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Stability Map of Multiple Time Delayed Fractional Order Systems
Mohammad Ali Pakzad,Mohammad Ali Nekoui 제어·로봇·시스템학회 2014 International Journal of Control, Automation, and Vol.12 No.1
In this paper, a novel method is presented to study the stability map of linear fractional order systems with multiple delays against uncertainties in delays. It is evident from the literature that the stability question of this class of dynamics has not been resolved yet. The backbone of the new methodology is inspired by an advanced clustering with frequency sweeping technique which enables the exhaustive determination of stability switching curves in the space of the delays. The proposed method detects all the stability regions exactly, in the parametric space of the time delays. An illustrative example is pre-sented to confirm the proposed method results.
Mohammad Ali Saghiri,Armen Asatourian,Ali Mohammad Saghiri,Fatereh Samadi,Steven M Morgano 대한예방치과학회 2020 International Journal of Clinical Preventive Denti Vol.16 No.3
Objective: This study was performed to evaluate the ability of four different electric power toothbrushes to remove dental plaque on a three-dimensional (3-D) study model. Methods: A 3-D, 360-degree model of 32 human teeth was made of polyester (ELEGOO Inc.). Then, eight photos were made (four teeth at a time) from each quadrant and used as the negative control group (0% plaque). Then plaque-like color spray chalk were added and cured on the teeth model; photos were made and used as the positive control group (100% plaque). The 3-D model of the teeth was placed on a rotatable axis and immersed in a basin mimicking the composition of artificial saliva and toothpaste. An apparatus with a mechanical arm was made to hold the toothbrushes during the plaque removal process and control the force of brushing. Twenty-four toothbrushes were prepared and divided into four experimental groups of 6 (n=6) including 1) Philips, 2) Oral-B, 3) Quip, and 4) Waterpik. Toothbrushing was performed for 2 minutes. After brushing, photos were taken, and the percentage of plaque removal was measured by using the ImageJ software. Data were analyzed by Kolmogorov–Smirnov, ANOVA, and post hoc Tukey tests. Results: The highest plaque removal values were observed in the Philips group, and the lowest were seen in the Quip group. Significant differences were only recorded between the values of Philips and the other groups (p<0.05). Conclusion: Within 2 minutes of brushing time, none of the power toothbrushes could completely remove artificial dental plaque.
Stability Analysis of Time-Delayed Linear Fractional-Order Systems
Mohammad Ali Pakzad,Sara Pakzad,Mohammad Ali Nekoui 제어·로봇·시스템학회 2013 International Journal of Control, Automation, and Vol.11 No.3
In this article, an exact and robust method for the determination of all the possible stability regions in the parametric space has been presented for the fractional order systems with time delay. Using the approach presented in this study, first, the transcendental terms have been eliminated from the characteristic equation and then, all the locations on the imaginary axis crossed by the roots and also their direction of crossing have been calculated. Finally, the concept of the stability as a function of the time delay has been described for a general class of linear fractional order systems with several commensurate delays. Prior to the conclusion, several examples have been given to validate the results of the proposed approach.
Mohammad Ali Ebrahimzadeh,Mohammad Mohammad Taheri,Ehsan Ahmadpour,Mahbobeh Montazeri,Shahabeddin Sarvi,Mohammad Akbari,Ahmad Daryani 대한약침학회 2017 Journal of pharmacopuncture Vol.20 No.3
Objectives: The currently available agents for use against toxoplasmosis have serious limitations. Thus, the aim of the present study was to investigate the anti-Toxoplasma gondii (T. gondii) activities of methanol extracts of Feijoa sellowiana (F. sellowiana) (leaves and fruits), Quercus castaneifolia (Q. castaneifolia) (fruits), and Allium paradoxum (A. paradoxum) (leaves) in vitro and in vivo. Methods: Vero cells were treated with different concentrations (from 0 to 400 μg/mL) of the above extracts or with pyrimethamine at a dose of 50 mg/mL (positive control). Then, the viabilities of the T. gondii-infected cells were measured by using colorimetric MTT (3-(4, 5-dimethylthiazol-2-yl) 2, 5-diphenyltetrazolium bromide) assays. In addition, the survival rates of mice acutely infected with 2 × 104 RH strain tachyzoites of T. gondii were examined in vivo after intraperitoneal injection of the extracts at doses of 100 and 200 mg/kg/day for 5 days. Results: In the in vitro anti- T. gondii assay, the IC50 values were 12.77, 180.2, 74.73, 213.2 and 163.8 μg/mL, and the selectivity indices were 6.05, 1.31, 0.35, 0.69 and 1.30 for the F. sellowiana (leaves and fruits), Q. castaneifolia, and A. paradoxum extracts and pyrimethamine, respectively. Moreover, the mice treated with F. sellowiana (leaves and fruits) achieved better results in terms of survival than the others (P < 0.05). Conclusion: The results of the current study indicate that methanol extract of F. sellowiana has significant anti-Toxoplasma activity. Further study should be conducted to investigate the potential bioactivity of this extract through bioactivity-guided fractionation.
