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Mohammad Tariqul Islam Ahmed Toaha Mobashsher Norbahiah Misran 《Journal of Infrared, Millimeter and Terahertz Waves》2010,31(12):1427-1437
A novel and simple coplanar waveguide fed compact antenna is introduced in this paper. The antenna structure combines the
advantages of CPW with those of the broadband antenna and simplifies the structure of the antenna by reducing the number of
metallization level to construct uni-planar antenna. Prototype of the proposed antenna have been constructed and studied experimentally.
The measured results agrees well with the simulated prediction and shows a broad bandwidth of 6 GHz ranging from 3.5 GHz to
9.5 GHz with VSWR ≤2 (return loss ≤−10 dB), which is equivalent to 92.3% impedance bandwidth centered at 6.5 GHz. The proposed
antenna shows stable radiation characteristics, gain and axial ratio of less than 1 dB over the whole operating bandwidth.
Furthermore, an extensive parametric study was performed to realize the relationship between the resonance frequencies of
the broadband antennas and different parameters which is helpful for advancement of the antenna design. 相似文献
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Wai-Fun Leong Kok-Whey Cheong Oi-Ming Lai Kamariah Long Yaakob B. Che Man Misni Misran Chin-Ping Tan 《Journal of the American Oil Chemists' Society》2011,88(5):717-725
The purpose of this study was to optimize the production parameters for water-soluble phytosterol nanodispersions. Response surface methodology (RSM) was employed to model and optimize three of the processing parameters: mixing time (t) by conventional homogenizer (1–20 min), mixing speed (v) by conventional homogenizer (1,000–9,000 rpm) and homogenization pressure (P) by high-pressure homogenizer (0.1–80 MPa). All responses [i.e., mean particle size (PS), polydispersity index (PDI) and phytosterols concentration (Phyto, mg/l)] fitted well to a reduced quadratic model by multiple regressions after manual elimination. For PS, PDI and Phyto, the coefficients of determination (R 2) were 0.9902, 0.9065 and 0.8878, respectively. The optimized processing parameters were 15.25 min mixing time, 7,000 rpm mixing speed and homogenization pressure 42.4 MPa. In the produced nanodispersions, the corresponding responses for the optimized preparation conditions were a PS of 52 nm, PDI of 0.3390 and a Phyto of 336 mg/l. 相似文献
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Liposomes have been used widely as carriers for active ingredients in cosmetics because of their ability to encapsulate both hydrophilic and hydrophobic compounds. In this work, fatty acid liposomes were prepared and introduced into olive oil-in-water emulsions stabilized by C14–C18 sucrose ester mixtures at pH 8.5. Light microscopy images of the emulsions showed evidence of the coexistence of oleic acid liposomes with the emulsions. As the alkyl chain length of the sucrose ester increased, the average droplet size decreased, while the zeta potential became more negative. Further decrease in droplet size was observed when borate buffer was added to the aqueous phase. The free fatty acids in the sucrose esters and olive oil are neutralized in borate buffer; consequently, fatty acid salts were produced and served as co-surfactants. The synergistic stabilization of emulsions by the mixture of sucrose esters and fatty acid salt resulted in higher stability, smaller droplet size, and lower polydispersity. The drastic increase in negative zeta potential was possibly due to the presence of free fatty acid salts in the emulsion systems. The flow curves at steady rate displayed five distinctive regions. The polydispersity of droplets enhanced the shear thickening effect at low shear rates and shear-banding effect at middle shear rates. Formation of fatty acid salts as co-surfactants caused the viscosities of the emulsions to increase by an order of magnitude. The presence of oleic acid liposome significantly reduced the viscosities of the emulsion by half an order of magnitude; this decreased viscosity helped enhance better spreadability. 相似文献
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Wai-Fun Leong Oi-Ming Lai Kamariah Long Yaakob B. Che Man Misni Misran Chin-Ping Tan 《Food chemistry》2011
The purpose of this study was to prepare and characterise water-soluble phytosterol nanodispersions for food formulation. The effects of several factors were examined: four different types of organic phases (hexane, isopropyl alcohol, ethanol and acetone), the organic to aqueous phase ratio and conventional homogenisation vs. high-pressure homogenisation. We demonstrated the feasibility of phytosterol nanodispersions production using an emulsification–evaporation technique. The results showed that hexane was able to produce the smallest particle size at a mean diameter of approximately 50 nm at monomodal distribution. Phytosterol nanodispersions prepared with a higher homogenisation pressure and a higher organic to aqueous phase ratio resulted in significantly larger phytosterol nanoparticles (P < 0.05). Phytosterol loss after high-pressure homogenisation ranged from 3% to 28%, and losses increased with increasing homogenisation pressure. Elimination of the organic phase by evaporation resulted in a phytosterol loss of 0.5–9%. 相似文献
