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Strategies to improve regenerative potential of mesenchymal stem cells

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World Journal of Stem Cells 2021年第12期13卷 1845-1862页

作者： mahmood S Choudhery Department of Biomedical Sciences King Edward Medical UniversityLahore 54000PunjabPakistan Department of Genetics and Molecular Biology University of Health SciencesLahore 54600PunjabPakistan

In the last few decades,stem cell-based therapies have gained attention worldwide for various diseases and *** stem cells,particularly mesenchymal stem cells(MSCs),are preferred due to their significant regenerative potential in cellular therapies and are currently involved in hundreds of clinical *** MSCs have high self-renewal as well as differentiation potential,such abilities are compromised with“advanced age”and“disease status”of the ***,cell-based therapies require high cell number for clinical applications that often require in vitro expansion of *** is pertinent to note that aged individuals are the main segment of population for stem cell-based therapies,however;autologous use of stem cells for such patients(aged and diseased)does not seem to give optimal results due to their compromised *** vitro expansion to obtain large numbers of cells also negatively affects the regenerative potential of *** is therefore essential to improve the regenerative potential of stem cells compromised due to“in vitro expansion”,“donor age”and“donor disease status”for their successful autologous *** current review has been organized to address the age and disease depleted function of resident adult stem cells,and the strategies to improve their *** combat the problem of decline in the regenerative potential of cells,this review focuses on the strategies that manipulate the cell environment such as hypoxia,heat shock,caloric restriction and preconditioning with different factors.

关键词： Hypoxia Stem cell aging Growth factors Heat shock Caloric restriction

Cu-Zn-Al2O3 nanocomposites: study of microstructure, corrosion, and wear properties

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International Journal of Minerals,Metallurgy and Materials 2017年第4期24卷 462-472页

作者： Mohammad Baghani mahmood Aliofkhazraei Mehdi Askari Department of Materials Science Faculty of Engineering Tarbiat Modares University Tehran Iran

Alumina nanoparticles were added to a Cu-Zn alloy to investigate their effect on the microstructural,tribological,and corrosion properties of the prepared alloys. Alloying was performed using a mixture of copper and zinc powders with 0vol% and 5vol% of α-Al nanopowder in a satellite ball mill. The results showed that the Cu-Zn solid solution formed after 18 h of mechanical alloying. The mechanically alloyed powder was compacted followed by sintering of the obtained green compacts at 750°C for 30 min. Alumina nanoparticles were uniformly distributed in the matrix of the Cu-Zn alloy. The tribological properties were evaluated by pin-on-disk wear tests,which revealed that,upon the addition of alumina nanoparticles,the coefficient of friction and the wear rate were reduced to 20% and 40%,respectively. The corrosion properties of the samples exposed to a 3.5wt% Na Cl solution were studied using the immersion and potentiodynamic polarization methods,which revealed that the addition of alumina nanoparticles reduced the corrosion current of the nanocomposite by 90%.

关键词： nanocomposites copper zinc alloys alumina microstructure corrosion wear properties

Structural characterization of AA 2024-MoSi_2 nanocomposite powders produced by mechanical milling

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International Journal of Minerals,Metallurgy and Materials 2013年第3期20卷 298-306页

作者： mahmood Sameezadeh Hassan Farhangi Massoud Emamy Center of Excellence for High Performance Materials School of Metallurgy and Materials College of Engineering University of Tehran

Nano-sized MoSi2 powder was produced successfully from commercially available MoSi2 by a mechanical milling process carried out for 100 h, and mechanical alloying was employed to synthesize AA 2024-MoSi2 nanocomposites, The effects of MoSi2 reinforcement and mechanical milling on the structure, morphology, and iron contamination of the produced materials were investigated using X-ray diffraction, scanning electron microscopy, and atomic absorption spectrometry. It is revealed that the morphology of the aluminum alloy changes continuously during milling from spherical to plate-like, irregular, and finally equiaxed. The presence of MoSi2 reinforcement accelerates the milling process and results in a smaller average particle size. The Williamson-Hall method determined that the crystallite size of the aluminum alloy in the composite powder is smaller than that of the unreinforced alloy at the same milling time and this size reaches 45 nm after 16 h milling time. The Fe contamination content is higher for the nanocomposite in comparison with the unreinforced alloy because of the wearing role of MoSi2 hard particles.

