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31.
S. Siavash Saei‐Dehkordi Aziz A. Fallah Mahbubeh Heidari‐Nasirabadi Mehran Moradi 《International Journal of Food Science & Technology》2012,47(8):1579-1585
This study aimed to determine the chemical composition, antimicrobial and antioxidative activity of Satureja khuzestanica Jamzad essential oil. The oil was analysed by GC and GC/MS. Twenty‐eight constituents were identified. The oxygenated monoterpenes (78.22%) were the principal compound group. Among them, carvacrol (53.86%) and thymol (19.84%) were the most abundant constituents. The oil exhibited an acceptable antimicrobial activity against most of the tested microorganisms. The checkerboard method was applied to determine fractional inhibitory concentration indices (FICIs) to interpret the synergetic, additive, indifference or antagonistic interactions between essential oil and each of antimicrobials (lysozyme, ciprofloxacin, fluconazole and amphotericin B) against food‐related microorganisms. The synergetic phenomenon (FICI ≤ 0.5) was observed in majority of combinations with the exception of the essential oil and lysozyme. The oil exhibited good 1,1‐diphenyl‐2‐picrylhydrazyl radical scavenging activity (IC50 = 28.71 μg mL?1). Also, the oil had strong antioxidative activity in β‐carotene‐linoleic acid assay relative antioxidant activity (RAA% = 95.45). This study demonstrated that the essential oil has beneficial biological properties and its simultaneous application with standard antimicrobials against food‐related microorganisms result in reduction in inhibitory doses of the antimicrobials in vitro. 相似文献
32.
33.
Mehran Dadkhah Mohammad Hossein Mosallanejad Luca luliano Abdollah Saboori 《金属学报(英文版)》2021,34(9):1173-1200
Nowadays, as an emerging technology, additive manufacturing(AM) has received numerous attentions from researchers around the world. The method comprises layer-by-layer manufacturing of products according to the 3D CAD models of the objects. Among other things, AM is capable of producing metal matrix composites(MMCs). Hence, plenty of works in the literature are dedicated to developing different types of MMCs through AM processes. Hence, this paper provides a comprehensive overview on the latest research that has been carried out on the development of the powder-based AM manufactured MMCs from a scientific and technological viewpoint, aimed at highlighting the opportunities and challenges of this innovative manufacturing process. For instance, it is documented that AM is not only able to resolve the reinforcement/matrix bonding issues usually faced with during conventional manufacturing of MMCs, but also it is capable of producing functionally graded composites and geometrically complex objects. Furthermore, it provides the opportunity for a uniform distribution of the reinforcing phase in the metallic matrix and is able to produce composites using refractory metals thanks to the local heat source employed in the method. Despite the aforementioned advantages, there are still some challenges needing more attention from the researchers. Rapid cooling nature of the process, significantly different coe fficient of expansion of the matrix and reinforcement, processability, and the lack of suitable parameters and standards for the production of defect-free AM MMCs seem to be among the most important issues to deal with in future works. 相似文献
34.
In this study, epoxy powder as a matrix was combined with different contents of silicon–aluminum–oxygen–nitrogen (SiAlON) nanoparticles using a planetary ball mill. Pure epoxy and nanocomposite powders were applied on the surface of plain carbon steel components by the electrostatic spraying method. Curing of the coatings was done in an oven or microwave for the appropriate time. The coating structure and morphology of the SiAlON nanoparticles were studied by scanning electron microscopy and transmission electron microscopy, respectively. The corrosion properties of the coatings were assessed by immersion, Tafel polarization, and electrochemical impedance spectroscopy tests in 3.5% NaCl solution. The results show that addition of 10 wt % SiAlON nanoparticles markedly increases the corrosion resistance of epoxy coatings. Thus, it can be inferred that the corrosion rate of these coatings is 15 to 18 times lower than that of pure epoxy samples and 8 to 11 times lower than coatings with 20 wt % SiAlON. The higher corrosion resistance of nanocomposite coatings can be attributed to the barrier properties of SiAlON nanoparticles. The tribological performance of the coatings was studied with the pin‐on‐disk test. The results of wear testing show that the samples containing 10 wt % SiAlON provide about five times more wear resistance than pure ones and about two times more than coatings with 20 wt % SiAlON. However, the coefficient of friction for nanocomposite coatings is reduced about 50% compared to the pure sample. Also, the curing process in either regime (oven or microwave) has the same effect on the corrosion and wear properties, and the coatings are completely crosslinked. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43855. 相似文献
35.
