Co-Generation of C2 Hydrocarbons and Synthesis Gases from Methane and Carbon Dioxide： a Thermodynamic Analysis

This paper deals with thermodynamic chemical equilibrium analysis using the method of direct minimization of Gibbs free energy for all possible CH4 and CO2 reactions. The effects of CO2/CH4 feed ratio, reaction temperature, and system pressure on equilibrium composition, conversion, selectivity and yield were studied. In addition, carbon and no carbon formation regions were also considered at various reaction temperatures and CO2/CH4 feed ratios in the reaction system at equilibrium. It was found that the reaction temperature above 1100 K and CO2/CH4 ratio=1 were favourable for synthesis gas production with H2/CO ratio unity, while carbon dioxide oxidative coupling of methane （CO2 OCM） reaction to produce ethane and ethylene is less favourable thermodynamically. Numerical results indicated that the no carbon formation region was at temperatures above 1000 K and CO2/CH4 ratio larger than 1.     

Rauniticine-allo-oxindole B and rauniticinic-allo acid B, new heteroyohimbine-type oxindole alkaloids from the stems of Malaysian Uncaria longiflora var. pteropoda

Two new heteroyohimbine-type oxindole alkaloids, rauniticine-allo-oxindole B and rauniticinic-allo acid B, have been successfully isolated from the stems extract of Malaysian Uncaria longiflora var. pteropoda. The structures of the two new alkaloids were determined by spectroscopic analysis.     

Synthesis of silver nanoparticles in chitosan, gelatin and chitosan/gelatin bionanocomposites by a chemical reducing agent and their characterization

In this research, silver nanoparticles (AgNPs) were synthesized in chitosan (Cts), Cts/gelatin and gelatin suspensions using a chemical reducing agent. Cts and gelatin were used as natural stabilizers and solid support, whereas AgNO(3) was used as the silver precursor. Sodium borohydride (NaBH(4)) was used as the reducing agent. The properties of AgNPs in Cts, Cts/gelatin and gelatin bionanocomposites (BNCs) were studied in terms of their surface plasmon resonance, crystalline structure, average diameter size, particle distributions, surface topography and functional groups. All the samples were characterized by UV-visible spectroscopy, powder X-ray diffraction, transmission electron microscopy, atomic force microscopy and Fourier transform infrared spectroscopy.     

Two new cluster ions, Ga[GaH3]4(5-) with a neopentane structure in Rb8Ga5H15 and [GaH2]n(n-) with a polyethylene structure in Rb(n)(GaH2)n, represent a new class of compounds with direct Ga-Ga bonds mimicking common hydrocarbons

The first examples of a new class of gallium hydride clusters with direct Ga-Ga bonds and common hydrocarbon structures are reported. Neutron powder diffraction was used to find a Ga[GaH(3)](4)(5-) cluster ion with a neopentane structure in a novel cubic structure type of Rb(8)Ga(5)H(15). Another cluster ion with a polyethylene structure, [GaH(2)](n)(n-), was found in a second novel (RbGaH(2))(n) hydride. These hydrocarbon-like clusters in gallium hydride materials have significant implications for the discovery of hydrides for hydrogen storage as well as for interesting electronic properties.     

Studies of fractal growth patterns in poly (ethylene oxide) and chitosan membranes

Polymer electrolyte membranes containing various weight percent of salt have been prepared in the authors’ laboratory for the study of their potential applications in solid state electrochemical devices; however, the polymer electrolyte membranes were found to become sort of media for fractal growth, months after they were prepared. Fractal growth patterns in polymer membranes of poly (ethylene oxide) and chitosan membranes have been analyzed, and their fractal dimensions were determined. A diffusion-limited aggregate model which is based on the Brownian motion theory is applied to simulate the experimentally obtained fractal patterns. The approach was extended by performing computer simulations with computing resources available. The fractal dimension values of the simulated and the experimentally obtained original fractal patterns were marginally close. This indicates that the simulation work has successfully produced fractal patterns that are in fairly acceptable conformity with the fractal patterns observed in the polymer membranes.     

