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排序方式: 共有469条查询结果,搜索用时 343 毫秒
461.
Wang J Chen YP Yao K Wilbon PA Zhang W Ren L Zhou J Nagarkatti M Wang C Chu F He X Decho AW Tang C 《Chemical communications (Cambridge, England)》2012,48(6):916-918
We report novel robust resin acid-derived antimicrobial agents that exhibit excellent antimicrobial activities against a broad spectrum of bacteria (6 Gram-positive and 7 Gram-negative) with selective lysis of microbial membranes over mammalian membranes. Our results indicate that hydrophobicity and unique structures of resin acids can be determining factors in dictating the antimicrobial activity. 相似文献
462.
The few picosecond time scale H-bond making and breaking in the system acetonitrile-methanol dominates the mechanism of vibrational coherence transfer that is evident in the shapes of both the linear and nonlinear IR spectra of the CN group. 相似文献
463.
By means of heterodyned two-dimensional IR photon echo experiments on liquid formamide and isotopomers the vibrational frequency dynamics of the N-H stretch mode, the C-D mode, and the C=O mode were obtained. In each case the vibrational frequency correlation function is fitted to three exponentials representing ultrafast (few femtoseconds), intermediate (hundreds of femtoseconds), and slow (many picoseconds) correlation times. In the case of N-H there is a significant underdamped contribution to the correlation decay that was not seen in previous experiments and is attributed to hydrogen-bond librational modes. This underdamped motion is not seen in the C-D or C=O correlation functions. The motions probed by the C-D bond are generally faster than those seen by N-H and C=O, indicating that the environment of C-D interchanges more rapidly, consistent with a weaker C-D...O=C bond. The correlation decays of N-H and C=O are similar, consistent with both being involved in strong H bonding. 相似文献
464.
Lee Richard C. H.; Wong C. W.; Xu Cheng-Zhong; Yim L. H.; Yung S. P. 《IMA Journal of Mathematical Control and Information》2006,23(1):97-111
** Email: spyung{at}hku.hk In this paper, we show that a delay control system can be robustlystabilized by certain closed-loop feedback if a Lyapunov-typecondition is fulfilled. 相似文献
465.
Dong-Oh Moon Mun-Ock Kim Chang-Hee Kang Jae-Dong Lee Yung Hyun Choi Gi-Young Kim 《Experimental & molecular medicine》2009,41(9):665-677
The JNK inhibitor SP600125 strongly inhibits cell proliferation in many human cancer cells by blocking cell-cycle progression and inducing apoptosis. Despite extensive study, the mechanism by which SP600125 inhibits mitosis-related effects in human leukemia cells remains unclear. We investigated the effects of SP600125 on the inhibition of cell proliferation and the cell cycle, and on microtubule dynamics in vivo and in vitro. Treatment of synchronized leukemia cells with varying concentrations of SP600125 results in significant G2/M cell cycle arrest with elevated p21 levels, phosphorylation of histone H3 within 24 h, and endoreduplication with elevated Cdk2 protein levels after 48 h. SP600125 also induces significant abnormal microtubule dynamics in vivo. High concentrations of SP600125 (200 µM) were required to disorganize microtubule polymerization in vitro. Additionally, SP600125-induced delayed apoptosis and cell death was accompanied by significant poly ADP-ribose polymerase (PARP) cleavage and caspase-3 activity in the late phase (at 72 h). Endoreduplication showed a greater increase in ectopic Bcl-2-expressing U937 cells at 72 h than in wild-type U937 cells without delayed apoptosis. These results indicate that Bcl-2 suppresses apoptosis and SP600125-induced G2/M arrest and endoreduplication. Therefore, we suggest that SP600125 induces mitotic arrest by inducing abnormal spindle microtubule dynamics. 相似文献
466.
Yun‐Gon Kim David J. Harvey Yung‐Hun Yang Chung‐Gyu Park Byung‐Gee Kim 《Journal of mass spectrometry : JMS》2009,44(10):1489-1499
Glycosphingolipid (GSL) is a major component of the plasma membrane in eukaryotic cells that is involved directly in a variety of immunological events via cell‐to‐cell or cell‐to‐protein interactions. In this study, qualitative and quantitative analyses of GSL‐derived glycans on endothelial cells and islets from a miniature pig were performed and their glycosylation patterns were compared. A total of 60 and 47 sialylated and neutral GSL‐derived glycans from the endothelial cells and islets, respectively, were characterized by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS) and collision‐induced fragmentation using positive‐ion electrospray ionization (ESI) ion‐trap tandem mass spectrometry (MS/MS). In accordance with previous immunohistochemistry studies, the α‐Gal‐terminated GSL was not detected but NeuGc‐terminated GSLs were newly detected from miniature pig islets. In addition, the neutral GSL‐derived glycans were relatively quantified by derivatization with carboxymethyl trimethylammonium hydrazide (so called Girard's T reagent) and MALDI‐TOF MS. The structural information of the GSL‐derived glycans from pig endothelial cells and islets suggests that special attention should be paid to all types of glycoconjugates expressed on pig tissues or cells for successful clinical xenotransplantation. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
467.
Up and down: Differential sensing of serine and tyrosine is achieved with aligned CdS nanowire arrays by exploring the pH‐dependent PL behavior of the nanowire arrays toward exposure to the two amino acid solutions (see picture).
468.
Xu Gen-Qi; Feng De-Xing; Yung Siu Pang 《IMA Journal of Mathematical Control and Information》2004,21(1):65-83
The Riesz basis property of the generalized eigenvector system
of a Timoshenko beam with boundary feedback controls appliedto two ends is studied in this paper. The spectral property
of the operator A determined by the closed loop system is investigated.It is shown that operator A has compact resolvent and generatesa C<sub>0</sub> semigroup, and its spectrum consistsof two branches and has two asymptotes under some conditions.Furthermore it is proved that the sequence of all generalizedeigenvectors of the system principal operator forms a Rieszbasis for the state Hilbert space. 相似文献
469.
Teng-I Yang Terumitsu Azuma Yu-Wen Huang Yuen Yung Hui Cheng-Tien Chiang Huan-Cheng Chang 《中国化学会会志》2023,70(3):451-459
The neutral nitrogen-vacancy (NV0) defects in diamond are photostable color centers, suitable for a wide range of applications in science and engineering. However, the photophysical properties of the centers have not yet been fully characterized. This work measured the stimulated emission cross sections of NV0 in a single-crystal diamond by two-photon excitation of its matrix at 344 nm. From the measured photoluminescence spectrum and the fluorescence lifetime of 20 ± 1 ns, we determined a peak stimulated emission cross section of 1.43 ± 0.07 × 10−17 cm2 at 650 nm for the NV0 centers. In addition, we have also examined the thermal shifts of the zero-phonon line of NV0 centers in nanoscale diamonds (~100 nm in diameter) over the temperature range of 30–120°C. A temperature measurement sensitivity of 0.2 K·Hz−1/2 was achieved, which is about two-fold better than that of NV−, despite that the fluorescence intensity of NV0 is about six-fold lower than that of NV− in the same nanoparticles. The result is attributed to the smaller electron–phonon coupling strength of the neutral center, compared with its negatively charged counterpart. 相似文献