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排序方式: 共有253条查询结果,搜索用时 218 毫秒
91.
Joseph Tsemeugne Emmanuel Sopbué Fondjo Jean-de-Dieu Tamokou Ignas Tonle Irene Chinda Kengne Arnaud Djintchui Ngongang Stephen Tamekou Lacmata Taoufik Rohand Jules Roger Kuiate Beibam Luc Sondengam 《Chemistry Central journal》2017,11(1):119
Background
A series of recently reported phenolic azo dyes 7a–e were prepared by coupling the thienyl diazonium sulfate of 3-Amino-4H-benzo[f]thieno[3,4-c](2H)chromen-4-one with selected diversely substituted phenolic and naphtholic derivatives. These compounds were evaluated for their antibacterial and antifungal activities. Furthermore their voltammetric behavior was compared at a glassy carbon electrode.Results
The voltammetric behavior of the five recently reported azo dyes has been compared at a glassy carbon electrode. It is shown that the azo dyes 7a–e with a hydroxyl group in the ortho position with respect to the azo bridge give rise to well defined, irreversible peaks for the oxidation and reduction process within a pH range of 2–7. The mechanisms of electrochemical oxidation of compound 7a–c and 7e are proposed. For the hydroxyl-substituted dyes, re-oxidation peaks were obtained in the subsequent scan. The antimicrobial activities of the reported compounds 7a–e along with the entire precursors 1–4 and 6a–e were performed against selected bacterial and fungal species and their activities compared to those of nystatin, griseofulvin and ciprofloxacin used as reference drugs.Conclusions
The present study showed significant antimicrobial activity of compounds 6d, 7a and 7c,e against the tested microorganisms; this result confirms the antimicrobial potency of azo compounds and some of their precursors.92.
Omemah Gliah Boguslaw Kruczek Seyed Gh. Etemad Jules Thibault 《Heat and Mass Transfer》2011,47(9):1171-1180
To properly simulate the condensation process and design a water recovery system from condensation of atmospheric water vapour
on a surface maintained below the dew point by radiative heat loss from the surface to night sky, an accurate estimation of
the effective sky temperature is required. To estimate the effective night sky temperature, an experimental system consisting
of a series of metal plates embedded on a heat transfer panel, a weather station and a control system was used. The results
obtained from theoretical analyses and preliminary experiments are presented and discussed. A special emphasis is given to
a mathematical solution of the system of equations that need to be solved to obtain the effective sky temperature. It is shown
that although the system of equations works well for the direct heat transfer problem, there is a serious difficulty to solve
the inverse heat transfer problem to retrieve the desired parameters. 相似文献
93.
Bean DE Muya JT Fowler PW Nguyen MT Ceulemans A 《Physical chemistry chemical physics : PCCP》2011,13(46):20855-20862
The ipsocentric method at the coupled Hartree-Fock level is used for the calculation of magnetically induced ring currents in the boron buckyball B(80), for both I(h) and distorted T(h) geometries. A close similarity between the current patterns in boron and carbon buckyballs is noted, but with a higher current density in B(80). Paratropic currents on the pentagons are predominant in the boron buckyball, and the central NICS value is positive. These observations support the conclusion that B(80) should be considered (weakly) anti-aromatic. The largest orbital contributions to the ring currents in both molecules are identified and related to specific excitations in the frontier orbital region. 相似文献
94.
Cantin K Rondeau-Gagné S Néabo JR Daigle M Morin JF 《Organic & biomolecular chemistry》2011,9(12):4440-4443
An amide-containing phenylacetylene macrocycle (PAM) has been synthesized and its gelation properties were studied in different solvents. Surprisingly, this macrocycle forms organogels at low concentration in many polar and apolar solvents. XRD and FTIR analysis suggest that this macrocycle forms stable supramolecular assemblies owing to H-bonding. Scanning electron microscopy analyses show the formation of bundles of nanofibrils, demonstrating the long-range organization of this material. 相似文献
95.
Muya JT De Proft F Geerlings P Nguyen MT Ceulemans A 《The journal of physical chemistry. A》2011,115(32):9069-9080
Density functional theory calculations at the B3LYP/SVP and B3LYP/6-311G(d) levels were carried out for a series of XH(3)B(80) complexes with X = {N, P, As, B, Al}. To probe the regioselectivity of B(80), the electronic Fukui function, the molecular electrostatic potential (MEP), and the natural bond orbital (NBO) were determined. These indices were shown to provide reliable guides to predict the relative reactivities of the boron buckyball sites. Thermodynamic stabilities of the complexes formed by the reaction of B(80) with nucleophiles (NH(3), PH(3), AsH(3)) and electrophiles (BH(3), AlH(3)) are in good agreement with the prediction of regioselectivity indicated on the basis of Fukui and MEP indices. The qualitative results suggest the boron buckyball to be an amphoteric and hard molecule. It has two distinct reactive sites localized on caps and frame, which act as acids and bases, respectively. Most of the complexes are stable with formation energies comparable to that of the analogous complexes of the borane molecule, BH(3)BH(3), BH(3)NH(3), and BH(3)AlH(3). The B-H-B bond characteristics of diborane are recovered in B(80)BH(3). Exohedral complexes are more stable than endohedral complexes. The most stable complexes are those with NH(3) on the caps and BH(3) on the pentagonal ring of B(80). 相似文献
96.
