Synthesis and application of some novel antimicrobial monoazonaphthalimide dyes: synthesis and characterisation

A series of novel monoazo dyes based on N‐pyridine‐1,8‐naphthalimides were prepared using 4‐amino‐N‐2‐aminomethylpyridine‐1,8‐naphthalimide as the diazo component and N,N‐diethyl‐meta‐toluidine, 3‐(N,N‐diethylamino)acetanilide and N‐hydroxyethyl‐N‐ethylaniline as the coupling components. The synthesised dyes were purified by utilising column and preparative thin‐layer chromatography methods. The characterisations of the prepared dyes were carried out by differential scanning calorimetery, thin‐layer chromatography (R_f values), Fourier Transform infrared, and proton and carbon nuclear magnetic resonance techniques. The in vitro antibacterial activity of the novel synthesised compounds against Escherichia coli, Staphylococcus aureus, Bacillus subtilis and their antifungal activity against Candida albicans were evaluated by use of conventional agar dilution procedures and a minimum inhibitory concentration. Some of these synthesised dyes demonstrated antibacterial activity against Gram‐positive bacteria in addition to antifungal activities.     

Numerical and Experimental Biomass Separation from Fermentation Process by Minihydrocyclones

Biomass particle separation is challenging in the pharmaceutical industry because of the smallness and lightness of such particles. Centrifugation is applied conventionally for batch separation. However, imposing multiple wash steps in order to eliminate culture residues and the high risk of extrinsic contamination hamper batch techniques. In this research, minihydrocyclones were introduced to provide a better solution for the mentioned limitations in continuous processes. Numerical separation of methylotrophic yeast from fermentation broth was carried out in three hydrocyclones with different lengths, and the most efficient one was examined experimentally. Three various feed flow rates and seven feed concentrations were evaluated. The concentration of biomass suspension in the product was raised to 20 %.     

An experimental approach for measuring carbon dioxide diffusion coefficient in water and oil under supercritical conditions

Several direct or indirect approaches have been proposed to measure diffusion coefficient of gases into liquids. The main complexity of indirect techniques such as pressure decay method is interpreting early pressure–time data which strongly affected by incubation period effect or convective instability. In the current approach, accurate apparatus and precise experimental setup including a high pressure and temperature PVT cell, a high precision Sanchez pump, heating and recording sub-system are implemented and a novel data analysis procedure is applied to modify pressure decay method. The effect of incubation period is reduced remarkably and diffusion coefficient of carbon dioxide in water in wide range of pressures and temperatures is determined and the effects of temperature, pressure and carbon dioxide phase alteration from gas to supercritical are investigated and the value of uncertainty is estimated.Furthermore, diffusion coefficient of CO_2 and methane in an oil sample from one of the Iranian southwest oil formations is determined precisely using the experimental approach while no incubation period is detected. The results showed that incubation period duration decreases with increasing diffusion coefficient. Additionally, when CO_2 state is gas, rate of increasing diffusion coefficient with pressure is decreased with temperature and when CO_2 state is supercritical, the rate of increasing diffusion coefficient with pressure is decreased significantly.     

Estimation of energy conservation benefits in excess air controlled gas-fired systems

The most significant energy consumers in energy related industries are boilers and other gas-fired systems. Combustion efficiency term commonly used for boilers and other fired systems and the information on either carbon dioxide (CO₂) or oxygen (O₂) in the exhaust gas can be used. The aim of this study is to develop a simple-to-use predictive tool which is easier than the existing approaches less complicated with fewer computations and suitable for combustion engineers for predicting the natural gas combustion efficiency as a function of excess air fraction and stack temperature rise (the difference between the flue gas temperature and the combustion air inlet temperature). The results of the proposed predictive tool can be used in follow-up calculations to determine relative operating efficiency and to establish energy conservation benefits for an excess air control program. Results show that the proposed predictive tool has a very good agreement with the reported data where the average absolute deviation percent is 0.1%. It should be noted that these calculations are based on assuming complete natural gas combustion at atmospheric pressure and the level of unburned combustibles is considered negligible. The proposed method is superior owing to its accuracy and clear numerical background, wherein the relevant coefficients can be retuned quickly for various cases. This proposed simple-to-use approach can be of immense practical value for the engineers and scientists to have a quick check on natural gas combustion efficiencies for wide range of operating conditions without the necessity of any pilot plant set up and experimental trials. In particular, process and combustion engineers would find the proposed approach to be user friendly involving transparent calculations with no complex expressions for their applications to the design and operation of natural gas-fired systems such as furnaces and boilers.     

RETRACTED ARTICLE: Investigation of Frying Oil Quality Using VIS/NIR Hyperspectral Analysis

Traditional chemical methods of analyzing frying oil quality are time-consuming and not amenable to on-line measurement. The main objective of this study was to evaluate quality changes of heated oils based on visible/near infrared spectral analysis using a hyperspectroradiometer. The reflectance spectra of the heated oils were analyzed within the range 400–1,750 nm. Acid value, total polar component, and viscosity of oil samples were used as indicators of different quality levels of oil. Partial least squares calibration models were developed for quantitative evaluations of these parameters. The R ² and root mean square error for each prediction were calculated to assess the prediction capability of calibration models. The study demonstrated that using the established calibration models, quality parameters could be predicted with R ² values over 0.92.     

