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991.
Structural determination of two new sesquiterpenes biotransformed from germacrone by Mucor alternata
Jia N Xiao Chi M Xiu Lan X Hong Wei J Dean G 《Magnetic resonance in chemistry : MRC》2008,46(2):178-181
Eight transformed sesquiterpenes of germacrone by Mucor alternata were obtained. Their structures were characterized on the basis of spectral methods including 2D NMR. Among them, (1S, 4S, 5S, 10R)-isozedoarondiol (2) and (1R, 4S, 5S, 10R)-diepoxy-12-hydroxygermacrone (3) are new compounds. 相似文献
992.
In the present work, through the path integral of Gaussian type correlation function, a new formalism based on Fermi-Golden Rule for calculating the rate constant of nonradiative decay process with Duschinsky rotation effect in polyatomic molecules is developed. The advantage of the present path-integral formalism is promoting-mode free. In order to get the rate constant, a "transition rate matrix" needs to be calculated. The rate constant calculated previously is only an approximation of diagonal elements of our "transition rate matrix " . The total rate should be the summation over all the matrix elements. 相似文献
993.
Rong J Lee LA Li K Harp B Mello CM Niu Z Wang Q 《Chemical communications (Cambridge, England)》2008,(41):5185-5187
Fibrillar M13 bacteriophages were used as basic building blocks to generate thin films with aligned nanogrooves, which, upon chemical grafting with RGD peptides, guide cell alignment and orient the cell outgrowth along defined directions. 相似文献
994.
Xiaoqing Liu Wenxin Niu Haijuan Li Shuang Han Lianzhe Hu Guobao Xu 《Electrochemistry communications》2008,10(9):1250-1253
An electrochemiluminescent glucose biosensor was proposed based on gold nanoparticle-catalyzed luminol electrochemiluminescence (ECL). Gold nanoparticles were self-assembled onto silica sol–gel network, and then glucose oxidase was adsorbed on the surface of gold nanoparticles. The surface assembly process and the electrochemistry and ECL behaviors of the biosensor were investigated. The assembled gold nanoparticles could efficiently electrocatalyze luminol ECL. ECL intensity of the biosensor depended on scan rate, luminol concentration, and size of gold nanoparticles. The response of the ECL biosensor was linear over the range 1 μM to 5 mM with a detection limit of 0.2 μM glucose and showed satisfying reproducibility, stability and selectivity. 相似文献
995.
In this paper, we consider the semilinear elliptic problem in Ω, u=0 on ∂Ω, where Ω is a smooth bounded domain in RN, N?4, , is the critical Sobolev exponent, K(x) is a continuous function. When Ω and K(x) are invariant under a group of orthogonal transformations, we prove the existence of nodal and positive solutions for 0<λ<λ1, where λ1 is the first Dirichlet eigenvalue of on Ω. 相似文献
996.
997.
Equilibrium ground state geometry configurations and their relevant electronic properties of four experimentally reported
asymmetric spirosilabifluorene derivatives are calculated by the HF(DFT)/6-31G(d) method. Their excited state geometries are
investigated using the CIS/6-31G(d) method. The absorption and emission spectra are evaluated using the TD-B3LYP/6-31G(d)
and TD-PBE0/6-31+G(d) levels both in gas phase and CHCl3 solvent. Our results show an excellent agreement with the experimental data on their optical properties. To predict the substitution
effect, the H/R (R = –NO2, –CN, –NH2 and –OCH3) substituted symmetric and asymmetric spirosilabifluorene derivatives are also investigated, and the optical properties of
H/R substituted derivatives are predicted in gas phase and CHCl3 solvent. In comparison with the parent compound, significant red-shift is predicted for the emission spectra of the di-substituted
symmetric derivatives with –NH2 (96 nm), –OCH3 (61 nm) and the push–pull (containing both –NH2 and –NO2) derivative (56 nm). It is found that the performance and the optical properties of these derivatives can be improved by
adding push–pull substitutents. The largest change in the electronic and optical properties of this system can be obtained
upon symmetric di-substitution among mono-, di-, tri- and tetra-substitutions.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
998.
A novel method is presented for controllably merging aqueous microdroplets within segmented flow microfluidic devices. Our approach involves exploiting the difference in hydrodynamic resistance of the continuous phase and the surface tension of the discrete phase through the use of passive structures contained within a microfluidic channel. Rows of pillars separated by distances smaller than the representative droplet dimension are installed within the fluidic network and define passive merging elements or chambers. Initial experiments demonstrate that such a merging element can controllably adjust the distance between adjacent droplets. In a typical scenario, a droplet will enter the chamber, slow down and stop. It will wait and then merge with the succeeding droplets until the surface tension is overwhelmed by the hydraulic pressure. We show that such a merging process is independent of the inter-droplet separation but rather dependent on the droplet size. Moreover, the number of droplets that can be merged at any time is also dependent on the mass flow rate and volume ratio between the droplets and the merging chamber. Finally, we note that the merging of droplet interfaces occurs within both compressing and the decompressing regimes. 相似文献
999.
Niu HT Su D Jiang X Yang W Yin Z He J Cheng JP 《Organic & biomolecular chemistry》2008,6(17):3038-3040
The nucleophilic nature of cyanide is used to create a simple, sensitive, and highly effective sensor, 2-(trifluoroacetylamino)anthraquinone (2-TFAQ), for the easy "naked-eye" detection of very low concentrations of cyanide in an aqueous environment. 相似文献
1000.
Niu HY Cai YQ Shi YL Wei FS Liu JM Jiang GB 《Analytical and bioanalytical chemistry》2008,392(5):927-935
A new kind of solid-phase extraction disk based on a sheet of single-walled carbon nanotubes (SWCNTs) is developed in this
study. The properties of such disks are tested, and different disks showed satisfactory reproducibility. One liter of aqueous
solution can pass through the disk within 10–100 min while still allowing good recoveries. Two disks (DD-disk) can be stacked
to enrich phthalate esters, bisphenol A (BPA), 4-n-nonylphenol (4-NP), 4-tert-octylphenol (4-OP) and chlorophenols from various volumes of solution. The results show that SWCNT
disks have high extraction ability for all analytes. The SWCNT disk can extract polar chlorophenols more efficiently than
a C18 disk from water solution. Unlike the activated carbon disk, analytes adsorbed by the new disks can be eluted completely with
8–15 mL of methanol or acetonitrile. Finally, the DD-disk system is used to pretreat 1000-mL real-world water samples spiked
with BPA, 4-OP and 4-NP. Detection limits of 7, 25, and 38 ng L−1 for BPA, 4-OP, and 4-NP, respectively, were achieved under optimized conditions. The advantages of this new disk include
its strong adsorption ability, its high flow rate and its easy preparation.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献