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排序方式: 共有500条查询结果,搜索用时 15 毫秒
1.
Richard R. Izac Maury M. Bandurraga John M. Wasylyk Fred W. Dunn William Fenical 《Tetrahedron》1982,38(2):301-304
Examinations of the extracts of 8 taxonomically-diverse marine soft-corals (Orders Gorgonaceae, Alcyonaceae and Stolonifera, Subclass Octocorallia, Phylum Cnidaria), have resulted in the isolation of 4 new sesquiterpenoids (1–4) of the germacrene type. Three previously known germacrene derivatives (5–7), and the elemane 8, have also been isolated, and complete 1H and 13C NMR assignments for these compounds are reported. 相似文献
2.
W. A. G. R. Al-Shahib A. S. Dunn 《Journal of polymer science. Part A, Polymer chemistry》1978,16(3):677-684
There is evidence in the literature that the rates of emulsion polymerization increase by a large factor as the alkyl chain length increases for a homologous series of surfactants. However, the area occupied by a surfactant molecule in a saturated monolayer at the polystryene/water interface is independent of chain length for alkyl sulfates so that, on the basis of Gardon's theory, equal rates of polymerization would be expected when equal concentrations of surfactants are used. There is a large increase in the number of polymer latex particles formed and in the rate of emulsion polymerization as the surfactant concentration is increased through the critical micelle concentration; this accounts for the large increases reported, because the lower members of the homologous series are below their critical micelle concentrations in most of the published studies. When a common concentration is chosen that is above the critical micelle concentration even for the lowest member of the series, only a relatively small increase in latex particle number and rate of emulsion polymerization with alkyl chain length of the surfactant is observed. This is attributable to an increase in the concentration of surfactant micelles. Good agreement with Gardon's theory is obtained when the concentration of micellar surfactant is used instead of the total surfactant concentration. 相似文献
3.
A. D. Dunn 《Journal of heterocyclic chemistry》1984,21(4):961-964
The reaction between methyl 2-cyanobenzoate and its pyridine analogues gave isoindolin-3-ones, phthalazin-4(3H)-ones and their corresponding aza analogues. Some reactions of 1-benzylaminoiminoisoindolin-3-one 5b were investigated. 相似文献
4.
Battaglia TM Dunn EE Lilley MD Holloway J Dable BK Marquardt BJ Booksh KS 《The Analyst》2004,129(7):602-606
The development of a field portable fiber optic Raman system modified from commercially available components that can operate remotely on battery power and withstand the corrosive environment of the hydrothermal vents is discussed. The Raman system is designed for continuous monitoring in the deep-sea environment. A 785 nm diode laser was used in conjunction with a sapphire ball fiber optic Raman probe, single board computer, and a CCD detector. Using the system at ambient conditions the detection limits of SO(4)(2-), CO(3)(2-) and NO(3)(-) were determined to be approximately 0.11, 0.36 and 0.12 g l(-1) respectively. Mimicking the cold conditions of the sea floor by placing the equipment in a refrigerator yielded slightly worse detection limits of approximately 0.16 g l(-1) for SO(4)(-2) and 0.20 g l(-1) for NO(3)(-). Addition of minerals commonly found in vent fluid plumes also decreased the detection limits to approximately 0.33 and 0.34 g l(-1) respectively for SO(4)(-2) and NO(3)(-). 相似文献
5.
The reactions of halopyridines containing an electron withdrawing group (-CN, -CO2R,-COMe, -NO2) with sulphur nucleophiles is reported. 相似文献
6.
Physical and chemical strategies that place designed molecules in spatially separated regions of surfactant-templated mesostructured silicate thin films are used to prepare films containing rhodamine 6G (R6G), lanthanide complexes, and both simultaneously. Fluorescence and photoexcitation spectra of R6G in amorphous and structured thin films show that it is located inside the surfactant micelles of structured thin films. A silylated ligand that binds lanthanides condenses to form part of the silica framework and causes the lanthanide to localize in the silica. Luminescence and photoexcitation spectra show that energy transfer from the metal complex to R6G occurs in the films. R6G quenches Tb emission in a concentration-dependent manner. Energy transfer efficiency is calculated using the Tb luminescence lifetime, and this quantity is used to calculate the distance between Tb and R6G with the aid of Forster theory. 相似文献
7.
