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31.
Hydroxylamine was found to be a mild reagent for conversion of arylboronic acids and their pinacolyl boronate esters into phenols. This procedure works on most arylboronic acids at room temperature, yielding phenols in moderate to good yields, and efficiently on arylboronates also yielding phenols in good yields. 相似文献
32.
Levasseur B Ebrahim AM Bandosz TJ 《Langmuir : the ACS journal of surfaces and colloids》2011,27(15):9379-9386
Mixed oxides Ce(1-x)Zr(x)O(2) prepared by slow coprecipitation in NaOH were tested for NO(2) adsorption in dynamic conditions at room temperature. The samples were characterized before and after exposure to NO(2) by XRD, N(2)-adsorption, thermal analysis, potentiometric titration, and FT-IR. Mixed oxides show a better NO(2) adsorption capacity than the parent materials (CeO(2) and Zr(OH)(4)). This effect is linked to the presence of reduced cerium and oxygen vacancies induced by the addition of Zr(4+) cations to the structure. The results indicate that NO(2) reacts with Ce(3+) to form nitrite and nitrate species on the surface. The NO retention increases with an increase in the Zr(OH)(4) content. A decrease in the density of -OH groups on the surface after the exposure to NO(2), suggests their involvement in reactive adsorption of NO and/or NO(2). From the structural point of view, no real difference was observed on the Ce(1-x)Zr(x)O(2) materials before and after exposure to NO(2). 相似文献
33.
Mohammad Hossein Tavakoli Hossein KarbaschiFeridoun Samavat Ebrahim Mohammadi-Manesh 《Journal of Crystal Growth》2010,312(21):3198-3203
A set of 2D finite element numerical simulation of induction heating process for an oxide Czochralski crystal growth system has been made for a range of f=1–100 kHz applied frequency of driving current. It was shown that the frequency selection has a marked effect in all basic induction phenomena, including electromagnetic field distribution, skin depth, coil efficiency, and intensity and structure of heating in the growth setup. 相似文献
34.
Fatemeh Saghatchi Ebrahim Ahmadi Zahra Mohamadnia Hassan Hajifatheali Hashem Tabebordbar Farnoosh Karimi 《Chemical Papers》2014,68(11):1555-1560
This study is aimed at atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) using a novel catalyst. The bis-(2-dodecylsulfanyl-ethyl)-amine (SNS) tridentate ligand with mixed donor atoms was synthesized in high purity using inexpensive reagents and was reacted with copper(I) bromide to produce the CuBr/SNS catalyst. The catalyst mediated living polymerization of MMA yielding polymers with controlled molecular masses and narrow molecular mass distributions (PDI < 1.25). Also, the kinetic plot exhibited a linear increase of ln([M]0/[M]) versus time, indicating constant concentration of propagating radicals during the polymerization. The products were characterized by 1H NMR, 13C NMR, FT-IR, UV-VIS, GC and elemental analyses (CHNS) and by GPC. 相似文献
35.
2,3-Dihydroquinazolin-4(1H)-one derivatives are synthesized via a one-pot,three component reaction of isatoic anhydride and an aromatic aldehyde with ammonium acetate or primary amine catalyzed by silica-bonded N-propylsulfamic acid(SBNPSA) in refluxing ethanol. 相似文献
36.
Andrei K. Whaley Weaam Ebrahim Mona El-Neketi Elena U. Ancheeva Ferhat Can Özkaya Nina I. Pryakhina Nadezhda U. Sipkina Vladimir G. Luzhanin Zhen Liu Peter Proksch 《Tetrahedron letters》2017,58(22):2171-2173
Chemical investigation of the aerial parts of Iris lactea afforded three new flavone C-glycosides including 4?-O-acetyl-embinin (1), 2?,4?-O-diacetyl-embinin (2) and 6″,4?-O-diacetyl-embinin (3) along with the known analogue embinin (4). Their structures were elucidated by 1D and 2D NMR spectroscopic analysis as well as by HRESIMS data. The sugars were characterized following acid hydrolysis of the respective glycosides and TLC analysis compared to known standards. Duplicated signals can be observed in the NMR spectra, indicating the presence of rotamers caused by rotational hindrance around the glycosyl-flavone CC linkage. All isolated compounds were tested for their antimicrobial and cytotoxic activities but found to be inactive. 相似文献
37.
