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This paper is one in a series reporting results from small telescope observations of variable young stars. Here, we study the repeating outbursts of three likely Be stars based on long-term optical, near-infrared, and mid-infrared photometry for all three objects, along with follow-up spectra for two of the three. The sources are characterised as rare, truly regularly outbursting Be stars. We interpret the photometric data within a framework for modelling light curve morphology, and find that the models correctly predict the burst shapes, including their larger amplitudes and later peaks towards longer wavelengths. We are thus able to infer the start and end times of mass loading into the circumstellar disks of these stars. The disk sizes are typically 3-6 times the areas of the central star. The disk temperatures are ~40%, and the disk luminosities are ~10% of those of the central Be star, respectively. The available spectroscopy is consistent with inside-out evolution of the disk. Higher excitation lines have larger velocity widths in their double-horned shaped emission profiles. Our observations and analysis support the decretion disk model for outbursting Be stars., Comment: Accepted for publication by MNRAS. 20 pages, 11 figures, 2 tables

Model-finders, such as SAT/SMT-solvers and Alloy, are used widely both directly and embedded in domain-specific tools. They support both conventional verification and, unlike other verification tools, property-free exploration. To do this effectively, they must produce output that helps users with these tasks. Unfortunately, the output of model-finders has seen relatively little rigorous human-factors study. Conventionally, these tools tend to show one satisfying instance at a time. Drawing inspiration from the cognitive science literature, we investigate two aspects of model-finder output: how many instances to show at once, and whether all instances must actually satisfy the input constraints. Using both controlled studies and open-ended talk-alouds, we show that there is benefit to showing negative instances in certain settings; the impact of multiple instances is less clear. Our work is a first step in a theoretically grounded approach to understanding how users engage cognitively with model-finder output, and how those tools might better support users in doing so.

OCT4 is a key mediator of induced pluripotent stem cell (iPSC) reprogramming, but the mechanistic insights into the role of exogenous OCT4 and timelines that initiate pluripotency remain to be resolved. Here, using measles reprogramming vectors, we present microRNA (miRNA) targeting of exogenous OCT4 to shut down its expression during the mesenchymal to the epithelial transition phase of reprogramming. We showed that exogenous OCT4 is required only for the initiation of reprogramming and is dispensable for the maturation stage. However, the continuous expression of SOX2, KLF4, and c-MYC is necessary for the maturation stage of the iPSC. Additionally, we demonstrate a novel application of miRNA targeting in a viral vector to contextually control the vector/transgene, ultimately leading to an improved reprogramming efficiency. This novel approach could be applied to other systems for improving the efficiency of vector-induced processes., Graphical abstract, Devaux and colleagues develop a novel miRNA-targeted measles vector that contextually suppress exogenous OCT4 during mesenchymal to epithelial transition (MET) and improve human reprogramming efficiency and kinetics. They show that while SOX2, KLF4, and cMYC are required for both the initiation and maturation stage of reprogramming, OCT4 is essential only for the initiation stage.

Australian climate change policy and its integration with Australia’s electricity markets have been fraught for at least two decades. The only enduring policy has been the Commonwealth Renewable Energy Target (RET). Despite the relative success of the RET in driving investment and reducing emissions, state governments have now pivoted towards contracts-for-difference (Cfds). In this article, we outline the issues associated with policy discontinuity and the large-scale RET and review its effectiveness as an emissions reduction tool and driver of electricity sector abatement. We find that the RET has been relatively successful across the key criteria of cost and emissions reductions and is a better policy instrument than contracts-for-difference, which are increasingly being adopted by state governments. Building on the work of Nelson et al. (2020), we propose a new approach, which would allow for continued use of Cfds but utilising the RET’s policy architecture.

