of the proposed algorithms is demonstrated by numerical simulation results. 相似文献