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排序方式: 共有1242条查询结果,搜索用时 15 毫秒
51.
Mohamed Abdin Yahya Saud Hamed Hafiz Muhammad Saleem Akhtar Dan Chen Shanza Mukhtar Peng Wan Asad Riaz Xiaoxiong Zeng 《International Journal of Food Science & Technology》2019,54(6):2084-2093
The objectives of this study were to determine the optimal extraction conditions of polyphenols from Syzygium cumini seeds by response surface methodology and investigate their antioxidant activity and inhibition on α-amylase and pancreatic lipase. As results, the optimal extraction conditions in the ultrasonic extraction process which maximised total polyphenols content, minimised the IC50 values of α-amylase and pancreatic lipase were determined as follows: extraction time 60 min, ethanol concentration 63% and solvent/solid ratio 44 mL g−1. The main phenolic compounds in partially purified fraction of Syzygium cumini seeds were catechin, epicatechin, kaempferol, gallic, 5-caffeoylquinic, caffeic and ferulic acids. In addition, the partially purified fraction inhibited 87.66 ± 5.55 and 86.61 ± 3.15% of α-amylase and pancreatic lipase, respectively. The results suggested that Syzygium cumini seeds could be explored as a natural antioxidant and could be used as a source of highly antidiabetic and anti-obesity bioactive compounds. 相似文献
52.
Faezeh Sharifi M. T. Hamed Mosavian Camellia Zarei 《Chemical Engineering Communications》2016,203(1):64-74
α-Tocopherol (α-Toc) has valuable biological activity, but its activity is limited when exposed to environmental factors. Nanocapsules can be used to overcome this problem. Using nanocapsules in the range of 100–200 nm is more beneficial. A 24 full factorial design was carried out to optimize the size of nanocapsules using the complex coacervation method. The four factors were the amount of the wall material, the ratio of core material to wall material, the pH of the solution, and the speed of the homogenizer. The smallest nanocapsules (176 nm) were obtained at a wall content (gelatine and pectin) of 0.8 mg, a percentage of core material (α-Toc) to wall material of 20%, a pH = 4.5, and a homogenizer speed of 12,000 rpm. The encapsulation efficiency was 90.6 ± 1.1%, and the encapsulation yield was 83.4 ± 1.6%. Assessment of the stability of α-Toc after 1 month showed that encapsulation could improve its stability in the presence of three influential factors: humidity, light, and temperature. 相似文献
53.
Rahmatollah Rahimi Azadeh Tadjarodi Mahboubeh Rabbani Hamed Kerdari Mina Imani 《Journal of Superconductivity and Novel Magnetism》2013,26(1):219-228
In this study, Ba-Cd-Sr-Ti doped Fe3O4 nanohollow spheres were successfully prepared via a simple solvothermal method. The crystal size, structure, morphology and elemental analysis of the as-prepared sample were investigated in detail by X-ray diffraction (XRD), FT-IR, scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy, respectively. Magnetic hysteresis measurement was carried out on a vibrant sample magnetometer (VSM) showing the soft ferromagnetic property at room temperature. The synthesized nanohollow spheres were employed as a photocatalyst to study the photocatalytic degradation of dye contaminations. The UV-Vis results showed that the specimen could well catalyze the decolorizing of congo red (CR) solution and a removal efficiency of 99.5 % was obtained at pH 6. The optical characteristic of the products was studied by estimating the band-gap energy based on diffuse-reflectance spectroscopy (DRS) which represented the doped magnetite with semiconductor metals to be more prone in the visible region as compared to UV region. Some factors such as initial dye concentration, pH, and contact time influencing the decomposition of CR were evaluated. 相似文献
54.
In recent years advanced high strength steels (AHSS) received increased interest for light structures with improved performance, but they are often sensitive to edge cracking during sheet metal forming. In this study mechanically sheared edges were characterized for three dual phase steels (DP600, DP780 and DP980), sheared with three die clearances (5%t, 10%t, 15%t) and along rolling and transverse directions. Microstructures of the materials were provided first, and then the sheared edges were examined by optical microscopy and scanning electron microscopy that reveal the morphology and random feature of the sheared edges. A factorial analysis was performed to reveal the general trends of the processing parameters on four edge zones. A new strain measurement method was used for characterizing strain distribution in the sheared region, which shows the peak strain to be higher than 3. The strain quickly decreases from sheared edge to interior, leaving a shear-affected zone of about 500 μm or 31% of the thickness. The fracture processes and involved mechanisms were discussed. 相似文献
55.
Christina Kopp Afshin Hosseini Shiva P. Singh Petra Regenhard Hamed Khalilvandi-Behroozyar Helga Sauerwein Manfred Mielenz 《International journal of molecular sciences》2014,15(11):21401-21418
The transition period in dairy cows (3 weeks prepartum until 3 weeks postpartum) is associated with substantial mobilization of energy stores, which is often associated with metabolic diseases. Nicotinic acid (NA) is an antilipolytic and lipid-lowering compound used to treat dyslipidaemia in humans, and it also reduces non-esterified fatty acids in cattle. In mice the G-protein coupled receptor 109A (GPR109A) ligand NA positively affects the secretion of adiponectin, an important modulator of glucose and fat metabolism. In cattle, the corresponding data linking NA to adiponectin are missing. Our objective was to examine the effects of NA on adiponectin and AMPK protein abundance and the expression of mRNAs of related genes such as chemerin, an adipokine that enhances adiponectin secretion in vitro. Differentiated bovine adipocytes were incubated with pertussis toxin (PTX) to verify the involvement of GPR signaling, and treated with 10 or 15 µM NA for 12 or 24 h. NA increased adiponectin concentrations (p ≤ 0.001) and the mRNA abundances of GPR109A (p ≤ 0.05) and chemerin (p ≤ 0.01). Pre-incubation with PTX reduced the adiponectin response to NA (p ≤ 0.001). The NA-stimulated secretion of adiponectin and the mRNA expression of chemerin in the bovine adipocytes were suggestive of GPR signaling-dependent improved insulin sensitivity and/or adipocyte metabolism in dairy cows. 相似文献
56.
