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41.
42.
Pandey S Ali M Kamath G Pandey S Baker SN Baker GA 《Analytical and bioanalytical chemistry》2012,403(8):2361-2366
Acridine orange (AO) was used as a fluorescent probe molecule to study the encapsulation of an alkylimidazolium cation from a water-soluble ionic liquid (IL) within two cavitand species, p-tetranitrocalix[4]arene (1) and calix[4]resorcinarene (2), both in alkaline aqueous media. The addition of IL to the preformed [1·AO] adduct resulted in significantly increased fluorescence due to the expulsion of AO from the inclusion complex to the aqueous phase by competitive recognition of the 1-alkyl-3-methylimidazolium cation ([C(n)mim](+), n = 4 and 6) by 1. Conversely, the fluorescence signal dropped upon the addition of IL to the [2·AO] host-guest complex due to unfavorable binding between [C(n)mim](+) and 2. The formation of these postulated adducts is corroborated using ab initio calculations, which also provide evidence for the location of [bmim](+) at the lower external rim of [2·AO], providing an explanation for the observed luminescence quenching in the latter case. These results point to a number of different paths for exploration, ranging from the fluorescence monitoring of IL contamination in groundwater to the "daisy chaining" of macrocyles toward supramolecular ionic networks. They also broadly encourage the exploration of ILs in host-guest-based optical and mass spectrometric sensory systems. 相似文献
43.
Y B S R Prasad V K Senecha H C Pant M P Kamath G S Solanki P K Tripathi A P Kulkarni S Gupta R Pareek A S Joshi N Sreedhar Sameer Nigam C P Navathe 《Pramana》2000,55(5-6):797-802
The x-ray emission from slab targets of copper irradiated by Nd:glass laser (1.054 μm, 5 and 15 ns) at intensities between 1012 and 1011W/cm2 has been studied. The x-ray emissions were monitored with the help of high quantum efficiency x-ray silicon photo diodes
and vacuum photo diodes, all covered with aluminium filters of different thickness. The x-ray intensity vs the laser intensity
has a scaling factor of (1.2–1.92). The relative x-ray conversion efficiency follows an empirical relationship which is in
close agreement with the one reported by Babonneau et al. The ion velocities were monitored using Langmuir probes placed at different angles and radial distances from the target
position. The variation of the ion velocity with the laser intensity follows a scaling of the form Φ
β
where β ∼0.22 which is in good agreement with the reported scaling factor values. The results on the x-ray emission from Cu plasma
are reported. 相似文献
44.
Anil Kamath Rajeev Motwani Krishna Palem Paul Spirakis 《Random Structures and Algorithms》1995,7(1):59-80
The classical occupancy problem is concerned with studying the number of empty bins resulting from a random allocation of m balls to n bins. We provide a series of tail bounds on the distribution of the number of empty bins. These tail bounds should find application in randomized algorithms and probabilistic analysis. Our motivating application is the following well-known conjecture on threshold phenomenon for the satisfiability problem. Consider random 3-SAT formulas with cn clauses over n variables, where each clause is chosen uniformly and independently from the space of all clauses of size 3. It has been conjectured that there is a sharp threshold for satisfiability at c* ≈? 4.2. We provide a strong upper bound on the value of c*, showing that for c > 4.758 a random 3-SAT formula is unsatisfiable with high probability. This result is based on a structural property, possibly of independent interest, whose proof needs several applications of the occupancy tail bounds. 相似文献
45.
46.
A simple and rapid method has been developed for the determination of isotopic radium, based on gamma-ray spectrometry. (228)Ra and (224)Ra are assayed by measuring the intensities of the photo-peaks in the 0.94 and the 2.62 MeV regions of the gamma-spectrum. The interference in these measurements, arising from the presence of the (226)Ra(210)Pb chain in the sample, is obviated by the almost complete expulsion of (222)Rn from the system. The precision of the method is +/-2% and +/-3 % in the determination of (228)Ra and (224)Ra respectively, the absolute sensitivities being 2 and 0.5 nCi. The method has been applied to evaluate the distribution of these isotopes in the various products of the Indian Rare-Earths Factory, Alwaye. 相似文献
47.
The determination of niobium at levels of 0.01% and below is required in certain specifications for stainless-steel welding electrodes, containing 2-3% molybdenum and 0.01% titanium. A method has been developed, based on initial extraction of niobium thiocyanate into butyl acetate followed by stripping with fluoride and re-extraction of niobium thiocyanate after masking of the fluoride by addition of boric acid. The absorbance of the extract is measured at 385 nm. Mo, Ti, V and W can be tolerated at 50 times the concentration of Nb. For higher amounts of Mo, corrections can also be applied. Ta should, however, be restricted to ten times the Nb level. Precision and accuracy of the method are satisfactory. The time taken for an individual determination is about an hour. The method is applicable to mild, low-alloy, stainless and niobium-stabilized steels. 相似文献
48.
J.N. Babu Reddy S. Vanishri Ganesh Kamath Suja Elizabeth H.L. Bhat D. Isakov M. Belsley E. de Matos Gomes T.L. Aroso 《Journal of Crystal Growth》2009,311(16):4044-4049
Cesium hydrogen l-malate monohydrate, CsH(C4H4O5)·H2O, is a new chiral open-framework semi-organic crystalline material with a second-harmonic generation efficiency one order of magnitude greater than KDP. Single crystals of this new material have been grown by the conventional slow cooling technique from aqueous solution. Grown crystals display both platy and prismatic morphologies depending on the imposed supersaturation. Hardness values measured using Vickers hardness indenter show considerable anisotropy. The resistivity behavior at room temperature and above, places the crystal between an ionic conductor and a dielectric. The single-crystal SHG efficiency estimated through Maker fringes experiment gives deff which is 4.24 times that of KDP. Single and multiple shot experiments performed on the grown crystals for the fundamental and second harmonic of pulsed Nd:YAG laser (1064 and 532 nm) show that it exhibits a high laser damage threshold which is a favorable property for nonlinear optical applications. 相似文献
49.
50.
Kiran G. K. Penki Tirupathi Rao Vishnu Kamath P. Munichandraiah N. 《Journal of Solid State Electrochemistry》2016,20(2):555-562
Journal of Solid State Electrochemistry - Electrodeposited Cu2O coatings with 111 out-of-plane orientation were found to have the lowest reversible discharge capacity as anodes for Li-ion cells.... 相似文献