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José Neri G.?Paniz érico Marlon de M.?Flores Ayrton F.?MartinsEmail author 《Mikrochimica acta》2005,152(1-2):89-92
With the aim of avoiding cumbersome sample treatment, we present a device for the introduction of solid soil samples into
AAS-flames for gold determination, as well as the proposition of earth from anthills as a gold occurrence indicator. A previous
ground sample of anthill earth (0.50 mg) was weighed directly into a small recipient of polyethylene which was then connected
to a sampling boronsilicate glass chamber. The sample was carried by an airflow (5 L min−1) to a quartz cell positioned between the burner top and the optical beam. The generated atomic vapor produced a transient
signal which was totally integrated in three seconds. The performance was compared with conventional flame atomic absorption
spectrometry after proper sample digestion. No significant differences were observed between both procedures (mean deviation
±1.90%), and a LOQ of 0.03 μg Au was achieved using the proposed method. The anthill earth was found to be very suitable for
indication of gold occurrence in soils and related materials. 相似文献
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S. Talatahari B. Farahmand AzarR. Sheikholeslami A.H. Gandomi 《Communications in Nonlinear Science & Numerical Simulation》2012,17(3):1312-1319
A novel chaotic improved imperialist competitive algorithm (CICA) is presented for global optimization. The ICA is a new meta-heuristic optimization developed based on a socio-politically motivated strategy and contains two main steps: the movement of the colonies and the imperialistic competition. Here different chaotic maps are utilized to improve the movement step of the algorithm. Seven different chaotic maps are investigated and the Logistic and Sinusoidal maps are found as the best choices. Comparing the new algorithm with the other ICA-based methods demonstrates the superiority of the CICA for the benchmark functions. 相似文献
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Cadmium determination in biological samples by direct solid sampling flame atomic absorption spectrometry 总被引:1,自引:0,他引:1
rico Marlon de Moraes Flores Jos Neri Gottfried Paniz Ayrton Figueiredo Martins Valderi L. Dressler Edson Irineu Müller Adilson Ben da Costa 《Spectrochimica Acta Part B: Atomic Spectroscopy》2002,57(12):2187-2193
A direct solid sampling flame atomic absorption spectrometric procedure for trace determination of cadmium in biological samples has been developed. Test samples (0.05–2.00 mg) were ground and weighed into small polyethylene vials, which were connected to the device for solid sample introduction into a conventional air/acetylene flame. Test samples were carried as a dry aerosol to a quartz cell, placed between the burner and the optical path, which had a perpendicular entrance and a slit in the upper part. The atomic vapor generated in the flame produced a transient signal that was totally integrated within 1 s. The effect of operating conditions and the extent of grinding on the analytical signal were evaluated. Background signals were always low and a characteristic mass of 0.29 ng Cd was obtained. Calibration was performed using different masses of solid certified reference materials. Results obtained for certified and in-house reference materials were typically within the 95% confidence interval of the certified and/or reference value, and the precision, expressed as relative standard deviation, was between 3.8 and 6.7%. The proposed system is simple and it might be adapted to conventional atomic absorption spectrometers allowing the determination of Cd in more than 80 test samples per hour, excluding weighing. 相似文献
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S M Sheikholeslami 《Pramana》1997,48(3):837-848
We study here the Cabibbo enhanced charmed baryon decays in theSU(4) semidynamical model. The weak Hamiltonian 20″ + 15 + 45 + 45* can have the parity violating amplitude for charmed baryon
decays. Decay width and α for some modes are also calculated. 相似文献
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O. Favaron H. Karami R. Khoeilar S. M. Sheikholeslami L. Volkmann 《Journal of Graph Theory》2010,64(4):323-329
Let G(V, E) be a simple, undirected graph where V is the set of vertices and E is the set of edges. A b‐dimensional cube is a Cartesian product I1×I2×···×Ib, where each Ii is a closed interval of unit length on the real line. The cubicity of G, denoted by cub(G), is the minimum positive integer b such that the vertices in G can be mapped to axis parallel b‐dimensional cubes in such a way that two vertices are adjacent in G if and only if their assigned cubes intersect. An interval graph is a graph that can be represented as the intersection of intervals on the real line—i.e. the vertices of an interval graph can be mapped to intervals on the real line such that two vertices are adjacent if and only if their corresponding intervals overlap. Suppose S(m) denotes a star graph on m+1 nodes. We define claw number ψ(G) of the graph to be the largest positive integer m such that S(m) is an induced subgraph of G. It can be easily shown that the cubicity of any graph is at least ?log2ψ(G)?. In this article, we show that for an interval graph G ?log2ψ(G)??cub(G)??log2ψ(G)?+2. It is not clear whether the upper bound of ?log2ψ(G)?+2 is tight: till now we are unable to find any interval graph with cub(G)>?log2ψ(G)?. We also show that for an interval graph G, cub(G)??log2α?, where α is the independence number of G. Therefore, in the special case of ψ(G)=α, cub(G) is exactly ?log2α2?. The concept of cubicity can be generalized by considering boxes instead of cubes. A b‐dimensional box is a Cartesian product I1×I2×···×Ib, where each Ii is a closed interval on the real line. The boxicity of a graph, denoted box(G), is the minimum k such that G is the intersection graph of k‐dimensional boxes. It is clear that box(G)?cub(G). From the above result, it follows that for any graph G, cub(G)?box(G)?log2α?. © 2010 Wiley Periodicals, Inc. J Graph Theory 65: 323–333, 2010 相似文献
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Keshteli A. Nematpour Sheikholeslami M. 《Journal of Thermal Analysis and Calorimetry》2020,140(1):381-396
Journal of Thermal Analysis and Calorimetry - In current modeling, solidification process within a three-dimensional triplex tube was numerically studied. In two sides, the cold water flow is used... 相似文献
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Sheikholeslami M. Sajjadi H. Amiri Delouei A. Atashafrooz M. Li Zhixiong 《Journal of Thermal Analysis and Calorimetry》2019,136(6):2477-2485
Journal of Thermal Analysis and Calorimetry - New numerical approach has been selected for simulating magnetic force and radiation influences on alumina transportation within a permeable medium. To... 相似文献
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M. SHEIKHOLESLAMI 《应用数学和力学(英文版)》2018,39(9):1341-1352
Forced convection heat transfer of ethylene glycol based nanofluid with Fe_3O_4 inside a porous medium is studied using the electric field. The control volume based finite element method(CVFEM) is selected for numerical simulation. The impact of the radiation parameter(R_d), the supplied voltage(?φ), the volume fraction of nanofluid(?), the Darcy number(Da), and the Reynolds number(Re) on nanofluid treatment is demonstrated. Results prove that thermal radiation increases the temperature gradient near the positive electrode. Distortion of isotherms increases with the enhance of the Darcy number and the Coulomb force. 相似文献