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241.
A combination of molybdatophosphoric acid and sodium nitrite in the presence of wet SiO2 was used as an effective nitrosating agent for the nitrosation of secondary amines under mild and heterogeneous conditions in good to excellent yields. Also, the results of a computational study are investigated in the gas phase for geometry and properties of proposed structures. 相似文献
242.
Connections between the covector mapping theorem and convergence of pseudospectral methods for optimal control 总被引:2,自引:0,他引:2
Qi Gong I. Michael Ross Wei Kang Fariba Fahroo 《Computational Optimization and Applications》2008,41(3):307-335
In recent years, many practical nonlinear optimal control problems have been solved by pseudospectral (PS) methods. In particular,
the Legendre PS method offers a Covector Mapping Theorem that blurs the distinction between traditional direct and indirect
methods for optimal control. In an effort to better understand the PS approach for solving control problems, we present consistency
results for nonlinear optimal control problems with mixed state and control constraints. A set of sufficient conditions is
proved under which a solution of the discretized optimal control problem converges to the continuous solution. Convergence
of the primal variables does not necessarily imply the convergence of the duals. This leads to a clarification of the Covector
Mapping Theorem in its relationship to the convergence properties of PS methods and its connections to constraint qualifications.
Conditions for the convergence of the duals are described and illustrated. An application of the ideas to the optimal attitude
control of NPSAT1, a highly nonlinear spacecraft, shows that the method performs well for real-world problems.
The research was supported in part by NPS, the Secretary of the Air Force, and AFOSR under grant number, F1ATA0-60-6-2G002. 相似文献
243.
Mehdi D. Esrafili Parisasadat Mousavian Fariba Mohammadian-Sabet 《Molecular physics》2019,117(1):58-66
Using high-level ab initio calculations, the cooperativity effects between an aerogen-bonding and a pnicogen- or chalcogen-bonding interactions are studied in ternary Y···PH2CN···ZO3 and Y···SHCN···ZO3 complexes (Y?=?NH3, N2 and Z?=?Ar, Kr, Xe). A detailed analysis of the structures, interaction energies and bonding properties is performed on these systems. For each set of the complexes, a favourable cooperativity is observed between Z···N and P/S···N interactions, especially in complexes involving NH3 and XeO3 molecules. It is found that for a given Y or Z, the amount of cooperativity effects in Y···PH2CN···ZO3 complexes are important than Y···SHCN···ZO3 ones. For each ternary complex considered, the effect of a Z···N aerogen bond on a P/S···N bond is more pronounced than that of a P/S···N bond on a Z···N bond. The mechanism of the cooperativity effects in the ternary complexes is studied by electron density difference, quantum theory of atoms in molecules and natural bond orbital analyses. The solvent effects are also studied on the interaction energy and cooperativity of Z···N and P/S···N bonds in the ternary systems. 相似文献
244.
Dadkhoda?GhazanfariEmail author Fariba?Najafizadeh Fereshteh?Khosravi 《Monatshefte für Chemie / Chemical Monthly》2004,135(11):1409-1413
Summary. 4-Aminoperoxybenzoic acid supported on silica gel in presence of air was found to be a selective and convenient oxidant for the oxidation of methylene groups in aryl ketones to convert them to -diketones. 相似文献
245.
Mazloum-Ardakani Mohammad Sabaghian Fariba Naderi Hamidreza Ebadi Azra Mohammadian-Sarcheshmeh Hamideh 《Journal of Solid State Electrochemistry》2020,24(3):571-582
Journal of Solid State Electrochemistry - A graphene aerogel cross-linked by p-phenylenediamine (PPDA) composite with Sm2O3 nanoparticles (AP.Sm) was synthesized as a novel nanocomposite via a... 相似文献
246.
Nikolaj S. Troelsen Elena Shanina Diego Gonzalez‐Romero Daniela Dankov Ida S. A. Jensen Katarzyna J.
niady Faranak Nami Hengxi Zhang Christoph Rademacher Ana Cuenda Charlotte H. Gotfredsen Mads H. Clausen 《Angewandte Chemie (International ed. in English)》2020,59(6):2204-2210
Fragment‐based drug discovery (FBDD) is a popular method in academia and the pharmaceutical industry for the discovery of early lead candidates. Despite its wide‐spread use, the approach still suffers from laborious screening workflows and a limited diversity in the fragments applied. Presented here is the design, synthesis, and biological evaluation of the first fragment library specifically tailored to tackle both these challenges. The 3F library of 115 fluorinated, Fsp3‐rich fragments is shape diverse and natural‐product‐like with desirable physicochemical properties. The library is perfectly suited for rapid and efficient screening by NMR spectroscopy in a two‐stage workflow of 19F NMR and subsequent 1H NMR methods. Hits against four diverse protein targets are widely distributed among the fragment scaffolds in the 3F library and a 67 % validation rate was achieved using secondary assays. This collection is the first synthetic fragment library tailor‐made for 19F NMR screening and the results demonstrate that the approach should find broad application in the FBDD community. 相似文献
247.
