Fatollahi A.H.,Alzahra University
European Physical Journal C | Year: 2017
The general theoretical ground for models based on compact angle coordinates is presented. It is observed that the proper dependence on compact coordinates has to be through the group elements and is achieved most naturally in a discrete-time formulation of the theory. By the construction, the discrete worldline inlaid by compact coordinates resembles the spin chains of magnetic systems. As examples, the models based on the groups U(1), ZN and SU(2) are explicitly constructed and their exact energy spectra are obtained. As the consequence of the minima in the spectra, the models exhibit a phase transition of first order. We attempt to fit the dynamics by the U(1) group to the proposed role for monopoles in the dual Meissner effect of the confinement mechanism. © 2017, The Author(s).
Maleknejad A.,Alzahra University |
Maleknejad A.,Institute for Research in Fundamental Sciences |
Sheikh-Jabbari M.M.,Institute for Research in Fundamental Sciences
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2013
Inflationary models are usually based on dynamics of one or more scalar fields coupled to gravity. In this work we present a new class of inflationary models, gauge-flation or non-Abelian gauge field inflation, where slow-roll inflation is driven by a non-Abelian gauge field. This class of models is based on a gauge field theory with a generic non-Abelian gauge group minimally coupled to gravity. We then focus on a particular gauge-flation model by specifying the action for the gauge theory. This model has two parameters which can be determined using the current cosmological data and has the prospect of being tested by Planck satellite data. Moreover, the values of these parameters are within the natural range of parameters in generic grand unified theories of particle physics. © 2013 Elsevier B.V.
Shiri M.,Alzahra University |
Zolfigol M.A.,Bu - Ali Sina University |
Kruger H.G.,University of KwaZulu - Natal |
Tanbakouchian Z.,Alzahra University
Chemical Reviews | Year: 2010
A study was conducted to investigate the synthesis of bis- and trisindolylmethanes (BIM and TIM). The study focused on investigating the variations found in synthesizing these useful aromatic heterocycles. It introduced different synthetic routes to 3,3'-BIMs, ranging from usual to more exotic methods. The preparation of 2,2'- and 2,3'-BIMs and yuehchukenes as a special kind of 2,3'-BIMs was presented along with other BIMs. The investigations revealed that BIMs were molecules containing two indolyl moieties connected to the same carbon atom. It was also demonstrated that 3,3'-BIMs were synthesized by an analogous reaction to the Ehrlich test where indoles reacted with aliphatic or aromatic aldehydes or ketones in the presence of an acid catalyst to produce azafulven. Several other types of BIMs were also found to be present in addition to 3,3'-, 2,3'-, and 2,2'-BIMs.
Boyaghchi F.A.,Alzahra University |
Heidarnejad P.,Alzahra University
Energy Conversion and Management | Year: 2015
This paper proposes a novel micro solar Combined Cooling, Heating and Power (CCHP) cycle integrated with Organic Rankine Cycle (ORC) for summer and winter seasons. The thermal storage tank is installed to correct the mismatch between the supply of the solar energy and the demand of thermal source consumed by the CCHP subsystem, thus the desired system could continuously and stably operate. The cycle is analyzed and optimized from the viewpoint of thermodynamics and thermoeconomics. For summer mode, the thermal efficiency, exergy efficiency and product cost rate are found to be 23.66%, 9.51% and 5114.5 $/year, while for winter mode, these values are 48.45%, 13.76% and 5688.1 $/year, respectively. Five key parameters, namely turbine inlet temperature, turbine inlet pressure, turbine back pressure, evaporator temperature and heater outlet temperature are selected as the decision variables to examine the performance of the overall system. The thermal efficiency, exergy efficiency and total product cost rate are selected as three objective functions and Genetic Algorithm (GA) is employed to find the final solutions to both single and multi-objective optimizations of the system. The results indicate that in summer, thermal efficiency, exergy efficiency and total product cost rate in optimum case are improved to 28%, 27% and 17%, respectively, while in winter, these values are 4%, 13% and 4%. © 2015 Elsevier Ltd. All rights reserved.
Esmaeili M.,Alzahra University |
Zeephongsekul P.,RMIT University
International Journal of Production Economics | Year: 2010
A seller-buyer supply chain represents a network consisting of a seller who wholesales a product to a buyer, who in turn retails it to the consumer. Most seller-buyer supply chains are modeled by non-cooperative and cooperative games under a deterministic and symmetric information pattern. Under a symmetric information pattern, the seller and buyer have complete information on each other's operations. However, in a supply chain, the buyer and seller, being independent entities, have private information about various aspects of their businesses which are not common knowledge. In this paper, several seller-buyer supply chain models are proposed under an asymmetric information pattern. The proposed models rely on the fact that the seller's setup/purchase costs are unknown to the buyer and the buyer withholds certain information related to market demand. The relationships between seller and buyer are modeled by non-cooperative Stackelberg games where buyer and seller take turn as leader and follower. In addition, a semi-cooperative model, where sharing marketing expenditure is used as an incentive strategy to reveal information, is proposed. Finally, numerical examples presented in this paper, including sensitivity analysis of some key parameters, seek to compare results between the different models considered. © 2009 Elsevier B.V. All rights reserved.
