Christopher F. Bauer

Nonmetal excitation in helium, neon, and argon microwave plasmas

Abstract This study has determined which nonmetal emission wavelengths are excited in microwave induced plasmas operated in argon, helium, and neon. Evaluation of the excitation energies associated with the nonmetal wavelengths observed relative to the energies of the rare gas metastable species which may be present in each instance indicates that collisional excitation by the rare gas molecule in the triplet state is most consistent with the data. Although this conclusion is the same as that proposed by B eenakker ( Spectrochim. Acta 32B , 173 (1977)), a detailed consideration shows that other excitation mechanisms may contribute to the observed spectra.

Learning and studying strategies used by general chemistry students with different affective characteristics

Students in general chemistry were partitioned into three groups by cluster analysis of six affective characteristics (emotional satisfaction, intellectual accessibility, chemistry self-concept, math self-concept, self-efficacy, and test anxiety). The at-home study strategies for exam preparation and in-class learning strategies differed among the three groups. Students in the high group (strongly positive affective characteristics) were more autonomous learners, reporting they understood the notes they took in lecture more frequently than the group with low (more negative) affective characteristics. The high group also relied less on tutors and teaching assistants for help when preparing for exams. Participating in explanatory behavior (with self or other students) was correlated positively with stronger exam performance, whereas rapt attention or assiduous note-taking in lecture was negatively correlated. The high and low affective groups were indistinct in their reports of amount of quality time spent studying, but did differ in their approach to using a practice exam as a resource.

Emissions of vapor-phase fluorine and ammonia from the Columbia coal-fired power plant

Gaseous fluorine and ammonia emissions from two pulverized-coal power plants were measured over a 6-month period. In one unit, emissions contained a median 1.5 mg/scm (standard cubic meter) NH/sub 3/ and 1.9 mg/scm F (86% of available F in coal). For the other unit, lower levels were found: 0.042 mg/scm NH/sub 3/ and 0.22 mg/scm F (4.2% of available F in coal). Ammonia varied by more than 10 times in each unit and was enhanced in Unit I by addition of ammonium carbonate to improve precipitator efficiency. Fluorine varied less than 50% in each unit. The difference in F between units was related circumstantially to ash content. Daily variation of F and NH/sub 3/ was less than 20%. Neither gas was in sufficient quantity relative to SO/sub 2/ to influence net acidity. Levels of F were comparable to those of other combustion sources and the aluminum industry. On a global scale, coal combustion is not a major source of either F or NH/sub 3/. Among anthropogenic sources, however, it is a significant contributor and may be important locally. In contrast, NH/sub 3/ emissions are negligible.

Variability of particulate trace element emissions from the Columbia coal-fired power plant, Portage, Wisconsin

Abstract Variability of particulate emissions from two pulverized-coal power plants was characterized over a 1 year period. Parameters evaluated for both total particles and 16 individual elements included volume concentrations, mass emission rates, enrichment factors, and size distributions. In general, variations over several weeks or more were much larger than those within a given day. The latter were often less than experimental error. Small particles were strongly enriched in As, Ba, Br, Cr, Se, Sb, and Zn. Weak or no enrichment was observed for Ce, Co, Eu, Fe, Hf, La, Na, Sc, and Th. Concentrations of individual elements varied by as much as 10 times at a given particle size, and the extent of small particle enrichment varied greatly between individual samples. Compositional correlations among submicron particles suggest the importance of coal mineralogy and combustion chemistry in determining behavior. The two combustion units were generally similar in behavior, although the newer unit often emitted a factor of 3 less particulate mass with somewhat smaller particle size. The Washington Mark III impactor with Teflon substrates adequately separated particles in lower stages but did not prevent small particles from being trapped on the upper stages.

Student perceptions of immediate feedback testing in student centered chemistry classes

Feedback is an important aspect of the learning process. The immediate feedback assessment technique (IF-AT®) form allows students to receive feedback on their answers during a testing event. Studies with introductory psychology students supported both perceived and real student learning gains when this form was used with testing. Knowing that negative student perceptions of innovative classroom techniques can create roadblocks, this research focused on gathering student responses to using IF-AT® forms for testing in general chemistry 1 and organic chemistry 2 classes at several institutions. Students’ perceptions on using the IF-AT® forms and how it influenced their thinking were gathered from a 16-item survey. The results of the student surveys are detailed and implementation strategies for using IF-AT® forms for chemistry testing are also outlined in this article.