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Nonionic Mixed Surfactant Stabilized Water-in-Oil Microemulsions for Active Ingredient In Vitro Sustained Release 下载免费PDF全文
Olive oil is an excellent dispersing medium for water‐in‐oil microemulsions as it helps hydrate the skin and enhances the release of the active ingredients. In this study, mixed surfactants containing Span® 80 with varied Tween® series at 1:1 ratio were prepared with olive oil and water to produce water‐in‐oil microemulsions. The microemulsions were used to study the in vitro release of the active ingredients with different water solubilities. A microemulsion olive oil/water/mixed surfactant (56:4:40 by weight) was selected from the constructed phase diagram for further physical characterization. The analysis showed that the microemulsion composed of Span® 80 and Tween® 80 (ST80) was the most suitable surfactant combination. Equal amounts of ascorbic acid, caffeine and lidocaine were solubilized in ST80 microemulsions to study their release rate. Physical evaluation of ST80 microemulsions incorporating the active ingredients showed no apparent change compared to the ST80 microemulsion alone. The in vitro release study showed that the rate of active ingredients released from the microemulsion into the receptor chamber depends on their hydrophobicity, whereby lidocaine and caffeine were fivefold and twice as fast, respectively, with respect to ascorbic acid. ST80 microemulsions show constant rate of active ingredient release, demonstrating the sustained release properties of the system. 相似文献
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A Comparative Approach for the Preparation and Physicochemical Characterization of Lecithin Liposomes Using Chloroform and Non‐Halogenated Solvents 下载免费PDF全文
Sumaira Naeem Lik Voon Kiew Lip Yong Chung Kiew Siaw Fui Misni Bin Misran 《Journal of surfactants and detergents》2015,18(4):579-587
Organic solvents used in various pharmaceutical preparations may be associated with chronic health effects, with special emphasis on halogenated solvents. Liposomes, lipid bilayer membrane carriers, have potential applications in targeted drug delivery systems. The non‐halogenated solvents, acetonitrile and ethanol, were used in comparison to commonly used chloroform. The effect of solvents and dispersion medium was demonstrated using physicochemical properties, stability studies and hemolytic activity. Increased sonication time showed decreased particle size in phosphate buffer saline and water medium. Vesicles prepared from all solvents exhibited better stability in phosphate saline buffer than water when evaluated by particle size and zeta potentials. Liposomes showed a positive zeta potential in buffer solution whereas liposomes in water showed negative zeta potential. In vitro hemolytic activity of liposomes was done with fresh human red blood cells. Results in buffer solution were in the range of 1–4 % which further proved this medium superior to pure water. The findings of this study are helpful in suggesting the formulation of thin films by less hazardous solvents in terms of the environmental integrity and human health. 相似文献
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A polymeric carrier has high potential as active ingredient delivery vehicle owing to its biocompatibility and biodegradability. In this work, pH dependency of the oppositely charged polymers in forming nanoparticle was investigated. A positively charged chitosan and a negatively charged κ-carrageenan were mixed at varied mass ratios (v/v) with a pH ranged from 3 to 6, respectively, to form nanoparticles through polyelectrolyte complexation. The main interest of this research, is to evaluate the effect of pH on the formation of stable active ingredients encapsulated nanoparticle for sustained release. Based on the FTIR result, the presence of new absorption band at 1584 cm?1 and slight shift in the spectrum, indicated the complexation of the polymers. The Zetasizer’s measurements showed that irrespective to the combination of chitosan and κ-carrageenan, increase in pH solution decreased the size and the zeta potential of the nanoparticles. Furthermore, depending on the combinations, the yield and the swelling percentage of the nanoparticle could reached up to 80 and 200%, respectively. Among the mass ratio combinations, the ratio 1:1 at pH 4 had the best physical properties. The encapsulation efficiency of the κ-carrageenan-chitosan nanoparticles exhibited higher preference towards more water soluble active ingredients, ascorbic acid as compared to caffeine and lidocaine. In addition, the slow release of active ingredients from the κ-carrageenan-chitosan nanoparticles, is plausibly due to the electrostatic interaction and compactness of the nanoparticles. Thus, they might be suitable for prolonged release applications. 相似文献
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Reflection phase response of microstrip stacked ring elements 总被引:1,自引:0,他引:1
A periodic array of grounded stacked ring elements is shown to provide a controllable reflection phase response which is determined by the ratio of their diameters. Simulated and measured results at X-band are used to demonstrate that this arrangement is suitable for broadband dual frequency reflectarray antennas 相似文献