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41.
Large dendrimers, noted G(n)-3(n+2)cage, containing 3(n+2) o-carborane cluster cages MeC(2)B(10)H(10) at their peripheries (n = number of generation noted G(n)) have been synthesized by Huisgen-type azide alkyne Cu(I)-catalyzed dipolar "click" cycloaddition reactions (CuAAC) between an o-carborane monomeric cluster containing an ethynyl group and arene-centered azido-terminated dendrimers G(n)-3(n+2)N(3) of generations 0, 1, and 2. Attempts to synthesize higher-generation dendrimers of this family yielded insoluble materials. The carborane dendrimers G(0)-9cage, G(1)-27cage, and G(2)-81cage have been characterized by (1)H, (13)C, (11)B NMR, elemental analysis, matrix-assisted laser desorption/ionization time of flight (MALDI-TOF) mass spectroscopy, and size exclusion chromatography (SEC) showing low polydispersities, dynamic light scattering (DLS) showing hydrodynamic diameters of 5.7 nm for the G(1)-27cage and the 12.9 nm for the G(2)-81cage. These dendrimers are extremely robust thermally, with 10% mass loss temperatures of 411 °C for the G(0)-9cage, 371 °C for the G(1)-27cage, and 392 °C for the G(2)-81cage. They all showed a strong absorption in the UV region peaking at 258 nm, whereas emission spectra of low intensities were observed between 280 and 480 nm. 相似文献
42.
Abstract
An enhanced rate of intramolecular nitrile oxide cycloaddition and hence a rapid synthesis of isoxazoles and isoxazolines is described. Formation of nitrile oxides from oximes using only 1 or 2 Eq (equivalents) of aqueous sodium hypochlorite solution is also described. 相似文献43.
Bipin Singh Koranga Mohan Narayan S. Uma Sankar 《International Journal of Theoretical Physics》2011,50(5):1515-1521
The recent measurement of Δ
sol
by the KamLAND experiment with very small errors, makes definitive predictions for the energy dependence of the solar neutrino
survival probability P
ee
. We fix Δ
sol
to be the KamLAND best fit value of 8×10−5 eV2 and study the energy dependence of P
ee
for solar neutrinos, in the framework of two flavour oscillations and also of three flavour oscillations. For the case of
two flavour oscillations, P
ee
has a measurable slope in the 5–8 MeV range but the solar spectrum measurements in this range find P
ee
to be flat. The predicted values of P
ee
, even for the best fit value of θ
sol
, differ by 2–3 σ from the Super-K measured values in each of the three energy bins of the 5–8 MeV range. If future measurements of solar neutrinos
by Super-K and SNO find a flat spectrum with reduced error bars (by a factor of 2), it will imply that two flavour oscillations
can no longer explain both KamLAND data and the solar spectrum. However a flat solar neutrino spectrum and the Δ
sol
measured by KamLAND can be reconciled in a three flavour oscillation framework with a moderate value of θ
13≈13°. 相似文献
44.
Bipin Singh Koranga Mohan Narayan 《International Journal of Theoretical Physics》2011,50(6):1831-1836
Quantum gravity (Planck scale effects) lead to an effective SU(2) L ×U(1) invariant dimension-5 Lagrangian involving neutrino and Higgs fields. On symmetry breaking, this operator gives rise to correction to the above masses and mixing. The gravitational interaction M X =M pl , we find that for degenerate neutrino mass spectrum, it is shown that the Majorana phase of the neutrino mixing matrix can effects in neutrino oscillation probability. 相似文献
45.
Kaushik Pal Uday Narayan Maiti Tapas Pal Majumder Subhas Chandra Debnath 《Applied Surface Science》2011,258(1):163-168
A series of novel wurtzite cadmium sulphide (CdS) nanowires with uniform diameter were synthesized by using a rapid and simple solvothermal route. CdS nano structures with certain morphology could be selectively produced by only varying the concentration of poly ethylene glycol (PEG) as a surfactant in the reaction system with cadmium acetate, sulphur powder and ethelynediamine (EDA). We extensively studied UV-vis absorption spectra, photoluminescence spectra after confirming CdS nanowires with diameter 24-25 nm and length ranging up to several nano meters by field emission scanning electron microscopy (FE-SEM). Therefore we may definitely propose a new formation mechanism of CdS nanowires assisted by PEG with its illustrating optical properties. 相似文献
46.
Ndubuisi B. Ukah Satyaprasad P. Senanayak Danish Adil Grant Knotts Jimmy Granstrom K. S. Narayan Suchi Guha 《Journal of Polymer Science.Polymer Physics》2013,51(21):1533-1542
Low‐operating voltage, high mobility, and stable organic field‐effect transistors (OFETs) using polymeric dielectrics such as pristine poly(4‐vinyl phenol) (PVP) and poly(methyl methacrylate) (PMMA), dissolved in solvents of high dipole moment, have been achieved. High dipole moment solvents such as propylene carbonate and dimethyl sulfoxide used for dissolving the polymer dielectric enhance the charge carrier mobilities by three orders of magnitude in pentacene OFETs compared with low dipole moment solvents. Fast switching circuits with patterned gate PVP‐based pentacene OFETs demonstrated a switching frequency of 75 kHz at input voltages of |5 V|. The frequency response of the OFETs is attributed to a high degree of dipolar‐order in dielectric films obtained from high‐polarity solvents and the resulting energetically ordered landscape for transport. Remarkably, these pentacene‐based OFETs exhibited high stability under bias stress and in air with negligible shifts in the threshold voltage. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013 , 51, 1533–1542 相似文献
47.
48.
4(3H)‐Quinazolinones were synthesized in high yields by one‐pot three‐component condensation of anthranilic acid, carboxylic acid and aniline in the presence of ionic liquid such as 1‐n‐butyl‐3‐methylimidazolium tetrafluoroborate (BMImBF4) as catalyst under solvent free and neutral conditions. 相似文献
49.
50.
Narayan Chandra Chakraborty Subenoy Chakraborty 《General Relativity and Gravitation》2002,34(4):453-459
The generalized Brans-Dicke (BD) Cosmology has been studied for Bianchi-I, Bianchi-III and Kantowski-Sachs anisotropic space-time models. Solutions have been obtained for radiation-dominated era, stiff matter epoch and other equations of state. 相似文献