Fully Bayesian inference for α-stable distributions using a Poisson series representation

In this paper we develop an approach to Bayesian Monte Carlo inference for skewed α-stable distributions. Based on a series representation of the stable law in terms of infinite summations of random Poisson process arrival times, our framework leads to a simple representation in terms of conditionally Gaussian distributions for certain latent variables. Inference can therefore be carried out straightforwardly using techniques such as auxiliary variables versions of Markov chain Monte Carlo (MCMC) methods. The Poisson series representation (PSR) is further extended to practical application by introducing an approximation of the series residual terms based on exact moment calculations. Simulations illustrate the proposed framework applied to skewed α-stable simulated and real-world data, successfully estimating the distribution parameter values and being consistent with other (non-Bayesian) approaches. The methods are highly suitable for incorporation into hierarchical Bayesian models, and in this case the conditionally Gaussian structure of our model will lead to very efficient computations compared to other approaches.Godsill acknowledges partial funding for the work from the EPSRC BTaRoT project EP/K020153/1, and Tatjana Lemke acknowledges PhD funding from Fraunhofer ITWM, Kaiserslautern.This is the author accepted manuscript. The final version is available from Elsevier via http://dx.doi.org/10.1016/j.dsp.2015.08.01

People-Environment Trade-offs in Managing Communal Rangelands of South Africa

Communal rangelands in South Africa support a range of ecosystem services including water provision, carbon sequestration and livestock production for different stakeholders. Delivering these in a sustainable and socially appropriate manner necessarily requires trade-offs to be made between the different environmental and social outcomes required. We draw on empirical fieldwork and a two-day participatory stakeholder workshop to report on the early stages of a project evaluating these trade-offs in communal rangelands of the uMzimvubu catchment in Eastern Cape Province. Our findings suggest that trade-offs will be necessary at a variety of different levels within this system. For example, a key activity within these rangelands is removal of invasive plants such as wattle (Acacia mearnsii) but the environmental gains are conflictual as although this increases water availability within the system, it potentially reduces stored carbon. Wattle removal also highlights a disconnection between people and policy. While current policy mandates complete eradication of wattle, none of the local communities involved in the research wished to see this, as most of them currently make use of the trees for a range of purposes including timber, fuelwood and even livestock feed. Furthermore, trade-offs are also required between different community members, in terms of the social outcomes rangelands can deliver for them. While men conceptualised rangelands largely in terms of maximising livestock production, women focused on the collection of natural resources such as timber, herbs and thatching grass, the latter requiring accumulation of biomass during the growing season and potentially removing areas of rangeland from grazing. Understanding the opposing goals for rangeland use that exist within and between different stakeholder groups is critical to evaluating the social and environmental trade-offs required and to reach a consensus approach to the governance and management of these systems

ELAV links paused Pol II to alternative polyadenylation in the Drosophila nervious system

Alternative polyadenylation (APA) has been implicated in a variety of developmental and disease processes. A particularly dramatic form of APA occurs in the developing nervous system of flies and mammals, whereby various developmental genes undergo coordinate 3' UTR extension. In Drosophila, the RNA-binding protein ELAV inhibits RNA processing at proximal polyadenylation sites, thereby fostering the formation of exceptionally long 3' UTRs. Here, we present evidence that paused Pol II promotes recruitment of ELAV to extended genes. Replacing promoters of extended genes with heterologous promoters blocks normal 3' extension in the nervous system, while extension-associated promoters can induce 3' extension in ectopic tissues expressing ELAV. Computational analyses suggest that promoter regions of extended genes tend to contain paused Pol II and associated cis-regulatory elements such as GAGA. ChIP-seq assays identify ELAV in the promoter regions of extended genes. Our study provides evidence for a regulatory link between promoter-proximal pausing and APA

Variability survey in the CoRoT SRa01 field: Implications of eclipsing binary distribution on cluster formation in NGC 2264

