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41.
Shaheen Faizi Fatima Farooqi Aneela Naz Farheen Ansari Shakeel Ahmed Khan 《Tetrahedron》2009,65(5):998-1004
A rare alkaloid, shahidine (1), having an unstable oxazoline core has been isolated as a major constituent from the fresh leaves of Aegle marmelos. It is moisture-sensitive, and found to be the parent compound of aegeline and other amides, however, it is stable in dimethyl sulfoxide. Its structure was established by spectroscopic analysis. Biogenetically, oxazolines may be considered as the precursor of hydroxy amides and oxazoles found in plants. Shahidine (1) showed activity against a few Gram-positive bacteria. 相似文献
42.
This paper introduces a Grammar-based Genetic Programming Hyper-Heuristic framework (GPHH) for evolving constructive heuristics for timetabling. In this application GP is used as an online learning method which evolves heuristics while solving the problem. In other words, the system keeps on evolving heuristics for a problem instance until a good solution is found. The framework is tested on some of the most widely used benchmarks in the field of exam timetabling and compared with the best state-of-the-art approaches. Results show that the framework is very competitive with other constructive techniques, and did outperform other hyper-heuristic frameworks on many occasions. 相似文献
43.
Glass RS Block E Lorance E Zakai UI Gruhn NE Jin J Zhang SZ 《Journal of the American Chemical Society》2006,128(39):12685-12692
The ionization energies of conformationally constrained, newly synthesized beta-disilanyl sulfides and selenides were determined by photoelectron spectroscopy. These ionization energies reflect substantial (0.53-0.75 eV) orbital destabilizations. The basis for these destabilizations was investigated by theoretical calculations, which reveal geometry-dependent interaction between sulfur or selenium lone pair orbitals and sigma-orbitals, especially Si-Si sigma-orbitals. These results presage facile redox chemistry for these compounds and significantly extend the concept of sigma-stabilization of electron-deficient centers. 相似文献
44.
The main purpose of this article is to present a mathematical model of ciliary motion in an annulus. In this analysis, the peristaltic motion of non-Newtonian Jeffrey six constant fluid is observed in an annulus with ciliated tips in the presence of heat and mass transfer. The effects of viscous dissipation are also considered. The flow equations of non-Newtonian fluid for the two-dimensional tube in cylindrical coordinates are simplified using the low Reynolds number and long wave-length approximations. The main equations for Jeffrey six constant fluid are considered in cylindrical coordinates system. The resulting nonlinear problem is solved using the regular perturbation technique in terms of a variant of small dimensionless parameter α. The results of the solutions for velocity, temperature and concentration field are presented graphically. Bk is Brinkman number, ST is soret number, and SH is the Schmidth number. Outcome for the longitudinal velocity, pressure rise, pressure gradient and stream lines are represented through graphs. In the history, the viscous-dissipation effect is usually represented by the Brinkman number. 相似文献
45.
Uzma Habib Amin Badshah Ulrich Flörke Rizwana Aleem Qureshi Bushra Mirza Nazar-ul-Islam Azeem Khan 《Journal of chemical crystallography》2009,39(10):730-734
Abstract The reaction of Cu(OOCCH3)2·H2O with (2,4-diamino-5-(3′,4′,5′-trimethoxybenzyl) pyrimidine (trimethoprim) in ethanolic solution at 80 °C affords the title
complex which has been characterized by elemental, IR, and NMR (1H and 13C).The crystal structure has been determined by single crystal X-ray diffraction. Compound 1 (C36H48Cu2N8O14) is triclinic, space group P-1 with a = 7.2676(4) ?, b = 11.6721(7) ?, c = 12.8279(8) ?, α = 95.839(1)°, β = 93.456(1)°, γ = 105.541(1)°, Z = 1. Two copper atoms are coordinated directly to each other as well as are held together by four bridging aceto groups.
Each copper atom is also bonded opposite the Cu–Cu vector to a trimethoprim molecule through the N(1) atom of the pyrimidine
ring. Trimethoprim acts as a monodentate ligand through the pyrimidine nitrogen N(1) atom. The complex was screened for the
activity against several bacteria, showing more activity against bacteria as compared to trimethoprim.
Graphical Abstract To enhance the activity of trimethoprim, its derivative was prepared and there bacterial activity against several bacteria
was analyzed.
相似文献
46.
Uzma Habib Amin Badshah Ulrich Flörke Rizwana Aleem Qureshi Bushra Mirza Nazar-ul-Islam Azeem Khan 《Journal of chemical crystallography》2009,39(8):607-611
Abstract The title copper (II) complex with Trimethoprim was prepared at 20–25 °C and its crystal structure was determined by single
crystal X-ray diffraction. Compound (C36H50Cu3N8O16) is triclinic, space group P-1 with a = 6.4642(5) ?, b = 12.5495(9) ?, c = 13.4911(10) ?, α = 77.518(1)°, β = 85.326(1)°, γ = 84.413(2)°, Z = 1. In this compound, three copper atoms are bonded to each other, two terminal coppers are bonded to three oxygen atoms
and N1 of pyrimidine ring of Trimethoprim and central copper is bonded to four oxygen atoms. The amino nitrogen atoms are not involved
in the coordination to the metal.
