Survival, reproduction and congestion: The spaceship problem re-examined

This paper re-examines the spaceship problem, i.e. the design of the optimal population under a fixed living space, by focusing on the dilemma between adding new beings and extending the life of existing beings. For that purpose, we characterize, under time-additive individual welfare depending negatively on population density, the preference ordering of a utilitarian social planner over lifetime-equal histories, i.e. histories with demographic conditions yielding an equal finite number of life-periods (imposed by resources constraints). The analysis of the spaceship problem contradicts widespread beliefs about the populationism of Classical Utilitarianism and the antipopulationism of Average Utilitarianism. We also study the invariance property exhibited by various utilitarian rankings to the total space available and to individual preferences. Finally, we compare histories for a spaceship with a stationary population, and try to accomodate intuitions about posterity and renewal of populations.environmental congestion ; fertility ; longevity ; population ethics ; utilitarianism ; renewal

Sustainability, resource substitution in energy inputs and learning

We assess the impact of the existence of a costly energy substitute (like wind, solar) for a non-renewable resource (like oil, coal) on the sustainability of consumption. The prospects for sustainability depend crucially on the costs of this substitute. If one can reduce the costs of the resource substitute via learning-by-using then we find that still this does not guarantee sustainability. Also, the poorer a country the less it will take the learning-by-using effect into account and the more likely it will be unsustainable.Renewable resource, non-renewable resource, substitution, sustainability, learningby- using.

Learning-by-doing and the Costs of a Backstop for Energy Transition and Sustainability

We assess the impact of being able to substitute an unlimited but costly energy substitute (like wind, solar) for a non-renewable resource (like oil, coal) in a model of sustainable growth. The prospects for sustainability on the optimal path depend crucially on the costs of this substitute.Furthermore, the poorer a country, measured in terms of capital stock at a given point in time, the later it should switch to the renewable substitute, and the more likely it will be unsustainable. Taking learning-by-doing in account, we find that this leads to an earlier switching time but does not guarantee sustainability.backstop technology; non-renewable resource; resource substitution; sustainability; learning-by-doing.

The electronic spectra of protonated PANH molecules

Aims. This study was designed to examine the viability of protonated nitrogen-substituted polycyclic aromatic hydrocarbons (H+PANHs) as candidates for the carriers of the diffuse interstellar bands (DIBs). Methods. We obtained the electronic spectra of two protonated PANH cations, protonated acridine and phenanthridine, using parent ion photo-fragment spectroscopy and generated theoretical electronic spectra using ab initio calculations. Results. We show that the spectra of the two species studied here do not correspond to known DIBs. However, based on the general properties derived from the spectra of these small protonated nitrogen-substituted PAHs, we propose that larger H+PANH cations represent good candidates for DIB carriers due to the expected positions of their electronic transitions in the UV-visible and their narrow spectral bands.Comment: 7 pages, 2 figures, accepted for publication in A&

Tradable pollution permits in dynamic general equilibrium: can optimality and acceptability be reconciled?

In this paper we study the optimal growth path and its decentralization in a two-sector overlapping- generations model with pollution. One sector (power generation) is polluting and the other (final good) is not. Pollution is regulated by tradable emission permits. The issue is whether the optimal growth path can be replicated in equilibrium with pollution permits, given that some permits must be issued free of charge for the sake of political acceptability. We provide a policy rule that allows optimality and acceptability to be reconciled.general equilibrium, optimal growth, pollution, tradable emission permits, acceptability

Comportamiento del actor: intriga, acción, movimiento

El autor analiza el comportamiento del actor, su forma de llevar a cabo la interpretación, y cómo está constituida la persona. Analiza el oficio del actor y las sensaciones y sentimientos que acompañan al mismo. Reflexiona sobre el mundo interno del actor y sobre la comunicación con el público y con los propios autores de los textos.The author analyses the behavior of the actor, his way of developing the interpretation of a role, and how it is constituted the personality. He analyses the actor’s profession and the emotions and feelings characteristic of it. He reflects upon the inner world of actors and about the communication with the audience and the author of the work.L’auteur analyse le comportement de l’acteur, sa manière de interpreter le rôle et comment se constitue la personne. Il analyse le métier de l’acteur, ses émotions et sensations, et réflechit sur le monde intérieur des acteurs et leur communication avec le public, d’ une part, et les autheurs, d’une autre

Longevity and environmental quality in an OLG model

Whereas existing OLG models with endogenous longevity neglect the impact of environmental quality on mortality, this paper studies the design of the optimal public intervention in a two-period OLG model where longevity is influenced positively by health expenditures, but negatively by pollution due to production. It is shown that if individuals, when choosing how much to spend on health, do not internalize the impact of their decision on environmental quality (i.e. the space available for each person), the decentralization of the social optimum requires a tax not only on capital income, but also, on health expenditures. The sensitivity of the optimal second-best public intervention is also explored numerically.longevity, health care, natural environment, pollution

Bankable emission permits under uncertainty and optimal risk-management rules.