Time-series photometry of the CoRoT field SRa01 was carried out with the Berlin Exoplanet Search Telescope II (BEST II) in 2008/2009. A total of 1,161 variable stars were detected, of which 241 were previously known and 920 are newly found. Several new, variable young stellar objects have been discovered. The study of the spatial distribution of eclipsing binaries revealed the higher relative frequency of Algols toward the center of the young open cluster NGC 2264. In general Algol frequency obeys an isotropic distribution of their angular momentum vectors, except inside the cluster, where a specific orientation of the inclinations is the case. We suggest that we see the orbital plane of the binaries almost edge-on.Comment: 18 pages, 8 figures, accepted for publication in Ap

The Berlin Exoplanet Search Telescope II. Catalog of Variable Stars. I. Characterization of Three Southern Target Fields

A photometric survey of three Southern target fields with BEST II yielded the detection of 2,406 previously unknown variable stars and an additional 617 stars with suspected variability. This study presents a catalog including their coordinates, magnitudes, light curves, ephemerides, amplitudes, and type of variability. In addition, the variability of 17 known objects is confirmed, thus validating the results. The catalog contains a number of known and new variables that are of interest for further astrophysical investigations, in order to, e.g., search for additional bodies in eclipsing binary systems, or to test stellar interior models. Altogether, 209,070 stars were monitored with BEST II during a total of 128 nights in 2009/2010. The overall variability fraction of 1.2-1.5% in these target fields is well comparable to similar ground-based photometric surveys. Within the main magnitude range of $R\in\left[11,17\right]$, we identify 0.67(3)% of all stars to be eclipsing binaries, which indicates a completeness of about one third for this particular type in comparison to space surveys.Comment: accepted to A

Can we predict the time of seedling emergence of spring wheat?

Non-Peer Reviewe

No-till can reduce the risk of heat stress in wheat

Non-Peer ReviewedNo-till farming (NT) is increasing in the Canadian Prairies in recent years because of the economic and environment benefits and its potential to sequester atmospheric carbon into the soil. Because surface residue and stubble act as insulation and impedes the exchange rate of thermal energy between the soil and the atmosphere, lower root-zone temperatures in the NT fields compared with that in the conventionally tilled (CT) fields were widely observed in the spring. Some studies found that low temperatures under NT persisted to the mid-season or throughout the whole growing season. Little attention, however, has been paid to the impact of the cooling effect of NT on the grain yield of wheat. The objective of this study was to investigate if NT could alleviate heat stress and benefit yield

Probing the interiors of the ice giants: Shock compression of water to 700 GPa and 3.8 g/ccm

Recently there has been tremendous increase in the number of identified extra-solar planetary systems. Our understanding of their formation is tied to exoplanet internal structure models, which rely upon equations of state of light elements and compounds like water. Here we present shock compression data for water with unprecedented accuracy that shows water equations of state commonly used in planetary modeling significantly overestimate the compressibility at conditions relevant to planetary interiors. Furthermore, we show its behavior at these conditions, including reflectivity and isentropic response, is well described by a recent first-principles based equation of state. These findings advocate this water model be used as the standard for modeling Neptune, Uranus, and "hot Neptune" exoplanets, and should improve our understanding of these types of planets.Comment: Accepted to Phys. Rev. Lett.; supplementary material attached including 2 figures and 2 tables; to view attachments, please download and extract the gzipped tar source file listed under "Other formats

Role of Solvent Compatibility in the Phase Behavior of Binary Solutions of Weakly Associating Multivalent Polymers

[Image: see text] Condensate formation of biopolymer solutions, prominently those of various intrinsically disordered proteins (IDPs), is often driven by “sticky” interactions between associating residues, multivalently present along the polymer backbone. Using a ternary mean-field “stickers-and-spacers” model, we demonstrate that if sticker association is of the order of a few times the thermal energy, a delicate balance between specific binding and nonspecific polymer–solvent interactions gives rise to a particularly rich ternary phase behavior under physiological circumstances. For a generic system represented by a solution comprising multiassociative scaffold and client polymers, the difference in solvent compatibility between the polymers modulates the nature of isothermal liquid–liquid phase separation (LLPS) between associative and segregative. The calculations reveal regimes of dualistic phase behavior, where both types of LLPS occur within the same phase diagram, either associated with the presence of multiple miscibility gaps or a flip in the slope of the tie-lines belonging to a single coexistence region