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71.
M. Sampoorna K.N. Nagendra H. Frisch 《Journal of Quantitative Spectroscopy & Radiative Transfer》2008,109(14):2349-2363
The polarized approximate lambda iteration (PALI) technique developed for the weak field Hanle effect relies on the decomposition of the Stokes parameters I, Q and U into six cylindrically symmetrical components. It has been applied to complete and partial frequency redistribution with redistribution matrices in which frequency redistribution is decoupled from scattering polarization. For partial frequency redistribution, the decoupling is obtained by an adequate decomposition of the frequency space into several domains. By angle-averaging frequency-dependent terms in the exact weak field Hanle redistribution matrix for a normal Zeeman triplet, we construct a redistribution matrix with coupling between frequency redistribution and polarization and no domain decomposition. The coupling is contained in generalized frequency redistribution functions that depend on the magnetic field. The redistribution matrix is expanded in the Landi Degl’Innocenti spherical tensors for polarimetry and the Stokes parameters are decomposed into cylindrically symmetrical components. A PALI method is set up for the calculation of these components. The Stokes parameters are calculated for different simple atmospheric models. The positive Q direction corresponds to the linear polarization perpendicular to the solar limb. It is shown that the frequency space decomposition may induce large errors on Stokes U in the transition region between line core and line wings but can safely be used for Stokes I and Q, the errors staying less than 1% at all the frequencies. 相似文献
72.
Chandrasekhar S Reddy MS Babu BN Jagadeesh B Prabhakar A Jagannadh B 《Journal of the American Chemical Society》2005,127(27):9664-9665
Tendencies of forming stable helices of heterooligomers composed of alternating rigid cis-beta-sugar amino acid and flexible beta-hGly motifs have been investigated, using a combination of molecular mechanics, CD, FT-IR, and NMR techniques. The results show that the solution structures of these oligomers exist as robust right-handed 14-helices. Here, we examine the role of conformationally rigid cis-beta-sugar amino acid in preorganizing the conformation of beta-hGly to form the 14-helix. Our findings also show that a right-handed 14-helix can be formed with as few as four properly sequenced heterogeneous residues. These results represent the expansion of the conformational pool of sugar amino acid in the design of well-folded 14-helices, which can be used to develop beta-peptides endowed with biological activity. 相似文献
73.
Nagendra K. Kaushik Yong Hee Kim Yong Gyu Han Eun Ha Choi 《Current Applied Physics》2013,13(1):176-180
Nonthermal plasma (an ionized gas) is emerging as a novel tool for the treatment of living tissues for biological and medical purposes. In this study we describe the effects of a nonthermal air jet plasma on the T98G brain cancer cell line. The results of this study reveal that the jet plasma inhibits brain cancer cell growth efficiently with the loss of clongenicity in the cells. The main goal of this study is to induce cell death in T98G cancer cells by the toxic effect of jet plasma. 相似文献
74.
Stereoselective synthesis of the C38–C54 segment of a marine metabolite halichondrin B comprising KLM and N rings with a C44 spiroketal including 10 chiral centers is described. The salient features of the synthesis are Carreira’s addition, Sharpless asymmetric dihydroxylation and double alkylation of TosMIC strategy and double vinyl coupling reactions. 相似文献
75.
Nucleic (DNA) acids having contiguous stretch of G sequence form quadruplex structure, which is very critical to control cell division. Recently the existence of G-quadruplex in RNA is also reported in presence of monovalent metal ion. PNA is a promising DNA analogue which binds strongly to DNA to form PNA:DNA duplex or PNA(2):DNA triplex. PNA also forms quadruplexes such G-quadruplex and i-motif in G and C-rich sequences respectively. aep-PNA containing a prolyl ring is one of several PNA analogues that provide rigidity and chirality in backbone and has binding affinity to natural DNA which is higher than that of PNA. Here we examine the ability of aep-PNA-G to form a quadruplex by UV, CD and mass spectroscopic techniques. 相似文献
76.
Enantiopure Nβ-Fmoc-amino alkyl isonitriles and amino acid esters have been employed as building blocks in Ugi four-component reaction (U-4CR) to yield 1,1′-iminodicarboxylated peptidomimetics. By employing trifluoroacetic acid as one of the components, a different outcome has been observed and rationalized. Ugi products are obtained as trifluoroacetamide adducts, which on further reaction under mild acidic conditions lead to the title compounds. The method has also been proven to be useful for the preparation of ethyl, benzyl and tert-butyl esters. 相似文献
77.
78.
Gowravaram Sabitha Chintam Nagendra ReddyAtla Raju Jhillu Singh Yadav 《Tetrahedron: Asymmetry》2011,22(4):493-498
A highly stereoselective synthesis of the naturally occurring lactone (−)-spicigerolide has been achieved utilizing OsO4-catalyzed dihydroxylation, CBS, Lindlar’s reductions, Still-Gennari, and Grignard reactions as the key reaction steps. 相似文献
79.
80.
Biswanath Das Cheruku Ravindra ReddySiddavatam Nagendra Maram Lingaiah 《Tetrahedron letters》2011,52(27):3496-3498
Cyclic sulfamidates (prepared from α-amino acids and β-amino alcohols) have been used for the first time for the synthesis of novel β-amino phosphonates (chiral and achiral) by treatment with dialkyl phosphites using sodium hydride. 2-Substituted and 1,2-disubtituted β-amino phosphonates have efficiently been prepared following this method. The products are formed in high yield (79-84%) within 8-12 h. 相似文献