Context: Linear Temporal Logic (LTL) has been used widely in verification. Its importance and popularity have only grown with the revival of temporal logic synthesis, and with new uses of LTL in robotics and planning activities. All these uses demand that the user have a clear understanding of what an LTL specification means. Inquiry: Despite the growing use of LTL, no studies have investigated the misconceptions users actually have in understanding LTL formulas. This paper addresses the gap with a first study of LTL misconceptions. Approach: We study researchers' and learners' understanding of LTL in four rounds (three written surveys, one talk-aloud) spread across a two-year timeframe. Concretely, we decompose "understanding LTL" into three questions. A person reading a spec needs to understand what it is saying, so we study the mapping from LTL to English. A person writing a spec needs to go in the other direction, so we study English to LTL. However, misconceptions could arise from two sources: a misunderstanding of LTL's syntax or of its underlying semantics. Therefore, we also study the relationship between formulas and specific traces. Knowledge: We find several misconceptions that have consequences for learners, tool builders, and designers of new property languages. These findings are already resulting in changes to the Alloy modeling language. We also find that the English to LTL direction was the most common source of errors; unfortunately, this is the critical "authoring" direction in which a subtle mistake can lead to a faulty system. We contribute study instruments that are useful for training learners (whether academic or industrial) who are getting acquainted with LTL, and we provide a code book to assist in the analysis of responses to similar-style questions. Grounding: Our findings are grounded in the responses to our survey rounds. Round 1 used Quizius to identify misconceptions among learners in a way that reduces the threat of expert blind spots. Rounds 2 and 3 confirm that both additional learners and researchers (who work in formal methods, robotics, and related fields) make similar errors. Round 4 adds deep support for our misconceptions via talk-aloud surveys. Importance This work provides useful answers to two critical but unexplored questions: in what ways is LTL tricky and what can be done about it? Our survey instruments can serve as a starting point for other studies.

The limitations of production subsidies for variable renewable energy (VRE) plant as a means of decarbonising electricity markets are well known. Despite this, production subsidies for VRE plant are the most prevalent form of policy intervention in Australia. In the absence of cost-effective storage, production subsidies for VRE plant can create incentives to produce electricity at times the system may not need it, thereby severing the link between the spot market and financial incentives to generate. Such production subsidies can also reduce the incentive for new VRE plant to participate in ‘firm’ forward derivative markets. In this paper, we examine two adjustments that could be made to production subsidies for VRE plant that would correct for these unintended consequences. Firstly, the quantum of the subsidy could be a function of the wholesale electricity price, electricity demand or emissions; and secondly, new generators would be ineligible to receive production subsidies without demonstrating that they are facilitating the supply of financial derivative contracts. The effect of both adjustments would be to increase the incentive of VRE plant to demand-follow; that is, make its output ‘firmer’.

Conventional methods used to adhere EEG electrodes are often uncomfortable. Here, we present a polymer-based water-soluble EEG adhesive that can be maintained for up to 6 days. The primary outcome measure of this study is the median electrode impedance at day 6.Impedance measurements for 841 EEG recordings using a 21 channel 10-20 configuration were remotely logged daily for 6 days after connection. A novel electrode adhesive was used to attach EEG electrodes. Patients were instructed to maintain their electrodes on day 4.Median electrode impedances were significantly below 10kOhms for each day of recording, with a median value on day 6 of 4.18kOhms. Impedance values were significantly lower on day 5 than on day 4, demonstrating that the maintenance process can reduce impedance. Except for day 4-5, the median impedance increased each day. No significant difference was found on the first or final day between clinics or residences from areas of different geographic remoteness.EEG is able to be recorded in patients homes for 6 days with acceptable impedance and no significant effect of regionality or patients age.To the best of our knowledge, this is the first report in the literature of impedance data from long-term ambulatory EEG studies.

Australian climate change policy has been applied haphazardly to Australia’s electricity markets for almost two decades. Federal and state level emissions trading frameworks have been introduced and subsequently repealed. Several studies have pointed to the significant costs imposed by such policy discontinuity. This article demonstrates that the use of production subsidies has also resulted in a ‘disorderly’ transition and has broken the link between the financial incentives for decarbonisation activities and the physical needs of the electricity system. We evaluate the various options for correcting this by introducing a stable, long-term climate change policy that integrates efficiently with electricity policy objectives. By applying a broad assessment framework, we are able to establish that a market mechanism aimed at pricing the externality implied by an independently set carbon budget is the most efficient policy response.