A carbon ionic liquid electrode (CILE) was used for the investigation of the electrochemical oxidation of phenolic compounds in acidic media using cyclic voltammetry, chronoamperometry and square wave voltammetry techniques. The results indicate that, contrary to many other electrodes, the oxidation of phenolic compounds on CILE is highly stable and does not result in electrode fouling. Cyclic voltammetry showed that phenolic compounds such as phenol, 2,4-dichlorophenol and catechol were oxidized at CILE and remained electroactive after multiple cycles and at high concentrations of phenol. The cyclic voltammetric response of the CILE is very stable with more than 99% of the initial activity remaining after 20 s of stirring of a 0.5 mM solution of phenol. 相似文献
248.
Hasegawa H Shinohara Y Masuda N Hashimoto T Ichida K 《Journal of mass spectrometry : JMS》2011,46(5):502-507
D-Serine is a co-agonist of the N-methyl-D-aspartate receptor in glutamate neurotransmission and has been proposed as a potential therapeutic agent for schizophrenia. However, D-serine also acts as a nephrotoxic substance in rats at high doses. To investigate the pharmacokinetics and toxicokinetics of D-serine, a method for the stereoselective determination of serine enantiomers in rat plasma was developed using GC-MS with selected ion monitoring (GC-MS-SIM). DL-[(2)H(3)]Serine was used as an internal standard to account for losses associated with the extraction, derivatization and chromatography. Serine enantiomers were purified by cation-exchange chromatography using BondElut SCX cartridge and derivatized with HCl in methanol to form methyl ester followed by subsequent N,O-diacylation with optically active (+)-α-methoxy-α-trifluoromethylphenylacetyl chloride to form epimeric amide. Quantitation was performed by SIM of the molecular-related ions of the epimers in the chemical ionization mode. The intra- and inter-day reproducibility of the assay was less than 5% for D-serine and 3% for L-serine. The method was successively applied to study the pharmacokinetics of D-serine in rats. 相似文献
249.
Saeed Shanehsazzadeh Mohammad Ali Oghabian Fariba Johari Daha Massoud Amanlou Barry J. Allen 《Journal of Radioanalytical and Nuclear Chemistry》2013,295(2):1517-1523
Recently ultrasmall superparamagnetic iron oxide (USPIO) nanoparticles (NPs) have been widely used for medical applications. One of their important applications is using these particles as MRI contrast agent. While various research works have been done about MRI application of USPIOs, there is limited research about their uptakes in various organs. The aim of this study was to evaluate the biodistribution of dextran coated iron oxide NPs labelled with 99mTc in various organs via intravenous injection in Balb/c mice. The magnetite NPs were dispersed in phosphate buffered saline and SnCl2 which was used as a reduction reagent. Subsequently, the radioisotope 99mTc was mixed directly into the reaction solution. The labeling efficiency of USPIOs labeled with 99mTc, was above 99 %. Sixty mice were sacrificed at 12 different time points (From 1 min to 48 h post injections; five mice at each time). The percentage of injected dose per gram of each organ was measured by direct counting for 19 harvested organs of the mice. The biodistribution of 99mTc-USPIO in Balb/c mice showed dramatic uptake in reticuloendothelial system. Accordingly, about 75 percent of injected dose was found in spleen and liver at 15 min post injection. More than 24 % of the NPs remain in liver after 48 h post-injection and their clearance is so fast in other organs. The results suggest that USPIOs as characterized in our study can be potentially used as contrast agent in MR Imaging, distributing reticuloendothelial system specially spleen and liver. 相似文献
250.
Shahram Moradi Zahra Farahani Azadeh Madadi Fariba Dashtestani Behnoush Alimadadi Saeed Abedini Khorrami 《Phosphorus, sulfur, and silicon and the related elements》2013,188(10):2733-2738
Hartree–Fock (HF) and hybrid density functional theory (B3LYP) calculations were performed on tropylium ion and 19 of its mono- and diheteroatomic derivatives. The aromaticity in this class of compounds is evaluated based on the nucleus independent chemical shift (NICS) values. The NICS values are calculated at the center of the rings NICS (0) and at 1Å above the molecular plane NICS (1). The geometry optimization and NICS calculations were carried out at the HF/6–311+G?? and at the B3LYP/6–311+G (2d, p) density functional level, respectively. These calculations in the effects of heteroatoms such as N, B, P, and Si are considered on aromaticity, molecular properties, NICS values, and structural parameters. 相似文献