Solid-phase electrochemical reduction of graphene oxide films in alkaline solution

Graphene oxide (GO) film was evaporated onto graphite and used as an electrode to produce electrochemically reduced graphene oxide (ERGO) films by electrochemical reduction in 6 M KOH solution through voltammetric cycling. Fourier transformed infrared and Raman spectroscopy confirmed the presence of ERGO. Electrochemical impedance spectroscopy characterization of ERGO and GO films in ferrocyanide/ferricyanide redox couple with 0.1 M KCl supporting electrolyte gave results that are in accordance with previous reports. Based on the EIS results, ERGO shows higher capacitance and lower charge transfer resistance compared to GO.     

Synthesis,Characterization, and Bioactivity Evaluation of Amorphous and Crystallized 58S Bioglass Nanopowders

The aim of this work was synthesis and characterization of amorphous and crystallized 58S nanopowders produced via sol‐gel method. According to the thermal analysis, the nanopowders were heat‐treated at 600°C and 1100°C. X‐ray diffraction results revealed that the phases of Wollastonite and tricalcium phosphate were formed at 1100°C. The in vitro tests showed that hydroxyl carbonate apatite was precipitated on both crystallized and amorphous nanopowders, while amorphous nanopowder showed a higher bioactivity than that of crystallized nanopowder. In contrast, mechanical properties of crystallized specimen were higher than those of amorphous specimen.     

Energy and exergy analyses of five conventional liquefied natural gas processes

In this paper, five conventional LNG processes were investigated by energy and exergy analysis methods. On the basis of the energy analysis, three‐stage process of Linde AG and Stat oil (mixed fluid cascade [MFC]) has less energy consumption than the other ones (0.254 kWh/kg liquefied natural gas). Also, coefficient of performance of the cycles of this process is higher compared with the other ones. Exergy analysis results showed that the maximum exergy efficiency is related to the MFC process (51.82%). However, performance of the MFC process in terms of quality and quantity of energy consumption is considerable. But using three cycles in this process needs more components and consequently more fixed costs. In this study, sensitivity of coefficient of performance, specific energy consumption, and indexes of exergy analysis were also analyzed versus important operating variables for all cases. Copyright © 2014 John Wiley & Sons, Ltd.     

Evaluation of Lepidium sativum seed and guar gum to improve dough rheology and quality parameters in composite rice–wheat bread

The effects of hydrocolloids in rice–wheat flour were studied. Hydrocolloids at 0%, 0.3%, 0.6% and 1% w/w (flour basis) and guar (G), Lepidium sativum seed (L) and guar-L. sativum seed (GL) gum were tested as additives to the rice/flour in various combinations. The quality parameters for the experiment were assessed with farinography, extensography, amylography and texture profile analysis. The evaluation of dough rheology showed that water absorption, dough development time, dough stability and viscosity all increased with the addition of hydrocolloids alone or in a combination. It was demonstrated that G₁L₁ promoted the highest effect. The mixing tolerance index and gelatinization temperature decreased with an increased hydrocolloid concentration. Extensibility value for the dough that incorporated guar and L. sativum seed gum increased with increasing hydrocolloid concentration from 0.3% to 0.6% and then decreased at 1%. The water activity of all bread didn't have significant differences with increasing hydrocolloids concentration but this parameter 24 decreased during storage. Firmness decreased with increasing hydrocolloid concentration and increased with increasing storage time. The sensory evaluation by a consumer panel gave the higher score for overall acceptability to G_0.3L_0.3 and G_0.3L_0.6 samples. The results also showed that G₁L₁, G₁L_0.6 and G_0.6L₁ samples had high specific volume and porosity.     

