The gas phase infrared spectra of the hydrated hydronium cluster ions H3O+⋅(H2O)n(n=1, 2, 3) have been observed from 3550 to 3800 cm−1. The new spectroscopic method developed for this study is a two color laser scheme consisting of a tunable cw infrared laser with 0.5 cm−1 resolution used to excite the O–H stretching vibrations and a cw CO2 laser that dissociates the vibrationally excited cluster ion through a multiphoton process. The apparatus is a tandem mass spectrometer with a radio frequency ion trap that utilizes the following scheme: the cluster ion to be studied is first mass selected; spectroscopic interrogation then occurs in the radio frequency ion trap; finally, a fragment ion is selected and detected using ion counting techniques. The vibrational spectra obtained in this manner are compared with that taken previously using a weakly bound H2 ‘‘messenger.’’ A spectrum of H7 O+3 taken using a neon messenger is also presented. Ab initio structure and frequency predictions by Remington and Schaefer are compared with the experimental results.

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This study presents the results of four experiments in the framework of processing instruction conducted with four language learner groups (Spanish, n ¼ 43; German, n ¼ 46; Russian, n ¼ 44; and French, n ¼ 48; discussed in that order). In each experiment, the processing problem was held constant (the First-Noun Principle) although the structure was unique to the language. The independent variables were explicit information prior to treatment and grammatical sensitivity as measured by the Modern Language Aptitude Test. Two dependent measures were included: (a) trials-to-criterion (how long it took participants to begin processing correctly) and (b) improvement over time (pretest/posttest). Results show that explicit information may be useful for the processing of some structures but not others; however, explicit information is not necessary. Results also show that grammatical sensitivity does not significantly correlate with any of the measures under any conditions except for the German group that received explicit information. Our conclusion is that when instructed SLA

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The infrared spectrum of C2H7+ has been obtained from 2500 to 4200 cm™1. The apparatus consists of a tandem mass spectrometer with a radio-frequency octopole ion trap. After initial mass selection of the C2H7+ in a sector magnet, the C2H7+ is spectroscopically probed by using a two-color laser scheme while being trapped under ultrahigh-vacuum conditions.The first laser is scanned from 2500 to 4200 cm™1 and excites a C-H stretching vibration. The second laser is a continuous-wave C02 laser and is used to dissociate the vibrationally excited parent ions through a multiphoton process. The fragment ion Hariharan et al.4-5.7

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Abstract. The case-based reasoning (CBR) methodology can be augmented with the ability to determine the confidence in the correctness of individual solutions. A confidence calculation can be added to the REUSE portion of the CBR methodology. The confidence calculation takes confidence indicators, like "number of cases retrieved with best solution" and "average similarity of cases which suggest an alternative solution," and generates a confidence value. The information gain algorithm C4.5 can be used to select the best confidence indicators by evaluating their usefulness in historical cases. A genetic algorithm can be used to optimize and maintain the confidence calculation.

ChemInform Abstract Using a new spectroscopic method, the gas phase IR spectra of the title cluster ions, produced in a high pressure corona discharge source, are observed between 3550 and 3800 cm-1. The spectroscopic method is a two color laser scheme consisting of a tunable cw IR laser with 0.5 cm-1 resolution used to excite the O-H stretching vibrations and a cw CO2 laser that dissociates the vibrationally excited cluster ion through a multiphoton process. The dissociation products are detected by combination of a tandem mass spectrometer and a rf ion trap. The spectra are compared with the previously taken spectra of H5O2+•H2, H7O3+•H2, H9O4+•H2, and H7O3+•Ne. A comparison with vibrational frequencies calculated using ab initio methods by Remington and Schaefer (unpublished) s also made.