Preparation and Characterization of Magnetite–Chitosan Nanoparticles and Evaluation of Their Cytotoxicity Effects on MCF7 and Fibroblast Cells

Nowadays, magnetic nanoparticles play a key role in drug treatment. However, if they are uncoated, they might aggregate and cause embolism in drug delivery. To avoid this, they are generally coated with polymers. In this investigation, magnetic nanoparticles (MNPs) were coated with chitosan through in situ co-precipitation process and their properties in addition to their cytotoxicity in MCF7 and fibroblast cells were analyzed. The results showed MNPs–chitosan nanoparticles would contain an average mean diameter of 32 nm and a saturation magnetization (M _S) value of 38.87 emu/g. To characterize the synthesized nanoparticles in terms of structural, morphological and magnetic properties, Fourier transform infrared (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermal gravimetric analysis (TGA) and vibrating sample magnetometry (VSM) studies were used. Toxicity test was also done to investigate whether their presence would cause any toxicity in the body; in addition, antibacterial assay was done to analyze if nanoparticles could be used as an antimicrobial agent.     

Surface characterization and biological properties of regular dentin,demineralized dentin,and deproteinized dentin

Bone autografts are often used for reconstruction of bone defects; however, due to the limitations of autografts, researchers have been in search of bone substitutes. Dentin is of particular interest for this purpose due to high similarity to bone. This in vitro study sought to assess the surface characteristics and biological properties of dentin samples prepared with different treatments. This study was conducted on regular (RD), demineralized (DemD), and deproteinized (DepD) dentin samples. X-ray diffraction and Fourier transform infrared spectroscopy were used for surface characterization. Samples were immersed in simulated body fluid, and their bioactivity was evaluated under a scanning electron microscope. The methyl thiazol tetrazolium assay, scanning electron microscope analysis and quantitative real-time polymerase chain reaction were performed, respectively to assess viability/proliferation, adhesion/morphology and osteoblast differentiation of cultured human dental pulp stem cells on dentin powders. Of the three dentin samples, DepD showed the highest and RD showed the lowest rate of formation and deposition of hydroxyapatite crystals. Although, the difference in superficial apatite was not significant among samples, functional groups on the surface, however, were more distinct on DepD. At four weeks, hydroxyapatite deposits were noted as needle-shaped accumulations on DemD sample and numerous hexagonal HA deposit masses were seen, covering the surface of DepD. The methyl thiazol tetrazolium, scanning electron microscope, and quantitative real-time polymerase chain reaction analyses during the 10-day cell culture on dentin powders showed the highest cell adhesion and viability and rapid differentiation in DepD. Based on the parameters evaluated in this in vitro study, DepD showed high rate of formation/deposition of hydroxyapatite crystals and adhesion/viability/osteogenic differentiation of human dental pulp stem cells, which may support its osteoinductive/osteoconductive potential for bone regeneration.     

A low‐power,area‐efficient multichannel receiver for micro MRI

A new integrated, low‐noise, low‐power, and area‐efficient multichannel receiver for magnetic resonance imaging (MRI) is described. The proposed receiver presents an alternative technique to overcome the use of multiple receiver front‐ends in parallel MRI. The receiver consists of three main stages: low‐noise pre‐amplifier, quadrature down‐converter, and a band pass filter (BPF). These components are used to receive the nuclear magnetic resonance signals from a 3 × 3 array of micro coils. These signals are combined using frequency domain multiplexing (FDM) method in the pre‐amplifier and BPF stages, then amplified and filtered to remove any out‐of‐band noise before providing it to an analog‐to‐digital converter at the low intermediate frequency stage. The receiver is designed using a 90 nm CMOS technology to operate at the main B₀ magnetic field of 9.4 T, which corresponds to 400 MHz. The receiver has an input referred noise voltage of 1.1 nV/√Hz, a total voltage gain of 87 dB, a power consumption of 69 mA from a 1 V supply voltage, and an area of 305 µm × 530 µm including the reference current and bias voltage circuits. Copyright © 2013 John Wiley & Sons, Ltd.     

Towards the performance evaluation of 4th generation wireless communication standards: LTE versus Mobile WiMAX

Advances in wireless communication protocols and networking toward support of the next generation of mobile and radio broadband technologies have contributed to a strong competition among various telecommunication standards in particular Long Term Evolution (LTE) and Mobile Worldwide Interoperability for Microwave Access (WiMAX). In this paper, we provide an in‐depth comparison analysis of LTE and Mobile WiMAX at the physical (PHY) layer by studying the most similar PHY configuration scenarios for these two technologies. Our study includes a throughput analysis of downlink (DL) and uplink (UL) transmissions in time division duplex with the least overhead possible and different antenna schemes as well as modulation and code rates. This study also performs an overhead analysis in both protocols to provide a more in‐depth understanding of the PHY layer capacity in various PHY layer configurations. Our simulation results generally show higher performance for LTE in both DL and UL transmission with 7 Mbps in DL and 5 Mbps in UL, when using one antenna port. However, by increasing the number of antennas for multiple‐input/multiple‐output configurations, the results illustrate a reduction in the performance of LTE compared to Mobile WiMAX. This arises from the increase in reference signal overhead in LTE from 4.7% in single‐input/single‐output (SISO) to 14.28% in 4 × 4 multiple‐input/multiple‐output (MIMO). Copyright © 2013 John Wiley & Sons, Ltd.     

