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991.
992.
Issa Yavari Rahimeh Hajinasiri S. Zahra Sayyed-Alangi 《Monatshefte für Chemie / Chemical Monthly》2009,20(6):205-207
Abstract
1-Ethyl-3-methylimidazolium bromide was used as a green recyclable alternative to volatile organic solvents for KOH catalyzed three-component synthesis of diethyl alkylsulfanylmethylmalonates from aldehydes, diethyl malonate, and alkylthiols. 相似文献993.
Laleh Hosseinzadeh Shahryar Abbasi Hossein Khani Zahra Khani 《Transition Metal Chemistry》2009,34(4):425-430
The complexation of Co(II) with 4-(2-pyridylazo)resorcinol (PAR) was studied by spectroscopy and voltammetry. In addition,
an adsorptive stripping voltammetric method was developed for the determination of ultra trace levels of Co(II) using a hanging
mercury drop electrode. The method is based on accumulation of Co(II) on a mercury electrode using PAR as the complexing agent.
The effects of instrumental and chemical parameters on the sensitivity of the method were investigated. The detection limit
of the method is 0.003 ng/mL. Most foreign species do not interfere with the determination. The high sensitivity and selectivity
of this method were demonstrated by determination of cobalt in blood and water samples. 相似文献
994.
M.A. Ramadan I.F. Lashien W.K. Zahra 《Communications in Nonlinear Science & Numerical Simulation》2009,14(4):1105-1114
In this paper, we develop quintic nonpolynomial spline methods for the numerical solution of fourth order two-point boundary value problems. Using this spline function a few consistency relations are derived for computing approximations to the solution of the problem. The present approach gives better approximations and generalizes all the existing polynomial spline methods up to order four. This approach has less computational cost. Convergence analysis of these methods is discussed. Two numerical examples are included to illustrate the practical usefulness of our methods. 相似文献
995.
Afsaneh Feiz Ghazaleh Imani Shakibaei Zahra Yasaei Hamid Reza Khavasi Ayoob Bazgir 《Helvetica chimica acta》2011,94(9):1628-1637
A new four‐component synthesis of spiro[4H‐indeno[1,2‐b]pyridine‐4,3′‐[3H]indoles] and spiro[acenaphthylene‐1(2H),4′‐[4H‐indeno[1,2‐b]pyridines] by the reaction of indane‐1,3‐dione, 1,3‐dicarbonyl compounds, isatins (=1H‐indole‐2,3‐diones) or acenaphthylene‐1,2‐dione, and AcONH4 in refluxing toluene in the presence of a catalytic amount of pyridine is reported. 相似文献
996.
A new micro-solid phase extraction method was developed by combining solid-phase extraction and stir bar sorptive extraction to benefit from the advantages of both techniques. A polypyrrole coating was electrochemically synthesized on the surface of an already used graphite furnace, employed in electro-thermal atomic absorption spectroscopy. The cylindrical geometry of the graphite tube provided a rather huge surface area, suitable for sorptive extraction. The novel sorbent coating was examined as an extracting medium to isolate malathion. Effects of different parameters such as extraction time, salt concentration, sample volume, desorption solvent and time were investigated and optimized. Under the optimized conditions, the limit of detection and limit of quantification of the developed method were 5 and 20?ng?L?1, respectively. The calibration curve showed linearity in the range of 0.1?C100???g?L?1 (R 2?=?0.9968). The precision was evaluated at 0.1 and 1???g?L?1 concentration levels and relative standard deviations (n?=?3) were found to be 10 and 7%, respectively. The developed method was successfully applied to the extraction of malathion from real river water and tap water samples, and relative recoveries at the spiked level of 0.1???g?L?1 were 94 and 97%, respectively. 相似文献
997.
998.
