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1.
Ali Ebrahimi Mostafa Habibi‐Khorassani Asiyeh Shahraki 《Photochemistry and photobiology》2013,89(1):74-82
Radical cationic repair process of cis–syn thymine dimer has been investigated when (1) sugar‐phosphate backbones were substituted by hydrogen atoms, (2) phosphate group was substituted by two hydrogen atoms each on a sugar ring and (3) sugar‐phosphate backbone was taken into account. The effect of the interactions between N1 and N1′ lone pairs and the C6‐C6′ antibonding orbital are the most important evidences for the cleavage of the C6‐C6′ bond in the first step of radical cationic repair mechanism in the absence of the sugar‐phosphate backbone. The impact of the N1 and N1′ lone pairs on the C6‐C6′ bond cleavage decreases and the energy barrier of the cleavage of that bond significantly increases in the presence of the deoxynucleoside sugars and the sugar‐phosphate backbone. 相似文献
2.
We report here an efficient method for the synthesis and characterization of [H-NMP]HSO4 and its application as an efficient catalyst and solvent for preparation of azides from corresponding alcohols under mild conditions. This processor showed high chemoselectivity for conversion of various alcohols to their corresponding azides. 相似文献
3.
In this article we study the n‐existential closure property of the block intersection graphs of infinite t‐(v, k, λ) designs for which the block size k and the index λ are both finite. We show that such block intersection graphs are 2‐e.c. when 2?t?k ? 1. When λ = 1 and 2?t?k, then a necessary and sufficient condition on n for the block intersection graph to be n‐e.c. is that n?min{t, ?(k ? 1)/(t ? 1)? + 1}. If λ?2 then we show that the block intersection graph is not n‐e.c. for any n?min{t + 1, ?k/t? + 1}, and that for 3?n?min{t, ?k/t?} the block intersection graph is potentially but not necessarily n‐e.c. The cases t = 1 and t = k are also discussed. © 2011 Wiley Periodicals, Inc. J Combin Designs 19: 85–94, 2011 相似文献
4.
This study treats the axisymmetric interaction of a plane compressional sound wave with a viscoelastic (viscous) prolate spheroidal particle (droplet) suspended in a boundless viscous fluid medium. The method of eigen‐function expansion along with the novel features of Havriliak‐Negami model for viscoelastic material behavior and the linearized equations of Navier‐Stokes for wave motion in a viscous non‐heat‐conducting compressible fluid are employed to develop a closed form series solution involving Spheroidal harmonics of complex argument. The complications arising due to the non‐orthogonality of angular Spheroidal functions corresponding to different wave numbers as well as problems associated with the appearance of additional angular dependent terms in the boundary conditions are all avoided by expansion of the angular Spheroidal functions in terms of Lengedre functions which are themselves expanded in terms of transcendental functions and subsequent integration, leading to a linear set of independent equations in terms of unknown scattering and transmission coefficients. The presented solution demonstrates that the acoustic characteristics of particulate suspensions are strongly influenced by spheroidicity of particle cross‐section. Limiting case involving an elastic (ideal) spheroidal particle (droplet) in an ideal fluid is considered and fair agreement with available solution is established. 相似文献
5.
This study treats the two‐dimensional interaction of a plane compressional sound wave with a viscoelastic fiber of elliptic cross‐section submerged in a boundless viscous nonheat‐conducting compressible fluid medium. The classical method of eigen‐function expansion along with the novel features of Havriliak‐Negami model for viscoelastic material behavior and the pertinent boundary conditions are used to develop a closed form series solution involving Mathieu and modified Mathieu functions of complex argument. The complications that arise because of the nonorthogonality of angular Mathieu functions corresponding to different wave numbers, as well as problems associated with the appearance of additional angular dependent terms in the boundary conditions, are all avoided by expansion of the angular Mathieu functions in terms of transcendental functions and subsequent integration, leading to a linear set of independent equations in terms of the unknown scattering coefficients. The presented solution demonstrates that acoustic characteristics of fiber suspensions are strongly influenced by cross‐sectional ellipticity of the fibers in addition to the dynamic viscoelastic properties of the fiber material. It also shows that the common rigid circular fiber approximations used to model fiber suspensions can not capture the important resonance and damping effects associated with the highly viscoelastic noncircular fibers. The proposed model is valid for a wide range of cross‐sectional geometries (aspect ratios) and incident wave frequencies where most numerical methods fail. Limiting case involving an elastic elliptic cylinder in an ideal fluid is considered and fair agreement with a recent solution is established. 相似文献
6.
