Negative Energy: Why Interdisciplinary Physics Requires Multiple Ontologies

Much recent work in physics education research has focused on ontological metaphors for energy, particularly the substance ontology and its pedagogical affordances. The concept of negative energy problematizes the substance ontology for energy, but in many instructional settings, the specific difficulties around negative energy are outweighed by the general advantages of the substance ontology. However, we claim that our interdisciplinary setting (a physics class that builds deep connections to biology and chemistry) leads to a different set of considerations and conclusions. In a course designed to draw interdisciplinary connections, the centrality of chemical bond energy in biology necessitates foregrounding negative energy from the beginning. We argue that the emphasis on negative energy requires a combination of substance and location ontologies. The location ontology enables energies both "above" and "below" zero. We present preliminary student data that illustrate difficulties in reasoning about negative energy, and the affordances of the location metaphor.Comment: 4 pages, submitted to PERC 2013 Proceeding

Chemical energy in an introductory physics course for the life sciences

Energy is a complex idea that cuts across scientific disciplines. For life science students, an approach to energy that incorporates chemical bonds and chemical reactions is better equipped to meet the needs of life sciences students than a traditional introductory physics approach that focuses primarily on mechanical energy. We present a curricular sequence, or thread, designed to build up students' understanding of chemical energy in an introductory physics course for the life sciences. This thread is designed to connect ideas about energy from physics, biology, and chemistry. We describe the kinds of connections among energetic concepts that we intended to develop to build interdisciplinary coherence, and present some examples of curriculum materials and student data that illustrate our approach.Comment: 11 page

Unknowns after the SNO Charged-Current Measurement

We perform a model-independent analysis of solar neutrino flux rates including the recent charged-current measurement at the Sudbury Neutrino Observatory (SNO). We derive a universal sum rule involving SNO and SuperKamiokande rates, and show that the SNO neutral-current measurement can not fix the fraction of solar $\nu_e$ oscillating to sterile neutrinos. The large uncertainty in the SSM $^8$B flux impedes a determination of the sterile neutrino fraction.Comment: Version to appear in PRL; includes analysis with anticipated SNO NC measuremen

Biologia e exigências térmicas do ácaro vermelho Tetranychus gigas Pritchard e Baker em soja.

bitstream/item/71549/1/ID-30974.pd

Uso de metodologia simples por análise de imagens para acompanhamento da proliferação de fungos em frutos fatiados.

bitstream/CNPDIA-2009-09/11851/1/BPD17_2006.pd

Dinâmica populacional do ácaro verde Mononychellus planki em cultivares de soja.

bitstream/item/71543/1/ID-30978.pd

Sterile dark matter and reionization

Sterile neutrinos with masses in the keV range can be the dark matter, and their emission from a supernova can explain the observed velocities of pulsars. The sterile neutrino decays could produce the x-ray radiation in the early universe, which could have an important effect on the formation of the first stars. X-rays could ionize gas and could catalyze the production of molecular hydrogen during the ``dark ages''. The increased fraction of molecular hydrogen could facilitate the cooling and collapse of the primordial gas clouds in which the first stars were formed.Comment: 4 pages, 2 figures, to appear in proceedings of 7th UCLA Symposium on sources and detection of dark matter and dark energy in the universe, 22-24 Feb 2006, Marina de Rey, Californi