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21.
Krishnan RS Mackay ME Hawker CJ Van Horn B 《Langmuir : the ACS journal of surfaces and colloids》2005,21(13):5770-5776
The control of dewetting for thin polymer films is a technical challenge and of significant academic interest. We have used polystyrene nanoparticles to inhibit dewetting of high molecular weight, linear polystyrene, demonstrating that molecular architecture has a unique effect on surface properties. Neutron reflectivity measurements were used to demonstrate that the nanoparticles were uniformly distributed in the thin (ca. 40 nm) film prior to high temperature annealing, yet after annealing, they were found to separate to the solid substrate, a silanized silicon wafer. Dewetting was eliminated when the nanoparticles separated to form a monolayer or above while below this surface coverage the dewetting dynamics was severely retarded. Blending linear polystyrene of similar molecular weight to the polystyrene nanoparticle with the high molecular weight polystyrene did not eliminate dewetting. 相似文献
22.
[reaction: see text] The solid-phase synthesis of N-alkyl-beta-keto)amides and 1,2,4,5-tetrasubstituted imidazoles was demonstrated using a traceless cleavage strategy based on benzylic acylammonium chloride reactivity. The approach enables the assembly of diverse compounds in a minimal number of steps in moderate to excellent yield (23-88%) and high purity (64-100%). 相似文献
23.
Here we report the synthesis of a novel PNA based neocuproine.Zn RNA cleaving agent; we demonstrate that such agents sequence specifically cleave a synthetic RNA target and in particular the RNA component of human telomerase. 相似文献
24.
A proton nmr follow-up provided conclusive evidence for the involvement of two sequential Claisen rearrangements in the thermal rearrangement of 1,4-diaryloxy-2-butynes to 11a-methylpterocarpans . A detailed study of the rearrangement of 1,4-diaryloxy-2-butynes in polyethyleneglycol-200 (PEG-200), indicated a definite possibility of selective synthesis of either benzofuron (3,2-b )benzofuran or benzofuro(2,3-b)benzofuran by varying the temperature of the reaction alone 相似文献
25.
Quantitative correlations between kinetic parameters (energy of activation, E), procedural factors (sample mass, m, and heating rate, φ) and the dependent variables (the temperature of inception of reaction, Ti, and temperature Tα at which a constant fraction α has decomposed) have been derived for differential thermal analysis (DTA) and differential scanning calorimetry (DSC). The relations have the same form as those derived from earlier TG studies. The dependent variables Ti and Tα are related to m, φ and E by the equations where C3 and C2 are constants, and where C4 and C5 are constants for a given α. The variation of C5 with α is given by C5 = a + b α where a and b are constants. The equations are applicable to TG, DTA and DSC. 相似文献
26.
The calculation of rovibrational transition energies and intensities is often hampered by the fact that vibrational states are strongly coupled by Coriolis terms. Because it invalidates the use of perturbation theory for the purpose of decoupling these states, the coupling makes it difficult to analyze spectra and to extract information from them. One either ignores the problem and hopes that the effect of the coupling is minimal or one is forced to diagonalize effective rovibrational matrices (rather than diagonalizing effective rotational matrices). In this paper we apply a procedure, based on a quantum mechanical canonical transformation for deriving decoupled effective rotational Hamiltonians. In previous papers we have used this technique to compute energy levels. In this paper we show that it can also be applied to determine intensities. The ideas are applied to the ethylene molecule. 相似文献
27.
A computer code and nonnumerical algorithm are developed to construct the edge group of a graph and to enumerate the edge colorings of graphs of chemical interest. The edge colorings of graphs have many applications in nuclear magnetic resonance (NMR), multiple quantum NMR, enumeration of structural isomers of unsaturated organic compounds, and in the construction of configurational integral expansion series in statistical mechanics. The code developed is applied to many NMR graphs, complete graphs containing up to 10 vertices, and the Petersen graph. 相似文献
28.
Raghavan Krishnan S. A. Lang Marshall M. Siegel 《Journal of heterocyclic chemistry》1986,23(6):1801-1804
The synthesis of 3-amino-7-chloro-1-ethyl-6-fluoro-4(1H)quinolinone derivatives is described. These were investigated for their antibacterial activity. 相似文献
29.
The stability constants of HgCl(-)(3) and HgCl(2-)(4) in 60% aqueous ethanol (v/v) were determined by spectroscopy at 25 degrees and constant ionic strength and acidity; beta(1) was 3 +/- 1 and beta(2) 9 +/-3. 相似文献
30.
De Jonghe S Lamote I Venkataraman K Boldin SA Hillaert U Rozenski J Hendrix C Busson R De Keukeleire D Van Calenbergh S Futerman AH Herdewijn P 《The Journal of organic chemistry》2002,67(3):988-996
The synthesis of a new series of D-erythro-homoceramide analogues is described. Several synthetic approaches were investigated. Homoceramides can be successfully synthesized from L-homoserine as chiral building block and a protected Weinreb-amide as a key intermediate. The synthesis of short-chain analogues with a heptyl side chain, as well as with a phenyl residue in the sphingoid part (instead of the naturally occurring tridecyl side chain), was effected. The homoceramides 15-17 and 24 were investigated for their potential to reverse the inhibitory effect of fumonisin B(1) on axonal growth. Unfortunately, none of the tested compounds showed any biological activity due to their lack of metabolism to glucosylhomoceramide. 相似文献