The Hilmer reforms served electricity consumers well over the first post-reform decade. However, three key issues emerged from the mid-2000s: (i) a significant and largely unnecessary rise in network expenditures; (ii) emissions policy discontinuity; and (iii) a large increase in wholesale prices due to rising fuel prices and the sudden exit of generators. The consequence was a doubling in retail prices. Deficiencies in cost-recovery mechanisms have meant price increases have disproportionately affected low-income households. We propose three key reforms as rectification: (i) integrating emissions reduction and energy policies; (ii) boosting network capacity utilisation; and (iii) improving cost recovery mechanisms.

Studying rotational variability of young stars is enabling us to investigate a multitude of properties of young star-disk systems. We utilise high cadence, multi-wavelength optical time series data from the Hunting Outbursting Young Stars citizen science project to identify periodic variables in the Pelican Nebula (IC5070). A double blind study using nine different period-finding algorithms was conducted and a sample of 59 periodic variables was identified. We find that a combination of four period finding algorithms can achieve a completeness of 85% and a contamination of 30% in identifying periods in inhomogeneous data sets. The best performing methods are periodograms that rely on fitting a sine curve. Utilising GaiaEDR3 data, we have identified an unbiased sample of 40 periodic YSOs, without using any colour or magnitude selections. With a 98.9% probability we can exclude a homogeneous YSO period distribution. Instead we find a bi-modal distribution with peaks at three and eight days. The sample has a disk fraction of 50%, and its statistical properties are in agreement with other similarly aged YSOs populations. In particular, we confirm that the presence of the disk is linked to predominantly slow rotation and find a probability of 4.8$\times$10$^{-3}$ that the observed relation between period and presence of a disk has occurred by chance. In our sample of periodic variables, we also find pulsating giants, an eclipsing binary, and potential YSOs in the foreground of IC5070., Comment: 25 pages, 14 figures, 5 tables, accepted for publication in MNRAS

We analyse the energy transition from coal to renewable. Our research contributes to the literature on transitions and grand challenges. Mitigating the effects of dangerous human-induced climate change requires Australia to adopt a ‘carbon budget’ of no more than 10 Gt between 2015 and 2050. To achieve this, the Australian electricity sector must reduce greenhouse gas emissions to at least net zero emissions by 2050. Australia’s strategic response to climate change will have a significant influence on greenhouse gas emissions across Asia and the Pacific. The transition to renewables has proved difficult. The Liddell case study, involving closure of an ageing coal-fired power station, shows how the transition was impeded by institutional decisions. While firm-level actors recognised opportunities, regulators resisted the transition. Our research illustrates that transitions for grand challenges may require a relational stakeholder review, beyond the concept of short-term win–wins. JEL Classification: L02, D02, Q05

Saunders and Bedford (2017) demonstrated that income levels are inadequate for some Australian households to maintain a basic standard of living. Analysing utility bills can extend this consideration of income adequacy issues given the essential nature of services such as electricity, telephony and water. This article builds on the work presented by Simshauser and Nelson (2014) about key demographic cohorts in Australia that have a high incidence of energy-related financial hardship. Our analysis indicates that energy related financial hardship is likely to be related to a combination of the following: family formation demographics; low-income (often reliant upon government income support); higher household size; and higher than average consumption. Our policy recommendations are relatively straightforward: development of tools to allow easier ‘shopping around’ by energy customers; cessation of credit-checking by energy retailers as a means of restricting access to energy offers; reform of state-based concessions frameworks; a lifting of income support for some key cohorts (e.g. unemployed); improvements to energy-efficiency standards; and amendments to tenancy laws to overcome potential principal-agent issues associated with uptake of new energy products and services such as embedded solar PV and battery storage.