J. G. Dunn A. C. Chamberlain N. G. Fisher J. Avraamides 《Journal of Thermal Analysis and Calorimetry》1997,49(3):1399-1408
The thermal decomposition of SEX in a nitrogen atmosphere was studied by coupled thermogravimetry-Fourier transform infrared spectroscopy (TG-FTIR), and by pyrolysis-gas chromatography-mass spectrometry (py-GC-MS). The TG curve exhibited two discrete mass losses of 45.8% and 17.8% respectively, at 200 and 257–364°C. The evolved gases identified as a result of the first mass loss were carbonyl sulfide (COS), ethanol (C2H5OH), ethanethiol (C2H5SH), carbon disulfide (CS2), diethyl sulfide ((C2H5)2S), diethyl carbonate ((C2H5O)2CO), diethyl disulfide ((C2H5)2S2), and carbonothioic acid, O, S, diethyl ester ((C2H5S)(C2H5O)CO). The gases identified as a result of the second mass loss were carbonyl sulfide, ethanethiol, and carbon disulfide. Hydrogen sulfide was detected in both mass losses by py-GC-MS, but not detected by FTIR. The solid residue was sodium hydrogen sulfide (NaSH).SEX was adsorbed onto activated carbon, and heated in nitrogen. Two discrete mass losses were still observed, but in the temperature ranges 100–186°C (7.8%) and 186–279°C (11.8%). Carbonyl sulfide and carbon disulfide were now the dominant gases evolved in each of the mass losses, and the other gaseous products were relatively minor. It was demonstrated that water adsorbed on the carbon hydrolysed the xanthate to cause the first mass loss, and any unhydrolysed material decomposed to give the second mass loss.Mr. N. G. Fisher would like to thank the A. J. Parker CRC for Hydrometallurgy for the provision of a PhD scholarship. 相似文献
8.
G. C. Farrington B. Dunn J. O. Thomas 《Applied Physics A: Materials Science & Processing》1983,32(3):159-161
The entire sodium ion content of sodium alumina (Na1.67Mg0.67Al10.33O17) can be replaced with a variety of lanthanide ions by simple diffusion reactions at moderate temperatures (500–700°C). Lanthanide alumina crystals are hard, clear, chemically stable, and have well-defined crystal structures. The fluorescence spectrum of Nd3+ in alumina is similar to that in YAG. The lifetime of the4
F
3/2 state of Nd3+ in completely-exchanged alumina (350s at 1021 Nd3+ cm–3) is about 45% longer than in YAG (240s at 1020Nd3+ cm–3). The lanthanide aluminas may be of considerable interest as new phosphor and laser host materials. 相似文献
9.
Yang Nan Subhash P. Upadhyaya Wei Xu Kathrine E. Hughes William J. Dunn Ludwig Bauer Hemendra N. Bhargava George A. Doss 《Journal of heterocyclic chemistry》1996,33(2):399-407
A number of (E)-7-arylidenenaltrexones were synthesized by azeotropic distillation of water from a benzene solution of naltrexone and an aromatic aldehyde (benzaldehyde, 4-chloro- and 4-fluorobenzaldehyde, 3-and 4-pyridinecarboxaldehyde and 1-methyl-2-imidazolecarboxaldehyde) using piperidine as a catalyst. In addition, (E)-7-benzylidenenaloxone was prepared by the previously published Claisen-Schmidt condensation using sodium hydroxide in methanol. The stereochemistry of these arylidene derivatives 3–9 was determined to be (E) by means of nuclear Overhauser enhancement experiments. The 13C nmr spectra of (E)- 3–9 are recorded in deuteriochloroform and those of the hydrochlorides in deuteriodimethyl sulfoxide. 相似文献
10.
Measuring the metabolome: current analytical technologies 总被引:44,自引:0,他引:44
The post-genomics era has brought with it ever increasing demands to observe and characterise variation within biological systems. This variation has been studied at the genomic (gene function), proteomic (protein regulation) and the metabolomic (small molecular weight metabolite) levels. Whilst genomics and proteomics are generally studied using microarrays (genomics) and 2D-gels or mass spectrometry (proteomics), the technique of choice is less obvious in the area of metabolomics. Much work has been published employing mass spectrometry, NMR spectroscopy and vibrational spectroscopic techniques, amongst others, for the study of variations within the metabolome in many animal, plant and microbial systems. This review discusses the advantages and disadvantages of each technique, putting the current status of the field of metabolomics in context, and providing examples of applications for each technique employed. 相似文献