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排序方式: 共有452条查询结果,搜索用时 55 毫秒
441.
S. Tangestaninejad M. Moghadam V. Mirkhani I. Mohammadpoor-Baltork K. Ghani 《Journal of the Iranian Chemical Society》2008,5(1):S71-S79
A new heterogeneous catalyst prepared by immobilization of MO2(acac)2 on Mobil Catalytic Material, MCM-41, is reported. This catalyst, MoO2(acac)2-MCM-41, was successfully applied for efficient epoxidation of olefins with tert-BuOOH in 1,2-dichloroethane as solvent. The catalyst was characterized by elemental analysis, FT-IR, UV-Vis, X-ray diffraction (XRD), and scanning electron microscopy (SEM). This catalyst can be reused several times without significant loss of its catalytic activity. 相似文献
442.
Aerial parts essential oil of Nepeta betonicifolia and N. saccharata were obtained by hydrodistillation and analysed by GC-FID and GC-MS. Thirty-three and eighteen components represented 97.9% and 98.2% of the total oils identified, respectively. Main compounds of the oil of N. betonicifolia were 4aα,7β,7aα-nepetalactone (42.0%), germacrene D (6.0%), triplal (5.2%), 1-nor-bourbonanone (4.0%) and 1,8-cineole (3.2%). The principal constituents of the essential oil of N. saccharata were found to be 4aβ,7α,7aβ-nepetalactone (66.9%), germacrene D (12.9%), sabinene (6.5%) and trans-caryophyllene (3.3%). The radical scavenging capacity (RSC) of methanol extracts and chloroform, butanol and water subfractions of aerial parts of N. betonicifolia and N. saccharata were evaluated by using DPPH, FRAP and ABTS assays. TPC of each extract was measured using Folin-Ciocalteau. The antioxidant activity of the butanolic subfractions of both plants was higher than other extracts examined. 相似文献
443.
Maryam Zakeri Majid Moghadam Iraj Mohammadpoor-Baltork Shahram Tangestaninejad Valiollah Mirkhani Ahmad Reza Khosropour Mohammad Alizadeh 《Transition Metal Chemistry》2012,37(1):45-53
The biomimetic epoxidation of alkenes catalyzed by tetraphenylporphyrinatomanganese(III) chloride, [Mn(TPP)Cl], immobilized
on multiwall carbon nanotubes modified with 4-aminopyridine and 4-aminophenol is reported. These heterogenized catalysts were
used as efficient and reusable catalysts for epoxidation of a variety of cyclic and linear alkenes with sodium periodate under
mild conditions. The catalysts, [Mn(TPP)Cl@amine-MWCNT], were characterized by physico-chemical and spectroscopic methods.
The effect of ultrasonic irradiation on these catalytic systems was also investigated. The catalysts were reused several times
without loss of their activity. 相似文献
444.
Seyed Mojtaba Taghizadeh Yadollah YaminiMohammad Hosein Naeeni Fatemeh MohamadniaReza Sardeh Moghadam 《Polymer Testing》2012,31(2):297-303
A simple and efficient method based on hollow fiber protected headspace liquid-phase in conjunction with high performance liquid chromatography has been introduced for extraction and determination of three residual monomers (2-ethylhexyl acrylate (EHA), vinyl acetate (VA), glycidyl methacrylate (GM)) in polymer latex. Using this methodology, the analytes of interest extracted from a sample are led into organic solvent located inside the porous hollow fiber membrane. Initially, several experimental parameters were controlled and optimized and the optimum conditions were reached with 8 cm neatly cut hollow fibers containing heptanol, which were exposed to the headspace of a 12 mL sample solution containing 20% (w/v) NaCl thermostated at 110 °C and stirred at 800 rpm for 20 min. Finally, 20 μL of the extraction solution was withdrawn into a syringe and injected into HPLC for analysis. The calibration curves were linear (r2 ≥ 0.994) over the concentration range of 0.05-10 mg L−1 for VA and 0.02-10 mg L−1 for other analytes. The relative standard deviation (RSD%) for three-replicate extractions and measurements was below 8.6%. The limits of detection of this method for quantitative determination of the analytes were found within the range of 0.005 to 0.011 mg kg−1 with the enrichment factors within the 5-164 range. The method was successfully applied for determination of residual monomers in polymer latex. 相似文献
445.
Peyman Niroomand 《Ricerche di matematica》2012,61(2):341-346
By a well-known result of Green (Proc R Soc A 237:574?C581, 1956) and the formal definition of Ellis and Wiegold (Bull Austral Math Soc 60:191?C196, 1999), there is an integer t, say corank(G), such that ${|\mathcal{M}(G)| = p^{\frac{1}{2}n(n-1)-t}}$ . In Niroomand (J Algebra 322:4479?C4482, 2009), the author showed for a non-abelian group G, corank(G)????log p (|G|)?2 and classified the structure of all non-abelian p-groups of corank log p (|G|)?2. In the present paper, we are interesting to characterize the structure of all p-groups of corank log p (|G|)?1. 相似文献
446.
