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CONTENTS
Volume 4, Number 3, September 2016
 

Abstract
The photocatalytic (PC) activity of anatase titania nanoparticles can be improved through codoping with transition metals and nitrogen. In addition, the PC activity can also be improved by creating monodisperse, mesoporous nanoparticles of titania. The question naturally arose as to whether combining these two characteristics would result in further improvement in the PC activity or not. Herein, we describe the synthesis and photocatalytic characteristics of codoped, monodisperse anatase titania. The transition metals tested in the polydisperse and the monodisperse forms were Mn, Co, Ni, and Cu. In each case, it was found that the monodisperse version had a higher PC activity compared to the corresponding polydisperse version.

Key Words
titania; codoped; phototcatalysis; macro-spores; micro-spheres; hydrothermal method; hybrid method

Address
John E. Mathis: Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA; Physical Sciences Department, Embry-Riddle Aeronautical University, Daytona Beach, FL 32114, USA
Michelle K. Kidder, Yunchao Li, Jinshui Zhang and M.P. Paranthaman: 1Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA

Abstract
The detailed study of acute and sub-acute toxicity of the complex polyvinylpyrrolidon (PVP 20 kDa)-wrapped fullerene C60 after intraperitoneal (ip) administration was carried out on adult male Wistar rats. The LD50 value of C60/PVP complex was found to be 7, 8 g/kg. In sub-acute study which lasted for 30 days the rats were exposed to daily administration of the complex in the doses of 350 or 700 mg/kg. All animals survived during the study and had no significant changes in clinical signs, organ weight, hematological and biochemical parameters of blood. The electrophysiological properties of myocardium and the excretory function of kidneys remained normal. Histological analysis of liver, kidney and spleen at the end of the study also did not demonstrate toxic alterations. It was thus established that intraperitoneal administration of complex C60/PVP has no toxic effect. These results suggest that C60/PVP has no acute and sub-acute toxicity and is a perspective substance for potential application in biology and medicine.

Key Words
fullerene C60; polyvinylpyrrolidone; complex; toxicity

Address
Marina A. Dumpis, Viktor V. Iljin, Elena V. Litasova, Dmitry N. Nikolaev, Valentina V. Bulion, Irina B. Krylova, Irina V. Okunevich, Olga M. Rodionova, Albina F. Safonova, Elena N. Selina and Levon B. Piotrovsky: Department of Neuropharmacology, Institute of Experimental Medicine, Academic Pavlov str. 12, Saint Petersburg 197376, Russia

Abstract
Addition of nano-SiO2 (NS) to geopolymer composites has been studied through measurement of compressive strengths, FTIR and XRD analysis. Alumino-silicate materials are coarse aggregate included waste concrete and demolished walls with its cementing binder, cement kiln dust (CKD) used and can possess a pronouncing activation for the geopolymer reaction resulting from the high alkali contents within. Materials prepared at water/binder ratios in a range of 0.30: 0.40 under curing of 40oC and 100% Relative Humidity (R.H.), while the used activator is sodium hydroxide in the ratio of 2 wt. %. First, CKD is added in the ratio from 10 up to 50 wt., %, and the demolished walls was varied depending on the used CKD content, while using constant ratio of waste concrete (40 wt., %). Second step, depending on the optimum CKD ratio resulted from the first one (40 wt. %), so the control geopolymer mix composed of cement kiln dust, demolished walls and waste concrete in the ratio (40:20:40, wt %). Nano-silica partially replaced waste concrete by 1 up to 8%. Results indicated that, compressive strengths of geopolymer mixes incorporating nano-silica were obviously higher than those control one, especially at early ages and specially with 3%NS.

Key Words
nanostructures; sol-gel growth; amorphous materials; composite materials; inorganic compounds

Address
H.M. Khater: Housing and Building National Research Centre (HBNRC), 87 El-Tahreer St., Dokki, Giza, P.O. Box 1770 Cairo, Egypt

Abstract
In the present study, thermo-electro-mechanical vibration characteristics of functionally graded piezoelectric (FGP) Timoshenko nanobeams subjected to in-plane thermal loads and applied electric voltage are carried out by presenting a Navier type solution for the first time. Three kinds of thermal loading, namely, uniform, linear and non-linear temperature rises through the thickness direction are considered. Thermoelectro-mechanical properties of FGP nanobeam are supposed to vary smoothly and continuously throughout the thickness based on power-law model. Eringen\'s nonlocal elasticity theory is exploited to describe the size dependency of nanobeam. Using Hamilton\'s principle, the nonlocal equations of motion together with corresponding boundary conditions based on Timoshenko beam theory are obtained for the free vibration analysis of graded piezoelectric nanobeams including size effect and they are solved applying analytical solution. According to the numerical results, it is revealed that the proposed modeling can provide accurate frequency results of the FGP nanobeams as compared to some cases in the literature. In following a parametric study is accompanied to examine the effects of several parameters such as various temperature distributions, external electric voltage, power-law index, nonlocal parameter and mode number on the natural frequencies of the size-dependent FGP nanobeams in detail. It is found that the small scale effect and thermo-electrical loading have a significant effect on natural frequencies of FGP nanobeams.

Key Words
functionally graded piezoelectric nanobeam; free vibration; Nonlocal elasticity theory; Thermal effect; Timoshenko beam theory

Address
Farzad Ebrahimiand Erfan Salari: Department of Mechanical Engineering, Faculty of Engineering, Imam Khomeini International University, Qazvin, Iran

Abstract
In this paper, buckling characteristics of nonhomogeneous functionally graded (FG) nanobeams embedded on elastic foundations are investigated based on third order shear deformation (Reddy) without using shear correction factors. Third-order shear deformation beam theory accounts for shear deformation effects by a parabolic variation of all displacements through the thickness, and verifies the stress-free boundary conditions on the top and bottom surfaces of the FG nanobeam. A two parameters elastic foundation including the linear Winkler springs along with the Pasternak shear layer is in contact with beam in deformation, which acts in tension as well as in compression. The material properties of FG nanobeam are supposed to vary gradually along the thickness and are estimated through the power-law and Mori–Tanaka models. The small scale effect is taken into consideration based on nonlocal elasticity theory of Eringen. Nonlocal equations of motion are derived through Hamilton\'s principle and they are solved applying analytical solution. Comparison between results of the present work and those available in literature shows the accuracy of this method. The obtained results are presented for the buckling analysis of the FG nanobeams such as the effects of foundation parameters, gradient index, nonlocal parameter and slenderness ratio in detail.

Key Words
buckling; third-order shear deformation beam theory; embedded functionally graded nanobeam; nonlocal elasticity theory

Address
Farzad Ebrahimi and Mohammad Reza Barati: Mechanical Engineering department, faculty of engineering, Imam Khomeini International University, P.O.B. 16818-34149, Qazvin, Iran


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