Khedri Z Muthana MM Li Y Muthana SM Yu H Cao H Chen X 《Chemical communications (Cambridge, England)》2012,48(27):3357-3359
A library of α2-3- and α2-6-linked sialyl galactosides containing C9-modified sialic acids was synthesized from C6-modified mannose derivatives using an efficient one-pot three-enzyme system. These sialosides were used in a high-throughput sialidase substrate specificity assay to elucidate the importance of C9-OH in sialidase recognition. 相似文献
999.
Acute toxicity evaluation, antibacterial, antioxidant and immunomodulatory effects of Melastoma malabathricum 总被引:1,自引:0,他引:1
Alnajar ZA Abdulla MA Ali HM Alshawsh MA Hadi AH 《Molecules (Basel, Switzerland)》2012,17(3):3547-3559
Melastoma malabathricum (MM) is a well-known plant in Malaysian traditional medicine, locally known as senduduk. Its ethanol and aqueous extracts have been used in the present investigation to study the immunomodulatory role on human peripheral blood mononuclear cell (PBMC), and the DPPH, ABTS and FRAP free radical scavenging activities were also measured. Total flavonoids and total phenolic contents were assayed and the antibacterial effect was tested against four species of bacteria; two Gram-positive (Staphylococcus aureus and Streptococcus agalactiae) and two Gram-negative (Escherichia coli and Klebsilla pneumonia). The tests were carried out using the disc diffusion, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) methods. Moreover, the acute toxicity was evaluated in vivo on the ethanol extract of MM to establish its safety when administered orally. In our results, both extracts of MM showed abilities to scavenge DPPH and ABTS free radicals, IC(50) values: (11.599 ± 0.84, 10.573 ± 0.58 μmol/L) and (62.657 ± 0.78, 63.939 ± 0.48 μmol/L) for ethanol and aqueous extracts respectively. Indeed the ethanol extract evidenced high phenolic content (384.33 ± 0.005 mg/g), flavonoids contents (85.8 ± 0.009 mg/g) and ferric reducing antioxidant power (33,590 ± 0.038 mmol/g), with high activity against S. aureus and S. agalactiae (11 ± 0.3 and 12 ± 0.6 mm inhibition zones). Likewise, the percentage of peripheral blood mononuclear cells (PBMC) viability was increased in response to MM, IC(50) values (1.781 ± 1.2 and 6.545 ± 0.93 μg/mL) for ethanol and aqueous extracts, respectively. In addition, our results showed that the MM extract is safe even at a high dose of 5,000 mg/kg and has no oral toxicity. These findings suggest the excellent medicinal bioactivity of MM and explain the popularity of this plant in the folk medicine as a remedy for different illnesses. 相似文献
1000.
Daryoush Afzali Rasool Jamshidi Sima Ghaseminezhad Zahra Afzali 《Arabian Journal of Chemistry》2012,5(4):461-466
A method for preconcentration of palladium at trace level on modified multiwalled carbon nanotubes columns and determination by flame atomic absorption spectrometry (FAAS) has been developed. Multiwalled carbon nanotubes (MWCNTs) were oxidized with concentrated HNO3 and the oxidized multiwalled carbon nanotubes were modified with 5-(4′-dimethylamino benzyliden)-rhodanine, and then were used as a solid sorbent for preconcentration of Pd(II) ions. Factors influencing sorption and desorption of Pd(II) ions were investigated. The sorption of Pd(II) ions was quantitative in the pH range of 1.0–4.5, whereas quantitative desorption occurs with 3.0 mL 0.4 mol L?1 thiourea. The amount of eluted palladium was measured using flame atomic absorption spectrometry. The effects of experimental parameters, including sample flow rate, eluent flow rate, and eluent concentration were investigated. The effect of coexisting ions showed no interference from most ions tested. The proposed method permitted a large enrichment factor (about 200). The relative standard deviation of the method was ±2.73% (for eight replicate determination of 2.0 μg mL?1 of Pd(II)) and the limit of detection was 0.3 ng mL?1. The method was applied to the determination of Pd(II) in water, road dust, and standard samples. 相似文献