Context: This work is based on property-based testing (PBT). PBT is an increasingly important form of software testing. Furthermore, it serves as a concrete gateway into the abstract area of formal methods. Specifically, we focus on students learning PBT methods. Inquiry: How well do students do at PBT? Our goal is to assess the quality of the predicates they write as part of PBT. Prior work introduced the idea of decomposing the predicate's property into a conjunction of independent subproperties. Testing the predicate against each subproperty gives a "semantic" understanding of their performance. Approach: The notion of independence of subproperties both seems intuitive and was an important condition in prior work. First, we show that this condition is overly restrictive and might hide valuable information: it both undercounts errors and makes it hard to capture misconceptions. Second, we introduce two forms of automation, one based on PBT tools and the other on SAT-solving, to enable testing of student predicates. Third, we compare the output of these automated tools against manually-constructed tests. Fourth, we also measure the performance of those tools. Finally, we re-assess student performance reported in prior work. Knowledge: We show the difficulty caused by the independent subproperty requirement. We provide insight into how to use automation effectively to assess PBT predicates. In particular, we discuss the steps we had to take to beat human performance. We also provide insight into how to make the automation work efficiently. Finally, we present a much richer account than prior work of how students did. Grounding: Our methods are grounded in mathematical logic. We also make use of well-understood principles of test generation from more formal specifications. This combination ensures the soundness of our work. We use standard methods to measure performance. Importance: As both educators and programmers, we believe PBT is a valuable tool for students to learn, and its importance will only grow as more developers appreciate its value. Effective teaching requires a clear understanding of student knowledge and progress. Our methods enable a rich and automated analysis of student performance on PBT that yields insight into their understanding and can capture misconceptions. We therefore expect these results to be valuable to educators.

The increase in the penetration of small- and utility-scale variable renewable energy across Australia’s National Electricity Market has increased the value to those supply- and demand-side resources that are flexible and dispatchable. On the demand side, digitalization, automation, the Internet of Things, and other technological advances are creating an increasing number of “prosumers” that are capable of responding to real-time price signals. This increasing dynamism in energy demand and supply, for both small- and large-scale customers, will be increasingly valuable and needed if the trilemma of lower prices, high reliability and system security, and emissions reductions is to be solved.

Configuring a service mesh often involves multiple parties, each of whom is responsible for separate portions of the overall system. This can result in miscommunication, silent and sudden errors, or a failure to meet goals. We identify two distinct modes of configuration that call for different solutions. We use synthesis algorithms to extract a set of properties---the envelope ---that each party needs the other to obey. Administrators can use the envelope to aid verification and synthesis or to support fault-localization and negotiation when goals conflict. This paper introduces the problem, lays out the modes, presents algorithms for to each, and gives a prototype implementation. We use this to show the feasibility of the approach in the microservices access-control domain and raise new research questions.

Context: The success of QuickCheck has led to the development of property-based testing (PBT) libraries for many languages and the process is getting increasing attention. However, unlike regular testing, PBT is not widespread in collegiate curricula. Furthermore, the value of PBT is not limited to software testing. The growing use of formal methods in, and the growth of software synthesis, all create demand for techniques to train students and developers in the art of specification writing. We posit that PBT forms a strong bridge between testing and the act of specification: it's a form of testing where the tester is actually writing abstract specifications. Inquiry: Even well-informed technologists mention the difficulty of finding good motivating examples for its use. We take steps to fill this lacuna. Approach & Knowledge: We find that the use of "relational" problems -- those for which an input may admit multiple valid outputs -- easily motivates the use of PBT. We also notice that such problems are readily available in the computer science pantheon of problems (e.g., many graph and sorting algorithms). We have been using these for some years now to teach PBT in collegiate courses. Grounding: In this paper, we describe the problems we use and report on students? completion of them. We believe the problems overcome some of the motivation issues described above. We also show that students can do quite well at PBT for these problems, suggesting that the topic is well within their reach. In the process, we introduce a simple method to evaluate the accuracy of their specifications, and use it to characterize their common mistakes. Importance: Based on our findings, we believe that relational problems are an underutilized motivating example for PBT. We hope this paper initiates a catalog of such problems for educators (and developers) to use, and also provides a concrete (though by no means exclusive) method to analyze the quality of PBT.

With continuous decline in the cost of distributed generation technologies, a stand-alone power system (SAPS), typically comprising solar photovoltaic (PV) integrated with battery storage, can increasingly substitute for a traditional connection to the network. This chapter examines two issues in this context, namely, (1) should the regulatory framework for SAPS-connected customers be the same as for grid-connected customers? and (2) should the regulatory framework for SAPS driven by different parties be the same? The answer to the first question is “broadly yes,” if the objective is to minimize the costs of transitioning on-grid customers to off-grid. The answer to the second question need not be “yes.” While our discussion is confined to Australia, the lessons learned have universal application.

