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91.
Mohd Abul Kalam Sultan Alshehri Aws Alshamsan Musaed Alkholief Raisuddin Ali 《Drug development and industrial pharmacy》2013,39(8):1258-1264
Gemfibrozil (GEM) is cholesterol-lowering agent which is being proposed as poorly water soluble drug (PWSD). Temperature based solubility values of GEM are not yet available in literature or any pharmacopoeia/monograph. Hence, the present studies were carried out to determine the solubility of PWSD GEM (as mole fraction) in various pharmaceutically used solvents such as water (H2O), methanol (MeOH), ethanol (EtOH), isopropanol (IPA), 1-butanol (1-BuOH), 2-butanol (2-BuOH), ethylene glycol (EG), propylene glycol (PG), polyethylene glycol-400 (PEG-400), ethyl acetate (EA), dimethyl sulfoxide (DMSO) and Transcutol® (THP) at the temperatures ranging from T?=?298.2 K–318.2?K under atmospheric pressure P?=?0.1?MPa. Equilibrium/experimental solubilities of GEM were recorded by applying a saturation shake flask methodology and regressed using ‘van’t Hoff and Apelblat models’. Hansen solubility parameters for GEM and various pharmaceutically used solvents were estimated using HSPiP software. The solid states of GEM (both in pure and equilibrated states) were studied by ‘Differential Scanning Calorimetry’ which confirmed no transformation of GEM after equilibrium. Experimental solubilities of GEM in mole fraction were observed maximum in THP (1.81?×?10?1) followed by DMSO, PEG-400, EA, 1-BuOH, 2-BuOH, IPA, EtOH, PG, MeOH, EG and H2O (3.24?×?10?6) at T?=?318.2 K and similar tendencies were also recorded at T?=?298.2 K, T?=?303.2 K, T?=?308.2 K and T?=?313.2 K. ‘Apparent thermodynamic analysis’ on experimental solubilities furnished ‘endothermic and entropy-driven dissolution’ of GEM in each pharmaceutically used solvent. 相似文献
92.
Cure reaction between a series of N-methylaniline-blocked polyisocyanates, based on 4,4′-methylenebis(phenyl isocyanate), poly(tetrahydrofuran) and several substituted N-methylanilines, and n-decanol has been studied. The solid-state isothermal cure reaction was carried out using hot-stage FTIR spectroscopy, in the temperature range of 125–145°C. The urea carbonyl absorption band of blocked polyisocyanate moiety was used to monitor the conversion of blocked polyisocyanate into polyurethane. Kinetic and thermodynamic parameters were calculated using normalized conversion curves. The overall order of cure reaction, for each of the blocked polyisocyanates was found to be first order. Based on the results of kinetics and reaction conditions used in this study, the elimination-addition (SN1) mechanism was suggested for the cure reaction between N-methylaniline-blocked polyisocyanates and n-decanol. The effect of substituents present in the blocking agents on the cure reaction of N-methylaniline-blocked polyisocyanates was investigated and found that the cure reaction of N-methylaniline-blocked polyisocyanates was retarded by electron-donating substituents and facilitated by electron withdrawing substituents. The observed high negative entropy of activation value supports the formation of a four-centered, intramolecularly hydrogen-bonded ring structure during transition state of the cure reaction. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
93.
Aptamer-polyelectrolyte microcapsules are prepared for potential use as triggered delivery vehicles and microreactors. The hollow microcapsules are prepared from the sulforhodamine B aptamer and the polyelectrolytes poly(allylamine hydrochloride) and poly(sodium 4-styrene-sulfonate), using layer-by-layer (LbL) film deposition templated on a sacrificial CaCO(3) spherical core. Scanning electron microscopy and confocal microscopy confirm the formation of spherical CaCO(3) cores and LbL-aptamer microcapsules. Colocalization studies with fluorescently-tagged aptamer and sulforhodamine B verify the ability of the aptamer to recognize its cognate target in the presence of the K(+) ions that are required for its characteristic G-quadruplex formation. Fluorescence recovery after photobleaching studies confirms a significant difference in the permeability of the aptamer-polyelectrolyte microcapsules for the sulforhodamine B dye target compared to control microcapsules prepared with a random oligonucleotide. These results suggest that aptamer-based 'smart' responsive films and microcapsules could be applied to problems of catalysis and controlled release. 相似文献
94.
Yusuf Dilgin Didem Giray Dilgin Zekerya Dursun H. ?smet Gökçel Delia Gligor Burcu Bayrak Bensu Ertek 《Electrochimica acta》2011,(3):1138
It was firstly described that a glassy carbon electrode electropolymerized with methylene blue shows an efficient photoelectrocatalytic activity towards NADH oxidation in a phosphate buffer solution (pH 7.0). In order to perform the photoelectrocatalytic determination of NADH in a flow injection analysis (FIA) system, a home-made flow electrochemical cell with a suitable transparent window for the irradiation of the electrode surface was constructed. The currents obtained from the photoamperometric measurements in the FIA system at optimum conditions (flow rate of carrier solution, 1.3 mL min−1; transmission tubing length, 10 cm; injection volume, 100 μL; and constant applied potential, +150 mV vs. Ag/AgCl) were linearly dependent on the NADH concentration and linear calibration curves were obtained in the range of 1.0 × 10−7–2.0 × 10−4 M. The detection limit was found to be 4.0 × 10−8 M for photoamperometric determination of NADH. 相似文献
95.
