News Article | August 22, 2016
Abstract: Physicists at the University of Basel have succeeded in watching a silver catalyst at work for the first time with the aid of an atomic force microscope. The observations made during an Ullmann reaction have allowed the researchers to calculate the energy turnover and, potentially, to optimize the catalysis. The study, which was performed with experts from Japan and Iran, has been published in the scientific journal Small. The Ullmann reaction examined is a chemical reaction in which silver atoms catalyze the bond between two carbon atoms to which iodine was previously bonded. Although scientists have known about this type of reaction since 1901 and used it for many important chemical conversions, it was not previously possible to observe the intermediate product of the reaction in detail. Using an atomic force microscope, the team of researchers led by Professor Ernst Meyer and Dr. Shigeki Kawai from the Swiss Nanoscience Institute and the Department of Physics at the University of Basel has now succeeded in displaying this reaction at atomic resolution. Surprisingly, it was revealed that the silver atoms react with the molecules at temperatures of around -120°C and seem to curve like a bridge over a river. In the second stage of the reaction, which requires the temperature to be increased to around 105°C and generates the end product, the silver atoms are freed again and two carbon atoms bond together. Calculating energy The Ullmann reaction has been used for chemical syntheses for a long time now. Interest in this linking of carbon atoms has recently increased again because it can be used to bind organic molecules to surfaces and produce solvent-free polymers. Detailed observations of how the catalysts work enable scientists to better understand the reaction process. Previous analyses failed to show the spatial arrangement of the organometallic intermediate product. The detailed images now obtained are the first to allow project partner Professor Stefan Goedecker (Department of Physics, University of Basel) to calculate the energy turnover of the Ullmann reaction examined. This data confirms the unusual spatial arrangement of the intermediate product and indicates how the reaction could be optimized. Relatively low temperatures The observed curving and flexibility of the molecules is probably the reason why the reaction requires relatively low temperatures of 105°C. The molecules are subject to mechanical tension and can therefore react more easily, that is at lower temperatures. If other catalysts could be used to generate intermediate products like these that are subject to tension, then catalytic reactions could also be possible at lower temperatures. This would make ecological and economic sense because traditional catalysts with platinum, rhodium, or palladium often require high operating temperatures of 500°C, which leads to the emission of waste gases in a cold state. ### The research work was the result of a collaboration between the Department of Physics at the University of Basel, the National Institute of Materials Science (Japan), the Japan Science and Technology Agency (Japan), the University of Tokyo (Japan), and Shadid Beheshti University (Iran). For more information, please click If you have a comment, please us. Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.
Kiaei M.,Islamic Azad University |
Tajik M.,Islamic Azad University |
Tajik M.,Beheshti University |
Vaysi R.,Islamic Azad University
Maderas: Ciencia y Tecnologia | Year: 2014
Plum (Prunus domestica) is one of the most widespread species of fruit trees in Asia and South-East Europe. There are large quantities of fruit wood trees without suitable usage in world. The aim of this research was to examine biometrical and chemical properties of the plum wood and its application in the pulp and paper industry. Five normal plum trees were randomly selected from Shahriyar province, Iran. A log cut down at stem (breast height) and branch for each of trees. The pith parts of cross-section were removed to examine the chemical (according to the TAPPI standard) and biometrical properties (according to the Franklin method). Results indicated that there were significant differences between stem and branch samples in fiber diameter and lumen diameter. Types of wood (branch and stem) had not significant differences on the chemical properties and fiber length, cell wall thickness and morphological properties. Among all of studied properties, the lignin, cellulose, fiber diameter, fiber lumen diameter, cell wall thickness and flexibility coefficient in branch wood is higher than stem wood. Although Runkel and flexibility coefficients of stem and branch fibers are lower than the accepted standard, but because of closing amount of lignin, extractive composition and fiber length to hardwood species, it can solve some of the problems of the lack of raw materials for paper production.
Mahdavi S.,Iranian Research Institute of Forests and Rangelands |
Kermanian H.,Beheshti University |
Ramezanl O.,Beheshti University |
Molavi S.,Beheshti University
Cellulose Chemistry and Technology | Year: 2013
Five successful non-indigenous clones, selected based on local adaptability from a total of fifteen, were studied for their kraft pulp production and a new ranking method based on technical and economic parameters was used to facilitate decision making in future plantation policies. Three logs were cut at the breast height of each clone with the age of 12 years. The best screen yield mean of five clones (52.58%) was achieved applying the cooking treatment combination of 170 CC, 45 min, 18% A.A., and 23% sulfidity. Physical and mechanical properties of the handsheets prepared from the pulp, namely average sheet apparent density, tear and burst indices and breaking length, were measured as 0.75 g cm-3, 10.67 mN m2 g-1, 5.20 kPa m2 g-1, and 7.60 km, respectively. A pair-wise comparison with nine objectives was carried out using Expert Choice software by two unweighted and weighted (technical and economic weighting) methods. The two ranking methods indicated that Costanzo and Triplo (clones of P. euroamericana) are the superior and, respectively, the inferior of the clones under study, considering the objectives of the hierarchy. The other clones were ordered differently, according to the priority of each of the methods. Despite the highest annual growth rate, sheet density and tear index, Vernirobensis (clone of P. euroamericana) was situated second in the ranking. The results indicated that the pulp strengths of all selected clones were higher than the strength requirement for kraft liner, according to ISIRI3054 standard.
Beigi H.,IAUN |
Pakzad P.,Beheshti University
WIT Transactions on Ecology and the Environment | Year: 2010
Tourism and the environment are so close to each other and the physical environment creates innumerable attraction for sustainable tourism. Geotourism as a new choice in sustainable tourism not only focuses on all natural and humanistic features but also considers the performance of one place. One can play an effective role in the national development and national economy diversification of the area by planning and recognizing the opportunities as well as the limitation of Geotourism. Thus, there are two questions here: 1. What are the potentialities and limitations of Geotourism development? 2. Which strategies are required for developing this type of tourism and following national and regional development? Using measurement and field studies methods and determination of the strengths, weaknesses, opportunities and threats by SWOT, the authors provide some strategies and suggestions for developing Geotourism in the Gavkhoni Wetland. Experimental analysis about this area presents that although the geotourist in this area is very various, this area is confronted with serious transregional threats. We will have a powerful Geotourism pole in this region, if the tourism infrastructure policies minimize and review. © 2010 WIT Press.