关键词： nanocomposites aluminum alloys mechanical milling microstructure

Performance of beacon safety message dissemination in Vehicular Ad hoc NETworks (VANETs)

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2007年第12期8卷 1990-2004页

作者： YOUSEFI Saleh FATHY mahmood BENSLIMANE Abderrahim Computer Engineering Faculty Iran University of Science and TechnologyNarmak Tehran 16846-13114 Tehran Iran Laboratoire d'Informatique d'Avignon LIA 339 chemin des Meinajaries BP 1228-84911 Avignon cedex 9 France

Currently, there is a growing belief that putting an IEEE 802.11-like radio into road vehicles can help the drivers to travel more safely. Message dissemination protocols are primordial for safety vehicular applications. There are two types of safety messages which may be exchanged between vehicles: alarm and beacon. In this paper we investigate the feasibility of deploying safety applications based on beacon message dissemination through extensive simulation study and pay special attention to the safety requirements. Vehicles are supposed to issue these messages periodically to announce to other vehicles their current situation and use received messages for preventing possible unsafe situations. We evaluate the performance of a single-hop dissemination protocol while taking into account the quality of service (QoS) metrics like delivery rate and delay. We realize that reliability is the main concern in beacon message dissemination. Thus, a new metric named effective range is defined which gives us more accurate facility for evaluating QoS in safety applications specifically. Then, in order to improve the performance, the effects of three parameters including vehicle's transmission range, message transmission's interval time and message payload size are studied. Due to special characteristics of the safety applications, we model the relationship between communication-level QoS and application-level QoS and evaluate them for different classes of safety applications. As a conclusion, the current technology of IEEE 802.11 MAC layer has still some challenges for automatic safety applications but it can provide acceptable QoS to driver assistance safety applications.

关键词： Safety applications Inter-vehicle communications Vehicular Ad hoc NETworks (VANETs) Application level QoS Effective range

Pseudo-in-situ stir casting: a new method for production of aluminum matrix composites with bimodal-sized B_4C reinforcement

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International Journal of Minerals,Metallurgy and Materials 2016年第8期23卷 981-990页

作者： Mohammad Raei Masoud Panjepour mahmood Meratian Department of Materials Engineering Isfahan University of Technology

A new method was applied to produce an Al-0.5wt%Ti-0.3wt%Zr/5vol%B_4C composite via stir casting with the aim of characterizing the microstructure of the resulting composite. For the production of the composite, large B4 C particles（larger than 75 μm） with no pre-heating were added to the stirred melt. Reflected-light microscopy, X-ray diffraction, scanning electron microscopy, field-emission scanning electron microscopy, laser particle size analysis, and image analysis using the Clemex software were performed on the cast samples for microstructural analysis and phase detection. The results revealed that as a consequence of thermal shock, B_4 C particle breakage occurred in the melt. The mechanism proposed for this phenomenon is that the exerted thermal shock in combination with the low thermal shock resistance of B_4 C and large size of the added B_4 C particles were the three key parameters responsible for B_4 C particle breakage. This breakage introduced small particles with sizes less than 10 μm and with no contamination on their surfaces into the melt. The mean particle distance measured via image analysis was approximately 60 μm. The coefficient of variation index, which was used as a measure of particle distribution homogeneity, showed some variations, indicating a relatively homogeneous distribution.

关键词： metal matrix composites particle-reinforced composites boron carbide casting thermal shock

CoP nanoparticles embedded in P and N co-doped carbon as efficient bifunctional electrocatalyst for water splitting

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Journal of Energy Chemistry 2017年第6期26卷 1223-1230页

作者： Zeqi Zhou nasir.mahmood Yongchao Zhang Lun Pan Li Wang Xiangwen Zhang Ji-Jun Zou Key Laboratory for Green Chemical Technology of the Ministry of Education School of Chemical Engineering and TechnologyTianjin UniversityTianjin 300072China Collaborative Innovative Center of Chemical Science and Engineering(Tianjin) Tianjin 300072China

Noble-metal-free hydrogen/oxygen evolution reaction(HER/OER) electrocatalysts, especially bifunctional electrocatalysts, are essential for overall water splitting, but their performance is impeded by many factors like poor electrical conductivity. Herein, we fabricated cobalt phosphide(Co P) nanoparticles embedded in P and N co-doped carbon(PNC) matrix(Co P@PNC) to fully realize the high activity of Co P by maximizing its conductivity. Simply a carbonization coupled phosphidation approach was utilized where Co ions and organic ligands of Co-MOF were transferred into Co P and P and N co-doped carbon. The synthesized material shows an ideal electrical conductivity, excellent HER(overpotential of-84 m V and-120 m V @10 m A cmin acidic and alkaline medias, respectively) and OER(overpotential of 330 m V@10 m A cmin alkaline media) performances. Further, Co P@PNC acts as a superior catalyst for both anode and cathode to catalyze overall water splitting and only requires an voltage of 1.52 V to deliver a current density of 10 m A cm, superior to the noble-metal catalysts system(Pt/C//IrO) and the reported noble-metal-free bifunctional electrocatalysts.