This article proposes a theory of banking of emission permits under conditions of regulatory uncertainty. Based on a two-period partial equilibrium framework, we examine the effects of increasing risk - in the sense of a mean-preserving spread - regarding a future permits allocation at the firm-level. We also examine the role of an agency to pool risks by re-allocating permits for a group of firms. Our results are twofold. First, an increase in risk may lead to changes in a firm’s banking strategy, depending on the third partial derivative of its production function with respect to pollution. Second, we define an optimal risk-sharing rule between agents to respond to political decision changes. Our results overall suggest that the bankability of permits may be used as a risk-management tool.Banking; Emission permits; Policy risk; Uncertainty;

Mytilus edulis haemocytes variability : technique, individual and environment

The widely distributed marine bivalve Mytilus edulis is used as a sentinel organism for ecological and toxicological assessments. As a filter feeder, it has the potential to bio-accumulate pollutants. It has been assumed that the cell concentration and cell type ratio of its circulating immune cells, haemocytes, could become complementary sub-lethal indicators of toxicology. These two parameters are respectively referred to as total haemocyte count (THC) and differential cell count (DCC). This study examines these commonly used methods, quantifies their limitations, and develops alternative techniques. The circulating immune cells are investigated to assess their fluctuations. Finally, impacts of environmental challenges on the circulating haemocytes are examined. Despite its importance in the field of Mytilus edulis immunology, THC evaluation is present in only 20% of publications in this field, and DCC in 10%. Ultimately, only 9% of papers consider both THC and DCC before further analyses. The remaining studies disregard THC and DDC, or regard these parameters as being constant and homogenous in M. edulis populations. This study initially quantifies the systematic error induced by sampling, and suggests improvements. For example, a systematic error of 26% is attributed to the use of low precision syringes, and can be reduced with use of higher precision sampling equipment. While the systematic errors in visual count and image analysis of THC and DCC evaluations are equivalent, the computerised methods allow the throughput of larger data sets, reduce workload, and avoid tedious eye counts. Flow cytometry was found to be the most accurate method in THC and DCC evaluation. Furthermore, repeated bleedings influence DCC, triggering the decrease of circulating eosinophils (up to 20%) and the increase of hyaline cells (up to 30%). To mitigate this reaction to sampling, a maximum volume of 50μl using a permanent cannulation is recommended. However, even with improved methods reducing systematic error by half, this study still reports variations as high as 20-fold in the haemocyte concentration in populations of healthy individuals. In addition, over a 2-hour period in a single cannulated individual, fluctuation of the DDC is observed to be as high as 30% for eosinophils, 10% for hyaline cells, and 20% for basophils. These measured variations are explained by haemocyte reservoirs in the tissues. Eosinophils are found in large numbers in epithelial association in the gills, guts and in the mantle, where their numbers have been evaluated at 3x10 7 As a case study, Mytilus edulis challenged with barium sulphate smothering, used by the oil industry in drilling muds, shows gill damage and their subsequent infiltration by eosinophils. In bacterial outbreak, basophilic cells are observed to infiltrate the tissue surrounding the stomach and eosinophils are depleted from the epithelium of the digestive tissues. THC is 10-fold lower than in healthy organisms and eosinophils are depleted from the haemolymph. cells. In conclusion, the THC and DDC methods are shown to be unreliable despite the use of more accurate methods. In addition, Mytilus edulis circulating haemocytes present large variations and the assumption of their homogeneity in terms of time, individuals or methods used cannot be made. These results challenge the conclusions of many past publications regarding causalities established between potential stresses and measured effects. Further research is necessary to understand the mechanisms regulating the circulating haemocytes, the inter-individual variability and to improve investigation methods

Modelling the trajectory of the corpses of mountaineers who disappeared in 1926 on Aletschgletscher, Switzerland

In this paper we reconstruct the space–time trajectory beneath the surface of Aletschgletscher, Switzerland, of the corpses of three mountaineers that disappeared in March 1926 and reappeared at the glacier surface in June 2012. Our method integrates the time-dependent velocity field of an existing full-Stokes glacier model, starting at the point where the corpses were found at the glacier surface. Our main result is that we were able to localize the immersion location where the brothers presumably died. As a second result, the upstream end point of the computed trajectory emerges very close to the glacier surface in 1926, giving a new and global validation of the glacier model in space and time. Testing the sensitivity of the immersion location obtained with respect to the model and other uncertainties indicates an area of 0.6% of the entire glacier area where the accident could have occurred. Our result suggests that death was not caused by an avalanche or a fall into a crevasse; instead, it is likely that the mountaineers became disoriented in prolonged severe weather conditions and froze to death