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81.
Mohammad Reza Shahsavari Alireza Namjoo Hossein Mohammadian Younes Saadat Soleyman Hosseinzadeh Samira Abdolbaghi 《Colloid Journal》2016,78(3):415-424
Dual-seeded dispersion polymerization (DSDP) of 2-ethylhexyl methacrylate with polystyrene (PS) and poly(methyl methacrylate) (PMMA) seed beads in the presence of saturated hydrocarbon droplets followed by evaporation of the hydrocarbon was studied. The effect of various polymerization conditions including initiator type and content, stabilizer type and concentration, and different hydrocarbon’s content on the shape of the obtained particles was investigated. The increase of concentration of 2,2'-azobis(isobutyronitrile) (AIBN) had no effect on the shape of the produced almond-shell-like PS particles, although it contributes in the formation of associated composite particles along with larger poly(2-ethylhexyl methacrylate) (PEHMA) beads produced by secondary nucleation. The experimental results showed that other initiators led to the formation of stable golf-ball-like PMMA particles as well as PS ones with symmetric shape. The type of stabilizer did not affect the shape of the particles. This observation suggests that unique almond-shelllike PS particles can be produced through a stabilizer-free DSDP process. The lowering of the concentration of hydrocarbons with long alkyl chains yielded stable disc-like PMMA particles. The formation of functional almond-shell-like particles by using light hydrocarbons was another interesting finding of this research. 相似文献
82.
NaY zeolite functionalized by sulfamic acid/Cu(OAc)_2[NaY/SA/Cu(Ⅱ)] was synthesized and used as a new,efficient and recyclable catalyst for preparation of formamides. This novel organic-inorganic hybrid catalyst was characterized by several techniques such as FT-IR, XRD, SEM, EDX and TG analysis.Chemoselectivity, easy procedure, excellent yields, very short reaction times, solvent-free and mild reaction conditions are some benefits of this new protocol. 相似文献
83.
An experimental investigation of the flow-front behavior of dilute and semi-dilute polymer solutions has been carried out to gain a better understanding of the underlying mechanisms leading to the occurrence of an unstable flow at the advancing flow-front during the filling of a rectangular Hele-Shaw cell. Our experimental results have revealed the existence of an elastic finger-like instability at the advancing flow-front that develops in semi-dilute solutions of high molecular weight polymers, with an onset time of approximately a few hundred milliseconds. Although at shear rates above critical, narrow finger patterns develop at the flow-front, their amplitude and number remain roughly constant throughout the flowing. At critical condition, no secondary flow was observed in the vicinity of the front region where the unstable flow develops. Transient response of the normal stress difference and the shear stress in the plate-and-plate geometry at shear rate above critical (for the elastic fingering instability in the Hele-Shaw cell) did not reveal any anomalous that could lead to the formation of such finger-like instabilities. These instabilities were observed for both the ideal elastic Boger fluids and shear thinning viscoelastic fluids. 相似文献
84.
Differential pulse polarography was used for simultaneous determination of Sn2+ and Pb2+. But there is a problem for simultaneous determination and it is high overlapped DPPs of mentioned cations that their determination is impossible in the presence of each other, so multivariate calibration methods as chemomatrics methods were used for this determination. There are some disadvantageous for multivariate calibration methods that can be solved by a new and simple method called net analyte signal standard addition method. This method has some advantages, such as: the use of a full voltammogram, realization in a single step, therefore it does not require calibration and prediction steps and only a few measurements are required for the determination. 相似文献
85.
Utility of 6‐Amino‐2‐thiouracils as a Core of Biologically Potent Polynitrogen–Sulfur Fused Heterocycles 下载免费PDF全文
Samira T. Rabie Reham A. Abdel‐Monem Nadia R. Mohamed Ahmed I. Hashem Afaf A. Nada 《Journal of heterocyclic chemistry》2014,51(Z1):E189-E196
One pot three‐component reaction was assisted to form some new pyridopyrimidine derivatives to be investigated as antimicrobial and antitumor agents. The newly synthesized compounds showed high significant antimicrobial activity against the applied strains of both Gram‐positive and Gram‐negative bacteria and fungi. The cytotoxic activity of some compounds was evaluated as inhibitor of growth in both human liver carcinoma and breast cell lines. The results showed that some compounds exhibited very high cytotoxicity against human liver cell line and breast cancer cells. 相似文献
86.
