排序方式: 共有287条查询结果,搜索用时 0 毫秒
51.
Elahe Moazzen Homeira Ebrahimzadeh Mostafa M. Amini Omid Sadeghi 《Journal of separation science》2013,36(11):1826-1833
In this work, for the first time, an ion‐imprinted polymer was developed for selective extraction and determination of gold ions. To increase the sorbent efficiency, this polymer was coated on a novel nanoporous carbon‐based material, carbohydrate‐derived Max‐Planck Gesellschaft 1, which is also the first example of grafting imprinted polymer on nanoporous‐carbon material. These particles were applied successfully for preconcentration of ultratrace amount of gold ions, following determination by flame atomic absorption spectrometry. Some effective factors on the efficiency of gold ions extraction, such as concentration and volume of eluent, sample and eluent flow rates, and also effect of interfering ions especially palladium and platinum ions, were investigated. The LOD was determined to be 0.27 ng/mL. Furthermore, the precision of the method was calculated to be 2.14% under optimal conditions with recovery more than 97.3%. The technique was also used to determine the concentration of gold ions in mine stone samples with satisfactory results. The accuracy of this method was investigated by determination of gold ions concentrations in several reference materials with certified gold content. 相似文献
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Omid Zabihi Mehran Aghaie Karim Zare 《Journal of Thermal Analysis and Calorimetry》2013,111(1):703-710
The thermo-physical properties of diglycidyl ether of bisphenol A (DGEBA)/isophoronediamine (IPDA) with iron nanoparticles were investigated using DSC, DMT, and TG analysis. Because of the higher values of the glass transition, it is recognized that the optimum behavior of the three-component system corresponds to the 10% loading level of iron nanoparticles. The addition of iron nanoparticles into the epoxy matrix resulted in a significant increment in the storage modulus and crosslink density. Also, the DGEBA/IPDA/10% iron nanoparticles showed an enhanced thermal stability owing to the introduction of iron nanoparticles as reinforcing filler. Curing reaction of DGEBA/IPDA with 10% iron nanoparticles was investigated by DSC at dynamic mode. Activation energy was calculated based on Kissinger method (66.52 kJ mol?1). Also, the advanced isoconversional method is utilized to describe the curing reaction process. In the dynamic DSC analyses, the curing kinetics could be successfully described with the two-parameter autocatalytic model (Sěsták–Berggren equation) and the overall reaction order was about 2.78. 相似文献
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Omid Yousefzade Sofia Valenti Jordi Puiggalí Hamid Garmabi Roberto Macovez 《Journal of Polymer Science.Polymer Physics》2019,57(4):222-233
Temperature‐modulated differential scanning calorimetry (TMDSC) and broadband dielectric spectroscopy (BDS) were employed to study the glass transition, size of the cooperative rearranging regions (CRRs), crystallization kinetics, and dielectric relaxation response of nanocomposites constituted by chain‐extended poly(L‐lactide) (PLLA) and carboxylated carbon nanotubes (f‐CNTs). The CRR size and the number of relaxing structural units decreased in the presence of crystals during isothermal crystallization. All samples displayed both a primary (α) and secondary (β) relaxation in BDS spectra. The relaxation dynamics of PLLA chains was barely affected by the presence of the f‐CNT. Constrained polymer chains and thickness of interphase (t i) were measured using dielectric spectra in tan δ representation. t i values were found to be 46 and 24 nm for sample containing 0.2 and 0.5% weight fraction of f‐CNT, respectively. All samples underwent partial crystallization (with roughly 30% of final crystalline fraction) some 15 or 20° above their glass‐transition temperature (T g). Crystallization leads to a fragile‐to‐strong transition in the temperature dependence of the cooperative α relaxation and to the increased visibility of a Maxwell–Wagner–Sillars (MWS) interfacial relaxation, which appears to be present in all samples. The heterogeneity of the polymeric samples was quantified in terms of a new parameter, the heterogeneity index (H). © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 222–233 相似文献
