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951.
B Koh G Kim HK Yoon JB Park R Kopelman W Cheng 《Langmuir : the ACS journal of surfaces and colloids》2012,28(32):11676-11686
DNA short oligo, surfactant, peptides, and polymer-assisted dispersion of single-walled carbon nanotube (SWCNTs) in aqueous solution have been intensively studied. It has been suggested that van der Waals interaction, π-π stacking, and hydrophobic interaction are major factors that account for the SWCNTs dispersion. Fluorophore and dye molecules such as Rhodamine B and fluorescein have both hydrophilic and hydrophobic moieties. These molecules also contain π-conjugated systems that can potentially interact with SWCNTs to induce its dispersion. Through a systematic study, here we show that SWCNTs can be dispersed in aqueous solution in the presence of various fluorophore or dye molecules. However, the ability of a fluorophore or dye molecule to disperse SWCNTs is not correlated with the stability of the fluorophore/dye-SWCNT complex, suggesting that the on-rate of fluorophore/dye binding to SWCNTs may dominate the efficiency of this process. We also examined the uptake of fluorophore molecules by mammalian cells when these molecules formed complexes with SWCNTs. The results can have potential applications in the delivery of poor cell-penetrating fluorophore molecules. 相似文献
952.
We give formulae for the first homology of the n-braid group and the pure 2-braid group over a finite graph in terms of graph-theoretic invariants. As immediate consequences, a graph is planar if and only if the first homology of the n-braid group over the graph is torsion-free and the conjectures about the first homology of the pure 2-braid groups over graphs in Farber and Hanbury (arXiv:1005.2300 [math.AT]) can be verified. We discover more characteristics of graph braid groups: the n-braid group over a planar graph and the pure 2-braid group over any graph have a presentation whose relators are words of commutators, and the 2-braid group and the pure 2-braid group over a planar graph have a presentation whose relators are commutators. The latter was a conjecture in Farley and Sabalka (J. Pure Appl. Algebra, 2012) and so we propose a similar conjecture for higher braid indices. 相似文献
953.
Sang Soo Yu Ki Hak Kim Young Eon Ihm Dojin Kim Hyojin Kim Soon Ku Hong Chang Soo Kim Hyun Ryu Sangjun Oh 《Journal of magnetism and magnetic materials》2006
Si1−xMnx (x?0.22) thin films were grown by using a thermal evaporator, and their magnetic and electrical properties were investigated. The Si1−xMnx semiconductors are amorphous when Mn concentration is 9.0 at% and less. The electrical resistivities of amorphous Si1−xMnx (x?0.09) semiconductor thin films are in the range of 9.86–6.59×10−4 Ω cm at room temperature and decrease with increasing Mn concentration. The amorphous Si1−xMnx (x?0.09) semiconductor thin films are p-type and hole densities are 3.73×1018–1.33×1022 cm−3 at room temperature. Low temperature magnetization characteristics reveal that amorphous Si1−xMnx (x?0.09) semiconductor thin films are paramagnetic. 相似文献
954.
Permethrin is the most popular synthetic pyrethroid insecticide used in agriculture and public health. For the assessment
of human exposure to permethrin, a competitive indirect enzyme-linked immunosorbent assay (ELISA) for the detection of the
glycine conjugate of a major metabolite, cis-/trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane-1-carboxylic acid (DCCA), of permethrin was developed based on a polyclonal
antibody. An assay based on an antibody with a high sensitivity was optimized and characterized. The IC50 value and the detection range for trans-DCCA–glycine, in the assay buffer were 1.2 and 0.2−7.0 μg/L, respectively. The antibody recognized trans-DCCA–glycine and the mixture of cis-/trans-DCCA–glycine with an isomer range from 30:70 to 50:50 nearly equally. Little or no cross-reactivity to permethrin and its
other free metabolites or glycine conjugates was measured. The integration of the ELISA and solid-phase extraction which was
used to reduce the matrix effect from human urine samples provided for analysis of total cis-/trans-DCCA–glycine at low parts per billion levels in the samples. The limit of quantitation of the target analyte was 1.0 μg/L
in urine with a limit of detection of 0.1 μg/L in buffer. This assay might be a useful tool for monitoring human exposure
to permethrin. 相似文献
955.
