478 research outputs found
Linking engagement and performance: The social network analysis perspective
Theories developed by Tinto and Nora identify academic performance, learning
gains, and involvement in learning communities as significant facets of student
engagement that, in turn, support student persistence. Collaborative learning
environments, such as those employed in the Modeling Instruction introductory
physics course, provide structure for student engagement by encouraging
peer-to-peer interactions. Because of the inherently social nature of
collaborative learning, we examine student interactions in the classroom using
network analysis. We use centrality---a family of measures that quantify how
connected or "central" a particular student is within the classroom
network---to study student engagement longitudinally. Bootstrapped linear
regression modeling shows that students' centrality predicts future academic
performance over and above prior GPA for three out of four centrality measures
tested. In particular, we find that closeness centrality explains 28 % more of
the variance than prior GPA alone. These results confirm that student
engagement in the classroom is critical to supporting academic performance.
Furthermore, we find that this relationship for social interactions does not
emerge until the second half of the semester, suggesting that classroom
community develops over time in a meaningful way
On the Number of Balanced Words of Given Length and Height over a Two-Letter Alphabet
We exhibit a recurrence on the number of discrete line segments joining two
integer points in the plane using an encoding of such segments as balanced
words of given length and height over the two-letter alphabet . We
give generating functions and study the asymptotic behaviour. As a particular
case, we focus on the symmetrical discrete segments which are encoded by
balanced palindromes.Comment: 24 page
Neural Posterior Estimation with Differentiable Simulators
Simulation-Based Inference (SBI) is a promising Bayesian inference framework
that alleviates the need for analytic likelihoods to estimate posterior
distributions. Recent advances using neural density estimators in SBI
algorithms have demonstrated the ability to achieve high-fidelity posteriors,
at the expense of a large number of simulations ; which makes their application
potentially very time-consuming when using complex physical simulations. In
this work we focus on boosting the sample-efficiency of posterior density
estimation using the gradients of the simulator. We present a new method to
perform Neural Posterior Estimation (NPE) with a differentiable simulator. We
demonstrate how gradient information helps constrain the shape of the posterior
and improves sample-efficiency.Comment: Accepted at the ICML 2022 Workshop on Machine Learning for
Astrophysic
The Relationship Between Molecular Gas, HI, and Star Formation in the Low-Mass, Low-Metallicity Magellanic Clouds
The Magellanic Clouds provide the only laboratory to study the effect of
metallicity and galaxy mass on molecular gas and star formation at high (~20
pc) resolution. We use the dust emission from HERITAGE Herschel data to map the
molecular gas in the Magellanic Clouds, avoiding the known biases of CO
emission as a tracer of H. Using our dust-based molecular gas estimates,
we find molecular gas depletion times of ~0.4 Gyr in the LMC and ~0.6 SMC at 1
kpc scales. These depletion times fall within the range found for normal disk
galaxies, but are shorter than the average value, which could be due to recent
bursts in star formation. We find no evidence for a strong intrinsic dependence
of the molecular gas depletion time on metallicity. We study the relationship
between gas and star formation rate across a range in size scales from 20 pc to
~1 kpc, including how the scatter in molecular gas depletion time changes with
size scale, and discuss the physical mechanisms driving the relationships. We
compare the metallicity-dependent star formation models of Ostriker, McKee, and
Leroy (2010) and Krumholz (2013) to our observations and find that they both
predict the trend in the data, suggesting that the inclusion of a diffuse
neutral medium is important at lower metallicity.Comment: 24 pages, 14 figures, accepted for publication in ApJ. FITS files of
the dust-based estimates of the H2 column densities for the LMC and SMC
(shown in Figures 2 and 3) will be available online through Ap
Haplotype Network Branch Diversity, a New Metric Combining Genetic and Topological Diversity to Compare the Complexity of Haplotype Networks
A common way of illustrating phylogeographic results is through the use of haplotype networks. While these networks help to visualize relationships between individuals, populations, and species, evolutionary studies often only quantitatively analyze genetic diversity among haplotypes and ignore other network properties. Here, we present a new metric, haplotype network branch diversity (HBd), as an easy way to quantifiably compare haplotype network complexity. Our metric builds off the logic of combining genetic and topological diversity to estimate complexity previously used by the published metric haplotype network diversity (HNd). However, unlike HNd which uses a combination of network features to produce complexity values that cannot be defined in probabilistic terms, thereby obscuring the values’ implication for a sampled population, HBd uses frequencies of haplotype classes to incorporate topological information of networks, keeping the focus on the population and providing easy-to-interpret probabilistic values for randomly sampled individuals. The goal of this study is to introduce this more intuitive metric and provide an R script that allows researchers to calculate diversity and complexity indices from haplotype networks. A group of datasets, generated manually (model dataset) and based on published data (empirical dataset), were used to illustrate the behavior of HBd and both of its terms, haplotype diversity, and a new index called branch diversity. Results followed a predicted trend in both model and empirical datasets, from low metric values in simple networks to high values in complex networks. In short, the new combined metric joins genetic and topological diversity of haplotype networks, into a single complexity value. Based on our analysis, we recommend the use of HBd, as it makes direct comparisons of network complexity straightforward and provides probabilistic values that can readily discriminate situations that are difficult to resolve with available metrics
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