Integrating ICT through multimodal discourse in a primary classroom

Most children talk to their parents about what they learned at school. Parents hear about books read, pictures drawn, stories written and games played. But how often do parents hear of children using ICT to make multimedia stories with a mathematical focus? In this paper the term “multimodality” will be used to describe such activities. Kress (2004) states that multimodality “deals with all the means we have for making meanings – the modes of representation – and considers their specific way of configuring the world.”Although digital technology is now available in most Australian schools, classroom use of such technology is not always creative and meaningful for learners. Recent state and federal government initiatives provide teachers with opportunities to integrate various digital technology applications into their classroom practice. In late 2011 a small research project was conducted with a class of Grade 4 students from an outer suburban Melbourne government school. As part of the project students planned and produced a multimedia artefact that explained some aspect of mathematics they had learned during the year.This paper outlines the planning and production of the multimedia artefacts created by the students, together with a brief discussion of some impediments to teacher use of technology that were identified by teachers at the school. Other issues considered include assessment and reporting in multiple subject areas based on one piece of student work, and the balancing of the relative importance of subject areas in integrated projects and tasks. The authors argue for the development and deliberate inclusion of integrated multimodal activities throughout the primary school curriculum

The cycling of carbon into and out of dust

Observational evidence seems to indicate that the depletion of interstellar carbon into dust shows rather wide variations and that carbon undergoes rather rapid recycling in the interstellar medium (ISM). Small hydrocarbon grains are processed in photo-dissociation regions by UV photons, by ion and electron collisions in interstellar shock waves and by cosmic rays. A significant fraction of hydrocarbon dust must therefore be re-formed by accretion in the dense, molecular ISM. A new dust model (Jones et al., Astron. Astrophys., 2013, 558, A62) shows that variations in the dust observables in the diffuse interstellar medium (nH = 1000 cm^3), can be explained by systematic and environmentally-driven changes in the small hydrocarbon grain population. Here we explore the consequences of gas-phase carbon accretion onto the surfaces of grains in the transition regions between the diffuse ISM and molecular clouds (e.g., Jones, Astron. Astrophys., 2013, 555, A39). We find that significant carbonaceous dust re-processing and/or mantle accretion can occur in the outer regions of molecular clouds and that this dust will have significantly different optical properties from the dust in the adjacent diffuse ISM. We conclude that the (re-)processing and cycling of carbon into and out of dust is perhaps the key to advancing our understanding of dust evolution in the ISM.Comment: 14 pages, 6 figure

Normality of orbit closures in the enhanced nilpotent cone

We continue the study of the closures of $GL(V)$-orbits in the enhanced nilpotent cone V\times\cN begun by the first two authors. We prove that each closure is an invariant-theoretic quotient of a suitably-defined enhanced quiver variety. We conjecture, and prove in special cases, that these enhanced quiver varieties are normal complete intersections, implying that the enhanced nilpotent orbit closures are also normal.Comment: 30 page

Observing and measuring the drinking mechanism in cats

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2008.Includes bibliographical references (leaf 25).This study explores the characteristics of the lapping mechanism in domestic cats (Felis catus). Using high-speed video, digital image processing, and weight measurements we quantify data pertaining to the frequency of lapping and the volume of liquid consumed per lap. These observations allow us to suggest a possible mathematical model for cat lapping. The results indicate that cats lap at a rate of 3.54 +/- 0.04 Hz. For the various fluids utilized in this study, the lapping rate was 3.35 +/- 0.05 Hz, 4.11 +/- 0.09 Hz, and 3.64 +/- 0.06 Hz for tuna, water, and yogurt mixtures, respectively. On average, cats were able to ingest 0.14 milliliters of fluid per lap with a standard deviation of 0.04 milliliters. These results show no indication of scooping behavior, and are inconclusive regarding the role of papillae. In the future, this work could contribute to an understanding of a more universal lapping mechanism utilized by various felids and other animals. The fluid mechanism that cats utilize to consume liquid could potentially be applied to a number of engineering applications in the developing field of biomimetics.by Anthony Jones.S.B

