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排序方式: 共有189条查询结果,搜索用时 15 毫秒
101.
Saima Y Khamarui S Gayen KS Pandit P Maiti DK 《Chemical communications (Cambridge, England)》2012,48(52):6601-6603
A cascade cyclization involving union of three imines by an organocatalyst proline is established to afford new fused-tetrahydroimidazo[1,5-c]imidazol-7-ones with excellent regio- and stereoselectivity. Another dehydrogenative cyclization by union of two imines is developed using the Cu(OTf)(2)-Ag(2)O combo catalyst to furnish functionalized imidazoles. 相似文献
102.
Jabbar Khalafy Fatemeh Majidi Arlan Ahmad Poursattar Marjani Vahid Sarchami 《Journal of heterocyclic chemistry》2020,57(11):3961-3969
An efficient and straightforward protocol for one-pot, three-component reaction of aryl glyoxal monohydrates 1a-h , 5-amino-1-aryl-3-methylpyrazoles 2a , b and 4-hydroxyquinoline-2(1H)-one ( 3 ) or 2-hydroxy-1,4-naphthoquinone ( 4 ) using silver nanoparticles (AgNPs) as a high performance nanocatalyst in H2O/EtOH at 60°C afforded the corresponding polyfunctionalized benzo[h]pyrazolo[3,4-b][1,6]naphthyridines 5a-h and benzo[g]pyrazolo[3,4-b]quinolines 6a-i , respectively. Excellent catalytic activity, high yields, employing green media and green nanocatalyst, cost-effective and simple procedure are some notable advantages of using AgNPs as a noble metal nanocatalyst in this synthetic strategy. The structures of fused heterocycles were confirmed by their Fourier transform infrared, proton nuclear magnetic resonance (1H-NMR), and 13C-NMR spectral data and microanalysis. 相似文献
103.
Jabbar Khalafy Mahnaz Ezzati Mehdi Rimaz Ahmad Poursattar Marjani Hooman Yaghoobnejad Asl 《Journal of the Iranian Chemical Society》2014,11(4):1067-1074
A study concerning the new substituted cinnoline synthesis is described. The use of a one-pot three-component method allows a simple regioselective and efficient synthesis of cinnoline derivatives via reaction of arylglyoxals with 1,3-cyclohexanedione and dimedone in the presence of hydrazine hydrate. 相似文献
104.
Wenjing Qi Jianming Zhao Wei Zhang Zhongyuan Liu Min Xu Saima Anjum Saadat Majeed Guobao Xu 《Analytica chimica acta》2013
Owing to its high affinity with phosphate, Zr(IV) can induce the aggregation of adenosine 5′-triphosphate (ATP)-stabilized AuNPs, leading to the change of surface plasmon resonance (SPR) absorption spectra and color of ATP-stabilized AuNP solutions. Based on these phenomena, visual and SPR sensors for Zr(IV) have been developed for the first time. The A660 nm/A518 nm values of ATP-stabilized AuNPs in SPR absorption spectra increase linearly with the concentrations of Zr(IV) from 0.5 μM to 100 μM (r = 0.9971) with a detection limit of 95 nM. A visual Zr(IV) detection is achieved with a detection limit of 30 μM. The sensor shows excellent selectivity against other metal ions, such as Cu2+, Fe3+, Cd2+, and Pb2+. The recoveries for the detection of 5 μM, 10 μM, 25 μM and 75 μM Zr(IV) in lake water samples are 96.0%, 97.0%, 95.6% and 102.4%, respectively. The recoveries of the proposed SPR method are comparable with those of ICP-OES method. 相似文献
105.
Shaista PARVEEN Saima KALSOOM Rifhat BIBI Ambreen ASGHAR Abdul HAMEED Waqar AHMED Abbas HASSAN 《Turkish Journal of Chemistry》2020,44(6):1610
The current investigation presents the synthesis, computational molecular-docking and biological activity studies of arylated thiazole coumarins. Aryl substituted thiazolyl coumarin derivatives were synthesized via Suzuki cross-coupling reaction. A detailed reaction condition optimization revealed that the Pd-PEPPSI-IPent precatalyst in only 2 mol% loading resulted in the desired product with high yield. The aim of this study was to examine the antimicrobial behavior of thiazole coumarin derivatives through in vitro and in silico studies. All the compounds showed activity against both antibacterial strains, Staphylococcus aureus and Escherichia coli, except 5d . Similarly, the compounds 5a , 5b , and 5d were found to be active against Trichoderma harzianum. The compound 5d of this series was found to have a higher activity with MIC 125 mg/ml against Trichoderma harzianum. Molecular studies showed the high activities of these compounds are due to the presence of strong H-bonding and π-π interaction with their respective targets. A good correlation was observed between computational and in vitro studies. 相似文献
106.
M. A. Chaudhri Q. Nadeem M. N. Chaudhri Q. Jabbar 《Journal of Radioanalytical and Nuclear Chemistry》2007,271(3):697-700
By making use of the 19F(p,αγ)16O reaction the F-concentrations of different varieties of tea leaves, of some international geochemical reference materials,
and of the bones and teeth of some experimental animals have been determined. The tea leaves from Ceylon (ordinary), Orange
Pekoe (special Ceylon), China (ordinary black), Lapsang Souchong (special smoked Chinese) and Darjeeling (India) were found
to contain 170 ppm, 170 ppm, 120 ppm, 160 ppm and 100 ppm of fluorine, respectively, The F-concentrations of established geochemical
reference materials, NIM-D, NIM-N, NIM-P and NIM-S, from the National Institute of Metallurgy, South Africa were determined
to be 60 ppm, 120 ppm, 130 ppm and 190 ppm, respectively. The bones of rabbits, who were given fluoridated water, were found
to contain much higher amount of fluorine than the bones of the control rabbit. Furthermore, the rabbits who were kept on
fluoridated water for 45 days, had almost double the amount of F in their bones than the rabbits who were given fluoridated
water for only 15 days. Similarly, the teeth of grown-up monkeys who were given fluoridated water since birth had double the
amount of fluorine than those of the control monkey. 相似文献
107.
