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排序方式: 共有118条查询结果,搜索用时 31 毫秒
61.
Shokooh Sadat Khaloo Shahla Mozaffari Parisa Alimohammadi Hadi Kargar Joliet Ordookhanian 《International Journal of Food Properties》2016,19(10):2272-2283
A chemically modified electrode was constructed by incorporating manganese (III) tetraphenyl porphyrine into a carbon paste matrix. The modified electrode was used as a sensitive electrochemical sensor for measuring of riboflavin. The constructed electrode exhibited catalytic properties for the electro-oxidation of riboflavin and lowered the over potential for the oxidation of this compound; consequently, the corresponding peak currents of riboflavin increased significantly. The modified electrode showed a near-Nernstian behavior for electro-oxidation of riboflavin hence, it could be a suitable voltammetric sensor for the fast and easy determination of riboflavin. A linear response in concentration range 1.0 × 10?8 – 1.0 × 10?5 M was obtained with a detection limit of 8.0 × 10?9 M (S /n = 3) for the determination of riboflavin. The electrode showed long-term stability and the standard deviation of the slope obtained after repeated calibration during a period of 3 months was 3.5% (n = 10). The modified electrode was used for differential pulse voltammetric determination of riboflavin in pharmaceutical and food samples. 相似文献
62.
Zandi As’ad Zanganeh Amirhossein Hemmati Farkhondeh Mohammadi-Roshandeh Jamshid 《Iranian Polymer Journal》2019,28(5):403-415
Iranian Polymer Journal - In this work, rice straw (RS) as an abundant biomass was chemically thermoplasticized through alkali pulping and benzylation reactions, which destroy inter- and... 相似文献
63.
Amir Ali Naziri Hossein Ali Khonakdar Farkhondeh Hemmati Seyed Hassan Jafari Morteza Ehsani 《应用聚合物科学杂志》2019,136(28):47750
The phase behavior of poly(ε-caprolactone) (PCL)/poly(styrene-co-acrylonitrile) (SAN) blends, with a lower critical solution temperature (LCST)-type phase diagram over a virtual upper critical solution temperature (UCST) one, was investigated through thermal analysis and dynamic rheological measurements as a function of ramp rate. The LCST phase diagram was detected rheologically from the observed slope changes in the dynamic temperature ramps of storage modulus (G′). The determined phase transition points along with the spinodal temperatures, which are estimated based on the theoretical approach of Ajji and Choplin's mean field theory, shift to higher temperatures by reducing the ramp rate. The detected shifts show a composition dependency. Far away from the critical point, the phase transition temperatures of PCL/SAN blends change more noticeably, which originates from the smaller magnitude of concentration fluctuations in the metastable region and the stronger competition between the phase dissolution and cooling rate. The Flory–Huggins interaction parameter (χ) was appropriately adjusted into the LCST phase boundary as a function of temperature and composition. The results confirmed that the adjusted χ has higher temperature dependency at larger ramp rate of the dynamic measurements. The experimentally combined LCST and UCST phase behavior were also verified by the compressible regular solution model. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47750. 相似文献
64.
Molecular dynamics simulations are performed to study the diffusion and permeation of gases, including argon, nitrogen, methane, carbon dioxide, and propane, in polystyrene over a wide range of temperatures. A jumping mechanism is observed for the diffusion of diffusants in polymer. The calculated diffusion coefficients agree well with the experimental data and with the results of former simulation studies. The relation between the diffusion coefficient and the molecular diameter is confirmed by the results. Our calculated results on the temperature-dependence of diffusion coefficients show that for some gases a break is seen, at the glass transition temperature, in the Arrhenius plot of ln (D) versus 1/T, while for some other light gases, argon and nitrogen, the plot is linear over the whole temperature range. We have also calculated the permeability coefficients, using the diffusion coefficients calculated in this work and our recently published solubility coefficients [Eslami and Müller-Plathe, Macromolecules 2007; 40:6413]. Our results show that the calculated permeability coefficients are higher than the experimental data by almost the same trend observed in the solubility calculations, but the ratios of calculated permeabilities are in a very good agreement with experiment. 相似文献
65.
Manije Darooghegi Mofrad Hadis Mozaffari Seyed Mohammad Mousavi Ali Sheikhi 《Critical reviews in food science and nutrition》2020,60(5):859-872
AbstractBackground: Previous studies reported inconsistent findings regarding the effects of psyllium supplementation on obesity measures. This systematic review and meta-analysis was performed to summarize data from available randomized clinical trials (RCTs) on the effect of psyllium supplementation on body weight, body mass index (BMI), and waist circumference (WC) in adults.Methods: PubMed, SCOPUS, Cochrane Library, and Google Scholar were searched to identify relevant articles up to August 2018. The effect sizes were presented as weighted mean difference (WMD) and 95% confidence intervals (CI) by using random effects model. To detect dose-response relationships, we used fractional polynomial modeling.Results: A total of 22 RCTs were included. Meta-analysis did not find any significant effect of psyllium supplementation on body weight (MD: ?0.28?kg, 95% CI: ?0.78, 0.21, p?=?0.268), BMI (MD: ?0.19?kg/m2, 95% CI: ?0.55, 0.15, p?=?0.27) and WC (MD: ?1.2?cm, 95% CI: ?2.6, 0.2, p?=?0.09). Subgroup analysis showed that psyllium dosage, kind of psyllium administration, duration of trial, study design, sample size, and gender were potential sources of heterogeneity. Moreover, there was nonlinear association between duration of psyllium consumption, BMI and WC.Conclusion: Psyllium supplementation does not reduce body weight, BMI, and WC significantly. 相似文献
66.
