Sharif Digital Repository

Bread scraps with transition metal oxide spinels were utilized to synthesize core–shell magnetic nanocatalyst. The prepared heterogeneous catalyst was characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET), thermogravimetric analysis (TGA), and transmission electron microscopy (TEM). This magnetic nanocatalyst opens up a new avenue to introduce a very useful and efficient catalytic system for the one-pot synthesis of tetraketone derivatives via Knoevenagel-Micheal reaction of 1,3 cyclohexanedione and benzaldehyde in ethanol as a green solvent at 50 °C, and one-pot four-component reaction of... 

Density functional theory method and B3LYP/6-31+G(d) level of theory were used to predict the acidity of barbiturates and their corresponding metabolites in the gas and solution phase (H2O). Polarized continuum model was applied to calculate pKa values of barbiturates and metabolites. A comparison between acidity of barbiturates and metabolites in the gas and solution phase indicates that the acidity strength of barbiturates enhances with the increase of intramolecular hydrogen bonds in metabolites. This acidity can increase to 9.47 kcal/mol in gas phase and 2.73 pKa units in solution phase for a typical metabolite of barbiturate due to the effect of intramolecular hydrogen bonds. Also,... 

An efficient catalyst-free one-pot three-component reaction was developed for the synthesis of a new family of N- A nd S-containing spirocyclic compounds. Various derivatives of spirobenzimidazolidine containing an indole scaffold were synthesized for the first time in a modestly toxic solvent and under mild reaction conditions. The reaction times were of the order of several minutes, and all the products were obtained in moderate to high yields (overall yields 58-80%). © Georg Thieme Verlag Stuttgart New York  

Magnetic nanofiber cellulose (NFC) was selected as a biopolymer surface for the reaction with ferric metformin and a novel nanocatalyst was prepared. This green heterogeneous organometallic catalyst was analyzed by physiochemical techniques. The new metformin drug complex supported on magnetic NFC was used as a powerful and efficient catalyst for the synthesis of functionalized 4H-pyrans derivatives. The antimicrobial activity of the products showed excellent activity against all the bacterial and fungal strains (especially compounds 7q and 6r). © 2022 Taylor & Francis Group, LLC  

Molecular dynamics (MD) simulation was utilized to study the role of asphaltene extracted from Gachsaran (an Iranian oilfield) at the synthetic oil-water interface. In agreement with experimental data, IFTs predicted by MD simulation for heptol/brine system showed a minima at around 50 vol.% n-heptane, reflecting the highest contribution of asphaltene into the interface. At greater n-heptane fractions, IFT was increased steadily. Simulation results suggest the asphaltene propensity for remaining in the bulk heptol phase rather related to the fraction of toluene in the mixture. Heptol ingredients, i.e., toluene and heptane, act differently with respect to asphaltene, where former tends to... 

The reaction of 2-chloroquinoline-3-carbaldehydes with indoline-2-thione in ethanol provides a series of novel indolo[3′,2′:5,6]thiopyrano[2,3-b]quinoline derivatives. The desired products were obtained in short reaction time and high yields (69-93%) under mild reaction conditions. © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim  

In the present study, metal complexes of 1-amidino-O-alkylureas were designed, synthesized and characterized by elemental analyses, FT-IR spectra, XRD, Mass analyses and scanning electron microscopy (SEM). All synthesized complexes were screen as α-Glucosidase inhibitors. According to the in vitro results, the Cu (II) complexes showed superior potency compared to other tested metal complexes. Particularly, [Cu(L-Me)2](Cl)2 (1b) showed the strongest inhibition against α-Glucosidase with an IC50 value of 2.75 ± 0.3 µM which was comparable to that of acarbose (IC50 = 750 µM). These findings are supported by the ligands and enzyme interactions through molecular docking. © 2021 Elsevier B.V  

A mathematical model is developed for analysis the dynamics of an intra-cavity laser spectroscopy and mode competition using the CO2 laser as the coherent source. The governing equations of system are derived and effect of the absorbing material on the laser modes, as a time-dependent term is considered. Thus, the application of the CO2 laser for intra-cavity laser spectroscopy with considering an inhomogeneous medium and effect of the absorbing material is investigated  

