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排序方式: 共有158条查询结果,搜索用时 15 毫秒
31.
M. R. Ganjali Tahereh Poursaberi Fatemeh Basiripour Masoud Salavati-Niassari Mohammad Yousefi Mojtaba Shamsipur 《Analytical and bioanalytical chemistry》2001,370(8):1091-1095
A PVC membrane electrode based on a cadmium–salen (N,N′-bis-salicylidene-1,2ethylenediamine) complex as an anion carrier is described. The electrode has an anti-Hofmeister selectivity
sequence with a preference for thiocyanate at pH 1.5–11.0. It has a linear response to thiocyanate from 1.0 × 10–6 to 1.0 × 10–1 mol L–1 with a slope of 59.1 ± 0.2 mV per decade, and a detection limit of 7 × 10–7 mol L–1. This electrode has high selectivity for thiocyanate relative to many common organic and inorganic anions. The proposed sensor
has a fast response time of approximately 15 s. It was applied to the determination of thiocyanate in a milk sample.
Received: 1 December 2000 / Revised: 19 April 2001 / Accepted: 30 April 2001 相似文献
32.
As a consequence of gravitational induced uncertainty, equation of motion for harmonic oscillator differs considerably from
usual quantum mechanical situation. This paper considers the dynamics of a simple harmonic oscillator in the context of Generalized
(Gravitational) Uncertainty Principle (GUP). Using Heisenberg Picture of quantum mechanics, we find time evolution of position
and momentum operators and we will show that expectation values have an unusual complicated mass dependence. Also we will
show that since the notion of locality breaks down, Ehrenfest theorem is not satisfied for harmonic oscillator in GUP. 相似文献
33.
Phosphate glasses doped with samarium oxide have been made using the melt quenching technique. The density of the glass was
determined using the Archimedes method while the Vickers hardness was measured using a micro-vicker tester. Both density and
hardness have shown an increasing trend with the addition of a small amount of Sm2O3. The refractive index was characterized using UV-visible spectroscopy and the Sellmeier fitting equation was used to verify
the result. The refractive index was found to vary from 1.972 to 1.807 depending on the wavelength and well agreed with the
fitting curve 相似文献
34.
In this report, we try to show the importance of incorporation of name reactions in the sequential cascade reaction in which significantly decreasing the number of steps towards an ideal and practical multi-step synthesis of natural products as well showing virtually all the advantages already mentioned for “Click Chemistry”. In addition, since the chiral inductions are desired for most of these sequential name reactions, their asymmetric catalyzed reactions were also described. 相似文献
35.
Novel sulfate ion-selective polymeric membrane electrode based on a derivative of pyrilium perchlorate 总被引:1,自引:0,他引:1
Ganjali MR Naji L Poursaberi T Taghizadeh M Pirelahi H Yousefi M Yeganeh-Faal A Shamsipur M 《Talanta》2002,58(2):359-366
A sulfate ion-selective PVC membrane sensor based on 4-(4-bromophenyl)-2,6-diphenylpyrilium perchlorate (BDPP) as a novel sensing material is successfully developed. The electrode shows a good selectivity for sulfate ion with respect to common organic and inorganic anions. The sensor exhibits a good linear response with slope of -28.9+/-0.5 mV per decade over the concentration range of 1.0x10(-6)-1.0x10(-2) M, and a detection limit of 8.0x10(-7) M of SO(4)(2-) ions. The electrode response is independent of pH in the range of 4.0-9.0. The proposed sensor was applied as an indicator electrode in potentiometric titration of sulfate and barium ions, and to the determination of zinc in zinc sulfate tablets. 相似文献
36.
