Adult Stem Cells of Orofacial Origin: Current Knowledge and Limitation and Future Trend in Regenerative Medicine

Mehdi Ebrahimi,Michael Botelho 한국조직공학과 재생의학회 2017 조직공학과 재생의학 Vol.14 No.6

Stem cell research is one of the most rapidly expanding field of medicine which provides significant opportunities for therapeutic and regenerative applications. Different types of stem cells have been isolated investigating their accessibility, control of the differentiation pathway and additional immunomodulatory properties. Bulk of the literature focus has been on the study and potential applications of adult stem cells (ASC) because of their low immunogenicity and reduced ethical considerations. This review paper summarizes the basic available literature on different types of ASC with special focus on stem cells from dental and orofacial origin. ASC have been isolated from different sources, however, isolation of ASC from orofacial tissues has provided a novel promising alternative. These cells offer a great potential in the future of therapeutic and regenerative medicine because of their remarkable availability at low cost while allowing minimally invasive isolation procedures. Furthermore, their immunomodulatory and anti-inflammatory potential is of particular interest. However, there are conflicting reports in the literature regarding their particular biology and full clinical potentials. Sound knowledge and higher control over proliferation and differentiation mechanisms are prerequisites for clinical applications of these cells. Therefore, further standardized basic and translational studies are required to increase the reproducibility and reduce the controversies of studies, which in turn facilitate comparison of related literature and enhance further development in the field.

Composition of Derivations on (semi) Prime I-rings

M. Mehdi Ebrahimi,H. Pajoohesh 경북대학교 자연과학대학 수학과 2004 Kyungpook mathematical journal Vol.44 No.2

In this paper first we show that the iterationdn ; n 2; of a non zero derivation d on a semi-prime `-ring R is not a derivation, and henced can not be nilpotent. Then we see that if R is prime and d1; ;dn ; n 2; are positive derivations on R with d1 dn a derivation, then at least one of these derivations must be zero. Finally, taking R to be a semiprime f-ring, we show that if for every x 2 R; dn (x) is central, then, under some mild conditions, there is a nonzero inner derivation on R such that (x)d(x) = d(x)(x) = 0.These results generalizes and improves the ones in [3], [8], and [9]. And show that imposing an order on a ring, making it an ordered ring, gives stronger results.

Optimal Energy Management of a Microgrid Incorporating a Novel Efcient Demand Response and Battery Storage System

Mehdi Mohammadjafari,Reza Ebrahimi,Vahid Parvin Darabad 대한전기학회 2020 Journal of Electrical Engineering & Technology Vol.15 No.2

In this paper, optimal economic management of a grid-connected microgrid (MG) with distributed energy resource (DER) and its interaction with incentive-based demand response programs (DRPs) is studied. The use of DR makes energy management system (EMS) of the MG an efcient tool in balancing the demand and supply, and therefore ensuring the network reliability. In this work, the cost function of customers is developed in the incentive-based DRP with the aim of receiving a more realistic incentive and then it is combined with EMS. Accordingly, the consumers ofer hourly power reduction bids based on which they are sorted and then incentive-based payment model is implemented. At times, due to full utilization of grid and MG resources, the supply–demand balance cannot be maintained by respecting the consumer ofers. Specifc energy policies and contracts are required in this case for mandatory power curtailment in exchange for higher incentive payments by MG operator (MGO). The objective function attempts to minimize operation costs of the MG units such as Diesel Generator fuels costs, cost of power exchange with the main grid, battery energy storage system (BESS) costs and in the mean time, maximize MGO DR beneft. On the other hand, simultaneous EMS and DR management leads to a complex non-linear problem, which can be solved using whale optimization algorithm (WOA) in MATLAB software. To assess the performance of the proposed new approach, a grid-connected MG with DERs and reducible power of consumers is studied within a 24-h time cycle. Also, to verify the scalability of the implemented system, an MG with aggregators and a large scale battery is considered. Simulation results show that incorporating a developed DR into EMS is an efcient way in optimal performance of both demand and supply sides in conjunction with the goals of economic operation of MGs.

