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Modified Time-Dependent Model for Flexural Capacity Assessment of Corroded RC Elements
Behrouz Akbarian Reshvanlou,Kiarash Nasserasadi,Jamal Ahmadi 대한토목학회 2021 KSCE JOURNAL OF CIVIL ENGINEERING Vol.25 No.10
The corrosion of embedded steel bars in concrete is one of the severe deterioration processes that can escalate the risk and reduce the durability and lifetime of concrete structures. Based on the literature, simultaneous corrosion of longitudinal and transverse bar is considered to estimate section capacity. In this research, a flexible multi-stage approach is proposed to differentiate between corrosion levels on longitudinal and transverse reinforcement based on their corrosion initiating time. The result indicated that the multi-stage approach provides higher capacity and curvature for the sections. A significant reduction in reinforced concrete (RC) sections' ductility after corrosion of confining bars and before starting corrosion of longitudinal rebars was observed, which illustrates the importance of stirrups corrosion effects on the sections' ductility. In the higher values of corrosion intensity, confined concrete's ultimate strain tends to reach the unconfined state. Using the energy-based method of calculating ultimate concrete compressive strain instead of approximate methods, a higher value of curvature ductility of corroded RC cross-sections is obtained.
Eslamian, Ladan,Rad, Nazila Akbarian,Nobar, Behnam Rahbani,Mortazavi, Seyed Alireza The Korean Dental Society of Anesthsiology 2018 Journal of Dental Anesthesia and Pain Medicine Vol.18 No.3
Background: The pain involved in orthodontic treatments may involve inflammatory processes. This study evaluated the effect of using a naproxen patch for pain reduction in the separating stage of fixed orthodontic treatment. Methods: In this double-blind, randomized, controlled clinical trial of 35 orthodontic patients (age: 14-19 years) who had pain during separator placement, each patient randomly placed naproxen and placebo patches in the first permanent molar region, in opposite quadrants of the same jaw. Patches were replaced every 8 hours until 3 days after separator placement. Patients recorded their pain perception at 2, 6, and 24 hours, and on days 2 (6 PM), 3 (10 AM and 6 PM), and 7 (10 AM and 6 PM), using a visual analog scale. Mean pain scores were compared for the two patches, and effects of sex and age thereon determined. Results: Data from 29 patients (21 girls, eight boys) were analyzed. Mean pain values decreased over time for both patches (P < 0.001). Recorded pain did not differ significantly between the sexes (P = 0.059) or between those aged <16 and those ${\geq}16years$ (P = 0.106). Mean pain recorded with naproxen patches was statistically significantly less than that with placebo patches at all time points (P = 0.004). Conclusion: The naproxen patch was more efficient than the placebo patch for reducing pain at all time points. The highest pain score was recorded at 6 hours, and the least pain was recorded at the $7^{th}$ day after separator placement.
Links between peptides and Mn oxide: nano-sized manganese oxide embedded in a peptide matrix
Najafpour, Mohammad Mahdi,Madadkhani, Sepideh,Akbarian, Somayyeh,Zand, Zahra,Hołyń,ska, Małgorzata,Kompany-Zareh, Mohsen,Tatsuya, Tomo,Singh, Jitendra Pal,Chae, Keun Hwa,Allakhverdiev, Suleyman I The Royal Society of Chemistry 2018 NEW JOURNAL OF CHEMISTRY Vol.42 No.12
<P>Herein we report on a poly-peptide/Mn oxide nanocomposite as a model for the water-oxidizing catalyst in Photosystem II. The material is obtained by the reaction of poly-l-tyrosine, Mn(OAc)2·4H2O and KMnO4. HRTEM images of the nanocomposite indicate the presence of nanoparticles dispersed in a poly-l-tyrosine matrix with no crystalline phases. A broad peak at ∼400-550 nm in the UV-visible spectrum is related to Mn oxide formation. X-ray absorption studies suggest that the Mn atoms are in the oxidation state of +IV and a coordination number of around three was obtained for Mn in the structure. The water-oxidizing activity of the material under electrochemical conditions was also investigated. Electrochemical experiments proved the presence of Mn(iv) oxide. Determination of oxygen coupled to electrochemistry revealed the role of poly-l-tyrosine in decreasing the overpotential for water oxidation. In the next step, the interaction of the nanocomposite and imidazole as a model for the tyrosine 161 and histidine 190 residues in Photosystem II was studied with fluorescence spectroscopy using the multivariate curve resolution-alternating least squares method.</P>
Enhancement of silane coating protective performance by using a polydimethylsiloxane additive
M. Mahdavian,B. Ramezanzadeh,M. Akbarian,M. Ramezanzadeh,P. Kardar,E. Alibakhshi,S. Farashi 한국공업화학회 2017 Journal of Industrial and Engineering Chemistry Vol.55 No.-
This work intends to study the effect of a polydimethylsiloxane additive on the protection performance of a hybrid silane coating on mild steel. Electrochemical impedance spectroscopy, polarization and electrochemical noise measurements and salt spray showed an increase in corrosion resistance of the silane coating in the presence of the additive. Silane films were examined by FTIR, water droplet contact angle, Vickers hardness and SEM. Results showed decrease in crosslinking density in the presence of the additive. Superior corrosion protection in the presence of additive was attributed to the enhanced hydrophobic character and flexibility of the coating.
A new strategy to make an artificial enzyme: photosystem II around nanosized manganese oxide
Najafpour, Mohammad Mahdi,Madadkhani, Sepideh,Akbarian, Somayyeh,Hołyń,ska, Małgorzata,Kompany-Zareh, Mohsen,Tomo, Tatsuya,Singh, Jitendra Pal,Chae, Keun Hwa,Allakhverdiev, Suleyman I. The Royal Society of Chemistry 2017 Catalysis Science & Technology Vol.7 No.19
<▼1><P>A new strategy to make an artificial enzyme was reported.</P></▼1><▼2><P>Herein we report a new strategy to disperse Mn oxide into the apoenzyme of photosystem II. The compound was characterized by scanning electron microscopy, transmission electron microscopy, UV-visible spectroscopy, Fourier transform infrared spectroscopy, X-ray absorption near edge structure, extended X-ray absorption fine structure, X-ray diffraction and some electrochemical methods. Under electrochemical conditions, the peaks attributed to Mn(ii)/(iii), Mn(iii)/(iv) and Mn(ii)/(iv) were assigned and compared with other manganese oxides. Linear sweep voltammetry shows that water electro-oxidation occurs at 80 mV less than that for the apoenzyme of photosystem II. Thus, Mn oxide maintains its water-oxidizing activity under these conditions. The compound is a new type of structural and functional model for the water-oxidizing complex in photosystem II.</P></▼2>