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101.
A rapid, efficient, and reliable access for the synthesis of an assortment of 4-methyl-7-alkyl/aryl/heteroaryl alkynyl coumarins has been developed by the copper, amine, and ligand-free Sonogashira cross-coupling reaction of 4-methyl-7-nonafluorobutylsulfonyloxy coumarin with various terminal alkynes under microwave irradiation. In the presence of a suitable catalyst, base, and solvent, the coupling reaction proceeded smoothly to give the diaryl alkynes in satisfactory to exceptional yields. Nonaflates coupled more efficiently than the corresponding triflates which yielded the detriflated product as well as the hydrolyzed product as competing side products along with the required product. The utilization of TBAF·3H2O as a mild base as well as a solvating agent was the key for success of the reaction. 相似文献
102.
Gavrilov AN McCauley RD Salgado-Kent C Tripovich J Burton C 《The Journal of the Acoustical Society of America》2011,130(6):3651-3660
Vocal characteristics of pygmy blue whales of the eastern Indian Ocean population were analyzed using data from a hydroacoustic station deployed off Cape Leeuwin in Western Australia as part of the Comprehensive Nuclear-Test-Ban Treaty monitoring network, from two acoustic observatories of the Australian Integrated Marine Observing System, and from individual sea noise loggers deployed in the Perth Canyon. These data have been collected from 2002 to 2010, inclusively. It is shown that the themes of pygmy blue whale songs consist of ether three or two repeating tonal sounds with harmonics. The most intense sound of the tonal theme was estimated to correspond to a source level of 179 ± 2 dB re 1 μPa at 1 m measured for 120 calls from seven different animals. Short-duration calls of impulsive downswept sound from pygmy blue whales were weaker with the source level estimated to vary between 168 to 176 dB. A gradual decrease in the call frequency with a mean rate estimated to be 0.35 ± 0.3 Hz/year was observed over nine years in the frequency of the third harmonic of tonal sound 2 in the whale song theme, which corresponds to a negative trend of about 0.12 Hz/year in the call fundamental frequency. 相似文献
103.
AbstractThe spineless cuttlefish Sepiella inermis encompasses a major share in the marine fisheries sector, and represents as a culinary delicacy in many cultures. Bioactivity-guided fractionation of methanol:ethyl acetate (MeOH:EtOAc, 1:1) extract of the edible parts of the species ensued in identification of two hexahydro chromenyl analogues namely, methyl 7-ethyl-hexahydro-8a-methyl-2H-chromene-4-carboxylate (1) and methyl 1-acetoxy-hexahydro-3-methyl-3-propyl-1H-isochromene-4-carboxylate (2). The isolated metabolites were checked for their radical scavenging and anti-inflammatory potentials by selective in vitro models. The isochromenyl derivative exhibited potential 2,2-diphenyl-1-picryl-hydrazil and 2,2′-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (IC50?<?0.45?mg mL?1) radical-scavenging capacities along with pro-inflammatory cyclooxygenase-2 (COX-2) (IC50 0.75?mg mL?1) and 5-lipoxygenase (5-LOX) (IC50 0.77?mg mL?1) inhibitory activities. The titled compounds displayed the selectivity indices (IC50 anti-COX-1/IC50 anti-COX-2) greater than 1.25, in comparison with synthetic anti-inflammatory drug ibuprofen (0.44), which attributed to their greater selectivity towards inducible pro-inflammatory enzyme COX-2. 相似文献
104.
105.
Dirichlet integrals and the associated Dirichlet statistical densities are widely used in various areas. Generalizations of
Dirichlet integrals and Dirichlet models to matrix-variate cases, when the matrices are real symmetric positive definite or
hermitian positive definite, are available [4]. Real scalar variables case of the Dirichlet models are generalized in various
directions. One such generalization of the type-2 or inverted Dirichlet is looked into in this article. Matrix-variate analogue,
when the matrices are hermitian positive definite, are worked out along with some properties which are mathematically and
statistically interesting. 相似文献
106.