Matrix Heterogeneity Effects on Gas Transport and Adsorption in Coalbed and Shale Gas Reservoirs 总被引:2,自引:0,他引:2
In coalbeds and shales, gas transport and storage are important for accurate prediction of production rates and for the consideration
of subsurface greenhouse gas sequestration. They involve coupled fluid phenomena in porous medium including viscous flow,
diffusive transport, and adsorption. Standard approach to describe gas–matrix interactions is deterministic and neglects the
effects of local spatial heterogeneities in porosity and material content of the matrix. In this study, adopting weak-noise
and mean-field approximations and using a statistical approach in spectral domain, matrix heterogeneity effects are investigated
in the presence of non-equilibrium adsorption with random partition coefficient. It is found that the local heterogeneities
can generate non-trivial transport and kinetic effects which retard gas release from the matrix and influence the ultimate
gas recovery adversely. Macro-transport shows 1/[1 + N
Pe
/(1 + N
Pe
)] dependence on the Péclet number, and persists at the diffusive ultra-low permeability limit. Macro-kinetics is directly
related to Thiele modulus by the following expression: N
Th
/(1 + 2N
Pe
). It leads to trapping of gas in the adsorbed phase during its release from the matrix, and to an adsorption threshold during
the gas uptake by the matrix. Both effects are proportional to the initially available adsorbed gas amount and becomes more
pronounced with the increasing variance of the porosity field. Consequently, a new upscaled deterministic gas mass balance
is proposed for practical purposes. Numerical results are presented showing free and adsorbed gas distributions and fractional
gas sorption curves for unipore coal matrix exhibiting Gaussian porosity distribution. This study is a unique approach for
our further understanding of the coalbeds and gas shales, and it is important for the development of sound numerical gas production
and sequestration models. 相似文献
38.
A. J. Blotcky W. C. Duckworth A. Ebrahim F. K. Hamel E. P. Rack R. B. Sharma 《Journal of Radioanalytical and Nuclear Chemistry》1989,134(1):151-160
Vanadium in serum was investigated by pre-irradiation chemistry neutron activation analysis employing anion exchange chromatography and post-irradiation neutron activation employing solvent extraction techniques. From a comparison of these techniques it is concluded that vanadium is present in human serum in the sub-ppb range. 相似文献
39.
Dadkhah Davood Zomorodi Mariam Hosseini Seyed Ebrahim 《International Journal of Theoretical Physics》2021,60(9):3271-3285
International Journal of Theoretical Physics - In the present work, a novel approach was proposed to optimize the teleportation cost in Distributed Quantum Circuits (DQCs) by applying a new... 相似文献
40.
This study aimed at polymerization of methyl methacrylate with novel catalysts in the atom transfer radical polymerization (ATRP) condition at 90 °C. This was accomplished using CuBr/N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (CuBr–AEAPTMS) as a homogeneous catalyst and one time with CuBr@AEAPTMS/SBA-15 as a heterogeneous catalyst. Catalysts were characterized using TGA, FT-IR, and UV–Vis spectroscopy. The structural analysis of the polymer was carried out by 13C NMR spectroscopy and GPC. Three characteristic parts of polymer produced by ATRP method including the initiator, monomer units, and end group was shown in 13C NMR spectra. In addition, the presence of C–Br unit showed that the polymerization process is alive. The 1H NMR analysis was used for kinetic investigation of methyl methacrylate polymerization with homogeneous and heterogeneous catalysts that showed high monomer conversion (98 and 90% after 35 min, respectively) and good control of molecular weight with a dispersity (Ð = 1.5–1.7). In addition, the plot of ln ([monomer]0/[monomer] t ) versus time gave linear relationships indicating a constant concentration of the propagating species throughout the polymerization. Finally, the results of the polymerization using heterogeneous catalyst compared with homogeneous catalyst revealed that it was according to ATRP method. 相似文献