Destruction of Interstellar Dust in Evolving Supernova Remnant Shock Waves

Supernova generated shock waves are responsible for most of the destruction of dust grains in the interstellar medium (ISM). Calculations of the dust destruction timescale have so far been carried out using plane parallel steady shocks, however that approximation breaks down when the destruction timescale becomes longer than that for the evolution of the supernova remnant (SNR) shock. In this paper we present new calculations of grain destruction in evolving, radiative SNRs. To facilitate comparison with the previous study by Jones et al. (1996), we adopt the same dust properties as in that paper. We find that the efficiencies of grain destruction are most divergent from those for a steady shock when the thermal history of a shocked gas parcel in the SNR differs significantly from that behind a steady shock. This occurs in shocks with velocities >~ 200 km/s for which the remnant is just beginning to go radiative. Assuming SNRs evolve in a warm phase dominated ISM, we find dust destruction timescales are increased by a factor of ~2 compared to those of Jones et al. (1996), who assumed a hot gas dominated ISM. Recent estimates of supernova rates and ISM mass lead to another factor of ~3 increase in the destruction timescales, resulting in a silicate grain destruction timescale of ~2-3 Gyr. These increases, while not able resolve the problem of the discrepant timescales for silicate grain destruction and creation, are an important step towards understanding the origin, and evolution of dust in the ISM.Comment: 30 pages, 8 figures, accepted for publication in the Astrophysical Journa

Interplay of dust alignment, grain growth and magnetic fields in polarization: lessons from the emission-to-extinction ratio

Polarized extinction and emission from dust in the interstellar medium (ISM) are hard to interpret, as they have a complex dependence on dust optical properties, grain alignment and magnetic field orientation. This is particularly true in molecular clouds. The data available today are not yet used to their full potential. The combination of emission and extinction, in particular, provides information not available from either of them alone. We combine data from the scientific literature on polarized dust extinction with Planck data on polarized emission and we use them to constrain the possible variations in dust and environmental conditions inside molecular clouds, and especially translucent lines of sight, taking into account magnetic field orientation. We focus on the dependence between \lambda_max -- the wavelength of maximum polarization in extinction -- and other observables such as the extinction polarization, the emission polarization and the ratio of the two. We set out to reproduce these correlations using Monte-Carlo simulations where the relevant quantities in a dust model -- grain alignment, size distribution and magnetic field orientation -- vary to mimic the diverse conditions expected inside molecular clouds. None of the quantities chosen can explain the observational data on its own: the best results are obtained when all quantities vary significantly across and within clouds. However, some of the data -- most notably the stars with low emission-to-extinction polarization ratio -- are not reproduced by our simulation. Our results suggest not only that dust evolution is necessary to explain polarization in molecular clouds, but that a simple change in size distribution is not sufficient to explain the data, and point the way for future and more sophisticated models

Constraining Coronal Heating: Employing Bayesian Analysis Techniques to Improve the Determination of Solar Atmospheric Plasma Parameters

One way of revealing the nature of the coronal heating mechanism is by comparing simple theoretical one dimensional hydrostatic loop models with observations at the temperature and/or density structure along these features. The most well-known method for dealing with comparisons like that is the $\chi^2$ approach. In this paper we consider the restrictions imposed by this approach and present an alternative way for making model comparisons using Bayesian statistics. In order to quantify our beliefs we use Bayes factors and information criteria such as AIC and BIC. Three simulated datasets are analyzed in order to validate the procedure and assess the effects of varying error bar size. Another two datasets (Ugarte-Urra et al., 2005; Priest et al., 2000) are re-analyzed using the method described above. In one of these two datasets (Ugarte-Urra et al., 2005), due to the error estimates in the observed temperature values, it is not posible to distinguish between the different heating mechanisms. For this we suggest that both Classical and Bayesian statistics should be applied in order to make safe assumptions about the nature of the coronal heating mechanisms

Ritual Awareness, Symbolism and Creativity in Shi Jing Poetics

For more than two thousand years, the collection of poetry simply referred to as the Shi Jing, (“The Classic of Poetry”, “Book of Odes” or “Book of Songs”), has shaped the Chinese literary landscape. The classic is one of the central influences on the development of later Chinese poetry, and can appropriately be considered a major contributor to the habits of expression, imagery and structure which remained dominant until the nineteenth century