Type-Directed Elaboration of Quasiquotations:A High-Level Syntax for Low-Level Reflection

Idris's reflection features allow Idris metaprograms to manipulate a representation of Idris's core language as a datatype, but these reflected terms were designed for ease of type checking and are therefore exceedingly verbose and tedious to work with. A simpler notation would make these programs both easier to read and easier to write. We describe a variation of quasiquotation that uses the language's compiler to translate high-level programs with holes into their corresponding reflected representation, both in pattern-matching and expression contexts. This provides a notation for reflected language that matches the notation used to write programs, allowing readable metaprograms

Mapping out the time-evolution of exoplanet processes

There are many competing theories and models describing the formation, migration and evolution of exoplanet systems. As both the precision with which we can characterize exoplanets and their host stars, and the number of systems for which we can make such a characterization increase, we begin to see pathways forward for validating these theories. In this white paper we identify predicted, observable correlations that are accessible in the near future, particularly trends in exoplanet populations, radii, orbits and atmospheres with host star age. By compiling a statistically significant sample of well-characterized exoplanets with precisely measured ages, we should be able to begin identifying the dominant processes governing the time-evolution of exoplanet systems.Comment: Astro2020 white pape

Understanding Adolescent Intentions to Smoke: An Examination of Relationships Among Social Influence, Prior Trial Behavior, and Antitobacco Campaign Advertising

Telephone interviews were conducted with more than 900 adolescents aged 12 to 18 as part of a multimillion dollar, statewide, antitobacco advertising campaign. The interviews addressed two primary questions: (1) Do counter-advertising campaign attitudes directly affect antismoking beliefs and intent in a manner similar to those of conventional advertisements? and (2) Can advertising campaign attitudes have a stronger effect on beliefs and intent for adolescents with prior smoking behavior and for adolescents exposed to social influence (i.e., friends, siblings, or adult smoker in the home)? The authors\u27 findings show that advertising campaign attitudes, prior trial behavior, and social influence all directly affect antismoking beliefs and that advertising campaign attitudes interact with prior trial behavior to strengthen antismoking beliefs. The results indicate that attitudes related to the campaign, prior trial behavior, and social influence directly influence intent, and advertising campaign attitudes interact with social influence and prior trial behavior to attenuate adolescent intent to smoke. In addition, the effect of advertising campaign attitudes in attenuating social influence and prior trial behavior effects on adolescent intent to smoke persists even when the authors account for strongly held beliefs about smoking. The authors discuss implications for countermarketing communications and the design and understanding of future antismoking campaigns

Inferring surface time of Minke whales from inter-surfacing interval data using a hidden Markov model

Surfacing rate data of Minke whales is an important factor used in the abundance estimates of Minke whale (Balaenoptera acutorostrata) stocks, both in aerial and vessel based surveys. Today, most abundance estimates of Minke whales rely on VHF-transmitters data rather than visual data. Visual data collected from land has the advantage of being relatively cheap to collect, which allows data to be collected from a larger number of individuals while causing no effect on the surfacing rates of the animals being studied, hence limiting biases. In this study, individual follows of Minke whales were conducted from a land-based station in Faxaflói bay, Iceland, and data on inter-breath intervals (IBI) were collected. Two distinct dive types were present within the surfacing data, which we defined as regular dives and deep dives. Those emerged from two different biological processes: whales spending time at the surface and whales engaging in foraging activities. A hidden Markov model was used to identify and define the density distribution of IBI as the observation state of these two hidden diving processes. Regular dives had a mean surfacing interval of 43 seconds (SD=44.8) and deep dives had a mean surfacing interval of 155 seconds (SD=115.1). The transition probabilities between the two dive types were estimated, from which the relative proportion spent in each dive type could be inferred. Minke whales perform regular dives during 62% and deep dives during 38% of their time. The relative proportions spent in each dive type can be used as estimates of how much time a whale will be typically at the surface available to be detected during cue counting surveys and to estimate the odds that a whale is in a long dive and therefore unlikely to be detected. Data was also collected from commercial whalewatching boats in the same bay, and were analysed together with the land based data to measure the effect of whalewatching boat interaction on Minke whale surface intervals. The proportion of time spent in deep dives decreased from 38% to 14% during interactions with whalewatching boats, while regular dives increased from 62% to 86%. The inter-surfacing interval used in abundance estimates of Minke whales in the North Atlantic today is derived from VHF-transmitter data and is about 77 seconds. Our mean values of surface intervals lies below and above this mean, which raises the question if a single mean value of surfacing interval can be used to make reliable abundance estimates of Minke whales, as both the dive type and the presence of vessels is likely to affect this value

Elaborator reflection : extending Idris in Idris

Many programming languages and proof assistants are defined by elaboration from a high-level language with a great deal of implicit information to a highly explicit core language. In many advanced languages, these elaboration facilities contain powerful tools for program construction, but these tools are rarely designed to be repurposed by users. We describe elaborator reflection, a paradigm for metaprogramming in which the elaboration machinery is made directly available to metaprograms, as well as a concrete realization of elaborator reflection in Idris, a functional language with full dependent types. We demonstrate the applicability of Idris’s reflected elaboration framework to a number of realistic problems, we discuss the motivation for the specific features of its design, and we explore the broader meaning of elaborator reflection as it can relate to other languages.Postprin

A vertebrate crossveinless 2 homologue modulates BMP activity and neural crest cell migration

Previous work has revealed that proteins that bind to bone morphogenetic proteins (BMPs) and inhibit their signalling have a crucial role in the spatial and temporal regulation of cell differentiation and cell migration by BMPs. We have identified a chick homologue of crossveinless 2, a Drosophila gene that was identified in genetic studies as a promoter of BMP-like signalling. Chick Cv-2 has a conserved structure of five cysteine-rich repeats similar to those found in several BMP antagonists, and a C-terminal Von Willebrand type D domain. Cv-2 is expressed in the chick embryo in a number of tissues at sites at which elevated BMP signalling is required. One such site of expression is premigratory neural crest, in which at trunk levels threshold levels of BMP activity are required to initiate cell migration. We show that, when overexpressed, Cv-2 can weakly antagonise BMP4 activity in Xenopus embryos, but that in other in vitro assays Cv-2 can increase the activity of co-expressed BMP4. Furthermore, we find that increased expression of Cv-2 causes premature onset of trunk neural crest cell migration in the chick embryo, indicative of Cv-2 acting to promote BMP activity at an endogenous site of expression. We therefore propose that BMP signalling is modulated both by antagonists and by Cv-2 that acts to elevate BMP activity

Structure and Dynamics of Minke Whale Surfacing Patterns in the Gulf of St. Lawrence, Canada

Funding: This work was supported by the Foundation for Marine Environment Research (ORES), Switzerland and Ocean Care, Switzerland. Copyright: © 2015 Christiansen et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are creditedPeer reviewedPublisher PD