The charm quark contribution to the proton structure function (SF) is investigated in the leading-order (LO) QCD at small
x region. A next-to-leading order (NLO) QCD analysis for the proton SF is made within the
renormalization scheme of the radiation parton evolution model (DGLAP). The valence quark distribution is obtained from the
relativistic quark-exchange calculation for the
mirror nuclei, i.e., 3He and 3H, which is based on a realistic model. The inverse Mellin technique is performed to extract the parton distribution in the
(x, Q
2)-plane. The calculated F
2
c
(x, Q
2) and F
2
p
(x, Q
2) as well as the longitudinal SF, F
L
p
(x, Q
2) are compared with the experimental data available at present, namely H1, ZEUS, and HERMES at HERA ring as well as other
theoretical models, especially the hard pomeron phenomenological model. 相似文献
447.
E. Bavafaye-Haghighi M.J. Yazdanpanah B. Kalaghchi H. Soltanian-Zadeh 《Mathematical and Computer Modelling》2009,49(7-8):1449-1464
Although Multiscale Cancer Modeling has a realistic view in the process of tumor growth, its numerical algorithm is time consuming. Therefore, it is problematic to run and to find the best treatment plan for chemotherapy, even in case of a small size of tissue. Using an artificial neural network, this paper simulates the multiscale cancer model faster than its numerical algorithm. In order to find the best treatment plan, it suggests applying a simpler avascular model called Gompertz. By using these proposed methods, multiscale cancer modeling may be extendable to chemotherapy for a realistic size of tissue.In order to simulate multiscale model, a hierarchical neural network called Nested Hierarchical Self Organizing Map (NHSOM) is used. The basis of the NHSOM is an enhanced version of SOM, with an adaptive vigilance parameter. Corresponding parameter and the overall bottom-up design guarantee the quality of clustering, and the embedded top-down architecture reduces computational complexity.Although by applying NHSOM, the process of simulation runs faster compared with that of the numerical algorithm, it is not possible to check a simple search space. As a result, a set containing the best treatment plans of a simpler model (Gompertz) is used. Additionally, it is assumed in this paper, that the distribution of drug in vessels has a linear relation with the blood flow rate. The technical advantage of this assumption is that by using a simple linear relation, a given diffusion of a drug dosage may be scaled to the desired one.By extracting a proper feature vector from the multiscale model and using NHSOM, applying the scaled-best treatment plans of Gompertz model is done for a small size of tissue. In addition, simulating the effect of stress reduction on normal tissue after chemotherapy is another advantage of using NHSOM, which is a kind of “emergent”. 相似文献
448.
Amin Yazdanpanah Goharrizi Ali Khaki-Sedigh Nariman Sepehri 《Chaos, solitons, and fractals》2009,41(5):2448-2455
A new approach to adaptive control of chaos in a class of nonlinear discrete-time-varying systems, using a delayed state feedback scheme, is presented. It is discussed that such systems can show chaotic behavior as their parameters change. A strategy is employed for on-line calculation of the Lyapunov exponents that will be used within an adaptive scheme that decides on the control effort to suppress the chaotic behavior once detected. The scheme is further augmented with a nonlinear observer for estimation of the states that are required by the controller but are hard to measure. Simulation results for chaotic control problem of Jin map are provided to show the effectiveness of the proposed scheme. 相似文献
449.
The notion of the exterior centralizer CGù(x){C_G^{^\wedge}(x)} of an element x of a group G is introduced in the present paper in order to improve some known results on the non-abelian tensor product of two groups.
We study the structure of G by looking at that of CGù(x){C_G^{^\wedge}(x)} and we find some bounds for the Schur multiplier M(G) of G. 相似文献
450.
Mohammad Reza Aziziyan Narjes Moghadam Davood Fathi Vahid Ahmadi 《Applied Physics A: Materials Science & Processing》2012,109(2):481-488
The effects of uniaxial and torsional strains on the double-lightly doped MOSCNT (DLD-MOSCNT) performances are investigated, using the non-equilibrium Green function (NEGF) formalism in mode space approach. The Hamiltonian of the device is obtained by a tight-binding approximation assuming that only p z orbitals are contributing in carrier transport. In all simulation processes, one mode with the lowest subband is considered. DLD-MOSCNT has a small band-to-band tunneling and almost eliminates the ambipolar behavior of I DS–V GS characteristics because of the band engineering. We use a modified model to demonstrate the strain effects on such a low OFF-current device. The results show that the strain effects mainly depend on the chiral vector and diameter of CNT. The strain causes band gap and carrier velocity changes, which result in variation of ON- or OFF-current. In addition, the subthreshold swing of this device under uniaxial strain is calculated, which is about 61 mV/Dec for 2 % tensile strain in (16,0) and for ?2 % compressive strain in (17,0). Under the uniaxial strain, in the case that the energy band gap increases, the variation of DIBL is very small. 相似文献