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关键词： Drug   Surfactant   Molecular interactions   Acoustical properties  

摘要： In view of understanding the nature of molecular interactions between surfactant and drug, here we report the experimental conductance (kappa), densities (rho) and ultrasonic velocities (u) of cationic surfactant cetyltrimethylammonium bromide, CTAB (0.5 11 mM) in 2.0 mM aqueous solution of antidiabetic drug metformin hydrochloride as a solvent at different temperatures (303.15, 308.15, 313.15 K). The critical micelle concentration, cmc of CTAB in aqueous solution containing drug was determined from conductance and surface tension study at 298.15, 303.15, 308.15, and 313.15 K. From the experimental density and ultrasonic velocity data, properties such as apparent molar volume (V-2,V-phi), isentropic compressibility (kappa(S)), apparent molar isentropic compressibility (kappa(S,2,phi)), specific acoustic impedance (Z), relative association (R-A) were calculated and interpreted in terms of drug-surfactant interactions and effect of electrolyte drug on micellization of surfactant. Structural changes in studied solution due to presence of organic drug and temperature have been investigated. The thermodynamic properties of micellization like values of Delta G(m)(0), Delta H-m(0), and Delta S-m(0) were calculated. The thermodynamics of micellization has been found to be spontaneous, exothermic and entropy driven process.

关键词： Asphalt mastic   Warm-mix asphalt (WMA)   Reclaimed asphalt pavement (RAP)   Rheological properties   Physico-chemical properties  

摘要： The present study investigated rheological and physico-chemical properties of warm-mix recycled asphalt mastics containing a high percentage (50%) of artificial reclaimed asphalt pavement (RAP) binder. The influence of two typical warm-mix additives (a wax-based R and a surfactant-based M), four mass ratios of filler to asphalt (0.0e1.5), and three aging states (unaged, short-term aged and long-term aged) was evaluated through the dynamic shear rheometer (DSR), bending beam rheometer (BBR), differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) tests. A total of 48 different mastics were tested and analyzed. The results showed that both the increasing RAP binder and filler contents had a stiffening effect on the asphalt mastics over the full range of testing temperatures and significantly reduced the linear viscoelastic strain limits of the mastics. The two warm-mix additives played quite different roles in changing the rheological properties of the mastics. Overall, the addition of the wax based R exhibited a softening effect on the mastics and thus was capable of offsetting the stiffening effect of applying the RAP binder and mineral fillers;whereas the impact of the surfactant-based M on the rheological properties of the mastics was found negligible. The difference of R and M in working mechanisms could be clearly characterized using the chemical FTIR spectra. (c) 2020 Elsevier Ltd. All rights reserved.

关键词： Atmospheric chemistry   Interfaces   Physical chemistry   Biomaterials   Molecules  

关键词： Iron   Catalysts   Viscosity   Petrochemicals   Molybdenum  

摘要： In this work, the catalytic aquathermolysis process of a Colombian heavy crude oil was studied. Reactivity tests were conducted in a microbatch reactor at 270 degrees C and saturation pressure of 5.5 MPa, during 66 h, using iron and molybdenum naphthenates in concentrations of 50-300 ppm as catalysts. The use of these catalysts reduced the gas yield from 1% to 4.2% w/w, the viscosity from 10% to 52.3% with iron naphthenate, and from 11.6% to 31.4% with molybdenum naphthenate. Crudes subjected to catalytic aquathermolysis increased their API gravity from 1.1 to 2.5 and 0.5 to 1.8 units, showing a significant decrease in complex fractions with boiling points above 340 degrees C and conversions in the order of 7% and 8% with respect to the precursors of molybdenum and iron naphthenates. Unlike other studies, the changes in the physical properties were correlated with changes in the chemical structure by ATR-FTIR spectroscopy. The average molecular parameters showed that the greatest differences with respect to the base crude oil were the length of the alkyl chains, the aromaticity, and the sulfurization. Results indicate different characteristics from the catalysts being studied, with iron naphthenate yielding better favorable effects in the change of the physicochemical properties of the improved crude oils. The experimental methodology proposed in this work indicates that the catalytic aquathermolysis process is a recovery method that allows for improving the properties of the crude oils, under reservoir conditions, due to the formation of products of smaller size and molecular weight.

关键词： Circuits   Electrical properties   Electrodes   Ions   Electrolytes  

摘要： Gold, as the noblest metal, is an appropriate model electrode to study electrochemical double layers. This study examines the frequency dispersion of the double layer of polished gold electrodes in perchloric acid with impedance spectroscopy under amplitude, electrolyte concentration, and potential variation. The dynamic perturbation of the double layer equilibrium by impedance measurements shows a constant phase (CP) response (phase angle of approximately -75 degrees), which is responsible for a frequency dispersion of the capacitance. The response is almost independent of the excitation amplitude, for which the CP behavior is ascribed to resistive-capacitive (RC) contributions of the electric field-driven ion separation instead of the previously reported diffusion-limited adsorption processes. The RC character of the double layer in combination with the electrolyte resistance is accompanied by a relaxation that can damp the ion movement and the related ion separation. At the relaxation frequency, the capacitance is found to be independent of the electrolyte concentration, which is attributed to a constant ratio of the contributions of damped ion movement and dielectric polarization of water molecules.

