Polyhydroxybutyrate/chitosan/bioglass nanocomposite as a novel electrospun scaffold: fabrication and characterization

Scaffolds and their features play a central role in tissue engineering; so this study is based on the production of a series of electrospun PHB/Chitosan/nBG nanocomposite scaffolds with 9 wt% polyhydroxybutyrate, 10, 15 and 20 wt% chitosan and 7.5, 10 and 15 wt% nanobioglass (nBG). Electrospinning process was performed with optimal conditions of spinning machine including voltage of 16 kV, syringe-collector spacing of 16 cm, and output rate of 1 µl per hour. The developed phases and the formation of chemical bonds between ceramic and polymer bands were studied through XRD and FTIR analyses. The FE-SEM and TEM analyses showed uniform morphology of nanofibers and dispersion of bioglass nanoparticles in the fiber structure. The presence of 10 wt% bioglass nanoparticles and 15 wt% chitosan increased the tensile strength of fibers to 3.42 MPa, which was about four times greater than strength of control sample (pure PHB). The developed fibers were kept 28 days in SBF solution and 60 days in PBS solution to assess their bioactivity and biodegradability. The results showed that the presence of bioglass nanoparticles leads to a dramatic increase in absorption of calcium and phosphorus ions and weight loss of scaffold. The developed scaffold can be used for bone and teeth tissue engineering applications.     

Prediction of Particle Deposition Using a Simplified Particle Model in Fully Developed Channel Flow

In this study the Eulerian particle model was modified to predict the particle deposition rate in fully developed channel flow. The modified model is less complicated and has much lower computation time. The performance of the simplified model was examined by comparing the particle deposition rate in a vertical channel with the experimental data for fully developed channel flow available in the literature. The effects of turbophoretic force, thermophoretic force, electrostatic force, gravitational force, Brownian/turbulent diffusion, and the wall roughness on the particle deposition rate were examined. The predictions of the modified particle model were in agreement with the experimental data.     

A COMPARISON OF A NOVEL RECUPERATIVE CONFIGURATION AND CONVENTIONAL METHANOL SYNTHESIS REACTOR

Coupling energy-intensive endothermic reaction systems with suitable exothermic reactions improves the thermal efficiency of processes and reduces the capital cost of the reactors. In this study, a steady-state heterogeneous model for a novel thermally coupled reactor, containing methanol synthesis reactions and cyclohexane dehydrogenation, was developed. This heat exchanger reactor consists of two fixed beds separated by a wall, where heat is transferred across the surface of the tube from the exothermic into the endothermic side. The co-current mode is investigated, and the simulation results are compared with corresponding data for an industrial methanol fixed bed reactor operated at the same feed conditions. The results show that although methanol productivity in the thermally coupled reactor is not higher than that in the conventional methanol reactor, benzene is also produced as an additional valuable product in a favorable manner, and autothermality is achieved within the reactor. This novel configuration can increase the methanol synthesis temperature at the first part of the reactor for higher process rates and then reduce the temperature at the second part of reactor for increasing thermodynamic equilibrium; those are two key issues in methanol reactor configurations. The influence of inlet temperature, molar flow rate, and shell diameter of the endothermic stream on reactor behavior is investigated. The results suggest that coupling of these reactions in co-current mode could be feasible and beneficial. Experimental proof-of-concept is needed to establish the validity and safe operation of the novel reactor.     

Thermogravimetric Analysis of a Cellulosic Fabric Incorporated by Synthetic Ammonium Magnesium Phosphate as a Flame-Retardant

We have investigated the effect of synthetic struvite (MgNH₄PO₄·6H₂o) on the flammability of a cellulosic fabric. It was synthesized by means of the multiple-bath method and deposited onto a cotton fabric. Its uniformity was ensured by means of squeeze rolls, obtaining the optimum effective add-on value of ammonium magnesium phosphate to impart flame retardancy to cotton fabric in the range of around 12 g anhydrous salt per 100 g fabric. A thermogravimetric analysis of pure cotton, treated cotton, and the salt was accomplished, and their thermograms were compared and commented upon. The results obtained fortified the chemical theory expressing the promotion of the formation of solid char rather than the formation of volatile pyrolysis products, during the fulfillment of thermal decomposition of the cellulosic substrate.     

Taguchi‐based analysis of polyamide 6/acrylonitrile–butadiene rubber/nanoclay nanocomposites: The role of processing variables

Applying the Taguchi method of experimental design, we prepared various polyamide 6 (PA6)/acrylonitrile butadiene rubber (NBR)/nanoclay nanocomposites under different processing conditions by melt mixing in an internal mixer. The effects of the processing variables, including the rotor speed, chamber temperature, and mixing order on the morphology, that is, the rubber particle size and interlayer distance, and the mechanical properties, that is, the tensile modulus and impact strength, were then investigated. As demonstrated with the Taguchi approach, the lower temperature associated with higher rotor speeds improved the mechanical properties of the 90/5/5 PA6/NBR/nanoclay systems. However, it was revealed that the mixing order did not affect the mechanical properties for the assigned composition. Hence, the simultaneous mixing of all the ingredients is seemingly the simplest way of mixing to obtain the desired mechanical properties. These results were confirmed with transmission and scanning electron microscopy observations and X‐ray diffraction measurements. Image analysis corresponding to the mean particle size of the NBR constituent was also performed. The optimum processing condition to achieve the appropriate mechanical properties is ultimately predicted by the Taguchi analysis and corresponded to a chamber temperature of 230°C and a screw speed of 80 rpm. Moreover, the simultaneous mixing of all of the ingredients was suggested for convenience. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 820‐828, 2013     