Mutations Closer to the Active Site Improve the Promiscuous Aldolase Activity of 4‐Oxalocrotonate Tautomerase More Effectively than Distant Mutations
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Mehran Rahimi Jan‐Ytzen van der Meer Dr. Edzard M. Geertsema Harshwardhan Poddar Dr. Bert‐Jan Baas Prof. Dr. Gerrit J. Poelarends 《Chembiochem : a European journal of chemical biology》2016,17(13):1225-1228
The enzyme 4‐oxalocrotonate tautomerase (4‐OT), which catalyzes enol–keto tautomerization as part of a degradative pathway for aromatic hydrocarbons, promiscuously catalyzes various carbon–carbon bond‐forming reactions. These include the aldol condensation of acetaldehyde with benzaldehyde to yield cinnamaldehyde. Here, we demonstrate that 4‐OT can be engineered into a more efficient aldolase for this condensation reaction, with a >5000‐fold improvement in catalytic efficiency (kcat/Km) and a >107‐fold change in reaction specificity, by exploring small libraries in which only “hotspots” are varied. The hotspots were identified by systematic mutagenesis (covering each residue), followed by a screen for single mutations that give a strong improvement in the desired aldolase activity. All beneficial mutations were near the active site of 4‐OT, thus underpinning the notion that new catalytic activities of a promiscuous enzyme are more effectively enhanced by mutations close to the active site. 相似文献
36.
Nima Bayat Mehran Rezaei Fereshteh Meshkani 《Korean Journal of Chemical Engineering》2016,33(2):490-499
Nickel catalysts supported on mesoporous nanocrystalline gamma alumina with various nickel loadings were prepared and employed for thermocatalytic decomposition of methane into CO x -free hydrogen and carbon nanofibers. The prepared catalysts with different nickel contents exhibited mesoporous structure with high surface area in the range of 121.3 to 66.2m2g?1. Increasing in nickel content decreased the pore volume and increased the crystallite size. The catalytic results revealed that the nickel content and operating temperature both play important roles on the catalytic performance of the prepared catalysts. The results showed that increasing in reaction temperature increased the initial conversion of catalysts and significantly decreased the catalyst lifetime. Scanning electron microscopy (SEM) analysis of the spent catalysts evaluated at different temperatures revealed the formation of intertwined carbon filaments. The results showed that increasing in reaction temperature decreased the diameters of nanofibers and increased the formation of encapsulating carbon. 相似文献
37.
Effect of modified single‐wall carbon nanotubes on mechanical and morphological properties of thermoplastic elastomer nanocomposites based on (polyamide 6)/(acrylonitrile butadiene rubber)
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Thermoplastic elastomer nanocomposites based on acrylonitrile butadiene rubber (NBR) and polyamide 6 (PA6), with acid functionalized single‐wall carbon nanotubes (SWNT), were prepared via a direct melt‐mixing process in an internal mixer. The influence of SWNT content (0, 0.5, 1, 1.5) on morphological properties of PA6/NBR with different ratios (80/20, 70/30, 60/40) were then investigated. Characterization of nanocomposites was conducted by using transmission electron microscopy, scanning electron microscopy, differential scanning calorimetry, and mechanical properties. Scanning electron microscopy micrographs proved the droplet‐matrix blend morphology in which the size of NBR droplets decreased as the SWNT loading increased, suggesting dispersion of SWNT in the PA6 phase. It was further proved by transmission electron microscopy images, showing homogenous dispersion of SWNT in the PA6 phase. Differential scanning calorimetry results showed a slightly reduced percentage of crystallinity in samples containing SWNT. The mechanical properties of nanocomposites indicated an enhancement in tensile strength, modulus, and hardness on increasing SWNT content. J. VINYL ADDIT. TECHNOL., 22:336–341, 2016. © 2014 Society of Plastics Engineers 相似文献
38.