Graphical Abstract To enhance the activity of trimethoprim, its derivative was prepared and there bacterial activity against several bacteria
was analyzed.
相似文献
47.
Md. Lutfor Rahman Hira Bablu Mandal Shaheen M. Sarkar M. Nomani Kabir Eddy M. Farid Sazmal E. Arshad 《高分子科学杂志,A辑:纯化学与应用化学》2016,53(8):515-522
A graft copolymerization was performed using free radical initiating process to prepare the poly(methyl acrylate) grafted copolymer from the tapioca cellulose. The desired material is poly(hydroxamic acid) ligand, which is synthesized from poly(methyl acrylate) grafted cellulose using hydroximation reaction. The tapioca cellulose, grafted cellulose and poly(hydroxamic acid) ligand were characterized by Infrared Spectroscopy and Field Emission Scanning Electron Microscope. The adsorption capacity with copper was found to be good, 210 mg g?1 with a faster adsorption rate (t1/2 = 10.5 min). The adsorption capacities for other heavy metal ions were also found to be strong such as Fe3+, Cr3+, Co3+ and Ni2+ were 191, 182, 202 and 173 mg g?1, respectively at pH 6. To predict the adsorption behavior, the heavy metal ions sorption onto ligand were well-fitted with the Langmuir isotherm model (R2 > 0.99), which suggest that the cellulose-based adsorbent i.e., poly(hydroxamic acid) ligand surface is homogenous and monolayer. The reusability was checked by the sorption/desorption process for six cycles and the sorption and extraction efficiency in each cycle was determined. This new adsorbent can be reused in many cycles without any significant loss in its original removal performances. 相似文献
48.
Since ferrites are highly sensitive to the additives present in or added to them, extensive work, to improve the properties of basic ferrites, has been carried out on these aspects. The present paper reports the effects of composition, frequency,and temperature on the dielectric behavior of a series of CuxZn1-xFe2O4 ferrite samples prepared by the usual ceramic technique. In order to improve the properties of the samples, low cost Fe2O3having 0.5 wt.% Si as an additive is selected to introduce into the system. The dielectric constant increases by increasing the Cu content, as the electron exchange of Cu2+= Cu+is responsible for the conduction and the polarization. However, the addition of Si could decrease the dielectric constant as it suppresses the ceramic grain growth and promotes the quality factor at higher frequencies.Dielectric constant ε and loss tangent tan δ of the mixed Cu–Zn ferrite decrease with increasing frequency, attributed to the Maxwell–Wagner polarization, which increases as the temperature increases. 相似文献
49.
In-keun Jung Jyoti L. Gurav Uzma K.H. Bangi Seungsu Baek Hyung-Ho Park 《Journal of Non》2012,358(3):550-556
Synthesis of multi-walled carbon nanotubes (MWCNTs) doped silica xerogel films was reported in this work. A crucial step of introducing MWCNTs was achieved by functionalizing them by acid treatment to form stable and homogenous SiO2/MWCNTs sol. Scanning electron microscopy showed spherical particles in honeycomb network structure for undoped xerogel films whereas dispersion and wrapping of MWCNTs in silica matrix was observed for MWCNTs doped films. Various bond formations during the sol–gel process and surface modification were confirmed using Fourier transform infra-red and detailed study on the chemical bonding state of the films was carried out using X-ray photoelectron spectroscopy. Nanoindentation studies showed that the mechanical properties of MWCNTs doped xerogel film increase dramatically: higher modulus (E = 2.127 ± 0.095 GPa) and hardness (H = 0.035 ± 0.017 GPa) values than those of pristine xerogel film (E = 0.234 ± 0.058 GPa, H = 0.01 ± 0.003 GPa). 相似文献
50.
The thermal decompositions of pure and mixed manganese carbonate and ammonium molybdate tetrahydrate in molar ratios of 3:1,
1:1 and1:3 were studied by DTA and TG techniques. The prepared mixed solid samples were calcined in air at 500, 750 or 1000°C
and then investigated by means of an XRD technique. The results revealed that manganese carbonate decomposed in the range
300–1000°C, within termediate formation of MnO2, Mn2O3 andMn3O4. Ammonium molybdate tetrahydrate first lost its water of crystallization on heating, and then decomposed, yielding water
and ammonia. At 340°C,MoO3 was the final product, which melts at 790°C. The thermal treatment of the mixed solids at 500, 750 or 1000°C led to solid-solid
interactions between the produced oxides, with the formation of manganese molybdate. At 1000°C, Mn2O3 and MoO3 were detected, due to the mutual stabilization effect of these oxides at this temperature.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献