Structural Chemistry - Twenty-nine ellagitannin derivatives and ellagic acid (EA) metabolites have been chosen to calculate the aqueous and DMSO acidity constants (pKa) and proton affinities (PA)... 相似文献
7.
Seyyed Javad Sabounchei Mohsen Sayadi Mehdi Bayat Asiyeh Sedghi Robert W. Gable 《Journal of Coordination Chemistry》2017,70(22):3727-3748
The phosphonium salts [Ph2P(CH2)nPPh2CH2C(O)C6H4-m-OMe]Br (n = 1 (S1) and n = 2 (S2)) were synthesized in the reaction of bis(diphenylphosphino)methane (dppm) and bis(diphenylphosphino)ethane (dppe) with 2-bromo-3?-methoxy acetophenone, respectively. Further treatment with NEt3 gave the phosphorus ylides Ph2P(CH2)nPPh2C(H)C(O)C6H4-m-OMe (n = 1 (Y1) and n = 2 (Y2)). These ligands were treated with [MCl2(cod)] (M = Pd or Pt; cod = 1,5-cyclooctadiene) to give the P, C-chelated complexes, [MCl2(Ph2P(CH2)nPPh2C(H)C(O)C6H4-m-OMe)] (n = 1, M = Pd (3), Pt (4), and n = 2, M = Pd (5), Pt (6)). These compounds were characterized by elemental analysis, spectroscopic methods, UV–visible, and fluorescence emission spectra. Further, the structures of complexes 3 and 6 were characterized crystallographically. The palladium complexes 3 and 5 proved to be excellent catalysts for the Suzuki reactions of various aryl chlorides. Also, a theoretical study on the structure of complexes 3–6 has been investigated at the BP86/def2-SVP level of theory. The strength and nature of donor?acceptor bonds between the phosphorus ylides (L) and MCl2 fragment in the [LMCl2] (M = Pd, Pt, L = Y1, Y2) were studied by NBO and energy decomposition analysis (EDA), as well as their natural orbitals for chemical valence variation (EDA-NOCV). 相似文献
8.
Successful deposition of Pd nanoparticles is described using MOF‐199 as a support. Various characterization techniques including FTIR, XRD, SEM, BET‐BJH, TG‐DTA, and NH3‐TPD were used to verify the efficiency of catalysts. Pd/MOF‐199 is utilized as a catalyst for Suzukie Miyaura reactions with reasonable to excellent reaction yields under reflux conditions in H2O: ethanol solvent. 相似文献
9.
Shahnaz Rostamizadeh Asiyeh Amirahmadi Nasrin Shadjou Ali M. Amani 《Journal of heterocyclic chemistry》2012,49(1):111-115
One‐pot four‐component synthesis of 1,8‐dioxo‐9‐aryl decahydroacridines in solvent‐free condition was efficiently performed in the presence of MCM‐41‐SO3H as a nanocatalyst and nanoreactor in good yields. The method provides several advantages such as low cost, operational and experimental simplicity, high yields, and short reaction times. J. Heterocyclic Chem., (2012). 相似文献
10.
A graph G is n ‐existentially closed ( n ‐e.c.) if for each pair ( A, B ) of disjoint subsets of V(G) with | A | + | B |≤ n there exists a vertex in V ( G )\( A ∪ B ) which is adjacent to each vertex in A and to no vertex in B . In this paper we study the n ‐existential closure property of block intersection graphs of infinite designs with infinite block size. © 2011 Wiley Periodicals, Inc. J Combin Designs 19:317‐327, 2011 相似文献