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Hydrophobic Cysteine Poly(disulfide)‐based Redox‐Hypersensitive Nanoparticle Platform for Cancer Theranostics 下载免费PDF全文
Dr. Jun Wu Dr. Lili Zhao Dr. Xiaoding Xu Dr. Nicolas Bertrand Dr. Won II Choi Dr. Basit Yameen Prof. Jinjun Shi Vishva Shah Matthew Mulvale James L. MacLean Prof. Omid C. Farokhzad 《Angewandte Chemie (International ed. in English)》2015,54(32):9218-9223
Selective tumor targeting and drug delivery are critical for cancer treatment. Stimulus‐sensitive nanoparticle (NP) systems have been designed to specifically respond to significant abnormalities in the tumor microenvironment, which could dramatically improve therapeutic performance in terms of enhanced efficiency, targetability, and reduced side‐effects. We report the development of a novel L ‐cysteine‐based poly (disulfide amide) (Cys‐PDSA) family for fabricating redox‐triggered NPs, with high hydrophobic drug loading capacity (up to 25 wt % docetaxel) and tunable properties. The polymers are synthesized through one‐step rapid polycondensation of two nontoxic building blocks: L ‐cystine ester and versatile fatty diacids, which make the polymer redox responsive and give it a tunable polymer structure, respectively. Alterations to the diacid structure could rationally tune the physicochemical properties of the polymers and the corresponding NPs, leading to the control of NP size, hydrophobicity, degradation rate, redox response, and secondary self‐assembly after NP reductive dissociation. In vitro and in vivo results demonstrate these NPs’ excellent biocompatibility, high selectivity of redox‐triggered drug release, and significant anticancer performance. This system provides a promising strategy for advanced anticancer theranostic applications. 相似文献
55.
Michael A. Schmidt Kishta KatipallyAntonio Ramirez Omid SoltaniXiaoping Hou Huiping ZhangBang-Chi Chen Xinhua QianRajendra P. Deshpande 《Tetrahedron letters》2012,53(31):3994-3997
Efforts to prepare ethyl 3-phenyl-4-(trifluoromethyl)isoxazole-5-carboxylate (1) by developing a regioselective 1,3-dipolar cycloaddition between phenyl nitrile oxide and various 4,4,4-trifluoromethyl crotonates are described. The substitution at the C2-position of crotonate dipolarophile 4 significantly influenced the regiochemistry and yield of the cycloaddition. Enol and enol ether-based crotonates underwent regioselective cycloadditions with phenyl nitrile oxide to provide 4-trifluoromethyl isoxazoles in good yields. 相似文献
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Iman Jafari Mohamadreza Shakiba Fatemeh Khosravi Seeram Ramakrishna Ehsan Abasi Ying Shen Teo Mohammadreza Kalaee Majid Abdouss Ahmad Ramazani S. A Omid Moradi Erfan Rezvani Ghomi 《Molecules (Basel, Switzerland)》2021,26(6)
The incorporation of nanofillers such as graphene into polymers has shown significant improvements in mechanical characteristics, thermal stability, and conductivity of resulting polymeric nanocomposites. To this aim, the influence of incorporation of graphene nanosheets into ultra-high molecular weight polyethylene (UHMWPE) on the thermal behavior and degradation kinetics of UHMWPE/graphene nanocomposites was investigated. Scanning electron microscopy (SEM) analysis revealed that graphene nanosheets were uniformly spread throughout the UHMWPE’s molecular chains. X-Ray Diffraction (XRD) data posited that the morphology of dispersed graphene sheets in UHMWPE was exfoliated. Non-isothermal differential scanning calorimetry (DSC) studies identified a more pronounced increase in melting temperatures and latent heat of fusions in nanocomposites compared to UHMWPE at lower concentrations of graphene. Thermogravimetric analysis (TGA) and derivative thermogravimetric (DTG) revealed that UHMWPE’s thermal stability has been improved via incorporating graphene nanosheets. Further, degradation kinetics of neat polymer and nanocomposites have been modeled using equations such as Friedman, Ozawa–Flynn–Wall (OFW), Kissinger, and Augis and Bennett’s. The "Model-Fitting Method” showed that the auto-catalytic nth-order mechanism provided a highly consistent and appropriate fit to describe the degradation mechanism of UHMWPE and its graphene nanocomposites. In addition, the calculated activation energy (Ea) of thermal degradation was enhanced by an increase in graphene concentration up to 2.1 wt.%, followed by a decrease in higher graphene content. 相似文献
