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991.
Marta Kdzierska Sara Blilid Katarzyna Miowska Joanna Koodziejczyk-Czepas Nadia Katir Mohammed Lahcini Abdelkrim El Kadib Maria Bryszewska 《International journal of molecular sciences》2021,22(21)
Marine polysaccharides are believed to be promising wound-dressing nanomaterials because of their biocompatibility, antibacterial and hemostatic activity, and ability to easily shape into transparent films, hydrogels, and porous foams that can provide a moist micro-environment and adsorb exudates. Current efforts are firmly focused on the preparation of novel polysaccharide-derived nanomaterials functionalized with chemical objects to meet the mechanical and biological requirements of ideal wound healing systems. In this contribution, we investigated the characteristics of six different cellulose-filled chitosan transparent films as potential factors that could help to accelerate wound healing. Both microcrystalline and nano-sized cellulose, as well as native and phosphorylated cellulose, were used as fillers to simultaneously elucidate the roles of size and functionalization. The assessment of their influences on hemostatic properties indicated that the tested nanocomposites shorten clotting times by affecting both the extrinsic and intrinsic pathways of the blood coagulation system. We also showed that all biocomposites have antioxidant capacity. Moreover, the cytotoxicity and genotoxicity of the materials against two cell lines, human BJ fibroblasts and human KERTr keratinocytes, was investigated. The nature of the cellulose used as a filler was found to influence their cytotoxicity at a relatively low level. Potential mechanisms of cytotoxicity were also investigated; only one (phosphorylated microcellulose-filled chitosan films) of the compounds tested produced reactive oxygen species (ROS) to a small extent, and some films reduced the level of ROS, probably due to their antioxidant properties. The transmembrane mitochondrial potential was very slightly lowered. These biocompatible films showed no genotoxicity, and very importantly for wound healing, most of them significantly accelerated migration of both fibroblasts and keratinocytes. 相似文献
992.
Fethi Bouras Mohammed El Hadi Attia Fouad Khaldi Mohammed Si-Ameur 《International Journal of Hydrogen Energy》2017,42(13):8932-8939
This study presents a numerical investigation of the effects of mixing methane/hydrogen on turbulent combustion processes taking place in a burner similar to that integrated in gas turbine power plants. Thereby, in comparison to the reference case where the burner is fuelled by 100% of methane, the variations of the axial velocity field, temperature field and mass fraction of carbon monoxide field are examined for different percentages of hydrogen fuel injection. The computed results, obtained by using the software Fluent-CFD, are compared and validated against experimental reference data. Results show that the hydrogen addition to the methane has an impact on all physical and chemical parameters of the reactive system. 相似文献
993.
Tabbi Wilberforce Zaki El-Hassan F.N. Khatib Ahmed Al Makky Ahmad Baroutaji James G. Carton James Thompson Abdul G. Olabi 《International Journal of Hydrogen Energy》2017,42(40):25639-25662
This report presents experimental results derived from a Proton Exchange Membrane fuel cell with a serpentine flow plate design. The investigation seeks to explore the effects of some parameters like cell operational temperature, humidification and atmospheric pressure on the general performance and efficiency of PEM fuel cell using MATLAB. A number of codes were written to generate the polarization curve for a single stack and five (5) cell stack fuel cell at various operating conditions. Detailed information of hydrogen and oxygen consumption and the effect they have on the fuel cell performance were critically analysed. The investigation concluded that the open circuit voltage generated was less than the theoretical voltage predicted in the literature. It was also noticed that an increase in current or current density reduced the voltage derived from the fuel cell stack. The experiment also clearly confirmed that when more current is being drawn from the fuel cell, more water will also be generated at the cathode section of the cell hence the need for an effective water management to improve the performance of the fuel cell. Other parameters like the stack efficiency and power density were also analysed using the experimental results obtained. 相似文献
994.
