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41.
Daixin Tong Keith D. Bartle Anthony A. Clifford Robert E. Robinson 《Journal of separation science》1992,15(8):505-509
A unified approach to sequential gas and supercritical fluid Chromatography using 50 μm i.d. open tubular columns is described. Sample introduction is performed by means of a rotary injection valve. In order that linear velocities can be optimized independently, a second rotary valve in the chromatographic oven is used to direct the flow of column eluate to the flame ionization detector through either fused silica tubing in GC, or a frit restrictor in SFC. Applications of sequential GC-SFC on a 50 μm i.d. open tubular column are demonstrated, and comparisons made between sequential GC-SFC on 50 and 100 μm i.d. columns. 相似文献
42.
Karen L. Frindell Matthew R. Robinson Alois Popitsch 《Journal of solid state chemistry》2003,172(1):81-88
Selected photoluminescence in the wavelength range of 600-1540 nm is generated by energy transfer from a light-gathering mesostructured host lattice to an appropriate rare earth ion. The mesoporous titania thin films, which have a well-ordered pore structure and two-phase walls made of amorphous titania and TiO2 nanocrystallites, were doped with up to 8 mol% lanthanide ions, and the ordered structure of the material was preserved. Exciting the titania in its band gap results in energy transfer and it is possible to observe photoluminescence from the crystal field states of the rare earth ions. This process is successful for certain rare earth ions (Sm3+, Eu3+, Yb3+, Nd3+, Er3+) and not for others (Tb3+, Tm3+). A mechanism has been proposed to explain this phenomenon, which involves energy transfer through surface states on titania nanocrystals to matching electronic states on the rare earth ions. 相似文献
43.
44.
Experimental data on initial hydrate formation conditions have been obtained for the nitrogen-propane-water system in the L1HG, L1L2H, and L1L2HG regions, where L1 is the water rich liquid phase, L2 is the hydrocarbon rich liquid phase, H is the hydrate and the G is the vapor phase. The measurements covered a range of temperatures from about 275 to 293 K and pressures from about 0.3 to 17.0 MPa. The concentrations covered for the L1HG region extended from 0.94 to 75.0 mole percent propane in the gas phase, and for the L1L2H region they extended from 83.1 to 99.0 mole percent in the condensed liquid phase. Four-phase measurements were made at concentrations of propane from 18.1 to 71.1 mole percent in the gas phase.The experimental data were used to find a fitted binary interaction parameter for predicting hydrate formation in systems containing nitrogen and propane. 相似文献
45.
L. Zhao L. Robinson R. L. Paul R. R. Greenberg S. L. Miao 《Journal of Radioanalytical and Nuclear Chemistry》2007,271(3):777-782
This paper describes the use of cold-neutron prompt-gamma activation analysis (CNPGAA) to determine carbon, nitrogen, and
phosphorus in the aquatic plant Typha domingensis, commonly known as cattail, during spring and fall seasons. According to studies of the Florida Everglades, cattail replaces
sawgrass as a result of nutrient enrichment from farm water runoff. Nutrient enrichment, especially phosphorus, in sediment
and the water column can lead to undesirable expansion. Early signs of this expansion are apparent in the Apalachicola River
floodplain near Apalachicola, Florida, USA. This research project is designed to use cattails as biomonitors of nutrient enrichment
in the lower Apalachicola River floodplain. Determination of carbon, nitrogen, and phosphorus in cattail using cold neutron
prompt-gamma activation has been developed in our previous studies at the CNPGAA facility at the National Institute of Standards
and Technology (NIST), USA. The results of numerous field samples, collected from the study area during spring and fall seasons
in 2002, will be presented in this paper. 相似文献
46.
Fischer indolisation of 2-aminophenyl ethyl ketone phenylhydrazone using glacial acetic acid saturated with hydrogen chloride as catalyst affords 3-methylindolo(l′:2′-3:4)2-methylquinazoline and 2-(2-aminophenyl)-3-methylindole. The latter compound is autoxidised to 2-(2-amino-phenyl)-3-hydroxy-3-methyl-3H-indole, a reaction which is shown to be dependent upon the presence of the primary amino group at the 2-position of the 2-phenyl substituent and which is much slower than the corresponding autoxidation of 2-(2-hydroxyphenyl)-3-methylindole to 3-hydroxy-2-(2-hydroxyphenyl)-3-methyl-3H-indole previously reported.Nitration of isopropyl phenyl ketone occurs preferentially at the ortho- rather than the meta- positions of the benzene nucleus. 相似文献
47.
Thermogravimetric determination of magnesium,potassium and lead by precipitation with dilituric acid
The thermolysis curves of magnesium, potassium, and lead diliturate have established that either the hydrated or anhydrous forms of these precipitates are stable enough for their gravimetric use to be possible. Magnesium and lead were determined by precipitation with dilituric acid while potassium was precipitated with trimethylamine diliturate. 相似文献
48.
Lee L Wang JX Adzić RR Robinson IK Gewirth AA 《Journal of the American Chemical Society》2001,123(36):8838-8843
X-ray reflectivity, cyclic voltammetry, and scanning tunneling microscopy (STM) are used to examine the structure of alpha-SiW12O4(4-) or silicotungstic acid (STA) adsorbed on Ag(100) in acid solution. The voltammetry shows that STA passivates the Ag surface relative to electron transfer to a solution redox species. STM images reveal the formation of a series of lattice structures, one of which can be associated with a commensurate ( radical13x radical13)R33.69 degrees structural model. X-ray reflectivity measurements show uniquely that STA orients with its four-fold axis perpendicular to the Ag(100) surface and that the center of the STA molecule is 4.90 A above the top layer of the Ag substrate. Analysis of bond lengths leads to a footprint of STA on Ag(100), in which the four terminal O atoms are located near the hollow sites and have a Ag-O bond length of 2.06 A. This bond length is consistent with a strong covalent interaction between STA and the Ag surface. 相似文献
49.
Regioselective and enantiospecific rhodium-catalyzed allylic amination with N-(arylsulfonyl)anilines
[reaction: see text]. The regioselective and enantiospecific rhodium-catalyzed allylic amination of secondary allylic carbonates 1 with N-(arylsulfonyl)anilines provides a convenient process for the construction of arylamines 2. This method, in conjunction with ring-closing metathesis and radical cyclization reactions, allows the direct construction of biologically relevant pharmacophores as exemplified by the construction of dihydroquinoline and dihydrobenzo[b]indoline derivatives. 相似文献
50.