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41.
Trevor R. Griffiths S. V. J. Lakshman A. Varada Rajulu 《Journal of chemical crystallography》1984,14(6):559-564
The optical absorption spectrum of the octahedral moiety CoCl4(H2O)2 in single crystal [(CH3)3NH]CoCl3·2H2O has been studied at room and liquidair temperatures. The observed ambient bands at 6800, 16,300, and 19,000 cm–1 have been assigned, respectively, to the transitions4
T
1(F) 4
T
2(F),4
A
2(F), and4
T
1 (P). The crystal field parameters evaluated areD
q
=B=850 cm–1, andC=4.63B. At liquid-air temperatures the4
T
1(P) band is seen to split into the expected four components
7,
8,
8, and
6, due to spin-orbit coupling, and the coupling coefficient was computed to be 525 cm–1. 相似文献
42.
43.
ESR spectra of Cu2+ in LiKSO4 have been studied at different temperatures. The measured g-values suggest a rhombic field for Cu2+ ion in the lattice. Optical absorption spectra of the crystal have been studied at room and liquid nitrogen temperatures. From the nature and position of the observed bands, they have been attributed to Cu2+ ions in D2h symmetry. The orbital reduction parameters obtained indicate a substantial degree of covalency in the bonding of the copper ion. 相似文献
44.
Direct arylation of the exocyclic amino groups of nucleosides represents a simple approach to N-aryl nucleoside derivatives. To date, one limitation has been that only electron-deficient aryl bromides and triflates possessed adequate reactivity for efficient, direct N-arylation of nucleosides. We demonstrate herein that Pd-Xantphos catalytic systems lead to successful N-arylation of suitably protected 2'-deoxyadenosine and 2'-deoxyguanosine with a wide range of aryl bromides. 相似文献
45.
B. S. Dandapat Bidyut Santra S. K. Singh 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2010,46(2):685-695
A thin viscous liquid film flow is developed over a stretching sheet under different non-linear stretching velocities in presence
of uniform transverse magnetic field. Evolution equation for the film thickness is derived using long-wave approximation of
thin liquid film and is solved numerically by using the Newton–Kantorovich method. It is observed that all types of stretching
produces film thinning, but non-monotonic stretching produces faster thinning at small distance from the origin. Effect of
the transverse magnetic field is to slow down the film thinning process. Observed flow behavior is explained physically. 相似文献
46.
Young L Arms DA Dufresne EM Dunford RW Ederer DL Höhr C Kanter EP Krässig B Landahl EC Peterson ER Rudati J Santra R Southworth SH 《Physical review letters》2006,97(8):083601
We have developed a synchrotron-based, time-resolved x-ray microprobe to investigate optical strong-field processes at intermediate intensities (10(14) - 10(15) W/cm2). This quantum-state specific probe has enabled the direct observation of orbital alignment in the residual ion produced by strong-field ionization of krypton atoms via resonant, polarized x-ray absorption. We found strong alignment to persist for a period long compared to the spin-orbit coupling time scale (6.2 fs). The observed degree of alignment can be explained by models that incorporate spin-orbit coupling. The methodology is applicable to a wide range of problems. 相似文献
47.
A Diazido Mannose Analogue as a Chemoenzymatic Synthon for Synthesizing Di‐N‐acetyllegionaminic Acid‐Containing Glycosides 下载免费PDF全文
Dr. Abhishek Santra An Xiao Dr. Hai Yu Wanqing Li Dr. Yanhong Li Linh Ngo Dr. John B. McArthur Prof. Dr. Xi Chen 《Angewandte Chemie (International ed. in English)》2018,57(11):2929-2933
A chemoenzymatic synthon was designed to expand the scope of the chemoenzymatic synthesis of carbohydrates. The synthon was enzymatically converted into carbohydrate analogues, which were readily derivatized chemically to produce the desired targets. The strategy is demonstrated for the synthesis of glycosides containing 7,9‐di‐N‐acetyllegionaminic acid (Leg5,7Ac2), a bacterial nonulosonic acid (NulO) analogue of sialic acid. A versatile library of α2‐3/6‐linked Leg5,7Ac2‐glycosides was built by using chemically synthesized 2,4‐diazido‐2,4,6‐trideoxymannose as a chemoenzymatic synthon for highly efficient one‐pot multienzyme (OPME) sialylation followed by downstream chemical conversion of the azido groups into acetamido groups. The syntheses required 10 steps from commercially available d ‐fucose and had an overall yield of 34–52 %, thus representing a significant improvement over previous methods. Free Leg5,7Ac2 monosaccharide was also synthesized by a sialic acid aldolase‐catalyzed reaction. 相似文献
48.
