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排序方式: 共有628条查询结果,搜索用时 31 毫秒
1.
Leila Torkian Mostafa M. Amini Tayebeh Gorji Omid Sadeghi 《Arabian Journal of Chemistry》2019,12(7):1315-1321
In this study, multiwalled carbon nanotube (MWCNT) was modified by the pyridine group using a silane agent and characterized by infrared spectroscopy (IR), thermal analysis (TG/DTA), and elemental analysis (CHN) and scanning electron microscopy (SEM). The application of this sorbent was investigated in determination of lead ions in aqueous samples, using flame atomic absorption spectrometry (FAAS). Through this study, different parameters such as pH and sample flow rate on adsorption process and eluent concentration, volume and flow rate were optimized. The limit of detection (LOD), the relative standard deviation and the recovery of the method were 2 ng mL?1, 1.3% and 99.7%, respectively. Two standard reference materials (NIST 1571 and NIST 1572) were used to verify accuracy of this method. Finally, the sorbent was successfully applied for extraction and determination of low levels of Pb(II) ions in aqueous samples. 相似文献
2.
This Note is an attempt to extend the mixed finite element method to a class of variational inequalities including the problems of Signorini and of unilateral contact in elasticity with or without friction. Existence and uniqueness for the continuous and the discrete problems as well as error estimates are established in a general abstract framework. As a result, the mixed approximation of the Signorini problem is proved to converge with an error bound in h3/4. To cite this article: L. Slimane et al., C. R. Acad. Sci. Paris, Ser. I 334 (2002) 87–92 相似文献
3.
Latifeh Navidpour Leila Karimi Mohsen Amini Mohssen Vosooghi Abbas Shafiee 《Journal of heterocyclic chemistry》2004,41(2):201-204
Arylation of the readily available 3‐alkythio‐5‐aryl‐1,2,4‐triazoles gave 5‐alkylthio‐1,3‐diaryl‐1,2,4‐triazoles in moderate yield. The structures of the latter were confirmed by NOE and 13C‐NMR. 相似文献
4.
Kochocki JA Allison WW Alner GJ Ambats I Ayres DS Balka LJ Barr GD Barrett WL Benjamin D Border P Brooks CB Cobb JH Cockerill DJ Coover K Courant H Dahlin B DasGupta U Dawson JW Edwards VW Fields TH Kirby-Gallagher LM Garcia-Garcia C Giles RH Goodman MC Heller K Heppelman S Hill N Hoftiezer JH Jankowski DJ Johns K Joyce T Kafka T Litchfield PJ Lopez FV Lowe M Mann WA Marshak ML May EN McMaster L Milburn RH Miller W Napier A Oliver WP Pearce GF Perkins DH Peterson EA Price LE Roback D Rosen DB 《Physical review D: Particles and fields》1990,42(9):2967-2973
5.
Paramagnetic enhancement of nuclear spin-lattice relaxation rates (PREs) was measured in aqueous solution of the trisaccharide raffinose in the presence of a gadolinium(III) complex, GdDTPA-BMA, used as a magnetic resonance imaging contrast agent. The relaxation enhancement of aqueous protons was measured over a broad range of magnetic fields, using field-cycling apparatus in addition to conventional spectrometers. The nuclear magnetic relaxation dispersion profile thus obtained was interpreted with a recently developed model, allowing for both inner- and outer-sphere relaxation. The relaxation enhancement for the carbon-13 nuclei in raffinose was studied under high-resolution conditions at three magnetic fields, whereas the sugar proton PRE was measured at two fields. The PRE of the sugar nuclei could be interpreted in a consistent way, assuming that it was caused by the outer-sphere mechanism. The electron spin relaxation was found to be a less important source of modulation of the electron-nuclear dipole-dipole interaction than the mutual translational diffusion. 相似文献
6.
