Treatment with platelet lysate induces endothelial differentiation of bone marrow mesenchymal stem cells under fluid shear stress

By considering stem cell-based therapies as a new hope for the treatment of some tragic diseases, marrow stromal cells or marrow mesenchymal stem cells (MSCs) were considered as a suitable and safe multipotential cell source for this new therapeutic approach. For this purpose, many investigations have been performed on differentiation of MSCs toward specific cell lines to overcome the demand for providing the organ specific cells for cell therapy or preparation of engineered tissues. In the present study, differentiation of MSCs to endothelial cells (ECs) by mechanical and chemical stimulation was evaluated. Fluid shear stress (FSS) was used as mechanical inducer, while platelet lysate (PL) and estradiol (E) were used as chemical induction factors. MSCs were placed under FSS with different forces (2, 5 and 10 dyn/cm²) for different periods (6, 12 and 24 hours). In some groups, PL and E were added to the culture media to evaluate their effect on expression of EC specific markers. This investigation revealed that FSS with low tension (2.5-5 dyn/cm²) for a long time (24 hours) or high tension (10 dyn/cm²) in short time (6 hours) in the presence of PL could differentiate MSCs toward ECs. The presence of PL was necessary for initiation of endothelial differentiation, and in the absence of PL, there was not any expression of CD34 and Cadherin5 (Cdh5) among cells. Adding E to the culture medium did not change the rate of endothelial differentiation under FSS. Generated endothelial progenitors could produce von Willebrand factor (vWF) after two weeks culture and also they formed tubular structures after culture on matrigel

A real-time energy management and speed controller for an electric vehicle powered by a hybrid energy storage system

A real-time unified speed control and power flow management system for an electric vehicle (EV) powered by a battery-supercapacitor hybrid energy storage system (HESS) is developed following a nonlinear control system technique. In view of the coupling between energy management and HESS sizing, a HESS sizing model is developed in this article to optimally determine the size of HESS to serve an EV using the controller designed. The objectives of the controller are to track the set speed of the vehicle with globally exponential stability and to make use of the HESS wisely to reduce battery stress. The design provides a compound controller by exploiting the physical origins of the vehicles' power demand. The controller and HESS sizing system designed are simulated on a standard urban dynamometer driving schedule and a recorded actual city driving cycle for a full-size EV to demonstrate their effectiveness.The National Research Foundation and the University of Pretoria.http://ieeexplore.ieee.org/xpl/RecentIssue.jsp?punumber=9424hj2020Electrical, Electronic and Computer Engineerin

Three dimensional modelling of the components in supercapacitors for proper understanding of the contribution of each parameter to the final electrochemical performance

Three dimensional (3D) modelling of supercapacitors (SCs) has been investigated for the first time to have a better understanding of and study the effect of each parameter on the final electrochemical results. Based on this model, the resistance of the electrolyte, membrane, current collectors and active materials have effects on the first intersection points on the real axis (x-axis) of the Nyquist plots (equivalent series resistance (ESR)). These results indicate inward shrinking of the cyclic voltammograms (CV) due to a small change in the leakage resistance and resistance of the faradic component of materials, and they also explain the parameters that lead to the deformation of the CV from ideal behaviour. The 3D model was verified with experiments using activated carbon-based SC devices. The experimental results confirmed the 3D model results and suggested that the proposed 3D model is reliable and can be used for the proper design of SC devices.http://www.rsc.org/journals-books-databases/about-journals/journal-of-materials-chemistry-a2019-09-28hj2018Electrical, Electronic and Computer EngineeringPhysic

Asymmetric supercapacitor based on activated expanded graphite and pinecone tree activated carbon with excellent stability

