排序方式: 共有17条查询结果,搜索用时 15 毫秒
1.
Nevenka Rajic Djordje Stojakovic Aleksander Recnik 《Journal of Physics and Chemistry of Solids》2011,72(6):800-803
Nanoparticles of NiO, ZnO and Cu2O crystallize when the Ni-, Zn- and Cu-exchanged natural clinoptilolite, respectively, are dehydrated by heating in air at 550 °C. The dehydration of Mn-exchanged clinoptilolite does not lead to the crystallization of manganese oxide but affects the crystallinity of the host clinoptilolite lattice, which becomes amorphous. The NiO, ZnO and Cu2O nanoparticles are found to be randomly dispersed in the clinoptilolite matrix. The particle size varies from 2 to 5 nm and exceeds the aperture of the clinoptilolite channel (approximately 0.4 nm), suggesting that the crystallization of the oxide phases takes place on the surfaces of clinoptilolite microcrystals. 相似文献
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Nevenka Rajic Djordje Stojakovic Natasa Zabukovec Logar Venceslav Kaucic 《Applied Surface Science》2010,257(5):1524-1532
The natural zeolite tuff (clinoptilolite) from a Serbian deposit has been studied as adsorbent for Ni(II) ions from aqueous solutions. Its sorption capacity at 298 K varies from 1.9 mg Ni g−1 (for the initial solution concentration of 100 mg Ni dm−3) to 3.8 mg Ni g−1 (for C0 = 600 mg Ni dm−3) and it increases 3 times at 338 K. The sorption is best described by the Sips isotherm model. The sorption kinetics follows the pseudo-second-order model, the activation energies being 7.44, 5.86, 6.62 and 6.63 kJ mol−1 for C0 = 100, 200, 300 and 400 mg Ni dm−3, respectively. The sorption involves a film diffusion, an intra-particle diffusion, and a chemical cation-exchange between the Na+ ions of clinoptilolite and the Ni2+ ions. The sorption is endothermic (ΔH° being 37.9, 33.4, 30.0, 27.7 and 24.3 kJ mol−1 for C0 = 100, 200, 300, 400 and 600 mg Ni dm−3, respectively) and spontaneous in the 298-338 K temperature range. Thermal treatment of the Ni(II)-loaded clinoptilolite results in the formation of spherical nano-NiO particles of approx. 5 nm in diameter which are randomly dispersed in the clinoptilolite lattice. 相似文献
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Ljiljana Arambašic Damir Bakic Rajna Rajic 《Journal of Fourier Analysis and Applications》2007,13(3):331-356
The article is devoted to dimension functions of orthonormal wavelets on the real line with dyadic dilations. We describe
properties of dimension functions and prove several characterization theorems. In addition, we provide a method of construction
of dimension functions. Various new examples of dimension functions and orthonormal wavelets are included. 相似文献
5.
This paper discusses the scattering of stress waves by defects in representative aircraft structures with multi-layered construction and geometry variation. The approaches for determining and enhancing the probability of detection of non-surface-penetrating defects in such structures as well as minimising the contributions of multi-layered construction and geometry variation to false indications are presented. The results demonstrate the importance of selecting the appropriate frequency and location of the sensor in monitoring sub-surface defects on these structures. The findings suggested that a computer solution of the problem may be required to determine the optimal combination of frequency and sensor location. This study suggests the possibility of incorporating structural health monitoring into the design of future structures which will constitute a significant leap in the current knowledge base of structural health monitoring. 相似文献
6.
Steva Levic Verica Djordjevic Nevenka Rajic Milan Milivojevic Branko Bugarski Viktor Nedovic 《Chemical Papers》2013,67(2):221-228
Electrostatic extrusion was applied to the encapsulation of 3-ethoxy-4-hydroxybenzaldehyde (ethyl vanillin) in calcium alginate and calcium alginate/poly(vinyl alcohol) beads. The calcium alginate/poly(vinyl alcohol) hydrogel spheres were formed after contact with the cross-linker solution of calcium chloride, followed by the freeze-thaw method for poly(vinyl alcohol) gel formation. The entrapment of aroma in beads was investigated by FTIR and thermal analysis (thermogravimetry/differential thermal gravimetry; TGA/DTG). The mass loss in the temperature range of 150?C300°C is related to degradation of the matrix and the release of ethyl vanillin. According to the DTG curve, the release of ethyl vanillin occurs at about 260°C. TGA measurements of the stored samples confirmed that formulations were stable for a period of one month. FTIR analysis provides no evidence for chemical interactions between flavour and alginate that would alter the nature of the functional groups in the flavour compound. 相似文献
7.
Tomislav Ivankovic Antonija Rajic Sanja Ercegovic Razic Sabine Rolland du Roscoat Zenun Skenderi 《Molecules (Basel, Switzerland)》2022,27(6)
Wool is considered to possibly exhibit antibacterial properties due to the ability of wool clothing to reduce the build-up of odor, which arises from the microbial activity of skin microbiota. Indeed, when tested with a widely used agar diffusion plate test method, even wool or other textiles not treated with any antimicrobial agent can be interpreted to show certain antibacterial effects due to the lack of growth under the specimen, as instructed in ISO 20645:2004 standard. Therefore, we analyzed in detail what happens to bacterial cells in contact with untreated wool and cotton fabric placed on inoculated agar plates by counting viable cells attached to the specimens after 1 and 24 h of contact. All wool and several cotton samples showed no growth under the specimen. Nevertheless, it was shown without a doubt that neither textile material kills bacteria or inhibits cell multiplication. A reasonable explanation is that bacterial cells firmly attach to wool fibers forming a biofilm during multiplication. When the specimen was lifted off the nutrient agar surface, the cells in the form of biofilm remained attached to the wool fibers, removing the biomass and resulting in a clear, no growth zone underneath it. By imaging the textile specimens with X-ray microtomography, we concluded that the degree of attachment could be dependent on surface topography. The results indicate that certain textiles, in this case, wool, could exhibit antibacterial properties by removing excess bacteria that grow on the textile/skin interface when taken off the body. 相似文献
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D. Stojakovic Nevenka Rajic Sanja Sajic Natasa Zabukovec Logar V. Kaucic 《Journal of Thermal Analysis and Calorimetry》2007,87(2):339-343
Kinetics of the thermal decomposition of 3-methylaminopropylamine which
was used as a structure-directing agent in the synthesis of AlPO4-21
has been studied under isothermal and non-isothermal conditions. The decomposition
is a single-step reaction occurring in the 573–663 K range. It is a
phase-boundary-controlled process, described by the ‘F2/3, R3’
kinetic model. The activation energy values obtained under the non-isothermal
and isothermal conditions lie in the 173–151 kJ mol–1
range. 相似文献
10.
Bogdan Prelesnik Rajna Herak Djordje Stojaković Dejan Poleti 《Monatshefte für Chemie / Chemical Monthly》1986,117(1):47-49
A preliminary X-ray single crystal analysis shows that [Cu(phthalate)(2,2-bipyridine)] · 2H2O is dimeric in structure, which is usually not encountered in Cu-phthalate complexes.
Ein dimerer Kupferkomplex mit Phthalsäure und 2,2-Bipyridyl (Kurze Mitteilung)
Zusammenfassung Eine vorläufige Röntgen-Einkristallanalyse zeigt, daß [Cu(Phthalat)(2,2-Bipyridyl)] · 2H2O dimer vorliegt, was bei Cu-Phthalatkomplexen gewöhnlich nicht der Fall ist.相似文献