On the Feasibility of Perpetual Growth in a Decentralized Economy Subject to Environmental Constraints

We propose an endogenous growth model of a decentralized economy subject to environmental constraints. In a basic version, we consider an economy where final production requires some material input and where research activities allow simultaneously productive firms to reduce the dependency of their production process on this input and to improve the quality of their output. We adopt a material balance approach and, in spite of the optimistic assumption that the material input is perfectly recyclable (and thus never exhausted), we show that material output growth is always a transitory phenomenon. When it exists, a balanced growth path is necessarily characterized by constant values of the material variables, long term economic growth taking exclusively the form of perpetual improvements in the quality of consumption goods. The material resource constraint is not solely a long term issue since it is also shown to affect the whole transitory dynamics of the (material) growth process. Renewable energy is introduced in an extension of our basic model. This extension does not affect qualitatively the features of a feasible balanced growth path but make its conditions of existence more restrictive.material balance, endogenous growth, recycling

Search for companions around Sirius

Since the discovery of Sirius-B about 130 yr ago, there have been several claims of a possible second companion around the brightest star Sirius-A. Such a companion could, in particular, be responsible of the suspected colour change of the star, now strongly suggested from two independent historical sources. We reported here on a new observation of the sky region around Sirius, to search for such a companion, using a coronographic device. By comparison of the new stellar field with a similar image obtained by us $\sim$13 yr ago and using the Sirius proper motion, we are able to eliminate the most obvious companion candidates down to a magnitude m$_v$$\sim$17 in a field from 30 arcsec to 2.5 arcmin of the central star. None of the visible stars appears consistent in magnitude and colours with what expected from current theoretical models and observations of low-mass stars. From the study of the same field, it is also shown that the Sirius companion, consistently reported by observers during the years 1920-1930, is most probably an unrelated m$_g$$\simeq$12 background star, now $\sim$ 1 arcmin away but located precisely on the Sirius proper motion trajectory. The closest apparent conjunction with Sirius was realized in 1937 with a minimum angular distance of 6.9 arcsec, of the same order than the Sirius A-B binary separation. The reported observations do not eliminate the possibility of a second companion but now confined the search to the more central 30 arcsec region around Sirius. In particular, the existence of a long period companion cannot definitively be ruled out since the arbitrary orientation of the orbit can yield an observed projected position on sky inside this more central region.Comment: 6 pages, 4 figures, published in Astronomy and Astrophysic

Molecular Forms of Acetylcholinesterase

Several molecular forms of acetylcholinesterase are obtained from Electrophorus or Torpedo electric organs. They have been characterized by physico-chemical methods and observed by electron microscopy. The most complex D form is made up of a globular »head« containing probably twelve subunits, or three tetrameric groups of subunits, attached to a rod like tail. Two other asymmetric forms, C and A, may be derived from it by removal of one or two tetramers from the »head«. These forms can ultimately be degraded by proteolytic digestion or sonication into tetrameric and dimeric active enzymes, G and G\u27. No striking difference in the catalytic properties of these forms could be demonstrated. An analysis of their thermal denaturation suggests · that internal breaks may exist in the polypeptide chains without being revealed ,in catalytic or sedimentation properties of the molecules. /\u27:,, H=I= values demonstrate stabilizing interactions in the more complex molecules. Analysis of subunits by SDS polyacrylamide gel electrophoresis shows that one main 90 000 subunit is progressively split into a 60 000 DFP-labelled chain together with smaller peptides jn the 30 000 range. No difference could be found between D and G subunit patterns which could ibe identified to the tail component. Comparing the molecular weight of A (one tetramer plus ta il) and G (tetramer), one finds that the mass of the tail should be in the 60 000-80 000 range. Recent micrographs suggest that it consists of three strands linked to the three tetramers in the head of D. We therefore propose a three stranded collagen like structure for the tail. We discuss the possible physiological role of the asymmetric structure o.f acetylcholinesterase and its implication with the membrane association of the enzyme. Multiple forms of acetylcholinesterase are not genetically determined i,sozymes but rather represent different states of association of the active monomern. The significance of multiple forms of acetylcholinesterase, especially in mammals, is considered

In situ high temperature TEM tensile testing of pseudo single crystalline Si for PhotoVoltaic applications

Single crystalline Silicon has the highest efficiency to convert sunlight into electricity. Its production is however costly. On the other hand, cheap polycrystalline Si cells can be produced, with a 10% lower PV conversion efficiency. A promising technique, dubbed mono-like Si consists in growing pseudo-single crystalline Si ingots from a tile of single crystalline seeds aligned at the bottom of the crucible. At the present time, this technique is confronted to the high density of defects that multiply during solidification, fueled by the thermal gradients generated in the furnace. Some of these defects have small impact on the electrical properties but others are heavy recombination sites and should be avoided. Here, we focus on dislocations, micro twins and grain boundaries. Their mutual interaction may act as stress concentrators or sinks. We are working at various scales (Fig. 1a-b) to understand these interactions that occur both at long ranges and atomic-scale processes. To gain insight about the later, we have started to tensile strain dedicated micro-samples in situ in the TEM at temperatures between 900 and 1000°C (the melting temperature of Si is 1414°C). We have shown that multiplication processes are initiated at existing GBs and that mobile dislocations are poorly affected by Peierls stresses at this temperature. Interactions of dislocations with twins (Fig 1c) are currently investigated, along with twin terminations and initiation sites

Kevoree Modeling Framework (KMF): Efficient modeling techniques for runtime use

The creation of Domain Specific Languages(DSL) counts as one of the main goals in the field of Model-Driven Software Engineering (MDSE). The main purpose of these DSLs is to facilitate the manipulation of domain specific concepts, by providing developers with specific tools for their domain of expertise. A natural approach to create DSLs is to reuse existing modeling standards and tools. In this area, the Eclipse Modeling Framework (EMF) has rapidly become the defacto standard in the MDSE for building Domain Specific Languages (DSL) and tools based on generative techniques. However, the use of EMF generated tools in domains like Internet of Things (IoT), Cloud Computing or Models@Runtime reaches several limitations. In this paper, we identify several properties the generated tools must comply with to be usable in other domains than desktop-based software systems. We then challenge EMF on these properties and describe our approach to overcome the limitations. Our approach, implemented in the Kevoree Modeling Framework (KMF), is finally evaluated according to the identified properties and compared to EMF.Comment: ISBN 978-2-87971-131-7; N° TR-SnT-2014-11 (2014