This work presents results obtained from the production of low-cost carbons from expanded graphite (EG) and pinecone (PC) biomass, activated in potassium hydroxide (KOH) and finally carbonized in argon and hydrogen atmosphere. A specific surface area of 808 m2 g−1 and 457 m2 g−1 were measured for activated pinecone carbon (APC) and activated expanded graphite (AEG), respectively. The electrochemical characterization of the novel materials in a 2-electrode configuration as supercapacitor electrode shows a specific capacitance of 69 F g−1 at 0.5 A g−1, high energy density of 24.6 W h kg−1 at a power density of 400 W kg−1. This asymmetric supercapacitor also exhibits outstanding stability after voltage holding at the maximum voltage for 110 h, suggesting that the asymmetric device based on different carbon materials has a huge capacity for a high-performance electrode in electrochemical applications.The National Research Foundation of South Africa (Grant Number: 61056).http://www.elsevier.com/locate/apenergy2018-12-01hj2018Electrical, Electronic and Computer Engineerin

Morphological characterization and impedance spectroscopy study of porous 3D carbons based on graphene foam-PVA/phenol-formaldehyde resin composite as an electrode material for supercapacitors

The design and fabrication of porous electrode materials is highly desirable for improving the performance of electrochemical supercapacitors (ECs) and thus, it is important to produce such porous materials in large quantities. In this study, we used a microwave method to produce porous carbonaceous materials designated as graphene foam/polyvinyl alcohol/formaldehyde (GF/PVA/F) and graphene foam-polyvinyl alcohol/phenol-formaldehyde (GF/PVA/PF) from graphene foam, phenol formaldehyde and polyvinyl alcohol (PVA). Scanning electron microscopy (SEM), Raman spectroscopy and Fourier-Transform Infrared Spectroscopy (FTIR) were used to characterize the surface morphology, structural defects and functional groups of the materials respectively. Based on these porous materials, the two symmetrical ECs fabricated exhibited a specific capacitance in the range of 0.62–1.92 F cm 2, phase angles of 81 and 84 and resistor–capacitor (RC) relaxation time constants of 4 and 14 seconds. The physicochemical properties of the electrolyte ion (diffusion) and its influence on the capacitive behavior of the porous materials were elucidated. These encouraging results demonstrate the versatile potential of these porous materials (GF/PVA/F and GF/PVA/PF) in developing high energy storage devices.South African Research Chairs Initiative of the South African Department of Science and Technology (SARCHi-DST), the National Research Foundation (NRF) and the University of Pretoria.http://www.rsc.org/advanceshb201

P3HT:PCBM/nickel-aluminum layered double hydroxide-graphene foam composites for supercapacitor electrodes

In this paper, a simple dip-coating technique is used to deposit a P3HT:PCBM/Nickel Aluminum layered double hydroxide-graphene foam (NiAl-LDH-GF) composite onto a nickel foam (NF) serving as a current collector. A self-organization of the polymer chains is assumed on the Ni-foam grid network during the slow “dark” drying process in normal air. Electrochemical cyclic voltammetry (CV) and constant charge-discharge (CD) measurements show an improvement in the supercapacitive behavior of the pristine P3HT:PCBM by an order of magnitude from 0.29 F cm-2 (P3HT:PCBM nanostructures) to 1.22 F cm-2 (P3HT:PCBM/NiAl-LDH-GF composite structure) resulting from the addition of NiAl-LDH-GF material at a current density of 2 mA cm-2. This capacitance retention after cycling at 10 mA cm-2 also demonstrates the electrode material’s potential for supercapacitor applications.South African Research Chairs Initiative (SARChI) of the Department of Science and Technology (DST) and the National Research Foundation (NRF).http://link.springer.com/journal/100082015-08-30hb201

