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91.
Nano-sized nickel ferrite (NiFe2O4) and cobalt ferrite particles (CoFe2O4) were successfully synthesized using a hydrothermal method. Techniques of X-ray diffraction, scanning electron microscope, Fourier transform infrared spectrometer, energy dispersive X-ray spectroscopy, vibrating sample magnetometer and transmission electron microscope have been used to characterize and study the as-synthesized NiFe2O4 and CoFe2O4 products. The results showed that the average size of the nickel and cobalt ferrite nanoparticles is smaller than 10 and 100 nm, respectively. The results of magnetic measurement showed that the synthesized NiFe2O4 and CoFe2O4 nanoparticles were superparamagnetic and soft ferromagnetic materials, respectively. Study of adsorption behavior showed that these nanoparticles can act as a good adsorbent for removing Pb2+. 相似文献
92.
Mohammad Haeri Mahsa Dehghani 《Communications in Nonlinear Science & Numerical Simulation》2009,14(3):880-891
In this paper the impulsive synchronization of general continuous chaotic and hyperchaotic systems is investigated. The robust stability of the synchronization method is examined in the presence of uncertainties both on linear and nonlinear parts of the system dynamics and the channel noise. Conditions on the impulse distances are derived for different cases. Numerical simulations are presented to show the effectiveness of the method. 相似文献
93.
Mohammad Mazloum Ardakani Hossein Dehghani Maryam Jalayer Hamid R Zare 《Analytical sciences》2004,20(12):1667-1672
The performance of silver metal complexes with meso-tetraphenylporphyrin ([H2T(4-CH3)]PP) as ionophores for ion-selective electrodes was studied. The electrode exhibited linear response with Nernstian slope of 59.2 +/- 1.0 mV per decade within the concentration range of 1.0 x 10(-7)-1.0 x 10(-1) M silver ions. The limit of detection as determined from the intersection of the extrapolated linear segments of the calibration plot, was 1.0 x 10(-7) M. The response time of the electrode was < 10 s over the entire concentration range. The silver-selective electrode exhibited good selectivity for Ag(I) with respect to alkali, alkaline earth and heavy metal ions. The electrodes could be used at least three months without a considerable divergence in their potential. The electrodes are suitable for use in aqueous solutions in a wide pH range of 3.0-9.0. They were used as indicator electrodes in titration of Ag(I) with sodium iodide solution and were successfully applied to direct determination of silver in real samples. 相似文献
94.
Majid M. Heravi Vahideh Zadsirjan Mahzad Dehghani Nastaran Hosseintash 《Tetrahedron: Asymmetry》2017,28(5):587-707
The aldol reaction is one of the most important carbon–carbon bond formations in synthetic organic chemistry. An enantioselective aldol reaction should provide an enantioenriched product. The organocatalytic asymmetric aldol reaction via an in situ generated enamine intermediate is one of the most powerful synthetic tools to achieve enantiomerically pure products. This approach is often used to obtain chiral β-hydroxycarbonyl compounds with excellent enantioselectivity. In this report, we update our previous review regarding the applications of organocatalysts in asymmetric aldol reactions leading to chiral β-hydroxycarbonyl compounds as versatile synthetic motifs frequently found in pharmaceutically desired intermediates and biologically active naturally occurring compounds. 相似文献
95.
An on-line solid phase extraction (SPE) preconcentration system coupled to flame atomic absorption spectrometer (FAAS) was developed for determination of copper and cadmium at μg L−1 level. The method is based on the on-line retention of copper and cadmium on a microcolumn of alumina modified with sodium dodecyl sulfate (SDS) and 1,10-phenanthroline and subsequent elution with ethanol and determination by FAAS. The effect of chemical and flow variables that could affect the performance of the system was investigated. The relative standard deviation (n = 6) at 20 μg L−1 level for copper and cadmium were 1.4 and 2.2% and the corresponding limits of detection (based on 3σ) were 0.04 and 0.14 μg L−1, respectively. The method was successfully applied to determination of copper and cadmium in human hair and water samples. 相似文献
96.
