An innovative approach to fabricate a thermosensitive melatonin-loaded conductive pluronic/chitosan hydrogel for myocardial tissue engineering

This study aimed at designing and fabrication of a novel injectable and thermosensitive melatonin-loaded pluronic/chitosan hydrogel containing gold nanoparticles (GNPs) and poly glycerol sebacate (PGS) for myocardial tissue engineering. The PGS nanoparticles were used as the melatonin (drug model) carrier. The gelation time, syringeability, stability, and swelling of the hydrogel were scrutinized. Rheological properties, chemical composition, and morphology of the samples were also investigated. The effect of GNPs addition on the electrical conductivity of hydrogel was assessed. The cytotoxicity of hydrogels was assessed through MTT assay in the exposure of H9C2 cells up to 7 days. Scanning electron microscopy was applied to evaluate the morphology of seeded cells. The synthesis parameters of PGS nanoparticles were optimized through which 2.5%w/v of PGS and 1:10 organic phase to aqueous phase (O/A) ratio were found desirable. The optimum hydrogel illustrated 2 min gelation time and was stable up to 20 days with 5% swelling in the first 12 h into phosphate buffered saline. The GNPs with a uniform distribution rendered the hydrogel electrically conductive (1500 μS/cm). According to the MTT assay results, 3.125 μM melatonin was considered as the suitable concentration by which a significant increase in the cell viability was observed. The results exhibited that the prepared hydrogel composed of pluronic/chitosan/GNPs, and 3.125 μM melatonin-loaded PGS nanoparticles could be applied as a promising scaffold for myocardial tissue engineering.     

Two-dimensional ARMA model order determination

Determination of the order of a model is the key first step towards modeling any dynamic systems, particularly two-dimensional processes. In this paper, a new method for two-dimensional (2-D) Gaussian ARMA model order determination is proposed. In the proposed method, the AR and MA orders are first independently determined, then the procedure for model order determination of the 2-D ARMA model is outlined. The model is assumed to be causal, stable, linear, and spatial shift-invariant with p₁×p₂ quarter-plane (QP) support. Numerical simulations are presented to show the effectiveness of the proposed new approach.     

MnO2/Cr2O3/PANI nanocomposites prepared by in situ oxidation polymerization method: Optical and electrical behaviors

Metal oxide–polyaniline (PANI) nanocomposite with spherical morphologies were prepared in a one-pot oxidation–reduction method via various salts as reactive oxidants. Aniline monomers polymerize as a shell on the surface of one-pot prepared metal oxides, when the aqueous solutions of aniline, a free-radical oxidant, and/or a metallic salt were exposed together. The particle size and morphology of as-prepared narrowly dispersed PANI nanocomposites were revealed by field emission scanning electron microscope images. Fourier transform infrared spectra of nanocomposites indicate that the PANI exists in the emeraldine form. The ultraviolet–visible analysis not only shows PANI is in the emeraldine form, but also indicates modified optical properties of PANI in the composite form. The hypsochromic shift of the n–π* and polaron transitions of PANI reveals the incorporation of PANI by metal oxides. The direct current (dc) electrical conductivity (σ) of as-prepared nanocomposites was measured by a four-probe method in the room temperature. Compared to PANI nanoparticles, the electrical conductivity of the composites increased with the presence of metal oxides in the nanocomposites. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47219.     

CNT–CdSe QDs nanocomposites: synthesis and photoluminescence studies

In this study, synthesis of carbon nanotube (CNT)–CdSe Quantum dots (QDs) nanocomposites has been investigated. CdSe QDs were synthesized via hydrothermal process. The chemical tendency of CNT and QDS was increased by precipitation after surface functionalization of CNTs (by carboxylated groups) and CdSe QDs (by silane groups), separately. The structure of nanocomposites was amorphous with a little amount of nanocrystalline cubic CdSe. The Fourier-transform infrared (FTIR) spectra and Raman spectrum revealed the strong chemical tendency of linkage between CNTs and QDs after functionalization on the surface of them. The morphology of nanocomposites depended on the QDs concentration and changed from aggregates of CNTs to the marvelous decoration of quantum dots on the ropes of CNTs. Transmission electron microscope (TEM) and atomic force microscope (AFM) images confirmed the adorable coatings of CNTs with CdSe QDs. The nanocomposites emitted in blue–green region with a maximum peak at 490 nm under the exposure of Ultraviolet (UV) light. Below 50 wt% QDs, the emission was quenched completely.     

System identification of two-dimensional continuous-time systems using wavelets as modulating functions

In this paper, parameter identification of two-dimensional continuous-time systems via two-dimensional modulating functions is proposed. In the proposed method, trigonometric functions and sine-cosine wavelets are used as modulating functions. By this, a partial differential equation on the finite-time intervals is converted into an algebraic equation linear in parameters. The parameters of the system can then be estimated using the least square algorithms. The underlying computations utilize a two-dimensional fast Fourier transform algorithm, without the need for estimating the unknown initial or boundary conditions, at the beginning of each finite-time interval. Numerical simulations are presented to show the effectiveness of the proposed algorithm.     