An in situ neutron diffraction measurement of the pressure–temperature evolution of a MgD2:TiD2 mixture

The hydrogen storage capacity of Mg–Ti–H films is approximately five times that of conventional metal hydride electrodes in NiMH-batteries. Mg and Ti are considered to be immiscible in the bulk and the ambient pressure phase diagram of Mg and Ti indicates that no binary stable bulk compounds are formed. However, in the presence of hydrogen, an Mg–Ti–H phase has been obtained by Kyoi et al. using a high pressure synthesis – where magnesium hydride is compacted with different TM-hydrides in an anvil cell at pressures of the order several GPa (4–8 GPa) and at a temperature of 873 K. In this work, we have proved the feasibility of in situ powder diffraction using the Paris–Edinburgh high pressure cell for the observation of structural changes on this system and we propose modifications to improve the output of the experiment.     

Conductivity and dielectric relaxation of Li salt in poly(ethylene oxide) and epoxidized natural rubber polymer electrolytes

Two types of polymer electrolytes were studied: poly(ethylene oxide) (PEO) and epoxidized natural rubber (ENR) both filled with lithium perchlorate. Universal dielectric behavior and impedance relaxation were investigated at room temperature over a wide range of salt concentration. Complex impedance plots exhibit one semicircle in some cases (PEO polymer electrolytes) with an extended spike at low frequencies. This implies a double layer capacity strongly influences conductivity at low frequencies. In the ENR–salt system, semicircles can be obtained only at very high concentrations. This points towards stable resistor dominated networks only develop at very high salt concentrations for this system. Centers of the semicircles lie below real axis indicating non-Debye dielectric relaxation. The relaxation peak broadens and shifts to higher frequencies with increasing salt content. It indicates that the relaxation time of polarization relaxations decreases with ascending salt content. Relaxations occur at extremely low salt concentrations in PEO and only at very high salt concentrations in ENR. Hence, conductivity of ENR–salt is one to two orders of magnitude lower as for PEO–salt.     

Sonication improves kasturi lime (Citrus microcarpa) juice quality

Freshly squeezed kasturi lime fruit juice was sonicated (for 0, 30 and 60min at 20°C, 25kHz frequency) to evaluate its impact on selected physico-chemical and antioxidant properties, such as pH, °Brix, titratable acidity, Hunter color values (L(?), a(?), b(?)), ascorbic acid, DPPH radical scavenging activity, total phenolics, antioxidant capacity, flavonoids and flavonols. Additionally, the effect of sonication treatments on the microbial load (TPC, yeast and mold) were also evaluated. Sonication of juice samples for 60min showed enhancement in most of the bioactive compounds compared to samples treated for 30min and control samples (untreated). Significant reductions in the microbial load corresponding to sonication time were also recorded. Results of the present study indicate that sonication may be employed as a suitable technique for kasturi lime juice processing, where antioxidant and other bioactive compound retention or enhancement is desired, along with the achievement of safety and quality standards.     

A practical acoustical absorption analysis of coir fiber based on rigid frame modeling

An analytical study based on rigid frame model is demonstrated to evaluate the acoustic absorption of coir fiber. Effects of different conditions such as combination of air gap and perforated plate (PP) are studied in this work. Materials used here are treated as rigid rather than elastic, since the flow resistivity of coir fiber is very low. The well-known rigid frame Johnson-Allard equivalent-fluid model is applied to obtain the acoustic impedance of single layer coir fiber. Atalla and Sgard model is employed to estimate the surface impedance of PP. Acoustic transmission approach (ATA) is utilized for adding various consecutive layers in multilayer structure. Models are examined in different conditions such as single layer coir fiber, coir fiber backed with air gap, single layer PP in combination with coir fiber and air gap. Experiments are conducted in impedance tube on normal incidence sound absorption to validate the results. Results from the measurement are found to be in well agreement with the theoretical absorption coefficients. The performance of the rigid frame modeling method is checked more specifically in all conditions, by the mean prediction error rate of normal incidence sound absorption coefficients. Comparison between the measured absorption coefficients and predicted by rigid frame method shows discrepancy lower than 20 and 15% for most of the conditions in the frequency range of 0.2?C1.5 and 1.5?C5 kHz, respectively. Moreover, acoustic absorption of various single and multilayer structures is compared with the simpler empirical methods such as Delany-Bazley and Miki model; and complicated method such as Biot-Allard Model and Allard Transfer Function (TF) method. Comparisons show that the presented method offers a better accuracy of the results than the empirical models. Subsequently, it can provide almost same absorption plot with Biot-Allard model (single layer combination) and TF method (multilayer combination) proving it to be a comprehensively easy and general analytical tool. Therefore, the rigid frame model can be implemented relatively easier than other similar models to analyze the acoustic absorption of coir fiber in most of the conditions.