Hossein Eslami Farkhondeh Mozaffari Ali Boushehri 《International Journal of Thermal Sciences》2001,40(11):853
An accurate Hartree–Fock dispersion individually damped (HFD-ID) potential type improved by Boyes for argon has been used as a core potential to calculate both the spherical and nonspherical contributions to the second virial coefficient of simple molecules. The auxiliary functions that occur in the perturbation terms for calculating the nonspherical contributions, have been calculated numerically and are tabulated over a wide range of temperatures from T*=0.5 to T*=10, where T*=kT/ and is the potential well-depth. By fitting the well-depth and the position of the minimum in the core potential, we have calculated the second virial coefficient of N2, O2, CO, NO, and CO2 over the whole temperature range reported in the literature. The calculated results are compared with the large body of experimental data in the literature, and with the pervious calculations by Boushehri et al. (1987). The agreement with both experimental data and theoretical calculations is quite good. 相似文献
67.
Seyed Majid Hosseiny Seyed Hassan Jafari Hossein Ali Khonakdar Farkhondeh Hemmati Mohammad Reza Kalaee 《应用聚合物科学杂志》2020,137(45):49401
In this study, the correlations between the mechanical performance and structural properties of injected-molded polyethylene (PE)/ethylene-vinyl acetate copolymer (EVA)/nanoclay (NC) nanocomposites are investigated by revisiting the interfacial phenomena and miscibility state of the component pairs. The effects of different parameters including the injection molding temperature, mixing sequence in melt-compounding process, blend composition, and nanoclay loading are studied. A great complexity arises in the filling and cooling process of the injected-molded parts owing to the phase behavior of the polyolefin blend, crystallization, and morphological changes. The injection molding temperature positively influences the elastic modulus, tensile strength and impact strength of PE/EVA/NC systems through the improvements in the PE/EVA partial miscibility, mutual solubility, and interfacial interactions of PE/clay and PE/EVA pairs. By applying a two-step mixing process before the injection molding, more nanoclay stacks with smaller thicknesses and larger clay interlayer spacing are formed. The stronger pinning effect of nanoparticles in the second mixing sequence retards the phase separation phenomenon of PE/EVA blend during the cooling stage. As a result of improved mutual PE/EVA solubility, the elastic modulus and tensile strength decrease and the impact resistance increases in the PE-rich systems. On the other hand, an opposite trend for these properties is found for the EVA-rich systems. 相似文献
68.
69.
Amir Ali Naziri Morteza Ehsani Hossein Ali Khonakdar Farkhondeh Hemmati Seyed Hassan Jafari 《应用聚合物科学杂志》2020,137(19):48679
The effects of spherical nanosilica particles on the lower critical solution temperature (LCST) phase diagram of poly(ε-caprolactone) (PCL)/poly(styrene-co-acrylonitrile) (SAN) blends are investigated by using isochronal dynamic temperature sweep tests at different cooling rates. A stronger dependency of the rheologically determined phase-transition points on the cooling rate is observed in the presence of nanoparticles, which results from the large contribution of entropic surface tension of chains in the Gibbs free energy of mixing and much slower rate of PCL/SAN phase dissolution. By alleviating the effects of kinetic factors, it is found that the drop in the LCST-type phase boundary of PCL/SAN blends by adding nanofiller is more apparent than real. However, the closest LCST phase diagram to the real steady-state thermodynamic diagram shows an unexpected shift to lower temperatures by adding nanosilica. The migration of nanosilica particles to the SAN domains especially at lower cooling rates in the dynamic measurements is the most likely explanation of these observations. The findings that prove the profound impact of kinetic factors in dynamic temperature measurements are reached in a hybrid system, wherein the SAN chains are preferentially absorbed on the surface of a nanofiller having very small primary particle size. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 137, 48679. 相似文献
70.
Mohammad Hossein Mozaffari Mahmud Khodadad 《Inverse Problems in Science & Engineering》2016,24(6):1048-1064
An inverse geometry problem of identifying simultaneously two irregular interfacial boundaries along with the mechanical properties of the interface domain located between the components of multiple (three) connected regions is investigated. A discrete number of displacement measurements obtained from a uniaxial tension test are used as extra information to solve this inverse problem. A unique combination of global and local optimization method is used, that is, the imperialist competitive algorithm (ICA) to find the best initial guesses of the unknown parameters to be used by the local optimization methods, that is, the conjugate gradient method (CGM) and the simplex method (SM). The CGM and SM are used in series. The performance of these local optimization methods is dependents on the initial guesses of the unknown boundaries and the mechanical properties, that is, Poisson’s ratio and Young’s modulus, so ICA provides the best initial guesses. The boundary elements method is employed to solve the direct two-dimensional (2D) elastostatics problem. A fitness function, which is the summation of squared differences between measured and computed displacements at identical locations on the exterior boundary, is minimized. Several example problems are solved and the accuracy of the obtained results is discussed. The influence of the value of the material properties of the subregions and the effect of measurement errors on the estimation process are also addressed. 相似文献