Ground-based adaptive optics coronagraphic performance under closed-loop predictive control

The discovery of the exoplanet Proxima b highlights the potential for the coming generation of giant segmented mirror telescopes (GSMTs) to characterize terrestrial --- potentially habitable --- planets orbiting nearby stars with direct imaging. This will require continued development and implementation of optimized adaptive optics systems feeding coronagraphs on the GSMTs. Such development should proceed with an understanding of the fundamental limits imposed by atmospheric turbulence. Here we seek to address this question with a semi-analytic framework for calculating the post-coronagraph contrast in a closed-loop AO system. We do this starting with the temporal power spectra of the Fourier basis calculated assuming frozen flow turbulence, and then apply closed-loop transfer functions. We include the benefits of a simple predictive controller, which we show could provide over a factor of 1400 gain in raw PSF contrast at 1 $\lambda/D$ on bright stars, and more than a factor of 30 gain on an I = 7.5 mag star such as Proxima. More sophisticated predictive control can be expected to improve this even further. Assuming a photon noise limited observing technique such as High Dispersion Coronagraphy, these gains in raw contrast will decrease integration times by the same large factors. Predictive control of atmospheric turbulence should therefore be seen as one of the key technologies which will enable ground-based telescopes to characterize terrrestrial planets.Comment: Accepted to JATI

What do teachers attend to in curriculum materials?

In this paper, we describe an emerging methodology using eye tracking to explore teachers’ curricular attending as they interact with curriculum materials to design a lesson in order to learn what teachers pay attention to and how this attention shifts during planning. We propose affordances of this new method, remark on some of its limitations, and propose future directions

On tt-core and self-conjugate (2t−1)(2t-1)-core partitions in arithmetic progressions

We extend recent results of Ono and Raji, relating the number of self-conjugate $7$-core partitions to Hurwitz class numbers. Furthermore, we give a combinatorial explanation for the curious equality $2\operatorname{sc}_7(8n+1) = \operatorname{c}_4(7n+2)$. We also conjecture that an equality of this shape holds if and only if $t=4$, proving the cases $t\in\{2,3,5\}$ and giving partial results for $t>5$

Youth Health Services, Development Programs, and Teenage Birth Rates in 55 California Cities

Many advocacy groups depict sexuality education, abstinence education, health services, and development services to teenagers as pivotal factors in their birth rates. Data from California’s 55 largest cities for 1990-2002 allow regression analyses of the associations between levels of health and development services to youth, socioeconomic factors such as poverty, and environmental factors such adult birth rates on rates of and changes in births to teenage mothers. The analysis found teenage birth rates vary 30-fold from California’s richest to poorest city. Socioeconomic and environmental factors, chiefly adult birth rates and youth poverty rates, are associated with nearly 90% of the variance in teen birth rates. Contrary to assertions by many advocates, lower-income teens have greater access to health, sexuality education, and development services, and the availability of these services is not associated with lower rates of or greater reductions over time in teenage birth rates

Think tank: water relations of Bromeliaceae in their evolutionary context

This is the final version of the article. It first appeared from Wiley via https://doi.org/10.1111/boj.12423Water relations represent a pivotal nexus in plant biology due to the multiplicity of functions affected by water status. Hydraulic properties of plant parts are therefore likely to be relevant to evolutionary trends in many taxa. Bromeliaceae encompass a wealth of morphological, physiological and ecological variations and the geographical and bioclimatic range of the family is also extensive. The diversification of bromeliad lineages is known to be correlated with the origins of a suite of key innovations, many of which relate directly or indirectly to water relations. However, little information is known regarding the role of change in morphoanatomical and hydraulic traits in the evolutionary origins of the classical ecophysiological functional types in Bromeliaceae or how this role relates to the diversification of specific lineages. In this paper, I present a synthesis of the current knowledge on bromeliad water relations and a qualitative model of the evolution of relevant traits in the context of the functional types. I use this model to introduce a manifesto for a new research programme on the integrative biology and evolution of bromeliad water-use strategies. The need for a wide-ranging survey of morphoanatomical and hydraulic traits across Bromeliaceae is stressed, as this would provide extensive insight into structure–function relationships of relevance to the evolutionary history of bromeliads and, more generally, to the evolutionary physiology of flowering plants.Natural Environment Research Counci

Curricular noticing: A comprehensive framework to describe teachers’ interactions with curriculum materials

Building on the work of Professional Noticing of Children’s Mathematical Thinking, we introduce the Curricular Noticing Framework to describe how teachers recognize opportunities within curriculum materials, understand their affordances and limitations, and use strategies to act on them. This framework builds on Remillard’s (2005) notion of participation with curriculum materials, connects with and broadens existing research on the relationship between teachers and written curriculum, and highlights new are as for research. We argue that once mathematics educators better understand the strategic curricular practices that support ambitious teaching, which we refer to as professional curricular noticing, then this knowledge can lead to recommendations for how to support the curricular work of teachers, particularly novice teachers