Production of dust by massive stars at high redshift

The large amounts of dust detected in sub-millimeter galaxies and quasars at high redshift pose a challenge to galaxy formation models and theories of cosmic dust formation. At z > 6 only stars of relatively high mass (> 3 Msun) are sufficiently short-lived to be potential stellar sources of dust. This review is devoted to identifying and quantifying the most important stellar channels of rapid dust formation. We ascertain the dust production efficiency of stars in the mass range 3-40 Msun using both observed and theoretical dust yields of evolved massive stars and supernovae (SNe) and provide analytical expressions for the dust production efficiencies in various scenarios. We also address the strong sensitivity of the total dust productivity to the initial mass function. From simple considerations, we find that, in the early Universe, high-mass (> 3 Msun) asymptotic giant branch stars can only be dominant dust producers if SNe generate <~ 3 x 10^-3 Msun of dust whereas SNe prevail if they are more efficient. We address the challenges in inferring dust masses and star-formation rates from observations of high-redshift galaxies. We conclude that significant SN dust production at high redshift is likely required to reproduce current dust mass estimates, possibly coupled with rapid dust grain growth in the interstellar medium.Comment: 72 pages, 9 figures, 5 tables; to be published in The Astronomy and Astrophysics Revie

Coalitions and public action in the reshaping of corporate responsibility: the case of the retail banking industry

This paper addresses the question of whether and how public action via civil society and/or government can meaningfully shape industry-wide corporate responsibility (ICR) behaviour. We explore how, in principle, ICR can come about and what conditions might be effective in promoting more ethical behaviour. We propose a framework to understand attempts to develop more responsible behaviour at an industry level through processes of negotiation and coalition building. We suggest that any attempt to meaningfully influence ICR would require stakeholders to possess both power and legitimacy; moreover, magnitude and urgency of the issue at stake may affect the ability to influence ICR. The framework is applied to the retail banking industry, focusing on post-crisis experiences in two countries—Spain and the UK—where there has been considerable pressure on the retail banking industry by civil society and/or government to change behaviours, especially to abandon unethical practices. We illustrate in this paper how corporate responsibility at the sector level in retail banking is the product of context-specific processes of negotiation between civil society and public authorities, on behalf of customers and other stakeholders, drawing on legal and other institutions to influence industry behaviour

The Amylases of Insects

Alpha-amylases are major digestive enzymes that act in the first step of maltopolysaccharide digestion. In insects, these enzymes have long been studied for applied as well as purely scientific purposes. In many species, amylases are produced by multiple gene copies. Rare species are devoid of Amy gene. They are predominantly secreted in the midgut but salivary expression is also frequent, with extraoral activity. Enzymological parameters are quite variable among insects, with visible trends according to phylogeny: Coleopteran amylases have acidic optimum activity, whereas dipteran amylases have neutral preference and lepidopteran ones have clear alkaline preference. The enzyme structure shows interesting variations shaped by evolutionary convergences, such as the recurrent loss of a loop involved in substrate handling. Many works have focused on the action of plant amylase inhibitors on pest insect amylases, in the frame of crop protection by transgenesis. It appears that sensitivity or resistance to inhibitors is finely tuned and very specific and that amylases and their inhibitors have coevolved. The multicopy feature of insect amylases appears to allow tissue-specific or stage-specific regulation, but also to broaden enzymological abilities, such as pH range, and to overcome plant inhibitory defenses

Ecdysone Control of Developmental Transitions: Lessons from Drosophila

The steroid hormone ecdysone is the central regulator of insect developmental transitions. Recent new advances in our understanding of ecdysone action have relied heavily on the application of Drosophila melanogaster molecular genetic tools to study insect metamorphosis. In this review, we focus on three major aspects of Drosophila ecdysone biology: (a) factors that regulate the timing of ecdysone release, (b) molecular basis of stage- and tissue-specific responses to ecdysone, and (c) feedback regulation and coordination of ecdysone signaling

Evidence for a sensitising pigment in fly photoreceptors

Many photoreceptor cells in invertebrates have a dual-peak spectral sensitivity. Evidence is presented that in fly photoreceptors the ultraviolet peak is due to a photostable pigment that absorbs light quanta and transfers the energy to the blue-absorbing visual pigment