Contexts for questioning: Two zones of teaching and learning in undergraduate science

This is the author's accepted manuscript. The final published article is available from the link below. Copyright @ Springer Science+Business Media B.V. 2012.Higher education institutions are currently undertaking a challenging process in moving from teacher-orientated to student-focused approaches. Students’ ability to asking questions is fundamental to developing critical reasoning, and to the process of scientific enquiry itself. Our premise is that questioning competences should become a central focus of current reforms in higher education. This study, part of a broader naturalistic research project, aims at developing a theoretical framework for conceptualizing different contexts for questioning, illustrating the application of the proposed framework (contextual questioning zones) and reflecting about some of the dimensions of teaching and learning, for overcoming some of the challenges that higher education institutions are facing presently. The discussion of two ‘opposite’ contexts of enquiry is based on qualitative data, gathered through close collaboration with four teachers of undergraduate biology at a Portuguese university. These teachers were observed during their ‘daily activity’ during an academic year. Data was also gathered by interviewing these teachers and 8 selected students, at the end of the year, and used to sustain the argumentation. The paper concludes with some reflections and suggestions to promote authentic enquiry-based learning experiences.Portuguese Fundação para a Ciência e a Tecnologi

Dynamics of opinion formation in a small-world network

The dynamical process of opinion formation within a model using a local majority opinion updating rule is studied numerically in networks with the small-world geometrical property. The network is one in which shortcuts are added to randomly chosen pairs of nodes in an underlying regular lattice. The presence of a small number of shortcuts is found to shorten the time to reach a consensus significantly. The effects of having shortcuts in a lattice of fixed spatial dimension are shown to be analogous to that of increasing the spatial dimension in regular lattices. The shortening of the consensus time is shown to be related to the shortening of the mean shortest path as shortcuts are added. Results can also be translated into that of the dynamics of a spin system in a small-world network.Comment: 10 pages, 5 figure

The Spread of Opinions and Proportional Voting

Election results are determined by numerous social factors that affect the formation of opinion of the voters, including the network of interactions between them and the dynamics of opinion influence. In this work we study the result of proportional elections using an opinion dynamics model similar to simple opinion spreading over a complex network. Erdos-Renyi, Barabasi-Albert, regular lattices and randomly augmented lattices are considered as models of the underlying social networks. The model reproduces the power law behavior of number of candidates with a given number of votes found in real elections with the correct slope, a cutoff for larger number of votes and a plateau for small number of votes. It is found that the small world property of the underlying network is fundamental for the emergence of the power law regime.Comment: 10 pages, 7 figure

Test beam Characterizations of 3D Silicon Pixel detectors

3D silicon detectors are characterized by cylindrical electrodes perpendicular to the surface and penetrating into the bulk material in contrast to standard Si detectors with planar electrodes on its top and bottom. This geometry renders them particularly interesting to be used in environments where standard silicon detectors have limitations, such as for example the radiation environment expected in an LHC upgrade. For the first time, several 3D sensors were assembled as hybrid pixel detectors using the ATLAS-pixel front-end chip and readout electronics. Devices with different electrode configurations have been characterized in a 100 GeV pion beam at the CERN SPS. Here we report results on unirradiated devices with three 3D electrodes per 50 x 400 um2 pixel area. Full charge collection is obtained already with comparatively low bias voltages around 10 V. Spatial resolution with binary readout is obtained as expected from the cell dimensions. Efficiencies of 95.9% +- 0.1 % for tracks parallel to the electrodes and of 99.9% +- 0.1 % at 15 degrees are measured. The homogeneity of the efficiency over the pixel area and charge sharing are characterized.Comment: 5 pages, 7 figure

Performance of networks of artificial neurons: The role of clustering

The performance of the Hopfield neural network model is numerically studied on various complex networks, such as the Watts-Strogatz network, the Barab{\'a}si-Albert network, and the neuronal network of the C. elegans. Through the use of a systematic way of controlling the clustering coefficient, with the degree of each neuron kept unchanged, we find that the networks with the lower clustering exhibit much better performance. The results are discussed in the practical viewpoint of application, and the biological implications are also suggested.Comment: 4 pages, to appear in PRE as Rapid Com

The old questions are the best: striving against invalidity in qualitative research

