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81.
Sina Modiri Mohsen Mohseni Ezeddin Mohajerani Isa A. Alidokht 《Iranian Polymer Journal》2012,21(8):547-556
Non-linear optical (NLO) dyes used as guests in polymeric films have recently attracted interests in optical applications. In this regard, dye-grafted polymeric systems can outperform conventional guest?Chost dye-containing films because they have lower loading limitations and aggregation problems. These give rise to enhanced molecular orientation. The work presented here is an attempt to study the laser-induced birefringence for a novel sol?Cgel based polymeric nanocomposite prepared by reacting an NLO dye (methyl red) and an epoxy silane coupling agent at different concentrations of dye. 3-Glycidoxy propyltrimethoxysilane was hydrolyzed and condensed to prepare a siloxane structure from which a dye-containing hybrid was obtained. The structural and morphological properties of the resulting nanocomposites were studied by FTIR spectroscopy, differential scanning calorimetry and transmission electron microscopy. Results showed that the dye was chemically attached to the siloxane structure built through sol?Cgel processing. This chemical modification leads to nanostructured morphology in which inorganic phase was entangled to the organic phase. The size of clusters formed was 60?C80?nm in dimension. The optical responses of nanocomposites were investigated at different process parameters, including dye concentration, film thickness and curing regimes. These were then discussed based on the photochemical and photothermal properties of the dye molecules, the rotation dynamic of which was shown to strongly depend on the physical and chemical properties of the host. The samples with 8 wt% of dye revealed the maximum birefringence, while the sample with 10 wt% showed the best memory effect. The best condition for curing was found to be 24?h. By increasing the film thickness, there was an increase in the amount of induced birefringence. 相似文献
82.
Sina Chaeichian Paula M. Wood‐Adams Suong V. Hoa 《Polymer Engineering and Science》2015,55(6):1303-1309
In this work, we explain why the incorporation of organically modified nano‐clay into unsaturated polyester resins, unlike epoxy, does not improve their fracture toughness despite continuing aggressive research activities based on this approach. The mechanism behind this phenomenon is explored by studying the effect of mixing method on improving the degree of exfoliation in simple nanocomposites and its final effect on fracture behaviour. Rheometry and X‐ray diffraction show that the two mixing methods lead to different degrees of exfoliation. The mechanical properties primarily depend on clay content and are less sensitive to degree of exfoliation. In the case of toughness, there is no observable effect of degree of exfoliation. This despite the increased fracture surface area evident in SEM images of the sample with finer exfoliation as compared with those of the sample with a lower degree of exfoliation. Dispersed silicate layers influence the toughness by increasing the tortuosity of the crack path locally while micron scale intercalated tactoids can result in crack deflection. Both of these mechanisms depend on localized plasticity for significant energy dissipation. Since unsaturated polyester has very low localized plasticity below ~90°C, one cannot significantly improve its room temperature toughness by manipulating the micro‐/nanostructure of the nanocomposite the nanocomposite without incorporating another material. This new understanding of the fracture behavior of unsaturated polyesters and their nanocomposites allows for the development of more complex toughened systems. POLYM. ENG. SCI., 55:1303–1309, 2015. © 2015 Society of Plastics Engineers 相似文献
83.
Saman Azodi‐Deilami Majid Abdouss Ebadullah Asadi Alireza Hassani Najafabadi Sadegh Sadeghi Sina Farzaneh Somayeh Asadi 《应用聚合物科学杂志》2014,131(23)
Herein, we report a magnetic molecularly imprinted polymers (m‐MIPs) using Fe3O4 as a magnetic component, carvedilol as a template molecule for the solid‐phase extraction (MISPE) as the sample clean‐up technique combined with high‐performance liquid chromatography (HPLC) and for the controlled release of carvedilol at different pH values of 1.0 (simulated gastric fluid), 6.8 (simulated intestinal fluid), and 7.4 (simulated biological fluid). The adsorption kinetics was modeled with the pseudo‐first‐order and pseudo‐second‐order kinetics, and the adsorption isotherms were fitted with Langmuir and Freundlich models. The performance of the m‐MIPs for the controlled release of carvedilol was assessed and results indicated that the magnetic MIPs also have potential applications in controlled drug release. Furthermore, the m‐MIPs were applied to the extraction of carvedilol from human blood plasma samples. Carvedilol can be quantified by this method in the 2–350 μg L?1 concentration range. The limit of detection and limit of quantification in plasma samples are 0.13 and 0.45 μg L?1. The results from HPLC showed good precision (3.5% for 50.0 μg L?1) and recoveries (between 85 and 93) using m‐MIP from human plasma samples. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41209. 相似文献
84.