Sertac Peker Figen Eren Giray Basak Durmus Nural Bekiroglu Betül Kargül 《Journal of Adhesion Science and Technology》2013,27(5):509-519
This study evaluated the effect of tooth preparation method (diamond bur vs. Er:YAG laser) on the microleakage levels of glass ionomers and resin composite. Human permanent premolars (N = 80) were randomly divided into two groups (n = 40). Cavities on half of the teeth were prepared using diamond bur for enamel and carbide bur for dentin and the other half using Er:YAG laser. The teeth were randomly divided into four groups according to the restoration materials, namely (a) ChemFil Rock (CFR), (b) IonoluxAC (IAC), (c) EQUIA system (EQA) and one resin composite (d) AeliteLS (ALS) (n = 10 per group). Microleakage (μm) was assessed at the occlusal and gingival margins after dye penetration (0.5% basic fuchsine for 24 h). On the occlusal aspect, while the cavity preparation types significantly affected the microleakage for CFR (p = 0.015), IAC (p = 0.001) glass ionomer restorations, it did not show significant effect for glass ionomer EQA (p = 0.09) and resin composite ALS (p = 0.2). Er:YAG laser presented less microleakage compared to bur preparation in all groups except for EQA. On the gingival aspect, microleakage decreased significantly for CFR (p = 0.02), IAC (p = 0.001), except for EQA where significant increase was observed (p = 0.001) with the use of Er:YAG laser. Microleakage decrease was not significant at the gingival region between diamond bur and Er:YAG laser for ALS (p = 0.663). At the occlusal and gingival sites in all groups within each preparation method, microleakage level was not significant. 相似文献
96.
Mostafa Nofal Sultan Aljahdali Yasser Albagory 《AEUE-International Journal of Electronics and Communications》2013,67(1):58-63
In this paper, some conventional filtering windows are modified and applied to uniform concentric circular antenna arrays (UCCA) for spatial smoothing and sidelobe reduction. The modified windows are applied to individual rings of the array that will taper the corresponding current amplitudes. The resulted sidelobe level, beamwidth and stability for amplitude errors are discussed for the different proposed tapering windows where it shows a sidelobe reduction to about 49 dB as in the case of Binomial UCCA while the Hamming window shows the most immunity to tapered amplitude errors. 相似文献
97.
Abstract Results are reported on the support effect on the catalytic activity in thiophene hydrodesulfurization (HDS) of sulfided Ni-Mo catalysts supported on pure niobia, mixed oxides of Nb2O5-TiO2 prepared by sol-gel method, and Nb2O5/TiO2 and Nb2O5/Al2O3 prepared by surface deposition. The prepared samples were characterized using N2 adsorption at ?196°C, X-ray diffraction (XRD), and temperature-programmed reduction (TPR) techniques. This study showed activity variation as a function of support composition. The activity of niobia-rich catalysts was no longer promoted by the synergy between Ni and Mo. The absence of synergy between molybdenum and nickel on niobia can be explained by the strong interaction of each metal with niobia at the expense of interaction with each other. It was found that 5 wt% Nb2O5/TiO2-supported catalyst was the better catalyst for thiophene HDS. It was shown that by means of an adequate support design it is possible to significantly increase the functionalities of HDS catalysts. Semiconducting supports like TiO2 can improve the HDS activity by exerting electronic effects on the active phase, helping in this way the formation of sulfur vacancies. The 5 wt% Nb2O5/TiO2 was also tested at high pressure with gas oil feedstock. It is observed with the hydrogeolysis of sulfur compounds against time-on-stream that the activity of this catalyst decreases fast with time. 相似文献
98.
Yee Sin Ang Shareef Sultan Asya Tawfiq Juncheng Cao Chao Zhang 《Journal of Infrared, Millimeter and Terahertz Waves》2012,33(8):816-824
We theoretically calculate the terahertz waves mixing effect in doped graphene with a finite bandgap. The temperature dependence of the nonlinear intraband optical response at bandgap opening of few tens of meV are investigated. When the external electric field is weak, a moderate level of bandgap opening is found to slightly enhance the nonlinear optical response. The optical response is however significantly altered under strong-field condition. The strong-field nonlinear optical conductivity exhibits two distinct response ‘hot spot’: (i) low temperature with large bandgap and (ii) high temperature with small bandgap. The electric field required for the nonlinear response to dominate over the linear response is typically in the order of 104 V/cm. This value increases rapidly by a factor of 10 in large bandgap and high temperature regimes. Our results suggest that photon mixing effect in gapped graphene is strongly gapped dependent and hence the bandgap opening has to be carefully engineered in order to optimize the photon mixing effect in gapped graphene. 相似文献
99.
The chemical polymerization of aniline in anhydrous medium was investigated using periodic acid, H5IO6 as an oxidant. This is the first time that H5IO6 has been used as an oxidant in the chemical synthesis of conductive polymers. The product was characterized by FTIR, UV–vis spectroscopies, scanning electron microscope (SEM), energy dispersive X-ray (EDX) spectroscopy, thermogravimetric (TG) analysis, and electrical conductivity measurements. EDX and thermogravimetric analysis showed that Pani includes ClO4− and iodine or iodide ion as dopants. Electrical conductivity of polyaniline with H5IO6 was measured as 100 S cm−1. H5IO6 oxidant produces first IO3− and then I2. Therefore, it could ensure both oxidation of aniline by IO3− and then doping polyaniline with I2, without any residual oxidant contamination. I2, which is a well known extrinsic dopant, was produced intrinsically in this study. Thus, H5IO6 was found to be an effective oxidant material for the chemical polymerization of aniline. 相似文献
100.
This paper describes the potential of the development of a seawater desalination system that combines the technologies of reverse osmosis (RO) and photovoltaic (PV) to deliver 100 m3/day of sweet water. Silicon cells are chosen for the PV array and the polyamide thin-film composite seawater Filmtec membranes are selected for the RO system. The software ROSA is adopted to study the influences of the feed pressure on the performance of the system. It is found that as the feed pressure increases, the specific energy of the plant decreases but the percentage of recovery increases. 相似文献