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41.
Stereoselective synthesis of 2'-C-methyl-cyclopropyl-fused carbanucleosides was accomplished via stereoselective cyclopropanation, regioselective cleavage of the isopropylidene group, stereoselective Grignard reaction, and cyclic sulfate chemistry. [reaction: see text] 相似文献
42.
Hye-Lim Lee TacGhee Yi Kyung Mi Woo Hyun-Mo Ryoo Gwan-Shik Kim Jeong-Hwa Baek 《Experimental & molecular medicine》2010,42(6):437-445
TNF-α, a proinflammatory cytokine, inhibits osteoblast differentiation under diverse inflammatory conditions; however, the underlying mechanisms in terms of the TNF-α signaling pathway remain unclear. In this study, we examined the role of Msx2 in TNF-α-mediated inhibition of alkaline phosphatase (ALP) expression and the signaling pathways involved. TNF-α down-regulated ALP expression induced by bone morphogenetic protein 2 (BMP2) in C2C12 and Runx2-/- calvarial cells. Over-expression of Msx2 suppressed BMP2-induced ALP expression. Furthermore, TNF-α induced Msx2 expression, and the knockdown of Msx2 by small interfering RNAs rescued ALP expression, which was inhibited by TNF-α. TNF-α activated the NF-κB and the JNK pathways. Inhibition of NF-κB or JNK activation reduced the inhibitory effect of TNF-α on ALP expression, whereas TNF-α-induced Msx2 expression was only suppressed by the inhibition of the NF-κB pathway. Taken together, these results indicate that Msx2 mediates the inhibitory action of TNF-α on BMP2-regulated osteoblast differentiation and that the TNF-α-activated NF-κB pathway is responsible for Msx2 induction. 相似文献
43.
Cheon Seoung Ryoo 《Journal of Applied Mathematics and Computing》2000,7(1):175-181
The purpose of this paper is to measure, with explicit constants as small as possible, a priori error bounds for approximation by picewise polynomials. These constants play an important role in the numerical verification method of solutions for obstacle problems by using finite element methods. 相似文献
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45.
The current work demonstrates that the standard adsorption analysis has a limited applicability for characterization of chemically modified porous silicas. Since low-pressure nitrogen adsorption isotherms are sensitive to the surface changes caused by chemical modification of silicas, these isotherms were successfully used to evaluate their surface heterogeneity during different stages of modification. The surface analysis was accomplished by using adsorption energy distributions and high-resolution comparative plots. 相似文献
46.
Sungkyu Choi Jae Ryong Kweon 《Numerical Methods for Partial Differential Equations》2008,24(5):1253-1264
It is shown that the inf‐sup condition, called the Babuska–Brezzi condition, is valid for certain mesh‐dependent norms on a nonconvex polygonal domain. A bilinear form that is derived by inserting the corner singularity expansion into the Laplace equation is considered. A mesh‐dependent fractional norm related to the least order of the corner singularity at a concave vertex is considered. © 2007 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2008 相似文献
47.
Synthesis of thermally stable mesoporous cerium oxide with nanocrystalline frameworks using mesoporous silica templates 总被引:1,自引:0,他引:1
Highly ordered mesoporous cerium oxides, composed of nanocrystalline pore walls and exhibiting high thermal stability even at 973 K, were synthesized using mesoporous silica templates with hexagonal p6mm and cubic Ia3d symmetries. 相似文献
48.
49.
In rationalizing the odd chromatographic behavior for the separation of the enantiomers of N-(3,5-dinitrobenzoyl)-alpha-arylalkylamines on HPLC chiral stationary phases (CSPs) derived from alpha-(6,7-dimethyl-1-naphthyl)alkylamines, we initially suggested the occurrence of two competing, opposite sense chiral recognition processes termed the "dipole-stacking process" and the "hydrogen-bonding process". A simplified "single mechanism" model was later suggested with the importance of face to edge pi-pi interaction between aromatic rings come to recognized. The initial and subsequent chiral recognition models can be differentiated by noting the chromatographic trends for the enantioseparation of a homologous series of N-(3,5-dinitrobenzoyl)-alpha-(p-alkylphenyl)ethylamines on the aforementioned CSPs. Data so obtained were consistent with the second "single mechanism" model but not with the first "two competing mechanism" model. From these results, it has been concluded that the "single mechanism" model is more plausible than the "two competing mechanism" model. 相似文献
50.
The photodissociation dynamics of vinyl bromide and perfluorovinyl bromide have been investigated at 234 nm using a photofragment ion imaging technique coupled with a state-selective [2+1] resonance-enhanced multiphoton ionization scheme. The nascent Br atoms stem from the primary C-Br bond dissociation leading to the formation of C2H3(X) and Br(2Pj;j=1/2,3/2). The obtained translational energy distributions have been well fitted by a single Boltzmann and three Gaussian functions. Boltzmann component has not been observed in the perfluorovinyl bromide. The repulsive 3A'(n,sigma *) state has been considered as the origin of the highest Gaussian components. Middle translational energy components with Gaussian shapes are produced from the 1A"(pi,sigma*) and/or 3A"(pi,sigma*) which are very close in energy. Low-energy Gaussian components are produced via predissociation from the 3A'(pi,pi*) state. The assignments have also been supported by the recoil anisotropy corresponding to the individual components. It is suggested that intersystem crossing from the triplet states to the ground state has been attributed to the Boltzmann component and the fluorination reduces the probability of this electronic relaxation process. 相似文献