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91.
Biomass - that is a new feather in your cap: palm shell powder was used as support for novel uranyl complexed cucurbit[5]uril oligomer to obtain a selective extractant for uranium. The key to the selectivity lies in the perfect environment of the two portals of cucurbit[5]uril for uranyl ion binding. 相似文献
92.
The paper reports the pulsed laser-based time-resolved time-dependent Photo-acoustic (PA) spectroscopy of NO2 gas in a specially designed multi mode-Resonant PA Cell which is made of Stainless Steel and has a “Q” value of the order of 79. Furthermore the designed cell allows us to excite some of the longitudinal, radial and azimuthal
resonance modes of the photo-acoustic signals simultaneously in a very efficient manner. The presence of many newly excited
modes occur at 7050 Hz, 10350 Hz and 14650 Hz frequencies is observed for the first time in NO2 at room temperature. These results are obtained by employing second harmonics i.e. λ=532 nm pulses from Q-switched Nd:YAG laser having 7 ns pulse duration. Some of the new acoustic spectrum lines at higher frequencies are recorded
between 0.5–10 ms data acquisition time, which also extends the frequency monitoring range of our system. The study also highlights
some of the important aspects such as the decaying behavior of some of these resonant acoustic spectrum lines occur on the
expense of others as well as the saturation behavior of some other modes in the NO2 gas sample. The estimated low level detection limit of NO2 buffered in air is of the order of 17.9 ppbV. 相似文献
93.
R.H. Chilkulwar S.D. Sharma N. Chaudhary S. Acharya Y.S. Mayya K.C. Mittal L.M. Gantayet 《Radiation measurements》2012,47(8):628-633
The high dose rate electron beams are increasingly being used for radiation processing of various products worldwide. A comprehensive dosimetric evaluation of an in-house developed 10 MeV industrial electron beam irradiator was carried out in static as well as in dynamic mode of irradiations. Radiochromic B3 film and graphite calorimeter were used for dosimetric measurements. The dose rate from the electron beam was also calculated using the empirical relation prescribed in the ASTM report E2232-02. The measured electron beam profile indicates the dose rate variation within 8% in the irradiated product boxes. The most probable energy determined from the depth dose distribution in PMMA, Al and water was found in agreement with the intended energy of the electron beam. Measured dose rate using radiochromic film and graphite calorimeter were found in good agreement with each other and also found comparable with the theoretically estimated dose rates. Experimentally measured dose rates were considered for the trial irradiation of medical and industrial products. Dosimetric data obtained through this study confirms the suitability of the irradiator for routine radiation processing of various products. 相似文献
94.
BM Kobilka AV Dubrovskiy MD Ewan AL Tomlinson RC Larock S Chaudhary M Jeffries-El 《Chemical communications (Cambridge, England)》2012,48(71):8919-8921
3,7-Diiodo-2,6-di(thiophen-2-yl)benzo[1,2-b:4,5-b']difurans are efficiently prepared by an iodine-promoted double cyclization. This new heterocyclic core is readily modified by the attachment of alkyl chains for improved solubility. The use of these compounds for the synthesis of new conjugated polymers is also reported. 相似文献
95.
Ruby Chauhan Ashavani Kumar Ram Pal Chaudhary 《Research on Chemical Intermediates》2012,38(7):1443-1453
Undoped and silver-doped TiO2 nanoparticles (Ti1?x Ag x O2, where x?=?0.00?C0.10) were synthesized by a sol?Cgel method. The synthesized products were characterized by X-ray diffraction (XRD), particle size analyzer (PSA), scanning electron microscope (SEM), and UV?CVisible spectrophotometer. XRD pattern confirmed the tetragonal structure of synthesized samples. Average crystallite size of synthesized nanoparticles was determined from X-ray line broadening using the Debye?CScherrer formula. The crystallite size was varied from 8 to 33?nm as the calcination temperature was increased from 300 to 800?°C. The incorporation of 3 to 5% Ag+ in place of Ti4+ provoked a decrease in the size of nanocrystals as compared to undoped TiO2. The SEM micrographs revealed the agglomerated spherical-like morphology of particles. SEM, PSA, and XRD measurements show that the particles size of the powder is in nanoscale. Optical absorption measurements indicated a red shift in the absorption band edge upon silver doping. Direct allowed band gap of undoped and Ag-doped TiO2 nanoparticles measured by UV?CVis spectrometer were 3.00 and 2.80?eV, respectively, at 500?°C. 相似文献
96.