JR Néabo C Vigier-Carrière S Rondeau-Gagné JF Morin 《Chemical communications (Cambridge, England)》2012,48(81):10144-10146
Carbon nanoparticles were obtained at room temperature by irradiating an organogel made from a 1,8-diaryloctatetrayne derivative in chloroform. During the topochemical polymerization, the morphology of the gel changes from fibers to soluble, yellow fluorescent nanoparticles in high yield. Analyses suggest that the resulting nanoparticles are made of amorphous graphitic carbon. 相似文献
97.
Changqing Dong Xinglei LiuWu Qin Qiang LuXiaoqiang Wang Simo ShiYongping Yang 《Applied Surface Science》2012,258(7):2562-2569
Reduction of metal oxide oxygen carrier has been attractive for direct CO oxidation and CO2 separation. To investigate the reduction behaviors of iron oxide prepared by supporting Fe2O3 on γ-Al2O3 and its effect on CO oxidation, fluidized-bed combustion experiments, thermogravimetric analyzer (TGA) experiments, and density functional theory (DFT) calculations were carried out. Gas yield (γCO2) increases significantly with the increase of temperature from 693 K to 1203 K, while carbon deposition decreases with the increase of temperature from 743 K to 1203 K, where temperature is a very important factor for CO oxidation by iron oxide. Further, it were quantitatively detected that the interaction between CO and Fe2O3, breakage of O-Fe bonds and formation of new C-O bonds, and effect of reduction degree were quantitatively detected. Based on adsorptions under different temperatures and reducing processes from Fe3+ into Fe2+, Fe+ and then into Fe, it was found that Fe2+ → Fe+ was the reaction-controlling step and the high oxidation state of iron is active for CO oxidation, where efficient partial reduction of Fe2O3 into FeO rather than complete reduction into iron may be more energy-saving for CO oxidation. 相似文献
98.
99.
Richard Li Erica F. Antunes Estelle Kalfon‐Cohen Akira Kudo Luiz Acauan Wei‐Chang D. Yang Canhui Wang Kehang Cui Andrew H. Liotta Ananth Govind Rajan Jules Gardener David C. Bell Michael S. Strano J. Alexander Liddle Renu Sharma Brian L. Wardle 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(27):9302-9307
Synthesis of low‐dimensional carbon nanomaterials such as carbon nanotubes (CNTs) is a key driver for achieving advances in energy storage, computing, and multifunctional composites, among other applications. Here, we report high‐yield thermal chemical vapor deposition (CVD) synthesis of CNTs catalyzed by reagent‐grade common sodium‐containing compounds, including NaCl, NaHCO3, Na2CO3, and NaOH, found in table salt, baking soda, and detergents, respectively. Coupled with an oxidative dehydrogenation reaction to crack acetylene at reduced temperatures, Na‐based nanoparticles have been observed to catalyze CNT growth at temperatures below 400 °C. Ex situ and in situ transmission electron microscopy (TEM) reveal unique CNT morphologies and growth characteristics, including a vaporizing Na catalyst phenomenon that we leverage to create CNTs without residual catalyst particles for applications that require metal‐free CNTs. Na is shown to synthesize CNTs on numerous substrates, and as the first alkali group metal catalyst demonstrated for CNT growth, holds great promise for expanding the understanding of nanocarbon synthesis. 相似文献
100.
Michael Schulte Dieter Lubda Axel Delp Jules Dingenen 《Journal of separation science》2000,23(1):100-105
The use of monolithic silica sorbents for the isolation of substances by preparative liquid chromatography is demonstrated. Preparative liquid chromatography is recognized as a valuable technique for the isolation and purification of substances in the pharmaceutical and fine chemicals industry. The system technology has meanwhile reached a high standard, and the greatest future improvements are expected to arise from new and improved adsorbents. Monolithic silica sorbents offer some unique features for preparative liquid chromatography. They exhibit high efficiencies even at high flow rates due to their fast convective mass transfer and can therefore be used at very high mobile phase velocities, leading to high productivity and hence to maximum process economy. The benefits of this new type of adsorbent are illustrated for an example in batch‐chromatographic mode and an example using the continuous simulated moving bed (SMB) technology. 相似文献