This chapter enters an old debate on the shape of validation processes in qualitative research. We discuss a reflective research validation framework related to teaching approaches and practices. The majority of investigations in this area draw mainly on indirect observation, semistructured interviews or the application of questionnaires and inventories. To this extent, only “half-the-story” has been reported. The validation framework here develops a five-part three stage structure, conceptualized as an “iterative-interactive-process,” integrating a set of strategies aimed at the “minimization of invalidity.” The application of the framework is illustrated through a longitudinal study investigating the relationship between classroom questioning practices and teachers’ preferential teaching approaches. Fieldwork in this naturalistic-interpretative research was conducted during four academic years and entailed close collaboration with a group of four university teachers lecturing biology to undergraduates.The authors acknowledge the financial support of Portuguese Fundac¸a˜o para a Cieˆncia e a Tecnologia (SFRH/BD/44611/2008; PTDC/CPE-CED/ 117516/2010).Portuguese Fundac ̧ a ̃ o para a Cieˆ ncia e a Tecnologia (SFRH/BD/44611/2008; PTDC/CPE-CED/ 117516/2010)

Transport Properties of Random Walks on Scale-Free/Regular-Lattice Hybrid Networks

We study numerically the mean access times for random walks on hybrid disordered structures formed by embedding scale-free networks into regular lattices, considering different transition rates for steps across lattice bonds ($F$) and across network shortcuts ($f$). For fast shortcuts ($f/F\gg 1$) and low shortcut densities, traversal time data collapse onto an universal curve, while a crossover behavior that can be related to the percolation threshold of the scale-free network component is identified at higher shortcut densities, in analogy to similar observations reported recently in Newman-Watts small-world networks. Furthermore, we observe that random walk traversal times are larger for networks with a higher degree of inhomogeneity in their shortcut distribution, and we discuss access time distributions as functions of the initial and final node degrees. These findings are relevant, in particular, when considering the optimization of existing information networks by the addition of a small number of fast shortcut connections.Comment: 8 pages, 6 figures; expanded discussions, added figures and references. To appear in J Stat Phy

Node-node distance distribution for growing networks

We present the simulation of the time evolution of the distance matrix. The result is the node-node distance distribution for various kinds of networks. For the exponential trees, analytical formulas are derived for the moments of the distance distribution.Comment: presented during the 37-th Polish Physicists' Meeting, Gdansk, Poland, 15-19 Sep. 2003, 6 pages, 3 figure

A measurement of the 4He(g,n) reaction from 23 < Eg < 70 MeV

A comprehensive set of 4He(g,n) absolute cross-section measurements has been performed at MAX-lab in Lund, Sweden. Tagged photons from 23 < Eg < 70 MeV were directed toward a liquid 4He target, and neutrons were identified using pulse-shape discrimination and the Time-of-flight Technique in two liquid-scintillator detector arrays. Seven-point angular distributions have been measured for fourteen photon energies. The results have been subjected to complementary Transition-coefficient and Legendre-coefficient analyses. The results are also compared to experimental data measured at comparable photon energies as well as Recoil-Corrected Continuum Shell Model, Resonating Group Method, and Effective Interaction Hyperspherical-Harmonic Expansion calculations. For photon energies below 29 MeV, the angle-integrated data are significantly larger than the values recommended by Calarco, Berman, and Donnelly in 1983.Comment: 16 pages, 14 figures, some more revisions, submitted to Physical Review

Hydrogen bond network topology in liquid water and methanol: a graph theory approach

Networks are increasingly recognized as important building blocks of various systems in nature and society. Water is known to possess an extended hydrogen bond network, in which the individual bonds are broken in the sub-picosecond range and still the network structure remains intact. We investigated and compared the topological properties of liquid water and methanol at various temperatures using concepts derived within the framework of graph and network theory (neighbour number and cycle size distribution, the distribution of local cyclic and local bonding coefficients, Laplacian spectra of the network, inverse participation ratio distribution of the eigenvalues and average localization distribution of a node) and compared them to small world and Erdős–Rényi random networks. Various characteristic properties (e.g. the local cyclic and bonding coefficients) of the network in liquid water could be reproduced by small world and/or Erdős–Rényi networks, but the ring size distribution of water is unique and none of the studied graph models could describe it. Using the inverse participation ratio of the Laplacian eigenvectors we characterized the network inhomogeneities found in water and showed that similar phenomena can be observed in Erdős–Rényi and small world graphs. We demonstrated that the topological properties of the hydrogen bond network found in liquid water systematically change with the temperature and that increasing temperature leads to a broader ring size distribution. We applied the studied topological indices to the network of water molecules with four hydrogen bonds, and showed that at low temperature (250 K) these molecules form a percolated or nearly-percolated network, while at ambient or high temperatures only small clusters of four-hydrogen bonded water molecules exist