Abstract. In response to increasing calls for the reform of the undergraduate science curriculum for life science majors and pre-medical students (Bio2010, Scientific Foundations for Future Physicians, Vision & Change), an interdisciplinary team has created NEXUS/Physics: a repurposing of an introductory physics curriculum for the life sciences. The curriculum interacts strongly and supportively with introductory biology and chemistry courses taken by life sciences students, with the goal of helping students build general, multi-discipline scientific competencies. In order to do this, our two-semester NEXUS/Physics course sequence is positioned as a second year course so students will have had some exposure to basic concepts in biology and chemistry. NEXUS/Physics stresses interdisciplinary examples and the content differs markedly from traditional introductory physics to facilitate this. It extends the discussion of energy to include interatomic potentials and chemical reactions, the discussion of thermodynamics to include enthalpy and Gibbs free energy, and includes a serious discussion of random vs. coherent motion including diffusion. The development of instructional materials is coordinated with careful education research. Both the new content and the results of the research are described in a series of papers for which this paper serves as an overview and context.

The one-electron reduction product of nitrate, the NO3 2- radical, was reinvestigated because of the contemporary interest in its reactivity in high-level liquid radioactive systems. Indirect observations suggest that the same dianion is produced by the precursor to the solvated electron. The redox potential of the couple NO3 -/NO3 2- was calculated, using several ab initio approaches combined with semiempirical solvation models, to be E° ≈ −1.1 V vs NHE. Using the theoretical prediction to guide the experiment, we find a value of E° = −0.89 V at zero ionic strength. Kinetic and free-energy-relationship arguments are used to question the acid−base equilibria and reaction mode that converts the NO3 2- to the oxidizing NO2 radical. It is proposed that the reaction of the dianion with various general acids is an O2- (i.e., water or OH-) transfer to the acid and not proton transfer to NO3 2-. Implications of the highly negative redox potential of the dianion and the existence of the protonated forms to practical systems are discussed.