Mohammed A. Amin Mohamed M. Ibrahim Adil A. Gobouri Gaber A.M. Mersal Nasser Y. Mostafa Tariq Altalhi Salih Al-Juaid 《International Journal of Hydrogen Energy》2017,42(41):25980-25995
A new chlorobis(2-aminomethylbenzimidazole)zinc(II) perchlorate complex [Zn(AMB)2Cl](ClO4) 1 has been synthesized and characterized. Spectral and X-ray structural features led to the conclusion that the zinc(II) complex has a square-pyramidal environment around zinc(II) center with coordination chromophore ZnN4Cl. Different amounts of complex 1 were supported on glassy carbon (GC) electrode yielding three GC-supported complex 1 electrodes with different loading densities (0.2, 0.4, and 0.8 mg cm?2). These electrodes were tested as molecular electrocatalysts for the hydrogen evolution reaction (HER) in phosphate buffer aqueous solutions (pH 7), employing linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS). Results showed that GC-complex 1 catalysts are highly active for the HER, and this catalytic activity enhances with the loading density. The one with the highest loading density (0.8 mg cm?2) exhibited high HER catalytic activity with low onset potential of ?140 mV vs. RHE and a high exchange current density of 0.22 mA cm?2. It required an overpotential of 240 mV to achieve a current density of 10 mA cm?2. It also recorded a turnover frequency (TOF) of 1722 mol of hydrogen per mole of catalyst per hour at overpotential 500 mV, which is comparable with the most active molecular electrocatalysts reported in the literature for H2 generation from aqueous neutral solutions. A catalytic cycle is proposed for the generation of hydrogen by complex 1 and the mechanism of the HER is discussed based on the measured Tafel slope (140 mV dec?1). 相似文献
995.
Abdul J Chaudhary John D Donaldson Susan M Grimes Mukhtar ‐ul‐ Hassan Robert J Spencer 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2000,75(5):353-358
In mixed industrial effluent the presence of metal ions can retard the destruction of organic contaminants and the efficiency of recovery of metal is reduced by the presence of the organic species. Results are presented for a copper–ethylenediaminetetra‐acetic acid (EDTA) system in which both effects occur. An electrochemical cell alone can be used to recover copper in pH range 1.5–4.5 but is not capable of achieving complete mineralisation of EDTA by anodic oxidation. A photolytic cell alone can achieve the destruction of EDTA at pH 3.5 but leaves copper in solution. A combined photolytic–electrochemical system using an activated carbon concentrator cathode achieves the rapid simultaneous destruction of EDTA and recovery of copper. © 2000 Society of Chemical Industry 相似文献
996.
Capillary viscometry has been employed to measure the viscosities of dilute polymer solutions over the temperature range ‐10 to 150 °C. A Group II base oil containing 95% saturates was used as solvent for an olefin copolymer (OCP), a hydrogenated diene copolymer (HDP), and a polymethacrylate (PMA). These three polymers represent the three major families of viscosity index (VI) improvers used nowadays in lubricant formulations. Intrinsic viscosities and Huggins' constants were also determined. The thickening effects of the olefin copolymer and the hydrogenated diene copolymer were found to be higher at low temperatures (e.g., 40 °C) than at higher ones (e.g., 100 °C), which phenomenon was attributed to stronger intermolecular hydrodynamic interactions at low temperatures, as indicated by the Huggins constants. For the hydrogenated diene copolymer and the polymethacrylate polymer, the viscosity increased abruptly when the temperature went below 10 °C. This unusual observation was attributed to the crystallisation of a small fraction of the base oil. Based on the intrinsic viscosity data, it was concluded that at temperatures between 10 and 150 °C, the polymer coil dimension remains a constant for the olefin copolymer and the hydrogenated diene copolymer VI improvers, but increases with increasing temperature for the polymethacrylate VI improver. 相似文献
997.
Imad A Ahmed Abdul Wahab K Ahmed Richard K Robinson 《Journal of the science of food and agriculture》1997,74(1):64-68
Segments of fruits from 12 varieties of date (Phoenix dactylifera) and three stages of maturation were inoculated with a toxigenic strain of Aspergillus parasiticus. During growth at 28°C for 10 days, 8 varieties supported appreciable aflatoxin production at the Khalal stage—the most popular stage for direct human consumption, with a maximum value in excess of 300 μg g-1 of fruit. Marked differences in susceptibility to infection and/or aflatoxin production were observed between varieties and/or stage of maturation. It was concluded that toxigenic aspergilli could proliferate on any date fruits that suffered mechanical damage in the field or during harvesting, and hence that such fruits should be considered as likely to be unfit for human or animal consumption. © 1997 SCI. 相似文献
998.
