K. Anne Miller, S. Zyto, D. Karger, J. Yoo, and E. Mazur. 2016. “
Analysis of student engagement in an online annotation system in the context of a flipped introductory physics class.” Phys. Rev. Phys. Educ. Res., 12, Pp. 020143:1–12.
Publisher's VersionAbstractWe discuss student participation in an online social annotation forum over two semesters of a flipped, introductory physics course at Harvard University. We find that students who engage in high-level discussion online, especially by providing answers to their peers’ questions, make more gains in conceptual understanding than students who do not. This is true regardless of students’ physics background. We find that we can steer online interaction towards more productive and engaging discussion by seeding the discussion and managing the size of the sections. Seeded sections produce higher quality annotations and a greater proportion of generative threads than unseeded sections. Larger sections produce longer threads; however, beyond a certain section size, the quality of the discussion decreases.
D. Inna Vulis, Y. Li, O. Reshef, P. Muñoz, M. Yin, S. Kita, M. Loncar, and E. Mazur. 2016. “
CMOS-compatible Zero-Index Metamaterial.” In . CLEO: Science and Innovations.
Publisher's VersionAbstractWe present an on-chip Dirac-cone metamaterial with an impedance- matched zero refractive index at lambda = 1550nm. The design is a square array of air holes in 220-nm silicon- oninsulator (SOI) which offers compatibility with complementary metal-oxide-semiconductor (CMOS) technology.
M. Gerhard Moebius, F. Herrera, S. Griesse-Nascimento, O. Reshef, C. C. Evans, G. G. Guerreschi, A. n. Aspuru-Guzik, and E. Mazur. 2016. “
Efficient photon triplet generation in integrated nanophotonic waveguides.” Optics Express, 24, Pp. 9932–9954.
Publisher's VersionAbstractGeneration of entangled photons in nonlinear media constitutes a basic building block of modern photonic quantum technology. Current optical materials are severely limited in their ability to produce three or more entangled photons in a single event due to weak nonlinearities and challenges achieving phase-matching. We use integrated nanophotonics to enhance nonlinear interactions and develop protocols to design multimode waveguides that enable sustained phase-matching for third-order spontaneous parametric down-conversion (TOSPDC). We predict a generation efficiency of 0.13 triplets/s/mW of pump power in TiO2-based integrated waveguides, an order of magnitude higher than previous theoretical and experimental demonstrations. We experimentally verify our device design methods in TiO2 waveguides using third-harmonic generation (THG), the reverse process of TOSPDC that is subject to the same phase-matching constraints. We finally discuss the effect of finite detector bandwidth and photon losses on the energy- time coherence properties of the expected TOSPDC source.
L. Tucker, R. E. Scherr, T. Zickler, and E. Mazur. 2016. “
Exclusively visual analysis of classroom group interactions.” Phys. Rev. Phys. Educ. Res., 12, Pp. 020142-1–020142-9.
Publisher's VersionAbstractLarge-scale audiovisual data that measure group learning are time consuming to collect and analyze. As an initial step towards scaling qualitative classroom observation, we qualitatively coded classroom video using an established coding scheme with and without its audio cues. We find that interrater reliability is as high when using visual data only—without audio—as when using both visual and audio data to code. Also, interrater reliability is high when comparing use of visual and audio data to visual-only data. We see a small bias to code interactions as group discussion when visual and audio data are used compared with video-only data. This work establishes that meaningful educational observation can be made through visual information alone. Further, it suggests that after initial work to create a coding scheme and validate it in each environment, computer-automated visual coding could drastically increase the breadth of qualitative studies and allow for meaningful educational analysis on a far greater scale.
S. H. Chung, M. R. Awal, J. Shay, M. M. McLoed, E. Mazur, and C. V. Gabel. 2016. “
Novel DLK-independent neuronal regeneration in Caenorhabditis elegans shares links with activity-dependent ectopic outgrowth.” Proc. Nat.l Acad. Sci., Pp. –.
AbstractDuring development, a neuron transitions from a state of rapid growth to a stable morphology, and neurons within the adult mammalian CNS lose their ability to effectively regenerate in response to injury. Here, we identify a novel form of neuronal regeneration, which is remarkably independent of DLK-1/DLK, KGB-1/JNK, and other MAPK signaling factors known to mediate regeneration in Caenorhabditis elegans, Drosophila, and mammals. This DLK-independent regeneration in C. elegans has direct genetic and molecular links to a well-studied form of endogenous activity-dependent ectopic axon outgrowth in the same neuron type. Both neuron outgrowth types are triggered by physical lesion of the sensory dendrite or mutations disrupting sensory activity, calcium signaling, or genes that restrict outgrowth during neuronal maturation, such as SAX-1/NDR kinase or UNC-43/CaMKII. These connections suggest that ectopic outgrowth represents a powerful platform for gene discovery in neuronal regeneration. Moreover, we note numerous similarities between C. elegans DLK-independent regeneration and lesion conditioning, a phenomenon producing robust regeneration in the mammalian CNS. Both regeneration types are triggered by lesion of a sensory neurite via reduction of neuronal activity and enhanced by disrupting L-type calcium channels or elevating cAMP. Taken as a whole, our study unites disparate forms of neuronal outgrowth to uncover fresh molecular insights into activity-dependent control of the adult nervous system’s intrinsic regenerative capacity.
N. Lasry, J. Guillemette, M. Dugdale, E. Charles, and E. Mazur. 2016. “
Peut-on apprendre sans désapprendre?” Pédagogie Collégiale, 29, Pp. 27–31.
Publisher's VersionAbstractD’après le romancier français Marcel Proust, «Le véritable voyage de découverte ne consiste pas à chercher de nouveaux paysages, mais à avoir de nouveaux yeux » (Proust, 1923). Ainsi, l’un des principaux objectifs de l’enseignement des sciences est d’aider les étudiants à modifier leur vision du monde. Cela est particulièrement important en physique, car les étudiants ont souvent des idées préconçues qui vont à l’encontre de ce qu’on tente de leur enseigner (Bransford, Brown et Cocking, 2000 ; Knight et Burciaga, 2004 ; Redish, 2003), précisément en ce qui concerne les concepts newtoniens. Parmi ces des décennies (Clement, 1982 ; Halloun et Hestenes, 1985a ; Halloun et Hestenes, 1985b ; Minstrell, 1982 ; Viennot, 1979), on estime qu'un grand nombre sont profondément ancrées dans leur esprit et difficiles à modifier (Dunbar, Fugelsang et Stein, 2007 ; Posner et collab., 1982 ; Vosniadou, 1992 et 1994). Nous pré- sentons ici quelques découvertes qui ont transformé notre propre perception de la façon dont les étudiants apprennent la physique. Plusieurs des idées que nous soumettons pourraient aussi s'appliquer à d'autres disciplines que ce soit dans un programme préuniversitaire ou technique.
O. Reshef, Y. Li, M. Yin, L. Christakis, D. Inna Vulis, P. Muñoz, S. Kita, M. Loncar, and E. Mazur. 2016. “
Phase-Matching in Dirac-Cone-Based Zero-Index Metamaterials.” In . CLEO: Applications and Technology.
Publisher's VersionAbstractUsing nonlinear scattering theory, we simulate nonlinear signal generation in 2-dimensional zero-index metamaterials based on a photonic Dirac cone at the Γ point. We observe unique phase- matching in multiple simultaneous directions as the index approaches zero.