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排序方式: 共有741条查询结果,搜索用时 15 毫秒
1.
Mohammad Reza Ganjali Morteza Rezapour Mohammad Reza Pourjavid Masoud Salavati-Niasari 《Analytical sciences》2003,19(8):1127-1131
A cobalt(II) derivative was used as a suitable ionophore for the preparation of a polymeric membrane nitrite-selective electrode. The electrode reveals a Nemstian behavior over a very wide NO2- ion concentration range (1.0 x 10(-6)-1.0 x 10(-1) M) and a very low detection limit (5.0 x 10(-7) M). The potentiometric response is independent of the pH of solution in the pH range 4.0-9.5. The electrode shows advantages such as low resistance, fast response and, most importantly, good selectivity relative to a wide variety of inorganic and organic anions. In fact, the selectivity behavior of the proposed NO2- ion-selective electrode shows great improvements compared to the previously reported electrodes for nitrite ion. The proposed electrodes could be used for at least 2 months without any significant changes in potentials. The electrode was successfully applied to the determination of nitrate ion concentrations in sausage and milk samples. 相似文献
2.
Sodium-dicyclohexyl- 18-crown-6 complex cation was used as carrier for the uphill transport of zinc as Zn(SCN)42? complex anion. By using L-cysteine as a metal ion acceptor in the receiving phase at the optimized pH of 7.6, the amount of zinc transport through the liquid membrane after 90 min was 97.2 ± 1.0%. The selectivity and efficiency of zinc transport from aqueous solutions containing equimolar mixtures of Ag+, Cd2+ Co2+, Cu2+, Fe2+, Ni2+, Pb2+, Pd2+, Sr2+, Bi3+, Cr3+ and Fe3+ ions was investigated. In the presence of NH2OH.HCl as a suitable masking agent in the source phase, the interfering effect of Cu2+ and Pb2+ ions was diminished drastically. 相似文献
3.
Summary In the present study the effects of addition of iron on the catalytic activity and Si tolerability of Pt/g-Al2O3in the total oxidation of volatile organic compounds were investigated. Preliminary results showed that there is a noticeable
improvement effect on Si-tolerance of catalyst, particularly for short term poison exposure. Bulk analysis of deposited silicon
on the catalyst surface indicated that both Pt/g-Al2O3and iron-doped pellets had roughly the same silicone uptakes. Deactivation of catalyst was reversible and much faster for
iron doped sample. The promoting effects of iron were related to its electronegativity and, to blocking of fewer Pt sites
when iron is present at the surface of the catalyst. 相似文献
4.
An investigation of dynamic mechanical, thermal, and electrical properties of housing materials for outdoor polymeric insulators 总被引:1,自引:0,他引:1
The present paper reports the results about a study of mechanical, thermal, dynamic mechanical and electrical properties of housing (weather shed) materials for outdoor polymeric insulators. Silicone rubber, ethylene-propylene-diene monomer (EPDM) and alloys of silicon-EPDM are known polymers for use as housing in high voltage insulators. The result of dynamical mechanical measurement shows that the storage modulus of blends enhances with increase EPDM in formulation. It can be seen from the result of TGA measurement that initial thermal degradation of silicone rubber improves by the effect of EPDM in blends. The blends of silicone-EPDM show good breakdown voltage strength compared to silicone rubber. Surface and volume resistance of silicone rubber improve by EPDM content. The mechanical properties of EPDM such as strength, modulus and elongation at break improve by silicone. 相似文献
5.
Milad Tavassoli Mahmood Alizadeh Sani Arezou Khezerlou Ali Ehsani Gholamreza Jahed-Khaniki David Julian McClements 《Molecules (Basel, Switzerland)》2022,27(10)
Nanocomposite biopolymer materials containing colorimetric pH-responsive indicators were prepared from gelatin and chitosan nanofibers. Plant-based extracts from barberry and saffron, which both contained anthocyanins, were used as pH indicators. Incorporation of the anthocyanins into the biopolymer films increased their mechanical, water-barrier, and light-screening properties. Infrared spectroscopy and scanning electron microscopy analysis indicated that a uniform biopolymer matrix was formed, with the anthocyanins distributed evenly throughout them. The anthocyanins in the composite films changed color in response to alterations in pH or ammonia gas levels, which was used to monitor changes in the freshness of packaged fish during storage. The anthocyanins also exhibited antioxidant and antimicrobial activity, which meant that they could also be used to slow down the degradation of the fish. Thus, natural anthocyanins could be used as both freshness indicators and preservatives in biopolymer-based nanocomposite packaging materials. These novel materials may therefore be useful alternatives to synthetic plastics for some food packaging applications, thereby improving the environmental friendliness and sustainability of the food supply. 相似文献
6.
7.
Dr. Tana Koudelakova Dr. Radka Chaloupkova Dr. Jan Brezovsky Dr. Zbynek Prokop Dr. Eva Sebestova Dr. Martin Hesseler Dr. Morteza Khabiri Maryia Plevaka Daryna Kulik Dr. Ivana Kuta Smatanova Dr. Pavlina Rezacova Dr. Rudiger Ettrich Prof. Uwe T. Bornscheuer Prof. Jiri Damborsky 《Angewandte Chemie (International ed. in English)》2013,52(7):1959-1963
8.
A template-free seeded short-time in situ hydrothermal treatment was carried out in a brass autoclave to synthesize crystalline mordenite (MOR) membranes on alumina-silicate disk supports with micro-scale pores. According to XRD analysis, MOR was the only zeolitic material present in the membrane layers on the supports. SEM examination of the membranes showed three different layers of the membrane thickness: (i) support sub-layer, (ii) mix penetrated mid-layer, the MOR crystals filling the pores among the support (about 4–5 μm), and (iii) MOR top-layer (about 4–5 μm). The crystalline bonds between MOR crystals of the membrane top-layer and the crystals of the support were clearly observed within the mid-layer. The continuous top-layer of zeolitic membrane was formed by many large and well-shaped crystals. The seeding treatment significantly enhanced the formation of MOR crystals onto the surface of the supports. EDAX analysis showed a Si/Al ratio of 6.8 for the MOR layer of the membrane. Due to their hydrophilic natures, the polycrystalline MOR membranes were found to be selective for continuous dehydration of different EtOH–water mixtures through an adsorption–diffusion–desorption mechanism. Both total permeation flux and separation factor of the membrane were found to increase by increasing temperature and water concentration of feed. The continuity and high crystallinity of the membrane top-layer led to the fairly high dehydration of EtOH. It was found that there was no pinhole within the layer and the morphology of the membrane was almost defect-free. 相似文献
9.
Let G be a 2k-edge-connected graph with and let for every . A spanning subgraph F of G is called an L-factor, if for every . In this article, we show that if for every , then G has a k-edge-connected L-factor. We also show that if and for every , then G has a k-edge-connected L-factor. 相似文献
10.
Reaction pathways of ethylene and carbon monoxide on the singlet and triplet potential energy surfaces (PESs) have been calculated at B3LYP/6-311++G (3df, 3dp), G3B3 and CCSD(T)//B3LYP levels. Reaction mechanisms have been investigated by analysis of various structures. Suggested reaction mechanisms reveal that 3P3(CH2CHCHO) and 3P4(CH3CCHO) are thermodynamically stable adducts with the negative value in Gibbs free energies on the triplet PES. In addition, results show that one intersystem crossing exists between triplet and singlet PESs, which are obtained by scanning of the C–C bond length in 1IN3 and 3IN7 species. 相似文献