Piperazine and methyldiethanolamine interrelationships in CO2 absorption by aqueous amine mixtures. Part II—Saturation rates of mixed reagent solutions

This work is a companion to a previous article, Part I, published in The Canadian Journal of Chemical Engineering, dealing with CO₂ absorption in aqueous solutions containing a single aminic reagent (specifically methyldiethanolamine (MDEA) or piperazine (PZ)). In this second part, different PZ/MDEA mixtures are experimentally studied and their performances are compared with that of the single reagents. It is indeed well known that small quantities of PZ added to MDEA aqueous solutions are sufficient to obtain a significant improvement in the kinetics of the process. PZ is considered an activator or promoter for MDEA, but the mechanism of this synergy has still not been clearly demonstrated. The aim of this study is an attempt to understand how PZ and MDEA can interact by experimentally analyzing this beneficial mutual effect and by explaining it with the help of a suitable yet not complex model. We believe that the involved chemistry is not more complex than that reported in Part I for the single reagents. According to our findings, it is MDEA that enhances the action of PZ, as opposed to what many authors claim. Moreover, our results seem to rule out the existence of any PZ shuttle effect.     

In situ emulsion polymerization and characterization of PVAc nanocomposites including colloidal silica nanoparticles for wood specimens bonding

Polyvinyl acetate (PVAc) nanocomposites for wood adhesives containing different amounts of colloidal silica nanoparticles (CSNs) were synthesized via in situ one-step emulsion polymerization. The adhesion strength of wood specimens bonded by PVAc nanocomposites was investigated by the tensile test. Thermal properties of PVAc nanocomposites were also characterized by differential scanning calorimetry and thermogravimetric analysis. Rheological and morphological properties of the PVAc nanocomposites were investigated using rheometric mechanical spectrometry and field emission scanning electron microscopy (FESEM), respectively. The obtaining results showed that the shear strength of PVAc nanocomposite including 1 wt. % CSNs has the highest shear and tensile strength about 4.7 and 3.2 MPa, respectively. A small increment of T_g (~3 °C) and considerable increment of the ash content proved the enhancement of PVAc thermal characterization in the presence of CSNs. FESEM results showed uniform dispersion of nanoparticles throughout the PVAc matrix due to using the in situ emulsion polymerization process. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48570.     

Siloxane‐based segmented poly(urethane‐urea) elastomer: Synthesis and characterization

A series of segmented poly(urethane‐urea) block copolymers were synthesized with varying proportions of polydimethylsiloxane diols in combination with polytetramethylene ether glycol (PTMG) using 4,4'‐methylenediphenyl diisocyanate followed by chain extension with a (50:50 mol %) mixture of 4,4'‐methylene‐bis(3‐chloro‐2,6‐diethylaniline) (M‐CDEA) and 1,4‐butanediol (BD). The molecular structures of polydimethylsiloxane urethane‐ureas were characterized by ATR‐FTIR and ¹H‐NMR spectroscopic techniques. Distribution of siloxane domain and its influence on surface roughness were investigated by scanning electron microscopy (SEM) and atomic forced microscopy (AFM), respectively. The mechanical and thermal properties of the elastomers were studied by thermogravimetric analysis, dynamical mechanical thermal analysis, and tensile measurement. The results showed that by incorporation of polydimethylsiloxane diol and M‐CDEA chain extender in polyurethane formulation, some improvements in thermal stability, fire resistance and surface hydrophilicity were achieved. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1743–1751, 2013     

Modified Cuckoo Optimization Algorithm (MCOA) to solve Precedence Constrained Sequencing Problem (PCSP)

In recent years, new meta-heuristic algorithms have been developed to solve optimization problems. Recently-introduced Cuckoo Optimization Algorithm (COA) has proven its excellent performance to solve different optimization problems. Precedence Constrained Sequencing Problem (PCSP) is related to locating the optimal sequence with the shortest traveling time among all feasible sequences. The problem is motivated by applications in networks, scheduling, project management, logistics, assembly flow and routing. Regarding numerous practical applications of PCSP, it can be asserted that PCSP is a useful tool for a variety of industrial planning and scheduling problems. However it can also be seen that the most approaches may not solve various types of PCSPs and in related papers considering definite conditions, a model is determined and solved. In this paper a new approach is presented for solving various types of PCSPs based on COA. Since COA at first was introduced to solve continuous optimization problems, in order to demonstrate the application of COA to find the optimal sequence of the PCSP, some proposed schemes have been applied in this paper with modifications in operators of the basic COA. In fact due to the discrete nature and characteristics of the PCSP, the basic COA should be modified to solve PSCPs. To evaluate the performance of the proposed algorithm, at first, an applied single machine scheduling problem from the literature that can be formulated as a PCSP and has optimal solution is described and solved. Then, several PCSP instances with different sizes from the literature that do not have optimal solutions are solved and results are compared to the algorithms of the literature. Computational results show that the proposed algorithm has better performance compared to presented well-known meta-heuristic algorithms presented to solve various types of PCSPs so far.     

A Silicon on Nothing LDMOS with Two Air Pillars in Gate Insulator for Power Applications

Silicon - This paper proposes a new silicon on nothing lateral double-diffused metal-oxide-semiconductor with two air gaps in the gate insulator (SON-APG LDMOS). Utilizing air for the buried layer...