The hydrolysis reactions of three (2-deoxy-/?-D-glucopyranosyl)pyridinium salts exhibit first-order rate constants that are independent of pH in the range of 4.4-10.1 pH units. Derived second-order rate constants for the hydrolysis reactions of (2-deoxy-/J-D-glucopyranosyl)-4'-bromoisoquinolinium bromide (5b) conducted in the presence of nucleophilic monoanions (µ = 2.0) including AcO-, Cl-, Br-, and N3-exhibit a Swain-Scott parameter (s) of 0.03 ± 0.05, indicating that these reactions show no sensitivity to the nature of the anion. However, a substantial quantity of the (2-deoxyglucopyranosyl)pyridinium salt hydrolysis product is formed as a result of a post-ratelimiting reaction involving a nucleophilic anion. Analysis of the product ratios indicates that the first-formed intermediate in the hydrolytic reaction is a solvent-separated ion painmolecule encounter complex. The data allow a calculated estimate of greater than 2.5 x 10-12 s for the lifetime of the glucopyranosyloxocarbenium ion in aqueous solution.

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Student self-evaluations have considerable potential in helping students become better learners. The present study was one teacher's first attempt to understand the role of students' self evaluations of their process and products in a science unit centred on open-ended projects. The research was interpretive and attempted to construct meanings relevant to the participants in the classroom. The data collected for this study included video tapes, transcripts of the videotapes, student self-reflection and self-evaluation writings, student project reports, student interviews, discussions with parents, teacher notes and observations, teaching assistant notes and observations and the assignment outlines. This article provides an interesting perspective on the social structure in student group self evaluation and a better understanding of the important role students' selfevaluations can play as part of an open-ended project learning environment.Evaluation of students' work is central to schooling. However, grading can be seen as an insidious technology that does more harm than good: it is used to stratify students into hierarchies which, because of the middle-class values on which they are built, are inherently biased against those from economically less fortunate classes (Foucault, 1975;Postman, 1992). The end effect is that grading systems shake some students out of the race for a reduced number of coveted spots at university . Evaluation, and grading as one of its embodiments, has, as all technologies, a significant political component.There exist a number of serious critiques of evaluation, especially of grading practices which relegate object status to students and, in their wake, have deleterious effects on students' constructions of Self (Roth, 1996; Roth & McGiun, 1998). For example, research in our group has shown that any single test in science is likely to be insufficient to assess students' competencies related to some science topic (McGiun & Roth, 1998;Welzel & Roth, 1998). What may be worse for many, different testing formats and social conditions show that competence, rather than being a uniform construct, is likely to vary with changing conditions so that it makes more sense to consider competence as having a heterogeneous topology within individuals and across settings (Roth, 1998d). On the other hand, involving students in the evaluation process can have some beneficial overall effects on student learning, views of the learning environment, and their levels of engagement (Roth, 1998c). Students become more active learners by setting their own targets, they are more thoughtful and creative due to ownership over all aspects of their project, and they display a greater vested interest in their own completion and their peers' completion of the criteria theyhelped to establish (Harris, 1997;Stefani, 1998).Teachers who work within educational systems do not have the option of broadly changing evaluation and grading practices from one day to the next. However, they do have the option to incorporate el...