Wan J Basirun Mehran Sookhakian Saeid Baradaran Mohammad R Mahmoudian Mehdi Ebadi 《Nanoscale research letters》2013,8(1):397
Graphene oxide (GO) film was evaporated onto graphite and used as an electrode to produce electrochemically reduced graphene oxide (ERGO) films by electrochemical reduction in 6 M KOH solution through voltammetric cycling. Fourier transformed infrared and Raman spectroscopy confirmed the presence of ERGO. Electrochemical impedance spectroscopy characterization of ERGO and GO films in ferrocyanide/ferricyanide redox couple with 0.1 M KCl supporting electrolyte gave results that are in accordance with previous reports. Based on the EIS results, ERGO shows higher capacitance and lower charge transfer resistance compared to GO. 相似文献
39.
Roxana Family Mehran Solati-Hashjin Shahram Namjoy Nik Ali Nemati 《Protection of Metals and Physical Chemistry of Surfaces》2012,48(6):688-691
In this study hydroxyapatite (HA)/zirconia/alumina composite coatings on titanium metal was carried out using Sol-Gel dip coating and calcination process. Hydroxyapatite-Alumina-Zirconia sol, coated samples in three processes by changing final sol stirring time, aging time, calcination temperature of synthesized powder and prepared coating and rate of coating. Some parts of prepared sol were also synthesized and became powder in all three processes. Scanning electron microscopy was used to estimate the particle size of the surface and for morphological analysis. The functional group and crystallization characteristics of the powders were analyzed using (FTIR) and X-Ray diffraction (XRD). Results show that the morphology of HA-Alumina-Zirconia coatings is more homogenous in the second process with 2 hours final sol stirring time, 20 hours aging time under stirring at 60, 675°C calcination temperature for coating and 850°C for powder and 60mm/min rate of dip coating. 相似文献
40.
Alieh Aminian Mehran Solati-HashjinAli Samadikuchaksaraei Farhad BakhshiFazel Gorjipour Arghavan FarzadiFattolah Moztarzadeh Martin Schmücker 《Ceramics International》2011,37(4):1219-1229
Silicon-substituted hydroxyapatite (Si-HA) with up to 1.8 wt% Si content was prepared successfully by a hydrothermal method, using Ca(NO3)2, (NH4)3PO4 or (NH4)2HPO4 and Si(OCH2CH3)4 (TEOS) as starting materials. Silicon has been incorporated in hydroxyapatite (HA) lattice by partially replacing phosphate (PO43−) groups with silicate (SiO44−) groups resulting in Si-HA described as Ca10(PO4)6−x(SiO4)x(OH)2−x. X-ray diffraction (XRD), Fourier transform IR spectroscopy (FTIR), inductively coupled plasma AES (ICP-AES) and scanning electron microscopy (SEM) techniques reveal that the substitution of phosphate groups by silicate groups causes some OH− loss to maintain the charge balance and changes the lattice parameters of HA. The crystal shape of Si-HA has not altered compared to silicon-free reference hydroxyapatite but Si-incorporation reduces the size of Si-HA crystallites. Based on in vitro tests, soaking the specimens in simulated body fluid (SBF), and MTT assays by human osteoblast-like cells, Si-substituted hydroxyapatite is more bioactive than pure hydroxyapatite. 相似文献