The present work describes radiation-induced effects of major seeds like Oryza sativa Cv-2233, Oryza sativa Cv-Shankar, Cicer arietinum Cv-local and seed-borne fungi like Alternaria sp., Aspergillus sp., Trichoderma sp. and Curvularia sp. 60Co gamma source at 25 °C emitting gamma ray at 1173 and 1332 keV energy was used for irradiation. Dose of gamma irradiation up to 3 kGy (0.12 kGy/h) was applied for exposing the seed and fungal spores. Significant depletion of the fungal population was noted with irradiation at 1–2 kGy, whereas germinating potential of the treated grain did not alter significantly. However, significant differential radiation response in delayed seed germination, colony formation of the fungal spores and their depletion of growth were noticed in a dose-dependent manner. The depletion of the fungal viability (germination) was noted within the irradiation dose range of 1–2 kGy for Alternaria sp. and Aspergillus sp., while 0.5–1 kGy for Trichoderma sp. and Curvularia sp. However, complete inhibition of all the selected fungi was observed above 2.5 kGy. 相似文献
49.
A novel class of O6-(benzotriazol-1-yl)inosine as well as the corresponding 2'-deoxy derivatives can be conveniently prepared by a reaction between sugar-protected or -unprotected inosine or 2'-deoxyinosine nucleosides and 1H-benzotriazol-1-yloxy-tris(dimethylamino)phosphonium hexafluorophosphate (BOP). The reaction appears to proceed via a nucleoside phosphonium salt, and in the absence of any additional nucleophile, the released 1-hydroxybenzotriazole undergoes reaction with the formed phosphonium salt leading to the requisite O6-(benzotriazol-1-yl)inosine or 2'-deoxyinosine derivatives. Isolation and characterization of the phosphonium salt as well as analysis by 31P{1H} NMR appear to be consistent with this reaction pathway. The resulting O6-(benzotriazol-1-yl)inosine derivatives are effective as electrophilic nucleosides, undergoing facile reactions with a variety of nucleophiles such as alcohols, phenols, amines, and a thiol. Unusual and challenging nucleoside derivatives such as an aryl-bridged dimer, a nucleoside-amino acid conjugate, and a nucleoside-nucleoside dimer have also been synthesized from the O6-(benzotriazol-1-yl)-2'-deoxyinosine derivative. Finally, a fully protected DNA building block, the O6-(benzotriazol-1-yl)-2'-deoxyinosine 5'-O-DMT 3'-O-phosphoramidite, has been prepared and a preliminary evaluation of its use for DNA modification has been performed. Results from these studies indicate several important facts: A single, simple methodological approach provides a class of stable, isolable ribo and 2'-deoxyribonucleoside derivatives that possess excellent reactivity for SNAr chemistry with a wide range of nucleophiles. Also, a benzotriazolyl nucleoside phosphoramidite appears to be a suitable reagent for incorporation into DNA for purposes of site-specific DNA modification. 相似文献
50.
A new route for the synthesis of linear and vinyl thioethers has been demonstrated using bare silica nanoparticle as catalyst at room temperature under solvent-free conditions. The catalyst can be reused up to six times without loss of catalytic activity. 相似文献