Hamid Reza Shokouhfar Hamed Jooypa Daryoosh Dideban 《Analog Integrated Circuits and Signal Processing》2018,95(2):295-306
In this paper, the context of modeling of the impact of mismatch and statistical variations on analogue circuit building blocks is emphasized. The aim is to develop a new algorithm which predicts the statistical behavior of important parameters of an amplifier including output resistance, voltage gain and trans-conductance. The relative error of standard deviation of statistical parameters will remain less than 5% compared with the most accurate Monte-Carlo (MC) simulations using atomistic library model-cards. In comparison with other models which are based on the normal distribution of parameters, the proposed model does not need this limiting presumption. On the other hand, the proposed algorithm is more efficient compared with time consuming MC atomistic simulations. 相似文献
57.
Hamed Aminzadeh 《Analog Integrated Circuits and Signal Processing》2018,95(2):271-282
Hybrid cascode feedforward compensation (HCFC) is an effective technique to stabilize nano-scale three-stage amplifiers driving ultra-large load capacitors. It divides the compensation capacitance and shares it between two high-speed local feedback loops embedded within the amplifier core. In this article, a systematic approach to analyze the transfer function and to evaluate the pole expressions of nano-scale HCFC amplifiers is presented. For the first time, the equivalent output impedance is successfully modeled to approximate the complicated transfer function of the HCFC amplifier without the need for lengthy pencil-and-paper calculations. An HCFC amplifier is designed and simulated in 90-nm CMOS technology, to verify the effectiveness of the new analytic approach. The simulated transfer function of the amplifier is almost identical to a calculated transfer function derived based on the new model. 相似文献
58.
Hamed Bazrafshan Razieh Shajareh Touba Zahra Alipour Tesieh Saeideh Dabirnia Bahram Nasernejad 《Chemical Engineering Communications》2017,204(10):1105-1112
In this study, Co3O4 nanosheets were synthesized through hydrothermal method using cobalt nitrate hexahydrate. X-ray diffraction, diffuse reflectance spectra, Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy, and field emission scanning electron microscopy were applied to investigate the properties of as-synthesized samples. Ultimately, the electrochemical and photoelectrochemical properties were evaluated by Mott–Schottky analysis and measuring photoconversion efficiency of Co3O4 nanosheets. The results indicated that Co3O4 nanosheets exhibited a maximum efficiency of 0.92% for water electrolysis under simulated 1.5 global sunlight air mass, which further suggests the excellent potential of Co3O4 nanosheets for application in hydrogen generation through photocatalytic water splitting. 相似文献
59.
Seyed Hamed Barghi Theodore T. TsotsisMuhammad Sahimi 《International Journal of Hydrogen Energy》2014
The question of chemisorption versus physisorption during hydrogen storage in carbon nanotubes (CNTs) is addressed experimentally. We utilize a powerful measurement technique based on a magnetic suspension balance coupled with a residual gas analyzer, and report new data for hydrogen sorption at pressures of up to 100 bar at 25 °C. The measured sorption capacity is less than 0.2 wt.%, and there is hysteresis in the sorption isotherms when multi-walled CNTs are exposed to hydrogen after pretreatment at elevated temperatures. The cause of the hysteresis is then studied, and is shown to be due to a combination of weak sorption – physisorption – and strong sorption – chemisorption – in the CNTs. Analysis of the experimental data enables us to calculate separately the individual hydrogen physisorption and chemisorption isotherms in CNTs that, to our knowledge, are reported for the first time here. The maximum measured hydrogen physisorption and chemisorption are 0.13 wt.% and 0.058 wt.%, respectively. 相似文献
60.
Ahmad Jonidi Jafari Babak Kakavandi Roshanak Rezaei Kalantary Hamed Gharibi Anvar Asadi Ali Azari Ali Akbar Babaei Afshin Takdastan 《Korean Journal of Chemical Engineering》2016,33(10):2878-2890
Discharging the effluents of textile wastewaters into potable water resources can endanger the ecosystem, due to their reactivity, toxicity, and chemical stability. In this research, the application of powder activated carbon modified with magnetite nanoparticles (PAC-MNPs) as an adsorbent for removal of reactive dyes (Reactive black 5 (RB5) and reactive red 120 (RR120)) was studied in a batch system. The adsorption performance was evaluated as a function of temperature, contact time and different adsorbent and adsorbate concentrations. The levels of factors were statistically optimized using Box-Behnken Design (BBD) from the response surface methodology (RSM) to maximize the efficiency of the system. The adsorption process of both dyes was fit with the pseudo-second order kinetic and Langmuir isotherm models. The identified optimum conditions of adsorption were 38.7 °C, 46.3 min, 0.8 g/L and 102 mg/L for temperature, contact time, adsorbent dose, and initial dyes concentration, respectively. According to the Langmuir isotherm, the maximum sorption capacities of 175.4 and 172.4 mg/g were obtained for RB5 and RR120, respectively. Thermodynamics studies indicated that the adsorption process of the reactive dyes was spontaneous, feasible, and endothermic. After five cycles, the adsorption efficiency was around 84 and 83% for RB5 and RR120, respectively. A high value of desorption was achieved, suggesting that the PAC-MNPs have a good potential in regeneration and reusability, and also can be effectively utilized in industrial applications. PAC-MNPs also show a good anti-interference potential for removal of reactive dyes in dye-industry wastewaters. 相似文献