A novel control system is developed to control dynamic behavior of a vehicle subject to road disturbances. The novelty of this paper is to apply the impedance control on an active vehicle suspension system operated by a hydraulic actuator. A relation between the passenger comfort and vehicle handling is derived using the impedance parameters. The impedance control law is simple, free of model and can be applied for a broad range of road conditions including a flat road. Impedance control is achieved through two interior loops which are force control of the actuator by feedback linearization and fuzzy control loop to track a desired body displacement provided by the impedance rule. The system stability is analyzed. A quarter-car model of suspension system and a nonlinear model of hydraulic actuator are used to simulate the control system. 相似文献
85.
Protein turnover studies on a proteome scale based on metabolic isotopic labeling can provide a systematic understanding of mechanisms for regulation of protein abundances and their transient behaviors. At this time, these large-scale studies typically utilize a simple kinetic model to extract protein dynamic information. Although many high-quality, protein isotope incorporation data are available from those experiments, accurate and additionally useful protein dynamic information cannot be extracted from the experimental data by use of the simple kinetic models. In this paper, we describe a formal connection between data obtained from elemental isotope labeling experiments and the well-known compartment modeling, and we demonstrate that an appropriate application of a compartment model to turnover of proteins from mammalian tissues can indeed lead to a better fitting of the experimental data. 相似文献
86.
Zhan Y Liu Z Najmaei S Ajayan PM Lou J 《Small (Weinheim an der Bergstrasse, Germany)》2012,8(7):966-971
Atomic-layered MoS(2) is synthesized directly on SiO(2) substrates by a scalable chemical vapor deposition method. The large-scale synthesis of an atomic-layered semiconductor directly on a dielectric layer paves the way for many facile device fabrication possibilities, expanding the important family of useful mono- or few-layer materials that possess exceptional properties, such as graphene and hexagonal boron nitride (h-BN). 相似文献
87.
88.
Di Wu Meng Qin Duo Xu Lan Wang Chaoyong Liu Jie Ren George Zhou Chen Chen Fengmei Yang Yanyan Li Yuan Zhao Ruyi Huang Sina Pourtaheri Chunsheng Kang Masakazu Kamata Irvin S. Y. Chen Zhanlong He Jing Wen Wei Chen Yunfeng Lu 《Advanced materials (Deerfield Beach, Fla.)》2019,31(18)
Central nervous system (CNS) diseases are the leading cause of morbidity and mortality; their treatment, however, remains constrained by the blood–brain barrier (BBB) that impedes the access of most therapeutics to the brain. A CNS delivery platform for protein therapeutics, which is achieved by encapsulating the proteins within nanocapsules that contain choline and acetylcholine analogues, is reported herein. Mediated by nicotinic acetylcholine receptors and choline transporters, such nanocapsules can effectively penetrate the BBB and deliver the therapeutics to the CNS, as demonstrated in mice and non‐human primates. This universal platform, in general, enables the delivery of any protein therapeutics of interest to the brain, opening a new avenue for the treatment of CNS diseases. 相似文献
89.
90.
Sina Najmaei Mahesh R. Neupane Barbara M. Nichols Robert A. Burke Alexander L. Mazzoni Matthew L. Chin Daniel A. Rhodes Luis Balicas Aaron D. Franklin Madan Dubey 《Small (Weinheim an der Bergstrasse, Germany)》2018,14(20)
The mechanisms of carrier transport in the cross‐plane crystal orientation of transition metal dichalcogenides are examined. The study of in‐plane electronic properties of these van der Waals compounds has been the main research focus in recent years. However, the distinctive physical anisotropies, short‐channel physics, and tunability of cross layer interactions can make the study of their electronic properties along the out‐of‐plane crystal orientation valuable. Here, the out‐of‐plane carrier transport mechanisms in niobium diselenide and hafnium disulfide are explored as two broadly different representative materials. Temperature‐dependent current–voltage measurements are preformed to examine the mechanisms involved. First principles simulations and a tunneling model are used to understand these results and quantify the barrier height and hopping distance properties. Using Raman spectroscopy, the thermal response of the chemical bonds is directly explored and the insight into the van der Waals gap properties is acquired. These results indicate that the distinct cross‐plane carrier transport characteristics of the two materials are a result of material thermal properties and thermally mediated transport of carriers through the van der Waals gaps. Exploring the cross‐plane electron transport, the exciting physics involved is unraveled and potential new avenues for the electronic applications of van der Waals layers are inspired. 相似文献