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61.
62.
The semileptonic decay width of heavy baryons such as (Λ
b
→ Λcev) has been estimated in the framework of a nonrelativistic field theoretic quark model where four component quark field
operators along with a harmonic oscillator wave function are used to describe translationally invariant hadronic states. The
present estimation does not make an explicit use of heavy quark symmetry and has a reasonable agreement with the experimentally
measured decay width, polarisation ratio and form factors with the harmonic oscillator radii and quark momentum distribution
inside the hadron as free parameters. 相似文献
63.
Ali Khalafi‐Nezhad MohammadNavidSoltani Rad GholamHossein Hakimelahi 《Helvetica chimica acta》2003,86(7):2396-2403
An efficient and rapid synthesis of phloroglucide analogs under microwave irradiation is described. The solid‐phase condensation reaction of the 4‐halo‐2,6‐bis(hydroxymethyl)phenols 1a , b with other substituted phenols in the presence of ZnCl2 afforded the target molecules in much higher yields than by classical solution‐phase synthesis and allowed us to prepare new phloroglucide analogs possessing sensitive functional groups difficult to access by established means. 相似文献
64.
Mohammad Ali Karimi Abdolhamid Hatefi-Mehrjardi Sayed Zia Mohammadi Alireza Mohadesi Mohammad Mazloum-Ardakani Mohammad Reza Hormozi Nezhad Asghar Askarpour Kabir 《Journal of the Iranian Chemical Society》2012,9(2):171-180
A new, simple, fast and reliable solid-phase extraction method has been developed for separation/preconcentration of trace amounts of Pb(II) using dithizone/sodium dodecyl sulfate-immobilized on alumina-coated magnetite nanoparticles, and its determination by flame atomic absorption spectrometry (FAAS) and graphite furnace atomic absorption spectrometry (GFAAS) after eluting with 4.0?mol?L?1 HNO3. Optimal experimental conditions including pH, sample volume, eluent concentration and volume, and co-existing ions have been studied and established. Under the optimal experimental conditions, the preconcentration factor, detection limit, linear range and relative standard deviation of Pb(II) using FAAS technique were 280 (for 560?mL of sample solution), 0.28?ng?mL?1, 1.4?C70?ng?mL?1 and 4.6% (for 10?ng?mL?1, n?=?10), respectively. These analytical parameters using GFAAS technique were 300 (for 600?mL of sample solution), 0.002?ng?mL?1, 0.006?C13.2?ng?mL?1 and 3.1% (for 5?ng?mL?1, n?=?10), respectively. The presented procedure was successfully applied for determination of Pb(II) content in opium, heroin, lipstick, plants and water samples. 相似文献
65.
Mohammad Navid SoltaniRad Ali Khalafi‐Nezhad Somayeh Babamohammadi Somayeh Behrouz 《Helvetica chimica acta》2010,93(12):2454-2466
A convenient and efficient method for a one‐pot conversion of N‐alkylisatins to N‐alkylisatin O‐alkyloximes 7a – 7n as potential chemotherapeutic agents is described (Scheme) (isatin=1H‐indole‐2,3‐dione). In this method, the microwave‐assisted three‐component reaction of N‐alkylisatins 8 , hydroxylamine hydrochloride, and diverse alkyl halides in the presence of K2CO3 and Bu4NBr furnishes the corresponding N‐alkylisatin O‐alkyloximes under solvent‐free condition in short times (2–10 min) and good to excellent yields (62–83%). The O‐alkylation of in situ generated isatin oximes with alkyl halides was achieved regioselectively, and (Z)‐O‐alkyloximes were produced dominantly. PM3 Semi‐empirical quantum‐mechanic calculations were performed to rationalize the evidences, and the calculations indicated a lower heat of formation for the (Z)‐O‐alkyloximes. 相似文献
66.
S. Sankar MR. Manikandan S.D. Gopal Ram T. Mahalingam G. Ravi 《Journal of Crystal Growth》2010,312(19):2729-2733
The microbial free single crystals of α and γ glycine were grown from gel at room temperature in a new chemical route. These crystals showed a superior quality than the solution grown crystals. The metastable α-form and the stable γ-form of glycine were crystallized in silica gel by solubility reduction method. The form of crystallization is confirmed by single crystal and powder X-ray diffraction analyses. The crystals of α and γ glycine were found to crystallize in monoclinic and hexagonal crystal systems, respectively. For analyzing the functional group and thermal stability of α and γ glycine crystals, spectroscopic and thermal analyses have been carried out. The dielectric studies were performed to find the dielectric constant of the grown crystals and the results are discussed. Second harmonic generation efficiency of the crystal was measured by Kurtz’s powder method using Nd:YAG laser and it was found to be 2.68 times that of potassium dihydrogen phosphate crystals. 相似文献
67.
Cloud point extraction, preconcentration and simultaneous spectrophotometric determination of nickel and cobalt in water samples 总被引:4,自引:0,他引:4
Safavi A Abdollahi H Hormozi Nezhad MR Kamali R 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2004,60(12):2897-2901
Cloud point extraction has been used for the preconcentration and simultaneous spectrophotometric determination of nickel and cobalt after the formation of a complex with 2-amino-cyclopentene-1-dithiocarboxylic acid (ACDA), and latter analysis by spectrophotometer using Triton X-114 as surfactant. The parameters affecting the separation phase and detection process were optimized. Under the optimum experimental conditions (i.e. pH=5, 0.07 mM ACDA, Triton X-114=0.25% (w/v)), calibration graphs were linear in the range of 20-500 and 20-200 microg l(-1) with detection limits of 10 and 7.5 microg l(-1) for Ni and Co, respectively. The method was applied to the determination of Ni and Co in natural and waste water samples with satisfactory results. 相似文献
68.
Sensitive indirect spectrophotometric determination of isoniazid 总被引:2,自引:0,他引:2
Safavi A Karimi MA Hormozi Nezhad MR Kamali R Saghir N 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2004,60(4):765-769
A simple, rapid, sensitive and accurate indirect spectrophotometric method for the microdetermination of isoniazid (INH) in pure form and pharmaceutical formulations is developed. The procedure is based on the reaction of copper(II) with isoniazid in the presence of neocuproine (NC). In the presence of neocuproine, copper(II) is reduced easily by isoniazid to a Cu(I)-neocuproine complex, which shows an absorption maximum at 454 nm. By measuring the absorbance of the complex at this wavelength, isoniazid can be determined in the range 0.3-3.5 microgml-1. This method was applied to the determination of isoniazid in pharmaceutical formulation and enabled the determination of the isoniazid in microgram quantities (0.3-3.5 microgml-1). The results obtained for the assay of pharmaceutical preparations compared well with those obtained by the official method and demonstrated good accuracy and precision. 相似文献
69.
70.
In this paper exact asymptotic formulae are found for singularvalues of the Cauchy operator and the logarithmic potentialtype operator (on a bounded domain), as well as their productswith Bergman's projection. It is shown that these spectral characteristicsdetect geometric properties of a domain (area and the lengthof the boundary). The hypothesis "can we hear the shape of adrum", from a paper by J.M. Anderson, D. Khavinson, and V. Lomonosov[Spectral properties of some integral operators arisingin potential theory, Quart. J. Math. Oxford (2) 43 (1992)387-407], is correct in the above sense. 1991 Mathematics SubjectClassification: 47B10. 相似文献