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51.
A novel O-heteroside, (3RS,4RS)-3,4-dihydroxy-4-(2-hydroxy-5-acetylphenyl)-2-[(beta-O-glucopyranosyl)methyl]-but-1-ene (1), named nauplathizine, and a previously known compound, acetophenone-4-O-glucoside (2), were isolated from the antibacterial acetone extract of the aerial parts of Nauplius aquaticus (L) (Asteraceae, Inulae). The structure of 1 was established via its acetylated derivative by means of spectroscopic and chemical data. 相似文献
52.
Anaerobic incubation of phorbol (1) from Croton tiglium with human intestinal bacteria afforded five metabolites: isophorbol (2), deoxyphorbol (3), 4beta,9alpha,20-trihydroxy-13,15-seco-1,6,15-tigliatriene-3,13-dione (4), 4beta,9alpha,20-trihydroxy-15,16,17-trinor-1,6-tigliadiene-3,13-dione (5) and 4beta,9a,20-trihydroxy-14(13-->12)-abeo-12alphaH-1,6-tigliadiene-3,13-dione (6). All these metabolites (2-6) were identified and characterized by spectroscopic means, including two-dimensional (2D)-NMR. Nine defined strains from the human intestine showed an ability to transform 1 to these metabolites. 相似文献
53.
The dissociation constants for o-carboxyphenylhydrazoethylacetoacetate (o-CPHEA) ligand, as well as the stability constants for the divalent metal complexes of Cu, (II), Ni (II), Co (II), Zn (II)and Cd (II) ions, have been calculated pH-meterically in different solvents. The dissociation constans pK1=4.10 and pK2=10.55 of the insoluble organic ligand are calculated in aqueous medium. The effect of solvents, the relation between stabilities and both electronegativities and ionization potential are studied. 相似文献
54.
Probing the Methyl Torsional Barriers of the E and Z Isomers of Butadienyl Acetate by Microwave Spectroscopy
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Atef Jabri Vinh Van Dr. Ha Vinh Lam Nguyen Prof.Dr. Wolfgang Stahl Dr. Isabelle Kleiner 《Chemphyschem》2016,17(17):2660-2665
The Fourier transform microwave spectra of the E and Z isomers of butadienyl acetate were measured in the frequency range from 2 to 26.5 GHz under molecular‐jet conditions. The most stable conformer of each isomer, in which all heavy atoms are located in a symmetry plane, was identified after analyzing the spectrum by comparison with the results from quantum‐chemical calculations. The barriers to internal rotation of the acetyl methyl group were found to be 149.1822(20) and 150.2128(48) cm?1 for the E and Z isomers, respectively, which are similar to that of vinyl acetate. A comparison between two theoretical approaches treating internal rotation, the rho axis method and combined axis method, was also performed. The influence of the alkyl R chain on the methyl torsional barriers in CH3 ‐COOR acetates was explored. 相似文献
55.
Fayed Eman A. Nosseir Eman S. Atef Ahmed El‑Kalyoubi Samar A. 《Molecular diversity》2022,26(1):341-363
Molecular Diversity - Several coumarin-containing substitute nitrogen heterocycles have recently received considerable importance due to their diverse pharmacological properties. One-pot and rapid... 相似文献
56.
Analysis of marine sediments of the studied localities provides investigators with data to characterise the composition of these sediments allowing for the identification of particular pollution sources. A study of texture, geochemistry, X-ray diffraction and natural radionuclide content of shallow marine sediments from Quseir harbour, Safaga harbour and El-Esh area in the Red Sea coast of Egypt was conducted for the purpose of assessing the possible influence of human activities on the composition of the sediments. The activity concentrations of the naturally occurring radionuclides 226Ra, 232Th and 40K were measured by using γ-ray spectrometry. The mean activity concentrations of 226Ra, 232Th and 40K in all areas studied were found to be 71±6, 66±5 and 92±7 Bq kg?1 for 226Ra, 83±5, 71±7 and 162±23 Bq kg?1 for 232Th and 513±10, 493±20 and 681±28 Bq kg?1 for 40K, respectively. The results of the study presented were compared with corresponding results obtained in other coastal and aquatic environments in the Red Sea. 相似文献
57.
In this paper, we are interested in the Laguerre hypergroup $\mathbb{K} = [0,\infty ) \times \mathbb{R}$ which is the fundamental manifold of the radial function space for the Heisenberg group. So, we consider the generalized shift operator generated by the dual of the Laguerre hypergroup which can be topologically identified with the so-called Heisenberg fan, the subset of ?2: $$\bigcup\limits_{j \in \mathbb{N}} {\left\{ {(\lambda ,\mu ) \in \mathbb{R}^2 :\mu = \left| \lambda \right|(2j + \alpha + 1),\lambda \ne 0} \right\} \cup \left\{ {(0,\mu ) \in \mathbb{R}^2 :\mu \geqslant 0} \right\}} ,$$ by means of which the maximal function is investigated. For 1 < p ?? ??, the L p ( )-boundedness and weak L 1( )-boundedness result for the maximal function is obtained. 相似文献
58.
Rahmouni Atef 《Mediterranean Journal of Mathematics》2013,10(1):333-351
In this paper, we give analogues of local uncertainty inequality on ${\mathbb{R}^n}$ for stratified Laguerre hypergroup, connected with the spectral analysis of a given homogeneous sublaplacian L, also indicate how local uncertainty inequalities imply global uncertainty inequalities. It would be interesting to note that we deduce the local uncertainty inequalities for the radial functions on the Heisenberg group. Finally, we extend Heisenberg-Pauli-Weyl uncertainty inequality by ultracontractive properties of the semigroups generated by the differential operator and on the estimate on the heat kernel. 相似文献
59.
In this work, we present a simple method for absolute quantification of plasma vitellogenin from both rainbow trout and Atlantic salmon. Plasma samples obtained from control and beta-estradiol induced fish were digested with trypsin. A characteristic 'signature peptide' was selected and analyzed by high performance liquid chromatography (HPLC) coupled to an electrospray quadrupole-time-of-flight tandem mass spectrometer, using a deuterated homolog peptide as an internal standard. The hybrid tandem mass spectrometer was operated in a 'pseudo' selected reaction-monitoring mode in which three diagnostic product ions were monitored for identification and quantification purposes. The reproducibility (coefficient of variation approximately 5%) and sensitivity (limit of quantification (LOQ) of 0.009 mg/ml) achieved by this simple assay allow it to be considered as an alternative to immunological assays. 相似文献
60.
We present an optical model based on Green’s function to investigate the effect of using single-wall carbon nanotube (SWCNT)
as anode for infrared quantum dot light-emitting devices (IR QD-LEDs). To the best of our knowledge, there is no report in
using SWCNT as anode in IR QD-LEDs. We have studied the emitted power distribution among the different optical modes (external
propagating mode (photon outcoupling efficiency), substrate, anode/organics, and surface plasmon modes (SP)), angular intensity
distribution, viewing angle effect on the optical characteristics, and the emission spectral characteristics. We have found
that the light outcoupling efficiency of IR QD-LEDs based on SWCNT as anode was increased nearly by a factor of 4 relative
to that one based on indium-tin oxide (ITO). We also investigated the effect of using different cathode materials on the optical
characteristics of IR QD-LEDs. 相似文献