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691.
In the present work, a new ligandless-dispersive liquid-liquid microextraction (LL-DLLME) method has been developed for preconcentration trace amounts of copper as a prior step to its determination by flame atomic absorption spectrometry. In the proposed approach 1,2-dicholorobenzene and ethanol were used as extraction and dispersive solvents, respectively. Some factors influencing on the extraction efficiency of copper and its subsequent determination were studied and optimized, such as the extraction and dispersive solvent type and volume, pH of sample solution, extraction time and salting out effect. Under the optimal conditions, the calibration curve was linear in the range of 1.0 ng mL−1-0.6 μg mL−1 of copper with R2 = 0.9985. Detection limit was 0.5 ng mL−1 in original solution (3Sb/m) and the relative standard deviation for seven replicate determination of 0.2 μg mL−1 copper was ±1.4%. The proposed method has been applied for determination of copper in standard and water samples with satisfactory results. 相似文献
692.
We present families of tableaux which interpolate between the classical semi-standard Young tableaux and matching field tableaux. Algebraically, this corresponds to SAGBI bases of Plücker algebras. We show that each such family of tableaux leads to a toric ideal, that can be realized as initial of the Plücker ideal, hence a toric degeneration for the flag variety. 相似文献
693.
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
694.
New 9-(alkyl or aryl)acenaphtho[l,2-b]furan-8-(alky or aryl)amine compounds has herein been reported by one-pot reaction of (acenaphthylen-l-yloxy)trimethylsilane,alkyl and aryl aldehydes,and aryl and alky isocyanides in refluxing DMF. 相似文献
695.
We associate a graph Γ G to a nonlocally cyclic group G (called the noncyclic graph of G) as follows: take G\ Cyc(G) as vertex set, where Cyc(G) = {x ? G| 〈x, y〉 is cyclic for all y ? G}, and join two vertices if they do not generate a cyclic subgroup. We study the properties of this graph and we establish some graph theoretical properties (such as regularity) of this graph in terms of the group ones. We prove that the clique number of Γ G is finite if and only if Γ G has no infinite clique. We prove that if G is a finite nilpotent group and H is a group with Γ G ? Γ H and |Cyc(G)| = |Cyc(H)| = 1, then H is a finite nilpotent group. We give some examples of groups G whose noncyclic graphs are “unique”, i.e., if Γ G ? Γ H for some group H, then G ? H. In view of these examples, we conjecture that every finite nonabelian simple group has a unique noncyclic graph. Also we give some examples of finite noncyclic groups G with the property that if Γ G ? Γ H for some group H, then |G| = |H|. These suggest the question whether the latter property holds for all finite noncyclic groups. 相似文献
696.
Javad Azizian Ali A. Mohammadi Ebrahim Soleimani Ali R. Karimi Mohammad R. Mohammadizadeh 《Journal of heterocyclic chemistry》2006,43(1):187-190
697.
An S-arithmetic Khintchine-type theorem for products of non-degenerate analytic p-adic manifolds is proved for the convergence case. In the p-adic case the divergence part is also obtained. 相似文献
698.
The Optimization utilization of raw material and components is one of the main challenges in production and project management success. Executives usually face with waste and shortage of raw material which cause delay and cost, however the material and required components are usually provided more than needed. Therefore planning to provide these components from existing spools of material is one of these challenges especially when the number of the needed material pieces and the existing spools are high. For instance, in power plant projects cables are usually provided in form of spools which later cut down to required pieces in the project location. Extraction of each needed piece of cable from specific existing spool is a decision to be made. In this paper, a heuristic method based on integrating Integer Goal Programming and Taguchi Method is suggested to optimize cutting down process of these materials. 相似文献
699.
G. Rezaei Behbehani M. Mirzaie M. Mehreshtiag L. Barzegar A. A. Saboury S. Mohammadi Gorgi 《Journal of solution chemistry》2012,41(4):581-588
The binding properties and structural changes of mushroom tyrosinase enzyme, MT, due to its interactions with phenyl dithiocarbamate (I) and p-phenylene-bis dithiocarbamate (II), were investigated at 27 and 37 °C in phosphate buffer (10?mmol?L?1) at pH = 6.8 by isothermal titration calorimetric (ITC). The extended solvation model was used to calculate the solvation parameters, which were attributed to the stability of this enzyme. Thermodynamic analysis indicated that the predominant mode of interaction was hydrophobic in the binding of compound I to MT, while the binding of II to MT essentially depends on electrostatic interactions. It seems that II is a more potent MT inhibitor due to its two charged head groups that are able to chelate copper ions in the active enzyme site. It was concluded that MT has two distinct sites for p-phenylene-bis and phenyl dithiocarbamate. 相似文献
700.
After a quick review of the Lane-Emden equation and its properties, a composite of two different polytropes is introduced
and some of the consequences are explored. The results are used to build a nonlinear electromagnetism with non-singular, solitonic
solutions as charged particles. 相似文献