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91.
Structural and electronic properties of a bistable redox-responsive molecular switch based on dibenzo[1,2]dithiine (PSBH) were studied using the DFT-B3LYP/6-31G* method. The results confirmed that the electrical conductivity of the closed form of considered molecular switch is higher than that of the open form. NBO electric charges on heavy atoms of biphenyl unit revealed that the positive charge on sulfur atoms reinforced, which caused the collapse of disulfide bond. 相似文献
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Yadollah Yamini Mohammad Rezaee Alireza Khanchi Mohammad Faraji Abolfazl Saleh 《Journal of chromatography. A》2010,1217(16):2358-2364
A simple, rapid and efficient dispersive liquid–liquid microextraction based on the solidification of floating organic drop (DLLME–SFO) method, followed by inductively coupled plasma-optical emission spectrometry (ICP-OES) was developed for the simultaneous preconcentration and determination of heavy metals in water samples. One variable at a time method was applied to select the type of extraction and disperser solvents. Then, an orthogonal array design (OAD) with OA16 (45) matrix was employed to study the effects of different parameters on the extraction efficiency. Under the best experimental conditions (extraction solvent: 140 μL of 1-undecanol; disperser solvent: 2.0 mL of acetone; ligand to metal mole ratio: 20; pH: 6 and without salt addition), the enhancement factor ranged from 57 to 96. The calibration graphs were linear in the range of 0.5–250 μg L−1 for Mn, 1.25–250 μg L−1 for Cr, Co and Cu with correlation coefficient (r) better than 0.990. The detection limits were between 0.1 and 0.3 μg L−1. Finally, the developed method was successfully applied to extraction and determination of the mentioned metal ions in the tap, sea and mineral water samples and satisfactory results were obtained. 相似文献
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Chemical speciation and contamination assessment of Zn and Cd by sequential extraction in surface sediment of Klang River, Malaysia 总被引:2,自引:0,他引:2
The concentration and chemical speciation of Cd and Zn as well as total organic carbon (TOC) were studied in surface sediments from 21 stations along Klang River. Sequential extraction technique (SET) was applied to assess the four (exchangeable, acid-reducible, oxidisable-organic and residual) fractions in surface sediment. And also, to obtain an overall classification of cadmium and zinc pollution in this area. This investigation was the first study on the basis of the chemical speciation of Cd and Zn in surface sediments of the Klang River. The total concentrations of metals were ranged (0.60–2.26 µg g− 1) for Cd and (33.26–268.24 µg g− 1) for Zn. The chemical speciation of Cd and Zn in most sampling stations were in the order of residual > acid-reducible > oxidisable-organic > exchangeable, and it showed that the Zn in Klang River surface sediments existed in the nonresistant fractions, whilst Cd existed in the resistant fraction. The degree of surface sediments contamination was determined for individual contamination factors (ICF) and global contamination factor (GCF). The result of ICF and GCF values showed that those stations located vicinity of municipal area had high potential risk to fauna and flora of the Klang River. The relationship between the concentration of cadmium and zinc at the oxidation-organic fraction with TOC in surface sediment was identified. The results showed that TOC had a positive function to complex with Cd and Zn in the surface sediment of Klang River. 相似文献
94.
A convenient, efficient and green synthesis of N‐heteroaryl aminonaphthols has been developed by one‐pot, three‐component condensation of β‐naphthol, heteroaryl amines and substituted benzaldehydes under solvent‐free conditions at elevated temperature. The advantages of these reactions are simplicity of the reaction procedure, short reaction times, simple work‐up, catalyst‐free conditions and pure products in good to excellent yields. 相似文献
95.
Farshid Samadi Abolfazl Mirzazadeh Mir Mohsen Pedram 《Applied Mathematical Modelling》2013,37(10-11):6683-6694
In the real world markets, demand is influenced by different parameters. Recently, many researchers have been interested in integrated production and marketing planning strategies in inventory models where demand depends on different parameters such as price and/or marketing expenditure. The quality of services that are offered to customers of a product is one of the most important parameters that affects demand in the real markets and has not been considered in development of inventory models. On the other hand, the cost parameters in real inventory systems and other parameters such as price, marketing and service elasticity to demand are imprecise and uncertain in nature. So, the notion of fuzziness can be applied to cope with this uncertainty. In this paper, a new fuzzy profit maximization inventory model with shortages is proposed. The demand is considered as a power function of price, marketing expenditure and service expenditure. Furthermore, unit cost is determined as a power function of order quantity. Since the proposed model is in a fuzzy environment, a fuzzy decision should be made to meet the decision criteria, and the results should be fuzzy. Therefore, the proposed model is formulated and solved using geometric programming and fuzzy optimization techniques to derive an approximation of the results’ membership functions. The model is illustrated with a numerical example and finally a case study is provided for evaluation and validation of the results of model. 相似文献
96.
Stoichiometric reaction of 2‐aminopyrimidine with formaldehyde in the presence of formic acid catalyst in water gave N,N′‐bis(2‐pyrimidinyl)methanediamine ( 5 ). Subsequent cyclocondensation of 5 with glyoxal in alcohol (MeOH, EtOH, PrOH and i‐PrOH) under reflux conditions led to the formation of the corresponding 4,5‐dialkoxy‐1,3‐bis(2‐pyrimidinyl)imidazolidines ( 6a‐d ). 4,5‐Dihydroxy‐1,3‐bis(2‐pyrimidinyl) imidazolidine ( 6e ) was obtained when the reaction was carried out in acetonitrile. Based on 1H NMR analysis, it was found that the trans‐dialkoxyimidazolidines ( 6 ) were selectively obtained in these cyclocondensation reactions. 相似文献
97.
A hydrophilic transparent triacetyl cellulose membrane was adopted as a pH optode by immobilizing highly selective and sensitive Nile blue indicator on the membrane. Contrary to the common procedure for determinations using optodes, in which a steady state response is measured, a new approach is introduced in which the dynamic response of the optode is used as the analytical signal. While in common procedures, pH optodes exhibit limited linear dynamic range (often 2–4 pH units only), it is shown that in a time-based flow method, an optode with only one acid-base indicator can be used for measurement in the pH range of 0–10. The procedure is simple, inexpensive and rapid. 相似文献
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A one-pot, three-component, Mannich condensation of electron-rich aromatic compounds such as 5-methyl-2-hydroxyphenyl sulfide, 2-aminopyrimidine, and various aromatic aldehydes were used to prepare a series of new unsymmetrical multidentate aminophenol ligands. These compounds were synthesized in solvent-free conditions as a fast, simple, convenient, and uncatalyzed method. Details of the reaction conditions are discussed. 相似文献