Symmetric supercapacitors based on porous 3D interconnected carbon framework

The construction and design of novel porous carbons for electric double-layer capacitors (EDLCs) application to meet the increasing demand and supply of energy is eminent. This is important because the pore volume (PV)/micropore volume (MV) in the porous network architecture of the carbon is mostly responsible for the ion traps in energy storage. Three dimensional carbon materials based on graphene materials with relatively high specific surface area (SSA) represents a promising material candidate for EDLCs applications. In this work, we synthesized highly porous carbon from graphene foam (GF) and polyvinyl alcohol PVA as a sacrificial template, and investigate their performance as electrodes for EDLCs applications. The as-produced carbons present a fairly large surface area (502 m2 g−1), and a highly porous interconnected framework with mesopore walls and micropore texture which are suitable as electrode for energy storage. As electrode material in a symmetric configuration the activated graphene foam (AGF) showed a specific capacitance of 65 F g−1, energy density of 12 Wh kg−1, power density of 0.4 kW kg−1, good rate performance and excellent long term stability in 1 M Na2SO4 aqueous with no capacitance loss after 3000 cycles.A. Bello acknowledges University of Pretoria and NRF financial support for his Postdoc fellowship, while D. Y. Momodu and F. Barzegar acknowledge financial support from University of Pretoria and the NRF for PhD bursaries.http://www.elsevier.com/locate/electactahj201

Preparation and characterization of porous carbon from expanded graphite for high energy density supercapacitor in aqueous electrolyte

In this work, we present the synthesis of low cost carbon nanosheets derived from expanded graphite dispersed in Polyvinylpyrrolidone, subsequently activated in KOH and finally carbonized in Ar atmosphere. Interconnected sheet-like structure with low concentration of oxygen (9.0 at.%) and a specific surface area of 457 m2 g-1 was obtained. The electrochemical characterization of the carbon material as supercapacitor electrode in a 2-electrode configuration shows high specific capacitance of 337 F g-1 at a current density of 0.5 A g-1 as well as high energy density of 37.9 Wh kg-1 at a power density of 450 W kg-1.This electrical double layer capacitor electrode also exhibits excellent stability after floating test for 120 h in 6 M KOH aqueous electrolyte. These results suggest that this activated expanded graphite (AEG) material has great potential for high performance electrode in energy storage applications.South African Research Chairs Initiative (SARChi) in Carbon Technology and Materials of the Department of Science and Technology (DST) and the National Research Foundation (NRF).http://www.elsevier.com/locate/cose2017-03-31hb2016Institute of Applied MaterialsInsurance and Actuarial ScienceInvestment and Trade Policy Centre (ITPC)JournalismJurisprudenceLaboratory for Microscopy and MicroanalysisLaw ClinicLaw Student AffairsLife Cycle EngineeringMammal Research InstituteMapungubwe museumMarketing and Communication ManagementMarketing ManagementMaterials Science and Metallurgical EngineeringMathematics and Applied MathematicsMaxillo-Facial and Oral SurgeryMechanical and Aeronautical EngineeringMedical MicrobiologyMedical OncologyMedical VirologyMercantile LawMicrobiology and Plant PathologyMining EngineeringModern European LanguagesMusicNeurologyNeuroscience ResearchNew Testament StudiesNuclear MedicineNursing ScienceObstetrics and GynaecologyOccupational TherapyOdontologyOld Testament StudiesOral Pathology and Oral BiologyOrthodonticsOrthopaedic SurgeryOtorhinolaryngologyPaediatrics and Child HealthParaclinical SciencesPeriodontics and Oral MedicinePharmacologyPhilosophyPhilosophy and Ethics of Mental HealthPhysic

Coniferous pine biomass : a novel insight into sustainable carbon materials for supercapacitors electrode

Low-cost biomass-derived activated porous carbon from natural pine cones is synthesized using hydrothermal approach followed by KOH activation and carbonization. The produced carbon materials have a high surface area of 1515 m2 g1 with a well-developed meso/micropores structure which is advantageous and favorable for mass transfer and ion accommodation for fast rate performance by providing pathways for electrolyte permeation and contact probability. Symmetric device fabricated using the obtained carbon material as electrode, exhibited good electrochemical performance with no degradation of capacitance after voltage holding at 1 V for about 60 h demonstrating good rate capability of the fabricated device. The results demonstrate the exciting potential of the pine cone derived carbons as a promising candidate for high-performance electrode materials for supercapacitors if fully explored.The South African Research Chairs Initiative of the Department of Science and Technology and National Research Foundation of South Africa (Grant No. 97994).http://www.elsevier.com/locate/matchemphys2017-10-31hb2016Physic