Enterotoxigenic Profiling of Emetic Toxin‐ and Enterotoxin‐Producing Bacillus cereus,Isolated from Food,Environmental, and Clinical Samples by Multiplex PCR

Bacillus cereus comprises the largest group of endospore‐forming bacteria and can cause emetic and diarrheal food poisoning. A total of 496 B. cereus strains isolated from various sources (food, environmental, clinical) were assessed by a multiplex PCR for the presence of enterotoxin genes. The detection rate of nheA, entFM, hblC, and cytK enterotoxin genes among all B. cereus strains was 92.33%, 77.21%, 59.47%, and 47.58%, respectively. Enterotoxigenic profiles were determined in emetic toxin‐ (8 patterns) and enterotoxin‐producing strains (12 patterns). The results provide important information on toxin prevalence and toxigenic profiles of B. cereus from various sources. Our findings revealed that B. cereus must be considered a serious health hazard and Bacillus thuringiensis should be considered of a greater potential concern to food safety among all B. cereus group members. Also, there is need for intensive and continuous monitoring of products embracing both emetic toxin and enterotoxin genes.     

Mathematical modelling of a hydrocracking reactor for triglyceride conversion to biofuel: model establishment and validation

In the study, a 2D, non‐isothermal, heterogeneous model of a triglyceride hydrocracking reactor is investigated. The internal heat and mass transfer within the phases in the reactor were considered using the film theory. The conservation equations for energy and mass were solved simultaneously using appropriate numerical techniques whose reliability was assessed by comparison of the results with previously reported experimental data. The modelling was performed with consideration of two proposed hydrocracking kinetic models. The model predictions showed reasonable correlation with published experimental data and conversion rates. The calculations indicated that at feed temperature of 380 °C, liquid hourly space velocity of 8 h^?1 and hydrogen : feed ratio of 1500:1, the total triglyceride conversion was 82.54% for four major classes of hydrocarbons (light, middle, heavy and oligomerised). In addition, the concentration distribution and temperature profile along the reactor were investigated. The product concentrations along the reactor show that higher rates of production at the beginning of the reactor were achieved because of high concentration of triglyceride due to the exothermic hydrocracking reactions and counter‐current flow modes of triglyceride and hydrogen; a jump of 90 °C was shown at the beginning of the reactor temperature profile. Copyright © 2014 John Wiley & Sons, Ltd.     

Facile one-pot synthesis of novel dicyanoanilines fused to tetrahydro-4H-thiopyran-4-one ring via Et3N/H2O catalyzed pseudo four-component reaction

A facile procedure is developed for one-pot synthesis of a new group of dicyanoanilines. Tetrahydro-4H-thiopyran-4-one, 1, undergoes a pseudo four-component reaction with various aldehydes bearing different groups and two equivalents of malononitrile in aqueous media in the presence of triethylamine (Et₃N). As a result, novel thiopyran-fused dicyanoanilines 4 are formed efficiently in the reaction mixtures in 90–97% yield within 9–12?h mixing at 40°C. Due to the polarity of the medium, products precipitate in the mixture spontaneously allowing for easy purification by recrystallization avoiding cumbersome chromatographic separations. Characterization of the products was performed by spectroscopic methods and, in one case, was further supported by X-ray crystallographic experiments.     

A comparison of co-current and counter-current modes of operation for a novel hydrogen-permselective membrane dual-type FTS reactor in GTL technology