Investigation of the Seismic Behavior of Brace Frames with New Corrugated All-Steel Buckling Restrained Brace

Mehdi Ebadi Jamkhaneh,Amir Homaioon Ebrahimi,Maedeh Shokri Amiri 한국강구조학회 2019 International Journal of Steel Structures Vol.19 No.4

All-steel buckling restrained brace (BRB) is a type of relatively new common bracings considering its low weight and whilst it is not required curing of mortar at the core of braces. In this study, a new form of all-steel BRB is introduced with corrugated edges of the core and the external sheath, and it was analyzed by using of fi nite element method. Existence of corrugated and ribbed edges led to enhance of buckling resistance. Numerical model was validated with laboratory samples, and after receiving an acceptable compliance in model behavior, the numerical models were off ered. In this analysis, key parameters were size of brace section and distance of gap between the internal and external sheaths. The most appropriate size for gap between the core and external tube was determined to be 10 mm. Upon specifying the non-linear modeling parameter, two cases of frame with ordinary concentrically brace and the proposed all-steel BRB were compared for three structures with 4, 8 and 12 fl oors using pushover and non-linear time history analysis. The results demonstrated that utilizing of the proposed BRB will lead to an increase in behavior coeffi cient and structure ductility as well as an alteration in performance level of tall structures from collapse prevention to life safety level.

Chemical incorporation of epoxy-modified graphene oxide into epoxy/novolac matrix for the improvement of thermal characteristics

Ebrahimi Hamidreza,Roghani-Mamaqani Hossein,Salami-Kalajahi Mehdi,Shahi Sina,Abdollahi Amin 한국탄소학회 2020 Carbon Letters Vol.30 No.1

Chemical incorporation of epoxy-modifed graphitic layers in epoxy/novolac phenolic resin matrices was carried out through co-curing of epoxy and novolac resins using triphenylphosphine as catalyst. First, (3-glycidyloxypropyl) trimethoxysilane (GPTMS) was grafted on graphene oxide (GO) surface to obtain epoxidized GO layers. Then epoxy resin and GPTMS-mod�ifed GO were incorporated into thermosetting reaction using novolac resin in the presence of triphenylphosphine. Covalent attachment of GPTMS-modifed GO to the resin matrices resulted in a hybrid composite with high thermal characteristics. Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis (TGA), X-ray dif�fraction, and Raman spectroscopy were used for approving modifcation of GO with GPTMS. The images resulted from scanning and transmission electron microscopies exhibited GO layers with lots of creases turning to smooth layers with a few thin ripples after modifcation with GPTMS. TGA results showed that thermal characteristics of resins were improved by the addition of GPTMS-modifed GO. Char residue of the hybrid composites containing 0.5 and 1 wt% of GPTMS-modifed GO reached 28.1 and 34.3%, respectively. Also, their maximum thermal degradation temperature was also increased by the incorporation of GPTMS-modifed GO.

Kinetics and Critical Conditions for Initiation of Dynamic Recrystallization During Hot Compression Deformation of AISI 321 Austenitic Stainless Steel

Mehdi Shaban Ghazani,Beitallah Eghbali,Gholamreza Ebrahimi 대한금속·재료학회 2017 METALS AND MATERIALS International Vol.23 No.5

Dynamic recrystallization behavior of AISI 321 austenitic stainless steel were studied using hot compressiontests over the range of temperatures from 900 °C to 1200 °C and strain rates from 0.001 s-1to 1 s-1. The criticalstrain and stress for initiation of dynamic recrystallization were determined by plotting strain hardening ratevs. stress curves and a constitutive equation describing the flow stress at strains lower than peak strain. Also, thestrain at maximum flow softening was obtained and the effect of deformation conditions (Z parameter) on thecritical strain and stress were analyzed. Finally, the volume fraction of dynamic recrystallization was calculated atdifferent deformation conditions using these critical values. Results showed that the model used for predictingthe kinetics of dynamic recrystallization has a great consistency with the data, in the form of θ-ε curves,directly acquired from experimental flow curves.

Experimental and Numerical Investigation of Steel Moment Resisting Frame with U-Shaped Metallic Yielding Damper

Mehdi Ebadi Jamkhaneh,Amir Homaioon Ebrahimi,Maedeh Shokri Amiri 한국강구조학회 2019 International Journal of Steel Structures Vol.19 No.3

