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131.
Flavones were prepared using a one-pot procedure starting from the corresponding 2′-hydroxyacetophenones. The latter were treated with 3 equiv of aroyl chloride in wet K2CO3/acetone (1% w/w water) to afford a good yield of flavone and a smaller amount of 3-aroylflavone. Evidence was obtained that the reaction proceeds via a triketone intermediate. When the reactants were heated in 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and pyridine, the 3-aroylflavone was obtained exclusively. Use of a stoichiometric amount of aroyl chloride afforded only the corresponding flavone. 相似文献
132.
Zal U��yun Wan Mahmood Che Abd Rahim Mohamed Zaharudin Ahmad Abdul Kadir Ishak 《Journal of Radioanalytical and Nuclear Chemistry》2011,287(1):255-260
A total of eight sediment cores with 50 cm length were taken in the Sabah and Sarawak coastal waters using a gravity corer in 2004 to estimate sedimentation rates using four mathematical models of CIC, Shukla-CIC, CRS and ADE. The average of sedimentation rate ranged from 0.24 to 0.48 cm year?1, which is calculated based on the vertical profile of 210Pbex in sediment core. The finding also showed that the sedimentation rates derived from four models were generally shown in good agreement with similar or comparable value at some stations. However, based on statistical analysis of paired sample t-test indicated that CIC model was the most accurate, reliable and suitable technique to determine the sedimentation rate in the coastal area. 相似文献
133.
Park JH Mamun MI Abd El-Aty AM Na TW Choi JH Ghafar MW Choi WJ Kim KS Kim SD Shim JH 《Biomedical chromatography : BMC》2011,25(1-2):155-163
In a continuation of our earlier work, a multiresidual analytical method using 48 frequently used neutral pesticides in a water matrix was developed and validated in this study. The samples were extracted with dichloromethane and the pesticides were analyzed via GC-NPD followed by confirmation with GC-MS. Good linearity was detected over a concentration range of 0.01-1.0 microg/mL with correlation coefficients (r(2) ) in excess of 0.982. The recoveries were measured between 70.7 and 111.4% for the majority of the targeted pesticides with relative standard deviations (RSDs) of less than 20%. The LODs and LOQs were in ranges of 0.1-2 and 0.33-6.6 microg/L, respectively. A total of 66 water samples were collected from different locations in Yeongsan and the Sumjin River, Republic of Korea, and were analyzed in accordance with the developed method. None of the water samples were determined to contain any of the targeted pesticides. The method has been shown to be simpler, faster, and more cost-effective than the method established by the Environmental Protection Agency (EPA). 相似文献
134.
Cheong KW Leow TC Rahman RN Basri M Rahman MB Salleh AB;Enzyme Microbial Technology Research Group 《Applied biochemistry and biotechnology》2011,164(3):362-375
A thermostable lipase from Geobacillus zalihae strain T1 was chemically modified using propionaldehyde via reductive alkylation. The targeted alkylation sites were lysines,
in which T1 lipase possessed 11 residues. Far-UV circular dichroism (CD) spectra of both native and alkylated enzyme showed
a similar broad minimum between 208 and 222 nm, thus suggesting a substantial amount of secondary structures in modified enzyme,
as compared with the corresponding native enzyme. The hydrolytic activity of the modified enzymes dropped drastically by nearly
15-fold upon chemical modification, despite both the native and modified form showed distinctive α-helical bands at 208 and
222 nm in CD spectra, leading us to the hypothesis of formation of a molten globule (MG)-like structure. As cooperative unfolding
transitions were observed, the modified lipase was distinguished from the native state, in which the former possessed a denaturation
temperature (T
m) in lower temperature range at 61 °C while the latter at 68 °C. This was further supported by 8-anilino-1-naphthalenesulfonic
acid (ANS) probed fluorescence which indicated higher exposure of hydrophobic residues, consequential of chemical modification.
Based on matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) analysis, a small number
of lysine residues were confirmed to be alkylated. 相似文献
135.
El-Wahab AH Al-Fifi ZI Bedair AH Ali FM Halawa AH El-Agrody AM 《Molecules (Basel, Switzerland)》2011,16(1):307-318
Vilsmeier formylation of 2-(1-phenylhydrazonoethyl)naphtho[2,1-b]furan (2) gave 3-naphtho[2,1-b]furan-2-yl-1-phenyl-1H-pyrazole-4-carbaldehyde (3), which was reacted with C- and N-nucleophiles to afford naphthofuranpyrazol derivatives 4-8. Treatment of 2-[(3-(naphtho[2,1-b]furan-2-yl)-1-phenyl-1H-pyrazol-4-yl)methylene]-malononitrile (4a) with reactants having active hydrogen and Et?N gave the corresponding pyrazoline, pyran and chromene addition product derivatives 10, 12 and 13, consisting of three different connected heterocyclic moieties. Reaction of 1-((3-(naphtho[2,1-b]furan-2-yl)-1-phenyl-1H-pyrazol-4-yl) methylene)-2-phenylhydrazone (6b) with AcONa and ethyl bromoacetate or chloroacetone afforded the thiazolidinone and methylthiazole derivatives 14 and 15, respectively. In addition, intramolecular cyclization of 6d with Ac?O afford the corresponding 1,3,4-thiadiazol-2-yl acetamide derivative 16. The structures of the synthesized compounds were confirmed by IR, 1H-NMR/13C-NMR and mass spectral studies. Compound 14 showed promising effects against the tested Gram positive and negative bacteria and fungi. 相似文献
136.