Energy efficient hybrid full adder design for digital signal processing in nanoelectronics

Analog Integrated Circuits and Signal Processing - In recent years, there has been a growing interest in energy efficient VLSI designs for portable devices. Full adder cell is one of the most...     

Low temperature and cost-effective growth of vertically aligned carbon nanofibers using spin-coated polymer-stabilized palladium nanocatalysts

We describe a fast and cost-effective process for the growth of carbon nanofibers (CNFs) at a temperature compatible with complementary metal oxide semiconductor technology, using highly stable polymer–Pd nanohybrid colloidal solutions of palladium catalyst nanoparticles (NPs). Two polymer–Pd nanohybrids, namely poly(lauryl methacrylate)-block-poly((2-acetoacetoxy)ethyl methacrylate)/Pd (LauMA_x-b-AEMA_y/Pd) and polyvinylpyrrolidone/Pd were prepared in organic solvents and spin-coated onto silicon substrates. Subsequently, vertically aligned CNFs were grown on these NPs by plasma enhanced chemical vapor deposition at different temperatures. The electrical properties of the grown CNFs were evaluated using an electrochemical method, commonly used for the characterization of supercapacitors. The results show that the polymer–Pd nanohybrid solutions offer the optimum size range of palladium catalyst NPs enabling the growth of CNFs at temperatures as low as 350 °C. Furthermore, the CNFs grown at such a low temperature are vertically aligned similar to the CNFs grown at 550 °C. Finally the capacitive behavior of these CNFs was similar to that of the CNFs grown at high temperature assuring the same electrical properties thus enabling their usage in different applications such as on-chip capacitors, interconnects, thermal heat sink and energy storage solutions.     

Effects of porosity and pore size distribution on mechanical strength reliability of industrial-scale catalyst during preparation and catalytic test steps

This paper investigates the effects of porosity and pore size distribution on crushing strength reliability of industrial-scale catalysts during their preparation and after reactor tests. Six supports, fabricated from two types of γ-alumina (type A, 119?m²/g; and type B, 343?m²/g), were used as starting materials. The supports were impregnated using a copper/zinc nitrate solution. The supports and catalysts, before and after the reactor tests, were characterized using XRD, ICP, SEM, and BET methods and were subjected to single particle crushing strength tests. The results revealed that the strength and Weibull modulus of all samples were decreased after the impregnation process due to the emergence of new flaws. In contrast, the partial sintering/necking of the interparticles during the reaction led to an increase of the crushing strength of the used catalysts. Furthermore, the porosity of the supports and catalysts from type A to type B γ-alumina were increased, leading to the strength decrease. Nevertheless, their Weibull modulus and strength reliability were increased due to the narrowing of pore size distribution in the range of mesopores.     

Fabrication of 5052Al/Al2O3 nanoceramic particle reinforced composite via friction stir processing route

In this research, microstructure and mechanical properties of 5052Al/Al₂O₃ surface composite fabricated by friction stir processing (FSP) and effect of different FSP pass on these properties were investigated. Two series of samples with and without powder were friction stir processed by one to four passes. Tensile test was used to evaluate mechanical properties of the composites and FSP zones. Also, microstructural observations were carried out using optical and scanning electron microscopes. Results showed that grain size of the stir zone decreased with increasing of FSP pass and the composite fabricated by four passes had submicron mean grain size. Also, increase in the FSP pass caused uniform distribution of Al₂O₃ particles in the matrix and fabrication of nano-composite after four passes with mean cluster size of 70 nm. Tensile test results indicated that tensile and yield strengths were higher and elongation was lower for composites fabricated by three and four passes in comparison to the friction stir processed materials produced without powder in the similar conditions and all FSP samples had higher elongation than base metal. In the best conditions, tensile strength and elongation of base material improved to 118% and 165% in composite fabricated by four passes respectively.     

Piecewise linear spine for speed–energy efficiency trade-off in quadruped robots

We compare the effects of linear and piecewise linear compliant spines on locomotion performance of quadruped robots in terms of energy efficiency and locomotion speed through a set of simulations and experiments. We first present a simple locomotion system that behaviorally resembles a bounding quadruped with flexible spine. Then, we show that robots with linear compliant spines have higher locomotion speed and lower cost of transportation in comparison with those with rigid spine. However, in linear case, optimal speed and minimum cost of transportation are attained at very different spine compliance values. Moreover, it is verified that fast and energy efficient locomotion can be achieved together when the spine flexibility is piecewise linear. Furthermore, it is shown that the robot with piecewise linear spine is more robust against changes in the load it carries. Superiority of piecewise linear spines over linear and rigid ones is additionally confirmed by simulating a quadruped robot in Webots and experiments on a crawling two-parts robot with flexible connection.