Ali M Nasir S Nguyen QH Sahoo JK Tahir MN Tremel W Ensinger W 《Journal of the American Chemical Society》2011,133(43):17307-17314
Here we demonstrate a novel biosensing platform for the detection of lactoferrin (LFN) via metal-organic frameworks, in which the metal ions have accessible free coordination sites for binding, inside the single conical nanopores fabricated in polymeric membrane. First, monolayer of amine-terminated terpyridine (metal-chelating ligand) is covalently immobilized on the inner walls of the nanopore via carbodiimide coupling chemistry. Second, iron-terpyridine (iron-terPy) complexes are obtained by treating the terpyridine modified-nanopores with ferrous sulfate solution. The immobilized iron-terPy complexes can be used as recognition elements to fabricate biosensing nanodevice. The working principle of the proposed biosensor is based on specific noncovalent interactions between LFN and chelated metal ions in the immobilized terpyridine monolayer, leading to the selective detection of analyte protein. In addition, control experiments proved that the designed biosensor exhibits excellent biospecificity and nonfouling properties. Furthermore, complementary experiments are conducted with multipore membranes containing an array of cylindrical nanopores. We demonstrate that in the presence of LFN in the feed solution, permeation of methyl viologen (MV(2+)) and 1,5-naphthalenedisulphate (NDS(2-)) is drastically suppressed across the iron-terPy modified membranes. On the basis of these findings, we envision that apart from conventional ligand-receptor interactions, the designing and immobilization of alternative functional ligands inside the synthetic nanopores would extend this method for the construction of new metal ion affinity-based biomimetic systems for the specific binding and recognition of other biomolecules. 相似文献
108.
Exact solutions for the flow of second grade fluid in annulus between torsionally oscillating cylinders 总被引:1,自引:0,他引:1
The velocity field and the associated shear stress corresponding to the torsional oscillatory flow of a second grade fluid, between two infinite coaxial circular cylinders, are determined by means of the Laplace and Hankel transforms. At time t = 0, the fluid and both the cylinders are at rest and at t = 0 + , cylinders suddenly begin to oscillate around their common axis in a simple harmonic way having angular frequencies ω 1 and ω 2 . The obtained solutions satisfy the governing differential equation and all imposed initial and boundary conditions. The solutions for the motion between the cylinders, when one of them is at rest, can be obtained from our general solutions. Furthermore, the corresponding solutions for Newtonian fluid are also obtained as limiting cases of our general solutions. 相似文献
109.
S. U. Rahman Matiullah F. Malik M. Rafique J. Anwar M. Ziafat A. Jabbar 《Journal of Radioanalytical and Nuclear Chemistry》2011,287(2):647-655
Soil samples were collected from different localities of districts Jhelum, Chakwal, Rawalpindi and Attock, Punjab Province,
Pakistan with an aim to measure naturally occurring radionuclides, namely 226Ra, 232Th, 40K and fallout 137Cs radionuclide using a P-type coaxial high purity germanium (HPGe) γ-ray spectrometer. Measured specific activities of 226Ra, 232Th and 40K in these soil samples ranged from 26.02 ± 7.11 to 93.54 ± 8.13 Bq kg−1, 29.34 ± 2.58 to 114.41 ± 2.80 Bq kg−1 and 348.15 ± 3.20 to 752.98 ± 4.20 Bq kg−1, respectively. Activity due to 137Cs was observed in some locations which ranged from 0.4 ± 0.2 to 7.8 ± 0.3 Bq kg−1. From the measured activity concentrations, radium equivalent activity concentrations were determined followed by calculations
of mean absorbed dose rate and mean annual effective dose for the inhabitants of the studied area. The mean radium equivalent
activity, internal and external hazard indices values came out to be 179.26 ± 11.93 Bq kg−1, 0.64 ± 0.05 and 0.48 ± 0.03, respectively. Indoors and outdoor average annual effective dose values were found to be 0.42 ± 0.03
and 0.10 ± 0.01 mSv, respectively. Present data have been compared with the published data for other parts of the world and
found to be safe for public and environment. 相似文献
110.
Sohaib?A.?QaziEmail author Abeera?Saeed Saima?Nasir Hammad?Omer 《Applied magnetic resonance》2017,48(5):461-471
Parallel magnetic resonance imaging (pMRI) and compressed sensing (CS) have been recently used to accelerate data acquisition process in MRI. Matrix inversion (for rectangular matrices) is required to reconstruct images from the acquired under-sampled data in various pMRI algorithms (e.g., SENSE, GRAPPA) and CS. Singular value decomposition (SVD) provides a mechanism to accurately estimate pseudo-inverse of a rectangular matrix. This work proposes the use of Jacobi SVD algorithm to reconstruct MR images from the acquired under-sampled data both in pMRI and in CS. The use of Jacobi SVD algorithm is proposed in advance MRI reconstruction algorithms, including SENSE, GRAPPA, and low-rank matrix estimation in L + S model for matrix inversion and estimation of singular values. Experiments are performed on 1.5T human head MRI data and 3T cardiac perfusion MRI data for different acceleration factors. The reconstructed images are analyzed using artifact power and central line profiles. The results show that the Jacobi SVD algorithm successfully reconstructs the images in SENSE, GRAPPA, and L + S algorithms. The benefit of using Jacobi SVD algorithm for MRI image reconstruction is its suitability for parallel computation on GPUs, which may be a great help in reducing the image reconstruction time. 相似文献