Solution combustion synthesis of FeCr2O4 powders for pigment applications: Effect of fuel type

Solution combustion synthesis of iron chromite was reported using iron(III) nitrate nonahydrate and chromium(III) nitrate nonahydrate as starting materials, as well as glycine, urea, citric acid, and ethylene glycol as fuels. The influence of fuel type on the structure, molecular, microstructure as well as chromatic properties of samples was investigated. The X-ray diffraction (XRD) patterns showed that unlike themodynamical prediction, glycine fuel led to strongest combustion and consequent highest XRD peak intensities and lower lattice parameters. Moreover, the change of fuel type and mixing of fuels affected XRD data. Fourier transform infrared analysis showed that the band position of Cr–O and Fe–O bonds were shifted to higher frequencies by using of fuels with weaker combustion reactions. In addition, scanning electron micrographs showed that different morphologies of FeCr₂O₄ particles were obtained depending on the fuel type and ratios. Energy-dispersive X-ray spectroscopy analysis of the samples showed that oxygen concentration of samples was less than that of stoichiometric ratio of FeCr₂O₄ due to local reducing atmosphere. Furthermore, chromatic properties of the powders showed that the pigment synthesized with glycine fuel has a better and lighter grayish brown color than the other ones and can be used as a suitable industrial candidate to create a brown color in the ceramic glaze.     

Electrospray preparation of propranolol‐loaded alginate beads: Effect of matrix reinforcement on loading and release profile

In the present study, propranolol loaded‐calcium alginate beads were prepared from concentrated solutions of sodium alginate, using combined method of electrospray and ionotropic gelation. The objectives of the study were to increase the propranolol‐HCl loading and to decrease its initial burst release. However, the effects of voltage, nozzle diameter, flow rate, and concentration of sodium alginate on size of the beads and drug entrapment efficiency (DEE) were also investigated. The matrix of alginate beads was reinforced with dextran sulfate and/or coated with chitosan. The mean particle size of the beads, their swelling behavior, and drug entrapment efficiency were characterized. Furthermore, the drug release profiles from the prepared beads in simulated gastric fluid and intestinal fluid were evaluated and compared. Among the parameters that affected the electrospray of alginate, voltage had a pronounced effect on the size of beads. The size of beads was reduced to a minimum value on increasing the voltage. Furthermore, increasing the flow rate, alginate concentration, and nozzle diameter and decreasing the voltage led to improvement in DEE. Enhancing the alginate concentration as well as coating with chitosan and reinforcing with dextran sulfate led to increase of the encapsulation efficiency and therefore decrease of the drug release rate in both pHs. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41334.     

Multi-generational pharmacophore modeling for ligands to the cholane steroid-recognition site in the β1 modulatory subunit of the BKCa channel

Large conductance, voltage- and Ca²⁺-gated K⁺ (BK_Ca) channels play a critical role in smooth muscle contractility and thus represent an emerging therapeutic target for drug development to treat vascular disease, gastrointestinal, bladder and uterine disorders. Several compounds are known to target the ubiquitously expressed BK_Ca channel-forming α subunit. In contrast, just a few are known to target the BK_Ca modulatory β₁ subunit, which is highly expressed in smooth muscle and scarce in most other tissues. Lack of available high-resolution structural data makes structure-based pharmacophore modeling of β₁ subunit-dependent BK_Ca channel activators a major challenge. Following recent discoveries of novel BK_Ca channel activators that act via β₁ subunit recognition, we performed ligand-based pharmacophore modeling that led to the successful creation and fine-tuning of a pharmacophore over several generations. Initial models were developed using physiologically active cholane steroids (bile acids) as template. However, as more compounds that act on BK_Ca β₁ have been discovered, our model has been refined to improve accuracy. Database searching with our best-performing model has uncovered several novel compounds as candidate BK_Ca β₁ subunit ligands. Eight of the identified compounds were experimentally screened and two proved to be activators of recombinant BK_Ca β₁ complexes. One of these activators, sobetirome, differs substantially in structure from any previously reported activator.     

Effect of partial replacement of sand with dry oyster shell on the long-term performance of concrete

To evaluate the practical application of crushed oyster shells (OS) as construction materials, an experimental study was performed based on equal materials proportion and the partial replacement of saturated-surface-dry (SSD) sand with dry oyster shell. More specifically, the long-term mechanical properties and durability of concrete with OS partially substituted for fine aggregate were investigated.Test results indicate that long-term strength of concrete with 10% OS replacement is almost identical to that of normal concrete. However, the long-term strength of concrete with 20% OS replacement is appreciably lower than that of normal concrete. Therefore, higher OS substitution has the possibility of negatively influencing the concrete long-term strength increment. Elastic modulus of concrete with OS replacement decreases as the substitution mixture ratio increases. Specifically, the modulus is reduced by approximately 10–15% when OS are used for 20% of the fine aggregate.The drying shrinkage strain increases as the substitution ratio (SR) of OS is increased. In addition, the existing model code for drying shrinkage and creep does not coincide with the test results of the present study. A prediction equation for drying shrinkage has been developed. The utilization of OS as a fine aggregate in concrete has a positive effect on freezing and thawing resistance and water permeability is also considerably improved. However, OS has no apparent effect on carbonation and chemical attack of concrete.Finally, it is noted that the strength, elastic modulus, drying shrinkage, freezing and thawing resistance, and permeability are significantly affected by increased OS substitution, particularly for long-term performance, while other properties such as creep and carbonation, as well as chemical attack test results, were not substantially affected.     

