Dielectrophoretic manipulation of ribosomal RNA

The manipulation of ribosomal RNA (rRNA) extracted from E. coli cells by dielectrophoresis (DEP) has been demonstrated over the range of 3 kHz-50 MHz using interdigitated microelectrodes. Quantitative measurement using total internal reflection fluorescence microscopy of the time dependent collection indicated a positive DEP response characterized by a plateau between 3 kHz and 1 MHz followed by a decrease in response at higher frequencies. Negative DEP was observed above 9 MHz. The positive DEP response below 1 MHz is described by the Clausius-Mossotti model and corresponds to an induced dipole moment of 3300 D with a polarizability of 7.8×10(-32) F m(2). The negative DEP response above 9 MHz indicates that the rRNA molecules exhibit a net moment of -250 D, to give an effective permittivity value of 78.5 ε(0), close to that of the aqueous suspending medium, and a relatively small surface conductance value of ～0.1 nS. This suggests that our rRNA samples have a fairly open structure accessible to the surrounding water molecules, with counterions strongly bound to the charged phosphate groups in the rRNA backbone. These results are the first demonstration of DEP for fast capture and release of rRNA units, opening new opportunities for rRNA-based biosensing devices.     

The organic puppet theatre

For most youngsters, the insides of their bodies are squishy, bloody, mysterious, and hard to understand. Definitely not looked upon as something to love, or even sneak a peek at! Sad commentary on awareness of our own health and well-being.Illustrated by Duane G. Barnhart This article is excerpted from The Organic Puppet Theatreavailable from Night Owl Press, 1537 West Iowa Ave., St. Paul, MN 55108 © 1983.     

Is 'School Effectiveness' Anti-Democratic?

This paper explores the connections between School Effectiveness as a research paradigm and developments in policy and practice. With a particular focus on the English school system, 'effectiveness' is examined as a discourse which underpins the accountability regime, and in terms of its influence on the related field of School Improvement. Anti-democratic tendencies in areas such as school leadership, teacher professionalism, curriculum and pedagogy are related to a failure, at the heart of the 'effectiveness' concept, to give critical consideration to social and educational aims.     

Effects of external reward on paired associate learning in a group setting

A study was conducted to determine the effects of external reward in the form of prizes on the performance of college students in a paired-associate learning task in which subjects were asked to recall a real word associated with a nonsense word. Two groups, one of whom was offered a prize, received the S-R pairs with no aid (no mediators); and two groups, one of whom was offered a prize, received the S-R pairs with a sentence-pictorial aid mediator. Results of two-way ANOVA supported the hypothesis that the No Prize/Aided and No Prize/NonAided groups would exhibit performance of higher quality than the groups offered prizes. The dependent measure was number of correct responses over six trials.     

A matching law analysis of the reinforcing efficacy of wheel running in rats

Previous research has demonstrated that running in a rotating wheel functions as a reinforcer for leverpressing in rats. In these studies, the pattern of responding was similar to the pattern of responding maintained by consummatory reinforcers, such as food and water. The present study investigated quantitative features of responding maintained by running. In previous experiments in which responses were reinforced according to variable-interval (VI) schedules and food and water served as the reinforcer, the equation for a rectangular hyperbola described the relationship between response rate and reinforcement rate. This experiment tested whether this quantitative regularity also applies to leverpressing maintained by the opportunity to run in a wheel. Fourteen male Wistar rats responded on levers for the opportunity to run. In each session, subjects were exposed to a series of VI schedules. An opportunity to run for 60 sec was the reinforcing consequence. Results showed that response rate was a negatively accelerated function of reinforcement rate, and the relationship between these two variables was described well by the equation for a rectangular hyperbola. To further test the similarity between running and consummatory reinforcers, the response requirement and access were manipulated. In previous experiments with food and water, these types of manipulations differentially changed the two parameters of the hyperbola. A similar pattern of results was obtained with wheel running. Thus, the equation appears to apply to running about as well as it does to consummatory reinforcers.     

Generalizability and Validity of the Use of a Case Analysis Assessment to Make Visible the Quality of Teacher Candidates

The use of case analysis as an accountability measure for demonstrating teacher candidates abilities to meet targeted course, institutional, and state teaching standards for student motivation and classroom management was evaluated. The findings supported the generalizability of case analysis ratings made using a standards-based scoring rubric, and the ratings were shown to differentiate levels of performance in accordance with those standards. Support for the content representativeness of the performance assessment was also obtained using criteria suggested by Crocker (1997), including the realism, frequency, necessity, and importance of the targeted teaching behaviors to actual teaching practice. The findings also provided initial support for the predictive validity of the case analysis assessment for appraising candidates overall abilities to manage a public school classroom.