关键词： Cobalt phosphide Electrocatalyst Hydrogen evolution reaction Oxygen evolution reaction Water splitting

Robust Control Design of Wheeled Inverted Pendulum Assistant Robot

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IEEE/CAA Journal of Automatica Sinica 2017年第4期4卷 628-638页

作者： Magdi S.Mahmoud Mohammad T.nasir Systems Engineering Department King Fahd University of Petroleum and MineralsDhahran 31261Saudi Arabia

This paper examines the design concept and mobile control strategy of the human assistant robot I-PENTAR(inverted pendulum type assistant robot). The motion equation is derived considering the non-holonomic constraint of the twowheeled mobile robot. Different optimal control approaches are applied to a linearized model of I-PENTAR. These include linear quadratic regulator(LQR), linear quadratic Gaussian control(LQG), H_2 control and H_∞ control. Simulation is performed for all the approaches yielding good performance results.

关键词： I-PENTAR robot linear quadratic regulator(LQR) control design model predictive control(MPC) observerbased feedback control robust H_∞ control

Machine Learning for Organic Photovoltaic Polymers:A Minireview

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Chinese Journal of Polymer Science 2022年第8期40卷 870-876,I0006页

作者： Asif mahmood Ahmad Irfan Jin-Liang Wang Beijing Key Laboratory of Photoelectronic/Electrophotonic Conversion Materials Key Laboratory of Medical Molecule Science and Pharmaceutics Engineering in Ministry of Industry and Information TechnologySchool of Chemistry and Chemical EngineeringBeijing Institute of TechnologyKey Laboratory of Cluster Science of Ministry of EducationBeijing100081China Department of Chemistry College of ScienceKing Khalid UniversityAbha61413Saudi Arabia

Machine learning is a powerful tool that can provide a way to revolutionize the material *** use for the designing and screening of materials for polymer solar cells is also *** of efficient polymeric materials for solar cells is really difficult *** have synthesized and fabricated so many *** the results and get feedback for further research requires an innovative *** this minireview,we provides brief introduction of machine *** importance of machine learning is also mentioned,and the application of machine learning for polymeric material design is *** key challenges that are hindering the wide spread use of machine are *** are also given to improve the use of data *** predictions using machine learning maybe not highly accurate but it definitely better than no prediction at all.

关键词： Machine learning Polymer solar cells Data science Descriptors Polymers

Effect of silica fume on the fresh and hardened properties of fly ash-based self-compacting geopolymer concrete

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International Journal of Minerals,Metallurgy and Materials 2013年第2期20卷 205-213页

作者： Fareed Ahmed Memon Muhd Fadhil Nuruddin nasir Shafiq Department of Civil Engineering Faculty of EngineeringUniversiti Teknologi PETRONAS Department of Civil Engineering Faculty of EngineeringMehran University of Engineering and Technology

The effect of silica fume on the fresh and hardened properties of fly ash-based self-compacting geopolymer concrete （SCGC） was investigated in this paper. The work focused on the concrete mixes with a fixed water-to-geopolymer solid （W/Gs） ratio of 0.33 by mass and a constant total binder content of 400 kg/m3. The mass fractions of silica fume that replaced fly ash in this research were 0wt%, 5wt%, 10wt%, and 15wt%. The workability-related fresh properties of SCGC were assessed through slump flow, V-funnel, and L-box test methods. Hardened concrete tests were limited to compressive, splitting tensile and flexural strengths, all of which were measured at the age of 1, 7, and 28 d after 48-h oven curing. The results indicate that the addition of silica fume as a partial replacement of fly ash results in the loss of workability; nevertheless, the mechanical properties of hardened SCGC are significantly improved by incorporating silica fume, especially up to 10wt%. Applying this percentage of silica fume results in 4.3% reduction in the slump flow; however, it increases the compressive strength by 6.9%, tensile strength by 12.8% and flexural strength by 11.5%.

关键词： geopolymer concrete silica fume fresh properties compressive strength tensile strength flexural strength