排序方式: 共有51条查询结果,搜索用时 15 毫秒
21.
Hamed Hamishehkar Jaber Emami Abdolhossein Rouholamini Najafabadi Kambiz Gilani Mohsen Minaiyan Hamid Mahdavi Ali Nokhodchi 《Colloids and surfaces. B, Biointerfaces》2009,74(1):340-349
Biodegradable polymeric microspheres are ideal vehicles for controlled delivery applications of drugs, peptides and proteins. Amongst them, poly(lactic-co-glycolic acid) (PLGA) has generated enormous interest due to their favorable properties and also has been approved by FDA for drug delivery. Insulin-loaded PLGA microparticles were prepared by our developed single phase oil in oil (o/o) emulsion solvent evaporation technique. Insulin, a model protein, was successfully loaded into microparticles by changing experimental variables such as polymer molecular weight, polymer concentration, surfactant concentration and stirring speed in order to optimize process variables on drug encapsulation efficiency, release rates, size and size distribution. A 24 full factorial design was employed to evaluate systematically the combined effect of variables on responses. Scanning electron microscope (SEM) confirmed spherical shapes, smooth surface morphology and microsphere structure without aggregation. FTIR and DSC results showed drug–polymer interaction. The encapsulation efficiency of insulin was mainly influenced by surfactant concentration. Moreover, polymer concentration and polymer molecular weight affected burst release of drug and size characteristics of microspheres, respectively. It was concluded that using PLGA with higher molecular weight, high surfactant and polymer concentrations led to a more appropriate encapsulation efficiency of insulin with low burst effect and desirable release pattern. 相似文献
22.
Alireza Pourhossein Masoud Madani Mohsen Shahlaei Kambiz Fakhri Parisa Alimohamadi Maryam Amiri 《Central European Journal of Chemistry》2009,7(3):382-387
A sensitive, simple and rapid method for ultra-trace determination of iron and manganese based on ultrasound assisted pseudodigestion
in citric acid fermentation medium samples (beet and cane molasses and raw sugar based mediums) is described. Parameters influencing
pseudo-digestion, such as sonication time, sample mass and solvent system were fully optimized. Final solutions obtained upon
sonication were analyzed by electrothermal atomic absorption spectrometry (ETAAS). The best conditions for metal pseudo-digestion
were as follows: a 25, 30 and 20 min sonication time for beet molasses, cane molasses and raw sugar based medium samples,
respectively, 0.7 g sample mass of raw sugar based samples, 0.5 g sample mass of molasses based samples and an extraction
mixture of concentrated HNO3-H2O2, in 25 mL of solvent. Analytical results obtained for the two metals by ultrasound assisted pseudo-digestion and conventional
wet digestion methods showed a good agreement. This method reduces the time required for all treatments (heating to dryness,
cooling and separation) in comparison with conventional wet digestion method. The accuracy of the method was tested by comparing
the obtained results with that of conventional wet digestion method.
相似文献
23.
Kambiz A. Mahabadi Isabel Rodriguez Chee Y. Lim Devendra K. Maurya Peter C. Hauser Nico F. de Rooij 《Electrophoresis》2010,31(6):1063-1070
An optimized capacitively coupled contactless conductivity detector for microchip electophoresis is presented. The detector consists of a pair of top–bottom excitation electrodes and a pair of pickup electrodes disposed onto a very thin plastic microfluidic chip. The detection cell formed by the electrodes is completely encased and shielded in a metal housing. These approaches allow for the enhancement of signal coupling and extraction from the detection cell that result in an improved signal‐to‐noise‐ratio and detection sensitivity. The improved detector performance is illustrated by the electrophoretic separation of six cations (NH, K+, Ca2+, Na+, Mg2+, Li+) with a detection limit of approximately 0.3 μM and the analysis of the anions (Br?, Cl?, NO, NO, SO, F?) with a detection limit of about 0.15 μM. These LODs are significantly improved compared with previous reports using the conventional top–top electrode geometry. The developed system was applied to the analysis of ions in bottled drinking water samples. 相似文献
24.
Hakimeh Sharafi Mahya Abdoli Hamidreza Hajfarajollah Nima Samie Leila Alidoust Habib Abbasi Jamshid Fooladi Hossein Shahbani Zahiri Kambiz Akbari Noghabi 《Applied biochemistry and biotechnology》2014,173(5):1236-1249
A biosurfactant-producing thermophile was isolated from the Kahrizak landfill of Tehran and identified as a bacterium belonging to the genus Aneurinibacillus. A thermostable lipopeptide-type biosurfactant was purified from the culture medium of this bacterium and showed stability in the temperature range of 20–90 °C and pH range of 5–10. The produced biosurfactant could reduce the surface tension of water from 72 to 43 mN/m with a CMC of 1.21 mg/mL. The strain growing at a temperature of 45 °C produces a substantial amount of 5 g/L of biosurfactant in the medium supplemented with sunflower oil as the sole carbon source. Response surface methodology was employed to optimize the biosurfactant production using sunflower oil, sodium nitrate, and yeast extract as variables. The optimization resulted in 6.75 g/L biosurfactant production, i.e., 35 % improved as compared to the unoptimized condition. Thin-layer chromatography, FTIR spectroscopy, 1H-NMR spectroscopy, and biochemical composition analysis confirmed the lipopeptide structure of the biosurfactant. 相似文献
25.
