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Tehrani, Mohammad,Eipakchi, H.R. Techno-Press 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.44 No.1
In this paper the dynamic behavior of a viscoelastic Timoshenko beam subjected to a concentrated moving load are studied analytically and numerically. The viscoelastic properties of the beam obey the linear standard model in shear and incompressible in bulk. The governing equation for Timoshenko beam theory is obtained in viscoelastic form using the correspondence principle. The analytical solution is based on the Fourier series and the numerical solution is performed with finite element method. The effects of the material properties and the load velocity are investigated on the responses by numerical and analytical methods. In addition, the results are compared with the Euler beam results.
A Novel Electromagnetic Actuation System for Magnetic Nanoparticle Guidance in Blood Vessels
Tehrani, Mohammad Dadkhah,Myeong Ok Kim,Jungwon Yoon IEEE 2014 IEEE transactions on magnetics Vol.50 No.7
<P>Targeted drug delivery using magnetic nanoparticles (MNPs) is a new therapeutic method and is being improved continually. However, recent improvements have focused mainly on the introduction and synthesis of special drugs and there are still limitations getting a drug to desired locations in the body, primarily owing to the small size of nanoparticles and the difficulty of controlling their movement in the body. This paper introduces a new electromagnetic actuation system for guiding MNPs in blood vessels. This system uses six electromagnets powered by currents that can generate a high-gradient magnetic field in the desired direction. A differential current coil (DCC) approach is used to calculate the current applied to each coil. Due to properties of the DCC approach, it is possible to use soft iron cores at the centers of the coils to amplify and concentrate the magnetic field in the desired region and generate a stronger magnetic force than the existing coil systems. To evaluate the performance of the actuation system, a model that guided nanoscale magnetic particles inside special channels was studied using commercial software. To improve the efficiency of the electromagnets for MNP guidance, the structural parameters of the cores and coils were chosen based on the simulation results to get the largest magnetic force in the region of interest, which was set as size of the mouse brain. The proposed actuation system is very compact and less expensive than previous systems. Furthermore, the simulation results demonstrated that the actuation system can generate adequate magnetophoretic forces for nanoparticle steering in a Y-shaped vascular model and can be potentially used as a propulsion tool for MNP guidance in blood vessels.</P>
A Novel Scheme for Nanoparticle Steering in Blood Vessels Using a Functionalized Magnetic Field
Tehrani, Mohammad Dadkhah,Yoon, Jong-Hwan,Kim, Myeong Ok,Yoon, Jungwon IEEE 2015 IEEE Transactions on Biomedical Engineering Vol.62 No.1
<P>Magnetic drug targeting is a drug delivery approach in which therapeutic magnetizable particles are injected, generally into blood vessels, and magnets are then used to guide and concentrate them in the diseased target organ. Although many analytical, simulation, and experimental studies on capturing schemes for drug targeting have been conducted, there are few studies on delivering the nanoparticles to the target region. Furthermore, the sticking phenomenon of particles to vessels walls near the injection point, and far from the target region, has not been addressed sufficiently. In this paper, the sticking issue and its relationship to nanoparticle steering are investigated in detail using numerical simulations. For wide ranges of blood vessel size, blood velocity, particle size, and applied magnetic field, three coefficient numbers are uniquely generalized: vessel elongation, normal exit time, and force rate. With respect these new parameters, we investigated particle distribution trends for a Y-shaped channel and computed ratios of correctly guided particles and particles remaining in the vessel. We found that the sticking of particles to vessels occurred because of low blood flow velocity near the vessel walls, which is the main reason for low targeting efficiency when using a constant magnetic gradient. To reduce the sticking ratio of nanoparticles, we propose a novel field function scheme that uses a simple time-varying function to separate the particles from the walls and guide them to the target point. The capabilities of the proposed scheme were examined by several simulations of both Y-shaped channels and realistic three-dimensional (3-D) model channels extracted from brain vessels. The results showed a significant decrease in particle adherence to walls during the delivery stage and confirmed the effectiveness of the proposed magnetic field function method for steering nanoparticles for targeted drug delivery.</P>
Mohammad Tehrani,H.R. Eipakchi 국제구조공학회 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.44 No.1
In this paper the dynamic behavior of a viscoelastic Timoshenko beam subjected to a concentrated moving load are studied analytically and numerically. The viscoelastic properties of the beam obey the linear standard model in shear and incompressible in bulk. The governing equation for Timoshenko beam theory is obtained in viscoelastic form using the correspondence principle. The analytical solution is based on the Fourier series and the numerical solution is performed with finite element method. The effects of the material properties and the load velocity are investigated on the responses by numerical and analytical methods. In addition, the results are compared with the Euler beam results.
Fahimeh Ramezani Tehrani,Marzieh Saei Ghare Naz,Razieh Bidhendi-Yarandi,Samira Behboudi-Gandevani 대한당뇨병학회 2022 Diabetes and Metabolism Journal Vol.46 No.4
Background: Evidence supporting various diagnostic criteria for diagnose gestational diabetes mellitus (GDM) are consensus-based, needs for additional evidence related to outcomes. Therefore, the aim of this systematic-review and meta-analysis was to assess the impact of different GDM diagnostic-criteria on the risk of adverse-neonatal-outcomes.Methods: Electronic databases including Scopus, PubMed, and Web of Sciences were searched to retrieve English original, population-based studies with the universal GDM screening approach, up to January-2020. GDM diagnostic criteria were classified in seven groups and International Association of the Diabetes and Pregnancy Study Groups (IADPSG) was considered as reference one. We used the Mantel–Haenszel method to calculate the pooled odds of events. The possibility of publication bias was examined by Begg’s test.Results: A total of 55 population-based studies consisting of 1,604,391 pregnant women with GDM and 7,770,855 non-GDM counterparts were included. Results showed that in all diagnostic-criteria subgroups, the risk of adverse neonatal outcomes including macrosomia, hyperbilirubinemia, respiratory distress syndrome, neonatal hypoglycemia, neonatal intensive care unit admission, preterm birth, and birth-trauma were significantly higher than the non-GDM counterparts were significantly higher than non-GDM counterparts. Meta-regression analysis revealed that the magnitude of neonatal risks in all diagnostic-criteria subgroups are similar.Conclusion: Our results showed that the risk of adverse-neonatal-outcome increased among women with GDM, but the magnitude of risk was not different among those women who were diagnosed through more or less intensive strategies. These findings may help health-care-providers and policy-makers to select the most cost-effective approach for the screening of GDM among pregnant women.
Masoud Kavosh Tehrani,Sayed Sajjad Mousavi Fard 한국광학회 2017 Current Optics and Photonics Vol.1 No.2
A diffraction limited optical system for head mounted displays (HMDs) was designed. This opticalsystem consists of four modules, including 1:5 mm and 5:30 mm beam expanders, polarization gratingpolarizationconversion system (PG-PCS) and refractive/diffractive projection optical module. The PG-PCSmodule transforms the unpolarized Gaussian beam to a linearly polarized beam and it simultaneouslyhomogenizes the spatial intensity profile. The optical projector module has a 30° field of view, a 22 mmeye relief, and a 10 mm exit pupil diameter with a compact structure. Common acrylic materials wereutilized in the optical design process; therefore, the final optical system was lightweight. The whole opticalsystem is suitable for a 0.7 inch liquid crystal on silicon microdisplay (LCOS) with HDTV resolution(1920×1080) and 8.0 μm pixel pitch.