This study introduces U-shape metallic yielding damper (UMYD) as an energy dissipation system. This damper may be used as a replaceable and cost-eff ective tool and fuse in structural frames to improve lateral ductility, energy absorption and damping of structural systems under earthquakes. A series of static cyclic tests were conducted in order to examine the performance of UMYD and the response of force-displacement, lateral strength, elastic stiff ness and energy absorption were achieved. Finite element numerical studies were conducted through changing damper geometrical parameters. Mathematical model was presented to estimate elastic stiff ness of damper and was compared with numerical specimen results, which acceptable conformity. Finite elements models indicated that UMYD abilities energy absorbability in large displacements without loss of strength and stiff ness, which may be a proper complementary system for lateral load-bearing systems. The behaviour of two 4- and 8-storey steel frames with moment resisting frame system was analysed under four diff erent earthquakes under two states of with and without damper. The seismic performance of frames was analysed with respect to fl oors inter-storey drift, frame base shear and fl oors shear. The non-linear time historey analysis results demonstrated that 8-storey frame without UMYD failed to maintain the structure performance level within life-safety level, whilst under all states using damper, performance level remained within such level and a decrease in fl oors shear and inter-storey drift was observed.

Sequential optimization strategy for hyaluronic acid extraction from eggshell and its partial characterization

Mehdi Khanmohammadi,Ali Baradar Khoshfetrat,Shahla Eskandarnezhad,Najimeh Feyze Sani,Sirus Ebrahimi 한국공업화학회 2014 Journal of Industrial and Engineering Chemistry Vol.20 No.6

The optimization of hyaluronic acid (HA) extraction from eggshell was studied by using a sequentialexperimentation approach. Using the results of factorial experiments, optimization experiments werecarried out by response surface methodology. The experimental data as well as the validation testsshowedthe optimum performance when the extraction pH and time were bounded in the ranges of 3.4–3.5 and3–3.4 days, respectively, at 9 ℃. The purified HAwas characterized by FTIR spectrum, harmonic mean sizeand average molecularweight. The study depicted the potential of eggshell as an alternative source for HAextraction to use in industry and medicine.

Numerical Investigation of the Behavior of MERO Joint System Under Combined Loading Regarding Helical Threads of Elements

Mehdi Ebadi Jamkhaneh,Amir Homaioon Ebrahimi,Maedeh Shokri Amiri 한국강구조학회 2020 International Journal of Steel Structures Vol.20 No.3

A comprehensive fi nite element (FE) model of bolt-ball joint, as called MERO joint, is presented in this paper for a double layer grid structure. In double layer grids, the main internal forces are axial forces. The defl ection and rotation patterns of the connector are studied under diff erent loading conditions using the ABAQUS FE software. The applied forces on the connector are determined using displacement control. In order to take into account the connector eff ects in structural analysis, their behavior under combined loading should be predicted. To determine the load–displacement relationship of the MERO connection, numerical models were carried out on a connector of this type using of 3D FE method. The obtained load–displacement and moment- rotation relationships were used under diff erent loads. The results of the FE simulation with experimental results have a good match. Compressive axial load increases the fl exural stiff ness of the connection and decreases the elastic bending moment. Furthermore, the equivalent stiff ness of bolt with the whole of complexities was proposed.

Effects of aqueous and methanolic extracts of Astragalus Longistylus on growth and proliferation of human dental pulp stem cells

Ebrahimi Maryam,Yaghoobi Mohammad Mehdi 경희대학교 융합한의과학연구소 2021 Oriental Pharmacy and Experimental Medicine Vol.21 No.1

Increasing stem cell proliferation and preventing their aging is a prerequisite for cell-based therapy. Astragalus Longistylushas been used as a medicinal plant for centuries and is widely dispersed in Iran. In this study, the effect of aqueous and metha-nolic extracts of A. Longistylus on the growth and proliferation of human dental pulp stem cells was investigated by MTT, BrdU and flow cytometry over 24 and 48 h. The antioxidant activity of the extracts was also measured by DPPH method. The expression of BTG1, CCND1, and HTERT genes were also analyzed by RT-qPCR. The results of the DPPH test showed that the aqueous and methanolic extracts at the concentration of 1000 μg/mL had 29.39% and 82.71% antioxidant activity, respectively. Both the aqueous and methanolic significantly increased the cell proliferation and DNA synthesis after 48 h as revealed by MTT and BrdU assay results. Cell cycle analysis showed that the cells arrested in the G1 phase upon treatment with both extracts after 24 h. However, after 48 h, the number of G1 cells was reduced while the number of cells in G2/M phase approached that of the control group. Meanwhile, expression of CCND1, TERT and BTG1 was reduced after 48 h by both extracts and increased following a 72 h treatment. Therefore, our findings demonstrate that the effect of the extracts on the cell proliferation was somewhat decreasing during 24 h and increasing after 48 h. These effects could be attributed to compounds such as flavonoids, polysaccharides, astragalosides, and calycosin.