Preparation of alginate and chitosan nanoparticles using a new reverse micellar system

Alginate and chitosan nanoparticles were prepared using a new reverse micelle system, composed of cetyltrimethylammonium bromide (CTAB) as a surfactant, isooctane as a solvent, and 1-hexananol as a co-solvent. The obtained nanoparticles were characterized by FTIR, DLS and TEM techniques. The main objective of this study was to investigate the effects of polymer concentration, water content, and volumetric ratio of co-solvent to solvent on the physical and morphological properties of the prepared nanoparticles. To evaluate the results, the design of experimental was initially carried out and then the obtained data were statistically analyzed using the Qualitek-4^? software. Results revealed that the size of the prepared alginate and chitosan nanoparticles varied in the range 220?C490 and 210?C1,050?nm, respectively. Furthermore, increasing either alginate or chitosan concentration increased the size of their nanoparticles. The results also showed that the size of nanoparticles was decreased with increasing the volumetric ratio of co-solvent/solvent. Finally, the size of alginate nanoparticles was increased by increasing the water content while it decreased the size of chitosan nanoparticles. Considering the statistical analysis of experiments, the polymer concentration is the major parameter affecting nanoparticles?? size. In contrast, water content has the smallest effect on the size of nanoparticles. However, the difference between the particle sizes of chitosan and alginate nanoparticles cab be attributed to the electrostatic repulsion between chitosan and CTAB.     

Comparison of the effect of laminar and turbulent flow regimes on thermal stresses and strains in an annular fin

Journal of Mechanical Science and Technology - We compared the effect of laminar and turbulent flow regimes on thermal stresses and strains in an annular fin. This comparison showed that...     

Solvothermal synthesis of g-C3N4 and ZnO nanoparticles on TiO2 nanotube as photoanode in DSSC

In this research, the dye-sensitized solar cells (DSSCs) were fabricated by using g-C₃N₄ and ZnO modified TiO₂nanotube (TNT) arrays as photoanodes. The TNT arrays were synthesized by the anodizing method. G-C₃N₄ and ZnO modified TNTs were synthesized via a solvothermal method in which ethylene glycol served as a solvent. The short circuit current (I_SC) and open-circuit voltage (V_OC) of DSSCs based on ZnO + g-C₃N₄modified TNTs photoanode considerably increased from 9.25 mA/cm⁻²to 14.68 mA/cm⁻², and from 0.707 mV to 0.695 mV, respectively, resulting in a135% increase in the efficiency compared with the pure TNT arrays photoanode. However, the DSSC fabricated with g-C₃N₄ TNT did not show much improvement in the conversion efficiency compared with the pure TNT arrays photoanode, implying more effective processes of the carrier production and transport between ZnO, g-C₃N₄ and TNTs. Also, the electrochemical impedance spectroscopy (EIS) and open-circuit voltage decay (OCVD) analyses showed that ZnO + g-C₃N₄ can promote the electron collecting rate, suppress he electron recombination and extend the electron lifetime.     

Modelling and optimization of Fischer–Tropsch products through iron catalyst in fixed-bed reactor

The most important issue for alternative renewable energy source instead of fossil fuels is environmental concern. Human energy supply from carbon waste has an important role in environmental health. Fischer–Tropsch synthesis is a reaction whereby carbon waste such as woods, foodstuffs, sewage, and any material that contains carbon in their structure, produces all oil derivatives including gasoline, diesel, etc. In this paper, the products model and the effective parameters of the model and also, the interaction between the parameters were investigated. $P_{{\text{H}}_2}$ and $T1P_{{\text{H}}_2}$ are effective parameters and interaction in the model, respectively. Finally, the optimization of products was discussed. The best operating conditions for minimizing CO₂ and CH₄ and maximizing C₂H₄ and C₂H₆ were investigated. This method can be suitable for environmental purposes.     

Novel fabrication of PdCu nanostructures decorated on graphene as excellent electrocatalyst toward ethanol oxidation

In this study, the electrochemical reduction reaction of copper(II) formate on the graphene/glassy carbon electrode (G/GCE) surface in the HCl (5 wt.%) was employed for fabrication of the PdCu nanostructures by galvanic displacement reaction. This method has a number of advantages including being environmentally-friendly, simplicity, inexpensiveness and fast. The PdCu nanostructures decorated on the G/GCE were fabricated in two steps: (1) electrochemical reduction reaction of copper(II) formate to Cu on the G/GCE and (2) the galvanic replacement reaction between Cu and Pd²⁺ ions. The physical and electrochemical properties of as-prepared PdCu/G were investigated via Field Emission Scanning Electron Microscopy, Energy Dispersive X-ray Spectroscopy, Cyclic Voltammetry, Chronoamperometry, and Electrochemical Impedance Spectroscopy. The PdCu/G compositional effect on ethanol oxidation in alkaline media is investigated. The results were shown that the catalytic activity and durability of PdCu/G catalyst are superior to those of Pd/C electrocatalyst for ethanol oxidation. The PdCu/G increased the current density 6.2 times more than Pd/C with a 50 mv negative shift in onset potential for electrooxidation of ethanol. Besides, the novel PdCu/G catalyst exhibits large electrochemically active surface area, lower apparent activation energy, higher levels of stability, poisoning tolerance, and lower charge transfer resistance compared to the Pd/C for the oxidation of ethanol.