Phase Diagram,Equilibrium Data,and Correlation for Aqueous Two-Phase System Formed by Tetrahydrofuran and Sorbitol

Theoretical Foundations of Chemical Engineering - The importance of aqueous two-phase systems has been increased recently as a method with greater performance capability in separation and...     

Effect of apple cider vinegar agent on the microstructure,phase evolution,and magnetic properties of CoFe2O4 magnetic nanoparticles

In the present study, spinel structure CoFe₂O₄ nanoparticles were successfully synthesized by the sol-gel auto-combustion technique. The effect of apple cider vinegar (ACV) addition as an organic biocompatible agent on the size, morphology, and magnetic properties of CoFe₂O₄ nanoparticles was investigated in detail. The phase evolution, particle size, and lattice parameter changes of the synthesized phase have been estimated by using Rietveld structure refinement analysis of X-ray powder diffraction data. Also, Fourier transform infrared spectra (FT-IR) of the samples verified the presence of two expected bands correspond to tetrahedral and octahedral metal-oxygen complexes within the spinel structure. Furthermore, microstructural observations revealed that ultrafine particles have a semi-spherical morphology. It was shown that the particles size decreased from ~45 to ~17 nm with an increase in the amount of ACV. Magnetic properties were carried out by vibrating sample magnetometer (VSM) at room temperature. Both the saturation magnetization (M_s) and coercivity (H_c) were found to be significantly dependent on the crystallite size and the amount of ACV.     

Compressive strength and wear properties of SiC/Al6061 composites reinforced with high contents of SiC fabricated by pressure-assisted infiltration

Pressure-assisted infiltration was used to synthesize SiC/Al 6061 composites containing high weight percentages of SiC. A combination of PEG and glass water was used to fabricate SiC preforms and the effect of the presence of glass water on the microstructure and mechanical properties of the preforms was evaluated by performing compression tests on the preforms. Also, the compressive strength and the hardness of the SiC/Al composites were investigated. The results revealed that the glass water improved the compressive strength of the preforms by about five times. The microstructural characterization of the composites showed that the penetration of the aluminum melt into the preforms was completed and almost no porosity could be seen in the microstructures of the composites. Moreover, the composite containing 75 wt% SiC exhibited the highest compressive strength as well as the maximum hardness. The results of the wear tests showed that increasing the SiC content reduces the wear rate so that the Al-75 wt% SiC composite has a lower wear rate and a lower coefficient of friction than those of Al-67 wt% SiC composite. This indicated higher wear resistance in these composites than the Al alloy due to the formation of a tribological layer on the surface of the composites.     

Microwave-Assisted Graphite-Support Synthesis of Imidazolones

5(4H)-Oxazolones react with ammonium acetate under microwave irradiation and using graphite as support in an eco-friendly process. The reaction was carried out under solvent-free conditions and the imidazolones were obtained quantitatively. Moreover the reaction time was reduced too.     

An adaptive tracking problem for a family of retarded time-delay plants

Most of the existing switching control techniques are developed specifically for finite-dimensional linear time-invariant (LTI) systems. In many practical applications, however, it is essential to take time delay into consideration in the modelling as the control system can be highly sensitive to delay. In this paper, a multi-model switching control algorithm is proposed for retarded time-delay systems. It is assumed that the plant is represented by a family of known multi-input multi-output, observable, LTI models with multiple delays in the states, and that corresponding to each model in the known family, there exists a high-performance finite-dimensional LTI controller. In addition, it is supposed that a bound on the magnitude of the external inputs and disturbances is available. It is then shown that the proposed switching controller can stabilize the uncertain system, and that under some mild conditions, output tracking can be achieved in the given problem setting. Copyright © 2007 John Wiley & Sons, Ltd.     

