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131.
A convenient synthetic strategy for the synthesis of the acidic pentasaccharide repeating unit and its trisaccharide fragment corresponding to the O-antigen of Shigella boydii type 6 has been successfully developed. A stereoselective sequential glycosylation method has been exploited to obtain the target tri- and pentasaccharide derivatives. Most of the synthetic intermediates were solid and prepared in high yields from commercially available reducing sugars following a series of protection–deprotection reactions. A late-stage TEMPO mediated selective oxidation reaction finally resulted in the pentasaccharide containing a glucuronic acid unit. A 2-(4-methoxyphenoxy) ethyl group has been chosen as the anomeric protecting group to provide trisaccharide and pentasaccharide derivatives linked to an ethylene glycol linker. 相似文献
132.
T. Shiroka C. Bucci R. De Renzi F. Galli G. Guidi G. H. Eaton P. J. C. King C. A. Scott K. Träger A. Breitrück M. Diaz Trigo A. Großmann K. Jungmann J. Merkel P. Neumayer I. Reinhard R. Santra L. Willmann V. Meyer E. Roduner R. Scheuermann M. C. Charlton P. Donnelly 《Applied magnetic resonance》2000,19(3-4):471-477
Standard muon spin rotation (μSR) spectroscopy implants 4 MeV spin-polarized positive muons to investigate the bulk properties of matter. Success in producing epithermal muons opens interesting possibilities for studying ultrathin films, interfaces, and even surfaces. At the ISIS Facility, Rutherford Appleton Laboratory (Chilton, UK), we have produced a pulsed ultraslow muon beam (E< 20 eV) and have performed the first μSR experiments. Due to the pulsed feature, the implantation time is automatically determined and, by adjusting the final muon energy between about 8 and 20 eV, depth slicing experiments are possible down to monolayers distances. We describe slicing experiments across a 20 nm copper film on quartz substrate with evidence for a 2 nm copper oxide surface layer. A preliminary experiment on a hexagonal cobalt film suggests the existence of muon precession in the local magnetic field. The results are discussed in relation to the morphological features of the film. 相似文献
133.
The reaction of [CpFe(CO)2]2 with NH4Se2P(OR)2 yields a novel reagent Cp(CO)2FeP(Se)(OR)2, which has demonstrated coordination properties at the Se center to form heterometallic clusters as well as reactivity at the Se site toward C-based electrophiles. 相似文献
134.
J.P. Maity S. Kar S. Banerjee A. Chakraborty S.C. Santra 《Radiation Physics and Chemistry》2009,78(11):1006-1010
We have reported an effective 60Co gamma irradiation method for the removal and long-time prevention of contaminating fungi of Oryza sativa cv-2233, without the losses of seed viabilities. The fungal growth and their population on gamma treated seeds was found to decrease significantly (p<0.05) with the increasing irradiation dose and storage time. Immediately after irradiation, the depletion of fungal population on rice seed was noticed (>50%) at 2 kGy, whereas total inhibition was noticed at 3 kGy after 1.5 month. 相似文献
135.
Bidyut Santra Bhabani S. Dandapat 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2009,80(11):688-700
A thin viscous liquid film flow is developed over a stretching sheet under different nonlinear stretching velocities. An 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. A comparison is made with the analytic solution obtained in [B. S. Dandapat, A. Kitamura,
B. Santra, “Transient film profile of thin liquid film flow on a stretching surface”, ZAMP, 57, 623-635 (2006)]. It is observed that all types of stretching produce film thinning but non-monotonic stretching produces
faster thinning at small distance from the origin. The velocity u along the stretching direction strongly depends on the distance along the stretching direction and the Froude number. 相似文献
136.
Synthesis of diethyl malonate based wholly aliphatic hyperbranched polyesters having suitable polar matrix for irreversible molecular encapsulation is carried out for the first time. 相似文献
137.
Senapoti Sanjoy Santra Prasanta Kumar Sinha Chittaranjan 《Transition Metal Chemistry》2002,27(8):888-894
2-(Arylazo)pyrimidines (aapm) are N,N-chelators which form palladium(II) complexes, Pd(aapm)Cl2
(1). The reaction of Pd(aapm)Cl2
(1) with arylamines (ArNH2) yields Pd(aapm-N-Ar)Cl, (2)–(7), complexes of the tridentate N,N,N-donor system in which arylamines are fused to the ortho C–H function of the pendant aryl ring in the coordinated 2-(arylazo)pyrimidine, leading to the C–N coupled product. Pd(aapm-N-Ar)Cl, complexes (2)–(7), exhibit a broad intense absorption band in n.i.r. region (870–920 nm), while the parent complex, Pd(aapm)Cl2, shows an intense absorption at 425 nm. Cyclic voltammograms of (2)–(7) exhibit an oxidation couple at positive potential to s.c.e. together with three reductions at negative side. The oxidation may involve conversion of the chelated azoarylamine to semibenzoquinone azoarylamine fragment. The reduction is due to the accommodation of electrons in the azoimine function. The absorption spectra in the n.i.r. region may be regarded as HOMO LUMO intravalence charge transfer (i.v.c.t.) transitions. 相似文献
138.
Meyer V Bagayev SN Baird PE Bakule P Boshier MG Breitruck A Cornish SL Dychkov S Eaton GH Grossmann A Hubl D Hughes VW Jungmann K Lane IC Liu YW Lucas D Matyugin Y Merkel J zu Putlitz G Reinhard I Sandars PG Santra R Schmidt PV Scott CA Toner WT Towrie M 《Physical review letters》2000,84(6):1136-1139
The 1s-2s interval has been measured in the muonium (&mgr;(+)e(-)) atom by Doppler-free two-photon pulsed laser spectroscopy. The frequency separation of the states was determined to be 2 455 528 941.0(9.8) MHz, in good agreement with quantum electrodynamics. The result may be interpreted as a measurement of the muon-electron charge ratio as -1-1.1(2.1)x10(-9). We expect significantly higher accuracy at future high flux muon sources and from cw laser technology. 相似文献
139.
Subenoy?ChakrabortyEmail author Batul?Chandra?Santra Nabajit?Chakravarty 《Pramana》2003,61(4):669-673
In this paper generalized scalar tensor theory has been considered in the background of anisotropic cosmological models, namely,
axially symmetric Bianchi-I, Bianchi-III and Kortowski-Sachs space-time. For bulk viscous fluid, both exponential and power-law
solutions have been studied and some assumptions among the physical parameters and solutions have been discussed. 相似文献
140.
The avalanches in the Abelian sandpile model have a compact structure and consist of shells. The different shells consist solely of sites that have toppled a fixed number of times. For the outermost shell the number is one and increases successively by one from an outer shell to the next inner shell. In this paper, we determine the size-distribution exponents of various categories of sites: sites that have toppled at least once, at least twice, at least thrice, only once and only twice. A particular subclass of avalanches is identified which have no shell structure and consist solely of sites which have toppled only once. The size distribution exponent of this type of clusters is determined. 相似文献