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Riyadh Zendin Mawlud Sangar S. Ahmed Sobhan Mortazavi-Derazkola Omid Amiri Zahra Salehi Peshawa H. Mahmood 《应用有机金属化学》2020,34(8):e5652
In this study, dendrite-like Sn nanocomposites were achieved by engineering the synthesis parameters. The dendritic Sn nanostructures show higher photocatalytic activity compared to nanoplate Sn and hierarchical Sn nanostructures. Flower-like Sn–Cu and cactus-like Sn–Ag nanostructures were prepared to improve the photocatalytic activity of Sn nanostructures. Adding Cu and Ag improved the photocatalytic activity of Sn by 24% and 46%, respectively. The photodegradation results revealed that the cactus-like Sn–Ag has a high degradation rate (5.3 × 10−4 mmol L−1 min−1) compared to the Sn nanostructures (2.9 × 10−4 mmol L−1 min−1). This work provides new insight into the design of highly efficient photocatalysts by engineering the morphology. 相似文献
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Omid Bagheri Faranak Sadegh Majid Moghadam Shahram Tangestaninejad Valiollah Mirkhani Iraj Mohammadpoor‐Baltork Mahsa Safiri 《应用有机金属化学》2014,28(5):337-346
The tetrakis(4‐N‐methylpyridinium)porphyrinatopalladium(II) iodide, [Pd(TMPyP)]I4, supported on Dowex 50WX8 and Amberlite IR‐120 ion‐exchange resins, was used as heterogeneous, recyclable and active catalyst for the Suzuki–Miyaura and Heck cross‐coupling reactions. These catalysts were applied to coupling of various aryl halides with phenylboronic acid and styrene in Suzuki and Heck reactions, respectively, and the corresponding products were obtained in excellent yields and short reaction times. The catalysts could be recovered easily by simple filtration and reused several times without significant loss of their catalytic activity. The catalysts were characterized by diffuse‐reflectance UV–visible spectroscopy and scanning electron microscopy, and their stability was confirmed by TGA. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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Omid Bozorg Haddad Mahsa Mirmomeni Mahboubeh Zarezadeh Mehrizi Miguel A. Mariño 《Computational Optimization and Applications》2010,47(1):97-128
Effective project management requires the development of a realistic plan and a clear communication of the plan from the beginning
to the end of the project. The critical path method (CPM) of scheduling is the fundamental tool used to develop and interconnect
project plans. Ensuring the integrity and transparency of those schedules is paramount for project success. The complex and
discrete nature of the solution domain for such problems causes failing of traditional and gradient-based methods in finding
the optimal or even feasible solution in some cases. The difficulties encountered in scheduling construction projects with
resource constraints are highlighted by means of a simplified bridge construction problem and a basic masonry construction
problem. The honey-bee mating optimization (HBMO) algorithm has been previously adopted to solve mathematical and engineering
problems and has proven to be efficient for searching optimal solutions in large-problem domains. This paper presents the
HBMO algorithm for scheduling projects with both constrained and unconstrained resources. Results show that the HBMO algorithm
is applicable to projects with or without resource constraints. Furthermore, results obtained are promising and compare well
with those of well-known heuristic approaches and gradient-based methods. 相似文献