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排序方式: 共有350条查询结果,搜索用时 20 毫秒
91.
Cozzolino AF Vargas-Baca I Mansour S Mahmoudkhani AH 《Journal of the American Chemical Society》2005,127(9):3184-3190
Organochalcogen-nitrogen heterocycles such as the 1,2,5-chalcogenadiazoles have a distinct tendency to establish intermolecular links in the solid state through secondary bonding interactions E...N (E = S, Se, Te). The association of these molecules was examined in detail using relativistic density functional theory. Although there is an important electrostatic component, the interaction between these molecules is dominated by contributions arising from orbital mixing, which can be interpreted as the donation of a nitrogen lone pair into the chalcogen-centered antibonding orbitals. Because of its more polar character and lower-lying antibonding orbitals, the tellurium derivatives possess the strongest association energies; these are so large that the binding strength is comparable to that of some hydrogen bonds. In the absence of steric constraints, telluradiazoles associate in a coplanar fashion forming ribbon polymers. However, bulky susbstituents could be used to direct the formation of either helical chains or discrete dimers. In addition to its strength, the coplanar dimer is characterized by being rigid, yet no activation barrier is expected for the association/dissociation process. These attributes strongly indicate that tellurium-nitrogen heterocycles have great potential as building blocks in supramolecular architecture. 相似文献
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93.
Russian Journal of Applied Chemistry - M-type strontium hexaferrite substituted by Zr4+, Zn2+, and Co2+ was firstly synthesized by a sol-gel auto combustion method. Then the polyaniline/hexaferrite... 相似文献
94.
95.
Mohammad Ehsan Taghavizadeh Yazdi Simin Nazarnezhad Seyed Hadi Mousavi Mohammad Sadegh Amiri Majid Darroudi Francesco Baino Saeid Kargozar 《Molecules (Basel, Switzerland)》2021,26(6)
The use of naturally occurring materials in biomedicine has been increasingly attracting the researchers’ interest and, in this regard, gum tragacanth (GT) is recently showing great promise as a therapeutic substance in tissue engineering and regenerative medicine. As a polysaccharide, GT can be easily extracted from the stems and branches of various species of Astragalus. This anionic polymer is known to be a biodegradable, non-allergenic, non-toxic, and non-carcinogenic material. The stability against microbial, heat and acid degradation has made GT an attractive material not only in industrial settings (e.g., food packaging) but also in biomedical approaches (e.g., drug delivery). Over time, GT has been shown to be a useful reagent in the formation and stabilization of metal nanoparticles in the context of green chemistry. With the advent of tissue engineering, GT has also been utilized for the fabrication of three-dimensional (3D) scaffolds applied for both hard and soft tissue healing strategies. However, more research is needed for defining GT applicability in the future of biomedical engineering. On this object, the present review aims to provide a state-of-the-art overview of GT in biomedicine and tries to open new horizons in the field based on its inherent characteristics. 相似文献
96.
Transport in Porous Media - Image-based simulations at pore scale provide direct insight into the impact of the microstructure on flow and transport processes in porous media. Diffusion is an... 相似文献
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98.
Saeid Rahimi‐Razin Vahid Haddadi‐Asl Mehdi Salami‐Kalajahi Farid Behboodi‐Sadabad Hossein Roghani‐Mamaqani 《国际化学动力学杂志》2012,44(8):555-569
A new approach was developed to functionalize multiwalled carbon nanotubes (MWCNTs) with a polymerizable methyl methacrylate (MMA) groups, and the structure of functionalized MWCNTs were characterized by FTIR, Raman, XPS, and TEM. Using the strategy of “grafting through,” poly(methyl methacrylate) (PMMA) chains were grafted onto the surface of MWCNTs during the in situ synthesis of MWCNT/PMMA nanocomposites over reversible addition‐fragmentation chain transfer (RAFT) polymerization. Kinetics of RAFT‐mediated polymerization of MMA in the presence of MMA‐grafted MWCNTs was studied by using gas chromatography and gel permeation chromatography. To further study, attached polymers were detached and their molecular characteristics were compared to freely formed chains. Results of kinetic studies showed that the utilized commercial chain transfer agent strictly reduced the rate of polymerization as well as relatively controlled molecular weights and narrow molecular weight distributions of free chains. MWCNTs showed a radical activity, retarding the polymerization and reducing the rate of reaction. The effect of MWCNTs concentrations on molecular weights and polydispersity indexes (PDI) was different at the surface and in the bulk. The molecular weights of free chains increased, and the PDI was decreased with increasing MWCNTs. © 2012 Wiley Periodicals, Inc. Int J Chem Kinet 44: 555–569, 2012 相似文献
99.
Mohammad Solimannejad Farshideh Hasanvand Jamshidi Saeid Amani 《Structural chemistry》2011,22(1):193-199
Ab initio calculations at MP2/6-311++G(d,p) computational level were used to analyze the interaction between a molecule of
the hydroperoxyl radical with 1 up to 4 molecules of ammonia. Three minima were found for 1:2 and 1:4 complexes of HOO and
NH3. Two complexes were located as minima on the potential energy surface of 1:3 complexes. Red shifts of the OH stretching frequency
upon complex formation in the range between 560 and 1,116 cm−1 are predicted. Cooperative effect in terms of stabilization energy is calculated for the studied clusters. The cooperative
effect is increased with the increasing size of studied clusters. The Quantum Theory Atoms in Molecules (QTAIM) theory was
also applied to explain the nature of the complexes. 相似文献
100.