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111.
Potassium fluoride was found to be an efficient catalyst and solid support for the synthesis of 3,5-disubstituted-1,2,4-oxadiazoles. In this work, a one-pot method for the synthesis of these compounds from the reaction of nitriles with hydroxylamine hydrochloride and acyl chloride in the presence of potassium fluoride under solvent-free conditions using microwave irradiation has been developed. The advantages of using potassium fluoride as a solid support in comparison to conventional solid supports are simple operation and convenient separation of the products. 相似文献
112.
Hamid?AssadiEmail author Heike?Emmerich 《The European Physical Journal B - Condensed Matter and Complex Systems》2013,86(4):178
It is a most common notion in traffic theory that driving in lanes and keeping lane changes to a minimum leads to smooth and laminar traffic flow, and hence to increased traffic capacity. On the other hand, there exist persistent vehicular traffic systems that are characterised by habitual disregarding of lane markings, and partial or complete loss of laminar traffic flow. Here, we explore the stability of such systems through a microscopic traffic flow model, where the degree of lane-discipline is taken as a variable, represented by the fraction of drivers that disregard lane markings completely. The results show that lane-free traffic may win over completely ordered traffic at high densities, and that partially ordered traffic leads to the poorest overall flow, while not considering the crash probability. Partial order in a lane-free system is similar to partial disorder in a lane-disciplined system in that both lead to decreased traffic capacity. This could explain the reason why standard enforcement methods, which rely on continuous increase of order, often fail to incur order to lane-free traffic systems. The results also provide an insight into the cooperative phenomena in open systems with self-driven particles. 相似文献
113.
We describe a method for the correction of slowly varying wavefront aberrations of low-quality telescope mirrors by using a DM in an active optical compensation system. Our goal is to reduce the surface wavefront error of low-cost multimeter-diameter mirrors from approximately 10 waves peak-to-valley (P-V), at a 1 microm wavelength, to approximately 1 wave or less. In a proof-of-concept demonstration using a 0.3m telescope at a wavelength of 633 nm, the rms wavefront error improved to 0.05 waves (0.26 waves P-V) from the original value of 1.4 waves rms (6.5 waves P-V). The Strehl ratio improved to 89% from the original value of 0.08%. The types of aberrations corrected include astigmatism, coma, defocus, trefoil, and higher-order aberrations. 相似文献
114.
Tahir AA Molloy KC Mazhar M Kociok-Köhn G Hamid M Dastgir S 《Inorganic chemistry》2005,44(25):9207-9212
Ba(dmae)2 (dmaeH=N,N-dimethylaminoethanol, C4H11NO) reacts with Co(acac)2 (acac=2,4-pentanedionate) to produce the trinuclear coordination complex [Ba2Co(acac)4(dmae)3(dmaeH)] in an 85% yield. Spectroscopic and single-crystal X-ray diffraction experiments indicate that the complex possesses a structure in which two barium atoms and a cobalt atom are bridged by acac and dmae groups. The barium centers are eight and nine coordinate with BaO7N and BaO7N2 coordination spheres while the cobalt is a more regular CoO5N octahedron. This 2:1 heterobimetallic molecular complex was investigated as precursor for the deposition of thin film by AACVD. The film was characterized by SEM and XRD. TGA shows that the complex starts thermal decomposition upon heating in nitrogen atmosphere at 105 degrees C to produce barium cobalt oxide material of a Ba2CoO3 composition with an orthorhombic structure. The synthetic approach detailed here represents a unique route to the formation of a heterobimetallic barium cobalt coordination complex. 相似文献
115.
Seyyed Mahmoud Mousavi Hamed Tavakoli Mohammad Samadfam Fatemeh Semnani Zahra Asadi Hamid Sepehrian 《Research on Chemical Intermediates》2013,39(3):951-959
Adsorption and recovery of uranium by nanoporous MCM-41 from aqueous solutions (synthetic solution and uranium conversion facility liquid waste) were investigated by use of a fixed-bed column (1.2 cm diameter and 3.0 cm height). Adsorption was carried out at flow rates 0.2 and 0.5 mL min?1, which correspond to retention times of 10 and 6 min. The maximum breakthrough capacity for uranium ions was achieved by use of nanoporous MCM-41 at the optimum pH of 3.6 and flow rate 0.2 mL min?1 (61.95 μg g?1). The Thomas and Yan models were applied to the experimental data, by use of linear regression, to determine the characteristics of the column for process design. The breakthrough curves calculated from the models were in good agreement with the experimental data. The elution behavior of uranium on nanoporous MCM-41 was studied with different eluents; the results showed that 0.1 M HCl is good eluent for uranium recovery. The regenerated column could be used in a multitude of adsorption–desorption cycles. 相似文献
116.
