Synthesis of Core-Shell Magnetic Supramolecular Nanocatalysts based on Amino-Functionalized Calix[4]arenes for the Synthesis of 4H-Chromenes by Ultrasonic Waves

One of the most common phenol-formaldehyde cyclic oligomers from hydroxyalkylation reactions that exhibit supramolecular chemistry are calixarenes. These macrocyclic compounds are qualified to act as synthetic catalysts due to their specific features including being able to form host-guest complexes, having unique structural scaffolds and their relative ease of chemical modifications with a variety of functions on their upper rim and lower rim. Here, a functional magnetic nanocatalyst was designed and synthesized by using a synthetic amino-functionalized calix[4]arene. Its catalytic activity was evaluated in a one-pot synthesis of 2-amino-4H-chromene derivatives. Besides, this novel magnetic nanocatalyst was characterized by spectroscopic and analytical techniques such as FT-IR, EDX, FE-SEM, TEM VSM, XRD analysis.     

Simultaneous production and utilization of methanol for methyl formate synthesis in a looped heat exchanger reactor configuration

In this investigation, a novel thermally coupled reactor (TCR) containing methyl formate (MF) production in the endothermic side and methanol synthesis in the exothermic side has been investigated. The interesting feature of this TCR is that productive methanol in the exothermic side could be recycled and used as feed of endothermic side for MF synthesis. Other important advantages of the proposed system are high production rates of hydrogen and MF. The configuration consists of two thermally coupled concentric tubular reactors. In these coupled reactors, autothermal system is obtained within the reactor. A steady-state heterogeneous model is used for simulation of the coupled reactor. The proposed model has been utilized to compare the performance of TCR with the conventional methanol reactor (CMR). Noticeable enhancement can be obtained in the performance of the reactors. The influence of operational parameters is studied on reactor performance. The results show that coupling of these reactions could be feasible and beneficial. Experimental proof-of-concept is required to validate the operation of the novel reactor.     

Applying different types of artificial neural network for modeling thermal conductivity of nanofluids containing silica particles

Journal of Thermal Analysis and Calorimetry - Nanofluids are widely applicable in thermal devices with porous structures. Silica nanoparticles have been dispersed in different heat transfer fluids...     

Transesterification of canola oil over Li/Ca-La mixed oxide catalyst: Kinetics and calcination temperature investigations

In this research, a solid 1%Li/Ca-La mixed oxide catalyst was prepared using co-precipitation method followed by wet impregnation. The prepared catalyst was used in the transesterification reaction of canola oil and methanol for biodiesel synthesis. The effects of calcination and reaction temperatures were investigated on the activity of the catalyst. In addition, rate of the reaction was studied through a kinetic model for which parameters were determined. Surface properties and structure of the catalyst were characterized through the powder X-ray diffraction (XRD), thermogravimetry/derivative thermogravimetry (TG/DTG), and Fourier transform infrared spectroscopy analysis. All these emphasized that the performance of the catalyst corresponded to the generation of the active sites and their thermal activation.     

Co3O4 nanoparticles prepared by oxidative precipitation method: an efficient and reusable heterogeneous catalyst for N-formylation of amines

Research on Chemical Intermediates - N-formylation of different amines was carried out with formic acid in the presence of the Co3O4 nanoparticles as an efficient, stable heterogeneous catalyst to...     

A new method to detect periodically correlated structure

In this paper, we introduce a new method to test whether a discrete-time periodically correlated model explains an observed time series. The proposed method is based on the estimation of the support of spectral measure. Comparisons between our procedure and the methods which were proposed by Broszkiewicz-Suwaj et al. (Phys A 336:196–205, 2004) show that our testing procedure is more powerful. We investigate the performance of the proposed method by using real and simulated datasets.     

Synthesis of pyrido[2′,1′:2,3]imidazo[4,5-c]isoquinolines via a one-pot,three-component reaction

A one-pot, three-component reaction for the synthesis of pyrido[2′,1′:2,3]imidazo[4,5-c]isoquinolines starting from 2-aminopyridines, phthalaldehyde, and trimethylsilyl cyanide in good to high yields is described.     

用聚(L-蛋氨酸)/纳米金修饰玻碳电极同时灵敏检测多巴胺和尿酸简

A novel electrochemical sensor was fabricated by electrodeposition of gold nanoparticles on a poly(L-methionine) (PMT)-modified glassy carbon electrode (GCE) to form a nano-Au/PMT composite-modified GCE (nano-Au/PMT/GCE). Scanning electron microscopy and electrochemical techniques were used to characterize the composite electrode. The modified electrode exhibited considerable electrocatalytic activity towards the oxidation of dopamine (DA) and uric acid (UA) in phosphate buffer solution (pH = 7.00). Differential pulse voltammetry revealed that the electrocatalytic oxidation currents of DA and UA were linearly related to concentration over the range of 5.0×10^-8 to 10^-6 mol/L for DA and 7.0×10^-8 to 10^-6 mol/L for UA. The detection limits were 3.7×10^-8 mol/L for DA and 4.5×10^-8 mol/L for UA at a signal-to-noise ratio of 3. According to our experimental results, nano-Au/PMT/GCE can be used as a sensitive and selective sensor for simultaneous determination of DA and UA.     

Microcavity‐Stabilized Quantum Cascade Laser

Narrow‐linewidth lasers are key elements in optical metrology and spectroscopy. Spectral purity of these lasers determines accuracy of the measurements and quality of collected data. Solid state and fiber lasers are stabilized to relatively large and complex external optical cavities or narrow atomic and molecular transitions to improve their spectral purity. While this stabilization technique is rather generic, its complexity increases tremendously moving to longer wavelenghts, to the infrared (IR) range. Inherent increase of losses of optical materials at longer wavelengths hinders realization of compact, room temperature, high finesse IR cavities suitable for laser stabilization. In this paper, we report on demonstration of quantum cascade lasers stabilized to high‐Q crystalline mid‐IR microcavities. The lasers operating at room temperature in the 4.3‐4.6 μm region have a linewidth approaching 10 kHz and are promising for on‐chip mid‐IR and IR spectrometers.