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101.
Wahl EH Fidric B Rella CW Koulikov S Kharlamov B Tan S Kachanov AA Richman BA Crosson ER Paldus BA Kalaskar S Bowling DR 《Isotopes in environmental and health studies》2006,42(1):21-35
Recent measurements of carbon isotopes in carbon dioxide using near-infrared, diode-laser-based cavity ring-down spectroscopy (CRDS) are presented. The CRDS system achieved good precision, often better than 0.2 per thousand, for 4% CO2 concentrations, and also achieved 0.15-0.25 per thousand precision in a 78 min measurement time with cryotrap-based pre-concentration of ambient CO2 concentrations (360 ppmv). These results were obtained with a CRDS system possessing a data rate of 40 ring-downs per second and a loss measurement of 4.0 x 10(-11) cm(-1) Hz(-1/2). Subsequently, the measurement time has been reduced to under 10 min. This standard of performance would enable a variety of high concentration (3-10%) isotopic measurements, such as medical human breath analysis or animal breath experiments. The extension of this ring-down to the 2 microm region would enable isotopic analysis at ambient concentrations, which, combined with the small size, robust design, and potential for frequent measurements at a remote site, make CRDS technology attractive for remote atmospheric measurement applications. 相似文献
102.
A Pressure Sensor Using Fiber Bragg Grating 总被引:6,自引:0,他引:6
103.
104.
The magnetization of amorphous antiferromagnetic manganese phosphate glass has been studied as a function of manganese concentration, temperature, and magnetic field. The experimental results are interpreted using a two spin model of amorphous antiferromagnetism where the probability of a given exchange interaction is calculated using crystalline Mn2P2O7 as a structural model. 相似文献
105.
Upon treatment with Fe(CO)5 in an aromatic hydrocarbon solvent aromatic acid chlorides gave an mixture of triarlmethane and tetraarylethane. The reaction may proceed via benzaldehyde and diarylmethanol intermediates. A free radical mechanism is proposed. 相似文献
106.
107.
Raman and infrared spectral data have been collected forp-dioxane and solvated and bound nitrate ions for Zn(NO3)2/p-dioxane/water systems. It is concluded that Zn2+ is preferentially solvated by water and that this aquation is also responsible for a lower concentration of ion pairs than is found for methanol/Zn(NO3)2 solutions for which the dielectric constant of the bulk solvent is similar. Values of K1 (M–1), the association constant for Zn(NO3)+, are 0.22±0.02 (2/1 solvent,D=12.6) and 0.071±0.01 (4/1 solvent,D=33.0). The log K1 against 1/D plot is not linear. 相似文献
108.
Mixed halocarborane anions, 1-H-CB11Y5X6- (X, Y = Cl, Br, I), have been prepared by treatment of [Me3NH][1-H-CB11H5X6] (X = Cl, Br, I) with proper halogenating reagents at 180-220 degrees C in a sealed tube in high yield. These new anions are fully characterized by 1H, 13C, and 11B NMR, IR, and negative-ion MALDI MS spectroscopy. Some are further confirmed by single-crystal X-ray analyses. The weakly coordinating nature of these anions is probed by 29Si chemical shifts of the resulting Pri3Si(1-H-CB11Y5X6) compounds. The results suggest that the coordinating ability of these anions is mainly dependent on the substituents at 7-12 positions (namely, X atoms), and the contribution from the upper belt substituents Y is relatively small. These suggestions are consistent with the results obtained from the structural study of silver salts of mixed halo- and perhalocarborane anions. 相似文献
109.
Myeong Soon Park Koon Ha Park Kun Jun Seung Rim Shin Sea Wha Oh 《Journal of heterocyclic chemistry》2002,39(6):1279-1281
2‐(2‐, 3‐, and 4‐Pyridyl)benzoxazole derivatives were prepared in excellent yields by the oxidative cyclization of phenolic Schiff bases with thianthrene cation radical perchlorate in the presence of 2,6‐di‐tert‐butyl‐4‐methylpyridine. 相似文献
110.
Vibrational spectral studies of ion-ion and ion-solvent interactions. I. Zinc nitrate in water 总被引:1,自引:0,他引:1
Raman and infrared line parameters of Zn(NO3)2-H2O systems ranging from dilute solutions (25°C) to ionic liquids of low water content (75°C) are reported. At 25°C the solutions contain a very low concentration of inner sphere [Zn(ONO2)(H2O)5]+, outer sphere [Zn(H2O)6]2+[NO3]–, Zn(H2O)
6
2+
, and NO
3
–
(aq.). In the ionic liquids the ion triplet also exists. Manifestations of a change from the octahedral coordination of zinc to tetrahedral coordination when the water content is very low include the appearance of a 285 cm–1 band from the zinc nitrate bond and a shift to higher frequencies of the band from zinc-water. 相似文献