Pictet-Spengler Synthesis of Some Thiophene[c]-Fused β-Carbolines

Summary. 5-(Substituted) thieno[2′,3′:5,6]pyrido[3,4-b]indoles were synthesized via cyclocondensation of 3-(3-aminothien-2-yl)indole with the appropriate aldehyde in the presence of boron trifluoride etherate under Pictet-Spengler reaction conditions. The constitution of the new compounds is evidenced from analytical and spectral (NMR and MS) data.     

An experimental investigation of polyacrylamide and sulfonated polyacrylamides based gels crosslinked with cr(III)-acetate for water shutoff in fractured oil reservoirs

Abstract

Water injection as one of the most efficient and worldwide extensively employed approach in homogenous oil reservoirs suffers from early water breakthrough time as well as low oil sweep efficiency values in fractured oil reservoirs. This study investigates the potential application of Cr(III)-acetate based gel polymer system in a typical water injection process using one fractured micromodel. For this purpose, three sulfonated polyacrylamides, different in solfunation degree, and one hydrolyzed polyacrylamide were studied regarding gelation time, gel strength and stability to find the optimized conditions in terms of polymer type and concentration, and polymer/Cr(III)-acetate ratio, which were subsequently used for one dynamic test. Results illustrated the optimized conditions as AN 105 polymer with concentration of 5000?ppm and polymer/Cr(III) ratio of 5. Moreover, results showed that implementing such gel system yields an increased oil recovery value of 24.46% OOIP at 1.55 PV and delays the breakthrough time from 0.47 PV to 0.51 PV.     

Effect of Nanoclay on Styrene and Butyl Acrylate AGET ATRP in Miniemulsion: Study of Nucleation Type,Kinetics, and Polymerization Control

Poly(styrene‐co‐butyl acrylate)/clay nanocomposites were synthesized in miniemulsion via activators generated by electron transfer (AGET) for atom transfer radical polymerization (ATRP). Optimum amounts of catalyst and reducing agent were chosen by considering a linear increase in ln([M₀]/[M]) versus time, narrow molecular distribution, and low polydispersity index (PDI). Critical micelle concentration and cross‐sectional surface area per surfactant head group were determined by surface tension analysis. Calculations show that droplet nucleation is the dominant mechanism of nucleation in a miniemulsion system, and there is no micelle in the system. Gel permeation chromatography was used to characterize molecular weight, PDI, and molecular weight distribution. After determination of appropriate conditions, poly(styrene‐co‐butyl acrylate)/clay nanocomposite latexes were synthesized. Low PDI, narrow molecular weights, and first‐order kinetics of the nanocomposites justify that polymerization is well controlled. Kinetics of polymerization decreases by clay loading. The apparent propagation rate constant (k_app) of polymerization in the case of poly(styrene‐co‐butyl acrylate) is 4.079 × 10^?6, which becomes 0.558 × 10^?6 in the case of poly(styrene‐co‐butyl acrylate)/clay nanocomposite with 2% nanoclay. A decrease in the polymerization rate is related to the hindrance effect of nanoclay layers on monomer diffusion toward the loci of growing macroradicals.     

Analysis of a gained nonlinear directional coupler pulse switch

We have investigated the switching performance of a gained (nonlinear directional coupler) NLDC switch in the presence of both 2nd and 4th order gain nonlinearities. In this system, we have achieved a nearly complete pulse switching at half beat length of the coupler which implies about 40% reduction in the switching length as compared to the switching length reported in Trillo et al. (1988). We have shown that at the half beat length the output energy of each branch is equal to that of the input energy and hence the gained NLDC switches have ability to be cascaded. Our initial investigations reveal that this gained NLDC switch has remarkable performance and potential to be used in ultra-fast optical communication systems.     

Thermal spin-transfer torque in magnetoelectronic devices

We predict that the magnetization direction of a ferromagnet can be reversed by the spin-transfer torque accompanying spin-polarized thermoelectric heat currents. We illustrate the concept by applying a finite-element theory of thermoelectric transport in disordered magnetoelectronic circuits and devices to metallic spin valves. When thermalization is not complete, a spin heat accumulation vector is found in the normal-metal spacer, i.e., a directional imbalance in the temperature of majority and minority spins.     

Pulsating flow in a heat exchanger

The problem of heat transfer in industrial processes, heat exchangers, and combustion chambers is formulated for a case where flow inside the chamber consists of a periodic motion imposed on a fully developed turbulent flow. It is shown that the velocity pulsations induce harmonic oscillations in temperature, thus breaking the temperature field into a steady mean part and a harmonic part. The interaction between the velocity and temperature oscillations introduces an extra term into the energy equation which reflects the effect of pulsations in producing higher heat transfer rates. The analysis shows that when the mean temperature is fully developed with constant heat flux at the wall, there is no effect of the velocity pulsations on the total heat transfer rate along the chamber. For the case where the mean temperature profile is not fully developed, analytical solutions are obtained for asymptotic values of the pulsations frequency. The results show the temperature gradient and its dependence on the frequency. These results are used to evaluate the feasibility of pulsating the flow in a heat exchanger for obtaining higher rates of heat transfer.     

Fischer-Tropsch synthesis over ruthenium-promoted Co/Al2O3 catalyst with different reduction procedures

The effect of reduction procedure on catalyst properties, activity and products selectivity of ruthenium-promoted Co/γ-Al2O3 catalyst in Fischer-Tropsch synthesis (FTS) was investigated. Catalyst samples were reduced with different reduction gas compositions and passivated before being characterized by TPR and XRD techniques. Different activity and product selectivity analyses were also performed. These results showed that the catalyst dispersion, particle size, and the degree of reduction changed with different reduction gas compositions, which were resulted from the water partial pressures in reduction process that give varying degrees of interaction with the support. It has been suggested that the FTS activity of cobalt catalyst was directly dependent on the catalyst reducibility. A reduction gas with a molar ratio of H2/He = 1 was used to prevent the formation of Co-support compound during catalyst reduction.     

Corrosion inhibition of mild steel in hydrochloric acid by betanin as a green inhibitor

The effect of betanin (2,6-pyridinedicarboxylic acid, 4-(2-(2-carboxy-5-(beta-D-glucopyr-anosyloxy)-2,3-dihydro-6-hydroxy-1H-indol-1-yl)ethenyl)-2,3-dihydro-(S-(R*,R*))) on the corrosion inhibition of mild steel has been investigated in 1 M HCl solution. Weight loss method, potentiodynamic polarization, and electrochemical impedance spectroscopy techniques were applied to study the mild steel corrosion behavior in the absence and presence of different concentrations of betanin under the influence of various experimental conditions. The results obtained showed that betanin is a good “green” inhibitor for mild steel in 1 M HCl solution. Scanning electron microscopy observations of the steel surface confirmed the protective role of the inhibitor. The polarization curves showed that betanin behaves mainly as a mixed-type inhibitor. Maximum inhibition efficiency (98%) is obtained at betanin concentrations of 0.01 M. The results obtained from weight loss, polarization, and impedance measurements are in good agreement.