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141.
Arkke J. Eskola Timo T. Reijonen Timo T. Pekkanen Petri Heinonen Satya P. Joshi Raimo S. Timonen 《Proceedings of the Combustion Institute》2021,38(1):813-821
The kinetics of the i-C4H5 (buta-1,3-dien-2-yl) radical reaction with molecular oxygen has been measured over a wide temperature range (275–852 K) at low pressures (0.8–3 Torr) in direct, time-resolved experiments. The measurements were performed using a laminar flow reactor coupled to photoionization mass spectrometer (PIMS), and laser photolysis of either chloroprene (2-chlorobuta-1,3-diene) or isoprene was used to produce the resonantly stabilized i-C4H5 radical. Under the experimental conditions, the measured bimolecular rate coefficient of i-C4H5 + O2 reaction is independent of bath gas density and exhibits weak, negative temperature dependency, and can be described by the expression k3 = (1.45 ± 0.05) × 10?12 × (T/298 K)?(0.13±0.05) cm3 s?1. The measured bimolecular rate coefficient is surprisingly fast for a resonantly stabilized radical. Under combustion conditions, the reactions of i-C4H5 radical with ethylene and acetylene are believed to play an important role in forming the first aromatic ring. However, the current measurements show that i-C4H5 + O2 reaction is significantly faster under combustion conditions than previous estimations suggest and, consequently, inhibits the soot forming propensity of i-C4H5 radicals. The bimolecular rate coefficient estimates used for the i-C4H5 + O2 reaction in recent combustion simulations show significant variation and are up to two orders of magnitude slower than the current, measured value. All estimates, in contrast to our measurements, predict a positive temperature dependency. The observed products for the i-C4H5 + O2 reaction were formaldehyde and ketene. This is in agreement with the one theoretical study available for i-C4H5 + O2 reaction, which predicts the main bimolecular product channels to be H2CO + C2H3 + CO and H2CCO + CH2CHO. 相似文献
142.
Naveen Satrawala Kamal N. Sharma Leah C. Matsinha Latisa Maqeda Shepherd Siangwata Gregory S. Smith Raj K. Joshi 《Tetrahedron letters》2017,58(28):2761-2764
Base-catalyzed C–C cross coupling of secondary alcohols and aryl-aldehydes was achieved, when an alcoholic solution of an aryl-aldehyde was stirred under reflux for 45 h in the presence of a catalytic (20 mol%) amount of K2CO3. The consistent formation of α,α′-bis-(benzylidene) alkanones was obtained in moderate to good yields using various secondary alcohols and substituted aryl-aldehydes. Herein, α,α′-bis-(benzylidene)alkanones, which are the classical products of Claisen-Schmidt (cross aldol) condensation, have been synthesized via an alternative strategy using secondary alcohols. Bis-(benzylidene) alkanones are an integral part of various drug regimes and the production of bis-(benzylidene) alkanones without using any precious metal is a major outcome of the present reaction. 相似文献
143.
Preparation of electrodeless discharge lamps for emission studies of uranium isotopes at trace level
G.K. Bhowmick R. Verma M.K. Verma V.A. Raman A.R. Joshi M.N. Deo L.M. Gantayet A.K. Tiwari K.L. Ramakumar Navin Kumar 《Spectrochimica Acta Part B: Atomic Spectroscopy》2010,65(12):1047-1051
A simplified method for preparation of electrodeless discharge lamp for uranium isotopes with specific concerns for 232U is described. Micro-gram quantities of solid uranium oxides and aqueous solution of uranium nitrate have been used as a starting material for in situ synthesis of uranium tetraiodide. High temperature iodination reaction is carried out in the presence of inert gas neon. By careful design, the preparation time and surface area of quartz reaction tubes have been reduced considerably. The latter decreases the level of contamination which has a direct bearing on the operational lifetime of the lamps. Incorporation of steps to purify the product from an unwanted material improved the stability of the lamps. The procedure provides a safe and convenient way of handling 232U in particular but can be extended in general to any actinides having radioactivity similar to that of freshly separated 232U. Characteristic emission of uranium isotopes have been recorded by Fourier Transform Spectrometer to show the satisfactory operation of the lamps as well as their usage for studying emission spectra of the specific isotope. 相似文献
144.
Pradeep Mathur Raj Kumar Joshi Amrendra K. Singh 《Journal of organometallic chemistry》2010,695(24):2687-2694
A facile, one pot, high yield synthesis of α,β-vinylester (1-14) and alkoxy substituted γ-lactones (15-28) has been achieved by the photochemical reaction of terminal acetylene (ferrocenyl phenyl trimethylsillyl, hexyl and cyclohexyl) with alcohol (methanol, ethanol and isopropanol) and carbon monoxide in presence of iron pentacarbonyl as a catalyst. The selectivity of the compounds depends on the time of photolysis of the reaction as well as the solvent used. A stable reaction intermediate ferrole was isolated, and further photolysis with alcohols, resulted in the formation of α,β-vinylester. All the compounds were fully characterised by spectroscopic methods and the molecular structures of compounds 1, 16, 17 and 20 were established crystallographically. 相似文献
145.
