排序方式: 共有164条查询结果,搜索用时 31 毫秒
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Poly(ether-block-amide) membranes were made via casting a solution on a nonsolvent (water) surface. In this research, effects of different parameters such as ratio of solvent mixture (n-butanol/isopropanol), temperature, composition of coagulation bath (water) and polymer concentration, on quality of the thin film membranes were studied. The mechanism of membrane formation involves solution spreading, solvent–nonsolvent exchange, and partial evaporation of the solvent steps. Solvent- nonsolvent exchange is the main step in membrane formation and determines membrane morphology. However, at higher temperature of polymeric solution greater portion of solvent evaporates. The results showed that type of demixing process (mutual affinity between solvent and nonsolvent) has important role in film formation. Also, addition of solvent to the nonsolvent bath is effective on membrane morphology. The film quality enhances with increasing isopropanol ratio in the solvent mixture. This behavior can be related to increasing of solution surface tension, reduction of interfacial tension between solution and nonsolvent and delayed solvent-nonsolvent demixing. Uniform films were made at a temperature rang of 60–80 °C and a polymer concentration of 4–7 wt%. Morphology of the membranes was investigated with scanning electron micrograph (SEM). Pervaporation of ethyl butyrate/water mixtures was studied using these membranes and high separation performance was achieved. For ethyl butyrate/water mixtures, It was observed that both permeation flux and separation factor increase with increasing ethyl butyrate content in the feed. Increasing temperature in limited range studied resulted in decreasing separation factor and increasing permeation flux. 相似文献
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Jurek Czyzowicz Wojciech Fraczak Mohammadreza Yazdani 《Journal of Discrete Algorithms》2008,6(1):28-36
Concatenation State Machine (CSM) is a labeled directed And–Or graph representing a deterministic push-down transducer. In the high-performance version of CSM, labels associated to edges are words (rather than letters) over the input alphabet. The throughput of a path p is defined as the sum of the lengths of the labels of the path, divided by the number of edges of p. The throughput of a CSM M is defined as the infimum of the throughput of all accepting paths of M. In this paper we give an algorithm, computing an ε-approximation of the throughput of a CSM M, where n is the number of nodes, m is the number of edges, and max (min) is the maximum (respectively, minimum) of the lengths of the edge labels of M. While we have been interested in a particular case of an And–Or graph representing a transducer, we have actually solved the following problem: if a real weight function is defined on the edges of an And–Or graph G, we compute an ε-approximation of the infimum of the complete hyper-path mean weights of G. This problem, if restricted to digraphs, is strongly connected to the problem of finding the minimum cycle mean. 相似文献
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Fakhar Majid Khodakhah Mohammadreza Mazyaki Ali Soubeyran Antoine Zafarani Jafar 《Journal of Global Optimization》2022,82(1):161-177
Journal of Global Optimization - This paper has two aspects. Mathematically, in the context of global optimization, it provides the existence of an optimum of a perturbed optimization problem that... 相似文献
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Mohammadreza Moghaddam-Manesh Dadkhoda Ghazanfari Enayatollah Sheikhhosseini Mohammadreza Akhgar 《应用有机金属化学》2020,34(4):e5543
New bioactive magnetic nanoparticles of spiro[indoline-3,4′-[1,3]dithiine]@Ni (NO3)2 supported on Fe3O4@SiO2@CPS were synthesized in five steps. The structure of synthesized magnetic nanoparticles was identified by using Energy-Dispersive X-ray spectroscopy (EDX), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), X-Ray Diffraction (XRD), Thermal Gravimetric Analysis (TGA), Infrared spectroscopy (FT-IR), Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES), Vibrating Sample Magnetometer (VSM) and Brunauer Emmett Teller (BET) surface analysis. Antimicrobial activity of the synthesized magnetic nanoparticles based on MIC (Minimum Inhibitory Concentration) and MBC (Minimum Bactericidal Concentration) and MFC (Minimum Fungicidal Concentration) values were also examined. Furthermore, the synthesized magnetic nanoparticles exhibited appropriate catalytic properties in the synthesis of the 3,4-dihydro-2H- pyran derivatives. 相似文献
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Elham Moradinia Mohammadreza Mansournia Zahra Aramesh‐Boroujeni Abdol‐Khalegh Bordbar 《应用有机金属化学》2019,33(5)
The new complexes of Cu (II) and Ni (II) of a tridentate Schiff base ligand derived from 9,10‐phenanthrenequinone and p‐toluic hydrazide have been synthesized and characterized by elemental analysis, electrical conductometry, FT‐IR, Mass, NMR and UV–Vis. The DFT calculations were carried out at B3LYP/6‐31G*(d) level for the determination of the optimized structure of the ligand and its complexes. The as‐synthesized compounds were screened for their antimicrobial activity. Also, their binding behavior with fish salmon‐DNA (FS‐DNA) and human serum albumin (HSA) were studied by different kinds of spectroscopic and molecular modeling techniques. The fluorescence data at different temperatures were applied in order to estimate the thermodynamics parameters of interactions of ligand and its complexes with DNA and HSA. The results showed that the as‐made compounds could bind to FS‐DNA and HSA via the groove binding as the major binding mode. According to molecular docking calculation and competitive binding experiments, these compounds bind to the minor groove of DNA and hydrophobic residues located in the subdomain IB of HSA. In addition, the molecular docking results kept in good consistence with experimental data. 相似文献
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Gholamhassan Imanzadeh Zahra Soltanizadeh Ali Khodayari Mohammadreza Zamanloo Yagoub Mansoori Jaber Salehzadeh 《中国化学》2012,30(4):891-899
An efficient and simple procedure for the synthesis of novel isatin derivatives is described. Michael addition of aniline Schiff bases of isatin or p‐toluidine Schiff bases of isatin to fumaric esters affords the Michael adduct compounds in good to high yields in the presence of K2CO3 and tetrabutylammonium bromide (TBAB) under solvent‐free conditions. Repeating of this reaction about spiro[1,3‐dioxolane‐2,3′‐indol]‐2′(1′H)‐one, as a Michael donor, in the presence of 1,4‐diazabicyclo[2.2.2]octane (DABCO) gives Michael adducts in remarkable yields under the same conditions. 相似文献
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Mehdi Shakourian-Fard Mohammadreza Nasiri Alireza Fattahi Majid Vafaeezadeh 《Structural chemistry》2012,23(3):857-865
Influence of the addition of water molecules (n = 1–6) on the interaction energy between Li+, Na+, K+ cations and indole molecule as tryptophan amino acid residue is considered at MP2(FULL)/6-311++G(d,p)//B3LYP/6-311++G(d,p)
levels of theory. The calculations suggest that the size of cation and the number of water molecules are two important factors
that affect the interaction energy between the hydrated metal cation and indole molecule. The strength of cation–π interactions
get substantially reduced when the metal ion is solvated or the size of metal cation increases. Quantum theory of atoms in
molecules analysis of cation–π interaction indicates that there is a correlation between the electron density (ρ(r)) in the cage critical points generated upon complexation and the distance between metal cation and centroid of phenyl ring
in indole molecule. 相似文献