Introduction of a chaotic dough mixer, part A: mathematical modeling and numerical simulation

The motivation of this work is to propose a special dough mixer with chaotic advection to take advantage of high performance mixing in chaotic mixers and to develop typical dough mixers. In order to prevent common difficulties encountered due to the dynamic mesh, a mathematical model was employed based on neglecting the transient term of the momentum equation using conceptual features from creeping flow. Then, the numerical simulation was performed using the bird Carreau dough model of Dhanasekharan. The mathematical model was further developed to complete the numerical procedure in order to find the required material point trajectories for assessing the presence of chaotic advection in the proposed mixer. In this approach, Lyapunov exponents were also calculated which quantify the exponential divergence of the initially close state-space trajectories and identify chaotic behavior of the system as well. The results indicated that the flow field was a combination of both chaotic and non-chaotic zones.     

Doping effects of Co on exo-hydrogenated narrow single-walled carbon nanotubes

Density functional theory (DFT) calculations with the generalized gradient approximation (GGA) were employed for a systematic study of electronic structure and morphologic characteristics of bare and exo-hydrogenated Co-doped single walled carbon nanotubes (CNTs). Two internally and one externally doping configurations for the cobalt adatoms were investigated. Binding energies, bond lengths and angles, under full and half converge of the adsorbed hydrogen atoms were calculated for both cases. Effect of hybridization between the Co-3d and the H-s orbitals showed that the exo-hydrogenated CNTs with full and half coverage cases would be stable in the internally doped Co atom systems; whereas, the stability of the hydrogenated systems under externally doped Co adatom was not trivial. In general, for the externally Co-doping, the Co atoms can act as additional adsorbents so the amount of total adsorbed hydrogens could be varied substantially; whereas, for the internally Co-doping the nature of the exo-hydrogenation (being atomic or molecular) shows nanotube's chirality dependent.     

Co‐delivery of methotrexate and doxorubicin via nanocarriers of star‐like poly(DMAEMA‐block‐HEMA‐block‐AAc) terpolymers

Combined therapy is a promising strategy for clinical cancer treatment with synergistic effects. The purpose of the work reported was to evaluate a smart nanocarrier for co‐delivery of doxorubicin (DOX) and methotrexate (MTX). Since star‐like nanocarriers can load a high dose of drugs with various properties, we developed star polymer nanomicelles based on poly[(2,2‐dimethylaminoethyl methacrylate)‐block‐(2‐hydroxyethyl methacrylate)‐block‐(acrylic acid)] having potential for multi‐drug delivery. The nanomicelles demonstrated high encapsulation efficiency, i.e. 97.1% for DOX and 79.5% for MTX. To this end, the star‐like terpolymers were synthesized via atom transfer radical polymerization with pentaerythritol as an initiator. The micellar properties and dual stimuli‐responsive behaviour of the terpolymers were investigated using transmission electron microscopy, field emission scanning electron microscopy and dynamic light scattering measurements, concluding that this co‐therapy offers a promising approach for cancer treatment. © 2019 Society of Chemical Industry     

A hardware oriented fuzzification algorithm and its VLSI implementation

An efficient fuzzification algorithm named as Dynamic Precision Fuzzification (DPF) is introduced in this paper which is mainly developed for hardware implementation. The DPF which might be generally used with any piecewise linear membership function, exploits an inherent capacity of the normal fuzzification algorithm to improve its efficiency when realized in a finite-precision implementation bed such as digital VLSI. The accuracy simulation results of the DPF and normal fuzzification method are presented and compared to show the superiority of the DPF. As the word-length is the most important parameter in a finite-precision implementation environment which determines the system cost-precision trade-off, the simulation results show that DPF provides suitable precision improvements with respect to traditional fuzzification without increasing the system word-length. The VLSI synthesis results of both methods are also presented to show that this considerable accuracy improvement is achieved by an acceptable increase in its VLSI implementation costs in terms of area, delay, and power consumption with respect to traditional methods.     

A novel microfluidics integrated biosensor based on a MEMS resonator

Microsystem Technologies - In this paper a sensor based on MEMS resonators is proposed for digital microfluidics applications. The sensor system consists of a disk as active area immobilized for...     

Effect of dimensional and material property uncertainties on thermal flexure microactuator response using probabilistic methods

Micromachining of microelectromechanical systems such as other fabrication processes has inherent variation that leads to uncertain dimensional and material properties. In this paper, the effect of material and feature dimension uncertainties due to fabrication process on electrothermal microactuator tip deflection is investigated. A simple and efficient uncertainty analysis method is used based on direct linearization method (DLM); uncertainty analysis is performed by creating second-order metamodel through Box-Behnken design and Monte Carlo simulation. The standard deviations of tip deflection obtained by these two probabilistic methods are very close. Simulation results have been validated by a comparison with experimental results in literature. Experimental results fall within 95% confidence boundary obtained by DLM method. Also, sensitivity analysis of microactuator has been explored; the results show that microactuator performance has been affected more by thermal expansion coefficient and microactuator gap uncertainties.     

The effect of process parameters on the size and morphology of poly(D,L‐lactide‐co‐glycolide) micro/nanoparticles prepared by an oil in oil emulsion/solvent evaporation technique

For the past few decades, there has been a considerable research interest in the area of biodegradable polymeric micro‐ and nanoparticles for tissue engineering, regenerative medicine, implants, stents, medical devices, and drug delivery systems. Poly(D,L ‐lactide‐co‐glycolide) (PLGA) is well‐known by its safety in biomedical preparations which has been approved for human use by the FDA. The goal of this study was to evaluate the influence of process parameters on size characteristics of PLGA microparticles prepared by oil in oil (o/o) solvent evaporation technique. This method has been introduced as one of the most appropriate methods for hydrophilic agents. Scanning electron microscopy showed that prepared particles were spherical with smooth surface without aggregation. Particle size varied from 570 nm to 29 μm in different experimental conditions. Stirring speed, polymer concentration, impeller type, and dropping size had a significant effect on the particle size. The polydispersity index of particles showed a strong relationship with the surfactant concentration, impeller type, and dropping size. It was concluded that increasing in temperature up to 50°C or changing in dropping rate has a little effect on reducing the size of PLGA particles. The residual solvent content in the final suspension was less than 0.1 ppm that is in appropriate range for biomedical application. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Prevalence and antimicrobial resistance of Campylobacter isolated from retail raw chicken and beef meat, Tehran, Iran

Campylobacter spp. is a leading cause of human diarrhea. The common source of infection is contaminated food, particularly poultry. The veterinary use of antimicrobial drugs has been suggested to be largely responsible for resistance in human isolates of this zoonotic pathogen. From April to October 2004, 241 samples of chicken and beef meat for sale in retail outlets in Tehran (Iran) were analyzed for the presence of Campylobacter. Totally, 88 (36.5%) Campylobacter strains were isolated. Campylobacter was isolated from a significantly larger number of chicken (63%) than beef (10%) meat (P < 0.0001). Susceptibilities of 72 strains were determined for eight antimicrobial drugs using the disk diffusion assay. Resistance to nalidixic acid was the most common finding (75%), followed by resistance to ciprofloxacin (69.4%), tetracycline (45.8%), amoxicillin (11.1%), streptomycin (4.2%), chloramphenicol (2.8%) and gentamicin (1.4%). None of the isolates was resistant to erythromycin. Multidrug resistance was seen in 75% of the Campylobacter strains.