An optical chemical sensor based on immobilization of 2-(5-bromo-2-pyridylazo)-5-(diethylamino)phenol (Br-PADAP) in Nafion membrane is described. The membranes were cast onto glass substrates and were used for the determination of nickel in aqueous solutions by spectrophotometry. The sensor system is highly transparent, mechanically stable and showed no evidence of reagent leaching. The influence of several parameters such as pH, ligand concentration, and type and concentration of regenerating solution were optimized. The sensor system showed good sensitivity in the range 0.5-20 μg ml−1 with a detection limit of 0.3 μg ml−1 Ni(II). The sensor has been incorporated into a home-made flow-through cell for determination of nickel in flowing streams with improved sensitivity, precision and detection limit. The calibration curve in the flow system was linear in the range 0.1-16 μg ml−1 with a detection limit of 0.07 μg ml−1. The sensor is easily regenerated by dilute nitric acid solution. The proposed method was successfully applied to the determination of nickel content in vegetable oil and chocolate samples and the results were compared with those obtained using atomic absorption spectrometry. 相似文献
37.
Mahmoud Mirmehrabi Sohrab Rohani Michael C. Jennings 《Acta Crystallographica. Section C, Structural Chemistry》2005,61(12):o695-o698
The crystal structure of the title compound (systematic name: 2′,3′‐didehydro‐2′,3′‐deoxythymidine), C10H12N2O4, consists of two molecules in the asymmetric unit bound together by hydrogen bonds. The conformational geometry differentiates this form of stavudine from its two previously published polymorphs. In addition, a different hydrogen‐bonding scheme is observed compared with the previous two structures. This polymorph is the thermodynamically most stable form of the antiviral drug, as evidenced by differential scanning calorimetry (DSC) and IR data. 相似文献
38.
Abdolali Alizadeh Tahereh Firuzyar Azadeh Mikaeili 《Journal of heterocyclic chemistry》2013,50(3):676-679
An efficient, one‐pot synthetic protocol for polyfunctionalized 1,4‐dihydropyridine‐fused‐1,3‐diazaheterocycles, a class of biologically active compounds, starting from 1,1‐bis(methylthio)‐2‐nitroethylene, 1,n‐diamine, arylaldehyde, and malononitrile is described. The reactions are completed within 12–15 h under refluxing conditions and in the presence of 10 mol % of piperidine as a basic catalyst to produce the title compounds in 60–75% yields. 相似文献
39.
Solgi Mehri Khazaei Ardeshir Akbarpour Tahereh 《Research on Chemical Intermediates》2022,48(6):2443-2468
Research on Chemical Intermediates - In the present study, magnetic nanocatalysts coated by carbon quantum dots (CQDs) and organic functional groups (Fe3O4@CQD@Si(OEt)(CH2)3@melamine@TC@Ni(NO3))... 相似文献
40.
Tahereh Khajvand Olia Alijanpour Mohammad Javad Chaichi Majid Vafaeezadeh Mohammad Mahmoodi Hashemi 《Analytical and bioanalytical chemistry》2015,407(20):6127-6136
The effects of six synthetic imidazolium-based ionic liquids (ILs) on the CuII-catalyzed chemiluminescence of lucigenin (Luc-CL) in the pH range 6.0–11 were investigated. Preliminary experiments found that the CL emission was strongly enhanced or inhibited in the presence of the ILs. The degree of enhancement or inhibition of the CL intensity in the presence of each IL was related to the molecular structure of the IL, the medium used, and the pH. The maximum enhancement of the CL intensity was observed at pH 9.0 (amplification factor?=?443). This decrease in the pH at which maximum CL enhancement occurred and the substantial signal amplification of the Luc-CL may be related to a strong interaction between CuII and the imidazolium ring of superior ILs at this pH. Additionally, the formation of IL microdomains in semi-aqueous media permitted more solubility of the product yielded by the Luc-CL reaction (N-methylacridone), which could increase the CL intensity. To obtain consistent data on the catalytic efficiency of CuII in the presence of various ILs as well as the corresponding CL emission intensities, fluorescence quantum yields (Φ F) of lucigenin were measured under the same conditions. Comparison of the data pointed to the mechanism that controls the properties of Luc-CL in the presence of the CuII/IL complexes. Based on the catalytic effect of the CuII/IL complex and the measurement of the enzymatically generated H2O2, a novel, simple, and sensitive CL method for determining glucose with a detection limit (LoD) of 6.5 μM was developed. Moreover, this method was satisfactorily applied to the determination of glucose in human serum and urine samples. 相似文献