The citizen Continental-America Telescopic Eclipse (CATE) Experiment was a new type of citizen science experiment designed to capture a time sequence of white-light coronal observations during totality from 17:16 to 18:48 UT on 2017 August 21. Using identical instruments the CATE group imaged the inner corona from 1 to 2.1 RSun with 1.″43 pixels at a cadence of 2.1 s. A slow coronal mass ejection (CME) started on the SW limb of the Sun before the total eclipse began. An analysis of CATE data from 17:22 to 17:39 UT maps the spatial distribution of coronal flow velocities from about 1.2 to 2.1 RSun, and shows the CME material accelerates from about 0 to 200 km s−1 across this part of the corona. This CME is observed by LASCO C2 at 3.1–13 RSun with a constant speed of 254 km s−1. The CATE and LASCO observations are not fit by either constant acceleration nor spatially uniform velocity change, and so the CME acceleration mechanism must produce variable acceleration in this region of the corona.

Prior studies establish that electricity systems across the globe need to transition toward renewable energy and that renters have a low adoption of effective means to do so through access to household solar photovoltaics (PV). Yet, the economic, environmental, and social costs of low PV adoption by people who have trouble paying their electricity bills (hardship customers), who are more likely to be low-income tenants, remain understudied. Drawing on electricity use data from an Australian energy retailer we compare the performance of PV for hardship customers against ‘average’ households. Results illustrate that if society could achieve greater solar PV installation on hardship homes, annual grid-based electricity consumption could be reduced by 40%, lowering greenhouse gas emissions by 1.6 tCO2e per household annually and energy bills by $2908 per low-income household over 15 years. We illustrate how Australian policy could be re-oriented to encourage greater PV adoption on hardship properties, including through support for a new market structure that distributes the economic benefits of PV between renters and landlords.

This paper considers the various supply-chain segments in the Australian NEM where significant adoption of renewable technologies has occurred. In the long-term, customers may be best served by 'fixed' or 'cap' style pricing contracts that allow unlimited energy consumption within a 'fixed' capacity band. This would be underpinned by economically regulated transmission and distribution 'demand' tariffs and a liquid market for innovative derivative products alongside an efficient wholesale energy dispatch engine.

Australia’s east-coast gas market has undergone significant transformation in the past decade. The discovery of non-conventional coal-seam gas reserves led to investment in three ‘lumpy’ LNG export facilities in Gladstone, Queensland. Drilling activity has subsequently slowed, a direct result of a soft global price for LNG. This slowdown, in an environment of a tripling of east-coast gas demand, has resulted in concerns about domestic gas shortages. To be clear, there is no lack of gas resources. Instead, the problem relates to the relative lumpiness of capital allocation and temporal instability driven by changing global circumstances. Utilising a simple partial equilibrium model, various options for overcoming these problems are analysed. Of these options, developing import infrastructure appears to be a ‘no regrets’ option that would ensure that the price floor, the LNG netback price, also becomes the market price cap.

In recent decades, many power systems have introduced electricity generator competition. Market designs have varied with some countries adopting ‘energy‐only’ markets and others utilising capacity remuneration mechanisms. With increasing deployment of cost competitive renewable energy and the introduction of policy measures to reduce greenhouse gas emissions, concerns are emerging about the sustainability of these market designs. In Australia, wholesale electricity prices have increased markedly – the result of a ‘disorderly’ transition away from coal to new renewable energy. This paper critically examines the ‘energy‐only’ market in a high‐penetration renewables system, with a particular focus on the vertically and horizontally restructured National Electricity Market (NEM). We propose that the ‘energy‐only’ market can indeed work within a decarbonised energy system. But as renewables increasingly replace coal‐fired power stations, ‘unintended consequences’ will need to be addressed to facilitate an ‘orderly’ transition. It will be important that policy ensures appropriate new investment in firm capacity is forthcoming; and pricing outcomes are acceptable given political economy constraints.