In this work, a comparison of co-current and counter-current modes of operation for a novel hydrogen-permselective membrane reactor for Fischer-Tropsch Synthesis (FTS) has been carried out. In both modes of operations, a system with two-catalyst bed instead of one single catalyst bed is developed for FTS reactions. In the first catalytic reactor, the synthesis gas is partly converted to products in a conventional water-cooled fixed-bed reactor, while in the second reactor which is a membrane fixed-bed reactor, the FTS reactions are completed and heat of reaction is used to preheat the feed synthesis gas to the first reactor. In the co-current mode, feed gas is entered into the tubes of the second reactor in the same direction with the reacting gas stream in shell side while in the counter-current mode the gas streams are in the opposite direction. Simulation results for both co-current and counter-current modes have been compared in terms of temperature, gasoline and CO₂ yields, H₂ and CO conversion, selectivity of components as well as permeation rate of hydrogen through the membrane. The results showed that the reactor in the co-current configuration operates with lower conversion and lower permeation rate of hydrogen, but it has more favorable profile of temperature. The counter-current mode of operation decreases undesired products such as CO₂ and CH₄ and also produces more gasoline.     

A sparse matrix open boundary method for finite element analysis

A novel implicit mapping method for handling exterior- and far-field problems is described. The method provides a way of maintaining sparsity. Several boundary methods are compared, and the implicit mapping approach is described in detail. In terms of complexity the proposed method is more expensive than a hybrid or ballooning method, but this cost is offset for many problems by its simplicity and the fact that far-field values are readily available. In addition, the method can be used to extend the range of boundary conditions available in a standard finite-element package to include inhomogeneous Neumann conditions     

Weighted Version of Extended Nearest Neighbors

This paper investigates the problem of stability analysis for switched complex dynamical networks with mixed time-varying delays and parameter uncertainties. The switched complex dynamical networks are composed of m modes that are switched from one to another based on time, state, etc. Although, the active subsystem is known in any instance, but the switching law such as transition probabilities are not known. The model for each mode is considered affine with matched and unmatched perturbations. The main purpose of the addressed problem is to design a filter error for the switched complex dynamical networks such that the dynamics of the error converges to the asymptotically irrespective of the admissible parameter variations with the gains. Then, by utilizing the Lyapunov functional method, the stochastic analysis combined with the matrix inequality techniques, a sufficient condition in terms of linear matrix inequalities is presented to ensure the $$H_\infty $$ performance of the complex dynamical system models. Finally, a numerical example is presented to illustrate the effectiveness of the proposed design method.     

Structural characterization and strengthening mechanism of forsterite nanostructured scaffolds synthesized by multistep sintering method

In this study, highly porous forsterite scaffolds with interconnected porosities were synthesized using multi-step sintering (MSS) method. The starting powder was nanosized forsterite, which was synthesized from talc and magnesium carbonate powders. The phase composition, average particle size and morphology of the produced forsterite powder were characterized by X-ray diffraction technique (XRD) and transition electron microscopy (TEM). Forsterite scaffolds were produced by foamy method using polymeric sponges. MSS process including three steps was used to efficiently sinter the forsterite nanopowders without destroying the initial porous structure of polymeric sponges. The results showed that MSS technique is an efficient and appropriate procedure to produce highly porous forsterite scaffolds with pore size in the range of 100–300?μm. The compressive strength, compressive modulus and porosity of C12 specimen (sintered at 1650?°C for 1?h with subsequent annealing at 1000?°C for 1000?min) was 1.88?MPa, 29.2?MPa, and 72.4%, respectively, which is very close to that of cancellous bone. The approach studied in this research can be developed for other nanostructure ceramics to produce highly porous scaffolds with interconnected porosities for load bearing applications.     

Three dimensional distribution of the mastic in asphalt composites

The microstructure of the fine aggregate matrix has a significant influence on the mechanical properties and evolution of damage in an asphalt mixture. This paper presents the findings from a study conducted to identify a quantitative method to characterize the three-dimensional microstructure of the matrix in an asphalt mixture. The influence of binder content, coarse aggregate gradation, and fine aggregate gradation on the microstructure of the matrix was also investigated. Results indicate that for a given aggregate type, binder content and aggregate gradation influence the degree of anisotropy whereas gradation of the coarse aggregate has the most influence on the direction of anisotropy of the asphalt mastic. Addition of asphalt binder or adjustments to the fine aggregate gradation also resulted in a more uniform spatial distribution of the asphalt mastic.