Introduction to the Geometer’s Angle

Geometer Rachel Fletcher introduces the Geometer’s Angle, a column in the Nexus Network Journal dedicated to geometrical constructions, the procedures for drawing them, their use, significance and symbolism.     

Characterization of polar organic compounds in the organic film on indoor and outdoor glass windows

Organic films on an impervious surface (window glass) were sampled at paired indoor-outdoor sites in July 2000 and characterized for their paraffinic and polar organic compositions along an urban-rural transect. Four classes of polar compounds (C11-C31 aliphatic monocarboxylic, C6-C14 dicarboxylic, nine aromatic polycarboxylic, and five terpenoid acids) constituted between 81 and 95% (w/w) of the total organic fraction analyzed comprising n-alkanes (C10-C36), 46 PAH, 97 PCBs, and 18 OC pesticides. Concentrations of the polar compounds plus their precursors, n-alkanes, ranged from 8 to 124 microg m(-20 and were dominated by monocarboxylic acids (67-89%, w/w). On outdoor windows, n-alkanes, aromatic acids, and terpenoid acids decreased in concentration along the urban-rural transect. The carbon preference index values and the interpretations of individual compounds indicate that the main sources of n-alkanes were plant waxes followed by petrogenic sources; monocarboxylic and dicarboxylic acids were from plant waxes and animal fats. Results of principal component analysis showed closer correspondence between outdoor and indoor signatures than among locations. In outdoor films, these compounds are suggested to play an important role in mediating chemical fate in urban areas by air-film exchange and facilitating "wash-off" due to their surfactant-like properties. In indoor films, these compounds provide a medium for the accumulation of more toxic compounds.     

Application of regional earthquake mitigation optimization

A linear program was developed to help seismically active communities decide: (1) how much to spend on pre-earthquake mitigation that aims to reduce future losses versus waiting until after an event and paying for reconstruction, and (2) which of the many possible mitigation activities to fund so as to minimize overall risk. The mitigation alternatives considered are structural upgrading policies for groups of buildings. Benefits of mitigation are losses avoided in future earthquakes, including structural, non-structural, contents, and time-related losses, and casualties. The model is intended to be used as a tool to support the public regional mitigation planning process. In realistic applications, the model includes millions of variables, thus requiring a special solution method. This paper focuses on two efficient solution algorithms to solve the model—a Dantzig–Wolfe decomposition algorithm and a greedy heuristic algorithm. A comprehensive numerical study compares the two algorithms in terms of solution quality and solution time. The study shows that, compared to the Dantzig–Wolfe algorithm, the heuristic algorithm is much faster as expected, and provides comparable solution quality.     

Mexican American middle school students' goal intentions in mathematics and science: A test of social cognitive career theory.

This study examined whether sociocontextual and sociocognitive variables explained the math/science goals of 409 Mexican American youth using a modified version of R. W. Lent, S. D. Brown, and G. Hackett's (1994) social cognitive career theory. Results from structural equation modeling indicated that the hypothesized model explained a significant amount of variance in math/science goals for both Mexican American girls and boys. Findings suggested that gender did not moderate relations among the variables in the hypothesized model. Results also suggested that most of the social cognitive career theory propositions tested were supported. Specifically, social class predicted math/science past performance accomplishments. Math/science past performance accomplishments and perceived parent support predicted math/science self-efficacy. Furthermore, math/science self-efficacy predicted math/science outcome expectations, and together with math/science interests, these sociocognitive variables predicted math/science interests and goals. Contrary to expectations, generation status, Anglo orientation, and Mexican orientation did not predict math/science past performance accomplishments, and past performance accomplishments did not predict math/science outcome expectations. Furthermore, Anglo orientation and perceived social support from parents, teachers, classmates, and a close friend did not predict math/science goals. Suggestions for future research and implications of the results are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effects of emotional content on reality-monitoring performance in young and older adults.

Reality monitoring refers to a person's ability to distinguish between perceived and imagined events. Prior research has demonstrated that young adults show a reality-monitoring advantage for negative arousing information as compared with neutral information. The present research examined whether this reality-monitoring benefit extends to positive information in young adults and whether older adults show a reality-monitoring advantage for emotional information of either valence. Two studies revealed no evidence for a reality-monitoring advantage for positive information; in both age groups, the reality-monitoring advantage existed only for negative information. Older adults were, however, more likely to remember that a positive item had been included on a study list than they were to remember that a nonemotional item had been studied. Young adults did not show this mnemonic enhancement for positive information. These results indicate that although older adults may show some mnemonic benefits for positive information (i.e., an enhanced ability to remember that a positive item was studied), they do not always show enhanced memory for source-specifying details of a positive item's presentation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)