56Ni dredge-up in Supernova 1987A

We use early-time observations of He I 10830 \AA to measure the extent of upward mixing of radioactive material in SN 1987A. This work develops and extends the work of Graham (1988), and places constraints on actual explosion models. The presence of the He I 10830 \AA (2s^{3}S--2p^{3}P) line at $\geq 10$ days post-explosion implies re-ionisation by $\gamma$-rays from upwardly-mixed radioactive material produced during the explosion. Using the unmixed explosion model 10H (Woosley 1988) as well as mixed versions of it, we estimated the $\gamma$-ray energy deposition by applying a purely absorptive radiative transfer calculation. The deposition energy was used to find the ionisation balance as a function of radius, and hence the 2s$^{3}$S population density profile. This was then applied to a spectral synthesis model and the synthetic spectra were compared with the observations. Neither model 10H nor the mixed version, 10HMM, succeeded in reproducing the observed He I 10830 \AA line. The discrepancy with the data found for 10HMM is particularly significant, as this model has successfully reproduced the X-ray and $\gamma$-ray observations and the UVOIR light curve. We find that a match to the He I line profile is achieved by reducing the extent of mixing in 10HMM. Our reduced-mixing models also reproduce the observed $\gamma$-ray line light curves and the iron-group velocities deduced from late-time infrared line profiles. We suggest that the He I line method provides a more sensitive measure of the extent of mixing in a type II supernova explosion.Comment: 18 pages, 5 figures, accepted for publication in MNRAS (uses epsf.sty - included

Supernovae in the nuclear regions of starburst galaxies

The feasibility of using near-infrared observations to discover supernovae in the nuclear and circumnuclear regions of nearby starburst galaxies is investigated. We provide updated estimates of the intrinsic core-collapse supernova rates in these regions. We discuss the problem of extinction, and present new estimates of the extinction towards 33 supernova remnants in the starburst galaxy M 82. This is done using H I and H_2 column density measurements. We estimate the molecular to atomic hydrogen mass ratio to be 7.4 +- 1.0 in M 82. We have assembled near-infrared photometric data for a total of 13 core-collapse supernovae, some unpublished hitherto. This constitutes the largest database of IR light curves for such events. We show that the IR light curves fall into two classes, ``ordinary'' and ``slow-declining''. Template JHKL light curves are derived for both classes. For ordinary core-collapse supernovae, the average peak JHKL absolute magnitudes are -18.4, -18.6, -18.6, and -19.0 respectively. The slow-declining core-collapse SNe are found to be significantly more luminous than the ordinary events, even at early times, having average peak JHKL absolute magnitudes of -19.9, -20.0, -20.0, and -20.4 respectively. We investigate the efficiency of a computerised image subtraction method in supernova detection. We then carry out a Monte Carlo simulation of a supernova search using K-band images of NGC 5962. The effects of extinction and observing strategy are discussed. We conclude that a modest observational programme will be able to discover a number of nuclear supernovae.Comment: 19 pages, 7 figures; accepted in MNRA