Preparation and properties of silicone‐containing poly(methyl methacrylate) gels

Poly(methyl methacrylate) (PMMA) gels with varying amounts of silicone and solvent and constant amounts of crosslinker were prepared by solution free radical crosslinking copolymerization of methyl methacrylate (MMA), ethylene glycol dimethacrylate (EGDM), tetraethoxysilane (TEOS) and vinyltriethoxysilane (VTES) comonomer systems. They were then studied in benzene at a total monomer concentration of 3.5 mol L^?1 and 70 °C. The conversion of monomer, volume swelling ratio, weight fraction and gel point were measured as a function of the reaction time, silicone concentration and benzene content up to the onset of macrogelation. Structural characteristics of the gels were examined by using equilibrium swelling in benzene, gel fraction and Fourier‐transform infrared (FTIR) analysis. The morphology of the copolymers was also investigated by SEM. Based on the obtained results, it was concluded that the FTIR data did not have the capacity to show the presence of the VTES or TEOS moiety in these kinds of copolymers. On the other hand, the variation of weight fraction of gel, W_g, and its equilibrium volume swelling ratio in benzene, q_v, exhibited the same behaviour as that of MMA/EGDM copolymers. Also, the dilution of the monomer mixture resulted in an increase in the gel point and swelling degree and a decrease in the percent of conversion and gel fraction. Finally, TEOS is not an ideal silicone compound for reaction in the MMA/EGDM copolymerization system, whereas VTES is a suitable silicone comonomer for this system and it has been proved useful. Copyright © 2005 Society of Chemical Industry     

Effects of vesnarinone, a novel orally active inotropic agent with an immunosuppressive action, on experimental cardiac transplantation in rats

BACKGROUND: Vesnarinone (VES) has been used for treatment of patients with congestive heart failure. In addition to inotropic effects, it seems to have immunosuppressive action. We tested the hypothesis that VES suppresses graft rejection, inotropic dysfunction caused by early rejection, and chronic coronary obstruction in a heterotopic rat cardiac transplantation model. METHODS: (1) To study acute rejection, hearts from Lewis-Brown Norway (LBN) rats were transplanted into Lewis rats, which were treated with or without VES (50 or 100 mg/kg/day orally). (2) In a functional study, LBN hearts with or without VES (100 mg/kg/ day) were isolated and perfused on day 3 after transplantation to assess inotropic response to isoproterenol (3 x 10(-8) M). (3) To study chronic rejection, Lewis hearts were transplanted into Fisher 344 rats, which were treated with or without VES (50 mg/kg/day) for 90 days. Coronary obstructive disease was assessed by morphometric analysis. There were five to six animals in each group. RESULTS: (1) VES (100 mg/kg/day) prolonged LBN heart survival (11.7 +/- 0.7 vs. 9.6 +/- 0.7 days in control; P < 0.05). (2) Left ventricular developed pressure was depressed in transplanted hearts regardless of VES treatment (84 +/- 12, 90 +/- 8 vs. 144 +/- 16 mmHg in untransplanted hearts; P < 0.01). The developed pressure after administration of isoproterenol in VES-treated hearts (184 +/- 20 mmHg) was higher than transplanted hearts without VES (118 +/- 16 mmHg; P < 0.05), and similar to untransplanted hearts (203 +/- 27 mmHg; P = NS). (3) Transplanted hearts treated with or without VES showed similar grades of rejection (2.0 +/- 0.3 vs. 2.6 +/- 0.2; P = NS), intimal area (6,996 +/- 3,186 vs. 13,441 +/- 5,165 microns2; NS), and coronary luminal obstruction (45 +/- 16% vs. 67 +/- 14%; NS). CONCLUSIONS: VES produces mild prolongation in survival of rat heart grafts, but has no significant effect on chronic graft atherosclerosis. VES preserves the positive inotropic effects of isoproterenol that are otherwise deteriorated by early acute rejection.     

Power-delay-product optimal repeater design for horizontal and vertical multilayer graphene nanoribbon interconnects

Journal of Computational Electronics - Power-delay-product optimal design of repeater size and number design for both horizontal and vertical multilayer graphene nanoribbon (MLGNR) interconnects is...     

Aqueous solution of Oxone as new oxidizing agent for multi-walled carbon nanotube functionalization

In this work, multi-wall carbon nanotube (MWCNT) was successfully modified using aqueous solution of Oxone as a new oxidant. The effect of oxidation temperature on various characteristics of the treated MWCNTs was also investigated. FTIR and titration analysis proved the formation of carboxyl, carbonyl and epoxide groups at the surface of MWCNTs. The concentration of the functional groups increased as the modification temperature increased. The presence of such oxygen containing groups at the surface of MWCNTs justified the long time stability of the treated MWCNTs suspensions in water and methanol. The modified MWCNTs showed higher entanglement compared to row MWCNT due to the cross-links adjacent effect of pendant functional groups. Finally, it was concluded that Oxone oxidation process destroys the structure of the MWCNTs, but not severe enough to unzip the MWCNTs.