Astrobiologists are rational but not Bayesian

The search for biosignatures is likely to generate controversial results, with no single biosignature being clear proof of the presence of life. Bayesian statistical frameworks have been suggested as a tool for testing the effect that a new observation has on our belief in the presence of life on another planet. We test this approach here using the tentative discovery of phosphine on Venus as an example of a possible detection of a biosignature on an otherwise well-characterized planet. We report on a survey of astrobiologists' views on the likelihood of life on Enceladus, Europa, Mars, Titan and Venus before the announcement of the detection of phosphine in Venus' atmosphere (the Bayesian Prior Probability) and after the announcement (the Posterior Probability). Survey results show that respondents have a general view on the likelihood of life on any world, independent of the relative ranking of specific bodies, and that there is a distinct ‘fans of icy moons’ sub-community. The announcement of the potential presence of phosphine on Venus resulted in the community showing a small but significant increase in its confidence that there was life on Venus; nevertheless the community still considers Venus to be the least likely abode of life among the five targets considered, last after Titan. We derive a Bayesian formulation that explicitly includes both the uncertainty in the interpretation of the signal as well as uncertainty in whether phosphine on Venus could have been produced by life. We show that although the community has shown rational restraint about a highly unexpected and still tentative detection, their changing expectations do not fit a Bayesian model.

Overtly Headed XPs and Irish Syntax-Prosody Mapping

Analyses of Irish phonological phrasing (Elfner 2012 et seq.) have been influential in shaping Match Theory (Selkirk 2011), an OT approach to mapping syntactic to prosodic structure. We solve two constraint ranking paradoxes concerning the relative ranking of Match and StrongStart. Irish data indicate that while XPs with silent heads can fail to map to phonological phrases in certain circumstances, overtly headed XPs cannot. They also indicate that rebracketing due to the constraint StrongStart occurs only sentence-initially, contrary to predictions. We account for these puzzles by invoking Van Handel's (2019) Match constraint which sees only XPs with overt heads, and by positing a new version of StrongStart which only applies to material at the left edge of the intonational phrase. Our analysis is developed using the Syntax-Prosody in Optimality Theory application (SPOT) and OTWorkplace.

A Parallel Approach to Mobile Affixation in Huave

Huave exhibits "mobile affixation", whereby the placement of individual affixes varies depending on the phonological properties of affix and stem. Kim (2008, 2010) analyzed these facts within a cyclic cophonology approach through the interaction between alignment constraints (McCarthy & Prince, 1993) and the phonological constraints *CC and DEP. Using the same core components, this paper develops an alternative, fully parallel analysis.In this approach, morphemes are unordered in the phonological input, every morpheme is indexed to its own (crucially gradient) alignment constraint, and output ordering is determined entirely through simultaneous constraint interaction. Notably, this analysis captures a previously unnoticed generalization about the stability of left/right order between affixes in the language.The main contribution of this new analysis is that it provides a principled distinction between mobile and immobile affixes: the order of affixes, as determined by the relative ranking of their alignment constraints, correlates with their ability to trigger epenthesis, as determined by their ranking relative to DEP. This follows from a parallel approach with a single language-wide ranking, but not from a cyclic cophonology account. Furthermore, this distinction can be tied directly to morphosyntactic structure via Zukoff's (2020) "Mirror Alignment Principle" and considerations of Base-Derivative faithfulness (Benua, 1997).

Quantifying Risk to Optimize Facility Integrity Management

Effective asset integrity management is supported through the understanding of the condition of the asset, and the quantification of the safety and uncertainty of its properties. Risk based and risk informed decision making can help operators prioritize inspections and repairs on mainline pipe, as well as within operator facilities. Setting operator system specific targets for reliability and risk can help operators better understand the condition of their system, and provide one means of determining whether integrity action or other risk treatment is required on a specific asset, either on the mainline pipe system or on a facility asset system. While mainline pipe condition is better understood through the use of inline inspection technology and non-destructive examination in the field, facility piping and storage condition is more difficult to understand due to the complexity and number of segments of assets within an operator’s facility, as well as the unpiggable nature of the majority of facility piping. To help resolve this issue, a risk quantification can be done for each segmented asset within a facility. A relative ranking of asset risks can help prioritize facility integrity activities and drive the planning and execution optimization. However, simply looking at a relative ranking of asset risks may not be enough to maximize risk reduction and achieve safety and reliability targets. This paper looks to expand on the implementation of Risk Based Inspection (RBI) standard in API 581 and explore more broadly how facility asset risk results can be used in integrity planning and decision making. The paper also examines the application of using finance principals to better quantify risk and carry out a meaningful cost benefit analysis to optimize integrity programs. Interpreting a quantified risk dollar amount is an industry challenge, and shedding light onto the value of applying reliability and risk models beyond the safety of an operator’s system can be extremely beneficial for operators to enhance cost efficiency. The quantification of risk helps support the optimization of spend and resource allocation to bring efficiencies into integrity management systems while maintaining focus on the right risk mitigation across an operator’s system.

Additive Scoring Rules for Discrete Sample Spaces

In this paper, we develop strictly proper scoring rules that may be used to evaluate the accuracy of a sequence of probabilistic forecasts. In practice, when forecasts are submitted for multiple uncertainties, competing forecasts are ranked by their cumulative or average score. Alternatively, one could score the implied joint distributions. We demonstrate that these measures of forecast accuracy disagree under some commonly used rules. Furthermore, and most importantly, we show that forecast rankings can depend on the selected scoring procedure. In other words, under some scoring rules, the relative ranking of probabilistic forecasts does not depend solely on the information content of those forecasts and the observed outcome. Instead, the relative ranking of forecasts is a function of the process by which those forecasts are evaluated. As an alternative, we describe additive and strongly additive strictly proper scoring rules, which have the property that the score for the joint distribution is equal to a sum of scores for the associated marginal and conditional distributions. We give methods for constructing additive rules and demonstrate that the logarithmic score is the only strongly additive rule. Finally, we connect the additive properties of scoring rules with analogous properties for a general class of entropy measures.

Underbalanced Drilling Optimum Methodology

A methodology to properly screen all UBD techniques to reduce failure/misapplication and align objectives with expectations had been absent. The paper addresses the latest enhancements to better understand and screen options for UBD operations according to two aspects: formation applicability and engineering applicability. The screening tool considers a range of economic and technical parameter to provide a relative ranking for each candidate of the Underbalanced drilling (UBD) technique. As a case, the methodology was available to optimize the UBD techniques in a risky exploration well in Xinjiang oilfield, which provided guidance and technical support to screen the UBD candidate, design the drilling modeconversion, and establish the emergency schedule.