Sadjadi S.,Alzahra University |
Heravi M.M.,Alzahra University
Tetrahedron | Year: 2011
The recent isocyanide-based synthesis of various types of heterocycles is reviewed. The report contains 98 references. © 2011 Elsevier Ltd © 2011 Elsevier Ltd. All rights reserved.
Heravi M.M.,Alzahra University |
Zadsirjan V.,Alzahra University
Tetrahedron Asymmetry | Year: 2013
Asymmetric aldol reactions of oxazolidinones as chiral auxiliaries have been achieved and attracted significant consideration as one of the most powerful synthetic tools for the carbon-carbon bond-forming reactions. The methodology has been highly successful in the stereoselective construction of a number of natural products, antibiotics, and other medicinally important compounds. The present review is focused on the utility and versatility of oxazolidinones (Evans chiral auxiliaries) in the asymmetric aldol condensations for the total synthesis of natural products and complex targets. © 2013 Elsevier Ltd. All rights reserved.
Shiri M.,Alzahra University
Chemical Reviews | Year: 2012
A study was conducted to demonstrate the use of indoles in multicomponent processes (MCP). The reaction of β-dicarbonyl compounds such as 4-hydroxycoumarin or triacetic acid lactone, and indole in the presence of an aldehyde led to the corresponding trimolecular condensed materials. Another approach was demonstrated in which a three-component condensation of salicaldehyde derivatives, malononitrile and indoles, catalyzed by InCl 3 or L-proline, formed indolyl chromanes. This protocol was extended to 2-hydroxynaphthalene-1-carboxaldehyde, indole, and malononitrile. A method for the synthesis of β-indolylketones in good yields via condensation of indoles, aromatic aldehydes, and deoxybenzoin with ultrasonic irradiation was also described to demonstrate the use of indoles in MCPs.
Ghanbari K.,Alzahra University
Synthetic Metals | Year: 2014
An electrochemical sensor was fabricated by electrodeposition of silver nanoparticles on pre-synthesized polypyrrole (PPy) nanofiber, forming a silver nanoparticle/PPy composite matrix on glassy carbon electrode (Ag/PPy/GCE). The electrochemical behavior and electrocatalytic activity of Ag/PPy/GCE were characterized by cyclic voltammetry. As an electrochemical sensor, the Ag/PPy/GCE exhibited strong catalytic activity toward the oxidation of hydrazine. The morphology of electrodes was characterized by scanning electron microscopy (SEM). The kinetic parameters such as the electron transfer coefficient (α) and the catalytic rate constant (kcat) for the oxidation of hydrazine were determined. The diffusion coefficient (D) of hydrazine in solution was also calculated by chronoamperometry. The detection limit of hydrazine was found to be 0.2 μM. Moreover, the sensor showed excellent sensitivity, selectivity, and stability. © 2014 Elsevier B.V.
Ghanbari Kh.,Alzahra University |
Hajheidari N.,Alzahra University
Analytical Biochemistry | Year: 2015
Novel zinc oxide (ZnO) nanosheets and copper oxide (CuxO, CuO, and Cu2O) decorated polypyrrole (PPy) nanofibers (ZnO-CuxO-PPy) have been successfully fabricated for the simultaneous determination of ascorbic acid (AA), dopamine (DA), and uric acid (UA). The morphology and structure of ZnO-CuxO-PPy nanocomposites were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman spectroscopy. Compared with the bare glassy carbon electrode (GCE), PPy/GCE, CuxO-PPy/GCE, and ZnO-PPy/GCE, ZnO-CuxO-PPy/GCE exhibits much higher electrocatalytic activities toward the oxidation of AA, DA, and UA with increasing peak currents and decreasing oxidation overpotentials. Cyclic voltammetry (CV) results show that AA, DA, and UA could be detected selectively and sensitively at ZnO-CuxO-PPy/GCE with peak-to-peak separation of 150 and 154 mV for AA-DA and DA-UA, respectively. The calibration curves for AA, DA, and UA were obtained in the ranges of 0.2 to 1.0 mM, 0.1 to 130.0 μM, and 0.5 to 70.0 μM, respectively. The lowest detection limits (signal/noise = 3) were 25.0, 0.04, and 0.2 μM for AA, DA, and UA, respectively. With good selectivity and sensitivity, the current method was applied to the determination of DA in injectable medicine and UA in urine samples. © 2015 Elsevier Inc. All rights reserved.