Measuring the competitiveness of the UK construction industry. Volume 1

EBS’s estimates of relative productivity in construction are as follows: 1. The US is about 25-35% ahead of the UK and Germany in terms of average labour productivity (ALP). 2. The UK is ahead of Germany in ALP on an output per worker basis, but not on an output per hour worked basis (this is due to Germans working fewer hours per week on average). These results are largely unchanged under various sensitivity tests, for example, using GDP PPP exchange rates instead of construction PPP exchange rates to convert national currencies to a common currency. The EBS estimate for the US-UK comparison is supported by UCL/DL (who estimate a US lead in ALP of 42% in 1999). UCL/DL’s estimates for the Germany-UK comparison are also similar to those of EBS, since they show Germany level with the UK in ALP on an output per worker basis, but ahead on an output per hour worked basis. Productivity comparisons of the UK with France are subject to difficulties. Depending on the exchange rates they use for conversion purposes, EBS find that France is well ahead of Britain on some measures of ALP (and indeed is close to the US) but on other measures French ALP is much the same as in Britain. UCL/DL argue strongly for using an exchange rate, which shows French construction ALP to be well ahead of the UK. They state that: ‘The French construction PPPs have been controversial for some time….[and tend to lead to] underestimates of French construction output’. There are difficulties in conducting this type of analysis that are hard to surmount, for example it is unlikely that labour inputs are well measured in any country because of illegal immigration, ‘ the hidden economy’, etc. However, unless there is reason to think that the proportion of uncounted construction workers is significantly higher or lower in Britain as compared to, say, the United States, then it seems reasonable to accept that ALP in the US construction industry is some way ahead of the UK. In many ways cross-country comparisons of productivity levels across the whole construction industry are not comparing like with like since the composition of construction output differs greatly from country to country. It is therefore hard to construct reliable national rankings based on aggregated data for construction given the present state of the data

Early-time Spitzer observations of the type II-Plateau supernova, 2004dj

We present mid-infrared observations with the Spitzer Space Telescope of the nearby type II-P supernova, SN 2004dj, at epochs of 89 to 129 days. We have obtained the first mid-IR spectra of any supernova apart from SN 1987A. A prominent [NiII] 6.64 micron line is observed, from which we deduce that the mass of stable nickel must be at least 2.2e10(-4) Msun. We also observe the red wing of the CO-fundamental band. We relate our findings to possible progenitors and favour an evolved star, most likely a red supergiant, with a probable initial mass between ~10 and 15 Msun.Comment: ApJ Letters (accepted

Envisioning Ontario’s Food and Organic Waste Disposal Ban: A Comparative Case Analysis

Roughly one-third, or 1.3 billion tonnes of edible food produced for human consumption is wasted around the world each year (Gustavsson et al., 2011). The production of food that is ultimately thrown away creates and exacerbates a host of economic, environmental, and social issues, including those related to greenhouse gas emissions, climate change, the depletion of finite resources, and food insecurity. Government, industry, and researchers around the world continue to assess the scope and cause of food waste, and investigate solutions through technology, regulation, and public outreach campaigns. In 2015, almost 3.7 million tonnes of food waste (including foods that could have been eaten and unavoidable waste such as vegetable peels) was generated in Ontario alone, and about 60 per cent of this waste was sent to landfill (Ministry of the Environment and Climate Change, 2018a). In 2017, Ontario put forward the Food and Organic Waste Framework, which contains an action plan and policy statement identifying how the province will address food waste within its borders. Within the Framework, Ontario states that a food and organic waste disposal ban regulation will be developed and implemented under the Environmental Protection Act, which will prohibit organic waste from ending up in disposal sites. This paper seeks to look at other jurisdictions in Canada that have implemented organic waste disposal bans in order to identify what these experiences can offer Ontario before implementing its own strategy. The key recommendation articulated throughout this paper is that food waste should be prevented above all other options, as it will have the greatest environmental, economic, and social benefits. This aligns with the frameworks guiding this research, including agroecology, the circular economy, and waste management hierarchy, and also fits within Ontario’s Food Hierarchy (which will be discussed later in this paper). Food waste prevention can be best achieved by facilitating coordination across the value chain (Gooch, Felfel, & Marenick, 2010). Ontario can support value chain coordination by funding research, reviewing existing regulations and programmes, and engaging with value chain stakeholders. Food waste prevention efforts would also benefit from developing programmes that shift behaviours at the household level, though this is secondary to value chain coordination. If food waste cannot be prevented, this paper offers recommendations for how recovered resources should be optimized in order of importance from (1) feeding people, (2) feeding livestock, and then (3) promoting soil health. These recommendations include additions and adjustments to existing regulations, legislations, and government-funded programmes, the use of tipping fees, reducing plastic contamination in the organic waste stream, and working with the agricultural community to ensure that compost meets their needs and is actively utilized by the industry to foster a viable end market