Joy Manners 《Optics Communications》1983,44(5):366-370
Radiation at 2.36 μm is produced by stimulated electronic Raman scattering in barium vapour. The pump radiation is provided by a XeCl excimer laser. Photon conversion efficiencies of up to 1% are observed. The variations of the infra-red Stokes output with barium number density and with pump intensity are described. 相似文献
107.
The sulphur containing inhibitors (I), cysteine (Cys) and sodium thiosulphate (THS), have been found to inhibit Hg(II) catalyzed exchange of cyanide in hexacyanoferrate(II) by nitroso-R-salt (NRS). The inhibitory effect of both the ligands are attributed to their binding tendencies with Hg(II) leading to the formation of catalyst-inhibitor (C-I) complex. The reactions have been followed spectrophotometrically in aqueous medium at 720 nm by noting the increase in absorbance of the green colour product, [Fe(CN)5NRS]3− at pH 6.50 ± 0.02, temp 25.0 ± 0.1 °C and ionic strength (μ) 0.1 M (KNO3). A most plausible mechanistic scheme involving the role of analytes (inhibitors) has been proposed. The values of equilibrium constants for complex formation between catalyst-inhibitor (KCI), catalyst-substrate (KS) and Mechaelis-Menton constant (Km) have been computed from the kinetic data. The linear calibration curves have been established between absorbance and inhibitor concentrations under specified conditions. Cys and THS have been determined in the range 1-5 × 10− 7 M and 4.9-16.9 × 10− 7 M respectively. The detection limits have been computed to be 1 × 10− 7 M and 4.9 × 10− 7 M for Cys and THS, respectively. 相似文献
108.
Zhang F Bartels MJ Pottenger LH Schisler MR Grundy JJ Gollapudi BB 《Rapid communications in mass spectrometry : RCM》2008,22(10):1455-1460
Hemoglobin adducts are often used as biomarkers for exposure to reactive chemicals in toxicology studies. Therefore, fast, sensitive, accurate, and reproducible methods for quantifying these protein adducts are key to evaluate test material dosimetry. A methodology has been developed for the quantitation of methylated hemoglobin adducts isolated from rats exposed to the model alkylating agent: methyl methane sulfonate (MMS). After 4 days of MMS exposure by oral gavage, hemoglobin was isolated from rat blood and digested with trypsin. The tryptic digestion solution was used for the adducted hemoglobin signature peptide quantitation via liquid chromatography/negative tandem mass spectrometry (LC/ESI-MS/MS). The limit of quantitation (LOQ) for the methylated hemoglobin beta chain N-terminal signature peptide (MeVHLTDAEK) was 1.95 ng/mL (5.9 pmol/mg globin). The calibration curves were linear over a concentration range of 1.95 to 625 ng/mL, with a correlation coefficient R2 >0.998, accuracy of 85.8 to 119.3%, and precision of 0.9 to 19.4%. 相似文献
109.
The one-electron oxidation of duplex DNA generates a nucleobase radical cation (electron "hole") that migrates long distances by a hopping mechanism. The radical cation reacts irreversibly with H2O or O2 to form oxidation products (damaged bases). In normal DNA (containing the four common DNA bases), reaction occurs most frequently at guanine. However, in DNA duplexes that do not contain guanine (i.e., those comprised exclusively of A/T base pairs), we discovered that reaction occurs primarily at thymine and gives products resulting from oxidation of the T-C5 methyl group and from addition to its C5-C6 double bond. This surprising result shows that it is the relative reactivity, not the stability, of a nucleobase radical cation that determines the nature of the products formed from oxidation of DNA. A mechanism for reaction is proposed whereby a thymine radical cation may either lose a proton from its methyl group or H2O/O2 may add across its double bond. In the latter case, addition may initiate a tandem reaction that converts both thymines of a TT step to oxidation products. 相似文献
110.