Kambiz Ansari Jasmine Yuen Shu Ying Peter C. Hauser Nico F. de Rooij Isabel Rodriguez 《Electrophoresis》2013,34(9-10):1390-1399
A new design for a compact portable lab‐on‐a‐chip instrument based on MCE and dual capacitively coupled contactless conductivity detection (dC4D) is described. The instrument is battery powered with total dimension of 14 × 25 × 8 cm3 (w × l × h), and weighs 1.2 kg. The device consists of a front electrophoresis compartment which has the chip holder and the chip, the associated high‐voltage electrodes for electrophoresis injection and separation and the detector. The detection cell is integrated into the device housing with an exchangeable plug‐and‐play cartridge format. The design of the dC4D cell has been optimized for maximum performance. The cartridge includes the top–bottom excitation and pick up electrodes incorporated into the cell and connected to push‐pull self‐latching pins that are insulated with plastic. The metal frame of the cartridge is grounded completely to eliminate electronic interferences. The cartridge is designed to clamp a thin fluidic chip at the detection point. The cartridges are replaceable whereby different cartridges have different detection electrode configurations to employ according to the sensitivity or resolution needed in the specific analytical application. The second compartment consists of all the electronics, data acquisition card, high‐voltage modules of up to ±5 kV both polarity, and batteries for 10 h of operation. The improved detector performance is illustrated by the electrophoresis analysis of six cations (NH4+, K+, Ca2+, Na+, Mg2+, Li+) with a detection limit of approximately 5 μM and the analysis of the anions (Br?, Cl?, NO2?, NO3?, SO42?, F?) with a detection limit of about 3 μM. Analytical capabilities of the instrument for food and medical applications were evaluated by simultaneous detection of organic and inorganic acids in fruit juice and inorganic cations and anions in rabbit blood samples and human urine samples are also demonstrated. 相似文献
26.
In this paper, in order to enhance the performance characteristics of photodetector, an InAs/GaAs quantum ring infrared photodetector (QRIP) with resonant cavity structure is proposed. For this purpose, distributed bragg reflectors (DBR) in the bottom of structure are used to reflect the transmitted beam back into the active region. For further confinement of light in the active region, a gold layer is added to structure as top reflector and the performance of structures is compared with and without top reflector. Numerical simulation results show that using resonant cavity structure can improve quantum efficiency and responsivity of photodetector. Furthermore, the specific detectivity of device can increase about one order of magnitude using resonant cavity structure. Results show specific detectivity, $\hbox {D}^{*}$ , about $\sim $ 10 $^{11}\,(\hbox {cm}\,\hbox {Hz}^{1/2}\hbox {/W})$ for conventional QRIP and $\sim $ 10 $^{12}\,(\hbox {cm}\,\hbox {Hz}^{1/2}\hbox {/W})$ for conventional QRIP embedded in resonant cavity. As a result of enhancement in detectivity, the operation temperature of detector can be increased up to about 150 K. 相似文献
27.
An experimental apparatus was built to measure the time constant of fine wet-bulb thermocouples in air. Rapid response solenoid valves (15 msec response time) were used to control airflow through tubing into which wet-bulb thermocouples were placed. Wet-bulb thermocouples (type T, 0.005 cm diameter) with the tip (bead) covered with a moistened wick were tested. Experiments were performed for air velocities ranging from 1.50 to 2.5 m sec?1 (Reynolds number of 2,500 to 4,500) and wet-bulb temperature ranging from 12.5 to 17.4°C. Experimental conditions were selected to simulate human respiratory conditions. Correlation between airflow velocity and wet-bulb thermocouple time constants was not significant at all levels. 相似文献
28.
29.
A quantum ring based intersubband photodetector is designed and its optical performance is studied based on a developed theoretical model. Intersubband absorption of quantum rings is numerically calculated for two transitions, from ground state to first excited state and to continuum energy and the effects of broadening mechanisms are studied. Device show responsivity about 0.2 A/W at T = 80 K and V = 2 V. Dark current of structure with and without the resonant tunneling barriers is calculated. Specific detectivity \((D^*)\) is studied at different temperatures and peak values about \(3\times 10^{12}\,\hbox {cm Hz}^{1/2}/\hbox {W}\) is obtained at T = 50 K. Results show that inclusion of resonant tunneling barriers leads to improvement in \(D^*\) about one order of magnitude. 相似文献
30.
Journal of Thermal Analysis and Calorimetry - This investigation provides a review on the applications of nanofluids in porous media. The transport phenomena in porous media have been of continuing... 相似文献