956.
Seung Hyun Kim Dae Hyun Kim Jin-Ho Park Eun Jung Choi Sunghyouk Park Ki Yong Lee Min-Ji Jeon Young Choong Kim Sang Hyun Sung 《Microchemical Journal》2010,94(2):118-124
Discrimination of Scrophularia spp. according to the geographic origin was tried in the present study using HPLC-DAD combined with multivariate analysis techniques. Five active constituents, angoroside C, harpagoside, 8-O-(E-p-methoxycinnamoyl)harpagide, E-cinnamic acid and E-p-methoxycinnamic acid, in forty four Scrophularia samples were simultaneously determined using HPLC-DAD. A principal component analysis of the content measurements clustered the samples according to their geographic origins, Andong, Uisung and China. A partial least squares-discrimination analysis was subsequently developed for the effective classification of the samples. This model showed comparatively good prediction ability for samples from Andong or China. The proposed method shows an efficient strategy for quality control of Scrophularia spp. 相似文献
957.
The oxygen permeation of Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) membranes was measured between 750 and 900 °C as a function of membrane thickness with or without La0.7Sr0.3CoO3 (LSC) coating layer under controlled PO2-gradient (Air/He). In order to see the relative effects of bulk diffusion and surface-exchange kinetics, the thickness of membrane was varied from 0.5 to 2.0 mm. The oxygen-permeation flux at 900 °C increased with LSC coating from that of uncoated membrane. For example, it increased ∼1.8 times for 1 mm-thick BSCF membrane. The characteristic membrane thickness (LC) which divides the bulk-diffusion limit and surface-exchange kinetics limit was estimated using the modified Wagner equation. The LC values were 0.55 and 1.10 mm at 900 °C for the coated and uncoated BSCF membranes, respectively, and decreased with decreasing temperature. 相似文献
958.
Duane E. Weisshaar Gary W. Earl Eric M. Villa Jessica L. Zierke Christopher J. Fry Kara L. Becvar Shik Ki Li Matthew C. Schafer 《国际化学动力学杂志》2010,42(4):221-225
Quaternary ammonium compounds are produced worldwide in hundreds of millions of pound volume annually for a plethora of end‐uses from fabric‐care formulations to asphalt emulsifiers, typically from nongreen alkylating reagents. The kinetics of a reaction employing dimethyl carbonate (DMC) as a green alkylating agent was investigated using three trialkylamines (tributylamine, trihexylamine, and trioctylamine) at several temperatures. Arrhenius and Eyring analysis of the data showed that values of Ea (79 kJ/mol), ΔH? (75 kJ/mol), and ΔS? (220 J/(mol K)) were the same for all three amine reactants, consistent with a report that Ea is independent of alkyl chain length when the chain length is greater than three carbons. Although rates are significantly slower with DMC than with other alkylating reagents, the resulting methyl carbonate anion has advantages for clean anion metathesis, which is important for some applications, especially those involving ionic liquids. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 221–225, 2010 相似文献
959.
960.
In this paper, we study a predator–prey system with an Ivlev-type functional response and impulsive control strategies containing a biological control (periodic impulsive immigration of the predator) and a chemical control (periodic pesticide spraying) with the same period, but not simultaneously. We find conditions for the local stability of the prey-free periodic solution by applying the Floquet theory of an impulsive differential equation and small amplitude perturbation techniques to the system. In addition, it is shown that the system is permanent under some conditions by using comparison results of impulsive differential inequalities. Moreover, we add a forcing term into the prey population’s intrinsic growth rate and find the conditions for the stability and for the permanence of this system. 相似文献