关键词： Atmospheric chemistry   Interfaces   Physical chemistry   Biomaterials   Molecules  

摘要： The large number of pollutants discharged into the aquatic environment may influence the physicochemical and biological qualities of the aquatic ecosystem. This study discloses the global quality of the surface waters and the effect of physicochemical variables on the abundance of the African freshwater crab Potamon algeriense inhabiting Zegzel watercourse, a mountain stream in the northeast of Morocco. Physicochemical variables including streamflow, water temperature, pH, dissolved oxygen, suspended matter, chloride, calcium, magnesium, ammonia, nitrite, nitrate, orthophosphate, and organic matter were evaluated monthly for one year (October 2017-September 2018). The evaluation of the physicochemical quality showed that the waters of all the stations studied are between the excellent and good quality classes concerning all the physicochemical variables and highlights also two variations with a tendency towards degradation, one spatial from upstream to downstream and the other seasonal from the wet to the dry period. The abundance of crabs was recorded to exhibit a positive correlation with dissolved oxygen, calcium (N = 44) (p < 0.01), and magnesium. However, a negative correlation has been noticed for streamflow (N = 1) (p < 0.01), water temperature, pH, suspended matter, chloride, ammonia, nitrite, nitrate, orthophosphate, and organic matter. The results obtained reveal that besides the biotic variables, the distribution of P. algeriense also depends on these specific environmental variables.

关键词： Pyrazoline   optical properties   sensor   metal ion  

摘要： The title compound 2-(3-(2,5-dimethylfuran-3-yl)-5-(9-ethyl-9H-carbazol-3-yl)-4,5-dihydro-1H-pyrazol-1-yl)benzo[d]thiazole (DEPT) was synthesized by the reaction of 2-hydrazinobenzothiazole with chalcone (DFCP). The structure of the DEPT was established by the spectroscopic techniques and elemental analysis. Photophysical and physicochemical properties of the DEPT chromophore was studied by absorption and fluorescence spectroscopy. The optical properties of newly synthesized DEPT chromophore were depended on the different polarity of the solvents. Effects of two surfactants cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS) of the DEPT chromophore were studied and suggested that, it can be used as probe to determine the critical micelle concentration of the CTAB and SDS surfactants. Moreover, DEPT chromophore can be used as fluorometric detection of selective Cu2+ metal ion. According to the obtained data, the fluorescence intensity of the DEPT was decreased intensity of the fluorescence spectra significantly by the concentration dependent manner. So the DEPT can be used as on to off fluorescence chemosensor for the detection of Cu2+ metal ion. Quenching behavior was explained by the Benesi-Hildebrand and Stern-Volmer mechanism.

关键词： edible film   navy bean starch   corn starch   physicochemical properties  

摘要： BACKGROUND Recently, there has been a great interest in developing new applications of edible dry beans (Phaseolus vulgarisL.). The utilization of starch, comprising the major component of dry bean seeds, for the preparation of edible films has just emerged. RESULTS In the present study, we chose navy bean as a model dry bean source, isolated its starch component, prepared edible films with different formulations (35 and 40 g L-1), and compared these with the films made using isolated and commercial corn starches. Sunflower oil at 10 g L(-1)was dispersed into film-forming solution to design composite films. The water vapor barrier property, mechanical properties and microstructure of starch films from navy bean and corn were studied to evaluate their potential for use in food packaging. All of the films had smooth and uniform surface and were transparent. CONCLUSION Navy bean starch film showed physicochemical and mechanical properties comparable to corn starch films, and the addition of sunflower oil could further improve the water vapor barrier and mechanical properties of films. The findings obtained in the present study demonstrate the potential of using navy bean starch to prepare edible films. (c) 2020 Society of Chemical Industry

关键词： Carvedilol   Solidified self-nanoemulsifying drug delivery system   Surface-modified microsphere   Solubility   Dissolution   Physicochemical property   Pharmacokinetics in rats  

摘要： In this study, a solidified self-nanoemulsifying drug delivery system (solidified SNEDDS) and surface-modified microspheres were developed for enhancing the oral bioavailability of carvedilol. Based on the aqueous solubility test, liquid SNEDDS was composed of Peceol (TM) (oil), Tween (R) 80 (surfactant), and Labrasol (R) (co-surfactant) at a weight ratio of 25/50/25, generating the smallest nanoemulsion droplet size. Then, carvedilol was added to liquid SNEDDS and spray-dried with Aerosil (R) to fabricate the solidified SNEDDS. Surface-modified microspheres were manufactured using copovidone (polymer) and Tween (R) 80 (surfactant) according to aqueous solubility test results. The proper ratio of copovidone and Tween (R) 80 was determined based on the solubility and dissolution test. Both prepared formulations and carvedilol powder were compared using four different criteria: physicochemical characteristics, solubility, dissolution, and oral bioavailability. For solidified SNEDDS, carvedilol was encapsulated in liquid SNEDDS and absorbed to the Aerosil (R) surface, leading to the conversion from a crystalline to an amorphous state. However, the drug maintained its crystal form in the surface-modified microspheres. Round and even-sized particles were attached to the rough surfaces of drug, suggesting that hydrophilic carriers adhered to the hydrophobic drug. All formulations significantly improved drug solubility, dissolution, plasma concentrations, C-max, and AUC compared to carvedilol powder. The parameters were ranked in the following order: solidified SNEDDS > surface-modified microspheres > carvedilol powder. As a result, different solubility-increasing mechanisms provided differences in performance. For carvedilol, the formation of a nano-emulsion in solidified SNEDDS resulted in an efficient supersaturated state, leading to improved solubility (similar to 6.1 fold), dissolution (similar to 1.8 fold), and oral bioavailability (similar to 1.4 fold) that was supe