Mustafa Aghazadeh Abbas-Ali Malek Barmi Hamid Mohammad Shiri 《Russian Journal of Electrochemistry》2013,49(4):344-353
Nanoparticles, nanospheres and nanorods of Y(OH)3 and Y2O3 were prepared via cathodic electrodeposition from chloride bath through applying different current densities. First, yttrium hydroxide precursors were cathodically grown on the cathode surface at the current densities of 2, 1, 0.5, 0.25 and 0.1 mA cm?2. Then hydroxide powders were heat-treated at 600°C for 3 h. The composition, crystal structure and morphology of the prepared oxide and hydroxide products were investigated by means of differential scanning calorimetery (DSC), X-ray diffraction (XRD), scanning and transmission electron microscopes (SEM and TEM) and FT-IR spectroscopy. Mechanism of base electrogeneration at the applied conditions, and intercalation of chloride ions in the deposit structure during the electrodeposition were proposed and confirmed by the XRD and TG analyses. The results showed that the structural and morphological properties of the products are directly dictated by the applied current density and it can be recognized as the main factor affecting on the cathodic electrodeposition of Y2O3. 相似文献
117.
Hamid Reza Shaterian Hassan Hadadzadeh 《Phosphorus, sulfur, and silicon and the related elements》2013,188(5):1059-1071
A novel and simple method for the chemoselective deprotection of S,S- and S,O-acetals and ketals in the presence of their O,O-analogs with electrophilic halogens to their corresponding carbonyl compounds is described using N-bromosuccinimide, N-chlorosuccinimide, 2,4,4,6-tetrabromo-2,5-cyclohexen-1-one, trichlorocyanuric acid, or molecular bromine in aqueous acetonitrile. The use of these reagents in the presence of hydrated silica gel provide efficient, novel, and mild procedures for the deprotection of cyclic and acyclic O,O-, S,S-, and S,O-acetals and ketals in excellent yields in short reaction times. 相似文献
118.
Hamid Reza Shaterian Asghar Hosseinian Majid Ghashang 《Phosphorus, sulfur, and silicon and the related elements》2013,188(12):3136-3144
Herein, we describe a green procedure for the one-pot preparation of 1,8-dioxo-octahydroxanthene derivatives by condensation of dimedone and substituted benzaldehydes in the presence of FeCl 3 -SiO 2 as an efficient and heterogeneous catalyst under microwave irradiation and thermal conditions. This method has the advantages of high yields, cleaner reactions, efficient and cost-effective method, simple methodology, short reaction times, easy workup, and greener conditions. 相似文献
119.
El Sayed H. El Ashry Laila F. Awad H. M. Abdel Hamid Atta I. Atta 《Journal of carbohydrate chemistry》2013,32(7):745-753
Microwave irradiation (MWI) has accelerated the synthesis of S‐(2,3,4,6‐tetra‐O‐acetyl‐β‐D‐glucopyranosyl)thiouronium bromide (2a), whose reaction with 2,3,4,6‐tetra‐O‐acetyl‐α‐D‐glucopyranosyl bromide (1a) in the presence of Et3N afforded stereoselectively the acetylated β,β‐1‐thiotrehalose 4a. Similarly, the respective D‐galactopyranosyl 4b and 2‐acetylamino‐2‐deoxy‐D‐glucopyranosyl 4c analog as well as 4,4′‐di‐O‐(2,3,4,6‐tetra‐O‐acetyl‐β‐D‐galactopyranosyl) 4d and 4,4′‐di‐O‐(2,3,4,6‐tetra‐O‐acetyl‐α‐D‐glucopyranosyl) 4e derivatives of 2,2′,3,3′,6,6′‐hexa‐O‐acetyl β,β‐1‐thiotrehalose were prepared. 相似文献
120.
Arash Ghorbani-Choghamarani Hamid Goudarziafshar Mohsen Nikoorazm Zahra Naseri 《中国化学快报》2011,22(12):1431-1434
A mixture of guanidinium nitrate and silica sulfuric acid acts as mild and heterogeneous media for the efficient mono nitration of phenolic compounds in dichloromethane at room temperature. 相似文献