Moraes ML Bonardi C Mendonça CR Campana PT Lottersberger J Tonarelli G Oliveira ON Beltramini LM 《Colloids and surfaces. B, Biointerfaces》2005,41(1):15-20
The study of interactions between biological molecules and model membranes is essential for the understanding of a number of physiological mechanisms involved in viral infections and dissemination. In this paper, the analysis of the interaction between a peptide from the p24 protein of Human Immunodeficiency Virus type 1 (HIV-1) and a phospholipid monolayer has pointed to a cooperative response in which very small amounts of peptide p24-1 (e.g. 0.05 mol%) can lead to measurable effects. Monolayer surface pressure and surface potential isotherms were affected for peptide concentrations as low as 0.05 mol%, with saturation at 0.5 mol%. The expansion effect from p24-1 is confirmed by changes in morphology of the monolayers using Brewster angle microscopy. Even though p24-1 is disordered in aqueous solutions, the interaction with dipalmitoyl phosphatidylcholine (DPPC) causes it to adopt an alpha-helix structure, as shown by circular dichroism (CD) data for multilamellar vesicles (MLV). The expansion of the phospholipid monolayer in a cooperative way may imply that p24-1 has potential antiviral activity, by participating in the cell rupture, with no need of specific receptors in the membrane. 相似文献
7.
Usein M Dzhemilev Vladimir A D'yakonov Leila O Khafizova Askhat G Ibragimov 《Tetrahedron》2004,60(6):1287-1291
Cyclo- and carbomagnesiation of 1,2-dienes with EtMgR′ (R′=Et, Br) in the presence of Cp2ZrCl2 catalyst lead to alkylidenemagnesiocyclopentanes. Deuterolysis provides insights into the reaction pathways. 相似文献
8.
Leila S. Boulos Mona H. N. Arsanious El-Sayed M. A. Yakout 《Monatshefte für Chemie / Chemical Monthly》2007,41(9):979-984
The reaction of 3-amino-2-phenyl-4(3H)-quinazolinone with oxovinylidenetriphenylphosphorane afforded 5-phenylpyrazolo[1,5-c] quinazoline-2(3H)-one and triphenylphosphine oxide. On the other hand, when quinazolinone reacts with phosphorus ylides, the corresponding
phosphorane adducts were obtained. Moreover, quinazolinone reacts with trisdialkylaminophosphines to give the new (dialkylamino)oxophosphonium
dipolar products. Possible reaction mechanisms are considered and the structural assignments are based on analytical and spectroscopic
results. 相似文献
9.
The effect of hydrochloric acid, boric acid, and silica content in alumina on its catalytic activity towards the decomposition of triethylamine was investigated at 310°, 320°, and 330°. The study was carried out in a flow system and the reaction product was analyzed chromotographically. Ethylene formation is a zero order reaction independent of the partial pressure of triethylamine. Treating γ-alumina with hydrochloric acid increases its catalytic activity towards ethylene formation whereas silica-alumina is less active than γ-alumina. Boric acid-treated alumina has the same activity of γ-alumina. Formation of ethylene from preadsorbed triethylamine was studied. The similarity between reactions of aliphatic alcohols and amines over acid catalysts is concluded. 相似文献
10.
Leila Saedi Zahra Javanshir Salah Khanahmadzadeh Maryam Maskanati Milad Nouraliei 《Molecular physics》2020,118(7)
ABSTRACTDensity functional theory calculations were used to investigate the potential application of an AlN nanocluster in the detection of H2S, COS, CS2 and SO2 gases. In overall, the order of strength of interaction of these gases with the nanocluster is as follows: SO2 (Ead?=??17.6?kcal/mol)?>?H2S (Ead?=??14.0?kcal/mol)?>?COS (Ead?=??8.4?kcal/mol)?>?CS2 (Ead?=??4.5?kcal/mol). This indicates that by increasing the electric dipole moment, the adsorption energy becomes more negative. We found that the Al12N12 nanocluster may be a promising work function-type sensor for SO2 gas among the studied gases. Also, it is an electronic sensor for both SO2 and CS2 gases but selectively acts between them because of their different effects on the electrical conductivity. It is neither work function-type nor electronic sensor for H2S and COS gases. The AlN nanocluster benefits from a short recovery time about 7.7?s and 18.0?ms for desorption of SO2 and CS2 gases from its surface at room temperature, respectively. It is also concluded that this cluster can work at a humid environment. 相似文献