Bashir Jarrar Amin AlDoaiss Ali Shati Mohammed AlKahtani Qais Jarrar 《IET nanobiotechnology / IET》2021,15(2):221
Silicon dioxide nanoparticles (SiO2 NPs) are widely invested in medicine, industry, agriculture, consuming products, optical imaging agents, cosmetics, and drug delivery. However, the toxicity of these NPs on human health and the ecosystem have not been extensively studied and little information is available about their behavioural toxicities. The current study aimed to find out the behavioural alterations that might be induced by chronic exposure to 10 nm SiO2 NPs. BALB/C mice were subjected to 36 injections of SiO2 NPs (2 mg/kg Bw) and subjected to 11 neurobehavioural tests: elevated plus‐maze test, elevated zero‐maze test, multiradial maze test, open field test, hole‐board test, light‐dark box test, forced swimming test, tail‐suspension test, Morris water‐maze test, Y‐maze test and multiple T‐maze test. Treated mice demonstrated anxiety‐like effect, depression tendency, behavioural despair stress, exploration and locomotors activity reduction with error induction in both reference and working memories. The findings may suggest that silica NPs are anxiogenic and could aggravate depression affecting memory, learning, overall activity and exploratory behaviour. Moreover, the findings may indicate that these nanomaterials (NMs) may induce potential oxidative stress in the body leading to neurobehavioural alterations with possible changes in the vital organ including the central nervous system. 相似文献
999.
Dimethyl meta-isopropenyl benzyl isocyanate (TMI®) is a bifunctional monomer with an unsaturation and an isocyanate group. Bulk copolymerizations of TMI with styrene, methyl methacrylate, and n-butyl acrylate were investigated. Polymerizations were carried out to low conversions in sealed test tubes at 70°C. The copolymer composition was determined using Fourier transform infrared (FTIR) spectroscopy. The data were analyzed using the terminal, as well as restricted penultimate, model of copolymerization. The method of Kelen-Tudos was used to calculate the reactivity ratios according to the terminal model. A nonlinear regression analysis was also carried out. Low reactivity ratio values for TMI were obtained for the copolymerizations with styrene and methyl methacrylate as a result of the inability of TMI to undergo homopolymerization. The value was higher for the copolymerization with n-butyl acrylate. Composition diagrams were generated, and the range of TMI concentration in the monomer charge for the preferential incorporation of TMI in the copolymer was identified. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 559–568, 1998 相似文献
1000.
Mohammed A. Al-Mohimeed C. C. Li 《International journal of imaging systems and technology》1998,9(4):214-229
There has been rapid progress in the application of wavelet transforms to image and image sequence compression. The standard discrete wavelet transform lacks transition invariance in image decomposition which will affect the accuracy of motion estimation from the decomposed subimages in video coding. In this article, we present a study of applying an almost shift-invariant wavelet transform with “oversampled frames” to image sequence compression. With minimal oversampling and biorthogonal spline wavelets in the almost shift-invariant wavelet transform, motion vectors can be more accurately estimated, contributing toward fewer prediction errors in comparison to those obtained with the standard discrete wavelet transform. Thus, an improved compression ratio can be obtained. We present two new algorithms, the full-motion oversampling algorithm (FMOS) and the reduced search multiresolution motion estimation algorithm (MRME), for estimating motion fields at different scales and in different subimages. In the latter, motion vectors at a higher resolution are approximated by the motion vector estimates at a lower resolution through proper scaling. Experiments were performed on three video sequences with a variety of motions including slow, fast, and zooming. Our results have shown that both algorithms, FMOS and MRME, using the almost shift-invariant oversampled frame wavelet transform have reduced prediction errors and enhanced the compression performance in terms of peak-signal-to-noise ratio (PSNR) for the same bit rate when compared to the existing full motion standard algorithm. © 1998 John Wiley & Sons, Inc. Int J Imaging Syst Technol, 9, 214–229, 1998 相似文献