Jitender M. Khurana Ankita Chaudhary Bhaskara Nand Anshika Lumb 《Tetrahedron letters》2012,53(24):3018-3022
The utilization of water as solvent and indium trichloride as promoter for the three-component combinatorial synthesis of a variety of bioactive pyrimidine and pyrazole derivatives (2–10) from aldehydes, 1,3-dicarbonyl compounds, and electron-rich amino heterocycles like 6-amino-1,3-dimethyl uracil and 3-methyl-1-phenyl-1H-pyrazol-5-amine catalyzed by indium trichloride under reflux has been studied. A new class of pyrimidine derivatives (2) has also been synthesized and the structure was confirmed by single crystal X-ray analysis. The reactions are environmentally benign, reaction product could be isolated easily and the catalyst could be recycled, which makes it an appealing synthetic protocol. 相似文献
97.
Ramesh Garlapati Narender Pottabathini Venkateshwarlu GurramAvinash B. Chaudhary Venkata Rao Chunduri Balaram Patro 《Tetrahedron letters》2012,53(38):5162-5166
6-Halo-2-cyclopropyl-3-(pyridyl-3-ylmethyl) quinazolin-4(3H)-one derivatives have been synthesized and utilized for amination reactions with aryl, heteroaryl and alkyl amines. Optimization of reaction conditions with different catalysts, ligands, bases, and solvents was conducted. The combination of Pd2(dba)3 with DavePhos (L3) proved to be best for these conversions in the presence of NaOtBu in 1,4-dioxane at 100 °C. The relative reactivities of 6-bromo and 6-chloro-2,3-disubstitued quinazolinones with p-toluidine were conducted and as anticipated the 6-bromo analogue was totally consumed and 6-chloro derivative was completely unreactive. 相似文献
98.
Determination of concentration of iodine in grass and cow milk by NAA methods using reactor neutrons
P. V. Geetha N. Karunakara Ujwal Prabhu P. M. Ravi J. Sudhakar Nicy Ajith K. K. Swain R. Acharya A. V. R. Reddy 《Journal of Radioanalytical and Nuclear Chemistry》2012,294(3):435-438
Instrumental and preconcentration methods of neutron activation analysis (NAA) have been standardized for the determination of concentration of iodine in grass and cow milk samples, respectively. To study the transfer of iodine from grass to milk, known quantity of grass spiked with potassium iodide solution was fed to a cow. The spiked grass samples and milk samples, obtained from the cow after the ingestion of spiked grass, were collected. Iodine was separated from the milk samples chemically using Dowex 1X8 anion exchange resin. Spiked grass and ion exchange resin samples were neutron irradiated and radioactive assay was carried out using a 45?% relative efficiency HPGe detector coupled to an 8k channel analyzer. Iodine concentrations in spiked grass samples were found to be in the range of 1,487?C2,002?mg?kg?1. Concentration of iodine in milk after 12?h of feeding the cow with spiked grass was 871?±?56???g?L?1 which was reduced to 334?±?32???g?L?1 after 48?h. 相似文献
99.
Heat and mass transfer effects on the unsteady flow of a micropolar fluid through a porous medium bounded by a semi-infinite vertical plate in a slip-flow regime are studied taking into account a homogeneous chemical reaction of the first order. A uniform magnetic field acts perpendicular to the porous surface absorb micropolar fluid with a suction velocity varying with time. The free stream velocity follows an exponentially increasing or decreasing small perturbation law. Using the approximate method, the expressions for the velocity microrotation, temperature, and concentration are obtained. Futher, the results of the skin friction coefficient, the couple stress coefficient, and the rate of heat and mass transfer at the wall are presented with various values of fluid properties and flow conditions. 相似文献
100.
Asymmetric aldol additions using chlorotitanium enolates of N-acyloxazolidinone, oxazolidinethione, and thiazolidinethione propionates proceed with high diastereoselectivity for the Evans or non-Evans syn product depending on the nature and amount of the base used. With 1 equiv of titanium tetrachloride and 2 equiv of (-)-sparteine as the base or 1 equiv of (-)-sparteine and 1 equiv of N-methyl-2-pyrrolidinone, selectivities of 97:3 to > 99:1 were obtained for the Evans syn aldol products using N-propionyl oxazolidinones, oxazolidinethiones, and thiazolidinethiones. The non-Evans syn aldol adducts are available with the oxazolidinethione and thiazolidinethiones by altering the Lewis acid/amine base ratios. The change in facial selectivity in the aldol additions is proposed to be a result of switching of mechanistic pathways between chelated and nonchelated transition states. The auxiliaries can be reductively removed or cleaved by nucleophilic acyl substitution. Iterative aldol sequences with high diastereoselectivity can also be accomplished. 相似文献