Hossein Dehghani Fatemeh Behnoudnia Mohammad Reza Mansournia Sara Bakhshayesh 《Journal of solution chemistry》2009,38(6):771-778
A spectrophotometric method was used for the molecular complexation of ICl3 with para-substituted meso-tetraarylporphyrins (H2t(4-X)pp; X: OCH3, CH(CH3)2, CH3, H and Cl) in methanol/chloroform (2.5% v/v) solution. The equilibrium constants and the thermodynamic parameters were measured
spectrophotometrically at various temperatures for 1:1 molecular complex formation of meso-tetraarylporphyrins as electron
donors with ICl3 as the electron acceptor. The formation constants for the molecular complexes change according to the following trend: [ICl3(H2t(4-OCH3)pp)]>[ICl3(H2t(4-CH(CH3)2)pp)]>[ICl3(H2t(4-CH3)pp)]>[ICl3(H2tpp)]>([ICl3(H2t(4-Cl)pp)]. Further, the thermodynamic parameters, ΔG
o,ΔH
o and ΔS
o, for formation of the complexes were obtained. 相似文献
97.
S. H. Hendi A. Sheykhi M. H. Dehghani 《The European Physical Journal C - Particles and Fields》2010,70(3):703-712
In this paper, we study topological AdS black branes of (n+1)-dimensional Einstein–Maxwell-dilaton theory and investigate their properties. We use the area law, surface gravity and
Gauss law interpretations to find entropy, temperature and electrical charge, respectively. We also employ the modified Brown
and York subtraction method to calculate the quasilocal mass of the solutions. We obtain a Smarr-type formula for the mass
as a function of the entropy and the charge, compute the temperature and the electric potential through the Smarr-type formula
and show that these thermodynamic quantities coincide with their values which are calculated through using the geometry. Finally,
we perform a stability analysis in the canonical ensemble and investigate the effects of the dilaton field and the size of
black brane on the thermal stability of the solutions. We find that large black branes are stable but for small black brane,
depending on the value of dilaton field and type of horizon, we encounter with some unstable phases. 相似文献
98.
We consider the existence of Taub–NUT solutions in third order Lovelock gravity with cosmological constant, and obtain the general form of these solutions in eight dimensions. We find that, as in the case of Gauss–Bonnet gravity and in contrast with the Taub–NUT solutions of Einstein gravity, the metric function depends on the specific form of the base factors on which one constructs the circle fibration. Thus, one may say that the independence of the NUT solutions on the geometry of the base space is not a robust feature of all generally covariant theories of gravity and is peculiar to Einstein gravity. We find that when Einstein gravity admits non-extremal NUT solutions with no curvature singularity at r=N, then there exists a non-extremal NUT solution in third order Lovelock gravity. In 8-dimensional spacetime, this happens when the metric of the base space is chosen to be CP3. Indeed, third order Lovelock gravity does not admit non-extreme NUT solutions with any other base space. This is another property which is peculiar to Einstein gravity. We also find that the third order Lovelock gravity admits extremal NUT solution when the base space is T2×T2×T2 or S2×T2×T2. We have extended these observations to two conjectures about the existence of NUT solutions in Lovelock gravity in any even-dimensional spacetime. 相似文献
99.
Based on the generalized uncertainty relation, the corrected Beckenstein–Hawking black hole entropy in the higher dimensional space–times is calculated. Using the corrected entropy, the black hole radiation is obtained in the tunneling formalism. 相似文献
100.
A nanoscale gradient continuum theory along with molecular dynamics simulations are employed to investigate the size-dependent surface energy of nanoplates. Molecular dynamics simulations reveal that upon nanoplate thickness reduction, the redistribution of surface energy density along thickness direction causes the decrease of the surface energy of nanoplate free surfaces. Via introducing a calibration benchmark, the length scale model parameter of the gradient continuum theory is methodically determined. The calibrated continuum theory is shown to well predict the size-dependent surface energy and the associated redistribution of surface energy density within nanoplates. 相似文献