Generalized linear mixed model for monitoring autocorrelated logistic regression profiles

Profile monitoring is used to monitor the regression relationship between a response variable and one or more explanatory variables over time. Many researches have been done in this area, but in most of them, the distribution of the response variable is assumed to be normal. However, this assumption is violated in many real case problems. In these instances, classic methods cannot be used for monitoring the profiles. For example, when the response variable is binary, logistic regression methods should be used rather than ordinary least square or other classic regression methods. There are some methods for monitoring logistic profiles in the literature, but the basic assumption of these methods is the independency of the consecutive observations, while this assumption is violated in some instances for example when the successive samples are taken in short intervals. This paper considers the effect of autocorrelation presence between the observations in different levels of the independent variable in a logistic regression profile on the monitoring procedure (T ² control chart) and proposes two remedies to account for the autocorrelation within logistic profiles. In one of the remedies, upper control limit of the traditional T ² control chart is modified. In the second one, we use a generalized linear mixed model (GLMM) to estimate the regression parameters and then use the T ² control chart for monitoring autocorrelated logistic regression profiles. Simulation studies show the better performance of T ² control chart when the regression parameters are estimated by the GLMM method under both step shifts and drifts.     

Simultaneous biodesulphurization and denitrification using an oil reservoir microbial culture: Effects of sulphide loading rate and sulphide to nitrate loading ratio

Biooxidation of sulphide under denitrifying conditions is a key process in control of souring in oil reservoirs and in treatment of gas and liquids contaminated with sulphide and nitrate. In this work, biooxidation of sulphide was studied using a representative culture originated from an oil reservoir. Effects of sulphide concentration, sulphide to nitrate molar ratio, and loading rates of sulphide and nitrate on their removal rates and composition of the end products were investigated. In the batch system sulphide removal rate passed through a maximum as sulphide concentration was increased from 2.1 to 16.3 mM, with the highest rate (2.06 mM h⁻¹) observed with 10.7 mM sulphide. Nitrate removal was coupled to sulphide oxidation and the highest removal rate was 1.05 mM h⁻¹. In the continuous bioreactors fed with 10 and 5, 15 and 7.5, and 20 and 10 mM sulphide and nitrate, cell wash-out occurred as dilution rate was increased above 0.15, 0.13 and 0.08 h⁻¹, respectively. Prior to cell wash-out linear increases in sulphide and nitrate removal rates were observed as loading rate was increased. The highest sulphide and nitrate removal rates of 2.0 and 0.92 mM h⁻¹ were obtained in the bioreactor fed with 15 mM sulphide and 7.5 mM nitrate at loading rates of 2.1 and 0.93 mM h⁻¹, respectively. Short residence times and high sulphide to nitrate ratios promoted the formation of sulphur, a desired end product for ex situ treatment of contaminated streams. Combination of long residence times and low sulphide to nitrate ratios, which favours formation of sulphate, is the suitable strategy for in situ removal of H₂S from oil reservoirs.     

Antioxidant Capacity and Phenolic Content of the Aqueous Extract of Commonly Consumed Cucurbits

The antioxidant capacity of commonly consumed cucurbits vegetable was determined by the DPPH, FRAP, Fe³⁺ reducing power, and hydrogen peroxide scavenging assay. The aqueous extract of Luffa cylindrica showed the highest value of phenolic content and antioxidant capacity based on FRAP, Fe³⁺ reducing power, and hydrogen peroxide scavenging assay. However, Laginaria siceraria extract showed the highest flavonoid and DPPH scavenging activities among all three cucurbits used in this study. Phenolic content in aqueous extracts of Luffa cylindrica and Laginaria siceraria was almost equal. Cucurbita maxima exhibited the lowest phenolic, flavonoid content, and exhibited the lowest power of antioxidant scavenging. The antioxidant capacity of cucurbits was significantly correlated (P < 0.05) with the phenolic content of their extracts. The antioxidant capacity of Luffa cylindrica and Laginaria siceraria have also shown a significant correlation (P < 0.05).     

Thermal Stability of <Emphasis Type="Italic">α</Emphasis> Phase of Titanium by Using X-Ray Diffraction

At room temperature and ambient pressure, crystalline titanium has a hexagonal-close-packed (hcp) lattice and at high temperature appears as a body-centered-cubic (bcc) structure. In fact, the phase transitions of titanium have been investigated under various pressures and temperatures. However, the phase transitions of titanium have been mostly reported at high pressure, while less attention has been paid to various ranges of high temperature. Therefore, in this study, we have considered the thermal stability of α phase of titanium by using X-ray diffraction (XRD) at high temperature. The observed experimental results of the diffraction show that the stability range of α phase varies between room temperature to around 923 K (650 °C).