Temporal and spatial analysis of dynamics of hybrid transversely excited atmospheric pressure (TEA)-CO2 lasers is studied using two different models with four and eight energy levels. These models are used for simulation of the laser and computing the output energy. Effects of several parameters such as input energies and gas mixture concentrations (especially presence of CO molecules) are also studied. © 2007 Elsevier Ltd. All rights reserved  

Using multiple antennas at the transmit and receive sides of a passive radar brings both the benefits of MIMO radar and passive radar. However one of the obstacles arisen in such configuration is the receive antennas placement in proper positions so that the radar performance is improved. Here we just consider the case of positioning one receiver among multiple illuminators of opportunity. Indeed it is a start for the solution of optimizing the geometry of the multiple receivers in a passive radar  

SbCl3 supported on montmorillonite K-10 is an efficient catalyst for the ring opening of epoxides with aromatic amines under solvent-free conditions and microwave irradiation to give the corresponding b-amino alcohols in high yields with high regioselectivity  

In this paper, we consider an integrated sensing and communication (ISAC) system with wireless power transfer (WPT) where an unmanned aerial vehicle (UAV)-based radar serves a group of energy-limited communication users in addition to its sensing functionality. In this architecture, the radar senses the environment in phase 1 (namely sensing phase) and mean-while, the communications users (nodes) harvest and store the energy from the radar transmit signal. The stored energy is then used for information transmission from the nodes to UAV in phase 2, i.e., uplink phase. Performance of the radar system depends on the transmit signal as well as the receive filter; the energy of the transmit... 

One of the important obstacles in MIMO (Multiple Input Multiple Output) radars is the issue of designing proper transmit signals. Indeed, the capability of signal design is a significant advantage in MIMO radars, through which, the system can achieve much better performance. Many different aspects of this performance improvement have been considered yet, and the transmit signals have been designed to attain such goal, e.g., getting higher SNR or better detector's performance at the receiver. However, an important tool for evaluating the radar's performance is its ambiguity function. In this paper, we consider the problem of transmit signal design, in order to optimize the ambiguity function... 

Two gains play key roles in recently developed MIMO wireless communication systems: "spatial diversity" gain and "spatial multiplexing" gain. The diversity gain refers to the capability to decrease the error rate of the MIMO channel, while the multiplexing gain implicitly refers to the amount of increase in the capacity of the MIMO channel. It has been shown that there is a fundamental tradeoff between these two types of gains, meaning interplay between increasing reliability (via an increase in the diversity gain) and increasing data rate (via an increase in the multiplexing gain). On the other hand, recently, MIMO radars have attracted much attention for their superior ability to enhance... 

It is a well known fact that using multiple antennas at transmit and receive sides improves the detection performance. However, in such multiple-input multiple-output (MIMO) configuration, proper positioning of transmitters and receivers is a big challenge that can have significant influence on the performance of the overall system. In addition, determining the power of each transmitter under a total power constraint is a problem that should be solved in order to enhance the performance and coverage of such a system. In this paper, we design the Neyman-Pearson detector under the Rayleigh scatter model and use it to introduce a criterion for the antenna placement at both transmit and receive... 

There has been much interest, recently, towards exploiting the Multiple-Input Multiple-Output (MIMO) technique in radar. It is shown that using multiple antennas at transmit and receive sides can improve the performance of the system. However, in order to analyze the system's performance, its ambiguity function, i.e. the ambiguity function of a MIMO radar, is needed to be defined. In this paper, beginning from the information theoretic definitions, we derive such function, specifically for a MIMO radar with widely separated antennas  

By combining the two ideas of MIMO (Multiple Input Multiple Output) and PCL (Passive Coherent Location) in radar, one can achieve the advantages of both recently developed techniques simultaneously. While using multiple antennas at the receive side provides a spatial diversity of the object to be detected, using multiple illuminators of opportunity, most importantly, makes the radar covert to the interceptors. One obstacle in such MIMO configuration is choosing the positions of the receive antennas. In this paper, after analyzing the Neyman-Pearson detector for the DVB-T based PCL, we introduce the probability of missed detection as a criterion to place the receive antenna. Here, we only...