"Twenty percent free!": So how much does the original bar weigh?

Ngarewa Hawera and Merilyn Taylor describe a rich task based on a real world situation that stimulated a great deal of mathematical reasoning. Their research on how students attempted the task is most revealing

[Review of] Carol Trosset. Welshness Performed: Welsh Concepts of Person and Society

Wales, ruled by native princes until the thirteenth-century and subsequently governed from London, contains a population of about three million, twenty percent of which speak an indigenous language

Control of nonenzymatic browning in intermediate-moisture foods

Series of compounds called humectants were found to decrease rate of browning when added to intermediate-moisture foods. Twenty percent level of humectant can increase shelf life of foods by factor of 5 or 6

Teaching Students and Teaching Each Other: The Importance of Peer Learning for Teachers

Using longitudinal elementary school teacher and student data, we document that students have larger test score gains when their teachers experience improvements in the observable characteristics of their colleagues. Using within-school and within-teacher variation, we further show that a teacher’s students have larger achievement gains in math and reading when she has more effective colleagues (based on estimated value-added from an out-of-sample preperiod). Spillovers are strongest for less-experienced teachers and persist over time, teachers perform best when they are the weakest of their peer group, and historical peer quality explains away about twenty percent of the own-teacher effect. These results suggest peer learning

Demonstration of negative group delays in a simple electronic circuit

We present a simple electronic circuit which produces negative group delays for base-band pulses. When a band-limited pulse is applied as the input, a forwarded pulse appears at the output. The negative group delays in lumped systems share the same mechanism with the superluminal light propagation, which is recently demonstrated in an absorption-free, anomalous dispersive medium [Wang et al., Nature 406, 277 (2000)]. In this circuit, the advance time more than twenty percent of the pulse width can easily be achieved. The time constants, which can be in the order of seconds, is slow enough to be observed with the naked eye by looking at the lamps driven by the pulses.Comment: 6pages,8 figure

The induced interaction in a Fermi gas with a BEC-BCS crossover

We study the effect of the induced interaction on the superfluid transition temperature of a Fermi gas with a BEC-BCS crossover. The Gorkov-Melik-Barkhudarov theory about the induced interaction is extended from the BCS side to the entire crossover, and the pairing fluctuation is treated in the approach by Nozi\`{e}res and Schmitt-Rink. At unitarity, the induced interaction reduces the transition temperature by about twenty percent. In the BCS limit, the transition temperature is reduced by a factor about 2.22, as found by Gorkov and Melik-Barkhudarov. Our result shows that the effect of the induced interaction is important both on the BCS side and in the unitary region.Comment: 11 pages, 3 figures, to be published in PR

Come ‘RAP’ With Us: Improving the Retention of Academically-Qualified Persons (RAP) with GPAs of 3.0 or Higher

Retention is an important area of concern for Virginia Commonwealth University (VCU). This project involves devising initiatives to identify and retain students with a high potential for academic success as outlined in the Strategic Plan for the Future of Virginia Commonwealth University, Phase II. It is theorized that by concentrating efforts on students (both in-state and out-of-state) with a cummulative GPA of 3.0 or higher, an improvement in the six-year graduation and freshmen retention rates can be realized. This would serve to enhance VCU’s status in the academic community (moving from Tier 3 to Tier 2 status) since twenty percent of the determining ranking of the U.S. News and World Report’s rankings are derived from the category of retention