Experimental and Numerical Investigation of a Novel Spiral Micromixer with Sinusoidal Channel Walls

A novel spiral micromixer with sinusoidal channel walls was designed to enhance the mixing index in the low to intermediate Reynolds number range (1 < Re < 100). To analyze the fluid flow, a set of numerical simulations were performed using the finite-difference method. The microchip was fabricated from polydimethylsiloxane, employing the soft-lithography technique. The degree of mixing was increased by 99.11 % when using the proposed micromixer, compared to 59.44 % for a simple spiral micromixer. The introduced microchannel drastically reduced the mixing length, increasing the mixing index of a 0.5-loop spiral-sinusoidal microchannel compared to that of the simple spiral microchannel with 1.5 loops. The mixing index of the 3-loop mixer was higher than that of the microchannel with 1.5 loops, and its pressure drop was increased.     

A novel stimuli-responsive magnetic hydrogel based on nature-inspired tragacanth gum for chemo/hyperthermia treatment of cancerous cells

Journal of Polymer Research - Derivatives of formyl pyrazole were synthesized by the reaction of acetophenone, 4-methyl acetophenone, 3-acetyl furan, 3-acetyl thiophen and phenyl hydrazine...     

Effects of Recycling on the Mechanical Behavior of Polypropylene at Room Temperature Through Statistical Analysis Method

This article reports the effects of recycled material percentage, annealing conditions, and glass fiber percentage on the mechanical behavior of injection molded polypropylene samples. Specimens were prepared with different percentages of recycled material ranging from 0 to 100%. Two groups of samples, i.e., non‐annealed and annealed at 150°C, were tested to investigate annealing effects. The effects of adding fiber (0–7.5%) to specimens was also investigated. It was found that increasing the amount of recycled material improves the material properties in a non‐linear trend. Annealing had a significant positive effect on both non‐fiber‐added and fiber‐added samples: it improved the yield stress of non‐reinforced polypropylene samples by more than 10% and their Young's modulus by about 50%. Fiber‐added materials showed more variability, and adding fiber also improved the Young's modulus and the yield stress of the samples by about 50%. The results indicate that the three factors investigated improved toughness of the injected polypropylene samples; however the effects are not significant. The study findings reveal that using recycled polypropylene has no significant effect on the material properties of polypropylene. POLYM. ENG. SCI., 56:1283–1290, 2016 © 2016 Society of Plastics Engineers     

Experimental Investigation on the Removal of p-Toluic Acid from Aqueous Solution using Functionalized Polymeric Sorbent

Polystyrene-divinylbenzene copolymer (PsDVB) was covalently functionalized with monoethanolamine (MEA), diethanolamine (DEA), and triethanolamine (TEA) by a simple method. The functionalized sorbents were characterized in terms of functionality and morphology, and used for the removal of p-toluic acid (p-TA) from aqueous solution. It was found that DEA-PsDVB has higher adsorption capacity than MEA- and TEA-PsDVB due to more accessible nitro and hydroxyl groups on its surface. Further investigation on the adsorptive properties of DEA-PsDVB indicated that the maximum uptake of p-TA occurred at the optimum pH of 5.3. The kinetics data was successfully represented by the pseudo-first-order model, and the behavior of the adsorption isotherms followed the Freundlich model well. Thermodynamic studies showed that the adsorption of p-TA onto DEA-PsDVB was an endothermic and spontaneous process along with the positive change in entropy. The regeneration of DEA-PsDVB was performed with 0.1 M NaOH solution, and results showed that 99% of the initial capacity was conserved after eight successive adsorption/regeneration cycles.     

Photobiomodulation Therapy and the Glymphatic System: Promising Applications for Augmenting the Brain Lymphatic Drainage System

The glymphatic system is a glial-dependent waste clearance pathway in the central nervous system, devoted to drain away waste metabolic products and soluble proteins such as amyloid-beta. An impaired brain glymphatic system can increase the incidence of neurovascular, neuroinflammatory, and neurodegenerative diseases. Photobiomodulation (PBM) therapy can serve as a non-invasive neuroprotective strategy for maintaining and optimizing effective brain waste clearance. In this review, we discuss the crucial role of the glymphatic drainage system in removing toxins and waste metabolites from the brain. We review recent animal research on the neurotherapeutic benefits of PBM therapy on glymphatic drainage and clearance. We also highlight cellular mechanisms of PBM on the cerebral glymphatic system. Animal research has shed light on the beneficial effects of PBM on the cerebral drainage system through the clearance of amyloid-beta via meningeal lymphatic vessels. Finally, PBM-mediated increase in the blood–brain barrier permeability with a subsequent rise in Aβ clearance from PBM-induced relaxation of lymphatic vessels via a vasodilation process will be discussed. We conclude that PBM promotion of cranial and extracranial lymphatic system function might be a promising strategy for the treatment of brain diseases associated with cerebrospinal fluid outflow abnormality.