Just-in-Time Teaching (JiTT) is an innovative method that enables faculty to increase interactivity in the classroom and engage students in learning. By creating a feedback loop between students' work at home and the classroom setting, time on task is improved in both quality and quantity. This paper includes an introduction to JiTT and evidence of its effectiveness. It concludes with a discussion of our efforts to disseminate JiTT since it was developed in the 1990's.
We have fabricated samples of the form YBaz(Cup9Ap/)306+r where A =Ti, Cr, Mn, Fe, Co, Ni, Cu, and Zn. The superconducting state was investigated by both resistance and magnetization measurements.In addition, the magnetic susceptibility above T, has been measured. T, was found to be strongly correlated with the size of the paramagnetic moments, largely due to scattering from the magnetic sites. In the sample containing Zn, however, T, was dramatically reduced due to fl. lling of the antibonding d band.Recently, the structure and composition of the single phase responsible for the high transition temperature (T, =94 K) superconductivity in the Y-Ba-Cu-0 system has been determined. ' The structure is a cuprate perovskite with composition YBa2Cu306~y (the l-2-3 compound). Interestingly, the superconductivity remains essentially unaff'ected by the substitution of Y with isoelectronic rate-earth elements that have a large localized magnetic moment. This has led to the conclusion that the superconductivity in this class of materials is confined to the Cu02-Ba-Cu02 layer assembly. In addition, the expected local density of states at the Fermi level, DOS(EF), should be small around the Ba + and Y3+ sites because of the stable Xe and Kr core electron structure. Thus, the main contribution to the DOS(EF) comes from the Cu d band and the spd hybridization states due to the Cu and 0 ions. Substitution of Cu with metallic elements should produce substantial changes in the superconducting properties which in turn allows the nature of the high-T, superconductivity and electronic structure to be elucidated.The ionic size and orbital structure of the 3d elements are close to those of Cu; we expect that the 3d elements will occupy the Cu sites if they are substituted into the 1-2-3 structure. We have taken the 1-2-3 system and performed a systematic substitution of the 3d elements for 10% of the Cu ions. The samples are represented by YBa2(Cuo9Ao~)30s+y, where A =Ti, Cr, Mn, Fe, Co, Ni, and Zn. This level of substitution provides a sizable change in T, in each case, but is not large enough to destroy superconductivity.A strong correlation between superconductivity and the electronic and magnetic behavior of the substituting elements has been observed.All of the samples were prepared by using the solidstate reaction method. Y203, BaCO3, CuO, and other 3d oxides were mixed, pressed, and sintered in the appropriate proportions under identical conditions. The sintering process was carried out at 950'C in an oxygen atmosphere with a few intermediate grindings. The parent sample YBa2Cu306+y was also made for comparison. The resistance of the samples was determined by using a standard four-wire probe with a computer controlled data-acquisition system. T, was chosen to be the midpoint of the superconducting transition. Magnetic susceptibility was measured with a SQUID magnetometer in the temperature range 5-400 K. X-ray diffraction revealed that the samples were all single phased, with the same perovskite-type structure as in the 1-2-3...
Discussion forums provide a channel for students to engage with peers and course material outside of class, accessible even to commuter and non-traditional populations. As such, forums can build classroom community as well as aid learning, but students do not always take up these tools. We use network analysis to compare three semesters of forum logs from an introductory calculus-based physics course. The networks show dense structures of collaboration that differ significantly between semesters, even though aggregate participation statistics remain steady. After characterizing network structure for each semester, we correlate centrality with final course grade. Finally, we use a backbone extraction procedure to clean up "noise" in the network and clarify centrality/grade correlations. We find that network centrality is positively linked with course success in the two semesters with denser forum networks, and is a more reliable indicator than non-network measures such as post count. Backbone extraction destroys these correlations, suggesting that the "noise" is in fact signal and further analysis of the discussion transcripts is required.
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