Rajendra D. Patil Girdhar Joshi Subbarayappa Adimurthy 《Monatshefte für Chemie / Chemical Monthly》2010,141(4):1093-1099
Abstract
Hydroarylation of styrenes with arenes/heteroarenes using KHSO4 (10 mol%) as an efficient heterogeneous catalyst is described. High conversion and selectivity (>99%) were observed for hydroarylation of styrenes with 2-naphthol at reflux temperature of 1,2-dichloroethane. Yields were quantitative with all styrenes. Moderate to good conversions and selectivities were achieved with other aromatics and heteroaromatics under the same conditions. Regeneration and reusability of KHSO4 were demonstrated. Addition of a trace amount of water could help to reactivate the KHSO4 through dispersion and to facilitate the hydroarylation reaction. 相似文献146.
147.
K. D. Parikh D. J. Dave B. B. Parekh M. J. Joshi 《Crystal Research and Technology》2010,45(6):603-610
Potassium Dihydrogen Phosphate (KDP) is an excellent inorganic nonlinear optical (NLO) material with different device applications. Most of amino acids possess NLO property; therefore, it is of interest to dope them in KDP crystals. In the present study, amino acid L‐alanine doped KDP crystals were grown by slow aqueous solvent evaporation technique. The doping of L‐alanine was confirmed by the paper chromatography, the CHN analysis and the FT‐IR spectroscopy. The powder XRD was carried out to assess the single phase nature of the samples. The effect of doping on thermal stability of the crystals was studied by TGA and the kinetic and thermodynamic parameters of dehydration were evaluated. As the amount of doping increased the thermal stability of crystals decreased. However, the second harmonic generation (SHG) efficiency and the UV‐Vis spectroscopy studies indicated that as the L‐alanine doping increased the SHG efficiency and optical transmission percentage increased. The dielectric behavior of the samples has been studied. The variation of dielectric constant, dielectric loss (tanδ), a.c.resistivity and a.c.conductivity with frequency of applied field in the range from 100 Hz to 100 kHz was studied. The dielectric constant and dielectric loss decreased with increase the value of frequency of applied field. The dielectric constant and the dielectric loss values of L‐alanine doped KDP crystals were lower than the pure KDP crystals. The results are discussed. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
148.
Temporal integration of loudness measured using categorical loudness scaling and matching procedures
Valente DL Joshi SN Jesteadt W 《The Journal of the Acoustical Society of America》2011,130(1):EL32-EL37
Temporal integration of loudness of 1 kHz tones with 5 and 200 ms durations was assessed in four subjects using two loudness measurement procedures: categorical loudness scaling (CLS) and loudness matching. CLS provides a reliable and efficient procedure for collecting data on the temporal integration of loudness and previously reported nonmonotonic behavior observed at mid-sound pressure level levels is replicated with this procedure. Stimuli that are assigned to the same category are effectively matched in loudness, allowing the measurement of temporal integration with CLS without curve-fitting, interpolation, or assumptions concerning the form of the loudness growth function. 相似文献
149.
Vossen A Seidl R Adachi I Aihara H Aushev T Balagura V Bartel W Bischofberger M Bondar A Bračko M Browder TE Chang MC Chen A Chen P Cheon BG Cho K Choi Y Eidelman S Feindt M Gaur V Gabyshev N Garmash A Golob B Perdekamp MG Haba J Hayasaka K Horii Y Hoshi Y Hou WS Hyun HJ Inami K Ishikawa A Iwabuchi M Iwasaki Y Iwashita T Joshi NJ Kichimi H Kim HO Kim MJ Ko BR Kumita T Lange JS Lee MJ Lee SH Leitgab M Li Y Liu C Liventsev D Louvot R McOnie S Miyata H Miyazaki Y Mizuk R Mohanty GB Nakano E 《Physical review letters》2011,107(7):072004
The interference fragmentation function translates the fragmentation of a quark with a transverse projection of the spin into an azimuthal asymmetry of two final-state hadrons. In e(+)e(-) annihilation the product of two interference fragmentation functions is measured. We report nonzero asymmetries for pairs of charge-ordered π(+)π(-) pairs, which indicate a significant interference fragmentation function in this channel. The results are obtained from a 672 fb(-1) data sample that contains 711 × 10(6) π(+)π(-) pairs and was collected at and near the Υ(4S) resonance, with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider. 相似文献
150.
We report a method for the measurement of nematic liquid crystal (NLC) cell parameters i.e., switching voltage, birefringence, retardation, dielectric anisotropy, average tilt angle and change in refractive index with applied DC voltage to LC material. The proposed method is based on optical interferometry and Fourier transform fringe analysis technique, in which we obtain 2-dimensional (2D) phase map of the interferograms as a function of applied voltage. Mach-Zehnder interferometer (MZI) was used for the study of cell parameters and interferograms were recorded at different applied DC voltages to NLC cell using CCD camera. From the phase map, 2D-refractive index distribution of the LC cell with applied voltage was reconstructed. Analytical equations are derived based on optical interferometry and then solved to obtain cell parameters. The present method is fast and can give 2D-cell parameters from only two quick interferograms. 相似文献