The present paper investigates phenomena brought about into the classic peristaltic mechanism by inclusion of non-Newtonian effects through a porous space in a channel. The peristaltic motion of a second-order fluid through a porous medium was studied for the case of a planar channel with harmonically undulating extensible walls. The system of the governing nonlinear PDE is solved by using the perturbation method to second-order in dimensionless wavenumber. The analytic solution has been obtained in the form of a stream function from which the axial pressure gradient has been derived. The flow is investigated in a wave frame of reference moving with velocity of the wave. Numerical calculations are carried out for the pressure rise and frictional force. The features of the flow characteristics are analyzed by plotting graphs and discussed in detail. 相似文献
137.
Abd El-Moneim Anwar Mohamed Mohamed Abd El-Hady Kassem Mohamed Abd Allah El-Hadidy 《Applied Mathematical Modelling》2011,35(9):4127-4139
This paper investigates a search problem for a brownian target motion on one of n-intersected real lines in which any information of the target position is not available to the searchers all the time. We have n-searchers start searching for the target from the origin that is the intersection point of these lines. Each of the searchers moves continuously along his line in both directions of the starting point. The purpose of this paper is to formulate a search model and find the condition under which the expected value of the first meeting time between one of the searchers and the target is finite. Also, we show the existence of the optimal search plan which minimizes the expected value of the first meeting time and find it. 相似文献
138.
Najib A. Odhah Kamal H. Awadalla Moawad I. Dessouky Fathi E. Abd El-Samie 《International Journal of Wireless Information Networks》2011,18(3):158-170
In this paper, frequency domain pre-equalization (Pre-FDE) is developed for broadband cyclic prefix-code division multiple
access (CP-CDMA) as a single carrier transmission scheme, and for multi carrier-CDMA (MC-CDMA) and orthogonal frequency division
multiplexing (OFDM) as multi carrier transmission schemes. A comparison study is held between these schemes and the traditional
equalization schemes. Experimental results show that pre-equalization improves significantly the performance of the single
and multi carrier communication systems with a very low complexity at the receiver. The comparative study between MIMO pre-equalization
for single carrier systems and for multi carrier systems shows that MIMO pre-equalization for single carrier systems outperforms
that for multi carrier systems in terms of bit error rate (BER) performance since single carrier transmission has more frequency
diversity than multi carrier transmission in the uncoded case. 相似文献
139.
Saleh MI Kusrini E Mohd Sarjidan MA Abd Majid WH 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,78(1):52-58
A mononuclear of [Eu(NO3)(Pic)(H2O)2(EO3)](Pic)·(0.73)H2O complex, where EO3=trietraethylene glycol and Pic=picrate anion, shows a red emission when used as an active layer in a single layer of ITO/EO3-Eu-Pic/Al configuration. The crystal structure of the complex consists of [Eu(NO3)(Pic)(H2O)2(EO3)]+ cation and [Pic]- anion. The Eu(III) ion is coordinated to the 10 oxygen atoms from one EO3 ligand, one Pic anion, one nitrate anion, and two water molecules. The complex is crystallized in triclinic with space group P-1. The hybrids in thin films I and II were prepared in the respective order solution concentrations of 15 and 20 mg/mL the emissive center. Comparing the photoluminescence (PL) and electroluminescence (EL) spectra, we can find that all emissions come from the characteristic transitions of the Eu(III) ion. The EL spectra of both thin films showed the occurrence of the most intense red-light emission around at 612 nm. Comparison of organic light-emitting device (OLED) current intensity characteristics as a function of voltage (I-V) show that the thin film I is better than those found for the thin film II. The thickness of the emitting layer is an important factor to control the current-voltage curve. The sharp and intense emission of the complex at low voltage indicates that the complex is a suitable and promising candidate for red-emitting materials. 相似文献
140.
Emad Abd‐Elrady Bernard Mulgrew 《International Journal of Communication Systems》2014,27(11):3266-3279
The main objective in distributed sensor networks is to reach agreement or consensus on values acquired by the sensors. A common methodology to approach this problem is using the iterative and weighted linear combination of those values to which each sensor has access. Different methods to compute appropriate weights have been extensively studied, but the resulting iterative algorithm still requires many iterations to provide a fairly good estimate of the consensus value. In this paper, different accelerating consensus approaches based on adaptive and non‐adaptive filtering techniques are studied and applied on the problem of acoustic source localization using the adaptive projected subgradient method. A comparative simulation study shows that the non‐adaptive polynomial filters based on Newton's interpolating polynomials and semi‐definite programming can provide more accelerated consensus and better estimation accuracy than adaptive filters evaluated using constrained affine projection algorithm or stochastic gradient algorithm provided that the network topology is known beforehand. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献