Adsorption and desorption of phenanthrene on carbon nanotubes in simulated gastrointestinal fluids

Adsorption of phenanthrene on carbon nanotubes (CNTs) and bioaccessibility of adsorbed phenanthrene were studied in simulated gastrointestinal fluids. Adsorption of phenanthrene on CNTs was suppressed in pepsin (800 mg/L) solution (gastric) and bile salt (500 and 5000 mg/L) fluids (intestinal). In addition to competitive sorption, pepsin and high-concentration bile salt (5000 mg/L, above critical micelle concentration) solubilized phenanthrene (3 and 30 times of the water solubility, respectively), thus substantially reduced phenanthrene adsorption on CNTs. Pepsin and bile salts also increased the rapidly desorbing phenanthrene fraction from CNTs. The rapidly desorbing phase lasted less than 1 h for all CNTs. Further, 43-69% of phenanthrene was released from CNTs after desorption in the simulated gastric and intestinal fluid at low bile salt concentration while 53-86% was released in the gastric and intestinal fluid at high bile salt concentration. These findings suggest that the release of residual hydrophobic organic compounds from CNTs could be enhanced by biomolecules such as pepsin and bile salts in the digestive tract, thus increasing the bioaccessibility of adsorbed phenanthrene and possibly the overall toxicity of phenanthrene associated CNTs.     

Analysis of antibiotic resistance patterns and detection of mecA gene in Staphylococcus aureus isolated from packaged hamburger

Presence of Staphylococcus aureus, antibiotic resistance pattern and PCR detection of mecA gene in isolated strains were investigated in total of 256 packaged hamburgers in Iran-Tehran. For this purpose we used standard disk-diffusion method and sensitive and specific PCR technique, respectively. Results showed that 25% of samples were positive for S. aureus. Resistance to meticillin, erythromycin, penicillin G, cefazolin, ciprofloxasin, vacomycin and amoxiclave was determined 89%, 20.3%, 18.7%, 15.6%, 14%, 26.6% and 12.5%, respectively. According to the obtained results from PCR analysis of methicillin-resistant S. aureus (MRSA), mecA gene was present in 100% of the resistant isolates, 0% of intermediate-resistance isolates and 25% of susceptible isolates. The results obtained from PCR detection of mecA gene showed high correlation with standard disk diffusion test.     

Numerical Solutions of Fractional Differential Equations by Using Fractional Taylor Basis

In this paper, a new numerical method for solving fractional differential equations (FDEs) is presented. The method is based upon the fractional Taylor basis approximations. The operational matrix of the fractional integration for the fractional Taylor basis is introduced. This matrix is then utilized to reduce the solution of the fractional differential equations to a system of algebraic equations. Illustrative examples are included to demonstrate the validity and applicability of this technique.      

Three‐dimensional multiscale finite element models for in‐service performance assessment of bridges

Accurate representation of the structural performance of civil engineering structures, specifically complex bridge structures, may be achieved through an efficient multiscale finite element (FE) model. Multiscale FE modeling couples multiple dimensions of elements in a single model. In this study, the selected existing multipoint constraint equations applied in planar coupling conditions are modified and refined for out‐of‐plane coupling conditions in a single three‐dimensional FE model. Also, the optimum location for the interface points of different elements is determined to improve the model's accuracy and efficiency. The present case study, the Memorial Bridge in Portsmouth, NH, is a vertical lift bridge, which includes novel gusset‐less connections. These connections have complex geometries and therefore require finer dimension elements to represent the structural behavior, while the remainder of the structure is modeled with coarser dimension elements. To achieve an accurate and efficient multiscale model of the Memorial Bridge, multiple global FE models are developed and the predicted structural responses are verified with respect to the field‐collected structural responses of the bridge.     

Hybrid blind interference alignment in homogeneous cellular networks with limited coherence time

The work presented in this paper is inspired by the user grouping approach of topological blind interference alignment (top‐BIA), which is a semi‐blind IA scheme and the fact that the partially connected networks can be advantageous in terms of degree of freedom (DoF) and sum rate. The hybrid‐BIA scheme proposed in the paper uses top‐BIA to group users that are randomly distributed in a dense small‐cell network and aims to reduce the supersymbol length and overcome the DoF loss of the state‐of‐the‐art hierarchical BIA (h‐BIA) technique. The proposed scheme is very suitable for channels where coherence time is limited and also could attain a good DoF over a small number of symbol extensions. Both the sum‐DoF and the network throughput for hybrid‐BIA is greater than that of h‐BIA. By varying the number of user groups, the paper shows that h‐BIA constitutes a special case of hybrid‐BIA. Finally, the paper demonstrates the effect of changing the number of transmit antennas and number of small cells on the sum‐DoF gain of hybrid‐BIA over that of h‐BIA.