Ali Mohammad Bananzadeh,Ali Akbar Hafezi,NamPhong Nguyen,Shapour Omidvari,Ahmad Mosalaei,Niloofar Ahmadloo,Mansour Ansari,Mohammad Mohammadianpanah 대한방사선종양학회 2021 Radiation Oncology Journal Vol.39 No.4
Purpose: This study was performed to investigate the efficacy and safety of short-course radiation therapy (SCRT) and sequential chemotherapy followed by delayed surgery in locally advancer rectal cancer with subgroup analysis between the older and young patients.Materials and Methods: In this single-arm phase II clinical trial, eligible patients with locally advanced rectal cancer (T3–4 and/or N1–2) were enrolled. All the patients received a median three sequential cycles of neoadjuvant CAPEOX (capecitabine + oxaliplatin) chemotherapy. A total dose of 25 Gy in five fractions during 1 week was prescribed to the gross tumor and regional lymph nodes. Surgery was performed about 8 weeks following radiotherapy. Pathologic complete response rate (pCR) and grade 3–4 toxicity were compared between older patients (≥65 years) and younger patients (<65 years).Results: Ninety-six patients with locally advanced rectal cancer were enrolled. There were 32 older patients and 64 younger patients. Overall pCR was 20.8% for all the patients. Older patients achieved similar pCR rate (18.7% vs. 21.8; p = 0.795) compared to younger patients. There was no statistically significance in terms of the tumor and the node downstaging or treatment-related toxicity between older patients and younger ones; however, the rate of sphincter-saving surgery was significantly more frequent in younger patients (73% vs. 53%; p=0.047) compared to older ones. All treatment-related toxicities were manageable and tolerable among older patients.Conclusion: Neoadjuvant SCRT and sequential chemotherapy followed by delayed surgery was safe and effective in older patients compared to young patients with locally advanced rectal cancer.
Ebrahimzadeh, Mohammad Ali,Taheri, Mohammad Mohammad,Ahmadpour, Ehsan,Montazeri, Mahbobeh,Sarvi, Shahabeddin,Akbari, Mohammad,Daryani, Ahmad KOREAN PHARMACOPUNCTURE INSTITUTE 2017 Journal of pharmacopuncture Vol.20 No.3
Objectives: The currently available agents for use against toxoplasmosis have serious limitations. Thus, the aim of the present study was to investigate the anti-Toxoplasma gondii (T. gondii) activities of methanol extracts of Feijoa sellowiana (F. sellowiana) (leaves and fruits), Quercus castaneifolia (Q. castaneifolia) (fruits), and Allium paradoxum (A. paradoxum) (leaves) in vitro and in vivo. Methods: Vero cells were treated with different concentrations (from 0 to $400{\mu}g/mL$) of the above extracts or with pyrimethamine at a dose of 50 mg/mL (positive control). Then, the viabilities of the T. gondii-infected cells were measured by using colorimetric MTT (3-(4, 5-dimethylthiazol-2-yl) 2, 5-diphenyltetrazolium bromide) assays. In addition, the survival rates of mice acutely infected with $2{\times}10^4$ RH strain tachyzoites of T. gondii were examined in vivo after intraperitoneal injection of the extracts at doses of 100 and 200 mg/kg/day for 5 days. Results: In the in vitro anti- T. gondii assay, the $IC_{50}$ values were 12.77, 180.2, 74.73, 213.2 and $163.8{\mu}g/mL$, and the selectivity indices were 6.05, 1.31, 0.35, 0.69 and 1.30 for the F. sellowiana (leaves and fruits), Q. castaneifolia, and A. paradoxum extracts and pyrimethamine, respectively. Moreover, the mice treated with F. sellowiana (leaves and fruits) achieved better results in terms of survival than the others (P < 0.05). Conclusion: The results of the current study indicate that methanol extract of F. sellowiana has significant anti-Toxoplasma activity. Further study should be conducted to investigate the potential bioactivity of this extract through bioactivity-guided fractionation.
Creep simulation of adhesively bonded joints using modified generalized time hardening model
Mohammad Ali Saeimi Sadigh 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.4
Creep behavior of double lap adhesively bonded joints was investigated using experimental tests and numerical analysis. Firstly, uniaxial creep tests were carried out to obtain the creep characteristics and constitutive parameters of the adhesive at different stress and temperature levels. Generalized time hardening model was used to predict the creep behavior of the adhesive. This model was modified to simulate the creep behavior at different stress and temperature levels. Secondly, the developed model was used to simulate the creep behavior of bonded joints using finite element based numerical analysis. Creep deformations of the joints were measured experimentally and good agreement was observed in comparison with the results obtained using numerical simulation. Afterward, stress redistribution due to the creep along the adhesively bonded joint was obtained numerically. It was observed that temperature level had a significant effect on the stress redistribution along the adhesive thickness.