Kinetic modeling of oxidative coupling of methane over Mn/Na2WO4/SiO2 catalyst

A comprehensive kinetic model for oxidative coupling of methane (OCM) on Mn/Na₂WO₄/SiO₂ catalyst was developed based on a microcatalytic reactor data. The methane conversion and ethylene, ethane, carbon monoxide and carbon dioxide selectivities were obtained in a wide range of operating conditions including 750 < T < 875 °C, 4 < CH₄/O₂ < 7.5 and space time between 30 and 160 kg · s/m³ at P = 657 mmHg. The reaction networks of five kinetic models with appropriate rate equation type were compared together. The kinetics rates parameters of each reaction network were estimated using genetic algorithm optimization method. After comparing the reaction networks, the reaction network presented by Stansch et al. was found to best represent the OCM reaction network and was further used in this work. This kinetic network considers both catalytic and gas-phase as well as primary and consecutive reaction steps to predict the performance of the OCM. Comparing the experimental and predicted data showed that presented model has a reasonable fit between the experimental data and the predicted values with average absolute relative deviation of ± 9.1%.     

Revealing the strain-hardening behavior of twinning-induced plasticity steels: Theory,simulations, experiments

We present a multiscale dislocation density-based constitutive model for the strain-hardening behavior in twinning-induced plasticity (TWIP) steels. The approach is a physics-based strain rate- and temperature-sensitive model which reflects microstructural investigations of twins and dislocation structures in TWIP steels. One distinct advantage of the approach is that the model parameters, some of which are derived by ab initio predictions, are physics-based and known within an order of magnitude. This allows more complex microstructural information to be included in the model without losing the ability to identify reasonable initial values and bounds for all parameters. Dislocation cells, grain size and twin volume fraction evolution are included. Particular attention is placed on the mechanism by which new deformation twins are nucleated, and a new formulation for the critical twinning stress is presented. Various temperatures were included in the parameter optimization process. Dissipative heating is also considered. The use of physically justified parameters enables the identification of a universal parameter set for the example of an Fe–22Mn–0.6C TWIP steel.     

Plastic relaxation of the internal stress induced by twinning

The back stress induced in a twin by the surrounding matrix is analysed using a simple two-dimensional finite element model of an elastic elliptical inclusion in a plastic medium. The influence of the ellipse aspect ratio, the matrix yield stress and the external loading on the internal shear stress are investigated. Comparison is made between isotropic and anisotropic yield criteria. It is seen that von Mises plasticity in the matrix (due to glide) leads to complete relaxation of the twin back stress. The closer the applied stress is to the stress required for macroscopic yielding of the matrix, the greater the relaxation of the back stress. To simulate the role of soft shear directions in the matrix, as seen for the case of easy basal slip in hexagonal close-packed metals, Hill’s anisotropic yield surface was employed. These simulations show relaxation of the back stress that is independent of the level of the applied stress. Comparison between simulations and experiments performed on a magnesium alloy reveals higher levels of relaxation in practice. This is possibly due to (i) further twinning as a relaxation mechanism and (ii) the occurrence of neighbouring grains ideally oriented for relaxation. Analytical expressions are developed to capture the trends seen in the simulation. A correction to bring these into line with experiment is proposed as a tentative means of applying the present findings in an analytical framework.     

Processing,characterization, room temperature mechanical properties and fracture behavior of hot extruded multi-scale B4C reinforced 5083 aluminum alloy based composites

Microstructural characteristics and mechanical behavior of hot extruded Al5083/B₄C nanocomposites were studied. Al5083 and Al5083/B₄C powders were milled for 50 h under argon atmosphere in attrition mill with rotational speed of 400 r/min. For increasing the elongation, milled powders were mixed with 30% and 50% unmilled aluminum powder (mass fraction) with mean particle size of >100 μm and <100 μm and then consolidated by hot pressing and hot extrusion with 9:1 extrusion ratio. Hot extruded samples were studied by optical microscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), tensile and hardness tests. The results showed that mechanical milling process and presence of B₄C particles increase the yield strength of Al5083 alloy from 130 to 566 MPa but strongly decrease elongation (from 11.3% to 0.49%). Adding <100 μm unmilled particles enhanced the ductility and reduced tensile strength and hardness, but using the >100 μm unmilled particles reduced the tensile strength and ductility at the same time. By increasing the content of unmilled particles failure mechanism changed from brittle to ductile.     

Structure and Principal Components Analyses Reveal an Intervarietal Fusion in Malaysian Mistletoe Fig (Ficus deltoidea Jack) Populations

Genetic structure and biodiversity of the medicinal plant Ficus deltoidea have rarely been scrutinized. To fill these lacunae, five varieties, consisting of 30 F. deltoidea accessions were collected across the country and studied on the basis of molecular and morphological data. Molecular analysis of the accessions was performed using nine Inter Simple Sequence Repeat (ISSR) markers, seven of which were detected as polymorphic markers. ISSR-based clustering generated four clusters supporting the geographical distribution of the accessions to some extent. The Jaccard’s similarity coefficient implied the existence of low diversity (0.50–0.75) in the studied population. STRUCTURE analysis showed a low differentiation among the sampling sites, while a moderate varietal differentiation was unveiled with two main populations of F. deltoidea. Our observations confirmed the occurrence of gene flow among the accessions; however, the highest degree of this genetic interference was related to the three accessions of FDDJ10, FDTT16 and FDKT25. These three accessions may be the genetic intervarietal fusion points of the plant’s population. Principal Components Analysis (PCA) relying on quantitative morphological characteristics resulted in two principal components with Eigenvalue >1 which made up 89.96% of the total variation. The cluster analysis performed by the eight quantitative characteristics led to grouping the accessions into four clusters with a Euclidean distance ranged between 0.06 and 1.10. Similarly, a four-cluster dendrogram was generated using qualitative traits. The qualitative characteristics were found to be more discriminating in the cluster and PCA analyses, while ISSRs were more informative on the evolution and genetic structure of the population.