Samira Dolati Hosseinali Zarei Riyaz Kharrat 《Journal of Dispersion Science and Technology》2014,35(7):970-983
In this work, two Iranian crude oils diluted in 1-methylnaphthalene (1-MN) were titrated with selected n-alkanes. Subsequently, samples were observed microscopically to determine the onset of asphaltene precipitation. A series of micrographs from de-asphaltening were used to show visible changes of the asphaltene sizes, shapes, and frequencies by addition the n-heptane to the subsamples after 5, 6, 11, and 24 hour lag times. The refractive indices (RI) of the titrated mixtures at different temperatures below and above the onset conditions were measured aiming to establish the asphaltene instability trend. Results show that for the diluted light and heavy crude oils, the onset of asphaltene precipitation is rather a gradual process with an almost constant slope of RI decrease due to the separation of asphaltene clusters from the mixture. This is a kinetically controlled process. Furthermore, the nature of the precipitant is likely to play a notable role. The rate of RI decreasing with temperature was approximately 0.0004/°C for both tested crude oils. 相似文献
87.
Hossein Motavalli Samira Fathezadeh Mojtaba Parhizkar 《International Journal of Theoretical Physics》2011,50(11):3390-3397
We present energy eigenvalues and corresponding eigenfunction of the relativistic Kemmer equation for Dirac oscillator. The
associated ladder operators being established, it is shown that these operators satisfy the commutation relation of the su(1,1)
group. A suitable representation of this group is presented and analytical matrix elements of some functions are obtained. 相似文献
88.
Samira M. Abozeid Didar Asik Gregory E. Sokolow Jonathan F. Lovell Alexander Y. Nazarenko Janet R. Morrow 《Angewandte Chemie (International ed. in English)》2020,59(29):12093-12097
Three paramagnetic CoII macrocyclic complexes containing 2‐hydroxypropyl pendant groups, 1,1′,1′′,1′′′‐(1,4,8,11‐tetraazacyclotetradecane‐1,4,8,11‐tetrayl)tetrakis‐ (propan‐2‐ol) ([Co(L1)]2+, 1,1′‐(4,11‐dibenzyl‐1,4,8,11‐tetraazacyclotetradecane‐1,8‐diyl)bis(propan‐2‐ol) ([Co(L2)]2+), and 1,1′‐(4,11‐dibenzyl‐1,4,8,11‐tetraazacyclotetradecane‐1,8‐diyl)bis(octadecan‐2‐ol) ([Co(L3)]2+) were synthesized to prepare transition metal liposomal chemical exchange saturation transfer (lipoCEST) agents. In solution, ([Co(L1)]2+) forms two isomers as shown by 1H NMR spectroscopy. X‐ray crystallographic studies show one isomer with 1,8‐pendants in cis‐configuration and a second isomer with 1,4‐pendants in trans‐configuration. The [Co(L2)]2+ complex has 1,8‐pendants in a cis‐configuration. Remarkably, the paramagnetic‐induced shift of water 1H NMR resonances in the presence of the [Co(L1)]2+ complex is as large as that observed for one of the most effective LnIII water proton shift agents. Incorporation of [Co(L1)]2+ into the liposome aqueous core, followed by dialysis against a solution of 300 mOsm L?1 produces a CEST peak at 3.5 ppm. Incorporation of the amphiphilic [Co(L3)]2+ complex into the liposome bilayer produces a more highly shifted CEST peak at ?13 ppm. Taken together, these data demonstrate the feasibility of preparing CoII lipoCEST agents. 相似文献
89.
Samira Rahmani-Nezhad Leila Khosravani Mina Saeedi Kouros Divsalar Loghman Firoozpour Yaghoub Pourshojaei 《合成通讯》2013,43(6):741-749
A series of coumarin–resveratrol hybrids, 3-arylcoumarin derivatives 3a–u, were synthesized through the intermolecular condensation reaction of various salicylaldehydes and phenylacetic acids in the presence of 1,4-diazabicyclo[2.2.2]octane under solvent-free conditions. All the synthesized compounds were screened for their inhibitory potency against soybean 15-lipoxygenase. Among them, three compounds (3c, 3j, and 3q) showed good enzyme-inhibitory activities. 相似文献
90.
Issa Yavari Jamil Sheykhahmadi Hamed Saffarian Nooshin Zahedi Samira Bahemmat Mohammad Reza Halvagar 《合成通讯》2013,43(19):2608-2614
AbstractThe four-component reaction among arylhydrazine, alkyl acetoacetate derivatives, alkyl isocyanides, and dialkyl acetylenedicarboxylates, leading to the formation of dialkyl 2-[(Z)-(alkylamino)(3-alkyl-5-oxo-1-phenyl-1,5-dihydro-4H-pyrazol-4-ylidene)methyl] fumarates is described. The structure of target compounds was confirmed using X-ray diffraction study. These pyrazolone derivatives contain a highly twisted exocyclic 1,3-butadiene moiety with skew (??=?87°) geometry. 相似文献